text stringlengths 26 3.6k | page_title stringlengths 1 71 | source stringclasses 1
value | token_count int64 10 512 | id stringlengths 2 8 | url stringlengths 31 117 | topic stringclasses 4
values | section stringlengths 4 49 ⌀ | sublist stringclasses 9
values |
|---|---|---|---|---|---|---|---|---|
The French mathematician Paul Lévy proved the following theorem, which gives a necessary and sufficient condition for a continuous -valued stochastic process to actually be -dimensional Brownian motion. Hence, Lévy's condition can actually be used as an alternative definition of Brownian motion.
Let be a continuous stochastic process on a probability space taking values in . Then the following are equivalent:
is a Brownian motion with respect to , i.e., the law of with respect to is the same as the law of an -dimensional Brownian motion, i.e., the push-forward measure is classical Wiener measure on .
both
is a martingale with respect to (and its own natural filtration); and
for all , is a martingale with respect to (and its own natural filtration), where denotes the Kronecker delta.
Spectral content
The spectral content of a stochastic process can be found from the power spectral density, formally defined as
where stands for the expected value. The power spectral density of Brownian motion is found to be
where is the diffusion coefficient of . For naturally occurring signals, the spectral content can be found from the power spectral density of a single realization, with finite available time, i.e.,
which for an individual realization of a Brownian motion trajectory, it is found to have expected value
and variance
For sufficiently long realization times, the expected value of the power spectrum of a single trajectory converges to the formally defined power spectral density but its coefficient of variation tends to This implies the distribution of is broad even in the infinite time limit.
Riemannian manifold
The infinitesimal generator (and hence characteristic operator) of a Brownian motion on is easily calculated to be , where denotes the Laplace operator. In image processing and computer vision, the Laplacian operator has been used for various tasks such as blob and edge detection. This observation is useful in defining Brownian motion on an -dimensional Riemannian manifold : a Brownian motion on is defined to be a diffusion on whose characteristic operator in local coordinates , , is given by , where is the Laplace–Beltrami operator given in local coordinates by
where in the sense of the inverse of a square matrix.
Narrow escape | Brownian motion | Wikipedia | 455 | 4436 | https://en.wikipedia.org/wiki/Brownian%20motion | Physical sciences | Thermodynamics | Physics |
The narrow escape problem is a ubiquitous problem in biology, biophysics and cellular biology which has the following formulation: a Brownian particle (ion, molecule, or protein) is confined to a bounded domain (a compartment or a cell) by a reflecting boundary, except for a small window through which it can escape. The narrow escape problem is that of calculating the mean escape time. This time diverges as the window shrinks, thus rendering the calculation a singular perturbation problem. | Brownian motion | Wikipedia | 97 | 4436 | https://en.wikipedia.org/wiki/Brownian%20motion | Physical sciences | Thermodynamics | Physics |
In computing, BIOS (, ; Basic Input/Output System, also known as the System BIOS, ROM BIOS, BIOS ROM or PC BIOS) is firmware used to provide runtime services for operating systems and programs and to perform hardware initialization during the booting process (power-on startup). The firmware comes pre-installed on the computer's motherboard.
The name originates from the Basic Input/Output System used in the CP/M operating system in 1975. The BIOS firmware was originally proprietary to the IBM PC; it was reverse engineered by some companies (such as Phoenix Technologies) looking to create compatible systems. The interface of that original system serves as a de facto standard.
The BIOS in older PCs initializes and tests the system hardware components (power-on self-test or POST for short), and loads a boot loader from a mass storage device which then initializes a kernel. In the era of DOS, the BIOS provided BIOS interrupt calls for the keyboard, display, storage, and other input/output (I/O) devices that standardized an interface to application programs and the operating system. More recent operating systems do not use the BIOS interrupt calls after startup.
Most BIOS implementations are specifically designed to work with a particular computer or motherboard model, by interfacing with various devices especially system chipset. Originally, BIOS firmware was stored in a ROM chip on the PC motherboard. In later computer systems, the BIOS contents are stored on flash memory so it can be rewritten without removing the chip from the motherboard. This allows easy, end-user updates to the BIOS firmware so new features can be added or bugs can be fixed, but it also creates a possibility for the computer to become infected with BIOS rootkits. Furthermore, a BIOS upgrade that fails could brick the motherboard.
Unified Extensible Firmware Interface (UEFI) is a successor to the legacy PC BIOS, aiming to address its technical limitations. UEFI firmware may include legacy BIOS compatibility to maintain compatibility with operating systems and option cards that do not support UEFI native operation. Since 2020, all PCs for Intel platforms no longer support Legacy BIOS. The last version of Microsoft Windows to officially support running on PCs which use legacy BIOS firmware is Windows 10 as Windows 11 requires a UEFI-compliant system (except for IoT Enterprise editions of Windows 11 since version 24H2). | BIOS | Wikipedia | 512 | 4473 | https://en.wikipedia.org/wiki/BIOS | Technology | Computer hardware | null |
History
The term BIOS (Basic Input/Output System) was created by Gary Kildall and first appeared in the CP/M operating system in 1975, describing the machine-specific part of CP/M loaded during boot time that interfaces directly with the hardware. (A CP/M machine usually has only a simple boot loader in its ROM.)
Versions of MS-DOS, PC DOS or DR-DOS contain a file called variously "IO.SYS", "IBMBIO.COM", "IBMBIO.SYS", or "DRBIOS.SYS"; this file is known as the "DOS BIOS" (also known as the "DOS I/O System") and contains the lower-level hardware-specific part of the operating system. Together with the underlying hardware-specific but operating system-independent "System BIOS", which resides in ROM, it represents the analogue to the "CP/M BIOS".
The BIOS originally proprietary to the IBM PC has been reverse engineered by some companies (such as Phoenix Technologies) looking to create compatible systems.
With the introduction of PS/2 machines, IBM divided the System BIOS into real- and protected-mode portions. The real-mode portion was meant to provide backward compatibility with existing operating systems such as DOS, and therefore was named "CBIOS" (for "Compatibility BIOS"), whereas the "ABIOS" (for "Advanced BIOS") provided new interfaces specifically suited for multitasking operating systems such as OS/2. | BIOS | Wikipedia | 315 | 4473 | https://en.wikipedia.org/wiki/BIOS | Technology | Computer hardware | null |
User interface
The BIOS of the original IBM PC and XT had no interactive user interface. Error codes or messages were displayed on the screen, or coded series of sounds were generated to signal errors when the power-on self-test (POST) had not proceeded to the point of successfully initializing a video display adapter. Options on the IBM PC and XT were set by switches and jumpers on the main board and on expansion cards. Starting around the mid-1990s, it became typical for the BIOS ROM to include a "BIOS configuration utility" (BCU) or "BIOS setup utility", accessed at system power-up by a particular key sequence. This program allowed the user to set system configuration options, of the type formerly set using DIP switches, through an interactive menu system controlled through the keyboard. In the interim period, IBM-compatible PCsincluding the IBM ATheld configuration settings in battery-backed RAM and used a bootable configuration program on floppy disk, not in the ROM, to set the configuration options contained in this memory. The floppy disk was supplied with the computer, and if it was lost the system settings could not be changed. The same applied in general to computers with an EISA bus, for which the configuration program was called an EISA Configuration Utility (ECU).
A modern Wintel-compatible computer provides a setup routine essentially unchanged in nature from the ROM-resident BIOS setup utilities of the late 1990s; the user can configure hardware options using the keyboard and video display. The modern Wintel machine may store the BIOS configuration settings in flash ROM, perhaps the same flash ROM that holds the BIOS itself.
Extensions (option ROMs) | BIOS | Wikipedia | 348 | 4473 | https://en.wikipedia.org/wiki/BIOS | Technology | Computer hardware | null |
Peripheral cards such as hard disk drive host bus adapters and video cards have their own firmware, and BIOS extension option ROM code may be a part of the expansion card firmware; that code provides additional capabilities in the BIOS. Code in option ROMs runs before the BIOS boots the operating system from mass storage. These ROMs typically test and initialize hardware, add new BIOS services, or replace existing BIOS services with their own services. For example, a SCSI controller usually has a BIOS extension ROM that adds support for hard drives connected through that controller. An extension ROM could in principle contain operating system, or it could implement an entirely different boot process such as network booting. Operation of an IBM-compatible computer system can be completely changed by removing or inserting an adapter card (or a ROM chip) that contains a BIOS extension ROM.
The motherboard BIOS typically contains code for initializing and bootstrapping integrated display and integrated storage. The initialization process can involve the execution of code related to the device being initialized, for locating the device, verifying the type of device, then establishing base registers, setting pointers, establishing interrupt vector tables, selecting paging modes which are ways for organizing available registers in devices, setting default values for accessing software routines related to interrupts, and setting the device's configuration using default values. In addition, plug-in adapter cards such as SCSI, RAID, network interface cards, and video cards often include their own BIOS (e.g. Video BIOS), complementing or replacing the system BIOS code for the given component. Even devices built into the motherboard can behave in this way; their option ROMs can be a part of the motherboard BIOS.
An add-in card requires an option ROM if the card is not supported by the motherboard BIOS and the card needs to be initialized or made accessible through BIOS services before the operating system can be loaded (usually this means it is required in the boot process). An additional advantage of ROM on some early PC systems (notably including the IBM PCjr) was that ROM was faster than main system RAM. (On modern systems, the case is very much the reverse of this, and BIOS ROM code is usually copied ("shadowed") into RAM so it will run faster.)
Physical placement | BIOS | Wikipedia | 486 | 4473 | https://en.wikipedia.org/wiki/BIOS | Technology | Computer hardware | null |
Option ROMs normally reside on adapter cards. However, the original PC, and perhaps also the PC XT, have a spare ROM socket on the motherboard (the "system board" in IBM's terms) into which an option ROM can be inserted, and the four ROMs that contain the BASIC interpreter can also be removed and replaced with custom ROMs which can be option ROMs. The IBM PCjr is unique among PCs in having two ROM cartridge slots on the front. Cartridges in these slots map into the same region of the upper memory area used for option ROMs, and the cartridges can contain option ROM modules that the BIOS would recognize. The cartridges can also contain other types of ROM modules, such as BASIC programs, that are handled differently. One PCjr cartridge can contain several ROM modules of different types, possibly stored together in one ROM chip.
Operation
System startup
The 8086 and 8088 start at physical address FFFF0h. The 80286 starts at physical address FFFFF0h. The 80386 and later x86 processors start at physical address FFFFFFF0h. When the system is initialized, the first instruction of the BIOS appears at that address.
If the system has just been powered up or the reset button was pressed ("cold boot"), the full power-on self-test (POST) is run. If Ctrl+Alt+Delete was pressed ("warm boot"), a special flag value stored in nonvolatile BIOS memory ("CMOS") tested by the BIOS allows bypass of the lengthy POST and memory detection.
The POST identifies, tests and initializes system devices such as the CPU, chipset, RAM, motherboard, video card, keyboard, mouse, hard disk drive, optical disc drive and other hardware, including integrated peripherals.
Early IBM PCs had a routine in the POST that would download a program into RAM through the keyboard port and run it. This feature was intended for factory test or diagnostic purposes. | BIOS | Wikipedia | 416 | 4473 | https://en.wikipedia.org/wiki/BIOS | Technology | Computer hardware | null |
After the motherboard BIOS completes its POST, most BIOS versions search for option ROM modules, also called BIOS extension ROMs, and execute them. The motherboard BIOS scans for extension ROMs in a portion of the "upper memory area" (the part of the x86 real-mode address space at and above address 0xA0000) and runs each ROM found, in order. To discover memory-mapped option ROMs, a BIOS implementation scans the real-mode address space from 0x0C0000 to 0x0F0000 on 2 KB (2,048 bytes) boundaries, looking for a two-byte ROM signature: 0x55 followed by 0xAA. In a valid expansion ROM, this signature is followed by a single byte indicating the number of 512-byte blocks the expansion ROM occupies in real memory, and the next byte is the option ROM's entry point (also known as its "entry offset"). If the ROM has a valid checksum, the BIOS transfers control to the entry address, which in a normal BIOS extension ROM should be the beginning of the extension's initialization routine.
At this point, the extension ROM code takes over, typically testing and initializing the hardware it controls and registering interrupt vectors for use by post-boot applications. It may use BIOS services (including those provided by previously initialized option ROMs) to provide a user configuration interface, to display diagnostic information, or to do anything else that it requires.
An option ROM should normally return to the BIOS after completing its initialization process. Once (and if) an option ROM returns, the BIOS continues searching for more option ROMs, calling each as it is found, until the entire option ROM area in the memory space has been scanned. It is possible that an option ROM will not return to BIOS, pre-empting the BIOS's boot sequence altogether.
Boot process
After the POST completes and, in a BIOS that supports option ROMs, after the option ROM scan is completed and all detected ROM modules with valid checksums have been called, the BIOS calls interrupt 19h to start boot processing. Post-boot, programs loaded can also call interrupt 19h to reboot the system, but they must be careful to disable interrupts and other asynchronous hardware processes that may interfere with the BIOS rebooting process, or else the system may hang or crash while it is rebooting. | BIOS | Wikipedia | 511 | 4473 | https://en.wikipedia.org/wiki/BIOS | Technology | Computer hardware | null |
When interrupt 19h is called, the BIOS attempts to locate boot loader software on a "boot device", such as a hard disk, a floppy disk, CD, or DVD. It loads and executes the first boot software it finds, giving it control of the PC.
The BIOS uses the boot devices set in Nonvolatile BIOS memory (CMOS), or, in the earliest PCs, DIP switches. The BIOS checks each device in order to see if it is bootable by attempting to load the first sector (boot sector). If the sector cannot be read, the BIOS proceeds to the next device. If the sector is read successfully, some BIOSes will also check for the boot sector signature 0x55 0xAA in the last two bytes of the sector (which is 512 bytes long), before accepting a boot sector and considering the device bootable.
When a bootable device is found, the BIOS transfers control to the loaded sector. The BIOS does not interpret the contents of the boot sector other than to possibly check for the boot sector signature in the last two bytes. Interpretation of data structures like partition tables and BIOS Parameter Blocks is done by the boot program in the boot sector itself or by other programs loaded through the boot process.
A non-disk device such as a network adapter attempts booting by a procedure that is defined by its option ROM or the equivalent integrated into the motherboard BIOS ROM. As such, option ROMs may also influence or supplant the boot process defined by the motherboard BIOS ROM.
With the El Torito optical media boot standard, the optical drive actually emulates a 3.5" high-density floppy disk to the BIOS for boot purposes. Reading the "first sector" of a CD-ROM or DVD-ROM is not a simply defined operation like it is on a floppy disk or a hard disk. Furthermore, the complexity of the medium makes it difficult to write a useful boot program in one sector. The bootable virtual floppy disk can contain software that provides access to the optical medium in its native format. | BIOS | Wikipedia | 433 | 4473 | https://en.wikipedia.org/wiki/BIOS | Technology | Computer hardware | null |
If an expansion ROM wishes to change the way the system boots (such as from a network device or a SCSI adapter) in a cooperative way, it can use the BIOS Boot Specification (BBS) API to register its ability to do so. Once the expansion ROMs have registered using the BBS APIs, the user can select among the available boot options from within the BIOS's user interface. This is why most BBS compliant PC BIOS implementations will not allow the user to enter the BIOS's user interface until the expansion ROMs have finished executing and registering themselves with the BBS API.
Also, if an expansion ROM wishes to change the way the system boots unilaterally, it can simply hook interrupt 19h or other interrupts normally called from interrupt 19h, such as interrupt 13h, the BIOS disk service, to intercept the BIOS boot process. Then it can replace the BIOS boot process with one of its own, or it can merely modify the boot sequence by inserting its own boot actions into it, by preventing the BIOS from detecting certain devices as bootable, or both. Before the BIOS Boot Specification was promulgated, this was the only way for expansion ROMs to implement boot capability for devices not supported for booting by the native BIOS of the motherboard.
Boot priority
The user can select the boot priority implemented by the BIOS. For example, most computers have a hard disk that is bootable, but sometimes there is a removable-media drive that has higher boot priority, so the user can cause a removable disk to be booted.
In most modern BIOSes, the boot priority order can be configured by the user. In older BIOSes, limited boot priority options are selectable; in the earliest BIOSes, a fixed priority scheme was implemented, with floppy disk drives first, fixed disks (i.e., hard disks) second, and typically no other boot devices supported, subject to modification of these rules by installed option ROMs. The BIOS in an early PC also usually would only boot from the first floppy disk drive or the first hard disk drive, even if there were two drives installed. | BIOS | Wikipedia | 448 | 4473 | https://en.wikipedia.org/wiki/BIOS | Technology | Computer hardware | null |
Boot failure
On the original IBM PC and XT, if no bootable disk was found, the BIOS would try to start ROM BASIC with the interrupt call to interrupt 18h. Since few programs used BASIC in ROM, clone PC makers left it out; then a computer that failed to boot from a disk would display "No ROM BASIC" and halt (in response to interrupt 18h).
Later computers would display a message like "No bootable disk found"; some would prompt for a disk to be inserted and a key to be pressed to retry the boot process. A modern BIOS may display nothing or may automatically enter the BIOS configuration utility when the boot process fails.
Boot environment
The environment for the boot program is very simple: the CPU is in real mode and the general-purpose and segment registers are undefined, except SS, SP, CS, and DL. CS:IP always points to physical address 0x07C00. What values CS and IP actually have is not well defined. Some BIOSes use a CS:IP of 0x0000:0x7C00 while others may use 0x07C0:0x0000. Because boot programs are always loaded at this fixed address, there is no need for a boot program to be relocatable. DL may contain the drive number, as used with interrupt 13h, of the boot device. SS:SP points to a valid stack that is presumably large enough to support hardware interrupts, but otherwise SS and SP are undefined. (A stack must be already set up in order for interrupts to be serviced, and interrupts must be enabled in order for the system timer-tick interrupt, which BIOS always uses at least to maintain the time-of-day count and which it initializes during POST, to be active and for the keyboard to work. The keyboard works even if the BIOS keyboard service is not called; keystrokes are received and placed in the 15-character type-ahead buffer maintained by BIOS.) The boot program must set up its own stack, because the size of the stack set up by BIOS is unknown and its location is likewise variable; although the boot program can investigate the default stack by examining SS:SP, it is easier and shorter to just unconditionally set up a new stack. | BIOS | Wikipedia | 479 | 4473 | https://en.wikipedia.org/wiki/BIOS | Technology | Computer hardware | null |
At boot time, all BIOS services are available, and the memory below address 0x00400 contains the interrupt vector table. BIOS POST has initialized the system timers, interrupt controller(s), DMA controller(s), and other motherboard/chipset hardware as necessary to bring all BIOS services to ready status. DRAM refresh for all system DRAM in conventional memory and extended memory, but not necessarily expanded memory, has been set up and is running. The interrupt vectors corresponding to the BIOS interrupts have been set to point at the appropriate entry points in the BIOS, hardware interrupt vectors for devices initialized by the BIOS have been set to point to the BIOS-provided ISRs, and some other interrupts, including ones that BIOS generates for programs to hook, have been set to a default dummy ISR that immediately returns. The BIOS maintains a reserved block of system RAM at addresses 0x00400–0x004FF with various parameters initialized during the POST. All memory at and above address 0x00500 can be used by the boot program; it may even overwrite itself.
Operating system services
The BIOS ROM is customized to the particular manufacturer's hardware, allowing low-level services (such as reading a keystroke or writing a sector of data to diskette) to be provided in a standardized way to programs, including operating systems. For example, an IBM PC might have either a monochrome or a color display adapter (using different display memory addresses and hardware), but a single, standard, BIOS system call may be invoked to display a character at a specified position on the screen in text mode or graphics mode.
The BIOS provides a small library of basic input/output functions to operate peripherals (such as the keyboard, rudimentary text and graphics display functions and so forth). When using MS-DOS, BIOS services could be accessed by an application program (or by MS-DOS) by executing an interrupt 13h interrupt instruction to access disk functions, or by executing one of a number of other documented BIOS interrupt calls to access video display, keyboard, cassette, and other device functions. | BIOS | Wikipedia | 449 | 4473 | https://en.wikipedia.org/wiki/BIOS | Technology | Computer hardware | null |
Operating systems and executive software that are designed to supersede this basic firmware functionality provide replacement software interfaces to application software. Applications can also provide these services to themselves. This began even in the 1980s under MS-DOS, when programmers observed that using the BIOS video services for graphics display were very slow. To increase the speed of screen output, many programs bypassed the BIOS and programmed the video display hardware directly. Other graphics programmers, particularly but not exclusively in the demoscene, observed that there were technical capabilities of the PC display adapters that were not supported by the IBM BIOS and could not be taken advantage of without circumventing it. Since the AT-compatible BIOS ran in Intel real mode, operating systems that ran in protected mode on 286 and later processors required hardware device drivers compatible with protected mode operation to replace BIOS services.
In modern PCs running modern operating systems (such as Windows and Linux) the BIOS interrupt calls are used only during booting and initial loading of operating systems. Before the operating system's first graphical screen is displayed, input and output are typically handled through BIOS. A boot menu such as the textual menu of Windows, which allows users to choose an operating system to boot, to boot into the safe mode, or to use the last known good configuration, is displayed through BIOS and receives keyboard input through BIOS.
Many modern PCs can still boot and run legacy operating systems such as MS-DOS or DR-DOS that rely heavily on BIOS for their console and disk I/O, providing that the system has a BIOS, or a CSM-capable UEFI firmware.
Processor microcode updates
Intel processors have reprogrammable microcode since the P6 microarchitecture. AMD processors have reprogrammable microcode since the K7 microarchitecture. The BIOS contain patches to the processor microcode that fix errors in the initial processor microcode; microcode is loaded into processor's SRAM so reprogramming is not persistent, thus loading of microcode updates is performed each time the system is powered up. Without reprogrammable microcode, an expensive processor swap would be required; for example, the Pentium FDIV bug became an expensive fiasco for Intel as it required a product recall because the original Pentium processor's defective microcode could not be reprogrammed. Operating systems can update main processor microcode also. | BIOS | Wikipedia | 499 | 4473 | https://en.wikipedia.org/wiki/BIOS | Technology | Computer hardware | null |
Identification
Some BIOSes contain a software licensing description table (SLIC), a digital signature placed inside the BIOS by the original equipment manufacturer (OEM), for example Dell. The SLIC is inserted into the ACPI data table and contains no active code.
Computer manufacturers that distribute OEM versions of Microsoft Windows and Microsoft application software can use the SLIC to authenticate licensing to the OEM Windows Installation disk and system recovery disc containing Windows software. Systems with a SLIC can be preactivated with an OEM product key, and they verify an XML formatted OEM certificate against the SLIC in the BIOS as a means of self-activating (see System Locked Preinstallation, SLP). If a user performs a fresh install of Windows, they will need to have possession of both the OEM key (either SLP or COA) and the digital certificate for their SLIC in order to bypass activation. This can be achieved if the user performs a restore using a pre-customised image provided by the OEM. Power users can copy the necessary certificate files from the OEM image, decode the SLP product key, then perform SLP activation manually.
Overclocking
Some BIOS implementations allow overclocking, an action in which the CPU is adjusted to a higher clock rate than its manufacturer rating for guaranteed capability. Overclocking may, however, seriously compromise system reliability in insufficiently cooled computers and generally shorten component lifespan. Overclocking, when incorrectly performed, may also cause components to overheat so quickly that they mechanically destroy themselves.
Modern use
Some older operating systems, for example MS-DOS, rely on the BIOS to carry out most input/output tasks within the PC.
Calling real mode BIOS services directly is inefficient for protected mode (and long mode) operating systems. BIOS interrupt calls are not used by modern multitasking operating systems after they initially load.
In the 1990s, BIOS provided some protected mode interfaces for Microsoft Windows and Unix-like operating systems, such as Advanced Power Management (APM), Plug and Play BIOS, Desktop Management Interface (DMI), VESA BIOS Extensions (VBE), e820 and MultiProcessor Specification (MPS). Starting from the year 2000, most BIOSes provide ACPI, SMBIOS, VBE and e820 interfaces for modern operating systems. | BIOS | Wikipedia | 497 | 4473 | https://en.wikipedia.org/wiki/BIOS | Technology | Computer hardware | null |
After operating systems load, the System Management Mode code is still running in SMRAM. Since 2010, BIOS technology is in a transitional process toward UEFI.
Configuration
Setup utility
Historically, the BIOS in the IBM PC and XT had no built-in user interface. The BIOS versions in earlier PCs (XT-class) were not software configurable; instead, users set the options via DIP switches on the motherboard. Later computers, including most IBM-compatibles with 80286 CPUs, had a battery-backed nonvolatile BIOS memory (CMOS RAM chip) that held BIOS settings. These settings, such as video-adapter type, memory size, and hard-disk parameters, could only be configured by running a configuration program from a disk, not built into the ROM. A special "reference diskette" was inserted in an IBM AT to configure settings such as memory size.
Early BIOS versions did not have passwords or boot-device selection options. The BIOS was hard-coded to boot from the first floppy drive, or, if that failed, the first hard disk. Access control in early AT-class machines was by a physical keylock switch (which was not hard to defeat if the computer case could be opened). Anyone who could switch on the computer could boot it.
Later, 386-class computers started integrating the BIOS setup utility in the ROM itself, alongside the BIOS code; these computers usually boot into the BIOS setup utility if a certain key or key combination is pressed, otherwise the BIOS POST and boot process are executed.
A modern BIOS setup utility has a text user interface (TUI) or graphical user interface (GUI) accessed by pressing a certain key on the keyboard when the PC starts. Usually, the key is advertised for short time during the early startup, for example "Press DEL to enter Setup".
The actual key depends on specific hardware. The settings key is most often Delete (Acer, ASRock, Asus PC, ECS, Gigabyte, MSI, Zotac) and F2 (Asus motherboard, Dell, Lenovo laptop, Origin PC, Samsung, Toshiba), but it can also be F1 (Lenovo desktop) and F10 (HP).
Features present in the BIOS setup utility typically include: | BIOS | Wikipedia | 488 | 4473 | https://en.wikipedia.org/wiki/BIOS | Technology | Computer hardware | null |
Configuring, enabling and disabling the hardware components
Setting the system time
Setting the boot order
Setting various passwords, such as a password for securing access to the BIOS user interface and preventing malicious users from booting the system from unauthorized portable storage devices, or a password for booting the system
Hardware monitoring
A modern BIOS setup screen often features a PC Health Status or a Hardware Monitoring tab, which directly interfaces with a Hardware Monitor chip of the mainboard. This makes it possible to monitor CPU and chassis temperature, the voltage provided by the power supply unit, as well as monitor and control the speed of the fans connected to the motherboard.
Once the system is booted, hardware monitoring and computer fan control is normally done directly by the Hardware Monitor chip itself, which can be a separate chip, interfaced through I²C or SMBus, or come as a part of a Super I/O solution, interfaced through Industry Standard Architecture (ISA) or Low Pin Count (LPC). Some operating systems, like NetBSD with envsys and OpenBSD with sysctl hw.sensors, feature integrated interfacing with hardware monitors.
However, in some circumstances, the BIOS also provides the underlying information about hardware monitoring through ACPI, in which case, the operating system may be using ACPI to perform hardware monitoring.
Reprogramming
In modern PCs the BIOS is stored in rewritable EEPROM or NOR flash memory, allowing the contents to be replaced and modified. This rewriting of the contents is sometimes termed flashing. It can be done by a special program, usually provided by the system's manufacturer, or at POST, with a BIOS image in a hard drive or USB flash drive. A file containing such contents is sometimes termed "a BIOS image". A BIOS might be reflashed in order to upgrade to a newer version to fix bugs or provide improved performance or to support newer hardware. Some computers also support updating the BIOS via an update floppy disk or a special partition on the hard drive.
Hardware | BIOS | Wikipedia | 425 | 4473 | https://en.wikipedia.org/wiki/BIOS | Technology | Computer hardware | null |
The original IBM PC BIOS (and cassette BASIC) was stored on mask-programmed read-only memory (ROM) chips in sockets on the motherboard. ROMs could be replaced, but not altered, by users. To allow for updates, many compatible computers used re-programmable BIOS memory devices such as EPROM, EEPROM and later flash memory (usually NOR flash) devices. According to Robert Braver, the president of the BIOS manufacturer Micro Firmware, Flash BIOS chips became common around 1995 because the electrically erasable PROM (EEPROM) chips are cheaper and easier to program than standard ultraviolet erasable PROM (EPROM) chips. Flash chips are programmed (and re-programmed) in-circuit, while EPROM chips need to be removed from the motherboard for re-programming. BIOS versions are upgraded to take advantage of newer versions of hardware and to correct bugs in previous revisions of BIOSes.
Beginning with the IBM AT, PCs supported a hardware clock settable through BIOS. It had a century bit which allowed for manually changing the century when the year 2000 happened. Most BIOS revisions created in 1995 and nearly all BIOS revisions in 1997 supported the year 2000 by setting the century bit automatically when the clock rolled past midnight, 31 December 1999.
The first flash chips were attached to the ISA bus. Starting in 1998, the BIOS flash moved to the LPC bus, following a new standard implementation known as "firmware hub" (FWH). In 2005, the BIOS flash memory moved to the SPI bus.
The size of the BIOS, and the capacity of the ROM, EEPROM, or other media it may be stored on, has increased over time as new features have been added to the code; BIOS versions now exist with sizes up to 32 megabytes. For contrast, the original IBM PC BIOS was contained in an 8 KB mask ROM. Some modern motherboards are including even bigger NAND flash memory ICs on board which are capable of storing whole compact operating systems, such as some Linux distributions. For example, some ASUS notebooks included Splashtop OS embedded into their NAND flash memory ICs. However, the idea of including an operating system along with BIOS in the ROM of a PC is not new; in the 1980s, Microsoft offered a ROM option for MS-DOS, and it was included in the ROMs of some PC clones such as the Tandy 1000 HX. | BIOS | Wikipedia | 506 | 4473 | https://en.wikipedia.org/wiki/BIOS | Technology | Computer hardware | null |
Another type of firmware chip was found on the IBM PC AT and early compatibles. In the AT, the keyboard interface was controlled by a microcontroller with its own programmable memory. On the IBM AT, that was a 40-pin socketed device, while some manufacturers used an EPROM version of this chip which resembled an EPROM. This controller was also assigned the A20 gate function to manage memory above the one-megabyte range; occasionally an upgrade of this "keyboard BIOS" was necessary to take advantage of software that could use upper memory.
The BIOS may contain components such as the Memory Reference Code (MRC), which is responsible for the memory initialization (e.g. SPD and memory timings initialization).
Modern BIOS includes
Intel Management Engine or AMD Platform Security Processor firmware.
Vendors and products
IBM published the entire listings of the BIOS for its original PC, PC XT, PC AT, and other contemporary PC models, in an appendix of the IBM PC Technical Reference Manual for each machine type. The effect of the publication of the BIOS listings is that anyone can see exactly what a definitive BIOS does and how it does it.
In May 1984, Phoenix Software Associates released its first ROM-BIOS. This BIOS enabled OEMs to build essentially fully compatible clones without having to reverse-engineer the IBM PC BIOS themselves, as Compaq had done for the Portable; it also helped fuel the growth in the PC-compatibles industry and sales of non-IBM versions of DOS. The first American Megatrends (AMI) BIOS was released in 1986.
New standards grafted onto the BIOS are usually without complete public documentation or any BIOS listings. As a result, it is not as easy to learn the intimate details about the many non-IBM additions to BIOS as about the core BIOS services. | BIOS | Wikipedia | 387 | 4473 | https://en.wikipedia.org/wiki/BIOS | Technology | Computer hardware | null |
Many PC motherboard suppliers licensed the BIOS "core" and toolkit from a commercial third party, known as an "independent BIOS vendor" or IBV. The motherboard manufacturer then customized this BIOS to suit its own hardware. For this reason, updated BIOSes are normally obtained directly from the motherboard manufacturer. Major IBVs included American Megatrends (AMI), Insyde Software, Phoenix Technologies, and Byosoft. Microid Research and Award Software were acquired by Phoenix Technologies in 1998; Phoenix later phased out the Award brand name (although Award Software is still credited in newer AwardBIOS versions and in UEFI firmwares). General Software, which was also acquired by Phoenix in 2007, sold BIOS for embedded systems based on Intel processors.
SeaBIOS is an open-source BIOS implementation.
Open-source BIOS replacements
The open-source community increased their effort to develop a replacement for proprietary BIOSes and their future incarnations with an open-sourced counterparts. Open Firmware was an early attempt to make an open specification for boot firmware. It was initially endorsed by IEEE in its IEEE 1275-1994 standard but was withdrawn in 2005. Later examples include the OpenBIOS, coreboot and libreboot projects. AMD provided product specifications for some chipsets using coreboot, and Google is sponsoring the project. Motherboard manufacturer Tyan offers coreboot next to the standard BIOS with their Opteron line of motherboards.
Security
EEPROM and flash memory chips are advantageous because they can be easily updated by the user; it is customary for hardware manufacturers to issue BIOS updates to upgrade their products, improve compatibility and remove bugs. However, this advantage had the risk that an improperly executed or aborted BIOS update could render the computer or device unusable. To avoid these situations, more recent BIOSes use a "boot block"; a portion of the BIOS which runs first and must be updated separately. This code verifies if the rest of the BIOS is intact (using hash checksums or other methods) before transferring control to it. If the boot block detects any corruption in the main BIOS, it will typically warn the user that a recovery process must be initiated by booting from removable media (floppy, CD or USB flash drive) so the user can try flashing the BIOS again. Some motherboards have a backup BIOS (sometimes referred to as DualBIOS boards) to recover from BIOS corruptions. | BIOS | Wikipedia | 510 | 4473 | https://en.wikipedia.org/wiki/BIOS | Technology | Computer hardware | null |
There are at least five known viruses that attack the BIOS. Two of which were for demonstration purposes. The first one found in the wild was Mebromi, targeting Chinese users.
The first BIOS virus was BIOS Meningitis, which instead of erasing BIOS chips it infected them. BIOS Meningitis was relatively harmless, compared to a virus like CIH.
The second BIOS virus was CIH, also known as the "Chernobyl Virus", which was able to erase flash ROM BIOS content on compatible chipsets. CIH appeared in mid-1998 and became active in April 1999. Often, infected computers could no longer boot, and people had to remove the flash ROM IC from the motherboard and reprogram it. CIH targeted the then-widespread Intel i430TX motherboard chipset and took advantage of the fact that the Windows 9x operating systems, also widespread at the time, allowed direct hardware access to all programs.
Modern systems are not vulnerable to CIH because of a variety of chipsets being used which are incompatible with the Intel i430TX chipset, and also other flash ROM IC types. There is also extra protection from accidental BIOS rewrites in the form of boot blocks which are protected from accidental overwrite or dual and quad BIOS equipped systems which may, in the event of a crash, use a backup BIOS. Also, all modern operating systems such as FreeBSD, Linux, macOS, Windows NT-based Windows OS like Windows 2000, Windows XP and newer, do not allow user-mode programs to have direct hardware access using a hardware abstraction layer.
As a result, as of 2008, CIH has become essentially harmless, at worst causing annoyance by infecting executable files and triggering antivirus software. Other BIOS viruses remain possible, however; since most Windows home users without Windows Vista/7's UAC run all applications with administrative privileges, a modern CIH-like virus could in principle still gain access to hardware without first using an exploit. The operating system OpenBSD prevents all users from having this access and the grsecurity patch for the Linux kernel also prevents this direct hardware access by default, the difference being an attacker requiring a much more difficult kernel level exploit or reboot of the machine. | BIOS | Wikipedia | 475 | 4473 | https://en.wikipedia.org/wiki/BIOS | Technology | Computer hardware | null |
The third BIOS virus was a technique presented by John Heasman, principal security consultant for UK-based Next-Generation Security Software. In 2006, at the Black Hat Security Conference, he showed how to elevate privileges and read physical memory, using malicious procedures that replaced normal ACPI functions stored in flash memory.
The fourth BIOS virus was a technique called "Persistent BIOS infection." It appeared in 2009 at the CanSecWest Security Conference in Vancouver, and at the SyScan Security Conference in Singapore. Researchers Anibal Sacco and Alfredo Ortega, from Core Security Technologies, demonstrated how to insert malicious code into the decompression routines in the BIOS, allowing for nearly full control of the PC at start-up, even before the operating system is booted. The proof-of-concept does not exploit a flaw in the BIOS implementation, but only involves the normal BIOS flashing procedures. Thus, it requires physical access to the machine, or for the user to be root. Despite these requirements, Ortega underlined the profound implications of his and Sacco's discovery: "We can patch a driver to drop a fully working rootkit. We even have a little code that can remove or disable antivirus."
Mebromi is a trojan which targets computers with AwardBIOS, Microsoft Windows, and antivirus software from two Chinese companies: Rising Antivirus and Jiangmin KV Antivirus. Mebromi installs a rootkit which infects the Master boot record.
In a December 2013 interview with 60 Minutes, Deborah Plunkett, Information Assurance Director for the US National Security Agency claimed the NSA had uncovered and thwarted a possible BIOS attack by a foreign nation state, targeting the US financial system. The program cited anonymous sources alleging it was a Chinese plot. However follow-up articles in The Guardian, The Atlantic, Wired and The Register refuted the NSA's claims.
Newer Intel platforms have Intel Boot Guard (IBG) technology enabled, this technology will check the BIOS digital signature at startup, and the IBG public key is fused into the PCH. End users can't disable this function.
Alternatives and successors | BIOS | Wikipedia | 442 | 4473 | https://en.wikipedia.org/wiki/BIOS | Technology | Computer hardware | null |
Unified Extensible Firmware Interface (UEFI) supplements the BIOS in many new machines. Initially written for the Intel Itanium architecture, UEFI is now available for x86 and Arm platforms; the specification development is driven by the Unified EFI Forum, an industry special interest group. EFI booting has been supported in only Microsoft Windows versions supporting GPT, the Linux kernel 2.6.1 and later, and macOS on Intel-based Macs. , new PC hardware predominantly ships with UEFI firmware. The architecture of the rootkit safeguard can also prevent the system from running the user's own software changes, which makes UEFI controversial as a legacy BIOS replacement in the open hardware community. Also, Windows 11 requires UEFI to boot, with the exception of IoT Enterprise editions of Windows 11. UEFI is required for devices shipping with Windows 8 and above.
Other alternatives to the functionality of the "Legacy BIOS" in the x86 world include coreboot and libreboot.
Some servers and workstations use a platform-independent Open Firmware (IEEE-1275) based on the Forth programming language; it is included with Sun's SPARC computers, IBM's RS/6000 line, and other PowerPC systems such as the CHRP motherboards, along with the x86-based OLPC XO-1.
As of at least 2015, Apple has removed legacy BIOS support from the UEFI monitor in Intel-based Macs. As such, the BIOS utility no longer supports the legacy option, and prints "Legacy mode not supported on this system".
In 2017, Intel announced that it would remove legacy BIOS support by 2020. Since 2019, new Intel platform OEM PCs no longer support the legacy option. | BIOS | Wikipedia | 370 | 4473 | https://en.wikipedia.org/wiki/BIOS | Technology | Computer hardware | null |
In condensed matter physics, a Bose–Einstein condensate (BEC) is a state of matter that is typically formed when a gas of bosons at very low densities is cooled to temperatures very close to absolute zero, i.e., . Under such conditions, a large fraction of bosons occupy the lowest quantum state, at which microscopic quantum-mechanical phenomena, particularly wavefunction interference, become apparent macroscopically.
More generally, condensation refers to the appearance of macroscopic occupation of one or several states: for example, in BCS theory, a superconductor is a condensate of Cooper pairs. As such, condensation can be associated with phase transition, and the macroscopic occupation of the state is the order parameter.
Bose–Einstein condensate was first predicted, generally, in 1924–1925 by Albert Einstein, crediting a pioneering paper by Satyendra Nath Bose on the new field now known as quantum statistics. In 1995, the Bose–Einstein condensate was created by Eric Cornell and Carl Wieman of the University of Colorado Boulder using rubidium atoms; later that year, Wolfgang Ketterle of MIT produced a BEC using sodium atoms. In 2001 Cornell, Wieman, and Ketterle shared the Nobel Prize in Physics "for the achievement of Bose–Einstein condensation in dilute gases of alkali atoms, and for early fundamental studies of the properties of the condensates".
History | Bose–Einstein condensate | Wikipedia | 299 | 4474 | https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein%20condensate | Physical sciences | States of matter | null |
Bose first sent a paper to Einstein on the quantum statistics of light quanta (now called photons), in which he derived Planck's quantum radiation law without any reference to classical physics. Einstein was impressed, translated the paper himself from English to German and submitted it for Bose to the Zeitschrift für Physik, which published it in 1924. (The Einstein manuscript, once believed to be lost, was found in a library at Leiden University in 2005.) Einstein then extended Bose's ideas to matter in two other papers. The result of their efforts is the concept of a Bose gas, governed by Bose–Einstein statistics, which describes the statistical distribution of identical particles with integer spin, now called bosons. Bosons are allowed to share a quantum state. Einstein proposed that cooling bosonic atoms to a very low temperature would cause them to fall (or "condense") into the lowest accessible quantum state, resulting in a new form of matter. Bosons include the photon, polaritons, magnons, some atoms and molecules (depending on the number of nucleons, see #Isotopes) such as atomic hydrogen, helium-4, lithium-7, rubidium-87 or strontium-84.
In 1938, Fritz London proposed the BEC as a mechanism for superfluidity in and superconductivity.
The quest to produce a Bose–Einstein condensate in the laboratory was stimulated by a paper published in 1976 by two program directors at the National Science Foundation (William Stwalley and Lewis Nosanow), proposing to use spin-polarized atomic hydrogen to produce a gaseous BEC. This led to the immediate pursuit of the idea by four independent research groups; these were led by Isaac Silvera (University of Amsterdam), Walter Hardy (University of British Columbia), Thomas Greytak (Massachusetts Institute of Technology) and David Lee (Cornell University). However, cooling atomic hydrogen turned out to be technically difficult, and Bose-Einstein condensation of atomic hydrogen was only realized in 1998. | Bose–Einstein condensate | Wikipedia | 421 | 4474 | https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein%20condensate | Physical sciences | States of matter | null |
On 5 June 1995, the first gaseous condensate was produced by Eric Cornell and Carl Wieman at the University of Colorado at Boulder NIST–JILA lab, in a gas of rubidium atoms cooled to 170 nanokelvins (nK). Shortly thereafter, Wolfgang Ketterle at MIT produced a Bose–Einstein Condensate in a gas of sodium atoms. For their achievements Cornell, Wieman, and Ketterle received the 2001 Nobel Prize in Physics. Bose-Einstein condensation of alkali gases is easier because they can be pre-cooled with laser cooling techniques, unlike atomic hydrogen at the time, which give a significant head start when performing the final forced evaporative cooling to cross the condensation threshold. These early studies founded the field of ultracold atoms, and hundreds of research groups around the world now routinely produce BECs of dilute atomic vapors in their labs.
Since 1995, many other atomic species have been condensed (see #Isotopes), and BECs have also been realized using molecules, polaritons, other quasi-particles. BECs of photons can also be made, for example, in dye microcavites with wavelength-scale mirror separation, making a two-dimensional harmonically confined photon gas with tunable chemical potential.
Critical temperature
This transition to BEC occurs below a critical temperature, which for a uniform three-dimensional gas consisting of non-interacting particles with no apparent internal degrees of freedom is given by
where:
is the critical temperature,
is the particle density,
is the mass per boson,
is the reduced Planck constant,
is the Boltzmann constant,
is the Riemann zeta function ().
Interactions shift the value, and the corrections can be calculated by mean-field theory.
This formula is derived from finding the gas degeneracy in the Bose gas using Bose–Einstein statistics.
The critical temperature depends on the density. A more concise and experimentally relevant condition involves the phase-space density , where
is the thermal de Broglie wavelength. It is a dimensionless quantity. The transition to BEC occurs when the phase-space density is greater than critical value:
in 3D uniform space. This is equivalent to the above condition on the temperature. In a 3D harmonic potential, the critical value is instead
where has to be understood as the peak density.
Derivation
Ideal Bose gas
For an ideal Bose gas we have the equation of state
where is the per-particle volume, is the thermal wavelength, is the fugacity, and | Bose–Einstein condensate | Wikipedia | 512 | 4474 | https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein%20condensate | Physical sciences | States of matter | null |
It is noticeable that is a monotonically growing function of in , which are the only values for which the series converge.
Recognizing that the second term on the right-hand side contains the expression for the average occupation number of the fundamental state , the equation of state can be rewritten as
Because the left term on the second equation must always be positive, , and because , a stronger condition is
which defines a transition between a gas phase and a condensed phase. On the critical region it is possible to define a critical temperature and thermal wavelength:
recovering the value indicated on the previous section. The critical values are such that if or , we are in the presence of a Bose–Einstein condensate.
Understanding what happens with the fraction of particles on the fundamental level is crucial. As so, write the equation of state for , obtaining
and equivalently
So, if , the fraction , and if , the fraction . At temperatures near to absolute 0, particles tend to condense in the fundamental state, which is the state with momentum .
Experimental observation
Superfluid helium-4
In 1938, Pyotr Kapitsa, John Allen and Don Misener discovered that helium-4 became a new kind of fluid, now known as a superfluid, at temperatures less than 2.17 K (the lambda point). Superfluid helium has many unusual properties, including zero viscosity (the ability to flow without dissipating energy) and the existence of quantized vortices. It was quickly believed that the superfluidity was due to partial Bose–Einstein condensation of the liquid. In fact, many properties of superfluid helium also appear in gaseous condensates created by Cornell, Wieman and Ketterle (see below). Superfluid helium-4 is a liquid rather than a gas, which means that the interactions between the atoms are relatively strong; the original theory of Bose–Einstein condensation must be heavily modified in order to describe it. Bose–Einstein condensation remains, however, fundamental to the superfluid properties of helium-4. Note that helium-3, a fermion, also enters a superfluid phase (at a much lower temperature) which can be explained by the formation of bosonic Cooper pairs of two atoms (see also fermionic condensate). | Bose–Einstein condensate | Wikipedia | 476 | 4474 | https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein%20condensate | Physical sciences | States of matter | null |
Dilute atomic gases
The first "pure" Bose–Einstein condensate was created by Eric Cornell, Carl Wieman, and co-workers at JILA on 5 June 1995. They cooled a dilute vapor of approximately two thousand rubidium-87 atoms to below 170 nK using a combination of laser cooling (a technique that won its inventors Steven Chu, Claude Cohen-Tannoudji, and William D. Phillips the 1997 Nobel Prize in Physics) and magnetic evaporative cooling. About four months later, an independent effort led by Wolfgang Ketterle at MIT condensed sodium-23. Ketterle's condensate had a hundred times more atoms, allowing important results such as the observation of quantum mechanical interference between two different condensates. Cornell, Wieman and Ketterle won the 2001 Nobel Prize in Physics for their achievements.
A group led by Randall Hulet at Rice University announced a condensate of lithium atoms only one month following the JILA work. Lithium has attractive interactions, causing the condensate to be unstable and collapse for all but a few atoms. Hulet's team subsequently showed the condensate could be stabilized by confinement quantum pressure for up to about 1000 atoms. Various isotopes have since been condensed.
Velocity-distribution data graph
In the image accompanying this article, the velocity-distribution data indicates the formation of a Bose–Einstein condensate out of a gas of rubidium atoms. The false colors indicate the number of atoms at each velocity, with red being the fewest and white being the most. The areas appearing white and light blue are at the lowest velocities. The peak is not infinitely narrow because of the Heisenberg uncertainty principle: spatially confined atoms have a minimum width velocity distribution. This width is given by the curvature of the magnetic potential in the given direction. More tightly confined directions have bigger widths in the ballistic velocity distribution. This anisotropy of the peak on the right is a purely quantum-mechanical effect and does not exist in the thermal distribution on the left. This graph served as the cover design for the 1999 textbook Thermal Physics by Ralph Baierlein.
Quasiparticles
Bose–Einstein condensation also applies to quasiparticles in solids. Magnons, excitons, and polaritons have integer spin which means they are bosons that can form condensates. | Bose–Einstein condensate | Wikipedia | 485 | 4474 | https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein%20condensate | Physical sciences | States of matter | null |
Magnons, electron spin waves, can be controlled by a magnetic field. Densities from the limit of a dilute gas to a strongly interacting Bose liquid are possible. Magnetic ordering is the analog of superfluidity. In 1999 condensation was demonstrated in antiferromagnetic , at temperatures as great as 14 K. The high transition temperature (relative to atomic gases) is due to the magnons' small mass (near that of an electron) and greater achievable density. In 2006, condensation in a ferromagnetic yttrium-iron-garnet thin film was seen even at room temperature, with optical pumping.
Excitons, electron-hole pairs, were predicted to condense at low temperature and high density by Boer et al., in 1961. Bilayer system experiments first demonstrated condensation in 2003, by Hall voltage disappearance. Fast optical exciton creation was used to form condensates in sub-kelvin in 2005 on.
Polariton condensation was first detected for exciton-polaritons in a quantum well microcavity kept at 5 K.
In zero gravity
In June 2020, the Cold Atom Laboratory experiment on board the International Space Station successfully created a BEC of rubidium atoms and observed them for over a second in free-fall. Although initially just a proof of function, early results showed that, in the microgravity environment of the ISS, about half of the atoms formed into a magnetically insensitive halo-like cloud around the main body of the BEC.
Models
Bose Einstein's non-interacting gas
Consider a collection of N non-interacting particles, which can each be in one of two quantum states, and . If the two states are equal in energy, each different configuration is equally likely.
If we can tell which particle is which, there are different configurations, since each particle can be in or independently. In almost all of the configurations, about half the particles are in and the other half in . The balance is a statistical effect: the number of configurations is largest when the particles are divided equally.
If the particles are indistinguishable, however, there are only different configurations. If there are particles in state , there are particles in state . Whether any particular particle is in state or in state cannot be determined, so each value of determines a unique quantum state for the whole system. | Bose–Einstein condensate | Wikipedia | 491 | 4474 | https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein%20condensate | Physical sciences | States of matter | null |
Suppose now that the energy of state is slightly greater than the energy of state by an amount . At temperature , a particle will have a lesser probability to be in state by . In the distinguishable case, the particle distribution will be biased slightly towards state . But in the indistinguishable case, since there is no statistical pressure toward equal numbers, the most-likely outcome is that most of the particles will collapse into state .
In the distinguishable case, for large N, the fraction in state can be computed. It is the same as flipping a coin with probability proportional to to land tails.
In the indistinguishable case, each value of is a single state, which has its own separate Boltzmann probability. So the probability distribution is exponential:
For large , the normalization constant is . The expected total number of particles not in the lowest energy state, in the limit that , is equal to
It does not grow when N is large; it just approaches a constant. This will be a negligible fraction of the total number of particles. So a collection of enough Bose particles in thermal equilibrium will mostly be in the ground state, with only a few in any excited state, no matter how small the energy difference.
Consider now a gas of particles, which can be in different momentum states labeled . If the number of particles is less than the number of thermally accessible states, for high temperatures and low densities, the particles will all be in different states. In this limit, the gas is classical. As the density increases or the temperature decreases, the number of accessible states per particle becomes smaller, and at some point, more particles will be forced into a single state than the maximum allowed for that state by statistical weighting. From this point on, any extra particle added will go into the ground state.
To calculate the transition temperature at any density, integrate, over all momentum states, the expression for maximum number of excited particles, :
When the integral (also known as Bose–Einstein integral) is evaluated with factors of and restored by dimensional analysis, it gives the critical temperature formula of the preceding section. Therefore, this integral defines the critical temperature and particle number corresponding to the conditions of negligible chemical potential . In Bose–Einstein statistics distribution, is actually still nonzero for BECs; however, is less than the ground state energy. Except when specifically talking about the ground state, can be approximated for most energy or momentum states as . | Bose–Einstein condensate | Wikipedia | 501 | 4474 | https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein%20condensate | Physical sciences | States of matter | null |
Bogoliubov theory for weakly interacting gas
Nikolay Bogoliubov considered perturbations on the limit of dilute gas, finding a finite pressure at zero temperature and positive chemical potential. This leads to corrections for the ground state. The Bogoliubov state has pressure : .
The original interacting system can be converted to a system of non-interacting particles with a dispersion law.
Gross–Pitaevskii equation
In some simplest cases, the state of condensed particles can be described with a nonlinear Schrödinger equation, also known as Gross–Pitaevskii or Ginzburg–Landau equation. The validity of this approach is actually limited to the case of ultracold temperatures, which fits well for the most alkali atoms experiments.
This approach originates from the assumption that the state of the BEC can be described by the unique wavefunction of the condensate . For a system of this nature, is interpreted as the particle density, so the total number of atoms is
Provided essentially all atoms are in the condensate (that is, have condensed to the ground state), and treating the bosons using mean-field theory, the energy (E) associated with the state is:
Minimizing this energy with respect to infinitesimal variations in , and holding the number of atoms constant, yields the Gross–Pitaevski equation (GPE) (also a non-linear Schrödinger equation):
where:
{|cellspacing="0" cellpadding="0"
|-
|
| is the mass of the bosons,
|-
|
| is the external potential, and
|-
|
| represents the inter-particle interactions.
|}
In the case of zero external potential, the dispersion law of interacting Bose–Einstein-condensed particles is given by so-called Bogoliubov spectrum (for ):
The Gross-Pitaevskii equation (GPE) provides a relatively good description of the behavior of atomic BEC's. However, GPE does not take into account the temperature dependence of dynamical variables, and is therefore valid only for .
It is not applicable, for example, for the condensates of excitons, magnons and photons, where the critical temperature is comparable to room temperature. | Bose–Einstein condensate | Wikipedia | 473 | 4474 | https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein%20condensate | Physical sciences | States of matter | null |
Numerical solution
The Gross-Pitaevskii equation is a partial differential equation in space and time variables. Usually it does not have analytic solution and
different numerical methods, such as split-step
Crank–Nicolson
and Fourier spectral methods, are used for its solution. There are different Fortran and C programs for its solution for contact interaction
and long-range dipolar interaction which can be freely used.
Weaknesses of Gross–Pitaevskii model
The Gross–Pitaevskii model of BEC is a physical approximation valid for certain classes of BECs. By construction, the GPE uses the following simplifications: it assumes that interactions between condensate particles are of the contact two-body type and also neglects anomalous contributions to self-energy. These assumptions are suitable mostly for the dilute three-dimensional condensates. If one relaxes any of these assumptions, the equation for the condensate wavefunction acquires the terms containing higher-order powers of the wavefunction. Moreover, for some physical systems the amount of such terms turns out to be infinite, therefore, the equation becomes essentially non-polynomial. The examples where this could happen are the Bose–Fermi composite condensates, effectively lower-dimensional condensates, and dense condensates and superfluid clusters and droplets. It is found that one has to go beyond the Gross-Pitaevskii equation. For example, the logarithmic term found in the Logarithmic Schrödinger equation must be added to the Gross-Pitaevskii equation along with a Ginzburg–Sobyanin contribution to correctly determine that the speed of sound scales as the cubic root of pressure for Helium-4 at very low temperatures in close agreement with experiment.
Other
However, it is clear that in a general case the behaviour of Bose–Einstein condensate can be described by coupled evolution equations for condensate density, superfluid velocity and distribution function of elementary excitations. This problem was solved in 1977 by Peletminskii et al. in microscopical approach. The Peletminskii equations are valid for any finite temperatures below the critical point. Years after, in 1985, Kirkpatrick and Dorfman obtained similar equations using another microscopical approach. The Peletminskii equations also reproduce Khalatnikov hydrodynamical equations for superfluid as a limiting case. | Bose–Einstein condensate | Wikipedia | 500 | 4474 | https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein%20condensate | Physical sciences | States of matter | null |
Superfluidity of BEC and Landau criterion
The phenomena of superfluidity of a Bose gas and superconductivity of a strongly-correlated Fermi gas (a gas of Cooper pairs) are tightly connected to Bose–Einstein condensation. Under corresponding conditions, below the temperature of phase transition, these phenomena were observed in helium-4 and different classes of superconductors. In this sense, the superconductivity is often called the superfluidity of Fermi gas. In the simplest form, the origin of superfluidity can be seen from the weakly interacting bosons model.
Peculiar properties
Quantized vortices
As in many other systems, vortices can exist in BECs.
Vortices can be created, for example, by "stirring" the condensate with lasers,
rotating the confining trap,
or by rapid cooling across the phase transition.
The vortex created will be a quantum vortex with core shape determined by the interactions. Fluid circulation around any point is quantized due to the single-valued nature of the order BEC order parameter or wavefunction, that can be written in the form where and are as in the cylindrical coordinate system, and is the angular quantum number (a.k.a. the "charge" of the vortex). Since the energy of a vortex is proportional to the square of its angular momentum, in trivial topology only vortices can exist in the steady state; Higher-charge vortices will have a tendency to split into vortices, if allowed by the topology of the geometry.
An axially symmetric (for instance, harmonic) confining potential is commonly used for the study of vortices in BEC. To determine , the energy of must be minimized, according to the constraint . This is usually done computationally, however, in a uniform medium, the following analytic form demonstrates the correct behavior, and is a good approximation:
Here, is the density far from the vortex and , where is the healing length of the condensate.
A singly charged vortex () is in the ground state, with its energy given by
where is the farthest distance from the vortices considered.(To obtain an energy which is well defined it is necessary to include this boundary .)
For multiply charged vortices () the energy is approximated by | Bose–Einstein condensate | Wikipedia | 483 | 4474 | https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein%20condensate | Physical sciences | States of matter | null |
which is greater than that of singly charged vortices, indicating that these multiply charged vortices are unstable to decay. Research has, however, indicated they are metastable states, so may have relatively long lifetimes.
Closely related to the creation of vortices in BECs is the generation of so-called dark solitons in one-dimensional BECs. These topological objects feature a phase gradient across their nodal plane, which stabilizes their shape even in propagation and interaction. Although solitons carry no charge and are thus prone to decay, relatively long-lived dark solitons have been produced and studied extensively.
Attractive interactions
Experiments led by Randall Hulet at Rice University from 1995 through 2000 showed that lithium condensates with attractive interactions could stably exist up to a critical atom number. Quench cooling the gas, they observed the condensate to grow, then subsequently collapse as the attraction overwhelmed the zero-point energy of the confining potential, in a burst reminiscent of a supernova, with an explosion preceded by an implosion.
Further work on attractive condensates was performed in 2000 by the JILA team, of Cornell, Wieman and coworkers. Their instrumentation now had better control so they used naturally attracting atoms of rubidium-85 (having negative atom–atom scattering length). Through Feshbach resonance involving a sweep of the magnetic field causing spin flip collisions, they lowered the characteristic, discrete energies at which rubidium bonds, making their Rb-85 atoms repulsive and creating a stable condensate. The reversible flip from attraction to repulsion stems from quantum interference among wave-like condensate atoms.
When the JILA team raised the magnetic field strength further, the condensate suddenly reverted to attraction, imploded and shrank beyond detection, then exploded, expelling about two-thirds of its 10,000 atoms. About half of the atoms in the condensate seemed to have disappeared from the experiment altogether, not seen in the cold remnant or expanding gas cloud. Carl Wieman explained that under current atomic theory this characteristic of Bose–Einstein condensate could not be explained because the energy state of an atom near absolute zero should not be enough to cause an implosion; however, subsequent mean-field theories have been proposed to explain it. Most likely they formed molecules of two rubidium atoms; energy gained by this bond imparts velocity sufficient to leave the trap without being detected. | Bose–Einstein condensate | Wikipedia | 504 | 4474 | https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein%20condensate | Physical sciences | States of matter | null |
The process of creation of molecular Bose condensate during the sweep of the magnetic field throughout the Feshbach resonance, as well as the reverse process, are described by the exactly solvable model that can explain many experimental observations.
Current research
Compared to more commonly encountered states of matter, Bose–Einstein condensates are extremely fragile. The slightest interaction with the external environment can be enough to warm them past the condensation threshold, eliminating their interesting properties and forming a normal gas.
Nevertheless, they have proven useful in exploring a wide range of questions in fundamental physics, and the years since the initial discoveries by the JILA and MIT groups have seen an increase in experimental and theoretical activity.
Bose–Einstein condensates composed of a wide range of isotopes have been produced; see below.
Fundamental research
Examples include experiments that have demonstrated interference between condensates due to wave–particle duality, the study of superfluidity and quantized vortices, the creation of bright matter wave solitons from Bose condensates confined to one dimension, and the slowing of light pulses to very low speeds using electromagnetically induced transparency. Vortices in Bose–Einstein condensates are also currently the subject of analogue gravity research, studying the possibility of modeling black holes and their related phenomena in such environments in the laboratory.
Experimenters have also realized "optical lattices", where the interference pattern from overlapping lasers provides a periodic potential. These are used to explore the transition between a superfluid and a Mott insulator.
They are also useful in studying Bose–Einstein condensation in fewer than three dimensions, for example the Lieb–Liniger model (an the limit of strong interactions, the Tonks–Girardeau gas) in 1D and the Berezinskii–Kosterlitz–Thouless transition in 2D. Indeed, a deep optical lattice allows the experimentalist to freeze the motion of the particles along one or two directions, effectively eliminating one or two dimension from the system.
Further, the sensitivity of the pinning transition of strongly interacting bosons confined in a shallow one-dimensional optical lattice originally observed by Haller has been explored via a tweaking of the primary optical lattice by a secondary weaker one. Thus for a resulting weak bichromatic optical lattice, it has been found that the pinning transition is robust against the
introduction of the weaker secondary optical lattice. | Bose–Einstein condensate | Wikipedia | 484 | 4474 | https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein%20condensate | Physical sciences | States of matter | null |
Studies of vortices in nonuniform Bose–Einstein condensates as well as excitations of these systems by the application of moving repulsive or attractive obstacles, have also been undertaken. Within this context, the conditions for order and chaos in the dynamics of a trapped Bose–Einstein condensate have been explored by the application of moving blue and red-detuned laser beams (hitting frequencies slightly above and below the resonance frequency, respectively) via the time-dependent Gross-Pitaevskii equation.
Applications
In 1999, Danish physicist Lene Hau led a team from Harvard University which slowed a beam of light to about 17 meters per second using a superfluid. Hau and her associates have since made a group of condensate atoms recoil from a light pulse such that they recorded the light's phase and amplitude, recovered by a second nearby condensate, in what they term "slow-light-mediated atomic matter-wave amplification" using Bose–Einstein condensates.
Another current research interest is the creation of Bose–Einstein condensates in microgravity in order to use its properties for high precision atom interferometry. The first demonstration of a BEC in weightlessness was achieved in 2008 at a drop tower in Bremen, Germany by a consortium of researchers led by Ernst M. Rasel from Leibniz University Hannover. The same team demonstrated in 2017 the first creation of a Bose–Einstein condensate in space and it is also the subject of two upcoming experiments on the International Space Station.
Researchers in the new field of atomtronics use the properties of Bose–Einstein condensates in the emerging quantum technology of matter-wave circuits.
In 1970, BECs were proposed by Emmanuel David Tannenbaum for anti-stealth technology.
Isotopes | Bose–Einstein condensate | Wikipedia | 367 | 4474 | https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein%20condensate | Physical sciences | States of matter | null |
Bose-Einstein condensation has mainly been observed on alkaline atoms, some of which have collisional properties particularly suitable for evaporative cooling in traps, and which where the first to laser-cooled. As of 2021, using ultra-low temperatures of or below, Bose–Einstein condensates had been obtained for a multitude of isotopes with more or less ease, mainly of alkali metal, alkaline earth metal, and lanthanide atoms (, , , , , , , , , , , , , , , , , , and metastable (orthohelium)). Research was finally successful in atomic hydrogen with the aid of the newly developed method of 'evaporative cooling'.
In contrast, the superfluid state of below is differs significantly from dilute degenerate atomic gases because the interaction between the atoms is strong. Only 8% of atoms are in the condensed fraction near absolute zero, rather than near 100% of a weakly interacting BEC.
The bosonic behavior of some of these alkaline gases appears odd at first sight, because their nuclei have half-integer total spin. It arises from the interplay of electronic and nuclear spins: at ultra-low temperatures and corresponding excitation energies, the half-integer total spin of the electronic shell (one outer electron) and half-integer total spin of the nucleus are coupled by a very weak hyperfine interaction. The total spin of the atom, arising from this coupling, is an integer value. Conversely, alkali isotopes which have an integer nuclear spin (such as and ) are fermions and can form degenerate Fermi gases, also called "Fermi condensates".
Cooling fermions to extremely low temperatures has created degenerate gases, subject to the Pauli exclusion principle. To exhibit Bose–Einstein condensation, the fermions must "pair up" to form bosonic compound particles (e.g. molecules or Cooper pairs). The first molecular condensates were created in November 2003 by the groups of Rudolf Grimm at the University of Innsbruck, Deborah S. Jin at the University of Colorado at Boulder and Wolfgang Ketterle at MIT. Jin quickly went on to create the first fermionic condensate, working with the same system but outside the molecular regime. | Bose–Einstein condensate | Wikipedia | 475 | 4474 | https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein%20condensate | Physical sciences | States of matter | null |
Continuous Bose–Einstein condensation
Limitations of evaporative cooling have restricted atomic BECs to "pulsed" operation, involving a highly inefficient duty cycle that discards more than 99% of atoms to reach BEC. Achieving continuous BEC has been a major open problem of experimental BEC research, driven by the same motivations as continuous optical laser development: high flux, high coherence matter waves produced continuously would enable new sensing applications.
Continuous BEC was achieved for the first time in 2022 with .
In solid state physics
In 2020, researchers reported the development of superconducting BEC and that there appears to be a "smooth transition between" BEC and Bardeen–Cooper–Shrieffer regimes.
Dark matter
P. Sikivie and Q. Yang showed that cold dark matter axions would form a Bose–Einstein condensate by thermalisation because of gravitational self-interactions. Axions have not yet been confirmed to exist. However the important search for them has been greatly enhanced with the completion of upgrades to the Axion Dark Matter Experiment (ADMX) at the University of Washington in early 2018.
In 2014, a potential dibaryon was detected at the Jülich Research Center at about 2380 MeV. The center claimed that the measurements confirm results from 2011, via a more replicable method. The particle existed for 10−23 seconds and was named d*(2380). This particle is hypothesized to consist of three up and three down quarks. It is theorized that groups of d* (d-stars) could form Bose–Einstein condensates due to prevailing low temperatures in the early universe, and that BECs made of such hexaquarks with trapped electrons could behave like dark matter.
In fiction
In the 2016 film Spectral, the US military battles mysterious enemy creatures fashioned out of Bose–Einstein condensates.
In the 2003 novel Blind Lake, scientists observe sentient life on a planet 51 light-years away using telescopes powered by Bose–Einstein condensate-based quantum computers.
The video game franchise Mass Effect has cryonic ammunition whose flavour text describes it as being filled with Bose–Einstein condensates. Upon impact, the bullets rupture and spray supercooled liquid on the enemy. | Bose–Einstein condensate | Wikipedia | 468 | 4474 | https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein%20condensate | Physical sciences | States of matter | null |
The Beer–Bouguer–Lambert (BBL) extinction law is an empirical relationship describing the attenuation in intensity of a radiation beam passing through a macroscopically homogenous medium with which it interacts. Formally, it states that the intensity of radiation decays exponentially in the absorbance of the medium, and that said absorbance is proportional to the length of beam passing through the medium, the concentration of interacting matter along that path, and a constant representing said matter's propensity to interact.
The extinction law's primary application is in chemical analysis, where it underlies the Beer–Lambert law, commonly called Beer's law. Beer's law states that a beam of visible light passing through a chemical solution of fixed geometry experiences absorption proportional to the solute concentration. Other applications appear in physical optics, where it quantifies astronomical extinction and the absorption of photons, neutrons, or rarefied gases.
Forms of the BBL law date back to the mid-eighteenth century, but it only took its modern form during the early twentieth.
History
The first work towards the BBL law began with astronomical observations Pierre Bouguer performed in the early eighteenth century and published in 1729. Bouguer needed to compensate for the refraction of light by the earth's atmosphere, and found it necessary to measure the local height of the atmosphere. The latter, he sought to obtain through variations in the observed intensity of known stars. When calibrating this effect, Bouguer discovered that light intensity had an exponential dependence on length traveled through the atmosphere (in Bouguer's terms, a geometric progression).
Bouguer's work was then popularized in Johann Heinrich Lambert's Photometria in 1760. Lambert expressed the law, which states that the loss of light intensity when it propagates in a medium is directly proportional to intensity and path length, in a mathematical form quite similar to that used in modern physics. Lambert began by assuming that the intensity of light traveling into an absorbing body would be given by the differential equation which is compatible with Bouguer's observations. The constant of proportionality was often termed the "optical density" of the body. As long as is constant along a distance , the exponential attenuation law, follows from integration. | Beer–Lambert law | Wikipedia | 467 | 4476 | https://en.wikipedia.org/wiki/Beer%E2%80%93Lambert%20law | Physical sciences | Optics | Physics |
In 1852, August Beer noticed that colored solutions also appeared to exhibit a similar attenuation relation. In his analysis, Beer does not discuss Bouguer and Lambert's prior work, writing in his introduction that "Concerning the absolute magnitude of the absorption that a particular ray of light suffers during its propagation through an absorbing medium, there is no information available." Beer may have omitted reference to Bouguer's work because there is a subtle physical difference between color absorption in solutions and astronomical contexts. Solutions are homogeneous and do not scatter light at common analytical wavelengths (ultraviolet, visible, or infrared), except at entry and exit. Thus light within a solution is reasonably approximated as due to absorption alone. In Bouguer's context, atmospheric dust or other inhomogeneities could also scatter light away from the detector. Modern texts combine the two laws because scattering and absorption have the same effect. Thus a scattering coefficient and an absorption coefficient can be combined into a total extinction coefficient .
Importantly, Beer also seems to have conceptualized his result in terms of a given thickness' opacity, writing "If is the coefficient (fraction) of diminution, then this coefficient (fraction) will have the value for double this thickness." Although this geometric progression is mathematically equivalent to the modern law, modern treatments instead emphasize the logarithm of , which clarifies that concentration and path length have equivalent effects on the absorption. An early, possibly the first, modern formulation was given by Robert Luther and Andreas Nikolopulos in 1913.
Mathematical formulations
There are several equivalent formulations of the BBL law, depending on the precise choice of measured quantities. All of them state that, provided that the physical state is held constant, the extinction process is linear in the intensity of radiation and amount of radiatively-active matter, a fact sometimes called the fundamental law of extinction. Many of them then connect the quantity of radiatively-active matter to a length traveled and a concentration or number density . The latter two are related by Avogadro's number: . | Beer–Lambert law | Wikipedia | 426 | 4476 | https://en.wikipedia.org/wiki/Beer%E2%80%93Lambert%20law | Physical sciences | Optics | Physics |
A collimated beam (directed radiation) with cross-sectional area will encounter particles (on average) during its travel. However, not all of these particles interact with the beam. Propensity to interact is a material-dependent property, typically summarized in absorptivity or scattering cross-section . These almost exhibit another Avogadro-type relationship: . The factor of appears because physicists tend to use natural logarithms and chemists decadal logarithms.
Beam intensity can also be described in terms of multiple variables: the intensity or radiant flux . In the case of a collimated beam, these are related by , but is often used in non-collimated contexts. The ratio of intensity (or flux) in to out is sometimes summarized as a transmittance coefficient .
When considering an extinction law, dimensional analysis can verify the consistency of the variables, as logarithms (being nonlinear) must always be dimensionless.
Formulation
The simplest formulation of Beer's relates the optical attenuation of a physical material containing a single attenuating species of uniform concentration to the optical path length through the sample and absorptivity of the species. This expression is:The quantities so equated are defined to be the absorbance , which depends on the logarithm base. The Naperian absorbance is then given by and satisfies
If multiple species in the material interact with the radiation, then their absorbances add. Thus a slightly more general formulation is that where the sum is over all possible radiation-interacting ("translucent") species, and indexes those species.
In situations where length may vary significantly, absorbance is sometimes summarized in terms of an attenuation coefficient
In atmospheric science and radiation shielding applications, the attenuation coefficient may vary significantly through an inhomogenous material. In those situations, the most general form of the Beer–Lambert law states that the total attenuation can be obtained by integrating the attenuation coefficient over small slices of the beamline: These formulations then reduce to the simpler versions when there is only one active species and the attenuation coefficients are constant.
Derivation
There are two factors that determine the degree to which a medium containing particles will attenuate a light beam: the number of particles encountered by the light beam, and the degree to which each particle extinguishes the light. | Beer–Lambert law | Wikipedia | 486 | 4476 | https://en.wikipedia.org/wiki/Beer%E2%80%93Lambert%20law | Physical sciences | Optics | Physics |
Assume that a beam of light enters a material sample. Define as an axis parallel to the direction of the beam. Divide the material sample into thin slices, perpendicular to the beam of light, with thickness sufficiently small that one particle in a slice cannot obscure another particle in the same slice when viewed along the direction. The radiant flux of the light that emerges from a slice is reduced, compared to that of the light that entered, by where is the (Napierian) attenuation coefficient, which yields the following first-order linear, ordinary differential equation:
The attenuation is caused by the photons that did not make it to the other side of the slice because of scattering or absorption. The solution to this differential equation is obtained by multiplying the integrating factorthroughout to obtainwhich simplifies due to the product rule (applied backwards) to
Integrating both sides and solving for for a material of real thickness , with the incident radiant flux upon the slice and the transmitted radiant flux givesand finally
Since the decadic attenuation coefficient is related to the (Napierian) attenuation coefficient by we also have
To describe the attenuation coefficient in a way independent of the number densities of the attenuating species of the material sample, one introduces the attenuation cross section has the dimension of an area; it expresses the likelihood of interaction between the particles of the beam and the particles of the species in the material sample:
One can also use the molar attenuation coefficients where is the Avogadro constant, to describe the attenuation coefficient in a way independent of the amount concentrations of the attenuating species of the material sample:
Validity
Under certain conditions the Beer–Lambert law fails to maintain a linear relationship between attenuation and concentration of analyte. These deviations are classified into three categories:
Real—fundamental deviations due to the limitations of the law itself.
Chemical—deviations observed due to specific chemical species of the sample which is being analyzed.
Instrument—deviations which occur due to how the attenuation measurements are made. | Beer–Lambert law | Wikipedia | 423 | 4476 | https://en.wikipedia.org/wiki/Beer%E2%80%93Lambert%20law | Physical sciences | Optics | Physics |
There are at least six conditions that need to be fulfilled in order for the Beer–Lambert law to be valid. These are:
The attenuators must act independently of each other.
The attenuating medium must be homogeneous in the interaction volume.
The attenuating medium must not scatter the radiation—no turbidity—unless this is accounted for as in DOAS.
The incident radiation must consist of parallel rays, each traversing the same length in the absorbing medium.
The incident radiation should preferably be monochromatic, or have at least a width that is narrower than that of the attenuating transition. Otherwise a spectrometer as detector for the power is needed instead of a photodiode which cannot discriminate between wavelengths.
The incident flux must not influence the atoms or molecules; it should only act as a non-invasive probe of the species under study. In particular, this implies that the light should not cause optical saturation or optical pumping, since such effects will deplete the lower level and possibly give rise to stimulated emission.
If any of these conditions are not fulfilled, there will be deviations from the Beer–Lambert law.
The law tends to break down at very high concentrations, especially if the material is highly scattering. Absorbance within range of 0.2 to 0.5 is ideal to maintain linearity in the Beer–Lambert law. If the radiation is especially intense, nonlinear optical processes can also cause variances. The main reason, however, is that the concentration dependence is in general non-linear and Beer's law is valid only under certain conditions as shown by derivation below. For strong oscillators and at high concentrations the deviations are stronger. If the molecules are closer to each other interactions can set in. These interactions can be roughly divided into physical and chemical interactions. Physical interaction do not alter the polarizability of the molecules as long as the interaction is not so strong that light and molecular quantum state intermix (strong coupling), but cause the attenuation cross sections to be non-additive via electromagnetic coupling. Chemical interactions in contrast change the polarizability and thus absorption.
In solids, attenuation is usually an addition of absorption coefficient (creation of electron-hole pairs) or scattering (for example Rayleigh scattering if the scattering centers are much smaller than the incident wavelength). Also note that for some systems we can put (1 over inelastic mean free path) in place of
Applications
In plasma physics | Beer–Lambert law | Wikipedia | 506 | 4476 | https://en.wikipedia.org/wiki/Beer%E2%80%93Lambert%20law | Physical sciences | Optics | Physics |
The BBL extinction law also arises as a solution to the BGK equation.
Chemical analysis by spectrophotometry
The Beer–Lambert law can be applied to the analysis of a mixture by spectrophotometry, without the need for extensive pre-processing of the sample. An example is the determination of bilirubin in blood plasma samples. The spectrum of pure bilirubin is known, so the molar attenuation coefficient is known. Measurements of decadic attenuation coefficient are made at one wavelength that is nearly unique for bilirubin and at a second wavelength in order to correct for possible interferences. The amount concentration is then given by
For a more complicated example, consider a mixture in solution containing two species at amount concentrations and . The decadic attenuation coefficient at any wavelength is, given by
Therefore, measurements at two wavelengths yields two equations in two unknowns and will suffice to determine the amount concentrations and as long as the molar attenuation coefficients of the two components, and are known at both wavelengths. This two system equation can be solved using Cramer's rule. In practice it is better to use linear least squares to determine the two amount concentrations from measurements made at more than two wavelengths. Mixtures containing more than two components can be analyzed in the same way, using a minimum of wavelengths for a mixture containing components.
The law is used widely in infra-red spectroscopy and near-infrared spectroscopy for analysis of polymer degradation and oxidation (also in biological tissue) as well as to measure the concentration of various compounds in different food samples. The carbonyl group attenuation at about 6 micrometres can be detected quite easily, and degree of oxidation of the polymer calculated.
In-atmosphere astronomy
The Bouguer–Lambert law may be applied to describe the attenuation of solar or stellar radiation as it travels through the atmosphere. In this case, there is scattering of radiation as well as absorption. The optical depth for a slant path is , where refers to a vertical path, is called the relative airmass, and for a plane-parallel atmosphere it is determined as where is the zenith angle corresponding to the given path. The Bouguer-Lambert law for the atmosphere is usually written | Beer–Lambert law | Wikipedia | 460 | 4476 | https://en.wikipedia.org/wiki/Beer%E2%80%93Lambert%20law | Physical sciences | Optics | Physics |
where each is the optical depth whose subscript identifies the source of the absorption or scattering it describes:
refers to aerosols (that absorb and scatter);
are uniformly mixed gases (mainly carbon dioxide (CO2) and molecular oxygen (O2) which only absorb);
is nitrogen dioxide, mainly due to urban pollution (absorption only);
are effects due to Raman scattering in the atmosphere;
is water vapour absorption;
is ozone (absorption only);
is Rayleigh scattering from molecular oxygen () and nitrogen () (responsible for the blue color of the sky);
the selection of the attenuators which have to be considered depends on the wavelength range and can include various other compounds. This can include tetraoxygen, HONO, formaldehyde, glyoxal, a series of halogen radicals and others.
is the optical mass or airmass factor, a term approximately equal (for small and moderate values of ) to where is the observed object's zenith angle (the angle measured from the direction perpendicular to the Earth's surface at the observation site). This equation can be used to retrieve , the aerosol optical thickness, which is necessary for the correction of satellite images and also important in accounting for the role of aerosols in climate. | Beer–Lambert law | Wikipedia | 264 | 4476 | https://en.wikipedia.org/wiki/Beer%E2%80%93Lambert%20law | Physical sciences | Optics | Physics |
Bakelite ( ), formally , is a thermosetting phenol formaldehyde resin, formed from a condensation reaction of phenol with formaldehyde. The first plastic made from synthetic components, it was developed by Leo Baekeland in Yonkers, New York, in 1907, and patented on December 7, 1909.
Bakelite was one of the first plastic-like materials to be introduced into the modern world and was popular because it could be moulded and then hardened into any shape.
Because of its electrical nonconductivity and heat-resistant properties, it became a great commercial success. It was used in electrical insulators, radio and telephone casings, and such diverse products as kitchenware, jewelry, pipe stems, children's toys, and firearms.
The retro appeal of old Bakelite products has made them collectible.
The creation of a synthetic plastic was revolutionary for the chemical industry, which at the time made most of its income from cloth dyes and explosives. Bakelite's commercial success inspired the industry to develop other synthetic plastics. As the world's first commercial synthetic plastic, Bakelite was named a National Historic Chemical Landmark by the American Chemical Society.
History
Bakelite was produced for the first time in 1872 by Adolf von Baeyer, though its use as a commercial product was not considered at the time.
Leo Baekeland was already wealthy due to his invention of Velox photographic paper when he began to investigate the reactions of phenol and formaldehyde in his home laboratory. Chemists had begun to recognize that many natural resins and fibers were polymers. Baekeland's initial intent was to find a replacement for shellac, a material in limited supply because it was made naturally from the secretion of lac insects (specifically Kerria lacca). He produced a soluble phenol-formaldehyde shellac called Novolak, but it was not a market success, even though it is still used to this day (e.g., as a photoresist). | Bakelite | Wikipedia | 426 | 4485 | https://en.wikipedia.org/wiki/Bakelite | Physical sciences | Polymers | Chemistry |
He then began experimenting on strengthening wood by impregnating it with a synthetic resin rather than coating it. By controlling the pressure and temperature applied to phenol and formaldehyde, he produced a hard moldable material that he named Bakelite, after himself. It was the first synthetic thermosetting plastic produced, and Baekeland speculated on "the thousand and one ... articles" it could be used to make. He considered the possibilities of using a wide variety of filling materials, including cotton, powdered bronze, and slate dust, but was most successful with wood and asbestos fibers, though asbestos was gradually abandoned by all manufacturers due to stricter environmental laws.
Baekeland filed a substantial number of related patents. Bakelite, his "method of making insoluble products of phenol and formaldehyde", was filed on July 13, 1907, and granted on December 7, 1909. He also filed for patent protection in other countries, including Belgium, Canada, Denmark, Hungary, Japan, Mexico, Russia, and Spain. He announced his invention at a meeting of the American Chemical Society on February 5, 1909.
Baekeland started semi-commercial production of his new material in his home laboratory, marketing it as a material for electrical insulators. In the summer of 1909, he licensed the continental European rights to Rütger AG. The subsidiary formed at that time, Bakelite AG, was the first to produce Bakelite on an industrial scale.
By 1910, Baekeland was producing enough material in the US to justify expansion. He formed the General Bakelite Company of Perth Amboy, New Jersey, as a U.S. company to manufacture and market his new industrial material, and made overseas connections to produce it in other countries.
The Bakelite Company produced "transparent" cast resin (which did not include filler) for a small market during the 1910s and 1920s. Blocks or rods of cast resin, also known as "artificial amber", were machined and carved to create items such as pipe stems, cigarette holders, and jewelry. However, the demand for molded plastics led the company to concentrate on molding rather than cast solid resins. | Bakelite | Wikipedia | 452 | 4485 | https://en.wikipedia.org/wiki/Bakelite | Physical sciences | Polymers | Chemistry |
The Bakelite Corporation was formed in 1922 after patent litigation favorable to Baekeland, from a merger of three companies: Baekeland's General Bakelite Company; the Condensite Company, founded by J. W. Aylesworth; and the Redmanol Chemical Products Company, founded by Lawrence V. Redman. Under director of advertising and public relations Allan Brown, who came to Bakelite from Condensite, Bakelite was aggressively marketed as "the material of a thousand uses". A filing for a trademark featuring the letter B above the mathematical symbol for infinity was made August 25, 1925, and claimed the mark was in use as of December 1, 1924. A wide variety of uses were listed in their trademark applications.
The first issue of Plastics magazine, October 1925, featured Bakelite on its cover and included the article "Bakelite – What It Is" by Allan Brown. The range of colors that were available included "black, brown, red, yellow, green, gray, blue, and blends of two or more of these". The article emphasized that Bakelite came in various forms.
In a 1925 report, the United States Tariff Commission hailed the commercial manufacture of synthetic phenolic resin as "distinctly an American achievement", and noted that "the publication of figures, however, would be a virtual disclosure of the production of an individual company".
In England, Bakelite Limited, a merger of three British phenol formaldehyde resin suppliers (Damard Lacquer Company Limited of Birmingham, Mouldensite Limited of Darley Dale and Redmanol Chemical Products Company of London), was formed in 1926. A new Bakelite factory opened in Tyseley, Birmingham, around 1928. It was the "heart of Bakelite production in the UK" until it closed in 1987.
A factory to produce phenolic resins and precursors opened in Bound Brook, New Jersey, in 1931.
In 1939, the companies were acquired by Union Carbide and Carbon Corporation.
In 2005, German Bakelite manufacturer Bakelite AG was acquired by Borden Chemical of Columbus, Ohio, now Hexion Inc. | Bakelite | Wikipedia | 449 | 4485 | https://en.wikipedia.org/wiki/Bakelite | Physical sciences | Polymers | Chemistry |
In addition to the original Bakelite material, these companies eventually made a wide range of other products, many of which were marketed under the brand name "Bakelite plastics". These included other types of cast phenolic resins similar to Catalin, and urea-formaldehyde resins, which could be made in brighter colors than .
Once Baekeland's heat and pressure patents expired in 1927, Bakelite Corporation faced serious competition from other companies. Because molded Bakelite incorporated fillers to give it strength, it tended to be made in concealing dark colors. In 1927, beads, bangles, and earrings were produced by the Catalin company, through a different process which enabled them to introduce 15 new colors. Translucent jewelry, poker chips and other items made of phenolic resins were introduced in the 1930s or 1940s by the Catalin company under the Prystal name. The creation of marbled phenolic resins may also be attributable to the Catalin company.
Synthesis
Making Bakelite is a multi-stage process. It begins with the heating of phenol and formaldehyde in the presence of a catalyst such as hydrochloric acid, zinc chloride, or the base ammonia. This creates a liquid condensation product, referred to as Bakelite A, which is soluble in alcohol, acetone, or additional phenol. Heated further, the product becomes partially soluble and can still be softened by heat. Sustained heating results in an "insoluble hard gum". However, the high temperatures required to create this tend to cause violent foaming of the mixture when done at standard atmospheric pressure, which results in the cooled material being porous and breakable. Baekeland's innovative step was to put his "last condensation product" into an egg-shaped "Bakelizer". By heating it under pressure, at about , Baekeland was able to suppress the foaming that would otherwise occur. The resulting substance is extremely hard and both infusible and insoluble.
Compression molding
Molded Bakelite forms in a condensation reaction of phenol and formaldehyde, with wood flour or asbestos fiber as a filler, under high pressure and heat in a time frame of a few minutes of curing. The result is a hard plastic material. Asbestos was gradually abandoned as filler because many countries banned the production of asbestos. | Bakelite | Wikipedia | 505 | 4485 | https://en.wikipedia.org/wiki/Bakelite | Physical sciences | Polymers | Chemistry |
Bakelite's molding process had a number of advantages. Bakelite resin could be provided either as powder or as preformed partially cured slugs, increasing the speed of the casting. Thermosetting resins such as Bakelite required heat and pressure during the molding cycle but could be removed from the molding process without being cooled, again making the molding process faster. Also, because of the smooth polished surface that resulted, Bakelite objects required less finishing. Millions of parts could be duplicated quickly and relatively cheaply.
Phenolic sheet
Another market for Bakelite resin was the creation of phenolic sheet materials. A phenolic sheet is a hard, dense material made by applying heat and pressure to layers of paper or glass cloth impregnated with synthetic resin. Paper, cotton fabrics, synthetic fabrics, glass fabrics, and unwoven fabrics are all possible materials used in lamination. When heat and pressure are applied, polymerization transforms the layers into thermosetting industrial laminated plastic.
Bakelite phenolic sheet is produced in many commercial grades and with various additives to meet diverse mechanical, electrical, and thermal requirements. Some common types include:
Paper reinforced NEMA XX per MIL-I-24768 PBG. Normal electrical applications, moderate mechanical strength, continuous operating temperature of .
Canvas-reinforced NEMA C per MIL-I-24768 TYPE FBM NEMA CE per MIL-I-24768 TYPE FBG. Good mechanical and impact strength with a continuous operating temperature of 250 °F.
Linen-reinforced NEMA L per MIL-I-24768 TYPE FBI NEMA LE per MIL-I-24768 TYPE FEI. Good mechanical and electrical strength. Recommended for intricate high-strength parts. Continuous operating temperature convert 250 °F.
Nylon reinforced NEMA N-1 per MIL-I-24768 TYPE NPG. Superior electrical properties under humid conditions, fungus resistant, continuous operating temperature of .
Properties
Bakelite has a number of important properties. It can be molded very quickly, decreasing production time. Moldings are smooth, retain their shape, and are resistant to heat, scratches, and destructive solvents. It is also resistant to electricity, and prized for its low conductivity. It is not flexible. | Bakelite | Wikipedia | 473 | 4485 | https://en.wikipedia.org/wiki/Bakelite | Physical sciences | Polymers | Chemistry |
Phenolic resin products may swell slightly under conditions of extreme humidity or perpetual dampness. When rubbed or burnt, Bakelite has a distinctive, acrid, sickly-sweet or fishy odor.
Applications and uses
The characteristics of Bakelite made it particularly suitable as a molding compound, an adhesive or binding agent, a varnish, and a protective coating, as well as for the emerging electrical and automobile industries because of its extraordinarily high resistance to electricity, heat, and chemical action.
The earliest commercial use of Bakelite in the electrical industry was the molding of tiny insulating bushings, made in 1908 for the Weston Electrical Instrument Corporation by Richard W. Seabury of the Boonton Rubber Company. Bakelite was soon used for non-conducting parts of telephones, radios, and other electrical devices, including bases and sockets for light bulbs and electron tubes (vacuum tubes), supports for any type of electrical components, automobile distributor caps, and other insulators. By 1912, it was being used to make billiard balls, since its elasticity and the sound it made were similar to ivory.
During World War I, Bakelite was used widely, particularly in electrical systems. Important projects included the Liberty airplane engine, the wireless telephone and radio phone, and the use of micarta-bakelite propellers in the NBS-1 bomber and the DH-4B aeroplane.
Bakelite's availability and ease and speed of molding helped to lower the costs and increase product availability so that telephones and radios became common household consumer goods. It was also very important to the developing automobile industry. It was soon found in myriad other consumer products ranging from pipe stems and buttons to saxophone mouthpieces, cameras, early machine guns, and appliance casings. Bakelite was also very commonly used in making molded grip panels on handguns, as furniture for submachine guns and machineguns, the classic Bakelite magazines for Kalashnikov rifles, as well as numerous knife handles and "scales" through the first half of the 20th century. | Bakelite | Wikipedia | 431 | 4485 | https://en.wikipedia.org/wiki/Bakelite | Physical sciences | Polymers | Chemistry |
Beginning in the 1920s, it became a popular material for jewelry. Designer Coco Chanel included Bakelite bracelets in her costume jewelry collections. Designers such as Elsa Schiaparelli used it for jewelry and also for specially designed dress buttons. Later, Diana Vreeland, editor of Vogue, was enthusiastic about Bakelite. Bakelite was also used to make presentation boxes for Breitling watches.
By 1930, designer Paul T. Frankl considered Bakelite a "Materia Nova", "expressive of our own age". By the 1930s, Bakelite was used for game pieces like chess pieces, poker chips, dominoes, and mahjong sets. Kitchenware made with Bakelite, including canisters and tableware, was promoted for its resistance to heat and to chipping. In the mid-1930s, Northland marketed a line of skis with a black "Ebonite" base, a coating of Bakelite. By 1935, it was used in solid-body electric guitars. Performers such as Jerry Byrd loved the tone of Bakelite guitars but found them difficult to keep in tune.
Charles Plimpton patented BAYKO in 1933 and rushed out his first construction sets for Christmas 1934. He called the toy Bayko Light Constructional Sets, the words "Bayko Light" being a pun on the word "Bakelite".
During World War II, Bakelite was used in a variety of wartime equipment including pilots' goggles and field telephones. It was also used for patriotic wartime jewelry. In 1943, the thermosetting phenolic resin was even considered for the manufacture of coins, due to a shortage of traditional material. Bakelite and other non-metal materials were tested for usage for the one cent coin in the US before the Mint settled on zinc-coated steel.
During World War II, Bakelite buttons were part of British uniforms. These included brown buttons for the Army and black buttons for the RAF.
In 1947, Dutch art forger Han van Meegeren was convicted of forgery, after chemist and curator Paul B. Coremans proved that a purported Vermeer contained Bakelite, which van Meegeren had used as a paint hardener.
Bakelite was sometimes used in the pistol grip, hand guard, and buttstock of firearms. The AKM and some early AK-74 rifles are frequently mistakenly identified as using Bakelite, but most were made with AG-4S. | Bakelite | Wikipedia | 509 | 4485 | https://en.wikipedia.org/wiki/Bakelite | Physical sciences | Polymers | Chemistry |
By the late 1940s, newer materials were superseding Bakelite in many areas. Phenolics are less frequently used in general consumer products today due to their cost and complexity of production and their brittle nature. They still appear in some applications where their specific properties are required, such as small precision-shaped components, molded disc brake cylinders, saucepan handles, electrical plugs, switches and parts for electrical irons, printed circuit boards, as well as in the area of inexpensive board and tabletop games produced in China, Hong Kong, and India. Items such as billiard balls, dominoes and pieces for board games such as chess, checkers, and backgammon are constructed of Bakelite for its look, durability, fine polish, weight, and sound. Common dice are sometimes made of Bakelite for weight and sound, but the majority are made of a thermoplastic polymer such as acrylonitrile butadiene styrene (ABS).
Bakelite continues to be used for wire insulation, brake pads and related automotive components, and industrial electrical-related applications. Bakelite stock is still manufactured and produced in sheet, rod, and tube form for industrial applications in the electronics, power generation, and aerospace industries, and under a variety of commercial brand names.
Phenolic resins have been commonly used in ablative heat shields. Soviet heatshields for ICBM warheads and spacecraft reentry consisted of asbestos textolite, impregnated with Bakelite. Bakelite is also used in the mounting of metal samples in metallography.
Collectible status
Bakelite items, particularly jewelry and radios, have become popular collectibles.
The term Bakelite is sometimes used in the resale market as a catch-all for various types of early plastics, including Catalin and Faturan, which may be brightly colored, as well as items made of true Bakelite material.
Due to its aesthetics, a similar material fakelite (fake bakelite) exists made from modern safer materials which do not contain asbestos.
Patents
The United States Patent and Trademark Office granted Baekeland a patent for a "Method of making insoluble products of phenol and formaldehyde" on December 7, 1909. Producing hard, compact, insoluble, and infusible condensation products of phenols and formaldehyde marked the beginning of the modern plastics industry. | Bakelite | Wikipedia | 506 | 4485 | https://en.wikipedia.org/wiki/Bakelite | Physical sciences | Polymers | Chemistry |
Similar plastics
Catalin is also a phenolic resin, similar to Bakelite, but contains different mineral fillers that allow the production of light colors.
Condensites are similar thermoset materials having much the same properties, characteristics, and uses.
Crystalate is an early plastic.
Faturan is a phenolic resin, also similar to Bakelite, that turns red over time, regardless of its original color.
Galalith is an early plastic derived from milk products.
Micarta is an early composite insulating plate that used Bakelite as a binding agent. It was developed in 1910 by the Westinghouse Electric & Manufacturing Company, which put the new material to use for casting synthetic blades for Westinghouse electric fans.
Novotext is a brand name for cotton textile-phenolic resin.
G-10 or garolite is made with fiberglass and epoxy resin. | Bakelite | Wikipedia | 188 | 4485 | https://en.wikipedia.org/wiki/Bakelite | Physical sciences | Polymers | Chemistry |
A bean is the seed of any plant in the legume family (Fabaceae) used as a vegetable for human consumption or animal feed. The seeds are often preserved through drying, but fresh beans are also sold. Most beans are traditionally soaked and boiled, but they can be cooked in many different ways, including frying and baking, and are used in many traditional dishes throughout the world. The unripe seedpods of some varieties are also eaten whole as green beans or edamame (immature soybean), but fully ripened beans contain toxins like phytohemagglutinin and require cooking.
Terminology
The word 'bean', for the Old World vegetable, existed in Old English, long before the New World genus Phaseolus was known in Europe. With the Columbian exchange of domestic plants between Europe and the Americas, use of the word was extended to pod-borne seeds of Phaseolus, such as the common bean and the runner bean, and the related genus Vigna. The term has long been applied generally to seeds of similar form, such as Old World soybeans and lupins, and to the fruits or seeds of unrelated plants such as coffee beans, vanilla beans, castor beans, and cocoa beans.
History
Beans in an early cultivated form were grown in Thailand from the early seventh millennium BCE, predating ceramics. Beans were deposited with the dead in ancient Egypt. Not until the second millennium BCE did cultivated, large-seeded broad beans appear in the Aegean region, Iberia, and transalpine Europe. In the Iliad (8th century BCE), there is a passing mention of beans and chickpeas cast on the threshing floor.
The oldest-known domesticated beans in the Americas were found in Guitarrero Cave, Peru, dated to around the second millennium BCE. Genetic analyses of the common bean Phaseolus show that it originated in Mesoamerica, and subsequently spread southward, along with maize and squash, traditional companion crops. | Bean | Wikipedia | 406 | 4487 | https://en.wikipedia.org/wiki/Bean | Biology and health sciences | Fabales | null |
Most of the kinds of beans commonly eaten today are part of the genus Phaseolus, which originated in the Americas. The first European to encounter them was Christopher Columbus, while exploring what may have been the Bahamas, and saw them growing in fields. Five kinds of Phaseolus beans were domesticated by pre-Columbian peoples, selecting pods that did not open and scatter their seeds when ripe: common beans (P. vulgaris) grown from Chile to the northern part of the United States; lima and sieva beans (P. lunatus); and the less widely distributed teparies (P. acutifolius), scarlet runner beans (P. coccineus), and polyanthus beans.
Pre-Columbian peoples as far north as the Atlantic seaboard grew beans in the "Three Sisters" method of companion planting. The beans were interplanted with maize and squash. Beans were cultivated across Chile in Pre-Hispanic times, likely as far south as the Chiloé Archipelago.
Diversity
Taxonomic range
Most beans are legumes, but from many different genera, native to different regions.
Conservation of cultivars
The biodiversity of bean cultivars is threatened by modern plant breeding, which selects a small number of the most productive varieties. Efforts are being made to conserve the germplasm of older varieties in different countries. As of 2023, the Norwegian Svalbard Global Seed Vault holds more than 40,000 accessions of Phaseolus bean species.
Cultivation
Agronomy
Unlike the closely related pea, beans are a summer crop that needs warm temperatures to grow. Legumes are capable of nitrogen fixation and hence need less fertiliser than most plants. Maturity is typically 55–60 days from planting to harvest. As the pods mature, they turn yellow and dry up, and the beans inside change from green to their mature colour. Many beans are vines needing external support, such as "bean cages" or poles. Native Americans customarily grew them along with corn and squash, the tall stalks acting as support for the beans.
More recently, the commercial "bush bean" which does not require support and produces all its pods simultaneously has been developed.
Production
The production data for legumes are published by FAO in three categories:
Pulses dry: all mature and dry seeds of leguminous plants except soybeans and groundnuts.
Oil crops: soybeans and groundnuts.
Fresh vegetable: immature green fresh fruits of leguminous plants. | Bean | Wikipedia | 509 | 4487 | https://en.wikipedia.org/wiki/Bean | Biology and health sciences | Fabales | null |
The following is a summary of FAO data.
The world leader in production of dry beans (Phaseolus spp), is India, followed by Myanmar (Burma) and Brazil. In Africa, the most important producer is Tanzania.
Source: UN Food and Agriculture Organization (FAO)
Uses
Nutrition
Raw green beans are 90% water, 7% carbohydrates, 2% protein, and contain negligible fat. In a reference serving, raw green beans supply 31 calories of food energy, and are a moderate source (10-19% of the Daily Value, DV) of vitamin C (15% DV) and vitamin B6 (11% DV), with no other micronutrients in significant content (table).
Culinary
Beans can be cooked in a wide variety of casseroles, curries, salads, soups, and stews. They can be served whole or mashed alongside meat or toast, or included in an omelette or a flatbread wrap. Other options are to include them in a bake with a cheese sauce, a Mexican-style chili con carne, or to use them as a meat substitute in a burger or in falafels. The French cassoulet is a slow-cooked stew with haricot beans, sausage, pork, mutton, and preserved goose. Soybeans can be processed into bean curd (tofu) or fermented into a cake (tempeh); these can be eaten fried or roasted like meat, or included in stir-fries, curries, and soups.
Other
Guar beans are used for their gum, a galactomannan polysaccharide. It is used to thicken and stabilise foods and other products.
Health concerns
Toxins
Some kinds of raw beans contain a harmful, flavourless toxin: the lectin phytohaemagglutinin, which must be destroyed by cooking. Red kidney beans are particularly toxic, but other types also pose risks of food poisoning. Even small quantities (4 or 5 raw beans) may cause severe stomachache, vomiting, and diarrhea. This risk does not apply to canned beans because they have already been cooked. A recommended method is to boil the beans for at least ten minutes; under-cooked beans may be more toxic than raw beans. | Bean | Wikipedia | 483 | 4487 | https://en.wikipedia.org/wiki/Bean | Biology and health sciences | Fabales | null |
Cooking beans, without bringing them to a boil, in a slow cooker at a temperature well below boiling may not destroy toxins. A case of poisoning by butter beans used to make falafel was reported; the beans were used instead of traditional broad beans or chickpeas, soaked and ground without boiling, made into patties, and shallow fried.
Bean poisoning is not well known in the medical community, and many cases may be misdiagnosed or never reported; figures appear not to be available. In the case of the UK National Poisons Information Service, available only to health professionals, the dangers of beans other than red beans were not flagged .
Fermentation is used in some parts of Africa to improve the nutritional value of beans by removing toxins. Inexpensive fermentation improves the nutritional impact of flour from dry beans and improves digestibility, according to research co-authored by Emire Shimelis, from the Food Engineering Program at Addis Ababa University. Beans are a major source of dietary protein in Kenya, Malawi, Tanzania, Uganda and Zambia.
Other hazards
It is common to make beansprouts by letting some types of bean, often mung beans, germinate in moist and warm conditions; beansprouts may be used as ingredients in cooked dishes, or eaten raw or lightly cooked. There have been many outbreaks of disease from bacterial contamination, often by salmonella, listeria, and Escherichia coli, of beansprouts not thoroughly cooked, some causing significant mortality.
Many types of bean like kidney bean contain significant amounts of antinutrients that inhibit some enzyme processes in the body. Phytic acid, present in beans, interferes with bone growth and interrupts vitamin D metabolism.
Many beans, including broad beans, navy beans, kidney beans and soybeans, contain large sugar molecules, oligosaccharides (particularly raffinose and stachyose). A suitable oligosaccharide-cleaving enzyme is necessary to digest these. As the human digestive tract does not contain such enzymes, consumed oligosaccharides are digested by bacteria in the large intestine, producing gases such as methane, released as flatulence.
In human society | Bean | Wikipedia | 458 | 4487 | https://en.wikipedia.org/wiki/Bean | Biology and health sciences | Fabales | null |
Beans have often been thought of as a food of the poor, as small farmers ate grains, vegetables, and got their protein from beans, while the wealthier classes were able to afford meat. European society has what Ken Albala calls "a class-based antagonism" to beans.
Different cultures agree in disliking the flatulence that beans cause, and possess their own seasonings to attempt to remedy it: Mexico uses the herb epazote; India the aromatic resin asafoetida; Germany applies the herb savory; in the Middle East, cumin; and Japan the seaweed kombu. A substance for which there is evidence of effectiveness in reducing flatulence is the enzyme alpha-galactosidase; extracted from the mould fungus Aspergillus niger, it breaks down glycolipids and glycoproteins. The reputation of beans for flatulence is the theme of a children's song "Beans, Beans, the Musical Fruit".
The Mexican jumping bean is a segment of a seed pod occupied by the larva of the moth Cydia saltitans, and sold as a novelty. The pods start to jump when warmed in the palm of the hand. Scientists have suggested that the random walk that results may help the larva to find shade and so to survive on hot days. | Bean | Wikipedia | 279 | 4487 | https://en.wikipedia.org/wiki/Bean | Biology and health sciences | Fabales | null |
The breasts are two prominences located on the upper ventral region of the torso among humans and other primates. Both sexes develop breasts from the same embryological tissues. The relative size and development of the breasts is a major secondary sex distinction between females and males. There is also considerable variation in size between individuals. Female humans are the only mammals which permanently develop breasts at puberty; all other mammals develop their mammary tissue during the latter period of pregnancy; at puberty, estrogens, in conjunction with growth hormone, cause permanent breast growth.
In females, the breast serves as the mammary gland, which produces and secretes milk to feed infants. Subcutaneous fat covers and envelops a network of ducts that converge on the nipple, and these tissues give the breast its distinct size and globular shape. At the ends of the ducts are lobules, or clusters of alveoli, where milk is produced and stored in response to hormonal signals. During pregnancy, the breast responds to a complex interaction of hormones, including estrogens, progesterone, and prolactin, that mediate the completion of its development, namely lobuloalveolar maturation, in preparation of lactation and breastfeeding.
Along with their major function in providing nutrition for infants, several cultures ascribe social and sexual characteristics to female breasts, and may regard bare breasts in public as immodest or indecent. Breasts have been featured in ancient and modern sculpture, art, and photography. Breasts can represent fertility, femininity, or abundance. They can figure prominently in the perception of a woman's body and sexual attractiveness. Breasts, especially the nipples, can be an erogenous zone.
Etymology and terminology
The English word breast derives from the Old English word from Proto-Germanic , from the Proto-Indo-European base . The breast spelling conforms to the Scottish and North English dialectal pronunciations. The Merriam-Webster Dictionary states that "Middle English , [comes] from Old English ; akin to Old High German ..., Old Irish [belly], [and] Russian "; the first known usage of the term was before the 12th century. | Breast | Wikipedia | 456 | 4489 | https://en.wikipedia.org/wiki/Breast | Biology and health sciences | Integumentary system | null |
Breasts is often used to refer to female breasts in particular, though the stricter anatomical term refers to the same region on members of either sex. Male breasts are sometimes referred to in the singular to mean the collective upper chest area, whereas female breasts are referred to in the plural unless speaking of a specific left or right breast.
A large number of colloquial terms for female breasts are used in English, ranging from fairly polite terms to vulgar or slang. Some vulgar slang expressions may be considered to be derogatory or sexist to women.
Evolutionary development
Humans are the only mammals whose breasts become permanently enlarged after sexual maturity (known in humans as puberty). The reason for this evolutionary change is unknown. Several hypotheses have been put forward:
A link has been proposed to processes for synthesizing the endogenous steroid hormone precursor dehydroepiandrosterone which takes place in fat rich regions of the body like the buttocks and breasts. These contributed to human brain development and played a part in increasing brain size. Breast enlargement may for this purpose have occurred as early as Homo ergaster (1.7–1.4 MYA). Other breast formation hypotheses may have then taken over as principal drivers.
It has been suggested by zoologists Avishag and Amotz Zahavi that the size of the human breasts can be explained by the handicap theory of sexual dimorphism. This would see the explanation for larger breasts as them being an honest display of the women's health and ability to grow and carry them in her life. Prospective mates can then evaluate the genes of a potential mate for their ability to sustain her health even with the additional energy demanding burden she is carrying.
The zoologist Desmond Morris describes a sociobiological approach in his science book The Naked Ape. He suggests, by making comparisons with the other primates, that breasts evolved to replace swelling buttocks as a sex signal of ovulation. He notes how humans have, relatively speaking, large penises as well as large breasts. Furthermore, early humans adopted bipedalism and face-to-face coitus. He therefore suggested enlarged sexual signals helped maintain the bond between a mated male and female even though they performed different duties and therefore were separated for lengths of time. | Breast | Wikipedia | 471 | 4489 | https://en.wikipedia.org/wiki/Breast | Biology and health sciences | Integumentary system | null |
A 2001 study proposed that the rounded shape of a woman's breast evolved to prevent the sucking infant offspring from suffocating while feeding at the teat; that is, because of the human infant's small jaw, which did not project from the face to reach the nipple, they might block the nostrils against the mother's breast if it were of a flatter form (compare with the common chimpanzee). Theoretically, as the human jaw receded into the face, the woman's body compensated with round breasts.
Ashley Montague (1965) proposed that breasts came about as an adaptation for infant feeding for a different reason, as early human ancestors adopted bipedalism and the loss of body hair. Human upright stance meant infants must be carried at the hip or shoulder instead of on the back as in the apes. This gives the infant less opportunity to find the nipple or the purchase to cling on to the mother's body hair. The mobility of the nipple on a large breast in most human females gives the infant more ability to find it, grasp it and feed.
Other suggestions include simply that permanent breasts attracted mates, that "pendulous" breasts gave infants something to cling to, or that permanent breasts shared the function of a camel's hump, to store fat as an energy reserve.
Structure
In women, the breasts overlie the pectoralis major muscles and extend on average from the level of the second rib to the level of the sixth rib in the front of the rib cage; thus, the breasts cover much of the chest area and the chest walls. At the front of the chest, the breast tissue can extend from the clavicle (collarbone) to the middle of the sternum (breastbone). At the sides of the chest, the breast tissue can extend into the axilla (armpit), and can reach as far to the back as the latissimus dorsi muscle, extending from the lower back to the humerus bone (the bone of the upper arm). As a mammary gland, the breast is composed of differing layers of tissue, predominantly two types: adipose tissue; and glandular tissue, which affects the lactation functions of the breasts. The natural resonant frequency of the human breast is about 2 hertz. | Breast | Wikipedia | 472 | 4489 | https://en.wikipedia.org/wiki/Breast | Biology and health sciences | Integumentary system | null |
Morphologically, the breast is tear-shaped. The superficial tissue layer (superficial fascia) is separated from the skin by 0.5–2.5 cm of subcutaneous fat (adipose tissue). The suspensory Cooper's ligaments are fibrous-tissue prolongations that radiate from the superficial fascia to the skin envelope. The female adult breast contains 14–18 irregular lactiferous lobes that converge at the nipple. The 2.0–4.5 mm milk ducts are immediately surrounded with dense connective tissue that support the glands. Milk exits the breast through the nipple, which is surrounded by a pigmented area of skin called the areola. The size of the areola can vary widely among women. The areola contains modified sweat glands known as Montgomery's glands. These glands secrete oily fluid that lubricate and protect the nipple during breastfeeding. Volatile compounds in these secretions may also serve as an olfactory stimulus for the newborn's appetite.
The dimensions and weight of the breast vary widely among women. A small-to-medium-sized breast weighs 500 grams (1.1 pounds) or less, and a large breast can weigh approximately 750 to 1,000 grams (1.7 to 2.2 pounds) or more. In terms of composition, the breasts are about 80 to 90% stromal tissue (fat and connective tissue), while epithelial or glandular tissue only accounts for about 10 to 20% of the volume of the breasts. The tissue composition ratios of the breast also vary among women. Some women's breasts have a higher proportion of glandular tissue than of adipose or connective tissues. The fat-to-connective-tissue ratio determines the density or firmness of the breast. During a woman's life, her breasts change size, shape, and weight due to hormonal changes during puberty, the menstrual cycle, pregnancy, breastfeeding, and menopause.
Glandular structure | Breast | Wikipedia | 420 | 4489 | https://en.wikipedia.org/wiki/Breast | Biology and health sciences | Integumentary system | null |
The breast is an apocrine gland that produces the milk used to feed an infant. The nipple of the breast is surrounded by the areola (nipple-areola complex). The areola has many sebaceous glands, and the skin color varies from pink to dark brown. The basic units of the breast are the terminal duct lobular units (TDLUs), which produce the fatty breast milk. They give the breast its offspring-feeding functions as a mammary gland. They are distributed throughout the body of the breast. Approximately two-thirds of the lactiferous tissue is within 30 mm of the base of the nipple. The terminal lactiferous ducts drain the milk from TDLUs into 4–18 lactiferous ducts, which drain to the nipple. The milk-glands-to-fat ratio is 2:1 in a lactating woman, and 1:1 in a non-lactating woman. In addition to the milk glands, the breast is also composed of connective tissues (collagen, elastin), white fat, and the suspensory Cooper's ligaments. Sensation in the breast is provided by the peripheral nervous system innervation by means of the front (anterior) and side (lateral) cutaneous branches of the fourth-, fifth-, and sixth intercostal nerves. The T-4 nerve (Thoracic spinal nerve 4), which innervates the dermatomic area, supplies sensation to the nipple-areola complex. | Breast | Wikipedia | 315 | 4489 | https://en.wikipedia.org/wiki/Breast | Biology and health sciences | Integumentary system | null |
Lymphatic drainage
Approximately 75% of the lymph from the breast travels to the axillary lymph nodes on the same side of the body, while 25% of the lymph travels to the parasternal nodes (beside the sternum bone). A small amount of remaining lymph travels to the other breast and to the abdominal lymph nodes. The subareolar region has a lymphatic plexus known as the "subareolar plexus of Sappey". The axillary lymph nodes include the pectoral (chest), subscapular (under the scapula), and humeral (humerus-bone area) lymph-node groups, which drain to the central axillary lymph nodes and to the apical axillary lymph nodes. The lymphatic drainage of the breasts is especially relevant to oncology because breast cancer is common to the mammary gland, and cancer cells can metastasize (break away) from a tumor and be dispersed to other parts of the body by means of the lymphatic system.
Morphology
The morphologic variations in the size, shape, volume, tissue density, pectoral locale, and spacing of the breasts determine their natural shape, appearance, and position on a woman's chest. Breast size and other characteristics do not predict the fat-to-milk-gland ratio or the potential for the woman to nurse an infant. The size and the shape of the breasts are influenced by normal-life hormonal changes (thelarche, menstruation, pregnancy, menopause) and medical conditions (e.g. virginal breast hypertrophy). The shape of the breasts is naturally determined by the support of the suspensory Cooper's ligaments, the underlying muscle and bone structures of the chest, and by the skin envelope. The suspensory ligaments sustain the breast from the clavicle (collarbone) and the clavico-pectoral fascia (collarbone and chest) by traversing and encompassing the fat and milk-gland tissues. The breast is positioned, affixed to, and supported upon the chest wall, while its shape is established and maintained by the skin envelope. In most women, one breast is slightly larger than the other. More obvious and persistent asymmetry in breast size occurs in up to 25% of women. | Breast | Wikipedia | 510 | 4489 | https://en.wikipedia.org/wiki/Breast | Biology and health sciences | Integumentary system | null |
The base of each breast is attached to the chest by the deep fascia over the pectoralis major muscles. The base of the breast is semi-circular, however the shape and position of the breast above the surface is variable. The space between the breast and the pectoralis major muscle, called retromammary space, gives mobility to the breast. The chest (thoracic cavity) progressively slopes outwards from the thoracic inlet (atop the breastbone) and above to the lowest ribs that support the breasts. The inframammary fold (IMF), where the lower portion of the breast meets the chest, is an anatomic feature created by the adherence of the breast skin and the underlying connective tissues of the chest; the IMF is the lower-most extent of the anatomic breast. Normal breast tissue has a texture that feels nodular or granular, with considerable variation from woman to woman.
Breasts have been categorized into four general morphological groups: "flat, spheric, protruded, and drooped", or "small/flat, large/inward, upward, and droopy".
Support
While it is a common belief that breastfeeding causes breasts to sag, researchers have found that a woman's breasts sag due to four key factors: cigarette smoking, number of pregnancies, gravity, and weight loss or gain. Women sometimes wear bras because they mistakenly believe they prevent breasts from sagging as they get older. Physicians, lingerie retailers, teenagers, and adult women used to believe that bras were medically required to support breasts. In a 1952 article in Parents' Magazine, Frank H. Crowell erroneously reported that it was important for teen girls to begin wearing bras early. According to Crowell, this would prevent sagging breasts, stretched blood vessels, and poor circulation later on. This belief was based on the false idea that breasts cannot anatomically support themselves.
Sports bras are sometimes used for cardiovascular exercise, sports bras are designed to secure the breasts closely to the body to prevent movement during high-motion activity such as running. Studies have indicated sports bras which are overly tight may restrict respiratory function.
Development | Breast | Wikipedia | 452 | 4489 | https://en.wikipedia.org/wiki/Breast | Biology and health sciences | Integumentary system | null |
The breasts are principally composed of adipose, glandular, and connective tissues. Because these tissues have hormone receptors, their sizes and volumes fluctuate according to the hormonal changes particular to thelarche (sprouting of breasts), menstruation (egg production), pregnancy (reproduction), lactation (feeding of offspring), and menopause (end of menstruation).
Puberty
The morphological structure of the human breast is identical in males and females until puberty. For pubescent girls in thelarche (the breast-development stage), the female sex hormones (principally estrogens) in conjunction with growth hormone promote the sprouting, growth, and development of the breasts. During this time, the mammary glands grow in size and volume and begin resting on the chest. These development stages of secondary sex characteristics (breasts, pubic hair, etc.) are illustrated in the five-stage Tanner scale.
During thelarche, the developing breasts are sometimes of unequal size, and usually the left breast is slightly larger. This condition of asymmetry is transitory and statistically normal in female physical and sexual development. Medical conditions can cause overdevelopment (e.g., virginal breast hypertrophy, macromastia) or underdevelopment (e.g., tuberous breast deformity, micromastia) in girls and women.
Approximately two years after the onset of puberty (a girl's first menstrual cycle), estrogen and growth hormone stimulate the development and growth of the glandular fat and suspensory tissues that compose the breast. This continues for approximately four years until the final shape of the breast (size, volume, density) is established at about the age of 21. Mammoplasia (breast enlargement) in girls begins at puberty, unlike all other primates, in which breasts enlarge only during lactation.
Hormone replacement therapy
Hormone replacement therapy, including gender-affirming hormone therapy, stimulates the growth of glandular and adipose tissue through estrogen supplementation.
In menopausal women, HRT helps restore breast volume and skin elasticity diminished by declining estrogen levels, typically using oral or transdermal estradiol. | Breast | Wikipedia | 475 | 4489 | https://en.wikipedia.org/wiki/Breast | Biology and health sciences | Integumentary system | null |
In gender-affirming hormone therapy, breast development is induced through feminizing HRT, often combining estrogen with anti-androgens to suppress testosterone. Maximum growth is usually achieved after 2–3 years.
Factors such as age, genetics, and hormone dosage influence outcomes.
Changes during the menstrual cycle
During the menstrual cycle, the breasts are enlarged by premenstrual water retention and temporary growth as influenced by changing hormone levels.
Pregnancy and breastfeeding
The breasts reach full maturity only when a woman's first pregnancy occurs. Changes to the breasts are among the first signs of pregnancy. The breasts become larger, the nipple-areola complex becomes larger and darker, the Montgomery's glands enlarge, and veins sometimes become more visible. Breast tenderness during pregnancy is common, especially during the first trimester. By mid-pregnancy, the breast is physiologically capable of lactation and some women can express colostrum, a form of breast milk.
Pregnancy causes elevated levels of the hormone prolactin, which has a key role in the production of milk. However, milk production is blocked by the hormones progesterone and estrogen until after delivery, when progesterone and estrogen levels plummet.
Menopause
At menopause, breast atrophy occurs. The breasts can decrease in size when the levels of circulating estrogen decline. The adipose tissue and milk glands also begin to wither. The breasts can also become enlarged from adverse side effects of combined oral contraceptive pills. The size of the breasts can also increase and decrease in response to weight fluctuations.
Physical changes to the breasts are often recorded in the stretch marks of the skin envelope; they can serve as historical indicators of the increments and the decrements of the size and volume of a woman's breasts throughout the course of her life.
Breast changes during menopause are sometimes treated with hormone replacement therapy.
Cancer
Breast cancer is a cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, milk rejection, fluid coming from the nipple, a newly inverted nipple, or a red or scaly patch of skin. In those with distant spread of the disease, there may be bone pain, swollen lymph nodes, shortness of breath, or yellow skin. | Breast | Wikipedia | 488 | 4489 | https://en.wikipedia.org/wiki/Breast | Biology and health sciences | Integumentary system | null |
Risk factors for developing breast cancer include obesity, a lack of physical exercise, alcohol consumption, hormone replacement therapy during menopause, ionizing radiation, an early age at first menstruation, having children late in life (or not at all), older age, having a prior history of breast cancer, and a family history of breast cancer. About five to ten percent of cases are the result of an inherited genetic predisposition, including BRCA mutations among others. Breast cancer most commonly develops in cells from the lining of milk ducts and the lobules that supply these ducts with milk. Cancers developing from the ducts are known as ductal carcinomas, while those developing from lobules are known as lobular carcinomas. There are more than 18 other sub-types of breast cancer. Some, such as ductal carcinoma in situ, develop from pre-invasive lesions. The diagnosis of breast cancer is confirmed by taking a biopsy of the concerning tissue. Once the diagnosis is made, further tests are carried out to determine if the cancer has spread beyond the breast and which treatments are most likely to be effective.
Breastfeeding
The primary function of the breasts, as mammary glands, is the nourishing of an infant with breast milk. Milk is produced in milk-secreting cells in the alveoli. When the breasts are stimulated by the suckling of her baby, the mother's brain secretes oxytocin. High levels of oxytocin trigger the contraction of muscle cells surrounding the alveoli, causing milk to flow along the ducts that connect the alveoli to the nipple.
Full-term newborns have an instinct and a need to suck on a nipple, and breastfed babies nurse for both nutrition and for comfort. Breast milk provides all necessary nutrients for the first six months of life, and then remains an important source of nutrition, alongside solid foods, until at least one or two years of age. | Breast | Wikipedia | 405 | 4489 | https://en.wikipedia.org/wiki/Breast | Biology and health sciences | Integumentary system | null |
Exercise
Biomechanical studies have demonstrated that, depending on the activity and the size of a woman's breast, when she walks or runs braless, her breasts may move up and down by or more, and also oscillate side to side. Researchers have also found that as women's breast size increased, they took part in less physical activity, especially vigorous exercise. Few very-large-breasted women jogged, for example. To avoid exercise-related discomfort and pain, medical experts suggest women wear a well-fitted sports bra during activity.
Clinical significance
The breast is susceptible to numerous benign and malignant conditions. The most frequent benign conditions are puerperal mastitis, fibrocystic breast changes and mastalgia.
Lactation unrelated to pregnancy is known as galactorrhea. It can be caused by certain drugs (such as antipsychotic medications), extreme physical stress, or endocrine disorders. Lactation in newborns is caused by hormones from the mother that crossed into the baby's bloodstream during pregnancy.
Breast cancer
Breast cancer is the most common cause of cancer death among women and it is one of the leading causes of death among women. Factors that appear to be implicated in decreasing the risk of breast cancer are regular breast examinations by health care professionals, regular mammograms, self-examination of breasts, healthy diet, exercise to decrease excess body fat, and breastfeeding.
Male breasts
Both females and males develop breasts from the same embryological tissues. Anatomically, male breasts do not normally contain lobules and acini that are present in females. In rare instances, it is possible for very few lobules to be present; this makes it possible for some men to develop lobular carcinoma of the breast. Normally, males produce lower levels of estrogens and higher levels of androgens, namely testosterone, which suppress the effects of estrogens in developing excessive breast tissue. In boys and men, abnormal breast development is manifested as gynecomastia, the consequence of a biochemical imbalance between the normal levels of estrogen and testosterone in the male body. Around 70% of boys temporarily develop breast tissue during adolescence. The condition usually resolves by itself within two years. When male lactation occurs, it is considered a symptom of a disorder of the pituitary gland.
Plastic surgery | Breast | Wikipedia | 486 | 4489 | https://en.wikipedia.org/wiki/Breast | Biology and health sciences | Integumentary system | null |
Plastic surgery can be performed to augment or reduce the size of breasts, or reconstruct the breast in cases of deformative disease, such as breast cancer. Breast augmentation and breast lift (mastopexy) procedures are done only for cosmetic reasons, whereas breast reduction is sometimes medically indicated. In cases where a woman's breasts are severely asymmetrical, surgery can be performed to either enlarge the smaller breast, reduce the size of the larger breast, or both.
Breast augmentation surgery generally does not interfere with future ability to breastfeed. Breast reduction surgery more frequently leads to decreased sensation in the nipple-areola complex, and to low milk supply in women who choose to breastfeed. Implants can interfere with mammography (breast x-ray images).
Society and culture
General
In Christian iconography, some works of art depict women with their breasts in their hands or on a platter, signifying that they died as a martyr by having their breasts severed; one example of this is Saint Agatha of Sicily.
Femen is a feminist activist group which uses topless protests as part of their campaigns against sex tourism religious institutions, sexism, and homophobia. Femen activists have been regularly detained by police in response to their protests.
There is a long history of female breasts being used by comedians as a subject for comedy fodder (e.g., British comic Benny Hill's burlesque/slapstick routines).
Art history
In European pre-historic societies, sculptures of female figures with pronounced or highly exaggerated breasts were common. A typical example is the so-called Venus of Willendorf, one of many Paleolithic Venus figurines with ample hips and bosom. Artifacts such as bowls, rock carvings and sacred statues with breasts have been recorded from 15,000 BC up to late antiquity all across Europe, North Africa and the Middle East.
Many female deities representing love and fertility were associated with breasts and breast milk. Figures of the Phoenician goddess Astarte were represented as pillars studded with breasts. Isis, an Egyptian goddess who represented, among many other things, ideal motherhood, was often portrayed as suckling pharaohs, thereby confirming their divine status as rulers. Even certain male deities representing regeneration and fertility were occasionally depicted with breast-like appendices, such as the river god Hapy who was considered to be responsible for the annual overflowing of the Nile. | Breast | Wikipedia | 503 | 4489 | https://en.wikipedia.org/wiki/Breast | Biology and health sciences | Integumentary system | null |
Female breasts were also prominent in Minoan art in the form of the famous Snake Goddess statuettes, and a few other pieces, though most female breasts are covered. In Ancient Greece there were several cults worshipping the "Kourotrophos", the suckling mother, represented by goddesses such as Gaia, Hera and Artemis. The worship of deities symbolized by the female breast in Greece became less common during the first millennium. The popular adoration of female goddesses decreased significantly during the rise of the Greek city states, a legacy which was passed on to the later Roman Empire.
During the middle of the first millennium BC, Greek culture experienced a gradual change in the perception of female breasts. Women in art were covered in clothing from the neck down, including female goddesses like Athena, the patron of Athens who represented heroic endeavor. There were exceptions: Aphrodite, the goddess of love, was more frequently portrayed fully nude, though in postures that were intended to portray shyness or modesty, a portrayal that has been compared to modern pin ups by historian Marilyn Yalom. Although nude men were depicted standing upright, most depictions of female nudity in Greek art occurred "usually with drapery near at hand and with a forward-bending, self-protecting posture". A popular legend at the time was of the Amazons, a tribe of fierce female warriors who socialized with men only for procreation and even removed one breast to become better warriors (the idea being that the right breast would interfere with the operation of a bow and arrow). The legend was a popular motif in art during Greek and Roman antiquity and served as an antithetical cautionary tale.
Body image
Many women regard their breasts as important to their sexual attractiveness, as a sign of femininity that is important to their sense of self. A woman with smaller breasts may regard her breasts as less attractive.
Clothing
Because breasts are mostly fatty tissue, their shape can—within limits—be molded by clothing, such as foundation garments. Bras are commonly worn by about 90% of Western women, and are often worn for support. The social norm in most Western cultures is to cover breasts in public, though the extent of coverage varies depending on the social context. Some religions ascribe a special status to the female breast, either in formal teachings or through symbolism. Islam forbids free women from exposing their breasts in public. | Breast | Wikipedia | 493 | 4489 | https://en.wikipedia.org/wiki/Breast | Biology and health sciences | Integumentary system | null |
Many cultures, including Western cultures in North America, associate breasts with sexuality and tend to regard bare breasts as immodest or indecent. In some cultures, like the Himba in northern Namibia, bare-breasted women are normal. In some African cultures, for example, the thigh is regarded as highly sexualized and never exposed in public, but breast exposure is not taboo. In a few Western countries and regions female toplessness at a beach is acceptable, although it may not be acceptable in the town center.
Social attitudes and laws regarding breastfeeding in public vary widely. In many countries, breastfeeding in public is common, legally protected, and generally not regarded as an issue. However, even though the practice may be legal or socially accepted, some mothers may nevertheless be reluctant to expose a breast in public to breastfeed due to actual or potential objections by other people, negative comments, or harassment. It is estimated that around 63% of mothers across the world have publicly breast-fed. Bare-breasted women are legal and culturally acceptable at public beaches in Australia and much of Europe. Filmmaker Lina Esco made a film entitled Free the Nipple, which is about "...laws against female toplessness or restrictions on images of female, but not male, nipples", which Esco states is an example of sexism in society.
Breast binding, also known as chest binding, is the flattening and hiding of breasts with constrictive materials such as cloth strips or purpose-built undergarments. Binders may also be used as alternatives to bras or for reasons of propriety. People who bind include women, trans men, non-binary people, and cisgender men with gynecomastia.
Sexual characteristic | Breast | Wikipedia | 358 | 4489 | https://en.wikipedia.org/wiki/Breast | Biology and health sciences | Integumentary system | null |
In some cultures, breasts play a role in human sexual activity. Breasts and especially the nipples are among the various human erogenous zones. They are sensitive to the touch as they have many nerve endings; and it is common to press or massage them with hands or orally before or during sexual activity. During sexual arousal, breast size increases, venous patterns across the breasts become more visible, and nipples harden. Compared to other primates, human breasts are proportionately large throughout adult females' lives. Some writers have suggested that they may have evolved as a visual signal of sexual maturity and fertility. In Patterns of Sexual Behavior, a 1951 analysis of 191 traditional cultures, the researchers noted that stimulation of the female breast by a male sexual partner "seemed absent in all subhuman forms, although it is common among the members of many different human societies."
Many people regard bare female breasts to be aesthetically pleasing or erotic, and they can elicit heightened sexual desires in men in many cultures. In the ancient Indian work the Kama Sutra, light scratching of the breasts with nails and biting with teeth are considered erotic. Some people show a sexual interest in female breasts distinct from that of the person, which may be regarded as a breast fetish. A number of Western fashions include clothing which accentuate the breasts, such as the use of push-up bras and decollete (plunging neckline) gowns and blouses which show cleavage. While U.S. culture prefers breasts that are youthful and upright, some cultures venerate women with drooping breasts, indicating mothering and the wisdom of experience.
Research conducted at the Victoria University of Wellington showed that breasts are often the first thing men look at, and for a longer time than other body parts. The writers of the study had initially speculated that the reason for this is due to endocrinology with larger breasts indicating higher levels of estrogen and a sign of greater fertility, but the researchers said that "Men may be looking more often at the breasts because they are simply aesthetically pleasing, regardless of the size." | Breast | Wikipedia | 422 | 4489 | https://en.wikipedia.org/wiki/Breast | Biology and health sciences | Integumentary system | null |
Some women report achieving an orgasm from nipple stimulation, but this is rare. Research suggests that the orgasms are genital orgasms, and may also be directly linked to "the genital area of the brain". In these cases, it seems that sensation from the nipples travels to the same part of the brain as sensations from the vagina, clitoris and cervix. Nipple stimulation may trigger uterine contractions, which then produce a sensation in the genital area of the brain.
Anthropomorphic geography
There are many mountains named after the breast because they resemble it in appearance and so are objects of religious and ancestral veneration as a fertility symbol and of well-being. In Asia, there was "Breast Mountain", which had a cave where the Buddhist monk Bodhidharma (Da Mo) spent much time in meditation. Other such breast mountains are Mount Elgon on the Uganda–Kenya border; and the Maiden Paps in Scotland; the ('Maiden's breast mountains') in Talim Island, Philippines, the twin hills known as the Paps of Anu ( or 'the breasts of Anu'), near Killarney in Ireland; the 2,086 m high or in the , Spain; in Thailand, in Puerto Rico; and the Breasts of Aphrodite in Mykonos, among many others. In the United States, the Teton Range is named after the French word for 'nipple'.
Measurement
The maturation and size of the breasts can be measured by a variety of different methods. These include Tanner staging, bra cup size, breast volume, breast–chest difference, the breast unit, breast hemicircumference, and breast circumference, among other measures. | Breast | Wikipedia | 356 | 4489 | https://en.wikipedia.org/wiki/Breast | Biology and health sciences | Integumentary system | null |
The British thermal unit (Btu) is a measure of heat, which is a form of energy. It was originally defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. It is also part of the United States customary units. The SI unit for energy is the joule (J); one Btu equals about 1,055 J (varying within the range of 1,054–1,060 J depending on the specific definition of BTU; see below).
While units of heat are often supplanted by energy units in scientific work, they are still used in some fields. For example, in the United States the price of natural gas is quoted in dollars per the amount of natural gas that would give 1 million Btu (1 "MMBtu") of heat energy if burned.
Definitions
A Btu was originally defined as the amount of heat required to raise the temperature of one pound of liquid water by one degree Fahrenheit at a constant pressure of one atmospheric unit. There are several different definitions of the Btu that differ slightly. This reflects the fact that the temperature change of a mass of water due to the addition of a specific amount of heat (calculated in energy units, usually joules) depends slightly upon the water's initial temperature. As seen in the table below, definitions of the Btu based on different water temperatures vary by up to 0.5%.
Prefixes
Units of kBtu are used in building energy use tracking and heating system sizing. Energy Use Index (EUI) represents kBtu per square foot of conditioned floor area. "k" stands for 1,000.
The unit Mbtu is used in natural gas and other industries to indicate 1,000 Btu. However, there is an ambiguity in that the metric system (SI) uses the prefix "M" to indicate 'Mega-', one million (1,000,000). Even so, "MMbtu" is often used to indicate one million Btu particularly in the oil and gas industry.
Energy analysts accustomed to the metric "k" ('kilo-') for 1,000 are more likely to use MBtu to represent one million, especially in documents where M represents one million in other energy or cost units, such as MW, MWh and $. | British thermal unit | Wikipedia | 484 | 4495 | https://en.wikipedia.org/wiki/British%20thermal%20unit | Physical sciences | Energy | Basics and measurement |
The unit 'therm' is used to represent 100,000 Btu. A decatherm is 10 therms or one million Btu. The unit quad is commonly used to represent one quadrillion (1015) Btu.
Conversions
One Btu is approximately:
(kilojoules)
(watt hours)
(calories)
(kilocalories)
25,031 to 25,160 ft⋅pdl (foot-poundal)
(foot-pounds-force)
5.40395 (lbf/in2)⋅ft3
A Btu can be approximated as the heat produced by burning a single wooden kitchen match or as the amount of energy it takes to lift a weight .
For natural gas
In natural gas pricing, the Canadian definition is that ≡ .
The energy content (high or low heating value) of a volume of natural gas varies with the composition of the natural gas, which means there is no universal conversion factor for energy to volume. of average natural gas yields ≈ 1,030 Btu (between 1,010 Btu and 1,070 Btu, depending on quality, when burned)
As a coarse approximation, of natural gas yields ≈ ≈ .
For natural gas price conversion ≈ 36.9 million Btu and ≈
BTU/h
The SI unit of power for heating and cooling systems is the watt. Btu per hour (Btu/h) is sometimes used in North America and the United Kingdom - the latter for air conditioning mainly, though "Btu/h" is sometimes abbreviated to just "Btu". MBH—thousands of Btu per hour—is also common.
1 W is approximately
1,000 Btu/h is approximately
1 hp is approximately | British thermal unit | Wikipedia | 357 | 4495 | https://en.wikipedia.org/wiki/British%20thermal%20unit | Physical sciences | Energy | Basics and measurement |
Associated units
1 ton of cooling, a common unit in North American refrigeration and air conditioning applications, is . It is the rate of heat transfer needed to freeze of water into ice in 24 hours.
In the United States and Canada, the R-value that describes the performance of thermal insulation is typically quoted in square foot degree Fahrenheit hours per British thermal unit (ft2⋅°F⋅h/Btu). For one square foot of the insulation, one Btu per hour of heat flows across the insulator for each degree of temperature difference across it.
1 therm is defined in the United States as 100,000 Btu using the definition. In the EU it was listed in 1979 with the BTUIT definition and planned to be discarded as a legal unit of trade by 1994. United Kingdom regulations were amended to replace therms with joules with effect from 1 January 2000. the therm was still used in natural gas pricing in the United Kingdom.
1 quad (short for quadrillion Btu) is 1015 Btu, which is about 1 exajoule (). Quads are used in the United States for representing the annual energy consumption of large economies: for example, the U.S. economy used 99.75 quads in 2005. One quad/year is about 33.43 gigawatts.
The Btu should not be confused with the Board of Trade Unit (BTU), an obsolete UK synonym for kilowatt hour ().
The Btu is often used to express the conversion-efficiency of heat into electrical energy in power plants. Figures are quoted in terms of the quantity of heat in Btu required to generate 1 kW⋅h of electrical energy. A typical coal-fired power plant works at , an efficiency of 32–33%.
The centigrade heat unit (CHU) is the amount of heat required to raise the temperature of of water by one Celsius degree. It is equal to 1.8 Btu or 1,899 joules. In 1974, this unit was "still sometimes used" in the United Kingdom as an alternative to Btu.
Another legacy unit for energy in the metric system is the calorie, which is defined as the amount of heat required to raise the temperature of one gram of water by one degree Celsius. | British thermal unit | Wikipedia | 478 | 4495 | https://en.wikipedia.org/wiki/British%20thermal%20unit | Physical sciences | Energy | Basics and measurement |
Biotechnology is a multidisciplinary field that involves the integration of natural sciences and engineering sciences in order to achieve the application of organisms and parts thereof for products and services.
The term biotechnology was first used by Károly Ereky in 1919 to refer to the production of products from raw materials with the aid of living organisms. The core principle of biotechnology involves harnessing biological systems and organisms, such as bacteria, yeast, and plants, to perform specific tasks or produce valuable substances.
Biotechnology had a significant impact on many areas of society, from medicine to agriculture to environmental science. One of the key techniques used in biotechnology is genetic engineering, which allows scientists to modify the genetic makeup of organisms to achieve desired outcomes. This can involve inserting genes from one organism into another, and consequently, create new traits or modifying existing ones.
Other important techniques used in biotechnology include tissue culture, which allows researchers to grow cells and tissues in the lab for research and medical purposes, and fermentation, which is used to produce a wide range of products such as beer, wine, and cheese.
The applications of biotechnology are diverse and have led to the development of products like life-saving drugs, biofuels, genetically modified crops, and innovative materials. It has also been used to address environmental challenges, such as developing biodegradable plastics and using microorganisms to clean up contaminated sites.
Biotechnology is a rapidly evolving field with significant potential to address pressing global challenges and improve the quality of life for people around the world; however, despite its numerous benefits, it also poses ethical and societal challenges, such as questions around genetic modification and intellectual property rights. As a result, there is ongoing debate and regulation surrounding the use and application of biotechnology in various industries and fields.
Definition | Biotechnology | Wikipedia | 356 | 4502 | https://en.wikipedia.org/wiki/Biotechnology | Technology | Food and health | null |
The concept of biotechnology encompasses a wide range of procedures for modifying living organisms for human purposes, going back to domestication of animals, cultivation of plants, and "improvements" to these through breeding programs that employ artificial selection and hybridization. Modern usage also includes genetic engineering, as well as cell and tissue culture technologies. The American Chemical Society defines biotechnology as the application of biological organisms, systems, or processes by various industries to learning about the science of life and the improvement of the value of materials and organisms, such as pharmaceuticals, crops, and livestock. As per the European Federation of Biotechnology, biotechnology is the integration of natural science and organisms, cells, parts thereof, and molecular analogues for products and services. Biotechnology is based on the basic biological sciences (e.g., molecular biology, biochemistry, cell biology, embryology, genetics, microbiology) and conversely provides methods to support and perform basic research in biology.
Biotechnology is the research and development in the laboratory using bioinformatics for exploration, extraction, exploitation, and production from any living organisms and any source of biomass by means of biochemical engineering where high value-added products could be planned (reproduced by biosynthesis, for example), forecasted, formulated, developed, manufactured, and marketed for the purpose of sustainable operations (for the return from bottomless initial investment on R & D) and gaining durable patents rights (for exclusives rights for sales, and prior to this to receive national and international approval from the results on animal experiment and human experiment, especially on the pharmaceutical branch of biotechnology to prevent any undetected side-effects or safety concerns by using the products). The utilization of biological processes, organisms or systems to produce products that are anticipated to improve human lives is termed biotechnology.
By contrast, bioengineering is generally thought of as a related field that more heavily emphasizes higher systems approaches (not necessarily the altering or using of biological materials directly) for interfacing with and utilizing living things. Bioengineering is the application of the principles of engineering and natural sciences to tissues, cells, and molecules. This can be considered as the use of knowledge from working with and manipulating biology to achieve a result that can improve functions in plants and animals. Relatedly, biomedical engineering is an overlapping field that often draws upon and applies biotechnology (by various definitions), especially in certain sub-fields of biomedical or chemical engineering such as tissue engineering, biopharmaceutical engineering, and genetic engineering.
History | Biotechnology | Wikipedia | 502 | 4502 | https://en.wikipedia.org/wiki/Biotechnology | Technology | Food and health | null |
Although not normally what first comes to mind, many forms of human-derived agriculture clearly fit the broad definition of "utilizing a biotechnological system to make products". Indeed, the cultivation of plants may be viewed as the earliest biotechnological enterprise.
Agriculture has been theorized to have become the dominant way of producing food since the Neolithic Revolution. Through early biotechnology, the earliest farmers selected and bred the best-suited crops (e.g., those with the highest yields) to produce enough food to support a growing population. As crops and fields became increasingly large and difficult to maintain, it was discovered that specific organisms and their by-products could effectively fertilize, restore nitrogen, and control pests. Throughout the history of agriculture, farmers have inadvertently altered the genetics of their crops through introducing them to new environments and breeding them with other plants — one of the first forms of biotechnology.
These processes also were included in early fermentation of beer. These processes were introduced in early Mesopotamia, Egypt, China and India, and still use the same basic biological methods. In brewing, malted grains (containing enzymes) convert starch from grains into sugar and then adding specific yeasts to produce beer. In this process, carbohydrates in the grains broke down into alcohols, such as ethanol. Later, other cultures produced the process of lactic acid fermentation, which produced other preserved foods, such as soy sauce. Fermentation was also used in this time period to produce leavened bread. Although the process of fermentation was not fully understood until Louis Pasteur's work in 1857, it is still the first use of biotechnology to convert a food source into another form.
Before the time of Charles Darwin's work and life, animal and plant scientists had already used selective breeding. Darwin added to that body of work with his scientific observations about the ability of science to change species. These accounts contributed to Darwin's theory of natural selection.
For thousands of years, humans have used selective breeding to improve the production of crops and livestock to use them for food. In selective breeding, organisms with desirable characteristics are mated to produce offspring with the same characteristics. For example, this technique was used with corn to produce the largest and sweetest crops. | Biotechnology | Wikipedia | 462 | 4502 | https://en.wikipedia.org/wiki/Biotechnology | Technology | Food and health | null |
In the early twentieth century scientists gained a greater understanding of microbiology and explored ways of manufacturing specific products. In 1917, Chaim Weizmann first used a pure microbiological culture in an industrial process, that of manufacturing corn starch using Clostridium acetobutylicum, to produce acetone, which the United Kingdom desperately needed to manufacture explosives during World War I.
Biotechnology has also led to the development of antibiotics. In 1928, Alexander Fleming discovered the mold Penicillium. His work led to the purification of the antibiotic formed by the mold by Howard Florey, Ernst Boris Chain and Norman Heatley – to form what we today know as penicillin. In 1940, penicillin became available for medicinal use to treat bacterial infections in humans.
The field of modern biotechnology is generally thought of as having been born in 1971 when Paul Berg's (Stanford) experiments in gene splicing had early success. Herbert W. Boyer (Univ. Calif. at San Francisco) and Stanley N. Cohen (Stanford) significantly advanced the new technology in 1972 by transferring genetic material into a bacterium, such that the imported material would be reproduced. The commercial viability of a biotechnology industry was significantly expanded on June 16, 1980, when the United States Supreme Court ruled that a genetically modified microorganism could be patented in the case of Diamond v. Chakrabarty. Indian-born Ananda Chakrabarty, working for General Electric, had modified a bacterium (of the genus Pseudomonas) capable of breaking down crude oil, which he proposed to use in treating oil spills. (Chakrabarty's work did not involve gene manipulation but rather the transfer of entire organelles between strains of the Pseudomonas bacterium). | Biotechnology | Wikipedia | 362 | 4502 | https://en.wikipedia.org/wiki/Biotechnology | Technology | Food and health | null |
The MOSFET invented at Bell Labs between 1955 and 1960, Two years later, Leland C. Clark and Champ Lyons invented the first biosensor in 1962. Biosensor MOSFETs were later developed, and they have since been widely used to measure physical, chemical, biological and environmental parameters. The first BioFET was the ion-sensitive field-effect transistor (ISFET), invented by Piet Bergveld in 1970. It is a special type of MOSFET, where the metal gate is replaced by an ion-sensitive membrane, electrolyte solution and reference electrode. The ISFET is widely used in biomedical applications, such as the detection of DNA hybridization, biomarker detection from blood, antibody detection, glucose measurement, pH sensing, and genetic technology.
By the mid-1980s, other BioFETs had been developed, including the gas sensor FET (GASFET), pressure sensor FET (PRESSFET), chemical field-effect transistor (ChemFET), reference ISFET (REFET), enzyme-modified FET (ENFET) and immunologically modified FET (IMFET). By the early 2000s, BioFETs such as the DNA field-effect transistor (DNAFET), gene-modified FET (GenFET) and cell-potential BioFET (CPFET) had been developed.
A factor influencing the biotechnology sector's success is improved intellectual property rights legislation—and enforcement—worldwide, as well as strengthened demand for medical and pharmaceutical products.
Rising demand for biofuels is expected to be good news for the biotechnology sector, with the Department of Energy estimating ethanol usage could reduce U.S. petroleum-derived fuel consumption by up to 30% by 2030. The biotechnology sector has allowed the U.S. farming industry to rapidly increase its supply of corn and soybeans—the main inputs into biofuels—by developing genetically modified seeds that resist pests and drought. By increasing farm productivity, biotechnology boosts biofuel production.
Examples
Biotechnology has applications in four major industrial areas, including health care (medical), crop production and agriculture, non-food (industrial) uses of crops and other products (e.g., biodegradable plastics, vegetable oil, biofuels), and environmental uses. | Biotechnology | Wikipedia | 490 | 4502 | https://en.wikipedia.org/wiki/Biotechnology | Technology | Food and health | null |
For example, one application of biotechnology is the directed use of microorganisms for the manufacture of organic products (examples include beer and milk products). Another example is using naturally present bacteria by the mining industry in bioleaching. Biotechnology is also used to recycle, treat waste, clean up sites contaminated by industrial activities (bioremediation), and also to produce biological weapons. | Biotechnology | Wikipedia | 80 | 4502 | https://en.wikipedia.org/wiki/Biotechnology | Technology | Food and health | null |
A series of derived terms have been coined to identify several branches of biotechnology, for example:
Bioinformatics (or "gold biotechnology") is an interdisciplinary field that addresses biological problems using computational techniques, and makes the rapid organization as well as analysis of biological data possible. The field may also be referred to as computational biology, and can be defined as, "conceptualizing biology in terms of molecules and then applying informatics techniques to understand and organize the information associated with these molecules, on a large scale". Bioinformatics plays a key role in various areas, such as functional genomics, structural genomics, and proteomics, and forms a key component in the biotechnology and pharmaceutical sector.
Blue biotechnology is based on the exploitation of sea resources to create products and industrial applications. This branch of biotechnology is the most used for the industries of refining and combustion principally on the production of bio-oils with photosynthetic micro-algae.
Green biotechnology is biotechnology applied to agricultural processes. An example would be the selection and domestication of plants via micropropagation. Another example is the designing of transgenic plants to grow under specific environments in the presence (or absence) of chemicals. One hope is that green biotechnology might produce more environmentally friendly solutions than traditional industrial agriculture. An example of this is the engineering of a plant to express a pesticide, thereby ending the need of external application of pesticides. An example of this would be Bt corn. Whether or not green biotechnology products such as this are ultimately more environmentally friendly is a topic of considerable debate. It is commonly considered as the next phase of green revolution, which can be seen as a platform to eradicate world hunger by using technologies which enable the production of more fertile and resistant, towards biotic and abiotic stress, plants and ensures application of environmentally friendly fertilizers and the use of biopesticides, it is mainly focused on the development of agriculture. On the other hand, some of the uses of green biotechnology involve microorganisms to clean and reduce waste.
Red biotechnology is the use of biotechnology in the medical and pharmaceutical industries, and health preservation. This branch involves the production of vaccines and antibiotics, regenerative therapies, creation of artificial organs and new diagnostics of diseases. As well as the development of hormones, stem cells, antibodies, siRNA and diagnostic tests. | Biotechnology | Wikipedia | 479 | 4502 | https://en.wikipedia.org/wiki/Biotechnology | Technology | Food and health | null |
White biotechnology, also known as industrial biotechnology, is biotechnology applied to industrial processes. An example is the designing of an organism to produce a useful chemical. Another example is the using of enzymes as industrial catalysts to either produce valuable chemicals or destroy hazardous/polluting chemicals. White biotechnology tends to consume less in resources than traditional processes used to produce industrial goods.
"Yellow biotechnology" refers to the use of biotechnology in food production (food industry), for example in making wine (winemaking), cheese (cheesemaking), and beer (brewing) by fermentation. It has also been used to refer to biotechnology applied to insects. This includes biotechnology-based approaches for the control of harmful insects, the characterisation and utilisation of active ingredients or genes of insects for research, or application in agriculture and medicine and various other approaches.
Gray biotechnology is dedicated to environmental applications, and focused on the maintenance of biodiversity and the remotion of pollutants.
Brown biotechnology is related to the management of arid lands and deserts. One application is the creation of enhanced seeds that resist extreme environmental conditions of arid regions, which is related to the innovation, creation of agriculture techniques and management of resources.
Violet biotechnology is related to law, ethical and philosophical issues around biotechnology.
Microbial biotechnology has been proposed for the rapidly emerging area of biotechnology applications in space and microgravity (space bioeconomy)
Dark biotechnology is the color associated with bioterrorism or biological weapons and biowarfare which uses microorganisms, and toxins to cause diseases and death in humans, livestock and crops. | Biotechnology | Wikipedia | 321 | 4502 | https://en.wikipedia.org/wiki/Biotechnology | Technology | Food and health | null |
Medicine
In medicine, modern biotechnology has many applications in areas such as pharmaceutical drug discoveries and production, pharmacogenomics, and genetic testing (or genetic screening). In 2021, nearly 40% of the total company value of pharmaceutical biotech companies worldwide were active in Oncology with Neurology and Rare Diseases being the other two big applications.
Pharmacogenomics (a combination of pharmacology and genomics) is the technology that analyses how genetic makeup affects an individual's response to drugs. Researchers in the field investigate the influence of genetic variation on drug responses in patients by correlating gene expression or single-nucleotide polymorphisms with a drug's efficacy or toxicity. The purpose of pharmacogenomics is to develop rational means to optimize drug therapy, with respect to the patients' genotype, to ensure maximum efficacy with minimal adverse effects. Such approaches promise the advent of "personalized medicine"; in which drugs and drug combinations are optimized for each individual's unique genetic makeup.
Biotechnology has contributed to the discovery and manufacturing of traditional small molecule pharmaceutical drugs as well as drugs that are the product of biotechnology – biopharmaceutics. Modern biotechnology can be used to manufacture existing medicines relatively easily and cheaply. The first genetically engineered products were medicines designed to treat human diseases. To cite one example, in 1978 Genentech developed synthetic humanized insulin by joining its gene with a plasmid vector inserted into the bacterium Escherichia coli. Insulin, widely used for the treatment of diabetes, was previously extracted from the pancreas of abattoir animals (cattle or pigs). The genetically engineered bacteria are able to produce large quantities of synthetic human insulin at relatively low cost. Biotechnology has also enabled emerging therapeutics like gene therapy. The application of biotechnology to basic science (for example through the Human Genome Project) has also dramatically improved our understanding of biology and as our scientific knowledge of normal and disease biology has increased, our ability to develop new medicines to treat previously untreatable diseases has increased as well. | Biotechnology | Wikipedia | 422 | 4502 | https://en.wikipedia.org/wiki/Biotechnology | Technology | Food and health | null |
Genetic testing allows the genetic diagnosis of vulnerabilities to inherited diseases, and can also be used to determine a child's parentage (genetic mother and father) or in general a person's ancestry. In addition to studying chromosomes to the level of individual genes, genetic testing in a broader sense includes biochemical tests for the possible presence of genetic diseases, or mutant forms of genes associated with increased risk of developing genetic disorders. Genetic testing identifies changes in chromosomes, genes, or proteins. Most of the time, testing is used to find changes that are associated with inherited disorders. The results of a genetic test can confirm or rule out a suspected genetic condition or help determine a person's chance of developing or passing on a genetic disorder. As of 2011 several hundred genetic tests were in use. Since genetic testing may open up ethical or psychological problems, genetic testing is often accompanied by genetic counseling.
Agriculture
Genetically modified crops ("GM crops", or "biotech crops") are plants used in agriculture, the DNA of which has been modified with genetic engineering techniques. In most cases, the main aim is to introduce a new trait that does not occur naturally in the species. Biotechnology firms can contribute to future food security by improving the nutrition and viability of urban agriculture. Furthermore, the protection of intellectual property rights encourages private sector investment in agrobiotechnology.
Examples in food crops include resistance to certain pests, diseases, stressful environmental conditions, resistance to chemical treatments (e.g. resistance to a herbicide), reduction of spoilage, or improving the nutrient profile of the crop. Examples in non-food crops include production of pharmaceutical agents, biofuels, and other industrially useful goods, as well as for bioremediation.
Farmers have widely adopted GM technology. Between 1996 and 2011, the total surface area of land cultivated with GM crops had increased by a factor of 94, from . 10% of the world's crop lands were planted with GM crops in 2010. As of 2011, 11 different transgenic crops were grown commercially on in 29 countries such as the US, Brazil, Argentina, India, Canada, China, Paraguay, Pakistan, South Africa, Uruguay, Bolivia, Australia, Philippines, Myanmar, Burkina Faso, Mexico and Spain. | Biotechnology | Wikipedia | 459 | 4502 | https://en.wikipedia.org/wiki/Biotechnology | Technology | Food and health | null |
Genetically modified foods are foods produced from organisms that have had specific changes introduced into their DNA with the methods of genetic engineering. These techniques have allowed for the introduction of new crop traits as well as a far greater control over a food's genetic structure than previously afforded by methods such as selective breeding and mutation breeding. Commercial sale of genetically modified foods began in 1994, when Calgene first marketed its Flavr Savr delayed ripening tomato. To date most genetic modification of foods have primarily focused on cash crops in high demand by farmers such as soybean, corn, canola, and cotton seed oil. These have been engineered for resistance to pathogens and herbicides and better nutrient profiles. GM livestock have also been experimentally developed; in November 2013 none were available on the market, but in 2015 the FDA approved the first GM salmon for commercial production and consumption.
There is a scientific consensus that currently available food derived from GM crops poses no greater risk to human health than conventional food, but that each GM food needs to be tested on a case-by-case basis before introduction. Nonetheless, members of the public are much less likely than scientists to perceive GM foods as safe. The legal and regulatory status of GM foods varies by country, with some nations banning or restricting them, and others permitting them with widely differing degrees of regulation.
GM crops also provide a number of ecological benefits, if not used in excess. Insect-resistant crops have proven to lower pesticide usage, therefore reducing the environmental impact of pesticides as a whole. However, opponents have objected to GM crops per se on several grounds, including environmental concerns, whether food produced from GM crops is safe, whether GM crops are needed to address the world's food needs, and economic concerns raised by the fact these organisms are subject to intellectual property law.
Biotechnology has several applications in the realm of food security. Crops like Golden rice are engineered to have higher nutritional content, and there is potential for food products with longer shelf lives. Though not a form of agricultural biotechnology, vaccines can help prevent diseases found in animal agriculture. Additionally, agricultural biotechnology can expedite breeding processes in order to yield faster results and provide greater quantities of food. Transgenic biofortification in cereals has been considered as a promising method to combat malnutrition in India and other countries. | Biotechnology | Wikipedia | 469 | 4502 | https://en.wikipedia.org/wiki/Biotechnology | Technology | Food and health | null |
Industrial
Industrial biotechnology (known mainly in Europe as white biotechnology) is the application of biotechnology for industrial purposes, including industrial fermentation. It includes the practice of using cells such as microorganisms, or components of cells like enzymes, to generate industrially useful products in sectors such as chemicals, food and feed, detergents, paper and pulp, textiles and biofuels. In the current decades, significant progress has been done in creating genetically modified organisms (GMOs) that enhance the diversity of applications and economical viability of industrial biotechnology. By using renewable raw materials to produce a variety of chemicals and fuels, industrial biotechnology is actively advancing towards lowering greenhouse gas emissions and moving away from a petrochemical-based economy.
Synthetic biology is considered one of the essential cornerstones in industrial biotechnology due to its financial and sustainable contribution to the manufacturing sector. Jointly biotechnology and synthetic biology play a crucial role in generating cost-effective products with nature-friendly features by using bio-based production instead of fossil-based. Synthetic biology can be used to engineer model microorganisms, such as Escherichia coli, by genome editing tools to enhance their ability to produce bio-based products, such as bioproduction of medicines and biofuels. For instance, E. coli and Saccharomyces cerevisiae in a consortium could be used as industrial microbes to produce precursors of the chemotherapeutic agent paclitaxel by applying the metabolic engineering in a co-culture approach to exploit the benefits from the two microbes. | Biotechnology | Wikipedia | 316 | 4502 | https://en.wikipedia.org/wiki/Biotechnology | Technology | Food and health | null |
Another example of synthetic biology applications in industrial biotechnology is the re-engineering of the metabolic pathways of E. coli by CRISPR and CRISPRi systems toward the production of a chemical known as 1,4-butanediol, which is used in fiber manufacturing. In order to produce 1,4-butanediol, the authors alter the metabolic regulation of the Escherichia coli by CRISPR to induce point mutation in the gltA gene, knockout of the sad gene, and knock-in six genes (cat1, sucD, 4hbd, cat2, bld, and bdh). Whereas CRISPRi system used to knockdown the three competing genes (gabD, ybgC, and tesB) that affect the biosynthesis pathway of 1,4-butanediol. Consequently, the yield of 1,4-butanediol significantly increased from 0.9 to 1.8 g/L.
Environmental
Environmental biotechnology includes various disciplines that play an essential role in reducing environmental waste and providing environmentally safe processes, such as biofiltration and biodegradation. The environment can be affected by biotechnologies, both positively and adversely. Vallero and others have argued that the difference between beneficial biotechnology (e.g., bioremediation is to clean up an oil spill or hazard chemical leak) versus the adverse effects stemming from biotechnological enterprises (e.g., flow of genetic material from transgenic organisms into wild strains) can be seen as applications and implications, respectively. Cleaning up environmental wastes is an example of an application of environmental biotechnology; whereas loss of biodiversity or loss of containment of a harmful microbe are examples of environmental implications of biotechnology.
Many cities have installed CityTrees, which use biotechnology to filter pollutants from urban atmospheres.
Regulation | Biotechnology | Wikipedia | 376 | 4502 | https://en.wikipedia.org/wiki/Biotechnology | Technology | Food and health | null |
The regulation of genetic engineering concerns approaches taken by governments to assess and manage the risks associated with the use of genetic engineering technology, and the development and release of genetically modified organisms (GMO), including genetically modified crops and genetically modified fish. There are differences in the regulation of GMOs between countries, with some of the most marked differences occurring between the US and Europe. Regulation varies in a given country depending on the intended use of the products of the genetic engineering. For example, a crop not intended for food use is generally not reviewed by authorities responsible for food safety. The European Union differentiates between approval for cultivation within the EU and approval for import and processing. While only a few GMOs have been approved for cultivation in the EU a number of GMOs have been approved for import and processing. The cultivation of GMOs has triggered a debate about the coexistence of GM and non-GM crops. Depending on the coexistence regulations, incentives for the cultivation of GM crops differ.
Database for the GMOs used in the EU
The EUginius (European GMO Initiative for a Unified Database System) database is intended to help companies, interested private users and competent authorities to find precise information on the presence, detection and identification of GMOs used in the European Union. The information is provided in English.
Learning
In 1988, after prompting from the United States Congress, the National Institute of General Medical Sciences (National Institutes of Health) (NIGMS) instituted a funding mechanism for biotechnology training. Universities nationwide compete for these funds to establish Biotechnology Training Programs (BTPs). Each successful application is generally funded for five years then must be competitively renewed. Graduate students in turn compete for acceptance into a BTP; if accepted, then stipend, tuition and health insurance support are provided for two or three years during the course of their PhD thesis work. Nineteen institutions offer NIGMS supported BTPs. Biotechnology training is also offered at the undergraduate level and in community colleges. | Biotechnology | Wikipedia | 400 | 4502 | https://en.wikipedia.org/wiki/Biotechnology | Technology | Food and health | null |
A ballpoint pen, also known as a biro (British English), ball pen (Hong Kong, Indonesia, Pakistani, Indian and Philippine English), or dot pen (Nepali English and South Asian English), is a pen that dispenses ink (usually in paste form) over a metal ball at its point, i.e., over a "ball point". The metals commonly used are steel, brass, or tungsten carbide. The design was conceived and developed as a cleaner and more reliable alternative to dip pens and fountain pens, and it is now the world's most-used writing instrument; millions are manufactured and sold daily. It has influenced art and graphic design and spawned an artwork genre.
History
Origins
The concept of using a "ball point" within a writing instrument to apply ink to paper has existed since the late 19th century. In these inventions, the ink was placed in a thin tube whose end was blocked by a tiny ball, held so that it could not slip into the tube or fall out of the pen.
The first patent for a ballpoint pen was issued on 30 October 1888 to John J. Loud, who was attempting to make a writing instrument that would be able to write "on rough surfaces—such as wood, coarse wrapping paper, and other articles" which fountain pens could not. Loud's pen had a small rotating steel ball held in place by a socket. Although it could be used to mark rough surfaces such as leather, as Loud intended, it proved too coarse for letter-writing. With no commercial viability, its potential went unexploited, and the patent eventually lapsed.
The manufacture of economical, reliable ballpoint pens as are known today arose from experimentation, modern chemistry, and the precision manufacturing capabilities of the early 20th century. Patents filed worldwide during early development are testaments to failed attempts at making the pens commercially viable and widely available. Early ballpoints did not deliver the ink evenly; overflow and clogging were among the obstacles faced by early inventors. If the ball socket were too tight or the ink too thick, it would not reach the paper. If the socket were too loose or the ink too thin, the pen would leak, or the ink would smear. Ink reservoirs pressurized by a piston, spring, capillary action, and gravity would all serve as solutions to ink-delivery and flow problems. | Ballpoint pen | Wikipedia | 490 | 4519 | https://en.wikipedia.org/wiki/Ballpoint%20pen | Technology | Writing tools | null |
László Bíró, a Hungarian newspaper editor (later a naturalized Argentine) frustrated by the amount of time that he wasted filling up fountain pens and cleaning up smudged pages, noticed that inks used in newspaper printing dried quickly, leaving the paper dry and smudge-free. He decided to create a pen using the same type of ink. Bíró enlisted the help of his brother György, a dentist with useful knowledge of chemistry, to develop viscous ink formulae for new ballpoint designs.
Bíró's innovation successfully coupled viscous ink with a ball-and-socket mechanism that allowed controlled flow while preventing ink from drying inside the reservoir. Bíró filed for a British patent on 15 June 1938.
In 1941, the Bíró brothers and a friend, Juan Jorge Meyne, fled Germany and moved to Argentina, where they formed "Bíró Pens of Argentina" and filed a new patent in 1943. Their pen was sold in Argentina as the "Birome", from the names Bíró and Meyne, which is how ballpoint pens are still known in that country. This new design was licensed by the British engineer Frederick George Miles and manufactured by his company Miles Aircraft, to be used by Royal Air Force aircrew as the "Biro". Ballpoint pens were found to be more versatile than fountain pens, especially in airplanes, where fountain pens were prone to leak.
Bíró's patent, and other early patents on ballpoint pens, often used the term "ball-point fountain pen".
Postwar proliferation
Following World War II, many companies vied to commercially produce their own ballpoint pen design. In pre-war Argentina, success of the Birome ballpoint was limited, but in mid-1945, the Eversharp Co., a maker of mechanical pencils, teamed up with Eberhard Faber Co. to license the rights from Birome for sales in the United States.
In 1946, a Spanish firm, Vila Sivill Hermanos, began to make a ballpoint, Regia Continua, and from 1953 to 1957 their factory also made Bic ballpoints, on contract with the French firm Société Bic. | Ballpoint pen | Wikipedia | 442 | 4519 | https://en.wikipedia.org/wiki/Ballpoint%20pen | Technology | Writing tools | null |
During the same period, American entrepreneur Milton Reynolds came across a Birome ballpoint pen during a business trip to Buenos Aires, Argentina. Recognizing commercial potential, he purchased several ballpoint samples, returned to the United States, and founded the Reynolds International Pen Company. Reynolds bypassed the Birome patent with sufficient design alterations to obtain an American patent, beating Eversharp and other competitors to introduce the pen to the US market. Debuting at Gimbels department store in New York City on 29 October 1945, for US$12.50 each (1945 US dollar value, about $ in dollars), "Reynolds Rocket" became the first commercially successful ballpoint pen. Reynolds went to great extremes to market the pen, with great success; Gimbel's sold many thousands of pens within one week. In Britain, the Miles-(Harry) Martin pen company was producing the first commercially successful ballpoint pens there by the end of 1945.
Neither Reynolds' nor Eversharp's ballpoint lived up to consumer expectations in America. Ballpoint pen sales peaked in 1946, and consumer interest subsequently plunged due to market saturation, going from luxury good to fungible consumable. By the early 1950s the ballpoint boom had subsided and Reynolds' company folded.
Paper Mate pens, among the emerging ballpoint brands of the 1950s, bought the rights to distribute their own ballpoint pens in Canada. Facing concerns about ink-reliability, Paper Mate pioneered new ink formulas and advertised them as "banker-approved". In 1954, Parker Pens released "The Jotter"—the company's first ballpoint—boasting additional features and technological advances which also included the use of tungsten-carbide textured ball-bearings in their pens. In less than a year, Parker sold several million pens at prices between three and nine dollars. In the 1960s, the failing Eversharp Co. sold its pen division to Parker and ultimately folded.
Marcel Bich also introduced a ballpoint pen to the American marketplace in the 1950s, licensed from Bíró and based on the Argentine designs. Bich shortened his name to Bic in 1953, forming the ballpoint brand Bic now recognized globally. Bic pens struggled until the company launched its "Writes First Time, Every Time!" advertising campaign in the 1960s. Competition during this era forced unit prices to drop considerably. | Ballpoint pen | Wikipedia | 479 | 4519 | https://en.wikipedia.org/wiki/Ballpoint%20pen | Technology | Writing tools | null |
Inks
Ballpoint pen ink is normally a paste containing around 25 to 40 percent dye. The dyes are suspended in a mixture of solvents and fatty acids. The most common of the solvents are benzyl alcohol or phenoxyethanol, which mix with the dyes and oils to create a smooth paste that dries quickly. This type of ink is also called "oil-based ink". The fatty acids help to lubricate the ball tip while writing. Hybrid inks also contain added lubricants in the ink to provide a smoother writing experience. The drying time of the ink varies depending upon the viscosity of the ink and the diameter of the ball.
In general, the more viscous the ink, the faster it will dry, but more writing pressure needs to be applied to dispense ink. But although they are less viscous, hybrid inks have a faster drying time compared to normal ballpoint inks. Also, a larger ball dispenses more ink and thus increases drying time.
The dyes used in blue and black ballpoint pens are basic dyes based on triarylmethane and acid dyes derived from diazo compounds or phthalocyanine. Common dyes in blue (and black) ink are Prussian blue, Victoria blue, methyl violet, crystal violet, and phthalocyanine blue. The dye eosin is commonly used for red ink.
The inks are resistant to water after drying but can be defaced by certain solvents which include acetone and various alcohols.
Types of ballpoint pens
Ballpoint pens are produced in both disposable and refillable models. Refills allow for the entire internal ink reservoir, including a ballpoint and socket, to be replaced. Such characteristics are usually associated with designer-type pens or those constructed of finer materials. The simplest types of ballpoint pens are disposable and have a cap to cover the tip when the pen is not in use, or a mechanism for retracting the tip, which varies between manufacturers but is usually a spring- or screw-mechanism. | Ballpoint pen | Wikipedia | 436 | 4519 | https://en.wikipedia.org/wiki/Ballpoint%20pen | Technology | Writing tools | null |
Rollerball pens employ the same ballpoint mechanics, but with the use of water-based inks instead of oil-based inks. Compared to oil-based ballpoints, rollerball pens are said to provide more fluid ink-flow, but the water-based inks will blot if held stationary against the writing surface. Water-based inks also remain wet longer when freshly applied and are thus prone to "smearing"—posing problems to left-handed people (or right handed people writing right-to-left script)—and "running", should the writing surface become wet.
Some ballpoint pens use a hybrid ink formulation whose viscosity is lower than that of standard ballpoint ink, but greater than rollerball ink. The ink dries faster than a gel pen to prevent smearing when writing. These pens are better suited for left-handed persons. Examples are the Zebra Surari, Uni-ball Jetstream and Pilot Acroball ranges. These pens are also labelled "extra smooth", as they offer a smoother writing experience compared to normal ballpoint pens.
Ballpoint pens with erasable ink were pioneered by the Paper Mate pen company. The ink formulas of erasable ballpoints have properties similar to rubber cement, allowing the ink to be literally rubbed clean from the writing surface before drying and eventually becoming permanent. Erasable ink is much thicker than standard ballpoint inks, requiring pressurized cartridges to facilitate inkflow—meaning they can also write upside-down. Though these pens are equipped with erasers, any eraser will suffice.
Ballpoint tips are fitted with balls whose diameter can vary from 0.28 mm to 1.6 mm. The ball diameter does not correspond to the width of the line produced by the pen. The line width depends on various factors like the type of ink and pressure applied. Some standard ball diameters are: 0.3 mm, 0.38 mm, 0.4 mm, 0.5 mm, 0.7 mm (fine), 0.8 mm, 1.0 mm (medium), 1.2 mm and 1.4 mm (broad). Pens with ball diameters as small as 0.18 mm have been made by Japanese companies, but are extremely rare. | Ballpoint pen | Wikipedia | 462 | 4519 | https://en.wikipedia.org/wiki/Ballpoint%20pen | Technology | Writing tools | null |
The inexpensive, disposable Bic Cristal (also simply "Bic pen" or "Biro") is reportedly the most widely sold pen in the world. It was the Bic company's first product and is still synonymous with the company name. The Bic Cristal is part of the permanent collection at the Museum of Modern Art in New York City, acknowledged for its industrial design. Its hexagonal barrel mimics that of a wooden pencil and is transparent, showing the ink level in the reservoir. Originally a sealed streamlined cap, the modern pen cap has a small hole at the top to meet safety standards, helping to prevent suffocation if children suck it into the throat.
Multi-pens are pens that feature multiple varying colored pen refills. Sometimes ballpoint refills are combined with another non-ballpoint refill, usually a mechanical pencil. Sometimes ballpoint pens combine a ballpoint tip on one end and touchscreen stylus on the other.
Ballpoint pens are sometimes provided free by businesses, such as hotels and banks, printed with a company's name and logo. Ballpoints have also been produced to commemorate events, such as a pen commemorating the 1963 assassination of President John F. Kennedy. These pens, known as "advertising pens," are the same as standard ballpoint pen models, but have become valued among collectors.
Sometimes ballpoint pens are also produced as design objects. With cases made of metal or wood, they become individually styled utility objects.
Use of ballpoint pens in space
It is generally believed that gravity is needed to coat the ball with ink. In fact most ballpoint pens on the Earth do not work when writing upside-down because the Earth's gravity pulls the ink inside the pen away from the tip of the pen. However, in the microgravity environment of space a regular ballpoint pen can still work, pointed in any direction, because the capillary forces in the ink are stronger than gravitational forces.
The functionality of a regular ballpoint pen in space was confirmed by ESA astronaut Pedro Duque in 2003. | Ballpoint pen | Wikipedia | 426 | 4519 | https://en.wikipedia.org/wiki/Ballpoint%20pen | Technology | Writing tools | null |
Technology developed by Fisher pens in the United States resulted in the production of what came to be known as the "Fisher Space Pen". Space Pens combine a more viscous ink with a pressurized ink reservoir that forces the ink toward the point. Unlike a standard ballpoint's ink container, the rear end of a Space Pen's pressurized reservoir is sealed, eliminating evaporation and leakage, thus allowing the pen to write upside-down, in zero-gravity environments, and allegedly underwater. Astronauts have made use of these pens in outer space.
As an art medium
The ballpoint pen has proven to be a versatile art medium for both professional artists and amateur doodlers. Low cost, availability, and portability are cited by practitioners as qualities which make this common writing tool a convenient art supply. Some artists use them within mixed-media works, while others use them solely as their medium-of-choice.
Effects not generally associated with ballpoint pens can be achieved. Traditional pen-and-ink techniques such as stippling and cross-hatching can be used to create half-tones or the illusion of form and volume. For artists whose interests necessitate precision line-work, ballpoints are an obvious attraction; ballpoint pens allow for sharp lines not as effectively executed using a brush. Finely applied, the resulting imagery has been mistaken for airbrushed artwork and photography, causing reactions of disbelief which ballpoint artist Lennie Mace refers to as the "Wow Factor".
Famous 20th-century artists including Andy Warhol, have utilized the ballpoint pen during their careers. Ballpoint pen artwork continues to attract interest in the 21st century, with many contemporary artists gaining recognition for their specific use of ballpoint pens as a medium. Korean-American artist Il Lee has been creating large-scale, abstract artwork since the late 1970s solely with ballpoint pens. Since the 1980s, Lennie Mace creates imaginative, ballpoint-only artwork of varying content and complexity, applied to unconventional surfaces including wood and denim. The artist coined terms such as "PENtings" and "Media Graffiti" to describe his varied output. British artist James Mylne has been creating photo-realistic artwork using mostly black ballpoints, sometimes with minimal mixed-media color. | Ballpoint pen | Wikipedia | 458 | 4519 | https://en.wikipedia.org/wiki/Ballpoint%20pen | Technology | Writing tools | null |
The ballpoint pen has several limitations as an art medium. Color availability and sensitivity of ink to light are among concerns of ballpoint pen artists. As a tool that uses ink, marks made with a ballpoint pen can generally not be erased. Additionally, "blobbing" ink on the drawing surface and "skipping" ink-flow require consideration when drawing with a ballpoint pen. Although the mechanics of ballpoint pens remain relatively unchanged, ink composition has evolved to solve certain problems over the years, resulting in unpredictable sensitivity to light and some extent of fading.
Manufacturing
The common ballpoint pen is a product of mass production, with components produced separately on assembly lines. Basic steps in the manufacturing process include the production of ink formulas, molding of metal and plastic components, and assembly. Marcel Bich (leading to Société Bic) was involved in developing the production of inexpensive ballpoint pens.
Although designs and construction vary between brands, basic components of all ballpoint pens are universal. Standard components of a ballpoint tip include the freely rotating "ball" itself (distributing the ink on the writing surface), a "socket" holding the ball in place, small "ink channels" that provide ink to the ball through the socket, and a self-contained "ink reservoir" supplying ink to the ball. In modern disposable pens, narrow plastic tubes contain the ink, which is compelled downward to the ball by gravity. Brass, steel, or tungsten carbide are used to manufacture the ball bearing-like points, then housed in a brass socket.
The function of these components can be observed at a larger scale in the ball-applicator of roll-on antiperspirant. The ballpoint tip delivers the ink to the writing surface while acting as a "buffer" between the ink in the reservoir and the air outside, preventing the quick-drying ink from drying inside the reservoir. Modern ballpoints are said to have a two-year shelf life, on average.
A ballpoint tip that can write comfortably for a long period of time is not easy to produce, as it requires high-precision machinery and thin high-grade steel alloy plates. China, which produces about 80 percent of the world's ballpoint pens, relied on imported ballpoint tips and metal alloys before 2017.
Standards
The International Organization for Standardization has published standards for ball point and roller ball pens: | Ballpoint pen | Wikipedia | 483 | 4519 | https://en.wikipedia.org/wiki/Ballpoint%20pen | Technology | Writing tools | null |
ISO 127561998: Drawing and writing instruments – Ball point pens – Vocabulary
ISO 12757-11998: Ball point pens and refills – Part 1: General use
ISO 12757-21998: Ball point pens and refills – Part 2: Documentary use (DOC)
ISO 14145-11998: Roller ball pens and refills – Part 1: General use
ISO 14145-21998: Roller ball pens and refills – Part 2: Documentary use (DOC)
Guinness World Records
The world's largest functioning ballpoint pen was made by Acharya Makunuri Srinivasa in India. The pen measures long and weighs .
The world's most popular pen is the Bic Cristal, with the 100 billionth model sold in September, 2006. The Bic Cristal was launched in December 1950 and roughly 57 are sold per second. | Ballpoint pen | Wikipedia | 189 | 4519 | https://en.wikipedia.org/wiki/Ballpoint%20pen | Technology | Writing tools | null |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.