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A blue moon will rise
Jeff Bezos has a lot of money and a space company. It's going to happen.
by David Grossman
The Washington Post/The Washington Post/Getty Images
SpaceX and Blue Origin are getting locked into a new battle, as part of a second space race focused on corporations over countries.
Blue Origin, the firm founded in 2000 by Amazon CEO Jeff Bezos, receives a somewhat smaller share of coverage than its competitors, but its plans for the future are interesting. In May 2019 the company demonstrated a dramatic vision for life in space: giant artificial ecosystems, orbiting the Earth, providing easy transport to the planet and other cities. In the more short term, the company aims to develop the infrastructure that could support these future projects with the New Glenn heavy orbital launch rocket and Blue Moon lunar lander, the latter of which is expected to launch in 2024.
Inverse predicts that Blue Origin will meet its target and launch Blue Moon in the 2020s.
This is #7 on Inverse’s 20 predictions for the 2020s.
Blue Origin: the new space race gets underway
Blue Origin has just one flying machine right now, but it's making big progress. The New Shepard rocket completed its 12th test flight in December, and set a new record by completing six flights with a single booster. It's designed to take six passengers to the Karman line at the edge of space before coming back to Earth.
What comes next could be even more impressive. The Blue Moon lander, under development for the past three years, was unveiled at an event in May 2019. It can send 3.6 metric tons to the lunar surface in its cargo form, while another designed to stretch can carry 6.5 metric tons.
The lander is powered by the BE-7, an engine that can offer 10,000 pounds of thrust through burning liquid hydrogen and oxygen. Blue Origin completed a hotfire of the engine at the Marshall Space Flight Center in June 2019.
In October 2019, the project got a big boost when it announced plans to collaborate with Lockheed Martin, Northrop Grumman, and Draper to help meet NASA's goal of sending a human to the moon by 2024. The ambitious mission, part of the Artemis program, is expected to put the first woman on the moon. The partnership means that where Blue Moon will land on the moon, Lockheed Martin will build the ascent portion.
As for why Bezos is pouring his money into this? Because he envisions a future for space where one trillion humans live in the solar system, supported by an expanding array of floating craft.
“Do we want stasis and rationing, or do we want dynamism and growth?” Bezos said in May 2019. There's not guarantee of social dynamism or growth from Blue Origin's journeys. But at least on a technical level, the company seems to be making all the right moves.
As 2019 draws to a close, Inverse is looking to the future. These are our 20 predictions for science and technology for the 2020s. Some are terrifying, some are fascinating, and others we can barely wait for. This has been #7. Read a related story here.
Related Tags | f4f2d349-9c3f-4b40-8acd-39f751c8c0c6 | full_CC | 0 | true | false |
### Nuprl Lemma : rng_sum_swap
`∀[r:Rng]. ∀[k,m:ℕ]. ∀[F:ℕm ⟶ ℕk ⟶ |r|].`
` ((Σ(r) 0 ≤ i < m. Σ(r) 0 ≤ j < k. F[i;j]) = (Σ(r) 0 ≤ j < k. Σ(r) 0 ≤ i < m. F[i;j]) ∈ |r|)`
Proof
Definitions occuring in Statement : rng_sum: rng_sum rng: `Rng` rng_car: `|r|` int_seg: `{i..j-}` nat: `ℕ` uall: `∀[x:A]. B[x]` so_apply: `x[s1;s2]` function: `x:A ⟶ B[x]` natural_number: `\$n` equal: `s = t ∈ T`
Definitions unfolded in proof : or: `P ∨ Q` decidable: `Dec(P)` rng: `Rng` prop: `ℙ` and: `P ∧ Q` top: `Top` all: `∀x:A. B[x]` exists: `∃x:A. B[x]` satisfiable_int_formula: `satisfiable_int_formula(fmla)` not: `¬A` uimplies: `b supposing a` ge: `i ≥ j ` false: `False` implies: `P `` Q` nat: `ℕ` member: `t ∈ T` uall: `∀[x:A]. B[x]` true: `True` so_apply: `x[s]` so_apply: `x[s1;s2]` so_lambda: `λ2x.t[x]` squash: `↓T` subtype_rel: `A ⊆r B` guard: `{T}` iff: `P `⇐⇒` Q` rev_implies: `P `` Q` infix_ap: `x f y` lelt: `i ≤ j < k` int_seg: `{i..j-}` so_lambda: `λ2x y.t[x; y]`
Lemmas referenced : rng_wf nat_wf int_term_value_subtract_lemma int_formula_prop_not_lemma itermSubtract_wf intformnot_wf subtract_wf decidable__le rng_car_wf int_seg_wf less_than_wf ge_wf int_formula_prop_wf int_formula_prop_less_lemma int_term_value_var_lemma int_term_value_constant_lemma int_formula_prop_le_lemma int_formula_prop_and_lemma intformless_wf itermVar_wf itermConstant_wf intformle_wf intformand_wf full-omega-unsat nat_properties rng_zero_wf rng_sum_wf equal_wf squash_wf true_wf rng_sum_unroll_base iff_weakening_equal rng_sum_unroll_hi rng_plus_zero rng_plus_wf lelt_wf decidable__lt int_seg_properties infix_ap_wf rng_sum_plus
Rules used in proof : unionElimination because_Cache functionEquality axiomEquality independent_pairFormation sqequalRule voidEquality voidElimination isect_memberEquality dependent_functionElimination intEquality int_eqEquality lambdaEquality dependent_pairFormation independent_functionElimination approximateComputation independent_isectElimination natural_numberEquality lambdaFormation intWeakElimination rename setElimination hypothesis hypothesisEquality thin isectElimination sqequalHypSubstitution extract_by_obid cut introduction isect_memberFormation sqequalReflexivity computationStep sqequalTransitivity sqequalSubstitution functionExtensionality applyEquality imageElimination equalityTransitivity equalitySymmetry universeEquality imageMemberEquality baseClosed productElimination dependent_set_memberEquality
Latex:
\mforall{}[r:Rng]. \mforall{}[k,m:\mBbbN{}]. \mforall{}[F:\mBbbN{}m {}\mrightarrow{} \mBbbN{}k {}\mrightarrow{} |r|].
((\mSigma{}(r) 0 \mleq{} i < m. \mSigma{}(r) 0 \mleq{} j < k. F[i;j]) = (\mSigma{}(r) 0 \mleq{} j < k. \mSigma{}(r) 0 \mleq{} i < m. F[i;j]))
Date html generated: 2018_05_21-PM-03_15_09
Last ObjectModification: 2017_12_11-PM-05_05_44
Theory : rings_1
Home Index | ed39fb30-0853-4e42-a69b-8f00eabb5561 | https://nuprl.org/wip/Algebra/rings_1/rng_sum_swap.html | 0 | true | false |
Start Omhoog
Charlie Brooker's screen burn
'After making them sweat, Hansen reveals his camera crew. Ta da! You're on Paedle's About!'
Charlie Brooker, The Guardian, May 31, 2008
When a TV show makes you feel sorry for potential child rapists, you know it's doing something wrong. To Catch A Predator is that show. It hails from America, where it's not some wacky bit of far-out cable madness, but a mainstream network broadcast; a staple feature of Dateline NBC
(a sort of Tonight with Sir Trevor McDonald minus Sir Trevor).
Here's the set-up for this week's episode: fearless, crusading adult volunteers for an anti-paedo watchdog group called Perverted Justice go on the internet and pretend to be 13-year-old girls. They wait until contacted by grown men, play along with the conversation when the subject turns to sex, then invite them over for an illegal fumble.
When the men turn up, they're greeted by an attractive young actress (who could just about pass for 13) who leads them into the garden and asks them to wait by the hot tub while she changes into something sexier.
The men pace excitedly, awaiting Lolita's return. But oh! Out pops Dateline's Chris Hansen instead! He's male, pushing 50, and doesn't look like he wants to play. Their faces fall like the Twin Towers. They mistake him for a cop.
"Did you come to have sex with a 13-year-old?" he asks.
"Oh no, sir," they splutter, "nothing could be further from my mind."
Then he brings out a transcript of their original web chat and asks them a bunch of questions about it - not to titillate, no God no - but in order that we viewers might forge a better understanding of the twisted mindset of the child sex predator. And because it'll make us guffaw like cartoon donkeys when they desperately try to explain away all the references to blowjobs and penis size in their chat room chinwag. It's the back-pedalling Olympics.
After making them sweat for several minutes, Chris reveals his camera crew and tells them they're on national television. Ta da! You're on Paedle's About!
At this point their faces tend to fall still further. They start crying and begging. Some of them probably poo themselves, although they don't show that. But the worst is yet to come: at this point, Chris unexpectedly waves them goodbye, and they walk out, sighing with relief... only to walk face-first into a bunch of armed police who hurl them to the ground and arrest them.
Then we get to see them being interviewed AGAIN, this time by the police, who aren't quite as debonair and charming as Chris
(and are markedly less keen on poring over all the online sex talk than him).
And then it's over. Justice prevails - provided you overlook the several billion troubling aspects to the show.
The overpowering whiff of entrapment, for one thing.
The collusion between reporters, vigilante groups and police for another.
And that "attractive young actress" who greets them by the door: make no mistake, she's hot. And at 18, she's US legal.
Presumably someone at To Catch A Predator HQ sat down with a bunch of audition tapes and spooled through it, trying to find a sexy 18-year-old who could pass for 13. They'll have stared at girl after girl, umming and ahhing over their chest sizes, until they found just the right one. And like I say, she's hot. But if you fancy her, you're a paedophile.
It's a pity robot technology isn't more advanced than it is, because the ultimate To Catch A Predator show could do away with the actress altogether. Instead, the men would be greeted by a convincing 17-year-old android, who'd instantly start having sex with them.
But oh! Just before they reached climax, a hatch would open in the top of her head, and a robotic version of Chris Hansen's face would emerge on a big bendy metal neck, barking accusations at them, and then the android's vagina would snap shut, trapping the pervert in position, and the robot body would transform into a steel cage from which they couldn't escape, and start delivering near-fatal electric shocks every five minutes to the delight of a self-righteous, audience, chanting Justice Prevails, Justice Prevails. Justice Prevails. Forever.
Start Omhoog | a08d6e6e-7eab-40d3-9948-fb8e99381b3e | null | 5 | true | true |
Open access peer-reviewed chapter
# Statistical Thermodynamics of Material Transport in Non-Isothermal Mixtures
By Semen Semenov and Martin Schimpf
Submitted: November 3rd 2010Reviewed: April 24th 2011Published: November 2nd 2011
DOI: 10.5772/19482
## 1. Introduction
This chapter outlines a theoretical framework for the microscopic approach to material transport in liquid mixtures, and applies that framework to binary one-phase systems. The material transport in this approach includes no hydrodynamic processes related to the macroscopic transfer of momenta. In analyzing the current state of thermodynamic theory, we indicate critically important refinements necessary to use non-equilibrium thermodynamics and statistical mechanics in the application to material transport in non-isothermal mixtures.
## 2. Thermodynamic theory of material transport in liquid mixtures: Role of the Gibbs-Duhem equation
The aim of this section is to outline the thermodynamic approach to material transport in mixtures of different components. The approach is based on the principle of local equilibrium, which assumes that thermodynamic principles hold in a small volume within a non-equilibrium system. Consequently, a small volume containing a macroscopic number of particles within a non-equilibrium system can be treated as an equilibrium system. A detailed discussion on this topic and references to earlier work are given by Gyarmati (1970). The conditions required for the validity of such a system are that both the temperature and molecular velocity of the particles change little over the scale of molecular length or mean free path (the latter change being small relative to the speed of sound). For a gas, these conditions are met with a temperature gradient below 104 K cm-1; for a liquid, where the heat conductivity is greater, the speed of sound higher and the mean free path is small, this condition for local equilibrium is more than fulfilled, provided the experimental temperature gradient is below 104K cm-1.
Thermodynamic expressions for material transport in liquids have been established based on equilibrium thermodynamics (Gibbs and Gibbs-Duhem equations), as well as on the principles of non-equilibrium thermodynamics (thermodynamic forces and fluxes). For a review of these models, see (De Groot, 1952; De Groot, Mazur, 1962; Kondepudi, Prigogine, 1999; Haase, 1969).
Non-equilibrium thermodynamics is based on the entropy production expression
Σ=Je(1T)i=1NJi(μiT)E1
where Jeis the energy flux, Jiare the component material fluxes, Nis the number of the components, μiare the chemical potentials of components, and Tis the temperature. The energy flux and the temperature distribution in the liquid are assumed to be known, whereas the material concentrations are determined by the continuity equations
nit=JiE2
Hereniis the numerical volume concentration of component iand tis time. Non-equilibrium thermodynamics defines the material flux as
Ji=niLi(μiT)niLiQ(1T)E3
where Liand LiQare individual molecular kinetic coefficients. The second term on the right-hand side of Eq. (3) represents the cross effect between material flux and heat flux.
The chemical potentials are expressed through component concentrations and other physical parameters (De Groot, 1952; De Groot, Mazur, 1962; Kondepudi, Prigogine, 1999):
μκ=l=12μknlnlv¯kP+μkTTE4
Here Pis the internal macroscopic pressure of the system and v¯k=μk/Pis the partial molecular volume, which is nearly equivalent to the specific molecular volumevk. Substituting Eq. (4) into Eq. (3), and using parameterqi=LiQ/Li, termed the molecular heat of transport, we obtain the equation for component material flux:
Ji=niLiT[k=1Nμinknkv¯iP+(μiTμi+qiT)T]E5
Defining the relation between the heat of transport and thermodynamic parameters is a key problem because the Soret coefficient, which is the parameter that characterizes the distribution of components concentrations in a temperature gradient, is expressed through the heat of transport (De Groot, 1952; De Groot, Mazur, 1962). A number of studies that offer approaches to calculating the heat of transport are cited in (Pan S et al., 2007).
Eq. (5) must be augmented by an equation for the macroscopic pressure gradient in the system. The simplest possible approach is to consider the pressure to be constant (De Groot, 1952; De Groot, Mazur, 1962; Kondepudi, Prigogine, 1999; Haase, 1969; Landau, Lifshitz, 1959), but pressure cannot be constant in a system with a non-uniform temperature and concentration. This issue is addressed with a well-known expression referred to as the Gibbs-Duhem equation (De Groot, 1952; De Groot, Mazur, 1962; Kondepudi, Prigogine, 1999; Haase, 1969; Landau, Lifshitz, 1959; Ghorayeb, Firoozabadi, 2000; Pan S et al., 2007):
P=i=1Nni(k=1Nμinknk+μiTT)E6
The Gibbs-Duhem equation defines the macroscopic pressure gradient in a thermodynamic system. In equilibrium thermodynamics the equation defines the potentiality of the thermodynamic functions (Kondepudi, Prigogine, 1999). In equilibrium thermodynamics the change in the thermodynamic function is determined only by the initial and final states of the systems, without consideration of the transition process itself. In non-equilibrium thermodynamics, Eq. (5) plays the role of expressing mechanical equilibrium in the system. According to the Prigogine theorem (De Groot, 1952; De Groot, Mazur, 1962; Kondepudi, Prigogine, 1999; Haase, 1969), pressure gradient cancels the volume forces expressed as the gradients of the chemical potentials and provides mechanical equilibrium in a thermodynamically stable system. However, in a non-isothermal system, the same authors considered a constant pressure and the left- and right-hand side of Eq. (6) were assumed to be zero simultaneously, which is both physically and mathematically invalid.
Substituting Eq. (6) into Eq. (5) we obtain the following equation for material flux:
Ji=ϕiLiviT[(1ϕi)(k=1Nμiϕkϕk+μiTT)kiNviϕkvkl=1Nμkϕlϕl+μkTT(μi+qi)TT]E7
In Eq. (7), the numeric volume concentrations of the components are replaced by their volume fractionsϕi=nivi, which obey the equation
i=1Nϕi=1E8
Using Eq. (8) and the standard rule of differentiation of a composite function
μk[ϕl,ϕ1(...,ϕl,...)]ϕlϕl=μkϕlϕl+μkϕ1ϕ1ϕlϕl=2μkϕlϕlE9
we can eliminate ϕ1and obtain Eq. (7) in a more compact form:
Ji=LiTkNϕivi[ϕk(2l>1Nμikϕlϕl+μikTT)(μi+qi)TT]E10
Hereϕ1is expressed through the other volume fractions using Eq. (8), and the following combined chemical potential is introduced:
μik=μivivkμkE11
We note that the volume fraction selected for elimination is arbitrary (any other volume fraction can be eliminated in the same manner), and that in subsequent mathematical expressions, we express the volume fraction of the first component through that of the others using Eq. (8).
Equations for the material fluxes are usually augmented by the following equation, which relates the material fluxes of components (De Groot, 1952; De Groot, Mazur, 1962; Kondepudi, Prigogine, 1999; Haase, 1969; Ghorayeb, Firoozabadi, 2000; Pan S et al., 2007):
i=1NviJi=0E12
Eq. (12) expresses the conservation mass in the considered system and the absence of any hydrodynamic mass transfer. Also, Eq. (12) is used to eliminate one of the components from the series of component fluxes expressed by Eq. (10). That material flux that is replaced in this way is arbitrary, and the resulting concentration distribution will depend on which flux is selected. The result is not significant in a dilute system, but in non-dilute systems this practice renders an ambiguous description of the material transport processes.
In addition to being mathematically inconsistent with Eq. (12) because there are N+1equations [i.e., NEq. (10) plus Eq. (12)] for N-1independent component concentrations, Eq. (10) predicts a drift in a pure liquid subjected to a temperature gradient. Thus, at ϕi=1Eq. (10) predicts
Ji=LiT(μi+qi)viTTE13
This result contradicts the basic principle of local equilibrium, and the notion of thermodiffusion as an effect that takes place in mixtures only. Moreover, Eq. (13) indicates that the achievement of a stationary state in a closed system is impossible, since material transport will occur even in a pure liquid.
The contradiction that a system cannot reach a stationary state, as expressed in Eq. (13), can be eliminated if we assume
qi=μiE14
With such an assumption Eq. (10) can be cast in the following form:
Ji=LiTkNϕiϕkvi(2l>1Nμikϕlϕl+μikTT)E15
Because the kinetic coefficients are usually calculated independently from thermodynamics, the material fluxes expressed by Eq. (15) cannot satisfy Eq. (12) for the general case. But in a closed and stationary system, whereJi=0, Eqs. (12) and (15) become consistent. In this case, any component flux can be expressed by Eq. (15) through summation of the other equations.
The condition of mechanical equilibrium for an isothermal homogeneous system, as well as the use of Eqs. (l) – (6) for non-isothermal systems, are closely related to the principle of local equilibrium (De Groot, 1952; De Groot, Mazur, 1962; Kondepudi, Prigogine, 1999; Haase, 1969). As argued in (Duhr, Braun, 2006; Weinert, Braun; 2008), thermodiffusion violates local equilibrium because the change in free energy across a particle is typically comparable to the thermal energy of the particle. However, their calculations predict that even for large (micron size) particles, the energy difference is no more than a few percent of kT.But the local equilibrium is determined by processes at molecular level, as will be discussed below, and this argumentation cannot be accepted.
## 3. Dynamic pressure gradient in open and non-stationary systems: Thermodynamic equations of material transport with the Soret coefficient as a thermodynamic parameter
Expressing the heats of transport by Eq. (14), we derived a set of consistent equations for material transport in a stationary closed system. However, expression for the heat of transport itself cannot yield consistent equations for material transport in a non-stationary and open system.
In an open system, the flux of a component may be nonzero because of transport across the system boundaries. Also, in a closed system that is non-stationary, the component material fluxes Jican be nonzero even though the total material flux in the system,J=i=1NviJi, is zero. In both these cases, the Gibbs-Duhem equation can no longer be used to determine the pressure in the system, and an alternate approach is necessary.
In previous works (Schimpf, Semenov, 2004; Semenov, Schimpf, 2005), we combined hydrodynamic calculations of the kinetic coefficients with the Fokker-Planck equations to obtain material transfer equations that contain dynamic parameters such as the cross-diffusion and thermal diffusion coefficients. In that approach, the macroscopic gradient of pressure in a binary system was calculated from equations of continuity of the same type as expressed by Eqs. (2) and (8). This same approach may be used for solving the material transport equations obtained by non-equilibrium thermodynamics.
In this approach, the continuity equations [Eq. (2)] are first expressed in the form
ϕit=ϕiLiT(2k>1Nμiϕkϕkv¯iP+μiTT)E16
Summing Eq. (16) for each component and utilizing Eq. (8) we obtain the following equation for the dynamic pressure gradient in an open non-stationary system:
P=[JT+i=1NϕiLi(2k>1Nμiϕkϕk+μiTT)]/i=1NϕiLiv¯iE17
Substituting Eq. (17) into Eq. (16) we obtain the material transport equations:
ϕit=ϕiLiT{[JT+j=1NϕjvjLj(2k>1Nμijϕkϕk+μijTT)]/k=1NϕkvkLk}E18
Comparing Eq. (18) with Eq. (15) for a stationary mixture shows that former contains an additional drift term ϕiviLiJk=1NϕkvkLkproportional to the total material flux through the open system. The term JTk=1NϕkvkLkin Eq. (17) describes the contribution of that drift to the pressure gradient. This additional component of the total material flux is attributed to barodiffusion, which is driven by the dynamic pressure gradient defined by Eq. (17). This dynamic pressure gradient is associated with viscous dissipation in the system. Parameter Jis independent of position in the system but is determined by material transfer across the system boundaries, which may vary over time.
If the system is open but stationary, molecules entering it through one of its boundary surfaces can leave it through another, thus creating a molecular drift that is independent of the existence of a temperature or pressure gradient. This drift is determined by conditions at the boundaries and is independent of any force applied to the system. For example, the system may have a component source at one boundary and a sink of the same component at opposite boundary. As molecules of a given species move between the two boundaries, they experience viscous friction, which creates a dynamic pressure gradient that induces barodiffusion in all molecular species. The pressure gradient that is induced by viscous friction in such a system is not considered in the Gibbs-Duhem equation.
Equations (6), (7), and (15) describe a system in hydrostatic equilibrium, without viscous friction caused by material flux due to material exchange through the system boundaries. Unlike the Gibbs-Duhem equation, Eq. (17) accounts for viscous friction forces and the resulting dynamic pressure gradient. For a closed stationary system, in whichJ=0andϕt=0, Eq. (18) is transformed into
k>1N(2j=1Nμijϕk)ϕk+(j=1NμijT)T=0E19
There are thermal diffusion experiments in which the system experiences periodic temperature changes. An example is the method used described by (Wiegand, Kohler, 2002), where thermodiffusion in liquids is observed within a dynamic temperature grating produced using a pulsed infrared laser. Because this technique involves changing the wall temperature, which changes the equilibrium adsorption constant, material fluxes vary with time, creating a periodicity in the inflow and outflow of material. A preliminary analysis shows that material fluxes to and from the walls have relaxation times on the order of a few microseconds until equilibrium is attained, and that such non-stationary material fluxes can be observed using dynamic temperature gratings.
The Soret coefficient is a common parameter used to characterize material transport in temperature gradients. For binary systems, Eq. (19) can be used to define the Soret coefficient as
ST=μ21PT2ϕ2(1ϕ2)μ21Pϕ2E20
where subscript Pis used to indicate that the derivatives are taken at constant pressure, as is the case in Eqs. (4) and (6). We can solve Eqs. (19) to express the “partial” Soret coefficient STkfor the k’th component through a factor of proportionality between ϕkandT.
## 4. Statistical mechanics of material transport: Chemical potentials at constant volume and pressure and the Laplace component of pressure in a molecular force field
The chemical potential at constant volume can be calculated using a modification of an expression derived in (Kirkwood, Boggs, 1942; Fisher, 1964):
μiV=μ0i+01dλj=1NϕjvjVoutigij(r,λ)Φij(r)dvE21
Here
μ0i=32kTln2πmikTh2+kTlnϕivikTlnZrotikTlnZvibiE22
is the chemical potential of an ideal gas of the respective non-interacting molecules (related to their kinetic energy), his Planck’s constant, miis the mass of the molecule, Zrotiand Zvibiare its rotational and vibrational statistical sums, respectively, and Voutiis the volume external to a molecule of the i’th component. The molecular vibrations make no significant contribution to the thermodynamic parameters except in special situations, which will not be discussed here. The rotational statistical sum for polyatomic molecules is written as (Landau, Lifshitz, 1980)
Zrot=πγh3(8π2kT)3I1I2I3E23
where γis the symmetry value, which is the number of possible rotations about the symmetry axes carrying the molecule into itself. For H2O and C2H5OH,γ=2; for NH3,γ=3; for CH4 and C6H6,γ=12. I1,I2,andI3are the principal values of the tensor of the moment of inertia.
In Eq. (21), parameter λdescribes the gradual “switching on” of the intermolecular interaction. A detailed description of this representation can be found in (Kirkwood, Boggs, 1942; Fisher, 1964). Parameter ris the distance between the molecule of the surrounding liquid and the center of the considered molecule; gij(r,λ)is the pair correlative function, which expresses the probability of finding a molecule of the surrounding liquid at r(r=|r|) if the considered molecule is placed atr=0; and Φijis the molecular interaction potential, known as the London potential (Ross, Morrison, 1988):
Φij=εij(σijr)6E24
Hereεijis the energy of interaction and σijis the minimal molecular approach distance. In the integration overVouti, the lower limit isr=σij.
There is no satisfactory simple method for calculating the pair correlation function in liquids, although it should approach unity at infinity. We will approximate it as
gij(r,λ)=1E25
With this approximation we assume that the local distribution of solvent molecules is not disturbed by the particle under consideration. The approximation is used widely in the theory of liquids and its effectiveness has been shown. For example, in (Bringuier, Bourdon, 2003, 2007), it was used in a kinetic approach to define the thermodiffusion of colloidal particles. In (Schimpf, Semenov, 2004; Semenov, Schimpf, 2000, 2005) the approximation was used in a hydrodynamic theory to define thermodiffusion in polymer solutions. The approximation of constant local density is also used in the theory of regular solutions (Kirkwood, 1939). With this approximation we obtain
μiV=μ0i+j=1NϕjvjVoutiΦij(r)dvE26
The terms under the summation sign are a simple modification of the expression obtained in (Bringuier, Bourdon, 2003, 2007).
In our calculations, we will use the fact that there is certain symmetry between the chemical potentials contained in Eq. (11). The term vivkμkcan be written asNikμk, where Nik=vivkis the number of the molecules of the k’th component that can be placed within the volume vibut are displaced by a molecule of i’th component. Using the known result that free energy is the sum of the chemical potentials we can say thatNikμkis the free energy or chemical potential of a virtual molecular particle consisting of molecules of the k’th component displaced by a molecule of the i’th component. For this reason we can extend the results obtained in the calculations of molecular chemical potential μiVof the second component to calculations of parameter NikμkVby a simple change in the respective designationsik. Regarding the concentration of these virtual particles, there are at least two approaches allowed:
1. we can assume that the volume fraction of the virtual particles is equal to the volume fraction of the real particles that displace molecules of the k’th component, i.e., their numeric concentration isϕivi. This approach means that only the actually displaced molecules are taken into account, and that they are each distinguishable from molecules of the k’th component in the surrounding liquid.
2. we can take into account the indistinguishability of the virtual particles. In this approach any group of the Nikmolecules of the k’th component can be considered as a virtual particle. In this case, the numeric volume concentration of these virtual molecules isϕkvi.
We have chosen to use the more general assumption b).
Using Eqs. (21) and (22), along with the definition of a virtual particle outlined above, we can define the combined chemical potential at constant volume μikV*as
μikV*=+kT(32lnmimNik+lnϕiϕk+lnZrotiZrotNik)+j=1NϕjvjVoutiΦij(r)dvj=1NϕjvjVoutiΦkjNkj(r)dvE27
where mNik=mkNikand ZrotNikare the mass and the rotational statistical sum of the virtual particle, respectively. In Eq. (27), the total interaction potential NikΦkjof the molecules included in the virtual particle is written asΦjNik. We will use the approximation
ΦjNik=NikΦkj=εkj(σijr)6E28
This approximation corresponds to the virtual particle having the size of a molecule of the i’th component and the energetic parameter of the k’th component.
In further development of the microscopic calculations it is important that the chemical potential be defined at constant pressure. Chemical potentials at constant pressure are related to those at constant volume μiVby the expression
μiP=μiV+VoutiΠidvE29
HereΠiis the local pressure distribution around the molecule. Eq. (29) expresses the relation between the forces acting on a molecular particle at constant versus changing local pressure. This equation is a simple generalization of a known equation (Haase, 1969) in which the pressure gradient is assumed to be constant along a length about the particle size.
Next we calculate the local pressure distributionΠi, which is widely used in hydrodynamic models of kinetic effects in liquids (Ruckenstein, 1981; Anderson, 1989; Schimpf, Semenov, 2004; Semenov, Schimpf, 2000, 2005). The local pressure distribution is usually obtained from the condition of the local mechanical equilibrium in the liquid around i’th molecular particle, a condition that is written as[Πi+j=1NϕjvjΦij(r)]=0. In (Semenov, Schimpf, 2009; Semenov, 2010) the local pressure distribution is used in a thermodynamic approach, where it is obtained by formulating the condition for establishing local equilibrium in a thin layer of thickness land area Swhen the layer shifts from position rto position r+dr. In this case, local equilibrium expresses the local conservation of specific free energy Fi(r)=Πi(r)+j=1NϕjvjΦij(r)in such a shift when the isothermal system is placed in a force field of the i’th molecule.
In the layer forming a closed surface, the change in the free energy is written as:
dFi(r)=[j=1NϕjvjΦij(r)+Πi]lSdr+j=1N[ϕjvjΦij(r)]ldS=0E30
where we consider changes in free energy due to both a change in the parameters of the layer volume (dV=Sdr) and a changedSin the area of the closed layer. For a spherical layer, the changes in volume and surface area are related asdV=2rdS, and we obtain the following modified equation of equilibrium for a closed spherical surface:
[j=1NϕjvjΦij(r)+Πi]+2j=1NϕjvjΦij(r)rr0=0E31
wherer0is the unit radial vector. The pressure gradient related to the change in surface area has the same nature as the Laplace pressure gradient discussed in (Landau, Lifshitz, 1980). Solving Eq. (31), we obtain
Πi=j=1Nϕjvj[Φij(r)+r2Φij(r')r'dr']E32
Substituting the pressure gradient from Eq. (32) into Eq. (29), and using Eqs. (24), (27), and (28), we obtain a general expression for the gradient in chemical potential at constant pressure in a non-isothermal and non-homogeneous system. We will not write the general expression here, rather we will derive the expression for binary systems.
## 5. The Soret coefficient in diluted binary molecular mixtures: The kinetic term in thermodiffusion is related to the difference in the mass and symmetry of molecules
In this section we present the results obtained in (Semenov, 2010, Semenov, Schimpf, 2011a). In diluted systems, the concentration dependence of the chemical potentials for the solute and solvent is well-known [e.g., see (Landau, Lifshitz, 1980)]:μ2(ϕ)=kTlnϕ, and μ1is practically independent of solute concentrationϕ=ϕ2. Thus, Eq. (20) for the Soret coefficient takes the form:
ST=μP*T2kTE33
whereμP*is
μ21P*E34
.
The equation for combined chemical potential at constant volume [Eq. (28)] using assumption b) in Section 3 takes the form
μV*=kT(32lnm2mN1lnϕ1ϕ+lnZrot1ZrotN1)+4πRΦ21(r)Φ11N1(r)v1r2drE35
where N1=N21is the number of solvent molecules displaced by molecule of the solute, Φ11N1is the potential of interaction between the virtual particle and a molecule of the solvent. The relation ϕ1=1ϕis also used in deriving Eq. (34). Because ln[ϕ/(1ϕ)]atϕ0, we expect the use of assumption a) in Section 3 for the concentration of virtual particles will yield a reasonable physical result.
In a dilute binary mixture, the equation for local pressure [Eq. (32)] takes the form
Πi=j=1NΦi1(r)v1+r2Φi1(r')v1r'dr'E36
where index iis related to the virtual particle or solute.
Using Eqs. (29), (34), we obtain the following expression for the temperature-induced gradient of the combined chemical potential of the diluted molecular mixture:
μP=kT(32lnm2mN1+lnZrot1ZrotN1)+Voutα1dvv1ϑTrΦ21(r')Φ11N1(r')r'dr'E37
Hereα1is the thermal expansion coefficient for the solvent and ϑTis the tangential component of the bulk temperature gradient. After substituting the expressions for the interaction potentials defined by Eqs. (23), (24), and (28) into Eq. (36), we obtain the following expression for the Soret coefficient in the diluted binary system:
ST=12T[32ln(m2mN1)+ln(γN1(I1I2I3)2γ2(I1I2I3)N1)]+π2α1σ123ε1218v1kT(ε11ε121)E38
In Eq. (37), the subscripts 2andN1are used again to denote the real and virtual particle, respectively.
The Soret coefficient expressed by Eq. (37) contains two main terms. The first term corresponds to the temperature derivative of the part of the chemical potential related to the solute kinetic energy. In turn, this kinetic term contains the contributions related to the translational and rotational movements of the solute in the solvent. The second term is related to the potential interaction of solute with solvent molecules. This potential term has the same structure as those obtained by the hydrodynamic approach in (Schimpf, Semenov, 2004; Semenov, Schimpf, 2005).
According to Eq. (37), both positive (from hot to cold wall) and negative (from cold to hot wall) thermodiffusion is possible. The molecules with larger mass (m2>mN1) and with a stronger interactions between solvent molecules (ε11>ε12) should demonstrate positive thermodiffusion. Thus, dilute aqueous solutions are expected to demonstrate positive thermophoresis. In (Ning, Wiegand, 2006), dilute aqueous solutions of acetone and dimethyl sulfoxide were shown to undergo positive thermophoresis. In that paper, a very high value of the Hildebrand parameter is given as an indication of the strong intermolecular interaction for water. More specifically, the value of the Hildebrand parameter exceeds by two-fold the respective parameters for other components.
Since the kinetic term in the Soret coefficient contains solute and solvent symmetry numbers, Eq. (37) predicts thermodiffusion in mixtures where the components are distinct only in symmetry, while being identical in respect to all other parameters. In (Wittko, Köhler, 2005) it was shown that the Soret coefficient in the binary mixtures containing the isotopically substituted cyclohexane can be in general approximated as the linear function
ST=SiT+amΔM+biΔIE39
where SiTis the contribution of the intermolecular interactions, amand biare coefficients, while ΔMandΔIare differences in the mass and moment of inertia, respectively, for the molecules constituting the binary mixture. According to Eq. (37), the coefficients are defined by
am=34TmN1E40
bi=(γN1)24T(γ2)2(I1I2I3)N1E41
In (Wittko, Köhler, 2005) the first coefficient was empirically determined for cyclohexane isomers to be am=0.99103K1at room temperature (T=300 K), while Eq. (39) yieldsam=0.03103K1(M1=84). There are several possible reasons for this discrepancy. The first term on the right side of Eq. (38) is not the only term with a mass dependence, as the second term also depends on mass. The empirical parameter amalso has an implicit dependence on mass that is not in the theoretical expression given by Eq. (39). The mass dependence of the second term in Eq. (37) will be much stronger when a change in mass occurs at the periphery of the molecule.
A sharp change in molecular symmetry upon isotopic substitution could also lead to a discrepancy between theory and experiment. Cyclohexane studied in (Wittko, Köhler, 2005) has high symmetry, as it can be carried into itself by six rotations about the axis perpendicular to the plane of the carbon ring and by two rotations around the axes placed in the plane of the ring and perpendicular to each other. Thus, cyclohexane hasγN1=24. The partial isotopic substitution breaks this symmetry. We can start from the assumption that for the substituted molecules,γ2=1. When the molecular geometry is not changed in the substitution and only the momentum of inertia related to the axis perpendicular to the ring plane is changed, the relative change in parameter bican be written as
(γN1)2(I1I2I3)2(γ2)2(I1I2I3)14T(γ2)2(I1I2I3)N1=(γN1)2(m2mN1)4T(γ2)2mN1+(γN1)2(γ2)24T(γ2)2E42
Eq. (41) yields
am=14TmN1[3+(γN1γ2)2]E43
Using the above parameters and Eq. (42), we obtainam5.7103K1, which is still about six-times greater than the empirical value from (Wittko, Köhler, 2005). The remaining discrepancy could be due to our overestimation of the degree of symmetry violation upon isotopic substitution. The true value of this parameter can be obtained withγ223. One should understand that the value of parameter γ2is to some extent conditional because the isotopic substitutions occur at random positions. Thus, it may be more relevant to use Eq. (42) to evaluate the characteristic degree of symmetry from an experimental measurement of amrather than trying to use theoretical values to predict thermodiffusion.
## 6. The Soret coefficient in diluted colloidal suspensions: Size dependence of the Soret coefficient and the applicability of thermodynamics
While thermodynamic approaches yield simple and clear expressions for the Soret coefficient, such approaches are the subject of rigorous debate. The thermodynamic or “energetic” approach has been criticized in the literature. Parola and Piazza (2004) note that the Soret coefficient obtained by thermodynamics should be proportional to a linear combination of the surface area and the volume of the particle, since it contains the parameterμikgiven by Eq. (11). They argue that empirical evidence indicates the Soret coefficient is directly proportional to particle size for colloidal particles [see numerous references in (Parola, Piazza, 2004)], and is practically independent of particle size for molecular species. By contrast, Duhr and Braun (2006) show the proportionality between the Soret coefficient and particle surface area, and use thermodynamics to explain their empirical data. Dhont et al (2007) also reports a Soret coefficient proportional to the square of the particle radius, as calculated by a quasi-thermodynamic method.
Let us consider the situation in which a thermodynamic calculation for a large particle as said contradicts the empirical data. For large particles, the total interaction potential is assumed to be the sum of the individual potentials for the atoms or molecules which are contained in the particle
Φi1*(r)=VinidVinviΦi1(|rir|)E44
Here Viniis the internal volume of the real or virtual particle andΦi1(|rir|)is the respective intermolecular potential given by Eq. (24) or (28) for the interaction between a molecule of a liquid placed at r(r=|r|) and an internal molecule or atom placed atri. Such potentials are referred to as Hamaker potential, and are used in studies of interactions between colloidal particles (Hunter, 1992; Ross, Morrison, 1988). In this and the following sections, viis the specific molecular volume of the atom or molecule in a real or virtual particle, respectively.
For a colloidal particle with radius R>>σij, the temperature distribution at the particle surface can be used instead of the bulk temperature gradient (Giddings et al, 1995), and the curvature of the particle surface can be ignored in calculating the respective integrals. This corresponds to the assumption that r'Randdv4πR2drin Eq. (36). To calculate the Hamaker potential, the expression calculated in (Ross, Morrison, 1988), which is based on the London potential, can be used:
Φi1*(y)=εi16σ213v2(1y+12+y+lny2+y)E45
Herey=xσ21, and xis the distance from the particle surface to the closest solvent molecule surface. Using Eqs. (36) and (44) we can obtain the following expression for the Soret coefficient of a colloidal particle:
ST=π2α1Rσ212ε212(n+2)v2kTσ213v1(ε11ε211)E46
Here nis ratio of particle to solvent thermal conductivity. The Soret coefficient for the colloidal particle is proportional toRσ215v1v2. In practice, this means that STis proportional to Rσ21since the ratio σ216v1v2is practically independent of molecular size. This proportionality is consistent with hydrodynamic theory [e.g., see (Anderson, 1989)], as well as with empirical data. The present theory explains also why the contribution of the kinetic term and the isotope effect has been observed only in molecular systems. In colloidal systems the potential related to intermolecular interactions is the prevailing factor due to the large value ofRσ212v1. Thus, the colloidal Soret coefficient is Rσ21times larger than its molecular counterpart. This result is also consistent with numerous experimental data and with hydrodynamic theory.
## 7. The Soret coefficient in diluted suspensions of charged particles: Contribution of electrostatic and non-electrostatic interactions to thermodiffusion
In this section we present the results obtained in (Semenov, Schimpf, 2011b). The colloidal particles discussed in the previous section are usually stabilized in suspensions by electrostatic interactions. Salt added to the suspension becomes dissociated into ions of opposite electric charge. These ions are adsorbed onto the particle surface and lead to the establishment of an electrostatic charge, giving the particle an electric potential. A diffuse layer of charge is established around the particle, in which counter-ions are accumulated. This diffuse layer is the electric double layer. The electric double layer, where an additional pressure is present, can contribute to thermodiffusion. It was shown in experiments that particle thermodiffusion is enhanced several times by the addition of salt [see citations in (Dhont, 2004)].
For a system of charged colloidal particles and molecular ions, the thermodynamic equations should be modified to include the respective electrostatic parameters. The basic thermodynamic equations, Eqs. (4) and (6), can be written as
μi=k=1Nμinknkv¯iP+μiTT+eiEE47
P=i=1Nni(k=1Nμinknk+μiTT+eiE)E48
where ei=μiΦis the electric charge of the respective ion, Φis the macroscopic electrical potential, and E=Φis the electric field strength. Substituting Eq. (47) into Eq. (46) we obtain the following material transport equations for a closed and stationary system:
Ji=0=LiTkNϕiϕkvi(l=1Nμikϕlϕl+μikTTμikΦE)E49
where
μikΦ=eiNikekE50
We will consider a quaternary diluted system that contains a background neutral solvent with concentrationϕ1, an electrolyte salt dissociated into ions with concentrationsϕ±=n±v±, and charged particles with concentrationϕ2that is so small that it makes no contribution to the physicochemical parameters of the system. In other words, we consider the thermophoresis of an isolated charged colloidal particle stabilized by an ionic surfactant. With a symmetric electrolyte, the ion concentrations are equal to maintain electric neutrality
vϕ+=v+ϕE51
In this case we can introduce the volume concentration of salt as ϕs=ϕ+(1+vv+)=ϕ(1+v+v)and formulate an approximate relationship in place of the exact form expressed by Eq. (8):
ϕs+ϕ1=1E52
Here the volume contribution of charged particles is ignored since their concentration is very low, i.e.ϕ2ϕsϕ1. Due to electric neutrality, the ion concentrations will be equal at any salt concentration and temperature, that is, the chemical potentials of the ions should be equal: μ+=μ(Landau, Lifshitz, 1980).
Using Eqs. (48) – (51) we obtain equations for the material fluxes, which are set to zero:
J2=0=ϕ2L2v2T[μ21ϕ2ϕ2+3μ21ϕsϕs+μ21TT+e2E]E53
J=0=ϕLvT(3μ1ϕsϕs+μ1TTeE)E54
J+=0=ϕ+L+v+T(3μ+1ϕsϕs+μ+1TT+eE)E55
where e+=e=e(symmetric electrolyte). We will not write the equation for the flux of background solventJ1because it yields no new information in comparison with Eqs. (52) -54), as shown above. Solving Eqs. (52) – (54), we obtain
ϕs=T(μ+1+μ1)T/3(μ+1+μ1)ϕsE56
2eE=3(μ1μ+1)ϕsϕs+(μ1μ+1)TTE57
Eq. (55) allows us to numerically evaluate the concentration gradient as
ϕsϕsSTsTE58
where STs103is the characteristic Soret coefficient for the salts. Salt concentrations are typically around 10-2-10-1mol/L,that isϕs104or lower. A typical maximum temperature gradient isT104K/cm. These values substituted into Eq. (57) yieldϕs104103cm1. The same evaluation applied to parameters in Eq. (56) shows that the first term on the right side of this equation is negligible, and the equation for thermoelectric power can be written as
E(μ1μ+1)TT2e=v+v2ev1μ1TTE59
For a non-electrolyte background solvent, parameter μ1/Tcan be evaluated asμ1/Tα1kT, where α1is the thermal expansion coefficient of the solvent (Semenov, Schimpf, 2009; Semenov, 2010). Usually, in liquids the thermal expansion coefficient is low enough (α1103K1) that the thermoelectric field strength does not exceed 1 V/cm. This electric field strength corresponds to the maximum temperature gradient discussed above. The electrophoretic velocity in such a field will be about 10-5-10-4cm/s. The thermophoretic velocities in such temperature gradients are usually at least one or two orders of magnitude higher.
These evaluations show that temperature-induced diffusion and electrophoresis of charged colloidal particle in a temperature gradient can be ignored, so that the expression for the Soret coefficient of a diluted suspension of such particles can be written as
S2T=ϕ2ϕ2T=μ21PTϕ2μ21Pϕ2=1kTμ21PTE60
Eq. (59) can also be used for microscopic calculations.
For an isolated particle placed in a liquid, the chemical potential at constant volume can be calculated using a modified procedure mentioned in the preceding section. In these calculations, we use both the Hamaker potential and the electrostatic potential of the electric double layer to account for the two types of the interactions in these systems. The chemical potential of the non-interacting molecules plays no role for colloid particles, as was shown above.
In a salt solution, the suspended particle interacts with both solvent molecules and dissolved ions. The two interactions can be described separately, as the salt concentration is usually very low and does not significantly change the solvent density. The first type of interaction uses Eqs. (25) and the Hamaker potential [Eq. (44)].
For the electrostatic interactions, the properties of diluted systems may be used, in which the pair correlative function has a Boltzmann form (Fisher, 1964; Hunter, 1992). Since there are two kinds of ions, Eq. (21) for the “electrostatic” part of the chemical potential at constant volume can be written as
μ2e=4πns01dλR(eλΦekTeλΦekT)Φe(r)r2dr=4πnskTR(eΦekT+eΦekT2)r2drE61
where ns=ϕsv++vis the numeric volume concentration of salt, and Φe=eΦis the electrostatic interaction energy.
Eq. (32) expressing the equilibrium condition for electrostatic interactions is written as
[(n+n)Φe(r)+Π]+2(n+n)Φe(r)r0R=0E62
wherer0is the unit radial vector. In Eq. (61) it is assumed that the particle radius is much larger than the characteristic thickness of the electric double layer. Solving Eq. (62) assuming a Boltzmann distribution for the ion concentration, as in (Ruckenstein, 1981; Anderson, 1989), we obtain
Πe=nskT(eΦekT+eΦekT2)2nsRr(eΦekTeΦekT)rΦe(r')dr'E63
Substituting the pressure gradient calculated from Eq. (62) into Eq. (29), utilizing Eq. (60), and considering the temperature-induced gradients related to the temperature dependence of the Boltzmann exponents, we obtain the temperature derivative in the gradient of the chemical potential for a charged colloidal particle, which is related to the electrostatic interactions in its electric double layer:
μ2PeT=4πnskR(n+2)Rdrr(eΦekT+eΦekT)Φe2(r')(kT)2dr'E64
Here nis again the ratio of particle to solvent thermal conductivity. For low potentials (Φe<kT), where the Debye-Hueckel theory should work, Eq. (63) takes the form
μ2PeT=8πnskR(n+2)RdrrΦe2(r')(kT)2dr'E65
Using an exponential distribution for the electric double layer potential, which is characteristic for low electrokinetic potentialsζ, we obtain from Eq. (64)
μ2PeT=8πnskRλD2(n+2)(eζkT)2E66
where λDis the Debye length [for a definition of Debye length, see (Landau, Lifshitz, 1980; Hunter, 1992)].
Calculation of the non-electrostatic (Hamaker) term in the thermodynamic expression for the Soret coefficient is carried out in the preceding section [Eq. (45)]. Combining this expression with Eq. (65), we obtain the Soret coefficient of an isolated charged colloidal particle in an electrolyte solution:
ST=8πnsRλD2T(n+2)(eζkT)2+π2α1Rσ212ε212(n+2)v2kTσ213v1(ε11ε211)E67
This thermodynamic expression for the Soret coefficient contains terms related to the electrostatic and Hamaker interactions of the suspended colloidal particle. The electrostatic term has the same structure as the respective expressions for the Soret coefficient obtained by other methods (Ruckenstein, 1981; Anderson, 1989; Parola, Piazza, 2004; Dhont, 2004). In the Hamaker term, the last term in the brackets reflects the effects related to displacing the solvent by particle. It is this effect that can cause a change in the direction of thermophoresis when the solvent is changed. However, such a reverse in the direction of thermophoresis can only occur when the electrostatic interactions are relatively weak. When electrostatic interactions prevail, only positive thermophoresis can be observed, as the displaced solvent molecules are not charged, therefore, the respective electrostatic term is zero. The numerous theoretical results on electrostatic contributions leading to a change in the direction of thermophoresis are wrong due to an incorrect use of the principle of local equilibrium in the hydrodynamic approach [see discussion in (Semenov, Schimpf, 2005)].
The relative role of the electrostatic mechanism can be evaluated by the following ratio:
8πnsv2α1TλD2σ212v1σ213(eζ)2(ε11ε21)kTE68
The physicochemical parameters contained in Eq. (67) are separated into several groups and are collected in the respective coefficients. Coefficient nsv2α1Tcontains the parameters related to concentration and its change with temperature, λD2σ212is the coefficient reflecting the respective lengths of the interaction, v1σ213reflects the geometry of the solvent molecules, and (eζ)2(ε11ε21)kTis the ratio of energetic parameters for the respective interactions. Only the first two of these four terms are always significantly distinct from unity. The characteristic length of the interaction is much higher for electrostatic interactions. Also, the characteristic density of ions or molecules in a liquid, which are involved in their electrostatic interaction with the colloidal particle, is much lower than the density of the solvent molecules. The values of these respective coefficients are λD2σ212103and nsv2α1T103for typical ion concentrations in water at room temperature. The energetic parameter may be small, (~0.1) when the colloidal particles are compatible with the solvent. Characteristic values of the energetic coefficient range from 0.1-10. Combining these numeric values, one can see that the ratio given by Eq. (67) lies in a range of 0.1-10and is governed primarily by the value of the electrokinetic potential ζand the difference in the energetic parameters of the Hamaker interactionε11ε21. Thus, calculation of the ratio given by Eq. (67) shows that either the electrostatic or the Hamaker contribution to particle thermophoresis may prevail, depending on the value of the particle’s energetic parameters. In the region of high Soret coefficients, particle thermophoresis is determined by electrostatic interactions and is positive. In the region of low Soret coefficients, thermophoresis is related to Hamaker interactions and can have different directions in different solvents.
## 8. Material transport equation in binary molecular mixtures: Concentration dependence of the Soret coefficient
In this section we present the results obtained in (Semenov, 2011). In a binary system in which the component concentrations are comparable, the material transport equations defined by Eq. (18) have the form
ϕt=[L2ϕ(1ϕ)(2μϕϕ+μTT)/T(1ϕ+L2v2L1v1ϕ)]E69
Eq. (68) can be used in the thermodynamical definition of the Soret coefficient [Eq. (59)]. The mass and thermodiffusion coefficients can be calculated in the same way as the Soret coefficient.
The microscopic models used to calculate the Soret Coefficient in (Ghorayeb, Firoozabadi, 2000; Pan S et al., 2007) ignore the requirement expressed by Eq. (10) and cannot yield a description of thermodiffusion that is unambiguous. Although the material transport equations based on non-equilibrium thermodynamics were used, the fact that the chemical potential at constant pressure must be used was not taken into account. In these articles there is also the problem that in the transition to a dilute system the entropy of mixing does not become zero, yielding unacceptably large Soret coefficients even for pure components. An expression for the Soret coefficient was obtained in (Dhont et al, 2007; Dhont, 2004) by a quasi-thermodynamic method. However, the expressions for the thermodiffusion coefficient in those works become zero at high dilution, where the standard expression for osmotic pressure is used. These results contradict empirical observation.
Using Eq. (27) with the notion of a virtual particle outlined above, and substituting the expression for interaction potential [Eqs. (24, 28)], we can write the combined chemical potential at constant volume μV*as
μV*=kT(32lnm2mN1lnϕ1ϕ+lnZrot2ZrotN1)++ϕv2[Vout2Φ22(r)dvVout1Φ12N1(r)dv]+1ϕv1[Vout2Φ21(r)dvVout1Φ11N1(r)dv]E70
In order to proceed to the calculation of chemical potentials at constant pressure using Eq. (29), we must calculate the local pressure distributionΠiusing Eq. (32). We can subsequently use Eqs. (29) and (33) to obtain an expression for the gradient of the combined chemical potential at constant pressure in a non-isothermal and non-homogeneous system:
μP*=[kTϕ(1ϕ)a(ε11+βε22ε121β)]ϕ++a[α2βϕ(1ε22ε12)α1(1ϕ)(1ε11ε12)]Tk(32lnm2mN1lnϕ1ϕ+lnZrot2ZrotN1)TE71
Here αiis the thermal expansion coefficient for the respective component, β=v1σ223v2σ123is the parameter characterizing the geometrical relationship between the different component molecules, and a=π2σ123ε129v1is the energetic parameter similar to the respective parameter in the van der Waals equation (Landau, Lifshitz, 1980) but characterizing the interaction between the different kinds of molecules. Then, using Eqs. (20), (70), we can write:
ST=τ(1ϕ)S1TϕS2T+STkin4(ϕ1/2)2+τ1E72
where τ=T/Tcis the ratio of the temperature at the point of measurement to the critical temperatureTc=ak(ε11+βε22ε121β), where phase layering in the system begins. Assuming thatβ1, the condition for parameter Tcto be positive is asε11+ε22>2ε12. This means that phase layering is possible when interactions between the identical molecules are stronger than those between different molecules. Whenε11+ε22<2ε12, the present theory predicts absolute miscibility in the system.
At temperatures lower than some positiveTc, when τ<1only solutions in a limited concentration range can exist. It this temperature range, only mixtures withϕϕ1*, ϕϕ2*can exist, whereϕ1,2*=(1±1τ)/2, which is equivalent to the equation that defines the boundary for phase layering in phase diagrams for regular solutions, as discussed in (Kondepudi, Prigogine, 1999). SiT=αia[(εii/ε12)1]/2kTis the “potential” Soret coefficient related to intermolecular interactions in dilute systems. These parameters can be both positive and negative depending on the relationship between parameters εiiandε12. When the intermolecular interaction is stronger between identical solutes, thermodiffusion is positive, and vice versa. This corresponds to the experimental data of Ning and Wiegand (2006).
When simplifications are taken into account, the equations expressed by the non-equilibrium thermodynamic approach are equivalent to expressions obtained in our hydrodynamic approach (Schimpf, Semenov, 2004; Semenov, Schimpf, 2005). Parameter STkinin Eq. (71) is the kinetic contribution to the Soret coefficient, and has the same form as the term in square brackets in Eq. (37). In deriving this “kinetic” Soret coefficient, we have made different assumptions regarding the properties and concentration of the virtual particles for different terms in Eq. (70).
In deriving the temperature derivative of the combined chemical potential at constant pressure in Eq. (70) we used assumption a) in Section 4, which corresponds to zero entropy of mixing. Without such an assumption a pure liquid would be predicted to drift when subjected to a temperature gradient. Furthermore, the term that corresponds to the entropy of mixing kln[ϕ/(1ϕ)]will approach infinity at low volume fractions, yielding unacceptably high negative values of the Soret coefficient. However, in deriving the concentration derivative we must accept assumption b) because without this assumption the term related to entropy of mixing in Eq. (70) is lost. Consequently, the concentration derivative becomes zero in dilute mixtures and the Soret coefficient approaches infinity.
Thus, we are required to use different assumptions regarding the properties of the virtual particles in the two expressions for diffusion and thermodiffusion flux. This situation reflects a general problem with statistical mechanics, which does not allow for the entropy of mixing for approaching the proper limit of zero at infinite dilution or as the difference in particle properties approaches zero. This situation is known as the Gibbs paradox.
In a diluted system, atϕ1, Eq. (71) is transformed into Eq. (37) at any temperature, providedϕϕ1*. At|τ|1, when the system is miscible at all concentrations, STis a linear function of the concentration
ST=(1ϕ)ST1ϕST2+STkinE73
Eq. (72) yields the main features for thermodiffusion of molecules in a one-phase system. It describes the situation where the Soret coefficient changes its sign at some volume fraction. Thus a change in sign with concentration is possible when the interaction between molecules of one component is strong enough, the interaction between molecules of the second component is weak, and the interaction between the different components has an intermediate value. Ignoring again the kinetic contribution, the condition for changing the sign change can be written as(ε22+ε11)/2>ε12>ε11or(ε22+ε11)/2<ε12<ε11. A good example of such a system is the binary mixture of water with certain alcohols, where a change of sign was observed (Ning, Wiegand, 2006).
## 9. Conclusion
Upon refinement, a model for thermodiffusion in liquids based on non-equilibrium thermodynamics yields a system of consistent equations for providing an unambiguous description of material transport in closed stationary systems. The macroscopic pressure gradient in such systems is determined by the Gibbs-Duhem equation. The only assumption used is that the heat of transport is equivalent to the negative of the chemical potential. In open and non-stationary systems, the macroscopic pressure gradient is calculated using modified material transport equations obtained by non-equilibrium thermodynamics, where the macroscopic pressure gradient is the unknown parameter. In that case, the Soret coefficient is expressed through combined chemical potentials at constant pressure. The resulting thermodynamic expressions allow for the use of statistical mechanics to relate the gradient in chemical potential to macroscopic parameters of the system.
This refined thermodynamic theory can be supplemented by microscopic calculations to explain the characteristic features of thermodiffusion in binary molecular solutions and suspensions. The approach yields the correct size dependence in the Soret coefficient and the correct relationship between the roles of electrostatic and Hamaker interactions in the thermodiffusion of colloidal particles. The theory illuminates the role of translational and rotational kinetic energy and the consequent dependence of thermodiffusion on molecular symmetry, as well as the isotopic effect. For non-dilute molecular mixtures, the refined thermodynamic theory explains the change in the direction of thermophoresis with concentration in certain mixtures, and the possibility of phase layering in the system. The concept of a Laplace-like pressure established in the force field of the particle under consideration plays an important role in microscopic calculations. Finally, the refinements make the thermodynamic theory consistent with hydrodynamic theories and with empirical data.
## 10. List of symbols
aEnergetic parameter characterizing the interaction between the different kinds of molecules
amEmpiric coefficient in Eq. (38)
biEmpiric coefficient in Eq. (38)
EElectric field strength
eiElectric charge of the respective ion
gijPair correlation function for respective componentshPlanck constant
I1,I2,I3and Principal values of the tensor of the moment of inertia
JTotal material flux in the system
JeEnergy flux
JiComponent material fluxes
kBoltzmann constant
Liand LiQIndividual molecular kinetic coefficients
lThickness of a spherical layer around the particle
miMolecular mass of the respective component
mN1Mass of the virtual particle
NNumber of components in the mixture
NikNumber of the molecules of the k’th component that are displaced by a molecule of i’th component
N1=N21Number of solvent molecules displaced by the solute in binary systems
nRatio of particle to solvent thermal conductivity
nsNumeric volume concentration of salt
niNumeric volume concentration of the respective component
PInternal macroscopic pressure of the system
qiMolecular heat of transport
rCoordinate of the correlated molecule when the considered particle is placed at r=0
riCoordinate of internal molecule or atom in the particle
SSurface area of a spherical layer around the particle
STSoret coefficient in binary systems
SiTContribution of the intermolecular interactions in Eq. (38)and in the Soret coefficient for diluted systems.
STs103Characteristic Soret coefficient for the salts
STkinContribution of kinetic energy to the Soret coefficient
TTemperature
TcCritical temperature, where phase layering in binary systems begins
tTime
VoutiVolume external to a molecule of the i’th component
ViniInternal volume of a molecule or atom of the i’th component
v¯kPartial molecular volume of respective component
vkIts specific molecular volume
xDistance from the colloid particle surface to the closest solvent molecule surface
yDimensionless distance from the colloid particle surface to the closest solvent molecule surface
ZrotRotational statistical sum for polyatomic molecules
ZrotiRotational statistical sum for the respective component
ZvibiVibrational statistical sum for the respective component
ZrotNikRotational statistical sum for the virtual particle of the molecules k’th component displaced by the molecule of i’th component
αiThermal expansion coefficient for the respective component
βParameter characterizing the geometrical relationship between the different component molecules
ΔIDifference in the moment of inertia for the molecules constituting the binary mixture
ΔMDifference in the mass for the molecules constituting the binary mixture
εijEnergy of interaction between the molecules of the respective components
Φij(r)Interaction potential for the respective molecules
ΦjNikTotal interaction potential of the atoms or molecules included in the respective virtual particle
Φi1*(r)Hamaker potential of isolated colloid particle
ΦMacroscopic electrical potential
Φe=eΦElectrostatic interaction energy
ϕ=ϕ2Volume fraction of the second component in binary mixtures
ϕiVolume fraction of the respective component
ϕ1,2*Boundary values of stable volume fractions in binary systems below the critical temperature
γiMolecular symmetry number for the respective component
γN1Molecular symmetry number for the virtual particle in binary mixture
λParameter which describes the gradual “switching on” of the intermolecular interaction
λDDebye length
μiChemical potential of the respective component
μ0iChemical potential of the ideal gas of the molecules or atoms of the respective component
μik=μivivkμkCombined chemical potential for the respective components
μP*=μ=μ21PCombined chemical potential at the constant pressure for the binary systems
μiP,μiVChemical potentials of the respective component at the constant pressure and volume, respectively
μ2eElectrostatic contribution to the chemical potential at the constant volume for the charged colloid particle
μ2PeElectrostatic contribution to the chemical potential at the constant pressure for the charged colloid particle
ΠiLocal pressure distribution around the respective molecule or particle
ΠeElectrostatic contribution to the local pressure distribution around the charged colloid particle
σijMinimal molecular approach distance
ζElectrokinetic potential
τ=T/TcRatio of the temperature at the point of measurement to the critical temperature
chapter PDF
Citations in RIS format
Citations in bibtex format
## More
© 2011 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3.0 License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
## How to cite and reference
### Cite this chapter Copy to clipboard
Semen Semenov and Martin Schimpf (November 2nd 2011). Statistical Thermodynamics of Material Transport in Non-Isothermal Mixtures, Thermodynamics - Interaction Studies - Solids, Liquids and Gases, Juan Carlos Moreno-Pirajan, IntechOpen, DOI: 10.5772/19482. Available from:
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vil in film: To what end?
On Aug. 12, I published two zero-star reviews, of "Deuce Bigalow: European Gigolo" and "Chaos." The first was a moronic comedy. Of the second, I wrote:
"'Chaos' is ugly, nihilistic, and cruel -- a film I regret having seen. I urge you to avoid it. Don't make the mistake of thinking it's 'only' a horror film, or a slasher film. It is an exercise in heartless cruelty and it ends with careless brutality. The movie denies not only the value of life, but the possibility of hope."
The "Deuce Bigalow" review speaks for itself. The review of "Chaos," which has not yet received a wide national release, deserves some discussion. I received a provocative letter from Steven Jay Bernheim, its producer, and David Defalco, its director, that is printed in an advertisement in the Weekend section of the Chicago Sun-Times. I reprint their letter here, followed by my response (which reveals important plot details).
Dear Mr. Ebert:
Thank you for reviewing our film, “Chaos,” and for your thoughtful comments. However, there are some issues you raised that we strongly feel we need to address. First, it is obvious that our film greatly upset you. In your own words, "it affected (you) strongly," and filled you "with sadness and disquiet." You admitted that the film "works." Nevertheless, you urged the public "to avoid it," and you went so far as to resort to expletives: "Why do we need this s--t?", you asked.
As your colleague at the Chicago Daily Herald commented, “Chaos” "marks the first real post-9/11 horror film," and "the horror reality has long ago surpassed the horror of Japanese movies and PG-13 films." Simply put, The Herald gets it and you do not.
Natalie Holloway. Kidnappings and beheadings in Iraq shown on the internet. Wives blasting jail guards with shotguns to free their husbands. The confessions of the BTK killer. These are events of the last few months. How else should filmmakers address this "ugly, nihilistic and cruel" reality -- other than with scenes that are "ugly, nihilistic and cruel," to use the words you used to describe “Chaos.”
Mr. Ebert, would you prefer it if instead we exploit these ugly, nihilistic and cruel events by sanitizing them, like the PG13 horror films do, or like the cable networks do, to titillate and attract audiences without exposing the real truth, the real evil?
Mr. Ebert, how do you want 21st Century evil to be portrayed in film and in the media? Tame and sanitized? Titillating and exploitive? Or do you want evil portrayed as it really is? "Ugly, nihilistic and cruel," as you say our film does it?
We tried to give you and the public something real. Real evil exists and cannot be ignored, sanitized or exploited. It needs to be shown just as it is, which is why we need this s—t, to use your own coarse words. And if this upsets you, or "disquiets" you, or leaves you "saddened," that's the point. So instead of telling the public to avoid this film, shouldn't you let them make their own decision?
Steven Jay Bernheim Producer, “Chaos”
David Defalco Director, “Chaos”
Here is my response (which reveals important plot details):
Dear Mr. Bernheim and Mr. Defalco:
Your film does "work," and as filmmakers you have undeniable skills and gifts. The question is, did you put them to a defensible purpose? I believed you did not. I urged my readers to avoid seeing the film. I have also urged them to see many films.
Moviegoers make up their own minds. Like many at the screening I attended, I left saddened and disgusted. Michael Mirasol, a fellow critic, asked me why I even wrote a review, and I answered: "It will get about the audience it would have gotten anyway, but it deserves to be dealt with and replied to."
Yes, you got a good review from the Daily Herald, but every other major critic who has seen the movie shares my view. Maybe we do "get it." As Michael Wilmington wrote in his zero-star review in the Chicago Tribune, the movie "definitely gave me the worst time I've had at a movie in years -- and I wouldn't recommend it to anyone but my worst enemies." And from Laura Kern at the New York Times: "Stay far, far away from this one." The line "why do we need this s - - t" was not original with me; I quoted it from Ed Gonzalez at slantmagazine.com, who did not use any dashes in his version. I find it ironic that the makers of "Chaos" would scold me for using "coarse" language and "resorting to expletives."
But there is a larger question here. In a time of dismay and dread, is it admirable for filmmakers to depict pure evil? Have 9/11, suicide bombers, serial killers and kidnappings created a world in which the response of the artist must be nihilistic and hopeless? At the end of your film, after the other characters have been killed in sadistic and gruesome ways, the only survivor is the one who is evil incarnate, and we hear his cold laughter under a screen that has gone dark.
I believe art can certainly be nihilistic and express hopelessness; the powerful movie "Open Water," about two scuba divers left behind by a tourist boat, is an example. I believe evil can win in fiction, as it often does in real life. But I prefer that the artist express an attitude toward that evil. It is not enough to record it; what do you think and feel about it? Your attitude is as detached as your hero's. If "Chaos" has a message, it is that evil reigns and will triumph. I don't believe so.
While it is true, as you argue, that evil cannot be ignored or sanitized, it can certainly be exploited, as "Chaos" demonstrates. You begin the film with one of those sanctimonious messages depicting the movie as a "warning" that will educate its viewers and possibly save their lives. But what are they to learn? That evil people will torture and murder them if they take any chances, go to parties, or walk in the woods? We can't live our lives in hiding.
Your real purpose in making "Chaos," I suspect, was not to educate, but to create a scandal that would draw an audience. There's always money to be made by going further and being more shocking. Sometimes there is also art to be found in that direction, but not this time.
That's because your film creates a closed system in which any alternative outcome is excluded; it is like a movie of a man falling to his death, which can have no developments except that he continues to fall, and no ending except that he dies. Pre-destination may be useful in theology, but as a narrative strategy, it is self-defeating.
I call your attention to two movies you have not mentioned: Ingmar Bergman's "The Virgin Spring" (1960) and Wes Craven's "The Last House on the Left" (1972). As Gonzalez, despite his "coarse" language, points out, your film follows "Last House" so closely "that Wes Craven could probably sue Defalco for a dual screenwriting credit and win." Craven, also indebted to Bergman, did a modern horror-film version of the Bergman film, which was set in medieval times. In it, a girl goes into the woods and is raped and murdered. Her killers later happen to stay overnight as guests of the grieving parents. When they discover who they are, the father exacts his revenge.
In the Craven version, there is also revenge; I gave the movie a four-star rating, because I felt it was uncommonly effective, even though it got many reviews as negative as my review of "Chaos." Craven, and to a greater degree Bergman, used the material as a way of dealing with tragedy, human loss, and human nature.
You use the material without pity, to look unblinkingly at a monster and his victims. The monster is given no responsibility, no motive, no context, no depth. Like a shark, he exists to kill. I am reminded of a great movie about a serial killer, actually named "Monster" (2003). In it, innocent people were murdered, but we were not invited to simply stare. The killer was allowed her humanity, which I believe all of us have, even the worst of us. It was possible to see her first as victim, then as murderer. The film did not excuse her behavior, but understood that it proceeded from evil done to her. If the film contained a "warning" to "educate" us, it was not that evil will destroy us, but that others will do onto us as we have done onto them. If we do not want monsters like Aileen Wuornos in our world, we should not allow them to have the childhoods that she had.
What I miss in your film is any sense of hope. Sometimes it is all that keeps us going. The message of futility and despair in "Chaos" is unrelieved, and while I do not require a "happy ending," I do appreciate some kind of catharsis. As the Greeks understood tragedy, it exists not to bury us in death and dismay, but to help us to deal with it, to accept it as a part of life, to learn about our own humanity from it. That is why the Greek tragedies were poems: The language ennobled the material.
Animals do not know they are going to die, and require no way to deal with that implacable fact. Humans, who know we will die, have been given the consolations of art, myth, hope, science, religion, philosophy, and even denial, even movies, to help us reconcile with that final fact. What I object to most of all in "Chaos" is not the sadism, the brutality, the torture, the nihilism, but the absence of any alternative to them. If the world has indeed become as evil as you think, then we need the redemptive power of artists, poets, philosophers and theologians more than ever.
Your answer, that the world is evil and therefore it is your responsibility to reflect it, is no answer at all, but a surrender.
Roger Ebert | 7aaa8e15-c125-4a51-913e-5d392f71a0aa | dclm-hero-run-fasttext_for_HF | 3 | true | true |
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Black Friday Sale
First practical plastic magnets created
By Matthew Killeya
30 August 2004
The world’s first plastic magnet to work at room temperature has passed the elementary test of magnetism. Its creators at the University of Durham in the UK have used it to pick up iron filings from a laboratory bench.
In 2001, chemists from the University of Nebraska-Lincoln claimed to have created the world’s first plastic magnet, but it only worked below 10 kelvin. Other researchers have made plastic magnets, but typically they only function at extremely low temperatures, or their magnetism at room temperature is too feeble to be of commercial use.
So the Durham team can claim to have made the first plastic magnet that could be used in everyday products. One of the most likely applications is in the magnetic coating of computer hard discs, which could lead to a new generation of high-capacity discs.
Jerry Torrance, a materials scientist based in California who is a consultant to some of the world’s largest electronics and engineering companies, including IBM, describes the work as “a significant scientific breakthrough”. However, he says that practical applications are probably still a long way off.
Free radicals
The new polymer was developed by Naveed Zaidi and his colleagues in Durham’s organic electroactive materials group. The team created the new polymer from two compounds, emeraldine base polyaniline (PANi) and tetracyanoquinodimethane (TCNQ). They chose PANi because it is a metal-like electrical conductor that is stable in air. TCNQ was chosen because of its propensity to form charged particles called free radicals.
In conventional magnets, magnetism is the result of electron spins lining up. In their polymer, the researchers hoped to mimic this mechanism by creating an alignment of free radicals.
At first the new polymer showed little sign of magnetism, and after three months the researchers had reached the point where they felt that trying to induce magnetism in this polymer was a waste of time. “Just as we were about to give up and try a different approach, we decided to check the samples for a last time,” says Sean Giblin.
It was a fortunate decision, because over the months the original polymer had developed magnetic properties. Further batches of the polymer confirmed its magnetism and ruled out the possibility that the magnetism had been caused by contamination. In addition, X-ray diffraction data showed an increase in the alignment of the polymer chains over three months, which probably accounts for the increase in magnetism.
Made to measure
Although the polymer’s magnetism is weak compared with conventional metal magnets, the researchers are confident that they can improve it.
“The reaction is not yet 100 per cent efficient along the polymer and the strength of effect varies throughout the material. Once we increase this efficiency, this overall strength will certainly increase,” says Zaidi.
The nature of polymer synthesis means that magnetic properties could effectively be made to measure, by varying the proportions of the initial chemicals. “This is only the beginning. From this initial polymer, much better systems can be synthesised in future,” says Zaidi.
And in addition to computer hard discs, the team thinks that plastic magnets could have important medical applications, for example in dentistry or the transducers used in cochlear implants. Organic magnetic materials are less likely to be rejected by the body. | 1bab72d5-971a-4805-946b-0cf37e3b38c5 | full_CC | 0 | true | false |
Boost Users :
Subject: [Boost-users] [Intrusive] Call custom function after tree rotations
From: Lukas Barth (lists_at_[hidden])
Date: 2017-05-31 14:54:03
I'm trying to implement an interval tree based on
boost::intrusive::rbtree. For such an interval tree, certain fixup
operations must be run after a node rotation. Now, as far as I can see
from the code (looking at rotate_* in bstree_algorithms), there is no
way of "hooking into"[0] these methods, right? Am I missing something?
What I need: After every operation that changes the
parent-child-relationship of nodes I need to touch all involved nodes.
At this point, I'm considering monkey-patching bstree_algorithms using
some preprocessor directives, but that is bound to fail spectacularly.
Any better ideas?
Kind regards, and thanks for any help,
[0] I know the term "hook" is overloaded differently with intrusive, but
I can't think of a better term.
Boost-users list run by williamkempf at hotmail.com, kalb at libertysoft.com, bjorn.karlsson at readsoft.com, gregod at cs.rpi.edu, wekempf at cox.net | 930cff8e-3132-4572-b847-88c253afbb55 | full_CC | 0 | true | false |
# Percentile Calculator for Grouped Data
Instructions: This percentile calculator for grouped data will calculate a percentile you specify, showing step-by-step, for the grouped sample data set provided by you in the form below. Grouped data is specified in class groups instead of individual values. It comes with ranges of values associated with a frequency. (For example, one range could be 2 - 6 and the frequency could be, say, 8, another range could be 7 - 10, with a frequency of 4, etc.)
Classes (Ex: 3-5. One per line)
Frequencies
Percentile (Ex: 0.75, 75%) =
The k-th percentile of a distribution corresponds to a point with the property that k% of the distribution is to the left of that value. In the case of grouped sample data, the percentiles can be only estimated, and for that purpose, the sample classes are organized in ascending order, and the corresponding cumulative frequencies are calculated as well. Then, the position of the k-th percentile $$P_k$$ is computed using the formula:
$L_P = \frac{n \cdot k}{100}$
We need to look at the table with cumulative frequencies, and find the first cumulative frequency that exceeds the value of $$L_P$$, and we know then that the corresponding class (Lower, Upper) is the one that contains the percentile we are looking for.
Now, we need to use interpolation to estimate where in the class (Lower, Upper) the corresponding percentile is located at. We use the following formula:
$P_k = \text{Lower} + \frac{ L_P - \text{Previous Cumulative} }{f_i} \times (\text{Upper} - \text{Lower})$
For ungrouped data, you can use our regular percentile calculator.
In case you have any suggestion, or if you would like to report a broken solver/calculator, please do not hesitate to contact us. | af95b5ec-0130-4037-8a0a-de83576b3ce0 | https://mathcracker.com/percentile-calculator-grouped-data | 0 | true | false |
2x04 Revolution:
Patriot Games
Revolution: Stagione 2, Episodio 4
Patriot Games (Patriot Games) e' l'episodio numero 4 della Stagione 2 della serie televisiva Revolution.
Girato in USA, prima visione USA Mercoledì 16 Ottobre 2013 su NBC. Prima visione italiana Mercoledì 19 Febbraio 2014 su Premium Action.
| ep. 24 di 42 |
Trama, Sinossi Episodio
Rachel si risveglia dopo essere stata ferita e scopre che Willoughby e' occupata dai Patrioti. Anche il suo amico Ken e' diventato uno di loro e infatti appena lui capisce che Rachel e' a conoscenza delle testate nucleari, prova a ucciderla, ma lei riesce a liberarsi e lo uccide. Ora, con l'aiuto di Miles proveranno a creare una Resistenza contro l'invasione dei Patrioti. Nel frattempo Charlie, insieme a Monroe, torna da sua madre e Tom riesce a conquistare la fiducia di Allenford.
Sinossi alternativa: Charlie sips a glass of whiskey in a Pottsboro, Texas bar. She gets woozy just as she spies a group of men closing in on her. They drugged her drink! As the attack begins, Monroe breaks down the door and ruthlessly dispatches all the lowlifes in the building, saving Charlie's life. Meanwhile, Rachel wakes up in her bed in Willoughby after sleeping for three days. She's covered in bandages, but she's survived. Outside, the tension in Willoughby seems to have disappeared, as have Titus' men. In their place is the U.S. Government, establishing order and peace throughout the town. Patriot Director Ed Truman introduces himself to Rachel and informs her of his plan to see much more of her in future. Injured while trying to break up a fight, Neville is late to work at the refugee camp. Deputy Director Vincent Cooke doesn't like Neville. Cooke's waiting in the wings for him the next time Neville slips up, ready to put a bullet in his head. Neville takes this in stride; Cooke has no idea the cobra he's stepped on. Later, as both men change out of their uniforms and into civvies, Neville notices a series of odd marks running up Cooke's left arm. Neville's found Cooke's Achilles' heel. That night, in a brothel, Neville pays off a hooker and enters a room where Cooke lays passed out in bed. Rachel is convinced the Patriots are up to something. Claiming Andover's men are still roaming the perimeter, they put Willoughby on lockdown. With plans to search the perimeter, Miles orders Rachel to stay put. During the town's Halloween party that night, Rachel searches Truman's office and finds a folder with the Eye of Providence on it. Inside is a map with the Willoughby Train Yard clearly circled. Why? Truman suddenly enters and catches Rachel. He angrily escorts her back to her father's home, where Dr. Porter promises it won't happen again. But the damage is done. Rachel knows something is up... and Truman knows Rachel's a problem. The Patriots catch a townsman named Bryce outside Willoughby. As Miles looks on from his hiding place, two swords thrash down to kill Bryce. In Willoughby, Dr. Porter begs Rachel to stop making everything her fight. He doesn't want to lose her again. Truman's aide, Scott, and the Patriots drive up with Bryce's body telling Dr. Porter the Clansmen got to him. This is why they're telling everyone not to travel beyond the gates… Elsewhere, Charlie comes to by a fire and finds Monroe sitting next to her. Monroe needs Charlie to take him to her mother, but Charlie is immune to his appeals. When she tries to attack him, Monroe easily gains control, then assures Charlie she has no choice in the matter. Aaron has another psychotic episode. He falls to the ground and hallucinates that he's traveling through Andover's camp. Suddenly Cynthia wakes him up, fearing the worst. Meanwhile, Miles searches the now-deserted Andover camp. He notices fireflies all around him, lit up with an intrinsic energy source... weird. Miles enters Titus' office, only to find the Clan leader still alive! Titus pulls a gun on Miles and blames him for the death of his beloved wife. He complains about "that Judas packing my family into a train." What is he talking about? Titus pulls the trigger but no bullet comes out, so Miles attacks. After a scuffle, Miles steps back, having planted a knife in Titus' stomach. Andover is dead. Rachel approaches her old friend Ken, Willoughby's butcher. She tells him her theory on the Patriots, and he promises to stand by her. After all, old friends need to stick together. Ken asks Rachel to walk down to his cellar with him to get wine, but when she spies the Eye of Providence, she realizes it's a trap. Rachel tries to escape, but Ken knocks her out and drags her deeper into the cellar. Rachel wakes up, suspended from the ceiling, while Ken digs her grave. He admits to being a Patriot for the last seven years. He's not supposed to hurt her, but he knows she must be stopped. Rachel bursts into action, managing to stun Ken. Using her body weight to rip her hand clean from its manacle, Rachel drops to the ground and kills her former friend. The grave now belongs to him. After a quick burial, Rachel grabs all the intel she can. Cooke wakes up in the brothel to find himself tied to the bed, with Neville sitting ominously at his side. Neville cuts to the chase: he needs a promotion and wants to know Jason's location. When Cooke continues to deny knowledge of Jason's whereabouts, Neville plunges a syringe into his arm: total overdose, then death. Back at the camp, Neville assumes Cooke's role without asking. Allenford checks in, but doesn't let on her surprise, telling Neville that Cooke was transferred. Miles sneaks into the Willoughby train yard to make a terrifying discovery: Scott is there with his Patriot men... and Garrett, Andover's second-in-command, who's now in Patriot uniform! They execute two people and place them on horseback. Miles grasps the entire ruse - the Patriots are perpetrating to win trust from a terrified citizenry. Suddenly, Miles is made, so he takes off for safety. Meanwhile, Aaron begins to see things again, this time while he sleeps. From a high angle, Aaron sees Miles escaping from Scott, Garrett and the Patriots. When two soldiers corner Miles, Aaron somehow sets them on fire. Aaron bolts awake in his own bed... how could... was that real... what has he done? Near the train yard, Miles stares in horror at two charred bodies as the swarm of fireflies drifts off into the night. Over whiskey, Miles and Rachel swap stories. Miles has no idea what happened but knows Willoughby is in a state of occupation, and every good occupation needs a resistance. He and Rachel can fix it. Rachel's worried. The last time she tried to fix something, she ended up ruining everything... Little do they know, Charlie and Monroe are a mere 10 miles outside Willoughby and headed their way.
Scheda Episodio
Titolo Italiano: Patriot Games
Titolo Originale: Patriot Games
Prima Visione Assoluta: Mercoledì 16 Ottobre 2013 su NBC
Prime Visione USA: Mercoledì 16 Ottobre 2013 su NBC
Prima Visione Italia: Mercoledì 19 Febbraio 2014 su Premium Action
Serie Televisiva: Revolution
Stagione: 2 - Episodio: 4
Nazione: USA
Durata: 45 minuti
Genere: Azione, Avventura, Drammatico, Fantascienza
Cast tecnico, Attori e Personaggi
Cast non ancora disponibile per questo episodio.
Cast e Ruoli principali della Serie:
foto Billy BurkeBilly Burke
Miles Matheson
Articoli e Recensioni
Non ci sono notizie per 2x04 - Patriot Games - Revolution.
Video e clip
Non ci sono video per 2x04 - Patriot Games - Revolution.
Foto e Immagini
[Schermo Intero]
2x04 - Patriot Games - Revolution [David Lyons, Tracy Spiridakos]
Foto e Immagini 2x04 - Patriot Games - Revolution
2x04 - Patriot Games - Revolution [David Lyons, Tracy Spiridakos]
2x04 - Patriot Games - Revolution [Steven Culp, Edward Truman]
2x04 - Patriot Games - Revolution [Elizabeth Mitchell]
2x04 - Patriot Games - Revolution [Steven Culp, Edward Truman]
2x04 - Patriot Games - Revolution [Tracy Spiridakos, Jeff Swearingen]
2x04 - Patriot Games - Revolution [David Lyons, Jeff Swearingen]
2x04 - Patriot Games - Revolution [Billy Burke]
2x04 - Patriot Games - Revolution [Billy Burke, Elizabeth Mitchell]
2x04 - Patriot Games - Revolution [Giancarlo Esposito]
2x04 - Patriot Games - Revolution [Ken Dawson, Elizabeth Mitchell]
2x04 - Patriot Games - Revolution [Billy Burke, Elizabeth Mitchell]
2x04 - Patriot Games - Revolution [Billy Burke, Elizabeth Mitchell]
Apri Box Commenti | 8dbe6017-46bb-4720-8aa8-f5131f82268b | null | 5 | true | true |
Did Homelander Really Kill a Crowd of People in The Boys? (with Video)
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The Boys are primarily known as a comic book series, but Amazon Prime’s streaming adaptation of the comic book – which contains a lot of changes and additions – has helped the series become a global phenomenon. Now, The Boys are full of mysteries and questions, regarding both specific characters and concepts. In this article, we are going to discuss a scene from Season 2 of the series where Homelander finally snaps and kills a bunch of random protesters. We are going to tell you whether he actually did it or not.
In Season 2, faced with a crowd challenging him, his ego, and his deeds, Homelander snaps after not being able to calm the crowd down. He uses his Hear Vision and kills all of the crowd members in public, thereby completely destroying his image of a noble superhero. Sadly for the world – and luckily for the crowd – it was just a fantasy and the scene did not actually happen outside of Homelander’s mind.
In the remainder of this article, we are going to talk about the scene in which Homelander seemingly kills a group of people simply because they thought he wasn’t all that. The goal of this article is to answer the question that’s been bothering fans since the episode premiere and to give you some facts about the character as well. Be careful, as there are going to be spoilers.
Does Homelander really kill a crowd of people in The Boys?
The scene we are talking about happened in Season 2 of The Boys and before we continue, you can check it out for yourselves:
Homelander visits Stan Edgar, where he asks to be consulted regarding further additions to the group of The Seven. Homelander threatens Stan that he might decide to on after his contract expires at the end of the calendar year. Stan then asks him what he knows about Frederick Vought, the founder of Vought.
Stan explains that Homelander feels like a superhero company when in reality, it is a pharmaceutical company and that Homelander is not their most valuable asset, but Compound V is. He accuses her of distributing Compound V to terrorists around the world and says that Homelander isn’t as important as he thinks.
Frustrated and angry, Homelander flies off to Becca’s house to see their son. As Homelander and Queen Maeve were discussing things during a break in the film, Ashley shows Homelander footage of her fight against another super-terrorist, which leads to Homelander killing the super-terrorist with her heat vision, but also killing an innocent teenager who also has the heat vision of Homelander succumbed.
Homelander ignores her and asks Ashley how many views the video got. He then goes to a demonstration where people are protesting Homelander for his war crime. Homelander gives a speech about freedom having a price, but this escalates the protest. Homelander then has a morbid vision of him using his heat vision on protesters and killing many people.
Still, then he decides to leave the protest and walks away. Troubled by the results of the protest, Homelander travels to Stormfront to help them regain popularity. Stormfront helps by spawning memes like “Better there than here” and denying the images as fake. Homelander enthusiastically returns, ending the confrontation between Starlight and Stormfront.
In one of the rare moments of gratitude, Homelander thanks her for her help, and Stormfront joins in asking how he can repay her. The two return to Seven Tower and have hardcore sadomasochistic sex. Homelander and Stormfront’s relationship becomes official as the two even engage in public sex in the same area moments after killing a criminal.
As you can see, Homelander did not actually kill a crowd of protesters, no. He fantasized about doing it because his ego couldn’t handle all the negative reception, but he still had enough self-control to just leave, rather than do what he actually wanted to do. That would, of course, confirm everyone’s suspicions and make it like the protesters were right about him, which would further his demise at that point.
Why does Homelander fantasize about killing a crowd of people?
In order to understand the answer to this question, we have to analyze Homelander’s personality. For a superhero, Homelander is pretty brutal and aggressive. He throws a bank robber in the air, drops him to his death, and brutalizes A-Train. He is highly intelligent as he put together a meticulous plan to get superheroes into the military. He is also charismatic and goes out in public to give him support.
Vought and the Seven have always been his home, so his worldview consists almost entirely of what Vought has built around the superheroes. So Homelaner has long since given up his civilian identity and is always called “Homelander” even by those closest to him. dr Vogelbaum was one of the last people who still knew him by the name “John”.
As that worldview begins to crumble, he shows signs of losing his temper. Homelander struggles to understand love and humanity because he grew up in a lab. There he was educated and taught. At a young age, for example, he “crushed” several teachers in whom he was looking for a mother while hugging.
This made Homelander sociopathic and amoral, he also intimidates the members of the Seven into keeping them informed while also killing anyone who stands in his way. This act of murder is also used to his advantage, as after Flight 37 crashed and all passengers died, Homelander believes he was destroyed by terrorists, thereby pushing both Vought and himself the superhuman gun control agenda.
How Was Homelander Killed in the Comics? (& 5 Theories for the Show)
He is sadistic and takes pleasure in the people he hurts or kills. Homelander also suffers from an Oedipus complex, which is projected onto Madelyn Stillwell, who is the closest thing to the mother. However, when she confesses her feelings of anxiety to him, his relationship with her doesn’t stop him from burning her eyes and skull.
When Queen Maeve joined the Seven, she and Homelander had a relationship of unknown duration, which probably ended when she recognized the personality behind his facade. Though people fear and love him, Homelander seems to have respect for Butcher. When the two finally confronted each other, Homelander was both intrigued and impressed that Billy Butcher isn’t afraid of him, but hates him passionately.
He wants a relationship with his son Ryan. He seems to be the only person he really likes and shows empathy as he pulls Ryan out of a crowd that is overwhelming him. When Ryan is taken away by Butcher, he causes a bloodbath as he kills the Vought units sent to pick him up.
As you can see, Homelander is a narcissistic person. He is a brutal superhero aware of his superiority, but he still lives on the popularity he has among the people. He feeds on it and it allows him to function normally; normally for him, that is. But, the issue with Homelander is, as is with all narcissists, that he despised when he is being challenged. The crowd did that, they called him a murderer and a villain, and his bloated ego simply couldn’t take it. That is why he fantasized about killing them although he had enough self-control to not do it really.
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MFC Virus uses PROPagate Injection
March 13, 2019
SonicWall Capture Labs Threat Research Team discovered another generic MFC Virus which is capable of copying itself and has a detrimental effect on the system it’s executed on by corrupting the system and destroying the data saved on your hard disk. The sample is written in MFC using C++ and uses the new PROPagate Injection technique to infect other processes running on the system.
The Virus has the following network information:
The virus scans the hard drive in search for “League of Legends” account details. If none exist the virus will keep copying itself and re-executing itself over and over until the hard-drive is completely full. During each iteration the processor will reach 100%. Meaning, you will not be able to use the computer while the copying process is in effect.
Sample Static Information:
Being that this Virus copies itself and executes over and over.
The static hashes for this file will continuously change for each iteration the sample copies itself.
Entropy, Compiler and Packer:
The sample is packed with in-line function VMProtect snippets of code:
This will give a lower entropy as the whole file isn’t virtualized.
However, someone will still be able to see 90% of the code base in Ida Pro.
Encryption Used:
The following crypto signatures usually means the sample is linked with a few different libraries like OpenSSL.
In this case the sample is linked with the libraries, deflate 1.1.3 and inflate 1.1.3 among others like libpng 1.6.9.
When this happens you will see a variety of encryption signatures inside KANAL:
There is also a variety of xor encryption throughout the sample as seen below:
Injection & Hooking Technique:
When the Windows SetWindowSubclass API is called it uses the Windows SetProp API to set one of the following structure members (UxSubclassInfo, or CC32SubclassInfo) to point to an area in memory. When the new message routine is called, it will then call the Windows GetProp API for the given window and once the function pointer is retrieved the memory area will be executed.
When it comes to the process at the lower of equal integrity level the Microsoft documentation states:
• SetProp is subject to the restrictions of User Interface Privilege Isolation (UIPI). A process can only call this function on a window belonging to a process of lesser or equal integrity level. When UIPI blocks property changes, GetLastError will return 5.
There are plenty of processes that we can choose from to modify their window property!
Using the technique described above we can freely modify the property of a window belonging to another process.
All we need is a structure that UxSubclassInfo/CC32SubclassInfo properties are using. This is actually pretty easy – you can check what SetProp is doing for these subclassed windows. You will quickly realize that the procedure is stored at the offset 0x14 from the beginning of that memory region (the structure is a bit more complex as it may contain a number of callbacks, but the first one is at 0x14).
So, injecting a small buffer into a target process, ensuring the expected structure is properly filled-in and and pointing to the payload and then changing the respective window property will ensure the payload is executed next time the message is received by the window (this can be enforced by sending a message).
1st Part:
2nd Part:
3rd Part:
4th Part:
INI Configuration:
Sample Testing System:
Windows 7 Professional x86 32-bit
SonicWall Gateway AntiVirus, provides protection against this threat:
• GAV: MalAgent.H_11825 (Trojan)
• GAV: MalAgent.J_58357 (Trojan)
• GAV:Neshta.A_68 (Virus) | 85b8e83e-8d62-476c-9cad-569b614d090b | null | 4 | true | true |
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A255238 Triangle T(n, m) of numbers of points of a square lattice covered by a circular disk of radius n (centered at any lattice point taken as origin) with ordinate y = m in the first quadrant. 4
1, 2, 1, 3, 2, 1, 4, 3, 3, 1, 5, 4, 4, 3, 1, 6, 5, 5, 5, 4, 1, 7, 6, 6, 6, 5, 4, 1, 8, 7, 7, 7, 6, 5, 4, 1, 9, 8, 8, 8, 7, 7, 6, 4, 1, 10, 9, 9, 9, 9, 8, 7, 6, 5, 1, 11, 10, 10, 10, 10, 9, 9, 8, 7, 5, 1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET 0,2 COMMENTS This entry is motivated by the proposal A255195 by Mats Granvik. See the MathWorld link on Gauss's circle problem. The first quadrant of a square lattice (x, y) with x = n >= 0, y = m >= 0, is considered. The number of lattice points covered by a circular disk of radius R = n around the origin having ordinate value y = m are denoted by T(n, m), for n >= 0 and m = 0, 1, ..., n. The same numbers occur if x and y are interchanged. One could also consider the row reversed triangle. The row sums give R(n) = A000603(n), n >= 0. The alternating row sums give A255239(n), n >= 0. The total number of square lattice points covered by a circular disk of radius n is A000328(n) = 4*R(n) - (4*n+3). LINKS E. W. Weisstein, World of Mathematics, Gauss's Circle Problem . FORMULA T(n, m) = 1 + floor(sqrt(n^2 - m^2)), 0 <= m <= n. EXAMPLE The triangle T(n, m) begins: n\m 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0: 1 1: 2 1 2: 3 2 1 3: 4 3 3 1 4: 5 4 4 3 1 5: 6 5 5 5 4 1 6: 7 6 6 6 5 4 1 7: 8 7 7 7 6 5 4 1 8: 9 8 8 8 7 7 6 4 1 9: 10 9 9 9 9 8 7 6 5 1 10: 11 10 10 10 10 9 9 8 7 5 1 11: 12 11 11 11 11 10 10 9 8 7 5 1 12: 13 12 12 12 12 11 11 10 9 8 7 5 1 13: 14 13 13 13 13 13 12 11 11 10 9 7 6 1 14: 15 14 14 14 14 14 13 13 12 11 10 9 8 6 1 15: 16 15 15 15 15 15 14 14 13 13 12 11 10 8 6 1 ... CROSSREFS Cf. A000603, A000328, A255239. Sequence in context: A133334 A003603 A278118 * A212536 A188277 A135227 Adjacent sequences: A255235 A255236 A255237 * A255239 A255240 A255241 KEYWORD nonn,easy,tabl AUTHOR Wolfdieter Lang, Mar 12 2015 STATUS approved
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Last modified November 27 12:51 EST 2021. Contains 349394 sequences. (Running on oeis4.) | 77d0d4d6-f2f0-4861-a711-6aa82485aa06 | http://oeis.org/A255238 | 0 | true | false |
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Comment: Re:Lucky you (Score 2) 243
by Havokmon (#45584705) Attached to: Ask Slashdot: Recommendations For Beautiful Network Cable Trays?
My company prides itself on an office environment that follows a modern design aesthetic: open floor plan, bold colors on the walls, cool lamps in the corners.
My lame company only prides itself on stupid shit like making good products and pleasing its customers.
Right. What stock should I be selling?
Comment: Re:ADHD - Euro perspective (Score 1) 65
by Havokmon (#45530917) Attached to: Book Review: Digital Outcasts
It is also completely wrong.
No it isn't. It is only partially wrong. AHDH is a real disorder. My brother suffered from. I know it when I see it. I regularly volunteer to help out in my son's elementary school classroom for two hours every Friday morning. I know all his classmates, and work with all of them regularly. They are all normal kids. None of them are even close to ADHD. Yet, since I started working with them, several of the boys have been put on medication. That is insane. But I can see how it happens. Shoving pills into the kids makes the teacher's job easier. The parents are happy because they can continue to let the kid sit in front of the TV and munch potato chips, which is much easier than being a responsible parent. And the doctor is guaranteed a steady income stream. All the incentives are in the wrong direction.
And those parents don't know what they're getting their kids into. Years from now, even after they discover they were sold a load of bullshit, they'll find out that all those 'psych rejects' who are now teachers have been busily inspecting their children's files and will be treating them decisively different from the rest of the students.
They'll be lucky if one of them slips up and lets the parents know that's happening. Though you can be sure it'll be discussed in the teacher's lounge.
Comment: Re:Funded by (Score 4, Insightful) 77
by Havokmon (#45474853) Attached to: Gartner: OpenStack Lacks Clarity
While I agree with your point, I have to also agree with a few of the points Gartner's analyst made. Ever try to implement OpenStack? Some things are okay (Virtual Machines), but other things are horribly convoluted (Virtual Routing). Version upgrades break previous functionality, and documentation is lacking so finding what actually broken requires lots of time and effort. Waiting for the documentation to catch up is fine until you need a feature or bug fix in the latest version.
I'm not claiming that it's horrible mind you, but rather pointing out that it needs some time to mature. Gartner's opinion does not mention the fact that OpenSource products like this can do very well (Apache, Linux, MariaDB/MySQL). At the same time, enough OpenSource projects fall off the Earth to have some concerns.
"A lie is best placed between two truths."
Gartner always makes some valid points. They are masters of manipulation.
While it sounds like you're well-informed, the majority of their followers are not and I would go so far as to say those people, even when reading the details presented within, rarely truly understand the content.
Comment: Re:Just like the new cancer test (Score 1) 282
by Havokmon (#45473873) Attached to: Affordable Blood Work In Four Hours Coming To Pharmacies
Keep in mind, the cost of the pharmaceutical company's studys used to verify the accuracy of the test and gain FDA approval likely pushes the cost-per-test up quite a bit.
FTFY. Preclinical, phase 1, phase 2, and phase 3 at a minimum
And then of course there needs to be someone licensed in reading the results, and prescribing a treatment.
My foot is killing me from gout, but I'm not dropping $200 for a doctors visit to get $10 in meds.
Comment: Re:"Dark Friday"? (Score 1) 307
by Havokmon (#45425156) Attached to: Alfred Poor Says HDTV Manufacturers are Hurting (Video)
The article mentions "Dark Friday" but links to a wiki page called "Black Friday". What is that about?
Many people refused to support the shopping event "Black Friday" on the grounds that it is racist towards people of other skin tones. The politically correct term is "Dark Friday", which is on the eve of "Darkie Weekend" during which most people don't have to work and can just laze about on their porches like monkies.
ROFL. That's most appropriate explanation I've ever seen.
Comment: Re:Outright bans are not smart (Score 1) 376
by Havokmon (#45402291) Attached to: WRT trans fats, the FDA should ...
It's not murder because you aren't requiring or forcing anyone to consume the poison. Under libertarian principles, without that act of force there's no crime. There may be contract and reputation issues, but those are meant to be resolved by the market.
To promote a government ban is to go against libertarian principles. So why call yourself (himself) a libertarian? "I'm a libertarian, except when I don't like something. Then I'm a happy to adopt statist solutions." Why not just accept that you (AC) are not actually a libertarian?
I consider myself Liberatrian, and I am well aware there are variations and non-absolutes to every belief system.
My problem here is the arrogant assumption that we're correct now, while we were 'correct' when we said butter=death in the 70s.
The best advice we have now is that artificial TransFats (in the current form) are bad. So to prevent any future issues with supply, or the letter of the law in the case where a future method of creating artificial 'TransFat' is found to be beneficial, I think the best solution is an additional tax with an expiration that can easily be renewed.
Comment: Re:Thank you - THIS (Score 2) 141
by Havokmon (#45373125) Attached to: Taking Google's QUIC For a Test Drive
> reliable UDP protocol You want a reliable *unreliable* datagram protocol protocol? Sounds like something guaranteed to fail. Everyone tries to reinvent TCP. Almost always they make something significantly worse. This is no exception.
I once worked at a company that made Parking Meters - and accepted credit cards at them. They sent their data over https, and had random issues with timeouts.
It turns out they would format their data in (very descriptive) XML, and discovered an excessively large file combined with an SSL handshake over crappy 2g connection took too long to transfer the data (it didn't help the programmers 'forgot' they hardcoded a timeout, so if the comms was just slow, it would throw a generic error and they blamed Apache for it).
In any case, the offshore dev team's solution was to create a UDP client/server protocol of their own.
It was working nicely when I left, and was PCI Compliant, but at that point we had no way to reliably monitor communications from the perspective of the meter because we (SysAdmins in charge of the backend systems) would have had to write proprietary code from non-existing documentation just to replicate what used to be a simple HTTP POST.
Some things look great, but aren't thought out all the way ...
Comment: I reported a similar issue to BofA in 2008 (Score 2) 157
by Havokmon (#45369625) Attached to: Credit Card Numbers Still Google-able
Completely against PCI Compliance, they were using your 'account number' (full card number) as your identifier when downloading your statement in PDF form. So their web server logs would have been chock full of credit card numbers in clear text. Doh!
The biggest problem was finding someone to report it to. Customer Service doesn't know dick about Compliance - I had to to cross my fingers that it would get escalated properly. It took about 6 months for that to change.
When I did this 'search test', Most of my hits were PDFs of credit card statements.
Comment: Re:How about SourceForge? (Score 1) 104
by Havokmon (#45367271) Attached to: Ask Slashdot: Tools For Managing Multiple Serial Console Servers?
What does "a community" have to do with whether the tools work or not?
To Quote - " I'd rather use some tools with more of a community than just the 4 of us."
He also never said that there were shortcomings in the toolset they created. It sounds like he may not like the database, maybe he wants a nicer front-end for managing the tables? But it's not described as 'the problem'.
Therefore, if they create a community around their own toolset, then the only problem actually described in the OP is resolved.
Comment: Re:I read the documents. (Score 0) 195
by Havokmon (#45290621Of course he was asked to hand over the SSL keys, he refused to hand over the requested information in the first place.
Duplicating incoming and outgoing email, on a server you own and apparently WROTE THE CODE FOR, is trivial. Even Exchange can do it. Page 7 is the request for mailbox contents, but a separate device is NOT REQUIRED . It should be obvious that using SMTP means the data is in clear text until it's encrypted - at rest.
At best, he's an incompetent admin, and you want him to secure your email?
"Time is an illusion. Lunchtime doubly so." -- Ford Prefect, _Hitchhiker's Guide to the Galaxy_ | 7dee3020-faf5-49de-8a88-afed1eef598d | dclm-hero-run-fasttext_for_HF | 3 | true | true |
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1 TV Recap
'Terra Nova': 'Instinct' recap
Jim Shannon in Terra Nova
Season 1, episode 3 | Aired Monday, Oct 3 2011 at 8:00pm EDT on Fox
This week's Terra Nova opens with three guys in a transport driving in the rain, only to suffer a flat tyre. As they inspect the damage, they are alerted by rustling sounds and screeches in the trees. They barely have time to investigate when they are attacked.
Back at Terra Nova, the Shannon kids take part in a survival training course with many of the other residents. As night falls and the family gets ready for bed, Zoe expresses her desire to sleep in the same room as her mother, rather than with Maddy.
In Elisabeth's room, a topless Jim starts making out with his wife but the pair are distracted by an annoying screeching noise. Jim, after a bit of pestering from Elisabeth, checks outside and finds a bird-like creature on top of the fence. He shoos it away, but when he returns, he sees Elisabeth cuddling Zoe.
The next day, Taylor tells Jim that he's lost contact with his supplier and wants to find his men. They theorise that the Sixers might have something to do with it. Meanwhile, Elisabeth spots an old friend - Malcolm - as he enters the medical center. Malcolm came on the fifth pilgrimage to Terra Nova, and they attended the same university. Just then, Jim arrives. When Malcolm learns Jim is Elisabeth's husband, he looks noticeably disappointed.
Out in the jungle, Jim and Taylor are searching for the missing men. Jim asks Taylor why the Sixers would want him dead, but Taylor dances around the question and instead says that someone inside Terra Nova is feeding Mira intel. In other words, there's a mole. Taylor suggests that Jim can use his lawman skills to figure out who it is.
The lads finally come across the missing men, and it doesn't look pretty. They're all dead, with their faces mutilated. Jim: "What the hell did this to them?" Taylor: "I don't know, but it wasn't Sixers."
Terra Nova S01E03: 'Instinct'
In Terra Nova, Josh and Skye are shopping around for food when Josh spots a hand-crafted guitar and plays a tune on it. The vendor is willing to sell the instrument for 60 terras.
The bodies of the deceased men have been brought back to the medical center. Elisabeth says she'll need to do an extensive post-mortem, but it appears the men were attacked from above as only their faces and necks were targetted. Jim then finds a claw, a possible clue as to what species they're dealing with. Taylor demands more answers by the end of the day.
Because Elisabeth is required to stay behind at the lab until late, Jim is tasked with cooking dinner and looking after the children for the night. While he fumbles around in the kitchen, Maddy asks her father how can you tell if someone likes you - obviously referring to Reynolds, who works in security.
When Elisabeth returns home, Jim curiously asks about Malcolm, finding out that he's a former flame of hers. But that doesn't dampen the mood, as the couple once again start getting sexual in the bedroom - only to be interrupted for a second time by screeching.
Jim and Josh head outside and find not one but three of the bird-like creatures perched on the fence. Josh hurls a rock at them, provoking them to attack. During Jim and Josh's successful attempt to get into the safe confines of their home, Jim's hand is clawed at - "I think we found out what killed those men."
Malcolm inspects Jim's hand the following morning and concludes that it's not a species that he's ever seen before. Smaller creatures like these usually don't attack unless provoked, so what is causing the pterosaurs to act so violently against them? Malcolm wants to research and learn more about the way they act, but Taylor has none of it, ordering that no-one leaves the compound.
When Malcolm leaves, Jim asks Taylor what the recruitment process in Terra Nova is like. Taylor informs him that department heads usually hand over a bunch of resumes, but he occasionally receives specific recommendations. In the case of Elisabeth, she was on an extremely short list of recommendations - which was submitted by none other than Malcolm.
Terra Nova S01E03: 'Instinct'
Josh and Skye return to the guitar seller, with the former wanting to initiate a trade. However, the vendor is not interested in anything but the platinum necklace he's wearing, something which is not for sale.
As they leave, Skye cottons on to the fact that the necklace was from the girl Josh left behind. Josh admits that he misses her and describes her as smart, funny, tough... "kind of like you". At this moment, Skye notices a flock of pterosaurs perched on the fence and points it out to (a surprisingly slow) Josh. The pair get up and start running when the hundreds of pterosaurs swoop down at the marketplace.
Fortunately, there are no fatalities - but a few dozen folks were injured in the attack. Malcolm picks up a dead specimen and says they're not from this region because they migrated. Migrations tend to be population-wide, so a lot more will be coming their way.
Thanks to thermal technology, Taylor and co learn that there are at least a million of them resting in the trees. Taylor then reveals that a few years back, he and his men found fragments of egg shells - thousands of them, in fact. He thought nothing of it at the time, but built Terra Nova there because they made the soil extremely fertile. The pterosaurs were born here, and now they're back to breed.
To combat the pterosaurs, Malcolm and Elisabeth need a male and female live specimen to analyse. As Jim is arming himself to go out and capture the specimens with Taylor, he tells Malcolm he's on to him. Malcolm, wanting another shot with Elisabeth, clearly thought Jim was still rotting in jail back in 2149.
The episode cuts to the next morning - pretty odd, actually, as we didn't get to see Jim and Taylor capturing the two live pterosaurs they have. But that doesn't matter right now, as Elisabeth figures out a way to solve the pterosaur problem.
Their pheromones regulate their spawning instincts, so if they could create a more powerful version, they could lure the creatures into another location and establish a new breeding ground. Time is short - they only have a couple of hours to get the solution right until Terra Nova is swarmed by the million or so animals.
Terra Nova S01E03: 'Instinct'
Everyone in Terra Nova is instructed to stay indoors, with a security member assigned to each household. Private Jenkins has been tasked to look after the Shannon family, joined by Skye after Josh asks she stay with him. However, it's Reynolds who shows up instead of Jenkins, claiming there was a mix-up in the duty roster. Jim to Maddy: "That's how you know a boy likes you."
The pterosaurs start coming in and attacking, though weirdly they don't seem to be anywhere near as lethal as the beginning of the episode despite their larger numbers. They soon start banging at the windows of the Shannon residence.
While Elisabeth and Malcolm are struggling to create the pheromones, a few pterosaurs enter the Shannon home through a vent. Reynolds is knocked down, so Josh and Skye drag him to the bedroom and shut the door with Maddy inside.
Everyone realizes that Zoe is still stuck in the living room - the youngest daughter is cowering underneath a stool. A pterosaur lands on the floor and sees her. It approaches the girl and gets ever-so-close before Josh gives a massive boot to the critter and gets Zoe to safety.
Elisabeth and Malcolm have finally created the pheromones, and Jim and Taylor load the transport and exit the gates while releasing the chemicals. All of the pterosaurs follow away from Terra Nova. In the welcome silence, Skye tells Josh she'll pay for the guitar he wants and kisses him on the cheek.
Jim and Taylor return the next day, a little worse for wear but getting the job done. The pterosaurs will migrate to the coastline now, and Terra Nova is safe for another day. Jim and Elisabeth head back home to see their children all sleeping in the living room. They take this opportunity to head into the bedroom and enjoy the moment to themselves...
Welcome to Terra Nova!
• 'Instinct' is a solid follow-up to the pilot. With less exposition and back-story, the episode feels tighter and better-paced.
• That said, the family dynamic could still use some work. It remains an important part of the show and has potential, but at the moment it's the least interesting part of Terra Nova.
• After spending much of last week rebelling against his father, it was great to see Josh protecting the household and kicking away the pterosaur to save Zoe.
• A lot of the setup from the pilot wasn't touched on this week. There was no mention of time travel or Taylor's missing son, and we didn't see any Sixers.
You May Like | 90fe1e19-4183-403f-a881-f42044604f06 | dclm-hero-run-fasttext_for_HF | 3 | true | true |
# Tag Info
56
There are physical and psychoacoustics reasons behind it. A vibrating string held by its two extremities can only vibrate at certain frequencies (cycles per second, expressed in Hertz, i.e. 440 Hz = 440 cycles/second), which relates to the characteristics of the string (e.g. its weight per unit of length, its flexibility) and how it is used (e.g. the ...
47
By definition this is not possible. Just intonation ratios are rational numbers, N/M where N, M are integers. Equal temperament is based on defining the smallest ratio as the n-th root of 2, 2^(1/n). For 12TET n = 12. What you are basically asking is if an irrational number can be made to exactly match a ratio of integers. This will never be possible....
38
The intervals between notes are "equal" not in the sense that the difference in Hz between them is the same, but the ratio a between them is the same. Let's say g is one semitone higher than f, then g = a f. Note Hz Ratio a to previous note, rounded to 3 decimal places A4 440.00 A#4 466.16 1.059 (466.16 / 440.0 = 1.059, and so on down the column)...
30
Let's get some terminology straight. In equal temperament, octaves aren't merely perfect; they are "just" or "pure". "Just" and "pure" are synonyms while "perfect" has a different technical meaning in music. Nevertheless, "just", "pure", and "perfect" happen to be the same when ...
28
This question seems to arise from a “linear” mental model of notes. C♭ C C♯ D♭ D D♯ E♭ E E♯ F♭ F F♯ G♭ G G♯ A♭ A A♯ B♭ B B♯ C♭ C C♯ Like a piano keyboard, but somehow with 31 notes per octave instead of 12. (Building or playing such an instrument is left as an exercise for the reader.) But instead, look at the notes in Circle of Fifths ...
28
The division of notes has to do with human perception and psychoacoustics. One description of human perception is the Weber-Fechner law, where a human will perceive equal changes in some sensory input, such as sound level or sound pitch, not by absolute level or value difference, but by the ratio of the change. e.g. larger values need a proportionately ...
28
Tuning in an ensemble is a skill in relative pitch, not absolute pitch. Players will hear what others are doing, and the group will come to a consensus organically. With instruments that are capable of microtuning adjustments, this will also lead to more just-tuned intervals. But what's important to note is that these tuning decisions happen on the fly, and ...
27
Note: For the sake of discussion, I'm limiting myself here to equal temperaments, which is the most common way of tuning keyboards. Other systems exist, of course, but would probably only confuse the matter. Why do B and C and E and F not have a sharp note between them? Simply because, acoustically speaking, there is no room in our current system for ...
27
Partly to allow the same, diatonic, piece to be played at different pitches as @Tim suggests. But also, I think, because music started getting more tonally adventurous within the SAME piece. When you start wanting to visit (say) the mediant key as well as just the dominant and subdominant, equal temperament is a must.
24
In principle, the answer is yes, with software instruments it is feasible to (re-)set the tuning so that you can realize music with modulation that stays in just intonation across these changes. The frequencies are directly accessible in sound synthesis environments like PureData or Overtone, and even just by setting the tuning information in a set of MIDI ...
24
Yes, but also due to the changes in piano construction. In some ways, a classical piece played on a modern piano might sound more true to the composer's original intent than the piano it was originally played on. Modern pianos are generally louder and brighter than the ones in the late 1700s and early 1800s. So loud passages, such as might be found in some ...
21
The other answers approach this from dividing the octave and showing that equal divisions must be irrational. Another way of looking at this is to consider whether we can compose an octave by successive multiplications with a rational number. The result is of course the same: we can't. Start with the Fundamental Theorem of Arithmetic: every integer ...
21
The temperament in a professional orchestra tends to vary between just intonation and equal temperament. If they are playing with a piano the strings will tend to adjust to the piano temperament where the difference would be audible and tend towards just intonation when they are playing alone. Woodwind instruments are built with the aim of playing in tune ...
20
What happens if you go down by the same steps: 440Hz 1 step down : 403.33Hz 2 steps down : 366.67Hz 3 steps down : 330.Hz ... 11 steps down : 36.67Hz 12 steps down : 0Hz 13 steps down : -36.67Hz So, using your "equally divided" logic, we are at zero Hz after 12 steps, and the next step beyond that is minus 37 Hz! What does that even mean? But ok, let's ...
19
Every note has a pitch, determined by the fundamental frequency of the sound wave that produces it. When you have two different notes, you have two different pitches, caused by two different frequencies. The distance between those pitches is called an interval, and corresponds to the ratio of the note's frequencies. For example, if one note is an octave ...
18
Some people seem to make the case that having some keys beat more than others (as is in the case in the older well-tempered tuning systems) is a feature not a bug. Yes, but I don't think that was ever a major consideration. Originally, all tuning systems just tried to give good approximation to just intonation (JI). At first just for a few neighbouring ...
17
You cannot even realize "just temperament" reliably when you are working with continuous-tone instruments like singers and trombones. Take a look at even something as old as J.S. Bach's mass in B minor, like the "Confiteor" which goes off-tonality somewhere after 2:30 (in this recording) and loses tonal center rather thoroughly between 3:00 and 4:00. The ...
16
You are exactly correct that it is the logarithmic nature of pitch that causes this effect. In cases like this, I find that a picture is helpful. Here I've labeled equally spaced octaves (1200 cents) along the x-axis (representing pitch). I've then labeled the corresponding frequencies on the y-axis as multiples of some arbitrary base frequency f. Note that ...
16
Yes, if not far more than 7 when you consider pitches outside of the diatonic scale and variations on A440! By "stray slightly to make a note sound more in tune," you're talking about just intonation. In 12-tone equal temperament, in C major, let's say C is our "zero-point." For the ensuing discussion, all pitches are based off of this 12TET where C is "0 ...
16
It is because B and C are closer together than the difference between B and B♯ and the difference between C and C♭. That is, they are all some sort of semitone apart. Alternatively, note that B♯ is also higher than C♭ in every 12-tone temperament, because in the 12-tone system B♯ is the same pitch as C, while C♭ is the same pitch as B. but this doesn't ...
16
Simply so that any music could be played in any key and it would sound the same. Problem with tuning to another temperament means that pieces sounded particularly good in some keys, and particularly bad in others. And re-tuning often isn't a quick answer - especially on instruments such as piano! Non-fretted stringed instruments, such as violins, trombones ...
15
As I understand the question, this is pure mathematics: No it is impossible. No matter, how many divisions you have, say n, the step width will always be nth root of two and therefore an irrational number. The just relations are rational numbers, so there will always be approximations, but the more you choose, i. e. the higher n is, the closer you will be ...
13
It is significant when you are trying to tune an instrument by ear, using the purity of intervals as your guide. You (and the pages you link) refer to jumping up 7 octaves vs. 12 fifths, but don't forget that any notes you reach that way can also be brought down by one or more octaves as well. To illustrate this, let's bring all the notes down into the same ...
13
It's a bit more complicated than may appear at first glance. Within a single key, if Just Intonation makes the I,IV, and V chords all (4,5,6) ratios, the ii chord will be off. The other question is what note to play as a melody note. Often, melodies are somewhat independent of the underlying chords (at least in CPP if not in Jazz and other Pop theories). I ...
13
The earliest use of equal temperament was on fretted instruments with fixed frets. The ratio of 17:18 for the string length for successive frets is a good approximation to equal temperament. The errors were well within the tolerance of other intonation issues such as non-uniform gut strings, and the different amounts of string bending on different frets ...
12
Standard tuning for solo violin in classical music is just intonation. Tune the A string and, from there, tune the other strings with just-intonated perfect fifths. Some times, as a compromise you may need to tune the violin temperate, for example when you need to play many open strings in duo/ensemble with a instrument not capable of just-intonation. ...
12
A trivial answer : yes. When I was quite young I wrote a computer program to spit out a succession of 'beeps' at random frequencies not related to any musical scale; I suspect many people who have a computer and a bit of an interest in music have done the same. In practice how close you could get to infinity (!) would be limited by the resolution at which ...
11
My answer is no, it isn't really possible to use a fingering technique to play an A440 recorder at A415. No professional would even try; they would instead, as Wheat noted, have a real A415 instrument or, if extremely confident and well rehearsed, transpose on-the-fly down a half-step. One can indeed bend most notes up or down quite a bit using half-holes, ...
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Explaining Mobile App Security in Simple Terms
For most of the businesses these days, mobile apps are the heart and soul when it comes to connecting with their customers all around the world. As these apps have access to huge volumes of sensitive business and user data, it becomes essential to protect them from threat actors.
And during the testing times of the COVID-19 pandemic, there has been a substantial rise of around 600% in the number of cybercrimes across the world. That is why businesses need to stress more towards strengthening their mobile application security infrastructure. So, let’s try to understand the basics of mobile app security, the underlying threats, and what best practices must be followed so as to protect your customers as well as your business.
What is Mobile App Security?
Mobile app security can be summarized as the set of tools and security practices employed to safeguard mobile applications from security risks like cyber-attacks and data theft. Mobile app security mainly focuses on the security requirements of the apps present on various mobile platforms like iOS, Android, and so on.
Basically, the techniques of mobile app security assess mobile applications for security vulnerabilities based on the platforms they are made for, their development and design framework, and who their end users are (like other businesses or end customers).
Why is Mobile App Security Important?
Mobile apps are at the center of most of our activities these days. Be it bank transactions, online shopping, planning travel, or getting in touch with everyone else, we depend on mobile apps for almost everything.
And in order to make all the functionalities possible, businesses track user information like their location, contact details, files on their devices, and several other metrics to boost their services. So, it becomes essential to protect such sensitive information from going into the hands of the bad guys and have security measures in place.
There are several other self-explanatory reasons which justify the importance of mobile app security:
• You can’t trust the third-party libraries and APIs your app relies on. So you need to have security measures in place.
• Compliance standards require your business to set up security measures for your app.
• If you have proper security measures in place, you can remotely delete data on stolen devices and be safe from data leakage.
5 Security Threats in Mobile Apps
Since we are discussing mobile application security, it becomes important to know where the real risk lies and what are some of the most commonly faced threats when it comes to mobile app security.
Data Theft
Data is the biggest asset when it comes to any online business or in fact any other business too. Leakage or theft of data is one of the biggest problems faced by mobile apps. Sometimes it’s unintentional and other times it’s due to their own fault as they ask for too many permissions and store voluminous data without having the security measures in place. There is a certain set of apps called “riskware” which transmit user data to remote servers where it is mined by cybercriminals.
Broken Cryptography
Broken cryptography often happens when weak encryption algorithms are used by developers during app development. Most of the time, they rely on familiar encryption algorithms with known security vulnerabilities in order to accelerate the app development process. As a result of this, hackers get the opportunity to exploit those vulnerabilities and gain access to user information.
Session Handling Issues
Session tokens are used by mobile apps to let users perform several functions without logging out of the session or re-authenticating. However, when these session tokens are not handled properly or somehow shared with threat actors, improper session handling occurs and hackers get a chance to impersonate users and steal information and whatnot.
Reverse Engineering
This is one of the most common attack vectors when it comes to mobile apps. Using this technique, hackers get detailed knowledge about the source code of the app, its algorithms, libraries, and other assets. This can be used to exploit the inherent vulnerabilities in the app and also gain access to back-end servers and other proprietary and user information.
Client-Side Injection
Upon exploitation, this vulnerability allows hackers to execute malicious code on the mobile device via the target application itself. This also allows the threat actors to have access to various functionalities of the user’s device and change its settings in the background.
Examples of Mobile App Security Flaws
Now that we understand the most potent threats when it comes to mobile app security, it becomes important to go through the security flaws that mobile apps still have despite having an idea about the threatening outcomes they can have. Here are a few examples of some of the most common security flaws found in mobile apps:
Insufficient Network Traffic Encryption:
Mobile apps generally don’t have the required level of protection when it comes to encrypting the network traffic. As a result, threat actors can sniff over sensitive communications and have access to sensitive information.
Session Expiration Flaws:
After the expiry of the user’s session, mobile apps generally fail to invalidate their session tokens. As a result, threat actors get an opportunity to use those session identifiers and impersonate users.
Insufficient Authentication/Authorization
Mobile apps generally fail to have adequate authorization/authentication checks to make sure that only the authorized parties have access to sensitive resources. Most of the time, this flaw results in hackers gaining access to important data without much of a hassle.
Mobile Application Security Best Practices
The best practices in mobile app security make sure that your app is free from all the security risks and is safe for public consumption. Keeping in mind the basic requirements of mobile app security, the following methods can be considered:
Focus on Data Security
You must establish the required guidelines regarding data security to safeguard your users from falling into the traps of the hackers. This may include deploying data encryption methods during data transfer and setting up firewalls and security checkpoints wherever necessary to protect user data.
Don't Save Passwords
Don't be an app that asks users to save their passwords for easy login later. In case of any security incident, these saved passwords can be exploited to gain access to personal information of users. The chances of password theft increase even further if they are not encrypted properly. So, it's better not to save user passwords or use proper hashing techniques if you are already doing so.
Focus on Session Management
It is important to end the session of users after a prolonged period of inactivity or after every time they log out of the session for increased protection. We have discussed above in detail how session handling issues can prove dangerous if not addressed to properly. No matter what, it is essential to enforce session log out and invalidate session tokens.
Implement Multi-Factor Authentication
Given the risks of hackers impersonating the users, it's best to have an added layer of security on your mobile application by implementing multi-factor authentication. This method also makes up for the weak passwords which could compromise the security of the app.
Rely on Penetration Testing
The best way to avoid any security issues on your business's mobile app is to adopt the methodology of penetration testing. It is done to check for the vulnerabilities present in your app. It involves assessing your app's encryption, password policies, permissions, and other features where security vulnerabilities might be present.
Final Thoughts
Mobile application security is a vast domain. Because of the rapid advancements in the functionalities of the apps, the ground for security vulnerabilities also gets bigger and bigger. However, with an improved understanding of the intricacies of mobile app security and also because of the rising number of attacks, businesses have now started to focus more on cybersecurity, especially on mobile app security.
Appknox Mobile App Security
Published on Mar 12, 2019
Written by Prateek Panda
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## Customer Cases
• #### Speed of the conveyor belt Calculator | Calculate Speed of ...
The Speed of the conveyor belt formula is defined as Conveyors move boxes at about the same speed as a person carrying them. This is about 65 feet per minute is calculated using speed_of_body = (Length * Flow rate)/ Weight of calculate Speed of the conveyor belt, you need Length (L), Flow rate (Fr) and Weight of Material (W L).With our tool, you need to enter the respective value ...
• #### Measuring of ManHour per (equivalent) Unit
Formula: Total number of hours spent on the production / number of pieces produced. For example, in a bakery, if 2 members of staff working 8 hours a day achieve a production of 200 pieces of bread, the man hour per unit is: (2x 8) / 200 = 16/ 200 = h ( minutes), hence manhour per .
• #### Direct Labor
For example, if it takes 100 hours to produce 1,000 items, 1 hour is needed to produce 10 products and hours to produce 1 unit. 3. Calculate the labor cost per unit. The labor cost per unit is obtained by multiplying the direct labor hourly rate by the time required to complete one unit of a product.
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There are many variations of Horse Power (HP) calculations found in historical and individual manufacturer's literature. The formulas below are used to determine the power requirements of a Bucket Elevator throughout the industry. Equation 1 – Power Formula. A basic power calculation is the measure of force over a distance per time period.
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If you need more help planning the Indoor Air Quality for your business or home, please give the experts at LakeAir a call . The data presented below are suggestions only. You should consult your local Government, OSHA or EPA for for any official requirements. Building / Room. Recommended Air Changes Per Hour. All spaces in general.
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The formula for speed and distance is the same for a car as any other object: distance ÷ time. So if you want to calculate the speed of a car at sixty miles an hour, the math is (60 x 5280) ÷ (60 x 60) = 88 feet per .
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Gas Flow Units. MMSCFD – Million standard cubic feet of gas per day – a common volume of gas measure (unit abbreviation MMscf) SCFD – Standard cubic feet per day (gas) SCFM – Standard cubic feet per minute (gas) Sm^3/hr – Standard cubic metre per hour defined at 15 deg. C – 59°F – for US Nm^3/hr – Normal cubic metre per hour defined at zero deg. C – 32°F – for countries ...
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Typically, when working on turnkey projects, they are essentially designed from the ground up and entail every aspect of our engineering capabilities. Please see this prime example of a 30 ton per hour shelling plant, Premium Peanut in Douglas, Georgia being constructed in this video.
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How to convert BPH to TPH ( or metric) Have you ever needed to convert bushels per hour (BPH) to tons per hour (TPH) or even metric tons per hour? Here is a look at how it's done. Or use the online calculator below to help you out.
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Raw . sending sugar 5 ton per hour screw conveyor price with sales webpage email address . Horse Power Rating For Conveying 2400 Tons Per Hour. . images for 250 300 tons per hour . Mobile Conveyors
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• #### The Formula of Opportunity Cost How to Calculate It ...
Jul 26, 2017 · Going back to our example, if you chose to spend an hour working as a bartender instead of as a mechanic, then you are actually giving up (50 mechanic / 25 bartender) = 2 of opportunity cost. This 2 says, for every dollar I earn working for one hour as a bartender, I sacrifice 2 working the same hour as a mechanic.
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The standard speed for most unit handling conveyors is 65 FPM (feet per minute) which works out to the average speed a person walks when carrying a 50pound box. This pace is ideal for many—but not all—order picking and assembly operations. There are always situations where transport through an area, into a process, or toward a packing operation can be accelerated.
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Find conveyor equipment calculators to help figure specs. Conveyor Lift Stockpile Volume Conveyor Horsepower Maximum Belt Capacity Idler Selector
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Calculations for screw conveyors power in kw p q x l x k x p power in kw q capacity in kg per hour l conveyor screw length m k icfrtion coefficient p calculations for screw conveyors capacity in m3 per hour q for horizontal transport q m3u,1 x d2 d x s x n x i capacity in kg per hour q for . Read More
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Insert the basis weight of the paper to be coated in the formula below. lbs/MSF = : MSF/ton: lbs/Ream = : MSF/ton: lbs/Ream = : Reams/ton: Metric Conversion: g/m² = : m²/mton: From the formulas below, enter dry pounds (or grams) of coating per area coated to calculate amount of dry coating per tonnage. dry lbs ...
• #### get average per hour? [SOLVED]
Mar 14, 2006 · Re: get average per hour? Assuming things is in A1, hours is in A2, result in A3. =A2*24/A1 (format Standard) The correct result is 0,.
• #### (PDF) Estimating Construction Equipment Productivity
Example A belt conveyor has a theoretical productivity of 2000 tons per hour. The time The time to accelerate to operating speed is min. Construct a simplified load growth curve for this
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Lee: "Getting framed for the biggest prank in history? Bad enough. Having to break out of detention every day to find out who set me up? Now that's the tricky part. Thought I'd crack the case when I got the prank mastermind's phone. Now I could find out who Radcircles was, right? Wrong. Access denied!" [A picture of the locked phone appears.] "Kinda like the secret passageway in the library suddenly under renovations–someone's on to me." [The passageway is seen disappearing.] "And they're locking me out! Whatever it is, Barrage is up to something." [Barrage is seen with Finnwich.] "His henchmen are robots, and he destroyed our phones when we messed up school inspection!" [Lee is shown decapitating a robot, and Barrage is seen destroying the phones.] "But I got Radcircles' phone back just in time." [A picture of Lee surreptitiously recovering the phone appears.] "And it will be cracked."
12:35:15
Lee: "In twenty-five minutes, lunch detention gets out. But at this rate, I might not make it back!"
[Lee is in the underground tunnels.]
Lee: "Okay, this time, I'm getting proof!" [He takes out his cell phone. A red light is blinking on it.] "Out of power? But then how is it flashing red?" [The sound of two cleaners draws Lee's attention. A similar red dot is flashing on their chestplates.] "I thought you guys were deactivated!"
[The cleaners pull out their crystal guns and advance on Lee.]
Earlier that day...7:54 AM
Holger: [singing] "Fries are flew as my pie!"
Lee: "Hey. Isn't that that lame song Cam likes so much?"
Camillio: [grumpy] "I so don't like that song, and it's eyes as blue as the sky."
Holger: "Vit new phone, song sound so good in my earholes!"
Brandy: [upset] "Leaping, where have you been, don't you ever check your phone?" [She walks up to him.]
Lee: [checking his phone] "Uh, sorry. Ha, new phone, still figuring it out."
Holger: [singing] "Skies make stew for my cry!"
Brandy: "'Kay, whatever, I've got this killer first history test, and quick, what year did the Mongol hordes ravage the Caucasus mountains?"
Lee: "I don't know that. Who knows that?"
Camillio: "Twelve-sixty. The Berke-Hulagu war."
Lee: [grinning] "Yeah. Weird, huh? Cam's crazy good at history."
[A whistle catches Lee's attention. He looks in its direction and sees Biffy hiding in a bush. The bully beckons him over.]
Lee: "Biff." [to Brandy] "So, Cam's the guy you wanna talk to if you need help." [He runs off.]
Camillio: [putting an arm around Brandy's shoulder] "Yo, chica for reals, if we don't remember the past, we're totally like doomed to repeat it yo. Some way famous dude with a mustache said that."
Brandy: "Yeah. That's great. So do you really know all this stuff?"
Camillio: "Did Genghis Khan drive a horse? Of course I do. It's mucho interesting."
Holger: [singing] "And guys like you they say hiiiiii-hooo."
Camillio: "And dude! Finito! You're like totally butchering that song, ohnkay?"
Brandy: "Fine. You're hired."
[Brandy leads Cam into the school. Two jocks walk by, listening to music.]
Evan: "Heard the new dance remix? Sounds so cool."
Holger: [overhearing] "Dance remix?" [excited] "Ooh! Holger must be downloading it now!"
[The jocks enter the school, on the way passing Lee, who is deep in conversation with a bush.]
Lee: "Don't worry, no one can see you, no one'll know we're friends. You look terrible." [Biffy has a five o'clock shadow, straggly hair, and bloodshot eyes.] "Did you stay up all night?"
Biffy: "Yes! And RRRRGH! I hate you phone!"
Lee: "So I take it you're still having trouble hacking it."
Biffy: "Every time I think I figured it–" [He begins ramming his head against the phone.] "Uuugh! Please can I smash it now!?!?!"
Lee: [grabbing the phone] "No! I need the info on it."
Biffy: "No. You need, is a room, full of supergeniuses, working around the clock, wi-with a supercomputer, and two, no, no, make it three, highly trained monkeys, and, AAAAHHH! I don't know! That phone has broken my brain!"
Lee: "Don't worry, I'll think of something. You should–" [Biffy falls asleep.] "Yeah. Nighty-night."
Tina: [over the intercom] "Would the following students report to Room 113b. Camillio Martinez and Toni Williams."
[A group of students enters the library. In this group are Lee and Holger.]
Principal General Barrage: "Hurry up! This ain't the slowpoke parade! Move out! Move in!" [to an emo] "You, over there. Double time!"
[The student runs in the direction indicated.]
Vice Principal Victoria: "General Principal Barrage, you're stressing out the students. Haven't you put them through enough lately?"
Principal General Barrage: [pretending to consider] "Mmm...nope!"
[The students stand at attention in a small group.]
Holger: [listening to music] "Holger is liking faster version more! Uh oot oot oot oot oot yah da-da-dah!"
[Lee turns away from his friend and spies a mathlete sneaking into the stacks.]
Lee: [to himself] "Strange. Where's Irwin going?"
Principal General Barrage: "O-kay lily lovers! Your vice principal, has something to tell you!"
Vice Principal Victoria: "Welcome students to the grand reopening of your state-of-the-art twenty-first century library." [pulling out a poster] "Made possible with donations from the Green Apple Splat Foundation." [Lee spots another boy sneaking into the stacks. He is followed by Nadine.] "Before our orientation, we have a gift from the good people at the Mobile Wireless Federation. Free phones for everyone who didn't get one yesterday!"
[The students cheer. Barrage groans and marches out of the room. While the other students walk forward to get their phones, Lee's attention is drawn by the sound of a hiss.]
Lee: [looking over] "Whoa, Tazelwurm sighting!" [The Red Tazelwurm hisses again and runs between two bookshelves.] "Is he–trying to get my attention?"
[Lee walks over to the shelves and peers down the aisle. He spots the Red Tazelwurm's shadow at the end of the aisle. The Red Tazelwurm hisses and moves on. Lee follows it to the end of the library, where his phone begins ringing. Lee answers it.]
Radcircles: "Knock knock."
Lee: "Ah ha. Lemme guess. Radcircles?"
Radcircles: "You won't know, 'cause you didn't say who's there."
Lee: "Hilarious! Any chance you wanna give me another number for your password?"
Radcircles: "And ruin our game? I already gave you a freebie. Give up! You'll never get it. Oh, and I have a present for you!"
[The phone sparks and electrocutes Lee.]
Lee: "Ow!" [He tosses the phone away.] "Oh, I so hate that guy!"
[Lee begins feeling around on the ground for his phone. Suddenly, the Red Tazelwurm uses its tail to push the phone over to Lee.]
Lee: "Whoa!"
[The Red Tazelwurm hisses and taps the glass wall at the back of the library. Lee taps it as well.]
Lee: "Trying to tell me something buddy?"
[The Red Tazelwurm hisses and moves off. Lee taps on the glass again, and someone taps him on the shoulder.]
Lee: [startled] "Aah!"
Holger: [startled] "Aah!"
Lee: [relieved] "Aw."
Holger: [chuckling] "Sorry, but Holger vundering have you heard dance remix of song?"
Lee: "Not now Holg, I think something's up with this wall." [He begins tapping on random parts of it.]
Holger: "Holger try too! For funness!"
[Holger and Lee tap on the glass wall. Meanwhile, the Red Tazelwurm slithers into a vent. Soon, sounds are emitted from behind the glass.]
Nadine: "What?"
Tech Nerd: "Ew!"
Grayson: "Let us out of here!"
[A door in the wall slides open, and the Red Tazelwurm pops out.]
Irwin: "It could have rabies!" [Irwin comes to the door and gasps when he sees Lee.]
Lee: "Whoa. You guys have a secret lair inside the secret passage?"
Irwin: "What secret passage?"
Lee: "C'mon, don't be such a doofus."
Tech Nerd: "Lee's hardcore. Took a robot's head clear off."
Lee: "Heh. You know it. Who da man." [They bump fists, and the tech nerd invites him in.] "Whoa. What the–"
[Irwin looks out into the library suspiciously and shuts the door.]
[Cam and Brandy are studying in the lunchroom.]
Brandy: "Ugh! How am I supposed to memorize everything in this whole book before the test? Help me."
Camillio: "Chill, chiquita. You just need to know the Cam method. Listen, Mister Rousseau is lazy. He always picks one chapter. And it's your first test so like, y'know, memorize chapter one. Chinese dynasties." [He puts on a pair of sunglasses.] "Now if you don't mind, el prez has some scouting to do." [He turns around and begins staring at a trio of cheerleaders.]
Brandy: [put off] "You like Toni? Really?"
Camillio: [taking off his sunglasses] "Why she say she like me?"
Brandy: "No, of course not she's so not your type you don't even know her."
Camillio: [lovesick] "Well, I, I know she likes to like, giggle. And she's always smiling. Mucho positive vibes. ¡Y muy caliente!"
Brandy: "So write a poem about it. I'm trying to study, and you're supposed to be helping."
[Brandy buries her nose in her book. Cam turns around and resumes staring at Toni from behind sunglasses.]
Camillio: "Hey, wait a minute! Since I showed you the Cam method, how about hooking me up with something?"
Brandy: [annoyed] "Fine, if I get an A, I'll help you, but seriously, her, you, not seeing it, don't like the odds, I wouldn't go there."
Camillio: [turning back around] "Whatever bro."
[Lee and Holger are now in the secret room. The room also has a some full bookshelves, a large cabinet, a portable surgical table, and a few high-powered computers. Beside Lee, Holger, and Irwin, the inhabitants of the room include Nadine, Grayson, the tech nerd, and Ruby.]
Irwin: "It's my secret base of operations. And no, you're still not welcome!"
Nadine: "Yours, please. I found it."
Tech Nerd: "Hey! I found it too."
[Nadine and the tech nerd remember falling into the room while being chased by hazmats.]
Nadine: "And I vote they can stay." [The tech nerd nods.] "Lee's chill."
Lee: "Thanks."
[Holger puts on a song and begins dancing. He bumps the surgical table, and an arm flops down. Holger gasps and reaches for the cover on the table.]
Irwin: "Hey, stay away from there!"
[Holger pulls the sheet partway off, revealing a decapitated cleaner.]
Holger: "AAAHH! AAAAAAAAHHHH! NO! HEAD! AAAAAHH! The tops of the shoulders is no more! No-ho-ho-ho!"
[Holger scrambles backwards on the floor like a crab. Lee walks up to the table.]
Lee: "What? You were the ones who turned the cleaners against us? Why do you have this? Planning another rampage?"
Nadine: "That wasn't us. We wanna make sure it never happens again."
Grayson: "Yeah. We scored this before Barrage came and took the head away."
Tech Nerd: "I call him Headless Jonesy."
Holger: [frightened] "I call him Scary McScarypants."
Irwin: "We need that head."
Lee: "Why, building a prom date, Irwin?"
[The group cracks up, much to Irwin's consternation.]
Irwin: "Silence!"
Grayson: [fiddling with the monitors] "If we get a complete hazmat, we can figure out how they work." [He brings up details of their scheme on the screens.]
Tech Nerd: "Yeah, and Lee could get us a head." [to Lee] "Since, you're like, ninja slash samurai good."
Ruby: [replaying security footage] "You did knock the head off. It's only fair that you get it back."
Lee: "Me? Are you crazy?"
[Lee stares at them. Suddenly, the words of Biffy pop into his head.]
Memory Biffy: "What you need, is a room, full of supergeniuses."
[Lee gasps. He has that room in front of him.]
Lee: "Thank you Biffy!" [to the group] "How good are you guys at hacking things?"
Irwin: "Our success rate is impeccable."
Lee: [holding up the phone] "Bet you can't hack this."
Irwin: "Please. I could hack that in my sleep, and still have time to dream about parabolic calculus."
Lee: "You unlock this phone, I'll get you the head. And we all figure out what makes these bad boys tick."
Irwin: "So hand it over."
Lee: "Ah, no way, I'm not leaving this with you. You're the leader of the Down With Lee Club! You hate me."
Irwin: [whispering to the others] "It's true. I really do hate him."
Nadine: [fed up] "Ugh, I'll handle it." [Lee hands the phone over to her.]
Tech Nerd: "And I'll warm up the computers!"
Holger: [clapping] "Ooh! Holger! Holger help too! I be standing guard. Keep I spy on sneaky Irvin guy, ja? And also, do perhaps some teensy dancing?" [He begins dancing to his music again.] "Ooh, ja ooh, little dance break!"
[The cheerleaders are hanging out in the hall between classes. Cam watches them until Brandy comes up behind him and pulls him into a hug.]
Brandy: [ecstatic] "Cam you were so right I totally aced that test!"
Camillio: "Hey heyhey, okay, now you can help me. Uh, go find out some girly gossip slash Cam-related stuff, m'kay? And tell her I can like uh, bench-press a moose or something macho like that."
Brandy: "Huh. Fine. No problem." [calling to the cheerleaders] "Toni! Cam likes you!"
[The cheerleaders giggle.]
Camillio: "Uh..." [hushed, to Brandy] "Gee thanks, like I couldn't do that?"
[Brandy waves goodbye and walks away. The cheerleaders turn back to their conversation.]
Camillio: [to himself] "'Kay Cam, Brandy tried to throw you off. But you the man, man! Make your move!" [He walks over to Toni with a swagger in his step.] "Hey hey, Camillio Martinez, school president. Perhaps you've seen me around town?"
[Toni's phone rings. She answers, and the prank song begins playing from it.]
Camillio: [to himself] "Whoa, totally dissed! Abort chiquitaleader mission pronto! Brandy totally messed up my mojo!"
[Cam scrams. Toni finishes her phone call, hangs up, and turns back to where Cam was last.]
Toni: [confused] "Cam? Where'd he go?"
[The other two cheerleaders point after him.]
[Lee and Biffy are in lunch detention.]
Biffy: "Seriously? A head? But they all disappeared in the big hazmat shutdown last week. The only one who knows where all those robot cleaners went is–" [Barrage throws the door to detention open.]
Principal General Barrage: "Weeeelll. If it ain't sad and pathetic." [He chuckles grimly.]
Lee: "Uh, sir? Just wondering. Whatever happened to all those janitors? Y'know, the robot ones."
Principal General Barrage: "That information is classified! Top secret! Need-to-know basis! In other words, it never happened."
Lee: "But, I was there–"
Principal General Barrage: "No! You were staring at the wall, and twiddling your useless thumbs!"
[The principal storms out and shuts the door behind him, effectively ending the conversation.]
Biffy: "Okay, problem solved. You need a head? Biffy's got a plan."
Lee: "That was fast."
Biffy: "Well that's how I roll. Fast and loose. Just get a piece off the robot your new pals have, hand it over to Principal Cyborg, and kaching! You're following him–"
Lee: [jumping in] "Following him to where he puts it! Dude! Why aren't you in the Genius Club?"
Biffy: "I hate clubs."
[Lee begins preparing to enter the vents. He places a phone call.]
Lee: "Ruby? Any chance you could spare a pinky? No not yours. The robot's!"
[Lee hangs up and climbs into the vents.]
[The principal and vice principal are having a discussion in the principal's office.]
Principal General Barrage: [angry] "What'd I say about accepting those phones?"
Vice Principal Victoria: "If everyone has one, we can prove to Blompkins that phones can be a teaching aid. And maybe save your job. You can't destroy their property, that was illegal."
[The vice principal leaves as the principal growls. Ruby sticks her head through the door.]
Ruby: "Mister Principal sir?" [She wanders into the office.]
Principal General Barrage: "What is it, private? Lee Ping trying to frame you for his dirty work again?"
Ruby: "No." [She brings her hands out from behind her back.] "I found this in the hall and thought you might want it."
[The principal takes the disembodied robot finger and stares at it.]
Principal General Barrage: "Everything's almost salvaged. Just need one more body, minus a head, and minus one finger." [to Ruby] "Much obliged, cadet."
Ruby: [backing out of the room] "Just doing my duty as a respectful student, sir."
[Lee has watched the exchange from inside of a vent located behind Barrage. He taps his earpiece.]
Lee: "Biff! She's made the handoff."
Principal General Barrage: [to himself] "Time to take this little pinky wee wee wee all the way home."
[The principal hits a button on his laptop, and part of the wall in his office slides away, revealing a door hidden behind it. Barrage types a code into a keypad by the door, and it opens into a tunnel. The general walks into the tunnel, carrying the finger with him.]
Biffy: "Dude. What's going on now?"
Lee: "Barrage has a secret passage in here."
[Lee takes the vent cover off, drops to the floor, and runs over to the tunnel. Before he can enter, however, the door slams shut in his face. Lee takes a gander at the look.]
Lee: "Hey, the lock is just like–"
[Lee pops out his key, opens it, and uses it on the tunnel door. The door slides away for him.]
Lee: "Heh." [He enters the tunnel.]
[Most of the Genius Club is focused on Radcircles' password encryption.]
Nadine: "It's an endless loop! There's no repeaters."
Tech Nerd: "What if it really is unhackable?"
Irwin: "There's always a pattern, and I can see it from here. Ugh, amateurs."
Nadine: "Okay, Einstein, care to enlighten us?"
Irwin: "And make it easy for Ping? Never." [turning to Holger] "And you. Really? Are you still attempting to dance?"
Holger: [insulted] "You dare dishonor Holger's dance moves?" [He slaps Irwin with a purple glove.]
Irwin: "Where'd you get the glove?"
Holger: "Holger have many gloves of slapping!" [He pulls out a white glove and slaps Irwin with it.] "And many gloves of challenging! Holger challenge you to dance-off! Till vun person go kafloofashoop! Holger vin, you helping your nerd friend, ja?"
Grayson: "I'm not a nerd!"
Nadine: "Yeah me neither."
[The tech nerd sighs.]
Irwin: "And if I win, which all calculations point to, you can't dance for the rest of the year!"
Holger: [confident] "Ha, Holger accept."
[Irwin rips off his clothes, revealing his dancing uniform underneath.]
Holger: "Huh?"
Irwin: "Wristband me. Do it!"
[The Genius Club provides him with the requisite bands, and Irwin shows a few seconds of his dancing prowess. Holger remembers how well Irwin can dance.]
Holger: "Oh no. What has Holger done?"
[Lee is in the clean metallic tunnels underneath the school. He sees the principal enter a room. He sneaks over to the doorway and looks inside.]
Principal General Barrage: "Almost all accounted for. When I get all the pieces together, I'll put y'all back in action!" [Inside the room is a rack full of cleaners.] "Stronger than before!"
[Barrage laughs as Lee gapes. He then puts the finger on a table next to a disembodied hazmat head.]
Lee: "Bingo." [using his earpiece] "Ground control, head acquired." [A squeal of feedback blasts into his ear.] "Ow!"
Principal General Barrage: [on alert] "Who goes there? State your clearance!"
[Lee stumbles away, but another blast of feedback pierces his eardrum.]
Lee: "Ahh!" [He falls onto the ground beside a big rock. Barrage's shadow looms over him.]
[Barrage has just exited the room when a loud hiss draws his attention.]
Principal General Barrage: "Huh?" [He looks in the opposite direction of Lee. The Red Tazelwurm leaps out of a vent.] "You again!" [Lee silently gets up and flees in the opposite direction.] "You've haunted these halls long enough!"
[The Red Tazelwurm runs away from Barrage, who gives chase. Lee breathes a sigh of relief.]
[Cam is in the cafeteria, playing a game on his phone.]
Camillio: "Hey come on! Cheap!" [He tosses the phone away and winces when he hears a shattering noise.] "Whoops." [He goes over and picks up his dented phone.] "Uh oh. That might've been bad." [The phone shoots sparks.] "Yeah. That was bad." [upset] "Aw man these new phones suck!" [He chucks the phone at the floor again. Brandy walks up.]
Brandy: "So, what happened to–" [mockingly] "–Toni?"
Camillio: [stressed] "She chose her phone over talking to me. You were supposed to make me look smooth! Thanks for nothing."
Brandy: "I know that was the deal–" [her phone rings] "–but I can't see you two together so it's probably for the best–" [the number is blocked] "–she is so not your type."
Camillio: "Oh yeah?" [The phone continues to ring.] "Who is my type aren't you gonna answer that thing?"
Brandy: "Someone shorter, less athletic, and no. I don't answer blocked numbers." [She hangs up on it.] "Trust me, she's not into you."
Toni: "Cam!" [She bounds up to him.] "I've been looking everywhere for you."
Camillio: "Hey there chica, what's going on?"
Toni: "Hiya Cam. So, I was just wondering–"
Brandy: "Ew! Gross! Lame flirting! Ciao." [She leaves.]
Toni: [offended] "Did you just call my Cam gross?"
Brandy: [coming back] "No, I was calling this whole thing gross, and your Cam? Whatever!"
Toni: "Don't whatever me!"
Brandy: "I'll whatever whoever I want to whatever!"
Toni: "Whatevs!"
Brandy: "Whatevs you!"
Camillio: "Girls? Fighting over me? Aw, awesome."
[Lee walks up to the disembodied head on the table.]
Lee: "That tazelwurm rocks." [He taps his earpiece.] "Dude, ya there? Why'd you tweak my headgear?"
Biffy: "I didn't. But I heard it here too. Maybe some bugs in the new phones. You better start heading back."
[Suddenly, the door slides open, revealing the Red Tazelwurm. The Red Tazelwurm hisses and points at a lever. Lee reaches for it and then stops.]
Lee: "Why are you helping me?"
Principal General Barrage: "Get back here mythological creature of the unknown!" [The Red Tazelwurm moves off again.] "That's an order!"
[Lee pulls the switch, and the section of the wall it's located on slides up to reveal another door. Lee uses his key to unlock it and walks through the door. His cell phone screen begins flashing an intermittent, beeping red circle–one that is echoed on the chestplate of one of the cleaners.]
[Holger and Irwin are still engaged in their dance-off.]
Irwin: [panting] "You'll never be able to keep up with me!"
Nadine: [unimpressed] "Anyone else bored with this?"
Ruby: "Yes."
Tech Nerd: "Totally."
Grayson: "Oh I'm done."
Irwin: "Hey! Pay attention. I'm totally about to execute a statistically flawless rumba-salsa-waltz." [He goes into a complicated dance move.] "Eat my vapor."
Holger: [copying Irwin's move] "It is the vapor of mine you will be dining on tonight, my friend."
Irwin: "Mine was better! Tell him."
Ruby: [staring at the computer screens] "Don't care."
Nadine: "Never will."
[Lee walks through the halls. Suddenly, he sees something through a doorway.]
Lee: "Whoa. Here it is again!"
[Lee walks into the room, which is labeled 113B. He sets the head down on a table and taps his earpiece.]
Lee: "I found that crazy brainwashing room again! And news flash, it's even crazier now!"
[Lee gets no response.]
Lee: "Biff? Biff! Man, what is Barrage up to?" [He walks over to a portable bulletin board.] "Plans for a Save The Rainforest Dance? I thought the theme was undecided."
[A beeping from behind the board catches his attention, and he pushes the board aside. On the other side is a large metal orb full of circuitry with wires protruding from it. In front of the orb is an electronic board with the pictures of several different students on it.]
Lee: "What is this?"
[As Lee watches, the wires plug into various parts of the board two at a time: Holger and Kimmie, Brad and Tina, Greta and Ed, Brandy and Dickie, and Toni and Cam.]
Lee: "Toni, Cam, Brandy, Dickie, all lumped together, what is this? Okay this time, I'm getting proof." [He holds up his phone to take a picture and notices a red circle blinking on it.] "Out of power? But then how is it flashing red?"
[Two cleaners enter the room. Lee gasps.]
Lee: "I thought you guys were deactivated!"
[The two hazmats pull out their crystalizing guns and advance on Lee.]
Lee: "Okay, my bad. Uh, any chance I could get that head back and just walk outta here?"
[Irwin and Holger are still dancing. The Genius Club has returned to trying to crack the code.]
Nadine: "I'm still not seeing any pattern. Anyone think Irwin was lying?" [crankily] "WOULD YOU GUYS TURN IT DOWN ALREADY! I'M TRYING TO THINK OVER HERE!"
Irwin: [to Holger] "You're good, but not good enough to withstand the awesomeness of this!"
[Irwin dances faster and laughs evilly. Holger is amazed by his dance moves.]
Irwin: "If you stop dancing I win!"
Holger: [tired] "Losing. Too. Much. Hydration. Must. Reach." [He reaches out for a bottle of water and squirts a bunch into his mouth. A smile comes to his face.] "H2O make Holger sparkle!"
[Irwin's mouth drops open, and he loses his concentration. This causes his legs to tangle, and Irwin stumbles and falls to the floor.]
Holger: [overjoyed] "Holger vins! Yahoo!"
Irwin: "Nooooo! Inconceivable!"
Holger: "Conceive it. Now, you tell nerds, your secret of numbers, ja?"
Grayson: "We're not nerds!"
Nadine: "We're geniuses!"
Irwin: [getting up] "I'm the only real genius. Can't you see it's the radius circle theorem?"
[The rest of the Genius Club looks at the encryption.]
Nadine: "Whoa. He's actually right."
Grayson: [typing] "Of course! And if that's the case, then it has to be one of these!"
[The cleaners are about to fire on Lee when the Red Tazelwurm drops from the vents and knocks two empty soda cans into the line of fire. They take the impact of the blasts and are crystalized, while the Red Tazelwurm goes over to Lee.]
Lee: "Wow, thanks!" [The hazmats fire again.] "Duck!"
[The Red Tazelwurm dives at Lee and takes them both beneath the bulletin board. Hearing the commotion, Barrage enters the room.]
Principal General Barrage: [upset] "What in blustery blazes of indigo infernos is going on in here!" [The hazmats fire on him, encasing him in crystal.] "Oh, you're gonna wish you never did that!" [He breaks out of his crystal prison.] "It's sweetie-pie time!"
[The general punches one of the hazmats, knocking it to the floor. The other one retreats, but is not able to escape Barrage's wrath, as Barrage proceeds to go to town on him. Lee uses the opportunity to leave, but stops at the door and eyes the head. The Red Tazelwurm appears beside it and knocks the head to Lee with its tail. They smile at each other, and Lee leaves. He makes his way through the tunnels and finds a door. He uses his key and is let out into the Genius Club's secret base.]
Grayson, Ruby, Nadine, and Tech Nerd: "Yaaaaayyy!"
Tech Nerd: "He did it!"
Holger: "Yoohoo!"
Lee: [panting] "Head! Phone!"
Nadine: "Almost..."
Ruby: "Wait for it..."
Tech Nerd: "Any second..."
[All of the numbers onscreen but four disappear. The ones left are 7, 3, 2, and 7. The phone unlocks.]
Ruby: [handing it over] "Phone!"
Lee: "Thanks, gotta jet." [He tosses the head to Irwin and runs out of the room.]
Irwin: "Huzzah! Finally. And the latch should be–" [He opens the faceplate.] "Odd."
Nadine: "What? Let me see."
Irwin: "Forceps! Quickly!" [The tech nerd hands him a pair of forceps, and Irwin uses them to remove a chip.] "This shouldn't be here. Whoever used to be in control of these, isn't anymore!"
Holger: [singing] "Dah dah dum DAAAHM!"
[The musical sting echoes Holger's tune.]
[By 8:09 at night, Lee has finally worked up the courage to see what's on the phone.]
Lee: "Okay Rad, it's time."
[A video chat window opens on Lee's computer.]
Camillio: "Yo, dude, ese, you missed like the greatest day! Girls were like fighting over me, bro! But uh, one was Brandy, so uh, dude you cool with that, 'cause I know like you and her, got a, you know you got a, got a–"
Lee: "Wait! Was the other Toni?"
Camillio: "Yeah! How'd you know?"
[Cam's signal is interrupted and replaced by that of Radcircles.]
Radcircles: "Knock–"
Lee: [quickly] "Knock knock!"
Radcircles: "Hey! That's my line."
Lee: "Uh, so sorry. You didn't say who's there."
Radcircles: "Sticking to the rules of knock-knock logic. Well played. Isn't it time to just give up your pointless quest to unlock my phone?"
Lee: "Oh, don't you worry there, buddy. I'll crack your phone. Someday." [He turns off his computer.] "Like today. Advantage: Ping." [He turns on the phone.] "Time to check out all your secrets, Rad!"
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Top definition
1. Any Hispanic/Latino male that skeets a lot or skeets very fast. If they skeet fast they are also an Early Skeeter. Also any Mexican Mouse that skeets a lot.
2. Skeety Gonzales was a famous Mexican Mouse that lived in the 60s and 70s and could possibly still be alive. Skeety Gonzales was the apprentice of the great Skeet Magee, the most famous Skeeter of all time. Skeety Gonzales crossed paths with Skeet Magee in 1968 and saw all the good Skeet Magee was doing and Magee taught Gonzalez the way of ejaculating in public to promote peace and ease racial tensions. Skeety did his part by easing species tensions between all animals. Skeety was just a small mouse but he sure could skeet. He would always make sure to masturbate in public at least 5 times a day. Skeety could also run really fast, his brother was the famous mouse speedy gonzales. Skeety Gonzales' most famous stunt was getting every female mouse in town pregnant and covering them with skeet juice (this could attribute to all the female mice in town turning white). Skeety was last seen in the late 70s, a decade after Skeet Magee disappeared. He repeated Magees famous last words, but in Spanish: "Vine, vi, yo skeeted, yo espero que usted haga lo mismo." (Skeety spoke very poor spanish at this time.)
Skeety's major traits are his ability to run extremely fast, and his comedic Mexican accent. He usually wears an oversized yellow sombrero, a white shirt and trousers, and a red ascot. His Brother is Speedy gonzales.
Bob: "Dude that one male mouse that I have got all the females pregnant!!!"
Dave: "How many females were there?"
Bob: "59!!!, and he turned all of em skeet white"
Dave: "Damn, Youve got urself a regular Skeety Gonzales!!!"
by David Skeet Jr. April 21, 2008
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It does not matter how you do it. It's a Fecal Mustache.
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GuruFocus has detected 2 Warning Signs with United States Steel Corp \$X.
More than 500,000 people have already joined GuruFocus to track the stocks they follow and exchange investment ideas.
United States Steel Corp (NYSE:X)
Net Cash per Share
\$-31.14 (As of Dec. 2016)
Net cash per share is calculated as Cash and Cash Equivalents minus Total Liabilities and then divided by Shares Outstanding. United States Steel Corp's net cash per share for the quarter that ended in Dec. 2016 was \$-31.14.
Definition
In the calculation of a companys net cash, assets other than cash and short term investments are considered to be worth nothing. But the company has to pay its debt and other liabilities in full. This is an extremely conservative way of valuation. Most companies have negative net cash. But sometimes a companys price may be lower than its net-cash.
United States Steel Corp's Net Cash Per Share for the fiscal year that ended in Dec. 2016 is calculated as
Net Cash Per Share (A: Dec. 2016 ) = (Cash and Cash Equivalents - Total Liabilities) / Shares Outstanding = (1515 - 6886) / 172.46 = -31.14
United States Steel Corp's Net Cash Per Share for the quarter that ended in Dec. 2016 is calculated as
Net Cash Per Share (Q: Dec. 2016 ) = (Cash and Cash Equivalents - Total Liabilities) / Shares Outstanding = (1515 - 6886) / 172.46 = -31.14
* All numbers are in millions except for per share data and ratio. All numbers are in their local exchange's currency.
Explanation
Ben Graham invested in situations where the companys stock price was lower than its net-cash. He assigned some value to the companys other current asset. The value is called Net Current Asset Value (NCAV). One research study, covering the years 1970 through 1983 showed that portfolios picked at the beginning of each year, and held for one year, returned 29.4 percent, on average, over the 13-year period, compared to 11.5 percent for the S&P 500 Index. Other studies of Grahams strategy produced similar results.
You can find companies that are traded below their Net Current Asset Value (NCAV) with our Net-Net screener. GuruFocus also publishes a monthly Net-Net newsletter.
Related Terms
Historical Data
* All numbers are in millions except for per share data and ratio. All numbers are in their local exchange's currency.
United States Steel Corp Annual Data
Dec07 Dec08 Dec09 Dec10 Dec11 Dec12 Dec13 Dec14 Dec15 Dec16 netcash -82.34 -90.04 -66.47 -76.01 -84.48 -77.42 -63.34 -47.10 -40.85 -31.14
United States Steel Corp Quarterly Data
Sep14 Dec14 Mar15 Jun15 Sep15 Dec15 Mar16 Jun16 Sep16 Dec16 netcash -46.81 -47.10 -45.38 -44.61 -46.87 -40.85 -42.95 -42.31 -31.43 -31.14
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