So, I snagged this Beyonce biography on a whim. I’m not big into biographies but seeing as Beyonce is such a big star I thought perhaps there might be a few nuggets of wisdom about her work ethic. I was not wrong. While this biography was informative, it did not feel like it was properly sanctioned from Beyonce’s camp nor did it feel like you were listening to the whole story. What it felt like was information gleaned from speculation, {Read More}

Introducing Pam

I realized that few mainstream books contain diverse and multicultural characters. I decided to help others hunt for books containing diversity. If you're ready to discover great books for people of all kind, stick around. I Volunteer. To read diversity.


Identify energy flows

Plant-wide transparency

This phase primarily involves identifying energy flows - with the objective of transparently showing the energy requirements of the various sub-processes. The data retrieved here already allow a first evaluation of the potential energy saving and create the basis for intelligent and efficient energy management.

Whether for electrical energy or other energy forms such as water, gas, compressed air etc.: Meaningful comparisons can only be made and practical and realistic optimization measures defined if precise usage values and power data are available over a longer period of time.

Efficient energy monitoring is indispensable in production and process automation as well as in the building sector, especially when it involves complex tasks. Only then can the relevant measured variables be precisely monitored and analyzed - for instance, electric power consumption, load profiles, temperatures and flow rates.

When it involves identifying energy flows, we can offer you powerful hardware and software solutions for all tasks that have been thought out in detail.


@inproceedings{2000960, author={Tokuo Yamaguchi and Sriram Subramanian and Yoshifumi Kitamura and Fumio Kishino }, title={Dynamics of strategic negotiations on SharedWell }, booktitle={Proceedings of the 4th Annual Conference on Collaboration Technologies }, pages={140--145}, month={August}, year={2008}, abstract={ a??SharedWella?? is a single display system that allows multiple users to interact with both private and public information in a face-to-face co-located setting. It is especially suited for strategic cooperative tasks which include both competitive and collaborative aspects. This type of collaboration, called strategic negotiations, requires users to perform three phases: identifying the right timing, using epistemic actions to draw attention, and evaluating the value of the negotiation. We conducted an observational study to investigate and evaluate deeper strategic negotiations on the SharedWell compared with other setups; a setup using notebooks and a real-world setup.}, abstract-url={http://www.cs.bris.ac.uk/Publications/pub_master.jsp?id=2000960}, keyword={}, pubtype={102} }


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Physicists renew interest in antimatter with latest discovery
Scientists have renewed their interest in antimatter, as physicists have measured the forces that make certain antimatter particles stick together. In a paper published in the journal Nature, scientists found that the force between antiproton pairs is attractive, similar to the strong nuclear force that holds protons together within atoms.

More than 500 scientists showed that the attractive force between antiprotons worked the way it does in matter, indicating that antimatter is not as different from matter as previously thought. The study paves the way for more discoveries regarding the matter-antimatter asymmetry after the Big Bang. It has long been a puzzle in particle physics why the Universe as we see it is made up mostly of ordinary matter, with hardly any antimatter around, even though the two should be more or less evenly spread.

"The Big Bang – the beginning of the universe – produced matter and antimatter in equal amounts. But that's not the world we see today. Antimatter is extremely rare. It's a huge mystery!" explained Aihong Tang, one of the scientists analyzing the data collected by the Relativistic Heavy Ion Collider (RHIC) STAR detector.

"Although this puzzle has been known for decades and little clues have emerged, it remains one of the big challenges of science. Anything we learn about the nature of antimatter can potentially contribute to solving this puzzle."

Strong attractive force

RHIC is a place where antimatter is produced. Production is done by smashing the nuclei of heavy atoms like gold into each other at nearly the speed of light. It aims to emulate the conditions of the Universe just a few microseconds after the Big Bang to figure out exactly what happened next.

The determining factors of the experiments were the effective range of the two antiprotons, or the measurement of how close two particles need to be to influence each other with their electric charges, and the scattering length, or how the particles deviate as they travel from the source to their destination.

"It could have been that antimatter didn't have the same attractive force as matter and would have helped explain how these differences, during the initial part of the Big Bang, might have resulted in antimatter not having survived in the shape of stars and planets, as matter did," physicist Frank Geurts said in a statement.

Measurements were difficult to take for a variety of reasons, especially considering how small they are. Both are measured in femtometers or one-quadrillionth of a meter. In the RHIC antiproton experiments, the scattering length was around 7.41 femtometers and the effective range was 2.14 femtometers, roughly similar to their proton counterparts.

"This discovery isn't a surprise," said Kefeng Xin, a contributing scientist to the study. "We've been studying the interaction between nucleons (particles that make up an atom's nucleus) for decades, and we've always thought the forces between antimatter particles are the same as for matter. But this is the first time we've been able to quantify it."

Antimatter discoveries

Aside from the experiments in the RHIC, advances on antimatter studies were made when antimatter galaxies, asteroids, and cosmic rays were detected and confirmed for the first time in the history of mankind. Using the Santilli Telescope paired with a Galileo telescope, Dr. Ruggero Santilli of  Thunder Energies Corporation (OTCQB:TNRG), along with his team of scientists, was able to make the first detection in the Epsilon Alpha and Epsilon Beta near the Vega region of the night sky.

The Santilli Telescope is the world's first truly new telescope since Galileo times, as it is the first and only optical instrument with concave lenses, specialized for the systematic search of antimatter galaxies. The images captured by the Santilli telescope showed anomalous streaks and circles that were not in the images of the same sky region captured by a Galileo telescope. This suggests that they were of antimatter origin, with streaks and circles of darkness, rather than light, as their main feature.

"The physical relevance of Prof. Santilli's detection of antimatter galaxies is evident not only for the ensuing new conception of the universe, but also for the protection of our planet against antimatter asteroids," stated Prof. S. Georgiev in one of the independent confirmations of the detections.

The results of these experiments and research prove that antimatter is not completely lost, and that there's no difference between the behaviour of matter and antimatter in terms of strong force. Scientists will have to continue the search for that X factor in antimatter that explains why and where it diminished greatly.

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How to visit

Their peace and quiet and purity are further qualities that make these islands so outstanding. To protect the environment and avoid mass tourism, access to visitors is limited to 2,200 people per day. During Easter week, at weekends in May and throughout the summer, there are regular boat services from Vigo, Baiona and Cangas de Morrazo. If you want to stay the night in the Cíes, you'll find a campsite with 800 places that opens in Easter week, and on subsequent weekends until June, and then regularly between June and September, providing the weather conditions allow a regular boat service. You need to make a booking over the Park’s Reservation Centre website or at the campsite information office (located in Vigo’s ferry port where you take the boat to the Cíes Islands) to use the facilities. Once you have made the booking, you need to show it at the campsite office at Vigo ferry port on the departure date. However, if you take the boat from Cangas or Baiona, you will need to show it at the campsite reception when you get to the island (no booking is required in Easter Week).

A perfect day at the beach and more

If you prefer sporting activities, hiking is an excellent way of exploring the Cíes Islands. There are four established itineraries that leave from the information kiosk and where you can discover the forests, Los Niños Lake, bird watching observatories, a pre-Roman settlement, and wonderful views of the cliffs in the western part of the islands from their lighthouses. The Visitor Centre is located on the site of the remains of the old San Estevo monastery, and can provide you with information on the different routes, the importance of the natural environment and the norms to be observed. What's more, guided tours are also arranged periodically. The Park’s Reservation Centre website has information on these tours and how to make a booking.

Come and discover the Cíes Islands and you won't be disappointed. You'll see that words alone are insufficient to describe 'the islands of the gods'. More information:Spanish National Parks reservations websiteRías Baixas tourist officeMinistry of the Environment. Islas Atlánticas National Park

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1993 Tour Finals RR: Pete Sampras vs Stefan Edberg

Pete Sampras d. Stefan Edberg 6-3 7-6(3)

Use the links below to see dozens of tables displaying detailed data on every aspect of this match. For further context, tour and player averages are visible for most cells when you move your cursor over them. These figures are based on other charted matches, including 1537 ATP matches, 972 ATP matches on hard, 37 Pete Sampras matches (28 on hard), and 13 Stefan Edberg matches (7 on hard). The more charted matches in the database, the more valuable this project becomes. Please try charting a match yourself.

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Crystal Clear?

J.W. Valley, University of Wisconsin, Madison

The zircon pictured here is from the Jack Hills region of Australia and supposedly confirms the earth is 4.4 billion years old.

Evolutionary scientists say they have confirmed that 4.4 billion years is the age of the earth’s earliest rocks. They arrived at this date using assumptions and interpretations of zircon crystals found in Australian sandstone.1 When examined, however, their conclusions are merely the top floor of an elaborate house of cards.

Zircon grains are found in rocks all over the earth. Scientists say they found one grain whose ancient core has been undisturbed since its formation.

Based on zircons’ crystallization temperature, scientists believe they originally crystallized in rock while the earth’s magma was cooling soon after the earth formed.

Upon this unobserved foundation, researchers built up a story leading to the formation of the sandstone, into which the zircons found their way. Their conclusions are based on four microscopic zircon crystals (of the hundreds they analyzed, they found only four that yielded dates older than 4.3 billion years).

The next three stories in this house of cards are the unverifiable assumptions of radiometric dating: that we can know the initial conditions, that we can be sure there was no contamination (for 4.4 billion years!), and that the radioactive decay rate has not changed.

The top floor of this shaky house is the researchers’ decision to rely on the dating of the zircon’s core, while discounting the fact that other parts of the same microscopic crystal gave wildly divergent dates—from 492 million years to 3.4 billion years. And to add a leaky roof to the wobbly edifice, they got an age of 5.5 billion years when they dated clusters of lead atoms in the crystal—but they promptly threw these dates out because they were “clearly” older than the earth.

What seems clear from the many different dates they yield is that these zircon crystals aren’t really frozen in time; and because of that, it is unrealistic to rely on any dates derived from them.

Evolutionary scientists claim zircon crystals can be accurate time clocks, but they discard any “time stamps” that don’t support their ancient timeline. Scripture, on the other hand, reveals the earth is young. God’s Word, the Bible, is the unchanging rock upon which we can interpret history.

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 Department: Department of Materials Science and Engineering
 Collection: UNT Theses and Dissertations
Advanced Technology for Source Drain Resistance Reduction in Nanoscale FinFETs
Barrier and long term creep properties of polymer nanocomposites.
The barrier properties and long term strength retention of polymers are of significant importance in a number of applications. Enhanced lifetime food packaging, substrates for OLED based flexible displays and long duration scientific balloons are among them. Higher material requirements in these applications drive the need for an accurate measurement system. Therefore, a new system was engineered with enhanced sensitivity and accuracy. Permeability of polymers is affected by permeant solubility and diffusion. One effort to decrease diffusion rates is via increasing the transport path length. We explore this through dispersion of layered silicates into polymers. Layered silicates with effective aspect ratio of 1000:1 have shown promise in improving the barrier and mechanical properties of polymers. The surface of these inorganic silicates was modified with surfactants to improve the interaction with organic polymers. The micro and nanoscale dispersion of the layered silicates was probed using optical and transmission microscopy as well as x-ray diffraction. Thermal transitions were analyzed using differential scanning calorimetry. Mechanical and permeability measurements were correlated to the dispersion and increased density. The essential structure-property relationships were established by comparing semicrystalline and amorphous polymers. Semicrystalline polymers selected were nylon-6 and polyethylene terephthalate. The amorphous polymer was polyethylene terphthalate-glycol. Densification due to the layered silicate in both semicrystalline and amorphous polymers was associated with significant impact on barrier and long term creep behavior. The inferences were confirmed by investigating a semi-crystalline polymer - polyethylene - above and below the glass transition. The results show that the layered silicate influences the amorphous segments in polymers and barrier properties are affected by synergistic influences of densification and uniform dispersion of the layered silicates. digital.library.unt.edu/ark:/67531/metadc5563/
Bioresorbable Polymer Blend Scaffold for Tissue Engineering
Bulk and interfacial effects on density in polymer nanocomposites
Characterization of cure kinetics and physical properties of a high performance, glass fiber-reinforced epoxy prepreg and a novel fluorine-modified, amine-cured commercial epoxy.
Charge interaction effects in epoxy with cation exchanged montmorillonite clay and carbon nanotubes.
Definition of brittleness: Connections between mechanical and tribological properties of polymers.
Deposition and characterization of pentacene film.
Many organic materials have been studied to be used as semiconductors, few of them being pentacene and polythiophene. Organic semiconductors have been investigated to make organic thin film transistors. Pentacene has been used in the active region of the transistors. Transistors fabricated with pentacene do not have very high mobility. But in some applications, high mobility is not needed. In such application other properties of organic transistors are used, such as, ease of production and flexibility. Organic thin film transistors (OTFT) can find use as low density storage devices, such as smart cards or I.D. tags, and displays. OTFT are compatible with polymeric substrates and hence can find use as flexible computer screens. This project aims at making 'smart clothes', the cheap way, with pentacene based OTFT. This problem in lieu of thesis describes a way to deposit pentacene films and characterize it. Pentacene films were deposited on substrates and characterized using x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The substrate used was ~1500Å platinum on silicon wafer or bare silicon wafer. was used. A deposition system for vacuum deposition of pentacene was assembled. The XRD data for deposited pentacene films shows the presence of two phases, single crystal phase (SCP) and thin film phase (TFP), and the increase in percentage of SCP with increase in substrate temperature during deposition or by annealing the deposited film, in vacuum, at 80°C. digital.library.unt.edu/ark:/67531/metadc4388/
Determination of wear in polymers using multiple scratch test.
Development of a Novel Grease Resistant Functional Coatings for Paper-based Packaging and Assessment of Application by Flexographic Press
Recent commercial developments have created a need for alternative materials and methods for imparting oil/grease resistance to paper and/or paperboard used in packaging. The performance of a novel grease resistant functional coating comprised of polyvinyl alcohol (PVA), sodium tetraborate pentahydrate (borate) and acetonedicarboxylic acid (ACDA) and the application of said coating by means of flexographic press is presented herein. Application criteria is developed, testing procedures described, and performance assessment of the developed coating materials are made. SEM images along with contact angle data suggest that coating performance is probably attributable to decreased mean pore size in conjunction with a slightly increased surface contact angle facilitated by crosslinking of PVA molecules by both borate ions and ACDA. digital.library.unt.edu/ark:/67531/metadc4554/
Device Engineering for Enhanced Efficiency from Platinum(II) Phosphorescent OLEDs
Phosphorescent organic light emitting diodes (PHOLEDs) based on efficient electrophosphorescent dopant, platinum(II)-pyridyltriazolate complex, bis[3,5-bis(2-pyridyl)-1,2,4-triazolato]platinum(II) (Pt(ptp)2) have been studied and improved with respect to power efficiency, external efficiency, chromacity and efficiency roll-off. By studying the electrical and optical behavior of the doped devices and functionality of the various constituent layers, devices with a maximum EQE of 20.8±0.2 % and power efficiency of 45.1±0.9 lm/W (77lm/W with luminaries) have been engineered. This improvement compares to devices whose emission initially could only be detected by a photomultiplier tube in a darkened environment. These devices consisted of a 65 % bis[3,5-bis(2-pyridyl)-1,2,4-triazolato]platinum(II) (Pt(ptp)2) doped into 4,4'-bis(carbazol-9-yl)triphenylamine (CBP) an EML layer, a hole transporting layer/electron blocker of 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), an electron transport layer of 1,3,5-tris(phenyl-2-benzimidazolyl)-benzene (TPBI), and a LiF/Al cathode. These devices show the acceptable range for warm white light quadrants and qualify to be called "warm white" even w/o adding another emissive layer. Dual EML devices composed of neat Pt(ptp)2 films emitting orange and CBP: Pt(ptp)2 film emitting blue-green produced a color rendering index (CRI) of 59 and color coordinates (CIE) of (0.47,0.49) at 1000Cd/m² with power efficiency of 12.6±0.2 lm/W and EQE of 10.8±0.2 %. Devices with two blue fluorescent emission layers as singlet filters and one broad yellow emission layer from CBP: Pt(ptp)2 displayed a CRI of 78 and CIE of (0.28,0.31) at 100Cd/m² with maximum power efficiency of 6.7±0.3 lm/W and EQE of 5.7±0.2 %. digital.library.unt.edu/ark:/67531/metadc30482/
Effect of Silyation on Organosilcate Glass Films
Photoresist stripping with oxygen plasma ashing destroys the functional groups in organosilicate glass films and induce moisture uptake, causing low-k dielectric degradation. In this study, hexamethyldisilazane (HMDS), triethylchlorosilane and tripropylchlorosilane are used to repair the damage to organosilicate glass by the O2 plasma ashing process. The optimization of the surface functionalization of the organosilicate glass by the silanes and the thermal stability of the functionalized surfaces are investigated. These experimental results show that HMDS is a promising technique to repair the damage to OSG during the photoresist removal processing and that the heat treatment of the functionalized surfaces causes degradation of the silanes deteriorating the hydrophobicity of the films. digital.library.unt.edu/ark:/67531/metadc4549/
Effects of Plasma, Temperature and Chemical Reactions on Porous Low Dielectric Films for Semiconductor Devices
Low-dielectric (k) films are one of the performance drivers for continued scaling of integrated circuit devices. These films are needed in microelectronic device interconnects to lower power consumption and minimize cross talk between metal lines that "interconnect" transistors. Low-k materials currently in production for the 45 and 65 nm node are most often organosilicate glasses (OSG) with dielectric constants near 2.8 and nominal porosities of 8-10%. The next generation of low-k materials will require k values 2.6 and below for the 45 nm device generation and beyond. The continuous decrease in device dimensions in ultra large scale integrated (ULSI) circuits have brought about the replacement of the silicon dioxide interconnect dielectric (ILD), which has a dielectric constant (k) of approximately 4.1, with low dielectric constant materials. Lowering the dielectric constant reduces the propagation delays, RC constant (R = the resistance of the metal lines; C = the line capacitance), and metal cross-talk between wires. In order to reduce the RC constants, a number of low-k materials have been studied for use as intermetal dielectrics. The k values of these dielectric materials can be lowered by replacing oxide films with carbon-based polymer films, incorporating hydrocarbon functional groups into oxide films (SiOCH films), or introducing porogens in the film during processing to create pores. However, additional integration issues such as damage to these materials caused by plasma etch, plasma ash, and wet etch processes are yet to be overcome. This dissertation reports the effects of plasma, temperature and chemical reactions on low-k SiOCH films. Plasma ash processes have been known to cause hydrophobic films to lose their hydrophobic methyl groups, rendering them to be hydrophilic. This allows the films to readily absorb moisture. Supercritical carbon dioxide (SC-CO2) can be used to transport silylating agents, hexamethyldisilazane (HMDS) and diethoxy-dimethlysilane (DEDMS), to functionalize the damaged surfaces of the ash-damaged films. The thermal stability of the low-k films after SC-CO2 treatment is also discussed by performing in-situ heat treatments on the films. UV curing has been shown to reduce the amount of pores while showing only a limited change dielectric constant. This work goes on to describe the effect of UV curing on low-k films after exposing the films to supercritical carbon dioxide (CO2) in combination with tetramethylorthosilicate (TMOS). digital.library.unt.edu/ark:/67531/metadc33192/
Electrical and Structure Properties of High-κ Barium Tantalite and Aluminum Oxide Interface with Zinc Oxide for Applications in Transparent Thin Film Transistors
ZnO has generated interest for flexible electronics/optoelectronic applications including transparent thin film transistors (TFTs). For this application, low temperature processes that simultaneously yield good electrical conductivity and optical transparency and that are compatible with flexible substrates such as plastic, are of paramount significance. Further, gate oxides are a critical component of TFTs, and must exhibit low leakage currents and self-healing breakdown in order to ensure optimal TFTs switching performance and reliability. Thus, the objective of this work was twofold: (1) develop an understanding of the processing-structure-property relationships of ZnO and high-κ BaTa2O6 and Al2O3 (2) understand the electronic defect structure of BaTa2O6 /ZnO and Al2O3/ZnO interfaces and develop insight to how such interfaces may impact the switching characteristics (speed and switching power) of TFTs featuring these materials. Of the ZnO films grown by atomic layer deposition (ALD), pulsed laser deposition (PLD) and magnetron sputtering at 100-200 °C, the latter method exhibited the best combination of n-type electrical conductivity and optical transparency. These determinations were made using a combination of photoluminescence, photoluminescence excitation, absorption edge and Hall measurements. Metal-insulator-semiconductor devices were then fabricated with sputtered ZnO and high-κ BaTa2O6 and Al2O3 and the interfaces of high-κ BaTa2O6 and Al2O3 with ZnO were analyzed using frequency dependent C-V and G-V measurements. The insulator films were deposited at room temperature by magnetron sputtering using optimized processing conditions. Although the Al2O3 films exhibited a lower breakdown strength and catastrophic breakdown behavior compared to BaTa2O6/ZnO interface, the Al2O3/ZnO interface was characterized by more than an order of magnitude smaller density of interface traps and interface trapped charge. The BaTa2O6 films in addition were characterized by a significantly higher concentration of fixed oxide charge. The transition from accumulation to inversion in the Al2O3 MIS structure was considerably sharper, and occurred at less than one tenth of the voltage required for the same transition in the BaTa2O6 case. The frequency dispersion effects were also noticeably more severe in the BaTa2O6 structures. XPS results suggest that acceptor-like structural defects associated with oxygen vacancies in the non-stoichiometric BaTa2O6 films are responsible for the extensive electrical trapping and poor high frequency response. The Al2O3 films were essentially stoichiometric. The results indicate that amorphous Al2O3 is better suited than BaTa2O6 as a gate oxide for transparent thin film transistor applications where low temperature processing is a prerequisite, assuming of course that the operation voltage of such devices is lower than the breakdown voltage. Also, the operation power for the devices with amorphous Al2O3 is lower than the case for devices with BaTa2O6 due to the smaller fixed oxide charges and interface trap density. digital.library.unt.edu/ark:/67531/metadc84233/
Electrochemical synthesis of CeO2 and CeO2/montmorillonite nanocomposites.
Nanocrystalline cerium oxide thin films on metal and semiconductor substrates have been fabricated with a novel electrodeposition approach - anodic oxidation. X-ray diffraction analysis indicated that as-produced cerium oxide films are characteristic face-centered cubic fluorite structure with 5 ~ 20 nm crystal sizes. X-ray photoelectron spectroscopy study probes the non-stoichiometry property of as-produced films. Raman spectroscopy and Scanning Electron Microscopy have been applied to analyze the films as well. Deposition mode, current density, reaction temperature and pH have also been investigated and the deposition condition has been optimized for preferred oriented film formation: galvanostatic deposition with current density of -0.06 mA/cm2, T > 50oC and 7 < pH < 10. Generally, potentiostatic deposition results in random structured cerium oxide films. Sintering of potentiostatic deposited cerium oxide films leads to crystal growth and reach nearly full density at 1100oC. It is demonstrated that in-air heating favors the 1:2 stoichiometry of CeO2. Nanocrystalline cerium oxide powders (4 ~ 10 nm) have been produced with anodic electrochemical synthesis. X-ray diffraction and Raman spectroscopy were employed to investigate lattice expansion phenomenon related to the nanoscale cerium oxide particles. The pH of reaction solution plays an important role in electrochemical synthesis of cerium oxide films and powder. Cyclic voltammetry and rotation disk electrode voltammetry have been used to study the reaction mechanisms. The results indicate that the film deposition and powder formation follow different reaction schemes. Ce(III)-L complexation is a reversible process, Ce3+ at medium basic pH region (7~10) is electrochemically oxidized to and then CeO2 film is deposited on the substrate. CE mechanism is suggested to be involved in the formation of films, free Ce3+ species is coordinated with OH- at high basic pH region (>10) to Ce2O3 immediately prior to electrochemically oxidation Ce2O3 to CeO2. CeO2 / montmorillonite nanocomposites were electrochemically produced. X-ray diffraction and Raman spectroscopy illustrate the retaining of FCC structure for cerium oxide. Fourier Transform Infrared Spectroscopy and Differential Scanning Calorimetry of composites indicate the insertion of montmorillonite platelets into the structural matrix of cerium oxide. Sintering study of the nanocomposites demonstrates that low concentration of montmorillonite platelet coordination into cerium oxide matrix increases crystal growth rate whereas high concentration of montmoillonite in nanocomposites retards the increase of crystallite size during the densification process. digital.library.unt.edu/ark:/67531/metadc4378/
Evaluation of hydrogen trapping in HfO2 high-κ dielectric thin films.
Hafnium based high-κ dielectrics are considered potential candidates to replace SiO2 or SiON as the gate dielectric in complementary metal oxide semiconductor (CMOS) devices. Hydrogen is one of the most significant elements in semiconductor technology because of its pervasiveness in various deposition and optimization processes of electronic structures. Therefore, it is important to understand the properties and behavior of hydrogen in semiconductors with the final aim of controlling and using hydrogen to improve electronic performance of electronic structures. Trap transformations under annealing treatments in hydrogen ambient normally involve passivation of traps at thermal SiO2/Si interfaces by hydrogen. High-κ dielectric films are believed to exhibit significantly higher charge trapping affinity than SiO2. In this thesis, study of hydrogen trapping in alternate gate dielectric candidates such as HfO2 during annealing in hydrogen ambient is presented. Rutherford backscattering spectroscopy (RBS), elastic recoil detection analysis (ERDA) and nuclear reaction analysis (NRA) were used to characterize these thin dielectric materials. It was demonstrated that hydrogen trapping in bulk HfO2 is significantly reduced for pre-oxidized HfO2 prior to forming gas anneals. This strong dependence on oxygen pre-processing is believed to be due to oxygen vacancies/deficiencies and hydrogen-carbon impurity complexes that originate from organic precursors used in chemical vapor depositions (CVD) of these dielectrics. digital.library.unt.edu/ark:/67531/metadc5596/
First Principle Calculations of the Structure and Electronic Properties of Pentacene Based Organic and ZnO Based Inorganic Semiconducting Materials
In this thesis, I utilize first principles density functional theory (DFT) based calculations to investigate the structure and electronic properties including charge transfer behaviors and work function of two types of materials: pentacene based organic semiconductors and ZnO transparent conducting oxides, with an aim to search for high mobility n-type organic semiconductors and fine tuning work functions of ZnO through surface modifications. Based on DFT calculations of numerous structure combinations, I proposed a pentacene and perfluoro-pentacene alternating hybrid structures as a new type of n-type semiconductor. Based on the DFT calculations and Marcus charge transfer theory analysis, the new structure has high charge mobility and can be a promising new n-type organic semiconductor material. DFT calculations have been used to systematically investigate the effect of surface organic absorbate and surface defects on the work function of ZnO. It was found that increasing surface coverage of organic groups and decreasing surface defects lead to decrease of work functions, in excellent agreement with experimental results. First principles based calculations thus can greatly contribute to the investigating and designing of new electronic materials. digital.library.unt.edu/ark:/67531/metadc115112/
First Principles Calculations of the Site Substitution Behavior in Gamma Prime Phase in Nickel Based Superalloys
Nickel based superalloys have superior high temperature mechanical strength, corrosion and creep resistance in harsh environments and found applications in the hot sections as turbine blades and turbine discs in jet engines and gas generator turbines in the aerospace and energy industries. The efficiency of these turbine engines depends on the turbine inlet temperature, which is determined by the high temperature strength and behavior of these superalloys. The microstructure of nickel based superalloys usually contains coherently precipitated gamma prime (?) Ni3Al phase within the random solid solution of the gamma () matrix, with the ? phase being the strengthening phase of the superalloys. How the alloying elements partition into the and ? phases and especially in the site occupancy behaviors in the strengthening ? phases play a critical role in their high temperature mechanical behaviors. The goal of this dissertation is to study the site substitution behavior of the major alloying elements including Cr, Co and Ti through first principles based calculations. Site substitution energies have been calculated using the anti-site formation, the standard defect formation formalism, and the vacancy formation based formalism. Elements such as Cr and Ti were found to show strong preference for Al sublattice, whereas Co was found to have a compositionally dependent site preference. In addition, the interaction energies between Cr-Cr, Co-Co, Ti-Ti and Cr-Co atoms have also been determined. Along with the charge transfer, chemical bonding and alloy chemistry associated with the substitutions has been investigated by examining the charge density distributions and electronic density of states to explain the chemical nature of the site substitution. Results show that Cr and Co atoms prefer to be close by on either Al sublattice or on a Ni-Al mixed lattice, suggesting a potential tendency of Cr and Co segregation in the ? phase. digital.library.unt.edu/ark:/67531/metadc149571/
Functionalization and characterization of porous low-κ dielectrics.
The incorporation of fluorine into SiO2 has been shown to reduce the dielectric constant of the existing materials by reducing the electrical polarizability. However, the incorporation of fluorine has also been shown to decrease film stability. Therefore, new efforts have been made to find different ways to further decrease the relative dielectric constant value of the existing low-k materials. One way to reduce the dielectric constant is by decreasing its density. This reduces the amount of polarizable materials. A good approach is increasing porosity of the film. Recently, fluorinated silica xerogel films have been identified as potential candidates for applications such as interlayer dielectric materials in CMOS technology. In addition to their low dielectric constants, these films present properties such as low refractive indices, low thermal conductivities, and high surface areas. Another approach to lower k is incorporating lighter atoms such as hydrogen or carbon. Silsesquioxane based materials are among them. However, additional integration issues such as damage to these materials caused by plasma etch, plasma ash, and wet etch processes are yet to be overcome. This dissertation reports the effects of triethoxyfluorosilane-based (TEFS) xerogel films when reacted with silylation agents. TEFS films were employed because they form robust silica networks and exhibit low dielectric constants. However, these films readily absorb moisture. Employing silylation reactions enhances film hydrophobicity and permits possible introduction of this film as an interlayer dielectric material. Also, this work describes the effects of SC-CO2 in combination with silylating agents used to functionalize the damaged surface of the ash-damaged MSQ films. Ashed MSQ films exhibit increased water adsorption and dielectric constants due to the carbon depletion and modification of the properties of the low-k material caused by interaction with plasma species. CO2 is widely used as a supercritical solvent, because of its easily accessible critical point, low cost, and non-hazardous nature. Its unique diffusion and surface tension properties make SC-CO2 a good candidate for treatment of porous ultra low-k materials. digital.library.unt.edu/ark:/67531/metadc5570/
Growth, Structure and Tribological Properties of Atomic Layer Deposited Lubricious Oxide Nanolaminates
Friction and wear mitigation is typically accomplished by introducing a shear accommodating layer (e.g., a thin film of liquid) between surfaces in sliding and/or rolling contacts. When the operating conditions are beyond the liquid realm, attention turns to solid coatings. Solid lubricants have been widely used in governmental and industrial applications for mitigation of wear and friction (tribological properties). Conventional examples of solid lubricants are MoS2, WS2, h-BN, and graphite; however, these and some others mostly perform best only for a limited range of operating conditions, e.g. ambient air versus dry nitrogen and room temperature versus high temperatures. Conversely, lubricious oxides have been studied lately as good potential candidates for solid lubricants because they are thermodynamically stable and environmentally robust. Oxide surfaces are generally inert and typically do not form strong adhesive bonds like metals/alloys in tribological contacts. Typical of these oxides is ZnO. The interest in ZnO is due to its potential for utility in a variety of applications. To this end, nanolaminates of ZnO, Al2O3, ZrO2 thin films have been deposited at varying sequences and thicknesses on silicon substrates and high temperature (M50) bearing steels by atomic layer deposition (ALD). The top lubricious, nanocrystalline ZnO layer was structurally-engineered to achieve low surface energy {0002}-orientated grain that provided low sliding friction coefficients (0.2 to 0.3), wear factors (range of 10-7 to 10-8 mm3/Nm) and good rolling contact fatigue resistance. The Al2O3 was intentionally made amorphous to achieve the {0002} preferred orientation while {101}-orientated tetragonal ZrO2 acted as a high toughness/load bearing layer. It was determined that the ZnO defective structure (oxygen sub-stoichiometric with growth stacking faults) aided in shear accommodation by re-orientating the nanocrystalline grains where they realigned to create new friction-reducing surfaces. Specifically, high resolution transmission electron microscopy (HRTEM) inside the wear surfaces revealed in an increase in both partial dislocation and basal stacking fault densities through intrafilm shear/slip of partial dislocations on the (0002) planes via a dislocation glide mechanism. This shear accommodation mode mitigated friction and prevented brittle fracture classically observed in higher friction microcrystalline and single crystal ZnO that has potential broad implications to other defective nanocrystalline ceramics. Overall, this work has demonstrated that environmentally-robust, lubricious ALD nanolaminates of ZnO/Al2O3/ZrO2 are good candidates for providing low friction and wear interfaces in moving mechanical assembles, such as fully assembled rolling element bearings and microelectromechanical systems (MEMS) that require thin (~10-200 nm), uniform and conformal films. digital.library.unt.edu/ark:/67531/metadc33186/
Hydrophobic, fluorinated silica xerogel for low-k applications.
A new hydrophobic hybrid silica film was synthesized by introducing one silicon precursor (as modifiers) into another precursor (network former). Hybrid films have improved properties. Hydrolysis and condensation of dimethyldiethoxysilane (DMDES) (solvent (EtOH) to DMDES molar ratio R = 4, water to DMDES molar ratio r = 4, 0.01 N HCl catalyst) was analyzed using high-resolution liquid 29Si NMR. It was found that after several hours, DMDES hydrolyzed and condensed into linear and cyclic species. Films from triethoxyfluorosilane (TEFS) have been shown to be promising interlayer dielectric materials for future integrated circuit applications due to their low dielectric constant and high mechanical properties (i.e., Young's modulus (E) and hardness (H)). Co-condensing with TEFS, linear structures from DMDES hydrolysis and condensation reactions rendered hybrid films hydrophobic, and cyclic structures induced the formation of pores. Hydrophobicity characterized by contact angle, thermal stability by thermogravimetric analysis (TGA), Fourier transform Infrared spectroscopy (FTIR), contact angle, and dynamic secondary ion mass spectroscopy (DSIMS), dielectric constant determined by impedance measurement, and mechanical properties (E and H) determined by nanoindentation of TEFS and TEFS + DMDES films were compared to study the effect of DMDES on the TEFS structure. Hybrid films were more hydrophobic and thermally stable. DMDES incorporation affected the dielectric constant, but showed little enhancement of mechanical properties. digital.library.unt.edu/ark:/67531/metadc4472/
Indentation induced deformation in metallic materials.
Nanoindentation has brought in many features of research over the past decade. This novel technique is capable of producing insights into the small ranges of deformation. This special point has brought a lot of focus in understanding the deformation behavior under the indenter. Nickel, iron, tungsten and copper-niobium alloy system were considered for a surface deformation study. All the samples exhibited a spectrum of residual deformation. The change in behavior with indentation and the materials responses to deformation at low and high loads is addressed in this study. A study on indenter geometry, which has a huge influence on the contact area and subsequently the hardness and modulus value, has been attempted. Deformation mechanisms that govern the plastic flow in materials at low loads of indentation and their sensitivity to the rate of strain imparted has been studied. A transition to elastic, plastic kind of a tendency to an elasto-plastic tendency was seen with an increase in the strain rate. All samples exhibited the same kind of behavior and a special focus is drawn in comparing the FCC nickel with BCC tungsten and iron where the persistence of the elastic, plastic response was addressed. However there is no absolute reason for the inconsistencies in the mechanical properties observed in preliminary testing, more insights can be provided with advanced microscopy techniques where the study can be focused more to understand the deformation behavior under the indenter. These experiments demonstrate that there is a wealth of information in the initial stages of indentation and has led to much more insights into the incipient stages of plasticity. digital.library.unt.edu/ark:/67531/metadc4904/
The Influence of Ohmic Metals and Oxide Deposition on the Structure and Electrical Properties of Multilayer Epitaxial Graphene on Silicon Carbide Substrates
Graphene has attracted significant research attention for next generation of semiconductor devices due to its high electron mobility and compatibility with planar semiconductor processing. In this dissertation, the influences of Ohmic metals and high dielectric (high-k) constant aluminum oxide (Al2O3) deposition on the structural and electrical properties of multi-layer epitaxial graphene (MLG) grown by graphitization of silicon carbide (SiC) substrates have been investigated. Uniform MLG was successfully grown by sublimation of silicon from epitaxy-ready, Si and C terminated, 6H-SiC wafers in high-vacuum and argon atmosphere. The graphene formation was accompanied by a significant enhancement of Ohmic behavior, and, was found to be sensitive to the temperature ramp-up rate and annealing time. High-resolution transmission electron microscopy (HRTEM) showed that the interface between the metal and SiC remained sharp and free of macroscopic defects even after 30 min, 1430 °C anneals. The impact of high dielectric constant Al2O3 and its deposition by radio frequency (RF) magnetron sputtering on the structural and electrical properties of MLG is discussed. HRTEM analysis confirms that the Al2O3/MLG interface is relatively sharp and that thickness approximation of the MLG using angle resolved X-ray photoelectron spectroscopy (ARXPS) as well as variable-angle spectroscopic ellipsometry (VASE) is accurate. The totality of results indicate that ARXPS can be used as a nondestructive tool to measure the thickness of MLG, and that RF sputtered Al2O3 can be used as a (high-k) constant gate oxide in multilayer grapheme based transistor applications. digital.library.unt.edu/ark:/67531/metadc68009/
An Integrated Approach to Determine Phenomenological Equations in Metallic Systems
It is highly desirable to be able to make predictions of properties in metallic materials based upon the composition of the material and the microstructure. Unfortunately, the complexity of real, multi-component, multi-phase engineering alloys makes the provision of constituent-based (i.e., composition or microstructure) phenomenological equations extremely difficult. Due to these difficulties, qualitative predictions are frequently used to study the influence of microstructure or composition on the properties. Neural networks were used as a tool to get a quantitative model from a database. However, the developed model is not a phenomenological model. In this study, a new method based upon the integration of three separate modeling approaches, specifically artificial neural networks, genetic algorithms, and monte carlo was proposed. These three methods, when coupled in the manner described in this study, allows for the extraction of phenomenological equations with a concurrent analysis of uncertainty. This approach has been applied to a multi-component, multi-phase microstructure exhibiting phases with varying spatial and morphological distributions. Specifically, this approach has been applied to derive a phenomenological equation for the prediction of yield strength in a+b processed Ti-6-4. The equation is consistent with not only the current dataset but also, where available, the limited information regarding certain parameters such as intrinsic yield strength of pure hexagonal close-packed alpha titanium. digital.library.unt.edu/ark:/67531/metadc177199/
Interspecimen Study of Bone to Relate Macromechanical, Nanomechanical and Compositional Changes Across the Femoral Cortex of Bone
Mechanics of bone is widely studied and researched, mainly for the study of fracture. This has been done mostly on a macro scale. In this work hierarchical nature of bone has been explored to investigate bone mechanics in more detail. Flexural test were done to classify the bones according to their strength and deflection. Raman spectroscopy analysis was done to map the mineralization, collagen crosslinking changes across the thickness of the bone. Nanoindentation was done to map indentation hardness and indentation modulus across femoral cortex of the bone. The results indicate that the composition of the bone changes across the thickness of the femoral cortex. The hypothesis is confirmed as increase in mineralization, carbonate to phosphate ratio and collagen crosslinking shows the effect as increased indentation hardness and modulus and decreased deflection. digital.library.unt.edu/ark:/67531/metadc271868/
Laser Modified Alumina: a Computational and Experimental Analysis
Laser surface modification involves rapid melting and solidification is an elegant technique used for locally tailoring the surface morphology of alumina in order to enhance its abrasive characteristics. COMSOL Multiphysics® based heat transfer modeling and experimental approaches were designed and used in this study for single and multiple laser tracks to achieve densely-packed multi-facet grains via temperature history, cooling rate, solidification, scanning electron micrographs, and wear rate. Multi-facet grains were produced at the center of laser track with primary dendrites extending toward the edge of single laser track. The multiple laser tracks study indicates the grain/dendrite size increases as the laser energy density increases resulting in multiplying the abrasive edges which in turn enhance the abrasive qualities. digital.library.unt.edu/ark:/67531/metadc177232/
Long Term Property Prediction of Polyethylene Nanocomposites
The amorphous fraction of semicrystalline polymers has long been thought to be a significant contributor to creep deformation. In polyethylene (PE) nanocomposites, the semicrystalline nature of the maleated PE compatibilizer leads to a limited ability to separate the role of the PE in the nanocomposite properties. This dissertation investigates blown films of linear low-density polyethylene (LLDPE) and its nanocomposites with montmorillonite-layered silicate (MLS). Addition of an amorphous ethylene propylene copolymer grafted maleic anhydride (amEP) was utilized to enhance the interaction between the PE and the MLS. The amorphous nature of the compatibilizer was used to differentiate the effect of the different components of the nanocomposites; namely the matrix, the filler, and the compatibilizer on the overall properties. Tensile test results of the nanocomposites indicate that the addition of amEP and MLS separately and together produces a synergistic effect on the mechanical properties of the neat PE Thermal transitions were analyzed using differential scanning calorimetry (DSC) to determine if the observed improvement in mechanical properties is related to changes in crystallinity. The effect of dispersion of the MLS in the matrix was investigated by using a combination of X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Mechanical measurements were correlated to the dispersion of the layered silicate particles in the matrix. The nonlinear time dependent creep of the material was analyzed by examining creep and recovery of the films with a Burger model and the Kohlrausch-Williams-Watts (KWW) relation. The effect of stress on the nonlinear behavior of the nanocomposites was investigated by analyzing creep-recovery at different stress levels. Stress-related creep constants and shift factors were determined for the material by using the Schapery nonlinear viscoelastic equation at room temperature. The effect of temperature on the tensile and creep properties of the nanocomposites was analyzed by examining tensile and creep-recovery behavior of the films at temperatures in the range of 25 to -100 oC. Within the measured temperature range, the materials showed a nonlinear temperature dependent response. The time-temperature superposition principle was successfully used to predict the long term behavior of LLDPE nanocomposites. digital.library.unt.edu/ark:/67531/metadc9738/
Low Temperature Polymeric Precursor Derived Zinc Oxide Thin Films
Zinc oxide (ZnO) is a versatile environmentally benign II-VI direct wide band gap semiconductor with several technologically plausible applications such as transparent conducting oxide in flat panel and flexible displays. Hence, ZnO thin films have to be processed below the glass transition temperatures of polymeric substrates used in flexible displays. ZnO thin films were synthesized via aqueous polymeric precursor process by different metallic salt routes using ethylene glycol, glycerol, citric acid, and ethylene diamine tetraacetic acid (EDTA) as chelating agents. ZnO thin films, derived from ethylene glycol based polymeric precursor, exhibit flower-like morphology whereas thin films derived of other precursors illustrate crack free nanocrystalline films. ZnO thin films on sapphire substrates show an increase in preferential orientation along the (002) plane with increase in annealing temperature. The polymeric precursors have also been used in fabricating maskless patterned ZnO thin films in a single step using the commercial Maskless Mesoscale Materials Deposition system. digital.library.unt.edu/ark:/67531/metadc5504/
A magnetorheological study of single-walled and multi-walled carbon nanotube dispersions in mineral oil and epoxy resin.
Single wall carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs) were dispersed in mineral oil and epoxy resin. The magnetorheological properties of these dispersions were studied using a parallel plate rheometer. Strain sweeps, frequency sweeps, magneto sweeps and steady shear tests were conducted in various magnetic fields. G', G", h* and ty increased with increasing magnetic field, which was partially attributed to the increasing degree of the alignment of nanotubes in a stronger magnetic field. The SWNT/mo dispersions exhibited more pronounced magnetic field dependence than SWNT/ep and MWNT/mo counterparts due to their much lower viscosity. The alignment of SWNTs in mineral oil increased with rising nanotube concentration up to 2.5vol% but were significantly restricted at 6.41vol% due to nanotube flocculation. digital.library.unt.edu/ark:/67531/metadc4742/
Maleic anhydride grafted polypropylene coatings on steel: Adhesion and wear.
Polymeric coatings are being used in a growing number of applications, contributing to protection against weather conditions and localized corrosion, reducing the friction and erosion wear on the substrate. In this study, various polypropylene (PP) coatings were applied onto steel substrates by compression molding. Chemical modification of PP has been performed to increase its adhesion to metallic surfaces by grafting of maleic anhydride (MAH) onto PP in the presence of dicumyl peroxide (DCP). Influence of different concentrations of MAH and DCP on the properties of resulting materials have been examined. The coated steel samples are characterized by scanning electron microscopy (SEM), shear adhesion testing, FTIR and tribometry. The coatings with 3 wt. % MAH have shown the maximum adhesion strength due to maximum amount of grafting. The wear rates increased with increasing the amount of MAH due to simultaneous increase in un-reacted MAH. digital.library.unt.edu/ark:/67531/metadc28452/
Measurement of Lattice Strain and Relaxation Effects in Strained Silicon Using X-ray Diffraction and Convergent Beam Electron Diffraction
The semiconductor industry has decreased silicon-based device feature sizes dramatically over the last two decades for improved performance. However, current technology has approached the limit of achievable enhancement via this method. Therefore, other techniques, including introducing stress into the silicon structure, are being used to further advance device performance. While these methods produce successful results, there is not a proven reliable method for stress and strain measurements on the nanometer scale characteristic of these devices. The ability to correlate local strain values with processing parameters and device performance would allow for more rapid improvements and better process control. In this research, x-ray diffraction and convergent beam electron diffraction have been utilized to quantify the strain behavior of simple and complex strained silicon-based systems. While the stress relaxation caused by thinning of the strained structures to electron transparency complicates these measurements, it has been quantified and shows reasonable agreement with expected values. The relaxation values have been incorporated into the strain determination from relative shifts in the higher order Laue zone lines visible in convergent beam electron diffraction patterns. The local strain values determined using three incident electron beam directions with different degrees of tilt relative to the device structure have been compared and exhibit excellent agreement. digital.library.unt.edu/ark:/67531/metadc3978/
Mechanics and Mechanisms of Creep and Ductile Fracture
The main aim of this dissertation is to relate measurable and hopefully controllable features of a material's microstructure to its observed failure modes to provide a basis for designing better materials. The understanding of creep in materials used at high temperatures is of prime engineering importance. Single crystal Ni-based superalloys used in turbine aerofoils of jet engines are exposed to long dwell times at very high temperatures. In contrast to current theories, creep tests on Ni-based superalloy specimens have shown size dependent creep response termed as the thickness debit effect. To investigate the mechanism of the thickness debit effect, isothermal creep tests were performed on uncoated Ni-based single crystal superalloy sheet specimens with two thicknesses and under two test conditions: a low temperature high stress condition and a high temperature low stress condition. At the high temperature, surface oxidation induced microstructural changes near the free surface forming a layered microstructure. Finite element calculations showed that this layered microstructure gave rise to local changes in the stress state. The specimens also contained nonuniform distribution of initial voids formed during the solidification and homogenization processes. The experiments showed that porosity evolution could play a significant role in the thickness debit effect. This motivated a basic mechanics study of porosity evolution in single crystals subjected to creep for a range of stress states. The study was performed using three-dimensional finite deformation finite element analysis of unit cells containing a single initially spherical void in a single crystal matrix. The materials are characterized by a rate-dependent crystal plasticity constitutive relation accounting for both primary and secondary creep. The effect of initial void spacing and creep exponent was also explored. Based on the experimental observations and results of finite element calculations a quantitative mechanistic model is proposed that can account for both bulk and surface damage effects and assess their relative roles in the observed thickness debit effect. Another set of calculations aim at relating the crack growth resistance and fracture surface morphology to material microstructure for ductile structural metals. The process that governs the ductile fracture of structural materials at room temperature is one of nucleation, growth and coalescence of micron scale voids, and involves large plastic deformations. Experimental studies have shown that fracture surfaces in a wide variety of materials and under a wide variety of loading conditions have remarkable scaling properties. For thirty years, the hope to relate the statistical characterization of fracture surfaces to a measure of a material's crack growth resistance has remained unfulfilled. Only recently has the capability been developed to calculate sufficient amounts of three dimensional ductile crack growth in heterogeneous microstructures to obtain a statistical characterization of the predicted fracture surfaces. This development has enabled the exploration of the relation of both fracture toughness and fracture surface statistics to material properties and microstructure when the fracture mechanism is one of void nucleation, growth and coalescence. The relation of both toughness and the statistical properties of fracture surfaces in calculations of heterogeneous microstructures to various microstructural features is discussed and a remarkable correlation between fracture surface roughness and fracture toughness is shown for the first time. digital.library.unt.edu/ark:/67531/metadc283799/
Mechanisms of Ordered Gamma Prime Precipitation in Nickel Base Superalloys
Commercial superalloys like Rene88DT are used in high temperature applications like turbine disk in aircraft jet engines due to their excellent high temperature properties, including strength, ductility, improved fracture toughness, fatigue resistance, enhanced creep and oxidation resistance. Typically this alloy's microstructure has L12-ordered precipitates dispersed in disordered face-centered cubic γ matrix. A typical industrially relevant heat-treatment often leads to the formation of multiple size ranges of γ¢ precipitates presumably arising from multiple nucleation bursts during the continuous cooling process. The morphology and distribution of these γ′ precipitates inside γ matrix influences the mechanical properties of these materials. Therefore, the study of thermodynamic and kinetic factors influencing the evolution of these precipitates and subsequent effects is both relevant for commercial applications as well as for a fundamental understanding of the underlying phase transformations. The present research is primarily focused on understanding the mechanism of formation of different generations of γ′ precipitates during continuous cooling by coupling scanning electron microscopy (SEM), energy filtered TEM and atom probe tomography (APT). In addition, the phase transformations leading to nucleation of γ′ phase has been a topic of controversy for decades. The present work, for the first time, gives a novel insight into the mechanism of order-disorder transformations and associated phase separation processes at atomistic length scales, by coupling high angle annular dark field (HAADF) - STEM imaging and APT. The results indicate that multiple competing mechanisms can operate during a single continuous cooling process leading to different generations of γ′ including a non-classical mechanism, operative at large undercoolings. digital.library.unt.edu/ark:/67531/metadc67949/
Micro and nano composites composed of a polymer matrix and a metal disperse phase.
Low density polyethylene (LDPE) and Hytrel (a thermoplastic elastomer) were used as polymeric matrices in polymer + metal composites. The concentration of micrometric (Al, Ag and Ni) as well as nanometric particles (Al and Ag) was varied from 0 to 10 %. Composites were prepared by blending followed by injection molding. The resulting samples were analyzed by scanning electron microscopy (SEM) and focused ion beam (FIB) in order to determine their microstructure. Certain mechanical properties of the composites were also determined. Static and dynamic friction was measured. The scratch resistance of the specimens was determined. A study of the wear mechanisms in the samples was performed. The Al micro- and nanoparticles as well as Ni microparticles are well dispersed throughout the material while Ag micro and nanoparticles tend to form agglomerates. Generally the presence of microcomposites affects negatively the mechanical properties. For the nanoparticles, composites with a higher elastic modulus than that of the neat materials are achievable. For both micro- and nanocomposites it is feasible to lower the friction values with respective to the neat polymers. The addition of metal particles to polymers also improves the scratch resistance of the composites, particularly so for microcomposites. The inclusion of Ag and Ni particles causes an increase in the wear loss volume while Al can reduce the wear for both polymeric matrices. digital.library.unt.edu/ark:/67531/metadc5135/
Microstructure Evolution in Laser Deposited Nickel-Titanium-Carbon in situ Metal Matrix Composite
Ni/TiC metal matrix composites have been processed using the laser engineered net shaping (LENS) process. As nickel does not form an equilibrium carbide phase, addition of a strong carbide former in the form of titanium reinforces the nickel matrix resulting in a promising hybrid material for both surface engineering as well as high temperature structural applications. Changing the relative amounts of titanium and carbon in the nickel matrix, relatively low volume fraction of refined homogeneously distributed carbide precipitates, formation of in-situ carbide precipitates and the microstructural changes are investigated. The composites have been characterized in detail using x-ray diffraction, scanning electron microscopy (including energy dispersive spectroscopy (XEDS) mapping and electron backscatter diffraction (EBSD)), Auger electron spectroscopy, and transmission (including high resolution) electron microscopy. Both primary and eutectic titanium carbides, observed in this composite, exhibited the fcc-TiC structure (NaCl-type). Details of the orientation relationship between Ni and TiC have been studied using SEM-EBSD and high resolution TEM. The results of micro-hardness and tribology tests indicate that these composites have a relatively high hardness and a steady-state friction coefficient of ~0.5, both of which are improvements in comparison to LENS deposited pure Ni. digital.library.unt.edu/ark:/67531/metadc33154/
Mist and Microstructure Characterization in End Milling Aisi 1018 Steel Using Microlubrication
Flood cooling is primarily used to cool and lubricate the cutting tool and workpiece interface during a machining process. But the adverse health effects caused by the use of flood coolants are drawing manufacturers' attention to develop methods for controlling occupational exposure to cutting fluids. Microlubrication serves as an alternative to flood cooling by reducing the volume of cutting fluid used in the machining process. Microlubrication minimizes the exposure of metal working fluids to the machining operators leading to an economical, safer and healthy workplace environment. In this dissertation, a vegetable based lubricant is used to conduct mist, microstructure and wear analyses during end milling AISI 1018 steel using microlubrication. A two-flute solid carbide cutting tool was used with varying cutting speed and feed rate levels with a constant depth of cut. A full factorial experiment with Multivariate Analysis of Variance (MANOVA) was conducted and regression models were generated along with parameter optimization for the flank wear, aerosol mass concentration and the aerosol particle size. MANOVA indicated that the speed and feed variables main effects are significant, but the interaction of (speed*feed) was not significant at 95% confidence level. The model was able to predict 69.44%, 68.06% and 42.90% of the variation in the data for both the flank wear side 1 and 2 and aerosol mass concentration, respectively. An adequate signal-to-noise precision ratio more than 4 was obtained for the models, indicating adequate signal to use the model as a predictor for both the flank wear sides and aerosol mass concentration. The highest average mass concentration of 8.32 mg/m3 was realized using cutting speed of 80 Surface feet per minute (SFM) and a feed rate of 0.003 Inches per tooth (IPT). The lowest average mass concentration of 5.91 mg/m3 was realized using treatment 120 SFM and 0.005 IPT. The cutting performance under microlubrication is five times better in terms of tool life and two times better in terms of materials removal volume under low cutting speed and feed rate combination as compared to high cutting speed and feed rate combination. Abrasion was the dominant wear mechanism for all the cutting tools under consideration. Other than abrasion, sliding adhesive wear of the workpiece materials was also observed. The scanning electron microscope investigation of the used cutting tools revealed micro-fatigue cracks, welded micro-chips and unusual built-up edges on the cutting tools flank and rake side. Higher tool life was observed in the lowest cutting speed and feed rate combination. Transmission electron microscopy analysis at failure for the treatment 120 SFM and 0.005 IPT helped to quantify the dislocation densities. Electron backscatter diffraction (EBSD) identified 4 to 8 µm grain size growth on the machined surface due to residual stresses that are the driving force for the grain boundaries motion to reduce its overall energy resulting in the slight grain growth. EBSD also showed that (001) textured ferrite grains before machining exhibited randomly orientated grains after machining. The study shows that with a proper selection of the cutting parameters, it is possible to obtain higher tool life in end milling under microlubrication. But more scientific studies are needed to lower the mass concentration of the aerosol particles, below the recommended value of 5 mg/m3 established by Occupational Safety and Health Administration (OSHA). digital.library.unt.edu/ark:/67531/metadc283858/
Modified epoxy coatings on mild steel: A study of tribology and surface energy.
A commercial epoxy was modified by adding fluorinated poly (aryl ether ketone) and in turn metal micro powders (Ni, Al, Zn, and Ag) and coated on mild steel. Two curing agents were used; triethylenetetramine (curing temperatures: 30 oC and 70 oC) and hexamethylenediamine (curing temperature: 80 oC). Variation in tribological properties (dynamic friction and wear) and surface energies with varying metal powders and curing agents was evaluated. When cured at 30 oC, friction and wear decreased significantly due to phase separation reaction being favored but increased when cured at 70 oC and 80 oC due to cross linking reaction being favored. There was a significant decrease in surface energies with the addition of modifiers. digital.library.unt.edu/ark:/67531/metadc12119/
Molecular Dynamics Simulations of the Structures of Europium Containing Silicate and Cerium Containing Aluminophosphate Glasses
Rare earth ion doped glasses find applications in optical and photonic devices such as optical windows, laser, and optical amplifiers, and as model systems for immobilization of nuclear waste. Macroscopic properties of these materials, such as luminescence efficiency and phase stability, depend strongly on the atomic structure of these glasses. In this thesis, I have studied the atomic level structure of rare earth doped silicate and aluminophosphate glasses by using molecular dynamics simulations. Extensive comparisons with experimental diffraction and NMR data were made to validate the structure models. Insights on the local environments of rare earth ions and their clustering behaviors and their dependence on glass compositions have been obtained. In this thesis, MD simulations have been used to investigate the structure of Eu2O3-doped silica and sodium silicate glasses to understand the glass composition effect on the rare earth ions local environment and their clustering behaviors in the glass matrix, for compositions with low rare earth oxide concentration (~1mol%). It was found that Eu–O distances and coordination numbers were different in silica (2.19-2.22 Å and 4.6-4.8) from those in sodium silicate (2.32 Å and 5.8). High tendencies of Eu clustering and short Eu-Eu distances in the range 3.40-3.90 Å were observed in pure silica glasses as compared to those of silicate glasses with much better dispersed Eu3+ ions and lower probability to form clusters. The results show Eu3+ clustering behavior dependence on the system size and suggest for low doping levels, over 12,000 atoms to obtain statistical meaningful results on the local environment and clustering for rigid silica-based glasses. The structures of four cerium aluminophosphate glasses have also been studied using MD simulations for systems of about 13,000 atoms to investigate aluminum and cerium ion environment and their distribution. P5+ and Al3+ local structures were found stable while those of Ce3+ and Ce4+ ions, through their coordination numbers and bond lengths, are glass composition-dependence. Cerium clusters were found in the high cerium glasses.P5+ coordination numbers around cerium revealed the preference of phosphorus ions in the second coordination shell. Total structure factors from MD simulations and experimental diffraction results show a general agreement from comparison for all the cerium aluminophosphate glasses and with compositional changes up to 25 Å-1. Aluminum enters the phosphate glass network mainly as AlO4 and AlO5 polyhedra only connected through corner sharing to PO4 tetrahedra identified by Q11(1 AlOx), Q12(2 AlOx), Q21(1 AlOx), and Q22(2 AlOx) species. digital.library.unt.edu/ark:/67531/metadc149624/
Morphological properties of poly (ethylene terephthalate) (PET) nanocomposites in relation to fracture toughness.
The effect of incorporation of montmorillonite layered silicate (MLS) on poly (ethylene terephthalate) (PET) matrix was investigated. MLS was added in varying concentration of 1 to 5 weight percent in the PET matrix. DSC and polarized optical microscopy were used to determine the crystallization effects of MLS addition. Non isothermal crystallization kinetics showed that the melting temperature and crystallization temperature decrease as the MLS percent increases. This delayed crystallization along with the irregular spherulitic shape indicates hindered crystallization in the presence of MLS platelets. The influence of this morphology was related with the fracture toughness of PET nanocomposites using essential work of fracture coupled with the infra red (IR) thermography. Both the essential as well as non essential work of fracture decreased on addition of MLS with nanocomposite showing reduced toughness. digital.library.unt.edu/ark:/67531/metadc4845/
Orientation, Microstructure and Pile-Up Effects on Nanoindentation Measurements of FCC and BCC Metals
This study deals with crystal orientation effect along with the effects of microstructure on the pile-ups which affect the nanoindentation measurements. Two metal classes, face centered cubic (FCC) and body centered cubic (BCC, are dealt with in the present study. The objective of this study was to find out the degree of inaccuracy induced in nanoindentation measurements by the inherent pile-ups and sink-ins. Also, it was the intention to find out how the formation of pile-ups is dependant upon the crystal structure and orientation of the plane of indentation. Nanoindentation, Nanovision, scanning electron microscopy, electron dispersive spectroscopy and electron backscattered diffraction techniques were used to determine the sample composition and crystal orientation. Surface topographical features like indentation pile-ups and sink-ins were measured and the effect of crystal orientation on them was studied. The results show that pile-up formation is not a random phenomenon, but is quite characteristic of the material. It depends on the type of stress imposed by a specific indenter, the depth of penetration, the microstructure and orientation of the plane of indentation. Pile-ups are formed along specific directions on a plane and this formation as well as the pile-up height and the contact radii with the indenter is dependant on the aforesaid parameters. These pile-ups affect the mechanical properties like elastic modulus and hardness measurements which are pivotal variables for specific applications in micro and nano scale devices. digital.library.unt.edu/ark:/67531/metadc6050/
Phase Separation and Second Phase Precipitation in Beta Titanium Alloys
The current understanding of the atomic scale phenomenon associated with the influence of beta phase instabilities on the evolution of microstructure in titanium alloys is limited due to their complex nature. Such beta phase instabilities include phase separation and precipitation of nano-scale omega and alpha phases in the beta matrix. The initial part of the present study focuses on omega precipitation within the beta matrix of model binary titanium molybdenum (Ti-Mo) alloys. Direct atomic scale observation of pre-transition omega-like embryos in quenched alloys, using aberration-corrected high resolution scanning transmission electron microscopy and atom probe tomography (APT) was compared and contrasted with the results of first principles computations performed using the Vienna ab initio simulation package (VASP) to present a novel mechanism of these special class of phase transformation. Thereafter the beta phase separation and subsequent alpha phase nucleation in a Ti-Mo-Al ternary alloy was investigated by coupling in-situ high energy synchrotron x-ray diffraction with ex-situ characterization studies performed using aberration corrected transmission electron microscopy and APT to develop a deeper understanding of the mechanism of transformation. Subsequently the formation of the omega phase in the presence of simultaneous development of compositional phase separation within the beta matrix phase of a Ti-10V-6Cu (wt%) alloy during continuous cooling has been investigated using a combination of transmission electron microscopy and atom probe tomography. The results of these investigations provided novel insights into the mechanisms of solid-state transformations in metallic systems by capturing the earliest stages of nucleation at atomic to near atomic spatial and compositional resolution. digital.library.unt.edu/ark:/67531/metadc67975/


Celebrating the centennial of a landmark in culinary chemistry

October 3rd, 2012 in Chemistry / Other

Billions of people around the world today will unknowingly perform a chemical reaction first reported 100 years ago. And the centennial of the Maillard reaction—which gives delightful flavor to foods ranging from grilled meat to baked bread to coffee—is the topic of a fascinating article in the current edition of Chemical & Engineering News. C&EN is the weekly news magazine of the American Chemical Society, the world's largest scientific society.

Sarah Everts, C&EN senior editor, explains in the article that French chemist Louis-Camille Maillard took a first stab at explaining the culinary delight that occurs when proteins and sugars in food interact at high temperature in a 1912 research paper. Focusing on the delicious flavors and appetizing colors that result from that chemistry, the research also established the foundations of modern food science.

Noting that Maillard can stake a claim to being the world's most widely practiced chemical reaction, the C&EN article explains that the reaction has a dark side. It also can produce potential carcinogens in certain foods. And scientists have discovered that the Maillard reaction also occurs spontaneously in the human body, producing substances linked to aging and a variety of diseases.

More information: "The Maillard Reaction Turns 100" cen.acs.org/articles/90/i40/Ma… ction-Turns-100.html

Provided by American Chemical Society

"Celebrating the centennial of a landmark in culinary chemistry." October 3rd, 2012. http://phys.org/news/2012-10-celebrating-centennial-landmark-culinary-chemistry.html


why are you so adorable!?! (◕‿◕✿)

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jen being ridiculously cute on live with kelly & michael

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imagine walking into class late one day and your blog is up on the projector

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my head canon is that when Regina was 17 and in love with Daniel, she thought she would run away with him one day and they’d live in a little cottage in the woods by the river and he would work in people’s stables, and she would be a seamstress, and they would have babies and pick flowers barefoot, and basically it’s my own head canons that make me weep.

They’d keep chickens, and just the one horse they could afford to feed and stall.

(But one was enough, with Daniel sitting sturdy and warm behind her, and they could ride far and free, together under an endless sky.)

And their house would be tiny, but full of laughter and warmth and love, because damn it all if Regina didn’t want a house FILLED with kids who she could cherish and protect the way her parents never did. They’d bring her wild apples, her favorite.

And maybe, far, far away, there was a king named Leopold, and he had nothing to do with Regina, in any way shape or form, ever.

You know she has this written down in her diary.

"…then Daniel and I are going to get married and she’s not invited! We’re going to buy a cute little cottage in the country and raise horses and teach people how to ride. And we’re going to have ten kids, and they can wear what they want and marry who they want and have any kind of work they want and Mother will never get to see them ever! And I’m going to talk to them about their feelings and ask them about their dreams and be the exact opposite of Mother in every way.”

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Met Angie again! She signed my magazine. She’s perfect! :)

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have you ever started crying for one reason then end up crying about every possible thing wrong with your life

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Imagine your icon as a lingerie model

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TAGGED AS: orphan black;


(593 5) 252 6281 / 252 7015

Hotel Galápagos

Hotel Solymar Galapagos Islands EcuadorThe Galapagos Islands are considered the world's greatest natural laboratory. Charles Darwin, the scientist, visited the islands in 1835 and his famous work "The Origin of Species" was published 23 years after this visit. Darwin's theory of evolution changed the scientific landscape.

Darwin studied island species, mainly finches and tortoises, his studies concluded that these species had evolved in different ways in each island.

Nature had adapted to the environment to better increase their chances of survival.

Hotel Solymar Galapagos Islands EcuadorGalapagos Giant Tortoises belong to the oldest reptiles and zoologists have classified in 14 races or subspecies belonging to three groups: sea turtles, freshwater and land tortoises.

The tortoises were almost extinct due to hunting by sailors in passing whale ships. It is estimated that at the beginning of the century, an American whaling fleet caught more than 13,000 tortoises. Because this over hunting, two species of tortoises on the islands of Floreana and Santa Fe are considered extinct. In 2012 the last of the Pinta island tortoises died, his name was "Lonesome George", he passed away in captivity in the Charles Darwin Research Station in Santa Cruz. The tortoise protection is one of the most important activities carried out by the Darwin Station. Its facilities house the captive breeding program of giant tortoises, which are housed and cared until they are 5 years old before being relocated to their original island of origin.

These animals do not stop their growth from birth to death. They have high resistance to water and lack of food. It is hypothesized that they can live up to 200 years.

Hotel Solymar Galapagos Islands EcuadorGalapagos hosts numerous genera and species of land and sea birds. Millions of years ago, migrating birds came to the islands and an adaptation processes modified species, differentiating them from the birds in the continent.

Pink flamingos are surely the most beautiful birds that came to the islands. They are found in the lagoons of Floreana and Isabella islands.

Other interesting birds are the Darwin's finches and the Magnificent frigates which can be observed in the majority of the islands, the Nazca boobies in Genovesa island, the world's 2nd smallest penguins in Isabella island and the Albatross in Español island.

Hotel Solymar Galapagos Islands EcuadorIguanas are endemic species of reptile in the Galapagos Islands. They are marine and land iguanas, each with different characteristics. The first are dark, almost black, Darwin called them "little geniuses of the night". These iguanas resting on the lava rocks and kept in absolute stillness, as only move when someone approaches them.

Its backbone is lined with spiny tips. Theodore Wolf mentioned that the marine iguana is the only remaining ancestor of marine dinosaurs that populated the planet ages ago.

The land iguana is dark yellow, feeds on cacti, palo santo leaves and moyuyo. They usually live in the drier parts of the islands and dig burrows between 15 and 20 inches deep.

Sea Lions

Hotel Solymar Galapagos Islands EcuadorAlso called "Lobos marinos" sea wolves in Spanish are a curious and playful mammal that are thought to have arrived in Galapagos on the Humboldt current.

The largest sea lion colonies are found on the islands of South Plazas, Fernandina and Fernandina. On Genovesa island there are fur sea lions, the only of their kind to live in such tropical climate.

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A Call to Accountability

Watch A Call to Accountability video.

By Dr. Charles Stanley

Scripture: Matthew 25:14-30

I. Introduction: We all love the freedoms enumerated and protected by our Constitution and should be grateful for the liberties we have as Americans. However, along with our wonderful rights come important responsibilities. As believers, we are accountable to God not only for the course of this country, but for the path we take in our lives. Therefore, we must live in a manner that not only glorifies the Father and edifies others but also preserves and protects the sacred values we hold dear.

II. Our liberty in Christ does not give us the right to indulge in sin.

A. Parents should talk daily to their children about the things of the Lord (Deut. 6:7).
B. Though our sins have been forgiven, we will still face consequences for the choices we make (Matt. 25:14-30). This can be seen vividly through Jesus' parable of the talents. The Lord gives us gifts, skills, resources, and talents, and we are responsible to use them in ways that honor Him. If we fail to do so, we forfeit our rewards in heaven.

III. What is accountability?

Accountability means we are answerable to others, and we should accept this responsibility as a gift from God. Not only does it provide a system of checks and balances that protect us from harm, but it also gives us unique opportunities to share our lives with others and encourage them.

IV. What biblical examples do we have concerning accountability?

A. Adam and Eve—Genesis 3:8-19
B. Samuel and Saul—1 Samuel 13:8-14
C. Nathan and David—2 Samuel 12:1-14
D. Jesus and Peter—Matthew 16:21-23

V. Why is accountability important for our lives?

A. Knowing that someone will ask about our conduct motivates us to do our best and encourages us to be good stewards of our time, talents, and resources.
B. When we're answerable to others, we are positioned for promotion. As those in authority review our work, they realize our potential.
C. Accountability inspires and protects us and those we're closest to, which makes our relationships even stronger.
D. We must regularly face the truth about our attitudes and actions, and examine whether we are staying in the center of God's will.
E. Being responsible to the Lord and others challenges us to maintain high standards, godly convictions, a transparent heart, and a trustworthy character.

VI. Why do people resist accountability?

A. Rebelliousness
B. Slothfulness
C. Fear of loss
D. Untrustworthiness
E. Pride

VII. What happens without accountability?

A. We cannot do our best.
B. Our resources may be wasted.
C. Spiritual growth will be hampered.
D. There will be divisions in our most important relationships.
E. We will miss opportunities, privileges, promotions, and rewards.
F. Others may feel free to take advantage of us.

VIII. Conclusion: Accountability is absolutely necessary in every aspect of our life, starting with relationships in our family and among fellow believers. However, we must also hold others in society responsible for what they do, whether they are in the church, the schools, or the government. These are serious days for our nation and world, and as believers, we are charged with defending the faith and proclaiming the gospel of salvation—the only true path to freedom from sin and death. We know the truth, so we cannot keep silent about it. Rather, we're accountable to declare the truth as passionately, effectively, and fearlessly as we can.

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The Bison of Yellowstone National Park
NPS Scientific Monograph No. 1
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OBJECTIVES OF THIS STUDY were to provide basic data on the life history, habits, and ecology of bison in Yellowstone National Park.

The original population of bison in historic times consisted of mountain bison, Bison bison athabascae. In spite of poaching to near-extermination by about 1901, a remnant of the subspecies survived and increased. Interbreeding with a population of plains bison, B. b. bison, introduced in 1902, began by the 1920s. The present bison population consists of hybrid descendants of the two subspecies.

The present wintering distribution within the park approximates that of the historic population, occurring in the three subunits of Lamar, Pelican, and Mary Mountain, none of which are geographically isolated from the others. The present summering population approximates the historic distribution only in the Upper Lamar-Mirror Plateau and Hayden Valley areas. A large west-side and a large northern summering population are lacking. Present (1968) numbers are half or less than those of probable historic numbers.

Examination of 71 females killed for population reduction purposes indicated that sexual maturity was not reached by most until 4 years of age, later than recorded some years ago. The observed pregnancy rate of 52% for females 2.5 years and older was also less than formerly recorded in Yellowstone. Brucellosis was not a factor which affected reproduction. Records and observations suggested that both calving season (in May on the winter ranges) and the breeding season (in late July to early August on the summer ranges) were shorter than formerly. The observed changes may reflect the shift from a semiranched population to a wild one.

Records from live-trapping operations in 1964-66 provided sex and age structure information. The records suggested that female survival was favored during the calf year, but that male survival was favored the next 3 years of life, after which differential survival could not be distinguished from the records. Adult bulls outnumbered adult cows, but this could be attributed to earlier reductions.

Age classes of the wintering population in the Mary Mountain area in 1964-65 were: calves, 16%; yearlings, 11%; 2.5-year-olds, 6%; 3.5-year-olds, 5%; and adults, 62%. These may change somewhat after a period with no reductions.

Observed spring calf percentages of mixed herd numbers for 3 of 5 years were 19-20%. Percentages of total population were approximately 11%. These percentages may also change if reductions are not made.

Significant mortality of calves at birth or just before or after was suggested by limited data. Thereafter, little mortality occurred during the first year. Nearly half the calves which survived into their first winter died before 2.5 years of age. Recruitment into the population occurred with survival to 3 years of age.

Population trends suggested that increases in the population were often very slow. Reductions by man apparently were not the sole factor which caused population decreases nor retarded increases. Parasites, diseases, predation, and emigration were not important. Environmental factors culminating in usual and more-than-usual winter mortality appeared important.

Herd groups followed definite patterns of seasonal movement. Spring migrations to summer ranges, occurring by the second week of June, appeared to be influenced by weather patterns and temperatures rather than snow melt or vegetation changes. Temporary fall movements occurred in conjunction with fall storms at higher elevations; final movements to winter ranges occurred by mid-November. Bull movements were somewhat more irregular.

Movements and distribution on summer range areas appeared more influenced by the presence of biting flies than by possible factors of breeding activity and vegetation changes. A species of Symphoromyia of the Rhagionidae was implicated.

Mixing and interchange between population subunits resulted in designation of three herds according to their use of winter range areas. These three subunits formed two breeding populations in summer. Little contact occurred between members of these two populations at any time.

The limited neckband information on marked adult cows suggested that they have an affinity for a given winter range regardless of summer movements. Temporary shifts of population segments from one winter range to another have occurred. Thus, although no population segment is isolated from another, the three exist as fairly separate entities in terms of winter range. This may explain the lack of population emigration to and reestablishment on unoccupied ranges either within or outside the park since historic times.

Analysis of 22 rumen samples showed that sedge was the most important forage item. Sedge, rush, and grasses provided 96% of the diet volume throughout the year. Forage availability did not appear to be a population-limiting factor under most conditions.

Population numbers in Pelican over a span of many years suggested that the levels were regulated by environmental influences which resulted in low reproduction and low increment rates. Larger increases in numbers during favorable periods have been offset periodically by heavy mortality during more severe winters. The minimum population level in this area may be governed by the presence of scattered thermal areas used in winter stress periods. A combination of factors such as extensive sedge bottoms together with some sagebrush-grassland uplands, open streams, and thermal areas may allow habitation over time by mixed herd groups of bison in this wintering valley.

Last Updated: 24-Jan-2005