Synthesis of M2AC (M = Ti, V, Cr, Nb, Zr, A = Al, Sn, S) (MAX) carbide phases and study of their physical behavior under extreme conditions

Materials known as Mn+1AXn phases, where n is 1, 2, or 3, and M represents an early transition metal, A an A-group element, and X is either Carbon and/or Nitrogen [1], are fast becoming technologically important materials due to the interesting combination of unique properties. However, a lot of important information about the high temperature and high pressure behavior of many of these compounds is still missing, which needs to be determined systematically. ^ In this dissertation the synthesis of M2AC (M = Ti, V, Cr, Nb, Zr) and A = (Al, Sn, S) compounds by arc melting, vacuum sintering and piston cylinder synthesis is presented along with the synthesis of Zr 2SC, which has been synthesized for first time in bulk form, by piston cylinder technique. The microstructural analysis by electron microscopy and phase analysis by x-ray diffraction is presented next. Finally, a critical analysis of the behavior of these compounds under the application of extreme pressure (as high as 50 GPa) and temperature (≈ 1000°C) is presented. ^ The high pressure studies, up to 50 GPa, showed that these compounds were structurally intact and their bulk moduli ranged from 140 to 190 GPa. The high temperature studies in the inert atmosphere showed that the M 2SnC compounds were unstable above 650°C and the expansion along the a-axis was higher than that along the c-axis, unlike the other phases. M2SC compounds on the other hand showed negligible difference in the thermal expansion along the two axes. The oxidation study revealed that Ti2AC (Al, S) compounds had highest resistance to oxidation while the M2SnC compounds had the least. Furthermore, from the oxidation study of these compounds, which were short time oxidation experiments, it was found that all of these compounds oxidized to their respective binary oxides. ^

The relationship between classroom interactions and exclusionary discipline as a social practice: A critical microethnograhy

Exclusionary school discipline results in students being removed from classrooms as a consequence of their disruptive behavior and may lead to subsequent suspension and/or expulsion. Literature documents that nondominant students, particularly Black males, are disproportionately impacted by exclusionary discipline, to the point that researchers from a variety of critical perspectives consider exclusionary school discipline an oppressive educational practice and condition. Little or no research examines specific teacher-student social interactions within classrooms that influence teachers’ decisions to use or not use exclusionary discipline. Therefore, this study set forth the central research question: In relation to classroom interactions in alternative education settings, what accounts for teachers’ use or non-use of exclusionary discipline with students? A critical social practice theory of learning served as the framework for exploring this question, and a critical microethnographic methodology informed the data collection and analysis. ^ Criterion sampling was used to select four classrooms in the same alternative education school with two teachers who frequently and two who rarely used exclusionary discipline. Nine stages of data collection and reconstructive data analysis were conducted. Data collection involved video recorded classroom observations, digitally recorded interviews of teachers and students discussing selected video segments, and individual teacher interviews. Reconstructive data analysis procedures involved hermeneutic inferencing of possible underlying meanings, critical discourse analysis, interactive power analysis and role analysis, thematic analysis of the interactions in each classroom, and a final comparative analysis of the four classrooms. ^ Four predominant themes of social interaction (resistance, conformism, accommodation, and negotiation) emerged with terminology adapted from Giroux’s (2001) theory of resistance in education and Third Space theory (Gutiérrez, 2008). Four types of power (normative, coercive, interactively established contracts, and charm), based on Carspecken’s (1996) typology, were found in the interactions between teacher and students in varying degrees for different purposes. ^ This research contributes to the knowledge base on teacher-student classroom interactions, specifically in relation to exclusionary discipline. Understanding how the themes and varying power relations influence their decisions and actions may enable teachers to reduce use of exclusionary discipline and remain focused on positive teacher-student academic interactions. ^

Organizational Behavior: Forgotten Variable in Safe Food

The war on foodborne illness in hotels and restaurants is based on microbiology and critical control points. The author argues that cooks, managers, instructors, researchers, and regulators need to start looking beyond this narrow base to include more organizational behavior processes in their arsenal.

Critical Analysis on the Structural and Magnetic Properties of Bulk and Nanocrystalline Cu-Fe-O

Nanocrystalline and bulk samples of “Fe”-doped CuO were prepared by coprecipitation and ceramic methods. Structural and compositional analyses were performed using X-ray diffraction, SEM, and EDAX. Traces of secondary phases such as CuFe2O4, Fe3O4, and α-Fe2O3 having peaks very close to that of the host CuO were identified from the Rietveld profile analysis and the SAED pattern of bulk and nanocrystalline Cu0.98Fe0.02O samples. Vibrating Sample Magnetometer (VSM) measurements show hysteresis at 300 K for all the samples. The ferrimagnetic Neel transition temperature () was found to be around 465°C irrespective of the content of “Fe”, which is close to the value of cubic CuFe2O4. High-pressure X-Ray diffraction studies were performed on 2% “Fe”-doped bulk CuO using synchrotron radiation. From the absence of any strong new peaks at high pressure, it is evident that the secondary phases if present could be less than the level of detection. Cu2O, which is diamagnetic by nature, was also doped with 1% of “Fe” and was found to show paramagnetic behavior in contrast to the “Fe” doped CuO. Hence the possibility of intrinsic magnetization of “Fe”-doped CuO apart from the secondary phases is discussed based on the magnetization and charge state of “Fe” and the host into which it is substituted.

The Relationship between Classroom Interactions and Exclusionary Discipline as a Social Practice: A Critical Microethnography

Exclusionary school discipline results in students being removed from classrooms as a consequence of their disruptive behavior and may lead to subsequent suspension and/or expulsion. Literature documents that nondominant students, particularly Black males, are disproportionately impacted by exclusionary discipline, to the point that researchers from a variety of critical perspectives consider exclusionary school discipline an oppressive educational practice and condition. Little or no research examines specific teacher-student social interactions within classrooms that influence teachers’ decisions to use or not use exclusionary discipline. Therefore, this study set forth the central research question: In relation to classroom interactions in alternative education settings, what accounts for teachers’ use or non-use of exclusionary discipline with students? A critical social practice theory of learning served as the framework for exploring this question, and a critical microethnographic methodology informed the data collection and analysis. Criterion sampling was used to select four classrooms in the same alternative education school with two teachers who frequently and two who rarely used exclusionary discipline. Nine stages of data collection and reconstructive data analysis were conducted. Data collection involved video recorded classroom observations, digitally recorded interviews of teachers and students discussing selected video segments, and individual teacher interviews. Reconstructive data analysis procedures involved hermeneutic inferencing of possible underlying meanings, critical discourse analysis, interactive power analysis and role analysis, thematic analysis of the interactions in each classroom, and a final comparative analysis of the four classrooms. Four predominant themes of social interaction (resistance, conformism, accommodation, and negotiation) emerged with terminology adapted from Giroux’s (2001) theory of resistance in education and Third Space theory (Gutiérrez, 2008). Four types of power (normative, coercive, interactively established contracts, and charm), based on Carspecken’s (1996) typology, were found in the interactions between teacher and students in varying degrees for different purposes. This research contributes to the knowledge base on teacher-student classroom interactions, specifically in relation to exclusionary discipline. Understanding how the themes and varying power relations influence their decisions and actions may enable teachers to reduce use of exclusionary discipline and remain focused on positive teacher-student academic interactions.

The critical role of intracavity dynamics in high-power mode-locked fiber lasers

We present a theoretical description of the generation of ultra-short, high-energy pulses in two laser cavities driven by periodic spectral filtering or dispersion management. Critical in driving the intra-cavity dynamics is the nontrivial phase profiles generated and their periodic modification from either spectral filtering or dispersion management. For laser cavities with a spectral filter, the theory gives a simple geometrical description of the intra-cavity dynamics and provides a simple and efficient method for optimizing the laser cavity performance. In the dispersion managed cavity, analysis shows the generated self-similar behavior to be governed by the porous media equation with a rapidly-varying, mean-zero diffusion coefficient whose solution is the well-known Barenblatt similarity solution with parabolic profile. © 2010 Copyright SPIE - The International Society for Optical Engineering.

The Role of TET Proteins in the Epigenetic Regulation of Neural Gene Expression and Behavior

Understanding how genes affect behavior is critical to develop precise therapies for human behavioral disorders. The ability to investigate the relationship between genes and behavior has been greatly advanced over the last few decades due to progress in gene-targeting technology. Recently, the Tet gene family was discovered and implicated in epigenetic modification of DNA methylation by converting 5-methylcytosine to 5-hydroxymethylcytosine (5hmC). 5hmC and its catalysts, the TET proteins, are highly abundant in the postnatal brain but with unclear functions. To investigate their neural functions, we generated new lines of Tet1 and Tet3 mutant mice using a gene targeting approach. We designed both mutations to cause a frameshift by deleting the largest coding exon of Tet1 (Tet1Δe4) and the catalytic domain of Tet3 (Tet3Δe7-9). As Tet1 is also highly expressed in embryonic stem cells (ESCs), we generated Tet1 homozygous deleted ESCs through sequential targeting to compare the function of Tet1 in the brain to its role in ESCs. To test our hypothesis that TET proteins epigenetically regulate transcription of key neural genes important for normal brain function, we examined transcriptional and epigenetic differences in the Tet1Δe4 mouse brain. The oxytocin receptor (OXTR), a neural gene implicated in social behaviors, is suggested to be epigenetically regulated by an unknown mechanism. Interestingly, several human studies have found associations between OXTR DNA hypermethylation and a wide spectrum of behavioral traits and neuropsychiatric disorders including autism spectrum disorders. Here we report the first evidence for an epigenetic mechanism of Oxtr transcription as expression of Oxtr is reduced in the brains of Tet1Δe4-/- mice. Likewise, the CpG island overlapping the promoter of Oxtr is hypermethylated during early embryonic development and persists into adulthood. We also discovered altered histone modifications at the hypermethylated regions, indicating the loss of TET1 has broad effects on the chromatin structure at Oxtr. Unexpectedly, we discovered an array of novel mRNA isoforms of Oxtr that are selectively reduced in Tet1Δe4-/- mice. Additionally, Tet1Δe4-/- mice display increased agonistic behaviors and impaired maternal care and short-term memory. Our findings support a novel role for TET1 in regulating Oxtr expression by preventing DNA hypermethylation and implicate TET1 in social behaviors, offering novel insight into Oxtr epigenetic regulation and its role in neuropsychiatric disorders.

Behavior Genetics and Post Genomics

The science of genetics is undergoing a paradigm shift. Recent discoveries, including the activity of retrotransposons, the extent of copy number variations, somatic and chromosomal mosaicism, and the nature of the epigenome as a regulator of DNA expressivity, are challenging a series of dogmas concerning the nature of the genome and the relationship between genotype and phenotype. DNA, once held to be the unchanging template of heredity, now appears subject to a good deal of environmental change; considered to be identical in all cells and tissues of the body, there is growing evidence that somatic mosaicism is the normal human condition; and treated as the sole biological agent of heritability, we now know that the epigenome, which regulates gene expressivity, can be inherited via the germline. These developments are particularly significant for behavior genetics for at least three reasons: First, these phenomena appear to be particularly prevalent in the human brain, and likely are involved in much of human behavior; second, they have important implications for the validity of heritability and gene association studies, the methodologies that largely define the discipline of behavior genetics; and third, they appear to play a critical role in development during the perinatal period, and in enabling phenotypic plasticity in offspring in particular. I examine one of the central claims to emerge from the use of heritability studies in the behavioral sciences, the principle of “minimal shared maternal effects,” in light of the growing awareness that the maternal perinatal environment is a critical venue for the exercise of adaptive phenotypic plasticity. This consideration has important implications for both developmental and evolutionary biology

Consumer Behavior and Firm Competition

Understanding consumer behavior is critical for firms' decision making. How consumers make decisions about what they want and buy directly affect the profits of firms. Therefore, it is important to consider consumer behaviors and incorporate them into the model when studying the optimal strategy of firms and competition between firms. In this dissertation, I study rich and interesting consumer behaviors and their impact on firms' strategy in two essays. The first essay considers consumers' shopping cost which leads to their preference for one-stop shopping. I examine how store visit costs and consumer knowledge about a product affect the strategic store choice of consumers and, in turn, the pricing, customer service and advertising decisions of competing retailers. My analysis offers insights on how specialty stores can compete with big-box retailers. In the second essay, I focus on a well-established psychology phenomenon, cognitive dissonance. I incorporate the idea of cognitive dissonance into a model of spatial competition and examine its implications for selling strategy. I provide new insight on the profitability of advance selling and spot selling as well as the pricing of bundle and its components. Collectively, two essays in this dissertation introduce novel ways to model consumer behaviors and help to understand the impact of consumer behaviors on firm profitability and strategy.

Temporomandibular joint pain: a critical role for Trpv4 in the trigeminal ganglion.

Temporomandibular joint disorder (TMJD) is known for its mastication-associated pain. TMJD is medically relevant because of its prevalence, severity, chronicity, the therapy-refractoriness of its pain, and its largely elusive pathogenesis. Against this background, we sought to investigate the pathogenetic contributions of the calcium-permeable TRPV4 ion channel, robustly expressed in the trigeminal ganglion sensory neurons, to TMJ inflammation and pain behavior. We demonstrate here that TRPV4 is critical for TMJ-inflammation-evoked pain behavior in mice and that trigeminal ganglion pronociceptive changes are TRPV4-dependent. As a quantitative metric, bite force was recorded as evidence of masticatory sensitization, in keeping with human translational studies. In Trpv4(-/-) mice with TMJ inflammation, attenuation of bite force was significantly less than in wildtype (WT) mice. Similar effects were seen with systemic application of a specific TRPV4 inhibitor. TMJ inflammation and mandibular bony changes were apparent after injections of complete Freund adjuvant but were remarkably independent of the Trpv4 genotype. It was intriguing that, as a result of TMJ inflammation, WT mice exhibited significant upregulation of TRPV4 and phosphorylated extracellular-signal-regulated kinase (ERK) in TMJ-innervating trigeminal sensory neurons, which were absent in Trpv4(-/-) mice. Mice with genetically-impaired MEK/ERK phosphorylation in neurons showed resistance to reduction of bite force similar to that of Trpv4(-/-) mice. Thus, TRPV4 is necessary for masticatory sensitization in TMJ inflammation and probably functions upstream of MEK/ERK phosphorylation in trigeminal ganglion sensory neurons in vivo. TRPV4 therefore represents a novel pronociceptive target in TMJ inflammation and should be considered a target of interest in human TMJD.

(Quantum-) critical dynamics of magnetoelectric materials

In this thesis the critical dynamics of several magnetoelectric compounds at their phase transition were examined. Mostly measurements of the dielectric properties in the frequency range of below 1 Hz up to 5 GHz were employed to evaluate the critical exponents for both magnetic field and temperature-dependent measurements. Most of the materials that are part of this work show anomalous behavior, especially at very low temperatures where quantum fluctuations are of the order of or even dominate those induced thermally. This anomalous behavior manifests in different forms. In Dy2Ti2O7 we demonstrate the existence of electric dipoles on magnetic monopoles. Here the dynamics at the critical endpoint located at 0.36K and in a magnetic field of 1T parallel to the [111] direction are of special interest. At this critical endpoint the expected critical slowing down of the dynamics could not only not be observed but instead the opposite, critical speeding-up by several orders of magnitude, could be demonstrated. Furthermore, we show that the phase diagram of Dy2Ti2O7 in this field direction can be reproduced solely from the dynamical properties, for example the resonance frequency of the observed relaxation that is connected to the monopole movement. Away from this point of the phase diagram the dynamics are slowing-down with reduction of temperature as one would expect. Additional measurements on Y2Ti2O7, a structurally identical but non-magnetic material, show only slowing down with reduction of temperature and no additional features. A possible explanation for the observed critical speeding-up is a coherent movement of magnetic monopoles close to the critical field that increases the resonance frequency by reducing the damping of the process. LiCuVO4 on the other hand behaves normally at its phase transition as long as the temperature is higher than 0.4 K. In this temperature regime the dynamics show critical slowing-down analogous to classical ferroelectric materials. This analogy extends also towards higher frequencies where the permittivity displays a ‘dispersion’ minimum that is temperature-dependent but of the order of 2 GHz. Below 0.4K the observed behavior changes drastically. Here we found no longer relaxational behavior but instead an excitation with very low energy. This low energy excitation was predicted by theory and is caused by nearly gapless soliton excitations within the 1D Cu2+ chains of LiCuVO4. Finally, in TbMnO3 the dynamics of the phase transition into the multiferroic phase was observed at roughly 27 K, a much higher temperature compared to the other materials. Here the expected critical slowing-down was observed, even though in low-frequency measurements this transition into the ferroelectric phase is overshadowed by the so-called c-axis relaxation. Therefore, only frequencies above 1MHz could be used to determine the critical exponents for both temperatureand magnetic-field-dependent measurements. This was done for both the peak frequency as well as the relaxation strength. In TbMnO3 an electromagnetic soft-mode with small optical weight causes the observed fluctuations, similar to the case of multiferroic MnWO4.

Effects of Wingwall Configurations on the Behavior of Integral Abutment Bridges

This research includes parametric studies performed with the use of three-dimensional nonlinear finite element models in order to investigate the effects of cantilever wingwall configurations on the behavior of integral abutment bridges located on straight alignment and zero skew. The parametric studies include all three types of cantilever wingwalls; inline, flared, and U-shaped wingwalls. Bridges analyzed vary in length from 100 to 1200 feet. Soil-structure and soil-pile interaction are included in the analysis. Loadings include dead load in combination with temperature loads in both rising and falling temperatures. Plasticity in the integral abutment piles is investigated by means of nonlinear plasticity models. Cracking in the abutments and stresses in the reinforcing steel are investigated by means of nonlinear concrete models. The effects of wingwall configurations are assessed in terms of stresses in the integral abutment piles, cracking in the abutment walls, stresses in the reinforcing steel of abutment walls, and axial forces induced in the steel girders. The models developed are analyzed for three types of soil behind the abutments and wingwalls; dense sand, medium dense sand, and loose sand. In addition, the models consider both the case of presence and absence of predrilled holes at the top nine feet of piles. The soil around the piles below the predrilled holes consists of very stiff clay. The results indicate that for the stresses in the piles, the critical load is temperature contraction and the most critical parameter is the use of predrilled holes. However, for both the stresses in the reinforcing steel and the axial forces induced in the girders, the critical load is temperature expansion and the critical parameter is the bridge length. In addition, the results indicate that the use of cantilever wingwalls in integral abutment bridges results in an increase in the magnitude of axial forces in the steel girders during temperature expansion and generation of pile plasticity at shorter bridge lengths compared to bridges built without cantilever wingwalls.

Hydric behavior of earth materials and the effects of their stabilization with cement or lime: study on repair mortars for historical rammed earth structures

Earthen building materials bear interesting environmental advantages and are the most appropriate to conserve historical earth constructions. To improve mechanical properties, these materials are often stabilized with cement or lime, but the impact of the stabilizers on the water transport properties, which are also critical, has been very rarely evaluated. We have tested four earth-based repair mortars applied on three distinct and representative rammed earth surfaces. Three mortars are based on earth collected from rammed earth buildings in south of Portugal and the fourth mortar is based on a commercial clayish earth. The main objective of the work was over the commercial earth mortar, applied stabilized and not stabilized on the three rammed earth surfaces to repair, to assess the influence of the stabilizers. The other three earth mortars (not stabilized) were applied on each type of rammed earth, representing the repair only made with local materials. The four unstabilized earth materials depicted nonlinear dependence on t1/2 during capillary suction. This behaviour was probably due to clay swelling. Stabilization with any of the four tested binders enabled the linear dependence of t1/2 expected from Washburn's equation, probably because the swelling did not take place in this case. However, the stabilizers also increased significantly the capillary suction and the capillary porosity of the materials. This means that, in addition to increasing the carbon footprint, stabilizers like cement and lime have functional disadvantages that discourage its use in repair mortars for raw earth construction.

A pilot study on the productivity and behavior of the gestating sow housed in a flex stall

Animal welfare is a controversial topic in modern animal agriculture, partly because it generates interest from both the scientific community and the general public. The housing of gestating sows, particularly individual housing, is one of the most critical concerns in farm animal welfare. We hypothesize that the physical size of the standard gestation stall may limit movement and evoke demands and challenges on the sow to affect the physiological and psychological well-being of the individually housed sow. Thus, improvements in the design of the individual gestation stall system that allow more freedom to move, such as increasing stall width or designing a stall that could accommodate the changing size of the pregnant sow, may improve sow welfare. The objective of this pilot study was to evaluate the effects of a width adjustable stall (FLEX) on productivity and behavior of dry sows. The experiment consisted of 3 replications (block 1, n=4 sows; block 2, n=4 sows; block 3, n=8 sows), and multi-parious sows were allotted to either a FLEX stall or standard gestation stall for 1 gestation period. Sow mid-girth (top of the back to bottom of the udder) was measured 5-6 times throughout gestation to determine the best time points for FLEX stall width expansions. FLEX stall width was adjusted according to mid-girth measurements, and expanded to achieve an additional 2 cm of space between the bottom of the sow’s udder and floor of the stall so that sows could lie in full lateral recumbency without touching the sides of the stall. Productivity data recorded included: sow body weight (BW) and BW gain, number of piglets born and born alive, proportions of piglets stillborn, mummified, lost between birth and weaning, and weaned, and litter and mean piglet birth BW, weaning BW, and average BW gain from birth-to-weaning. Lesions were recorded on d 21 and d 111 of gestation. Sub-pilot behavior data were observed and registered for replicate 1 sows using continuous video-records for the l2 hour lights on period (period 1, 0600-1000; period 2, 1000-1400; period 3, 1400-1800) prior FLEX stall adjustment and 12 hour lights on period post adjustment on d 21, 22, 23, 43, 44, 45, 93, 94, 95. A randomized complete block design with a 2 × 2 factorial arrangement for treatments was used to analyze sow productivity and performance traits. Data were analyzed using the Mixed Models procedure of SAS. A preliminary analysis of data means and numerical trends was used to analyze sow behavior measurements. Sows housed in a FLEX stall had more (P < 0.05) total born and a tendency for more piglets born alive (P = 0.06) than sows housed in a standard stall. Sow body weight also tended to be higher (P = 0.06) for sows housed in a FLEX stall compared to sows housed in a standard stall. There were numerical trends for mean durations of sit, lay, lay (OUT), and eat behaviors to be greater for sows housed in a FLEX stall compared with sows housed in a standard stall. The mean duration of lay (IN) behavior tended to be numerically less for sows housed in a FLEX stall compared with sows housed in a standard stall. There were numerical trends for the mean durations of stand and drink behaviors to be greater for sows housed in a standard stall compared with sows housed in a FLEX stall. The mean frequencies of postural changes and mean durations of oral-nasal-facial and sham-chew behaviors were numerically similar between types of gestation stall. Mean durations and numerical trends indicate that time of day influenced all of the behaviors assessed in this study. The results of this pilot study indicate that the adjustable FLEX stall may affect sow productivity and behavior differently than the standard gestation stall, and thus potentially improve sow well-being. Future research should continue to compare the new FLEX stall design to current housing systems in use and examine physiological traits and immune status in addition to behavioral and productivity traits to assess the effects that this housing system has on the overall welfare of the gestating sow.

Dr. Bailey: An exemplar of critical care

We often confuse praise and being nice and polite with appreciative, positive behavior and actions. However, the distinction between positive and negative is not so clear. Some seemingly negative behaviors and actions effectively evoke positive emotions and behavior. Criticism and honest candor can serve a positive function, helping us to learn and grow. This paper makes a case for critical care. Such communication is direct and specific but not malicious. The character of Dr. Bailey from the U.S. TV show Grey’s Anatomy is used as an example of someone who demonstrates critical care.