Lattice gas models derived from effective field theory

We start from a low-energy effective field theory for interacting fermions on the lattice and expand in the hopping parameter to derive the nearest-neighbor interactions for a lattice gas model. In this model the renormalization of couplings for different lattice spacings is inherited from the effective field theory, systematic errors can be estimated a priori, and the breakdown of the lattice gas model description at low temperatures can be understood quantitatively. We apply the lattice gas method to neutron matter and compare with results from a recent quantum simulation.Comment: 13 pages, 4 figure

Design, Development and Thermal Analysis of Reusable Li-Ion Battery Module for Future Mobile and Stationary Applications

open access articleThe performance, energy storage capacity, safety, and lifetime of lithium-ion battery cells of different chemistries are very sensitive to operating and environmental temperatures. The cells generate heat by current passing through their internal resistances, and chemical reactions can generate additional, sometimes uncontrollable, heat if the temperature within the cells reaches the trigger temperature. Therefore, a high-performance battery cooling system that maintains cells as close to the ideal temperature as possible is needed to enable the highest possible discharge current rates while still providing a sufficient safety margin. This paper presents a novel design, preliminary development, and results for an inexpensive reusable, liquid-cooled, modular, hexagonal battery module that may be suitable for some mobile and stationary applications that have high charge and or discharge rate requirements. The battery temperature rise was measured experimentally for a six parallel 18650 cylindrical cell demonstrator module over complete discharge cycles at discharge rates of 1C, 2C and 3C. The measured temperature rises at the hottest point in the cells, at the anode terminal, were found to be 6, 17 and 22 °C, respectively. The thermal resistance of the system was estimated to be below 0.2 K/W at a coolant flow rate of 0.001 Kg/s. The proposed liquid cooled module appeared to be an effective solution for maintaining cylindrical Li-ion cells close to their optimum working temperature

Asymmetric additions to dienes catalysed by a dithiophosphoric acid.

Chiral Brønsted acids (proton donors) have been shown to facilitate a broad range of asymmetric chemical transformations under catalytic conditions without requiring additional toxic or expensive metals. Although the catalysts developed thus far are remarkably effective at activating polarized functional groups, it is not clear whether organic Brønsted acids can be used to catalyse highly enantioselective transformations of unactivated carbon-carbon multiple bonds. This deficiency persists despite the fact that racemic acid-catalysed Markovnikov additions to alkenes are well known chemical transformations. Here we show that chiral dithiophosphoric acids can catalyse the intramolecular hydroamination and hydroarylation of dienes and allenes to generate heterocyclic products in exceptional yield and enantiomeric excess. We present a mechanistic hypothesis that involves the addition of the acid catalyst to the diene, followed by nucleophilic displacement of the resulting dithiophosphate intermediate; we also report mass spectroscopic and deuterium labelling studies in support of the proposed mechanism. The catalysts and concepts revealed in this study should prove applicable to other asymmetric functionalizations of unsaturated systems

High temperature reliability of power module substrates

The thermal cycling reliability of candidate copper and aluminium power substrates has been assessed for use at temperatures exceeding 300°C peak using a combination of thermal cycling, nanoindentation and finite element modelling to understand the relative stresses and evolution of the mechanical properties. The results include the relative cycling lifetimes up to 350°C, demonstrating almost an order of magnitude higher lifetime for active metal brazed Al / AlN substrates over Cu / Si3N4, but four times more severe roughening and cracking of the Ni-P plating's on the Al / AlN (DBA) substrates. The nonlinear finite element modelling illustrated that the yield strength of the metal and the thickness of the ceramic are the main stress controlling factors, but comparisons with the cycling lifetime results demonstrated that the fracture toughness (resistance) of the ceramic is the over-riding controlling factor for the overall passive thermal cycling lifetimes. In order to achieve the highest substrate lifetime for the highly stressed high temperature thermal cycled applications, the optimum solution appears to be annealed copper, brazed on to a thicker than normal or higher fracture toughness Si3N4 ceramic

Novel dispersion representation of rectangular dielectric guides with application to leaky-wave antennas

A novel method for graphically and mathematically representing the dispersion characteristics of electromagnetic dielectric structures is presented. The method has been used to develop closed-form formulas to find the longitudinal propagation constant and useful frequency range for a number of popular rectangular dielectric waveguide types. These formulas are presented in terms of their material dependency and are guide size and operating frequency independent. Their form is so trivial that these characteristics can now be found in just a few seconds using a basic calculator, yet still with second order accuracy. In addition, improvements have been made to a number of well-known formulas normally associated with periodic grating leaky-wave antennas. These improvements allow the width of the metal strip grating to be taken into consideration to derive the correct main beam angle, array factor pattern and grating limits. Previously, the grating width was neglected by the formulas and the resulting error was unacceptably high.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Globalization and Anti-americanism: a Study of Singaporean College Students

The purpose of this study was to examine the relationship between Singaporean college students' attitudes toward America and three mass mediated inputs (U.S. entertainment, U.S. multinational advertising and U.S. government sponsored communication). Participants in the study were 328 undergraduate students at the Management Development Institute of Singapore. Each student completed a questionnaire containing several attitudinal scales and demographic questions. The students also viewed five television commercials produced by the U.S. Department of State in a pre-post experiment of advertising effectiveness. ANOVAs, t-tests, Pearson's r, multiple regression and qualitative analysis were used to analyze data and provide answers to 20 research questions. Findings and conclusions./ Overall, Singaporean college students held slightly negative attitudes toward America. However, the students felt more negative toward the U.S. government than the U.S. people. The students consume a large amount of U.S. entertainmenSchool of Teaching and Curriculum Leadershi

Lives, language, and leadership: english teachers as leaders

This study investigates the relationships among literature, educational leadership and teaching. A review of professional literature suggests that literature, leadership and teaching share the characteristics of meaning making, dialogue, artistic/aesthetic experience, transformation, and empathy. The purpose of the study was to consider current educational leaders interpretations of their experiences as humanities instructors and its connection to leadership in their current positions. The author reflects on preparation paths for prospective leaders as well. Three life stories were collected from current educational leaders who previously served as English instructors. Narrative inquiry methodology was utilized, and texts were analyzed using selectivity, slippage, silence, and intertextuality (Casey, 1993; Casey, 1995-1996). Each leader was positioned within a leadership paradigm based on their language and interpretive experiences as leaders. While all felt explicitly that their experiences as English instructors impacted their style and beliefs as educational leaders, textual analysis suggested that family background and personal experiences most influence leadership style and philosophy

Self-renewal of single mouse hematopoietic stem cells is reduced by JAK2V617F without compromising progenitor cell expansion

Recent descriptions of significant heterogeneity in normal stem cells and cancers have altered our understanding of tumorigenesis, emphasizing the need to understand how single stem cells are subverted to cause tumors. Human myeloproliferative neoplasms (MPNs) are thought to reflect transformation of a hematopoietic stem cell (HSC) and the majority harbor an acquired V617F mutation in the JAK2 tyrosine kinase, making them a paradigm for studying the early stages of tumor establishment and progression. The consequences of activating tyrosine kinase mutations for stem and progenitor cell behavior are unclear. In this article, we identify a distinct cellular mechanism operative in stem cells. By using conditional knock-in mice, we show that the HSC defect resulting from expression of heterozygous human JAK2V617F is both quantitative (reduced HSC numbers) and qualitative (lineage biases and reduced self-renewal per HSC). The defect is intrinsic to individual HSCs and their progeny are skewed toward proliferation and differentiation as evidenced by single cell and transplantation assays. Aged JAK2V617F show a more pronounced defect as assessed by transplantation, but mice that transform reacquire competitive self-renewal ability. Quantitative analysis of HSC-derived clones was used to model the fate choices of normal and JAK2-mutant HSCs and indicates that JAK2V617F reduces self-renewal of individual HSCs but leaves progenitor expansion intact. This conclusion is supported by paired daughter cell analyses, which indicate that JAK2-mutant HSCs more often give rise to two differentiated daughter cells. Together these data suggest that acquisition of JAK2V617F alone is insufficient for clonal expansion and disease progression and causes eventual HSC exhaustion. Moreover, our results show that clonal expansion of progenitor cells provides a window in which collaborating mutations can accumulate to drive disease progression. Characterizing the mechanism(s) of JAK2V617F subclinical clonal expansions and the transition to overt MPNs will illuminate the earliest stages of tumor establishment and subclone competition, fundamentally shifting the way we treat and manage cancers

TIM, ray-tracing program for forbidden optics

TIM (The Interactive METATOY) is a ray-tracing program specifically tailored towards our research in METATOYs, which are optical components that appear to be able to create wave-optically forbidden light-ray fields. For this reason, TIM possesses features not found in other ray-tracing programs. TIM can either be used interactively or by modifying the openly available source code; in both cases, it can easily be run as an applet embedded in a web page. Here we describe the basic structure of TIM's source code and how to extend it, and we give examples of how we have used TIM in our own research.Comment: 19 pages, 15 figure