First-principles calculations of the crystal structure, electronic structure, and thermodynamic stability of Be(BH4)2

Alanates and boranates are intensively studied because of their potential use as hydrogen storage materials. In this paper, we present a first-principles study of the electronic structure and the energetics of beryllium boranate BeBH42. From total energy calculations, we show that—in contrast to the other boranates and alanates—hydrogen desorption directly to the elements is likely and is at least competitive with desorption to the elemental hydride BeH2. The formation enthalpy of BeBH42 is only −0.14 eV/H2 at T=0 K. This low value can be rationalized by the participation of all atoms in the covalent bonding, which is in contrast to the ionic bonding observed in other boranates. From calculations of thermodynamic properties at finite temperature, we estimate a decomposition temperature of 162 K at a pressure of 1 bar

Ab initio study on the effects of transition metal doping of Mg2NiH4

Mg2NiH4 is a promising hydrogen storage material with fast (de)hydrogenation kinetics. Its hydrogen desorption enthalpy, however, is too large for practical applications. In this paper we study the effects of transition metal doping by first-principles density functional theory calculations. We show that the hydrogen desorption enthalpy can be reduced by ~0.1 eV/H2 if one in eight Ni atoms is replaced by Cu or Fe. Replacing Ni by Co atoms, however, increases the hydrogen desorption enthalpy. We study the thermodynamic stability of the dopants in the hydrogenated and dehydrogenated phases. Doping with Co or Cu leads to marginally stable compounds, whereas doping with Fe leads to an unstable compound. The optical response of Mg2NiH4 is also substantially affected by doping. The optical gap in Mg2NiH4 is ~1.7 eV. Doping with Co, Fe or Cu leads to impurity bands that reduce the optical gap by up to 0.5 eV.Comment: 8 pages, 4 figure

Interactions of adsorbed CO2_2 on water ice at low temperatures

We present a computational study into the adsorption properties of CO$_2$ on amorphous and crystalline water surfaces under astrophysically relevant conditions. Water and carbon dioxide are two of the most dominant species in the icy mantles of interstellar dust grains and a thorough understanding of their solid phase interactions at low temperatures is crucial for understanding the structural evolution of the ices due to thermal segregation. In this paper, a new H$_2$O-CO$_2$ interaction potential is proposed and used to model the ballistic deposition of CO$_2$ layers on water ice surfaces, and to study the individual binding sites at low coverages. Contrary to recent experimental results, we do not observe CO$_2$ island formation on any type of water substrate. Additionally, density functional theory calculations are performed to assess the importance of induced electrostatic interactions.Comment: Accepted for publication in Physical Chemistry Chemical Physic

Low work function of the (1000) Ca2N surface

Polymer diodes require cathodes that do not corrode the polymer but do have low work function to minimize the electron injection barrier. First-principles calculations demonstrate that the work function of the (1000) surface of the compound Ca2N is half an eV lower than that of the elemental metal Ca (2.35 vs. 2.87 eV). Moreover its reactivity is expected to be smaller. This makes Ca2N an interesting candidate to replace calcium as cathode material for polymer light emitting diode devices.Comment: 3 pages, 4 figures, accepted by J. Appl. Phy

Half-metallicity and efficient spin injection in AlN/GaN:Cr (0001) heterostructure

First-principles investigations of the structural, electronic and magnetic properties of Cr-doped AlN/GaN (0001) heterostructures reveal that Cr segregates into the GaN region, that these interfaces retain their important half-metallic character and thus yield efficient (100 %) spin polarized injection from a ferromagnetic GaN:Cr electrode through an AlN tunnel barrier - whose height and width can be controlled by adjusting the Al concentration in the graded bandgap engineered Al(1-x)Ga(x)N (0001) layers.Comment: submitted for publicatio

Offspring conceived through ART have normal thyroid function in adolescence and as young adults

STUDY QUESTION: Are there differences in thyroid function between adolescents and young adults conceived with and without ART? SUMMARY ANSWER: This study demonstrated no evidence of clinically relevant differences in thyroid function between adolescents and young adults conceived with and without ART. WHAT IS KNOWN ALREADY: Studies to date have reported an increase in subclinical hypothyroidism in offspring conceived after ART. It has been suggested that the increase in maternal estrogen (E2) after fresh embryo transfers could affect thyroid function of the offspring. Suboptimal thyroid function at a young age can cause irreversible damage to the central nervous system, which makes early detection and correct treatment essential. STUDY DESIGN, SIZE, DURATION: The Growing Up Healthy Study (GUHS) is a prospective cohort study, which aimed to recruit all adolescents born after conception with ART between 1991 and 2001 in the study area. The included participants (n = 303, aged 13-20 years) completed various health assessments. Depending on the age at enrolment, participants completed thyroid assessments at the 14-or 20-year follow-up. The outcomes of these replicated thyroid assessments were compared to those of participants conceived without ART from the Raine Study Generation 2 (Gen2). The Gen2 participants (n = 2868) were born between 1989 and 1992 and have been recognized to be representative of the local population. PARTICIPANTS/MATERIALS, SETTING, METHODS: Thyroid function assessments were compared between n = 134 GUHS and n = 1359 Gen2 adolescents at age 14 years and between n = 47 GUHS and n = 914 Gen2 young adults at age 20 years. The following mean thyroid hormone concentrations were compared between the cohorts: Thyroid-stimulating hormone (TSH), free triiodothyronine (fT3), free thyroxine (fT4) and thyroid peroxidase antibodies (TPOAb). The prevalence of the following thyroid hormone profiles, based on individual thyroid hormone concentrations, was compared: euthyroidism, subclinical and overt hypo-and hyperthyroidism and thyroid autoimmunity. Outcomes were compared between the cohorts, and univariately between fresh embryo transfers (ET) and frozen ET (FET) within the GUHS. The correlation between maternal peak E2 concentrations (pE2) and fT4 was assessed within the GUHS. MAIN RESULTS AND THE ROLE OF CHANCE: All mean thyroid function outcomes fell within the normal range. At both ages, we report no differences in TSH concentrations. At age 14 years, lower fT3 concentrations (4.80 versus 5.35 pmol/L, P \u3c 0.001) and higher fT4 concentrations (12.76 versus 12.19 pmol/L, P \u3c 0.001) were detected in the GUHS adolescents compared to Gen2 adolescents. At age 20 years, higher fT3 and fT4 concentrations were reported in GUHS adolescents (4.91 versus 4.63 pmol/L, P = 0.012; 13.43 versus 12.45 pmol/L, P \u3c 0.001, respectively) compared to Gen2 participants. No differences in the prevalence of subclinical and overt hypo-and hyperthyroidism or thyroid autoimmunity were demonstrated between the cohorts at age 14 and 20 years. Thyroid function did not differ between ET and FET, and no correlation between pE2 and fT4 was reported. LIMITATIONS, REASONS FOR CAUTION: The observational nature of the study limits the ability to prove causation. Furthermore, the comparison of ET and FET offspring at age 20 years may be lacking power. We were unable to differentiate between different types of ART (e.g. IVF versus ICSI) owing to the low number of ICSI cycles at the time of study. As ART laboratory and clinic data were collected contemporaneously with the time of treatment, no other data pertaining to the ART cycles were sought retrospectively; hence, some factors could not be accounted for. WIDER IMPLICATIONS OF THE FINDINGS: This study does not support previous findings of clinically relevant differences in thyroid function when comparing a cohort of adolescents conceived after ART to counterparts conceived without ART. The minor differences detected in fT3 and fT4 were considered not biologically relevant. Although these findings appear reassuring, they warrant reinvestigation in adulthood. STUDY FUNDING/COMPETING INTERESTS: This project was funded by an NHMRC Grant (Hart et al., ID 1042269). R.J.H. is the Medical Director of Fertility Specialists of Western Australia and a shareholder in Western IVF. He has received educational sponsorship from MSD, Merck-Serono and Ferring Pharmaceuticals. P.B. is the Scientific Director of Concept Fertility Centre, Subiaco, Western Australia. J.L.Y. is the Medical Director and a shareholder of PIVET Medical Centre, Perth, Western Australia. TRIAL REGISTRATION NUMBER: N/A

GPU Accelerated counterexample generation in LTL model checking

Strongly Connected Component (SCC) based searching is one of the most popular LTL model checking algorithms. When the SCCs are huge, the counterexample generation process can be time-consuming, especially when dealing with fairness assumptions. In this work, we propose a GPU accelerated counterexample generation algorithm, which improves the performance by parallelizing the Breadth First Search (BFS) used in the counterexample generation. BFS work is irregular, which means it is hard to allocate resources and may suffer from imbalanced load. We make use of the features of latest CUDA Compute Architecture-NVIDIA Kepler GK110 to achieve the dynamic parallelism and memory hierarchy so as to handle the irregular searching pattern in BFS.We build dynamic queue management, task scheduler and path recording such that the counterexample generation process can be completely finished by GPU without involving CPU. We have implemented the proposed approach in PAT model checker. Our experiments show that our approach is effective and scalable. ?Springer International Publishing Switzerland 2014.EI0413-429882

Is timed branching bisimilarity a congruence indeed?

We show that timed branching bisimilarity as defined by Van der Zwaag [17] and Baeten and Middelburg [2] is not an equivalence relation, in case of a dense time domain. We propose an adaptation based on Van der Zwaag's definition, and prove that the resulting timed branching bisimilarity is an equivalence indeed. Furthermore, we prove that in case of a discrete time domain, Van der Zwaag's definition and our adaptation coincide. Finally, we prove that a rooted version of timed branching bisimilarity is a congruence over a basic timed process algebra containing parallelism, successful termination and deadlock