Production of a pseudo-scalar Higgs boson at hadron colliders at next-to-next-to leading order

The production cross section for pseudo-scalar Higgs bosons at hadron colliders is computed at next-to-next-to-leading order (NNLO) in QCD. The pseudo-scalar Higgs is assumed to couple only to top quarks. The NNLO effects are evaluated using an effective lagrangian where the top quarks are integrated out. The NNLO corrections are similar in size to those found for scalar Higgs boson production.Comment: 20 pages, 6 figures, JHEP style, Minor changes, Journal reference adde

The effects of sitaxentan on sildenafil pharmacokinetics and pharmacodynamics in healthy subjects

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: * Endothelin-A receptor antagonists (ETRAs) and phosphodiesterase-type 5 inhibitors are approved monotherapies for the treatment of pulmonary arterial hypertension; combining agents from these two drug classes could be beneficial. * There is a significant pharmacokinetic (PK) interaction between the ETRA bosentan and the phosphodiesterase-type 5 inhibitor sildenafil. * This study assessed whether the ETRA sitaxentan similarly impacts the PK of sildenafil. WHAT THIS STUDY ADDS: * This study demonstrates that sitaxentan has little effect on sildenafil PK and pharmacodynamics and that no dose adjustment of either agent is required upon co-administration of sildenafil with sitaxentan. AIMS: This study evaluated the effects of sitaxentan on the pharmacodynamic [systemic blood pressure (BP)] and pharmacokinetic (PK) parameters of sildenafil in healthy volunteers. METHODS: Healthy subjects (18-60 years, n= 24) were randomized into two sequence groups. Group 1 received sitaxentan sodium 100 mg daily (7 days), followed by placebo (7 days). Group 2 received placebo (7 days), followed by sitaxentan sodium 100 mg (7 days). On day 7 of each treatment period, participants received sildenafil 100 mg. PK parameters and BP were analysed on day 7 in each treatment period. RESULTS: Sildenafil exposure was slightly higher [AUC(infinity) geometric mean ratio (GMR), 128%] when co-administered with sitaxentan 100 mg vs. placebo, demonstrating a weak, but statistically significant interaction (90% confidence interval 115.5%, 141.2%). The mean maximum positive (E(max)+) and maximum negative (E(max)-) changes from baseline in both systolic and diastolic BP were comparable for sitaxentan and placebo (range 4.8-7.3 mmHg) with three of four geometric mean ratios falling within the equivalence window, suggesting that the drug interaction was not clinically significant. Adverse events were similar between sitaxentan 100 mg (39%) and placebo (30%). No deaths or serious adverse events occurred during the study. CONCLUSION: The dose of sildenafil does not need to be adjusted when co-administered with sitaxentan

Modeling the sorption dynamics of NaH using a reactive force field

We have parametrized a reactive force field for NaH, ReaxFFNaH, against a training set of ab initio derived data. To ascertain that ReaxFFNaH is properly parametrized, a comparison between ab initio heats of formation of small representative NaH clusters with ReaxFFNaH was done. The results and trend of ReaxFFNaH are found to be consistent with ab initio values. Further validation includes comparing the equations of state of condensed phases of Na and NaH as calculated from ab initio and ReaxFFNaH. There is a good match between the two results, showing that ReaxFFNaH is correctly parametrized by the ab initio training set. ReaxFFNaH has been used to study the dynamics of hydrogen desorption in NaH particles. We find that ReaxFFNaH properly describes the surface molecular hydrogen charge transfer during the abstraction process. Results on heat of desorption versus cluster size shows that there is a strong dependence on the heat of desorption on the particle size, which implies that nanostructuring enhances desorption process. To gain more insight into the structural transformations of NaH during thermal decomposition, we performed a heating run in a molecular dynamics simulation. These runs exhibit a series of drops in potential energy, associated with cluster fragmentation and desorption of molecular hydrogen. This is consistent with experimental evidence that NaH dissociates at its melting point into smaller fragments

Predictions of melting, crystallization, and local atomic arrangements of aluminum clusters using a reactive force field

A parametrized reactive force field model for aluminum ReaxFFAl has been developed based on density functional theory (DFT) data. A comparison has been made between DFT and ReaxFFAl outputs to ascertain whether ReaxFFAl is properly parametrized and to check if the output of the latter has correlation with DFT results. Further checks include comparing the equations of state of condensed phases of Al as calculated from DFT and ReaxFFAl. There is a good match between the two results, again showing that ReaxFFAl is correctly parametrized as per the DFT input. Simulated annealing has been performed on aluminum clusters Aln using ReaxFFAl to find the stable isomers of the clusters. A plot of stability function versus cluster size shows the existence of highly stable clusters (magic clusters). Quantum mechanically these magic clusters arise due to the complete filling of the orbital shells. However, since force fields do not care about electrons but work on the assumption of validity of Born–Oppenheimer approximation, the magic clusters are therefore correlated with high structural symmetry. There is a rapid decline in surface energy contribution due to the triangulated nature of the surface atoms leading to higher coordination number. The bulk binding energy is computed to be 76.8 kcal/mol. This gives confidence in the suitability of ReaxFF for studying and understanding the underlying dynamics in aluminum clusters. In the quantification of the growth of cluster it is seen that as the size of the clusters increase there is preference for the coexistence of fcc/hcp orders at the expense of simple icosahedral ordering, although there is some contribution from distorted icosahedral ordering. It is found that even for aluminum clusters with 512 atoms distorted icosahedral ordering exists. For clusters with N≥256 atoms fcc ordering dominates, which implies that at this point we are already on the threshold of bulklike bonding

Parametrization of a reactive force field for aluminum hydride

A reactive force field, REAXFF, for aluminum hydride has been developed based on density functional theory (DFT) derived data. REAXFF_(AlH_3) is used to study the dynamics governing hydrogen desorption in AlH_3. During the abstraction process of surface molecular hydrogen charge transfer is found to be well described by REAXFF_(AlH_3). Results on heat of desorption versus cluster size show that there is a strong dependence of the heat of desorption on the particle size, which implies that nanostructuring enhances desorption process. In the gas phase, it was observed that small alane clusters agglomerated into a bigger cluster. After agglomeration molecular hydrogen was desorbed from the structure. This thermodynamically driven spontaneous agglomeration followed by desorption of molecular hydrogen provides a mechanism on how mobile alane clusters can facilitate the mass transport of aluminum atoms during the thermal decomposition of NaAlH_4

Modeling of Hydrogen Storage Materials: A Reactive Force Field for NaH

Parameterization of a reactive force field for NaH is done using ab initio derived data. The parameterized force field(ReaxFFNaH) is used to study the dynamics governing hydrogen desorption in NaH. During the abstraction process of surface molecular hydrogen charge transfer is found to be well described by the parameterized force field. To gain more insight into the mechanism governing structural transformation of NaH during thermal decomposition a heating run in a molecular dynamics simulation is done. The result shows that a clear signature of hydrogen desorption is the fall in potential energy surface during heating

Multiscale modeling of interaction of alane clusters on Al(111) surfaces: A reactive force field and infrared absorption spectroscopy approach

We have used reactive force field (ReaxFF) to investigate the mechanism of interaction of alanes on Al(111) surface. Our simulations show that, on the Al(111) surface, alanes oligomerize into larger alanes. In addition, from our simulations, adsorption of atomic hydrogen on Al(111) surface leads to the formation of alanes via H-induced etching of aluminum atoms from the surface. The alanes then agglomerate at the step edges forming stringlike conformations. The identification of these stringlike intermediates as a precursor to the bulk hydride phase allows us to explain the loss of resolution in surface IR experiments with increasing hydrogen coverage on single crystal Al(111) surface. This is in excellent agreement with the experimental works of Go et al. [ E. Go, K. Thuermer, and J. E. Reutt-Robey, Surf. Sci. 437, 377 (1999) ]. The mobility of alanes molecules has been studied using molecular dynamics and it is found that the migration energy barrier of Al_(2)H_6 is 2.99 kcal/mol while the prefactor is D_0 = 2.82 × 10^(−3) cm^2/s. We further investigated the interaction between an alane and an aluminum vacancy using classical molecular dynamics simulations. We found that a vacancy acts as a trap for alane, and eventually fractionates/annihilates it. These results show that ReaxFF can be used, in conjunction with ab initio methods, to study complex reactions on surfaces at both ambient and elevated temperature conditions

The arthroscopic treatment of displaced tibial spine fractures in children and adolescents using Meniscus Arrows®

This article summarises the results of a newly developed technique that utilises Meniscus Arrows(A (R)) for the arthroscopic fixation of displaced tibial spine fractures in children and adolescents. Twelve tibial spine fractures in the knees of eleven children between 6 and 15 years old, with an average age of 12 years, were arthroscopically fixed with Meniscus Arrows(A (R)), after a reduction of their fractures. This was followed by 5 weeks immobilisation in a plaster of Paris. Postoperative follow-up included radiographs, Lachmann tests on all of the children's knees and KT-1000 tests of eight out of twelve of the children's knees. The postoperative follow-up time ranged from 3 to 10 years, with patients being seen for an average of 4 years. All of the fractures consolidated uneventfully, and all of the patients returned unrestricted to their previous activity level. The Lachmann tests revealed no, or a non-functional, laxity in any of the patients' knees. The KT-1000 tests showed a difference between the operated side, and non-operated side, of between 3 mm in the first knee operated on and an average of 1 mm in the remaining knees. The arthroscopic fixation of tibial spine fractures using Meniscus Arrows(A (R)) showed that this minimally invasive procedure resulted in the uneventful consolidation of all twelve of the fractures, with excellent results, and without the need for a second, hardware removal, operation. Level of Evidence: Level IV

Integrability of irrotational silent cosmological models

We revisit the issue of integrability conditions for the irrotational silent cosmological models. We formulate the problem both in 1+3 covariant and 1+3 orthonormal frame notation, and show there exists a series of constraint equations that need to be satisfied. These conditions hold identically for FLRW-linearised silent models, but not in the general exact non-linear case. Thus there is a linearisation instability, and it is highly unlikely that there is a large class of silent models. We conjecture that there are no spatially inhomogeneous solutions with Weyl curvature of Petrov type I, and indicate further issues that await clarification.Comment: Minor corrections and improvements; 1 new reference; to appear Class. Quantum Grav.; 16 pages Ioplpp

Before it is too late: professional responsibilities in late-onset Alzheimer's research and pre-symptomatic prediction

The development of a wide array of molecular and neuroscientific biomarkers can provide the possibility to visualize the course of Alzheimer’s disease (AD) at early stages. Many of these biomarkers are aimed at detecting not only a preclinical, but also a pre-symptomatic state. They are supposed to facilitate clinical trials aiming at treatments that attack the disease at its earliest stage or even prevent it. The increasing number of such biomarkers currently tested and now partly proposed for clinical implementation calls for critical reflection on their aims, social benefits, and risks. This position paper summarizes major challenges and responsibilities. Its focus is on the ethical and social problems involved in the organization and application of dementia research, as well as in healthcare provision from a cross-national point of view. The paper is based on a discussion of leading dementia experts from neuroscience, neurology, social sciences, and bioethics in the United States and Europe. It thus reflects a notable consensus across various disciplines and national backgrounds. We intend to initiate a debate on the need for actions within the researchers’ national and international communities