Computational study of zeolite-proton-palladium chemistry

A density functional theory study of the interaction of a Pd atom with the zeolitic Bronsted acid site is reported. Whereas reduction of Pd2+ to Pd-0 and 2H(+) is strongly exothermic, the energy of exchange of a single proton between Pd-0 and the zeolite is found to be nearly thermodynamically neutral. Reaction energy diagrams are presented for proton-assisted CO hydrogenation and hydratio

The Localization Transition of the Two-Dimensional Lorentz Model

We investigate the dynamics of a single tracer particle performing Brownian motion in a two-dimensional course of randomly distributed hard obstacles. At a certain critical obstacle density, the motion of the tracer becomes anomalous over many decades in time, which is rationalized in terms of an underlying percolation transition of the void space. In the vicinity of this critical density the dynamics follows the anomalous one up to a crossover time scale where the motion becomes either diffusive or localized. We analyze the scaling behavior of the time-dependent diffusion coefficient D(t) including corrections to scaling. Away from the critical density, D(t) exhibits universal hydrodynamic long-time tails both in the diffusive as well as in the localized phase.Comment: 13 pages, 7 figures

Glassiness and constrained dynamics of a short-range non-disordered spin model

We study the low temperature dynamics of a two dimensional short-range spin system with uniform ferromagnetic interactions, which displays glassiness at low temperatures despite the absence of disorder or frustration. The model has a dual description in terms of free defects subject to dynamical constraints, and is an explicit realization of the ``hierarchically constrained dynamics'' scenario for glassy systems. We give a number of exact results for the statics of the model, and study in detail the dynamical behaviour of one-time and two-time quantities. We also consider the role played by the configurational entropy, which can be computed exactly, in the relation between fluctuations and response.Comment: 10 pages, 9 figures; minor changes, references adde

Estrogen Replacement in Turner Syndrome: Literature Review and Practical Considerations

Context: Most girls with Turner syndrome (TS) have hypergonadotropic hypogonadism and need hormonal replacement for induction of puberty and then for maintaining secondary sex characteristics, attaining peak bone mass, and uterine growth. The optimal estrogen replacement regimen is still being studied. Evidence Acquisition: We conducted a systematic search of PubMed for studies related to TS and puberty. Evidence Synthesis: The goals of replacement are to mimic normal timing and progression of physical and social development while minimizing risks. Treatment should begin at age 11 to 12 years, with dose increases over 2 to 3 years. Initiation with low-dose estradiol (E2) is crucial to preserve growth potential. Delaying estrogen replacement may be deleterious to bone and uterine health. For adults who have undergone pubertal development, we suggest transdermal estrogen and oral progestin and discuss other approaches. We discuss linear growth, lipids, liver function, blood pressure, neurocognition, socialization, and bone and uterine health as related to hormonal replacement. Conclusion: Evidence supports the effectiveness of starting pubertal estrogen replacement with low-dose transdermal E2. When transdermal E2 is unavailable or the patient prefers, evidence supports use of oral micronized E2 or an intramuscular preparation. Only when these are unavailable should ethinyl E2 be prescribed. We recommend against the use of conjugated estrogens. Once progestin is added, many women prefer the ease of use of a pill containing both an estrogen and a progestin. The risks and benefits of different types of preparations, with examples, are discussed

Next-generation sequencing-based genome diagnostics across clinical genetics centers: Implementation choices and their effects

Implementation of next-generation DNA sequencing (NGS) technology into routine diagnostic genome care requires strategic choices. Instead of theoretical discussions on the consequences of such choices, we compared NGS-based diagnostic practices in eight clinical genetic centers in the Netherlands, based on genetic testing of nine pre-selected patients with cardiomyopathy. We highlight critical implementation choices, including the specific contributions of laboratory and medical specialists, bioinformaticians and researchers to diagnostic genome care, and how these affect interpretation and reporting of variants. Reported pathogenic mutations were consistent for all but one patient. Of the two centers that were inconsistent in their diagnosis, one reported to have found 'no causal variant', thereby underdiagnosing this patient. The other provided an alternative diagnosis, identifying another variant as causal than the other centers. Ethical and legal analysis showed that informed consent procedures in all centers were generally adequate for diagnostic NGS applications that target a limited set of genes, but not for exome- and genome-based diagnosis. We propose changes to further improve and align these procedures, taking into account the blurring boundary between diagnostics and research, and specific counseling options for exome- and genome-based diagnostics. We conclude that alternative diagnoses may infer a certain level of 'greediness' to come to a positive diagnosis in interpreting sequencing results. Moreover, there is an increasing interdependence of clinic, diagnostics and research departments for comprehensive diagnostic genome care. Therefore, we invite clinical geneticists, physicians, researchers, bioinformatics experts and patients to reconsider their role and position in future diagnostic genome care

Modeling Translation in Protein Synthesis with TASEP: A Tutorial and Recent Developments

The phenomenon of protein synthesis has been modeled in terms of totally asymmetric simple exclusion processes (TASEP) since 1968. In this article, we provide a tutorial of the biological and mathematical aspects of this approach. We also summarize several new results, concerned with limited resources in the cell and simple estimates for the current (protein production rate) of a TASEP with inhomogeneous hopping rates, reflecting the characteristics of real genes.Comment: 25 pages, 7 figure

A tidal disruption event coincident with a high-energy neutrino

High Energy Astrophysic

Gonadotropin-releasing hormone: physiological and therapeutic aspects, agonists and antagonists

Rapid advances in the understanding of gonadotropin-releasing hormone (GnRH) actions and in development of new agonist and antagonist analogues of GnRH have taken place over the past several years. As a result, new compounds are now available to treat patients with various disorders of reproductive function. Used as probes of biologic processes, these compounds will also allow a greater depth of understanding of basic biologic processes

Computational study of zeolite-proton-palladium chemistry

A density functional theory study of the interaction of a Pd atom with the zeolitic Bronsted acid site is reported. Whereas reduction of Pd2+ to Pd-0 and 2H(+) is strongly exothermic, the energy of exchange of a single proton between Pd-0 and the zeolite is found to be nearly thermodynamically neutral. Reaction energy diagrams are presented for proton-assisted CO hydrogenation and hydratio