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We present a fully general derivation of the Laplace–Young formula and discuss the interplay between the intrinsic surface geometry and the extrinsic one ensuing from the immersion of the surface in the ordinary Euclidean three-dimensional space. We prove that the (reversible) work done in a general surface deformation can be expressed in terms of the surface stress tensor and the variation of the intrinsic surface metric. [ABSTRACT FROM AUTHOR]

We prove that conservation of the stress tensor is a consequence of the invariance of the partition function under canonical diffeomorphisms. From this observation a simple and general derivation of the formula which gives the local expression of the stress tensor of a molecular system in terms of its microscopic degrees of freedom readily follows. The derivation is valid in the canonical as well as the microcanonical ensemble. It works both in the classical and in the quantum mechanical settings and for arbitrary boundary conditions. In particular, if periodic boundary conditions are assigned to the system, the usual minimal-image prescription is naturally born out for mathematical consistency. An interesting outcome of our general analysis is that only in the case of a short-range interaction potential a truly local formula for the stress tensor can exist. [ABSTRACT FROM AUTHOR]

We prove that the stress tensor, τab, of a molecular system with arbitrary, short-range interactions can be point-wisely expressed as the functional derivative of the partition function with respect to the local deformation tensor. In this approach, the set of components of τab has a simple interpretation as the set of Lagrangian multipliers which one needs to introduce to enforce the conditions relating point particle displacements to the body local deformation tensor. The question of the possible nonuniqueness of the formula for τab is discussed. [ABSTRACT FROM AUTHOR]

Abstract The present study characterizes the relationship between the endogenous mu opioid peptides endomorphin-1 (EM-1) and endomorphin-2 (EM-2) and several splice variants of the cloned mu opioid receptor (MOR-1) encoded by the mu opioid receptor gene (Oprm ). Confocal laser microscopy revealed that fibers containing EM-2-like immunoreactivity (-LI) were distributed in close apposition to fibers showing MOR-1-LI (exon 4-LI) and to MOR-1C-LI (exons 7/8/9-LI) in the superficial laminae of the lumbar spinal cord. We also observed colocalization of EM-2-LI and MOR-1-LI in a few fibers of lamina II, and colocalization of EM-2-LI and MOR-1C-LI in laminae I–II, and V–VI. To assess the functional relevance of the MOR-1 variants in endomorphin analgesia, we examined the effects of antisense treatments that targeted individual exons within the Oprm1 gene on EM-1 and EM-2 analgesia in the tail flick test. This antisense mapping study implied mu opioid receptor mechanisms for the endomorphins are distinct from those of morphine or morphine-6β-glucuronide (M6G). [ABSTRACT FROM AUTHOR]

Ocular GvHD affects about 40-60% of patients receiving bone marrow transplantation. Ocular complaints worsen quality of life (QoL), which, besides survival time, is a primary end point in a patient's follow-up. The aim of our study was to assess the ocular surface status and vision-related QoL (VRQoL) and explore the potential determinants in VRQoL in patients with chronic GvHD with ocular involvement. In this cross-sectional study, we investigated 40 patients with ocular GvHD after allogeneic hematopoietic stem cell transplantation assessing ocular symptoms and signs, VRQoL and ophthalmologic parameters. The median age was 52.1 years; 32.5% were females. Most of them presented a multiple organ involvement. Ophthalmological parameter examinations were on average abnormal. Corneal staining was severe/very severe in 25%; conjunctival staining in 10% of subjects. The worse QoL scores were on 'general vision', 'ocular pain', 'vision-specific mental health' and 'vision-specific role difficulties'. Both symptoms and sign scores indicate poor VRQoL. A lower VRQoL was related to schooling level, job position, underlying disease and extracorporeal photopheresis. Corneal staining, Schirmer and tear film breakup time were negatively associated to visual function-related subscales. An accurate ophthalmological and VRQoL assessment should be mandatory for a long time to promptly recognize early signs of ocular suffering, and to prevent irreversible ocular complications. [ABSTRACT FROM AUTHOR]

With a combination of modern spectroscopic techniques and numerical first principle simulations it is possible to investigate the physico-chemical basis of the β-amyloid aggregation phenomenon, which is suspected to be at the basis of the development of the Alzheimer disease. On the experimental side, in fact, X-ray absorption spectroscopy can be successfully used to determine the atomic structure around the metal binding site in samples where β-amyloid peptides are complexed with either Cu2+ or Zn2+ ions. Exploiting spectroscopic information obtained on a selected set of fragments of the natural Aβ-peptide, the residues that along the sequence are coordinated to the metal are identified. Although copper data can be consistently interpreted assuming that oligopeptides encompassing the minimal 1–16 amino acidic sequence display a metal coordination mode which involves three Histidines (His6, His13, and His14), in complexes with zinc a four Histidines coordination mode is seen to be preferred. Lacking a fourth Histidine in the Aβ1–16 fragment, this geometrical arrangement hints to a Zn2+ promoted inter-peptide aggregation mode. On the theoretical side, first principle ab initio molecular dynamics simulations of the Car–Parrinello type, which have proved to be of invaluable help in understanding the microscopic mechanisms of chemical bonding both in solid-state physics and structural biophysics, have been employed in an effort to give a microscopic basis and find a phenomenological interpretation of the body of available experimental data on Aβ-peptides–metal complexes. Using medium size PC-clusters as well as larger parallel platforms, it is possible to deal with systems comprising 300–500 atoms and 1,000–2,000 electrons for simulation times as long as 2–3 ps. We present structural results that nicely compare with NMR and XAS data. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [ABSTRACT FROM AUTHOR]

The progress in high performance computing we are witnessing today offers the possibility of accurate electron density calculations of systems in realistic physico-chemical conditions. In this paper, we present a strategy aimed at performing a first-principle computation of the low energy part of the X-ray Absorption Spectroscopy (XAS) spectrum based on the density functional theory calculation of the electronic potential. To test its effectiveness, we apply the method to the computation of the X-ray absorption near edge structure part of the XAS spectrum in the paradigmatic, but simple case of Cu2+ in water. In order to keep into account the effect of the metal site structure fluctuations in determining the experimental signal, the theoretical spectrum is evaluated as the average over the computed spectra of a statistically significant number of simulated metal site configurations. The comparison of experimental data with theoretical calculations suggests that Cu2+ lives preferentially in a square-pyramidal geometry. The remarkable success of this approach in the interpretation of XAS data makes us optimistic about the possibility of extending the computational strategy we have outlined to the more interesting case of molecules of biological relevance bound to transition metal ions. [ABSTRACT FROM AUTHOR]

An amendment to this paper has been published and can be accessed via a link at the top of the paper. [ABSTRACT FROM AUTHOR]

First principle ab initio molecular dynamics simulations of the Car–Parrinello type have proved to be of invaluable help in understanding the microscopic mechanisms of chemical bonding both in solid state physics and in structural biophysics. In this work we present as a test case a study of the Cu coordination mode at the Prion Protein binding sites localized in the N-terminal octarepeat region. Using medium size PC-clusters, we are able to deal with systems with up to about 350 atoms and 103 electrons for as long as ∼2 ps. With a foreseeable forthcoming scaling up of the available CPU times by a factor 103, one can hope to be soon able to simulate systems of biological interest of realistic size and for physical times of the order of the nanosecond [ABSTRACT FROM AUTHOR]

The phase structure of zero temperature twisted mass lattice QCD is investigated. We find strong metastabilities in the plaquette observable in correspondence of which the untwisted quark mass assumes positive or negative values. We provide interpretations of this phenomenon in terms of chiral symmetry breaking and the effective potential model of Sharpe and Singleton. [ABSTRACT FROM AUTHOR]

Using lattice simulations we demonstrate from first principles the existence of a nonperturbative mechanism for elementary particle mass generation in models with gauge fields, fermions, and scalars, if an exact invariance forbids power divergent fermion masses and fermionic chiral symmetries broken at UV scale are maximally restored. We show that in the Nambu-Goldstone phase a fermion mass term, unrelated to the Yukawa operator, is dynamically generated. In models with electroweak interactions weak boson masses are also generated, opening new scenarios for beyond the standard model physics. [ABSTRACT FROM AUTHOR]