Nuclear motion effects on the density matrix of crystals: An ab initio Monte Carlo harmonic approach

In the frame of the Born-Oppenheimer approximation, nuclear motions in crystals can be simulated rather accurately using a harmonic model. In turn, the electronic first-order density matrix (DM) can be expressed as the statistically weighted average over all its determinations each resulting from an instantaneous nuclear configuration. This model has been implemented in a computational scheme which adopts an ab initio one-electron (Hartree-Fock or Kohn-Sham) Hamiltonian in the CRYSTAL program. After selecting a supercell of reasonable size and solving the corresponding vibrational problem in the harmonic approximation, a Metropolis algorithm is adopted for generating a sample of nuclear configurations which reflects their probability distribution at a given temperature. For each configuration in the sample the "instantaneous" DM is calculated, and its contribution to the observables of interest is extracted. Translational and point symmetry of the crystal as reflected in its average DM are fully exploited. The influence of zero-point and thermal motion of nuclei on such important first-order observables as x-ray structure factors and Compton profiles can thus be estimated.     

Analysis of Bile Acids Profile in Human Serum by Ultrafiltration Clean-up and LC-MS/MS

Bile acids (BAs) are useful biomarkers for the diagnosis of many diseases. The pathologies related to bile acid synthesis are often expressed in the first years of life and may lead to serious liver injury. Here we present a sensitive and rapid method for the analysis of the main 14 bile acids in human serum by liquid chromatography-tandem mass spectrometry. The chromatographic separation is performed using a core–shell column which provides improved separation, highly desirable considering the small structural differences among the analytes. All isomeric BAs of interest were resolved in less than 9 min. Sample pretreatment consisted in ultrafiltration of serum after addition of methanol by means of centrifugal filter devices. The calculated LOQs ranged between 2 and 5 ng mL⁻¹ with linearity of the calibration curves in the 5–5,000 ng mL⁻¹ range for all the BAs. The extraction recoveries for all the analytes were higher than 80 %. Intra-day and inter-day coefficients of variation were all below 15 %. The method proposed has been validated and has been applied for the analysis of serum of pediatric patients. This simple procedure allowed minimal consumption of serum sample (about 100 μL) and a rapid assay, easily implementable in routine analysis.

     

Aging Process Effects on the Characteristics of Vacuum Residue Oxidation Products with the Addition of Crumb Rubber

This paper considers the effect of aging processes on viscoelastic characteristics of vacuum residue oxidation products modified with crumb rubber. Viscoelastic properties were compared to original bitumen raw material-vacuum residue and vacuum residue oxidation products during short-term and long-term aging. The complex shear modulus of the vacuum residue and its oxidation products decreased with an increase in temperature. Short-term aging resulted in increased shear modulus for all samples.The vacuum residue oxidation product modified with crumb rubber had the maximum values of the rutting parameter and fatigue parameter. There was an expansion of the temperature range of plasticity: for the vacuum residue oxidation product with crumb rubber, its value was 67.2 °C. The curves of the black diagram of the modified vacuum residue oxidation product are shifted towards smaller phase angles with the increase in the shear modulus, which indicates the increase in the stiffness and elasticity of the rubber bitumen binders. The vacuum residue oxidation product modified with crumb rubber corresponded to the rubber bitumen binder of the grade RBB 60/90, according to its physical and mechanical indicators.     

Tin,Titanium, Tantalum,Vanadium and Niobium Oxide Based Sensors to Detect Colorectal Cancer Exhalations in Blood Samples

User-friendly, low-cost equipment for preventive screening of severe or deadly pathologies are one of the most sought devices by the National Health Services, as they allow early disease detection and treatment, often avoiding its degeneration. In recent years more and more research groups are developing devices aimed at these goals employing gas sensors. Here, nanostructured chemoresistive metal oxide (MOX) sensors were employed in a patented prototype aimed to detect volatile organic compounds (VOCs), exhaled by blood samples collected from patients affected by colorectal cancer and from healthy subjects as a control. Four sensors, carefully selected after many years of laboratory tests on biological samples (cultured cells, human stools, human biopsies, etc.), were based here on various percentages of tin, tungsten, titanium, niobium, tantalum and vanadium oxides. Sensor voltage responses were statistically analyzed also with the receiver operating characteristic (ROC) curves, that allowed the identification of the cut-off discriminating between healthy and tumor affected subjects for each sensor, leading to an estimate of sensitivity and specificity parameters. ROC analysis demonstrated that sensors employing tin and titanium oxides decorated with gold nanoparticles gave sensitivities up to 80% yet with a specificity of 70%.     

Synthesis of novel simplified eleutheside analogues with potent microtubule-stabilizing activity, using ring-closing metathesis as the key-step

The synthesis of a number of novel simplified eleutheside analogues with potent tubulin-assembling and microtubule-stabilizing properties is described, using ring-closing metathesis as the key-step for obtaining the 6-10 fused bicyclic ring system.     

Krichever Maps,Faà di Bruno Polynomials,and Cohomology in KP Theory

We study the geometrical meaning of the Faà di Bruno polynomials in the context of KP theory. They provide a basis in a subspace W of the universal Grassmannian associated to the KP hierarchy. When W comes from geometrical data via the Krichever map, the Faà di Bruno recursion relation turns out to be the cocycle condition for (the Welters hypercohomology group describing) the deformations of the dynamical line bundle on the spectral curve together with the meromorphic sections which give rise to the Krichever map. Starting from this, one sees that the whole KP hierarchy has a similar cohomological meaning.     

EPR Study of Triplet Defects in Ca2CuO3

Ca₂CuO₃ is an essentially diamagnetic oxide, in spite of its EPR spectrum. The latter is similar to literature spectra attributed to dimers or clusters formed by copper ions. A model based on the formation of triplet-state defects involving two neighbor copper ions is then discussed to explain these experimental observations. These defects would also propagate in the crystal and interact with each other.