A hemisystem of a nonclassical generalised quadrangle

The concept of a hemisystem of a generalised quadrangle has its roots in the work of B. Segre, and this term is used here to denote a set of points such that every line ℓ meets in half of the points of ℓ. If one takes the point-line geometry on the points of the hemisystem, then one obtains a partial quadrangle and hence a strongly regular point graph. The only previously known hemisystems of generalised quadrangles of order (q, q ²) were those of the elliptic quadric , q odd. We show in this paper that there exists a hemisystem of the Fisher–Thas–Walker–Kantor generalised quadrangle of order (5, 5²), which leads to a new partial quadrangle. Moreover, we can construct from our hemisystem the 3· A ₇-hemisystem of , first constructed by Cossidente and Penttila.      

Gradient bounds for the horizontal <Emphasis Type="Italic">p</Emphasis>-Laplacian on a Carnot group and some applications

In a Carnot group we prove a new priori bound for the right-invariant horizontal gradient of smooth solutions of a class of quasilinear equations which are modeled on the so-called horizontal p-Laplacian. Exploiting such bound and a regularization procedure based on difference quotients we obtain the C^1,a_loc{C^{1,\alpha}_{loc}} regularity of weak solutions which possess some special symmetries. For instance, in the first Heisenberg group \mathbbH¹{\mathbb{H}^{1}} we obtain such regularity for all weak solutions of the horizontal p-Laplacian, with p ≥ 2, which are of the form u(z, t) = u(|z|, t).     

Remarkable Tuning of the Coordination and Photophysical Properties of Lanthanide Ions in a Series of Tetrazole‐Based Complexes

A series of seven new tetrazole‐based ligands (L1, L3–L8) containing terpyridine or bipyridine chromophores suited to the formation of luminescent complexes of lanthanides have been synthesized. All ligands were prepared from the respective carbonitriles by thermal cycloaddition of sodium azide. The crystal structures of the homoleptic terpyridine–tetrazolate complexes [Ln(Li)₂]NHEt₃ (Ln=Nd, Eu, Tb for i=1, 2; Ln=Eu for i=3, 4) and of the monoaquo bypyridine–tetrazolate complex [Eu(H₂O)(L7)₂]NHEt₃ were determined. The tetradentate bipyridine–tetrazolate ligand forms nonhelical complexes that can contain a water molecule coordinated to the metal. Conversely, the pentadentate terpyridine–tetrazolate ligands wrap around the metal, thereby preventing solvent coordination and forming chiral double‐helical complexes similarly to the analogue terpyridine–carboxylate. Proton NMR spectroscopy studies show that the solid‐state structures of these complexes are retained in solution and indicate the kinetic stability of the hydrophobic complexes of terpyridine–tetrazolates. UV spectroscopy results suggest that terpyridine–tetrazolate complexes have a similar stability to their carboxylate analogues, which is sufficient for their isolation in aerobic conditions. The replacement of the carboxylate group with tetrazolate extends the absorption window of the corresponding terpyridine‐ (≈20 nm) and bipyridine‐based (25 nm) complexes towards the visible region (up to 440 nm). Moreover, the substitution of the terpyridine–tetrazolate system with different groups in the ligand series L3–L6 has a very important effect on both absorption spectra and luminescence efficiency of their lanthanide complexes. The tetrazole‐based ligands L1 and L3–L8 sensitize efficiently the luminescent emission of lanthanide ions in the visible and near‐IR regions with quantum yields ranging from 5 to 53 % for Eu^III complexes, 6 to 35 % for Tb^III complexes, and 0.1 to 0.3 % for Nd^III complexes, which is among the highest reported for a neodymium complex. The luminescence efficiency could be related to the energy of the ligand triplet states, which are strongly correlated to the ligand structures.     

优化便携设备中大输出电流DC-DC转换的热耗散

精心选择器件和良好的热设计能帮助工程师优化应用于移动设备的超小型DC-DC转换器设计,实现功率密度的增加,同时还保证可靠性。     

Automatic identification of audio recordings based on statistical modeling

This paper describes a methodology for the automatic identification of audio recordings of ethnic music. The identification is based on an application of hidden Markov models (HMMs), which are automatically built from a representation of the music pieces to be identified. States of the HMMs are labeled with music events, and the transition and observation probabilities are directly computed from the information on the music piece. The recordings are modeled by a set of acoustic features that are computed according with the characteristics of the music events. Three alternative approaches, based on typical applications of HMMs, are proposed to perform the identification. Tests carried out on collections of recordings showed that the methodology can achieve good results, and the identification rate is high enough to suggest applications for automatic retrieval of metadata and for the identification of alternative recordings of the same piece.     

Geometry and Self-stress of Single-Wall Carbon Nanotubes and Graphene via a Discrete Model Based on a 2nd-Generation REBO Potential

Formulae for the biaxial moduli along the directions of principal stress for \((\mathit{hkl})\) interfaces of cubic materials are given for situations in which there is equi-biaxial strain within the plane. These formulae are relevant in the consideration of the deposition of thin films on single crystal substrates such as silicon. Within a particular \((\mathit{hkl})\), the directions defining these principal biaxial moduli are shown to be those along which there are the extreme values of the shear modulus and Poisson’s ratio. Conditions for stationary values of the biaxial moduli are also derived, from which the conditions for the global extrema of the biaxial moduli are established.     

Dynamical changes in hydration water accompanying lysozyme thermal denaturation

We study the dynamics of the first hydration shell of lysozyme to determine the role of hydration water that accompanies lysozyme thermal denaturation. We use nuclear magnetic resonance spectroscopy to investigate both the translational and rotational contributions. Data on proton self-diffusion and reorentational correlation time indicate that the kinetics of the lysozyme folding/unfolding process is controlled by the dynamics of the water molecules in the first hydration shell. When the hydration water dynamics change, because of the weakening of the hydrogen bond network, the three-dimensional structure of the lysozyme is lost and denaturation is triggered. Our data indicates that at temperatures above approximately 315 K, water behaves as a simple liquid and is no longer a good solvent.     

Development of new CdZnTe detectors for room‐temperature high‐flux radiation measurements

Recently, CdZnTe (CZT) detectors have been widely proposed and developed for room‐temperature X‐ray spectroscopy even at high fluxes, and great efforts have been made on both the device and the crystal growth technologies. In this work, the performance of new travelling‐heater‐method (THM)‐grown CZT detectors, recently developed at IMEM‐CNR Parma, Italy, is presented. Thick planar detectors (3 mm thick) with gold electroless contacts were realised, with a planar cathode covering the detector surface (4.1 mm × 4.1 mm) and a central anode (2 mm × 2 mm) surrounded by a guard‐ring electrode. The detectors, characterized by low leakage currents at room temperature (4.7 nA cm^?2 at 1000 V cm^?1), allow good room‐temperature operation even at high bias voltages (>7000 V cm^?1). At low rates (200 counts s^?1), the detectors exhibit an energy resolution around 4% FWHM at 59.5 keV (²⁴¹Am source) up to 2200 V, by using commercial front‐end electronics (A250F/NF charge‐sensitive preamplifier, Amptek, USA; nominal equivalent noise charge of 100 electrons RMS). At high rates (1 Mcounts s^?1), the detectors, coupled to a custom‐designed digital pulse processing electronics developed at DiFC of University of Palermo (Italy), show low spectroscopic degradations: energy resolution values of 8% and 9.7% FWHM at 59.5 keV (²⁴¹Am source) were measured, with throughputs of 0.4% and 60% at 1 Mcounts s^?1, respectively. An energy resolution of 7.7% FWHM at 122.1 keV (⁵⁷Co source) with a throughput of 50% was obtained at 550 kcounts s^?1 (energy resolution of 3.2% at low rate). These activities are in the framework of an Italian research project on the development of energy‐resolved photon‐counting systems for high‐flux energy‐resolved X‐ray imaging.     

Longitudinal anisotropy of the photoinduced molecular migration in azobenzene polymer films

The effects of tightly focused, higher-order laser beams on the photoinduced molecular migration and surface deformations in azobenzene polymer films are investigated. We demonstrate that the surface relief is principally triggered by longitudinal fields, i.e., electric fields polarized along the optical axis of the focused beam. Our findings can be explained by the translational diffusion of isomerized chromophores when the constraining effect of the polymer-air interface is considered.     

Decomposition of the angular ESR spectra of fossil tooth enamel fragments

The ESR spectra of a fragment of fossil tooth enamel were measured by rotating it in 10° increments over 360° around its three major axes. We used an automated simulated annealing (SA) procedure for the mathematical decomposition of the spectra. The SA approach is particularly robust in finding global solutions rather than getting stuck in local minima. All angular measurements could be fitted with four Gaussian lines, all of which could be attributed to components of CO₂^? radicals. The results imply that the tooth enamel fragment contains at least two different types of oriented CO₂^? radicals, plus about 9% of non-oriented CO₂^? radicals. The oriented components were tentatively attributed to axial and orthorhombic CO₂^? radicals. Their explicit locations in the crystal domains of the tooth enamel remain unresolved.