KLOE高分辨电磁量能器

本文描述了ＫＬＯＥ高分辨电磁量能器的设计和结构，着重介绍了获得铅和闪烁光纤取样量能器优良性能的关键技术。为了研究这种量能器的性能，建造了２ｈ和一个全尺寸的量能器模块，其中两个小模块分别是一桶部模块和一个端盖模埠，本文给出了这三个模块的实验结果。     

Driving Spin and Charge in Quantum Wells by Surface Acoustic Waves

Recent experiments have shown the potential of surface acoustic waves as a mean for transporting charge and spin in quantum wells. In particular, they have proven highly effective for the coherent transport of spin‐polarized wave packets, suggesting their potential in spintronics applications. Motivated by these experimental observations, the spin and charge dynamics in a quantum well under surface acoustic waves is theoretically studied. It is shown that the dynamics acquires a simple and transparent form in a reference frame co‐moving with the surface acoustic wave. The results, e.g., the calculated spin relaxation and precession lengths, are in excellent agreement with recent experimental observations.     

A model to manage a large number of transactions: a case study

The aim of this paper is to present a model for the Computer Centre of an important Italian banking group. The model groups data and transactions to deal with the large dimension of the Centre. The transactions arrivals are considered as Posson stochastic variables and the probability values are estimated. Some computational results are given.     

Phase transitions of a main-chain thermotropic copolyester: crystallization,melting behaviour and glass-transition studied by DSC

Summary The thermal behaviour of a main-chain thermotropic co-polyester has been investigated by Differential Scanning Calorimetry. Crystallization and melting have been studied through the effect of the annealing time and temperature on the transition temperatures and enthalpies. Two melting peaks are observed, the first one clearly developping on annealing. Hypotheses are suggested about the crystallization mechanism. The glass-transition (rate-dependent) appears broadened and does not show hysteresis on heating and cooling through the transition temperature.     

A novel approach to the tailoring of polymers for advanced composites and optical applications,involving the synthesis of liquid crystalline epoxy resins

The authors describe the features of liquid crystalline epoxy resins having both high and low crosslinking densities. These materials seem to be very promising as matrices in advanced composites and in optical and electro-optical applications because of their peculiar properties. The importance of factors like molecular rigidity, nature of the curing agent, and curing temperature for the development of such properties are analyzed. The authors showed that amines produce thermosets having high T_gs and high fracture toughness. In particular, the enhancement of this last parameter is very promising if a new generation of matrices is to be sought for manufacturing composites. In the case of acids as curing agents, thermosets having lower T_gs and more ordered mesophases can be obtained. In this case, LC elastomers can be prepared that can find applications in the optical industry as waveguides or electro-optical devices.     

Nanocomposite polymer films containing carvacrol for antimicrobial active packaging

Nanocomposite films based on low‐density polyethylene (LDPE) containing carvacrol were prepared and characterized with the aim to get antimicrobial active packaging. Organo‐modified montmorillonite (MMT) was used as filler. The weak interaction between LDPE and clay led to the formation of intercalated systems. On the other hand, strong interaction between carvacrol and organosilicate allowed a good dispersion of the oil into the clay galleries, promoting the swelling of MMT stacks and a higher polymer/clay interface. As a result, carvacrol was protected against thermal degradation and its release from the films was efficiently delayed. Moreover, outstanding thermal oxidative stability as well as improved oxygen barrier properties were detected in the nanocomposite containing carvacrol. The presence of clay and carvacrol also increased LDPE crystallinity, due to an enhanced nucleation activity, while the mechanical properties of the films were slightly affected. The antimicrobial properties of carvacrol containing films were tested, showing a significant activity against several bacterial strains, which is preserved in presence of the clay. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Enzymatic fluorination in Streptomyces cattleya takes place with an inversion of configuration consistent with an SN2 reaction mechanism

The stereochemical course of the recently isolated fluorination enzyme from Streptomyces cattleya has been evaluated. The enzyme mediates a reaction between the fluoride ion and S- adenosyl-L-methionine (SAM) to generate 5'-fluoro-5'-deoxyadenosine (5'-FDA). Preparation of (5'R)-[5-(2)H(1)]-ATP generated (5'R)-[5-(2)H(1)]-5'-FDA in a coupled enzyme assay involving SAM synthase and the fluorinase. The stereochemical analysis of the product relied on (2)H NMR analysis in a chiral liquid-crystalline medium. It is concluded that the enzyme catalyses the fluorination with an inversion of configuration consistent with an S(N)2 reaction mechanism.     

Selective oxidation of methane to formaldehyde and C2 hydrocarbons over double layered Sr/La2O3 and MoO3/SiO2 catalyst bed

A double layered catalyst bed of Sr/La₂O₃ followed by MoO₃/SiO₂ has been used to produce C₂ hydrocarbons and formaldehyde from a CH₄/air mixture with a formaldehyde space time yield of 187 g (kg cat)^–1 h^–1, which is significantly higher than those yields obtained with single bed catalysts or with mechanically mixed catalyst bed at ambient pressure and 630 ° C.     

A Theoretical Study of Steady State and Transient Condensation on Axisymmetric Fins Under Combined Capillary and Gravitational Forces

The present work attempts to model the case of combined gravitational and capillary motion of condensate for an axisymmetric fin under steady and transient fin operation conditions. The focus here is to examine the structure of the mathematical problem and to develop suitable numerical techniques rather than yield information on the macroscopic condensate flow rate and fin efficiency. The problem is formulated starting from general conditions and is simplified step by step by introducing corresponding assumptions. The particular fin shape of a paraboloid from revolution is chosen and the equations are properly non-dimensionalized. A vast reduction of the number of problem parameters is achieved in this way. The cases of isothermal fin, steady state operation and dynamic operation are treated separately using specialized numerical solution techniques developed for each case in order to improve computational efficiency and accuracy. Typical results of fin temperature and condensate film thickness are presented and discussed.