200A GeV S+Au反应中光子产生的低横动量增强

用建立在LUND弦模型特别是PYTHIA事件产生器基础上的描写极端相对论性核-核碰撞的强子和弦级联模型--JPCIAE研究了入射能量为200A GeV的S+Au中心碰撞中光子产生.模型同时考虑了部分子QCD散射过程、强子末态相互作用以及强子衰变等光子产生反应道并作了协调处理.JPCIAE模型计算结果很好再现了WA93实验数据所呈现的低横动量增强效应.     

Superconducting properties of amorphous transition metal alloys

We have co-sputtered amorphous films of several Mo and W-based superconducting alloys. Measurements of T_c, ($\text{d}\text{H}{}_{\mathrm{c2}}\text{d}\text{T}$)_Tc and the normal state resistivity near T_c were made on a number of these alloys. Our results and other data from the literature are studied to examine the correlation between T_c and the dressed density of states at the Fermi level.     

The nilpotence height of

A 20-year-old conjecture about the mod 2 Steenrod algebra The method of Walker and Wood is used to completely determine the nilpotence height of the elements in the Steenrod algebra at the prime 2. In particular, it is shown that for all , . In addition, several interesting relations in are developed in order to carry out the proof.

     

The History of Skunk Defensive Secretion Research

The striped skunk (Mephitis mephitis) is widely known for the highly odoriferous defensive secretion it uses to repel predators. Chemists have sporadically investigated the chemical composition of this secretion for many years. In this research, a number of chemicals have been incorrectly attributed to this secretion and the errors incorporated into the chemical literature. The major component in skunk spray was erroneously believed to be l-butanethiol, until it was later shown that the actual compound was (E)-2-butene-l-thiol. More recently, two studies identified the third major compound in the secretion as either (E)-2-butenyl methyl disulfide or (E)-2-butenyl propyl sulfide. These structural assignments were incorrect and the compound was later shown to be (E)-2-butenyl thioacetate. Two investigations have reported chemicals that could not be confirmed in a later study, so these compounds may have been artifacts produced during isolation or analysis. The striped skunks secretion is similar to, but different from, the defensive secretions of two other skunk species, the spotted skunk (Spilogale gracilis) and the hog-nosed skunk (Conepatus mesoleucus).Folklore asserts that tomato juice will neutralize the odor of skunk spray, but human olfactory fatigue can explain the apparent disappearance of the odor on sprayed pets. The odoriferous thiols in skunk spray can easily be neutralized by oxidation to sulfonic acids.     

Electroclinic effects in a homogeneously aligned smectic A cell

The electroclinic effect, in a material having a first order S_A to S_C* transition, is studied using the half leaky guided mode geometry. Using an approximately 1 μm thick, homogeneously aligned cell, the voltage induced director twist is characterized at a few temperatures in the S_A phase. The mean field theory readily explains the data recorded at low fields where a linear dependence on voltage is found. However, at higher fields, an unexpected saturation occurs which is most likely caused by the influence of strong surface anchoring forces.