Vicious random walkers in the limit of a large number of walkers

The vicious random walker problem on a line is studied in the limit of a large number of walkers. The multidimensional integral representing the probability that thep walkers will survive a timet (denotedP _t ^(p) ) is shown to be analogous to the partition function of a particular one-component Coulomb gas. By assuming the existence of the thermodynamic limit for the Coulomb gas, one can deduce asymptotic formulas forP _t ^(p) in the large-p, large-t limit. A straightforward analysis gives rigorous asymptotic formulas for the probability that after a timet the walkers are in their initial configuration (this event is termed a reunion). Consequently, asymptotic formulas for the conditional probability of a reunion, given that all walkers survive, are derived. Also, an asymptotic formula for the conditional probability density that any walker will arrive at a particular point in timet, given that allp walkers survive, is calculated in the limittp.     

顶空气相色谱法测定延生护宝液中甲醇残留量

本文用顶空气相色谱法，以ＧＤＸ－１０１为固定相，测定了延生护宝液中甲醇残留量，方法的回收率在８５．９％－１０１．６％之间，变异系数０．３％，最小检出量１．０ｍｇ／Ｌ。     

天然气和氧偶联制环氧乙烷催化剂的反应性能

研制了天然气和氧经偶联反应制环氧乙烷的Ａｇ－Ｂａ－Ｃｓ／Ａｌ２Ｏ３催化剂（ＮＥＯ－１）。用Ｎ２＋Ｏ２＋Ｃ２Ｈ４和偶联产物气加氧作原料气，在２５０℃，空速２５００ｈ＾－１时，乙烯转化率和ＥＯ选择性分别达到了３０％和８０％，ＮＥＯ－１催化具有适宜的比表面和孔结构，用ＸＰＳ分析发现，与新鲜的催化相比，经活化和反应后的催化剂表面的Ｂａ，Ｃｓ原子浓度增高，并具有较多的吸附氧物种。     

铁(Ⅲ)-邻菲罗啉溶液体系的光化学还原 Ⅱ.气相色谱法研究光化反应机理

关于Fe(Ⅲ)-邻菲罗啉(phen)溶液的光化学还原现象的记载可追溯到十九世纪末。     

裂解色谱法研究PMR型聚酰亚胺前体的反应过程

用裂解气相色谱法研究ＰＭＲ型聚酰亚胺前体在反应中的化学变化过程，以裂解产物醇和环戊二烯的生成率表示酰胺化或酰亚胺化及交联的程度，结果表明，酰胺化或酰亚胺化在５０℃以下不发生，在１８０～２２０℃完成，降冰片烯端基在１５０℃以下不发生交联反应，在２８０℃，１０～１８小时可完成交联反应。     

毛细管气相色谱法测定5种中草药中有机氯农药的残留量

建立了怀牛夕等 5种中草药中六六六及滴滴涕异构体含量的气相色谱分析方法。样品以石油醚 +丙酮在索氏提取器中提取 ,提取液以浓硫酸净化。采用SE 30弹性石英毛细管柱分离样品 ,GC ECD检测六六六、滴滴涕农药的残留量。方法的线性范围为 5 .7× 10 - 7～ 2 .8× 10 - 4μg ;最小检测量为 1.3× 10 - 1 4～ 2 .5×10 - 1 2 g ;加样平均回收率为 88.8%～ 99.1% ;RSD为 0 .9%～ 5 .3%。     

白酒中C_9－C_（18）脂肪酸的气相色谱分析

白酒中Ｃ＿９－Ｃ＿（１８）脂肪酸的气相色谱分析周在德，曾永昌（四川大学化学系成都６１００６４）关键词气相色谱法，白酒，Ｃ＿９－Ｃ＿（１８）脂肪酸。白酒中脂肪酸的含量及相互比例关系，极大地影响着白酒的色，香，味，风格￣（［１］［２］）。一般采用的化学分...     

A supported gold catalyst for the elimination of hydrogen from CO2 feed gas in the production of urea

Supported gold catalyst for eliminating hydrogen from CO₂ feed gas in the production of urea is found to be superior to other industrial catalysts (e.g. Pt/Al₂O₃ and PdPt/Al₂O₃) in catalytic activity and resistance to sulfur poisoning.     

Synthesis, X-ray crystal structures, and gas sorption properties of pillared square grid nets based on paddle-wheel motifs: implications for hydrogen storage in porous materials

A systematic modulation of organic ligands connecting dinuclear paddle-wheel motifs leads to a series of isomorphous metal-organic porous materials that have a three-dimensional connectivity and interconnected pores. Aromatic dicarboxylates such as 1,4-benzenedicarboxylate (1,4-bdc), tetramethylterephthalate (tmbdc), 1,4-naphthalenedicarboxylate (1,4-ndc), tetrafluoroterephthalate (tfbdc), or 2,6-naphthalenedicarboxylate (2,6-ndc) are linear linkers that form two-dimensional layers, and diamine ligands, 4-diazabicyclo[2.2.2]octane (dabco) or 4,4'-dipyridyl (bpy), coordinate at both sides of Zn(2) paddle-wheel units to bridge the layers vertically. The resulting open frameworks [Zn(2)(1,4-bdc)(2)(dabco)] (1), [Zn(2)(1,4-bdc)(tmbdc)(dabco)] (2), [Zn(2)(tmbdc)(2)(dabco)] (3), [Zn(2)(1,4-ndc)(2)(dabco)] (4), [Zn(2)(tfbdc)(2)(dabco)] (5), and [Zn(2)(tmbdc)(2)(bpy)] (8) possess varying size of pores and free apertures originating from the side groups of the 1,4-bdc derivatives. [Zn(2)(1,4-bdc)(2)(bpy)] (6) and [Zn(2)(2,6-ndc)(2)(bpy)] (7) have two- and threefold interpenetrating structures, respectively. The non-interpenetrating frameworks (1-5 and 8) possess surface areas in the range of 1450-2090 m(2)g(-1) and hydrogen sorption capacities of 1.7-2.1 wt % at 78 K and 1 atm. A detailed analysis of the sorption data in conjunction with structural similarities and differences concludes that porous materials with straight channels and large openings do not perform better than those with wavy channels and small openings in terms of hydrogen storage through physisorption.