A new proof of Korzhik's result on burst distributions

We obtain a simple derivation of Korzhik's result on the burst distribution of a linear code.     

Conformational studies of substituted nitroanilines: geometry of 2-methyl-5-nitroaniline

The title compound (C₇H₈N₂O₂), is monoclinic, space group P2₁/n, witha=9.552(2),b=5.677(2),c=13.586(3)Å, =92.68(2)⁰, andD _x=1.374 g-cm^–3 forZ=4. The refinement converged toR=0.043,wR=0.038. The molecule is approximately planar, with dihedral angles of 3.7(2.1)⁰ between the amino group and the aromatic ring, and 3.2(2)⁰ between the nitro group and the ring. According to the UV spectrum in solution, the molecular geometry indicates weak intramolecular charge transfer. The three-dimensional structure is stabilized by three intermolecular H bonds. A bifurcated one induces the formation of chains along , while the other two link molecules that belong to adjacent chains and are related by an inversion center.     

SiO2内保护层对LiB3O5晶体倍频增透膜损伤阈值的影响

 利用离子辅助电子束沉积方法在LiB₃O₅基底上镀制了不加SiO₂内保护层和加SiO₂内保护层的倍频增透膜，测量了两类薄膜在波长1 064 nm多脉冲辐照下的激光损伤阈值，获得了两种不同的损伤形貌，并对损伤原因作了初步探讨。实验结果表明：保护层的加入把由基底膜层界面缺陷吸收所决定的阈值改变到由HfO₂膜层内缺陷吸收所决定的阈值，显著提高了倍频增透膜的抗激光损伤能力。     

Effect of iridium loading on HZSM-5 for isomerization of n-heptane

The effect of iridium loading on the properties and catalytic isomerization of n-heptane over Ir-HZSM-5 is studied. Ir-HZSM-5 was prepared by impregnation method and subjected to isomerization process in the presence of flowing hydrogen gas. XRD and BET studies show that the presence of iridium stabilizes the crystalline structure of HZSM-5, leading to more ordered framework structure and larger surface area. TGA and FTIR results substantiate that iridium species interacts with OH group on the surface of HZSM-5. Pyridine FT-IR study verifies the interaction between iridium and surface OH group slightly increased the Bro¨nsted and Lewis acid sites without changing the lattice structure of HZSM-5. The presence of iridium and the increase of strong Lewis acid sites on HZSM-5 were found to bring an increase about 4.1%, 33.2% and 11.8% in conversion, selectivity and yield of n-heptane isomerization, respectively.     

Multicoloring and Mycielski construction

The generalized Mycielskians of graphs (also known as cones over graphs) are the natural generalization of the Mycielskians of graphs (which were first introduced by Mycielski in 1955). Given a graph G and any integer p?0, one can transform G into a new graph μ_p(G), the p-Mycielskian of G. In this paper, we study the kth chromatic numbers χ_k of Mycielskians and generalized Mycielskians of graphs. We show that χ_k(G)+1?χ_k(μ(G))?χ_k(G)+k, where both upper and lower bounds are attainable. We then investigate the kth chromatic number of Mycielskians of cycles and determine the kth chromatic number of p-Mycielskian of a complete graph K_n for any integers k?1, p?0 and n?2. Finally, we prove that if a graph G is a/b-colorable then the p-Mycielskian of G, μ_p(G), is (at+b^p+1)/bt-colorable, where . And thus obtain graphs G with m(G) grows exponentially with the order of G, where m(G) is the minimal denominator of a a/b-coloring of G with χ_f(G)=a/b.     

Independence polynomials of k-tree related graphs

An independent set of a graph G is a set of pairwise non-adjacent vertices. Let α(G) denote the cardinality of a maximum independent set and f_s(G) for 0≤s≤α(G) denote the number of independent sets of s vertices. The independence polynomial defined first by Gutman and Harary has been the focus of considerable research recently. Wingard bounded the coefficients f_s(T) for trees T with n vertices: for s≥2. We generalize this result to bounds for a very large class of graphs, maximal k-degenerate graphs, a class which includes all k-trees. Additionally, we characterize all instances where our bounds are achieved, and determine exactly the independence polynomials of several classes of k-tree related graphs. Our main theorems generalize several related results known before.     

固相配位化学反应研究——ⅩⅩⅩⅩⅠ.[Co(NH_3)_5(H_2O)]Br_3,[Cr(NH_3)_5(H_2O)](NO_3)_3与无机盐KY(Y=Cl,Br,Ⅰ)的固相反应动力学研究

本文主要用气相色谱逸出气体分析方法,借助于红外、紫外可见漫反射谱等手段研究了[Co(NH_3)_5(H_2O)]Br_3、[Cr(NH_3)_5(H_2O)](NO_3)_3与无机盐KY(Y=Cl,Br,Ⅰ)的固相反应,计算了失水与失氨的动力学参数,发现第一步反应失水生成一取代中间产物,其活化能与外加阴离子无关,为S_N1过程。第二步失氨反应活化能与中心离子M以及取代基Y有关,当M=Co(Ⅲ)时,反应体系的失氨活化能大小有下列顺序:Cl>Br>Ⅰ(E值分别为187、155、98kJ·mol~(-1)),M=Cr(Ⅲ)时则正好相反:Ⅰ>Br>Cl(E值分别为213、146、79 kJ·mol~(-1))。     

Synthesis and modification of new biodegradable copolymers: Serine/glycolic acid based copolymers

Serine/glycolic acid-based biodegradable polymers have been prepared by ring-opening homopolymerization of 3-(O-benzyl)-L -serinylmorpholine-2,5-dione, and ring-opening copolymerization of the morpholine-2,5-dione derivative and L -lactide/ϵ-caprolactone. The homopolymerization was carried out in the melt at 165°C for 3 min using stannous octanoate as the initiator and continued at lower reaction temperatures (130–150°C) for 48 h, using a molar ratio of monomer and initiator of 1000 yielded a polymer of M_n = 4000. The polymer prepared by homopolymerization of the morpholine-2,5-dione derivative was composed of alternating protected serine and glycolic acid residues. Random copolymers of serine and glycolic acid and L -lactic acid/ϵ-caprolactone were synthesized by copolymerization reaction of 3-(O-benzyl)-L -serinylmorpholine-2,5-dione and lactide or ϵ-caprolactone in the melt at 165°C for 3 min and further reaction at 130°C using stannous octanoate as an initiator. The polymers were deprotected and functionalized through the side chain hydroxyl group of serine residues with an acrylate moiety for applications in injectable drug delivery, cell encapsulation. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1901–1907, 1997     

氧原子在Pt低指数面上的吸附和振动

应用原子和表面簇合物相互作用的5参数Morse势方法（简称5-MP）对O-Pt低指数表面体系进行了研究,并获得了全部临界点特性.计算结果表明,氧原子在Pt(100)面上只存在四重吸附态.在缺行重构的(110)面上,氧原子仍吸附于三重位,随着覆盖度的增加还会嵌切吸附于长桥位;通过分析三重态振动指纹性质的遗传和遗变,确认实验观察到的59.49和40.90 meV损失谱分别为氧原子在三重位和长桥位吸附态的表面垂直振动.     

4-甲基-1，2，3-噻二唑-5-甲酸构筑的锌配合物的合成、晶体结构及与DNA作用

由4-甲基-1,2,3-噻二唑-5-甲酸（HMTC,C₄H₄N₂O₂S）分别和1,3-双（4-吡啶基）-丙烷（bpp）、菲咯啉（phen）合成了2个锌配合物[Zn（MTC）₂（bpp）]_n（1）和[Zn（MTC）（phen）（H₂O）₂]（MTC）（2）。用元素分析、红外光谱、粉末X射线衍射、热重分析对配合物进行了表征,并通过单晶X射线衍射测定了配合物的晶体结构。结果表明：配合物1是二维网状结构,属于单斜晶系,P2₁/c空间群,中心金属锌（Ⅱ）离子的配位构型是扭曲的四面体结构。配合物2是二维层状结构,属于三斜晶系,P1空间群,中心金属锌（Ⅱ）离子的配位构型是变形的三角双锥结构。用溴化乙锭荧光探针法测定了配体和配合物对EB-DNA复合体系相互作用,实验结果显示无论配体还是配合物均能使EB-DNA复合体系发生不同程度的荧光猝灭,且配合物的作用强度远大于配体。