On the uniqueness of solutions to the Poisson equations for average cost Markov chains with unbounded cost functions

We consider the Poisson equations for denumerable Markov chains with unbounded cost functions. Solutions to the Poisson equations exist in the Banach space of bounded real-valued functions with respect to a weighted supremum norm such that the Markov chain is geometrically ergodic. Under minor additional assumptions the solution is also unique. We give a novel probabilistic proof of this fact using relations between ergodicity and recurrence. The expressions involved in the Poisson equations have many solutions in general. However, the solution that has a finite norm with respect to the weighted supremum norm is the unique solution to the Poisson equations. We illustrate how to determine this solution by considering three queueing examples: a multi-server queue, two independent single server queues, and a priority queue with dependence between the queues.     

Solution composition and thermal denaturation for the production of single-stranded PCR amplicons: Piperidine-induced destabilization of the DNA duplex?

Strategies to produce single-stranded PCR amplicons for detection by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) were investigated using modified electrospray solutions and by thermally denaturing the duplex structures with a resistively heated electrospray ionization source. A synthetic 20-mer oligonucleotide annealed to its complementary strand was used as a model system for initial experiments. Electrospray solutions were altered by varying the relative proportion of aqueous phase in efforts to induce destabilization of the double helix. When the electrospray solution contains a 25% aqueous content, the 20-mer oligonucleotide is detected in its double-stranded form. Increasing the proportion of aqueous phase in the electrospray solution to 60% destabilized the double helix, resulting in the detection of only single-stranded species. This strategy was extended to an 82-bp polymerase chain reaction (PCR) product derived from the human tyrosine hydroxylase gene (HUMTH01). In efforts to destabilize the 82-bp PCR product, electrospray solutions reaching 70% aqueous content were necessary to promote the detection of only single-stranded amplicons. Implementation of the resistively heated transfer line and an electrospray solution in which the oligonucleotide is on the threshold of duplex stability allowed for double-stranded and single-stranded species to be generated from the same ESI solutions at both ambient and elevated transfer line temperatures, respectively, without disruption of the electrospray process. The volatile base piperidine, present at 20 mM concentrations in the electrospray solution, was found to play a critical role in the formation of single-stranded species at the higher aqueous percentages and a duplex destabilization mechanism has been proposed.     

Nature of metal binding sites in Cu(II) complexes with histidine and related N-coordinating ligands, as studied by EXAFS

Knowledge of the complexes formed by N-coordinating ligands and Cu(II) ions is of relevance in understanding the interactions of this ion with biomolecules. Within this framework, we investigated Cu(II) complexation with mono- and polydentate ligands, such as ammonia, ethylenediamine (en), and phthalocyanine (Pc). The obtained Cu-N coordination distances were 2.02 A for [Cu(NH(3))(4)](2+), 2.01 A for [Cu(en)(2)](2+), and 1.95 A for CuPc. The shorter bond distance found for CuPc is attributed to the macrocyclic effect. In addition to the structure of the first shell, information on higher coordination shells of the chelate ligands could be extracted by EXAFS, thus allowing discrimination among the different coordination modes. This was possible due to the geometry of the complexes, where the absorbing Cu atoms are coplanar with the four N atoms forming the first coordination shell of the complex. For this reason multiple scattering contributions become relevant, thus allowing determination of higher shells. This knowledge has been used to gain information about the structure of the 1:2 complexes formed by Cu(II) ions with the amino acids histidine and glycine, both showing a high affinity for Cu(II) ions. The in-solution structure of these complexes, particularly that with histidine, is not clear yet, probably due to the various possible coordination modes. In this case the square-planar arrangements glycine-histamine and histamine-histamine as well as tetrahedral coordination modes have been considered. The obtained first-shell Cu-N coordination distance for this complex is 1.99 A. The results of the higher shells EXAFS analysis point to the fact that the predominant coordination mode is the so-called histamine-histamine one in which both histidine molecules coordinate Cu(II) cations through N atoms from the amino group and from the imidazole ring.     

二苯并噻吩在分散型钼催化剂和原位产生的氢存在下的加氢脱硫 Ⅰ.产物分布和反应网络

研究了水/甲苯乳化液中二苯并噻吩(硫芴,DBT)在分散型钼酸和磷钼酸催化剂存在下的加氢脱硫反应.反应在高压釜中于340℃及经水煤气转换反应(WGSR)产生的原位氢存在下进行.用GC和GC-MS 鉴定、分析了气体和液体产物的组成.结果表明:在反应过程中部分加氢的中间产物1,2,3,4-四氢硫芴(4H-DBT)和1,2,3,4,10,11-六氢硫芴(6H-DBT)的浓度相当高,但二联苯的浓度相对较低,说明加氢路径与氢解路径相当.提出的硫芴加氢脱硫反应网络包含两个反应途径:噻吩环先直接氢解脱硫,紧接着苯环加氢途径;苯环先加氢,然后噻吩环氢解脱硫途径.同时,还包含环烷环的异构化反应.     

二苯并噻吩在分散型钼催化剂和原位产生的氢存在下的加氢脱硫Ⅲ.催化剂前身物、硫化氢、一氧化碳和水对反应的影响

研究了水水/甲苯乳化液中二苯并噻吩(硫芴)在分散型钼酸、磷钼酸和四硫钼酸铵催化剂存在下的加氢脱硫反应.反应在高压釜中于340℃及三种不同的气氛即H2,H2/H2O和CO/H2O(CO和H2O经水煤气转换反应(WGSR)产生原位氢)的存在下进行.用GC和GC-MS鉴定、分析了气体和液体产物的组成.结果表明:对硫芴的加氢脱硫反应,在分散型四硫钼酸铵催化剂存在下,原位产生的氢的效果仅比加入的氢气稍好,而在分散型钼酸和磷钼酸催化剂存在下,原位产生的氢远比加入的氢气有效.实验结果还表明:硫化氢能显著提高分散型钼酸和磷钼酸催化剂的加氢脱硫活性,但在分散型四硫钼酸铵催化剂存在下,硫化氢能促进加氢反应而抑制氢解反应.一氧化碳和水均选择性地抑制氢解反应.     

二苯并噻吩在分散型钼催化剂和原位产生的氢存在下的加氢脱硫Ⅱ. 原位氢和分子氢的比较(英)

研 究了水／ 甲苯 乳化液 中二苯 并噻 吩（ 硫 芴） 在 分散 型钼酸 、磷钼 酸和四 硫钼 酸铵催 化剂 存在下 的加氢脱 硫反应． 反应在 高压釜 中于３４０ ℃ 及三种 不同 的气 氛 即 Ｈ２ , Ｈ２／ Ｈ２ Ｏ 和 Ｃ Ｏ／ Ｈ２ Ｏ（ Ｃ Ｏ 和 Ｈ２ Ｏ 经 水 煤气转换反 应（ Ｗ Ｇ Ｓ Ｒ） 产生原 位氢） 的 存在下进 行． 用 Ｇ Ｃ 和 Ｇ Ｃ Ｍ Ｓ 鉴定 、分 析了 气 体和 液体 产 物的 组成 ． 结果表明： 对硫芴 的加氢 脱硫反应 ,在分散 型钼酸 和磷 钼 酸存 在下 ,原 位产 生 的氢 比加 入 的分 子氢 更 为有 效． 动力学研 究结果 表明： Ｗ Ｇ Ｓ Ｒ 反应 比硫芴的 加氢脱硫 反应快 ５ ～１０ 倍, 说明在原 位氢存 在下硫芴 的加 氢脱 硫反应是速 度控制 步骤． 总之,试 验结果证 实,在分 散型催化 剂和 原位 氢存 在 下的 加氢 过 程是 重油 乳 状液 改 质和破乳 的有效方 法．     

二苯并噻吩在分散型钼催化剂和原位产生的氢存在下的加氢脱硫Ⅰ. 产物分布和反应网络(英)

研究 了水／ 甲苯 乳化液 中二苯并 噻吩（ 硫 芴, Ｄ Ｂ Ｔ） 在 分散型钼 酸和磷 钼酸催 化剂 存在 下的 加氢 脱硫反应 ． 反应 在高压釜 中于３４０ ℃ 及经 水 煤气 转换 反 应（ Ｗ Ｇ Ｓ Ｒ） 产 生的 原位 氢 存在 下 进行． 用 Ｇ Ｃ 和 Ｇ Ｃ Ｍ Ｓ鉴定、分析了气 体和液体 产物的 组成． 结果表明 ： 在 反应过程 中部分加 氢的中 间产物 １ ,２ ,３ ,４四 氢硫 芴（４ Ｈ Ｄ Ｂ Ｔ） 和１ ,２ ,３ ,４ ,１０ ,１１六 氢硫芴（６ Ｈ Ｄ Ｂ Ｔ） 的 浓度相 当高,但 二联 苯的 浓度 相对 较 低,说 明加 氢 路径 与 氢解路径相 当． 提出的硫 芴加氢脱 硫反 应 网 络包 含 两个 反 应 途径 ： 噻吩 环 先 直接 氢 解脱 硫, 紧 接 着苯 环 加氢 途径; 苯环先 加氢,然 后噻吩环 氢解脱硫 途径． 同时,还 包含环 烷环的异 构化反 应．     

Infrared near-field microscopy with the Vanderbilt free electron laser: overview and perspectives

Scanning near-field optical microscopy (SNOM) makes it routinely possible to overcome the fundamental diffraction limit of standard (far-field) microscopy. Recently, aperture-based infrared SNOM performed in the spectroscopic mode, using the Vanderbilt University free electron laser, started delivering spatially-resolved information on the distribution of chemical species and on other laterally-fluctuating properties. The practical examples presented here show the great potential of this new technique both in materials science and in life sciences.     

Conventional and modified Schwarzschild objective for EUV lithography: design relations

The design criteria of a Schwarzschild-type optical system are reviewed in relation to its use as an imaging system in an extreme ultraviolet lithography setup. Both the conventional and the modified reductor imaging configurations are considered, and the respective performances, as far as the geometrical resolution in the image plane is concerned, are compared. In this connection, a formal relation defining the modified configuration is elaborated, refining a rather naïve definition presented in an earlier work. The dependence of the geometrical resolution on the image-space numerical aperture for a given magnification is investigated in detail for both configurations. So, the advantages of the modified configuration with respect to the conventional one are clearly evidenced. The results of a semi-analytical procedure are compared with those obtained from a numerical simulation performed by an optical design program. The Schwarzschild objective based system under implementation at the ENEA Frascati Center within the context of the Italian FIRB project for EUV lithography has been used as a model. Best-fit functions accounting for the behaviour of the system parameters vs. the numerical aperture are reported; they can be a useful guide for the design of Schwarzschild objective type optical systems.