Solution Structure of Mesobiliverdin XIIIα Bridged Between the Propionic Acid Substituents [1]

Summary.  The solution structure of two intramolecular diesters (methylene and 1,3-propylidene) of mesobiliverdin-XIIIα was studied and compared with that of the corresponding dimethyl ester. The UV/Vis absorption spectra, chiral discrimination with ethyl (S)-(−)-lactate, and the ¹H NMR spectra (ROESY) show that the cyclization of the propionate substituents of biliverdins does not significantly affect the helix structure or its (P) ⇌ (M) interconversion. The internal methylene diester does not show conformational heterogeneity of the propionate substituents and probably exists only in one diastereomeric form. In this case, the results point to a simultaneous racemization of the tetrapyrrole helix and the bridge cycle. The methylene diester of mesoprotoporphyrin was also synthesized. In this case, the geometry of the propionate chains is probably similar to that present in some hemoproteins. Received November 27, 1997. Accepted December 3, 1997     

Base-induced Brönsted Acid Sites on Dealuminated HY Zeolite: A Solid-state NMR Spectroscopy Study

Using trimethylphosphine (TMP) and d₅-pyridine(deuterated pyridine) as the basic probe molecules, the concentrations of Brönsted acid sites on both HY zeolite and dealuminated HY zeolite have been quantitatively determined using solid-state ¹H and ³¹P magic-angle spinning (MAS) NMR. After adsorption of the probe molecules, the concentration of Brönsted acid sites on the dealuminated HY zeolite increases by about 25%, whereas that in the parent HY sample remains almost unchanged. The increase in the concentration of Brönsted acid sites is due to the appearance of base-induced Brönsted acid sites in the dealuminated HY zeolite. The terminal SiOH in the vicinity of the aluminum atom is “induced” to form a bridging hydroxyl group (SiOHAl) in the presence of the basic probe molecules. The mechanism of formation of the induced Brönsted acid sites has also been discussed.     

Characterization of Copper(II), nickel(II), cobalt(II) and palladium(II) complexes of vicinal oxime-imine ligands; induced chelate isomerism in the same molecule of the nickel(II) complex

Summary Metal complexes of the title ligands were characterized in order to determine the factors influencing the stability of chelate isomerism in the same molecule. The ligands were prepared by 1:1 condensation of isonitrosoacetylacetone (Hiso) with eithero-aminophenol (H₂ isoaph),p-aminophenol (H₂ isopph), or aniline (Hisoanil). The following complexes have been synthesized: [(isoaph)Cu]₄, (Hisoaph)₂Co, (Hisopph)₂ M·nH₂O (M=Ni(II), n=2;M=Pd(II), n=0;M=Co(II), n=2), [(isopph) Cu·H₂O]₂, and (isoanil)₂ M (M=Ni(II), Cu(II), Co(II), or Pd(II)). Both chelate rings in these metal complexes are five-membered. Transimination of one –C=N–C₆H₅ group to –C=NH in (isoanil)₂Ni produced a six-membered chelate ring in (isoim)Ni(isoanil). The induced chelate isomerism is ascribed to intermolecular hydrogen bonding of the imino-hydrogen and the basic nitrogen of the same six-membered chelate ring of an adjacent square planar molecule. Other types of hydrogen bondings with the oximato oxygen (intra- or intermolecular) favour the formation of five-membered chelate rings. Analytical, spectroscopic, and magnetic moment data are in accordance with the suggested formulations.Part of the Ph.D. thesis of Sana M. Imam     

二次发射微波电子枪的倍增特性

 利用3DRun程序通过数值模拟计算，对二次发射微波电子枪的束流倍增特性作了研究。用1维模型计算了束流倍增与腔两极间距离以及腔中场强的关系，并详细给出了腔两极间距离为10mm,场强为5-4MV/m时出射电子纵向聚束及能量聚焦过程；利用3DRun程序研究了在高频场及粒子束本身空间电荷场的共同作用下，束流在3维运动过程中的倍增特性，计算了出射束流的发射度。通过计算表明：二次发射微波电子枪可以提供低发射度、高流强的电子束。     

Experimental verification of an equivalent circuit for the characterization of electrothermal micropumps: High pumping velocities induced by the external inductance at driving voltages below 5 V

Electrothermal micropumps (ETμPs) use local heating to create conductivity and permittivity gradients in the pump medium. In the presence of such gradients, an external AC electric field influences smeared spatial charges in the bulk of the medium. When there is also a symmetry break, the field‐charge interaction results in an effective volumetric force resulting in medium pumping. The advantages of the ETμP principle are the absence of moving parts, the opportunity to passivate all the pump structures, homogeneous pump‐channel cross‐sections, as well as force plateaus in broad frequency ranges. The ETμPs consisted of a DC‐heating element and AC field electrodes arranged in a 1000 μm × 250 μm × 60 μm (length × width × height) channel. They were processed as platinum structures on glass carriers. An equivalent‐circuit diagram allowed us to model the frequency‐dependent pumping velocities of passivated and nonpassivated ETμPs, which were measured at medium conductivities up to 1.0 S/m in the 300 kHz to 52 MHz frequency range. The temperature distributions within the pumps were controlled by thermochromic beads. Under resonance conditions, an additional inductance induced a tenfold pump‐velocity increase to more than 50 μm/s at driving voltages of 5 V_rms. A further miniaturization of the pumps is viewed as quite feasible.     

Weighted Harmonic Bloch Spaces and Gleason's Problem

The harmonic function spaces are considered on the unit ball, which unify the Bloch space ( s = 1) and the Lipschitz spaces (0 < s < 1). This article presents a characterization of when s > 1 and gives a solution of Gleason's problem in for any s > 0.     

A joint optimisation model for inventory replenishment,product assortment,shelf space and display area allocation decisions

In this paper, we propose an optimisation model to determine the product assortment, inventory replenishment, display area and shelf space allocation decisions that jointly maximize the retailer’s profit under shelf space and backroom storage constraints. The variety of products to be displayed in the retail store, their display locations within the store, their ordering quantities, and the allocated shelf space in each display area are considered as decision variables to be determined by the proposed integrated model. In the model formulation, we include the inventory investment costs, which are proportional to the average inventory, and storage and display costs as components of the inventory costs and make a clear distinction between showroom and backroom inventories. We also consider the effect of the display area location on the item demand. The developed model is a mixed integer non-linear program that we solved using LINGO software. Numerical examples are used to illustrate the developed model.     

Induced Ramsey-type theorems

We present a unified approach to proving Ramsey-type theorems for graphs with a forbidden induced subgraph which can be used to extend and improve the earlier results of Rödl, Erd?s-Hajnal, Prömel-Rödl, Nikiforov, Chung-Graham, and ?uczak-Rödl. The proofs are based on a simple lemma (generalizing one by Graham, Rödl, and Ruciński) that can be used as a replacement for Szemerédi's regularity lemma, thereby giving much better bounds. The same approach can be also used to show that pseudo-random graphs have strong induced Ramsey properties. This leads to explicit constructions for upper bounds on various induced Ramsey numbers.     

用平移网络逼近函数及其导数

若Х（ｘ）∈Ｗ１Ｍ（Ｒ＾ｄ），利用Х构造出具体的平移网络逼近Ｓｏｂｏｌｅｖ空间中的函数并给出逼近阶的估计。     

半连续格和半代数格的映射性质

研究了半连续格及半代数格的一些映射性质,讨论了强连续格的函数空间,给出了强连续格到方体的嵌入定理.