防水型碳化钨气体扩散电极的研究

碳化钨(WC)以高硬度、高耐磨性的特性历来深受治金学家重视,常用它制造刀具、量具和模具,近二十余年才将其作为催化剂加以研究.这些年来,人们已发现WC催化剂具有较强的耐酸性、良好的导电性和电催化活性,且不受任何浓度的一氧化碳和几个PPM的硫化氢中毒,在加氢和脱氢方面,某些性质很类似于铂,故颇受人们关注. 本工作采用与常规不同的制备方法,制成高活性碳化钨粉末催化剂,曾先后对WC粉末在不同气氛中的热稳定性、几种溶液中的电化学稳定性及其阳极氧化机理进行了研究,并将WC粉末用作电催化剂制成半防水型氢电极,以碳为氯电极材料,单电池电极面积0.1m~2,由10个单电池按复极式串联成20D余瓦的氢-氯燃料电池组,在工厂中连续运行三个月,WC氢电极性能保持稳定。在此基础上,为进一步提高WC氢电极活性,提出了防水型WC气体扩散电极的研究.本文主要报导碳化钨粉末制备中物相组成、比表面及其电极制备条件对电极活性的影响,以及该电极的主要性能。     

Preparation and characterization of poly (N-isopropylacrylamide-co-dimethylaminoethyl methacrylate) microgel latexes

Monodisperse cationic thermosensitive latex microgels have been prepared by radical-initiated precipitation polymerization of N-isopropylacrylamide, methylene bisacrylamide using 2,2′-azobis(2-amidinopropane hydrochloride) as an initiator and dimethylaminoethyl methacrylate (DMAEMA) as a cationic monomer. The final microgel latexes were characterized with respect to water-soluble polymer formation, particle size and size distribution. Adding cationic monomer (DMAEMA) was found to drastically affect the particle size, but not the size distribution as observed both by transmission electron microscopy and quasielastic light scattering (QELS). However, too high a DMAEMA concentration in the feed composition led to enhanced formation of water-soluble polymer. The volume phase-transition temperature of cleaned microgels examined by QELS (particle size versus temperature) was found to be around 32 °C and was slightly dependent on the concentration of the cationic monomer. The volume phase-transition temperature range becomes broader with increasing cationic monomer concentration. In addition, the pH of the polymerization medium was found to affect the final particle size and amount of water-soluble polymer formed. Received: 29 March 2001 Accepted: 2 July 2001     

Preparation and optical properties of titania-doped hybrid polymer via anhydrous sol-gel process

Incorporation of metal alkoxides (Ti, Zr, etc.) for tuning the optical properties of silica glasses by the sol-gel process is of significant interest for optical applications. In this paper, we report an anhydrous sol-gel process for preparation of photosensitive titania-doped hybrid glassy polymer with good homogeneity and high doping concentration (TiO₂ up to 40 mol%). The process consists of two steps: in the first step methacryloxypropyltrimethoxysilane (MPS) is hydrolyzed by boric acid through ligand exchange reaction (OH↔OR) under anhydrous conditions; and in the second step dimethyldimethoxysilane (DMDMS), diphenyldimethoxysilane (DPhDMS) and titanium ethoxide (TET) were added to condense with the silanols formed in the first step. The optical properties of the synthesized hybrid polymer were studied, and results showed that the hybrid material has low OH absorption, low optical losses (0.45 dB/cm at 1550 nm and 0.16 dB/cm at 1310 nm respectively), and good thermo-optical linearity with tuneable refractive index. The effect of TiO₂ doping in reducing the OH concentration of the hybrid material was observed, and the mechanism for this effect is discussed.     

亚硫酰氯阴极还原的半对数极化曲线

目前正在广泛研究的鲤/亚硫酰氯(Li/SOCl_2)电池是迄今为止比能量最高的一种新型化学电源。提高电池的性能和可靠性与电池反应的化学和电化学性质直接有关。但是,SOCl_2的还原过程相当复杂,对其反应机理迄今尚无明确的结论。由于SOCl_2还原时伴随着LiCl的沉积,当用常规电极测量时难以得到稳态极化曲线,因而至今未见报道SOCl_2还原反应的半对数极化曲线。微电极的单位表面上极限液相传质速度较高,且测量时较易得到稳态电流。因此,采用微电极方法可在一定程度上避开上述困难,研究SOCl_2还原反应的机理。     

Analgesic Buxus alkaloids with Enhanced Selectivity for the Low-Voltage-Gated Calcium Channel Cav3.2 over Cav3.1 through a New Binding Mode

Low-voltage-gated calcium channels (LVGCCs; Ca_v3.1-3.3) represent promising drug targets for epilepsy, pain, and essential tremor. At present, modulators with heightened selectivity for a subtype of LVGCCs are still highly desired. In this study we explored three classes of Buxus alkaloids and identified 9(10/19)abeo-artanes Buxusemine H and Buxusemine L (BXSL) as an unprecedented type of Ca_v3.2 inhibitors. Particularly, BXSL exhibited Ca_v3.2 inhibition comparable to Z944, a non-subtype-selective LVGCCs inhibitor under clinical trial. While lacking specificity for Ca_v3.3, BXSL showed a 30-fold selectivity of Ca_v3.2 over Ca_v3.1. As compared to several well-known inhibitors, the experimental and computational studies suggested BXSL exhibits a distinct binding mode to Ca_v3.2, notably through the essential interaction with serine-1543 in domain III. Furthermore, BXSL showed minimal impact on various recombinant and native nociceptive ion channels, while significantly reducing the excitability of isolated mouse dorsal root ganglion neurons. Animal studies in wild-type and Ca_v3.2 knock-out mice revealed that BXSL (5 mg/kg), by inhibiting Ca_v3.2, exhibits an analgesic effect equivalent to Z944 (10 mg/kg) or mibefradil (10 mg/kg). Moreover, we proposed a structural rationale for the high selectivity of 9(10/19)abeo-artane-type alkaloids towards Ca_v3.2 over Ca_v3.1. This study introduces a novel analgesic agent and valuable molecular insight for structure-based innovative Ca_v3.2 drug development.     

Preparation and Spectroscopy of Aluminosilicate Films Deposited on Graphite Surfaces via an Anhydrous Sol-Gel Route

Anhydrous aluminosilicate sols with Al : Si molar ratio ranging from 1 : 10 to 1 : 5 were prepared by a two-step anhydrous sol-gel process, in which tetraethoxysilane (TEOS) is pre-hydrolysed by formic acid, followed by addition of aluminium ethoxide. Unlike the case of aqueous sol-gel routes, where the Si–O–Al network homogeneity is greatly restricted by precipitation of Al(OH)₃, this anhydrous route yields clear, homogeneous sols. The sol formation and densification processes were investigated by infrared spectroscopy and X-ray powder diffraction (XRD) techniques, and the existence of Al–O–Si linkages was confirmed. To demonstrate an application of the anhydrous sol-gel process, aluminosilicate films were deposited onto graphite surfaces by dip coating and densified at 800°C under nitrogen, and their protective effect was evaluated.     

Toughness,trees, and walks

A graph is t‐tough if the number of components of G\S is at most |S|/t for every cutset S ⊆ V (G). A k‐walk in a graph is a spanning closed walk using each vertex at most k times. When k = 1, a 1‐walk is a Hamilton cycle, and a longstanding conjecture by Chvátal is that every sufficiently tough graph has a 1‐walk. When k ≥ 3, Jackson and Wormald used a result of Win to show that every sufficiently tough graph has a k‐walk. We fill in the gap between k = 1 and k ≥ 3 by showing that, when k = 2, every sufficiently tough (specifically, 4‐tough) graph has a 2‐walk. To do this we first provide a new proof for and generalize a result by Win on the existence of a k‐tree, a spanning tree with every vertex of degree at most k. We also provide new examples of tough graphs with no k‐walk for k ≥ 2. © 2000 John Wiley & Sons, Inc. J Graph Theory 33:125–137, 2000     

Two schemes of multiparty quantum direct secret sharing via a six-particle GHZ state

In this paper, two new efficient multiparty quantum direct secret sharing schemes are proposed via a six-particle GHZ state and Bell measurements. In the first scheme, based on the theory of security cryptanalysis, the secret message of the sender is directly encoded into the transmitted particles, and all the agents can obtain their information by performing bell measurement on the received particles, and then cooperate to recover the information of the sender. In the second scheme, we define a new secret shared coding method by performing local unitary operations on the transmitted particles, then agents perform Bell measurements on their own particles respectively, and feedback the measurement to the dealer. If the agent's results are matched with the previous coding method, the protocol will work out.In addition, the proposed two schemes have the following common advantages: the sender can send all prepared particles to the receiver, and can send an arbitrary key to the receiver, rather than a random secret key; the proposed schemes do not need to insert any detection sets to detect eavesdropping and can resist both existing attacks and spoofing attacks by dishonest agents. The sender need not to retain any photons, so the sender's quantum memory could be omitted here.     

Two Forms Schemes of Deterministic Remote State Preparation for Four-Qubit Cluster-Type State

Two deterministic schemes are put forward to preparing an arbitrary four-qubit cluster-type state remotely by using two Bell states as quantum channel. The coefficients of the prepared states can be not only real, but also complex. To accomplish the schemes, we introduce some novel sets of ingenious measurement basis vectors. Especially, for complex coefficients case, we give two different forms schemes. The receiver will reconstruct the initial state by means of some appropriate unitary operations. The outstanding advantage of the present schemes is that the success probability in all the considered remote state preparation (RSP) can reach 1.

     

硫酸水溶液中铅阳极膜形成及其结构的非现场FTIR反射吸收光谱—电化学研究

本文用非现场红外反射吸收光谱方法和电化学循环伏安法研究了1.0mol·dm~(-3)H_2SO_4中-0.6至2.5伏电势范围内(相对SCE)Pb阳极膜的形成及其可能的结构。在此电势区内Pb阳极膜中始终存在硫酸铅或碱式硫酸铅,其中SO_4~(2-)主要以桥式双齿配位方式与Pb~(2+)结合。另外,上述电势范围内生成的膜中无可检测量的H_2O和OH~-存在。