Oligodeoxyribonucleotide analogues with bridging dimethylene sulfide,sulfoxide, and sulfone groups. Toward a second-generation model of nucleic acid structure

Short DNA analogues with bridging dimethylene sulfide, sulfoxide, and sulfone groups replacing the phosphate diesters (S-DNAs) were synthesized from building blocks prepared via two routes, both starting from D-glucose. Building blocks for RNA analogues were prepared by stereoselective introduction of nucleobase into a 2'-acylated ribose analogue. The ribose analogues were converted to deoxyribose analogues by replacement of a 3'-OH group by a thioacetyl unit, followed by photolytic deoxygenation or radical-based 2'-deoxygenation. DNA analogues joined via CH(2)(-)S-CH(2) units were prepared by S(N)2 displacement of a 6'-mesyl group on one building block using a thiolate nucleophile of another. 4,4'-Dimethoxytrityl protection and deprotection schemes were established for both the thiol and hydroxyl groups. The corresponding sulfoxide DNA analogues were obtained by oxidation with hydrogen peroxide. Sulfone DNA analogues were obtained by oxidation of the sulfide DNA with persulfate or hydrogen peroxide in the presence of a titanium silicate catalyst. The physical properties of several representative oligonucleotide analogues were examined, and interpreted in light of a "second-generation" model for DNA strand-strand recognition, a model that emphasizes the role of the polyanionic backbone in diminishing unwanted tendencies of highly functionalized molecules to form "structure" in solution. Even short sulfide-linked DNA analogues displayed association properties different from those displayed by standard DNA molecules. Complex formation observed with sulfide-linked tetramers by HPLC study in different solvents suggested that the complex is formed using hydrogen bonding. Sulfone-linked dinucleotides display Watson-Crick behavior; the tetramer, however, displayed self-structure. Self-structure and self-aggregation become more prominent as the length of the oligonucleotide analogues increases. The tendency to self-aggregate can be decreased by adding a charged sulfonate group to the 3'-end of the DNA analogue. Features of the second-generation model are important for many areas of nucleic acid chemistry, from the design of nucleic acid therapeutic agents to the search for life on other planets.     

纳米分辨率的三维形貌检测仪

从光干涉方式，瞳窗关系和光源带宽等基本关系出发，利用空间不变系统理论解析了相移显微干涉检测系统中衍射效应的影响。为了减小横向分辨率对纵向分辨率的影响，利用相关信息提取或数字滤波的方法，获得了纳米分辨率的三维形貌。     

Chemical Reactions and Kinetics of the Carbon Monoxide Coupling in the Presence of

The chemical reactions and kinetics of the catalytic coupling reaction of carbon monoxide to diethyl oxalate were studied in the presence of hydrogen over a supported palladium catalyst in the gaseous phase at the typical coupling reaction conditions. The experiments were performed in a continuous flow fixed-bed reactor. The results indicated that hydrogen only reacts with ethyl nitrite to form ethanol, and kinetic studies revealed that the rate-determining step is the surface reaction of adsorbed hydrogen and the ethoxy radical (EtO-). A kinetic model is proposed and a comparison of the observed and calculated conversions showed that the rate expressions are of rather high confidence.     

A New Approach to α—Bromochalcones

α-Bromo benzolymethylene triphenylphosphorane 3 has been synthesized by the reaction of benzoylmethylene triphenylphosphorane 1 with N-bromosuccinimide in the yield of 87% and can react with aromatic aldehydes 4 to give α-bromochalcones 5 in good yields.     

Entropy of self-gravitating radiation

We examine the entropy of self-gravitating radiation confined to a spherical box of radiusR in the context of general relativity. We expect that configurations (i.e., initial data) which extremize total entropy will be spherically symmetric, time symmetric distributions of radiation in local thermodynamic equilibrium. Assuming this is the case, we prove that extrema ofS coincide precisely with static equilibrium configurations of the radiation fluid. Furthermore, dynamically stable equilibrium configurations are shown to coincide with local maxima ofS. The equilibrium configurations and their entropies are calculated and their properties are discussed. However, it is shown that entropies higher than these local extrema can be achieved and, indeed, arbitrarily high entropies can be attained by configurations inside of or outside but arbitrarily near their own Schwarzschild radius. However, if we limit consideration to configurations which are outside their own Schwarzschild radius by at least one radiation wavelength, then the entropy is bounded and we find S_max MR, whereM is the total mass. This supports the validity for self-gravitating systems of the Bekenstein upper limit on the entropy to energy ratio of material bodies.     

Ca(1)(-)(x)Na(2)(x)Al(2)B(2)O(7): a structure with tunable density of Na(+) vacancies

A series of samples with the composition Ca(1)(-)(x)Na(2)(x)Al(2)B(2)O(7) (0 < x < or = 1) was investigated and a hexagonal structure with unusually large range of homogeneity (at least from x = 0.01 to 0.95) was revealed. The hexagonal phase consists of [Al(2)B(2)O(7)](infinity)(2)(-) lamellae stacked along the c axis, as in CaAl(2)B(2)O(7) and Na(2)Al(2)B(2)O(7). Nevertheless, the configuration and stacking sequence of the [Al(2)B(2)O(7)](infinity)(2)(-) lamellae are different in these three structures. In the hexagonal structure of Ca(1)(-)(x)()Na(2)(x)()Al(2)B(2)O(7), Ca and half Na cations (Na1) statistically occupy the same crystallographic site which is located between the [Al(2)B(2)O(7)](infinity)(2)(-) lamellae, the other half Na cations (Na2) distribute in the planes bisecting the [Al(2)B(2)O(7)](infinity)(2)(-) lamellae. Depending on the composition, the site occupation factor of Na2 site can vary in the same range as x, leading to a tunable density of Na(+) vacancies in the structure. The AlO(4) tetrahedra and BO(3) triangles in the structure tilt in appropriate ways to improve the bond valence sum of Na2 cations which are not sufficiently bonded to the anions.     

三重四极杆电感耦合等离子体质谱(ICP-MS)法测定氧化铕中13种稀土杂质元素

稀土杂质元素直接影响高纯单金属稀土材料的整体性能,是高科技领域许多材料的重要组成部分。通过考察最佳的消解酸量、温度、时间、氧气反应气流量、稀释气流量,建立了基于三重四极杆电感耦合等离子体质谱仪(ICP-MS/MS)直接测定氧化铕中13种稀土杂质元素分析方法。该方法采用0.1%基体直接进样,可以很大程度提高前处理分析效率。利用碰撞模式测定氧化铕稀土中的Y、La、Pr、Nd、Sm、Gd、Tb、Dy、Ho、Er、Yb、Lu元素,氧气质量转移模式测定氧化铕中的Tm,两种模式结合可以有效去除多原子干扰,实现氧化铕的稳定测试分析。通过对氧化铕标准物质（GBW02902）直接测定分析,结果表明,在碰撞和氧气质量转移模式下,各元素线性相关系数（r）均大于 0.9999,方法检出限为0.001~0.023 mg/kg,测试精密度优于1.99%,13种元素的测试值都在认定值的不确定度范围之内。该分析方法操作简单,测试稳定,效率高,为实验室进行氧化铕材料中REE杂质的准确测试分析提供思路和借鉴。     

全自动高温水解-离子色谱法测定氧化镧铈中氟、氯

为探究稀土氧化物中氟(F)和氯(Cl)元素含量的快速检测方法,通过全自动高温水解仪对氧化镧铈样品进行前处理,并利用氢氧根体系离子色谱仪检测吸收液中F-、Cl-离子的含量,建立了基于全自动高温水解-离子色谱法测定氧化镧铈中的F、Cl元素含量的快速检测方法,该方法有效避免了传统前处理方法过程复杂、分析时间慢、极易受人为干扰的问题。称取0.3g氧化镧铈样品,在氧气流量为300 mL/min,1100 ℃高温下水解燃烧20 min,吸收定容为体积20mL的吸收液,以NAOH(15mmol/L)作为淋洗液,经色谱柱分离,测得F-与Cl-在质量浓度为1.00 mg/L-15.00 mg/L范围内,质量浓度与离子色谱峰面积呈线性关系,相关系数均为0.9999。检出限分别为0.003mg/L和0.12mg/L。全自动高温水解仪联用离子色谱仪检测系统对氧化镧铈中F-的平均加标回收率测定结果为98.4%,标准偏差RSD为0.94%;对Cl-的加标回收率测定结果为97.8%,RSD为2.86%。说明该方法较高准确度及精密度,测试结果准确可靠满足企业和检测机构的测试需求,为稀土氧化中氟、氯元素含量的研究及相关产品的开发提供了理论基础。     

Joint Optimization of Control Strategy and Energy Consumption for Energy Harvesting WSAN

With the rapid development of wireless sensor technology, recent progress in wireless sensor and actuator networks (WSANs) with energy harvesting provide the possibility for various real-time applications. Meanwhile, extensive research activities are carried out in the fields of efficient energy allocation and control strategy design. However, the joint design considering physical plant control, energy harvesting, and consumption is rarely concerned in existing works. In this paper, in order to enhance system control stability and promote quality of service for the WSAN energy efficiency, a novel three-step joint optimization algorithm is proposed through control strategy and energy management analysis. First, the optimal sampling interval can be obtained based on energy harvesting, consumption, and remaining conditions. Then, the control gain for each sampling interval is derived by using a backward iteration. Finally, the optimal control strategy is determined as a linear function of the current plant states and previous control strategies. The application of UAV formation flight system demonstrates that better system performance and control stability can be achieved by the proposed joint optimization design for all poor, sufficient, and general energy harvesting scenarios.