Two hyperfinite constructions of the brownian bridge

Infinitesimal Analysis is used to give two constructions of the brownian bridge process. In the first construction a hyperfinite tied down random walk is used and a brownian bridge is obtained via the standard part map. As a consequence it is shown that the brownian bridge is the weak limit of a sequence of normalized tied down random walks. The second construction is based on a hyperfinite uniform empirical process. This construction gives an almost trivial proof of Donsker's Invariance Principle for the uniform empirical process     

On a bulk arrival bulk service infinite service queue

This paper considers an infinite server queue in continuous time in which arrivals are in batches of variable size X and service is provided in groups of fixed size R. We obtain analytical results for the number of busy servers and waiting customers at arbitrary time points. For the number of busy servers, we obtain a recursive relation for the partial binomial moments both in transient and steady states. Special cases are also discussed     

Comparative analysis of the machine repair Problem with imperfect coverage and service pressure condition

In this paper we analyze the warm-standby M/M/R machine repair problem with multiple imperfect coverage which involving the service pressure condition. When an operating machine (or warm standby) fails, it may be immediately detected, located, and replaced with a coverage probability c by a standby if one is available. We use a recursive method to develop the steady-state analytic solutions which are used to calculate various system performance measures. The total expected profit function per unit time is derived to determine the joint optimal values at the maximum profit. We first utilize the direct search method to measure the various characteristics of the profit function followed by Quasi-Newton method to search the optimal solutions. Furthermore, the particle swarm optimization (PSO) algorithm is implemented to find the optimal combinations of parameters in the pursuit of maximum profit. Finally, a comparative analysis of the Quasi-Newton method with the PSO algorithm has demonstrated that the PSO algorithm provides a powerful tool to perform the optimization problem.     

Competitive strategies for an online generalized assignment problem with a service consecution constraint

This work studies a variant of the online generalized assignment problem, where there are m ? 2 heterogeneous servers to process n requests which arrive one by one over time. Each request must either be assigned to one of the servers or be rejected upon its arrival, before knowing any information of future requests. There is a corresponding weight (or revenue) for assigning each request to a server, and the objective is to maximize the total weights obtained from all the requests. We study the above problem with a service consecution constraint, such that at any time each server is only allowed to process up to d consecutive requests.     

"地小氢"和"月小氢"

Hydrogen is the most abundant chemical element in the Universe and is tightly related to human life. This article personifies hydrogen, bringing a close interaction between the hydrogen on the moon and the hydrogen on the Earth. Through lively and interesting dialogues, the history of hydrogen discovery and the properties are introduced, and the application of hydrogen in different aspects of the future is prospected.     

Structural modification of BODIPY: Improve its applicability

BODIPY has been considered a potential scaffold because of their neutral total charge, sharp absorption,and emission with high fluorescence quantum yield. However, the drawback of emission wavelength at less than 600 nm and hydrophobicity limit its application. One of the extremely interesting properties of BODIPY is that small modifications to their structures could be able to tune their properties, mainly including the absorption/emission wavelength and the hydrophilicity. This review focuses on the modification at different positions of BODIPY to improve the water-solubility and emission wavelength that describe their spectral, photophysical properties and applicability, which is helpful for the researchers to rationally design BODIPY dyes to adapt a wide range of applications.     

无患子三萜皂苷研究进展

无患子是一种集工业、药用、观赏、生态于一体的多功能综合利用价值极高的经济树种,近年来,由于其具有较高的商业价值和药理活性,受到了广泛的重视。迄今文献中报道的无患子中分离鉴定的三萜皂苷类化合物有71种,具有抗菌、抗肿瘤、保护心脑血管、保护肝脏、抗生育、杀虫等多种生物活性和良好的非离子表面活性作用,在医药、食品保健、日化和农业等领域应用前景广阔。本文对其皂苷的种类、提取与分离及其应用进行了综述,以期为今后无患子的研究、开发与利用提供参考。     

Characterization of Cyclodextrin Glucanotransferase Produced by <Emphasis Type="Italic">Bacillus megaterium</Emphasis>

Cyclodextrin glucanotransferase, produced by Bacillus megaterium, was characterized, and the biochemical properties of the purified enzyme were determined. The substrate specificity of the enzyme was tested with different α-1,4-glucans. Cyclodextrin glucanotransferase displayed maximum activity in the case of soluble starch, with a K _m value of 3.4 g/L. The optimal pH and temperature values for the cyclization reaction were 7.2 and 60 °C, respectively. The enzyme was stable at pH 6.0–10.5 and 30 °C. The enzyme activity was activated by Sr²⁺, Mg²⁺, Co²⁺, Mn²⁺, and Cu²⁺, and it was inhibited by Zn²⁺and Ag⁺. The molecular mass of cyclodextrin glucanotransferase was established to be 73,400 Da by sodium dodecyl sulfate–polyacrylamide gel electrophoresis, 68,200 Da by gel chromatography, and 75,000 Da by mass spectrometry. The monomer form of the enzyme was confirmed by the analysis of the N-terminal amino acid sequence. Cyclodextrin glucanotransferase formed all three types of cyclodextrins, but the predominant product was β-cyclodextrin.     

Synthesis and direct interactions of silver colloidal nanoparticles with pollutant gases

Silver nanoparticles (NPs) were synthesized in organic solvents. Spontaneous reduction of silver salts takes place in N,N′-dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO) at room temperature. The formed colloids are not stable without a stabilizing agent, hence rarely used, and inexpensive organic molecules (β-cyclodextrin and cholic acid) were used as surface modifiers in DMF. The stabilization was successful; the Ag NPs remained stable for more than 3 months. Additionally, Ag NPs were prepared using Ag-2-ethylhexanoate and Na-citrate as capping agent in DMSO. The resulting NPs are stable, of 4.4 nm average size, and at the same time reactive for catalytic purposes. The interaction of Ag NPs with pollutant atmospheric gases (NO and SO₂) was studied. UV–visible spectra show the oxidation of silver and the very efficient reduction of NO at room temperature. SO₂ molecules are adsorbed on the NPs surface, causing their aggregation and precipitation.