Green chemistry and sustainability metrics in the pharmaceutical manufacturing sector

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Fast-cycle trace analysis of dioxin in flue gas. Monitoring of the incineration of dioxin-containing waste from seveso

The fast trace analysis method used to monitor 2,3,7,8-TCDD in stack gas during the incineration of the waste from Seveso is described. The sampling of volatile organic compounds from flue gases, distributed between all three aggregation states, is based on a micromethod developed for the trace analysis of water using a specially dimensioned adsorptive charcoal filter (1.5 mg charcoal). In conjunction with subsequent GC/MS measurements the rapid “fast cycle trace analysis” ensured specific 2,3,7,8-TCDD detection down to 100 pg per m³ flue gas in cycle times of about 1–2 hours.     

Fouling Mitigation in a Heat Exchanger: High Cycles of Concentration for a Cooling-Tower Application

The purpose of the present study is to investigate the effect of a physical water treatment (PWT) technology on fouling mitigation in a simulated cooling tower operating at high cycles of concentration. Hard water was produced by evaporating pure water in a circulating open cooling tower, where dissolved calcium carbonate ions became concentrated with time. Heat transfer tests were conducted in a rectangular channel by varying the cycle of concentration (COC) from 5 to 10, and fouling resistances were measured over 270 hrs for each case with and without the PWT treatment. Another test was conducted with no blowdown case with and without the PWT treatment. The fouling resistance at 5 cycles with the PWT treatment was about 70% less than that in the case without the PWT treatment at the end of 270-hr tests. Even at 10 cycles, the PWT treatment reduced the fouling resistance by 60% from the value for the no treatment case. Thus, one can conclude that the PWT technology can help circulating cooling-tower water at relatively high COC for significant freshwater conservation, while keeping fouling resistances below industry standards.     

Efficient algorithm for calculating short cycles in Tanner graph based on matrix computation

Loop distribution of Tanner graph affects the BER performance of low-density parity-check codes(LDPC) decoding.To count short cycles in the Tanner graph efficiently,a side by side recursion algorithm based on matrix computation was proposed.Firstly,5 basic graph structures were defined to realize recursive calculate in the implementation process.Compared with previous works,the algorithm provided many methods for counting the same length of cycles.The same result confirmed the correctness of the algorithm.The new algorithm could not only calculate the total number of cycles,but also gave the number each edge participating in fixed-length cycles.Its complexity was proportional to the product of D and square of N,where D was the average degree of variable nodes,and N denoted the code length.For LDPC codes,D was far less than N.For most of the LDPC codes,the calculation for numbers of cycle-length g、g+2、g+4 was only several seconds.     

A QM/MM study on the reaction pathway leading to 2‐Aceto‐2‐hydroxybutyrate in the catalytic cycle of AHAS

The reaction between the intermediate 2‐hydroxyethyl‐thiamin diphosphate (HEThDP^?) and 2‐ketobutyrate, in the third step of the catalytic cycle of acetodydroxy acid synthase, is addressed from a theoretical point of view by means of hybrid quantum/molecular mechanical calculations. The QM region includes one molecule of 2‐ketobutyrate, the HEThDP^? intermediate, and the residues Arg 380 y Glu 139; whereas the MM region includes the rest of the protein. The study includes potential energy surface scans to identify and characterize critical points on it, transition state search and activation barrier calculations. The results show that the reaction occurs via a two‐step mechanism corresponding to the carboligation and proton transfer in the first stage; and the product release in the second step. © 2014 Wiley Periodicals, Inc.     

Impact of proliferation strategies on food web viability in a model with closed nutrient cycle

A food web model with a closed nutrient cycle is presented and analyzed via Monte Carlo simulations. The model consists of three trophic levels, each of which is populated by animals of one distinct species. While the species at the intermediate level feeds on the basal species, and is eaten by the predators living at the highest level, the basal species itself uses the detritus of animals from higher levels as the food resource. The individual organisms remain localized, but the species can invade new lattice areas via proliferation. The impact of different proliferation strategies on the viability of the system is investigated. From the phase diagrams generated in the simulations it follows that in general a strategy with the intermediate level species searching for food is the best for the survival of the system. The results indicate that both the intermediate and top level species play a critical role in maintaining the structure of the system.     

Reliability of Cu nanoparticle joint for high temperature power electronics

Power cycle reliability of Cu nanoparticle joint has been studied for high temperature operation of power devices. Al₂O₃ heater chips and Cu–65 wt% Mo baseplates were joined by Cu nanoparticles and Sn–0.7Cu and power cycle tests of 65/200 °C and 65/250 °C were carried out on the joints. The Cu nanoparticles were prepared by reducing Cu carbonate in ethylene glycol with dodecanoic acid + dodecyl amine (C12) and decanoic acid and decyl amine (C10) as capping agents. A power cycle test of 65/200 °C did not inflict severe damage on the Cu nanoparticle joints so that there were not many cracks formed after 3000 cycles. Vertical cracks were formed in the C12 Cu nanoparticle joint after 3000 cycles of 65/250 °C test, however the maximum temperature during the power cycle test did not change at all because vertical cracks did not have an effect on preventing heat flow. On the contrary, lateral cracks were completely formed in the Sn–0.7Cu soldered joint after 200 cycles of 65/200 °C test and in the C10 Cu nanoparticle joint after 360 cycles of 65/250 °C test. In these experiments, the maximum temperatures were rapidly increased because heat conduction was prevented across the formed lateral cracks.     

钟摆模型极限环的存在性研究

钟摆系统是一类典型的分段光滑系统,结合Filippov系统刻画语言,解释了当钟摆无能量补充时,钟摆最终会停止在滑动集上的原因.利用数值模拟的方法,给出钟摆系统在有能量补充时,存在极限环的条件.最后,结合环域定理证明了一般的钟摆模型存在唯一稳定的极限环.     

Binding Number,Minimum Degree,and Cycle Structure in Graphs

A well‐known theorem of Woodall states that if a graph G has binding number at least 3/2, then G is hamiltonian. We generalize Woodall's theorem as follows.