Effect of third-phase properties on benzyl-n-butyl ether synthesis in phase transfer catalytic system

The production of benzyl-n-butyl ether from benzyl chloride and n-butanol is studied in phase transfer catalytic system. A third phase is formed when polyethylene glycol (PEG) and dodecane are used as the phase transfer catalyst (PTC) and an organic solvent, respectively. The production rate at the three-phase system is higher by seven times than that at the two-phase system. The ether production rate and its selectivity are dependent on the initial concentration of n-butanol. These are affected by the properties of the third phase, especially the concentrations of n-butanol and water in the third phase.

n-Butanol reacts with benzyl chloride and potassium hydroxide simultaneously. The reaction between n-butanol and potassium hydroxide occurs in the aqueous phase. Then, the selectivity of ether on a basis of initial n-butanol is below 0.6 in a stirred tank batch reactor. The selectivity is much improved at 0.9 by using a static triphase batch reactor in which the organic and aqueous phases are separated by the third phase. The interphase mass transfer can be accelerated by ultrasonic device.     

Neural dysfunction and metabolic imbalances in diabetic rats. Prevention by acetyl-L-carnitine

The rationale for these experiments is that administration of L-carnitine and/or short-chain acylcarnitines attenuates myocardial dysfunction 1) in hearts from diabetic animals (in which L-carnitine levels are decreased); 2) induced by ischemia-reperfusion in hearts from nondiabetic animals; and 3) in nondiabetic humans with ischemic heart disease. The objective of these studies was to investigate whether imbalances in carnitine metabolism play a role in the pathogenesis of diabetic peripheral neuropathy. The major findings in rats with streptozotocin-induced diabetes of 4-6 weeks duration were that 24-h urinary carnitine excretion was increased approximately twofold and L-carnitine levels were decreased in plasma (46%) and sciatic nerve endoneurium (31%). These changes in carnitine levels/excretion were associated with decreased caudal nerve conduction velocity (10-15%) and sciatic nerve changes in Na(+)-K(+)-ATPase activity (decreased 50%), Mg(2+)-ATPase (decreased 65%), 1,2-diacyl-sn-glycerol (DAG) (decreased 40%), vascular albumin permeation (increased 60%), and blood flow (increased 65%). Treatment with acetyl-L-carnitine normalized plasma and endoneurial L-carnitine levels and prevented all of these metabolic and functional changes except the increased blood flow, which was unaffected, and the reduction in DAG, which decreased another 40%. In conclusion, these observations 1) demonstrate a link between imbalances in carnitine metabolism and several metabolic and functional abnormalities associated with diabetic polyneuropathy and 2) indicate that decreased sciatic nerve endoneurial ATPase activity (ouabain-sensitive and insensitive) in this model of diabetes is associated with decreased DAG.     

Frequency-domain measurement of carrier escape times in MQW electro-absorption optical modulators

Frequency-domain measurement of carrier escape times in reverse-biased multiple-quantum wells (MQW's) is proposed and demonstrated. Measurement and analysis of opto-to-electrical (OE) frequency response give the escape times of both electrons and holes with excellent time resolution. Using this technique, we measured escape times in an InGaAs-InAlAs MQW electro-absorption modulator and estimated the carrier density in the wells during optical input. This measurement can clarify the optical saturation effect in optical devices such as MQW electro-absorption modulators.     

Transient behavior of recycle reactor with consecutive reaction

Experimental and theoretical transient behavior of a recycle system were studied for a plug flow reactor with a mixing tank and a recycle line. The consecutive reaction chosen for experimental study was the hydrolysis of diethyl succinate through monoethyl succinate to succinic acid on a strong acid ion exchange resin at 50°C. Both realistic and simplified models were developed to simulate the transient behavior of the recycle system. The simplified model was more useful than the realistic model because analytical solutions could be obtained. The approach time to the steady state is presented for the recycle reactor.     

Graph construction with the maximum number of trees by continuous edge addition

A simple computational algorithm is presented to construct a graph with the maximum number of trees by adding edges one by one. The number of trees of a graph would become an index to estimate the overall reliability of probabilistic communication networks with the same link probabilities. Our procedure, Max-trees, selects one edge that gives the maximum number of trees among edges not included in the original graph. This process is continuously repeated at each step of adding an edge, when we get the sequence of new edges to be added. As examples of the execution results, the edge sequence and the maximum number of trees are shown for two types of starting graph, which are a tree of series edges and a star-shaped tree for nodes n = 7 and 8. To see how many trees these graphs have, the minimum numbers of trees for graphs with the same number of nodes and edges are similarly calculated by the minimum-version algorithm Min-trees. An edge sequence of Max-trees makes long cycles, and that of Min-trees makes cycles of three for as long as possible. The ratio of the maximum number of trees to the minimum number of trees is about 1 to 6 for these examples. This work was presented in part at the 11th International Symposium on Artificial Life and Robotics, Oita, Japan, January 23–25, 2006     

Similarity-Based Models of Word Cooccurrence Probabilities

In many applications of natural language processing (NLP) it is necessary to determine the likelihood of a given word combination. For example, a speech recognizer may need to determine which of the two word combinations eat a peach and eat a beach is more likely. Statistical NLP methods determine the likelihood of a word combination from its frequency in a training corpus. However, the nature of language is such that many word combinations are infrequent and do not occur in any given corpus. In this work we propose a method for estimating the probability of such previously unseen word combinations using available information on most similar words.We describe probabilistic word association models based on distributional word similarity, and apply them to two tasks, language modeling and pseudo-word disambiguation. In the language modeling task, a similarity-based model is used to improve probability estimates for unseen bigrams in a back-off language model. The similarity-based method yields a 20% perplexity improvement in the prediction of unseen bigrams and statistically significant reductions in speech-recognition error.We also compare four similarity-based estimation methods against back-off and maximum-likelihood estimation methods on a pseudo-word sense disambiguation task in which we controlled for both unigram and bigram frequency to avoid giving too much weight to easy-to-disambiguate high-frequency configurations. The similarity-based methods perform up to 40% better on this particular task.     

Dependence of alcohol vapor‐induced crystallization on gas and vapor permeabilities of poly(lactic acid) films

The effects of methanol and ethanol vapor‐induced crystallization on vapor and gas permeabilities and on the structure of poly(lactic acid) (PLA) films were systematically investigated. At high temperature conditions, the vapor permeability of PLA films decreased with increasing exposure time. The PLA films that were exposed to alcohol vapor became slightly cloudy, and no changes in chemical structure were observed. Alcohol vapor‐induced crystallization formed α‐crystal structure. The vapor permeability decreased with increasing crystallinity. However, nitrogen permeability slightly increased after vapor‐induced crystallization. The dependence of crystallinity on vapor and gas permeabilities was different from each penetrant. Total crystalline structures, including continuous crystal structures, remaining amorphous regions, and their interface depend on vapor and gas permeabilities. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40140.     

Primers‐4‐Yeast: a comprehensive web tool for planning primers for Saccharomyces cerevisiae

The budding yeast Saccharomyces cerevisiae is a key model organism of functional genomics, due to its ease and speed of genetic manipulations. In fact, in this yeast, the requirement for homologous sequences for recombination purposes is so small that 40 base pairs (bp) are sufficient. Hence, an enormous variety of genetic manipulations can be performed by simply planning primers with the correct homology, using a defined set of transformation plasmids. Although designing primers for yeast transformations and for the verification of their correct insertion is a common task in all yeast laboratories, primer planning is usually done manually and a tool that would enable easy, automated primer planning for the yeast research community is still lacking. Here we introduce Primers‐4‐Yeast, a web tool that allows primers to be designed in batches for S. cerevisiae gene‐targeting transformations, and for the validation of correct insertions. This novel tool enables fast, automated, accurate primer planning for large sets of genes, introduces consistency in primer planning and is therefore suggested to serve as a standard in yeast research. Primers‐4‐Yeast is available at: http://www.weizmann.ac.il/Primers‐4‐Yeast Copyright © 2013 John Wiley & Sons, Ltd.     

Large Photothermal Effect in Sub‐40 nm h‐BN Nanostructures Patterned Via High‐Resolution Ion Beam

The controlled nanoscale patterning of 2D materials is a promising approach for engineering the optoelectronic, thermal, and mechanical properties of these materials to achieve novel functionalities and devices. Herein, high‐resolution patterning of hexagonal boron nitride (h‐BN) is demonstrated via both helium and neon ion beams and an optimal dosage range for both ions that serve as a baseline for insulating 2D materials is identified. Through this nanofabrication approach, a grating with a 35 nm pitch, individual structure sizes down to 20 nm, and additional nanostructures created by patterning crystal step edges are demonstrated. Raman spectroscopy is used to study the defects induced by the ion beam patterning and is correlated to scanning probe microscopy. Photothermal and scanning near‐field optical microscopy measure the resulting near‐field absorption and scattering of the nanostructures. These measurements reveal a large photothermal expansion of nanostructured h‐BN that is dependent on the height to width aspect ratio of the nanostructures. This effect is attributed to the large anisotropy of the thermal expansion coefficients of h‐BN and the nanostructuring implemented. The photothermal expansion should be present in other van der Waals materials with large anisotropy and can lead to applications such as nanomechanical switches driven by light.