BACKGROUND Optically pure acetoin (AC) is an important platform chemical which has been widely used to synthesize novel optically active α-hydroxyketone derivatives and liquid crystal composites. RESULTS In this study, slaC and gldA encoding meso-2,3-butanediol dehydrogenase (meso-2,3-BDH) and glycerol dehydrogenase (GDH), respectively, in S. marcescens MG1 were knocked out to block the conve...

Purpose: To prepare oral sustained release matrix tablets of a highly water soluble drug, tramadol hydrochloride, and to evaluate the effect of concentration of the hydrophobic polymer content and method of preparation on drug release. Methods: The tablets were a mixture of both tramadol hydrochloride and glyceryl palmitostearate (GP) prepared by melt granulation (MG1, MG2, MG3 and MG4 in ratio...

[1] We present first-principles results for elastic moduli (bulk, K, and shear, G) and acoustic velocities (compressional, VP, shear, VS, and bulk VΦ) of olivine (a) and wadsleyite (b) (Fex,Mg1 x)2SiO4, at high pressure (P) and temperature (T) with varying iron content (0≤ x≤ 0.125). Pressure and temperature derivatives of these properties are analyzed. We show that adding 12.5% of Fe in forste...

OBJECTIVE ATP-binding cassette transporter G1 (ABCG1) mediates cholesterol efflux to lipidated lipoproteins. Conflicting data about cellular localization of ABCG1 and its effect on cholesterol efflux have been reported. Here, we investigated the underlying mechanisms for these different observations. APPROACH AND RESULTS Confocal microscopy and biotinylation were used to assess cell surface l...

In this paper, a hybrid overlay/underlay cognitive radio system is modeled as an M/M/1 queue where the rate of arrival and the service capacity are subject to Poisson alternations. Each packet as a customer arriving at the queue makes a decision to join the queue or not. Upon arrival, the individual decision of each packet is optimized based on his observation about the queue length and the sta...

This paper presents the transient solution of a variant working vacation queue with balking. Customers arrive according to a Poisson process and decide to join the queue with probability $b$ or balk with $bar{b} = 1-b$. As soon as the system becomes empty, the server takes working vacation. The service times during regular busy period and working vacation period, and vacation times are assumed ...

We consider a model of two M/M/1 queues, served by a single server. The service policy for this polling model is of threshold type: the server serves queue 1 exhaustively, and does not remain at an empty queue if the other one is non-empty. It switches from queue 2 to queue 1 when the size of the latter queue reaches some level T , either preemptively or non-preemptively. All switches are insta...

We consider two coupled queues with a generalized processor sharing service discipline. The second queue has a much smaller Poisson arrival rate than the first queue, while the customer service times are of comparable magnitude. The processor sharing server devotes most of its resources to the first queue, except when it is empty. The fraction of resources devoted to the second queue is small, ...

We study N-queues single-server fluid polling systems, where a fluid is continuously flowing into the queues at queue-dependent rates. When visiting and serving a queue, the server reduces the amount of fluid in that queue at a queue-dependent rate. Switching from queue i to queue j requires two random-duration steps: (i) departing queue i, and (ii) reaching queue j. The length of time the serv...

This paper studies virtual machine (VM) scheduling in a queueing cloud computing system with stochastical arrivals of heterogeneous jobs by considering jobs’ delay requirements. The delay-optimal VM such is formulated as multi-resource multi-class problem minimize the average job completion time, which often NP-hard. To solve problem, we first propose model that buffers same type one que...