The Mx/G/1 queue with queue length dependent service times

We deal with the MX/G/1 queue where service times depend on the queue length at the service initiation. By using Markov renewal theory, we derive the queue length distribution at departure epochs. We also obtain the transient queue length distribution at time t and its limiting distribution and the virtual waiting time distribution. The numerical results for transient mean queue length and queue length distributions are given.Bong Dae Choi, Yeong Cheol Kim, Yang Woo Shin, and Charles E. M. Pearc

Effect of Osteoconductive Hyaluronate Hydrogels on Calvarial Bone Regeneration

11Yscopu

Quantitatively Controlled Fabrication of Uniaxially Aligned Nanofibrous Scaffold for Cell Adhesion

In light of tissue engineering, development of a functional and controllable scaffold which can promote cell proliferation and differentiation is crucial. In this study, we introduce a controllable collection method of the electrospinning process for regularly-distributed and uniaxially oriented nanofiber scaffold and evaluate the effects of aligned nanofiber density on adhesion of dermal fibroblasts. The suggested spinning collector features an inclined void gap, which allows easy transfer of uniformly aligned fibers onto other surfaces. By undergoing multiple transfers, the density of the nanofibers can be quantitatively controlled. The resultant polycaprolactone (PCL) nanofibers had well-defined nanotopography in a 400–600 nm range. Human dermal fibroblasts were seeded on aligned nanofiber scaffolds of different densities achieved by varying the number of transfers. Cell morphology and actin stress fiber formation was accessed after seven days. The experimental results indicate that the contact guidance of the cells along the fiber alignment can be more activated with more than one guidance feature on a cell; that is, the high density of fiber is attained in so much that fiber spacing gets below the cell size

Advanced diamond-reinforced metal matrix composites via cold spray: properties and deposition mechanism

Diamond-reinforced metal matrix composites (DMMC) have great potential for wear-resistance applications due to the superior hardness of the diamond component. Cold spray as an emerging coating technique is able to fabricate coatings or bulk materials without exceeding the material melting point, thereby significantly lowering the risk of oxidation, phase transformation, and excessive thermal residual stress. In this paper, thick DMMC coatings were deposited onto aluminum alloy substrate via cold spray of three feedstock powders: copper-clad diamond and pure copper, and their mixtures. It was found that, due to its low processing temperature, cold spray is able to prevent graphitization of the diamond in the DMMC coatings. Further to that, the original diamond phase was almost completely retained in the DMMC coatings. In case of the coatings fabricated from copper-clad diamond powders only, its mass fraction reached 43 wt.%, i.e. value higher than in any previous studies using conventional pre-mixed powders. Furthermore, it was found that the added copper content powders acted as a buffer, effectively preventing the fracture of the diamond particles in the coating. Finally, the wear test on the coatings showed that the cold sprayed DMMC coatings had excellent wear-resistance properties due to the diamond reinforcement

Percutaneous nephrostomy for nondilated renal collecting system with ultrasound and fluoroscopic guidance: The results of a 10-year experience

PURPOSEThis study aimed to evaluate the technical success rate, complications, and radiation doses of ultrasound- and fluoroscopy-guided percutaneous nephrostomy (PCN) in patients with a nondi- lated renal collecting system.METHODSOver a 10-year period, 50 patients were referred for PCN of 60 kidneys with a nondilated renal collecting system. The patients included 22 males and 28 females with a mean age of 63.2 years (range: 35-87 years). The most common reason for PCN in these patients was postoperative ure- teral leaks and/or fistula (21/50 patients). PCN was performed under ultrasound and fluoroscopic guidance. During PCN, intravenous contrast media or diuretics were not used. Technical success rate, complications, procedure time, and radiation exposure of the procedure were retrospec- tively evaluated.RESULTSUltrasound- and fluoroscopy-guided PCN for nondilated renal collecting system showed a suc- cess rate of 83.3% (50/60 kidneys) in the initial attempt. Four PCNs were repeated and were suc- cessful after the initial PCN failure. There was 1 major complication of bleeding that required transfusion in 1.9% (1/54) PCNs and there were minor complications of transient gross hematuria through the PCN catheter in 31.5% (17/54) PCNs. Mean duration of the procedure was 15.97 ± 7.81 min and median fluoroscopy time was 4.2 min (range: 1.2-15.3 min). Median dose area product and cumulative dose were 345.37 μGy·m2 (range: 42.57-1659.76 μGy·m2) and 46.9 mGy (range: 7.7-267.8 mGy), respectively.CONCLUSIONUltrasound- and fluoroscopy-guided PCN for nondilated renal collecting system was feasible with acceptable technical success rate, complication rate, procedure time, and radiation exposure