Spinal codes

Spinal codes are a new class of rateless codes that enable wireless networks to cope with time-varying channel conditions in a natural way, without requiring any explicit bit rate selection. The key idea in the code is the sequential application of a pseudo-random hash function to the message bits to produce a sequence of coded symbols for transmission. This encoding ensures that two input messages that differ in even one bit lead to very different coded sequences after the point at which they differ, providing good resilience to noise and bit errors. To decode spinal codes, this paper develops an approximate maximum-likelihood decoder, called the bubble decoder, which runs in time polynomial in the message size and achieves the Shannon capacity over both additive white Gaussian noise (AWGN) and binary symmetric channel (BSC) models. Experimental results obtained from a software implementation of a linear-time decoder show that spinal codes achieve higher throughput than fixed-rate LDPC codes, rateless Raptor codes, and the layered rateless coding approach of Strider, across a range of channel conditions and message sizes. An early hardware prototype that can decode at 10 Mbits/s in FPGA demonstrates that spinal codes are a practical construction.Massachusetts Institute of Technology (Irwin and Joan Jacobs Presidential Fellowship)Massachusetts Institute of Technology (Claude E. Shannon Assistantship)Intel Corporation (Intel Fellowship

Special features in powder preparation, pressing, and sintering of uranium dioxide

Nuclear ceramic grade UO2 powders are usually prepared by the wet chemical ammonium diuranate route. The powders are pressed and sintered before incorporation into nuclear fuel assemblies. The processing is complex at all stages and the specifications are stringent. In powder preparation, slow addition of the precipitating reagent at a low temperature is recommended. The conditions for the drying of the precipitate, calcination and reduction are chosen to result in an agglomerate free, fine and porous powder that does not require milling or binder addition and is capable of being compacted and sintered to desired density with a homogeneous microstructure. The pressing conditions are chosen to give compacts that are free from defects such as cracking, chipping and end-capping. Sintering conditions are such that desintering, bloating, weathering and nitriding are avoided. Some insights that have been gained in powder preparation, pressing and sintering are presented in this paper. The relationship between powder characteristics and pressing and sintering properties is described

Admixed binders and lubricants in ceramic powder pressing-A study of zinc behenate additive

136-139<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:"times="" roman";mso-ansi-language:en-us;="" mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">Admixed lubricants are used to bring down compaction and ejection pressures, and to increase packing efficiency in ceramic powder pressing. Admixed binders are used for increasing green strength of the compact. The stronger and denser green compacts so obtained, sinter to high densities without defects and with minimal shrinkage, leading to very high acceptance rates in large scale production. Zinc behenate powder has been used as a lubricant cum binder for uranium dioxide with very good results. Green density versus compaction pressure has been obtained. Weight loss with temperature of free and admixed zinc behenate and carbon and zinc loss in admixed compact and other data are presented. On the other hand, the use of zinc behenate could lead to bloating and high nitrogen values in sintered uranium dioxide under some conditions of processing, which have been identified.</span

The AP-1/NF-kappa B double inhibitor SP100030 can revert muscle wasting during experimental cancer cachexia

Moore-Carrasco, R. Department of Clinical Biochemistry and Immunohematology, Faculty of Health Sciences, Universidad de Talca, Casilla N° 747, Talca.Daily treatment of rats bearing the cachectic Yoshida AH-130 ascites hepatoma with the double inhibitor of NF-κB and AP-1 SP100030 at a dose of 1 mg/kg of body weight resulted in a clear amelioration of the cachectic effect, especially at the level of skeletal muscle. Thus, tumour-bearing rats treated with SP100030 showed a significant recovery in the weights of gastrocnemius, EDL, tibialis and cardiac muscles. In addition, treatment with the inhibitor affected both liver and kidney weights. The amelioration in muscle weight was accompanied by an increase in MyoD gene expression, the main transcription factor of muscle tissue involved in muscle differentiation, in gastrocnemius muscle. At the dose used in this study, SP100030 was an effective inhibitor of AP-1; however, the NF-κB transcription factor was not affected. The effects of the inhibitor seem to be at the level of proteolysis since lower total proteolytic rates were found when incubating isolated rat muscles in the presence of SP100030. The inhibitor influenced the gene expression of the ubiquitin-conjugating enzyme E214K in skeletal muscle of tumour-bearing rats; this enzyme seems to be the main regulator of the activity of the main proteolytic system involved during cancer cachexia, the ubiquitin-proteasome system. In conclusion, treatment of cachectic tumour-bearing rats with SP100030 results in an amelioration of the muscle wasting effect, suggesting that the AP-1 signaling cascade plays an important role in the signaling of muscle wasting associated with disease

Start-up Strategy for Continuous Bioreactors

Abstract - The start-up of continuous bioreactors is solved as an optimal control problem. The choice of the dilution rate as the control variable reduces the dimension of the system by making the use of the global balance equation unnecessary for the solution of the optimization problem. Therefore, for systems described by four or less mass balance equations, it is always possible to obtain an analytical expression for the singular arc as a function of only the state variables. The steady state conditions are shown to satisfy the singular arc expression and, based on this knowledge, a feeding strategy is proposed which leads the reactor from an initial state to the steady state of maximum productivit