Biomass cofiring at Seward Station

Sithe Energies, under a cooperative agreement with EPRI, the US Department of Energy, the Biomass Interest Group (BIG) and the Upgraded Coal Interest Group (UCIG), has developed a demonstration of cofiring biomass with pulverized coal at the Seward Generating Station on Boiler #12. This demonstration, constructed and tested by Foster Wheeler Development Corporation (FWDC) included construction of a facility to receive, screen, store and transport sawdust into a front-fired pulverized coal boiler. This facility has several distinctive features including the sawdust receiving system, the silo storage for processed biomass, and the injection system using the centerpipe of the coal burners. The biomass is prepared separately and transported separately from the coal. The wood waste is then injected into the center of the coal flame and burned there for optimum biofuel performance.

This demonstration, involving an extended period of cofiring testing, is based upon successful parametric tests conducted in December, 1996 and July, 1997. These tests documented the impact of cofiring, in the short term, on capacity, efficiency and emissions. Those results are now being evaluated over a long-term period. Additionally, operational and maintenance issues are being addressed with this demonstration and modifications have been made to improve the handling of the fuel. This paper describes the cofiring system, and reviews progress to date with the combustion tests.     

The impact of choline availability on muscle lipid metabolism

Consumption of choline-rich foods is essential to ensure membrane integrity, neurotransmission and genomic methylation pathways. Insufficient dietary choline supply can cause choline deficiency (CD) which manifests in the development of non-alcoholic fatty liver disease. There is very limited information regarding the effect of CD on non-hepatic tissues such as muscle. In this study, we induced CD in muscle cells and investigated the effect on choline transport, phosphatidylcholine (PC), fatty acid and triacylglycerol (TAG, fat) metabolism. Choline transport was stable across the plasma membrane of CD cells but significantly impaired in mitochondria. The main choline-transporter SLC44A1 was down-regulated by CD at the mRNA level, and SLC44A1 protein was reduced in total cell lysates and isolated mitochondria. CD significantly reduced PC synthesis but PC degradation was unaffected. PC from CD muscle was modified and contained more monounsaturated fatty acids at the expense of saturated fatty acids. Surprisingly, CD muscle cells also accumulated TAG in the form of large lipid droplets. Those droplets were formed from endogenous fatty acids and by slower TAG metabolism. This study established for the first time that choline availability affects muscle membrane lipid composition and intracellular lipid metabolism, and underlines the significance of choline-rich foods for proper muscle function.     

Nonlinear PI control of fed-batch processes for growth rate regulation

This paper deals with the regulation of the biomass specific growth rate, which is an important goal in many fed-batch fermentation processes. The proposed control system is based on the minimal model paradigm, requiring only biomass and volume measurement along with some bounds on the reaction rate. The controller has the structure of a partial state feed-back with adjustable gain. An integral-proportional control algorithm is designed to adjust this gain. It is inspired in concepts of invariant control and system immersion. First, a nonlinear integral action that makes invariant a goal manifold defined by a reference model dynamics is developed. Then, a proportional output error feed-back is incorporated to the control law with the aim of fastening convergence. Stability is investigated in detail using Lyapunov functions. To implement the control law, an estimation of the growth rate is required like any other PI-like controller. Because of its strong convergence properties, a sliding observer that requires the same process information as the controller is used for this task, although conventional continuous observers can alternatively be used provided they are fast enough to preserve stability. Simulation results showing the transient response and robustness features of the controller under nominal and perturbed scenarios are presented.     

Recurrent liver failure with severe rhabdomyolysis after liver transplantation for carbon tetrachloride intoxication

Acute liver failure due to intoxication is a rare indication for liver transplantation which a usually has a good prognosis. We herein report the case of a young male, who underwent orthotopic liver transplantation for acute liver failure due to carbon tetrachloride intoxication. Apart from hepatic and renal failure, the patient also developed severe rhabdomyolysis, which has not thus far been described as a toxic effect of this chemical agent. Despite forced hyperventilation, which is known to be the most effective means of eliminating the specifically lipophylic agent, as well as excessive plasma exchange following intravenous administration of fat emulsions, liver failure recurred when blood carbon tetrachloride concentrations were already at non-toxic levels. Retransplantation of the liver together with a kidney was only temporarily successful, since the patient died due to aspergillus sepsis. Based on this experience, we would recommend that whenever possible in patients with carbon tetrachloride intoxication, liver transplant should be delayed until most of the toxic agent has been eliminated in order to prevent fatal graft damage.     

Analysis of the radiobiology of ytterbium-169 and iodine-125 permanent brachytherapy implants

Recently, Yb-169 has been considered as a potential replacement for I-125 and Pd-103 in permanent implants. In spite of the uncertainties in the parameters necessary for an accurate radiobiological modelling, the linear quadratic model can be useful in the comparative evaluation of the radiotherapeutic merit of similar implants. In order to find out if a Yb-169 permanent implant can be made biologically 'equivalent' to an I-125 implant, we studied the dependence of local control on the tumour cell radiosensitivity and on the balance between the rate of tumour cell killing and tumour cell proliferation, for rapidly and slowly proliferating tumours. The extrapolated response dose (ERD) has been calculated for tumour and late reacting normal tissue for both types of implants and the possible biological restrictions due to the normal tissue tolerance have been discussed. Our theoretical analysis is consistent with the clinical results published for I-125 permanent implants in prostate tumours and meningiomas. It predicts that Yb-169, which has only recently been used in human tumours, can provide comparable tumour control for permanent implants in slowly proliferating tumours with an initial dose rate of 13 cGy h-1. Control might be extended to rapidly proliferating tumours by increasing the initial dose rate within a range consistent with an acceptable level of normal tissue late reaction.     

Quasi-Upward Planarity

An upward planar drawing of a directed graph (digraph) is a planar drawing such that all the edges are represented by curves monotonically increasing in the vertical direction. In this paper we introduce and study the concept of quasi-upward planarity. Quasi-upward planarity allows us to extend the upward planarity theory to a large class of digraphs including digraphs that also have directed cycles. First, we characterize the digraphs that have a quasi-upward planar drawing. Second, we give a polynomial time algorithm for computing ``optimal'' quasi-upward planar drawings within a given planar embedding. Further, we apply branch and bound techniques to the problem of computing optimal quasi-upward planar drawings, considering all possible planar embeddings. The paper also contains experimental results about the proposed techniques.     

Optimization of fully aligned bioactive electrospun fibers for “in vitro” nerve guidance

Complex architecture of natural tissues such as nerves requires the use of multifunctional scaffolds with peculiar topological and biochemical signals able to address cell behavior towards specific events at the cellular (microscale) and macromolecular (nanoscale) level. In this context, the electrospinning technique is useful to generate fiber assemblies having peculiar fiber diameters at the nanoscale and patterned by unidirectional ways, to facilitate neurite extension via contact guidance. Following a bio-mimetic approach, fully aligned polycaprolactone fibers blended with gelatin macromolecules have been fabricated as potential bioactive substrate for nerve regeneration. Morphological and topographic aspects of electrospun fibers assessed by SEM/AFM microscopy supported by image analyses elaboration allow estimating an increase of fully aligned fibers from 5 to 39 % as collector rotating rate increases from 1,000 to 3,000 rpm. We verify that fully alignment of fibers positively influences in vitro response of hMSC and PC-12 cells in neurogenic way. Immunostaining images show that the presence of topological defects, i.e., kinks—due to more frequent fiber crossing—in the case of randomly organized fiber assembly concurs to interfere with proper neurite outgrowth. On the contrary, fully aligned fibers without kinks offer a more efficient contact guidance to direct the orientation of nerve cells along the fibers respect to randomly organized ones, promoting a high elongation of neurites at 7 days and the formation of bipolar extensions. So, this confirms that the topological cue of fully alignment of fibers elicits a favorable environment for nerve regeneration.     

Familial lead poisoning from contaminated wine

Three members of a family were found be suffering from lead poisoning of nonindustrial origin, the causative agent being the home-produced wine left to ferment in a glazed earthenware vat. The clinical and neurophysiological features are discussed in the light of similar cases in the literature. Correct diagnosis and early treatment of nonindustrial lead polyneuropathy are often extremely difficult because of the elusive nature of the exposure.     

Colloidal macromolecular phenomena. Part II. Novel microcrystals of polymers

Colloidal microcrystalline cellulose, introduced in 1961, now is a successful commercial product with growing world-wide markets. This paper describes some major findings of our continuing research to convert fibrous or fiber-forming polymer systems into new colloidal microcrystalline physical states without going through a homogeneous molecular solution phase. Several novel microcrystalline colloidal products from the following natural and/or synthetic polymeric raw materials are described and compared for the first time: cellulose, amylose, collagen, nylon, and chrysotile mineral silicates. Many previously unpublished electron micrographs are presented. These products demonstrate a new and growing field of colloidal microcrystalline polymer science. They open up increasing opportunities for new polymer products based on the original concept, namely, the unhinging of polymer microcrystals from their natural or synthetic network and then by appropriate mechanical energy, releasing them as discrete, submicron colloidal polymer microcrystals dispersed in various liquid media to form unique gel systems, or reaggregated in the dry state to form porous colloidal particles.