Search

The existence of market clearing prices that support competitive equilibrium prices in electric power market with nonconvexities is addressed.

A method for determining the optimal combination of a group of assets for enabling combinatorial auctions for obtaining better allocations in biddings is presented.

The effect of discrete bid levels in oral auctions is examined. The choice of levels at which bids are allowed and a model simulation are likewise evaluated to determine several possible approaches. It is shown that revenue losses due to such discrete levels is conditioned by drawing private bid values from a uniform distribution. In addition, increasing the number of levels makes the bid-taker's projected loss asymptotically proportional to the square of the number of allowed bid levels.

Abstract: Pancreatic islet encapsulation within biosynthetic materials has had limited clinical success due to loss of islet function and cell death. As an alternative encapsulation material, a silk-based scaffold was developed to reestablish the islet microenvironment lost during cell isolation. Islets were encapsulated with ECM proteins (laminin and collagen IV) and mesenchymal stromal cells (MSCs), known to have immunomodulatory properties or to enhance islet cell graft survival and function. After a 7 day in vitro encapsulation, islets remained viable and maintained insulin secretion in response to glucose stimulation. Islets encapsulated with collagen IV, or laminin had increased insulin secretion at day 2 and day 7, respectively. A 3.2-fold synergistic improvement in islet insulin secretion was observed when islets were co-encapsulated with MSCs and ECM proteins. Furthermore, encapsulated islets had increased gene expression of functional genes; insulin I, insulin II, glucagon, somatostatin, and PDX-1, and lower expression of the de-differentiation genes cytokeratin 19 and vimentin compared to non-encapsulated cells. This work demonstrates that encapsulation in silk with both MSCs and ECM proteins enhances islet function and with further development may have potential as a suitable platform for islet delivery in vivo. [Copyright &y& Elsevier]

Abstract: Background: Micronutrient-responsive cerebral dysfunction (MRCD) is known to occur after gastric restrictive and malabsorptive weight loss surgery. Wernicke''s encephalopathy (WE) is often considered the etiology, but many cases without thiamine deficiency have been reported. It is important to recognize that other micronutrient-responsive cerebral dysfunctions exist in this high-risk group. We evaluated the published data for evidence of MRCD after gastric restrictive and malabsorptive weight loss surgery. Methods: A search of PubMed and OVID was conducted to identify all published cases of cerebral dysfunction after gastric restrictive and malabsorptive weight loss surgery. The cases were compared using the presenting clinical signs and symptoms and objective confirmatory findings. The cases were stratified according to the type of surgery and the known or suspected etiology of the cerebral dysfunction. Results: A total of 65 cases of cerebral dysfunction after gastric restrictive and/or malabsorptive weight loss surgery were identified. A careful analysis of all cases revealed that 48 (73.8%) could be attributed to WE. The remaining cases represented a subset with a pattern of cerebral dysfunction incompatible with WE. This condition most likely resulted from multiple micronutrient deficiencies (MRCD). Patients with MRCD were more likely to have undergone a malabsorptive surgical procedure (P = .001), to present with dysarthria (P <.001), and less likely to have ophthalmoplegia (P <.001) or nystagmus (P = .02) compared with those with WE. Conclusion: Current evidence supports the identification of MRCD after malabsorptive weight loss surgery that is not compatible with WE. Clinicians should be aware of this clinical entity and be prepared to treat it appropriately. [Copyright &y& Elsevier]

There has been much thought given to ways that might fix deregulated markets, and there is still no agreement on the correct fix. The once-pseudonymous Price C. Watts thinks it is time to think seriously about ways to reregulate where deregulation has failed. Here are some steps to get us there. [Copyright &y& Elsevier]

Abstract: Significant deficiencies of both fat- and water-soluble vitamins have been reported to occur after malabsorptive bariatric surgery. However, despite the potential for neurologic manifestations of such deficiencies, few cases of central neurologic dysfunction have been reported. Our group previously reported reversible neurologic dysfunction as an unusual manifestation of vitamin deficiency in a postjejunoileostomy patient. We report on a second case of reversible neurologic dysfunction associated with severe, prolonged vitamin deficiency many years after jejunoileostomy. Neurologic function returned to normal with vitamin repletion. Patients who have undergone malabsorptive surgery are at risk of late metabolic complications and should be closely monitored. [Copyright &y& Elsevier]

Abstract: Previously, it was suggested that feedback connections from higher- to lower-level areas carry predictions of lower-level neural activities, whereas feedforward connections carry the residual error between the predictions and the actual lower-level activities [Rao, R.P.N., Ballard, D.H., 1999. Nature Neuroscience 2, 79–87.]. A computational model implementing the hypothesis learned simple cell receptive fields when exposed to natural images. Here, we use predictive feedback to explain tuning properties in medial superior temporal area (MST). We implement the hypothesis using a new, biologically plausible, algorithm based on matching pursuit, which retains all the features of the previous implementation, including its ability to efficiently encode input. When presented with natural images, the model developed receptive field properties as found in primary visual cortex. In addition, when exposed to visual motion input resulting from movements through space, the model learned receptive field properties resembling those in MST. These results corroborate the idea that predictive feedback is a general principle used by the visual system to efficiently encode natural input. [Copyright &y& Elsevier]

Abstract: We studied the kinetics of hepatic uptake of liposomes during serum-free recirculating perfusion of rat livers. Liposomes consisted of phosphatidylcholine, cholesterol and phosphatidylserine in a 6:4:0 or a 3:4:3 molar ratio and were radiolabelled with [3H]cholesteryl oleyl ether. The negatively charged liposomes were taken up to a 10-fold higher extent than the neutral ones. Hepatic uptake of fluorescently labelled liposomes was examined by fluorescence microscopy. The neutral liposomes displayed a typical Kupffer cell distribution pattern, in addition to weak diffuse staining of the parenchyma, while the negatively charged liposomes showed a characteristic sinusoidal lining pattern, consistent with an endothelial localization. In addition, scattered Kupffer cell staining was distinguished as well as diffuse parenchymal fluorescence. The mainly endothelial localisation of the negatively charged liposomes was confirmed by determining radioactivity in endothelial and Kupffer cells isolated following a 1-h perfusion. Perfusion in the presence of polyinosinic acid, an inhibitor of scavenger receptor activity, reduced the rate of uptake of the negatively charged liposomes twofold, indicating the involvement of this receptor in the elimination mechanism. These results are compatible with earlier in vitro studies on liposome uptake by isolated endothelial cells and Kupffer cells, which showed that in the absence of serum also endothelial cells in situ are able to take up massive amounts of negatively charged liposomes. The present results emphasize that the high in vitro endothelial cell uptake in the absence of serum from earlier observations was not an artifact induced by the cell isolation procedure. [Copyright &y& Elsevier]

A simple mathematical model is described which provides estimation procedures for comparing college-level, distance teaching costs with on-campus operations. It distinguishes content distribution from interaction costs, where cost equals work time required of teachers. In ordinary classroom teaching, content distribution costs rise with student throughput in quantal units that depend on class size. Interaction costs rise only moderately with the number of students. In asynchronous distance courses with asynchronous interactions with students, content distribution expenses are independent of throughput, but the costs of instructive interactions rise sharply with the number of students. As a consequence, distance teaching costs can become high when interactive procedures are very time-demanding. High-quality institutions, that rely heavily on tuition income, will be more likely to survive in the competitive world of distance education, if scientific research and technological developments succeed in making the interactive components of instruction less effortful for teachers and in making content development more efficient. [Copyright &y& Elsevier]

In auction spot markets, suppliers with a relatively small percentage of total capacity have been able to exercise extreme market power during high-demand periods. One remedy is a system that prevents suppliers with the capacity and incentive for exercising such unilateral power from having any role in setting the market-clearing price. [Copyright &y& Elsevier]

Presents an analysis of electricity auctions and how daily repetition of auctions can have a major effect on how they proceed. Models of repeated games; Literature on repeated auctions; Design issues for frequently repeated electricity auctions.

Discusses several views on using auctions to value stranded assets by electric utilities in the United States. Proposals of Jon Lesser and Malcolm Ainspan; Valuation of the bidders on the assets; Impact of information on bidding strategy; Interaction with environmental law; Inaccuracy of Lesser and Ainspan on bidding.

To determine the influence of weight loss with or without adequate calcium intake on bone turnover and density, we examined the influence of dietary restriction of calcium or energy on body weight (BW), bone mineral density (BMD) and bone turnover in both younger (3 mo) and older (10 mo) female rats (n = 66). Diets were designed to allow feeding at two levels of calcium intake (normal = 78 mg/d and low = 15 mg/d) and two levels of energy intake (normal and 40% restriction) while keeping the intake of protein, fat, fiber, vitamins and other minerals equal between groups. Thus rats received either a control diet (CNTL), a diet restricted in calcium, energy or both for 9 wk. Energy restriction reduced BW 5-21% (P < 0.01) and elevated bone formation 10-20% (P < 0.05) in both age groups. Bone resorption was 20-40% above CNTL values (P < 0.05), in rats fed all three restricted diets. In younger rats, BMD increased over time in all groups (P < 0.05), but final BMD was lower in calcium restricted groups compared with CNTL (P < 0.01). In older rats, CNTL had a significantly greater final BMD (P < 0.05) than diet-restricted groups. These data indicate that, in both younger and older rats, dietary restriction of calcium or energy results in an elevated rate of bone turnover. BMD is compromised by calcium restriction in both younger and older rats, whereas only older rats were negatively influenced by dietary energy restriction. Thus the present study indicates a detrimental effect of low-energy diets, as well as inadequate calcium intake, on bone density in mature rats. [ABSTRACT FROM AUTHOR]

Aeromonas veronii , a bacterium found in freshwater, is an unusual pathogen in healthy patients. We present a case report of a rare, aggressive subtype in a young, immunocompetent individual. History of injury in an aquatic environment and culture data are key for identification of the causal agent and should dictate acute clinical management and antibiotic therapy. Coverage should include cephalosporins, quinolones, or sulfas if Aeromonas is suspected, and adjusted depending on culture and sensitivity. Early surgical exploration, incision and drainage, and appropriate antimicrobial therapy are the cornerstones for successful treatment of these aggressive, sometimes life-threatening infections. [ABSTRACT FROM AUTHOR]

[Display omitted] • The higher the fat content, the more odorants accumulated in the fat phase. • Odorant distribution in the fat and particle phase was related to their polarity. • Amorphous sucrose was found to adsorb acetic acid from the cocoa butter phase. • Acetic acid amount increased in model systems with crystalline sugar/ cocoa solids. Understanding mechanisms inside the conche is inevitable for targeted conching. Therefore, distribution and transition of aroma-active volatiles (acetic acid, benzaldehyde, (R,S)-(±)-linalool, 2,3,5,6-tetramethylpyrazine, 2-phenylethanol, and 2-phenylethyl acetate) between the different components of dark chocolate (cocoa butter, cocoa particles, sugar particles) were studied. Different model systems were designed and aroma-analytically analyzed by stable isotope dilution analysis. Diffusion mechanisms of selected aroma-active compounds within the chocolate mass depended on their physico-chemical properties and the mass composition, such as fat content and crystallization state of the sugar particles. The compound accumulation in the fat phase increased with decreasing compound polarity and increasing fat content. In the presence of cocoa particles, a 1.5-fold fat content resulted in a 1.6-fold higher proportional acetic acid concentration in the fat phase. Further, total acetic acid concentrations raised in all model systems containing crystalline sugar or cocoa particles (by 13.8–56.9 %), indicating the formation of free acetic acid. [ABSTRACT FROM AUTHOR]

Studies estimate that the incidence of genital anomalies could be as high as 1 in 300 births. While it is rare for an infant to present with truly ambiguous genitalia, it is plausible that the pediatric nurse will encounter a patient with disorders of sexual development in his or her career. Cases of disorders of sexual development are challenging due to complexities of diagnosis, gender assignment, uncertain outcomes, treatment options, and psychosocial stressors. This article discusses the evaluation and management of children with disorders of sexual development and the nurse's role as child advocate and family educator. [ABSTRACT FROM AUTHOR]

Significant loss of preservative was observed during filling of drug products during filling line stops. This study evaluated the losses of three commonly used preservatives in protein drugs, i.e. benzyl alcohol, phenol, and m -cresol. Concentration losses during static incubation were quantified and interpreted with regard to the potential driving forces for the underlying sorption, diffusion, and desorption steps. Partitioning from the solution into the silicone polymer was identified as the most decisive parameter for the extent of preservative loss. Additionally, the influence of tubing inner diameter, starting concentration as well as silicone tubing type was evaluated. Theoretical calculations assuming equilibrium between solution and tubing inner surface and one-directional diffusion following Fick’s first law were used to approximate experimental data. Since significant losses were found already after few minutes, adequate measures must be taken to avoid deviations during filling of preservative-containing protein solutions that may impact product quality or antimicrobial efficacy. As a possible alternative to the highly permeable silicone tubing, a specific make of fluoropolymer tubing was identified being suitable for peristaltic pumps and not showing any preservative losses. [ABSTRACT FROM AUTHOR]

Abstract: The efficient coding hypothesis posits that sensory systems are adapted to the regularities of their signal input so as to reduce redundancy in the resulting representations. It is therefore important to characterize the regularities of natural signals to gain insight into the processing of natural stimuli. While measurements of statistical regularity in vision have focused on photographic images of natural environments it has been much less investigated, how the specific imaging process embodied by the organism’s eye induces statistical dependencies on the natural input to the visual system. This has allowed using the convenient assumption that natural image data are homogeneous across the visual field. Here we give up on this assumption and show how the imaging process in a human model eye influences the local statistics of the natural input to the visual system across the entire visual field. Artificial scenes with three-dimensional edge elements were generated and the influence of the imaging projection onto the back of a spherical model eye were quantified. These distributions show a strong radial influence of the imaging process on the resulting edge statistics with increasing eccentricity from the model fovea. This influence is further quantified through computation of the second order intensity statistics as a function of eccentricity from the center of projection using samples from the dead leaves image model. Using data from a naturalistic virtual environment, which allows generation of correctly projected images onto the model eye across the entire field of view, we quantified the second order dependencies as function of the position in the visual field using a new generalized parameterization of the power spectra. Finally, we compared this analysis with a commonly used natural image database, the van Hateren database, and show good agreement within the small field of view available in these photographic images. We conclude by providing a detailed quantitative analysis of the second order statistical dependencies of the natural input to the visual system across the visual field and demonstrating the importance of considering the influence of the sensory system on the statistical regularities of the input to the visual system. [Copyright &y& Elsevier]