InterPack2003-35151 CONSTRUCTING A TRADE-OFF SURFACE FOR EXTRUDED HEAT SINKS EXPOSED TO FORCED CONVECTION

ABSTRACT In modern electronic components power densities are being increased continuously while the size and weight decrease. The effective dissipating of the heat produced by these components has now become a major design problem. Ordinary heat sinks often used to dissipate this heat, can in many instances no longer be used. Heat sinks therefore need to be designed and optimized for specific applications. The design of these heat sinks requires a difficult trade-off between conflicting parameters, e.g. mass or material cost, maximum temperature and pressure drop. Since these parameters influence one another, optimum designs require the use of mathematical optimization techniques. In the case of heat sinks, the thermal engineer would typically like to optimize the design simultaneously for three design parameters. The parameters are maximum heat sink temperature, mass and pressure drop. In the formulation of such an optimization problem, where more than one design criterion is important, the engineer currently has to assign the relative importance of each design criteria before starting the optimization. A better approach is to perform a range of optimization problems where the relative importance of the design criteria is varied systematically to obtain a trade-off surface of optimum heat sinks. This surface can then be used to investigate the influence of the different design criteria on each other and to select the optimum heat sink for a specific application. In this study such a trade-off surface is created for an extruded heat sink exposed to forced convection. The constructing of this surface is obtained by combining a semi-empirical simulation program, QFin 3.0 with the DYNAMIC-Q optimization method

The impact of neuron morphology on cortical network architecture

The neurons in the cerebral cortex are not randomly interconnected. This specificity in wiring can result from synapse formation mechanisms that connect neurons, depending on their electrical activity and genetically defined identity. Here, we report that the morphological properties of the neurons provide an additional prominent source by which wiring specificity emerges in cortical networks. This morphologically determined wiring specificity reflects similarities between the neurons’ axo-dendritic projections patterns, the packing density, and the cellular diversity of the neuropil. The higher these three factors are, the more recurrent is the topology of the network. Conversely, the lower these factors are, the more feedforward is the network’s topology. These principles predict the empirically observed occurrences of clusters of synapses, cell type-specific connectivity patterns, and nonrandom network motifs. Thus, we demonstrate that wiring specificity emerges in the cerebral cortex at subcellular, cellular, and network scales from the specific morphological properties of its neuronal constituents

former title: A theory for the emergence of neocortical network architecture

Developmental programs that guide neurons and their neurites into specific subvolumes of the mammalian neocortex give rise to lifelong constraints for the formation of synaptic connections. To what degree do these constraints affect cortical wiring diagrams? Here we introduce an inverse modeling approach to show how cortical networks would appear if they were solely due to the spatial distributions of neurons and neurites. We find that neurite packing density and morphological diversity will inevitably translate into non-random pairwise and higher-order connectivity statistics. More importantly, we show that these non-random wiring properties are not arbitrary, but instead reflect the specific structural organization of the underlying neuropil. Our predictions are consistent with the empirically observed wiring specificity from subcellular to network scales. Thus, independent from learning and genetically encoded wiring rules, many of the properties that define the neocortex’ characteristic network architecture may emerge as a result of neuron and neurite development

Gain of 20q11.21 in human pluripotent stem cells impairs TGF-β-dependent neuroectodermal commitment

Gain of 20q11.21 is one of the most common recurrent genomic aberrations in human pluripotent stem cells. Although it is known that overexpression of the antiapoptotic gene Bcl-xL confers a survival advantage to the abnormal cells, their differentiation capacity has not been fully investigated. RNA sequencing of mutant and control hESC lines, and a line transgenically overexpressing Bcl-xL, shows that overexpression of Bcl-xL is sufficient to cause most transcriptional changes induced by the gain of 20q11.21. Moreover, the differentially expressed genes in mutant and Bcl-xL overexpressing lines are enriched for genes involved in TGF-beta- and SMAD-mediated signaling, and neuron differentiation. Finally, we show that this altered signaling has a dramatic negative effect on neuroectodermal differentiation, while the cells maintain their ability to differentiate to mesendoderm derivatives. These findings stress the importance of thorough genetic testing of the lines before their use in research or the clinic

Nuclear medium modifications of the NN interaction via quasielastic (p⃗,p⃗′\vec p,\vec p ') and (p⃗,n⃗\vec{p},\vec{n}) scattering

Within the relativistic PWIA, spin observables have been recalculated for quasielastic ($\vec p,\vec p '$) and ($\vec p,\vec n$) reactions on a $^{40}$Ca target. The incident proton energy ranges from 135 to 300 MeV while the transferred momentum is kept fixed at 1.97 fm^{-1}. In the present calculations, new Horowitz-Love--Franey relativistic NN amplitudes have been generated in order to yield improved and more quantitative spin observable values than before. The sensitivities of the various spin observables to the NN interaction parameters, such as (1) the presence of the surrounding nuclear medium, (2) a pseudoscalar versus a pseudovector interaction term, and (3) exchange effects, point to spin observables which should preferably be measured at certain laboratory proton energies, in order to test current nuclear models. This study also shows that nuclear medium effects become more important at lower proton energies ($\leq$ 200 MeV). A comparison to the limited available data indicates that the relativistic parametrization of the NN scattering amplitudes in terms of only the five Fermi invariants (the SVPAT form) is questionable.Comment: 10 pages, 6 Postscript figures, uses psfig.sty and article.sty, submitted to Phys. Rev.

Polarization transfer observables for quasielastic proton-nucleus scattering in terms of a complete Lorentz invariant representation of the NN scattering matrix

For the calculation of polarization transfer observables for quasielastic scattering of protons on nuclei, a formalism in the context of the Relativistic Plane Wave Impulse Approximation is developed, in which the interaction matrix is expanded in terms of a complete set of 44 independent invariant amplitudes. A boson-exchange model is used to predict the 39 amplitudes which were omitted in the formerly used five-term parameterization(the SPVAT form) of the nucleon-nucleon scattering matrix. Use of the complete set of amplitudes eliminates the arbitrariness of the five-term representation.Comment: 29 pages, 2 figure

The development of a toxicity database using freshwater macroinvertebrates, and its application to the protection of South African water resources

There is a growing international trend towards the protection of freshwater resources from pollution by imposing instream guidelines and specified waste-discharge conditions. Current methods for devising freshwater quality guidelines are based on species sensitivity distributions (SSDs) that are used to identify pollutant concentrations, ensuring the protection of a modelled percentage of species (95% protection is a common goal). SSDs are derived from the toxicity test results of as many taxa as possible for each polluting substance. Waste-discharge licences can be for single substances, specified in terms of chemical concentrations, and derived in conjunction with instream guidelines; or for complex mixtures, specified in terms of toxic units. In both cases toxicity test results are the core data used. The emphasis on SSDs calls into question the species constituting the test populations. It is likely that SSDs based in part on the responses of local organisms will achieve superior site-specific ecological protection. Until the early 1990s, there were very few data on the tolerances of South African freshwater organisms. In the intervening decade, the Unilever Centre for Environmental Water Quality at Rhodes University has developed a toxicity database that, to date, records the responses of 21 South African freshwater taxa to 26 single-substance pollutants or mixtures. This is the most comprehensive database of South African toxicity responses available and has been used in the drawing up of methods and guidelines to protect water resources. This paper aims to make these data available and to describe applications of the data using selected case studies

Combined use of hyperthermia and radiation therapy for treating locally advanced cervical carcinoma (Withdrawn Paper, art. no. CD006377, 2010)

Hyperthermia is a type of cancer treatment in which body tissue is exposed to high temperatures to damage and kill cancer cells. It was introduced into clinical oncology practice several decades ago. Positive clinical results, mostly obtained in single institutions, resulted in clinical implementation albeit in a limited number of cancer centres worldwide. Because large scale randomised clinical trials (RCTs) are lacking, firm conclusions cannot be drawn regarding its definitive role as an adjunct to radiotherapy in the treatment of locally advanced cervical carcinoma (LACC).To assess whether adding hyperthermia to standard radiotherapy for LACC has an impact on (1) local tumour control, (2) survival and (3) treatment related morbidity.The electronic databases of the Cochrane Central Register of Controlled Trials (CENTRAL), (Issue 1, 2009) and Cochrane Gynaecological Cancer Groups Specialised Register, MEDLINE, EMBASE, online databases for trial registration, handsearching of journals and conference abstracts, reviews, reference lists, and contacts with experts were used to identify potentially eligible trials, published and unpublished until January 2009.RCTs comparing radiotherapy alone (RT) versus combined hyperthermia and radiotherapy (RHT) in patients with LACC.Between 1987 and 2009 the results of six RCTs were published, these were used for the current analysis.74% of patients had FIGO stage IIIB LACC. Treatment outcome was significantly better for patients receiving the combined treatment (Figures 1 to 3). The pooled data analysis yielded a significantly higher complete response rate (relative risk (RR) 0.56; 95% confidence interval (CI) 0.39 to 0.79; p <0.001), a significantly reduced local recurrence rate at 3 years (hazard ratio (HR) 0.48; 95% CI 0.37 to 0.63; p <0.001) and a significanly better overall survival (OS) at three years following the combined treatment with RHT(HR 0.67; 95% CI 0.45 to 0.99; p = 0.05). No significant difference was observed in treatment related acute (RR 0.99; 95% CI 0.30 to 3.31; p = 0.99) or late grade 3 to 4 toxicity (RR 1.01; CI 95% 0.44 to 2.30; p = 0.96) between both treatments.The limited number of patients available for analysis, methodological flaws and a significant over-representation of patients with FIGO stage IIIB prohibit drawing definite conclusions regarding the impact of adding hyperthermia to standard radiotherapy. However, available data do suggest that the addition of hyperthermia improves local tumour control and overall survival in patients with locally advanced cervical carcinoma without affecting treatment related grade 3 to 4 acute or late toxicity