Heatline and Energy-Flux-Vector Visualization of Natural Convection in a Porous Cavity Occupied by a Fluid with Temperature-Dependent Viscosity

Temperature-dependent viscosity effects in buoyancy driven flow in a porous-saturated enclosure is studied numerically, based on the general model of momentum transfer in a porous medium. The exponential form of the viscosity-temperature relation is applied. Both cases of viscosity increase and decrease versus temperature are considered. Application of the effective Rayleigh number concept and the reference temperature approach are investigated. Use of heatlines and the energy flux vectors are illustrated for a more comprehensive analysis of the problem

In vitro transfection of HeLa cells with temperature sensitive polycationic copolymers

Cataloged from PDF version of article.In this study, we investigated different types of polyethyleneimine (PEI) and their block copolymers with N-isopropylacrylamide (NIPA) as temperature-sensitive polycationic non-viral vectors for transfection of HeLa cells in cell culture media. First carboxyl-terminated poly(NIPA) was synthesized and then copolymerized with PEIs branched or linear and with two different molecular weights (2 and 25 kDa). Addition of PEI units to the poly(NIPA) chains increased the LCST values up to body temperature. Zeta potentials of the copolymers were significantly lower than the corresponding PEI homopolymers. A green fluorescent protein expressing plasmid was used as a model. Complexes of this plasmid both with PEIs and their copolymers were formed. The zeta potentials of these complexes were between -3.1 and +21.3. Higher values were observed for the complexes prepared with branched and higher molecular weight PEIs. Copolymerization caused a profound decrease in the positive charges. Particle sizes of the complexes were in the range of 190-1235 nm. Using high polymer/plasmid ratios caused aggregation. The smallest complexes were obtained with the copolymer prepared with branched PEI with 25-kDa molecular weight. Copolymers were able to squeeze plasmid DNA more at the body temperature. Cytotoxicity was observed with PEIs especially with the branched higher molecular weights. Copolymerization reduced the cytotoxicity. The best in vitro DNA uptake efficiency (70%) was achieved with the complex prepared with poly(NIPA)/PEI25B. However, poly(NIPA)/PEI25L was the most successful vector for an effective gene expression without any significant toxicity. © 2004 Elsevier B.V. All rights reserved

Numerical analysis of heat transfer in cooling of fish packages

The present work aims at finding the optimal finite difference scheme for the solution of problems involving pure heat transfer from the surface of solids suddenly exposed to a cooling environment. Fish samples in the form of infinite slab were considered, and a generalized mathematical model was constructed in dimensionless form. A more representative and accurate set of experimental data is chosen from the experimental work for comparison with the numerical results and evaluation of numerical schemes. In the analysis, a fully explicit finite difference scheme, an implicit finite difference scheme and different combination schemes with varying values of weighting factor are thoroughly studied. The characteristic dimension (half thickness of the slab) is divided into a number of divisions; n = 5, 10, 20, 30, 40, 50 and 100, respectively. All the possible options of the Fourier number increments are taken one by one to give the best convergence and minimal truncation error. The simplest explicit finite difference scheme with n = 10 and Fourier number increments one sixth of the square of the space division size appears to be highly reliable and accurate for such applications

Acupuncture Point Localization Varies Among Acupuncturists

Background: Studies assessing the point-specific effect of acupuncture or the characteristics of acupuncture points (APs) tend to yield inconclusive results. In order to identify a possible confounding factor, we aimed to examine the variability in AP localization by means of a survey. Material and Methods: Attendees of the 14th ICMART (International Council of Medical Acupuncture and Related Techniques) congress as well as DAGfA (German Medical Society of Acupuncture) lecturers and students were asked to locate and mark the APs LI 10 and TH 5 on a research assistant's arm. Identified points were transferred into a coordinate system, and the respective bivariate distribution function was calculated. Additionally, participants filled out a questionnaire about their acupuncture education and experience, the acupuncture style and point localization techniques used most frequently, and their estimation of the size of an AP. Results: The areas of the ellipses, theoretically containing 95% of AP localizations, varied between 44.49 and 5.18 cm(2). The largest distance between 2 identified points was 8.45 cm for LI 10 and 5.3 cm for TH 5. Apart from being trained at the same school, no other factor could be identified that determined the variability in AP localization. Conclusion: Our results indicate that congruity of AP localization among experienced acupuncturists might be low. Although there are some limitations to our results, this possible bias should be taken into account when conducting acupuncture trials and interpreting results of previous acupuncture studies

Chromatin profiling of cortical neurons identifies individual epigenetic signatures in schizophrenia

Both heritability and environment contribute to risk for schizophrenia. However, the molecular mechanisms of interactions between genetic and non-genetic factors remain unclear. Epigenetic regulation of neuronal genome may be a presumable mechanism in pathogenesis of schizophrenia. Here, we performed analysis of open chromatin landscape of gene promoters in prefrontal cortical (PFC) neurons from schizophrenic patients. We cataloged cell-type-based epigenetic signals of transcriptional start sites (TSS) marked by histone H3-K4 trimethylation (H3K4me3) across the genome in PFC from multiple schizophrenia subjects and age-matched control individuals. One of the top-ranked chromatin alterations was found in the major histocompatibility (MHC) locus on chromosome 6 highlighting the overlap between genetic and epigenetic risk factors in schizophrenia. The chromosome conformation capture (3C) analysis in human brain cells revealed the architecture of multipoint chromatin interactions between the schizophrenia-associated genetic and epigenetic polymorphic sites and distantly located HLA-DRB5 and BTNL2 genes. In addition, schizophrenia-specific chromatin modifications in neurons were particularly prominent for non-coding RNA genes, including an uncharacterized LINC01115 gene and recently identified BNRNA_052780. Notably, protein-coding genes with altered epigenetic state in schizophrenia are enriched for oxidative stress and cell motility pathways. Our results imply the rare individual epigenetic alterations in brain neurons are involved in the pathogenesis of schizophrenia

Structure-based design and synthesis of antiparasitic pyrrolopyrimidines targeting pteridine reductase 1

The treatment of Human African Trypanosomiasis remains a major unmet health need in sub-Saharan Africa. Approaches involving new molecular targets are important and pteridine reductase 1 (PTR1), an enzyme that reduces dihydrobiopterin in Trypanosoma spp. has been identified as a candidate target and it has been shown previously that substituted pyrrolo[2,3-d]pyrimidines are inhibitors of PTR1 from T. brucei (J. Med. Chem. 2010, 53, 221-229). In this study, 61 new pyrrolo[2,3-d]pyrimidines have been prepared, designed with input from new crystal structures of 23 of these compounds complexed with PTR1, and evaluated in screens for enzyme inhibitory activity against PTR1 and in vitro antitrypanosomal activity. 8 compounds were sufficiently active in both screens to take forward to in vivo evaluation. Thus although evidence for trypanocidal activity in a stage I disease model in mice was obtained, the compounds were too toxic to mice for further development

Ice formation modelling around the coils of an ice storage tank

This paper aims to develop a dynamic model of the charging process of a commercial ice-storage tank. Firstly, three different 1st order and 2nd order numerical schemes have been compared to solve the transport equation of the heat transfer fluid. Euler s method has finally been chosen as the mass flow rate can vary throughout the charging and it avoids the oscillations which are introduced by Lax-Wendroff s and MacCormack s method. Secondly, the heat transfer outside the coils is analyzed. The numerical complications involved in the creation of the first ice layer around the tubes are discussed and an electrical resistance model is introduced to avoid this problem. The model results have provided a very good agreement with experimental measurements of charging tests which have been performed on a CALMAC ICEBANK tank with a capacity of 172 kWh. The model helps to predict the final part of the latent heat transfer process, where the thermal power is decreased due to the contact between the ice layers around adjacent tubes of the tank.Biosca Taronger, J.; Payá Herrero, J.; López Navarro, A.; Corberán Salvador, JM. (2012). Ice formation modelling around the coils of an ice storage tank. Journal of Physics: Conference Series. 395:12133-12142. doi:10.1088/1742-6596/395/1/012133S1213312142395Zalba, B., Marı́n, J. M., Cabeza, L. F., & Mehling, H. (2003). Review on thermal energy storage with phase change: materials, heat transfer analysis and applications. Applied Thermal Engineering, 23(3), 251-283. doi:10.1016/s1359-4311(02)00192-8Gebhart, B., & Mollendorf, J. C. (1978). Buoyancy-induced flows in water under conditions in which density extrema may arise. Journal of Fluid Mechanics, 89(4), 673-707. doi:10.1017/s0022112078002803Chen, S.-L., & Lee, T.-S. (1998). A study of supercooling phenomenon and freezing probability of water inside horizontal cylinders. International Journal of Heat and Mass Transfer, 41(4-5), 769-783. doi:10.1016/s0017-9310(97)00134-

An influenza virus-inspired polymer system for the timed release of siRNA

Small interfering RNA silences specific genes by interfering with mRNA translation, and acts to modulate or inhibit specific biological pathways; a therapy that holds great promise in the cure of many diseases. However, the naked small interfering RNA is susceptible to degradation by plasma and tissue nucleases and due to its negative charge unable to cross the cell membrane. Here we report a new polymer carrier designed to mimic the influenza virus escape mechanism from the endosome, followed by a timed release of the small interfering RNA in the cytosol through a self-catalyzed polymer degradation process. Our polymer changes to a negatively charged and non-toxic polymer after the release of small interfering RNA, presenting potential for multiple repeat doses and long-term treatment of diseases