4,697 research outputs found

    Elastic properties of magnetosome chains

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    Laminar flow of two miscible fluids in a simple network

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    When a fluid comprised of multiple phases or constituents flows through a network, non-linear phenomena such as multiple stable equilibrium states and spontaneous oscillations can occur. Such behavior has been observed or predicted in a number of networks including the flow of blood through the microcirculation, the flow of picoliter droplets through microfluidic devices, the flow of magma through lava tubes, and two-phase flow in refrigeration systems. While the existence of non-linear phenomena in a network with many inter-connections containing fluids with complex rheology may seem unsurprising, this paper demonstrates that even simple networks containing Newtonian fluids in laminar flow can demonstrate multiple equilibria. The paper describes a theoretical and experimental investigation of the laminar flow of two miscible Newtonian fluids of different density and viscosity through a simple network. The fluids stratify due to gravity and remain as nearly distinct phases with some mixing occurring only by diffusion. This fluid system has the advantage that it is easily controlled and modeled, yet contains the key ingredients for network non-linearities. Experiments and 3D simulations are first used to explore how phases distribute at a single T-junction. Once the phase separation at a single junction is known, a network model is developed which predicts multiple equilibria in the simplest of networks. The existence of multiple stable equilibria is confirmed experimentally and a criteria for their existence is developed. The network results are generic and could be applied to or found in different physical systems

    Minimizing the Transaction Time Difference for NOMA-Based Mobile Edge Computing

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    Non orthogonal multiple access (NOMA) and mobile edge computing (MEC) are evolving as key enablers for fifth generation (5G) networks as this combination can provide high spectral efficiency, improved quality-of-service (QoS), and lower latency. This letter aims to minimize the transaction time difference of two NOMA paired users offloading data to MEC servers by optimizing their transmission powers and computational resources of severs using a successive convex approximation method. The equalization of transaction time for paired users reduces the wastage of both frequency and computational resources, and improves effective throughput of the system to 19% on average

    Indole-3-carbinol suppresses NF-κB activity and stimulates the p53 pathway in pre-B acute lymphoblastic leukemia cells

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    B cell precursor acute lymphoblastic leukemia (BCP-ALL) is the most common type of cancer in children. Dramatic improvements in primary therapy for childhood ALL have led to an overall cure rate of 80 , providing opportunities for innovative combined-modality strategies that would increase cure rates while reducing the toxic side effects of current intensive regimens. In this study, we report that indole-3-carbinol (I3C), a natural phytochemical found in cruciferous vegetables, had anti-leukemic properties in BCP-ALL NALM-6 cells. I3C induced cell growth inhibition by G1 cell cycle arrest and triggered apoptosis in a dose- and time-dependent manner. p53, p21, and Bax proteins showed increased expression after I3C treatment. Real-time PCR analysis of pro-apoptotic p53 target genes revealed up-regulation of PUMA, NOXA, and Apaf-1. I3C also suppressed constitutive nuclear factor-κB (NF-κB) activation and inhibited the protein expression of NF-kappa B-regulated antiapoptotic (IAP1, Bcl-xL, Bcl-2, XIAP) and proliferative (c-Myc) gene products. Coadministration of I3C with the topoisomerase II inhibitor, doxorubicin, potentiates cytotoxic effects compared with either agent alone. Apoptosis induction by the drug combination was associated with enhanced caspase-9 activation and PARP cleavage. Furthermore, I3C abolished doxorubicin-induced NF-κB activity as evidenced by decreased nuclear accumulation of p65, inhibition of IκBα phosphorylation and its degradation, and decreased NF-κB DNA-binding activity. Western blot analysis revealed that doxorubicin-induced Bcl-2 protein expression was inhibited by I3C. Overall, our results indicated that using nontoxic agents, such as I3C, in combination with anthracyclines might provide a new insight into the development of novel combination therapies in childhood BCP-ALL. © 2015, International Society of Oncology and BioMarkers (ISOBM)

    Allometric equations for determining volume and biomass of Acer monspessulanum L. subsp. cinerascens multi-stemmed trees

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    Due to the importance of Acer monspessulanum in Iranian mountain forests, a study was carried out to reliably estimate its woody biomass and growing volume via allometric equations. Four transects, five trees in each were chosen randomly. The characteristics of standing trees including: diameter at root collar, height, number of stems and crown width were measured, then trees were finally cut down. Trunk and branches were separated and weighed. Some disks were taken and moved to the laboratory to determine the dry/fresh weight ratio and wood specific gravity and subsequently to calculate the dry weight of trunk, branch as well as aboveground biomass. Linear regression analysis was conducted to create allometric equations. Results showed that there was a strong and significant correlation between volume/biomass of Acer monspessulanum and quantitative characteristics of standing trees. The most robust predictors of volume and aboveground biomass were found to be crown width and crown area (R^2 = 0.83) followed by equivalent diameter at root collar (R^2 = 0.81). The normalized rootmean-square error amounts were found to be under 20% for most models especially for predicting biomass of branches. Tree height combined with equivalent diameter at root collar (EDRC) explained 87% of the variations in volume and biomass, creating precise models. It is concluded that crown diameter and EDRC can predict biomass and the volume of A. monspessulanum as a multi-stemmed tree with high accuracy and precision

    High pressure induced precipitation in Al7075 alloy

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    Precipitate-matrix interactions govern the mechanical behavior of precipitate strengthened Al-based alloys. These alloys find a wide range of applications ranging from aerospace to automobile and naval industries due to their low cost and high strength to weight ratio. Structures made from Al-based alloys undergo complex loading conditions such as high strain rate impact, which involves high pressures. Here we use diamond anvil cells to study the behavior of Al-based Al7075 alloy under quasi-hydrostatic and non-hydrostatic pressure up to ~53 GPa. In situ X-ray diffraction (XRD) and pre- and post-compression transmission electron microscopy (TEM) imaging are used to analyze microstructural changes and estimate high pressure strength. We find a bulk modulus of 75.2 +- 1.9 GPa using quasi-hydrostatic pressure XRD measurements. XRD showed that non-hydrostatic pressure leads to a significant increase in defect density and peak broadening with pressure cycling. XRD mapping under non-hydrostatic pressure revealed that the region with the highest local pressure had the greatest increase in defect nucleation, whereas the region with the largest local pressure gradient underwent texturing and had larger grains. TEM analysis showed that pressure cycling led to the nucleation and growth of many precipitates. The significant increase in defect and precipitate density leads to an increase in strength for Al7075 alloy at high pressures.Comment: 15 pages, 5 figure

    Prevalence and genotyping identification of Cryptosporidium in adult ruminants in central Iran

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    Background Apicomplexan parasites of the genus Cryptosporidium infect a wide range of animal species as well as humans. Cryptosporidium spp. can cause life threatening diarrhea especially in young animals, children, immunocompromised patients and malnourished individuals. Asymptomatic cryptosporidial infections in animals can also occur, making these animals potential reservoirs of infection. Methods In the present study, a molecular survey of Cryptosporidium spp. in ruminants that were slaughtered for human consumption in Yazd Province, located in central Iran was conducted. Faeces were collected per-rectum from 484 animals including 192 cattle, 192 sheep and 100 goats. DNA was extracted from all samples and screened for Cryptosporidium by PCR amplification of the 18S rRNA gene. Positives were Sanger sequenced and further subtyped by sequence analysis of the 60 kDa glycoprotein (gp60) locus. Results In total, Cryptosporidium spp. were detected in 22 animals: C. andersoni and C. bovis in seven and two cattle faecal samples, respectively, C. ubiquitum in five sheep, and C. xiaoi in six sheep and two goat samples, respectively. To our knowledge, this study provides for the first time, molecular information concerning Cryptosporidium species infecting goats in Iran, and is also the first report of C. ubiquitum and C. xiaoi from ruminants in Iran. Conclusion The presence of potentially zoonotic species of Cryptosporidium in ruminants in this region may suggest that livestock could potentially contribute to human cryptosporidiosis, in particular among farmers and slaughterhouse workers, in the area. Further molecular studies on local human populations are required to more accurately understand the epidemiology and transmission dynamics of Cryptosporidium spp. in this region

    In vitro cell culture of amniotic fluid keratinocytes on amniotic membrane: the ideal tissue for repairing skin ulcers

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    OBJECTIVE: The amniotic fluid contains a large population of stem keratinocytes demonstrating minimal immunological rejection. Recent evidence suggests that stem cells from the amniotic fluid can be employed in the field of tissue engineering. In this work we identified precursors of the epithelial cells and expanded them in vitro.MATERIALS AND METHODS: After collecting samples of amniotic fluid and separating the cells via centrifugation, we seeded a portion of these cells in selection media to analyze the proliferation of epithelial cells. The stem cells precursors of keratinocytes were identified through specific markers. The expression of these markers was evaluated by immunofluorescence and reverse transcription polymerase chain reaction (PCR).RESULTS: The stem cells demonstrated 90% confluence, after undergoing proliferation in the selection medium for 15 days. Most of these cells tested positive for the keratinocyte-specific markers, but negative for stem cell specific markers. Of note, the identity of the keratinocytes was well established even after several subcultures.CONCLUSIONS: These results suggested that it is feasible to isolate and expand differentiated cell populations in the amniotic fluid from precursor cells. Furthermore, amniotic membranes can be utilized as scaffolds to grow keratinocytes, which can be potentially exploited in areas of skin ulcer transplantation and tissue engineering interventions