Spin relaxation in a germanium nanowire

We report experimental study of spin transport in nanowirespin valve structures consisting of three layers—cobalt, germanium, and nickel. The spin diffusion length in the Ge is estimated to be about 400nm at 1.9K and the corresponding spin relaxation time is about 4ns. At 100K, the spin diffusion length drops to 180nm and the relaxation time is about 0.81ns. These short relaxation times, which depend weakly on temperature, are caused by strong surface roughness scattering that causes rapid spin relaxation via the Elliott-Yafet mode [Elliott, Phys. Rev.96, 266 (1954)]

Hematopoietic progenitors express embryonic stem cell and germ layer genes

Cell therapy for tissue regeneration requires cells with high self-renewal potential and with the capacity to differentiate into multiple differentiated cell lineages, like embryonic stem cells (ESCs) and adult somatic cells induced to pluripotency (iPSCs) by genetic manipulation. Here we report that normal adult mammalian bone marrow contains cells, expressing the cell surface antigen CD34, that naturally express the genes that are characteristic of ESCs and that are required to generate iPSCs. In addition, these CD34+ cells spontaneously express, without genetic manipulation, genes characteristic of the three embryonic germ layers ectoderm, mesoderm and endoderm. In addition to the neural lineage genes we previously reported in these CD34+ cells, we found that they express genes of the mesodermal cardiac muscle lineage and of the endodermal pancreatic lineage as well as intestinal lineage genes. Thus, these normal cells in the adult spontaneously exhibit the characteristics of embryonic-like stem cells

Simulation analysis of blood flow and selective drug particle delivery to the targeted tumors cerebral artery-tissue region

Brain is the most intricate organ of human body. The development of new therapeutic techniques for Brain tumor diseases is a difficult task, yet these treatments are not effective for almost all the brain diseases. Presence of Blood Brain Barrier (BBB) is the main challenge in development of drugs to treat brain diseases in most of the cases. Among several brain diseases, brain tumors often have poor prognosis, which depends and changes according to the type of the tumor. In this study a three-dimensional computational simulation model for analyzing multifunctional drug distribution through the cerebral artery and adjacent tissue region with tumor is considered. The simulation model includes solution of governing equations of blood flow dynamics based on Navier-Stokes equations and mass species transport based on Lagrangian particle flow dynamics in the artery network and capillaries of the adjacent tissue-tumor regions subjected to typical cardiac cycle. The main objective is to evaluate the effective delivery of selective drug particles to the targeted tumor region with variation in the selective multifunctional particle types and sizes

Intelli MAC Layer Protocol for Cognitive Radio Networks

According to the FCC (Federal Communications Commission) [11], the utilization of the spectrum has been increasing rapidly over a wide range of frequency bands. There are various reasons that cause this dynamic growth. One reason is increase in network capacity. Another reason is increase in mobile services needed to carry over the spectrum. In order to overcome the shortage of spectrum due to increased usage, Cognitive Radio (CR) technology has been introduced. Cognitive Radios can utilize idle spectrum holes that are not occupied by the Primary Users (PUs) for performing temporary wireless communication tasks. PUs are licensed users which own and have access to certain spectrum bands. Challenging issues that need to be addressed by the CRs are spectrum sensing, spectrum sharing, spectrum management and spectrum mobility. The main contribution of this thesis is to design a new MAC layer protocol in order to determine the behavior of Secondary Users (SUs) based on PUs transmission history while taking into account both PUs and SUs. SUs are non licensed users which transmit only on those spectrum bands that are unutilized by the PUs. SUs usually observe the activity of PUs on spectrum bands. This new protocol allows the CR nodes to sense, share and manage access of the nodes to the spectrum. This protocol prevents any damage caused by SUs to the PUs transmission. Also, the new MAC protocol will negotiate the spectrum by assisting the CRs to identify the underutilized spectrum based on channel conditions such as channel throughput, channel data rate, channel score, channel utilization and packet error rate (PER). The Intelli MAC layer protocol measures transmission time among PUs and reduces channel sensing time for SUs. For managing the entire network, this protocol uses the concept of Harmonious Channel (HC). This protocol uses multiple half duplex transceivers for carrying data communication among users

AN OPENDSS FRAMEWORK OF AN 100% PV PENETRATION MICROGRID

The purpose of this thesis is to understand how the microgrid with 100% PV penetration reacts to multiple scenarios. This is done by creating a framework or test model in OPENDSS and ETAP. The stability is tested by creating a test scenario that tests the safety equipment in place and also provides insight in to problems that might arise in the near future as Renewable energy penetration reaches new levels. The fast approaching problem of electric vehicles becoming increasingly popular is also investigated. The methodology is to have a simulation model mimicking the actual SD village. Then the results from the simulation model are compared with that of the actual test values. And also the performance of the microgrid under multiple scenarios can be found out