Emission of whistler waves from an ionospheric tether

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 121-122).In this thesis, we analyze how electromagnetic waves propagate in ionosphere around the earth which is magnetized plasma. We calculate the electromagnetic wave field made by a dipole antenna at an arbitrary observation point far from the antenna using the Stationary Phase Method. With this wave field, wave energy flux is calculated, and by integrating this wave energy flux on the sphere around the antenna, the radiation resistance of this antenna is computed. We compare the results with some past analytical and experimental works. We also analyze the wave propagation characteristics. The wave propagation ways are different for different wave frequencies. We precisely analyze this different wave propagation ways by analyzing the group velocity and k surface of the wave. There are intense radiation directions. We discuss the nature of these intense radiation directions and compare the characteristics with the past works. There are spatial oscillations of wave fields and wave energy flux. We also discuss the reason of this oscillation and compare with the past works.by Yu Takiguchi.S.M

β-tricalcium Phosphate/Collagen Composites Improve Bone Regeneration in Rat Calvarial Bone Defects

Autogenous bone grafting is the most widely accepted approach for repairing bone defects, yet limitations in the donor site and subsequent morbidity associated with harvesting bone from other sites remain as major concerns. Consequently, synthetic bone-like biocomposites have drawn much attention as a novel regenerative strategy. This study evaluated the regenerative properties of our prototype β-TCP/collagen composite in an animal model. We prepared the original β-TCP/collagen composite by mixing an acidic atelocollagen gel and alkaline colloidal β-TCP, and Raman microspectroscopy of the composite revealed the typical spectral features attributable to bone after manual mixing. We then transplanted either the composite or collagen alone into a full-thickness trephine defect made in the calvarial bone of rats. At 8 weeks after implantation, the elastic modulus of regenerated bone that developed alongside the composite was comparable to that of native cortical bone. Decalcification and processing of the calvarial bones for histological observation revealed that the β-TCP/collagen enabled better bone regenerative properties compared to collagen alone. Our newly developed β-TCP/collagen composite imitates the structural properties of bone, and thus provides a potentially useful scaffold material to support the mechanical integrity of regenerated bone

Image Annotation with Concept Level Feature Using PLSA+CCA

Abstract. Digital cameras have made it much easier to take photos, but organizing those photos is difficult. As a result, many people have thousands of photos in some miscellaneous folder on their hard disk . If computer can understand and manage these photos for us, we can save time. Also it will be useful for indexing and searching the web images. In this paper we propose an image annotation system with concept level search using PLSA+CCA,which generates the appropriate keywords to annotate the query image using large-scale image database

IAPP aggregation and cellular toxicity are inhibited by 1,2,3,4,6-penta-O-galloyl-β-D-glucose

The polyphenol, 1,2,3,4,6-penta-O-galloyl-β-D-glucose (PGG) has been found to exhibit a host of positive pharmacologic activities, including anti-cancer and anti-diabetic. Little is known about the mode of action of PGG in yielding these positive activities. We show here that PGG is a potent inhibitor of IAPP (islet amyloid polypeptide, amylin) aggregation. Preventing the initial aggregation event of IAPP is one strategy for slowing, and possibly preventing, the toxic effects of IAPP oligomeric intermediates. Equal molar ratios of PGG to IAPP substantially reduced the ability of IAPP to bind thioflavin T. Atomic force microscopy revealed that PGG prevented amyloid-based fiber formation under rigorous conditions conducive to forming IAPP aggregates. PGG was also found to protect PC12 rat cells from toxic IAPP. PGG was compared to the known amyloid inhibitors (and structural relatives); tannic acid and gallic acid. In every test, PGG was far superior to tannic and gallic acids at inhibiting amyloid aggregation. These results indicate that PGG is a potent inhibitor of IAPP amyloid aggregation and a potential lead molecule for development of an amyloid inhibiting therapeutic

Development and evaluation of a master-slave robot system for single-incision laparoscopic surgery

Single-incision laparoscopic surgery (SILS) brings cosmetic benefits for patients, but this procedure is more difficult than laparoscopic surgery. In order to reduce surgeons' burden, we have developed a master-slave robot system which can provide robot-assisted SILS as if it were performing conventional laparoscopic surgery and confirmed the feasibility of our proposed system. The proposed system is composed of an input device (master side), a surgical robot system (slave side), and a control PC. To perform SILS in the same style as regular laparoscopic surgery, input instruments are inserted into multiple incisions, and the tip position and pose of the left-sided (right-sided) robotic instrument on the slave side follow those of the right-sided (left-sided) input instruments on the master side by means of a control command from the PC. To validate the proposed system, we defined four operating conditions and conducted simulation experiments and physical experiments with surgeons under these conditions, then compared the results. In the simulation experiments, we found learning effects between trials (P = 0.00013 0.1), and the task time of our system was significantly shorter than the simulated SILS (P = 0.011 < 0.05). In the physical experiments, our system performed SILS more easily, efficiently, and intuitively than the other operating conditions. Our proposed system enabled the surgeons to perform SILS as if they were operating conventionally with laparoscopic techniques.ArticleINTERNATIONAL JOURNAL OF COMPUTER ASSISTED RADIOLOGY AND SURGERY. 7(2):289-296 (2012)journal articl

Usefulness of brain natriuretic peptide for predicting left atrial appendage thrombus in patients with unanticoagulated nonvalvular persistent atrial fibrillation

AbstractBackgroundThe CHADS2 scoring system is simple and widely accepted for predicting thromboembolism in patients with nonvalvular atrial fibrillation (NVAF). Although congestive heart failure (CHF) is a component of the CHADS2 score, the definition of CHF remains unclear. We previously reported that the presence of CHF was a strong predictor of left atrial appendage (LAA) thrombus. Therefore, the present study aimed to elucidate the relationship between LAA thrombus and the brain natriuretic peptide (BNP) level in patients with unanticoagulated NVAF.MethodsThe study included 524 consecutive patients with NVAF who had undergone transesophageal echocardiography to detect intracardiac thrombus before cardioversion between January 2006 and December 2008, at Hiroshima City Asa Hospital. The exclusion criteria were as follows: paroxysmal atrial fibrillation, unknown BNP levels, prothrombin time international normalized ratio ≥2.0, and hospitalization for systemic thromboembolism.ResultsReceiver operating characteristic analysis yielded optimal plasma BNP cut-off levels of 157.1pg/mL (area under the curve, 0.91; p<0.01) and 251.2pg/mL (area under the curve, 0.70; p<0.01) for identifying CHF and detecting LAA thrombus, respectively. Multivariate analyses demonstrated that a BNP level >251.2pg/mL was an independent predictor of LAA thrombus (odds ratio, 3.51; 95% confidence interval, 1.08–10.7; p=0.046).ConclusionsIn patients with unanticoagulated NVAF, a BNP level >251.2pg/mL may be helpful for predicting the incidence of LAA thrombus and may be used as a surrogate marker of CHF. The BNP level is clinically useful for the risk stratification of systemic thromboembolism in patients with unanticoagulated NVAF

Switched reluctance motor design for electric vehicles based on harmonics and back EMF analysis

Permanent magnet synchronous motors are widely accepted in automotive applications. The high torque density, high rotational speed with maximum efficiency in electric vehicle applications is technically challenging for motor design. However, these machines are expensive and difficult to work at high-temperature harsh environment due to permanent magnets demagnetisation features. Alternatively, switched reluctance motors can provide similar output characteristics and a wider speed. Thus these are considered to be more fault tolerant and more reliable. This study proposes a 20 kW, three-phase switched reluctance motor and analyse its overall performance and harmonic contents. The study is conducted by optimising the slot filling factor, excitation voltage and switching sequence of an asymmetrical half bridge converter. A finite element model is used to predict the core and copper losses and other influencing parameters. Simulation results are presented and analysed the effectiveness of the proposed switched reluctance motor (SRM)

CCR5AS lncRNA variation differentially regulates CCR5, influencing HIV disease outcome.

Multiple genome-wide studies have identified associations between outcome of human immunodeficiency virus (HIV) infection and polymorphisms in and around the gene encoding the HIV co-receptor CCR5, but the functional basis for the strongest of these associations, rs1015164A/G, is unknown. We found that rs1015164 marks variation in an activating transcription factor 1 binding site that controls expression of the antisense long noncoding RNA (lncRNA) CCR5AS. Knockdown or enhancement of CCR5AS expression resulted in a corresponding change in CCR5 expression on CD4+ T cells. CCR5AS interfered with interactions between the RNA-binding protein Raly and the CCR5 3' untranslated region, protecting CCR5 messenger RNA from Raly-mediated degradation. Reduction in CCR5 expression through inhibition of CCR5AS diminished infection of CD4+ T cells with CCR5-tropic HIV in vitro. These data represent a rare determination of the functional importance of a genome-wide disease association where expression of a lncRNA affects HIV infection and disease progression