On the Nature of Propagating Intensity Disturbances in Polar Plumes during the 2017 Total Solar Eclipse

The propagating intensity disturbances (PIDs) in plumes are still poorly understood and their identity (magnetoacoustic waves or flows) remains an open question. We investigate PIDs in five plumes located in the northern polar coronal hole observed during the 2017 total solar eclipse. Three plumes are associated with coronal bright points, jets and macrospicules at their base (active plumes) and the other two plumes are not (quiet plumes). The electron temperature at the base of the plumes is obtained from the filter ratio of images taken with the X-ray Telescope on board Hinode and the passband ratio around 400 nm from an eclipse instrument, the Diagnostic Coronagraph Experiment (DICE). The phase speed (v_r), frequency (omega), and wavenumber (k) of the PIDs in the plumes are obtained by applying a Fourier transformation to the space-time (r-t plane) plots in images taken with the Atmospheric Imaging Assembly (AIA) in three different wavelength channels (171 A, 193 A, and 211 A). We found that the PIDs in the higher temperature AIA channels, 193 and 211 A, are faster than that of the cooler AIA 171 A channel. This tendency is more significant for the active plumes than the quiet ones. The observed speed ratio (~1.3) between the AIA 171 and 193 A channels is similar to the theoretical value (1.25) of a slow magnetoacoustic wave. Our results support the idea that PIDs in plumes represent a superposition of slow magnetoacoustic waves and plasma outflows that consist of dense cool flows and hot coronal jets.Comment: 18 pages, 8 figures, accepted for publication in Ap

Design of a low power variable length decoder for MPEG-2 system

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (p. 81-82).by SeongHwan Cho.M.S

Energy efficient radio frequency communication systems for wireless microsensors

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.Includes bibliographical references (p. 131-137).Emerging distributed wireless microsensor networks will enable the reliable and fault tolerant monitoring of the environment. Microsensors are required to operate for years from a small energy source while maintaining a reliable communication link to the base station. In order to reduce the energy consumption of the sensor network, two aspects of the system design hierarchy are explored: design of the communication protocol and implementation of the RF transmitter. In the first part of the thesis, energy efficient communication protocols for a coordinated static sensor network are proposed. A detailed communication energy model, obtained from measurements, is introduced that incorporates the non-ideal behavior of the physical layer electronics. This includes the frequency errors and start-up energy costs of the radio, which dominate energy consumption for short packet, low duty cycle communication. Using this model, various communication protocols are proposed from an energy perspective, such as MAC protocols, bandwidth allocation methods and modulation schemes. In the second part of the thesis, design methodologies for an energy efficient transmitter are presented for a low power, fast start-up and high data rate radio.(cont.) The transmitter is based on a [Epsilon]-[Delta] fractional-N synthesizer that exploits trade-offs between the analog and digital components to reduce the power consumption. The transmitter employs closed loop direct VCO modulation for high data rate FSK modulation and a variable loop bandwidth technique to achieve fast start-up time. A prototype transmitter that demonstrates these techniques is implemented using 0.25[mu]m CMOS. The test chip achieves 20[mu]s is start-up time with an effective data rate of 2.5Mbps while consuming 22mW.by SeongHwan Cho.Ph.D

Implementation of Efficient 5G AKA Protocol for Light-Weight Environment

There is a critical vulnerability in the 5G AKA protocol of the 3GPP. We propose a protocol that compensates for these vulnerabilities and speed up the existing protocol; and the study implements this protocol to experiment with the vulnerabilities. The protocol uses the Light-weight Encryption Algorithm and is expected to be n3 times faster in than with the application of Advanced Encryption Standard algorithms. By using this algorithm, we improve the protocol efficiently, reduced the power consumed

A 6.5-GHz Energy-Efficient BFSK Modulator for Wireless Sensor Applications

A 6.5-GHz FSK modulator suitable for low power wireless sensor network is presented. The energy efficient modulator employs closed-loop direct VCO modulation to achieve high data rate, multistage variable loop bandwidth technique for fast startup time and 6-1 for reduced power consumption in the synthesizer with fine resolution in frequency channel selection. The modulator, implemented using 0.25- m CMOS, achieves 20- s startup time with an effective data rate of 2.5 Mb/s while consuming 22 mW

Heterogeneous population of macrophages in the development of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is characterized by a spectrum of hepatic diseases, including fatty liver, non-alcoholic steatohepatitis, cirrhosis, and hepatocellular carcinoma. NAFLD is a hepatic manifestation of metabolic syndrome and has become the leading cause of liver transplantation, necessitating an in-depth understanding of its underlying pathogenic mechanisms and the identification of viable drug targets. Although fatty liver is benign and does not exert marked liver damage or inflammation, NAFLD progression involves inflammatory processes facilitated by immune cells. Macrophages and monocytes constitute the pool of innate immune cells that contribute to NAFLD development in association with other cell types, such as neutrophils, T cells, and natural killer cells. The concept that macrophages contribute to the inflammatory processes in NAFLD development has long been debated; however, the remarkable advances in experimental techniques have rapidly uncovered new subpopulations of macrophages and monocytes, whose functions need to be comprehensively elucidated. The current review focuses on the recent expansion of our knowledge of the heterogeneous population of macrophages crucially involved in NAFLD development. In addition, the present paper discusses ongoing efforts to target macrophages and inflammatory processes to develop optimal therapeutic agents against non-alcoholic steatohepatitis