Analysis of Turnability for a Three Terminal Microwave Network

Three-terminal microwave networks can be shown to exhibit qualities that would make them desirable to be used as multiple terminal devices. Using microwave theory, where instantaneous voltage is a function of position on the line, this situation will be examined. These devices use the interference principle of propagating waves as the basis of their characteristics. This investigation will probe a three- terminal microwave network with one input and two output. This configuration acts similar to a splitter where the outputs may be controlled. These three terminals, plus manipulation of the lengths of each side, actually makes this a four terminal device, much like a transistor with one source, one gate, and two drains. The three terminal network will be examined in a situation such that the lengths of two of the sides will be varied and the wavelength will be held constant. The power of the signal at each of the output terminals, along with reflected power will be recorded. By using a case where the total length of the ring is an integer number of wavelengths, two cases of behavior arise. One case exhibits qualities much like the Aharanov-Bohm effect. The other case has tendencies to reflect most of the incoming signal, except near equal length sides

Long-term effects on ash characteristics and diesel particulate filter performance

Thesis (Nav. E. and S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (p. 87-90).Diesel particulate filters (DPF) have seen widespread growth as an effective means for meeting increasingly rigorous particle emissions regulations. There is growing interest to exploit passive regeneration of DPFs to reduce fuel consumption accompanying traditional active regeneration. Incombustible material or ash, mainly derived from metallic additives in the engine lubricant, accumulates in the DPF over time. This ash accumulation increases flow restriction and rise in pressure drop across the DPF. The growth of pressure drop adversely impacts engine performance and fuel economy. This study built upon previous research to evaluate the different effects of regeneration strategy on ash packing and distribution within DPFs. Since passive regeneration relies on a catalyzed reaction, the interactions of ash with the catalyst will play an important role. Passive regeneration is specifically dependent on exhaust feed gas composition, exhaust conditions including temperature and flow rate, catalyst type and configuration, and the state of DPF loading during prior to passive regeneration. The goal of the study is to address the long-term effects of regeneration parameters on ash accumulations and the resulting impact of ash on the DPF catalyst performance. Experiments were conducted that focused on pressure drop measurements over the lifetime of diesel particulate filters with different regeneration methods coupled with post mortem ash characterization. These experiments provide insight to how these regeneration methods impact the DPF performance. These results, among few fundamental data of this kind, correlate changes in diesel particulate filter performance with exhaust conditions, regeneration strategy, and ash morphological characteristics. Outcomes are useful in optimizing the design of the combined engine-aftertreatment- lubricant system for future diesel engines, balancing the necessities of additives for adequate engine protection with the requirements for robust aftertreatment systems.by Michael J. Bahr.Nav.E.and S.M

Can off-field ‘brains’ provide a competitive advantage in professional football?

‘Working-fast and working-slow’ in sport describes the concept that practice and research can be integrated to improve high-performance outcomes and enhance professional practice.1 ‘Working-fast’ is the task of the fast-thinking, intuitive practitioner operating on ‘the ground’ at a frenetic pace, interacting with coaches and athletes, and delivering the daily preparation programme. ‘Working-slow’ is key for the team's deliberate, focused researcher acting as the resident sceptic, operating behind the scenes on tasks that the ‘fast-practitioner’ may not have time and/or skills to undertake. Such hidden, but important, tasks include determining measurement noise/error in performance tests, establishing proof of concept for new ideas and ensuring validity of methods. Embedding research into the fast environment of high-performance football may provide a competitive advantage using ethical and evidence-based methods.

Multivariate discrimination and the Higgs + W/Z search

A systematic method for optimizing multivariate discriminants is developed and applied to the important example of a light Higgs boson search at the Tevatron and the LHC. The Significance Improvement Characteristic (SIC), defined as the signal efficiency of a cut or multivariate discriminant divided by the square root of the background efficiency, is shown to be an extremely powerful visualization tool. SIC curves demonstrate numerical instabilities in the multivariate discriminants, show convergence as the number of variables is increased, and display the sensitivity to the optimal cut values. For our application, we concentrate on Higgs boson production in association with a W or Z boson with H -> bb and compare to the irreducible standard model background, Z/W + bb. We explore thousands of experimentally motivated, physically motivated, and unmotivated single variable discriminants. Along with the standard kinematic variables, a number of new ones, such as twist, are described which should have applicability to many processes. We find that some single variables, such as the pull angle, are weak discriminants, but when combined with others they provide important marginal improvement. We also find that multiple Higgs boson-candidate mass measures, such as from mild and aggressively trimmed jets, when combined may provide additional discriminating power. Comparing the significance improvement from our variables to those used in recent CDF and DZero searches, we find that a 10-20% improvement in significance against Z/W + bb is possible. Our analysis also suggests that the H + W/Z channel with H -> bb is also viable at the LHC, without requiring a hard cut on the W/Z transverse momentum.Comment: 41 pages, 5 tables, 29 figure

Plasma bile acids are not associated with energy metabolism in humans

Bile acids (BA) have recently been shown to increase energy expenditure in mice, but this concept has not been tested in humans. Therefore, we investigated the relationship between plasma BA levels and energy expenditure in humans. Type 2 diabetic (T2DM) patients (n = 12) and gender, age and BMI-matched healthy controls (n = 12) were studied before and after 8 weeks of treatment with a BA sequestrant. In addition, patients with liver cirrhosis (n = 46) were investigated, since these display elevated plasma BA together with increased energy expenditure. This group was compared to gender-, age- and BMI-matched healthy controls (n = 20). Fasting plasma levels of total BA and individual BA species as well as resting energy expenditure were determined. In response to treatment with the BA sequestrant, plasma deoxycholic acid (DCA) levels decreased in controls (-60%, p &lt;0.05) and T2DM (-32%, p &lt;0.05), while chenodeoxycholic acid (CDCA) decreased in controls only (-33%, p &lt;0.05). Energy expenditure did not differ between T2DM and controls at baseline and, in contrast to plasma BA levels, was unaffected by treatment with the BA sequestrant. Total BA as well as individual BA species did not correlate with energy expenditure at any time throughout the study. Patients with cirrhosis displayed on average an increase in energy expenditure of 18% compared to values predicted by the Harris-Benedict equation, and plasma levels of total BA (up to 12-fold) and individual BA (up to 20-fold) were increased over a wide range. However, neither total nor individual plasma BA levels correlated with energy expenditure. In addition, energy expenditure was identical in patients with a cholestatic versus a non-cholestatic origin of liver disease while plasma total BA levels differed four-fold between the groups. In conclusion, in the various (patho) physiological conditions studied, plasma BA levels were not associated with changes in energy expenditure. Therefore, our data do not support an important role of circulating BA in the control of human energy metabolism.</p

The Underlying Event and the Total Cross Section from Tevatron to the LHC

Multiple partonic interactions are widely used to simulate the hadronic final state in high energy hadronic collisions, and successfully describe many features of the data. It is important to make maximum use of the available physical constraints on such models, particularly given the large extrapolation from current high energy data to LHC energies. In eikonal models, the rate of multiparton interactions is coupled to the energy dependence of the total cross section. Using a Monte Carlo implementation of such a model, we study the connection between the total cross section, the jet cross section, and the underlying event. By imposing internal consistency on the model, we derive constraints on its parameters at the LHC. By imposing internal consistency on the model and comparing to current data we constrain the allowed range of its parameters. We show that measurements of the total proton-proton cross-section at the LHC are likely to break this internal consistency, and thus to require an extension of the model. Likely such extensions are that hard scatters probe a denser matter distribution inside the proton in impact parameter space than soft scatters, a conclusion also supported by Tevatron data on double-parton scattering, and/or that the basic parameters of the model are energy dependent.Comment: 17 pages, 6 figures, version accepted by JHE

Clinical Relevance of Transjugular Liver Biopsy in Comparison with Percutaneous and Laparoscopic Liver Biopsy

Background. Transjugular liver biopsy (TJLB) is frequently used to obtain liver specimens in high-risk patients. However, TJLB sample size possibly limits their clinical relevance. Methods. 102 patients that underwent TJLB were included. Clinical parameters and outcome of TJLB were analyzed. Control samples consisted of 112 minilaparoscopic liver biopsies (mLLBs) and 100 percutaneous liver biopsies (PLBs). Results. Fewer portal tracts were detected in TJLB (4.3 ± 0.3) in comparison with PLB (11.7 ± 0.5) and mLLB (11.0 ± 0.6). No difference regarding the specification of indeterminate liver disease and staging/grading of chronic hepatitis was observed. In acute liver failure (n = 32), a proportion of hepatocellular necrosis beyond 25% was associated with a higher rate of death or liver transplantation. Conclusions. Despite smaller biopsy samples the impact on the clinical decision process was found to be comparable to PLB and mLLB. TJLB represents a helpful tool to determine hepatocellular necrosis rates in patients with acute liver failure

Divisors in a Dedekind domain

5 páginas.-- 1991 Mathematics Subject Classification: 11R04, 11A05.Peer reviewe