Gender and Overconfidence

Do males differ from females in terms of self-confidence? The structure of the Economics I exam at Stockholm University provides an opportunity to shed some light on this question. By answering an extra, optional question, the students can aim for a higher mark. We find a clear gender difference in that male students are more inclined than female students to take this opportunity. This difference in selfassessment is more pronounced among younger than among older students.Overconfidence; gender differences; exam behavior; exam results

Interference Cancellation in a Full duplex System

In a full duplex system as WCDMA a mobile phone transmits and receives at the same time, but at different frequencies. The transmitted signal will cause interference in the receiver which must be suppressed to not get degraded sensitivity in the receiver. This Master Thesis was carried out at Ericsson Mobile Platforms in Lund and the purpose was to examine a method to suppress the interference in the digital domain of a WCDMA transceiver. The method is based on that information from the transmitter is fed forward to the receiver to be able to recreate a resembled replica of the interference and subtract it from the desired signal. Further an adaptive least mean square algorithm is used to estimate correct amount of the interference and to provide a tracking ability for temperature variations. A simulator model was developed in matlab to be able to analyze the interference and design a proper cancellation block between the transmitter and the receiver. This simulator model was designed with complexity reductions that did not affect the study of the phenomena. According to simulations, the LMS algorithm turned out to be a sufficient choice concerning rate of convergence, misadjustment and robustness. The main limitation of the improvement by using a cancellation block, was instead determined by the distortion in the transmitter. The trend today is to achieve lower and lower distortions in the uplink making this method more interesting

Detecting a Light Stop from Top Decays at the Tevatron

We study the possibility of discovering or excluding a light top squark (stop) based on top quark decays in the t-tbar events produced at the Fermilab Tevatron. In particular, we consider the Minimal Supersymmetric Standard Model with the sparticle spectrum m_{chi^+_1}+m_b, M_W+m_{chi^0_1}+m_b > m_{stop} > m_{chi^0_1}+m_c, where chi^0_1 is the lightest neutralino and chi^+_1 is the lightest chargino, so that t -> stop chi^0_1 and stop -> c chi^0_1. All other sparticle masses are assumed to be heavier than m_t. Such a spectrum seeks to explain the experimental values of alpha_s(M_Z^2), R_b and A_{LR} obtained from LEP/SLC data. We find that the prospect to observe a light stop via this channel at the Tevatron is very promising.Comment: 12 pages with 1 Postscript figure using psfig.sty. Postscript file available at http://sgi2.hep.anl.gov:8001/index.htm

OIL CORROSION AND CONDUCTING CU 2 S DEPOSITION IN POWER TRANSFORMER WINDINGS

SUMMARY Copper corrosion and Cu 2 S deposition, has recently led to failures of transformers & shunt reactors during service. Units from several different operators and several OEMs have been affected. Analysis of actual failure cases showed that these transformers were well within established industry standard practice regarding design as well as operation, and used oil that fulfilled international material standards. Sealed units with rubber sack appear primarily to have been affected. Final failure has occurred as a turn-to-turn breakdown in the HV windings, and inspection of the failed windings showed deposits in the winding consisting of Cuprous Sulphide, Cu 2 S, an electrically conducting compound. The deposits varied within the winding, usually with more deposits in the upper part of the windings, but the complex deposition pattern could not be explained simply by the temperature distribution. We have carried out comprehensive corrosion research aiming at a thorough understanding of the phenomenon, and have reproduced the corrosion as well as the deposition of Cu 2 S in our laboratories. The influence of the gas content of the oil, and other parameters have been studied under very well controlled circumstances, and a number of different oils have been evaluated at temperatures ranging from 80 to 150 °C. The main finding is that Cu 2 S deposition occurs only for certain oils, which can cause corrosion and deposition under the typical environment of a sealed power transformer. With such oils deposition has been demonstrated over a wide temperatures range, from as low as 80 °C, and on a variety of solid materials. These oils further show a very strong oxygen dependence of the deposition, which explains much of the observed complex deposition patterns in the failed units. Real failures have all occurred with transformer oils that passed the corrosion tests in the international standards, DIN 51353 and ASTM D1275 respectively. Improved test methods are clearly needed that can take into account the observed oxygen dependence, an important factor present in real transformers. A Covered Conductor Deposition (CCD) test has demonstrated a superior selectivity for identifying the corrosive oils that have caused actual failures in transformers, and is thus a very promising type of test

Shikonin Increases Glucose Uptake in Skeletal Muscle Cells and Improves Plasma Glucose Levels in Diabetic Goto-Kakizaki Rats

Glucose is the most common substrate for energy metabolism. Despite the varying demands for glucose, the body needs to regulate its internal environment and maintain a constant and stable condition. Glucose homeostasis requires harmonized interaction between several tissues, achieving equilibrium between glucose output and uptake. In this thesis we aimed to investigate factors modulating glucose homeostasis in a rat model of type 2 diabetes, the Goto-Kakizaki (GK) rat. In addition, we investigated sex differences in hepatic carbohydrate and lipid metabolism in healthy rats. In Paper I, three-week but not three-day treatment with a Southeast Asian herb, Gynostemma pentaphyllum (GP), significantly reduced plasma glucose (PG) levels in GK rats. An intra-peritoneal glucose tolerance test (IPGTT) was significantly improved in GP-treated compared to placebo-treated group. In the GP treated rats, the glucose response in an intra-peritoneal pyruvate tolerance test was significantly lower, indicating decreased gluconeogenesis, and hepatic glucose output (HGO) was reduced. GP-treatment significantly reduced hepatic glycogen content, but not glycogen synthase activity. The study provides evidence that the GP extract exerted anti-diabetic effect in GK rats, reducing PG levels and HGO, suggesting that GP improves the hepatic insulin sensitivity by suppressing gluconeogenesis. In Paper II, shikonin, a naphthoquinone derived from the Chinese plant Lithospermum erythrorhizon, increased glucose uptake in L6 myotubes, but did not phosphorylate Akt. Furthermore we found no evidence for the involvement of AMP activated protein kinase (AMPK) in shikonin induced glucose uptake. Shikonin increased the intracellular levels of calcium in these cells and stimulated the translocation of GLUT4 from intracellular vesicles to the cell surface in L6 myotubes. In GK rats treated with shikonin once daily for 4 days, PG levels were significantly decreased. In an insulin sensitivity test, the absolute PG levels were significantly lower in the shikonin-treated rats. These findings suggest that shikonin increases glucose uptake in muscle cells via an insulin-independent pathway dependent on calcium. In Paper III, GK and control Wistar rats were injected daily for up to 4 weeks with either a non-hematopoietic erythropoietin analog ARA290 or with placebo. PG levels in GK but not Wistar rats were significantly lower in ARA290-treated compared to placebo. After 2 and 4 weeks, the IPGTT was significantly improved in ARA290 treated GK rats. In insulin and pyruvate tolerance tests, glucose responses were similar in ARA290 and placebo groups. In isolated GK rat islets, glucose-stimulated insulin release was two-fold higher and islet intracellular calcium concentrations in response to several secretagogues were significantly higher in ARA290-treated than in placebo-treated GK rats. These findings indicate that treatment with ARA290 significantly improved glucose tolerance in diabetic GK rats, most likely due to improvement of insulin release. In Paper IV, sex differences in hepatic carbohydrate and lipid metabolism were characterized in healthy rats. No sex-differences were observed regarding hepatic triglyceride content, fatty acid oxidation rates or insulin sensitivity. Male rats had higher ratios of insulin to glucagon levels, increased hepatic glycogen content, a lower degree of AMPK phosphorylation, a higher rate of glucose production and higher expression levels of gluconeogenic genes, as compared to female rats. A sex-dependent response to mild starvation was observed with males being more sensitive. In conclusion, sex-differences reflect a higher capacity of the healthy male rat liver to respond to increased energy demands. Key words: glucose homeostasis, type 2 diabetes, GK rats, L6 myotubes, hepatic glucose output, insulin sensitivity, sex differences

Differential Production Cross Section of Z Bosons as a Function of Transverse Momentum at sqrt{s}=1.8 TeV

We present a measurement of the transverse momentum distribution of Z bosons produced in ppbar collisions at sqrt{s}=1.8 TeV using data collected by the D0 experiment at the Fermilab Tevatron Collider during 1994--1996. We find good agreement between our data and a current resummation calculation. We also use our data to extract values of the non-perturbative parameters for a particular version of the resummation formalism, obtaining significantly more precise values than previous determinations.Comment: 10 pages, 2 figures, submitted to Phys. Rev. Letters v2 has margin error correcte

Jet Production via Strongly-Interacting Color-Singlet Exchange in ppˉp\bar{p} Collisions

A study of the particle multiplicity between jets with large rapidity separation has been performed using the D{\O}detector at the Fermilab Tevatron $p\bar{p}$ Collider operating at $\sqrt{s}=1.8$ TeV. A significant excess of low-multiplicity events is observed above the expectation for color-exchange processes. The measured fractional excess is $1.07 \pm 0.10({\rm stat})^{+ 0.25}_{- 0.13}({\rm syst})$, which is consistent with a strongly-interacting color-singlet (colorless) exchange process and cannot be explained by electroweak exchange alone. A lower limit of 0.80% (95% C.L.) is obtained on the fraction of dijet events with color-singlet exchange, independent of the rapidity gap survival probability.Comment: 15 pages (REVTeX), 3 PS figs (uuencoded/tar compressed, epsf.sty) Complete postscript available at http://d0sgi0.fnal.gov/d0pubs/journals.html Submitted to Physical Review Letter

A trial to evaluate the effect of the sodium–glucose co‐transporter 2 inhibitor dapagliflozin on morbidity and mortality in patients with heart failure and reduced left ventricular ejection fraction (DAPA‐HF)

Background: Sodium–glucose co‐transporter 2 (SGLT2) inhibitors have been shown to reduce the risk of incident heart failure hospitalization in individuals with type 2 diabetes who have, or are at high risk of, cardiovascular disease. Most patients in these trials did not have heart failure at baseline and the effect of SGLT2 inhibitors on outcomes in individuals with established heart failure (with or without diabetes) is unknown. Design and methods: The Dapagliflozin And Prevention of Adverse‐outcomes in Heart Failure trial (DAPA‐HF) is an international, multicentre, parallel group, randomized, double‐blind, study in patients with chronic heart failure, evaluating the effect of dapagliflozin 10 mg, compared with placebo, given once daily, in addition to standard care, on the primary composite outcome of a worsening heart failure event (hospitalization or equivalent event, i.e. an urgent heart failure visit) or cardiovascular death. Patients with and without diabetes are eligible and must have a left ventricular ejection fraction ≤ 40%, a moderately elevated N‐terminal pro B‐type natriuretic peptide level, and an estimated glomerular filtration rate ≥ 30 mL/min/1.73 m2. The trial is event‐driven, with a target of 844 primary outcomes. Secondary outcomes include the composite of total heart failure hospitalizations (including repeat episodes), and cardiovascular death and patient‐reported outcomes. A total of 4744 patients have been randomized. Conclusions: DAPA‐HF will determine the efficacy and safety of the SGLT2 inhibitor dapagliflozin, added to conventional therapy, in a broad spectrum of patients with heart failure and reduced ejection fraction

Hard Single Diffraction in pbarp Collisions at root-s = 630 and 1800 GeV

Using the D0 detector, we have studied events produced in proton-antiproton collisions that contain large forward regions with very little energy deposition (``rapidity gaps'') and concurrent jet production at center-of-mass energies of root-s = 630 and 1800 Gev. The fractions of forward and central jet events associated with such rapidity gaps are measured and compared to predictions from Monte Carlo models. For hard diffractive candidate events, we use the calorimeter to extract the fractional momentum loss of the scattered protons.Comment: 11 pages 4 figures. submitted to PR

Small Angle J/Psi Production in ppbar Collisions at sqrt(s)=1.8TeV

This paper presents the first measurement of the inclusive J/Psi production cross section in the forward pseudorapidity region 2.5<|eta|<3.7 in ppbar collisions at sqrt(s)=1.8TeV. The results are based on 9.8 pb-1 of data collected using the D0 detector at the Fermilab Tevatron Collider. The inclusive J/Psi cross section for transverse momenta between 1 and 16 GeV/c is compared with theoretical models of charmonium production.Comment: 6 pages, 3 figures, text file REVTEX, figures encapsulated postscript. PACS: 13.20.Gd, 13.25.Gv, 13.85.Qk, 12.38.Q