Metastable Cosmic Strings in Realistic Models

We investigate the stability of the electroweak Z-string at high temperatures. Our results show that while finite temperature corrections can improve the stability of the Z-string, their effect is not strong enough to stabilize the Z-string in the standard electroweak model. Consequently, the Z-string will be unstable even under the conditions present during the electroweak phase transition. We then consider phenomenologically viable models based on the gauge group $SU(2)_L \times SU(2)_R \times U(1)_{B-L}$ and show that metastable strings exist and are stable to small perturbations for a large region of the parameter space for these models. We also show that these strings are superconducting with bosonic charge carriers. The string superconductivity may be able to stabilize segments and loops against dynamical contraction. Possible implications of these strings for cosmology are discussed.Comment: 24 pages, 2 figures (available on request); HUTP-92/A032, Fermilab-Pub-92/228-

STUDIES ON THE PROPERTIES OF RETINAL ALCOHOL DEHYDROGENASE FROM THE RAT

An NAD-dependent alcohol dehydrogenase (alcohol:NAD oxidoreductase; EC 1.1.1.1) has been isolated and partially purified from the retinal cytosol of the rat. Its substrate specificity and sensitivity to inhibitors of hepatic alcohol dehydrogenase have been investigated. Ethanol, 1-propanol and 1-butanol served as substrates for this enzyme but the K m values were more than 100-fold higher than those reported for hepatic alcohol dehydrogenase. Methanol and retinol were unreactive with this alcohol dehydrogenase. Inhibition by pyrazole was observed but the K t was about 100-fold higher than the value observed for hepatic alcohol dehydrogenase. n -Butyraldoxime inhibited retinal alcohol dehydrogenase with a K t of 2 ΜM, a value which approximates its K t for hepatic alcohol dehydrogenase. 1, 10-Phenanthroline was ineffective as an inhibitor. Oxidation of retinol was observed in retinal homogenates in the presence of NADP but no inhibition was observed with ethanol, methanol or pyrazole. We conclude that oxidation of retinol is not catalysed by soluble retinal alcohol dehydrogenase.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65178/1/j.1471-4159.1971.tb00195.x.pd

Design and testing of an integrated circuit for multi-electrode neural recording

Journal ArticleWe have developed a single-chip neural recording system with wireless power delivery and telemetry. The 0.5-μm CMOS IC is designed to be bonded to the back of a 100-channel Utah Electrode Array. A pad near each amplifier allows connection of the chip to the MEMS electrode array. The complete Integrated Neural Interface will receive power wirelessly through a 2.64-MHz inductive link. A clock, regulated supply, and commands are derived from the power signal .The neural amplifiers each have a gain of 60 dB. A 10-bit charge-redistribution ADC is used to digitize the signal from one amplifier selected with an analog MUX. Digitizing all channels simultaneously would generate prohibitively high data rates; therefore, we perform data reduction by incorporating one-bit "spike detectors" into each amplifier. Neural data is transmitted off chip using an -integrated 433-MHz FSK transmitter. The chip measures 4.7×5.9 mm2 and consumes 13.5 mW of power

Low-power integrated circuit for a wireless 100-electrode neural recording system

Journal ArticleIn the past decade, neuroscientists and clinicians have begun to use implantable MEMS multielectrode arrays (e.g., [1]) to observe the simultaneous activity of many neurons in the brain. By observing the action potentials, or "spikes," of many neurons in a localized region of the brain it is possible to gather enough information to predict hand trajectories in real time during reaching tasks [2]. Recent experiments have shown that it is possible to develop neuroprosthetic devices - machines controlled directly by thoughts - if the activity of multiple neurons can be observed

Signal amplification, detection and transmission in a wireless 100-electrode neural recording system

Journal ArticleWe are developing a fully-implantable neural recording system with wireless power and data transfer. As part of this system, we have developed a low-power integrated circuit that performs power rectification and and regulation, reception of configuration data, neural signal amplification and filtering, spike detection, neural signal digitization and RF transmission. The chip includes 88 amplifiers having a gain of 60 dB from 1 to 5 kHz. An integrated ADC operates at 15 kSamples/sec with 9-bit resolution. A 433-MHz RF transmitter uses FSK The modulation to transmit one digitized neural signal and spike detection data from all channels. Total power consumption is 13.5 mW

Validation of adaptive threshold spike detector for neural recording

Journal ArticleWe compare the performance of algorithms for automatic spike detection in neural recording applications. Each algorithm sets a threshold based on an estimate of the background noise level. The adaptive spike detection algorithm is suitable for implementation in analog VLSI; results from a proof-of-concept chip using neural data are presented. We also present simulation results of algorithm performance on neural data and compare it to other methods of threshold level adjustment based on the root-mean-square (rms) voltage measured over a finite window. We show that the adaptive spike detection algorithm measures the background noise level accurately despite the presence of large-amplitude action potentials and multi-unit hash. Simulation results enable us to optimize the algorithm parameters, leading to an improved spike detector circuit that is currently being developed

Depressive Rumination: Investigating Mechanisms to Improve Cognitive Behavioural Treatments

Rumination has been identified as a core process in the development and maintenance of depression. Treatments targeting ruminative processes may, therefore, be particularly helpful for treating chronic and recurrent depression. The development of such treatments requires translational research that marries clinical trials, process–outcome research, and basic experimental research that investigates the mechanisms underpinning pathological rumination. For example, a program of experimental research has demonstrated that there are distinct processing modes during rumination that have distinct functional effects for the consequences of rumination on a range of clinically relevant cognitive and emotional processes: an adaptive style characterized by more concrete, specific processing and a maladaptive style characterized by abstract, overgeneral processing. Based on this experimental work, two new treatments for depression have been developed and evaluated: (a) rumination-focused cognitive therapy, an individual-based face-to-face therapy, which has encouraging results in the treatment of residual depression in an extended case series and a pilot randomized controlled trial; and (b) concreteness training, a facilitated self-help intervention intended to increase specificity of processing in patients with depression, which has beneficial findings in a proof-of-principle study in a dysphoric population. These findings indicate the potential value of process–outcome research (a) explicitly targeting identified vulnerability processes and (b) developing interventions informed by research into basic mechanisms

Investigating the associations between adiposity, life course overweight trajectories, and telomere length

Obesity may accelerate ageing through chronic inflammation. To further examine this association, we assessed current adiposity, adiposity at early adulthood and life course overweight trajectories in relation to leukocyte telomere length (LTL). We included a total of 7,008 nationally representative U.S. residents and collected information on objectively measured body mass index (BMI), waist circumference and percent body fat. BMI at age 25 and overweight trajectories were assessed using self-reported history. Leukocyte telomere length (LTL) relative to a standard DNA reference (T/S ratio) was quantified by polymerase chain reaction (PCR). Linear regression models were used to examine the difference in LTL across adiposity measures at examination, BMI at age 25, and overweight trajectories. A 0.2% decrease in telomere length (95% CI: -0.3 to -0.07%) was observed for every kg/m2 increase in BMI, whereas a unit increase in waist circumference (cm) and percent body fat contributed to a 0.09% and 0.01% decrease in LTL, respectively. Higher BMI and being obese at age 25 contributed to lower LTL at older ages. Associations between weight loss through life course and LTL were observed, which further marked the importance of life course adiposity dynamics as a determinant of ageing