Performance of the Lead/Liquid Argon Shower Counter System of the Mark II Detector at SPEAR

Although the cryogenic and electronic problems of a large lead/liquid argon shower system such as in the Mark II require considerable attention to detail during design, construction, and set-up, the performance of a large system equals that of small test systems and agrees well with reasonable expectations. The shower detector system of the Mark II has been mechanically, cryogenically, and electronically very reliable during eighteen months of normal operation at SPEAR. Performance has provided a good compromise among the various demands upon shower detection. The system has enabled physics measurements previously untenable to other e+e- detectors.     

Ocular effects of exposure to triethylamine in the sand core cold box of a foundry

OBJECTIVES: To assess the acute and chronic ophthalmological effects of triethylamine exposure among foundry workers. METHODS: Ocular effects on people currently, previously, and never exposed to triethylamine in a foundry cold box were studied at two points in time. The initial phase included an ocular examination with a slit lamp to assess corneal health, a visual acuity test, and a questionnaire to assess vision symptoms. The follow up included measurements of corneal thickness with an ultrasonic pachymeter and the vision symptoms questionnaire before and after the shift and at the beginning and end of the week. Personal air measurements for triethylamine were also obtained during the follow up. RESULTS: The vision symptoms of blurriness, halos around lights, and blue hazy vision occurred more often in currently exposed workers than those previously or never exposed to triethylamine. Air concentrations of triethylamine ranged from < 0.33 mg/m3 to 20.3 mg/m3. Among currently exposed workers, symptoms were more common among those with exposure to > 10 mg/m3 of triethylamine (odds ratio (OR) = 3.0, 95% confidence interval (95% CI) 0.35-25.6). No differences in corneal thickness were found in currently or previously exposed workers and those never exposed. No increase in corneal thickness was found after v before the shift. CONCLUSION: Despite low concentrations of triethylamine and no corneal oedema, workers exposed to triethylamine reported vision symptoms. Possible explanations for these symptoms without corneal oedema are that triethylamine affects ciliary muscle function or that the corneal oedema was transient and not present when corneal thickness measurements were taken. No chronic effects were found in previously exposed workers. Further research is needed to elucidate the mechanism for the reported vision symptoms, which occurred below the current United States eight hour time weighted standard of 100 mg/m3 and the American Conference of Governmental Industrial Hygienists (ACGIH) recommended value at the time of our study of 40 mg/m3. We recommend that air concentrations be maintained to meet the current recommended ACGIH threshold of 4.1 mg/m3.     

Efficiently structured CDMA receiver with near-far immunity

A Gaussian code division multiple access (CDMA) channel is shared by K active users who transmit asynchronously with BPSK modulation by independent binary data streams. A conventional direct sequence CDMA receiver has only limited capability for suppressing cochannel multiple user interference (MUI) from the K-1 other CDMA signals while attempting to receive and demodulate each CDMA signal. A new and efficient feedback receiver structure is described for coherent demodulation of the K asynchronous CDMA signals. By incorporating adaptive cancellation of the cochannel MUI in a feedback structure, the new design offers the following advantages: protection of the receiver's synchronization loops as well as its data demodulators against MUI; lower bit error rate (BER) than the conventional receiver for equal-strength as well as near-far MUI; and implementation simplicity close to that of the conventional CDMA receiver. It is shown that all the CDMA signals are canceled to a common level determined by N₀, the one-sided power spectral density of the input AWGN; the bandwidth spreading ratio N; and K. The BER for any signal may be computed as if the N₀ matched filter input were multiplied by the factor (6N/π)(1.5 N+1-K) for K⩽1.5 N. Computer simulations corroborate this result. A straightforward enhancement to the receiver structure is shown to allow it to overcome the deleterious affects of multipath propagation     

Groupdrink: The effects of alcohol on intergroup competitiveness.

Alcohol is often consumed in group settings. The present article examines the effect of alcohol on intergroup competitiveness through the use of a prisoner's dilemma game. One hundred fifty-eight college students participated in the study, either individually or as a member of a 4-person experimental single-sex group. Participants consumed either alcohol (1.13 g ethanol/kg body weight) or a placebo. Results show no effect of alcohol on cooperative choice within individuals. However, groups were significantly less cooperative after consuming alcohol than they were after consuming a placebo. In addition, after consuming alcohol, groups were less cooperative than were individuals. Results are discussed in terms of the way alcohol may affect focus of attention on group-level cues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective autonomic blockade of conditioned and unconditioned cardiovascular changes in rhesus monkeys (Macaca mulatta).

Examined changes in heart rate and systolic and diastolic blood pressures in 8 rhesus monkeys during 6 sessions of differential classical conditioning. The conditioned stimuli consisted of tones differing in frequency, and the unconditioned stimuli consisted of tail shock. Both the CRs and UCRs consisted of increases in heart rate and in systolic and diastolic pressures, but blood pressure CRs sometimes occurred in the absence of heart rate CRs. In Exp II, graded doses of the selective blocking agents propranolol, phentolamine, and atropine methylnitrate were systemically administered to 4 of the Ss prior to additional conditioning sessions. Results suggest that the CRs and UCRs were mediated by both sympathetic and parasympathetic influences. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transition-path theory calculations on non-uniform meshes in two and three dimensions using finite elements

Rare events between states in complex systems are fundamental in many scientific fields and can be studied by building reaction pathways. A theoretical framework to analyze reaction pathways is provided by transition-path theory (TPT). The central object in TPT is the committor function, which is found by solution of the backward-Kolmogorov equation on a given potential. Once determined, the committor can be used to calculate reactive fluxes and rates, among other important quantities. We demonstrate here that the committor can be calculated using the method of finite elements on non-uniform meshes. We show that this approach makes it feasible to perform TPT calculations on 3D potentials because it requires many fewer degrees of freedom than a regular-mesh finite-difference approach. In various illustrative 2D and 3D problems, we calculate the committor function and reaction rates at different temperatures, and we discuss effects of temperatures and simple entropic barriers on the structure of the committor and the reaction rate constants.     

Multi-dimensional treatment planning: I. Delineation of anatomy

We discuss the scope of a multi-dimensional treatment program designed to assist in planning radiation therapy. It includes: synthesis of diagnostic information; techniques for the assessment and delineation of anatomy; fully three-dimensional simulation of therapy; calculation and assessment of dose distributions; verification of treatment delivery; and assessment of the patient during and after treatment. In this paper we present details of techniques for the assessment and delineation of anatomy, including the display of CT information in three dimensions and the ability to draw on and edit the image displays.