Direct measurement of the spectral transfer function of a laser based anemometer

The effect of a continuous-wave (cw) laser based anemometer's probe volume on the measurement of wind turbulence is studied in this paper. Wind speed time series acquired by both a remote sensing cw laser anemometer, whose line-of-sight was aligned with the wind direction, and by a reference sensor (sonic anemometer) located in the same direction, were used. The spectral transfer function, which describes the attenuation of the power spectral density of the wind speed turbulence, was calculated and found to be in good agreement with the theoretical exponential function, which is based on the properties of the probe volume of a focused Gaussian laser beam. Parameters such as fluctuations of the wind direction, as well as the overestimation of the laser Doppler spectrum threshold, were found to affect the calculation of the spectral transfer function by introducing high frequency noise.     

Impact of Flashover Fire Conditions on Exposed Energized Electrical Cords/Cables

There has been prior research exploring the exposure of common electrical cords and cables to fire, but that has traditionally been at the lab scale and under near steady-state exposures. The goal of these experiments was to expose six types of cords and cables in a room-scale compartment with a fuel load sufficient to drive the compartment through flashover. The basic test design was to expose the cords and cables on the floor of a compartment to a growing fire to determine the conditions under which the cord/cable would trip the circuit protection device. All of the cords were energized and installed on a non-combustible surface. The six cables and cords were protected by three different circuit protection devices which were remote from the thermal exposure. This configuration resulted in 18 exposures per experiment. The room fires experiments consisted of three replicate fires with two sofas as the main fuel source, two replicate fires with one sofa as the main fuel source and one fire with two sofas and vinyl-covered MDF paneling on three walls in the room. Each fuel package was sufficient to support flashover conditions in the room. The average peak heat release rate of the sofa fueled compartment fires with gypsum board ceiling and walls prior to suppression was 6.8 MW. The addition of vinyl covered MDF wall paneling on three of the compartment walls increased the pre-suppression peak heat release rate to 12 MW. In each experiment during post flashover exposure, the insulation on the cords and cables ignited and burned through, exposing bare wire. During this period, the circuits faulted. Assessments of both the thermal exposure and physical damage to the cords did not reveal any correlation between the thermal exposure, cord/cable damage, and trip type.     

Association between patient psychosocial characteristics and receipt of in‐center nocturnal hemodialysis among prevalent dialysis patients

Introduction: Compared to traditional in‐center hemodialysis (HD), in‐center nocturnal dialysis (INHD) is characterized by longer sessions and nighttime administration, which may lead to better outcomes for some patients. Given the importance of patient choice in the decision to initiate INHD, we explored associations between patients’ psychosocial characteristics and their receipt of INHD. Methods: Among hemodialysis patients at a medium‐sized dialysis organization, we identified INHD patients as those for whom ≥80% of dialysis sessions were INHD sessions—starting at 6:30 pm or later and lasting ≥5 hours—over the 3 months (≥20 sessions total) after their first INHD session. We extracted dialysis session data from electronic medical records and psychosocial data from social worker assessments. We tested associations of patients’ psychosocial characteristics—as well as demographic and clinical characteristics—with INHD receipt among all hemodialysis patients (INHD and HD) in bivariate analyses and multivariable logistic regression models. Findings: Among 759 patients with complete data, we identified 47 (6.2%) as INHD patients. On average, these patients were more likely than HD patients to be employed (full‐time 10.6% vs. 5.2%; part‐time 17.0% vs. 4.2%; P < 0.001), and they were significantly less likely to require ambulatory assistance (14.9% vs. 39.6%, P < 0.001). In multivariable regressions, we found that part‐time employment (versus being unemployed) was associated with a 7.1 percentage‐point higher likelihood of being an INHD patient (P = 0.01), and the negative association with ambulatory assistance needs approached statistical significance (P = 0.056). No other psychosocial factors included in this main regression analysis were statistically significantly associated with INHD patient status. Discussion: Researchers comparing the outcomes of patients undergoing INHD versus other treatment modalities will need to account for differences in employment status—and other factors like requiring ambulatory assistance and age which may predict the ability to work—between INHD users and comparison patients to avoid bias in estimates.     

Inhibition of Nitrosomonas europaea by Monoterpenes from Coastal Redwood (Sequoia sempervirens) in Whole-Cell Studies

Inhibition by allelochemicals, including monoterpenes, has been suggested as a factor in the extremely low nitrification rates observed in coastal redwood forests. Similarities between the molecular structure of known nitrification inhibitors and some conifer monoterpenes have been suggested as one reason for the inhibition of autotrophic nitrifiers by conifer monoterpenes. The effect of monolerpenes on nitrification rate and growth of Nitrosomonas europaea was examined in whole-cell pure culture experiments using the five most abundant monoterpenes in coastal redwood needles. These are (in order of decreasing concentration in the needles) limonene, α-pinenc, sabinene, myrcene, and γ-terpinene. Four of the five compounds significantly inhibited growth of N. europaea in batch culture experiments. Short-term kinetic studies of the two most inhibitory monoterpenes, limonene and α-pinene, were performed on whole cells to evaluate the mode of interaction between these chemicals and nitrification rates. Inhibition constants (K _i) of limonene (38 μM) and α-pinene (95 μM) were determined. Lineweaver-Burk plots of nitrification in the presence of monoterpenes appear to fit a noncompetitive inhibition model; however, the mechanisms of inhibition may be more complex.     

Porosity and tensile ductility in Al-Zn alloys

The tensile ductility of Al-Zn alloys processed in two different ways was examined over a broad range of temperature and strain rates. The different processing conditions produced materials with differing initial void andJor inclusion contents. If all the defects present are assumed to be in the form of voids, their respective volume fractions in the two alloys are 0.5 and 1.5 pct. Testing at temperatures from 77 to 480 K encompasses a range of mechanical behavior, ranging from brittle to superplastic. The poorly processed material has markedly less ductility than the one containing fewer defects both at high temperatures and at near cryogenic ones (196 K), where the alloys are marginally ductile. Increasing strain rate embrittles alloys in the temperature range 196 K to 300 K. At 196 K the strain rate needed to induce brittleness in the low defect alloy is over two orders of magnitude higher than in the alloy with a greater voidJinclusion content. Critical embrittling strain rates at room temperature are in the range common to conventional metal-forming operations for the poorly processed alloy, and thus cold formability devolves importantly on initial processing. In the vicinity of room temperature and at low strain rates, tensile ductility is greater for alloys with a higher defect concentration; this behavior is related to the development of multiple necks in the poorly processed materials. At the highest temperatures investigated, tensile ductility correlates directly with strain rate sensitivity and material defect concentration. Materials with low defect concentrations resist neck development during quasi-uniform flow to a much greater degree than do those with a high defect concentration. B. HARRIPRASHAD, formerly Graduate Student at Michigan Technological University T. H. COURTNEY, formerly Professor, Department of Metallurgical Engineering, and Dean of the Graduate School at Michigan Technological University.