Assessing Friction Characteristics of Liquid Lubricants

The decline of fossil fuel reserves and the increasing awareness of greenhouse gas emissions have been the primary driving forces behind the need to conserve energy. To improve fuel efficiency friction modifiers are commonly blended into lubricants. Reduction of friction will clearly lead to less energy requirements. However, an accurate evaluation of lubricant performance is not possible using existing test equipment. The main reason is that current test rigs require operating conditions that induce wear so that the measurement of friction in these rigs is not a real evaluation of friction. The paper will detail the design and commissioning of a purpose built test rig to measure frictional characteristics of various oils as well as the results of the tests performed

A Spectropolarimetric Comparison of the Type II-Plateau Supernovae SN 2008bk and SN 2004dj

The Type II-Plateau supernova (SN II-P) SN 2004dj was the first SN II-P for which spectropolarimetry data were obtained with fine temporal sampling before, during, and after the fall off of the photometric plateau -- the point that marks the transition from the photospheric to the nebular phase in SNe II-P. Unpolarized during the plateau, SN 2004dj showed a dramatic spike in polarization during the descent off of the plateau, and then exhibited a smooth polarization decline over the next two hundred days. This behavior was interpreted by Leonard et al. (2006) as evidence for a strongly non-spherical explosion mechanism that had imprinted asphericity only in the innermost ejecta. In this brief report, we compare nine similarly well-sampled epochs of spectropolarimetry of the Type II-P SN 2008bk to those of SN 2004dj. In contrast to SN 2004dj, SN 2008bk became polarized well before the end of the plateau and also retained a nearly constant level of polarization through the early nebular phase. Curiously, although the onset and persistence of polarization differ between the two objects, the detailed spectropolarimetric characteristics at the epochs of recorded maximum polarization for the two objects are extremely similar, feature by feature. We briefly interpret the data in light of non-Local-Thermodynamic Equilibrium, time-dependent radiative-transfer simulations specifically crafted for SN II-P ejecta.Comment: 4 pages, 1 figure, to appear in AIP conference proceedings: Stellar Polarimetry, From Birth to Death, eds. J. Hoffman, B. Whitney, and J. Bjorkma

Comparable Worth in a General Equilibrium Model of the U.S. Economy

This paper presents a computable general equilibrium model that simulates the effects on employment, output, wages, and economic efficiency of introducing comparable worth into the U.S. economy. The model calculates economy-wide aggregate impacts and disaggregated results for individuals grouped by sex, marital status, and education. The effects depend on the hiring rules that would accompany comparable worth, the source of existing male-female wage differentials, the extent of coverage of comparable worth, the intra-household behavior of married couples, and demand and supply elasticities. If, after comparable worth is introduced, employers are constrained to employ men and women in historical proportions, the adverse effects on aggregate employment, output, and efficiency would be much larger than if the employment constraint is based on applicant proportions. If existing wage gaps are the result of sex differences in productivity, the adverse of facts of comparable worth are relatively large; but if they are the result of discrimination, the efficiency losses are much smaller. If only part of the economy is subject to comparable worth, the efficiency loss is reduced under the productivity gap assumption, but increased if the wage gap is the result of discrimination. The redistributive effects of comparable worth on married men and women are sensitive to assumptions about intra-household behavior and the size of the gains from marriage. By contrast, unmarried women appear to benefit from comparable worth under most sets of assumptions while unmarried men lose.

Growth and Mortality of Shoots in Three Populations of Typha glauca Godr.

A double sampling technique and permanent quadrats were used to monitor seasonal changes in shoot density and aboveground standing crop in three Minnesota Typha glauca populations. Shoot growth began several weeks later in stands located in floating mats (Boot Lake and Cedar Creek) relative to a nonfloating stand (Lauderdale). Mortality reduced shoot density by 10.8% at Boot Lake, 6.3% at Cedar Creek, and by 53% at Lauderdale. Shoot death was largely confined to smaller than average shoots at Boot Lake and Cedar Creek. At Lauderdale many relatively large shoots were killed by a lepidopteran stem borer (Archanara oblonga Grt.) or a mammalian herbivore. Peak standing crop occurred at different times at the three sites and was 329 g/m2 at Boot Lake, 645 g/m2 at Cedar Creek, and 868 g/m2 at Lauderdale. These values underestimated actual aboveground productivity by 4.9, 0.5, and 6.3% at the three sites, respectively

The Wide Field Imaging Interferometry Testbed

We are developing a Wide-Field Imaging Interferometry Testbed (WIIT) in support of design studies for NASA's future space interferometry missions, in particular the SPIRIT and SPECS far-infrared/submillimeter interferometers. WIIT operates at optical wavelengths and uses Michelson beam combination to achieve both wide-field imaging and high-resolution spectroscopy. It will be used chiefly to test the feasibility of using a large-format detector array at the image plane of the sky to obtain wide-field interferometry images through mosaicing techniques. In this setup each detector pixel records interferograms corresponding to averaging a particular pointing range on the sky as the optical path length is scanned and as the baseline separation and orientation is varied. The final image is constructed through spatial and spectral Fourier transforms of the recorded interferograms for each pixel, followed by a mosaic/joint-deconvolution procedure of all the pixels. In this manner the image within the pointing range of each detector pixel is further resolved to an angular resolution corresponding to the maximum baseline separation for fringe measurements. We present the motivation for building the testbed, show the optical, mechanical, control, and data system design, and describe the image processing requirements and algorithms. WIIT is presently under construction at NASA's Goddard Space Flight Center.Comment: 7 pages, 3 figures, IEEE Aerospace Conference 200

Characterization of 40-Gbit/s pulses generated using a lithium niobate modulator at 1550 nm using frequency resolved optical gating

The characteristics of 40-Gbit/s pulses generated by exploiting the nonlinear characteristics of a Mach-Zender Lithium Niobate modulator are presented. A high spectral resolution frequency resolved optical gating apparatus has been developed to allow for the complete characterization of the intensity and phase of these pulses. The use of these measurements to simplify the design and optimization of an 80-Gbit/s pulse source, based on this 40-Gbit/s source followed by a nonlinear fiber compressor and multiplexer, is also demonstrated

Investigating Habituation to Premonitory Urges in Behavior Therapy for Tic Disorders

Behavior therapy is effective for Persistent Tic Disorders (PTDs), but behavioral processes facilitating tic reduction are not well understood. One process, habituation, is thought to create tic reduction through decreases in premonitory urge severity. The current study tested whether premonitory urges decreased in youth with PTDs (N = 126) and adults with PTDs (N = 122) who participated in parallel randomized clinical trials comparing behavior therapy to psychoeducation and supportive therapy (PST). Trends in premonitory urges, tic severity, and treatment outcome were analyzed according to the predictions of a habituation model, whereby urge severity would be expected to decrease in those who responded to behavior therapy. Although adults who responded to behavior therapy showed a significant trend of declining premonitory urge severity across treatment, results failed to demonstrate that behavior therapy specifically caused changes in premonitory urge severity. In addition, reductions in premonitory urge severity in those who responded to behavior therapy were significant greater than those who did not respond to behavior therapy but no different than those who responded or did not respond to PST. Children with PTDs failed to show any significant changes in premonitory urges. Reductions in premonitory urge severity did not mediate the relationship between treatment and outcome in either adults or children. These results cast doubt on the notion that habituation is the therapeutic process underlying the effectiveness of behavior therapy, which has immediate implications for the psychoeducation and therapeutic rationale presented in clinical practice. Moreover, there may be important developmental changes in premonitory urges in PTDs, and alternative models of therapeutic change warrant investigation