A study of the thermal conductance of bolted joints Final report

Design-oriented approach for predicting thermal resistance of bolted lap joint including bibliograph

Highway and runway traction studies - The problem, history, objectives, and NASA program

Review of highway and runway traction studie

An investigation of environmental factors associated with the current and proposed jetty systems at Belle Pass, Louisiana

The history of the existing jetty system at Belle Pass was investigated to determine its past effect on the littoral currents and beach erosion. Present flow patterns and erosion rates were also studied, along with the prevailing recession rates of local beaches not influenced by the jetty system. Aerial photographs and maps were used in conjunction with periodic hydraulic measurements, ground observations, and physical measurements of beach erosion. A scale model was constructed to further the study of flow patterns and velocities. It is shown that the existing jetty has not adversely affected the coastline in the area; erosive processes have been retarded by the jetty and its companion groin. Future erosion patterns are predicted, and projected effects of the proposed jetty system are given

Photometry of VS0329+1250: A New, Short-Period SU Ursae Majoris Star

Time-resolved CCD photometry is presented of the recently-discovered (V~15 at maximum light) eruptive variable star in Taurus, which we dub VS0329+1250. A total of ~20 hr of data obtained over six nights reveals superhumps in the light curves, confirming the star as a member of the SU UMa class of dwarf novae. The superhumps recur with a mean period of 0.053394(7) days (76.89 min), which represents the shortest superhump period known in a classical SU UMa star. A quadratic fit to the timings of superhump maxima reveals that the superhump period was increasing at a rate given by dP/dt ~ (2.1 +/- 0.8) x 10^{-5} over the course of our observations. An empirical relation between orbital period and the absolute visual magnitude of dwarf novae at maximum light, suggests that VS0329+1250 lies at a distance of ~1.2 +/- 0.2 kpc.Comment: V2 - The paper has been modified to incorporate the referee's comments, and has now been accepted for publication in the PASP. The most significant change is that we are now able to confirm that the superhump period was increasing during the course of our observation

Detection of orbital and superhump periods in Nova V2574 Ophiuchi (2004)

We present the results of 37 nights of CCD unfiltered photometry of nova V2574 Oph (2004) from 2004 and 2005. We find two periods of 0.14164 d (~3.40 h) and 0.14773 d (~3.55 h) in the 2005 data. The 2004 data show variability on a similar timescale, but no coherent periodicity was found. We suggest that the longer periodicity is the orbital period of the underlying binary system and that the shorter period represents a negative superhump. The 3.40 h period is about 4% shorter than the orbital period and obeys the relation between superhump period deficit and binary period. The detection of superhumps in the light curve is evidence of the presence of a precessing accretion disk in this binary system shortly after the nova outburst. From the maximum magnitude - rate of decline relation, we estimate the decay rate t_2 = 17+/-4 d and a maximum absolute visual magnitude of M_Vmax = -7.7+/-1.7 mag.Comment: 6 pages, 6 figures, 2 .sty files, AJ accepted, minor change to one of reference

Development and Validation of the Microbiology for Health Sciences Concept Inventory

Identifying misconceptions in student learning is a valuable practice for evaluating student learning gains and directing educational interventions. By accurately identifying students’ knowledge and misconceptions about microbiology concepts, instructors can design effective classroom practices centered on student understanding. Following the development of ASM’s Curriculum Guidelines in 2012, we developed a concept inventory, the Microbiology for Health Sciences Concept Inventory (MHSCI), that measures learning gains and identifies student misconceptions in health sciences microbiology classrooms. The 23-question MHSCI was delivered to a wide variety of students at multiple institution types. Psychometric analysis identified that the MHSCI instrument is both discriminatory and reliable in measuring student learning gains. The MHSCI results correlated with course outcomes, showing the value of using the instrument alongside course level assessments to measure student learning. The MHSCI is a reliable and efficient way to measure student learning in microbiology and can be used both as a faculty development tool and an effective student assessment tool

Long-term optical and X-ray observations of the old novae DI Lacertae and V841 Ophiuchi

We present an analysis of ground-based optical photometry and spectroscopy, and Rossi X-ray Timing Explorer X-ray observations of the old novae DI Lacertae and V841 Ophiuchi. Our optical photometry data (obtained with the automated photometry telescope RoboScope) comprise an almost decade-long light curve for each star, while the contemporaneous spectroscopy and X-ray observations repeatedly sampled each nova during separate intervals of ~45-55 d in length. The long-term optical light curves of both novae reveal quasiperiodic variability on typical time scales of ~30-50 d with amplitudes of dV ~ 0.4-0.8 mag. V841 Oph also displays a long-term, sinusoidal modulation of its optical light on a time scale of 3.5-5 yr. The optical spectra of these novae display quite different characteristics from each other, with DI Lac showing narrow Balmer emission cores situated in broad absorption troughs while V841 Oph exhibits strong single-peaked Balmer, He I and He II emission lines. We find little change between spectra obtained during different optical brightness states. The X-ray count rates for both novae were very low (< ~1.5 ct/s) and there was no reliable correlation between X-ray and optical brightness. The combined X-ray spectrum of DI Lac is best fit by a bremsstrahlung emission model (with kT ~ 4 keV and N_H < 1.8x10^22 cm^-3); the X-ray spectrum of V841 Oph is too weak to allow model fitting. We discuss the possible origin of variability in these old novae in terms of magnetic activity on the secondary star, dwarf nova type disk instabilities, and the ``hibernation'' scenario for cataclysmic variable stars.Comment: 16 pages, 9 figures, 4 tables; accepted by PASP on 28 August 2000 for the December 2000 issu

Circumstellar disks in binary star systems

In this paper we study the evolution of viscous and radiative circumstellar disks under the influence of a companion star. We focus on the eccentric {\gamma} Cephei and {\alpha} Centauri system as examples and compare the disk quantities such as disk eccentricity and precession rate to previous isothermal simulations. We perform two-dimensional hydrodynamical simulations of the binary star systems under the assumption of coplanarity of the disk, host star and binary companion. We use the grid-based, staggered mesh code FARGO with an additional energy equation to which we added radiative cooling based on opacity tables. The eccentric binary companion perturbs the disk around the primary star periodically. Upon passing periastron spirals arms are induced that wind from the outer disk towards the star. In isothermal simulations this results in disk eccentricities up to {\epsilon}_disk ~ 0.2, but in more realistic radiative models we obtain much smaller eccentricities of about {\epsilon}_disk ~ 0.04 - 0.06 with no real precession. Models with varying viscosity and disk mass indicate show that disks with less mass have lower temperatures and higher disk eccentricity. The rather large high disk eccentricities, as indicated in previous isothermal disk simulations, implied a more difficult planet formation in the {\gamma} Cephei system due to the enhanced collision velocities of planetesimals. We have shown that under more realistic conditions with radiative cooling the disk become less eccentric and thus planet formation may be made easier. However, we estimate that the viscosity in the disk has to very small, with {\alpha} \lesssim 0.001, because otherwise the disk's lifetime will be too short to allow planet formation to occur along the core instability scenario. We estimate that the periodic heating of the disk in eccentric binaries will be observable in the mid-IR regime.Comment: 12 pages, 15 figures, accepted for publication in A&

What Our Hands Say: Exploring Gesture Use in Subgroups of Children With Language Delay

Purpose The aim of this study was to investigate whether children with receptive-expressive language delay (R/ELD) and expressive-only language delay (ELD) differ in their use of gesture; to examine relationships between their use of gesture, symbolic comprehension, and language; to consider implications for assessment and for the nature of problems underlying different profiles of early language delay. Method Twelve children with ELD (8 boys, 4 girls) and 10 children with R/ELD (8 boys, 2 girls), aged 2–3 years, were assessed on measures of gesture use and symbolic comprehension. Results Performance of the R/ELD group was significantly poorer than performance of the ELD group on measures of gesture and symbolic comprehension. Gesture use and symbolic comprehension were significantly associated with receptive language, but associations with expressive language were not significant. Conclusions Findings of this study support previous research pointing to links between gesture and language development, and more specifically, between delays in gesture, symbolic understanding, and receptive rather than expressive language. Given potentially important implications for the nature of problems underlying ELD and R/ELD, and for assessment of children with language delay, this preliminary study invites further investigation comparing the use of different gesture types in samples of children matched on age and nonverbal IQ

A model of superoutbursts in binaries of SU UMa type

A new mechanism explaining superoutbursts in binaries of SU UMa type is proposed. In the framework of this mechanism the accretion rate increase leading to the superoutburst is associated with formation of a spiral wave of a new "precessional" type in inner gasdynamically unperturbed parts of the accretion disc. The possibility of existence of this type of waves was suggested in our previous work (astro-ph/0403053). The features of the "precessional" spiral wave allow explaining both the energy release during the outburst and all its observational manifestations. The distinctive characteristic of a superoutburst in a SU UMa type star is the appearance of the superhump on the light curve. The proposed model reproduces well the formation of the superhump as well as its observational features, such as the period that is 3-7% longer than the orbital one and the detectability of superhumps regardless of the binary inclination.Comment: LaTeX, 20 pages, 4 figures, to be published in Astron. Z