Static and Dynamic Spectroscopy of (Al,Ga)As/GaAs Microdisk Lasers with Interface Fluctuation Quantum Dots

We have studied the steady state and dynamic optical properties of semiconductor microdisk lasers whose active region contains interface fluctuation quantum dots in GaAs/(Ga,Al)As quantum wells. Steady-state measurements of the stimulated emission via whispering gallery modes yield a quality factor $Q \sim 5600$ and a coupling constant $\beta \sim 0.09$. The broad gain spectrum produces mode hopping between spectrally adjacent whispering gallery modes as a function of temperature and excitation power. Time- and energy-resolved photoluminescence measurements show that the emission rise and decay rates increase significantly with excitation power. Marked differences are observed between the radiative decay rates in processed and unprocessed samples.Comment: To appear in Phys. Rev.

The distribution and taxonomy of Kangaroo rats (genus dipodomys) of Utah

journal articleThe first comprehensive work on the mammals of Utah was published by Barnes in 1922. In this work (Barnes 1922:86-87) only two kangaroo rats were known from the confines of the state. They were known at that time as Perodipus montcmus utahensis and Perodipus longipes. In Barnes revised edition (1927:107-108) these same two forms were still the only ones recognized for the state. They were now named Dipodomys ordii utahensis and Dipodomys ordii longipes. Grinnell (1919:203) had synonymized perodipus under the older name Dipodomys. Goldman (1917:109) placed these two Utah forms under Dipodomys ordii

Stellar Activity and its Implications for Exoplanet Detection on GJ 176

We present an in-depth analysis of stellar activity and its effects on radial velocity (RV) for the M2 dwarf GJ 176 based on spectra taken over 10 years from the High Resolution Spectrograph on the Hobby-Eberly Telescope. These data are supplemented with spectra from previous observations with the HIRES and HARPS spectrographs, and V- and R-band photometry taken over 6 years at the Dyer and Fairborn observatories. Previous studies of GJ 176 revealed a super-Earth exoplanet in an 8.8-day orbit. However, the velocities of this star are also known to be contaminated by activity, particularly at the 39-day stellar rotation period. We have examined the magnetic activity of GJ 176 using the sodium I D lines, which have been shown to be a sensitive activity tracer in cool stars. In addition to rotational modulation, we see evidence of a long-term trend in our Na I D index, which may be part of a long-period activity cycle. The sodium index is well correlated with our RVs, and we show that this activity trend drives a corresponding slope in RV. Interestingly, the rotation signal remains in phase in photometry, but not in the spectral activity indicators. We interpret this phenomenon as the result of one or more large spot complexes or active regions which dominate the photometric variability, while the spectral indices are driven by the overall magnetic activity across the stellar surface. In light of these results, we discuss the potential for correcting activity signals in the RVs of M dwarfs.Comment: Accepted for publication in Ap

The Rotation Period of the Planet-Hosting Star HD 189733

We present synoptic optical photometry of HD 189733, the chromospherically active parent star of one of the most intensively studied exoplanets. We have significantly extended the timespan of our previously reported observations and refined the estimate of the stellar rotation period by more than an order of magnitude: $P = 11.953\pm 0.009$ days. We derive a lower limit on the inclination of the stellar rotation axis of 56\arcdeg (with 95% confidence), corroborating earlier evidence that the stellar spin axis and planetary orbital axis are well aligned.Comment: To appear in A

An evaluation of the implementation of Georgia's Pre-k program: Report of the findings from the Georgia Early Childhood Study (2002-03)

After ten years, Georgia continues to lead the nation in providing full day, publicly subsidized Pre-K to four-year-olds whose parents choose to enroll them. In this report, we assess the extent to which differences in the way Pre-K is implemented affect children's development. Do teachers with higher levels of education have more positive impacts on children's development? Do teaching styles make a difference in terms of children's outcomes by the end of kindergarten? Do children taught using certain curricula fare better than those taught using others? Answers to questions such as these can assist Pre-K administrators in refining Georgia's program and inform those in other states who are developing or expanding their prekindergarten programs

Effect of prolonged space flight on cardiac function and dimensions

Echocardiographic studies were performed preflight 5 days before launch and on recovery day and 1, 2, 4, 11, 31 and 68 days postflight. From these echocardiograms measurements were made. From these primary measurements, left ventricular end-diastolic volume, end-systolic volume, stroke volume, and mass were derived using the accepted assumptions. Findings in the Scientist Pilot and Pilot resemble those seen in trained distance runners. Wall thickness measurements were normal in all three crewmembers preflight. Postflight basal studies were unchanged in the Commander on recovery day through 68 days postflight in both the Scientist Pilot and Pilot, however, the left ventricular end-diastolic volume, stroke volume, and mass were decreased slightly. Left ventricular function curves were constructed for the Commander and Pilot by plotting stroke volume versus end-diastolic volume. In both astronauts, preflight and postflight data fell on the same straight line demonstrating that no deterioration in cardiac function had occurred. These data indicate that the cardiovascular system adapts well to prolonged weightlessness and suggest that alterations in cardiac dimensions and function are unlikely to limit man's future in space

A safe method for the retrieval of a dislocated trial head in total hip arthroplasty

Total hip arthroplasty is a life changing procedure providing a significant improvement in the quality of life for those receiving treatment. An 81-year-old male with severe right sided hip osteoarthritis underwent uncemented total hiparthroplasty. Intraoperatively the 32mm trial head dislodged from the trial stem over the anterior rim of the acetabulum relocating to within the pelvic cavity. Time efficient retrieval was performed during primary surgery through a mini-incision at the iliac crest

Comparison of the Effects of Supplemental Red Palm Oil and Sunflower oil on Maternal Vitamin A Status.

Conflicting results have been reported on the ability of dietary carotenoids to improve vitamin A status in lactating women. Red palm oil is one of the richest dietary sources of beta-carotene. We aimed to determine the efficacy of red palm oil in increasing retinol and provitamin A status in pregnant and lactating women. Ninety rural, pregnant Tanzanian women from 3 randomly selected villages were recruited during their third trimester to participate in 3 dietary intervention groups: a control group, who were encouraged to maintain the traditional practice of eating staples with dark-green leafy vegetables, and 2 study groups, who were given either sunflower or red palm oil for use in household food preparations. The intervention lasted 6 mo. Plasma samples were collected at the third trimester and 1 and 3 mo postpartum, and breast-milk samples were collected 1 and 3 mo postpartum. Supplementation with red palm oil, which is rich in provitamin A, increased alpha- and beta-carotene concentrations significantly (P < 0.001) in both plasma and breast milk. Plasma retinol concentrations were similar in all dietary groups. Breast-milk retinol concentrations tended to decrease from 1 to 3 mo postpartum in the control group, but were maintained in both oil groups. The difference in change in breast-milk retinol concentration between the red palm oil group and the control group was significant (P = 0.041). Consumption of red palm oil increases concentrations of alpha- and beta-carotene in both breast milk and serum and maintains breast-milk retinol concentrations. Sunflower oil consumption seems to conserve breast-milk retinol similarly to consumption of red palm oil. Breast-milk retinol might be maintained through increased dietary intake of these vegetable oils and use of mild cooking preparation methods (such as the addition of oil at the end of cooking and avoidance of frying)

BUMC Annual Report

Annual report of the Boston University Medical Center