1,099 research outputs found
Development of Temperature and Humidity-Based Indicators for Diagnosing Problems in Low Tonnage, Split System Air Conditioners
This paper presents results of a survey of the
literature and identifies the most common degraded
conditions associated with low-tonnage air
conditioners. Other laboratory studies as well as
marketed diagnostic systems are also summarized. A
procedure for identification of useful, low-cost
temperature-based indicators of degraded conditions
has been developed at the Energy Systems
Laboratory, Texas A&M University in College
Station, TX under contract to Honeywell. This paper
presents the methodology used to identify the
temperature-based indicators for the most common
degraded conditions gleaned from the literature
Hypoxic pre-conditioning increases the infiltration of endothelial cells into scaffolds for dermal regeneration pre-seeded with mesenchymal stem cells.
Many therapies using mesenchymal stem cells (MSC) rely on their ability to produce and release paracrine signals with chemotactic and pro-angiogenic activity. These characteristics, however, are mostly studied under standard in vitro culture conditions. In contrast, various novel cell-based therapies imply pre-seeding MSC into bio-artificial scaffolds. Here we describe human bone marrow-derived MSC seeded in Integra matrices, a common type of scaffold for dermal regeneration (SDR). We show and measured the distribution of MSC within the SDR, where cells clearly establish physical interactions with the scaffold, exhibiting constant metabolic activity for at least 15 days. In the SDR, MSC secrete VEGF and SDF-1α and induce transwell migration of CD34(+) hematopoietic/endothelial progenitor cells, which is inhibited in the presence of a CXCR4/SDF-1α antagonist. MSC in SDR respond to hypoxia by altering levels of angiogenic signals such as Angiogenin, Serpin-1, uPA, and IL-8. Finally, we show that MSC-containing SDR that have been pre-incubated in hypoxia show higher infiltration of endothelial cells after implantation into immune deficient mice. Our data show that MSC are fully functional ex vivo when implanted into SDR. In addition, our results strongly support the notion of hypoxic pre-conditioning MSC-containing SDR, in order to promote angiogenesis in the wounds
Detecting Planets Around Very Low Mass Stars with the Radial Velocity Method
The detection of planets around very low-mass stars with the radial velocity
method is hampered by the fact that these stars are very faint at optical
wavelengths where the most high-precision spectrometers operate. We investigate
the precision that can be achieved in radial velocity measurements of low mass
stars in the near infrared (nIR) Y-, J-, and H-bands, and we compare it to the
precision achievable in the optical. For early-M stars, radial velocity
measurements in the nIR offer no or only marginal advantage in comparison to
optical measurements. Although they emit more flux in the nIR, the richness of
spectral features in the optical outweighs the flux difference. We find that
nIR measurement can be as precise than optical measurements in stars of
spectral type ~M4, and from there the nIR gains in precision towards cooler
objects. We studied potential calibration strategies in the nIR finding that a
stable spectrograph with a ThAr calibration can offer enough wavelength
stability for m/s precision. Furthermore, we simulate the wavelength-dependent
influence of activity (cool spots) on radial velocity measurements from optical
to nIR wavelengths. Our spot simulations reveal that the radial velocity jitter
does not decrease as dramatically towards longer wavelengths as often thought.
The jitter strongly depends on the details of the spots, i.e., on spot
temperature and the spectral appearance of the spot. Forthcoming nIR
spectrographs will allow the search for planets with a particular advantage in
mid- and late-M stars. Activity will remain an issue, but simultaneous
observations at optical and nIR wavelengths can provide strong constraints on
spot properties in active stars.Comment: accepted by ApJ, v2 accepted revision with new precision
calculations, abstract abride
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The Status of Six-Man Football in the High Schools of Texas and a Manual for Coaches
This thesis examines the status of six-man football in Texas high schools
A cool starspot or a second transiting planet in the TrES-1 system?
We investigate the origin of a flux increase found during a transit of
TrES-1, observed with the HST. This feature in the HST light curve cannot be
attributed to noise and is supposedly a dark area on the stellar surface of the
host star eclipsed by TrES-1 during its transit. We investigate the likeliness
of two possible hypothesis for its origin: A starspot or a second transiting
planet. We made use of several transit observations of TrES-1 from space with
the HST and from ground with the IAC-80 telescope. On the basis of these
observations we did a statistical study of flux variations in each of the
observed events, to investigate if similar flux increases are present in other
parts of the data set. The HST observation presents a single clear flux rise
during a transit whereas the ground observations led to the detection of two
such events but with low significance. In the case of having observed a
starspot in the HST data, assuming a central impact between the spot and
TrES-1, we would obtain a lower limit for the spot radius of 42000 km. For this
radius the spot temperature would be 4690 K, 560 K lower then the stellar
surface of 5250 K. For a putative second transiting planet we can set a lower
limit for its radius at 0.37 R and for periods of less than 10.5 days, we
can set an upper limit at 0.72 R. Assuming a conventional interpretation,
then this HST observation constitutes the detection of a starspot.
Alternatively, this flux rise might also be caused by an additional transiting
planet. The true nature of the origin can be revealed if a wavelength
dependency of the flux rise can be shown or discarded with a higher certainty.
Additionally, the presence of a second planet can also be detected by radial
velocity measurements.Comment: 8 pages, 6 figures, accepted for publication in A&
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