6,086 research outputs found
CHARACTER ASSESSMENT, GENUS LEVEL BOUNDARIES, AND PHYLOGENETIC ANALYSES OF THE FAMILY RHACOPHORIDAE:: A REVIEW AND PRESENT DAY STATUS
The first comprehensive phylogenetic analysis of the family Rhacophoridae was conducted by Liem (1970) scoring 81 species for 36 morphological characters. Channing (1989), in a reanalysis of Liem’s study, produced a phylogenetic hypothesis different from that of Liem. We compared the two studies and produced a third phylogenetic hypothesis based on the same characters. We also present the synapomorphic characters from Liem that define the major clades and each genus within the family. Finally, we summarize intergeneric relationships within the family as hypothesized by other studies, and the family’s current status as it relates to other ranoid families
Spectral Response of the Pulsationally-Induced Shocks in the Atmosphere of BW Vulpeculae
The star BW Vul excites an extremely strong radial pulsation that grows in
its envelope and is responsible for visible shock features in the continuum
flux and spectral line profiles emerging in the atmosphere At two phases
separated by 0.8 cycles. Material propelled upwards in the atmosphere from the
shock returns to the lower photosphere where it creates a second shock just
before the start of the next cycle. We have obtained three nights of echelle
data for this star over about 5 pulsation cycles (P = 0.201 days) in order to
evaluate the effects of on a number of important lines in the spectrum,
including the HeI 5875A and 6678A lines. These data were supplemented by
archival high-dispersion IUE (UV) data from 1994. A comparison of profiles of
the two HeI lines during the peak of the infall activity suggests that
differences in the development of the blue wing at this time are due to heating
and short-lived formations of an optically thin layer above the atmospheric
region compressed by the infall. This discovery and the well-known decreases in
equivalent widths of the CII 6578-83A doublet at the two shock phases, suggests
that shock flattens the temperature gradient and produces heating in heating
the upper atmosphere. Except for absorptions in the blue wings of the UV
resonance lines, we find no evidence for sequential shock delays arriving at
various regions of line formation of the photosphere (a "Van Hoof effect").
Phase lags cited by some former observers may be false indicators arising from
varying degrees of desaturation of multiple lines, such as for the red HeI
lines. In addition, an apparent lag in the equivalent width curve of lines
arising from less excited atomic levels could instead be caused by post-shock
cooling, followed by a rebound shock.Comment: 12 pages in Latex/MNRAS format, 9 eps-format figure
Acceleration of Wound Healing with High Voltage, Monophasic, Pulsed Current
The purpose of this study was to determine whether high voltage electrical stimulation accelerates the rate of healing of dermal ulcers. Sixteen patients with stage IV decubitus ulcers, ranging in age from 20 to 89 years, participated in the study. The patients were assigned randomly to either a Treatment Group (n = 9) or a Control Group (n = 7). Patients in the Treatment Group received daily electrical stimulation from a commercial high voltage generator. Patients in the Control Group had the electrodes applied daily but received no stimulation. The ulcers of patients in the Treatment Group healed at a mean rate of 44.8% a week and healed 100% over a mean period of 7.3 weeks. The ulcers of patients in the Control Group increased in area an average of 11.6% a week and increased 28.9% over a mean period of 7.4 weeks. The results of this study suggest that high voltage stimulation accelerates the healing rate of stage IV decubitus ulcers in human subjects
A three channel telemetry system
A three channel telemetry system intended for biomedical applications is described. The transmitter is implemented in a single chip using a 2 micron BiCMOS processes. The operation of the system and the test results from the latest chip are discussed. One channel is always dedicated to temperature measurement while the other two channels are generic. The generic channels carry information from transducers that are interfaced to the system through on-chip general purpose operational amplifiers. The generic channels have different bandwidths: one from dc to 250 Hz and the other from dc to 1300 Hz. Each generic channel modulates a current controlled oscillator to produce a frequency modulated signal. The two frequency modulated signals are summed and used to amplitude modulate the temperature signal which acts as a carrier. A near-field inductive link telemeters the combined signals over a short distance. The chip operates on a supply voltage anywhere from 2.5 to 3.6 Volts and draws less than 1 mA when transmitting a signal. The chip can be incorporated into ingestible, implantable and other configurations. The device can free the patient from tethered data collection systems and reduces the possibility of infection from subcutaneous leads. Data telemetry can increase patient comfort leading to a greater acceptance of monitoring
Repetitive Delone Sets and Quasicrystals
This paper considers the problem of characterizing the simplest discrete
point sets that are aperiodic, using invariants based on topological dynamics.
A Delone set whose patch-counting function N(T), for radius T, is finite for
all T is called repetitive if there is a function M(T) such that every ball of
radius M(T)+T contains a copy of each kind of patch of radius T that occurs in
the set. This is equivalent to the minimality of an associated topological
dynamical system with R^n-action. There is a lower bound for M(T) in terms of
N(T), namely N(T) = O(M(T)^n), but no general upper bound.
The complexity of a repetitive Delone set can be measured by the growth rate
of its repetitivity function M(T). For example, M(T) is bounded if and only if
the set is a crystal. A set is called is linearly repetitive if M(T) = O(T) and
densely repetitive if M(T) = O(N(T))^{1/n}). We show that linearly repetitive
sets and densely repetitive sets have strict uniform patch frequencies, i.e.
the associated topological dynamical system is strictly ergodic. It follows
that such sets are diffractive. In the reverse direction, we construct a
repetitive Delone set in R^n which has
M(T) = O(T(log T)^{2/n}(log log log T)^{4/n}), but does not have uniform
patch frequencies. Aperiodic linearly repetitive sets have many claims to be
the simplest class of aperiodic sets, and we propose considering them as a
notion of "perfectly ordered quasicrystal".Comment: To appear in "Ergodic Theory and Dynamical Systems" vol.23 (2003). 37
pages. Uses packages latexsym, ifthen, cite and files amssym.def, amssym.te
Chronic Dermal Ulcer Healing Enhanced with Monophasic Pulsed Electrical Stimulation
The purposes of this randomized, double-blind, multicenter study were to compare healing of chronic dermal ulcers treated with pulsed electrical stimulation with healing of similar wounds treated with sham electrical stimulation and to evaluate patient tolerance to the therapeutic protocol. Forty-seven patients, aged 29 to 91 years, with 50 stage II, III, and IV ulcers were randomly assigned to either a treatment group (n=26) or a control (sham treatment) group (n=24). Treated wounds received 30 minutes of pulsed cathodal electrical stimulation twice daily at a pulse frequency of 128 pulses per second (pps) and a peak amplitude of 29.2 mA if the wound contained necrotic tissue or any drainage that was not serosanguinous. A saline-moistened nontreatment electrode was applied 30.5 cm (12 in) cephalad from the wound. This protocol was continued for 3 days after the wound was debrided or exhibited serosanguinous drainage. Thereafter, the polarity of the treatment electrode on the wound was changed every 3 days until the wound progressed to a stage II classification. The pulse frequency was then reduced to 64 pps, and the treatment electrode polarity was changed daily until the wound was healed. Patients in the control group were treated with the same protocol, except they received sham electrical stimulation. After 4 weeks, wounds in the treatment and control groups were 44% and 67% of their initial size, respectively. The healing rates per week for the treatment and control groups were 14% and 8.25%, respectively. The results of this study indicate that pulsed electrical stimulation has a beneficial effect on healing stage II, III, and IV chronic dermal ulcers
An analysis of ultraviolet spectra of Extreme Helium Stars and new clues to their origins
Abundances of about 18 elements including the heavy elements Y and Zr are
determined from Hubble Space Telescope Space Telescope Imaging Spectrograph
ultraviolet spectra of seven extreme helium stars (EHes): LSE 78, BD+10 2179,
V1920 Cyg, HD 124448, PV Tel, LS IV -1 2, and FQ Aqr. New optical spectra of
the three stars -- BD+10 2179, V1920 Cyg, and HD 124448 were analysed. The
abundance analyses is done using LTE line formation and LTE model atmospheres
especially constructed for these EHe stars. The stellar parameters derived from
an EHe's UV spectrum are in satisfactory agreement with those derived from its
optical spectrum. Adopted abundances for the seven EHes are from a combination
of the UV and optical analyses. Published results for an additional ten EHes
provide abundances obtained in a nearly uniform manner for a total of 17 EHes,
the largest sample on record. The initial metallicity of an EHe is indicated by
the abundance of elements from Al to Ni; Fe is adopted to be the representative
of initial metallicity. Iron abundances range from approximately solar to about
one-hundredth of solar. Clues to EHe evolution are contained within the H, He,
C, N, O, Y, and Zr abundances. Two novel results are (i) the O abundance for
some stars is close to the predicted initial abundance yet the N abundance
indicates almost complete conversion of initial C, N, and O to N by the
CNO-cycles; (ii) three of the seven stars with UV spectra show a strong
enhancement of Y and Zr attributable to an s-process. The observed compositions
are discussed in light of expectations from accretion of a He white dwarf by a
CO white dwarf.Comment: 126 pages, 15 figures, 20 Tables, accepted for publication in the Ap
Abundance analyses of helium-rich subluminous B stars
The connection between helium-rich hot subdwarfs of spectral types O and B
(He-sdB) has been relatively unexplored since the latter were found in
significant numbers in the 1980's. In order to explore this connection further,
we have analysed the surface composition of six He-sdB stars, including LB
1766, LB 3229, SB 21 (= Ton-S 137 = BPS 29503-0009), BPS 22940-0009, BPS
29496-0010, and BPS 22956-0094. Opacity-sampled line-blanketed model
atmospheres have been used to derive atmospheric properties and elemental
abundances. All the stars are moderately metal-poor compared with the Sun
([Fe/H] ~ -0.5). Four stars are nitrogen-rich, two of these are carbon-rich,
and at least four appear to be neon-rich. The data are insufficient to rule out
binarity in any of the sample. The surface composition and locus of the N-rich
He-sdBs are currently best explained by the merger of two helium white dwarfs,
or possibly by the merger of a helium white dwarf with a post-sdB white dwarf.
C-rich He-sdBs require further investigation.Comment: Accepted 2010 July
Space station thermal control surfaces
Mission planning documents were used to analyze the radiator design and thermal control surface requirements for both space station and 25-kW power module, to analyze the missions, and to determine the thermal control technology needed to satisfy both sets of requirements. Parameters such as thermal control coating degradation, vehicle attitude, self eclipsing, variation in solar constant, albedo, and Earth emission are considered. Four computer programs were developed which provide a preliminary design and evaluation tool for active radiator systems in LEO and GEO. Two programs were developed as general programs for space station analysis. Both types of programs find the radiator-flow solution and evaluate external heat loads in the same way. Fortran listings are included
Double white dwarf mergers and elemental surface abundances in extreme helium and R Coronae Borealis stars
The surface abundances of extreme helium (EHe) and R Coronae Borealis (RCB)
stars are discussed in terms of the merger of a carbon-oxygen white dwarf with
a helium white dwarf. The model is expressed as a linear mixture of the
individual layers of both constituent white dwarfs, taking account of the
specific evolution of each star. In developing this recipe from previous
versions, particular attention has been given to the inter-shell abundances of
the asymptotic giant branch star which evolved to become the carbon-oxygen
white dwarf. Thus the surface composition of the merged star is estimated as a
function of the initial mass and metallicity of its progenitor. The question of
whether additional nucleosynthesis occurs during the white dwarf merger has
been examined.
The high observed abundances of carbon and oxygen must either originate by
dredge-up from the core of the carbon-oxygen white dwarf during a cold merger
or be generated directly by alpha-burning during a hot merger. The presence of
large quantities of O18 may be consistent with both scenarios, since a
significant O18 pocket develops at the carbon/helium boundary in a number of
our post-AGB models.
The production of fluorine, neon and phosphorus in the AGB intershell
produces n overabundance at the surface of the merged stars, but generally not
in sufficient quantity. However, the evidence for an AGB origin for these
elements points to progenitor stars with initial masses in the range 1.9 - 3
solar masses.
There is not yet sufficient information to discriminate the origin (fossil or
prompt) of all the abundance anomalies observed in EHe and RCB stars. Further
work is required on argon and s-process elements in the AGB intershell, and on
the predicted yields of all elements from a hot merger.Comment: 20 pages, 8 figures, 3 tables, MNRAS in pres
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