3,407 research outputs found
Mapping the Shores of the Brown Dwarf Desert III: Young Moving Groups
We present the results of an aperture masking interferometry survey for
substellar companions around 67 members of the young (~8-200Myr) nearby
(~5-86pc) AB Doradus, Beta Pictoris, Hercules-Lyra, TW Hya, and
Tucana-Horologium stellar associations. Observations were made at near infrared
wavelengths between 1.2-3.8 microns using the adaptive optics facilities of the
Keck II, VLT UT4, and Palomar Hale Telescopes. Typical contrast ratios of
~100-200 were achieved at angular separations between ~40-320mas, with our
survey being 100% complete for companions with masses below 0.25\msolar across
this range. We report the discovery of a \msolar companion to
HIP14807, as well as the detections and orbits of previously known stellar
companions to HD16760, HD113449, and HD160934. We show that the companion to
HD16760 is in a face-on orbit, resulting in an upward revision of its mass from
\mjupiter to \msolar. No substellar
companions were detected around any of our sample members, despite our ability
to detect companions with masses below 80\mjupiter for 50 of our targets: of
these, our sensitivity extended down to 40\mjupiter around 30 targets, with a
subset of 22 subject to the still more stringent limit of 20\mjupiter. A
statistical analysis of our non-detection of substellar companions allows us to
place constraints on their frequency around ~0.2-1.5\msolar stars. In
particular, considering companion mass distributions that have been proposed in
the literature, we obtain an upper limit estimate of ~9-11% for the frequency
of 20-80\mjupiter companions between 3-30AU at 95% confidence, assuming that
their semimajor axes are distributed according to in this range.Comment: Accepted by Ap
Changes in midbrain pain receptor expression, gait and behavioral sensitivity in a rat model of radiculopathy.
Intervertebral disc herniation may contribute to inflammatory processes that associate with radicular pain and motor deficits. Molecular changes at the affected dorsal root ganglion (DRG), spinal cord, and even midbrain, have been documented in rat models of radiculopathy or nerve injury. The objective of this study was to evaluate gait and the expression of key pain receptors in the midbrain in a rodent model of radiculopathy. Radiculopathy was induced by harvesting tail nucleus pulposus (NP) and placing upon the right L5 DRG in rats (NP-treated, n=12). Tail NP was discarded in sham-operated animals (n=12). Mechanical allodynia, weight-bearing, and gait were evaluated in all animals over time. At 1 and 4 weeks after surgery, astrocyte and microglial activation was tested in DRG sections. Midbrain sections were similarly evaluated for immunoreactivity to serotonin (5HT(2B)), mu-opioid (µ-OR), and metabotropic glutamate (mGluR4 and 5) receptor antibodies. NP-treated animals placed less weight on the affected limb 1 week after surgery and experienced mechanical hypersensitivity over the duration of the study. Astroctye activation was observed at DRGs only at 4 weeks after surgery. Findings for pain receptors in the midbrain of NP-treated rats included an increased expression of 5HT(2B) at 1, but not 4 weeks; increased expression of µ-OR and mGluR5 at 1 and 4 weeks (periaqueductal gray region only); and no changes in expression of mGluR4 at any point in this study. These observations provide support for the hypothesis that the midbrain responds to DRG injury with a transient change in receptors regulating pain responses
Izolirano povećanje klitorisa zbog pravog hermafroditizma
True hermaphroditism represents a heterogeneous condition in terms of its phenotypic presentation and genetic background. There is a wide spectrum ranging from frankly male to frankly female external genitalia, however, with a predominance of ambiguity. The most frequently observed karyotype is 46,XX, followed by various types of chromosome mosaicism, whereas the rarest one is 46,XY. Simultaneous presence of testicular and ovarian tissue either in separate gonads or in one named ovotestisis required for the diagnosis. In neonatal period our patient was noted to have isolated clitorimegaly (15 mm) with otherwise normal female external genitalia and no palpable gonads either in labia or in inguinal areas. The levels of electrolytes, 17-hydroxyprogesterone (17 OH P), androstenedione and renin were within the reference values. Baseline plasma level of testosterone was elevated as well as its response in the human chorionic gonadotropin (hCG) stimulation test. The presence of uterus was discovered by imaging techniques but gonadal localization was not possible. Karyotype was 46,XY. According to clinical and laboratory findings, the diagnosis of 46,XY partial gonadal dysgenesis was made. During surgery, reduction of clitoris was performed while laparotomy revealed a right ovotestis (confirmed by histology) which was removed. The left gonad was not identified and biopsy of suspected tissue revealed fallopian tube. Considering obvious female appearance of external genitalia and its potential function, it was suggested that the baby should be reared as a girl. As there is no clinical, laboratory or imaging finding which could differ true hermaphroditism from some other types of intersex, definitive diagnosis depends on gonadal histology.Pravi hermafroditizam heterogena je skupina stanja prema o fenotipskoj prezentaciji i genetskoj osnovi. Moguć je cijeli spektar od potpuno muških do potpuno ženskih vanjskih genitalija, ipak uz prevlast dvosmislenih genitalija. Najzastupljeniji je kariogram 46 XX, zatim razni oblici mozaicizma, a tek potom 46 XY. Istodobno prisutno tkivo testisa i ovarija nalazi se u odvojenim gonadama ili u okviru jedne gonade, ovotestisu. Naše dijete je u novorođenačkoj dobi imalo izoliranu hipertrofiju klitorisa (15 mm), uz inače uredne ženske vanjske genitalije, bez palpabilnih gonada bilo u labijama ili ingvinalnom području. Razina elektrolita, 17 OH P, androstenediona i renina bila je uredna. Bazalna razina testosterona te odgovor u HCG testu bili su pozitivni. Slikovnim pretragama utvrdili smo prisutnost uterusa, ali lokalizacija gonada nije bila moguća. Kariogram je 46,XY. Prema kliničkim i laboratorijskim nalazima postavljena je dijagnoza 46,XY parcijalne gonadne disgeneze. Tijekom operacijskog zahvata učinjena je redukcija klitorisa te laparotomija kojom se je locirala i odstranila desna gonada, patohistološki nalaz koje je upućivao na ovotestis. Lijeva gonada nije sa sigurnošću locirana pa je učinjena samo biopsija pretpostavljenog tkiva PHD nalaz kojega je odgovarao stjenci jajovoda. S obzirom na izrazitu feminiziranost vanjskih genitalija u fenotipskom i funkcionalnom smislu preporučeno je da se dijete odgaja kao žensko. Kako ne postoji osobitost koja bi klinički, laboratorijski ili slikovno razlikovala pravi hermafroditizam od nekih drugih oblika interseksa, konačna dijagnoza ovisi o patohistološkom nalazu gonada
The Parkes Galactic Meridian Survey (PGMS): observations and CMB polarization foreground analysis
We present observations and CMB foreground analysis of the Parkes Galactic
Meridian Survey (PGMS), an investigation of the Galactic latitude behaviour of
the polarized synchrotron emission at 2.3 GHz with the Parkes Radio Telescope.
The survey consists of a 5-deg wide strip along the Galactic meridian l=254-deg
extending from Galactic plane to South Galactic pole. We identify three zones
distinguished by polarized emission properties: the disc, the halo, and a
transition region connecting them. The halo section lies at latitudes |b| >
40-deg and has weak and smooth polarized emission mostly at large scale with
steep angular power spectra of median slope . The
disc region covers the latitudes |b|<20-deg and has a brighter, more complex
emission dominated by the small scales with flatter spectra of median slope
. The transition region has steep spectra as in the
halo, but the emission increases toward the Galactic plane from halo to disc
levels. The change of slope and emission structure at b \sim -20\degr is
sudden, indicating a sharp disc-halo transition. The whole halo section is just
one environment extended over 50-deg with very low emission which, once scaled
to 70GHz, is equivalent to the CMB B-Mode emission for a tensor-to-scalar
perturbation power ratio r_halo = 3.3 +/- 0.4 x 10^{-3}. Applying a
conservative cleaning procedure, we estimate an r detection limit of at 70~GHz (3-sigma C.L.) and, assuming a dust polariztion
fraction <12%, at 150~GHz. The 150-GHz limit
matches the goals of planned sub-orbital experiments, which can therefore be
conducted at this high frequency. The 70-GHz limit is close to the goal of
proposed next generation space missions, which thus might not strictly require
space-based platforms.Comment: 23 pages, 22 Figures. Accepted for publication on MNRAS. Some figures
have been reduced in resolution. Replaced with the accepted version, 3
figures, more details on instrument performances, and map of polarization
spectral index adde
Low Mass Stars and Brown Dwarfs in Praesepe
Presented are the results of a large and deep optical-near-infrared
multi-epoch survey of the Praesepe open star cluster using data from the UKIDSS
Galactic Clusters Survey. Multiple colour magnitude diagrams were used to
select potential members and proper motions were used to assign levels of
membership probability. From our sample, 145 objects were designated as high
probability members (p >= 0.6) with most of these having been found by previous
surveys although 14 new cluster members are also identified. Our membership
assignment is restricted to the bright sample of objects (Z < 18). From the
fainter sample, 39 candidates were found from an examination of multiple colour
magnitude plots. Of these, 2 have small but significant membership
probabilities. Finally, using theoretical models, cluster luminosity and mass
functions were plotted with the later being fitted with a power law of alpha =
1.11 +/- 0.37 for the mass range 0.6 to 0.125 Msun and an assumed cluster age
of 500 Myrs in the UKIDSS Z photometric band. Likewise taking an assumed
cluster age of 1 Gyr we find alpha = 1.10 +/- 0.37. Similar values were also
found for the J and K bands. These results compare favourably with the result
of Kraus & Hillenbrand (2007) (alpha = 1.4 +/- 0.2) but are significantly lower
than that of the more recent study conducted by Boudreault et al. (2009) (alpha
= 1.8 +/- 0.1).Comment: 21 pages, 11 figures, 3 tables and 4 appendices. Accepted for
publication in MNRAS, corrected a missing referenc
On the Deformation of a Hyperelastic Tube Due to Steady Viscous Flow Within
In this chapter, we analyze the steady-state microscale fluid--structure
interaction (FSI) between a generalized Newtonian fluid and a hyperelastic
tube. Physiological flows, especially in hemodynamics, serve as primary
examples of such FSI phenomena. The small scale of the physical system renders
the flow field, under the power-law rheological model, amenable to a
closed-form solution using the lubrication approximation. On the other hand,
negligible shear stresses on the walls of a long vessel allow the structure to
be treated as a pressure vessel. The constitutive equation for the microtube is
prescribed via the strain energy functional for an incompressible, isotropic
Mooney--Rivlin material. We employ both the thin- and thick-walled formulations
of the pressure vessel theory, and derive the static relation between the
pressure load and the deformation of the structure. We harness the latter to
determine the flow rate--pressure drop relationship for non-Newtonian flow in
thin- and thick-walled soft hyperelastic microtubes. Through illustrative
examples, we discuss how a hyperelastic tube supports the same pressure load as
a linearly elastic tube with smaller deformation, thus requiring a higher
pressure drop across itself to maintain a fixed flow rate.Comment: 19 pages, 3 figures, Springer book class; v2: minor revisions, final
form of invited contribution to the Springer volume entitled "Dynamical
Processes in Generalized Continua and Structures" (in honour of Academician
D.I. Indeitsev), eds. H. Altenbach, A. Belyaev, V. A. Eremeyev, A. Krivtsov
and A. V. Porubo
Polarimetric receiver in the forty gigahertz band: new instrument for the Q-U-I joint Tenerife experiment
This paper describes the analysis, design and characterization of a polarimetric receiver developed for covering the 35 to 47 GHz frequency band in the new instrument aimed at completing the ground-based Q-U-I Joint Tenerife Experiment. This experiment is designed to measure polarization in the Cosmic Microwave Background. The described high frequency instrument is a HEMT-based array composed of 29 pixels. A thorough analysis of the behaviour of the proposed receiver, based on electronic phase switching, is presented for a noise-like linearly polarized input signal, obtaining simultaneously I, Q and U Stokes parameters of the input signal. Wideband subsystems are designed, assembled and characterized for the polarimeter. Their performances are described showing appropriate results within the 35-to-47 GHz frequency band. Functionality tests are performed at room and cryogenic temperatures with adequate results for both temperature conditions, which validate the receiver concept and performance.The authors would like to thank the Spanish Ministry of Economy, Industry and Competitiveness for the financial support provided through the CONSOLIDER-INGENIO 2010 program under the grant CSD2010-00064 and under the grant ESP2015-70646-C2-2-R
Cosmological anti-deSitter space-times and time-dependent AdS/CFT correspondence
We study classes of five-dimensional cosmological solutions with negative
curvature, which are obtained from static solutions by an exchange of a spatial
and temporal coordinate, and in some cases by an analytic continuation. Such
solutions provide a suitable laboratory to address the time-dependent AdS/CFT
correspondence. For a specific example we address in detail the calculation of
the boundary stress-energy and the Wilson line and find disagreement with the
standard AdS/CFT correspondence. We trace these discrepancies to the
time-dependent effects, such as particle creation, which we further study for
specific backgrounds. We also identify specific time-dependent backgrounds that
reproduce the correct conformal anomaly. For such backgrounds the calculation
of the Wilson line in the adiabatic approximation indicates only a Coulomb
repulsion.Comment: LaTeX file, 47 pages, discussion is extended, version to appear in
PR
Performance evaluation of a lossy transmission lines based diode detector at cryogenic temperature
This work is focused on the design, fabrication, and performance analysis of a square-law Schottky diodedetector based on lossy transmission lines working under cryogenic temperature (15 K). The design analysis of a microwave detector, based on a planar gallium-arsenide low effective Schottky barrier height diode, is reported, which is aimed for achieving large input return loss as well as flat sensitivity versus frequency. The designed circuit demonstrates good sensitivity, as well as a good return loss in a wide bandwidth at Ka-band, at both room (300 K) and cryogenic (15 K) temperatures. A good sensitivity of 1000 mV/mW and input return loss better than 12 dB have been achieved when it works as a zero-bias Schottky diodedetector at room temperature, increasing the sensitivity up to a minimum of 2200 mV/mW, with the need of a DC bias current, at cryogenic temperature.This work has been funded by the Spanish Ministry for Economy and Competitiveness under the CONSOLIDER-INGENIO 2010 programme under the Reference No. CSD2010-00064. The authors would like to thank Eva Cuerno and Ana Pérez for the assistance in the assembly of the circuit
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