7,008 research outputs found
Close encounters involving free-floating planets in star clusters
Instabilities in planetary systems can result in the ejection of planets from
their host system, resulting in free-floating planets (FFPs). If this occurs in
a star cluster, the FFP may remain bound to the star cluster for some time and
interact with the other cluster members until it is ejected. Here, we use
-body simulations to characterise close star-planet and planet-planet
encounters and the dynamical fate of the FFP population in star clusters
containing single or binary star members. We find that FFPs ejected
from their planetary system at low velocities typically leave the star cluster
40% earlier than their host stars, and experience tens of close ( AU)
encounters with other stars and planets before they escape. The fraction of
FFPs that experiences a close encounter depends on both the stellar density and
the initial velocity distribution of the FFPs. Approximately half of the close
encounters occur within the first 30 Myr, and only 10% occur after 100 Myr. The
periastron velocity distribution for all encounters is well-described by a
modified Maxwell-Bolzmann distribution, and the periastron distance
distribution is linear over almost the entire range of distances considered,
and flattens off for very close encounters due to strong gravitational
focusing. Close encounters with FFPs can perturb existing planetary systems and
their debris structures, and they can result in re-capture of FFPs. In
addition, these FFP populations may be observed in young star clusters in
imaging surveys; a comparison between observations and dynamical predictions
may provide clues to the early phases of stellar and planetary dynamics in star
clusters.Comment: Accepted for publication in MNRAS; 18 pages, 12 figure
Experimental characterization of deployable trusses and joints
The structural dynamic properties of trusses are strongly affected by the characteristics of joints connecting the individual beam elements. Joints are particularly significant in that they are often the source of nonlinearities and energy dissipation. While the joints themselves may be physically simple, direct measurement is often necessary to obtain a mathematical description suitable for inclusion in a system model. Force state mapping is a flexible, practical test method for obtaining such a description, particularly when significant nonlinear effects are present. It involves measurement of the relationship, nonlinear or linear, between force transmitted through a joint and the relative displacement and velocity across it. An apparatus and procedure for force state mapping are described. Results are presented from tests of joints used in a lightweight, composite, deployable truss built by the Boeing Aerospace Company. The results from the joint tests are used to develop a model of a full 4-bay truss segment. The truss segment was statically and dynamically tested. The results of the truss tests are presented and compared with the analytical predictions from the model
A New Light Higgs Boson and Short-Baseline Neutrino Anomalies
The low-energy excesses observed by the MiniBooNE experiment have, to date,
defied a convinc- ing explanation under the standard model even with
accommodation for non-zero neutrino mass. In this paper we explore a new
oscillation mechanism to explain these anomalies, invoking a light neu-
trinophilic Higgs boson, conceived to induce a low Dirac neutrino mass in
accord with experimental limits. Beam neutrinos forward-scattering off of a
locally over-dense relic neutrino background give rise to a novel matter-effect
with an energy-specific resonance. An enhanced oscillation around this
resonance peak produces flavor transitions which are highly consistent with the
MiniBooNE neutrino- and antineutrino-mode data sets. The model provides
substantially improved values beyond either the no-oscillation
hypothesis or the more commonly explored 3+1 sterile neutrino hy- pothesis.
This mechanism would introduce distinctive signatures at each baseline in the
upcoming SBN program at Fermilab, presenting opportunities for further
exploration.Comment: 11 pages, 6 figures, submitted to PR
Feline hypersomatotropism and acromegaly tumorigenesis: a potential role for the AIP gene
Acromegaly in humans is usually sporadic, however up to 20% of familial isolated pituitary adenomas are caused by germline sequence variants of the aryl-hydrocarbon-receptor interacting protein (AIP) gene. Feline acromegaly has similarities to human acromegalic families with AIP mutations. The aim of this study was to sequence the feline AIP gene, identify sequence variants and compare the AIP gene sequence between feline acromegalic and control cats, and in acromegalic siblings. The feline AIP gene was amplified through PCR using whole blood genomic DNA from 10 acromegalic and 10 control cats, and 3 sibling pairs affected by acromegaly. PCR products were sequenced and compared with the published predicted feline AIP gene. A single nonsynonymous SNP was identified in exon 1 (AIP:c.9T > G) of two acromegalic cats and none of the control cats, as well as both members of one sibling pair. The region of this SNP is considered essential for the interaction of the AIP protein with its receptor. This sequence variant has not previously been reported in humans. Two additional synonymous sequence variants were identified (AIP:c.481C > T and AIP:c.826C > T). This is the first molecular study to investigate a potential genetic cause of feline acromegaly and identified a nonsynonymous AIP single nucleotide polymorphism in 20% of the acromegalic cat population evaluated, as well as in one of the sibling pairs evaluated
Prospective evaluation of a protocol for transitioning porcine lente insulintreated diabetic cats to human recombinant protamine zinc insulin
Objectives The objective was to evaluate a nadir-led protocol for transitioning porcine lente insulin suspension (PLIS)-treated diabetic cats onto human recombinant protamine zinc insulin (PZIR).
Methods Recently diagnosed (<5 months) diabetic cats, treated with PLIS q12h for 6 weeks, were recruited. Fructosamine, 24 h blood glucose curve (BGC), quality of life assessment (DIAQoL-pet score) and Diabetic Clinical Score (DCS) were assessed at enrolment (PLIS-treated) and 2, 4 and 12 weeks after transitioning to PZIR (starting dose 0.2-0.7 U/kg q12h). Short duration of insulin action was defined as <9 h. Linear mixed effects modelling assessed for change in fructosamine, mean blood glucose (MBG) during BGCs, DIAQoL-pet score, DCS and q12h insulin dose. McNemar's tests compared the proportion of cats with hypoglycaemia at week 0 (PLIS-treated) and week 4 (PZIR-treated).
Results Twenty-two cats were recruited. Median PLIS dose at enrolment was 0.5 U/kg (interquartile range 0.3-0.7 U/kg) q12h, equalling median PZIR starting dose (0.5 U/kg; interquartile range 0.3-0.7 U/kg q12h). Transitioning was followed by significant decreases in fructosamine (P = 0.00007), insulin dose (P = 0.02), DCS (P = 8.1 x 10(-8)) and DIAQoL-pet score (P = 0.003), indicating improved quality of life. MBG did not alter significantly (P = 0.1). Five cats (22.7%) achieved remission. Hypoglycaemia was recorded in 30/190 12 h BGCs (15.8%) and five cats experienced clinical hypoglycaemia. The proportion of cats with hypoglycaemia did not differ between PLIS (week 0) and PZIR (week 4) (P = 1.0). Duration of action was analysed in 19 cats. Six cats (31.6%) showed short duration of action on PLIS, compared with two cats (10.5%) after 4 weeks on PZIR. All six cats with short PLIS duration showed duration of 9 h on PZIR.
Conclusions and relevance Used alongside a low-carbohydrate diet, transitioning to PZIR was associated with significantly improved clinical signs and quality of life, with some cats achieving remission. Transition to PZIR should be considered for cats with short duration of action on PLIS
Serum N-Terminal Type III Procollagen Propeptide: An Indicator of Growth Hormone Excess and Response to Treatment in Feline Hypersomatotropism
BACKGROUND: Nâterminal type III procollagen propeptide (PIIINP) is a biomarker of soft tissue proliferation. Hypersomatotropism (HS) is associated with soft tissue proliferation. HYPOTHESIS: Serum PIIINP is increased in cats with HS and decreases with effective treatment, and may be an additional tool in the diagnosis and treatment of feline HS. ANIMALS: Cats with uncomplicated diabetes mellitus (DM; n = 30) and with HSâinduced DM (HSDM; n = 30). Preâ and posttreatment samples were available from 5 cats undergoing radiotherapy (RT) and 16 cats undergoing hypophysectomy (HPX). METHODS: Retrospective and prospective crossâsectional study. Analytical performance of a serum PIIINP ELISA was assessed and validated for use in cats. PIIINP and insulinâlike growth factor 1 (IGFâ1) radioimmunoassays (RIA) were performed preâ and postâtreatment in cats with DM and HSDM. PIIINP and IGFâ1 were compared between cats treated by RT and HPX. RESULTS: Serum PIIINP concentrations were significantly higher (P < .001) in HSDM cats (median, 19.6 ng/mL; range, 1.7â27.9) compared to DM cats (median, 5.0 ng/mL; range, 2.1â10.4). A cutâoff of 10.5 ng/mL allowed differentiation between DM and HSDM cats with 87% sensitivity and 100% specificity (area under the curve [AUC], 0.91; 95% confidence interval [CI], 0.82â1). After RT, PIIINP increased significantly (P = .043) with no significant change in IGFâ1 concentrations. After HPX, serum PIIINP (P = .034) and IGFâ1 concentrations (P < .001) decreased significantly. CONCLUSION AND CLINICAL IMPORTANCE: PIIINP concentrations are increased in cats with untreated HSDM compared to those with DM, demonstrating the effect of excess GH on soft tissue. PIIINP concentrations decreased after HPX in most HSDM cats
Cryogenic microstripline-on-Kapton microwave interconnects
Simple broadband microwave interconnects are needed for increasing the size
of focal plane heterodyne radiometer arrays. We have measured loss and
cross-talk for arrays of microstrip transmission lines in flex circuit
technology at 297 and 77 K, finding good performance to at least 20 GHz. The
dielectric constant of Kapton substrates changes very little from 297 to 77 K,
and the electrical loss drops. The small cross-sectional area of metal in a
printed circuit structure yields overall thermal conductivities similar to
stainless steel coaxial cable. Operationally, the main performance tradeoffs
are between crosstalk and thermal conductivity. We tested a patterned ground
plane to reduce heat flux.Comment: 3 pages, 3 figures, submitted to The Review of Scientific Instrument
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