350 research outputs found
The Effect of Crystallization on the Pulsations of White Dwarf Stars
We consider the pulsational properties of white dwarf star models with
temperatures appropriate for the ZZ Ceti instability strip and with masses
large enough that they should be substantially crystallized. Our work is
motivated by the existence of a potentially crystallized DAV, BPM 37093, and
the expectation that digital surveys in progress will yield many more such
massive pulsators.
A crystallized core makes possible a new class of oscillations, the torsional
modes, although we expect these modes to couple at most weakly to any motions
in the fluid and therefore to remain unobservable. The p-modes should be
affected at the level of a few percent in period, but are unlikely to be
present with observable amplitudes in crystallizing white dwarfs any more than
they are in the other ZZ Ceti's. Most relevant to the observed light variations
in white dwarfs are the g-modes. We find that the kinetic energy of these modes
is effectively excluded from the crystallized cores of our models. As
increasing crystallization pushes these modes farther out from the center, the
mean period spacing between radial overtones increases substantially with the
crystallized mass fraction. In addition, the degree and structure of mode
trapping is affected. The fact that some periods are strongly affected by
changes in the crystallized mass fraction while others are not suggests that we
may be able to disentangle the effects of crystallization from those due to
different surface layer masses.Comment: 18 pages, 5 figures, accepted on 1999 July 2 for publication in the
Astrophysical Journa
Gravitational wave emission from a magnetically deformed non-barotropic neutron star
A strong candidate for a source of gravitational waves is a highly
magnetised, rapidly rotating neutron star (magnetar) deformed by internal
magnetic stresses. We calculate the mass quadrupole moment by perturbing a
zeroth-order hydrostatic equilibrium by an axisymmetric magnetic field with a
\emph{linked poloidal-toroidal structure}. In this work, we do \emph{not}
require the model star to obey a barotropic equation of state (as a realistic
neutron star is not barotropic), allowing us to explore the hydromagnetic
equilibria with fewer constraints. We derive the relation between the ratio of
poloidal-to-total field energy and ellipticity and briefly
compare our results to those obtained using the barotropic assumption. Then, we
present some examples of how our results can be applied to astrophysical
contexts. First, we show how our formulae, in conjunction with current
gravitational wave (non-)detections of the Crab pulsar and the Cassiopeia A
central compact object (Cas A CCO), can be used to constrain the strength of
the internal toroidal fields of those objects. We find that, for the Crab
pulsar (whose canonical equatorial dipole field strength, inferred from spin
down, is T) to emit detectable gravitational radiation, the
neutron star must have a strong toroidal field component, with maximum internal
toroidal field strength T; for gravitational
waves to be detected from the Cas A CCO at 300 Hz, T, whereas detection at 100 Hz would require T. Using our results, we also show how the gravitational wave signal
emitted by a magnetar immediately after its birth (assuming it is born rapidly
rotating, with ) makes such a newborn magnetar a stronger
candidate for gravitational wave detection than, for example, an SGR giant
flare.Comment: 15 pages, 8 figures, 2 table
Alterations in size, number, and morphology of gustatory papillae and taste buds in BDNF null mutant mice demonstrate neural dependence of developing taste organs
Sensory ganglia that innervate taste buds and gustatory papillae (geniculate and petrosal) are reduced in volume by about 40% in mice with a targeted deletion of the gene for brain-derived neurotrophic factor (BDNF). In contrast, the trigeminal ganglion, which innervates papillae but not taste buds on the anterior tongue, is reduced by only about 18%. These specific alterations in ganglia that innervate taste organs make possible a test for roles of lingual innervation in the development of appropriate number, morphology, and spatial pattern of fungiform and circumvallate papillae and associated taste buds. We studied tongues of BDNF null mutant and wild-type littermates and made quantitative analyses of all fungiform papillae on the anterior tongue, the single circumvallate papilla on the posterior tongue, and all taste buds in both papilla types. Fungiform papillae and taste buds were reduced in number by about 60% and were substantially smaller in diameter in mutant mice 15–25 days postnatal. Remaining fungiform papillae were selectively concentrated in the tongue tip region. The circumvallate papilla was reduced in diameter and length by about 40%, and papilla morphology was disrupted. Taste bud number in the circumvallate was reduced by about 70% in mutant tongues, and the remaining taste buds were smaller than those on wild-type tongues. Our results demonstrate a selective dependence of taste organs on a full complement of appropriate innervation for normal growth and morphogenesis. Effects on papillae are not random but are more pronounced in specific lingual regions. Although the geniculate and petrosal ganglia sustain at least half of their normal complement of cell number in BDNF −/− mice, remaining ganglion cells do not substitute for lost neurons to rescue taste organs at control numbers. Whereas gustatory ganglia and the taste papillae initially form independently, our results suggest interdependence in later development because ganglia derive BDNF support from target organs and papillae require sensory innervation for morphogenesis. J. Comp. Neurol. 409:13–24, 1999.  © 1999 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34453/1/2_ftp.pd
Komagataeibacter Tool Kit (KTK): A Modular Cloning System for Multigene Constructs and Programmed Protein Secretion from Cellulose Producing Bacteria
Bacteria proficient at producing cellulose are an attractive synthetic biology host for the emerging field of Engineered Living Materials (ELMs). Species from the Komagataeibacter genus produce high yields of pure cellulose materials in a short time with minimal resources, and pioneering work has shown that genetic engineering in these strains is possible and can be used to modify the material and its production. To accelerate synthetic biology progress in these bacteria, we introduce here the Komagataeibacter tool kit (KTK), a standardized modular cloning system based on Golden Gate DNA assembly that allows DNA parts to be combined to build complex multigene constructs expressed in bacteria from plasmids. Working in Komagataeibacter rhaeticus, we describe basic parts for this system, including promoters, fusion tags, and reporter proteins, before showcasing how the assembly system enables more complex designs. Specifically, we use KTK cloning to reformat the Escherichia coli curli amyloid fiber system for functional expression in K. rhaeticus, and go on to modify it as a system for programming protein secretion from the cellulose producing bacteria. With this toolkit, we aim to accelerate modular synthetic biology in these bacteria, and enable more rapid progress in the emerging ELMs community
Development of an enhanced health-economic model and cost-effectiveness analysis of tiotropium + olodaterol Respimat® fixed-dose combination for chronic obstructive pulmonary disease patients in Italy
Background: The objective of this study was to compare the cost-effectiveness of the fixed-dose combination (FDC) of tiotropium + olodaterol Respimat® FDC with tiotropium alone for patients with chronic obstructive pulmonary disease (COPD) in the Italian health care setting using a newly developed patient-level Markov model that reflects the current understanding of the disease. Methods: While previously published models have largely been based around a cohort approach using a Markov structure and GOLD stage stratification, an individual-level Markov approach was selected for the new model. Using patient-level data from the twin TOnado trials assessing Tiotropium + olodaterol Respimat® FDC versus tiotropium, outcomes were modelled based on the trough forced expiratory volume (tFEV1) of over 1000 patients in each treatment arm, tracked individually at trial visits through the 52-week trial period, and after the trial period it was assumed to decline at a constant rate based on disease stage. Exacerbation risk was estimated based on a random-effects logistic regression analysis of exacerbations in UPLIFT. Mortality by age and disease stage was estimated from an analysis of TIOSPIR trial data. Cost of bronchodilators and other medications, routine management, and costs of treatment for moderate and severe exacerbations for the Italian setting were included. A cost-effectiveness analysis was conducted over a 15-year time horizon from the perspective of the Italian National Health Service. Results: Aggregating total costs and quality-adjusted life years (QALYs) for each treatment cohort over 15 years and comparing tiotropium + olodaterol Respimat® FDC with tiotropium alone, resulted in mean incremental co
Decrease in tobacco consumption after treatment with topiramate and aripiprazole: a case report
<p>Abstract</p> <p>Introduction</p> <p>A large part of research into drug addiction focuses on mesolimbic dopamine circuitry; however, both alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and/or kainate and dopamine D2 receptors can play a role in maintaining the established addiction.</p> <p>Case presentation</p> <p>We report the case of a 34-year-old man who compulsively smoked 80 to 100 cigarettes each day. After receiving treatment with topiramate and aripiprazole, his tobacco consumption was dramatically reduced.</p> <p>Conclusion</p> <p>Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and/or kainate blocking agents and a dopamine D2 receptor partial agonist may be novel instruments for nicotine abuse disorders.</p
Catalog of Galactic Beta Cephei Stars
We present an extensive and up-to-date catalog of Galactic Beta Cephei stars.
This catalog is intended to give a comprehensive overview of observational
characteristics of all known Beta Cephei stars. 93 stars could be confirmed to
be Beta Cephei stars. For some stars we re-analyzed published data or conducted
our own analyses. 61 stars were rejected from the final Beta Cephei list, and
77 stars are suspected to be Beta Cephei stars. A list of critically selected
pulsation frequencies for confirmed Beta Cephei stars is also presented. We
analyze the Beta Cephei stars as a group, such as the distributions of their
spectral types, projected rotational velocities, radial velocities, pulsation
periods, and Galactic coordinates. We confirm that the majority of these stars
are multiperiodic pulsators. We show that, besides two exceptions, the Beta
Cephei stars with high pulsation amplitudes are slow rotators. We construct a
theoretical HR diagram that suggests that almost all 93 Beta Cephei stars are
MS objects. We discuss the observational boundaries of Beta Cephei pulsation
and their physical parameters. We corroborate that the excited pulsation modes
are near to the radial fundamental mode in frequency and we show that the mass
distribution of the stars peaks at 12 solar masses. We point out that the
theoretical instability strip of the Beta Cephei stars is filled neither at the
cool nor at the hot end and attempt to explain this observation
Roll out of a successful antimicrobial stewardship programme in Lagos University Teaching Hospital Nigeria using the Global-Point Prevalence Survey
Background: Antimicrobial resistance (AMR) has become a public health emergency with increasing rates and spread globally. Antimicrobial stewardship (AMS) has been advocated to reduce the burden of antimicrobial resistance, promote rational and appropriate use of antibiotics and improve clinical outcomes. Education and training are one of the AMS interventions to improve antimicrobial use. We present the roll out of a successful AMS programme with education and training using the Global-PPS as data collection tool to measure AMS interventions and impact.Methodology: This was a cross sectional study on the implementation of an AMS programme at the Lagos University Teaching Hospital. Global PPS was conducted in 2015 to collect baseline data which was used to identify targets for quality improvement in AMS and was repeated in 2017 and 2018 to measure impact of AMS interventions. AMS interventions included education, feedback of Global-PPS result and writing of the hospitalwide antibiotic policy based on the baseline data.Results: Out of the 746 inpatients surveyed, 476 (68.3%) had received at least one antimicrobial on the days of Global-PPS. The antimicrobial prescribing rates reduced significantly over the three time periods. In 2015, 82.5% were placed on antimicrobials, 65.5% in 2017 and 51.1% in 2018 (p<0.00001). The documentation of indication for treatment significantly improved from 53.4% in 2015 to 97.2% in 2018 (p<0.0001). Stop review date also significantly improved from 28.7% to 70.2% in 2018 (p<0.00001). Surgical prophylaxis for more than 24 hours reduced significantly from 93.3% in 2015 to 65.7% in 2018 (p=0.002) even though the prevalence was still high. The three most commonly administered antimicrobial groups were third generation cephalosporins, imidazole derivatives and quinolones. The most commonly prescribed antibiotics for surgical prophylaxis were ceftriaxone and metronidazole in 2015 and ceftriaxone in 2017.Conclusion: The use of education and training as AMS intervention in a limited resource setting clearly made impact on antimicrobial prescribing patterns in the hospital. Global-PPS is useful to set quality improvement targets and for monitoring, evaluation and surveillance of an AMS programme.
Keywords: Antibiotic, Stewardship, Resistance, Education, Global-PP
Randomised controlled trial of first-line tyrosine-kinase inhibitor (TKI) versus intercalated TKI with chemotherapy for EGFR-mutated nonsmall cell lung cancer
Introduction Previous studies have shown interference between epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors and chemotherapy in the cell cycle, thus reducing efficacy. In this randomised controlled trial we investigated whether intercalated erlotinib with chemotherapy was superior compared to erlotinib alone in untreated advanced EGFR-mutated nonsmall cell lung cancer (NSCLC). Materials and methods Treatment-naïve patients with an activating EGFR mutation, ECOG performance score of 0–3 and adequate organ function were randomly assigned 1:1 to either four cycles of cisplatin-pemetrexed with intercalated erlotinib (day 2–16 out of 21 days per cycle) followed by pemetrexed and erlotinib maintenance (CPE) or erlotinib monotherapy. The primary end-point was progression-free survival (PFS). Secondary end-points were overall survival, objective response rate (ORR) and toxicity. Results Between April 2014 and September 2016, 22 patients were randomised equally into both arms; the study was stopped due to slow accrual. Median follow-up was 64 months. Median PFS was 13.7 months (95% CI 5.2–18.8) for CPE and 10.3 months (95% CI 7.1–15.5; hazard ratio (HR) 0.62, 95% CI 0.25–1.57) for erlotinib monotherapy; when compensating for number of days receiving erlotinib, PFS of the CPE arm was superior (HR 0.24, 95% CI 0.07–0.83; p=0.02). ORR was 64% for CPE versus 55% for erlotinib monotherapy. Median overall survival was 31.7 months (95% CI 21.8–61.9 months) for CPE compared to 17.2 months (95% CI 11.5–45.5 months) for erlotinib monotherapy (HR 0.58, 95% CI 0.22–1.41 months). Patients treated with CPE had higher rates of treatment-related fatigue, anorexia, weight loss and renal toxicity. Conclusion Intercalating erlotinib with cisplatin-pemetrexed provides a longer PFS compared to erlotinib alone in EGFR-mutated NSCLC at the expense of more toxicity
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