1,750 research outputs found
Observational Constraints on the Generalized Chaplygin Gas
In this paper we study a quintessence cosmological model in which the dark
energy component is considered to be the Generalized Chaplygin Gas and the
curvature of the three-geometry is taken into account. Two parameters
characterize this sort of fluid, the and the parameters. We use
different astronomical data for restricting these parameters. It is shown that
the constraint agrees enough well with the astronomical
observations.Comment: Accepted by IJMPD; 18 pages; 10 Figure
Particle Size Measurements From the First Fundamentals of Ice Crystal Icing Physics Test in the NASA Propulsion Systems Laboratory
This paper presents particle measurements by the Artium Technologies, Inc. Phase Doppler Interferometer and High Speed Imaging instruments from the first Fundamental Ice Crystal Icing Physics test conducted in the NASA Propulsion Systems Laboratory. The work focuses on humidity sweeps at a larger and a smaller median volumetric diameter. The particle size distribution, number density, and water content measured by the Phase Doppler Interferometer and High Speed Imaging instruments from the sweeps are presented and compared. The current capability for these two instruments to measure and discriminate ICI conditions is examined
Expansion Thoracoplasty Affects Lung Growth and Morphology in a Rabbit Model: A Pilot Study
Background: Thoracic insufficiency syndrome represents a novel form of postnatal restrictive respiratory disease occurring in children with early-onset scoliosis and chest wall anomalies. Expansion thoracoplasty improves lung volumes in children with thoracic insufficiency syndrome; however, how it affects lung development is unknown. Questions/purposes: Using a rabbit model of thoracic insufficiency syndrome, we evaluated the effect of expansion thoracoplasty on the response of biologic mechanisms in the alveolar microstructure. Methods: Using archived material from a previous experiment, 10 4-week-old New Zealand rabbits were divided into three groups: normal (n = 3), disease (n = 3), and treated (n = 4). Left ribs four to eight were tethered in seven rabbits at age 5 weeks to induce hypoplasia of the left hemithorax (disease). At age 10 weeks, four of these rabbits were treated by expansion thoracoplasty (treated). At age 24 weeks, lungs were excised and processed. Alveolar density and parenchymal airspace were measured on histologic sections. Immunohistochemistry was performed for vascular endothelial growth factor receptor 2 (angiogenesis), KI-67 (cell proliferation), and RAM-11 (macrophages). Results: Alveolar walls were poorly perfused and airspace fraction was larger (emphysematous) in disease rabbits than normal or treated rabbits. Immunohistochemistry provided inconclusive evidence to support the concept that pulmonary hypoplasia is induced by thoracic insufficiency syndrome and controlled by expansion thoracoplasty. Conclusions: Treatment of thoracic insufficiency syndrome by expansion thoracoplasty may prevent emphysematous changes in the alveolar microstructure, thereby enhancing gas exchange
Direct on-chip differentiation of intestinal tubules from induced pluripotent stem cells
Intestinal organoids have emerged as the new paradigm for modelling the healthy and diseased intestine with patient-relevant properties. In this study, we show directed differentiation of induced pluripotent stem cells towards intestinal-like phenotype within a microfluidic device. iPSCs are cultured against a gel in microfluidic chips of the OrganoPlate, in which they undergo stepwise differentiation. Cells form a tubular structure, lose their stem cell markers and start expressing mature intestinal markers, including markers for Paneth cells, enterocytes and neuroendocrine cells. Tubes develop barrier properties as confirmed by transepithelial electrical resistance (TEER). Lastly, we show that tubules respond to pro-inflammatory cytokine triggers. The whole procedure for differentiation lasts 14 days, making it an efficient process to make patient-specific organoid tubules. We anticipate the usage of the platform for disease modelling and drug candidate screening
Compensatory Puffing With Lower Nicotine Concentration E-liquids Increases Carbonyl Exposure in E-cigarette Aerosols
Introduction: Article 20 of the European Tobacco Products Directive (EU-TPD) specifies that
e-liquids should not contain nicotine in excess of 20 mg/mL, thus many vapers may be compelled
to switch to lower concentrations and in so doing, may engage in more intensive puffing. This
study aimed to establish whether more intensive puffing produces higher levels of carbonyl compounds
in e-cigarette aerosols.
Methods: Using the HPLC-UV diode array method, four carbonyl compounds (formaldehyde, acetaldehyde,
acetone, and acrolein) were measured in liquids and aerosols from nicotine solutions of
24 and 6 mg/mL. Aerosols were generated using a smoking machine configured to replicate puffing
topography data previously obtained from 12 experienced e-cigarette users.
Results: Carbonyl levels in aerosols from the puffing regimen of 6 mg/mL were significantly higher
(p < .05 using independent samples t tests) compared with those of 24 mg/mL nicotine. For the 6 and
24 mg/mL nicotine aerosols respectively, means ± SD for formaldehyde levels were 3.41 ± 0.94, and 1.49 ±
0.30 μg per hour (μg/h) of e-cigarette use. Means ± SD for acetaldehyde levels were 2.17 ± 0.36 and 1.04 ±
0.13 μg/h. Means ± SD for acetone levels were 0.73 ± 0.20 and 0.28 ± 0.14 μg/h. Acrolein was not detected.
Conclusions: Higher levels of carbonyls associated with more intensive puffing suggest that vapers
switching to lower nicotine concentrations (either due to the EU-TPD implementation or personal
choice), may increase their exposure to these compounds. Based on real human puffing topography
data, this study suggests that limiting nicotine concentrations to 20 mg/mL may not result in
the desired harm minimalization effect.
Implications: More intensive puffing regimens associated with the use of low nicotine concentration
e-liquids can lead to higher levels of carbonyl generation in the aerosol. Although in need of replication
in a larger sample outside a laboratory, this study provides pragmatic empirical data on the potential
risks of compensatory puffing behaviors in vapers, and can help to inform future regulatory decisions
on nicotine e-liquid concentrations. The cap on nicotine concentration at 20 mg/mL set by the EU-TPD
may therefore have the unintended consequence of encouraging use of lower nicotine concentration
e-liquid, in turn increasing exposure to carbonyl compounds through compensatory puffing
Nuclear effects on lepton polarization in charged-current quasielastic neutrino scattering
We use a correlated local Fermi gas (LFG) model, which accounts also for long
distance corrections of the RPA type and final-state interactions, to compute
the polarization of the final lepton in charged-current quasielastic neutrino
scattering. The present model has been successfully used in recent studies of
inclusive neutrino nucleus processes and muon capture. We investigate the
relevance of nuclear effects in the particular case of polarization in
tau-neutrino induced reactions for several kinematics of relevance for neutrino
oscillation experiments.Comment: 13 pages, 8 figure
Recommended from our members
Insights into Pathophysiology from Medication-induced Tremor
Background: Medication-induced tremor (MIT) is common in clinical practice and there are many medications/drugs that can cause or exacerbate tremors. MIT typically occurs by enhancement of physiological tremor (EPT), but not all drugs cause tremor in this way. In this manuscript, we review how some common examples of MIT have informed us about the pathophysiology of tremor.
Methods: We performed a PubMed literature search for published articles dealing with MIT and attempted to identify articles that especially dealt with the medication’s mechanism of inducing tremor.
Results: There is a paucity of literature that deals with the mechanisms of MIT, with most manuscripts only describing the frequency and clinical settings where MIT is observed. That being said, MIT emanates from multiple mechanisms depending on the drug and it often takes an individualized approach to manage MIT in a given patient.
Discussion: MIT has provided some insight into the mechanisms of tremors we see in clinical practice. The exact mechanism of MIT is unknown for most medications that cause tremor, but it is assumed that in most cases physiological tremor is influenced by these medications. Some medications (epinephrine) that cause EPT likely lead to tremor by peripheral mechanisms in the muscle (β-adrenergic agonists), but others may influence the central component (amitriptyline). Other drugs can cause tremor, presumably by blockade of dopamine receptors in the basal ganglia (dopamine-blocking agents), by secondary effects such as causing hyperthyroidism (amiodarone), or by other mechanisms. We will attempt to discuss what is known and unknown about the pathophysiology of the most common MITs
Density growth in Kantowski-Sachs cosmologies with cosmological constant
In this work the growth of density perturbations in Kantowski-Sachs
cosmologies with a positive cosmological constant is studied, using the 1+3 and
1+1+2 covariant formalisms. For each wave number we obtain a closed system for
scalars formed from quantities that are zero on the background and hence are
gauge-invariant. The solutions to this system are then analyzed both
analytically and numerically. In particular the effects of anisotropy and the
behaviour close to a bounce in the cosmic scale factor are considered. We find
that typically the density gradient in the bouncing directions experiences a
local maximum at or slightly after the bounce.Comment: 33 pages, 17 picture
- …