1,483 research outputs found
A solution for galactic disks with Yukawian gravitational potential
We present a new solution for the rotation curves of galactic disks with
gravitational potential of the Yukawa type. We follow the technique employed by
Toomre in 1963 in the study of galactic disks in the Newtonian theory. This new
solution allows an easy comparison between the Newtonian solution and the
Yukawian one. Therefore, constraints on the parameters of theories of
gravitation can be imposed, which in the weak field limit reduce to Yukawian
potentials. We then apply our formulae to the study of rotation curves for a
zero-thickness exponential disk and compare it with the Newtonian case studied
by Freeman in 1970. As an application of the mathematical tool developed here,
we show that in any theory of gravity with a massive graviton (this means a
gravitational potential of the Yukawa type), a strong limit can be imposed on
the mass (m_g) of this particle. For example, in order to obtain a galactic
disk with a scale length of b ~ 10 kpc, we should have a massive graviton of
m_g << 10^{-59} g. This result is much more restrictive than those inferred
from solar system observations.Comment: 7 pages; 1 eps figure; to appear in General Relativity and
Gravitatio
Expression of chicken hepatic type I and type III iodothyronine deiodinases during embryonic development
In embryonic chicken liver (ECL) two types of iodothyronine deiodinases
are expressed: D1 and D3. D1 catalyzes the activation as well as the
inactivation of thyroid hormone by outer and inner ring deiodination,
respectively. D3 only catalyzes inner ring deiodination. D1 and D3 have
been cloned from mammals and amphibians and shown to contain a
selenocysteine (Sec) residue. We characterized chicken D1 and D3
complementary DNAs (cDNAs) and studied the expression of hepatic D1 and D3
messenger RNAs (mRNAs) during embryonic development. Oligonucleotides
based on two amino acid sequences strongly conserved in the different
deiodinases (NFGSCTSecP and YIEEAH) were used for reverse
transcription-PCR of poly(A+) RNA isolated from embryonic day 17 (E17)
chicken liver, resulting in the amplification of two 117-bp DNA fragments.
Screening of an E17 chicken liver cDNA library with these probes led to
the isolation of two cDNA clones, ECL1711 and ECL1715. The ECL1711 clone
was 1360 bp long and lacked a translation start site. Sequence alignment
showed that it shared highest sequence identity with D1s from other
vertebrates and that the coding sequence probably lacked the first five
nucleotides. An ATG start codon was engineered by site-directed
mutagenesis, generating a mutant (ECL1711M) with four additional codons
(coding for MGTR). The open reading frame of ECL1711M coded for a
249-amino acid protein showing 58-62% identity with mammalian D1s. An
in-frame TGA codon was located at position 127, which is translated as Sec
in the presence ofa Sec insertion sequence (SECIS) identified in the
3'-untranslated region. Enzyme activity expressed in COS-1 cells by
transfection with ECL1711M showed the same catalytic, substrate, and
inhibitor specificities as native chicken D1. The ECL1715 clone was 1366
bp long and also lacked a translation start site. Sequence alignment
showed that it was most homologous with D3 from other species and that the
coding sequence lacked approximately the first 46 nucleotides. The deduced
amino acid sequence showed 62-72% identity with the D3 sequences from
other species, including a putative Sec residue at a corresponding
position. The 3'-untranslated region of ECL1715 also contained a SECIS
element. These results indicate that ECL1711 and ECL1715 are
near-full-length cDNA clones for chicken D1 and D3 selenoproteins,
respectively. The ontogeny of D1 and D3 expression in chicken liver was
studied between E14 and 1 day after hatching (C1). D1 activity showed a
gradual increase from E14 until C1, whereas D1 mRNA level remained
relatively constant. D3 activity and mRNA level were highly significantly
correlated, showing an increase from E14 to E17 and a strong decrease
thereafter. These results suggest that the regulation of chicken hepatic
D3 expression during embryonic development occurs predominantly at the
pretranslational level
Characterization of a propylthiouracil-insensitive type I iodothyronine deiodinase
Mammalian type I iodothyronine deiodinase (D1) activates and inactivates
thyroid hormone by outer ring deiodination (ORD) and inner ring
deiodination (IRD), respectively, and is potently inhibited by
propylthiouracil (PTU). Here we describe the cloning and characterization
of a complementary DNA encoding a PTU-insensitive D1 from teleost fish
(Oreochromis niloticus, tilapia). This complementary DNA codes for a
protein of 248 amino acids, including a putative selenocysteine (Sec)
residue, encoded by a TGA triplet, at position 126. The 3' untranslated
region contains two putative Sec insertion sequence (SECIS) elements.
Recombinant enzyme expressed in COS-1 cells catalyzes both ORD of T4 and
rT3 and IRD of T3 and T3 sulfate with the same substrate specificity as
native tilapia D1 (tD1), i.e. rT3 >> T4 > T3 sulfate > T3. Native and
recombinant tD1 show equally low sensitivities to inhibition by PTU,
iodoacetate, and gold thioglucose compared with the potent inhibitions
observed with mammalian D1s. Because the residue 2 positions downstream
from Sec is Pro in tD1 and in all (PTU-insensitive) type II and type III
iodothyronine deiodinases but Ser in all PTU-sensitive D1s, we prepared
the Pro128Ser mutant of tD1. The mutant enzyme showed strongly decreased
ORD and somewhat increased IRD activity, but was still insensitive to PTU.
These results provide new information about the structure-activity
relationship of D1 concerning two characteristic properties, i.e.
catalysis of both ORD and IRD, and inhibition by PTU
Quantum limits on phase-shift detection using multimode interferometers
Fundamental phase-shift detection properties of optical multimode
interferometers are analyzed. Limits on perfectly distinguishable phase shifts
are derived for general quantum states of a given average energy. In contrast
to earlier work, the limits are found to be independent of the number of
interfering modes. However, the reported bounds are consistent with the
Heisenberg limit. A short discussion on the concept of well-defined relative
phase is also included.Comment: 6 pages, 3 figures, REVTeX, uses epsf.st
Higgs Scalar-Tensor Theory for Gravity and the Flat Rotation Curves of Spiral Galaxies
The scalar-tensor theory of gravity with the Higgs field as scalar field is
presented. For central symmetry it reproduces the empirically measured flat
rotation curves of galaxies. We approximate the galaxy by a polytropic gas
sphere with the polytropic index and a massive core.Comment: 17 pages, 12 figure
Atrial fibrillation detection using insertable cardiac monitor after stroke: a real-word cohort study
First published: 09 November 2022Objective: This study aimed to report the realâworld atrial fibrillation (AF) diagnostic yield of the implantable cardiac monitor (ICM) in patients with stroke or transient ischemic attack (TIA), and compare it to patients with an ICM for unexplained syncope. Methods: We used patient data from device clinics across the United States of America with ICM remote monitoring via PaceMateâą, implanted for stroke or TIA, and unexplained syncope. Patients with known AF or atrial flutter were excluded. The outcome was AF lasting â„2 min, adjudicated by International Board of Heart Rhythm Examiners certified cardiac device specialists. Results: We included a total of 2469 patients, 51.1% with stroke or TIA (mean age: 69.7 [SD: 12.2] years, 41.1% female) and 48.9% with syncope (mean age: 67.0 [SD: 17.1] years, 59.4% female). The cumulative AF detection rate in patients with stroke or TIA was 5.5%, 8.9%, and 14.0% at 12, 24, and 36 months, respectively. The median episode duration was 73 (interquartile range: 10â456) min, ranging from 2 min to 40.9 days, with 52.3%, 28.6%, and 4.4% of episodes lasting at least 1, 6, and 24 h, respectively. AF detection was increased by age (adjusted hazard ratio [for every 1âyear increase]: 1.024, 95% confidence interval: 1.008â1.040; p = .003), but was not influenced by sex (p = .089). For comparison, the cumulative detection rate at 12, 24, and 36 months were, respectively, 2.4%, 5.2%, and 7.4% in patients with syncope. Conclusion: Patients with stroke or TIA have a higher rate of AF detection. However, this realâworld study shows significantly lower AF detection rates than what has been previously reported.Jean J. Noubiap, Gijo Thomas, Melissa E. Middeldorp, John L. Fitzgerald, Curtis Harper, Prashanthan Sander
Scaling of Island Growth in Pb Overlayers on Cu(001)
The growth and ordering of a Pb layer deposited on Cu(001) at 150 K has been
studied using atom beam scattering. At low coverage, ordered Pb islands with a
large square unit cell and nearly hexagonal internal structure are formed. This
is a high order commensurate phase with 30 atoms in the unit cell. From the
measurement of the island diffraction peak profiles we find a power law for the
mean island - size versus coverage with an exponent . A
scaling behavior of growth is confirmed and a simple model describing island
growth is presented. Due to the high degeneracy of the monolayer phase,
different islands do not diffract coherently. Therefore, when islands merge
they still diffract as separate islands and coalescence effects are thus
negligible. From the result for we conclude that the island density is
approximately a constant in the coverage range where the
ordered islands are observed. We thus conclude that most islands nucleate at
and then grow in an approximately self similar fashion as
increases.Comment: 23 pages, 10 Figures (available upon request). SU-PHYS-93-443-375
Sex disparities in enrolment and reporting of outcomes by sex in contemporary clinical trials of atrial fibrillation
Background:Underrepresentation of females in randomized controlled trials (RCTs)limits generalizability and quality of the evidence guiding treatment of females. This study aimed to measure the sex disparities in participants' recruitment in RCTs of atrial fibrillation (AF) and determine associated factors, and to describe the frequency of outcomes reported by sex. Methods:MEDLINE was searched to identify RCTs of AF published between January 1, 2011, and November 20, 2021, in 12 topâtier journals. We measured the enrollment of females using the enrollment disparity difference (EDD) which is the difference between the proportion of females in the trial and the proportion of females with AF in the underlying general population (obtained from the Global Burden of Disease). Randomâeffects metaâanalyses of the EDD were performed, and multivariable metaâregression was used to explore factors associated with disparity estimates. We also determined the proportion of trials that included sexâstratified results. Results:Out of 1133 records screened, 142 trials were included, reporting on a total of 133 532 participants. The randomâeffects summary EDD wasâ0.125 (95%confidence interval [CI] =â0.143 toâ0.108), indicating that females were underâenrolled by 12.5 percentage points. Female enrollment was higher in trials with higher sample size (750, adjusted odds ratio [aOR] 1.065, 95% CI:1.008â1.125), higher mean participants' age (aOR: 1.006, 95% CI: 1.002â1.009), and lower in trials conducted in North America compared to Europe (aOR: 0.945, 95% CI:0.898â0.995). Only 36 trials (25.4%) reported outcomes by sex, and of these 29(80.6%) performed statistical testing of the sexâbyâtreatment interaction. Conclusion:Females remain substantially less represented in RCTs of AF, and sexâstratified reporting of primary outcomes is infrequent. These findings call for urgent action to improve sex equity in enrollment and sexâstratified outcomes' reporting in RCTs of AF.Jean Jacques Noubiap, Gijo Thomas, Ulrich Flore Nyaga, John L. Fitzgerald, Celine Gallagher, Melissa E. Middeldorp, Prashanthan Sander
Comparative assessment of filtration- and precipitation-based methods for the concentration of SARS-CoV-2 and other viruses from wastewater
Wastewater-based epidemiology (WBE) has been widely used to track levels of SARS-CoV-2 infection in the community during the COVID-19 pandemic. Due to the rapid expansion of WBE, many methods have been used and developed for virus concentration and detection in wastewater. However, very little information is available on the relative performance of these approaches. In this study, we compared the performance of five commonly used wastewater concentration methods for the detection and quantification of pathogenic viruses (SARS-CoV-2, norovirus, rotavirus, influenza, and measles viruses), fecal indicator viruses (crAssphage, adenovirus, pepper mild mottle virus), and process control viruses (murine norovirus and bacteriophage Phi6) in laboratory spiking experiments. The methods evaluated included those based on either ultrafiltration (Amicon centrifugation units and InnovaPrep device) or precipitation (using polyethylene glycol [PEG], beef extract-enhanced PEG, and ammonium sulfate). The two best methods were further tested on 115 unspiked wastewater samples. We found that the volume and composition of the wastewater and the characteristics of the target viruses greatly affected virus recovery, regardless of the method used for concentration. All tested methods are suitable for routine virus concentration; however, the Amicon ultrafiltration method and the beef extract-enhanced PEG precipitation methods yielded the best recoveries. We recommend the use of ultrafiltration-based concentration for low sample volumes with high virus titers and ammonium levels and the use of precipitation-based concentration for rare pathogen detection in high-volume samples. IMPORTANCE As wastewater-based epidemiology is utilized for the surveillance of COVID-19 at the community level in many countries, it is crucial to develop and validate reliable methods for virus detection in sewage. The most important step in viral detection is the efficient concentration of the virus particles and/or their genome for subsequent analysis. In this study, we compared five different methods for the detection and quantification of different viruses in wastewater. We found that dead-end ultrafiltration and beef extract-enhanced polyethylene glycol precipitation were the most reliable approaches. We also discovered that sample volume and physico-chemical properties have a great effect on virus recovery. Hence, wastewater process methods and start volumes should be carefully selected in ongoing and future wastewater-based national surveillance programs for COVID-19 and beyond
Comparative assessment of filtration- and precipitation-based methods for the concentration of SARS-CoV-2 and other viruses from wastewater
Wastewater-based epidemiology (WBE) has been widely used to track levels of SARS-CoV-2 infection in the community during the COVID-19 pandemic. Due to the rapid expansion of WBE, many methods have been used and developed for virus concentration and detection in wastewater. However, very little information is available on the relative performance of these approaches. In this study, we compared the performance of five commonly used wastewater concentration methods for the detection and quantification of pathogenic viruses (SARS-CoV-2, norovirus, rotavirus, influenza, and measles viruses), fecal indicator viruses (crAssphage, adenovirus, pepper mild mottle virus), and process control viruses (murine norovirus and bacteriophage Phi6) in laboratory spiking experiments. The methods evaluated included those based on either ultrafiltration (Amicon centrifugation units and InnovaPrep device) or precipitation (using polyethylene glycol [PEG], beef extract-enhanced PEG, and ammonium sulfate). The two best methods were further tested on 115 unspiked wastewater samples. We found that the volume and composition of the wastewater and the characteristics of the target viruses greatly affected virus recovery, regardless of the method used for concentration. All tested methods are suitable for routine virus concentration; however, the Amicon ultrafiltration method and the beef extract-enhanced PEG precipitation methods yielded the best recoveries. We recommend the use of ultrafiltration-based concentration for low sample volumes with high virus titers and ammonium levels and the use of precipitation-based concentration for rare pathogen detection in high-volume samples
- âŠ