scholarly journals Solution to the debris disc mass problem: planetesimals are born small?

2020 ◽  
Vol 500 (1) ◽  
pp. 718-735
Author(s):  
Alexander V Krivov ◽  
Mark C Wyatt
Keyword(s):  
Total Mass ◽  
Thermal Emission ◽  
Kuiper Belt ◽  
Dust Production ◽  
Mass Problem ◽  
Planetary Orbits ◽  
Cascade Models ◽  
Giant Impacts ◽  
Rule Out

ABSTRACT Debris belts on the periphery of planetary systems, encompassing the region occupied by planetary orbits, are massive analogues of the Solar system’s Kuiper belt. They are detected by thermal emission of dust released in collisions amongst directly unobservable larger bodies that carry most of the debris disc mass. We estimate the total mass of the discs by extrapolating up the mass of emitting dust with the help of collisional cascade models. The resulting mass of bright debris discs appears to be unrealistically large, exceeding the mass of solids available in the systems at the preceding protoplanetary stage. We discuss this ‘mass problem’ in detail and investigate possible solutions to it. These include uncertainties in the dust opacity and planetesimal strength, variation of the bulk density with size, steepening of the size distribution by damping processes, the role of the unknown ‘collisional age’ of the discs, and dust production in recent giant impacts. While we cannot rule out the possibility that a combination of these might help, we argue that the easiest solution would be to assume that planetesimals in systems with bright debris discs were ‘born small’, with sizes in the kilometre range, especially at large distances from the stars. This conclusion would necessitate revisions to the existing planetesimal formation models, and may have a range of implications for planet formation. We also discuss potential tests to constrain the largest planetesimal sizes and debris disc masses.

scholarly journals Effects of Rifaximin on Luminal and Wall-Adhered Gut Commensal Microbiota in Mice

2021 ◽  
Vol 22 (2) ◽  
pp. 500
Author(s):  
Marina Ferrer ◽  
Mònica Aguilera ◽  
Vicente Martinez
Keyword(s):  
Fluorescent In Situ Hybridization ◽  
Fragment Length Polymorphism ◽  
Functional Gastrointestinal Disorders ◽  
Antibacterial Properties ◽  
Broad Spectrum Antibiotic ◽  
Commensal Microbiota ◽  
Bacterial Biodiversity ◽  
Rule Out

Rifaximin is a broad-spectrum antibiotic that ameliorates symptomatology in inflammatory/functional gastrointestinal disorders. We assessed changes in gut commensal microbiota (GCM) and Toll-like receptors (TLRs) associated to rifaximin treatment in mice. Adult C57BL/6NCrl mice were treated (7/14 days) with rifaximin (50/150 mg/mouse/day, PO). Luminal and wall-adhered ceco-colonic GCM were characterized by fluorescent in situ hybridization (FISH) and microbial profiles determined by terminal restriction fragment length polymorphism (T-RFLP). Colonic expression of TLR2/3/4/5/7 and immune-related markers was assessed (RT-qPCR). Regardless the period of treatment or the dose, rifaximin did not alter total bacterial counts or bacterial biodiversity. Only a modest increase in Bacteroides spp. (150 mg/1-week treatment) was detected. In control conditions, only Clostridium spp. and Bifidobacterium spp. were found attached to the colonic epithelium. Rifaximin showed a tendency to favour their adherence after a 1-week, but not 2-week, treatment period. Minor up-regulation in TLRs expression was observed. Only the 50 mg dose for 1-week led to a significant increase (by 3-fold) in TLR-4 expression. No changes in the expression of immune-related markers were observed. Rifaximin, although its antibacterial properties, induces minor changes in luminal and wall-adhered GCM in healthy mice. Moreover, no modulation of TLRs or local immune systems was observed. These findings, in normal conditions, do not rule out a modulatory role of rifaximin in inflammatory and or dysbiotic states of the gut.

scholarly journals DARK MATTER DYNAMICS AND INDIRECT DETECTION

2005 ◽  
Vol 20 (14) ◽  
pp. 1021-1036 ◽  
Author(s):  
GIANFRANCO BERTONE ◽  
DAVID MERRITT
Keyword(s):  
Dark Matter ◽  
Total Mass ◽  
Galactic Center ◽  
Direct Detection ◽  
Indirect Detection ◽  
Matter Distribution ◽  
Dark Matter Distribution ◽  
Particle Dark Matter ◽  
The Universe ◽  
Rule Out

Non-baryonic, or "dark", matter is believed to be a major component of the total mass budget of the Universe. We review the candidates for particle dark matter and discuss the prospects for direct detection (via interaction of dark matter particles with laboratory detectors) and indirect detection (via observations of the products of dark matter self-annihilations), focusing in particular on the Galactic center, which is among the most promising targets for indirect detection studies. The gravitational potential at the Galactic center is dominated by stars and by the supermassive black hole, and the dark matter distribution is expected to evolve on sub-parsec scales due to interaction with these components. We discuss the dominant interaction mechanisms and show how they can be used to rule out certain extreme models for the dark matter distribution, thus increasing the information that can be gleaned from indirect detection searches.

scholarly journals Role of host star variability in the detectability of planetary phase curves

2019 ◽  
Vol 621 ◽  
pp. A44
Author(s):  
D. Hidalgo ◽  
R. Alonso ◽  
E. Pallé
Keyword(s):  
Effective Temperature ◽  
Thermal Emission ◽  
Total Duration ◽  
Phase Curve ◽  
Single Orbit ◽  
Reflected Light ◽  
Planetary Orbits ◽  
Minimum Number ◽  
Temperature Ranges ◽  
Low Amplitude

Phase curves, or the change in observed illumination of the planet as it orbits around its host star, help us to characterize their atmospheres. However, the variability of the host star can make their detection challenging. The presence of starspots, faculae, flares, and rotational effects introduce brightness variations that can hide other flux variations related to the presence of an exoplanet: ellipsoidal variation, Doppler boosting, and a combination of reflected light and thermal emission from the planet. Here we present a study to quantify the effect of stellar variability on the detectability of phase curves in the optical. In the first stage we simulated ideal data, with different white noise levels, and with cadences and total duration matching a quarter of the Kepler mission. We performed injection and recovery tests to evaluate the minimum number of planetary orbits that need to be observed in order to determine the amplitude of the phase curve with an accuracy of 15%. We also evaluate the effect of a simplistic stellar variability signal with low amplitude in order to provide strong constraints on the minimum number of orbits needed under these ideal conditions. In the second stage we applied these methods to data from Q9 of the Kepler mission, known for its low instrumental noise. The injection and recovery tests are performed on a selected sample of the less noisy stars in different effective temperature ranges. Even for the shortest explored planet period of 1 day, we find that observing a single orbit of the planet fails to detect accurately more than 90% of the inserted amplitude. The best recovery rates, close to 48%, are obtained after 10 orbits of a 1 day period planet with the largest explored amplitude of 150 ppm. The temperature range of the host stars providing better recovery ratios is 5500 K < Teff < 6000 K. Our results provide guidelines to selecting the best targets in which phase curves can be measured to the greatest accuracy, given the variability and effective temperature of its host star, which is of interest for the upcoming TESS, CHEOPS, and PLATO space missions.

Narcolepsy: Differential Diagnosis or Etiology in Some Cases of Bipolar Disorder and Schizophrenia?

CNS Spectrums ◽  
2003 ◽  
Vol 8 (2) ◽  
pp. 120-126 ◽  
Author(s):  
Alan B. Douglass
Keyword(s):  
Bipolar Disorder ◽  
Differential Diagnosis ◽  
Psychiatric Patients ◽  
Human Leukocyte ◽  
Sleep Paralysis ◽  
Leukocyte Antigen ◽  
Psychotic Features ◽  
Hypnagogic Hallucinations ◽  
Rule Out

AbstractDoes narcolepsy, a neurological disease, need to be considered when diagnosing major mental illness? Clinicians have reported cases of narcolepsy with prominent hypnagogic hallucinations that were mistakenly diagnosed as schizophrenia. In some bipolar disorder patients with narcolepsy, the HH resulted in their receiving a more severe diagnosis (ie, bipolar disorder with psychotic features or schizoaffective disorder). The role of narcolepsy in psychiatric patients has remained obscure and problematic, and it may be more prevalent than commonly believed. Classical narcolepsy patients display the clinical “tetrad”—cataplexy, hypnagogic hallucinations, daytime sleep attacks, and sleep paralysis. Over 85% also display the human leukocyte antigen marker DQB10602 (subset of DQ6). Since 1998, discoveries in neuroanatomy and neurophysiology have greatly advanced the understanding of narcolepsy, which involves a nearly total loss of the recently discovered orexin/hypocretin (hypocretin) neurons of the hypothalamus, likely by an autoimmune mechanism. Hypocretin neurons normally supply excitatory signals to brainstem nuclei producing norepinephrine, serotonin, histamine, and dopamine, with resultant suppression of sleep. They also project to basal forebrain areas and cortex. A literature review regarding the differential diagnosis of narcolepsy, affective disorder, and schizophrenia is presented. Furthermore, it is now possible to rule out classical narcolepsy in difficult psychiatric cases. Surprisingly, psychotic patients with narcolepsy will likely require stimulants to fully recover. Many conventional antipsychotic drugs would worsen their symptoms and make them appear to become a “chronic psychotic,” while in fact they can now be properly diagnosed and treated.

scholarly journals Inanimate Objects and the Environment Are Far From Contributing to COVID-19 Spread

2021 ◽  
Author(s):  
Ana Luiza Silva Rocha ◽  
Josilene Pinheiro ◽  
Thamilin Costa Nakamura ◽  
José Domingos Santos da Silva ◽  
Beatriz Gonçalves Silva Rocha ◽  
...  
Keyword(s):  
Sampling Method ◽  
Environmental Temperature ◽  
Cell Phones ◽  
Market Area ◽  
P Gene ◽  
Human Rnase ◽  
Reference Hospital ◽  
Market Areas ◽  
Rule Out

Abstract It is not clear if COVID-19 can be indirectly transmitted. It is not possible to conclude the role of environment in transmission of SARS-CoV-2 without studying areas in which people transit in great amounts, such as market areas. In this work we aimed to better understand the role of environment in the spread of COVID-19. We investigated the presence of SARS-CoV-2 in inanimate objects as well as in the air and in the sewage using RT-qPCR. We studied both, a reference market area and a COVID-19 reference hospital at Barreiras city, Brazil. We collected and analyzed a total of 268 samples from mask fronts, cell phones, paper moneys, card machines, sewage, air and bedding during the ascendant phase of the epidemiological curve of COVID-19 in Barreiras. As a result, we detected the human RNAse P gene in most of samples, which indicates the presence of human cells in specimens. However, we did not detect any trace of SARS-CoV-2 in all samples analyzed. To rule out the possibility of problems in sampling method we tested detection of SARS-CoV-2 by RT-qPCR in laboratory conditions to reproduce environmental temperature and humidity. As a result, we showed detection of the virus in different conditions. We conclude that our sampling method reliable and that, strikingly, the environment and inanimate materials do not have an important role in COVID-19 transmission.

scholarly journals Role of Aspirin for primary prevention of cardiovascular and all-cause mortality events in diabetes: An updated meta-analysis of randomized controlled trials.

2021 ◽  
Author(s):  
Hua Ma ◽  
QIng Gu ◽  
Huining Niu ◽  
Xiaohua Li ◽  
Rong Wang
Keyword(s):  
Cardiovascular Disease ◽  
Primary Prevention ◽  
Meta Analysis ◽  
Significant Risk ◽  
Diabetic Patients ◽  
Primary Endpoints ◽  
All Cause Mortality ◽  
Patients With Diabetes ◽  
Rule Out

Background: The use of Aspirin in the primary prevention of cardiovascular disease (CVD) is still a topic of debate, especially in patients with diabetes. The present meta-analysis aims to rule out the efficacy of Aspirin in patients with diabetes and to compare the effectiveness of Aspirin with a placebo (or no treatment) for the primary prevention of CVD and all-cause mortality events in people with diabetes. Materials and Methods: An extensive and systematic search was conducted in Medline (via PubMed), Cinahl (via Ebsco), Scopus, and Web of Sciences from 1988 to December 2020. A detailed literature search was conducted using Aspirin, cardiovascular disease (CVD), diabetes, and efficacy to identify trials of patients with diabetes who received Aspirin for primary prevention of CVD. Demographic details with the primary outcome of events and bleeding outcomes were analyzed. The risk of bias (RoB) in included studies was evaluated using the QUADAS-2 tool. Results: A total of 5 studies out of 13 were included with 23,570 diabetic patients; 11,738 allocated to Aspirin and 11,832 allocated to the placebo group. In patients with diabetes, there was no difference between Aspirin and placebo with respect to the risk of all-cause death with a confidence interval (CI) varying 0.63 to 1.17. In addition, there were no differences in the bleeding outcomes with an odds ratio of 1.4411 (CI 0.47 to 4.34). Conclusion: Aspirin has no significant risk on primary endpoints of cardiovascular events and the bleeding outcomes in diabetic patients compared to placebo. More research on the use of Aspirin alone or in combination with other antiplatelet drugs is required in patients with diabetes to supplement currently available research.

Abstract 19143: Role of Cardiac Biomarkers in Diagnosing Takotsubo Cardiomyopathy from Left Anterior Descending Artery ST Elevation Myocardial Infarction

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Ghulam Akbar ◽  
Marwan Badri ◽  
Catherine Prince ◽  
Wajeeha Saeed ◽  
Ghazi Mirrani ◽  
...  
Keyword(s):  
Coronary Angiography ◽  
Observational Studies ◽  
Troponin I ◽  
Cardiac Biomarkers ◽  
Lv Function ◽  
St Elevation ◽  
Subsequent Improvement ◽  
Echocardiographic Findings ◽  
Rule Out

Introduction: Takostubo cardiomyopathy (TK) and STEMI in the proximal to mid LAD territory (LAD-S) may have similar clinical, ECG and echocardiographic presentation. The two can only be differentiated using coronary angiography. Hypothesis: We hypothesized that the ratio of serum BNP to troponin-I(TnI) will help in distinguishing TK from LAD-S. Previously it has been studied in TK and STEMI from any coronary artery lesion. This is the first study to tease out LAD-S and TK by using BNP/TnI ratio . Methods: We retrospectively compared patients who presented with LAD-S and patients with TK (confirmed with non-obstructive coronary angiography, classic echocardiographic appearance and subsequent improvement of LV function). Patients who did not have BNP and TnI available were excluded. Results: Out of 313 patients with LAD-S and 464 with possible TK, 39 and 62 patients were included respectively. Mean BNP and TnI levels were 788, 57.6ng/dl and 923, 3.4ng/dl in LAD-S and TK respectively. A BNP/TnI ratio of ≤6.4 was 100% sensitive and 41% specific to diagnose LAD-S, and therefore has 100% negative predictive value. A BNP/TnI ratio of ≥2388 was 80% sensitive and 93% specific for diagnosing TK. Conclusion: BNP/TnI ratio <6.4 is reliable to rule out TK and lead to the diagnosis of LAD-S in patients with typical echocardiographic findings. Further, larger observational studies are needed to validate the use of biomarkers for this purpose.

scholarly journals Contributions and Prospects for Spectral Classification of Stars with Objective Prism Techniques

1979 ◽  
Vol 47 ◽  
pp. 127-136
Author(s):  
E. K. Kharadze
Keyword(s):  
Galactic Structure ◽  
Spectral Classification ◽  
Missing Mass ◽  
Mass Problem ◽  
Important Stage ◽  
Objective Prism ◽  
Low Dispersion

The following topics will be discussed: a) A few historical comments; b) MK classification - the most important stage of classification work; c) Recently revealed peculiarity features and the problem of further differentiation of the classification scale; d) Classification work in the USSR; e) The role of classification results with respect to galactic structure studies; f) Low dispersion spectra and faint M-type stars and the missing mass problem; g) Extraterrestrial spectral observations: new promising means for research.

Intracellular pH regulation in rabbit S3 proximal tubule: basolateral Cl-HCO3 exchange and Na-HCO3 cotransport

1990 ◽  
Vol 258 (2) ◽  
pp. F371-F381 ◽  
Author(s):  
N. L. Nakhoul ◽  
L. K. Chen ◽  
W. F. Boron
Keyword(s):  
Proximal Tubule ◽  
Intracellular Ph ◽  
Initial Rate ◽  
Ph Regulation ◽  
Basolateral Membrane ◽  
Intracellular Ph Regulation ◽  
S3 Segment ◽  
Absorbance Spectra ◽  
Rule Out

We studied the role of basolateral HCO3- transport in the regulation of intracellular pH (pHi) in the isolated perfused S3 segment of the rabbit proximal tubule. pHi was calculated from absorbance spectra of the pH-sensitive dye dimethylcarboxyfluorescein. Solutions were normally buffered to pH 7.4 at 37 degrees C with 25 mM HCO3- 5% CO2. pHi fell by approximately 0.17 when luminal [HCO3-] was lowered to 5 mM at fixed PCO2 (i.e., reducing pH to 6.8) but by approximately 0.42 when [HCO3-] in the bath (i.e., basolateral solution) was lowered to 5 mM. The pHi decrease elicited by reducing bath [HCO3-] was substantially reduced by removal of Cl- or Na+, suggesting that components of basolateral HCO3- transport are Cl- and/or Na+ dependent. We tested for the presence of basolateral Cl-HCO3 exchange by removing bath Cl-. This caused pHi to increase by approximately 0.23, with an initial rate of approximately 100 X 10(-4) pH/s. Although the initial rate of this pHi increase was not reduced by removing Na+ bilaterally, it was substantially lowered by the nominal removal of HCO3- from bath and lumen or by the addition of 0.1 mM 4,4'-diisothiocyanostilbene-2,2'-disulfonate (DIDS) to the bath. The results thus suggest that a Na-independent Cl-HCO3 exchanger is present at the basolateral membrane. We tested for the presence of basolateral Na-HCO3 cotransport by removing bath Na+. This caused pHi to fall reversibly by approximately 0.26 with initial rates of pHi decline and recovery being approximately 30 and approximately 41 X 10(-4) pH/s, respectively. Although the bilateral removal of Cl- had no effect on these rates, the nominal removal of HCO3- or the presence of DIDS substantially slowed the pHi changes. Thus, in addition to a Cl-HCO3 exchanger, the basolateral membrane of the S3 proximal tubule also appears to possess a Na-HCO3 cotransport mechanism. The data do not rule out the possibility of other basolateral HCO3- transporters.

scholarly journals A Study on the Potential Role of Occlusal Fissure Fractures in the Etiopathogenesis of Equine Cheek Teeth Apical Infections

2019 ◽  
Vol 36 (3) ◽  
pp. 171-178 ◽  
Author(s):  
Katherina Y. Wellman ◽  
Padraic M. Dixon
Keyword(s):  
Computed Tomography ◽  
Methylene Blue ◽  
Potential Role ◽  
Histological Study ◽  
Extraction Process ◽  
Dental Tissue ◽  
Rule Out

Thirty-nine equine cheek teeth diagnosed as having anachoretic apical infections and also having occlusal fissure fractures, but without occlusal pulpar exposure, that had been orally extracted without causing occlusal damage and 10 control teeth were used in this study. The teeth were individually imaged by computed tomography, occlusally stained with methylene blue and visually reexamined, then sectioned subocclusally at 5 mm intervals until the fissure fractures could no longer be detected. A limited histological study was then performed on 7 apically infected and 5 control teeth. Standard computed tomography only detected 1 of 39 fissure fractures. Thirteen of the 39 stained teeth had subocclusal fissure fractures visually identified at approximately 6 mm beneath the surface, and in 9 of these 13 teeth the fissure fractures had deeper staining to a level immediately above or into a pulp horn, indicating a potential route for bacterial pulpitis. However, the current study cannot rule out the possibility that the extraction process, long-term formalin storage, or the processing of teeth may have allowed for deeper staining. Additionally, methylene blue may penetrate dental tissue more readily than bacteria can invade. Further studies on the potential role of fissure fractures in the etiopathogenesis of cheek teeth apical infection are warranted.

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