2,375 research outputs found
Morphologies of protostellar outflows: An ALMA view
The formation of stars is usually accompanied by the launching of
protostellar outflows. Observations with the Atacama Large
Millimetre/sub-millimetre Array (ALMA) will soon revolutionalise our
understanding of the morphologies and kinematics of these objects. In this
paper, we present synthetic ALMA observations of protostellar outflows based on
numerical magnetohydrodynamic collapse simulations. We find significant
velocity gradients in our outflow models and a very prominent helical structure
within the outflows. We speculate that the disk wind found in the ALMA Science
Verification Data of HD 163296 presents a first instance of such an
observation
√n-consistent parameter estimation for systems of ordinary differential equations : bypassing numerical integration via smoothing
We consider the problem of parameter estimation for a system of ordinary differential equations from noisy observations on a solution of the system. In case the system is nonlinear, as it typically is in practical applications, an analytic solution to it usually does not exist. Consequently, straightforward estimation methods like the ordinary least squares method depend on repetitive use of numerical integration in order to determine the solution of the system for each of the parameter values considered, and to find subsequently the parameter estimate that minimises the objective function. This induces a huge computational load to such estimation methods. We propose an estimator that is defined as a minimiser of an appropriate distance between a nonparametrically estimated derivative of the solution and the right-hand side of the system applied to a nonparametrically estimated solution. Our estimator bypasses numerical integration altogether and reduces the amount of computational time drastically compared to ordinary least squares. Moreover, we show that under suitable regularity conditions this estimation procedure leads to a vn-consistent estimator of the parameter of interest
Determination of molecular spectroscopic parameters and energy-transfer rates by double-resonance spectroscopy
The spectroscopy of small to medium-size polyatomic molecules can be extremely complex, especially in higher-lying overtone and combination vibrational levels. The high density of levels also complicates the understanding of inelastic collision processes, which is required to model energy transfer and collision broadening of spectral lines. Both of these problems can be addressed by double-resonance spectroscopy, i.e., time-resolved pump-probe measurements using microwave, infrared, near-infrared, and visible-wavelength sources. Information on excited-state spectroscopy, transition moments, inelastic energy transfer rates and propensity rules, and pressure-broadening parameters may be obtained from such experiments. Examples are given for several species of importance in planetary atmospheres, including ozone, silane, ethane, and ammonia
Identification of Concealed Insect Infestations Using a Passive Ultrasound Monitor
Concealed insect infestations in stored grain are responsible for large economic losses worldwide, and have traditionally been difficult to detect arid quantify. A simple method of infestation detection and quantification has been developed, taking advantage of the ultrasonic emissions generated by the feeding activity of the insects. The acoustic signals generated by the insects are characterized as bursts of energy in the frequency range of 5 to 75 kHz, varying with the variety of seed being examined. These signals can be detected reliably by monitoring the seeds for sounds in a frequency band between 30 and 50 kHz. The stage of development of an insect, and thus the amount of damage of which the insect is capable, can be predicted by studying a time series of these signals. A basic signal acquisition procedure has been developed which amplifies the variations in the pattern of acoustic signals associated with different stages of larval development for the cowpea weevil. A histogram is constructed to describe the time intervals between successive feeding events, and is compared to typical histograms associated with each stage of development. In over 80% of the cases, an acquired histogram from a cowpea weevil at a known stage of development was most similar to the typical histogram associated with insects at the same stage of development. Using this correlation to quantify an infestation could lead to a significant reduction in the use of pesticides for insect eradication
Adult Mesenchymal Hamartoma of the Liver: Case Report and Literature Review
Mesenchymal hamartoma of the liver (MHL) is a rare benign lesion occurring primarily in the pediatric population. While the precise pathogenesis of the tumor is not certain, the most common theory relates to aberrant mesenchyme development in the portal tract likely related to the bile ducts. A 53-year-old female was evaluated for an incidental liver mass. Initial CT scan showed a cystic lesion in the right lobe of the liver and follow-up imaging revealed an increase in size and the percent solid component within the mass. In view of these changes, a nondiagnostic biopsy was obtained followed by extirpation of the lesion. Gross pathological review of the lesion identified a 9 × 9 × 7.5 cm, pink-yellow-tan, gelatinous mass, with a >1 cm clear surgical margin. Histologically, the mass consisted of benign dilated bile ducts, as well as myxoid stroma with spindle cells showing smooth muscle differentiation. The patient was discharged home on postoperative day five. A review of the literature for MHL in adults reports 30 previous cases, predominantly published as individual case reports describing the size, lobe(s) of the liver affected, and the cystic/solid nature of the tumor. MHL in adults may represent a potentially premalignant lesion, as the emerging literature supports a potential relationship between MHL and malignant undifferentiated embryonal sarcoma in regards to cytogenetic analysis. Aggressive surgical management of MHL in adults is mandated when feasible
Distressed personality is associated with lower psychological well-being and life satisfaction, but not disability or disease activity in rheumatoid arthritis patients
The distressed personality type (“type D personality”) has been shown to be associated with low quality of life and higher morbidity and mortality in various patient groups. Because the role of type D personality is unknown in patients with rheumatoid arthritis (RA), the aim of the present study was to investigate the association of type D personality with aspects of quality of life and disease activity in RA patients. In addition, a potential buffering effect by accepting mindfulness was examined. Participants were 147 patients between 22 and 87 years of age. Patients completed relevant questionnaires at home and the disease activity score was determined. After controlling for potentially confounding variables, multivariate analyses of covariance showed an association of type D personality with a lower satisfaction with life (p < 0.001) and a lower psychological well-being (p < 0.001), but not disease activity in RA patients. Although mindfulness was associated with a higher satisfaction with life (p = 0.02) and positive mood (p = 0.01), it did not diminish the unfavourable associations between type D and well-being. In conclusion, although type D personality is related with lower well-being, it does not seem to be associated with disability or disease activity in RA patients
Different colonization patterns of Aspergillus terreus in patients with cystic fibrosis
Due to the abnormal viscosity of airway secretions, patients with cystic fibrosis (CF) are athigh risk of fungal colonization of the respiratory tract. Aspergillus fumigatus is by far the most common fungal specie encountered in the CF context, but other species are increasingly reported such as Scedosporium spp. or Geosmithia argillacea, as well as other aspergilli including Aspergillus terreus. In our experience, this saprophytic fungus ranks the third among the filamentous fungi colonizing the respiratory tract of CF patients. Additionally, although relatively uncommon, infections caused by A. terreus present a high mortality rate due to its usually low susceptibility to systemic antifungals. Nevertheless, little is known about the epidemiology of A. terreus colonization/infections. In the present study, nine short tandem repeats of A. terreus were used to genotype 122 clinical isolates recovered from sputum samples from five patients with CF followed-up in two distinct hospitals in France (Angers and Giens hospitals). Sputum samples were collected over a two-month to seven-year period depending on the patients, and for each sample, all the obtained isolates were studied, with a maximum of five per sample. Three colonization patterns were observed. The first colonization pattern consisted of a chronic colonization (defined as the presence of the same genotype in at least two successive samples collected over a minimum period of two months) by a largely dominant genotype associated with two or three other genotypes found occasionally (patient 4) or over a short period (patient 3). The second colonization pattern consisted of a chronic colonization by two distinct genotypes simultaneously detected (patients 1 and 2). For the last patient (patient 5), who was followed during four years, 16 isolates recovered from 6 sputum samples were analyzed, corresponding to 8 genetically distinct genotypes which succeeded to each other. Numerous questions therefore raise from these different colonization patterns, regarding (i) the origin of the contamination of the patients by this relatively uncommon environmental fungus, (ii) the differences between genotypes in their ability to chronically colonize the airways of the CF patients, or (iii) the differences between CF patients in their individual susceptibility to same genotypes
Possible impacts of climate change on freezing rain in south-central Canada using downscaled future climate scenarios
Freezing rain is a major atmospheric hazard in mid-latitude nations of the globe. Among all Canadian hydrometeorological hazards, freezing rain is associated with the highest damage costs per event. Using synoptic weather typing to identify the occurrence of freezing rain events, this study estimates changes in future freezing rain events under future climate scenarios for south-central Canada. Synoptic weather typing consists of principal components analysis, an average linkage clustering procedure (i.e., a hierarchical agglomerative cluster method), and discriminant function analysis (a nonhierarchical method). Meteorological data used in the analysis included hourly surface observations from 15 selected weather stations and six atmospheric levels of six-hourly National Centers for Environmental Prediction (NCEP) upper-air reanalysis weather variables for the winter months (November–April) of 1958/59–2000/01. A statistical downscaling method was used to downscale four general circulation model (GCM) scenarios to the selected weather stations. Using downscaled scenarios, discriminant function analysis was used to project the occurrence of future weather types. The within-type frequency of future freezing rain events is assumed to be directly proportional to the change in frequency of future freezing rain-related weather types <br><br> The results showed that with warming temperatures in a future climate, percentage increases in the occurrence of freezing rain events in the north of the study area are likely to be greater than those in the south. By the 2050s, freezing rain events for the three colder months (December–February) could increase by about 85% (95% confidence interval – CI: ±13%), 60% (95% CI: ±9%), and 40% (95% CI: ±6%) in northern Ontario, eastern Ontario (including Montreal, Quebec), and southern Ontario, respectively. The increase by the 2080s could be even greater: about 135% (95% CI: ±20%), 95% (95% CI: ±13%), and 45% (95% CI: ±9%). For the three warmer months (November, March, April), the percentage increases in future freezing rain events are projected to be much smaller with some areas showing either a decrease or little change in frequency of freezing rain. On average, northern Ontario could experience about 10% (95% CI: ±2%) and 20% (95% CI: ±4%) more freezing rain events by the 2050s and 2080s, respectively. However, future freezing rain events in southern Ontario could decrease about 10% (95% CI: ±3%) and 15% (95% CI: ±5%) by the 2050s and 2080s, respectively. In eastern Ontario (including Montreal, Quebec), the frequency of future freezing rain events is projected to remain the same as it is currently
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