113 research outputs found
Weak Alfvén-wave turbulence revisited
Weak Alfvénic turbulence in a periodic domain is considered as a mixed state of Alfvén waves interacting with the two-dimensional (2D) condensate. Unlike in standard treatments, no spectral continuity between the two is assumed, and, indeed, none is found. If the 2D modes are not directly forced, k−2 and k−1 spectra are found for the Alfvén waves and the 2D modes, respectively, with the latter less energetic than the former. The wave number at which their energies become comparable marks the transition to strong turbulence. For imbalanced energy injection, the spectra are similar, and the Elsasser ratio scales as the ratio of the energy fluxes in the counterpropagating Alfvén waves. If the 2D modes are forced, a 2D inverse cascade dominates the dynamics at the largest scales, but at small enough scales, the same weak and then strong regimes as described above are achieved
UTJECAJ DULJINE IGS BAZE NA TOČNOST POZICIONIRANJA GNSS-A
Since the establishment of the International GNSS Service (IGS) stations, they have been used as control stations for assigning the Precise point positioning (PPP) positions using one Global Navigation Satellite System (GNSS) receiver, which has increased from day-to-day. There are some factors affecting the accuracy of PPP positioning. This research aims to investigate the relation between the IGS distance and observed field points as well as to attempt to describe that relation mathematically/statically. For the realization of that aim, two field points are fixed inside the Assiut University campus and observed successively for a session of 24 hour observation. The position of each field point is assigned with the help of each one of the available IGS station products. It must be known that these products are found after observations in three files (IGU, IGR, and final IGS), whereas IGU is used directly as real-time data (ultra-rapid), IGR (rapid) is used through (17-41 hours) after observation, and (final IGS) used after 12 – 18 days. Coordinates and point errors of each field points are computed and represented. It has been found that the errors have a positive relation with the available IGS stations distances. The relation between these distances and point positioning errors have been represented and described according to a model. The accuracy of the presented model is (R ≅ .98, x2 ≅ 2.5 × 10-3).Od uspostave postaja Međunarodnoga GNSS servisa (IGS) iz dana u dan povećava se korištenje kontrolnih stanica za dodjelu položaja precizne točke (PPP) pomoću jednoga prijamnika Globalnoga satelitskog navigacijskog sustava (GNSS). Postoje neki čimbenici koji utječu na točnost PPP pozicioniranja. Cilj je ovoga istraživanja istražiti odnos između IGS udaljenosti i promatranih točaka polja te opisati taj odnos matematički i statički. Za realizaciju toga cilja dvije terenske točke fiksirane su unutar kampusa Sveučilišta Assiut i promatrane sukcesivno tijekom sesije promatranja od 24 sata. Položaj svake točke polja dodjeljuje se uz pomoć svakoga od dostupnih proizvoda IGS stanica. Bitno je napomenuti da se ti produkti nalaze u tri datoteke (IGU, IGR i konačni IGS) nakon promatranja, dok se IGU koristi izravno kao podatci u stvarnome vremenu (ultra-rapid), IGR (rapid) kroz 17 – 41 sat nakon promatranja, a konačni IGS nakon 12 – 18 dana. Koordinate i pogreške točaka svake točke polja izračunane su i prikazane. Utvrđeno je da su pogreške u pozitivnom odnosu s dostupnim udaljenostima IGS postaja. Odnos između tih udaljenosti i pogrešaka pozicioniranja točke prikazan je i opisan prema modelu. Točnost je prikazanoga modela R ≅ .98, x2 ≅ 2.5 × 10-3
Study of Treg FOXP3 in childhood bronchial asthma in relation to corticosteroid therapy
Background: T cells are considered the main cells responsible for production of suppressive cytokines, and play a key role in balancing the immune responses to maintain the peripheral tolerance against allergens. Objective: The present study investigates T regulatory (Treg) forkheadwinged helix protein 3 FOXP3 expression in childhood asthma and its relation to corticosteroid therapy. Methods: In this case control study, Treg FOXP3 was measured in blood of 60 children using real time polymerase chain reaction (RT-PCR) technique. Two asthmatic groups were included, one on corticosteroid therapy (20 patients) and the other not on corticosteroid treatment (20 patients). They were compared to 20 healthy children as controls. Results: FOXP3 concentration was significantly elevated in asthmatic patients (90 ± 77.4) compared to healthy children (12.844 ± 10.6) (p= 0.000). FOXP3 was significantly more elevated in asthmatics on corticosteroids (161.158 ± 63.9) than steroid naive asthmatics (36.038 ± 23.4) (p=0.000). Levels of Treg FOXP3 in asthmatics with inhaled corticosteroids (mean 151.16 ± 53.79) were almost similar to FOXP3 in asthmatics with systemic corticosteroids (161.49±72.5) (p>0.05). FOXP3 levels did not differ with smoking, asthma severity or disease control and did not correlate with age, FEV1, blood lymphocytes percentage or eosinophils percentage. Conclusion: Asthmatics have increased expression of FOXP3, and corticosteroid therapy –whether oral or inhaled - enhances FOXP3 expression.Keywords: FOXP3, Treg, Corticosteroids, Bronchial asthma, Transcription factors, CytokinesEgypt J Pediatr Allergy Immunol 2012;10(1):39-43
Gastroesophageal reflux in mechanically ventilated pediatric patients and its relation to ventilator-associated pneumonia
The "zeroth law" of turbulence: Isotropic turbulence simulations revisited
The dimensionless kinetic energy dissipation rate C_epsilon is estimated from
numerical simulations of statistically stationary isotropic box turbulence that
is slightly compressible. The Taylor microscale Reynolds number Re_lambda range
is 20 < Re_lambda < 220 and the statistical stationarity is achieved with a
random phase forcing method. The strong Re_lambda dependence of C_epsilon
abates when Re_lambda approx. 100 after which C_epsilon slowly approaches
approx 0.5 a value slightly different to previously reported simulations but in
good agreement with experimental results. If C_epsilon is estimated at a
specific time step from the time series of the quantities involved it is
necessary to account for the time lag between energy injection and energy
dissipation. Also, the resulting value can differ from the ensemble averaged
value by up to +-30%. This may explain the spread in results from previously
published estimates of C_epsilon.Comment: 7 pages, 7 figures. Submitted to Phys. Rev.
Bottleneck effect in three-dimensional turbulence simulations
At numerical resolutions around and above, three-dimensional energy
spectra from turbulence simulations begin to show noticeably shallower spectra
than near the dissipation wavenumber (`bottleneck effect'). This
effect is shown to be significantly weaker in one-dimensional spectra such as
those obtained in wind tunnel turbulence. The difference can be understood in
terms of the transformation between one-dimensional and three-dimensional
energy spectra under the assumption that the turbulent velocity field is
isotropic. Transversal and longitudinal energy spectra are similar and can both
accurately be computed from the full three-dimensional spectra. Second-order
structure functions are less susceptible to the bottleneck effect and may be
better suited for inferring the scaling exponent from numerical simulation
data.Comment: 8 pages, 6 figure
Adolescent transport and unintentional injuries: a systematic analysis using the Global Burden of Disease Study 2019
Background: Globally, transport and unintentional injuries persist as leading preventable causes of mortality and morbidity for adolescents. We sought to report comprehensive trends in injury-related mortality and morbidity for adolescents aged 10–24 years during the past three decades. Methods: Using the Global Burden of Disease, Injuries, and Risk Factors 2019 Study, we analysed mortality and disability-adjusted life-years (DALYs) attributed to transport and unintentional injuries for adolescents in 204 countries. Burden is reported in absolute numbers and age-standardised rates per 100 000 population by sex, age group (10–14, 15–19, and 20–24 years), and sociodemographic index (SDI) with 95% uncertainty intervals (UIs). We report percentage changes in deaths and DALYs between 1990 and 2019. Findings: In 2019, 369 061 deaths (of which 214 337 [58%] were transport related) and 31·1 million DALYs (of which 16·2 million [52%] were transport related) among adolescents aged 10–24 years were caused by transport and unintentional injuries combined. If compared with other causes, transport and unintentional injuries combined accounted for 25% of deaths and 14% of DALYs in 2019, and showed little improvement from 1990 when such injuries accounted for 26% of adolescent deaths and 17% of adolescent DALYs. Throughout adolescence, transport and unintentional injury fatality rates increased by age group. The unintentional injury burden was higher among males than females for all injury types, except for injuries related to fire, heat, and hot substances, or to adverse effects of medical treatment. From 1990 to 2019, global mortality rates declined by 34·4% (from 17·5 to 11·5 per 100 000) for transport injuries, and by 47·7% (from 15·9 to 8·3 per 100 000) for unintentional injuries. However, in low-SDI nations the absolute number of deaths increased (by 80·5% to 42 774 for transport injuries and by 39·4% to 31 961 for unintentional injuries). In the high-SDI quintile in 2010–19, the rate per 100 000 of transport injury DALYs was reduced by 16·7%, from 838 in 2010 to 699 in 2019. This was a substantially slower pace of reduction compared with the 48·5% reduction between 1990 and 2010, from 1626 per 100 000 in 1990 to 838 per 100 000 in 2010. Between 2010 and 2019, the rate of unintentional injury DALYs per 100 000 also remained largely unchanged in high-SDI countries (555 in 2010 vs 554 in 2019; 0·2% reduction). The number and rate of adolescent deaths and DALYs owing to environmental heat and cold exposure increased for the high-SDI quintile during 2010–19. Interpretation: As other causes of mortality are addressed, inadequate progress in reducing transport and unintentional injury mortality as a proportion of adolescent deaths becomes apparent. The relative shift in the burden of injury from high-SDI countries to low and low–middle-SDI countries necessitates focused action, including global donor, government, and industry investment in injury prevention. The persisting burden of DALYs related to transport and unintentional injuries indicates a need to prioritise innovative measures for the primary prevention of adolescent injury. Funding: Bill & Melinda Gates Foundation
Spatial, temporal, and demographic patterns in prevalence of chewing tobacco use in 204 countries and territories, 1990-2019 : a systematic analysis from the Global Burden of Disease Study 2019
Interpretation Chewing tobacco remains a substantial public health problem in several regions of the world, and predominantly in south Asia. We found little change in the prevalence of chewing tobacco use between 1990 and 2019, and that control efforts have had much larger effects on the prevalence of smoking tobacco use than on chewing tobacco use in some countries. Mitigating the health effects of chewing tobacco requires stronger regulations and policies that specifically target use of chewing tobacco, especially in countries with high prevalence. Findings In 2019, 273 center dot 9 million (95% uncertainty interval 258 center dot 5 to 290 center dot 9) people aged 15 years and older used chewing tobacco, and the global age-standardised prevalence of chewing tobacco use was 4 center dot 72% (4 center dot 46 to 5 center dot 01). 228 center dot 2 million (213 center dot 6 to 244 center dot 7; 83 center dot 29% [82 center dot 15 to 84 center dot 42]) chewing tobacco users lived in the south Asia region. Prevalence among young people aged 15-19 years was over 10% in seven locations in 2019. Although global agestandardised prevalence of smoking tobacco use decreased significantly between 1990 and 2019 (annualised rate of change: -1 center dot 21% [-1 center dot 26 to -1 center dot 16]), similar progress was not observed for chewing tobacco (0 center dot 46% [0 center dot 13 to 0 center dot 79]). Among the 12 highest prevalence countries (Bangladesh, Bhutan, Cambodia, India, Madagascar, Marshall Islands, Myanmar, Nepal, Pakistan, Palau, Sri Lanka, and Yemen), only Yemen had a significant decrease in the prevalence of chewing tobacco use, which was among males between 1990 and 2019 (-0 center dot 94% [-1 center dot 72 to -0 center dot 14]), compared with nine of 12 countries that had significant decreases in the prevalence of smoking tobacco. Among females, none of these 12 countries had significant decreases in prevalence of chewing tobacco use, whereas seven of 12 countries had a significant decrease in the prevalence of tobacco smoking use for the period. Summary Background Chewing tobacco and other types of smokeless tobacco use have had less attention from the global health community than smoked tobacco use. However, the practice is popular in many parts of the world and has been linked to several adverse health outcomes. Understanding trends in prevalence with age, over time, and by location and sex is important for policy setting and in relation to monitoring and assessing commitment to the WHO Framework Convention on Tobacco Control. Methods We estimated prevalence of chewing tobacco use as part of the Global Burden of Diseases, Injuries, and Risk Factors Study 2019 using a modelling strategy that used information on multiple types of smokeless tobacco products. We generated a time series of prevalence of chewing tobacco use among individuals aged 15 years and older from 1990 to 2019 in 204 countries and territories, including age-sex specific estimates. We also compared these trends to those of smoked tobacco over the same time period. Findings In 2019, 273 & middot;9 million (95% uncertainty interval 258 & middot;5 to 290 & middot;9) people aged 15 years and older used chewing tobacco, and the global age-standardised prevalence of chewing tobacco use was 4 & middot;72% (4 & middot;46 to 5 & middot;01). 228 & middot;2 million (213 & middot;6 to 244 & middot;7; 83 & middot;29% [82 & middot;15 to 84 & middot;42]) chewing tobacco users lived in the south Asia region. Prevalence among young people aged 15-19 years was over 10% in seven locations in 2019. Although global age standardised prevalence of smoking tobacco use decreased significantly between 1990 and 2019 (annualised rate of change: -1 & middot;21% [-1 & middot;26 to -1 & middot;16]), similar progress was not observed for chewing tobacco (0 & middot;46% [0 & middot;13 to 0 & middot;79]). Among the 12 highest prevalence countries (Bangladesh, Bhutan, Cambodia, India, Madagascar, Marshall Islands, Myanmar, Nepal, Pakistan, Palau, Sri Lanka, and Yemen), only Yemen had a significant decrease in the prevalence of chewing tobacco use, which was among males between 1990 and 2019 (-0 & middot;94% [-1 & middot;72 to -0 & middot;14]), compared with nine of 12 countries that had significant decreases in the prevalence of smoking tobacco. Among females, none of these 12 countries had significant decreases in prevalence of chewing tobacco use, whereas seven of 12 countries had a significant decrease in the prevalence of tobacco smoking use for the period. Interpretation Chewing tobacco remains a substantial public health problem in several regions of the world, and predominantly in south Asia. We found little change in the prevalence of chewing tobacco use between 1990 and 2019, and that control efforts have had much larger effects on the prevalence of smoking tobacco use than on chewing tobacco use in some countries. Mitigating the health effects of chewing tobacco requires stronger regulations and policies that specifically target use of chewing tobacco, especially in countries with high prevalence. Copyright (c) 2021 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license.Peer reviewe
Burnout among surgeons before and during the SARS-CoV-2 pandemic: an international survey
Background: SARS-CoV-2 pandemic has had many significant impacts within the surgical realm, and surgeons have been obligated to reconsider almost every aspect of daily clinical practice. Methods: This is a cross-sectional study reported in compliance with the CHERRIES guidelines and conducted through an online platform from June 14th to July 15th, 2020. The primary outcome was the burden of burnout during the pandemic indicated by the validated Shirom-Melamed Burnout Measure. Results: Nine hundred fifty-four surgeons completed the survey. The median length of practice was 10 years; 78.2% included were male with a median age of 37 years old, 39.5% were consultants, 68.9% were general surgeons, and 55.7% were affiliated with an academic institution. Overall, there was a significant increase in the mean burnout score during the pandemic; longer years of practice and older age were significantly associated with less burnout. There were significant reductions in the median number of outpatient visits, operated cases, on-call hours, emergency visits, and research work, so, 48.2% of respondents felt that the training resources were insufficient. The majority (81.3%) of respondents reported that their hospitals were included in the management of COVID-19, 66.5% felt their roles had been minimized; 41% were asked to assist in non-surgical medical practices, and 37.6% of respondents were included in COVID-19 management. Conclusions: There was a significant burnout among trainees. Almost all aspects of clinical and research activities were affected with a significant reduction in the volume of research, outpatient clinic visits, surgical procedures, on-call hours, and emergency cases hindering the training. Trial registration: The study was registered on clicaltrials.gov "NCT04433286" on 16/06/2020
- …