Abstract Our life is strongly affected by turbulent convective flows, driven by time-dependent thermal forcing, especially diurnal heating of the Earth’s surface by the Sun. In a laboratory ...experiment, we investigate their analogues: We study complex and extraordinary properties of turbulent buoyancy driven flows generated due to periodic modulation of the temperature of the plates of a Rayleigh–Bénard cell, with amplitudes both smaller and larger than either the positive or negative mean temperature difference between the top and bottom. We probe the turbulent flow of our working fluid – cryogenic helium gas – using temperature sensors placed in the cell interior and embedded in its plates. We discuss spatial and temporal structure of the heat flow, generalize validity of Nusselt versus Rayleigh number scaling Nu $$\propto$$ ∝ Ra $$^\gamma$$ γ with $$\gamma \approx {1/3}$$ γ ≈ 1 / 3 at very high Ra for modulated convection and argue that this system represents a benchmark model which helps us understand the energy budget of ocean currents or weather formation on Earth subject to diurnal Sun heating as well as similar natural flows on Earth-like planets.
Study objective Methanol poisoning outbreaks are a global public health issue, with delayed treatment causing poor outcomes. Out-of-hospital ethanol administration may improve outcome, but the ...difficulty of conducting research in outbreaks has meant that its effects have never been assessed. We study the effect of out-of-hospital ethanol in patients treated during a methanol outbreak in the Czech Republic between 2012 and 2014. Methods This was an observational case-series study of 100 hospitalized patients with confirmed methanol poisoning. Out-of-hospital ethanol as a “first aid antidote” was administered by paramedic or medical staff before the confirmation of diagnosis to 30 patients; 70 patients did not receive out-of-hospital ethanol from the staff (12 patients self-administered ethanol shortly before presentation). Results The state of consciousness at first contact with paramedic or medical staff, delay to admission, and serum methanol concentration were similar among groups. The median serum ethanol level on admission in the patients with out-of-hospital administration by paramedic or medical staff was 84.3 mg/dL (interquartile range 32.7 to 129.5 mg/dL). No patients with positive serum ethanol level on admission died compared with 21 with negative serum ethanol level (0% versus 36.2%). Patients receiving out-of-hospital ethanol survived without visual and central nervous system sequelae more often than those not receiving it (90.5% versus 19.0%). A positive association was present between out-of-hospital ethanol administration by paramedic or medical staff, serum ethanol concentration on admission, and both total survival and survival without sequelae of poisoning. Conclusion We found a positive association between out-of-hospital ethanol administration and improved clinical outcome. During mass methanol outbreaks, conscious adults with suspected poisoning should be considered for administration of out-of-hospital ethanol to reduce morbidity and mortality.
We perform an experimental study of turbulent Rayleigh–Bénard convection up to very high Rayleigh number,
$10^{8}<Ra<10^{14}$
, in a cylindrical aspect ratio one cell, 30 cm in height, filled with ...cryogenic helium gas. We monitor temperature fluctuations in the convective flow with four small (0.2 mm) sensors positioned in pairs 1.5 cm from the sidewalls and 2.5 cm vertically apart and symmetrically around the mid-height of the cell. Based on one-point and two-point correlations of the temperature fluctuations, we determine different types of Reynolds numbers,
$\mathit{Re}$
, associated with the large-scale circulation (LSC). We observe a transition between two types of
$\mathit{Re}(\mathit{Ra})$
scaling around
$\mathit{Ra}=10^{10}{-}10^{11}$
, which is accompanied by a scaling change of the skewness of the probability distribution functions (PDFs) of the temperature fluctuations. The
$\mathit{Re}(\mathit{Ra})$
dependencies measured near the sidewall at Prandtl number
$\mathit{Pr}\sim 1$
are consistent with the
$\mathit{Ra}^{4/9}\mathit{Pr}^{-2/3}$
scaling above the transition, while for
$\mathit{Ra}<10^{10}$
, the
$\mathit{Re}(\mathit{Ra})$
dependencies are steeper. It seems likely that this change in
$\mathit{Re}(\mathit{Ra})$
scaling is linked to the previously reported change in the Nusselt number
$\mathit{Nu}(\mathit{Ra})$
scaling. This behaviour is in agreement with independent cryogenic laboratory experiments with
$\mathit{Pr}\sim 1$
, but markedly different from the
$\mathit{Re}$
scaling obtained in water experiments (
$\mathit{Pr}\sim 3.3{-}5.6$
). We discuss the results in comparison with different versions of the Grossmann–Lohse theory.
We present experimental results on the heat transfer efficiency of cryogenic turbulent Rayleigh-Bénard convection (RBC) in a cylindrical cell 0.3 m in both diameter and height which has improvements ...with respect to various corrections connected with finite thermal conductivity of sidewalls and plates. The heat transfer efficiency described by the Nusselt number is investigated for the range of Rayleigh number , with the Prandtl number varying such that , using cryogenic He gas with well-known and in situ tunable properties as a working fluid. For our data (both corrected and uncorrected) agree with suitably corrected data from similar cryogenic experiments and are consistent with . Up to , our data could be treated as Oberbeck-Boussinesq data. For , the heat transfer efficiency becomes affected by non-Oberbeck-Boussinesq (NOB) effects, causing asymmetry of the top and bottom boundary layers. For , the Nusselt number closely follows if and are evaluated on the basis of the working fluid properties at the directly measured bulk temperature, , and suitable corrections are taken into account. In contrast, if the mean temperature is determined as an arithmetic mean of the bottom and top plate temperatures, displays spurious crossover to higher that might be misinterpreted as a transition to the ultimate Kraichnan regime. The second step of our analysis, reported here for the first time, is to ignore the NOB effects affecting the top half of the RBC cell. We replace it by the inverted nearly OB bottom half in order to eliminate the boundary layer asymmetry. This leads to the effective temperature difference , where denotes the bottom plate temperature, and to effective and values. The effective heat transfer efficiency obtained, showing no tendency of crossover to the ultimate regime up to in , is reported and discussed.
We report the results of the visual evoked potentials (VEP) examination in patients after severe poisoning by methanol.
The group of 47 patients (38 males and 9 females) was assembled out of persons ...who survived an outbreak of poisoning by the methanol adulterated alcohol beverages, which happened in the Czech Republic in 2012-2013. The visual evoked potentials examination was performed using monocular checkerboard pattern-reversal stimulation. Two criteria of abnormality were chosen: missing evoked response, and wave P1 latency > 117 ms. Non-parametric statistical methods (median, range, and the median test) were used to analyze factors influencing the VEP abnormality.
The visual evoked potential was abnormal in 20 patients (43%), 5 of them had normal visual acuity on the Snellen chart. The VEP abnormality did not correlate significantly with initial serum concentrations of methanol, formic acid or lactate; however, it showed statistically significant inverse relation to the initial serum pH: the subgroup with the abnormal VEP had significantly lower median pH in comparison with the subgroup with the normal VEP (7.16 vs. 7.34, p = 0.04). The abnormality was not related to chronic alcohol abuse.
The visual evoked potentials examination appeared sensitive enough to detected even subclinical impairment of the optic system. Metabolic acidosis is likely to be the key factor related to the development of visual damage induced by methanol. The examination performed with a delay of 1-9 months after the poisoning documented the situation relatively early after the event. It is considered as a baseline for the planned long-term follow-up of the patients, which will make it possible to assess the dynamics of the observed changes, their reversibility, and the occurrence of potential late sequelae.
When a hot body A is thermally connected to a cold body B, the textbook knowledge is that heat flows from A to B. Here, we describe the opposite case in which heat flows from a colder but constantly ...heated body B to a hotter but constantly cooled body A through a two-phase liquid–vapor system. Specifically, we provide experimental evidence that heat flows through liquid and vapor phases of cryogenic helium from the constantly heated, but cooler, bottom plate of a Rayleigh–Bénard convection cell to its hotter, but constantly cooled, top plate. The bottom plate is heated uniformly, and the top plate is cooled by heat exchange with liquid helium maintained at 4.2 K. Additionally, for certain experimental conditions, a rain of helium droplets is detected by small sensors placed in the cell at about one-half of its height.
Modelling of large-scale natural (thermally-generated) turbulent flows (such as the turbulent convection in Earth’s atmosphere, oceans, or Sun) is approached in laboratory experiments in the ...simplified model system called the Rayleigh-Bénard convection (RBC). We present preliminary measurements of vertical temperature profiles in the cell with the height of 4:7 m, 7:15m in diameter, obtained at the Barrel of Ilmenau (BOI), the worldwide largest experimental setup to study highly turbulent RBC, newly equipped with the Luna ODiSI-B optical fibre system. In our configuration, the system permits to measure the temperature with a high spatial resolution of 5mm along a very thin glass optical fibre with the length of 5m and seems to be perfectly suited for measurement of time series of instantaneous vertical temperature profiles. The system was supplemented with the two Pt100 vertically movable probes specially designed by us for reference temperature profiles measurements.
The aim of the study was to develop a computational module for the prediction of compressive force on the L4/L5 disc suitable for use in field settings.
The value of compressive force is intended to ...be used as a proxy measure of the mechanical burden of low-back when performing work activities. The compressive force predicted by the module in a particular worker should be compared with the NIOSH limit value of 3,400 N for the assessment of lumbar spine load during manual lifting tasks. Exceeding the limit will be considered as the fulfilment of "hygienic criterion" that should be met to acknowledge low-back disorder as an occupational disease. To develop the computational module we used the ergonomic software TECNOMATIX Classic Jack taking into account the anthropometric parameters of a worker and ergonomic parameters of his/her work activity.
We calculated compressive forces on the L4/L5 disc in about 1,300 simulated combinations of various factors influencing compressive force. Parameters which turned out to be crucial for the compression of L4/L5 disc were included in the computational algorithm.
Our study was primarily aimed at the assessment of lumbar disorders as occupational diseases. Moreover, the study can contribute to the recommendation of preventive measures to decrease health risks in occupations associated with the overload of low-back region. The graphic maps generated by the computational module enable a fast and exact analysis of particular job.
Between 1992 and 2005, 72 cases of occupational hypersensitive pneumonitis were reported to the Czech National Registry of Occupational Diseases. This represented 0.24% of all occupational diseases ...reported in the Czech Republic during that period. The greatest number of cases occurred in 1997 (10 cases), of which men constituted 58.3% (42 cases) and women 41.7% (30 cases). The most prevalent cases were farmer's lung (50 cases), malt worker's lung (7 cases) and chemical worker's lung (6 cases). Agriculture was the most common economic activity (total 48 cases), with cattleman and dairyman (total 26 cases) the most frequent occupations; less common were tractor driver (8 cases) and maltster (7 cases). Typical case reports after different exposures are presented. A peak in frequency was observed in the age groups of 45-49 and 50-54yr (20.8% and 19.4% of cases, respectively) and within the first four years of employment (22.2% of cases). Median age was 48yr and median exposure 12.5yr. Incidence was in the range of 0.00-0.20 per 100,000 workers, which appears rather low. Due to the difficult diagnostics of hypersensitive pneumonitis, the actual number of cases is undoubtedly higher, and this disease is probably under-reported.
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