369 research outputs found
Влияние различных методов седации у больных с острой тяжелой черепно-мозговой травмой на перекисное окисление липидов
Objective: to study the impact of various sedation methods on lipid peroxidation in patients with acute severe brain injury. Subjects and methods. For this, 44 victims with this condition were examined. According the option of posttraumatic sedation therapy, the victims were divided into 3 groups: 1) 12 patients in whom sodium oxybutyrate was used for sedation; 2) 12 received thiopental sodium; 3) 20 patients were given propofol. The lipid peroxidation and antioxidant system were judged from the serum levels of fatty acid hydroperoxides and secondary lipid peroxidation products (malonic dialdehyde) and from the content of the endogenous antioxidant a-tocopherol. Results. The study performed indicated that the highest concentrations of fatty acid hydroperoxides were observed in Groups 1 and 2 within the first 24 posttraumatic hours. In Group 3 where propofol was used for sedation, the concentration of the hydroperoxides remained in the normal range although there was a tendency for their rise. Conclusion. Thus, propofol is the agent of choice for sedation that prevents the activation of lipid peroxidation and stabilizes some indices of the antioxidant system in patients with acute severe brain injury. Key words: brain injury, lipid peroxidation, sedation, sodium oxybutyrate, thiopental sodium, propofol.Цель исследования — изучить влияние различных методов седации у больных с острой тяжелой черепно-мозговой травмой на перекисное окисление липидов. Материал и методы. Для достижения указанной цели обследованы 44 пострадавших с острой тяжелой черепно-мозговой травмой. В зависимости от вида седационной терапии, проводившейся в посттравматическом периоде, больные были разделены на 3 группы. В I группу (12 чел.) вошли больные, которым с целью седации использовался оксибутират натрия, во II группе (12 чел.) больных применялся тиопентал натрия, и в III группе больных (20 чел.) вводился пропофол. О состоянии перекисного окисления липидов и антиоксидантной системы судили по уровню в сыворотке крови гидроперекисей жирных кислот и вторичных продуктов перекисного окисления липидов — малонового диальдегида, содержанию эндогенного антиоксиданта альфа-токоферола. Результаты. Проведенное исследование показало, что в 1-е сутки посттравматического периода наиболее высокие концентрации гидроперекисей жирных кислот отмечались в I и II группах больных. В III же группе больных, где для седации использовался пропофол, концентрация гидроперекисей оставались в пределах нормальных значений, хотя также оставалась тенденция к их росту. Заключение. Таким образом, наиболее благоприятным вариантом седации, предупреждающей активацию перекисного окисления липидов и стабилизирующей некоторые показатели антиоксидантной системы у больных с острой тяжелой черепно-мозговой травмой является пропофол. Ключевые слова: черепно-мозговая травма, перекисное окисление липидов, седация, оксибутират натрия, тиопентал натрия, пропофол
Initial Results from the CHOOZ Long Baseline Reactor Neutrino Oscillation Experiment
Initial results are presented from CHOOZ, a long-baseline reactor-neutrino
vacuum-oscillation experiment. Electron antineutrinos were detected by a liquid
scintillation calorimeter located at a distance of about 1 km. The detector was
constructed in a tunnel protected from cosmic rays by a 300 MWE rock
overburden. This massive shielding strongly reduced potentially troublesome
backgrounds due to cosmic-ray muons, leading to a background rate of about one
event per day, more than an order of magnitude smaller than the observed
neutrino signal. From the statistical agreement between detected and expected
neutrino event rates, we find (at 90% confidence level) no evidence for
neutrino oscillations in the electron antineutrino disappearance mode for the
parameter region given approximately by deltam**2 > 0.9 10**(-3) eV**2 for
maximum mixing and (sin(2 theta)**2) > 0.18 for large deltam**2.Comment: 13 pages, Latex, submitted to Physics Letters
Limits on Neutrino Oscillations from the CHOOZ Experiment
We present new results based on the entire CHOOZ data sample. We find (at 90%
confidence level) no evidence for neutrino oscillations in the anti_nue
disappearance mode, for the parameter region given by approximately Delta m**2
> 7 x 10**-4 eV^2 for maximum mixing, and sin**2(2 theta) = 0.10 for large
Delta m**2. Lower sensitivity results, based only on the comparison of the
positron spectra from the two different-distance nuclear reactors, are also
presented; these are independent of the absolute normalization of the anti_nue
flux, the cross section, the number of target protons and the detector
efficiencies.Comment: 19 pages, 11 figures, Latex fil
Search for neutrino oscillations on a long base-line at the CHOOZ nuclear power station
This final article about the CHOOZ experiment presents a complete description
of the electron antineutrino source and detector, the calibration methods and
stability checks, the event reconstruction procedures and the Monte Carlo
simulation. The data analysis, systematic effects and the methods used to reach
our conclusions are fully discussed. Some new remarks are presented on the
deduction of the confidence limits and on the correct treatment of systematic
errors.Comment: 41 pages, 59 figures, Latex file, accepted for publication by
Eur.Phys.J.
Antineutrino-Deuteron Experiment at Krasnoyrsk
This report is represented the results of some experiments, which carried out
at the neutrino underground laboratory of Kranoyarsk nuclear plant.Comment: 8 pages, 3 figure
Impact of ocean acidification on thermal tolerance and acid–base regulation of Mytilus edulis from the White Sea
Ocean warming and acidification are two important environmental drivers affecting marine organisms. Organisms living at high latitudes might be especially threatened in near future, as current environmental changes are larger and occur faster. Therefore, we investigated the effect of hypercapnia on thermal tolerance and physiological performance of sub-Arctic Mytilus edulis from the White Sea. Mussels were exposed (2 weeks) to 390 µatm (control) and 1,120 µatm CO2 (year 2100) before respiration rate (MO2), anaerobic metabolite (succinate) level, haemolymph acid-base status, and intracellular pH (pHi) were determined during acute warming (10-28°C, 3°C over night).
In normocapnic mussels, warming induced MO2 to rise exponentially until it levelled off beyond a breakpoint temperature of 20.5°C. Concurrently, haemolymph PCO2 rose significantly >19°C followed by a decrease in PO2 indicating the pejus temperature (TP, onset of thermal limitation). Succinate started to accumulate at 28°C under normocapnia defining the critical temperature (TC). pHi was maintained during warming until it dropped at 28°C, in line with the concomitant transition to anaerobiosis. At acclimation temperature, CO2 had only a minor impact. During warming, MO2 was stimulated by CO2 resulting in an elevated breakpoint of 25.8°C. Nevertheless, alterations in haemolymph gases (>16°C) and the concomitant changes of pHi and succinate level (25°C) occurred at lower temperature under hypercapnia versus normocapnia indicating a downward shift of both thermal limits TP and TC by CO2.
Compared to temperate conspecifics, sub-Arctic mussels showed an enhanced thermal sensitivity, exacerbated further by hypercapnia, indicating their potential vulnerability to environmental changes projected for 2100
Measurement of the solar 8B neutrino rate with a liquid scintillator target and 3 MeV energy threshold in the Borexino detector
We report the measurement of electron neutrino elastic scattering from 8B
solar neutrinos with 3 MeV energy threshold by the Borexino detector in Gran
Sasso (Italy). The rate of solar neutrino-induced electron scattering events
above this energy in Borexino is 0.217 +- 0.038 (stat) +- 0.008 (syst) cpd/100
t, which corresponds to the equivalent unoscillated flux of (2.4 +- 0.4 (stat)
+- 0.1 (syst))x10^6 cm^-2 s^-1, in good agreement with measurements from SNO
and SuperKamiokaNDE. Assuming the 8B neutrino flux predicted by the high
metallicity Standard Solar Model, the average 8B neutrino survival probability
above 3 MeV is measured to be 0.29+-0.10. The survival probabilities for 7Be
and 8B neutrinos as measured by Borexino differ by 1.9 sigma. These results are
consistent with the prediction of the MSW-LMA solution of a transition in the
solar electron neutrino survival probability between the low energy
vacuum-driven and the high-energy matter-enhanced solar neutrino oscillation
regimes.Comment: 10 pages, 8 figures, 6 table
Muon and Cosmogenic Neutron Detection in Borexino
Borexino, a liquid scintillator detector at LNGS, is designed for the
detection of neutrinos and antineutrinos from the Sun, supernovae, nuclear
reactors, and the Earth. The feeble nature of these signals requires a strong
suppression of backgrounds below a few MeV. Very low intrinsic radiogenic
contamination of all detector components needs to be accompanied by the
efficient identification of muons and of muon-induced backgrounds. Muons
produce unstable nuclei by spallation processes along their trajectory through
the detector whose decays can mimic the expected signals; for isotopes with
half-lives longer than a few seconds, the dead time induced by a muon-related
veto becomes unacceptably long, unless its application can be restricted to a
sub-volume along the muon track. Consequently, not only the identification of
muons with very high efficiency but also a precise reconstruction of their
tracks is of primary importance for the physics program of the experiment. The
Borexino inner detector is surrounded by an outer water-Cherenkov detector that
plays a fundamental role in accomplishing this task. The detector design
principles and their implementation are described. The strategies adopted to
identify muons are reviewed and their efficiency is evaluated. The overall muon
veto efficiency is found to be 99.992% or better. Ad-hoc track reconstruction
algorithms developed are presented. Their performance is tested against muon
events of known direction such as those from the CNGS neutrino beam, test
tracks available from a dedicated External Muon Tracker and cosmic muons whose
angular distribution reflects the local overburden profile. The achieved
angular resolution is 3-5 deg and the lateral resolution is 35-50 cm, depending
on the impact parameter of the crossing muon. The methods implemented to
efficiently tag cosmogenic neutrons are also presented.Comment: 42 pages. 32 figures on 37 files. Uses JINST.cls. 1 auxiliary file
(defines.tex) with TEX macros. submitted to Journal of Instrumentatio
- …