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1.
Phys Rev E ; 103(6-1): 063212, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-34271636

RESUMO

Microparticle suspensions in a polarity-switched discharge plasma of the Plasmakristall-4 facility on board the International Space Station exhibit string-like order. As pointed out in [Phys. Rev. Research 2, 033314 (2020)2643-156410.1103/PhysRevResearch.2.033314], the string-order is subject to evolution on the timescale of minutes at constant gas pressure and constant parameters of polarity switching. We perform a detailed analysis of this evolution using the pair correlations and length spectrum of the string-like clusters (SLCs). Average exponential decay rate of the SLC length spectrum is used as a measure of string order. The analysis shows that the improvement of the string-like order is accompanied by the decrease of the thickness of the microparticle suspension, microparticle number density, and total amount of microparticles in the field of view. This suggests that the observed long-term evolution of the string-like order is caused by the redistribution of the microparticles, which significantly modifies the plasma conditions.

2.
Phys Rev E ; 97(4-1): 043203, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29758751

RESUMO

Three-dimensional plasma crystals are often described as Yukawa systems for which a phase transition between the crystal structures fcc and bcc has been predicted. However, experimental investigations of this transition are missing. We use a fast scanning video camera to record the crystallization process of 70 000 microparticles and investigate the existence of the fcc-bcc phase transition at neutral gas pressures of 30, 40, and 50 Pa. To analyze the crystal, robust phase diagrams with the help of a machine learning algorithm are calculated. This work shows that the phase transition can be investigated experimentally and makes a comparison with numerical results of Yukawa systems. The phase transition is analyzed in dependence on the screening parameter and structural order. We suggest that the transition is an effect of gravitational compression of the plasma crystal. Experimental investigations of the fcc-bcc phase transition will provide an opportunity to estimate the coupling strength Γ by comparison with numerical results of Yukawa systems.

3.
Opt Lett ; 36(18): 3699-701, 2011 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-21931437

RESUMO

A simple method of characterization of suspensions of spherical nanoparticles with monotonically variable size is proposed. It allows for the in situ measurement of the particle size as well as spectral dependence of their refractive indices. The method requires three optical channels: one for the illumination of a suspension by white light and two for the measurements of the spectra of scattered light. Parameters of the particles are determined by fitting the measured temporal spectral surfaces by the calculated Mie scattering functions. The method is applied to the particles being grown in a low-pressure reactive plasma of a discharge in an acetylene-argon mixture.

4.
J Environ Sci Health B ; 45(8): 783-9, 2010 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-20954045

RESUMO

In the present study, a new sensitive and simple kinetic-spectrophotometric method for the determination of the insecticide diflubenzuron [1-(4-chlorophenyl)-3-(2,6-diflubenzoil)urea] is proposed. The method is based on the inhibited effect of diflubenzuron on the oxidation of sulphanilic acid (SA) by hydrogen peroxide in phosphate buffer in presence Cu(II) ion. Diflubenzuron was determined with linear calibration graph in the interval from 0.31 to 3.1 µg mL⁻¹ and from 3.1 to 31.0 µg mL⁻¹. The optimized conditions yielded a theoretical detection limit of 0.18 µg mL⁻¹ corresponding to 0.036 mg kg(-1)mushroom sample based on the 3S(b) criterion. The RSD is 5.03-1.83 % and 2.81-0.71 % for the concentration interval of diflubenzuron 0.31-3.1 µg mL⁻¹ and 3.1-31.0 µg mL⁻¹, respectively. The reaction was followed spectrophotometrically at 370 nm. The kinetic parameters of the reaction are reported, and the rate equations are suggested. The developed procedure was successfully applied to the rapid determination of diflubenzuron in spiked mushroom samples of different mushroom species. The HPLC method was used like a comparative method to verify results.


Assuntos
Agaricales/química , Cromatografia Líquida de Alta Pressão/métodos , Diflubenzuron/química , Inseticidas/química , Espectrofotometria/métodos , Agaricales/efeitos dos fármacos , Contaminação de Alimentos/análise , Cinética
5.
Phys Rev Lett ; 101(23): 235001, 2008 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-19113560

RESUMO

Steady-state clouds of microparticles were observed, levitating in a low-frequency glow discharge generated in an elongated vertical glass tube. A heated ring was attached to the tube wall outside, so that the particles, exhibiting a global convective motion, were confined vertically in the region above the location of the heater. It is shown that the particle vortices were induced by the convection of neutral gas, and the mechanism responsible for the gas convection was the thermal creep along the inhomogeneously heated tube walls. The phenomenon of thermal creep, which commonly occurs in rarefied gases under the presence of thermal gradients, should generally play a substantial role in experiments with complex plasmas.

6.
Phys Rev Lett ; 101(12): 125002, 2008 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-18851380

RESUMO

We report on the first three-dimensional (3D) complex plasma structure analysis for an experiment that was performed in an elongated discharge tube in the absence of striations. The low frequency discharge was established with 1 kHz alternating dc current through a cylindrical glass tube filled with neon at 30 Pa. The injected particle cloud consisted of monodisperse microparticles. A scanning laser sheet and a camera were used to determine the particle position in 3D. The observed cylindrical-shaped particle cloud showed an ordered structure with a distinct outer particle shell. The observations are in agreement with performed molecular dynamics simulations.

8.
Clin Otolaryngol ; 32(4): 261-7, 2007 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-17651267

RESUMO

OBJECTIVES: To compare postoperative recovery in children between 4 and 12 years undergoing tonsillectomy, using either coblation tonsillectomy or dissection tonsillectomy with bipolar diathermy haemostasis. DESIGN: A prospective, single blind, randomised controlled trial. SETTING: ENT clinic, University Teaching Hospital. PARTICIPANTS: Forty paediatric patients, aged between 4 and 12 years and between 16 and 60 kg in weight with standard indication for tonsillectomy. METHODS: Patients were randomly allocated to either coblation tonsillectomy or dissection tonsillectomy groups. Patients, parents, and nurses were blinded for operation method. Parents were asked to fill out a postoperative diary from 1 to 10 days. MAIN OUTCOME MEASURES: Primary outcomes were scored for postoperative pain, nutrition, activity, and use of analgetics for each of the 10 postoperative days. Secondary outcomes were estimated from the nurses' postoperative data and 10-day follow-up statistics regarding crossing of the two-score limit. RESULTS: The groups were statistically comparable by age, weight and operation type. There was no significant difference in operation time in two groups. Intra-operative bleeding was significantly less in the coblation group. Statistically significant differences between dissection tonsillectomy and coblation tonsillectomy were found in the day when a score of two of five was passed in pain scores (9.6 versus 6.2), nutrition scores (8.9 versus 6.6), activity score (8.4 versus 6.6) and medicine intake (9.4 versus 6.4), We found parallelism, between regression lines, that indicates better postoperative life quality for the coblation tonsillectomy group and approximately 2 days' shorter recovery time. CONCLUSION: In our pilot study, patients undergoing coblation tonsillectomy reported less pain, quicker return to normal diet, quicker return to normal activity, and less use of analgetics over a 10-day period than patients undergoing dissection tonsillectomy. Our results indicate that the recovery period for coblation tonsillectomy was approximately 2 days shorter and demonstrated less morbidity.


Assuntos
Diatermia/métodos , Hemostasia Cirúrgica/métodos , Tonsilectomia/métodos , Analgésicos/administração & dosagem , Distribuição de Qui-Quadrado , Criança , Feminino , Humanos , Masculino , Estado Nutricional , Medição da Dor , Projetos Piloto , Complicações Pós-Operatórias , Estudos Prospectivos , Análise de Regressão , Estatísticas não Paramétricas , Resultado do Tratamento
9.
Adv Gerontol ; 20(4): 75-8, 2007.
Artigo em Inglês | MEDLINE | ID: mdl-18383715

RESUMO

The prevalence of colorectal cancer (CRC) increases significantly with age, with 40% of patients in Europe being older than 74 years of age at the time of initial diagnosis. The individualized management of the older-aged patient with cancer is based on the answers to the following questions: 1) will the patient die of cancer or with cancer; 2) will the patient suffer cancer-related morbidity; and 3) is the patient able to handle the toxicity of treatment? More than chronological age, the following parameters are important when elderly patients are to be treated with antineoplastic agents: general condition, liver function, kidney function and bone marrow status. Frail elderly with malignant disease should not be treated with cytostatic therapy. In the case of fit elderly, the standard chemotherapy (i.e. FOLFOX) regimen could be administered. In elderly ineligible for combination chemotherapy, the capecitabine used orally, as a single-agent therapy, is an important therapeutic option for colorectal cancer.


Assuntos
Antineoplásicos , Neoplasias Colorretais/tratamento farmacológico , Idoso , Antineoplásicos/administração & dosagem , Antineoplásicos/efeitos adversos , Antineoplásicos/uso terapêutico , Neoplasias Colorretais/mortalidade , Neoplasias Colorretais/patologia , Intervalo Livre de Doença , Humanos , Estadiamento de Neoplasias
10.
Anal Sci ; 19(6): 913-6, 2003 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-12834234

RESUMO

The kinetic method is based on a catalytic effect on the oxidation of sodium pyrogallol-5-sulfonate by hydrogenperoxide. The reaction is followed spectrophotometrically at 436.8 nm. The kinetic parameters of the reaction are reported and a rate equation is suggested. The calibration graph is linear in the range 10-200 ng cm(-3). The effects of certain foreign ions upon the reaction rate were determined for the assessment of the selectivity of the method. This method has high sensitivity and good selectivity when anions are concerned as well. That is why it can be successfully applied to determination of iodide in real samples (mineral water and soil) directly after the elimination of cations, which interfere. The method was applied to determine iodide in natural waters and soil.

11.
Talanta ; 42(9): 1273-8, 1995 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-18966354

RESUMO

A kinetic method is described for the determination of iron(III) based on its catalytic effect on the oxidation of sodium pyrogallol-5-sulphonate by hydrogen peroxide. The reaction was followed spectrophotometrically by measuring the rate of change in the absorbance of the coloured product at 436.8 nm. Nanogram amounts of iron(III) (2.0-75.0 ng cm(-3)) can be determined with good accuracy and reproducibility. The influence of foreign ions on the results was investigated and the method was found to be adequately selective. It has been applied satisfactorily to the determination of iron(III) in tap water samples. The kinetic parameters of both the catalysed and uncatalysed reactions are reported.

13.
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