Electroviscous forces on a charged particle suspended in a flowing liquid

1997 ◽  
Vol 338 ◽  
pp. 1-34 ◽  
Author(s):  
R. G. COX

The force on a charged solid particle (of general shape) suspended in a flowing polar fluid (e.g. an aqueous electrolyte solution) in the presence of a solid bounding wall (of general shape) is obtained for the situation in which the electrical double-layer thickness is very much smaller than the particle size (and the distance between particle and wall). The very general results so obtained are applied to the sedimentation of a charged spherical particle in an unbounded polar fluid (with no walls present) for which the drag force is found to be in complete agreement with Ohshima et al. (1984). However, there is disagreement between the present results and those obtained in a number of published papers owing to incorrect assumptions being made in the latter as to what physical mechanism gives rise to the dominant contribution to the electroviscous force on the particle.

2001 ◽  
Vol 7 (5) ◽  
pp. 257-265 ◽  
Author(s):  
E J Nordal ◽  
D Moseng ◽  
B Kvammen ◽  
M-L Løchen

We compared the diagnoses made by one dermatologist via telemedicine with those of another dermatologist made in a face-to-face consultation. The patients first underwent a teledermatology consultation and then a face-to-face consultation. A general practitioner was present with the patient in the videoconference studio. Videoconferencing equipment connected at 384 kbit/s was used. The doctor-patient relationship and the satisfaction of the patients and dermatologists in the two settings were assessed, as well as technical conditions during the videoconferences. There were 121 patients, with a mean age of 40 years (range 17-82 years). There was a high degree of concordance between the two sets of diagnoses, with 72% complete agreement and 14% partial agreement between the two dermatologists. A total of 116 patients (96% of those included) completed a questionnaire. Both the patients and the dermatologists were in general satisfied with the videoconferences. Videoconferencing with a participating general practitioner may be useful in dermatology, but the technique should be used only for selected patients.


2020 ◽  
Vol 26 (1) ◽  
pp. 82-93
Author(s):  
Reihaneh Radmanesh ◽  
◽  
Mohsen Nabi Meybodi ◽  
Vahid Ramezani ◽  
Maryam Akrami ◽  
...  

Aims: Any pharmaceutical product made in pharmacy, hospital or factory may be contaminated with microbes. This contamination can originate from raw materials or during production. Hence, it is important to study the physical and chemical properties and stability of compounded drugs. Methods & Materials: In this study, first a specific sample of prescribed medication was ordered from 63 pharmacies in Yazd, Iran. After collecting the samples, the amount of microbial contamination, viscosity and particle size distribution and their stability were investigated and their results were compared to the standard levels. Findings: Based on the results, 31.7% of the samples had discoloration and 23.8% showed creaming phenomenon. In terms of particle size distribution, 57.1% of the samples had a 20-40 μm particle size and 49.2% had a viscosity equal to 2500-3000 centipoise. Regarding stability, 12.6% of the samples underwnet phase change at 30-40°C. About of the amount of hydroquinone in samples, 35% had acceptable amount. In 23.8% of the samples, fungal infection was observed. Conclusion: Contrary to a popular belief that the compounded medicines produced in pharmacies have microbial contamination, the results of this study showed that the microbial contamination of these compounded medications is low.


2006 ◽  
Vol 52 (9) ◽  
pp. 1722-1727 ◽  
Author(s):  
Wayne Ensign ◽  
Nicole Hill ◽  
Christopher B Heward

Abstract Background: Our study seeks to clarify the extent of differences in analytical results, from a clinical perspective, among 4 leading technologies currently used in clinical reference laboratories for the analysis of LDL subfractions: gradient gel electrophoresis (GGE), ultracentrifugation–vertical auto profile (VAP), nuclear magnetic resonance (NMR), and tube gel electrophoresis (TGE). Methods: We collected 4 simultaneous blood samples from 40 persons (30 males and 10 females) to determine LDL subclasses in 4 different clinical reference laboratories using different methods for analysis. LDL subfractions were assessed according to LDL particle size and the results categorized according to LDL phenotype. We compared results obtained from the different technologies. Results: We observed substantial heterogeneity of results and interpretations among the 4 methods. Complete agreement among methods with respect to LDL subclass phenotyping occurred in only 8% (n = 3) of the persons studied. NMR and GGE agreed most frequently at 70% (n = 28), whereas VAP matched least often. Conclusions: As measurement of LDL subclasses becomes increasingly important, standardization of methods is needed. Variation among currently available methods renders them unreliable and limits their clinical usefulness.


1954 ◽  
Vol 27 (4) ◽  
pp. 1051-1060 ◽  
Author(s):  
Alfred Nisonoff ◽  
W. E. Messer ◽  
L. H. Howland

Abstract A method based on Stokes' law, involving the use of an ordinary laboratory centrifuge, is described for the determination of particle size distribution in GR-S latexes. It is shown to be valid by tests for reproducibility and by comparison with the results of light and electron microscopy. In applying the method, several unusually fluid high-solids latexes made in the pilot plant were found to be characterized by a wide distribution of particle sizes. Data on various latexes in plant production are reported.


1991 ◽  
Vol 35 (A) ◽  
pp. 57-62 ◽  
Author(s):  
C. J. Sparks ◽  
R. Kumar ◽  
E. D. Specht ◽  
P. Zschack ◽  
G. E. Ice ◽  
...  

AbstractThe effect of sample granularity on diffracted x-ray intensity was evaluated by measuring the 2θ dependence of x-ray fluorescence from various samples. Measurements were made in the symmetric geometry on samples ranging from single crystals to highly absorbing coarse powders. A characteristic shape for the absorption correction was observed. A demonstration of the sensitivity of Rietveld refined site occupation parameters is made on CuAu and Cu50Au44Ni6 alloys refined with and without granularity corrections. These alloys provide a good example of the effect of granularity due to their large linear x-ray absorption coefficients. Sample granularity and refined thermal parameters obtained from the Rietveld analysis were found to be correlated. Without a granularity correction, the refined thermal parameters are too low and can actually become negative in an attempt to compensate for granularity, A general shape for granularity correction can be included in refinement procedures. If no granularity correction is included, data should be restricted to above 30° 2θ, and thermal parameters should be ignored unless extreme precautions are taken to produce <5 (μm particles and high packing densities.


Author(s):  
Л.И. Морозова ◽  
А.В. Николаев ◽  
С.А. Пулинец

В работе делается попытка обобщить результаты наблюдений еще до конца не понятого явления, обычно называемого «линейные облачные аномалии» (ЛОА), наблюдае- мого над областями подготовки сильных землетрясений или интенсификации тектонической активности. В англоязычной литературе можно найти более лаконичное называние «earthquakeclouds». Несмотря на достаточно богатую литературу по этому вопросу, до сих пор остается не выясненной физическая при- рода ЛОА. Цель работы. Именно выяснения физического механизма формирования ЛОА перед землетря- сениями приставляет собой наиболее актуальную задачу. В данной работе мы делаем шаг впередв данном направлении, потому что основной целью нашего исследования является поиск источников формирова- ния ЛОА. Методы исследования. Нами получены экспериментальные доказательства, что ЛОА всех типов имеют зародышевые структуры в нижней атмосфере на уровне порядка 100 м от поверхности Земли, что доказывает связь генезиса ЛОА с процессами, инициируемыми в земной коре. Источником информации, используемой для проверки процессов формирования ЛОА, являются метеорологические данные, полу- чаемые из ассимилятивной модели GEOSFP, получаемые вблизи поверхности земли. Результаты работы. Сделана попытка проследить генезис ЛОА от поверхности земли до уровня сформировавшейся облач- ной структуры, и предложен физический механизм генерации ЛОА, в том числе поддержания их геоме- трической линейности в условиях турбулентной атмосферы. Данная работа была задумана совместно с ушедшим от нас А. В. Николаевым, мы постараемся включить в работу всё, что обсуждалось с ним при её подготовке, в том числе с учетом его принципиального мнения, что «неясность физических принципов не может быть причиной недоверия к экспериментальным результатам». Ключевые слова: линейные облачные аномалии, землетрясение, облачная гряда, прогноз землетря- сений An attempt is made in present paper to generalize the results of observations of the not yet fully understood phenomenon, usually called “linear cloud anomalies” (LCA), observed over the areas of impending strong earthquakes or intensification of tectonic activity. In the English-language literature, you can find a more concise name “earthquake clouds”. Despite the fairly rich literature on this issue, the physical nature of LСA remains unclear. Aim. It is the identificationof the physical mechanism of the formation of LCA before earthquakes that is the most urgent problem. In this work, we take a step forward in this direction, because the main aim of our study is to find the sources for the formation of LCA. Methods. We have obtained experimental evidence that LCA of all types have embryonic structures in the lower atmosphere at a level of about 100 m from the Earth’s surface, which proves the connection between the LCA genesis and the processes initiated in the earth’s crust. The source of information used to verify the formation of LCA is the meteorological data obtained near the earth’s surface from the assimilative model GEOS FP. Results. An attempt is made to trace the genesis of LСA from the earth’s surface to the level of the formed cloud structure, and a physical mechanism for the generation of LСA is proposed, including maintaining their geometric linearity under conditions of a turbulent atmosphere. This work was conceived together with A. V. Nikolaev, we will try to include in the work everything that was discussed with him during its preparation, including his principled opinion that “the lack of clarity of physical principles cannot be the reason for distrust of experimental results


Author(s):  
Oleg V. Grechin ◽  
Pavel R. Smirnov

At the X-ray diffraction analysis of high concentrated aqueous electrolyte solutions with multiply charged cations small angle maxima or pre-peaks are arising on scattering intensity curves (IC) (at about 1 Å). Their existence is connected with structural appearance so called “intermediate-range order”. Previously for explanation of this phenomenon some not completely correct hypotheses were suggested. On the example of raw X-ray diffraction data of some aqueous electrolyte solutions in wide concentration range collected by using MoKα-radiation the dynamic of small angle maxima shape change has been studied. It has been noted that pre-peaks absence on IC of cesium iodide and chloride solutions is not supporting the hypothesis about pure small angle contribution from “heavy” ions [1, 2]. In the case of Al3+, Sc3+, Fe3+ chloride solutions relative similarity of IC shapes has been noted for solutions with similar concentrations. The common tendency of pre-peaks position and intensity change has also been followed up. At the same time at comparing of saturated neodymium and ytterbium chloride and bromide solutions IC unexpectable pre-peaks position relative shift for bromide solutions to the long range distance comparing with chloride solutions has also been noted. These observations do not find complete agreement with hypothesis on realization in the structure mainly inter cationic distances [3, 4] and on existence in solutions “liquid type quasi-close-packing for cations” [5, 6]. On the basis of mainly realistic explanation of the pre-peak appearance reason from [7] the authors of this paper propose their own version. Noted shift of pre-peak position with concentration decreasing has been made in accordance with consideration described earlier for lanthanide solutions [8, 9]. The conclusion about pre-peaks on IC arising nature is conditioned by ordered interionic distribution which depends not only on ionic nature but also on solution concentration. For high concentrated solutions with considerable solvent deficit the quasi-periodic inter complex distribution has been supposed. The composition of structure determined cationic complexes has also been discussed. The diluted aqueous electrolyte solutions structure is determined by simple cationic and anionic complexes equidistant distribution.


1971 ◽  
Vol 15 ◽  
pp. 534-538
Author(s):  
A. L. Allen ◽  
V. C. Rose

The effect of resin particles on copper x-ray fluorescence was studied. For any given resin size the relationship between copper concentration and x-ray intensity was linear. As the particle size decreased, the x-ray intensity increased for any given copper concentration. The general shape of the curves are similar to the ones predicted by Bernstein for a minor constituent in a power sample. This study indicates that the variation in intensity with particle size can be eliminated by using resins with a mean particle diameter of 56 microns or less.


2014 ◽  
Vol 7 (3) ◽  
pp. 1137-1157 ◽  
Author(s):  
J. C. Kaiser ◽  
J. Hendricks ◽  
M. Righi ◽  
N. Riemer ◽  
R. A. Zaveri ◽  
...  

Abstract. We introduce MADE3 (Modal Aerosol Dynamics model for Europe, adapted for global applications, 3rd generation; version: MADE3v2.0b), an aerosol dynamics submodel for application within the MESSy framework (Modular Earth Submodel System). MADE3 builds on the predecessor aerosol submodels MADE and MADE-in. Its main new features are the explicit representation of coarse mode particle interactions both with other particles and with condensable gases, and the inclusion of hydrochloric acid (HCl) / chloride (Cl) partitioning between the gas and condensed phases. The aerosol size distribution is represented in the new submodel as a superposition of nine lognormal modes: one for fully soluble particles, one for insoluble particles, and one for mixed particles in each of three size ranges (Aitken, accumulation, and coarse mode size ranges). In order to assess the performance of MADE3 we compare it to its predecessor MADE and to the much more detailed particle-resolved aerosol model PartMC-MOSAIC in a box model simulation of an idealised marine boundary layer test case. MADE3 and MADE results are very similar, except in the coarse mode, where the aerosol is dominated by sea spray particles. Cl is reduced in MADE3 with respect to MADE due to the HCl / Cl partitioning that leads to Cl removal from the sea spray aerosol in our test case. Additionally, the aerosol nitrate concentration is higher in MADE3 due to the condensation of nitric acid on coarse mode particles. MADE3 and PartMC-MOSAIC show substantial differences in the fine particle size distributions (sizes &amp;lesssim; 2 μm) that could be relevant when simulating climate effects on a global scale. Nevertheless, the agreement between MADE3 and PartMC-MOSAIC is very good when it comes to coarse particle size distributions (sizes &amp;gtrsim; 2 μm), and also in terms of aerosol composition. Considering these results and the well-established ability of MADE in reproducing observed aerosol loadings and composition, MADE3 seems suitable for application within a global model.


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