Aging in velocity autocorrelations in granular gas of viscoelastic particles in two dimensions

We use large-scale molecular dynamics simulations to study aging of the velocity autocorrelation function of a force-free granular gas consisting of viscoelastic particles. We study the velocity autocorrelation function for a simplified model where the coefficient of restitution is constant for all collisions, but depends on current temperature of granular gas, it is called quasi-constant coefficient of restitution ε_eff. From our simulation results, it is observed that A(τ_w, τ) depends independently on both τ and τ_w. Initially, A(τ_w, τ) decays exponentially but later as τ_w increases, A(τ_w, τ) decays slowly due to emergence of correlations in velocity field. The explicit dependence of A(τ_w, τ) on τ_w implies that the system exhibits aging property.     

Solubility of lanthanum in strontium titanate in oxygen-rich atmospheres

Perovskite (ABO₃)-type lanthanum substituted strontium titanate ceramics (lanthanum content x), which had been sintered in pure oxygen at 1400 °C, were investigated from x = 0 up to x = 0.6 by light optical and scanning electron microscopic means in conjunction with X-ray analysis, X-ray diffraction, and pyconometry in order to determine the mechanism being responsible for the compensation of the electronic excess charge resulting from the "donor" lanthanum. A pure strontium vacancy compensation mechanism was observed for lanthanum contents up to x = 0.3. Above x = 0.4 titanium vacancies occur additionally but their concentration remains negligible compared to the predominating strontium vacancies. No indication of a solubility limit of lanthanum at x = 0.4, as stated in former works was observed. At x = 0.5 and 0.6 the lattice structure was found to be slightly distorted, tetragonally and orthorhombically, respectively. The lattice parameter obeys Vegard’s law up to the end member La_2/3□_1/3TiO₃ (□: vacant site). These results were completely confirmed by pycnometry data. This revised version was published online in November 2006 with corrections to the Cover Date.     

Assessment of research fields in Scopus and Web of Science in the view of national research evaluation in Slovenia

Web of Science (wos) and scopus have often been compared with regard to user interface, countries, institutions, author sets, etc., but rarely employing a more systematic assessment of major research fields and national production. The aim of this study was to appraise the differences among major research fields in scopus and wos based on a standardized classification of fields and assessed for the case of an entire country (Slovenia). We analyzed all documents and citations received by authors who were actively engaged in research in Slovenia between 1996 and 2011 (50,000 unique documents by 10,000 researchers). Documents were tracked and linked to scopus and wos using complex algorithms in the Slovenian cobiss bibliographic system and sicris research system where the subject areas or research fields of all documents are harmonized by the Frascati/oecd classification, thus offsetting some major differences between wos and scopus in database-specific subject schemes as well as limitations of deriving data directly from databases. scopus leads over wos in indexed documents as well as citations in all research fields. This is especially evident in social sciences, humanities, and engineering & technology. The least citations per document were received in humanities and most citations in medical and natural sciences, which exhibit similar counts. Engineering & technology reveals only half the citations per document compared to the previous two fields. Agriculture is found in the middle. The established differences between databases and research fields provide the Slovenian research funding agency with additional criteria for a more balanced evaluation of research.     

Assurance of accuracy in determinations of contents of micro components in samples of very pure substances and in environmental specimens

We propose an approach allowing us to use preliminary enrichment (concentration) in accordance with the characteristic features of the method for taking into account the resulting systematic error based on the relationship between the systematic error of the analysis results and the determined content. This allows us to avoid a number of difficulties specific to quantitative determination of very low contents with substantial improvement in the accuracy of the final analysis result.Translated from Izmeritel'naya Tekhnika, No. 2, pp. 58–60, February, 1995.     

Preliminary evaluation of the in vitro release and in vivo absorption in rabbits of the modified-release dosage forms

Objective: The suitability of the rabbit as an animal model for the primary screening and selection of the pilot scale batches during the early stages of the formulation development was studied.

Materials and methods: Three modified-release formulations of aminophylline consisted of Carbopol® 971P/HPMC K4M (F-I), and HPMC K100M (F-II) or HPMC K4M (F-III) were used. Commercial products were Aminofilin retard 350?mg tablets, Srbolek, Serbia (R-I) and Phyllocontin^® 350, tablets Purdue Frederic, Canada (R-II).

Results: Calculated release rate constants and the ?2 values between R-I/F-I (84.1) and R-II/F-III (83.4) indicated similar in vitro release while the coefficient n showed presence of different mechanisms of release from Anomalous transport, Fickian diffusion to Case-II transport. Higher T_max, was found in the rabbits, dosed with F-II (12.00?h), F-III (10.50?h), and R-II (15.00?h) formulation. The highest C_max (9.22?mg/L) was obtained with F-II, similar lower values was seen for F-I and F-III, while commercial products showed the lowest values R-I (5.58?mg/L) and R-II (4.18?mg/L). Higher AUC values were detected for all three formulations (from 115.90 to 204.06 mgh/L) in relation to commercial products (105.33 and 113.25 mgh/L).

Discussion and conclusion: The results demonstrated a good correlation of Level A (r² = 0.97) for the two formulations (F-I, F-III) and commercial product (R-I) indicates that there is a reasonable assumption that the rabbit might be use as a model for the preliminary comparison of scale up formulations in the early stages of the product development.     

Influence of the Initiation Length in Predictions of Life in Fretting Fatigue

Abstract: Two different phases are usually distinguished in the crack growth process: initiation and propagation. Within the models used in determining fatigue life, there are many that combine both phases, determining total life as the sum of the number of cycles spent in initiation, N_i, and propagation, N_p. In order to apply these models, it is necessary to define the crack length at which it is considered that initiation finishes and propagation begins: initiation length, a_i. This length is usually defined a priori based on the size of the smallest detectable crack, on the definition of failure in the S‐N curve, or by choosing the value that better fits the experimental results. The object of this paper is to analyse the influence of this initiation length over the estimated fatigue life in fretting fatigue. The model used calculates the initiation phase from an S‐N curve where the propagation cycles from the defined initiation length have been subtracted. This model is applied to a group of fretting fatigue tests with spherical contact.     

Role of peroxynitrite in oxidation of f-element ions in HNO3 solutions

Published data on the kinetics of Ce(III) oxidation with ozone in HNO₃ solutions are analyzed. The formation of peroxynitrite in the course of ozonation of nitric acid solutions, hypothesized previously in the literature, is confirmed. Peroxynitrite is capable to oxidize Ce(III), but with time it decomposes to HNO₂ and H₂O₂, which reduce Ce(IV). Similar phenomenon is observed in ozonation of nitric acid solutions of berkelium.     

Naturalistic study of rider's behaviour in initial training in France: Evidence of limitations in the educational content

This paper analyses motorcycle educational content in a number of French motorcycle schools on the basis of a naturalistic study of riders’ and trainers’ behaviour. The aim is to specify the situations delivered in motorcycle schools and to study the rider's activity in these situations. The methodology includes ethnographic observation within the motorcycle schools and the longitudinal monitoring of 14 trainee motorcyclists during their initial training. The training situations were described by the combination of audio–visual recordings and interviews data (i.e. concomitant or interruptive verbalization, and self-confrontation data). The results permit to (1) compare the “real” and “official” durations of track and on-road training, (2) characterize the real training situations, (3) describe the preferred forms of instruction, and (4) conduct an in-depth analysis of the situations used during training in traffic. The discussion show, in first, the poverty of the training situations which are based on the repetition of the exercises in the test, and, in second, disparities between the riding situations encountered during training and the demands made by riding in natural traffic. The usefulness and the applications of this type of approach – based on the integration of the rider's point of view notably by self-confrontation interview – for understanding real riding behaviours and how such approaches could supplement vehicle-based data are discussed in a large conclusion.     

Surface Cracking of Steels in the Process of Cyclic Deformation in Aqueous Media

We study the conditions of surface cracking of steels for pipelines of power-generating equipment subjected to cyclic deformation in aqueous media. A new parameter is proposed for the evaluation of the corrosion fatigue of materials, namely, a certain characteristic level of stresses within the limits of the loading cycle ( = _s ) above which the deformed surface undergoes noticeable electrochemical activation. A model scheme of the surface corrosion-fatigue cracking regarded as a result of the synergetic action of cyclic stresses and electrochemical processes is proposed. A criterion of initiation of a surface crack of length a relating the characteristic stress _s to the maximum stress in a cycle _max, the strength of corrosion current I _cor, and the constants of electrochemical dissolution of the metal on the deformed surface is established. On this basis, we propose an engineering estimate for the period of initiation of surface corrosion-fatigue cracks.     

The role of parents and non-parents in the supervision of learner drivers in Australia

The purpose of this study was to contrast the role of parental and non-parental (sibling, other family and non-family) supervisors in the supervision of learner drivers in graduated driver licensing systems. The sample consisted of 522 supervisors from the Australian states of Queensland (n = 204, 39%) and New South Wales (n = 318, 61%). The learner licence requirements in these two states are similar, although learners in Queensland are required to accrue 100 h of supervision in a log book while those in New South Wales are required to accrue 120 h. Approximately 50 per cent of the sample (n = 255) were parents of the learner driver while the remainder of the sample were either siblings (n = 72, 13.8%), other family members (n = 153, 29.3%) or non-family (n = 114, 21.8%). Parents were more likely than siblings, other family or non-family members to be the primary supervisor of the learner driver. Siblings provided fewer hours of practice when compared with other supervisor types while the median and mode suggest that parents provided the most hours of practice to learner drivers. This study demonstrates that non-parental supervisors, such as siblings, other family members and non-family, at least in jurisdictions that require 100 or 120 h of practice, are important in facilitating learner drivers to accumulate sufficient supervised driving practice.     

Addition effects of aluminum and in situ formation of alumina in MoSi2

Phase composition change and mechanical properties at room temperature of MoSi₂ materials with the addition of aluminum were investigated. An explanation was given to the appearance of Mo₅Si₃ when hot pressing MoSi₂ raw powder containing oxygen. The mechanical properties including Vickers hardness, bending strength and fracture toughness were improved with the addition of aluminum up to the limit content needed for absorbing the oxygen in MoSi₂ raw powder. More aluminum addition than the limit content (in this study it is 5 wt %) will result in the formation of Mo(Si ,Al)₂ and Si. The in situ formed Al₂O₃ could act as a crack pinning element. However, because the thermal expansion coefficients of Al₂O₃ and MoSi₂ are near and there is a strong bonding between them, the toughening effect by such in situ formed small Al₂O₃ particles (less than 2 m) is limited.     

Fracture of concrete in compression

The paper presents the results of notched mortar and concrete prisms tested in compression. Crack patterns, compressive strain variation, variation of tensile strain at the tip of notch, ultimate strength and critical strain energy release rate of the specimens are given and discussed.

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Résumé Des essais de compression ont été effectués sur des prismes entaillés afin d'étudier la rupture en compression du mortier de ciment et du béton. On a pris ici en compte comme paramètre 4 valeurs différentes de la longueur et 3 angles d'inclinaison différents de l'entaille. Les effets de l'entaille ont été étudiés d'après la fissuration, la relation déformation/contrainte de compression, les déformations de traction à la pointe de l'entaille et la résistance maximale des éprouvettes essayées. On a aussi déterminé et noté les valeurs de vitesse de libération de l'énergie de déformation critique. On estime que de nouvelles études sont nécessaires pour aboutir à des méthodes pertinentes de détermination de la résilience du béton en compression.

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The parameters of nonequilibrium microwave discharge in nitrogen in a tube in a rectangular waveguide

Computer codes are developed for the processing of emission spectra of nonequilibrium plasma in nitrogen for the purpose of obtaining information about the translational T _g and rotational T _rot temperatures, the populations of vibrational levels in the ground electron and electron-excited states, the electron energy distribution function, the electron concentration N _e , and the electric field intensity E. The computer codes are used to determine the parameters of microwave-discharge plasma in nitrogen in discharge systems of two types, namely, in a discharge tube (with a radius of 1 cm), which crosses a rectangular waveguide (plasmatron on the H ₁₀ wavelength, at a pressure of 1.7 torr and absorbed power density of 1.5 W/cm³), and in a discharge section of similar structure on the basis of prismatic resonator (at a pressure of 1.0 torr and absorbed power density of 0.4 W/cm³). The mechanisms of population of the N₂(C ³Π_u) state are treated.     

Behavior of Trace Amounts of Cd and Zn in Sorption and Coprecipitation in Tetrahydrofuran Solutions

Sorption of trace amounts of ¹⁰⁹Cd and ⁶⁵Zn on zeolites NaX and NaA in the presence of divalent lanthanides Ln²⁺ (Ln = Tm, Dy, Nd) from tetrahydrofuran (THF) solutions is studied. In contrast to ¹³⁷Cs⁺ and similar to ⁸⁵Sr²⁺, trace amounts of ¹⁰⁹Cd and ⁶⁵Zn are not practically sorbed on zeolites (about 99% of these radionuclides remains in the solution). The distribution coefficients K _d of ¹⁰⁹Cd and ⁶⁵Zn are ∼0.3 and ∼0.4 ml g⁻¹, respectively. In THF solutions, Tm²⁺ is oxidized to Tm³⁺, and TmI₃ ⋅ 3THF is precipitated. Study of cocrystallization of trace amounts of ¹⁰⁹Cd and ⁶⁵Zn and also of ⁸⁵Sr with this precipitate from THF solutions containing Tm²⁺ revealed that, in contrast to ⁸⁵Sr²⁺, ¹⁰⁹Cd and ⁶⁵Zn traces cocrystallize with the solid solvate phase. The cocrystallization coefficients D of ¹⁰⁹Cd and ⁶⁵Zn increase with increasing Tm³⁺/Tm²⁺ ratio in the solution. The mechanism suggested is that, in the presence of Tm²⁺, ¹⁰⁹Cd²⁺ and ⁶⁵Zn²⁺ are reduced to single-charged cations M⁺, which then rapidly react with the double-charged cations M²⁺ with the formation of dimers M ₂ ³⁺ (M = Cd, Zn).__________Translated from Radiokhimiya, Vol. 47, No. 3, 2005, pp. 261–264.Original Russian Text Copyright © 2005 by Veleshko, Kulyukhin.     

Stability of cracks in elastic and in elastic plastic materials

The theory of the stability of cracks in an elastic material is summarized. The theory is extended to the case of a non-work-hardening elastic plastic material and is applied to a number of crack geometries and loadings.

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Zusammenfassung Die Theorie der Risstabilitat irn elastischen Material wird zusammengefasst. Anschliessend wird these Theorie ausgedehnt auf durch Behandlung nicht härtbare elastisch-plastische Materialien Bowie auf verschiedenartige Rissformen and Belastungen angewandt.

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Résumé On a resumé la théorie de la stabilité des fissures dans un material elastíque. Cette théorie est étendue au cas de materiaux elasto-plastique non sujets au durcissement par écrouissage, est appliquée a plusieurs types de géometries de fissures et de conditions de sollicitations.

     

Change in the nature of hydrodynamic cavitation in nonuniform magnetic fields

It is known that in nonuniform magnetic fields the precavitation properties of aqueous media change, leading to an increase in the irreversible physicochemical changes.Notation l length of zone II - D and d diameters of tubes I, III, and II - p_I, p_II, p_III pressures in regions I, II, and III - p_cr critical pressure at which cavitation occurs - p_cr and p _cr ⁰ critical pressures in the magnetic field and when there is no magnetic field - [V_I, V_II, V_III] velocities of the liquid in regions I, II, and III - V_II, lim velocity of the liquid at which breakdown of the hydrated layer occurs for a certain value of the induction - V_cr and V _cr ⁰ critical velocities at which cavitation occurs in the magnetic field and when there is no magnetic field - p_a atmospheric pressure - p_sv saturation-vapor pressure at the given temperature - density of the liquid - kinematic viscosity - Re Reynolds number - Re_cr critical Reynolds number - c_gf and c_gd concentrations of free and dissolved gases in the magnetic field and when there is no magnetic field - c_gf and c_gd, and c _gf ⁰ and c _gd ⁰ concentrations of free and dissolved gases in the magnetic field and when there is no magnetic field - _sc space-charge density - electrical conductivity in the volume of the liquid - _b electrical conductivity in the boundary layer - _l , _g, _d dielectric constants of the liquid in the volume, of the gas in the bubbles, and of the diffusion layer - j, j_b, j_i, and j_T current density of the general, boundary layer, induced and current flow - f_MHD and f_EHD volume forces of magnetohydrodynamic and electrodynamic nature (per unit volume) - p_MHD pressure in the liquid due to the action of the magnetohydrodynamic forces - ₀ limiting shear stress in the liquid - B magnetic induction - E electric field strength in the volume of the liquid Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 35, No. 5, pp. 842–850, November, 1978.     

Mechanism of in situ formation of AlN in Al melt using nitrogen gas

In situ processing of AlN particle reinforced aluminum composites was investigated using a gas bubbling method with nitrogen gas as the gaseous precursor and pure aluminum as the starting matrix in the temperature range of 1173–1573 K. The products were characterized using XRD, SEM, and EDS techniques. Experimental results showed that it is feasible to synthesize AlN particle reinforced Al composites in situ using purified nitrogen gas. Significant AlN was synthesized by bubbling deoxidized N₂ through Al melt. The AlN particles synthesized in situ were small in size (<10 m) and were enriched in the top part of the product formed in the crucible. Directly bubbling commercial purity nitrogen gas did not lead to formation of significant AlN due to the deleterious effect of the trace oxygen impurities in the bubbling gas. The deleterious effect of trace oxygen impurities on the mechanism of formation of AlN in the Al-N system was critically analyzed from both thermodynamic and kinetic points of view. Chemisorption of O₂ molecules at the gas bubble-Al melt interface is more favorable and much faster than that of N₂, thereby inhibiting chemisorption of N₂ molecules. Significant AlN can be formed only at the content of oxygen below a critical value in the N₂ bubbling gas.     

Thermodynamics of the liquid-solid interface in dilute solutions of3He in4He

We show that the (p, T, x) phase diagram of⁴He close to melting pressure (25.3 bars) with small concentrations of³He and at very low temperatures has several unanticipated and novel features. For pressures between 25.3 bars and a triple point pressurep*, estimated to be 25.8 bars, we find a dilute liquid solution of³He in equilibrium with solid⁴He. The concentration of the liquidx _c increases from zero to the dilute liquid solubility limitx ₀ as the pressure increases from the pure⁴He melting pressure atT=0 top*. We explore the possibility of self-cooling by lowering the pressure throughp*. We also consider the effects of a strong magnetic field, and show that it lowersx _c. An estimate of the kinetic growth coefficient is given. Finally, we discuss the possible adsorption of³He on the melting front and the consequent faceting enhancement of the solid⁴He.     

Antibacterial effect of 317L stainless steel contained copper in prevention of implant-related infection in vitro and in vivo

Bone and intramedullary bacterial infections are one of the most serious complications of the surgical repair of fractures. To reduce the incidence of implant-related infections, several biomaterial surface treatments with integrated antibiotics, antiseptics, or metal ions have been developed for implants. In this study, we evaluated the antibacterial activity and biocompatibility of 317L stainless steel containing 4.5% copper alloy (317L–Cu) in vitro and in vivo using an animal model. Common pathogens of implant-related infections are Staphylococcus aureus and Escherichia coli, which were injected into implant materials to study their antimicrobial potential. We compared antimicrobial potential of 317L–Cu with 317L stainless steel (317L) and titanium (Ti–6Al–4V) alloys as controls. Compared with controls, 317L–Cu materials inhibited colonization by both bacteria in vitro and in vivo. Compared with 317L and Ti–6Al–4V controls, 317L–Cu showed no significant difference in colony formation of osteoblast-like cells on metal surfaces after 72 h of incubation in vitro. Metal screws containing these materials were also made for our vivo study in a rabbit model. Tissue-implants were analyzed for infection and inflammatory changes by hematoxylin–eosin staining of implants in bone. The screw tract inflammation and infection of 317L–Cu was minimal, although some inflammatory cells gathered at acutely infected sites. In addition, after materials had been implanted for 14 days in vivo, the expression of insulin-like growth factor-1 (IGF-1) in osteoblasts around 317L–Cu screws tracts had increased compared with 317L and Ti–6Al–4V controls. Overall, 317L–Cu demonstrated strong antimicrobial activity and biocompatibility in vitro and in vivo and may be used as a biomaterial to reduce implant-related infections.     

Heat transfer in the flow of low-density air in narrow channels

Results are given from measurements on air flow in narrow channels; relationships in dimensionless terms are derived for the heat transfer over a wide range in speed (1–120 m/sec) and in pressure (1 · 10⁵ > P > 1.33 · 10³) N/m².Notation V volume flow rate of air - N total number of buret divisions - P₀ pressure in measuring tank - l length of measuring section of buret - t time of oil column rise to the height h_i - n number of buret division corresponding to_i - _o, _m specific weights of oil and mercury - c scale division of buret - h₂ height of oil drop in measuring cylinder - v₀ total volume of system from needle throttle to heat exchanger inlet - P_p pressure at heat exchanger inlet - T_p, T₀ temperature at heat exchanger inlet and of surrounding air - G flow rate in mass terms - c_p mean specific heat of air - t temperature variation over measuring section - Nu, Re Nusselt and Reynolds numbers - l, d length and diameter of channel Translated from Inzhenerno-Fizicheskii Zhurnal, vol. 20, No. 5, pp. 879–883, May, 1971.