The β ⇄ α transformation in dilute Ti-Mo alloys

An investigation has been made of the various phase transformations which occur when dilute Ti-Mo (0.5 and 1.0 wt% Mo) alloys are cooled from the phase field and are subsequently tempered in the + phase field. The morphology of the decomposition products varied with cooling rate and can be correlated with the competition between the formation of by martensitic and by diffusional processes. On isothermal transformation below theM _s, or upon tempering, phase precipitates grow heterogeneously from the supersaturated plates formed by shear. The precipitate habit plane is irrational and corresponds to the {334} plane.Formerly at Imperial College.     

Low-temperature hall coefficient for α-U and some dilute U-Mo solid solutions

Measurements of the Hall coefficient R _H have been made as a function of temperature between 4 and 100 K for single-crystal and polycrystal -U and -phase U-Mo alloys containing 0.6, 3, and 7 at % Mo. A strong temperature dependence for R _H, leading to a change in its sign for the single-crystal sample, is found for the uranium below 45 K. Alloying with Mo reduces the temperature dependence of R _H and that for the 7 at % Mo alloy is temperature independent. The anomalous transport behavior for the uranium is linked with the anomalies which have been observed in many of the physical properties of uranium around 45 K, and the possibility that these are due to a change in Fermi surface topology resulting from a periodic lattice distortion associated with charge density wave formation is discussed.Supported by the Australian Research Grants Committee.     

Self-diffusion of poly (ethylene oxide) – modified paclitaxel in dilute aqueous solutions

In order to make the hydrophobic anti-cancer drug Paclitaxel watersoluble, it was coupled to highly uniform poly (ethylene oxide) (PEO) with the molar mass M_w = 5,000 g/mol with a self-immolating succinate linker. The concentration and temperature dependence of the unrestricted molecular mobility of the molecules (long-time self-diffusion) in homogeneous aqueous (D₂O) solution was studied by gradient field NMR around body temperature in the highly dilute region. The concentration dependence of the friction coefficient, and the self-diffusion coefficient is unexpectedly strong and probably caused by peculiarities of the shape and/or the flexibility of the molecules rather than their size. Dedicated to Prof. Dr. W. S. Veeman, Gerhard-Mercator-University, Duisburg, on the occasion of his 60th birthday     

Polarization at metal–biomolecular interfaces in solution

Metal surfaces in contact with water, surfactants and biopolymers experience attractive polarization owing to induced charges. This fundamental physical interaction complements stronger epitaxial and covalent surface interactions and remains difficult to measure experimentally. We present a first step to quantify polarization on even gold (Au) surfaces in contact with water and with aqueous solutions of peptides of different charge state (A3 and Flg-Na3) by molecular dynamics simulation in all-atomic resolution and a posteriori computation of the image potential. Attractive polarization scales with the magnitude of atomic charges and with the length of multi-poles in the aqueous phase such as the distance between cationic and anionic groups. The polarization energy per surface area is similar on aqueous Au {1 1 1} and Au {1 0 0} interfaces of approximately −50 mJ m⁻² and decreases to −70 mJ m⁻² in the presence of charged peptides. In molecular terms, the polarization energy corresponds to −2.3 and −0.1 kJ mol⁻¹ for water in the first and second molecular layers on the metal surface, and to between −40 and 0 kJ mol⁻¹ for individual amino acids in the peptides depending on the charge state, multi-pole length and proximity to the surface. The net contribution of polarization to peptide adsorption on the metal surface is determined by the balance between polarization by the peptide and loss of polarization by replaced surface-bound water. On metal surfaces with significant epitaxial attraction of peptides such as Au {1 1 1}, polarization contributes only 10–20% to total adsorption related to similar polarity of water and of amino acids. On metal surfaces with weak epitaxial attraction of peptides such as Au {1 0 0}, polarization is a major contribution to adsorption, especially for charged peptides (−80 kJ mol⁻¹ for peptide Flg-Na₃). A remaining water interlayer between the metal surface and the peptide then reduces losses in polarization energy by replaced surface-bound water. Computed polarization energies are sensitive to the precise location of the image plane (within tenths of Angstroms near the jellium edge). The computational method can be extended to complex nanometre and micrometer-size surface topologies.     

Transport properties in the superfluid phase of dilute3He-4He mixtures nearT λ

A cell for the simultaneous measurements of temperature and³He concentration gradients, induced by a heat currentQ across a fluid helium layer is described. This cell is operated over the temperature range 1.7T<2.5 K. Measurement of the anomalous boundary resistance R_b in superfluid⁴He(X(³He)2 ppb) near T for heat currents between 8 and 47 µW/cm² are described. The results for both the weakly divergent and the heat-dependent, more strongly divergent contributions to R _b are presented. The observed amplitude of the linear part is found to be larger than predictions by Onuki, by Ginzburg and Sobaynin and by Frank and Dohm, and also larger than recent data by Duncan and Ahlers (DA). These discrepancies are discussed in the light of the effective boundary area in the cell. The nonlinear part of R _b is consistent with the data by DA. It is found that the maximum observed R _b at the superfluid transition is independent ofQ. Analysis of the conductivity data of mixtures leads to the conjecture that R _b will decrease will the addition of³He. Our measurement of both the effective thermal diffusion ratiok _T ^* and of the thermal conductivity _eff over the range 10^–6<X<5×10^–2 show departures from the predictions by Khalatnikov. In particular forX<10^–3,k _T ^* is found to be a function of X, and _eff deviates from the predicted _effX ^–1. This last result confirms measurements with a previous cell. In the appendices, determinations and tabulations of auxiliary thermodynamic derivatives, such as (V/X)_T,P and (S/X)_T,P are presented.     

CFD modeling of dilute phase pneumatic conveying in a horizontal pipe using Euler–Euler approach

ABSTRACT

Computational fluid dynamics simulations were performed to investigate the behavior of dilute phase pneumatic conveying of plastic pellets in a horizontal circular pipe. The pellets are 200?µm in diameter and 1000?kg/m³ in density. A parametric study was performed to investigate the effects of turbulence model and model collision parameters on pressure drop, solid’s volume fraction and velocity profiles. Among model collision parameters, specularity coefficient has considerable effect on the pressure drop. Moreover, the results from simulations carried out for different solid loadings and velocities were compared with experimental data found in the literature. The air velocities range from 6 to 15?m/s and solids to air mass flow ratios range from 1 to 3. At higher air velocities, the pressure drops predicted by the standard k-omega turbulence model are higher than the pressure drops predicted by the standard k-epsilon model. In contrast, at lower gas velocities, the standard k-epsilon model predicts higher pressure drops compared to the standard k-omega turbulence model. However, no significant difference in solids and air velocity profiles is observed for the two different turbulence models.     

Promoting patient safety: is technology the solution?

BACKGROUND: On April 30, 2001, the Cleveland Clinic Foundation and Cleveland Clinic Health System Quality Institute sponsored a 1-day conference focused on technology in patient safety. PATIENT SAFETY-A CALL TO ACTION: Kenneth W. Kizer focused on ten high-priority patient safety strategies identified by the National Quality Forum-including implementing recognized "safe practices", recognizing and dealing with professional misconduct, and supporting efforts to create a nonpunitive environment for health care error reporting. CULTURAL IMPLICATIONS OF INTRODUCING NEW TECHNOLOGY: Randolph A. Miller described a computerized clinician order-entry system used to provide decision support, reduce excess test ordering, introduce cost savings, and meet regulations for inpatient radiology and cardiology tests. USING BAR CODES TO ELIMINATE MEDICATION ERRORS: Jeff Ramirez reported on the Veterans Health Administration's use of bar coding technology for point-of-care validation of medication administration, which has resulted in improvements in response time; the efficiency of the dispensing, delivery, and administration process; and patient care. HOW TO MAKE COMPUTERS TEAM PLAYERS: The knowledge base exists to design computers as team players that expand human expertise and help health care practitioners better create safety. Yet David D. Woods challenged the audience to anticipate the changing shape of iatrogenic risk as a result of increasing dependence on automation in health care. TECHNOLOGY AND MEDICATION SYSTEMS: Mark Neuenschwander spoke about automating various steps within the medication use system, through computerized prescriber order entry and bedside scanning. FUTURE TECHNOLOGICAL POSSIBILITIES: Charles Denham suggested how technology may aid health care professionals in their care of patients, such as in using predictive modeling to identify the risks of therapeutic intervention.     

A meshless solution to two-dimensional convection–diffusion problems

An integral equation domain decomposition method has been implemented in a meshless fashion. The method exploits the advantage of placing the source point always in the centre of circular sub-domains in order to avoid singular or near-singular integrals. Three equations for two-dimensional (2D) or four for three-dimensional (3D) potential problems are required at each node. The first equation is the integral equation arising from the application of the Green's identities and the remaining equations are the derivatives of the first equation in respect to space coordinates. Radial basis function interpolation is applied in order to obtain the values of the field variable and partial derivatives at the boundary of the circular sub-domains, providing this way the boundary conditions for solution of the integral equations at the nodes (centres of circles). Dual reciprocity method (DRM) has been applied to convert the domain integrals into boundary integrals, though the approach is general and can be applied without the DRM. The accuracy and robustness of the method has been tested on a convection–diffusion problem. The results obtained using the current approach have been compared with previously reported results obtained using the finite element method (FEM), and the DRM multi-domain approach (DRM-MD) showing similar level of accuracy.     

Monitoring of scaling in dilute phase pneumatic conveying systems using non-intrusive acoustic sensors – A feasibility study

Scale formation in pneumatic conveying systems is a major industrial challenge. The underlying scale formation mechanisms can be intricate as they often involve a combination of several mutually enhancing binding forces and can be affected by a number of different factors. A non-intrusive monitoring technique capable of measuring scale growth would be a valuable tool to investigate different scaling mechanisms. In this study, the feasibility of an active acoustic sensor technique for monitoring of scale growth in a pneumatic conveying system is evaluated. Tests are performed in a pilot scale pneumatic conveying system transporting sand in dilute phase. The acoustic sensors conducts measurements on test pipes which are coated with a primer/powder mixture, one layer after the other, to simulate scale progression. Reference measurements of the coating layer thickness in the test pipes are obtained by a laser imaging technique for each added coating layer. A multivariate method is used to calibrate prediction models of the scale thickness using acoustic measurements as independent variables and the reference measurements as the dependent variable. Results show that the active monitoring method is capable of monitoring scale growth in pneumatic conveying systems and that dilute phase conveying of sand does not affect the precision of predictions made by the method.     

Intersection assistance: A safe solution for older drivers?

Within the next few decades, the number of older drivers operating a vehicle will increase rapidly (Eurostat, 2011). As age increases so does physical vulnerability, age-related impairments, and the risk of being involved in a fatal crashes. Older drivers experience problems in driving situations that require divided attention and decision making under time pressure as reflected by their overrepresentation in at-fault crashes on intersections. Advanced Driver Assistance Systems (ADAS) especially designed to support older drivers crossing intersections might counteract these difficulties. In a longer-term driving simulator study, the effects of an intersection assistant on driving were evaluated. 18 older drivers (M = 71.44 years) returned repeatedly completing a ride either with or without a support system in a driving simulator. In order to test the intersection assistance, eight intersections were depicted for further analyses. Results show that ADAS affects driving. Equipped with ADAS, drivers allocated more attention to the road center rather than the left and right, crossed intersections in shorter time, engaged in higher speeds, and crossed more often with a critical time-to-collision (TTC) value. The implications of results are discussed in terms of behavioral adaptation and safety.     

The semi-elliptical surface crack—A solution by the alternating method

A numerical solution to the three-dimensional equations of elasticity is presented for the problem of a semi-elliptical surface crack in the surface of a finite thickness solid. The alternating method is used to develop the numerical results which incorporate the effects on the stress intensity factor due to the presence of both the front and the back surfaces. The stress intensity factor is presented as a function of position along the crack border for a variety of crack shapes and crack depths. A comparison of the results of this study is made with previous theoretical and experimental work.

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Résumé Une solution numérique à équations tridimensionnelles d'élasticité est présentée pour le problème de la fissure de surface semi-elliptique située en surface ou en solide d'épaisseurs finies.La méthode proposée est utilisée pour développer des résultats numériques qui incorporent les effets des facteurs d'intensité des contraintes associée à la fois des surfaces recto et verso du solide. Le facteur d'intensité des contraintes est décrit pour diverses positions de la fissure et ce dans divers cas de formes et de profondeurs de fissuration. Une comparaison est faite entre les résultats de cette étude et des travaux théoriques et expérimentaux antérieurs.

     

Padé approximants for the numerical solution of singular integral equations

Summary A method for accelerating the convergence of the numerical solution of a singular integral equation, based on Padé Approximants, is given in this paper. At first the general form of the Padé Table and of the “epsilon” algorithm are presented. Taking into consideration the classical quadrature method, based on the Gauss-Jacobi quadrature rule, an approximate formula is derived for the unknown density function of the Cauchy-type singular integral equation or of the equivalent Fredholm integral equation. In this formula applying the “epsilon” algorithm to the solution for the stress intensity factors, the convergence is achieved after a few operations. The number of numerical operations required for the determination of stress intensity factors is considerable reduced, when compared to the number of operations required for a classical type of solution. Illustrative examples are given, indicating the efficiency of the method.     

Solid solution formation at the sintering of hydroxyapatite–fluorapatite ceramics

Fluorhydroxyapatite ceramics are increasingly studied for the use as biomaterials due to their good integration ability in the bone tissue and higher resorption resistance compared to the common hydroxyapatite (HA) ceramics. This study is aimed at the X-ray diffraction investigation of the interaction between HA and fluorapatite (FA) particulates in the sintering temperature range up to 1300 °C. The lattice parameters were calculated in dependence of both the FA content in the powder mixtures and the sintering temperature. From those data, the solid solution formation is concluded, at least in the temperature range from 1200 to 1300 °C. Energy-dispersive X-ray microanalysis confirmed the fluorine distribution to be almost uniform in the sintered at 1300 °C ceramics.