Volatility of mercury in water

The rate of volatilization of mercury and oxygen from the aqueous phase to the gas phase was studied by bubbling with nitrogen. The ratio, K_L^Hg/K_L^O₂, of the mass transfer coefficient of mercury to that of oxygen was determined in the temperature range 278–308 K. The ratio of 0.94 ± 0.08 which was obtained was found to be higher than that for 19 other substances, such as krypton, radon, ethylene, methylene chloride and benzene, quoted in the literature. Thus, mercury was found to be readily volatilized from the aqueous to the gas phase, despite having a much lower vapor pressure and a higher molecular weight than the other substances.     

Fracture toughness of selectively reinforced Al2124 alloy: precrack tip in the aluminium alloy side

Abstract

The fracture toughness of Al2124/Al2124+SiC bimaterials is affected by thermal residual stresses, elastic/plastic mismatch, precrack tip position, and failure mechanism. When the precrack tip is in the Al2124 side, final catastrophic failure occurs when ductile fracture of the Al2124 layer between the precrack tip and the composite side takes place, followed by fracture of the composite layer. For a precrack tip 2·0 mm from the interface, K _Q(5%) values are lower than the 'Al2124 only' value due to the near crack tip tensile residual stresses and higher stress triaxiality within the Al alloy ligament. At 0·5 mm from the interface, K _Q(5%) values increase and are usually as high as the 'Al2124 only' value due to the stronger shielding of the elastic/plastic mismatch. If the precrack tip is 2·0 mm from the interface, K _crit values of the bimaterial are higher than the 'Al2124 only' value and this is deduced to be due to the elastic/plastic mismatch shielding. At 0·5 mm from the interface, K _crit values are reduced because both the near tip tensile residual stress is higher and stress triaxiality levels of the ductile ligament are higher, although the elastic/plastic mismatch shielding is also higher at this position.     

Effect of Low Dialysate Flow Rate on Hemodialyzer Mass Transfer Area Coefficients for Urea and Creatinine

Recent work has shown that the dialyzer mass transfer area coefficient (K_oA) for urea increases when the dialysate flow rate is increased from 500 to 800 mL/min. In this study we determined urea and creatinine clearances for two commercial dialyzers containing polysulfone hollow fibers in vitro at 37°C, a nominal blood flow rate of 300 mL/ min, and dialysate flow rates (Q_d) ranging from 100 to 800 mL/min. A standard bicarbonate dialysis solution was used in both the blood and dialysate flow pathways, and clearances were calculated from solute concentrations in the input and output flows on both the blood and dialysate sides. Urea and creatinine K_oA values, calculated from the mean of the blood and dialysate side clearances, increased (p < 0.01) with increasing Q_d over the entire range studied. The increase in both urea and creatinine K_oA with increasing Q_d was proportional to the K_oA value. These data show that changes in Q_d alter small solute clearances greater than predicted assuming a constant K_oA.     

The effect of particles on the gas velocity in a free turbulent flow

The article describes experimental studies carrid out to investigate the interaction between gas and particles in a free turbulent two-phase flow at the outlet from a rather long vertical tube.Notation A cross-sectional area of the flow - A ₀ initial cross-sectional area of the flow - d diameter of the flow - d _p average diameter of particles - I _i initial momentum of the two-phase flow - k mass ratio of particles and gas (k=m _p/m _g) - k ₀ mass ratio of particles and gas in the initial cross-section of the two-phase flow (x=0) - m _g mass flow rate of gas - m _p mass flow rate of particles - r instantaneous radius of the flow - r ₀ radius of the initial cross-section of the flow - r _1/2 normal distance from the flow axis to the point at which the velocity of gas is equal to the half of the axial velocity - R cross-sectional radius of the flow - u velocity - u _a air velocity - u _fa gas velocity on the flow axis - u _g gas velocity - u _av average gas velocity in the initial cross-section for two-phase and single-phase flows - u ₀ gas velocity on the axis of the initial cross-section of the flow - u _p particle velocity - x distance along the axis from the original of coordinates - _g gas density Institute of Nuclear Research Vina, Laboratory of Thermal and Power Engineering, Belgrade, Yugoslavia. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 3, pp. 361–365, May–June, 1995.     

Non-linear diffusive flood routing

Summary A flood routing model based on a non-linear diffusion-convection equation is presented. Simplifying assumptions are made regarding the river geometry, and for the initial and boundary conditions. Solutions of the non-linear equation are discussed in terms of applicability and compared to solutions of the corresponding linearized equation. Stability aspects are investigated and two different numerical schemes are examined. Finally, results are compared to prototype observations, and the computation procedure is explained in detail.Notation A cross-sectional area - b constant river width - B variable river width - F Froude number - g gravitational acceleration - h flow depth - S _f frictional gradient - S ₀ bottom slope - K roughness coefficient - m cotangent of channel side-wall angle - p lateral inflow intensity - q discharge per unit width - q ₀ initial discharge per unit width - q ^* maximum discharge per unit width - Q non-dimensional discharge - Q ₀ non-dimensional initial discharge - Q ^* non-dimensional initial discharge surplus - Q _max non-dimensional maximum discharge - relative maximum discharge - dimensional discharge - r hydrograph shape parameter - R hydraulic radius - t time - T non-dimensional time - v average velocity - x longitudinal coordinate - X non-dimensional longitudinal coordinate - y relative flow depth - Y non-dimensional flow depth - diffusion coefficient With 11 Figures     

Dielectric and piezoelectric properties of Bi<Subscript>0·5</Subscript>(Na<Subscript>0·82</Subscript>K<Subscript>0·18</Subscript>)<Subscript>0·5</Subscript> TiO<Subscript>3</Subscript>-LiSbO<Subscript>3</Subscript> lead-free piezoelectric ceramics

The (1−x)Bi_0·5(Na_0·82K_0·18)_0·5TiO_3−x LiSbO₃ (x = 0−0·03) lead-free piezoelectric ceramics were fabricated by a conventional solid-state reaction method and the effect of LiSbO₃ addition on microstructure and electrical properties of the ceramics was investigated. The results of XRD measurement show that Li⁺ and Sb⁵⁺ diffuse into the Bi_0·5(Na_0·82K_0·18)_0·5TiO₃ lattices to form a solid solution with a pure perovskite structure. The LiSbO₃ addition has no remarkable effect on the crystal structure. However, a significant change in grain size took place. Simultaneously, with increasing amount of LiSbO₃, the temperature for a antiferroelectric to paraelectric phase transition clearly increases. The piezoelectric constant d ₃₃ and the electromechanical coupling factor k _p show an obvious improvement by adding small amount of LiSbO₃, which shows optimum values of d ₃₃ = 175 pC/N and k _p = 0·36 at x = 0·01.     

Radiative-convective heat transfer for high-temperature two-phase flow around bodies

Some methods for determining the basic parameters of high-temperature two-phase flows and the results of investigation of radiative—convective heat transfer with a flowing body in a flow are presented.Notation x=x/d, x distance from the plasmatron nozzle exit section - d diameter of the plasmatron nozzle - q=q_p/q₀, q_p heat flux in the vicinity of the critical point of the surface in a flow given the gas flow - q₀ neat flux in the absence of particles in the flow - _p mass concentration of particles in the flow - G_p mass flow rate of the condensed phase - G_g mass flow rate of the gas phase Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 64, No. 3, pp. 300–303, March 1993.     

Pressure-induced band cross-over in Pb1−x Sn x Te

Resistivity and thermoelectric power studies have been carried out on two semiconductor alloy systems viz Pb_0·8Sn_0·2Te and Pb_0·6Sn_0·4Te up to 35 kbar pressure. Thermoelectric power and resistivity data on Pb_0·8Sn_0·2Te indicate that the energy gapE _g=E _{L −} ⁶ −E _{L 6} ⁺ decreases with pressure resulting in a zero gap state near 35 kbar pressure. TEP studies on the alloy system Pb_0·6Sn_0·4Te provide direct evidence for a pressure induced L ₆ ⁻ →L ₆ ⁺ cross over transition.     

In situ templating synthesis of conic Ba0·5Sr0·5Co0·8Fe0·2O3?δ perovskite at elevated temperature

Conic Ba_0·5Sr_0·5Co_0·8Fe_0·2O_3−δ (BSCF) functional composite oxide was synthesized via a simple in situ templating process. The treatment of the solid precursor with concentrated nitric acid resulted in the mismatch of ionic radius at A-site and B-site of the ABO₃ perovskite, due to the oxidation of cobalt/iron ions, and the formation of Ba_0·5Sr_0·5(NO₃)₂ solid solution. Therefore, instead of the direct formation of BSCF oxide, an intermediate phase of Ba_0·5Sr_0·5CoO₃ (BSC) in hexagonal lattice structure and with conic particle shape was preferentially formed during calcination at low temperature. BSCF perovskite was then produced by the in situ templating of BSC with iron diffusing into the BSC lattice during calcination at high temperature. Well-crystallized BSCF particles in conic shape were obtained by the calcination of the nitric acid treated precursor at 900°C.     

Growth kinetics and cultivation of Spirulina platensis

Abstract

Growth kinetics and cultivation technique of Spirulina platensis were studied by using 1 liter Roux‐flask. Optimum temperature and pH for Spirulina platensis under continuous illumination of white fluorescent light were found to be 30°C and 9.5 respectively. In the logarithmic growth phase, growth followed Monod's equation; the maximum specific growth rate, μ_m , and saturation constant, K_L , were 2.0 day^‐1 and 9.2 klux respectively. During the linear growth phase, it followed the equation: dX/dt=μ_mln (1+I ₀ /K_L )/ah ₁, where I ₀ is the growth limiting factor. Growth yield of the algae ranged 0.01–0.02 g‐cell/kcal. Photosynthesis efficiency ranged 6–12%. Growth was inhibited as P_{o 2} in the gaseous phase increased to 95%. An automatic controller for pH of culture medium was devised with the feeding of CO₂ gas. Such an automatic operation promoted the algae productivity (4.5 g dry wt./l) and also improved the medium utilization.     

Designing and upgrading model of pre-denitrification systems

This paper reports a three-substrate steady-state integrated model, whose unknowns are expressed in explicit terms once concentrations of nitrogen compounds in the effluent flow are fixed. The model can be applied both to design and to upgrade wastewater treatment plants. The model is also able to evaluate the flexibility of existing wastewater treatment plants, which represents the capacity of the system to operate under different working conditions caused by increases in influent load or reductions in effluent quality standards. In this case the admissible variation of influent load or effluent concentration can be measured using suitable dimensionless flexibility indexes.List of symbols Q influent flow [L³ T^–1] - R₁ sludge recycle flow ratio - R₂ aerated mixed liquor recycle flow ratio - V_D denitrification reactor volume [L³] - V_N nitrification reactor volume [L³] - S biodegradable organic substrate concentration [M L^–3] - N-NH₄ ammonia nitrogen concentration [M L^–3] - N-NO₃ nitrate nitrogen concentration [M L^–3] - N_tot total nitrogen concentration [M L^–3] - O₂ oxygen concentration in the nitrification reactor [M L^–3] - X_H heterotrophic biomass concentration [M L^–3] - X_AUT autotrophic biomass concentration [M L^–3] - maximum removal rate of biodegradable organic substrate for an assigned value of temperature [T^–1] - maximum removal rate of nitrate for an assigned value of temperature [T^–1] - maximum removal rate of ammonia nitrogen for assigned values of pH and temperature [T^–1] - _S removal rate of biodegradable organic substrate [T^–1] - _D removal rate of nitrate [T^–1] - _N removal rate of ammonia nitrogen [T^–1] - K_S saturation coefficient for biodegradable organic substrate [M L^–3] - K_D saturation coefficient for nitrate [M L^–3] - K_SD saturation coefficient for organic substrate in the denitrification kinetic [M L^–3] - K_N saturation coefficient for ammonia nitrogen [M L^–3] - saturation coefficient for oxygen [M L^–3] - Y_H yield coefficient for heterotrophic microorganisms in the biodegradable organic substrate removal process - Y_D yield coefficient for heterotrophic microorganisms in the nitrate nitrogen removal process - Y_AUT yield coefficient for autotrophic microorganisms in the ammonia nitrogen removal process - (X_H)_r heterotrophic biomass concentration in the recycle sludge [M L^–3] - (X_AUT)_r autotrophic biomass concentration in the recycle sludge [M L^–3] - biodegradable organic mass consumption for unitary nitrate nitrogen mass reduction in the denitrification reactor - nitrogen consumption in the biodegradable organic oxidation process by mean of heterotrophic biomass     

Superstructures in Ba0·6K0·4BiO3−y and BaPb1−x Bi x O3−y

The perovskite compounds Ba_0·6K_0·4BiO₃ and BaPb_1−x Bi _x O₃ (x=0·9, 0·5, 0·25) have been investigated by high resolution electron microscopy and selected area electron diffraction. Several superlattices produced byin situ electron beam reduction have been observed. Ordered atomic arrangements in the reduced materials are discussed.     

Magnetization and initial permeability studies of Nd3+ substituted Zn-Mg ferrite system

Polycrystalline ferrites, Zn _x Mg_1−x Fe_2−y Nd _y O₄ (x=0·00, 0·20, 0·40, 0·60, 0·80 and 1·00;y=0·00, 0·05 and 0·10), were prepared by standard ceramic method. The compositions, on characterization by X-ray diffraction, showed formation of single phase cubic spinels. Magnetic study of the compositions showed increase in magnetic moment,nβ, with Zn²⁺ concentration up tox=0·4 and a decrease thereafter. This was attributed to the existence of canted spin. The compositions forx=0·8 and 1·0 showed paramagnetic behaviour at and above room temperature. The substitution of Nd³⁺ ion caused reduction in the magnetic moment and Curie temperatures. Substituted Nd³⁺ ion showed its occupancy on octahedral (B) site. The dependence of the initial permeability was studied in the temperature range 298 K-700 K. This μ_i-T curve reflects the positive temperature coefficient of initial permeability for the compositionsx≤0·4 andy=0·00. On substitution of Nd³⁺ ion (i.e.y=0·05 and 0·10), the μ_i-T curves flatten, showing almost temperature independence of initial permeability. This is explained by positive contribution to the anisotropy constant,K ₁, by substituted rare-earth, Nd³⁺ ion.     

Adaptive Distribution-free Regression Methods and their Applications

We consider the model Y = βx + Z, where the random variable Z has a continuoustype distribution that can be badly skewed, contaminated, or censored. To test the hypothesis H ₀ : β = β₀, we use the distribution-free statistic K(β₀) = Σc(Q _i )a(R _i ), where c(·) and a(·) are increasing score functions and Q _i and R _i are the respective ranks of x _i and y _i – β₀ x _i . The score functions c(·) and a(·) can be adapted or chosen after observing the data without destroying the distribution-free nature of the test. A Monte Carlo study is presented which illustrates the excellent performance of an adaptive test when a wide range of distributions is considered for the residuals. Interval and point estimates of sβ can be found by employing the “inverse” of the testing procedure. These results are used to find estimates of the percentile lines. Two examples are given which involve lifetimes of electric motor insulation and grade point averages of beginning university students, respectively.     

Biological artificial fluid-induced non-lamellar phases in glyceryl monooleate: the kinetics pathway and its digestive process by bile salts

Background: The cubic (Q_II) phase is a promising sustained-release system. However, its rigid gel-like propensity is highly viscous, which makes it difficult to handle in pharmaceutical applications. To circumvent this problem, a less viscous lamellar (L_α) phase that could spontaneously transform to Q_II phase by the introduction of water or biological artificial fluid can be used. However, the kinetics pathway of phase transition, susceptibility to digestive processes and impact of the transition on drug release are not yet well understood.

Method: We investigated various biological artificial fluid-induced L_α to inverse Q_II phase transition over time in glyceryl monooleate (GMO) by water penetration scan and light polarizing microscopy. To reveal the structure stability, fluorescence spectroscopy studies were conducted using pyrene as a probe. Furthermore, the release mechanism of pyrene as a lipophilic drug model in the spontaneously formed Q_II was investigated.

Result: Although hexagonal (H_II) mesophases occurred when phosphate buffered saline (PBS) 7.4, 0.1?M HCl or sodium taurocholate (NaTC) solutions were introduced to GMO at room temperature, they disappear with the exception of 0.1?M HCl at 37?°C. Compared with 25?°C, L_α to Q_II phase transition was in a faster rate as almost completely transforms were observed after 2?h post-immersion. The spontaneously formed mesophases were stable over 24?h immersions in PBS or pancreatic lipase solutions as proven by the extremely low fluorescence signal, however they were digestible by bile salts. This result indicated that digestion by bile salts was the major pathway instead of digestion by lipases. Moreover, pyrene fluorescence spectroscopy confirmed that the digestion by bile salts induced the formation of GMO–bile salt mixed micelles whose performance depended on the bile salt concentrations. This dependence influenced the drug release from the spontaneously formed Q_II phase.

Conclusion: All the results concluded that temperature, pH and ionic strength tendencies for the formation of non-lamellar structures greatly influenced the self-assembly process, thereby affecting the final mesophase structure. The results of this study are important to understand the lamellar to non-lamellar lipid-phase transitions and their possible pharmaceutical applications.     

Transferring biological sequence analysis tools to break-point detection for on-line monitoring: A control chart based on the local score

The Lindley process defined for the queuing file domain is equivalent to the cumulative sum (CUSUM) process used for break-point detection in process control. The maximum of the Lindley process, called local score, is used to highlight atypical regions in biological sequences, and its distribution has been established by different manners. I propose here to use the local score and also a partial maximum of the Lindley process over the immediate past to create control charts. Stopping time corresponds to the first time where the statistic achieves a statistical significance less than a given threshold α in ]0,1[, the instantaneous first error rate. The local score p value is computed using existing theoretical results. I establish here the exact distribution of the partial maximum of the Lindley process. Performance of the control charts is evaluated by Monte Carlo estimation of the average run lengths for an in-control process (ARL₀) and for an out-of-control process (ARL₁). I also use the standard deviation of the run length (SdRL) and the extra quadratic loss (EQL). Comparison with the usual and recent control charts present in the literature shows that the local score control chart outperforms the others with a much larger ARL₀ and ARL₁ smaller or of the same order. Many interesting openings exist for the local score chart: not only Gaussian model but also any of them, Markovian dependance of the data, both location and dispersion monitoring at the same time can be considered.     

Effect of annealing and quenching on superconductivity in Pb and Sb-doped Bi2Sr2Ca2Cu3O x

Samples of the series Bi_1·9−x Pb _x Sb_0·1Sr₂Ca₂Cu₃O _y withx=0, 0·1, 0·2, 0·3 and 0·4 were prepared by the solid-state route. The X-ray and d.c. electrical resistivity data on furnace-cooled and quenched samples are presented. Though the starting composition is 2223, the end products were multiphase with 4334 as the major phase. A superconducting transition withT _c=100K was observed in the pure 2223 sample after quenching. The furnace-cooled samples were metallic, while samples withx=0·1, 0·2 and 0·3 were superconducting after quenching. The amount of the 4334 phase decreases with increasing Pb content. Quenching seems to be favourable for the formation of the 4334 phase.     

The effect of input gas ratio on the growth behavior of chemical vapor deposited SiC films

In an effort to protect a RBSC (reaction-bonded silicon carbide) reaction tube, SiC films were chemically vapor deposited on RBSC substrates. SiC films were prepared to investigate the effect of the input gas ratios (dilute ratio, = P _H2/P _MTS = Q _H2/Q _MTS) on the growth behavior using MTS (metyltrichlorosilane, CH₃SiCly₃) as a source in hydrogen atmosphere. The growth rate of SiC films increased and then decreased with the decrease of the input gas ratio at the deposition temperature of 1250°C. The microstructure and preferred orientation of SiC films were changed with the input gas ratio; Granular type grain structure exhibited the preferred orientation of (111) plane in the high input gas ratio region ( = 3–10). Faceted columnar grain structure showed the preferred orientation of (220) plane at the low input gas ratios ( = 1–2). The growth behavior of CVD SiC films with the input gas ratio was correlated with the change of the deposition mechanism from surface kinetics to mass transfer.     

Steady state crack growth in elastic-viscoplastic materials

A recent theory of Hart for the steady state propagation of a mode III crack in a ductile material is extended to modes I and II. When a crack is moving at non-zero velocity v, it is shown that for a broad class of materials the stress state at the crack tip is characterized by a r ^1/2 singularity and by a local stress intensity factor K. The local K is the sum of the apparent stress intensity factor K _A and a plastic contribution K _P. The value of K _A is calculated from the remote loading and the crack geometry under the assumption of linear elastic response alone. The quantity K _P characterizes stress relief of non-elastic flow. Numerical calculations are made to determine K as a function of K _A and v for elastic-viscoplastic materials. A dependence of v on K _A is obtained by imposing a kinetic law for v as a function of K. The plots of v vs. K _A show that below some critical values of K _A, steady state conditions cannot be sustained. Corresponding to the threshold value of K _A there is a definite value for the velocity.     

Thermal accommodation coefficient of gases on controlled solid surfaces: Argon-tungsten system

The knowledge of the thermal accommodation coefficient for gases on well-controlled surfaces as a function of temperature is imperative to understanding the mechanism of interphase heat transfer on the microscopic level. With this goal in view, a heat transfer column instrument is designed, fabricated, assembled, and tested for the specific case a argon—tungsten system. With 99.9999%, pure argon, six sets of data are taken in the rarefied gas region in the maximum temperature range of 500–1500 K. Four sets of these measurements are in the temperature-jump region and are analyzed by the constant-power method to compute the thermal accommodation coefficient of argon on a controlled tungsten surface. The other two sets are taken under free-molecular flow conditions and are interpreted in accordance with the man-free-path kinetic theory for the low-pressure regime. These data are compared and discussed in the context of reported data in the literature and interpreted in the light of the surface condition and finish of the tungsten wire.Nomenclature A area of the solid surface - C _j constants in Eq. (3); j=0, 1, 2, 3, and 4 - E _i incident energy flux - E _r reflected energy flux - E _s reflected energy flux when the interaction between the gas and the solid atoms is complete - g temperature-jump distance - L half-length of the metal wire - M molecular weight of the gas - P gas pressure - Q _H total thermal energy conducted by the gas per unit time from the hot surface - Q_KT total thermal energy conducted by the gas per unit time if the striking gas molecules were to attain thermal equilibrium with the hot surface - R molar gas constant - r radial coordinate - r _f radius of the hot wire - S sticking coefficient - S_o initial sticking coefficient - T temperature - T _e linearly extrapolated gas temperature on the hot-wire surface - T _g temperature of the impinging gas molecules - T _H temperature of the hot surface - T _i temperature of the incident gas stream - T _r temperature of the gas molecules receding after collision with the solid surface - T _s temperature of the solid surface Greek Symbols thermal accommodation coefficient for the gas—solid surface - resistivity of the metal wire - gas coverage on the solid surface For an explanation of symbols, see Nomenclature.