Short Time Range Research Articles

Monitoring of dihydroxyacetone production during oxidation of glycerol by immobilized Gluconobacter oxydans cells with an enzyme biosensor.

A bi-enzymatic biosensor for monitoring of dihydroxyacetone production during oxidation of glycerol by bacterial cells of Gluconobacter oxydans is presented. Galactose oxidase oxidizes dihydroxyacetone efficiently producing hydrogen peroxide, which reacts with co-immobilized peroxidase and ferrocene pre-adsorbed on graphite electrode. This mediator-based bi-enzymatic biosensor possesses very high sensitivity (4.7 µA/mM in phosphate buffer), low detection limit (0.8 µM, signal/noise = 3), short response time (22 s, 95% of steady-state) and broad linear range (0.002-0.55 mM in phosphate buffer). The effect of pH, temperature, type of buffer, as well as different stabilizers (combinations of a polyelectrolyte and a polyol) on the sensor performance were carefully optimized and discussed. Dihydroxyacetone produced during a batch conversion of glycerol by the pectate-immobilized bacteria in an air-lift reactor was determined by the biosensor and by reference spectrophotometric method. Both methods were compared and were in a very good correlation. The main advantage of the biosensor is a very short time needed for sample analysis (less than 1 min).

Efecto de los parámetros de deformación y de la temperatura de precalentamiento sobre la temperatura de no recristalización en aceros microaleados con Nb y Nb-Ti

The main objective of the present work has been to determinate the no-recrystallisation temperature ( T nr ) of two Nb-bearing steels and two Nb-Ti microalloyed steels. The T nr has been obtained performing multipass torsion tests under continuous cooling conditions. The influence of deformation parameters: interpass time, t ep , pass strain, e, and strain rate, έ and reheating temperature, T , on the non-recrystallisation temperature has been investigated. In the range of short interpass time ( t ep T nr decreases as interpass time increases. For intermediate interpass time, precipitation takes place leading to an increase in the T nr . However, in the range of long interpass time ( t ep > 60 s), precipitated particles coarse loosing its effectiveness as recrystallisation retarding agents, which leads again to a decrease in the no-recrystallisation temperature. The T nr decreases with increasing pass strain following this type of relationship: T nr = β∙e -α . Moreover, an increase in the strain rate leads to a decrease in the non-recrystallisation temperature. By increasing the reheating temperature, the amount of dissolved elements that can precipitate at lower temperatures rises, which results in an increase of the T nr . 18 Leaching of vanadium from sulphuric acid manufacture spent catalysts Lixiviacion de vanadio de catalizadores agotados procedentes de la fabricacion del acido sulfurico

Nuclear Resonant Quasielastic Scattering from Fe Cations in Nafion Membranes: Effect of Dynamics in a Short Time Range

The effect of the diffusive motion in a short time range on the nuclear resonant quasielastic scattering spectrum is presented. The solution of the Langevin equation, which describes the motion of the diffusing particle in a short time range as well as that in a long time range, was applied to analyze the nuclear resonant scattering spectrum of Fe cations in Nafion membranes instead of the solution of the generally-used simple diffusion equation which does not describe the diffusive motion in a short time range correctly. It made improvements in the fitting especially at the wings of the data as compared with the solution of the simple diffusion equation. The characteristic time of the diffusive motion of Fe ions in Nafion is estimated to be about 10 -14 s. By the detailed analysis of the high energy part of nuclear resonant scattering spectrum, it is possible to reveal diffusive motion even in the short time range as ∼10 -14 s.

Oscillation of Separation Distance between Paired Typhoon-Scale Vortices.

The oscillation of separation distance between centers of interacting binary vortices of typhoon-scale in a quiescent environment is investigated numerically with a vorticity equation. It is found that the separation distance between interacting vortices exhibits a tendency to oscillate with time regardless of whether they merge eventually or repel each other. The amplitude of oscillation depends on the initial separation distance as well as the structure of the vortex. The beta-effect has little influence on it during the first couple of days, but becomes important beyond that, due to the secondary circulaions. The maximum amplitude reaches more than one hundred kilometers for the case of strong vortices with a moderate size. The period of oscillation, typically one day or longer, in general, increases with the initial separation distance and shows an increasing tendency with time for foxed initial separation distance. With a simple analysis on the angular momentum, the oscillation of separation distance is described in terms of the eddy-mean interaction based on the plane polar coordinate system of which the origin is the center of binary vortices. In agreement with the previous studies, the analysis indicates that for paired vortices that rapidly merge together (repel each other) the anomaly or the deviation from the axisymmetric part, in average, has a phase line of inward-right tilt (inward-left tilt) near the origin. However, in a case where the vortices do not readily merge or repel in a short time range but maintain the temporal oscillation in the separation distance with a large amplitude, the phase configuration of the anomaly exhibits the alternation between the inward-right and inward-left phase tilt.

Effect of supplementation with organic selenium on mercury status as measured by mercury in pubic hair

The purpose of this study was to evaluate the effect of four months of yeast-based selenium supplementation on selenium and mercury status in subjects with low serum selenium. The study was carried out in Rakvere, Estonia. Pubic hair mercury, serum selenium and blood selenium concentrations in 23 subjects (serum selenium < 90 micrograms/l) were investigated before and after selenium supplementation. Thirteen subjects were randomized into the selenium supplementation group and ten into the placebo group. The selenium supplementation group received daily 100 micrograms of selenomethionine. Selenium supplementation reduced pubic hair mercury level by 34% (p = 0.005) and elevated serum selenium by 73% and blood selenium by 59% in the supplemented group (p < 0.001 for both). The study indicates that mercury accumulation in pubic hair can be reduced by dietary supplementation with small daily amounts of organic selenium in a short range of time.

A comparison of different ways to approximate time-to-line crossing (TLC) during car driving

Three experiments are presented in which the accuracy of different methods to approximate time-to-line crossing is assessed. In the first experiment TLC was computed, using a trigonometric method, during normal driving while the vehicle stayed in lane. The minima of TLC were compared with two approximations and it was found computing TLC as lateral distance divided by lateral velocity gave poor results. It was concluded that this simple approximation is not suitable for measuring TLC minima in studies of driver behaviour. A way of computing TLC that takes account of the curved path of the vehicle resulted in a good fit of TLC minima. In two other experiments the vehicle exceeded the lane boundary, either intentionally as a result of a lane change manoeuvre, or unintentionally as a result of impaired driving. In these cases no TLC minima exists since these only occur as a result of correcting steering actions to stay within the lane. In contrast to normal lane keeping, it was found that prior to crossing the lane boundary, the simple approximation resulted in more accurate estimation of available time before the lane boundary is exceeded compared to the more complex approximation. This indicates that for lane keeping support systems and systems that detect when the driver has fallen asleep and drifts out of lane, a simple algorithm for TLC estimation may give reliable results, while this algorithm is not accurate enough for more fundamental studies of driver behaviour. However, the reliability of the approximation is only satisfactory over a very short time range before the lane boundary is actual exceeded. This may result in warnings that come too late and result in too little time to respond for the driver.

Stress relaxation behaviour of dipalmitoyl phosphatidylcholine monolayers spread on the surface of a pendant drop

Dipalmitoyl phosphatidylcholine (DPPC) monolayers were characterised by surface pressure/area isotherms ( π/ A) and surface dilational rheological parameters at temperatures 20–40°C. The methods used were the Langmuir trough and the pendant drop micro-film balance. The latter allows accurate measurements at higher temperatures and transient drop deformation. Stable DPPC monolayers were found only for low surface pressures, π<15 mN m −1. At higher monolayer compression π decreases over a long time, mainly caused by molecular rearrangement processes in the monolayer starting in the coexisting region. At π>25 mN m −1 and 20°C relaxation experiments give evident of rupturing, brittle monolayer structures. At higher temperatures the monolayers became more fluid-like. π/ A-isotherms determined by using both methods principally agree with each other, but show also remarkable differences, which cannot be explained so far satisfactory. Transient drop relaxation experiments were analysed for the short time range (600 s). At 20°C the dilational modulus ( ε r) and the surface dilational viscosity ( ξ r) passes a stationary maximum at 0.54 nm 2 molecule −1 and increase strongly at higher surface coverage, thus indicating crystalline monolayer structure. Increasing temperature from 20 to 30°C causes a rapid decrease of ε r and ξ r and a shift of the stationary maximum to lower surface coverage. No evidence for crystalline structure is found. Further increase of temperature causes ε r and ξ r increase again. This increase is caused by a rising relaxation time, while the elasticity does not change in the same manner. Such intermediate decrease of ε r and ξ r in the range 30–40°C appears to be unusual and can be interpreted as a consequence of strong DPPC interactions and strongly pronounced retardation of monolayer deformation. The study is discussed in connection to the physiology of breathing. For pulmonary surfactants the observed behaviour seems to be understandable. It is however interesting that such complex behaviour is observed for monolayers consisting of DPPC only.

Linear Viscoelastic Characterization of Polymer Melts with Long Relaxation Times

Melts of linear polyethylenes (HDPE) have broad retardation and relaxation spectra that can be determined by combining oscillatory and long duration creep/creep recovery tests. For a commercial HDPE the necessary sample preparation (stabilization), testing (at 170 °C), and data conversion are described. For long time testing incomplete creep/creep recovery is preferred because the strain is kept within the linear range and reaches a final, constant value. The measured recoverable compliance, (t), is converted into a discrete retardation spectrum {Li, τi‘}. For the short time range the dynamic moduli are measured and converted into the dynamic compliances and finally the retardation spectrum L(τ‘). Both spectra overlap and form a combined spectrum over 7.5 decades of retardation time τ‘. From this the dynamic compliances are recalculated and converted into the dynamic moduli. These are used for computing the weighted relaxation spectrum, τH(τ), ranging from τ = 0.01−2.5 × 105 s. τH(τ) has a maximum at τ = ...

Temper embrittlement in the HAZ of 2¼ Cr-1Mo steel induced by reheating after SR treatment: Study of temper embrittlement in HAZ of Cr-Mo steels (4th report)

Summary The temper embrittlement affecting the HAZ of 2 1/4Cr-1Mo steel subjected to SR treatment and subsequent reheating is investigated with synthetic HAZ specimens and compared with the embrittlement observed in specimens tempered in the same temperature range without SR treatment (direct tempering). The synthetic HAZ specimens are de-embrittled on application of suitable SR treatment (975 K × 5 hours). Subsequent reheating at 775 to 925 K, however, produces four different types of embrittlement in the specimens. These are the second, third, fourth, and fifth types of embrittlement already identified in the direct-tempered specimens. The first type of embrittlement which occurs during direct tempering in the shortest time range does not appear after SR treatment. The second type (the short-term type), which occurs over a wide time-temperature range during direct tempering, only appears in a narrow range after SR treatment. The third and fourth types (the long-term types) occur just as intensively as during direct tempering. The fifth type (the high-temperature type) also appears after SR treatment. This suggests that embrittlement in the short-term range is to some extent suppressed by SR treatment, but the types of embrittlement arising in the long-term range and high-temperature range occur after SR treatment as well. The ‘step cooling process’ can be applied for short-term detection of temper embrittlement in this steel. However, there is considered to be little or no embrittlement promotion effect due to step cooling per se.

Aquatic biotoxins: design and implementation of seafood safety monitoring programs.

Naturally occurring toxicants are usually odorless, tasteless, and generally undetectable by any simple chemical test. Various programs have been established that are effective in reducing risks associated with these toxicants in food. These programs include setting regulatory limits, monitoring susceptible commodities for toxin levels, and using decontamination procedures. Bioassays have been used traditionally to monitor suspect products. All traditional bioassays, however, have one common disadvantage, i.e., the lack of specificity for individual toxins. The lack of available reference standards for specific toxins has also hampered implementation of monitoring programs. Utilizing the knowledge gained with regulatory monitoring and decontamination programs for other toxins, e.g., aflatoxin, similar seafood safety programs can be developed for aquatic biotoxins that will reduce risks and hazards associated with the contaminant to practicable levels and help to preserve an adequate food supply. Research is needed in several areas identified in this article. International cooperation has an important role in achieving these essential elements. Global programs will help in the adequate management of risks associated with aquatic biotoxins. To have an effective monitoring program, it is necessary to define precisely the local needs for information in a short or long time range. It is necessary to have basic knowledge about the biological, chemical, and physical conditions as well as temporal and geographic variations within the region of interest (2). Regardless of the overall success of fish/shellfish toxin monitoring plans, emergencies will occur. Therefore, contingency plans should be developed so there will be no misunderstanding of what actions to take (148). In general, however, the structure of the program must be kept as simple as possible to facilitate fast and uncomplicated flow of information among the various organizations and individuals involved (2). Public health and safety requires the removal of any toxic shellfish from the market, within practicability, and closure of any suspect harvest area. It should be important to remember that economic value of the fish or shellfish resource is always secondary to public health and safety (148).

Surface Behavior of Spread Sodium Eicosanyl Sulfate Monolayers: 2. Surface Stress Relaxation Behavior

The surface behavior of spread sodium eicosanyl sulfate monolayers is characterized by determining the dilational moduli from different π/Aisotherms and from surface stress relaxation experiments in the short-time range (<10 min). The elasticities derived from the π/Aisotherms differ depending on the experimental conditions. The quasi-equilibrium isotherm displays a plateau in the range of coexistence of the condensed and the expanded phases and strong increases caused by the formation of a solid-like phase. In contrast, nonequilibrium π/Aisotherms yield effective elasticities showing a maximum within the phase coexistence range. The formation of a solid phase cannot be detected because of the onset of monolayer collapse. Different stress relaxation experiments were carried out for monolayer compression and dilation using transient drop volume jumps. Depending on the experimental run, these experiments lead to consistent and complementary results with those derived from π/Aisotherms under comparable conditions. The stress recoveries yield a relaxation time, a dilation viscosity, and a parameter characterizing the homogeneity of the relaxation process. The stress relaxation is interpreted accounting for both the nonequilibrium between the monolayer and the bulk phase and the nonequilibrium within the monolayer. The influence of alkylsulfate hydrolysis on the presented results was checked. It was found that within the time scale of the experiments no influence of hydrolysis could be detected.

Superficial tension of blood and urine in diabetic nephropathy

Dynamic surface tension (ST) of the blood serum and urine was studied in patients with diabetic nephropathy by the method of maximal pressure in a vesicle using MPT2 computer tensiometer (LAUDA, Germany). The angle of the slope of blood tensiogram curve increased and urinary ST decreased at t = 1 sec in patients with type I diabetics in comparison with those with type II condition. The development of the nephrotic syndrome and chronic renal insufficiency was associated with decrease of ST in the range of short (t = 0.01 sec) and medium (t = 1 sec) times of surface life and of the equilibrium (static) ST (at t -&gt; go/. The parameters of interphase tensiometry correlated with the content of protein and lipid surfactants in biological fluids.

Confining medium and absorptive overlay: Their effects on a laser-induced shock wave

In this paper the characteristics (such as amplitude, width) of a laser-induced shock wave under confining conditions is studied. For engineering applications, a physical study of this method is useful in order to optimize this technique. We have first introduced a new pressure gauge – PVDF (polyvenyliden fluoride) gauge with short rise time and wide linear response range. Experimentally, by measuring the generated pressures under different confining materials, the relationship between the pressures and the acoustic impedance of confining materials, is illustrated, which somewhat agrees with the theoretical calculation. We have also found that under confining conditions laser-induced shock waves persist longer than a laser pulse. Then, the effects of black paint overlay (absorptive overlay) is studied. We experimentally point out that a black paint overlay placed before an irradiated target can greatly increase the generated pressure under any confining material in our experiments for its beneficial effect on the plasma-generating process. To our surprise, comparing the impulse ( P max · τ ), which the shock wave induced under absorptive overlay executes on the target, to that induced under no black paint overlay, the increase ratio is approximately equal.

Analysis of Drain Currents During Switching off a-Si:H Based Thin Film Transistors

ABSTRACTWe present measurements and analysis of a-Si:H thin film transistor (TFT) transients when the gate voltage switches the device from a conducting to a non-conducting state. The drain current transient has been monitored in the medium-long (Ims-100s) time range and exhibits a power law decay extending to at least 10 seconds. The decay has been studied over a range of drain voltages and gate off-state voltages. Measured data show that the gate off-state can help to obtain a low drain leakage current at long times when high drain voltages are being used.However, the decay at low drain voltages shows little sensitivity to different gate off-state voltages. An analytical model is developed, based on the relaxation of the Fermi level toward mid-gap in a spatially uniform TFT channel. The model shows how deep defects are responsible for the current decay slope at long times, while shallower states determine the slope in the short time range. An energy-independent defect density would produce a 1/t slope for the current decay. Shallow states and deep states affect in opposite ways the slope since their density is energydependent in opposite ways as Fermi level moves deeper into the band-gap. Furthermore, long decay times are associated with a wider depletion region in the channel and increase the total number of defect states involved. A steeper decay than 1/t is expected and observed for shorttime ranges, while a more gradual (about 1/t1/2) one corresponds to long time measurements. The implications of the transient decay for the performance of active matrix arrays will be discussed.

Ｃｒ‐Ｍｏ鋼熱影響部の焼もどし脆化に関する研究 第４報 ＳＲ処理後の再加熱によって２ １／４Ｃｒ‐１Ｍｏ鋼ＨＡＺに生じる焼もどし脆化

Temper embrittlement, which occurs in HAZ of 2 1/4Cr-1Mo steel subjected to SR treatment and subsequent reheating, was investigated by using synthetic HAZ specimen, and it was compared with embrittlement observed in specimens tempered in same temperature range without SR treatment (direct tempering). With a suitable SR treatment (975 K for 5 hours) synthetic HAZ specimen became de-embrittled state. However, subsequent reheating at 775 to 925 K produced in specimens four different types of embrittlement. Those were second, third, fourth and fifth types, which had already been recognized in direct tempered specimens. The first type of embrittlement which arose in direct tempering in shortest time range did not appear after SR treatment. The second type (the short time type), which occurred in a wide time-temperature range in direct tempering, arose only in a narrow one after SR treatment. The third and fourth types (the long time types) arose intensively as case of direct tempering. The fifth type (the high temperature type) appeared also after SR treatment. It will be concluded that embrittlement in short time range is suppressed to some extent by SR treatment, but those arising in long time range and high temperature one arose after SR treatment as well. It was found that the step-cooling also could reveal temper embrittlement of this steel. However, an essential advantage of this process over isothermal tempering shown above was not recognized from view point of promoting embrittlement.

An intercomparison between a global variable mesh and two limited area models on a case of rapid cyclogenesis

This study has been carried out in order to investigate the predictability of a rapidly developing storm over the Mediterranean area, by comparing the behaviour of three different meteorological models. The models chosen are the global, variable mesh, model ARPEGE, which is running operationally at Meteo-France, and two limited area models, namely ALADIN (also developed at Meteo-France) and BOLAM (developed in Italy, mainly at FISBAT). This comparison study has been performed by a cooperation among the French Meteorological Service and the National Research Council of Italy (CNR) FISBAT and IFA institutes. In this paper we present the results obtained by integrating the models on a short time-range, corresponding to the developing stage of a strong cyclone that moved rather quickly to the North from Northern Africa, associated with perturbed weather and distinct mesoscale features. In particular, this cyclone was characterized by a low-level warm core, associated with very strong winds and precipitation. All the three models were successful in describing the main characteristics of this cyclogenesis event, in particular the rapid evolution of the low level vortex. However, important differences emerged in “forecasting” the value of the pressure minimum, its position and time evolution, and the associated distribution of precipitation. When the large scales are treated by using analyzed rather than forecast lateral boundary conditions, the two LAMs perform better than the global model in simulating the low evolution but the global high resolution model better describes the general features of the cyclogenesis. Differences in model performance are found especially in the distribution of precipitation forecasts, suggesting two main conclusions: insufficient descriptions of mountains can change the location of the precipitation release, the precipitation scheme of the ALADIN model is sensitive to the lateral boundary conditions. The overestimation of the cyclone in BOLAM seems due to an oversensitivity to the latent heat release that intensifies the circulation in the cyclone core.

Place and Public Finance

READING over Elton's work afresh now, sadly, there will be no more, prompts a series of reflections. It is a great body of writing both in quality and quantity: but it is extremely narrow. Elton wrote about a remarkably short time range to which he repeatedly returned. He had little patience with Wolsey, no great interest in the history of the 1540s or 1550s and his excursion into the history of Elizabeth's earlier parliaments was not one which evidently brought him much pleasure. His first book established the reputation of Thomas Cromwell: one of his last pieces of writing considered how much or how little his view of Cromwell had changed, and the very last piece to be published was a defence of Cromwel from modern claims of corruption. It is hard to think of another major historian who has made so good a living from so short a temporal span. It is also striking how little of Elton's output is actually about politics: he was essentially a student of institutions and even ideas rather than of the interaction of men. His later interest in the law seems almost a rejection of politics.

The short time regime of segmental dynamics of glass‐forming polymers

AbstractThe short time regime (10−13 s ≤ t ≤ 10−11 s) of the segmental dynamics of several glass‐forming polymers with different chemical microstructure and glass‐transition temperature has been investigated by means of time of flight (TOF) neutron scattering techniques. In this paper we present a summary of the main results obtained as well as the theoretical framework proposed by us to interpret these results. The main conclusion is that the segmental dynamics of glass‐forming polymers display in the very short time range (t = 2 ps) a crossover from a simple exponential behaviour towards a non‐exponential regime. The first exponential decay, which is controlled by C‐C rotational barriers, can be understood as a trace of the behaviour of the system in absence of the effects (correlations, cooperativity, memory effects…) which characterise the dense supercooled liquid like state against the normal liquid state. The non‐exponential regime at t &gt; 2 ps corresponds to what is usually understood as α and β relaxations. Some implications of these results are also discussed.

Pulsed dextran release from calcium-alginate gel beads

Sodium alginate forms a hydrogel upon contact with calcium ions in aqueous solution due to the physical crosslinking (chelation) between the carboxylate anions of guluronate units in alginate and the calcium ions. Alginate disintegration (dissolution) in phosphate buffered saline solution (pH 7.4, Ca 2+-, Mg 2+-free) occurs completely in a short time period after a certain lag time. Calcium ion release from the alginate gels is believed to be an influential factor in alginate dissolution. Using this alginate dissolution mechanism, we tried to release macromolecular dextran (nominal molecular weight of 145 000) in a pulsatile manner. As was expected, dextran with molecular weight of 145 000 was released completely in a short time range after a certain lag time. The lag time could be controlled by either alginate molecular weight, alginate concentration in the preparation, or gel beads size. The larger the diameter of the alginate gel beads, the later the observed release time onset. Thereafter dextran was released without changing release rate. Furthermore, we have succeeded to release dextran in a pulsatile fashion using calcium-alginate gel beads by mixing different bead sizes. These results indicate that pulsatile release of macromolecular drugs such as peptides and proteins could be achieved using calcium-alginate gel beads.

Twelve-frame camera for soft X-ray

THE procedure of inertial confinement fusion (ICF) takes place in sub-nanosecond period. In order to investigate the hydrodynamic instability and asymmetry during the implosion, we need to measure the two-dimensional distribution of plasmas temperature and density as well as its relationship with time. For this purpose, an X-ray picosecond multiframe technique has been developed. Traditionally, there are two techniques for gating images, i. e. swept framing and gated microchannel-plate (MCP) framing. Because the former has spatial loss in short exposure time and little dynamic range, the latter is recently in routine