Increasing Dwell Time Research Articles

Laser Direct Writing of Aluminum Conductor Lines from a Liquid Phase Precursor

ABSTRACTAluminum conductor lines were deposited on Si substrates from liquid phase triisobutylaluminum (TIBA) using a scanned argon ion laser. The vertical growth rate of Al lines initially increased, then decreased with increasing dwell time. The maximum vertical growth rate occurred at a particular dwell time depending upon the laser power. Lower vertical growth rates at longer dwell times are propably caused by the depletion of the reactant at the reaction site. A volcano deposit shape was observed, which became more pronounced as dwell time increased. The conductivity of the as-deposited Al lines decreased with increasing dwell time for our experimental conditions. To study the deposition kinetics and calculate the activation energy, the temperature rise on the Si surface was calculated by solving the nonlinear heat equation using finite difference method.

Slugging and recompression characterisation of some blends of pharmaceutical excipients

Abstract Slugs of microcrystalline cellulose (MCC), dibasic calcium phosphate (DCP) and spray-dried lactose (SDL) were compressed, either on their own or in various combinations, between 12.7 mm flat faced punches on a single punch tabletting machine at 10 different pressures. 10 tablets of each batch were compressed and the crushing strengths for five were determined. The remaining slugs were screened through an oscillating granulator and recompressed at the same pressure used initially. The crushing strengths of the final tablets were again determined. The mean yield pressures were evaluated for the slugs utilizing Heckel analysis. The results indicated that the hardest tablets were produced using 75% MCC:25% DCP. The mean yield pressure values showed that on addition of a further excipient to MCC there is a move away from predominantly plastic deformation. This was very noticeable with blends of MCC and DCP. The latter excipient has a high mean yield pressure value which implies that it is a brittle material which deforms by fragmentation. It would seem that fragmentation of DCP within the 75% MCC:25% DCP blend enhances bonding on compaction and so leads to increased crushing strength. However, for all slugged tablets there was a reduction in the crushing strength of the tablet after the second, compression for all the materials investigated. This would indicate that the extent of plastic deformation is less when the materials are compressed twice, compared to when the materials are compacted once. It was concluded that the slugging process is therefore independent of an increase in dwell time.

The predominant operation parameters and alternative controllability in the square-wave current pulse process for coloring SUS 304 stainless steel

Colored film are deposited on an SUS 304 substrate at 75°C in a 2.5 M CrO 3 + 5 M H 2SO 4 solution under appropriate operation conditions by the square-wave current pulse method. Various charge densities and frequencies are obtained by adjustment of the current supply and dwell time. It is observed that a controllable colored film is achieved when the ratio of positive to negative charge density is 1 to 1. Films of the same color sequence can be deposited under various positive or negative current supplies and different positive or negative dwell times. However, colored films could not be deposited if the ratio of positive to negative charge density is 1 to 3. The corresponding potentials measured near the specimen surface during the coloring process with the aid of a reference electrode also reflect variations in the pulse. The steady potential of 1090 mV with respect to a saturated calomel electrode (SCE) is detected in the positive current region, which is equivalent to the nucleation potential of films in the conventional Inco method. However, the corresponding cathodic potential increases with increasing dwell time in the negative applied current region. Among various operation parameters of coloring process in this study, the corresponding cathodic potential is closely related to the color tone of deposited films. The indicated potential values of 200 mV (SCE), 450 mV (SCE), 700 mV (SCE) and 900 mV (SCE) exhibit colors of brown, blue, gold and purple respectively. The desired color tone of the films can be modulated well by the adjustment of the corresponding cathodic potential.

The influence of dwell time on reliability of SMT solder joints under thermal cycling

The influence of dwell time on mechanical behaviour and fatigue life of SMT solder joints under thermal cycling has been investigated. The dwell time has two effects on the mechanical behaviour of SMT solder joints under thermal cycling: first, in the dwell time of high-temperature part, the stress in SMT solder joints will notably relax, and secondly, as the dwell time increase, the stress in solder joints in the low-temperature part of thermal cycling increases. With the increase of dwell time, the life of SMT solder joints under thermal cycling exponentially decreases.

Survival of Listeria monocytogenes in Postpasteurized Precooked Beef Roasts

The potential for Listeria monocytogenes to survive various times and temperatures of postpasteurization in precooked beef roasts was investigated. Precooked eye of round roasts were inoculated with 109 cells of L. monocytogenes per package prior to packaging in cook-in bags and postpasteurization. Four groups of roasts (n = 54) each containing 27 uninoculated and 27 inoculated roasts were allotted to four pasteurization treatments consisting of two different exposure temperatures (91°C, 96°C) and two different dwell times (3 min, 5 min). Equal numbers of inoculated and uninoculated roasts from each treatment were then stored at 4 and 10°C. Triplicate samples of inoculated and uninoculated roasts were sampled on day 1, 4, 8, and 12 for product stored at 10°C and 1, 8, 14, 28, and 56 d for product stored at 4°C. Survivors were encountered for every treatment employed. The lethality of the treatment was directly related to an increase in dwell time and postpasteurization temperature. Treatment 4 (96°C, 5 min) was found to decrease the L. monocytogenes population the greatest (p < 0.05) and also maintained a lower (p < 0.05) count from its initial inoculum level during storage at both 4 and 10°C.

Cell Function and Viability in Glucose Polymer Peritoneal Dialysis Fluids

To investigate the biocompatibility profile of a new peritoneal dialysis fluid containing glucose polymer (GPF). Viability and function of peripheral neutrophils (PMN) from healthy donors and cultured human peritoneal mesothelial cells were assessed in vitro after exposure to dialysis fluids. Phagocytosis, leukotriene B4 synthesis, and respiratory burst activation were measured following stimulation with serum-treated zymosan (STZ) or opsonized Staphylococcus epidermidis (S. epidermidis). Bacterial growth in the fluids was also investigated. In vivo pH equilibration of GPF and subsequent respiratory burst activation following incubation in spent dialysate were studied. For all the host defense parameters measured, commercial dialysis fluids (Dianeal; 1.36% and 3.86% glucose) and GPF (pH 5.2) were significantly more inhibitory than the control buffer (pH 7.3). Mesothelial cell viability was reduced by all the fluids tested irrespective of pH. Glucose polymer fluid was significantly more inhibitory than Dianeal 1.36% for STZ phagocytosis and respiratory burst activation. In contrast, it was less suppressive than Dianeal 3.86% for LTB4 synthesis. For all parameters tested, except LTB4 generation, there was a marked effect of pH, with GPF being significantly more inhibitory at pH 5.2 than at pH 7.3. None of the fluids tested supported the growth of S. epidermidis, although the viable counts in GFP were significantly higher than in Dianeal. Fluid inhibition of PMN respiratory burst activation and cytotoxicity were reduced in a time-dependent manner following increasing dwell time in vivo. GPF does not appear to be significantly different from Dianeal as far as host defense parameters are concerned. However, the cell viability and bacterial survival data suggest some possibly negative aspects of this fluid formation.

A study of failure of SMT solder joints under thermal cycles by statistics

In this paper, a simulated ceramic chip carrier has been designed to study the reliability of SMT (surface mount technology) solder joints under thermal cycles. Using this simulated ceramic chip carrier, the influence of the solder joint position, the temperature range of thermal cycle and the dwell time on the reliability of SMT solder joints under thermal cycles has been studied using statistics. The results show that the reliability of middle solder joints (MSJ) is statistically higher than that of side solder joints (SSJ). With a rise in the maximum temperature of the thermal cycle and the increase of dwell time, the reliability of SMT solder joints reduces notably. The solder joint reliability of the gold-plated carrier has a greater sensitivity to the dwell time and maximum temperature of the thermal cycle than that of the nickel-plated carrier, which may be related to the intermetallics between the solder and the metal plating of carrier.

Direct writing of Ag-lines on Mn-Zn ferrite by laser-induced thermal decomposition by CH3COOAg

Laser-induced direct writing of silver lines on a ferrite surface from a silver acetate (CH3COOAg) thin layer has been investigated. The deposition is a thermochemical process and the threshold temperature for thermal decomposition of CH3COOAg is about 380° C. About 100% of Ag in the deposited lines has been achieved. The width of the deposited Ag-lines increased with the increase in laser power, and it can be accurately estimated by the temperature profile induced by laser irradiation within the power region below the melting point of ferrite. A line thickness of micron order can be formed both on a ferrite surface and on a deposited SiO2 surface, whereas the line width decreased with the increase in beam dwell time due to the vaporization of both CH3COOAg precursor and deposited Ag material.

A possible mechanism for accelerated atherogenesis in male versus female rats.

Dietary fat and cholesterol enter the circulation as chylomicrons. They are removed from the circulation by attachment to lipoprotein lipase located on the endothelial surfaces. As the result of lipoprotein lipase action, chylomicrons are partially hydrolyzed and then reenter the circulation as remnants, which are rapidly cleared by the liver. We investigated the fate of 3H-retinol- and 14C-cholesterol-labeled chylomicrons injected into male and female rats. The disappearance curves of chylomicrons from the circulation were not significantly different in males and females, which suggests that translocation from plasma to endothelium is similar for both sexes. However, in male rats, the "dwell time" of chylomicrons on the endothelium was significantly prolonged. At 10 and 20 minutes after chylomicron injection, more label was found in the livers of female than male rats. The opposite was true for hearts. Male hearts contained significantly more endothelium-bound chylomicrons when compared with female hearts. This increase in dwell time may allow greater cholesterol deposition in the endothelium of male rats. The more rapid processing of chylomicrons was associated with a 300% greater postheparin lipoprotein lipase in female rats, which suggests a greater enzyme density at chylomicron attachment points on endothelium.

Pharmacokinetics and metabolism of intravenous and oral fleroxacin in subjects with normal and impaired renal function and in patients on continuous ambulatory peritoneal dialysis

The pharmacokinetics of fleroxacin, including the formation of N-demethyl and N-oxide fleroxacin after the administration of single intravenous (100-mg) and oral (400-mg) doses, was investigated in 26 subjects with various levels of renal function, including 7 patients on continuous ambulatory peritoneal dialysis. Fleroxacin was well tolerated by all subjects. The volume of distribution, systemic availability, and peak concentration after the administration of oral fleroxacin were independent of the glomerular filtration rate. As a consequence of a declining renal clearance but not nonrenal clearance, the total body clearance of fleroxacin declined with decreasing glomerular filtration rate from 1.41 +/- 0.23 ml/min per kg in subjects with normal renal function to 0.58 +/- 0.13 ml/min per kg in patients with end-stage renal disease (r = 0.84, P less than 0.001). The analysis revealed that the N-oxide metabolite exhibited formation-limited kinetics and the N-demethyl metabolite exhibited elimination-limited kinetics. The areas under the curve of both metabolites increased with declining renal function. In patients on continuous ambulatory peritoneal dialysis the mean dialysate/plasma concentration ratio of fleroxacin increased from 0.52 +/- 0.11 to 0.71 +/- 0.13 (P less than 0.001) with increasing dwell time, resulting in a 7.8 +/- 3.6% recovery of unchanged fleroxacin in peritoneal dialysate. In conclusion, (i) a 50% reduction of the maintenance dose is recommended in patients with a renal function below 20 to 30 ml/min per 1.73 m2, and (ii) therapeutic concentrations of fleroxacin in the peritoneal dialysate should be achievable after oral administration in patients on continuous ambulatory peritoneal dialysis.

Effect of mechanical treatment on the reactivity of ammonium perchlorate

Thermal reactivities of ammonium perchlorate (AP) pressed at 1500 kg cm−2 for various dwell times ranging from 0 to 45 min have been investigated. Reactivity of AP is observed to (a) increase with increase of dwell time up to 15 min and (b) decrease for the compacts obtained at higher dwell times. X-ray diffraction profiles of the compacts indicated a broadening up to 15 min dwell time and a narrowing thereafter. The increase in the reactivity has been attributed to the increase in the number of gross imperfections and plastic deformation of particles. The decrease in the reactivity is explained in terms of recrystallization after plastic deformation. Local heating is shown to exist during compaction though its macroscopic effect is insignificant during compaction of AP.

Evaluation of Mechanical Deaeration Parameters for High Vacuum Canned Foods

ABSTRACTIn mechanical deaeration of sliced apples, pears and cut green beans, increasing fill temperatures or chamber vacuum enhanced product deaeration, whereas increasing dwell time under vacuum from 3 to 9 sec did not (p &lt; 0.05). Product ability to resist explosion when subject to sudden vacuum varied with products, firmness and temperature. Control of fill temperature was necessary for proper removal of oxygen from the canned products.

Host Defence in Continuous Ambulatory Peritoneal Dialysis: The Effect of the Dialysate on Phagocyte Function

Peritoneal dialysis fluid was examined after dwell periods of from 30 min to 18 h. Macrophages formed more than 70% of all cells recovered, irrespective of dwell time. The viability of these cells was 95% or greater even in 30 min effluent. Peritoneal macrophages and polymorphonuclear leucocytes were incubated in unused peritoneal dialysis fluid. By 30 min the viability of polymorphonuclear leucocytes had fallen to 50% but that of peritoneal macrophages was still 84%. However, phagocytosis of unopsonized zymosan by both cell types was depressed after only 10 min exposure. Peritoneal dialysis effluents obtained after dwell times of 30-180 min were examined for their effect on phagocytosis in vitro. These fluids suppressed peritoneal macrophages function as compared to RPMI 1640. Effluent after an overnight dwell did not affect phagocytosis. The suppressant effect decreased with increasing dwell time. Polymorphonuclear leucocytes were affected to a greater degree than peritoneal macrophages. Tests showed that this decreased phagocytosis was not due to cell death nor was it due to the osmolality or lactate content of the dialysate. Adjusting pH only improved cell function slightly. Phagocyte function appears to be depressed for clinically significant periods of the CAPD cycle.

The hemodynamic forces acting on thrombi, from incipient attachment of single cells to maturity and embolization

We consider the steady fluid forces acting on a thrombus from the time of first contact of a single cell with a natural or artificial surface, through the attachment process and growth to embolization. For a hemi-spherical or cylindrical attached cell of height less than 1 100 – 1 20 th of the channel width, shear and tensile stresses are solely dependent on viscosity and on the ratio of average fluid velocity to channel width v t D t (shear rate). Large values of this ratio reduce adhesion and increase embolization. The average shear stress on such cell is ∼ 1–10 Pa (10–100 dyn cm 2), the average tensile stress about three times higher. For other shapes and larger protrusions, stress varies with protrusion height as well. Maturing thrombi composed of cell aggregates embedded in a fibrin mesh do not appear to allow significant fluid flow through their porous structure. The interior forces are then due solely to hydrostatic pressure and initially vary directly with v t D t and inversely with thrombus height H p , thus favouring embolization at an early stage and in arterial systems. Rough surfaces are identified as causing an increase in dwell-time and possibly immobilizing an unattached cell due to ‘negative lift’.

Temperature effects in hot forging dies

The paper is concerned with the physical and metallurgical changes that occur in hot forging dies. These changes are examined by the execution of simple upsetting tests on a Petro-Forge high speed hammer. Each test involves the forging of 1000 steel (En 8) billets using flat dies in two materials, No.5 and H.50 steels. The temperature conditions for each test are varied by changes in the dwell time, from 5 ms to 1 s, and by the use of either unlubricated dies or dies lubricated with a colloidal graphite-water mix. Macroscopic examinations of the surfaces, and microscopic examinations and microhardness tests of surface sections are carried out on each pair of dies. It is found that dwell time affects the condition of the die surfaces in two distinct areas, for both die materials. In the die centre, with lubricated dies, a mild form of cracking present at the shortest dwell time, disappears as the dwell time increases. In contrast, away from the die centre, where metal flow and die surface temperatures are likely to be at a maximum, severe cracking is present at the longest dwell time and this reduces to a minimum as the dwell time is reduced. There was little evidence of cracking in any area with unlubricated dies. The micro-examinations reveal the presence of a layer of martensite away from the die centre with lubricated dies, the layer thickness increasing with dwell time. It is also thicker with No.5 than with H.50 dies. No transformation is evident at the die centre, nor when unlubricated dies are used. It is argued that during hot forging there are four possible temperature-cycles per blow with respect to the minimum and maximum surface temperatures in relation to the austenite and martensite transformation temperatures, and in only one case is martensite found in the die surface. This case corresponds to the conditions reported, when a water-based lubricant is applied and when the dwell time is sufficiently long for austenite to be formed. The effects of the dwell time and of a change in die material prove this supposition. The effects of temperature cycling and phase transformations on the thermal fatigue of the dies is discussed. It is concluded that transformation is the major cause of the severe cracking created in certain die areas of the reported results. It is stated that the use of coolants, as opposed to lubricants, in hot forging is a compromise and can be detrimental except where long dwell or contact times lead to severe softening of the working surfaces of the dies.

Experience with self carburation of natural gas during clinker burning in a rotary kiln

During the heating of rotary kilns it is desirable to use self carburation of natural gas. In this case there is an increase in the temperature in the sinter zone, and an improvement in heat exchange, a reduction in the preparatory zone for the fired material, and an increase in the length of the sinter zone; there is also an increase in the dwell time of the material in the high-temperature zone. It is necessary to carry out wider investigations on the rational combustion of natural gas in rotary kilns for burning various types of refractory materials. Attention should be drawn to the development of economic methods of carburation or self carburation of the natural-gas flame in rotary kilns, and compact, satisfactorily operating burner devices giving luminous flames.