High Bath Research Articles

PARTICLE HEAT TRANSFER COEFFICIENTS UNDER VARIOUS RETORT OPERATING CONDITIONS WITH END‐OVER‐END ROTATION

Forced convection heat transfer in cans was studied experimentally during end‐over‐end sterilization in a full‐immersion, hot‐water rotary sterilizer. A polypropylene spherical particle (diameter = 19 mm) was suspended in a high temperature bath oil (Newtonian liquid) using a flexible fine‐wire thermocouple attached to the can wall providing uninhibited heat transfer conditions. the overall heat transfer coefficient, U, was determined using a lumped capacity heat balance approach and the fluid‐to‐particle heat transfer coefficient, hfp, was determined from transient temperature data at the center of the particle using a finite difference computer simulation. the effects of retort temperature (110 to 130C), rotational speed (0 to 20 rpm), radius of rotation (0 to 27 cm) and can headspace (6.4 and 10 mm) were examined on the associated heat transfer coefficients. Higher heat transfer coefficients were obtained with increasing values of all four variables, and the effects of rotational speed and headspace were more significant than those of retort temperature and radius of rotation. U values ranged from 120 to 187 W/m2. K and hfp values ranged from 23 to 145 W/m2. K depending on the operating conditions.

Functional relevance of anaerobic metabolism in the isolated respiratory network of newborn rats.

Respiratory (C3-C5) activity and extracellular K+, pH and Ca2+ (aKe, pHe, [Ca]e, respectively) in the ventral respiratory group (VRG) were measured in vitro. In brainstem-spinal cord preparations from 0- to 1-day-old rats, lowering of bath glucose content from 30 to 10 mM for 1 h did not affect aKe or rhythmic activity. In preparations from 2- to 3-day-old animals, however, an aKe rise by about 1 mM and disturbance of rhythm occurred after a delay of 50 min. Glucose-free saline resulted, after about 30 min, in reversible blockade of respiratory rhythm and an aKe rise by more than 8 mM, whereas pHe remained unaffected. Exposure to anoxia for 30 min after 1 h of pre-incubation in 10 mM glucose led to a progressive rise of aKe, and a fall of [Ca]e. The concomitant suppression of rhythm was irreversible in preparations from 2- to 3-day-old animals. Similar effects on aKe and [Ca]e and irreversible blockade of rhythm were revealed during anoxia in glucose-free solution, or by addition of 2-5 mM iodoacetate to oxygenated or hypoxic solutions. Iodoacetate led to a slow increase of pHe by more than 0.2 pH units, which was accelerated by anoxia. Our findings show that normal respiratory network functions in the en bloc medulla, in particular from rats older than 1 day, depend on high bath glucose levels, necessary for effective utilization of anaerobic metabolism.

Sequential Experimental Study and Optimisation of an Acid Copper Pattern Plating Process

Sequential application of fractional factorial and response surface designs in the regression modelling and optimisation of a multi‐parameter type manufacturing process is presented. In particular, the coating thickness variation of an acid copper plating process was minimised with high bath acidity, high cathodic current density and large anode‐cathode separation. Statistically designed experiments are shown to be highly effective in studying the effects and interactions of the various process factors.

Interpolymer reaction between antimicrobial polycation and polyanions grafted to cellulose fibre

The characteristics and features of the interpolymer reaction (IPR) between a polymeric antimicrobial substance (AS) containing basic groups — poly-1,2-dimethyl-5-vinylpyridinium methylsulfate (PDMVPMS), and graft copolymers of cellulose of varying structure containing acid groups (C-gr-PAA-Na, C-gr-PMAA-Na, C-gr-PSSA-Na) were established. It was found that with a high bath modulus, IPR takes place for a long time; the structure of the polyanion chain grafted to the cellulose and the presence of “cross-links” in the graft chains affect the kinetics of IPR and the composition of the polyelectrolyte complexes (PEC) formed. It was shown that the characteristics of the IPR investigated differ significantly from the characteristics of IPR with the participation of polymethyldiallylammonium chloride (PDAC), another antimicrobial polycation containing a quaternary ammonium group, and the same graft polyanions.

Immersion Deposition of Gold

A uniform, bright, high purity gold deposit can be obtained by using a dip gold plating process, characterized by high bath stability. The properties of the deposit have been examined by SEM, SRD and XPS.

Crypt base cells show forskolin-induced Cl− secretion but no cation inward conductance

Whole-cell patch-clamp studies in base cells of isolated colonic crypts of rats pretreated with dexamethasone were performed to examine the effects of stimulation by forskolin (10 micromol/l). The experiments were designed in order to distinguish between two postulated effector mechanisms: the activation of a non-selective cation channel and the activation of Cl- channels. As shown in an accompanying report, forskolin depolarizes the membrane voltage (Vm) by some 40-50 mV and enhances the whole-cell membrane conductance (Gm) substantially in these cells. In this report all experiments were performed in the presence of forskolin. A reduction of the bath Na+ concentration from 145 to 2 mmol/l led to a hyperpolarization of Vm by some 20-30 mV. This hyperpolarization occurred very slowly suggesting that the hyperpolarization produced by the low-Na+ solution was caused indirectly and not by a change in the equilibrium potential for Na+, ENa+. A complete kinetic analysis of the effect on voltage of bath Na+ revealed a saturation-type relation with a high apparent affinity for Na+ of around 5-10 mmol/l. A reduction in bath Cl- concentration from 145 to 32 mmol/l caused a depolarization of Vm from -34 +/- 3 to -20 +/- 4 mV (n = 13) in the presence of a high bath Na+ concentration, but had the opposite effect at low (5 mmol/l) Na+ concentrations: Vm was hyperpolarized from -46 +/- 4 to -62 +/- 6 mV (n = 13). If the effect of Na+ on Vm was caused by a non-selective cation channel the opposite would have been expected. To test directly whether the Na+2Cl-K+ cotransporter was responsible for the effects of changes in bath Na+ on Vm, the effects of increasing concentrations of several loop diuretics were examined. Furosemide, piretanide, torasemide and bumetanide (up to 0.1-0.5 mmol/l) all hyperpolarized Vm, albeit only by less than 10 mV. Another subclass of loop diuretics containing a tetrazolate in position 1 [e.g. azosemide, no. 19A and no. 20A from Schlatter E, Greger R, Weidtke C (1983) Pflüger Arch 396: 210-217] were much more effective. Azosemide hyperpolarized Vm from -46 +/- 3 to -74 +/- 2 mV (n = 18) and reduced Gm from 11 +/- 1 to 4 +/- 1 nS (n = 14). These data indicate that forskolin stimulates Cl- secretion in these cells by a mechanism fully compatible with the current scheme for exocrine secretion involving the Na+2Cl-K+ cotransporter.

Density matrix model for hydrogen transfer in the benzoic acid dimer

The double hydrogen transfer in benzoic acid dimers (‘the system’) embedded in a crystal (‘the bath’) is studied with time-dependent density matrix theory. The Liouville-von Neumann equation is solved for a two-dimensional model, using a state representation for the operators, and a polynomial expansion to treat the time evolution of the reduced nuclear density matrix. The bath-induced vibrational relaxation and dephasing processes are treated within the Lindblad formalism, with interlevel transition probabilities obtained from a microscopic perturbative theory due to Meyer and Ernst. The approach of various initial non-equilibrium states towards thermal equilibrium, is monitored with the help of: (i) state populations, (ii) system-bath energy exchange, (iii) the von Neumann and relative entropies and (iv) the decay of ‘coherences’. Simulations are carried out at low and at high bath temperatures.

A semiclassical approach to dissipation in quantum mechanics

Employing the path integral formalism, we study a quantum (test) system coupled to an environment consisting of infinitely many harmonic oscillators. A simple semiclassical approxi- mation, in which only real classical trajectories are required, is used to derive the propagator of the reduced density matrix for Ohmic dissipation and high temperatures. The inclusion of a summation over trajectories with the correct Maslov phases in the final expression for the propagator permits investigation of nonharmonic test systems. In a numerical example for a Morse oscillator interacting with a high temperature heat bath, the semiclassical result, obtained by the method described here, correctly displays the suppression of quantum behavior as observed in the exact calculation.

Reversible histochemical modifications of endoplasmic reticulum following arginine vasopressin stimulation of granular cells of toad bladder

The endoplasmic reticulum is generally absent from schematic representations of transport phenomena, although it shows a well-organized network in most transport epithelial cells. In order to examine the correlation between this organelle and cellular activity, bladders of Bufo marinus were studied under different experimental conditions and fixed by immersion in glutaraldehyde, followed by OsO4 impregnation for 3 days. Normal granular and mitochondria-rich cells showed a rich cytoplasmic network of canaliculi, well-impregnated by osmium deposits. Following a 2 to 15-min stimulation (serosal bath) with arginine vasopressin, the V2 receptor agonist dD-arginine-vasopressin or cyclic AMP (cAMP), the staining of endoplasmic reticulum in granular cells disappeared. After washing out of the hormone or the agonist, impregnation of the endoplasmic reticulum could be observed once again. Arginine vasopressin did not modify the impregnation of endoplasmic reticulum of either mitochondria-rich or basal cells. Our data indicate a correlation between the reactivity of endoplasmic reticulum to osmium, and a cAMP-dependent effect of arginine vasopressin through its V2 receptors. Incubation of arginine vasopressin through its V2 receptors. Incubation of toad bladders carried out with agents interfering with cellular calcium (calcium ionophores, high or low bath calcium) or with calcium release from the endoplasmic reticulum (TMB-8, thapsigargin) suggested that an early step in the cAMP-dependent effect of arginine vasopressin must involve the release of intracellular calcium from the endoplasmic reticulum. However, calcium ATPases in this organelle do not seem to participate in the hormonal effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Thermodynamics of dynamic nuclear polarization

Dynamic nuclear polarization is presented as a Carnot cycle where the high temperature bath consists of the crystal lattice and the low temperature bath consists of the nuclear spin system. It is explained how modulation of the magnetic field or microwave frequency can be interpreted as improvements leading to a more ideal Carnot cycle.

Measurement of bubble characteristics in a molten iron bath at 1600 °C using an electroresistivity probe

A two-needle, electroresistivity probe was developed to measure bubble characteristics such as gas holdup, bubble frequency, and bubble rising velocity in a molten iron bath at 1600 °C. The probe’s electrode was made of a 0.5-mm platinum wire coated with ZrO2 cement and an outer coat of alumina as insulator. The life of this probe at 1600 °C was 15 to 20 minutes, making it possible to systematically measure bubble characteristics. The measured values of the bubble characteristics were compared with their respective empirical correlations derived from cold model experiments. Good agreement between the measured values and the empirical correlations was seen for each bubble characteristic. This electroresistivity probe allows us to measure bubble characteristics in actual metallurgical reactors with gas injection at high bath temperatures.

ALLOYING REACTION CONTROL IN PRODUCTION OF GALVANNEALED STEEL

Alloying reaction in production of galvannealed steel was studied in unsteady-state diffusion conditions analogous to the industrial galvannealing process along with varying aluminum concentrations in the molten zinc bath. High bath aluminum concentration and rapid heating rate suppress the growth of not only the ζ phase, but also the Γ1 phase. The alloying temperature should be chosen in the vicinity of 773K in order to provide a coating predominantly composed of the δ1 phase. These results are discussed in accordance with the concept that the galvannealing process proceeds as a nonequilibrium zinc-iron reaction in an unsteady-state diffusion condition.

Large Ca(2+)-activated K+ channels responsive to angiotensin II in cultured human mesangial cells.

The patch-clamp method was used to determine the properties and response to angiotensin II (ANG II) of K+ channels in subpassages of human mesangial cell cultures. In cell-attached patches, with 140 mM KCl in the bath and cell potential equal to 40 mV, the open probability (Po) of large K+ channels (MKCa) was 0.8 with 0.5 mM Ca2+ in the bath and < 0.05 if the bath Ca2+ concentration was reduced to 1.0 microM. Open and closed dwell-time histograms of MKCa displayed both fast and slow time constants. Addition of ANG II (100 nM) to the bath solution (Ca2+ = 1.0 microM) increased the Po of MKCa in cyclic bursts by decreasing the time constant of the slow closed state. In excised inside-out patches, the mean single-channel conductance of MKCa was 206 pS in symmetrical 140 mM KCl. The selectivity sequence, established in asymmetrical cationic solutions, was K+ (1.0) > Rb+ (0.54) > NH+4 (0.11) > > Cs+ = Na+ (< 0.05). The Po of MKCa was increased by depolarizing potentials and high bath Ca2+. The Boltzmann distribution was consistent with an effective valence of 1.0, and the Hill coefficient for Ca2+ activation was 0.52. We conclude that MKCa has properties similar to large Ca(2+)-activated K+ channels and may act to repolarize the membrane of mesangial cells in response to an agonist-induced mobilization of intracellular Ca2+.

ATP-sensitive K(+)-selective channels of inner medullary collecting duct cells

The inner medullary collecting duct (IMCD) in vivo has the capacity to either secrete or reabsorb K+. However, a selective K+ conductance has not been described previously in the IMCD. In the present study, the patch-clamp method was used to determine the presence and properties of K(+)-selective channels in the apical membrane of the inner medullary collecting duct cell line, mIMCD-3. Two types of K(+)-selective channels were observed in both cell-attached and excised patches. The most predominant K+ channel, a smaller conductance K+ channel (SK), was present in cell-attached patches with 140 mM KCl (high bath K+) but not with 135 mM NaCl plus 5 mM KCl (low bath K+) in the bathing solution. The single-channel conductance of SK was 36 pS with inward currents and 29 pS with outward currents in symmetrical 140 mM KCl. SK was insensitive to both voltage and Ca2+. However, SK was inhibited significantly by millimolar concentrations of ATP in excised patches. A second K(+)-selective channel [a larger K+ channel (BK)] displayed a single-channel conductance equal to 132 pS with inward currents and 90 pS with outward currents in symmetrical 140 mM KCl solutions. BK was intermittently activated in excised inside-out patches by Mg(2+)-ATP in concentrations from 1 to 5 mM. With complete removal of Mg2+, BK was insensitive to ATP. BK was also insensitive to potential and Ca2+ and was observed in cell-attached patches with 140 mM KCl in the bath solution. Both channels were blocked reversibly by 1 mM Ba2+ from the intracellular surface but not by external Ba2+.(ABSTRACT TRUNCATED AT 250 WORDS)

Hydrogen transport and fracture toughness of case hardened steel

The purpose of this study is to assess the effects of effective case depth (ECD) and tempering temperature on hydrogen transport and fracture toughness of carburized AISI 8620 alloy steel. The material was machined into thin discs for permeation and into compact-tension specimens for fracture toughness measurements. The specimens were pack carburized at 930 °C and cooled to ambient temperature. The carburized specimens were austenitized at 840 °C in a high temperature salt bath, then oil quenched and tempered at various temperatures for one hour. Assessment of hydrogen transport was conducted by the electrochemical permeation technique. Both permeability and effective diffusivity decrease as ECD increases and tempering temperature decreases. Fracture toughness of pre-charged carburized 8620 steel increased with depth of carburization. Fracture toughness of hydrogen pre-charged carburized 8620 steel was minimum at tempering temperatures between about 150–400 °C. The results indicated good empirical correlation between fracture toughness and apparent solubility at higher ECD and tempering temperature. While this study shows that correlations exist, there are compositional and microstructural factors to be sorted out before any definitive relationship can be established.

Brownian dynamics study of a multiply-occupied cation channel: application to understanding permeation in potassium channels

The behavior of a multiply-occupied cation-selective channel has been computed by Brownian dynamics. The length, cross-section, ion-ion repulsion force, and ionic mobility within the channel are all estimated from data and physical reasoning. The only free parameter is a partition energy at the mouth of the channel, defining the free energy of an ion in the channel compared to the bath. It is presumed that this partition energy is associated with the energetics of exchanging a bulk hydration environment for a channel hydration environment. Varying the partition energy alone, keeping all other parameters fixed, gives approximately the full range of magnitudes of single channel conductances seen experimentally for K channels. Setting the partition energy at -11 kT makes the computed channel look similar to a squid axon K channel with respect to magnitude of conductance, shape of the I-V curve, non-unity of Ussing flux ratio exponents, decrease of current and increase of conductance with extracellular ion accumulation, and saturation at high ion concentration in the bathing solution. The model includes no preferred binding sites (local free energy minima) for ions in the channel. Therefore it follows that none of the above-mentioned properties of K channels are strong evidence for the existence of such sites. The model does not show supersaturation of current at very high bathing concentrations nor any pronounced voltage-dependence of the Ussing flux ratio exponent, suggesting that these features would require additional details not included in the model presented herein.

Equilibrium space charge distribution in a quadrupole ion trap

A simple model provides a basis for evaluating the ion spatial distribution in a quadrupole (Paul) ion trap and its effect on the total potential (trap potential plus space charge) acting on ions in the trap. By combining the pseudopotential approximation introduced by Dehmelt 25 years ago with the assumption of thermal equilibrium (leading to a Boltzmann ion energy distribution), the resulting ion spatial distribution (for ions of a single mass-to-charge ratio) depends only on total number of ions, trap pseudopotential, and temperature. (The equilibrium assumption is justified by the high helium bath gas pressure at which analytical quadrupole ion traps are typically operated.) The electric potential generated by the ion space charge may be generated from Poisson's equation subject to a Boltzmann ion energy distribution. However, because the ion distribution depends in turn on the total potential, solving for the potential and the ion distribution is no longer a simple boundary condition differential equation problem; an iterative procedure is required to obtain a self-consistent result. For the particularly convenient operating condition, a z = q 2 z /4 [in which a z = -8 qU/mρ 2 0 Ω 2, and q z = -4 qV/mρ 2 0 Ω 2 where U and V are direct current and radiofrequency (frequency, Ω) voltages applied to the trap, m/q is ion mass-to-charge ratio, and ρ 0 is the radius of the ring electrode at the z = 0 midplane], both the pseudopotential and the ion distribution become spherically symmetric. The resulting one-dimensional problem may be solved by a simple optimization procedure. The present model accounts qualitatively for the dependence of total potential and ion distribution on number of ions (higher ion density or lower temperature flattens the total potential and widens the spatial distribution of ions) and pseudopotential (higher pseudopotential increases ion density near the center of the trap without widening the ion spatial distribution.)

Whole-cell currents in single and confluent M-1 mouse cortical collecting duct cells.

M-1 cells, derived from a microdissected cortical collecting duct of a transgenic mouse, grown to confluence on a permeable support, develop a lumen-negative amiloride-sensitive transepithelial potential, reabsorb sodium, and secrete potassium. Electron micrographs show morphological features typical of principal cells in vivo. Using the patch clamp technique distinct differences are detected in whole-cell membrane current and voltage (Vm) between single M-1 cells 24 h after seeding vs cells grown to confluence. (a) Under control conditions (pipette: KCl-Ringer; bath: NaCl-Ringer) Vm averages -42.7 +/- 3.4 mV in single cells vs -16.8 +/- 4.1 mV in confluent cells. Whole-cell conductance (Gcell) in confluent cells is 2.6 times higher than in single cells. Cell capacitance values are not significantly different in single vs confluent M-1 cells, arguing against electrical coupling of confluent M-1 cells. (b) In confluent cells, 10(-4)-10(-5) M amiloride hyperpolarizes Vm to -39.7 +/- 3.0 mV and the amiloride-sensitive fractional conductance of 0.31 shows a sodium to potassium selectivity ratio of approximately 15. In contrast, single cells express no significant amiloride-sensitive conductance. (c) In single M-1 cells, Gcell is dominated by an inwardly rectifying K-conductance, as exposure to high bath K causes a large depolarization and doubling of Gcell. The barium-sensitive fraction of Gcell in symmetrical KCl-Ringer is 0.49 and voltage dependent. (d) In contrast, neither high K nor barium in the apical bath affect confluent M-1 cells, showing that confluent cells lack a significant apical K conductance. (e) Application of 500 microM glibenclamide reduces whole-cell currents in both single and confluent M-1 cells with a glibenclamide-sensitive fractional conductance of 0.71 and 0.83 in single and confluent cells, respectively. Glibenclamide inhibition occurs slower in confluent M-1 cells than in single cells, suggesting a basolateral action of this lipophilic drug on ATP-sensitive basolateral K channels in M-1 cells. (f) A component of the whole-cell conductance in M-1 cells appears as a deactivating outward current during large depolarizing voltage pulses and is abolished by extracellular chloride removal. The deactivating chloride current averages 103.6 +/- 16.1 pA/cell, comprises 24% of the outward current, and decays with a time constant of 179 +/- 13 ms. The outward to inward conductance ratio obtained from deactivating currents and tail currents is 2.4, indicating an outwardly rectifying chloride conductance.

Prolonged field bursts in the dentate gyrus: dependence on low calcium, high potassium, and nonsynaptic mechanisms.

1. The dentate gyrus has been proposed to be a gate for entry of neuronal activity into the hippocampus. This function would give it a critical role in the propagation of seizure activity in that region. The hallmark of epileptiform activity in the dentate itself, often referred to as "maximal dentate activation" (MDA), has not been reproduced previously in vitro. 2. With the use of rat hippocampal slices, bath [Ca2+] was decreased, and [K+] was increased concurrently to simulate conditions found during intense neuronal activity in vivo. Both evoked and spontaneous field bursts were observed in the dentate granule cell layer under these conditions. These bursts were similar to MDA, consisting of a prolonged negative shift in extracellular potential with large-amplitude population spikes. 3. In 0.5 mM bath [Ca2+], single stimuli applied to the perforant path could evoke prolonged field bursts in the dentate only when bath [K+] was > or = 9 mM. However, repetitive stimulation (10 Hz) of the perforant path could elicit similar dentate responses when bath [K+] was as low as 5 mM. 4. In 0.5 mM bath [Ca2+], interictal-type bursts appeared spontaneously in CA1 and CA3 when bath [K+] was > or = 5 mM but were lost when [K+] was > 9 mM. Spontaneous seizurelike activity in the dentate required a higher minimum bath [K+] (9 mM) and persisted at [K+] of 11 mM. 5. Stimulation-evoked field bursts in the dentate altered epileptiform activity in CA3. At bath [K+] insufficient to cause spontaneous CA3 bursts, CA3 was activated transiently when prolonged field bursts occurred in the dentate. At higher bath [K+] in which spontaneous CA3 bursts did occur, they were depressed during the dentate bursts. 6. Deletion of Ca2+ from the bath; the addition of 30 microM each of bicuculline methiodide, D,L-2-amino-5-phosphonopentanoate (AP-5), and 6,7-dinitroquinoxaline-2,3-dione (DNQX); or the combination of both manipulations did not block antidromically evoked or spontaneous prolonged field bursts in the dentate. Thus the mechanisms maintaining and propagating these events did not require fast amino acid-mediated synaptic transmission. 7. The concurrent alteration of [K+] and [Ca2+] required to produce prolonged field bursts in the dentate underscores the positive feedback relationship between neuronal excitation and extracellular ionic concentrations, whereas the ability of synaptic stimulation to trigger nonsynaptic seizurelike events such as these prolonged field bursts may be relevant to the transition from interictal to ictal activity in vivo.(ABSTRACT TRUNCATED AT 400 WORDS)

Coherent-incoherent transition and relaxation in condensed-phase tunneling systems.

The tunneling dynamics of the spin-boson problem has been computed using discretized path-integral simulations for temperatures T and couplings, i.e., the Kondo parameter \ensuremath{\alpha}, spanning the entire T-\ensuremath{\alpha} plane. The inherent problem of alternating weights has been solved using a combination of the stationary-phase Monte Carlo method and contour-distortion techniques. A transition from coherent to purely incoherent relaxation was observed for the spin correlation function. The time correlation functions and the location of the coherent-incoherent boundary on the T-\ensuremath{\alpha} plane are well described by the noninteracting-blip approximation. In the deep-tunneling limit of large \ensuremath{\alpha}, low T, and high bath frequency, the system relaxes exponentially, with its relaxation time constant following a power-law temperature dependence, in accord with perturbation theory. At higher T and low bath frequency, the relaxation time crosses over to a classical Arrhenius temperature dependence, reflecting the onset of activated processes. For a narrow region within 1/21, numerical results suggest that the system undergoes incoherent relaxation, with a short-time exponential decay, followed by a long-time tail of the power-law type. The short-time exponential relaxation time follows a peculiar power-law temperature dependence, with the relaxation rate increasing as a function of decreasing temperature.