Winding Modes Research Articles

Antimetabolites

Antimetabolites have revolutionized filtration surgery in patients with a high risk of scarring postoperatively. There are many different categories of patients with different healing responses, and these patients may need different degrees of wound modulation. For patients with a high risk of failure due to scarring, intraoperative mitomycin-C (MMC) appears to be superior to 5-fluouracil (5-FU) injections in terms of intraocular pressure (IOP) control, convenience, and corneal side effects. For lower risk patients, weaker intraoperative agents such as 5-FU may be more appropriate. Long-term complications of antimetabolites may include leaking blebs, hypotony with maculopathy, and an increased incidence of endophthalmitis. The rationale behind the choice of antimetabolite and surgical details, including the technique of antimetabolite application, surgical site positioning, conjunctival edge protection, scleral flap, and suture technique are discussed

Unwinding strings and T-duality of Kaluza–Klein and H-monopoles

A fundamental string with non-zero winding number can unwind in the presence of a Kaluza-Klein monopole. We use this fact to deduce the presence of a zero mode for the Kaluza-Klein monopole corresponding to excitations carrying H electric charge and we study the coupling of this zero mode to fundamental strings. We also a describe a T-dual process in which the momentum of a fundamental string ``unwinds'' in the presence of a H monopole. We use the coupling of string winding modes to the dyon collective coordinate of the Kaluza-Klein monopole to argue that there are stringy corrections to the Kaluza-Klein monopole which are in accordance with T-duality.

Gravity wave signature simultaneously observed in the oxygen atom and electron density profiles in the lower thermosphere

The fine structures of lower thermospheric atomic oxygen and electron density profiles obtained by a rocket experiment were investigated, assuming that these structures are due to a quasimonochromatic internal gravity wave. The height variation of the horizontal wind amplitude is similar to that of the intrinsic horizontal phase speed below ∼105 km, implying an evidence of saturation effects. At higher altitudes, the dissipation due to molecular diffusion was suggested. The wavy variation of the intrinsic horizontal phase speed with height can be explained by the mean wind modulation due to an atmospheric tide. The horizontal phase velocity vector inferred is interpreted as a consequence of selective transmission of internal gravity waves in lower atmosphere.

Correlations of atmospheric dynamics with solar wind‐induced changes of air‐Earth current density into cloud tops

We analyze reported correlations between solar activity and weather and climate and show that in six independent data sets there is a correlation of measured changes in atmospheric dynamics with measured or inferred changes in vertical atmospheric air‐earth current density. The current density changes are due to external modulation of the global electric circuit by the solar wind. We describe the several ways in which the solar wind modulates the global circuit, and the observations that support a simple model of the circuit, with two return paths in parallel. One return path is at low latitudes with relatively constant impedance and the other is at high latitudes and is responsive to solar wind modulation. The six independent data sets exhibiting the correlations include meteorological and air‐earth current density changes on the 10 to 12‐year solar cycle as well as on the day‐to‐day timescales of Forbush decreases of galactic cosmic ray flux and of heliospheric current sheet crossings. The geographic locations include northern and southern high latitudes as well as the tropics. In regions where these correlations are found, there exists free energy in the form of supercooled water droplets near the tops of clouds that are unstable with respect to precipitation. Laboratory data and models suggest that electrostatic charge accumulating on supercooled droplets and aerosols near cloud tops affects the probability of ice nucleation and droplet freezing, enhancing the rate of growth and sedimentation of ice crystals. This proposed mechanism is also an explanation for another longstanding meteorological problem, the discrepancy between measurements at cloud tops of initial concentrations of ice and of concentrations of ice‐forming nuclei. For light cloud cover the effect of increases in ice nucleation and sedimentation can be to reduce cloud opacity and albedo. For storm cloud systems the effect can be to enhance precipitation rates and latent heat release intensifying the storm. In several cases, measured or inferred storm intensification (or weakening) is directly related to measured or inferred increases (or decreases) of air‐earth current density. Thus electrical effects on cloud microphysics may serve as connecting links between the observed or inferred increases in air‐earth current density and the observed changes in atmospheric dynamics. In cases where thunderstorm electric fields are generated there are additional cloud microphysical effects that might contribute to the correlations. We discuss the present uncertainties regarding solar wind effects on the distribution of air‐earth current density in the global electric circuit and regarding the relevant cloud microphysics. Much work is required to quantify these effects and evaluate their importance relative to competing processes.

A self-colliding stellar wind model for SN 1979C

SN 1979C shows significant deviations from the well-established Chevalier minishell model for the general, long-term radio light-curve behaviour. The implication is that the deviations are primarily due to fluctuations in the radio emission. In Chevalier's mini-shell model the radio emission is directly related to the density in the circumstellar shell which is established by mass-loss from the red supergiant progenitor star, suggesting that the deviations are the result of density variations in the shell. A possible mechanism which could account for such variations is the dynamical modulation of the red supergiant wind by a binary companion. In order to explore the feasibility of such a mechanism in relation to SN 1979C, we determine the associated circumstellar shells using numerical hydrodynamics and calculate radio light curves from the resulting shells using a modified mini-shell model. We compare these light curves with the observations and find that it is possible to account for the deviations from the standard mini-shell model, thus confirming the feasibility of the binary scenario.

Numerical experiments on string cosmology

We investigate some classical aspects of fundamental strings via numerical experiments. In particular, we study the thermodynamics of a string network within a toroidal universe, as a function of string energy density and space dimension. We find that when the energy density of the system is low, the dominant part of the string is in the form of closed loops of the shortest allowed size, which correspond to the momentum string modes. At a certain critical energy density corresponding to the Hagedorn temperature, the system undergoes a phase transition characterized by the formation of very long loops, winding a number of times around the torus. These loops correspond to the winding string modes. As the energy density is increased, all the extra energy goes into these long strings. We then study the lifetime of winding modes as a function of the space dimension. We find that in the low-energy density regime, long winding strings decay only if the space dimension of the toroidal universe is equal to 3. This finding supports the proposed cosmological scenario by Brandenberger and Vafa, which attempts to explain the space dimension and to avoid the initial singularity by means of string theory.

Effects of spacer geometry on pressure drop, mass transfer, mixing behavior, and residence time distribution

Net-type turbulence promotors or grids, so-called spacers, play an important role in membrane systems referring to problems of mass transfer, homogenizing and mixing behavior. In spiral wound modules and electrodialysis stacks spacers have several functions as supporting nets (stabilisators) and as turbulence promotors to increase mass transfer rates and reduce fouling layers. Spacers show a number of geometric and fluid-dynamic parameters like, e.g., the distance between two grid rods (wavelength), the inclination angle of the grid rods and the Reynolds number. The effects of these parameters on the local flow and mass transport phenomena in narrow rectangular ducts including different spacers are investigated in gas flows in a wind tunnel. For this purpose spacers were enlarged geometrically similar and a fundamental study of the geometric parameters, based on the results of Schock [1], led to a new definition of the hydraulic diameter of spacers.

気体・蒸気分離膜の実用化の現状と展望 有機蒸気分離膜によるＶＯＣ処理装置

A new equipment for VOC (Volatile Organic Compounds) recovery in the gas mixture has been commercialized by the membrane separation process.This membrane is fabricated into spiral wound module and thevacuum system with the membrane separation process is selected as operation system.Our membrane systems are applied to treatments of gas streams containing high levels of VOC (about 2% by volume). In these cases, membrane systems can achieve much higher VOC recovery rates at much lower operating costs than condensation alone.

Membrane based system for ultrapure hydrofluoric acid etching solutions

The use of membranes to reprocess thousands of tons of hydrofluoric acid (HF) etching solutions per year is different from all previous applications of reverse osmosis (RO) and opens new opportunities for membrane based technologies. This novel application is based on both water and hydrofluoric acid permeating the RO membrane while all other impurities are rejected by it. For the first time, a spiral wound module was used here to process feeds representative of the complex multicomponent hydrofluoric acid etching solutions found in a wafer fabrication laboratory. Our new results were obtained with spiral wound membrane modules to determine the rejection and permeation of the various components along with the fluxes obtainable in realistic systems. HF was found to permeate almost 100% through the membranes while over 90% of the fluosilicic acid (the major impurity) is rejected, in a single pass. The higher the concentration of fluosilicic acid in the range of interest the better the rejection of it. Detailed analysis of the trace elements present in such HF etching solutions, which are responsible for “killer” defects in semiconductor device manufacturing, show over 99% removal of these elements in a single pass by the membranes. The economic analysis of the process indicates that reverse osmosis is attractive for the treatment of spent HF etching solutions. The performance of such spiral wound membrane systems, which represent closely the behavior of actual industrial HF reprocessors, is shown here to have tremendous potential both for reprocessing the etching solutions waste and may be feasible for ultrapurifying VLSI and ULSI grade virgin hydrofluoric acid.

Solar Wind Modulation of the Global Electric Circuit and Apparent Effects on Cloud Microphysics, Latent Heat Release, and Tropospheric Dynamics.

The solar wind modulation of the energy distribution and flux of galactic cosmic rays causes 11 year cycles in the latitude distribution of air-earth current density in the global electric circuit. Similar changes occur with solar activity on the day to day time scale. At least 3 independent data sets correlate changes in tropospheric winds and vorticity with measured and modelled changes in air-earth current density in the troposphere. These are (1) the decadal oscillations in winter in the North Atlantic region, with period averaging 11 ± 2 years over the last 120 years, and which appear to have been phase locked to the solar cycle except for a period of generally low solar activity prior to 1925; (2) the decrease in 500 mbar Vorticity Area Index (VAI) in winter at times of Forbush decreases of cosmic ray flux; and (3) decreases of 500 mbar VAI in winter at times of solar wind magnetic sector boundary passages, when volcanic aerosols from Agung and El Chicon were in the global stratosphere, together with solar wind sector modulated relativistic electron precipitation. One possible physical mechanism connecting changes in air-earth current density with changes in tropospheric dynamics is via the accumulation of electrostatic charge at cloud tops affecting the microphysics of ice nucleation and precipitation, with consequences for latent heat release and the intensification of winter cyclones.

Process water recovery from pulp bleaching effluents by an NF/ED hybrid process

A membrane hybrid process of nanofiltration (NF) and electrodialysis (ED) is optimised to recover water from the E1 alkaline pulp bleaching effluent. This highly coloured effluent has a high content of organic and organochlorinated compounds and salts. NF is selected to remove organic compounds and undertake partial desalination. A high degree of water purity is further achieved using ED to reduce sodium chloride concentration to a level of 350 ppm. The effluent was processed by a NF pilot plant with 1.7 m 2 spiral wound module. A model solution of NF permeate was used for ED pilot plant tests at room temperature. The effect of increasing temperature on ED performance was studied on the laboratory scale. A model including experimental data was used to simulate and optimise the hybrid process.

Dichloroethane Removal from Gas Streams by an Extractive Membrane Bioreactor

AbstractA novel extractive membrane bioreactor (EMB) system, in which a silicone rubber membrane separates a contaminated gas stream from an aerated biomedium, extracted and biodegraded 1,2‐dichloroethane (DCE) from a gaseous waste stream. Selective transfer of the organic compound takes place through the silicone membrane to the biomedium, where biodegradation occurs. At a gas flow rate of 770 mL min−1 and an average DCE concentration of 0.65 mg L−1, the EMB, with 2.5 m2 of membrane surface contained in a spirally wound module, degraded 91% of the DCE. A biofilm grew on the membrane surface and caused a 600 mbar pressure drop at steady state conditions. The chloride ions released by DCE mineralization were 99% of the stoichiometric amount, while 60% of the total amount of carbon crossing the membrane as DCE was bioconverted to CO2. The overall mass transfer coefficient across the membrane in the absence of microbial activity was (0.8‐1.3) × 10−6 m s−1 and was controlled by the liquid film resistance. Extensive biofilm growth significantly lowered the DCE flux. Comparison of the EMB to a direct bioscrubbing process showed that the EMB system has superior volumetric efficiency.

Internal variability in a perpetual January integration of a troposphere-stratosphere-mesosphere GCM

A 1200-day perpetual January integration of the Berlin troposphere-stratosphere-mesosphere general circulation model (GCM) has been performed with constant boundary conditions. The long-term mean climatology represents the response to the different forcing terms in the zonal-mean momentum budget: the winter stratospheric mean climatology is determined by the balance between the mean meridional circulation (m.m.c.), acting via the Coriolis force, and the Eliassen–Palm flux divergence. The winter stratospheric mean state oscillates between periods of strong wind (undisturbed conditions) and weaker winds (following minor warmings) on periods of several hundred days; this is the response to transient eddy forcing from the troposphere which has an almost-red power spectrum, with maximum power on time-scales of tens of days. As previously found in observations, there is a near cancellation between the wave- and the m.m.c.-induced forcing of the mean flow, but the acceleration is well correlated with the wave forcing. The dominant spatial modes of variability of the GCM are isolated using principal-component analysis. The dominant orthogonal modes of wind and temperature extend from the winter into the summer hemisphere. They represent structures close to thermal-wind balance, with a dipolar structure in the lower stratospheric temperature field associated with variations in the strength of the polar-night jet and weaker wind anomalies in the summer subtropics (22°S, 5hPa). There is some evidence of long-period fluctuations in the vertical velocity in the lower tropical stratosphere associated with the high-latitude velocity variations; these are consistent with the equatorial temperature anomalies. Time-delayed point correlations with the zonal velocity at 62°N, 1 hPa reveal that the weak anticorrelation of velocity in the northern subtropics (28°N, 1 hPa), which is weak at zero-lag, increases with time to about 58% at 20-days lag. Singular-spectrum analysis of the zonal velocity at the three reference points, which isolates orthogonal modes of temporal variability, reveals that the correlations are increased when only the low-frequency velocity variations are considered.

Internal variability in a perpetual January integration of a troposphere‐stratosphere‐mesosphere GCM

AbstractA 1200‐day perpetual January integration of the Berlin troposphere‐stratosphere‐mesosphere general circulation model (GCM) has been performed with constant boundary conditions. The long‐term mean climatology represents the response to the different forcing terms in the zonal‐mean momentum budget: the winter stratospheric mean climatology is determined by the balance between the mean meridional circulation (m.m.c.), acting via the Coriolis force, and the Eliassen–Palm flux divergence. The winter stratospheric mean state oscillates between periods of strong wind (undisturbed conditions) and weaker winds (following minor warmings) on periods of several hundred days; this is the response to transient eddy forcing from the troposphere which has an almost‐red power spectrum, with maximum power on time‐scales of tens of days. As previously found in observations, there is a near cancellation between the wave‐ and the m.m.c.‐induced forcing of the mean flow, but the acceleration is well correlated with the wave forcing. The dominant spatial modes of variability of the GCM are isolated using principal‐component analysis. The dominant orthogonal modes of wind and temperature extend from the winter into the summer hemisphere. They represent structures close to thermal‐wind balance, with a dipolar structure in the lower stratospheric temperature field associated with variations in the strength of the polar‐night jet and weaker wind anomalies in the summer subtropics (22°S, 5hPa). There is some evidence of long‐period fluctuations in the vertical velocity in the lower tropical stratosphere associated with the high‐latitude velocity variations; these are consistent with the equatorial temperature anomalies. Time‐delayed point correlations with the zonal velocity at 62°N, 1 hPa reveal that the weak anticorrelation of velocity in the northern subtropics (28°N, 1 hPa), which is weak at zero‐lag, increases with time to about 58% at 20‐days lag. Singular‐spectrum analysis of the zonal velocity at the three reference points, which isolates orthogonal modes of temporal variability, reveals that the correlations are increased when only the low‐frequency velocity variations are considered.

Wind Modulation of Small-scale Plumes From Yin-Yang Bay

Wind Modulation of Small-scale Plumes From Yin-Yang Bay

The economic optimization of spiral wound membrane modules for the pervaporative removal of VOCs from water

A model was developed to estimate the cost of removing relatively hydrophobic VOCs from water with a pervaporation-based separation process. Evaluation of the economic model showed that the choice f a feed-side spacer in a spiral wound module has a strong effect on the total separation cost. Several spacers that yield relatively low cost separations have been identified. The choice of permeate spacer was found to have only a small effect on the process economics, though all the permeate spacers evaluated were relatively thick and open. The most economical operation is predicted to occur with moderate permeate pressures (10–12 mmHg) and membranes ∼22 μm thick. The specific VOC to be removed from the feed water has a significant effect on the process economics. For VOCs with relatively high Henry's law constants, the model shows that the development of lower cost membranes with performance qualities similar to silicone rubber will be the most effective means of reducing the separation costs of this process.

Stratospheric volcanic aerosols and changes in air‐earth current density at solar wind magnetic sector boundaries as conditions for the Wilcox tropospheric vorticity effect

A correlation between tropospheric dynamics and solar wind magnetic fields that disappeared in the early 1970s reappeared with a new injection of volcanic aerosols into the stratosphere. A similar pattern of correlation has been found for changes in current density in the global electric circuit and for changes in relativistic electron precipitation. Several other weather and climate variations have been found to correlate with changes in air‐earth current density due to solar wind modulation of the global electric circuit. The accumulation of electrostatic charge on supercooled droplets at cloud tops responds to air‐earth current density changes. A mechanism linking the effects of charge accumulation to changes in ice nucleation, precipitation efficiency, latent heat retention and perturbations in atmospheric dynamics is thus as an explanation for this and other solar wind ‐ atmospheric electricity ‐ weather and climate correlations.

Variable soft X-ray absorption and excess of VELA X-1

We present preliminary results from a study of the stellar wind modulation of the X-ray spectrum of Vela X-1 using the broad-band (2-200 keV) data obtained in period 1988-1991 with the TTM and HEXE instruments on-board the MIR space station. We find that the hydrogen column density of the absorbing material varies from a negligible value up to 7 x 10<SUP>23</SUP> atoms cm<SUP>-2</SUP>. A soft X-ray flux excess, when compared with the extrapolation of the spectrum measured at higher energies with absorption due to cold matter, is detectable at all binary phases. It is variable and exhibits two different patterns of behavior. The soft excess is strong in the phase range when the column density is low and is then approximately correlated with the source flux. When the column density is high no such correlation is seen.

2D quantum gravity in the proper-time gauge

A two-loop (cylinder) amplitude of the 2d pure gravity theory is obtained in the proper-time gauge ( g 00 = 1, g 01 = g 10 = 0) in the continuum formulation. The constraint T 01 = 0 is solved and used to reduce the problem of field theory to that of quantum mechanics. This reduction can also be proved by using a conformal Ward identity. The amplitude depends on the lengths l 1, l 2 of the boundaries, the proper time T and a non-negative integer m associated with winding modes around the boundaries.

Modeling of Multicomponent Countercurrent Gas Permeators

Modeling of gas permeation in hollow-fiber or spiral wound modules necessitates considering the effect of permeate pressure variation along the module length which could have a significant effect on the prediction of the exit compositions and membrane area requirements depending on the membrane characteristics and module geometry. The transport equations governing the permeator performance are a set of coupled nonlinear differential equations. The complexity of the solution procedure for these equations increases with the number of components in the mixture and consideration of pressure variation. Thus, there is a need for simplified solution methodologies which could reduce the computational efforts. This paper presents a solution methodology to solve the multicomponent gas permeator transport equations in a countercurrent flow pattern, taking the permeate pressure variation into consideration. The present method yields analytical expressions for flow rates, permeate pressure, membrane area, and compositions along the length of the permeator.