Tubular Space Research Articles

Light Intensity Distribution in a Dual-Lamp Photoreactor

Photochemical and photocatalytic reactors are being widely used in the wastewater treatment and water/air purification. One of the popular reactor configurations for water purification is the multiple lamp tubular reactor. The efficiency of purification in a photoreactor is determined by the distribution of UV radiation within the tubular space. In this study, the light intensity distribution in a two-lamp photoreactor has been evaluated using a finite volume scheme (which is essentially a variant of the discrete ordinate model). The irradiated space was divided into a number of finite volumes and angles (directional discretisation). Simulations were performed for both homogenous and heterogenous (with titania catalyst) reactors. Contours of incident radiation and local volumetric rate of energy absorption were plotted and analysed. Model predictions were used to assess the effect of catalyst loading on the light intensity distribution inside various reactor configurations. The optimum value of the distance between lamps in a 2-lamp photoreactor was found to be dependent on the optical properties of the photocatalyst used. Model predictions were found to match-well qualitatively with the published data from the literature.

Tubular space trusses with simple and reinforced end-flattened nodes-an overview and experiments

The use of tubular space frames made of continuous chord members has substantially increased over the last few years. This growth is mainly due to lower fabrication costs and high erection speed associated with these structural systems. The chord members are usually made of cold-formed shapes or tubes. The connection between the chords and diagonal members is commonly made by staking end-flattened diagonal members over the chords linked by a single large diameter bolt. In spite of this fact, the actual structural behaviour of these connections is still not fully understood. This paper describes six full-scale tests performed on spatial structures to investigate their structural response. Based on these experiments, the structural behaviour, up to collapse, of simple eccentric and reinforced eccentric nodes was discussed. A study of structural reinforcements, created to improve the structural load carrying capacity and minimise deflections, is also one of the main foci of the present paper.

Quantitative morphometry of lupus nephritis: The significance of collagen, tubular space, and inflammatory infiltrate

Lupus nephritis encompasses a wide range of parenchymal injuries and severity. Better predictors of outcome are needed for patients newly diagnosed with lupus nephritis, so that an appropriate management strategy may be selected. A single-center cohort of first renal biopsies for lupus nephritis was chosen. Histologic sections of whole biopsy cores were stained with picro-Sirius red, and light microscopic images (x100) were digitally captured. Using a simple, freely available software package, the cortex of each biopsy was evaluated for four different parameters: area occupied by nuclei, intratubular space, fibrillary collagen, and collagenous matrix. Clinical and laboratory data were collected retrospectively from the time of biopsy and throughout follow-up. A high nuclear index at initial biopsy correlated with clinical parameters of disease activity, at the time of biopsy. High collagen matrix index predicted both relapse and progression to end-stage renal disease (ESRD). The fibrillary collagen index predicted progressive disease as assessed by doubling of serum creatinine, and relapse. Increased tubular space also predicted progressive disease as determined by doubling of creatinine and renal death. A simple automated system for objectively scoring biopsies of lupus nephritis predicts renal survival and may provide a useful adjunct to guide patient management.

Crystal Structure of the Membrane Fusion Protein, MexA, of the Multidrug Transporter in Pseudomonas aeruginosa

The MexAB-OprM efflux pump of Pseudomonas aeruginosa is central to multidrug resistance of this organism, which infects immunocompromised hospital patients. The MexA, MexB, and OprM subunits were assumed to function as the membrane fusion protein, the body of the transporter, and the outer membrane channel protein, respectively. For better understanding of this important xenobiotic transporter, we show the x-ray crystallographic structure of MexA at a resolution of 2.40 A. The global MexA structure showed unforeseen new features with a spiral assembly of six and seven protomers that were joined together at one end by a pseudo 2-fold image. The protomer showed a new protein structure with a tandem arrangement consisting of at least three domains and presumably one more. The rod domain had a long hairpin of twisted coiled-coil that extended to one end. The second domain adjacent to the rod alpha-helical domain was globular and constructed by a cluster of eight short beta-sheets. The third domain located distal to the alpha-helical rod was globular and composed of seven short beta-sheets and one short alpha-helix. The 13-mer was shaped like a woven rattan cylinder with a large internal tubular space and widely opened flared ends. The 6-mer and 7-mer had a funnel-like structure consisting of a tubular rod at one side and a widely opened flared funnel top at the other side. Based on these results, we constructed a model of the MexAB-OprM pump assembly. The three pairs of MexA dimers interacted with the periplasmic alpha-barrel domain of OprM via the alpha-helical hairpin, the second domain interacted with both MexB and OprM at their contact site, and the third and disordered domains probably interacted with the distal domain of MexB. In this fashion, the MexA subunit connected MexB and OprM, indicating that MexA is the membrane bridge protein.

Full-frontal collision simulations and analyses of tubular space frame bodywork for sedan car

Full-frontal collision simulations and analyses of tubular space frame bodywork for sedan car

Dust explosibility of metal powders

Vacuum chamber is a new method to suppress the gas explosion. The explosion propagation characteristics have been studied in an L-shaped channel (tubes joined a right angle) with a vacuum chamber in the region of joining of the tubes. The vacuum chamber separated from the inner tubular space with the help of a diaphragm pierced by firing pin. The results demonstrate that the effect of explosion suppression of vacuum chamber is related to the break-up time of diaphragm and the position of the explosive flame front. When the diaphragm breaks up, the shorter the distance of flame front propagation is, the closer the flame front gets to the vacuum chamber, and the better effect of explosion suppression is, conversely, the worse the effect of explosion suppression is.

A Simple Preparative Method to Evaluate Total UV Protection by Commercial Sunscreens

The optical transparency of a cellulose membrane in the UV region is equivalent to that of a high-quality quartz plate. A simple preparative method to obtain UV absorption spectra of sunscreens over two length regions, UVB and UVA, is presented with some experimental results obtained using a Visking tubular membrane. The thickness of the optical path can be controlled by simple squeezing at the surface of the membrane holding the creamy sample in the tubular space on a flat plate.

Welding Automation in Space‐Frame Bridge Construction

The SPACES system has been proposed as an alternative for long‐span bridge construction. Tubular space frames offer a structurally more efficient solution for bridges, but they have been considered too expensive because the joints at the nodal intersections of the tubular members are difficult and expensive to weld. The benefits of the SPACES system can only be realized by using a computer‐integrated construction system to drive down the fabrication costs. A key component of the computer‐integrated construction is the robotic welding system. This article describes the development of a lightweight automated welding system for the joining of tubular members. It addresses the geometry of intersecting cylinders and the kinematics and design of a 5‐degree‐of‐freedom manipulator. Summary solutions are given for both. The control software is described briefly, and mention of the welding tests and overall business process is also made. A consortium of U.K. industry and universities is conducting the work.

Advanced plastic hinge analysis for the design of tubular space frames

The basic theory of a two-surface plastic hinge analysis program is presented, focusing on the inelastic stiffness formulation of a three-dimensional beam–column element. Material non-linear behaviour is considered by allowing yielding to occur at the element end and mid-length sections. Simple beams and columns were analysed to demonstrate the capability of the analysis model in predicting the bending and buckling behaviour of frame members. Several tubular space frame structures, including tubular braced frames, a lattice dome and a barrel vault with pre-tensioned cables, were analysed to illustrate the qualities and limitations of the analyses in predicting the systems' strength and behaviour. The design implication of geometrical imperfections on the limit load of the system is also highlighted.

Modelling action potentials and membrane currents of mammalian skeletal muscle fibres in coherence with potassium concentration changes in the T-tubular system.

During prolonged activity the action potentials of skeletal muscle fibres change their shape. A model study was made as to whether potassium accumulation and removal in the tubular space is important with respect to those variations. Classical Hodgkin-Huxley type sodium and (potassium) delayed rectifier currents were used to determine the sarcolemmal and tubular action potentials. The resting membrane potential was described with a chloride conductance, a potassium conductance (inward rather than outward rectifier) and a sodium conductance (minor influence) in both sarcolemmal and tubular membranes. The two potassium conductances, the Na-K pump and the potassium diffusion between tubular compartments and to the external medium contributed to the settlement of the potassium concentration in the tubular space. This space was divided into 20 coupled concentric compartments. In the longitudinal direction the fibre was a cable series of 56 short segments. All the results are concerned with one of the middle segments. During action potentials, potassium accumulates in the tubular space by outward current through both the delayed and inward rectifier potassium conductances. In between the action potentials the potassium concentration decreases in all compartments owing to potassium removal processes. In the outer tubular compartment the diffusion-driven potassium export to the bathing solution is the main process. In the inner tubular compartment, potassium removal is mainly effected by re-uptake into the sarcoplasm by means of the inward rectifier and the Na-K pump. This inward transport of potassium strongly reduces the positive shift of the tubular resting membrane potential and the consequent decrease of the action potential amplitude caused by inactivation of the sodium channels. Therefore, both potassium removal processes maintain excitability of the tubular membrane in the centre of the fibre, promote excitation-contraction coupling and contribute to the prevention of fatigue.

A new type of CO 2 sensor built up with plasma polymerized polyaniline thin film

Electric conductivity of polyaniline thin film formed by r.f. (1 MHz) plasma excitation changes in exposure to CO 2 gas. The polyaniline thin film (ca 2000 Å thick) is set between parallel plates of Au thin film electrode of which one side of the electrode used the obliquely deposited film (ca 180 Å thick) to allow passage of the gas into the polyaniline thin film. Current measurement between the electrodes biased with 1.5 V lithium cell was carried out for the sensor being kept in a tubular space (ca 30 cm 3) while the gas flow (1 ~ 2.0 l/min) is in the condition of ‘ON’ to ‘OFF’. The film conductivity of the sensor with an active area of 34.3 mm 2 increases approximately six times in magnitude, which is proportional to the area and to the level of the flowing gas. The data show that the changes in current are reversible and respond rapidly below l s.

Altered organic anion and osmolyte content and excretion in rat polycystic kidney disease: an NMR study.

Polycystic kidney disease (PKD) is the fourth most common cause of end-stage renal disease and the most common potentially lethal inherited disease in humans. Early identification of carriers of dominant PKD in the absence of genetic markers is problematic in both humans and the Han:SPRD-cy/+ rat, a model of PKD that shares many features of human disease. We undertook a proton magnetic resonance imaging (MRI) study of young Han:SPRD-cy/+ and unaffected Han:SPRD(-)+/+ animals to determine whether carrier status could be identified based upon image appearance or signal characteristics. Affected animals demonstrated significant prolongation of longitudinal relaxation time (T1) and transverse relaxation time (T2) in both cystic renal cortex and noncystic renal medulla. Both of these measurements correlated significantly with whole kidney section tubular luminal space measurements, a correlate of water space, in the renal cortex, but only T1 in renal medulla showed a relationship to tubular luminal volume measured throughout the kidney. Urine and perchloric acid kidney extracts were studied using proton nuclear magnetic resonance (1H-NMR) spectroscopy to test the hypothesis that imaging differences implied specific urinary and tissue biochemical differences between affected and normal animals. 1H-NMR spectra of urine from cy/+ animals showed significantly increased excretion of alanine, citrate, succinate, and, 2-oxoglutarate but not methylamine compounds compared with +/+ animals. 1H-NMR spectra of aqueous perchloric acid kidney extracts confirmed reduced concentrations of the above ions and others involved in the citric acid cycle, as well the osmolytes betaine, taurine, and glycerophosphocholine PKD in the Han:SPRD-cy/+ rat is associated with distinct early MRI changes and alterations in urinary and tissue levels of organic anions and osmolytes.

Optimum Finned Tubular Space Radiator

A two-dimensional finite-difference method of analysis is employed to elicit information pertaining to the thermal performance characteristics of a tubular space radiator with attached fins. The potential importance of the base surface interaction is brought out. The analysis takes into account the variation of base temperature, which has not been considered so far. A wide range of thermal and geometric parameters that are normally employed in the design of a tubular radiator has been considered. The existence of an optimum fin height and its dependence on other parameters have been explored. A new dimensionless heat dissipation parameter has been defined, and correlations that would aid the designer are presented.

Thermodynamic optimization of tubular space radiators

T0)] P = perimeter of the tubular radiator, ra/, m Q = heat transfer rate, W Re — Reynolds number based on diameter, nondimensional S = entropy generation rate, W/K T = temperature, K TR = temperature ratio, nondimensional, T0/Tm V = velocity of fluid, m/s X = horizontal coordinate, m Ap = pressure drop, N/m2 e = total hemispherical emissivity of the radiator surface p = density of fluid, kg/m3 or = Stefan-Boltzmann constant, 5.67 X 1CT 8 W/m2 K4 (f> = nondimensional heat transfer rate, Q/7rkL(Tin — T 0) Subscripts

鋼管立体トラスに用いられる球継手のダイアフラム補強に関する研究

The strength of hollow steel spheres used as nodes in tubular space trusses is investigated. In the previous papers [Refs. 1,2 and 3], the authors have reported experimental and analytical studies of the strength of balls without any stiffener subjected to direct uniaxial force from the circular tubes welded to ,the ball. In the practice, as a ball is usually fabricated from two cold-formed hemispheres, the ball has often an interior diaphragm in its equatorial plane for the purpose of easily fabricating as well as reinforcement. Uniaxial compressive tests of the ball joint with/without an interior diaphragm were carried out to investigate the effect of the reinforcement. Method of limit analysis is used to estimate the effect of the reinforcement by the interior diaphragm. Further, a practical formula which is obtained by superposing the diaphragm strength on the ball strength is proposed for predicting the strength of the balls with the interior diaphragm.

Sensitivity of Sertoli and leydig cells to xenobiotics in in vitro models

Different chemicals are known to cause testicular damage in the human male and experimental animals. However, the ability to assess the potential and mechanism of action leading to chemically-induced damage in men has been hampered by a lack of good predictive models. Although many of these chemicals were found to impair reproductive capacity in various laboratory animals, only some have caused reproductive damage in men. Mammalian spermatogenesis takes place within the avascular seminiferous tubules of the testis. Specialized tight junctions, which form between adjacent Sertoli cells at the time of puberty, divide the tubular space into the basal and adluminal compartments, and create a “blood-testis” barrier that restricts passage of substances and ions from the circulation. Thus, the completion of meiosis and post-meiotic germ cell differentiation, which take place in the adluminal compartment, are isolated from circulating substances unable to cross the blood-testis barrier. It seems feasible, therefore, that damage to the germ cells induced by testicular toxicants may be mediated through other cells in the testis such as the Sertoli, peritubular, or Leydig cells. A recently developed two-compartment system for culture of testicular cells can simulate, to some degree, the normal physiologic conditions. In principle, Sertoli cells isolated from mammalian testes are cultured on a permeable support (that is millipore filter) between two fluid compartments. They form a highly polarized epithelial layer with characteristics tight junctions that restrict the passage of substances between the two compartments, in analogy to the blood-testis barrier. We believe this system provides an excellent in vitro model for determining the ability of chemicals to: a) alter the permeability of the blood-testis barrier, b) impair the secretory function of Sertoli cells, or c) affect their viability, all of which could indirectly affect the germ cells. We have utilized this system for examining the effects of cadmium chloride (CdCl 2) and other toxic substances known to affect the testis. The Leydig cell toxicity was investigated in testicular perfusion system or cultures of isolated Leydig cells.

The effective thermal conductivity of a metalhydride bed packed in a multiple-waved sheet metal structure

The effective thermal conductivity (ETC) of a hydrogen-MmNi 4.51Al 0.47 hydride system * was measured under equilibrium pressure conditions between approximately 0.001 and 5 MPa. In the system, a multilayer waved sheet structure made of copper was used to ensure improved heat transfer in the metal hydride bed where the contact surfaces of copper sheets were soldered by applying amorphous thin films placed between the copper sheet and the inner surfaces of the reactor tubes. * Mm denotes mischmetall, a mixture of rare earth metals. The maximum value obtained in this experiment was found to give an ETC of14.0 W m −1 K −1 by packing the metal hydride powder in a tubular space of which only 6% was occupied by the metallic structure used for improving the ETC. There was no distinguishable difference in the effective thermal conductivity between the hydriding and dehydriding processes. The effect of temperature was observed to be small in the range 303–363 K. The ETC increased by approximately 2.5 W m −1 K −1 owing to the volume expansion of the metal hydride particles and the increase in the contact surface of the particles. An empirical equation is proposed to estimate the ETC of the proposed metalhydride composite by considering the effects of the thermal conductivities of the metal hydride bed itself and the metallic structure used to improve the ETC as a function of the hydrogen concentration of the metal hydride.

Behavior of Damaged Tubular Structural Members

An analytical model of dented tubular members is constructed. Using this model, an ultimate strength interaction relationship between axial force and biaxial bending moments is derived. The implementation of this interaction relationship to take account of denting and bending damage in the analysis of nonlinear behavior of tubular space frames by ISUM (the Idealized Structural Unit Method) is described. An experimental study of the behavior of dented members subjected to pure bending is reported. Comparison with theoretical predictions is presented.

Inward rectification in the transverse tubular system of frog skeletal muscle studied with potentiometric dyes.

The non-penetrating potentiometric dyes NK2367 and WW375 were used to investigate the effect of inward rectification on the weighted-average tubular membrane potential in single frog muscle fibres voltage clamped using a three-Vaseline-gap method. In 100 mM-K solution, when inward rectification was activated by hyperpolarization the steady-state amplitude of the transverse tubular system (T-system) optical signal was reduced, and its rise time was faster than that recorded for an equivalent depolarization. The voltage dependence of the optical attenuation followed that of inward rectification, increasing with increasing hyperpolarization. For a voltage-clamp step of -140 mV the optical attenuation was 0.72 which corresponds to a weighted-average T-system potential change of 100 mV. When inward rectification was blocked in a Cs, TEA solution the optical attenuation was also abolished. The voltage dependence of the block of the inward currents in solutions containing low concentrations of Cs was also reflected in the T-system optical signals. Our results were satisfactorily predicted by a radial cable model of the T-system, assuming the same specific inward rectifier conductance in surface and tubular membranes. This analysis predicts that the measured optical attenuation corresponds to a decrease in the tubular space constant, lambda T, from 120 micron under passive conditions to about 40 micron when inward rectification is fully, activated. The voltage dependence of inward rectification measured at the surface membrane was reasonably well predicted by assuming that the specific conductance obeyed a Boltzmann type of voltage dependence; the major effect of tubular decrements was to reduce the steepness of the total (surface + T-system) conductance-voltage relation.

El-plastic Behavior and Ultimate Strength of Damaged Tubular Members

An analytical model of dented tubular members is constructed. Using this model, an ultimate strength interaction relationship between axial force and biaxial bending moments is derived. The implementation of this interaction relationship to take account of denting and bending damage in the analysis of nonlinear behavior of tubular space frames by ISUM (the Idealized Structural Unit Method) is described. An experimental study of the behavior of dented members subjected to pure bending is reported. Comparison with theoretical predictions is presented.