Porous Rods Research Articles

Analysis of the conditions of necking in a porous rod subjected to tension

We analyze the conditions of necking in a thermoviscoplastic rod subjected to tension in broad ranges of strain rates and temperatures. Numerical calculations take into account complex constitutive relations for the material of the rod, the process of heat transfer in the rod, and the presence of discontinuities. The stability of uniform tension is investigated by the linear analysis of perturbations in a long-wave approximation based on limiting the expansions of perturbations into Fourier series to the first term. The roots of the polynomials obtained in this case are analyzed using the Routh-Hurwitz theory. After this, the results are improved by applying nonlinear analysis. This introduces corrections into the data of linear analysis by taking into account the influence of the amplitude dependence of perturbations on the stability of plastic deformation. The numerical results demonstrate that the length of the wave of perturbations considerably affects the rate of its damping and growth, whereas the evolution of perturbations is practically independent of the initial amplitude. The presence of discontinuities in the deformed rod makes necking much easier but is not a necessary condition of necking

Continuous production and separation of ethanol without effluence of wastewater using a distiller integrated SCM-reactor system

Continuous ethanol production without effluence of wastewater was carried out using a closed circulation system which integrated a cell retention culture system and a distillation system to separate ethanol. The stirred ceramic membrane reactor (SCMR), a jar fermentor fitted with asymmetric porous alumina ceramic membrane rods, was used for retaining high density of cells and extraction of the culture supernatant that was continuously sent to the distiller to evaporate ethanol. After the distillation process, the residual solution of the culture supernatant was returned to the SCMR via a heat exchanger. Two types of strains of Saccharomyces cerevisiae; a flocculating IR2 strain and a sake-brewing K901 strain, were cultured using the integrated fermentation system for continuous production of ethanol. When the ethanol concentration reached 60 g/ l, the culture supernatant was extracted by filtration from the SCMR and sent to the distiller. During the repeated ethanol fermentation and recycling of the medium, cell concentration of K901 strain was increased to 236 g/ l and the productivity of ethanol reached 13.1 g · l −1 · h −1, which was higher than the productivity of 12.5 g · l −1 · h −1 achieved by immobilized cells on calcium alginate beads (CAB). In addition, the productivity was further increased to 14.5 g · l −1 · h −1 by immobilized K901 cells on CAB retained in the SCMR. In contrast, the flocculating IR2 strain was found to accumulate into crusts of cells on the surface of the ceramic filter and thereby the productivity of ethanol considerably decreased because of the reduced filtration performance. These results showed that the long-lasting and high filtration performance was essential for the increase in the productivity of ethanol using the integrated system that consisted of the SCMR and the distiller.

A Novel Method of Tear Collection

To develop a rapid, user-friendly method of tear collection to facilitate tear-protein analysis. Tears were collected from a total of 19 normal volunteers without evidence of ocular-surface disease with either porous polyester rods or glass-capillary micropipettes. Tear-collection rate and recovery of two tear proteins, epidermal growth factor (EGF, low abundance) and lactoferrin (LFR, high abundance) were compared between polyester rods and glass-capillary micropipettes. The recovery of LFR and EGF and the stability of these proteins after storage at -70 degrees C were quantitated by specific monoclonal enzyme-linked immunosorbent assay (ELISA). Polyester rods collected tears an average of 3.9-fold faster than glass-capillary micropipettes (p < 0.001). Both methods were comparable in efficacy of protein recovery. The polyester rods demonstrated a trend toward enhanced recovery, but this difference was not statistically significant (p = 0.12, LFR; p = 0.055, EGF). Analysis of the reliability and reproducibility of the tear-collection assay system revealed that ELISA analysis is highly reproducible, but there is significant day-to-day variation in tear-protein levels of both LFR and EGF for a given volunteer. Both LFR and EGF displayed a trend toward enhanced detection by ELISA shortly after freezing at -70 degrees C and slow decay after storage at -70 degrees C for up to 72 and 105 days, respectively. After stimulation of reflex tearing via the nasolacrimal reflex, LFR levels remained relatively constant, whereas EGF levels for most patients declined and then plateaued. Polyester rods provide a more rapid, user-friendly alternative to glass-capillary micropipettes for the collection and analysis of tear fluid and tear proteins. Polyester rods may have greater clinical utility, facilitating routine analysis of the preocular tear film.

Influence of laser radiation on the electrodiffusion of molecular ions in a porous glass rod

The influence of laser radiation on the electrodiffusion of dye ions in porous glass has been investigated. It is shown that when the molecular ions are exposed to intense photoexcitation, the rate of electrodiffusion in the porous glass is reduced substantially. The influence of temperature on the electrodiffusion process is studied.

Effect of skeleton size on the performance of octadecylsilylated continuous porous silica columns in reversed-phase liquid chromatography

We prepared continuous porous silica rods that had silica skeletons with sizes of 1.0–1.7 μm and through-pores of 1.5–1.8 μm, and evaluated their performance as a column in reversed-phase liquid chromatography. The mesoporous silica monoliths (mesopore size: 14 or 24 nm) were derivatized to C 18 phase by on-column reaction with octadecyldimethyl-N,N-diethylaminosilane. The C 18 silica rods gave minimum plate heights of 10–15 μm for aromatic hydrocarbons in 80% methanol and 20–30 μm for insulin in acetonitrile-water mixtures in the presence of trifluoroacetic acid. The performance of the silica rods at a high flow-rate was much better than that of conventional columns packed with 5 μm C 18 silica particles with pores of 12 or 30 nm, especially for high-molecular-mass species. Silica rods with the smaller sized silica skeletons resulted in Van Deemter plots showing a minimum plate height at the higher linear velocity of the mobile phase and a smaller dependence of plate height on the linear velocity. Separation impedance of less than 1000 was achieved with the continuous silica columns. The higher performance and lower pressure drop of silica rods at high flow-rates compared with particle-packed columns is provided by the small silica skeletons and large through-pores.

Octadecylsilylated Porous Silica Rods as Separation Media for Reversed-Phase Liquid Chromatography

Continuous porous silica rods consisting of a mesoporous (pore size, 14 or 25 nm) silica skeleton of ∼1 μm size and through-pores of ∼1.7 μm were prepared and derivatized to C(18) phase by on-column reaction with octadecyldimethyl-(N,N-diethylamino)silane. The C(18) silica rods gave plate heights of 10-20 μm for aromatic hydrocarbons in 80% methanol and 20-40 μm for insulin in acetonitrile-water mixtures in the presence of trifluoroacetic acid. The performance of the silica rods was much better at a high flow rate than that of conventional columns packed with 5 μm C(18) silica particles having 12 and 30 nm pores, especially for high molecular weight species.

Graphite Electrodes Containing Nanometer-Sized Metal Particles and Their Use in the Synthesis of Single-Walled Carbon Nanotube Composites

Composite graphite/metal(0) electrodes were prepared by the absorbtion of organic solutions of metal carbonyls or aqueous solutions of metal salts into high-purity porous graphite rods. The metal carbonyls were converted to the CO-free metal(0) species by heating the composites under an atmosphere of N2 and then under reduced pressure at 1000 °C. The metal-salt-containing graphite rods were heated under an atmosphere of H2 at 1000 °C to reduce the salts to the corresponding metal(0) species. This procedure permitted dispersion of metal(0) throughout the graphite rod with average metal particle sizes in the range 6.2−11.6 nm by transmission electron microscopy (TEM) analysis. Metals used were Ag, Co, Cu, Fe, La, Ni, and Pt. The composite graphite/metal(0) electrodes were vaporized in a plasma discharge apparatus under a helium atmosphere. The Co, Fe, Ni, and Pt all catalyzed single-walled nanotubule (bucky tube) growth. The soot material from the Co, Fe, and Ni-containing rods had a foam-rubber-like texture. All the metal-containing soots, except for the La-derived material, could be press molded into pellets, without the use of a binder. Data from the trace remaining ligand analyses, powder X-ray diffraction, TEM, conductivity measurements, and surface area analyses are presented. The properties of the arc-derived soots prepared by this method are compared to the soots prepared by standard cored rod/metal(0) methods.

Synthesis, Characterization, and Neutron Activation of Holmium Metallofullerenes

Isolation of the first macroscopic quantities of endohedral holmium metallofullerenes (principally Ho@C{sub 82}, Ho{sub 2}@C{sub 82}, and Ho{sub 3}@C{sub 82} by LD-TOF mass spectrometry) has been accomplished by carbon-arc and preparative HPLC methodologies. The detailed procedure for production and isolation of the metallofullerenes includes a new technique whereby holmium-impregnated electrodes are prepared simply by soaking porous graphite rods in an ethanolic solution of Ho(NO{sub 3}){sub 3}.xH{sub 2}O. Monoisotopic {sup 165}Ho offers a unique combination of advantages for neutron-activation studies of metallofullerenes, and purified samples containing {sup 165}Ho@C{sub 82}, {sup 165}Ho{sub 2}@C{sub 82}, and {sup 165}Ho{sub 3}@C{sub 82} have been activated by high-flux neutron irradiation ({Phi} = 4 x 10{sup 13}n cm{sup -2} s{sup -1}) to generate {sup 166}Ho metallofullerenes, which undergo {beta}{sup -} decay to produce stable {sup 166}Er. Chemical workup of the irradiated samples, followed by re-irradiation, has been used to demonstrate that observed decomposition of holmium metallofullerenes is due mainly to `fast` neutron damage rather than to holmium atom nuclear recoil (E{sub max} = 200 eV). This implies that metallofullerene damage can be minimized by using neutron fluxes with the highest possible thermal component. 60 refs., 4 figs.

Biodegradable Ceramic–Collagen Composite Implanted in Rabbit Tibiae

To develop an artificial bone substitute that would be gradually degraded and replaced by the regenerating natural bone, a carbonate apatite type I atelocollagen (82/12 in v/v%) composite was designed. The carbonate apatite synthesized at 58 degrees C demonstrated a crystallinity similar to that of natural bone. Type I atelocollagen was purified from human umbilical cords. Carbonate apatite-atelocollagen composite rods (diameter 6 mm x height 10 mm) were irradiated by ultraviolet ray (wave length 254 nm) for 4 hr to increase the collagen fibrillar cross links. Rabbit tibiae were dissected to prepare an artificial total bone defect (length 10 mm). The composites and porous hydroxyapatite rods, sintered at 1200 degrees C, were implanted into the defects and the tibiae were fixed by external osseofixators. The implanted composites were gradually degraded in the lesions, and the regenerated bone totally replaced the defects within 6 weeks, while the hydroxyapatite rod implanted lesions were not replaced by bone. No specific histologic abnormalities appeared in either the hydroxyapatite or composite rod implanted lesions.

Hydrophilization of Porous Polystyrene-Based Continuous Rod Column

Reactive porous rods of poly[(chloromethyl)styrene-co-divinylbenzene] have been prepared for the first time by copolymerization of the monomers in the presence of a porogenic diluent. A two-step modification process involving reaction with ethylenediamine followed by reaction with gamma-gluconolactone leads to a porous medium that has highly hydrophilic surface functionalities. Preliminary chromatographic evaluation with both small molecules such as alkylbenzenes in reversed-phase mode and large proteins in hydrophobic adsorption and ion-exchange modes demonstrates that the surface of the modified rods possesses a hydrophilicity that is comparable to that of the best hydrophilic HPLC packings.

Observations of lubricated rolling contact fatigue on silicon nitride rods

Lubricated rolling fatigue tests on silicon nitride rods are discussed. Fully densified micro-porous and porous silicon nitride rods are tested using a disc-on-rod method. Failure modes and surface fatigue spalls are examined using scanning electron and light microscopy. The degree of porosity in silicon nitride and its influence on manufacture and quality is discussed.

Osteogenesis in muscle with composite graft of hydroxyapatite and autogenous calvarial periosteum: A preliminary report

To investigate the bone forming activity of composite grafts of hydroxyapatite (HA) and autogenous calvarial periosteum, porous HA rods with or without the periosteum were implanted into the back muscle of white rabbits. They were harvested 3 and 6 months after implantation and studied histologically and microradiographically. Bone formation in the pores of HA occurred in three out of four composite implants of the 3 month group, and four out of five implants of the 6 month group. The two specimens without bone formation revealed irregular calcified tissue outside the HA implant. No formation of bone and calcified tissue took place in any of the specimens with HA alone. These results indicate the potential of this new experimental system of ectopic osteogenesis and offer the possibility of a new improved bone graft consisting of HA and autogenous periosteum.

Performance Study of Zn / ZnCl2, NH 4Cl / Polyaniline / Carbon Battery

A secondary battery of the type , carbon is described. The polymer was electrodeposited on porous carbon rods, in the form of consistent, rather thick, highly porous, and low‐resistance layers. The battery was assembled in a configuration similar to that of the classical R‐6 dry cell. The performance of the battery has been studied, and it shows characteristics comparable to those of conventional systems: moderate specific energy (50–100 Wh · kg−1), very good coulombic efficiency (70–100%), low self‐discharge rate (<1% day), and excellent cyclability at high current densities.

Mass transfer in supercritical fluid extraction of a binary aromatic mixture, naphthalene and phenanthrene, from porous rods

Supercritical extraction of naphthalene—phenanthrene mixtures from porous rods has been studied at temperatures above and below their melting points. Despite the different solubilities of both components in the solvent (carbon dioxide), the selectivity of the process is very low. This is due to the eutectic phase behaviour of the aromatic mixture which effects a phase separation within the pores. The more volatile component, naphthalene, becomes impoverished in an outer zone and retreats, leaving a porous layer of crystallized phenanthrene behind. The formation of this layer increases the diffusional resistance of the naphthalene. A model has been proposed which is based on the assumption that the dissolution of both components takes place at different extraction fronts. Solubilities of mixtures and their diffusion coefficients in carbon dioxide were measured for mass transfer calculations. The diffusional resistance of the outer boundary layer and the resistance of the pores were determined. If the mixture dissolves near the surface of the cylinder, the mass transfer coefficient is strongly enhanced by free convection within the annular gap which is formed by the cylinder and the extraction vessel. This was observed when liquefied mixtures were extracted. During a first extraction period, liquefied mixtures dissolved from the surface of the cylinder because of the capillary transport of liquid and an increase in liquid volume by dissolved gas.

Characterization of silica glasses sintered under Cl2 ambients

Chlorine incorporated into silica glasses by sintering porous soot rods under Cl2/He atmosphere or by fabricating with plasma methods were found to be mostly as ≡SiCl, which gives rise to an optical absorption tail above ≂7.5 eV. The cross section of the optical absorption at ≂7.77 eV (160 nm) was found to be 1.14×1020 cm2. This value was almost the same as that of ≡SiCl in SiCl4 molecule in the gas phase. A minor fraction (10−3∼10−1) was found to be present as Cl2 molecule, which gives the absorption band at 3.8 eV.

Optical properties of silica glasses having O2 and Cl2 molecules

ABSTRACTOxygen or chlorine was incorporated into silica glasses by sintering porous soot rods under 02/He or C12/He atmosphere. In case of oxygen, the Schumann-Runge band of 02 molecule was found in VUV region. An absorption band at 4. 8eV having 1. 9eV emission was generated with irradiation of excimer laser. We proposed that such optical properties were due to 02 molecule trapped in glass because they were similar to photochemistry of 02 molecule in the gas phase which could be shown as:When silica glasses were fabricated under chlorine ambient, a minor fraction was found to be present as Cl2 molecule trapped in the glass, which gives the absorption band at 3.8eV.

Plastic deformation of porous axisymmetric bimetallic rods in rigid dies

Plastic deformation of porous axisymmetric bimetallic rods in rigid dies

Preparation and activity of carbonic anhydrase immobilized on porous silica beads and graphite rods

Techniques for the immobilization of bovine carbonic anhydrase (BCA) on porous silica beads and graphite are presented. Surface coverage on porous silica beads was found to be 1.5 x 10(-5) mmol BCA/m(2), and on graphite it was 1.7 x 10(-3) mmol BCA/m(2) nominal surface area. Greater than 97% (silica support) and 85% (graphite support) enzyme activity was maintained upon storage of the immobilized enzyme for 50 days in pH 8 buffer at 4 degrees C. After 500 days storage, the porous silica bead immobilized enzyme exhibited over 70% activity. Operational stability of the enzyme on silica at 23 degrees C and pH 8 was found to be 50% after 30 days. Catalytic activity expressed as an apparent second-order rate constant K'(Enz) for the hydrolysis of p-nitrophenyl acetate (p-NPA) catalyzed by BCA immobilized on silica beads and graphite at pH 8 and 25 degrees C is 2.6 x 10(2) and 5.6 x 10(2) M(-1)s(-1) respectively. The corresponding K(ENZ) value for the free enzyme is 9.1 x 10(2) M(-1)s(-1). Activity of the immobilized enzyme was found to vary with pH in such a manner that the active site pK, on the porous silica bead support is 6.75, and on graphite it is 7.41. Possible reasons for a microenvironmental influence on carbonic anhydrase pK(a), are discussed. Comparison with literature data shows that the enzyme surface coverage on silica beads reported here is superior to previously reported data on silica beads and polyacrylamide gels and is comparable to an organic matrix support. Shifts in BCA-active site pK(a) values with support material, a lack of pH dependent activity studies in the literature, and differing criteria for reporting enzyme activity complicate literature comparisons of activity; however, immobilized BCA reported here generally exhibits comparable or greater activity than previous reports for immobilized BCA.

Mass transfer for dissolving solids in supercritical carbon dioxide Part II: Resistance in the porous layer

The internal mass transfer resistance was measured by dissolving naphthalene from a porous insoluble rod in a stream of supercritical carbon dioxide. Initially the pores of the porous medium (sintered bronze) were filled with naphthalene. During dissolution the naphthalene surface retreats into the porous rod and the length of the diffusion path increases. The tortuosity factor for the porous material was determined from experimental data. The temperature was varied from 35 to 55 °C, the pressure from 118 to 226 bar and the mean pore diameter was either 8 or 20 μm. The results show that the tortuosity factor does not depend on the pressure and pore diameter. This result was to be expected since the mean free path of the molecules is much smaller than the pore diameter. The average tortuosity factor, however, decreased with increase of temperature. From this temperature dependence surface diffusion of the solute absorbed on the pore wall is concluded to take place and thereby to contribute to the observed overall rate of mass transfer.

Wind-directed Pheromone Trap for Drone Honey Bees (Hymenoptera: Apidae)

A portable pheromone-trap system was developed for monitoring drone honey bee, Apis mellifera L., populations. The wind-directed system included a white nylon net, pheromone lure (porous polyethylene rod treated with synthetic E -9-oxo-2-decenoic acid [9-ODA]), 6.1-m support, and sample bag holder. The trapping site and anemotactic flight behavior of drones affected capture rates. Traps baited with 5 or 10 mg synthetic 9-ODA routinely captured 150–300 drones per 3 min during the 90-min periods of peak flight. Nonreusable lure components, including 5 mg synthetic 9-ODA, cost approximately one-fourth of the minimum price for two virgin queens. This trap system has potential as a survey and management tool for Africanized honey bee suppression programs and for control of local drone populations by queen breeders.