Small Glass Beads Research Articles

Enhancement by acetylene of the decomposition of nitric oxide in soil

The acetylene inhibition technique is a widely used method to measure denitrification rates in soil. This technique is based on the inhibition of the N 2O reductase with high concentrations of acetylene (about 10%). We tested possible artifacts created by using this technique under oxic conditions. Parts per billion concentrations of NO, an intermediate of the denitrification, were converted to NO 2 within seconds when both O 2 and acetylene were present. There was no conversion of NO under anoxic conditions or with acetylene concentrations < 0.1%. Propyne and 1-butyne also caused the conversion of NO to NO 2, although to a lesser extent. In the absence of soil, the reaction stopped when an equilibrium between NO and NO 2 was reached. The NO 2 concentration at equilibrium increased with increasing temperature and with increasing acetylene concentrations up to 1%. Addition of small glass beads, quartz sand or sea sand also increased the NO 2 concentration. We assume that acetylene (> 0.1%), especially in the presence of surfaces, stimulated the chemical reaction 2NO + O 2 → 2NO 2. In the presence of soil, NO 2 accumulated only transiently and was then taken up by the soil. Use of 15NO resulted in 50% recovery of the label in the nitrate and nitrite fractions of the soil, indicating that NO 2 was probably chemically converted to nitrate, nitrite and other N compounds. The NO decomposition in the presence of acetylene was observed in all 14 soils tested and occurred in autoclaved and non-sterile soil with the same rate. The rate of NO decomposition increased with increasing acetylene concentration and with an increasing amount of soil, and decreased with increasing soil water content. In general, acetylene (> 0.1%) enhanced the decomposition of NO in soil by factors of 5–557.

Highly sensitive gas chromatographic analysis of ethanol in whole blood, serum, urine, and fecal supernatants by the direct injection method

A highly sensitive, reproducible, and rapid gas chromatographic method for ethanol determination in various biological specimens (human whole blood, serum, urine, and fecal supernatants) was developed. The method involves direct injection of the biological specimen into the gas chromatograph, without any pretreatment. Contamination of the gas chromatographic column with nonvolatile material was prevented by the use of a glass liner in the injector. This liner, which acted as a precolumn, was partly filled with small glass beads. Injection was performed in between the glass beads. More than 50 injections of the various biological specimens could be done before the liner had to be replaced by a new one. This injection technique between glass beads allows direct injection of large sample volumes up to 10 microL without disturbing the gas chromatographic separation. Injection of these large sample volumes made the method very sensitive. The detection limit for ethanol amounted to 0.1 mg/L (2 mumol/L) when using an injection volume of 5 microL. Attention has also been paid to simultaneously monitoring ethanol, methanol, acetaldehyde, and acetone in blood and urine of control subjects.

Contact Force Distribution Beneath a Three-Dimensional Granular Pile

A simple elasto-optical method has been used to measure the normal force distribution under three-dimensional conical piles, for a range of granular materials. The method is based on the measurement of contact diameters of a monolayer of steel balls between the pile and an elastomeric substrate. Experiments on sandpiles confirm the existence of counterintuitive dips in the pressure at the centre of the pile, as reported previously in the literature; the dips were also found in piles of small (ca. 180 pm diameter) glass beads. They were suppressed, however, on increasing the glass bead diameter by a factor of ca. 3. Variations in surface roughness were found to have little effect on the pressure profiles. The probability density function for the normal contact force was approximately negative exponential in form.

Sequential Atomic Absorption Spectrophotometric Determination of Arsenite–Cyanide and Carbonate–Cyanide Mixtures Using an On-Line Preconcentration Technique in a Flow System

Binary mixtures containing arsenite with cyanide and carbonate with cyanide were analyzed using atomic absorption spectrometry (AAS) in a flow system. The two anions present in a mixture were precipitated by a stream of silver ions and left to preconcentrate for two minutes in a Tygon tube containing small glass beads; then a solvent (acid solution) was passed which dissolved the precipitate other than silver cyanide, followed by an ammonia solution which dissolved the silver cyanide precipitate. The method is simple and precise and the throughput is ∼15 samples/hr.

The Influence of Boundaries on the Volumetric Behavior of Solid and Hollow Cylindrical Specimens of Glass Beads

Laboratory shear tests were conducted on moderately dense assemblies of large and small glass beads in both solid and hollow cylindrical triaxial devices using either stress-controlled or strain-controlled lateral boundaries. The specimens were sheared in triaxial compression and extension, maintaining the mean stress constant, and volume strains were monitored. The results indicated that the mold used in preparing the specimen created a strong but localized ordering of particles at the boundary and that this type of initial fabric had an important effect on the volumetric behavior of the hollow cylinder specimens. There were also indications that the strain-controlled and the stress-controlled boundaries produced significantly different volume strains at the initial stage of shearing and that increasing the degree of strain-control decreased the amount of initial contraction. In order to compliment these observations, additional triaxial compression and extension tests were carried out with a series of solid cylindrical specimens of different diameters using the small glass bead assembly. The mean stress was again fixed and care was taken to eliminate friction at the top and bottom boundaries. In triaxial extension, the smaller diameter specimens exhibited densification greater than that of the larger diameter specimens. In triaxial compression, the volume change was approximately the same for all diameter specimens. These results support the presence of an initial local anisotropy associated with the mold and indicate that specimens should be at least 150 particle diameters in thickness in order that this anisotropy be negligible.

A laser interferometer for sub-nanometre measurements in the cochlea

A modification of a light microscope is described here which allows measurement of nanometre movements along the optical axis of the microscope. The light path is reflected off 10-μm-diametre small glass beads which are individually imaged with the microscope objective. The interferometer is under computer control to allow it to remain in quadrature and so maximise sensitivity. The algorithm is described. Although the techniques are applied to detection of movements of the cochlear partition, they can be used to measure sub-micron movements of any reflecting structures accessible to microscopy.

On the application of plasma pulses generated by electromagnetic and electrothermal launchers for surface treatment

Various types of electrothermal and electromagnetic launchers have been developed to simulate micrometeoroid and space debris impacts. The flow of hot and dense high-velocity plasma generated in these launchers has been used to accelerate small glass beads. The targets have been shielded from the plasma in prior work. This paper presents the application of these plasma pulse accelerators to investigate the direct influence of the fast, high density plasma on material surfaces. The plasma has been supplemented with different materials to achieve coatings with specific properties. Relations involving changes in material properties have been investigated. Electromagnetic and electrothermal launchers can be used to generate short high-energy plasma pulses. The interaction of such plasma pulses with metallic surfaces generates very hard surface layers, which are very resistant to friction corrosion.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An archaeological investigation of Sira Bay, Aden, Republic of Yemen

Archaeological excavations at Guishan in the southern end of Taiwan have recovered more than a hundred glass beads dating to mid-1st millennium CE. This research investigates the exchange of glass beads between Guishan, eastern Taiwan and Southeast Asia, by analysing the styles, chemical composition and microstructure of 64 glass beads from Guishan, using SEM-EDS, EPMA and LA-ICP-MS. The findings suggest that beads with an m-Na-Al glass and v-Na-Ca composition are the most common, supporting evidence for bead exchange between Guishan and Southeast Asia, originated in South Asia and Western Asia. Furthermore, most m-Na-Al glasses were coloured by copper, and different types of copper-based additives may have been used for different colours, indicating the beads may be derived from multiple production centres or workshops via Southeast Asia. Conversely, the glass bead compositions suggest that glass bead exchange between other contemporary sites in Taiwan is less evident at Guishan, except for one type of yellow glass bead containing bone ash which is different. This bone-ash containing yellow glass at Guishan is firstly identified in Iron Age Taiwan as well as around the South China Sea region. Its counterparts are also found from archaeological sites in southeastern and coastal eastern Taiwan, which might indicate small scale glass bead exchange. This evidence together suggests a dynamic glass bead exchange network between Guishan, eastern Taiwan, Southeast Asia and beyond.

Reversible axial segregation of binary mixtures of granular materials.

Measurements of axial segregation of binary mixtures of glass beads having different diameters in a rotating horizontal cylinder are reported. For rotation speeds of \ensuremath{\sim}15 rpm a mixed state quickly (within a few minutes) segregates into sharp bands of alternating large and small glass beads along the axis of rotation. Decreasing the rotation speed to \ensuremath{\sim}5 rpm causes the bands to disappear, restoring the mixed state. The process is reversible upon increasing the rotation rate, though the exact location and width of the bands vary from run to run. The axial segregation phenomena are analyzed in terms of a diffusion equation where the effective diffusion coefficient is the difference between segregating drift and normal Fickian diffusion.

The effect of fly-ash particulates on the atmospheric corrosion of zinc and mild steel

The atmospheric corrosion of zinc and mild steel was investigated in the laboratory at relative humidities of 65%, 80% and 90% in unpolluted atmospheres and at a relative humidity of 80% in atmospheres containing HCl and SO 2 pollutant gases. In order to investigate the effect of atmospheric particulates on corrosion rates, metal samples were contaminated with three coal and three oil fly-ashes from different industrial sources. Control specimens were either uncontaminated or contaminated with small glass beads of similar size to the fly-ashes < 45 μm. In unpolluted atmospheres, particulate contamination increased corrosion in approximate proportion to the quantity of leachable ionic species present in the fly-ash. Additionally, glass beads slightly increased corrosion rates probably due to differential aeration effects and an increased local time-of-wetness in the vicinity of the beads. In polluted environments, the corrosion rates of the specimens increased and the additional effect of fly-ash contamination on the corrosion rates was consequently decreased in proportion to the presentation rate of pollutant. There was no significant additional increase in corrosion rates with SO 2 pollutant and fly-ash contamination, indicating that effects due to catalytic oxidation of SO 2 to sulphuric acid or sulphates were not significant. Overall, this study provides strong evidence that the atmospheric corrosion rates of metals are dependent on the conductance of the thin-film surface electrolyte and that the first-order effect of contaminant particles is to increase solution conductance and hence corrosion rates.

Improved oral absorption of a poorly water-soluble drug, HO-221, by wet-bead milling producing particles in submicron region.

N-[[[4-(5-Bromo-2-pyrimidinyloxy)-3-chlorophenyl]amino]carbonyl]-2 -nitrobenzamide (HO-221) is being developed as an anticancer agent with a novel mode of action. HO-221 shows poor oral absorption and is only slightly soluble in water (0.055 micrograms/ml at 37 degrees C). In this study, it was shown that the reduction in particle size of HO-221 to the submicron region (0.453 microm, mean by volume) could be achieved by a wet milling in a decaglycerin monolaurate aqueous solution with small glass beads. The wet milling suspension obtained showed improved dissolution rate and oral absorption in rats. A solid dosage form could also be made from that suspension with addition of sucrose palmitate which prevented aggregation caused by the hydrophobic interaction. The solid dosage form thus obtained showed twice as much oral absorption in dogs as the preparation made by dry milling.

Dissemination and fractionation of projectile materials in the impact melts from Wabar Crater, Saudi Arabia

Abstract— We have analyzed small, ballistically dispersed melt samples in the form of aerodynamically shaped spheres, dumbbells, teardrops, etc., from Wabar Crater, Saudi Arabia, and have compared these to our previous study of the more massive, black and white melt specimens. The smaller melt samples differ from the more massive melts in that they are petrographically and chemically more homogeneous, possess fewer, more diffuse schlieren and contain much less clastic detritus. These observations suggest higher peak temperatures for the smaller melt samples than for the massive black and white melts which represent Wabar's major melt‐zone.Analyses of the Wabar and Nejed (paired with Wabar) meteorites permit detailed comparison of the unaltered projectile with impactor residues in the melts. Siderophile element concentrations indicate that the small glass beads commonly contain &gt; 10% meteoritic component, compared to &lt; 5% for the massive black and white melts. One glass bead was found to contain ∼ 17% meteoritic component. Based on models for melt production during cratering, we deduce that more meteoritic material was mixed with the upper stratigraphic horizons of Wabar's melt zone than with the lower parts. Siderophile elements in all Wabar melt specimens are fractionated relative to the Wabar‐Nejed meteorite and have Fe/Ni ratios up to ∼ 1.8 times that of Wabar‐Nejed for the most siderophile element‐rich glasses. The abundance sequence of siderophiles in the melts relative to the projectile is Fe ≅ Co &gt; Ni ≅ Ir ≅ As » Au. Although this sequence seems incompatible with simple vapor fractionation of either elements or oxides, we believe that a complex vapor fractionation process most likely produced the observed siderophile element abundances.Our sample suite should be representative of all materials found in and around the Wabar structure, and we conclude that substantial quantities of the projectile were lost to the atmosphere, most likely as vapor. No fractionation of lithophile elements is observed in the glasses relative to the target rocks. Although fractionation of the impactor must have occurred prior to intimate mixing of projectile and target, details of the actual fractionation mechanism(s) remain poorly understood. The results of this study indicate that caution is necessary when attempting to define impactor types and masses from compositional data for impact melts from other craters.

Stereotaxic lesions of the hippocampus in monkeys: determination of surgical coordinates and analysis of lesions using magnetic resonance imaging

A technique is described for producing accurate stereotaxic lesions of the hippocampus in monkeys. This technique overcomes the problem that the size and shape of the brain can vary considerably from monkey to monkey. Magnetic resonance imaging (MRI) is used to create an individual brain atlas for each monkey. The atlas is then used to derive coordinates for making stereotaxic radio frequency lesions of the hippocampus. There are two key features of this procedure. First, a specially-designed, acrylic, stereotaxic headholder was constructed that could be used safely with the MR magnet. Second, small glass beads, anchored to the skull of the monkey, served as common landmarks from which lesion coordinates were determined in the MR images and then again in neurosurgery. MRI techniques are also described for determining the extent of tissue damage postoperatively. This technique could also prove useful in other areas of neuroscience research that depend on accurate stereotaxic placement of electrodes (e.g., electrophysiological studies and neuroanatomic tracing studies).

Wind tunnel investigations of roofs on fuel-tanks in connection with rain-water contamination

An undesirable high water content was observed in fuel tanks with floating covers. At low cover levels and at higher wind velocities a significant number of raindrops hit the inner wall of the tank and the rain water ran down through the small openings in the sealing into the fuel. The model investigations in the wind tunnel had the aim to determine the diameter of the smallest possible auxiliary roof which give sufficient rainshelter to the inner side under various rainfall conditions. The raindrops were simulated with small glass-beads with a mean diameter of 0.1 mm. A special bead-spraying device was used to ensure a homogeneous distribution in the test area. The number of glass beads falling into the tank was investigated for several rainfall angles and with different cover levels. After these tests the pressure distribution above and under the roof model was measured to obtain the pressure coefficients necessary for calculating the additional wind loads affecting the construction.

High-resolution data processing for phase-Doppler measurements in a complex two-phase flow

Measurements of the particle size and velocity in a gas-solid two-phase flow using the phase-Doppler technique based on transient recorder data processing and the cross-spectral density (CSD) function are improved in accuracy by introducing new complex interpolation functions to the discrete frequency lines. The improvements of the accuracy for size and velocity measurements are additionally based on the use of an external electronic unit, which is allowed to trigger the transient recorder near the peak of the envelope of the band-pass filtered bursts. This procedure could improve the signal-to-noise ratio of the processed part of the signal and hence the accuracy and data rate. A simultaneous measurement of the gas velocity is achieved by seeding the flow with small spherical glass beads which have the same refractive index as the dispersed phase particles. The identification of signals from these seeding particles-with a diameter less than 4 mu m-is based on the phase between the two signals.

Analysis of Dictyostelium mucoroides Macrocysts by Using a Simple Breakage and Fractionation Procedure

A method is described for the breakage and fractionation of Dictyostelium macrocysts. It involves vortexing with large glass beads to disrupt the macrocyst wall followed by differential low-speed centrifugation. It yields fractions containing purified wall material and intact endocytes. The endocytes can themselves be disrupted by using smaller glass beads.

The effect of poloxamer 188 on the rate of in vitro thrombolysis mediated by t-PA and streptokinase

Poloxamer 188 is a nonionic block copolymer surfactant which is undergoing clinical trials as a haemorheologic agent. A simulated thrombus preparation was designed to evaluate its effects on fibrinolysis and thrombolysis under flow conditions similar to those which might be encountered within an occlusive coronary thrombus. 125I labelled human fibrinogen (20 μCi/ml) was mixed with platelet-poor citrated plasma, recalcified, and allowed to clot for 1 h at 37°C in a tuberculin syringe filled with small glass beads. This produced a fibrin clot permeated with microscopic channels simulating those of a recently formed thrombus. After washing the plasma bead clots for 30 min with normal saline, heparinised blood containing tissue plasminogen activator (t-PA) or streptokinase, with and without 0.1% poloxamer 188, was added to the columns and rates of flow and elution of 12 125-fibrin degradation products were measured. Poloxamer 188 alone had no ability to lyse fibrin. However, it increased the rate at which t-PA or streptokinase caused lysis of simulated thrombi by as much as 4-fold. This accelerated lysis was associated with up to a 20-fold increase in flow through the thrombus and with elution of larger fragments of fibrin, but not with increased plasmin activity as assessed with a colourimetric substrate. Consequently, poloxamer 188 appeared to accelerate thrombolysis without directly affecting any of the components of the fibrinolytic system. We propose that the ability of poloxamer 188 to modulate thrombolysis is due to its haemorheologic properties.

Determination of bilayer membrane bending stiffness by tether formation from giant, thin-walled vesicles

The curvature elastic modulus (bending stiffness) of stearoyloleoyl phosphatidylcholine (SOPC) bilayer membrane is determined from membrane tether formation experiments. R. E. Waugh and R. M. Hochmuth 1987. Biophys. J. 52:391-400) have shown that the radius of a bilayer cylinder (tether) is inversely related to the force supported along its axis. The coefficient that relates the axial force on the tether to the tether radius is the membrane bending stiffness. Thus, the bending stiffness can be calculated directly from measurements of the tether radius as a function of force. Giant (10-50-microns diam) thin-walled vesicles were aspirated into a micropipette and a tether was pulled out of the surface by gravitational forces on small glass beads that had adhered to the vesicle surface. Because the vesicle keeps constant surface area and volume, formation of the tether requires displacement of material from the projection of the vesicle in the pipette. Tethers can be made to grow longer or shorter or to maintain equilibrium by adjusting the aspiration pressure in the micropipette at constant tether force. The ratio of the change in the length of the tether to the change in the projection length is proportional to the ratio of the pipette radius to the tether radius. Thus, knowing the density and diameter of the glass beads and measuring the displacement of the projection as a function of tether length, independent determinations of the force on the tether and the tether radius were obtained. The bending stiffness for an SOPC bilayer obtained from these data is approximately 2.0 x 10(-12) dyn cm, for tether radii in the range of 20-100 nm. An equilibrium relationship between pressure and tether force is derived which closely matches experimental observation.

9] Platelet interaction with artificial surfaces: in vitro evaluation

This chapter describes the in vitro evaluation of platelet interaction with artificial surfaces. The glass-bead-column method allows surface-induced platelet adhesion, aggregation, and secretion to be examined for any material that can be prepared in a bead form or coated onto glass beads by deposition from solution. Bead columns are exposed to flowing whole blood, anticoagulated with sodium citrate, and maintained at 37° temperature. Platelet retention is determined by comparing the number of platelets entering and leaving the columns. Platelet secretion is assayed by measuring extracellular serotonin and β -thromboglobulin levels in the effluent blood. Platelet lysis is monitored by measuring extracellular lactate dehydrogenase levels, and the relative effects of adhesion and aggregation are assessed by scanning electron microscopy. The passage of blood through columns packed with small polymer-coated glass beads is a severe test of platelet–surface compatibility because of the large surface area to blood volume ratio. A 2-mL column packed with 0.3-mm-diameter beads provides ∼300 cm 2 of surface area, which, at a point in time, is exposed to ∼0.5 mL of blood. This is equivalent to spreading a film of blood 17 pm thick on a flat surface and represents approximately one-tenth of the surface-to-volume ratio of a capillary bed.

COMPARATIVE RESPONSES OF FERAL AND LABORATORY TRICHOGRAMMA SPP. (HYMENOPTERA: TRICHOGRAMMATIDAE) TO HELIOTHIS SPP. (LEPIDOPTERA: NOCTUIDAE) MOTH SCALES AND INERT PARTICLES

A laboratory assay of the klinokinetic response of Trichogramma spp. to scales of Heliothis virescens (F.) and Heliothis zea (Boddie) was investigated. The assay indicated significant behavioral response to materials similar in size to lepidopteran scales (small glass beads, cotton fibers); however, response to these materials was significantly less than response to H. virescens scales. The assay did not distinguish any difference in response to H. zea scales betewen naturally occurring and laboratory-bred Trichogramma exiguum Pinto and Platner. Physiological status (freshly emerged, virgin vs. 3–4 day-old, mated) of the H. zea moths from which scales originated affected scale response, but anatomical origin (abdominal tip vs. abdominal venter vs. wing) of host scales did not.