Small Samples Of Material Research Articles

Spot welder for making small electrical contacts

A capacitive-discharge spot welder is described which is primarily intended for making electrical connections between small (<25–150 μm diameter) wires and samples of metallic materials, although it can be used in many applications where miniature welds must be made. It has been particularly useful in allowing low resistance (several mΩ) contacts to be created on samples of rare earth and actinide intermetallic compounds which are highly resistant to soldering. The device has a minimum time constant of about 25 μs and can deliver a maximum of between 700 μJ and 400 mJ of energy to the weld region, depending on the resistance of the latter. A suitable electrode holder is also described, and considerations for choosing the electrode materials, selecting the contact wires, preparing the sample, and creating a weld are discussed.

On the cultivation of free-living marine and estuarine nematodes

Although a large body of literature exists on the systematics and ecology of free-living marine and brackish-water nematodes, key questions on the nature and magnitude of interactions between nematodes and other organisms in the benthos remain unanswered. Relatively few authors have investigated live nematodes in food web studies or in experiments dealing with the nematodes’ response to a varying environment. It is mainly for the latter purpose that attempts have been made to maintain, rear and cultivate selected species. This paper describes the methodology used for the maintenance, rearing, and eventual permanent agnotobiotic cultivation of a variety of estuarine nematodes. Spot plates, where small samples of sediment or macrophyte material are inoculated on a sloppy agar layer, have been used for the purpose of maintenance and initial cultivation. Those species that reproduce on spot plates are then selected for monospecific cultivation on agar layers with different nutrient enrichments and with micro-organisms cotransferred from the spot plates as food. Mixtures of bacto and nutrient agar prepared in artificial seawater were specifically suitable for the xenic cultivation of nine bacterivorous and, when supplied with Erdschreiber nutrients, two algivorous/bacterivorous nematode species. Up to three generations of five other nematode species have been reared under laboratory conditions, and several more were kept alive and active for variable periods of time on agar. Generation times observed on spot plates forAdoncholaimus fuscus andOncholaimus oxyuris were substantially shorter than previously published estimates and suggest a correspondingly higher predatory and scavenging potency for these and related enoplids. A procedure for the long-term storage of nematodes at −80°C with glycerol as a cryoprotectant was successfully used forDiplolaimella dievengatensis, Panagrolaimus sp. 1, andPellioditis marina, but not forDiplolaimelloides meyli. The authors have also summarized the existing literature on the cultivation of marine and brackish-water nematodes. Continuous cultivation appears to have been successful mainly for Aufwuchs and epiphytic nematodes; only few sediment-dwellers have been established in permanent culture. Of only just over 30 species that have ever been cultivated, more than half belong to one family (Monhysteridae) and three are Rhabditida, an order poorly represented in the marine environment. Four species have been grown in monoxenic and one in axenic culture, the latter though with limited success. It is concluded that our understanding of the basic nutritional requirements of marine nematodes is as yet insufficient, and that the culture techniques which have so far mainly deployed agar or liquid substrates, while being suitable for the cultivation of Aufwuchs and epiphytic nematodes, do not accurately enough mimic gradients specific of the natural habitat of many sediment-dwellers.

Neutronics Analysis of the International Fusion Materials Irradiation Facility High-Flux Test Volume

The purpose of the International Fusion Materials Irradiation Facility (IFMIF) is to provide irradiation conditions of a typical deuterium-tritium (D-T) fusion reactor for small material samples, but with higher irradiation levels. An extensive code and data development has been performed, allowing a comprehensive neutronic analysis of the high-flux test volume. New data evaluations for neutron interactions and responses at high energies (20 to 50 MeV) were performed and processed, and a Monte Carlo neutron source model for the Li(d,xn) reaction was developed for use with the MCNP neutron transport code.The neutron flux density was found to be >1014 n·cm-2·s-1 throughout the anticipated high-flux test volume with a high-energy fraction (>14 MeV) of ~20%. The available test volume with >20 dpa/full-power year in iron was found to be 550 ± 180 cm3. This uncertainty is due almost entirely to the uncertainty in the total neutron yield. Hydrogen and helium production rates were calculated and a helium/dpa ratio between 10 and 12 appm/dpa was found, which is similar to that found in a D-T fusion reactor. IFMIF was found to provide an adequate environment for the simulation of D-T fusion reactors, but more work is required to extend and improve the current data and tools.

Simultaneous Thermal Diffusivity and Thermal Conductivity Measurements of Mantle Materials up to 10GPa.

A one-dimensional transient (pulse) method for thermophysical property measurements has been applied to small samples of mantle materials in a uniaxial split-sphere high-pressure apparatus. Thermal diffusivity and thermal conductivity of fused silica and garnet have been measured. At pressures up to 8. 3 GPa the thermal conductivity and the thermal diffusivity of fused silica decrease with increasing pressure. For a principal mantle mineral, garnet, the pressure derivatives of thermal conductivity and the thermal diffusivity are positive: they are 2 per cent of increase a GPa at room temperature over 5 GPa.

Thermal decomposition studies of energetic materials using confined rapid thermolysis / FTIR spectroscopy

An experimental setup for performing rapid thermolysis studies of small samples of energetic materials is described. In this setup, about 8 μL of a liquid sample or about 2 mg of a solid sample is heated at rates exceeding 1500 K/s to a set temperature where decomposition occurs. The rapid heating is achieved as a result of confining the sample between two closely spaced isothermal surfaces. The gaseous decomposition products depart from the confined space through a rectangular slit into the region of detection. The evolved gases are quantified using FTIR absorption spectroscopy by accounting for the instrument line shape. To illustrate the use of this setup, the thermolysis behaviors of three different energetic materials are examined. These materials include HMX, RDX, and HAN, all of which are considered as highly energetic propellant ingredients. The results obtained in this study of the temporal evolution of species concentrations from these ingredients are in reasonably close agreement with results available in the literature.

An Apparatus to Measure the Relaxation of Crop Samples following Compression

An apparatus has been constructed to obtain a fundamental understanding of the relaxation, after compression, of small samples of straw or other plant material, and to allow measurement of the influence of material properties such as age and moisture content. The device has been used to apply pressures of up to 150 MPa to straw samples of 5 mm diameter and typically of 0·3 to 0·5 mm thickness and, after the load was removed, to measure the recovery or change in thickness with time to an accuracy of better than 0·01 mm. The accuracy of the measurement system was confirmed by the consistent results obtained when a steel reference plate was used in place of the sample. In over 50 tests carried out on straw samples to test the potential of the device, moisture content was found to have a greater effect on relaxation than did the age of the material or the position on the plant from which the sample was taken.

Correlation of pyrolysis mass spectrometry and outer membrane protein profiles of Clostridium difficile.

To perform pyrolysis mass spectrometry (PyMS), a small sample of colony material is thermally degraded in a vacuum, thus yielding mixed volatile products whose composition reflects that of the organism. Mass spectrometric analysis of the products yields spectra that can be compared statistically; consequently, fine differences in cell composition can be detected [1]. Typing by PyMS is rapid, inexpensive, automated, and non-species-specific and has a high throughput (100-150 isolates per day) [2]. It has been used successfully to type isolates recovered during nosocomial outbreaks of Clostridium difficile infection [3] and now is a routine typing method for this organism in the United Kingdom. However, PyMS is a fingerprinting method; no permanent type designation has been assigned, and variations between different analytical batches prevent interbatch comparisons of spectra. This difficulty in routine typing of C. difficile is overcome by including representative isolates from any outbreak with further batches of isolates recovered in the same hospital. Our aim, for two reasons, was to develop the capability to predict C. difficile serotypes based on the scheme of Delmee et al. [4] from PyMS data. First, these serotypes correlate well with pathogenicity; isolates of groups G and H are commonly associated with nosocomial outbreaks, and serogroup F strains do not produce toxin A [5]. Furthermore, the results of outer membrane protein (OMP) profiles [6] and SDS-PAGE analysis of whole-cell protein [7] correlated well for these serogroups, thus indicating an underlying subdivision of the species that affects many of their properties. Second, assignment of a predicted serotype would, in effect, produce a permanent type designation for isolates. Nosocomial outbreaks of cross-infection due to most organisms tend to be of limited duration and scope, and the advantages of permanent type designations in these outbreaks are minimal. However, those investigators involved in the analysis of community outbreaks rightly criticize fingerprinting methods for their inability to assign the permanent type designations that are required for much broader temporal and geographic surveillance. Although permanent type designations

Calculation and Benchmarking of an Azimuthal Pressure Vessel Neutron Fluence Distribution Using the Boxer Code and Scraping Experiments

The light water reactor BOXER code was used to determine the fast azimuthal neutron fluence distribution at the inner surface of the reactor pressure vessel after the tenth cycle of a pressurized water reactor (PWR). Using a cross-section library in 45 groups, fixed-source calculations in transport theory and x-y geometry were carried out to determine the fast azimuthal neutron flux distribution at the inner surface of the pressure vessel for four different cycles. From these results, the fast azimuthal neutron fluence after the tenth cycle was estimated and compared with the results obtained from scraping test experiments. In these experiments, small samples of material were taken from the inner surface of the pressure vessel. The fast neutron fluence was then determined form the measured activity of the samples. Comparing the BOXER and scraping test results have maximal differences of 15%, which is very good, considering the factor of 10{sup 3} neutron attenuation between the reactor core and the pressure vessel. To compare the BOXER results with an independent code, the 21st cycle of the PWR was also calculated with the TWODANT two-dimensional transport code, using the same group structure and cross-section library. Deviations in the fast azimuthal flux distribution weremore » found to be <3%, which verifies the accuracy of the BOXER results.« less

RADIOCARBON DATES FOR BEESWAX FIGURES IN THE PREHISTORIC ROCK ART OF NORTHERN AUSTRALIA

Accelerator mass spectrometry radiocarbon ages have been taken for a test suite of small samples of material removed from some of the ‘beeswax’art figures found in rock shelters in northern Australia. The results indicate that we can reliably date this unique form of rock art with no noticeable damage. We had not expected to find figures of any great antiquity, and so we were surprised to find that the ages obtained spanned the time period from the recent past to about 4000 BP.

A Method for the Measurement of the Emanation Factor for 222Rn in Small Samples of Porous Materials

A Method for the Measurement of the Emanation Factor for 222Rn in Small Samples of Porous Materials

Determination of ultrasonic attenuation in small samples of solid material by scanning acoustic microscopy with phase contrast

The attenuation of solid material or droplets of viscous liquids deposited on planar substrates is measured in the frequency regime from 300 MHz to 1.2 GHz by scanning acoustic microscopy with phase contrast. The observed spatial variations of the phases and amplitudes of the ultrasonic waves reflected from the objects contain sufficient information to determine the attenuation and velocity of ultrasonic waves in acoustically isotropic samples of minimal thickness about 1 μm and lateral extension down to 10 μm. The basic principles are discussed and an approximate treatment is presented together with typical results.

Development of an enzyme immunoassay for the determination of tobacco alkaloids in plant material

A competitive enzyme immunoassay (EIA), using anti-nornicotine antibodies is described. The specificity of these antibodies was checked by a high pressure liquid chromotographic (HPLC) procedure. Following purification, the alkaloid extracts were simultaneously analysed by EIA and HPLC and similar results were obtained. The high sensitivity of EIA and its good specificity toward the major tobacco alkaloids enabled us to perform analysis on crude extracts prepared from very small samples (ca. 1 mg dry weight) of plant material. The method can therefore be applied to the localization of alkaloids in Nicotiana plants and cell suspensions.

Demagnetization effect in strip-line cavity measurements

Stripline resonant cavities are useful for measuring the effective high-frequency permeability of small samples of high-permeability thin-film materials. However, in such an open magnetic circuit device, the effect of sample demagnetization can seriously degrade measurement accuracy unless it is recognized and corrected. Measurements with accuracy degraded by sample demagnetization are readily identified using the demagnetization effect map that is given. Approximate correction of these measurements can be accomplished by using the demagnetization correction equation and estimated demagnetization factor for the stripline resonant cavity configuration that is shown. The accuracy of this demagnetization correction is limited by the use of the approximate demagnetization factor.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Computer-controlled mechanical testing machine for small samples of biological viscoelastic materials

Time dependency in the mechanical properties of viscoelastic materials means that a variety of tests is often required to fully characterize their properties. Computer control is the best way of controlling loads and displacements and the rate at which they are applied, as well as recording and analysing the data produced. This paper describes apparatus for measuring the viscoelastic properties of articular cartilage in compression which is readily adaptable to any small sample in which accurate strain measurements require small, carefully controlled displacements. An IBM-type microcomputer is used to control a stepper motor driving a ball screw with a positional accuracy of about 1 μm.

A simple and sensitive bioassay for the detection of toxic materials using a unicellular green alga.

A simple assay for phytotoxicity, using small scale cultures of Chlorella vulgaris, is described. Growth after 3 days' incubation in 0.5 cm(3) medium is assessed by DMSO-acetone extraction and chlorophyll determination. The method is sensitive enough to detect phytotoxicity in small samples of material and this is illustrated by the inhibitory effects of microgram additions of copper, cadmium and zinc.

Dynamic modulus measurements made with the dynamic mechanical thermal analyzer

Polymer Laboratories' dynamic mechanical thermal analyzer (DTMA) measures the dynamic Young's or shear modulus and loss factor of viscoelastic materials. The DMTA infers the modulus and loss factor by measuring the response of a small sample to forced vibrations in a small material sample. An optimal sample geometry is selected for a given Young's modulus range by considering effects such as thermal stress, shear deflection in short beams, and system compliance. The goal is to minimize these combined errors in the dynamic Young's modulus and loss factor measurement over the full madulus range. As a result of this analysis recommended DMTA test procedures are presented.

Sensitivity analysis of Polymer Laboratories' dynamic mechanical thermal analyzer

Polymer Laboratories' dynamic mechanical thermal analyzer (DTMA) measures the dynamic Young's or shear modulus and loss factor of viscoelastic materials. The DMTA infers the modulus and loss factor by measuring the response of a small sample to forced vibrations in a small material sample. An analysis of the parameters affecting the DMTA dynamic modulus and loss factor data is presented. Test results are affected by errors in the input parameters or by violating the assumptions leading to the solution. The extent to which either error affects the test results is quantified. As a result of this analysis, recommended DMTA test procedures are presented.

Organoleads in the environment: A review

The automobile and its use have been proposed as major sources of environmental organolead compounds. However, confirmation of this proposition was not possible until analytical technology evolved to give sufficient sensitivity to detect small quantities of lead species in small samples of environmental materials. It was further hypothesized that various biochemical pathways could convert inorganic lead ion to organolead species, a proposal which has been examined by several groups over many years. Once it was unequivocally established that organolead species can occur in the environment as a result of anthropogenic activity or naturally occurring biotic or abiotic processes, our group and others have examined the possible and likely biochemical effects associated with the environmental processes of organolead species. Research in this area has focused on examining the interactions of certain algae with a variety of organolead species. This paper discusses the evolution of environmental organolead biogeochemical research over the past 15 years.

Electronic system for the measurement of flow resistance

A measurement system has been developed that can determine flow resistances quickly and accurately and can be used to complement acoustical measurements on the same samples. The use of electronic components permits measurements to be made 20–50 times faster than with the commonly used Leonard apparatus. Variable-capacitance pressure transducers are used to measure pressure differences across both the test sample and a laminar flow element with known flow resistance (these two in series): For steady nonpulsating flow, the ratio of flow resistances equals the ratio of measured pressure differences. The rate of air flow through the sample is adjusted using a mass flow controller; flows of 10−3–1 cm3 s−1 can be controlled to better than 1%. Flow resistances between 1 and 105 g cm−4 s−1 can be determined with an accuracy of better than 1.6%. The corresponding range of flow resistivities of porous materials that can be determined with the present sample holder is 1–106 cgs-rayl cm−1. Initial measurements have been made using small circular orifices and samples of porous material.

The measurement of absorption coefficient and acoustic impedance using spherical waves and a transfer function method

The normal‐incidence absorption coefficient (or complex impedance) of an acoustical material is usually measured in a standing wave tube using plane wave excitation. In order to obtain valid high‐frequency data, a tube with a small cross section is required. But, quite often, the absorptive properties of the small sample of material that is tested are not representative of those of the larger sample from which it has been taken. An engineering method has been described [M. A. Nobile, Proc. NOISE‐CON '87, Penn State University, 8–10 June 1987, pp. 611–616] that shows that large samples of materials (or outdoor ground surfaces) can be evaluated using spherical waves in a hemi‐anechoic environment. As with the standing‐wave tube method (per ASTM E‐1050), this new method utilizes random noise excitation and computes the transfer function between two closely spaced microphones. The accuracy is limited primarily by diffraction from the edges of the finite sample, which is not taken into account. This paper will address the theoretical aspects of the problem and present some recent experimental results.