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The dates presented in this paper comprise results of determinations made on archaeologic and geologic material from Socialist Republic Vietnam since 1969. Radioactivity was measured twice for 48 hours with gas proportional counters of Houtermans-Oeschger type, using methane at 1000mm Hg pressure as filling gas. Influence of cosmic and local environmental radiation on the counters was reduced with 30 tons of shielding material as described earlier (R, 1970, v 12, p 400-420).
The following list includes selected geologic and pollen dated samples measured since 1965. After moving to new laboratory quarters, we increased shielding to 470 g/cm2 on all sides and 660g/cm2 at the top. Background of our Houtermans-Oeschger-type counters filled with 700 mm Hg of acetylene is now:
This date list covers age measurements carried out at the Radiocarbon Dating Laboratory of the German Academy of Sciences of Berlin (DAW) since 1963 and is a continuation of our first date list (Berlin I). Procedures and methods of preparing the samples are essentially the same. We completed our laboratory with a second electronic counting apparatus. Two further proportional counters with internal anticoincidence (Houtermann-Oeschger counters) are made from an old railway-car axle. The total volume of these counters is 4 L, the effective volume 2.2 L, the background 2.0 counts/min at 700 Torr (acetylene filling), and the contemporary standard value (0.95 NBS oxalic acid) is 20 counts/min. Each sample is measured twice, first for 48 hr and after 8 days for another 24 hr. Data have been calculated on the basis of a C14 half-life of 5570 yr (Godwin, 1962). Errors listed include the standard deviations (1σ) of the counting rates of the contemporary samples, the background and the unknown samples. Calculated errors less than 100 yr have been increased to that figure as a minimum.
Corrections have not been made for C13 content. Mass spectrometrics C13 measurements of some samples indicate that errors resulting from fractionation are minimal.
This list includes selected dates of archaeologic samples from DDR, Czechoslovakia, Hungary and the Soviet Union made between 1966 and 1969. As in previous lists the major portion of dates are concerned with Neolithic and Early Bronze age period in Middle and SE Europe.
The C14 Laboratory of the German Academy of Sciences of Berlin (DAW) began to obtain dates in 1961. The focus of research is in archaeology. Samples, coll. in close collaboration with the DAW's Institut für Vor- und Frühgeschichte, are mainly from the Neolithic of central and southeastern Europe, and contribute to the continuing discussion (Milojčić, 1961; Müller-Beck, 1961) of the chronology of this period.
We present V and I photometry of the globular cluster systems of the early-type galaxies NGC 1374, NGC 1379, NGC 1387, NGC 1427, and NGC 1399, obtained with the 100 inch telescope of Las Campanas Observatory.
In situ observations of comet Halley provided the first photographs of a cometary nucleus and yielded information about its environment, including the emitted gas and dust. The relation between these measurements and properties of and processes on the nucleus is established by theoretical modelling, while laboratory experiments may provide some of the physical parameters needed. In addition, laboratory tests can stimulate new ideas for processes that may be relevant to cometary physics. Processes to be studied in detail by large-scale laboratory experiments may include: (1) heat transport phenomena during sublimation of porous ice-dust mixtures, (2) material modification and chemical fractionation caused by the sublimation processes, (3) buildup and destruction of dust mantles, (4) detailed studies of gas release from mixtures of volatile ices, and (S) the investigation of ice and dust particle release mechanisms. The KOSI-team (Kometensimulation) carried out sublimation experiments with ice-mineral mixtures in a large Space Simulator. During initial experiments, cylindrical samples of 30-cm diameter and 15-cm thickness were irradiated with up to 2700–W/m2 light energy. The samples consisted of water-ice or water- and CO2-ice mineral mixtures. The experiments showed the importance of advection for heat transport into the interior. It was found that the sublimation of CO2 advances into the sample at a higher speed than that of water vapor release. Therefore, emission of volatile gases responded to insolation changes with a time lag of several hours. The ratio of the emitted gas species, as well as the dust-to-gas mass ratio, differs significantly from the values within the sample. A partly permeable refractory mantle of minerals and carbonaceous material developed with time. Dust and ice particle emission has been observed to occur from irradiated dirty ices as well as from dust mantles.
Dust particles originating from comets are an important constituent of the interplanetary dust regime. In order to study the ejection mechanisms from the cometary nucleus surface simulation experiments in the laboratory have been performed. Samples consisting of water ice, carbon dioxide ice and dust grains have been studied when they are irradiated by artificial sunlight within a cooled vacuum system. It has been shown that particle emission is extremely dependent on the initial composition of the samples. For samples with a distinct amount of non-volatile, mineral particles the formation of a dust mantle and, as a consequence, rapid decrease of particle ejection has been observed.
The Solar Wind Generation Experiment consists of a UV Coronal Spectrometer (UVCS) provided by the Harvard-Smithsonian Center for Astrophysics and a White Light Coronagraph (WLC) of the High Altitude Observatory. The instruments are similar to those flown together on three sounding rocket flights [1,2,3] but they have enhanced capabilities to take advantage of Spartan’s 27 hour observing period. The two instruments comprise a payload for Spartan 2, which is a self-contained instrument carrier that provides on-board data storage, power, thermal control, sun pointing and an observing program sequencer. Spartan is launched and deployed by the Shuttle and spends about 27 orbits in a detached mode before it is recovered and returned to the ground for data tape retrieval and post-flight instrument calibration.
This case of a 65-year-old male with dermatillomania, diffuse anxiety symptoms, and avoidant personality disorder (PD) illustrates the interference of attention-deficit hyperactivity disorder (ADHD) in the diagnostic process and during schema-focused therapy. In conclusion, ADHD in older adults and interference with PD is a subject of clinical importance and worth further investigation.
The structure of crystals can be described by defining size and shape of a unit cell and the positions of the atoms within it. Many materials, however, exhibit a glassy or amorphous structure. Such disordered structures are described by structure factors. These are usually determined by small angle scattering experiments. The angular distribution recorded in these experiments is related to the structure factor. In this work we present an alternative approach using elemental maps obtained in an energy filtering transmission electron microscope. In this way we can even obtain chemically resolved partial structure factors giving additional information on the specimen.
Carbon coated silica made by flame synthesis was investigated for reinforcement of styrene-butadiene (SBR) rubber. These composite silica/carbon fillers were examined through small angle x-ray scattering (SAXS), TEM, and AFM showing that these fillers have a rough fractal surface and have fractal aggregate structures. The carbon coated silica fillers were compounded with elastomers and their effect on reinforcement was measured using dynamic mechanical analysis and tensile testing. These fillers were also compared to commercial fumed silica, carbon black, and carbon black/silica composite fillers.
There is considerable interest in insulators with static dielectric constants lower than SiO2; an alloy system attracting recent attention is Si-O-F. Alloying of F atoms into plasma-deposited SiO2 films leads to major changes in the SiO2 bond-stretching and -bending infrared bands accounting for a significant fraction of the reduction in the dielectric constant. These changes are explained by F induced modifications of force constants and effective charges of the neighboring Si-O-Si groups.
Electron Spectroscopic Imaging (ESI) in an energy filtering TEM is a new analytical technique which allows one to obtain two-dimensional elemental distribution images. In the present paper the detection limits of the new technique will be discussed. Si3N4 ceramics with different thicknesses of the amorphous oxide grain boundary layers have been chosen as a model system. Quantitative results have been obtained on three different energy filtering instruments and will be compared with the results of theoretical calculations. The application of ESI for the mapping of near edge fine structure will be discussed.
A novel polymer has been developed for use as a thin film dielectric in the interconnect structure of high density integrated circuits. The coating is applied to the substrate as an oligomeric solution, SiLK*, using conventional spin coating equipment and produces highly uniform films after curing at 400 °C to 450 °C. The oligomeric solution, with a viscosity of ca. 30 cPs, is readily handled on standard thin film coating equipment. Polymerization does not require a catalyst. There is no water evolved during the polymerization. The resulting polymer network is an aromatic hydrocarbon with an isotropie structure and contains no fluorine.
The properties of the cured films are designed to permit integration with current ILD processes. In particular, the rate of weight-loss during isothermal exposures at 450 °C is ca. 0.7 wt.%/hour. The dielectric constant of cured SiLK has been measured at 2.65. The refractive index in both the in-plane and out-of-plane directions is 1.63. The flow characteristics of SiLK lead to broad topographic planarization and permit the filling of gaps at least as narrow as 0.1 μm. The glass transition temperature for the fully cured film is greater than 490 °C. The coefficient of thermal expansivity is 66 ppm/°C below the glass transition temperature. The stress in fully cured films on Si wafers is ca. 60 MPa at room temperature. The fracture toughness measured on thin films is 0.62 MPa m ½. Thin coatings absorb less than 0.25 wt.% water when exposed to 80% relative humidity at room temperature.
Using Si and GaAs substrates, the coefficient of thermal expansion (CTE) and the bi-axial modulus of thin hydrogen silsesquioxanes (HSQ) films are deduced by means of wafer curvature measurement. The same properties of plasma-enhanced CVD oxide are also reported.
Interactions between fluorinated polyimide and aluminum under different thermal treatment conditions have been investigated using transmission electron microscopy (TEM) and x-ray diffractometry (XRD) techniques over a wide temperature range. Our results suggest that the oxygen from the dielectric materials may result in the oxidation of the underlying aluminum either on the surface or along the grain boundary. This work implies that processing conditions, such as curing temperature and time, may play critical roles in affecting the performance of polymeric dielectric materials.
Two series of Ni-Mn-Ga thin films with two different compositions and various thicknesses in the submicron range are investigated with respect to their structural and magnetic properties. The films are fabricated by sputter deposition on alumina substrates and subsequent heat treatment. The martensitic transformation occurs well above room temperature showing a small thermal hysteresis width of about 6 K. The magnetic properties turn out to be thickness-dependent in the submicron range. In particular, in-plane magnetic susceptibilities increase and critical field strengths for onset of saturation decrease for decreasing thickness down to 0.1 μm by factors of 3–5 depending on the chemical composition. The Curie temperature TC decreases by about 25 K for samples with TC higher than the martensitic transformation.
The gastrointestinal tract is a complex milieu as a result of interaction between dietary ingredients and the intestinal bacteria. Following the European ban on the use of in-feed antibiotics, research has focused mainly on the potentially beneficial activities of the intestinal microbiota. Fermentable carbohydrates, or ‘prebiotics’, such as non-digestible oligosaccharides, are considered to have beneficial effects on the composition and activity of the indigenous microbiota, which can enhance the resistance of the host against colonisation of pathogenic bacteria in the GIT. Only a limited number of prebiotics has been tested in broilers that include fructo-oligosaccharides, inulin, mannan-oligosaccharides, alpha gluco-oligosaccharides, isomalto-oligosaccharides, different kestoses and lactose along with its derivatives. This review provides an overview pertaining to the potential impact of prebiotics on the intestinal bacterial population in broilers and summarizes the data regarding the role of prebiotics in preventing the colonisation of enteropathogens especially Salmonella spp., Campylobacter spp. and Clostridium spp. Moreover, the influence of prebiotics on the intestinal bacterial fermentation profile, particularly short chain fatty acids, ammonia and lactate, is also discussed. Prebiotics have been found to affect the intestinal bacterial population particularly elevating the caecal count of Lactobacillus spp. and Bifidobacterium spp. The effect of prebiotics on the intestinal bacteria is also evident in terms of change in the total concentration or relative proportion of short chain fatty acids. The ability of prebiotics in controlling the colonisation of different enterpathogens especially Salmonella spp., Clostridium perfringens or Campylobacter spp. showed inconsistent results depending upon the available literature.