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The experimental study of atomic chlorine absorption spectra using a flash-pyrolysis system and a 2-m normal incidence spectrograph in the wavelength region 95 nm to 61 nm has produced photoabsorption cross sections, wavelength measurements, and line series identification involving the 3P, 1D and 1S limits. Absorption spectra originating from both levels ( and ) of the ground state have been produced by this method.
We comment on the conjecture by Parker et al. (2016) that Antarctic
toothfish recently returned to McMurdo Sound, arguing that this species never
departed. Instead, as deduced from a 40-year fishing effort, toothfish water column
prevalence became markedly reduced where bottom depths are <500 m, with research
continuing to show their presence on the bottom or above the bottom where depths are
deeper. We also counter arguments that toothfish departed, and remained absent,
during and following a five-year presence of mega-icebergs residing near the opposite
coast of Ross Island, the icebergs inhibiting or fomenting conditions that
discouraged toothfish presence in the Sound. Available analyses reveal that toothfish
movement into the Sound was probably not significantly affected, and additionally
that neither changes in hydrography nor in primary productivity in the Sound would
have been sufficient to impact toothfish presence through food web alteration. We
hypothesize that the local effect of predation by seals and whales and the regional
effect of a fishery targeting the largest toothfish (those neutrally buoyant and thus
capable of occupying upper levels of the water column) has resulted in the remaining
toothfish now being found predominantly closer to the bottom at greater depths.
This article presents the results of a multiscalar analysis of 168 radiocarbon dates from Neolithic and Copper Age sites on the Great Hungarian Plain. We examined chronological patterns at different geographic scales to explore socioeconomic changes that occurred during the transition from the Neolithic to the Copper Age. The beginning and end of the Late Neolithic (5000–4500 cal BC) and Early Copper Age (4500–4000 cal BC) were modeled with 14C dates calibrated with the CALIB 5.01 program and IntCal04 calibration curve. Our attempts to identify chronological subphases within these 500-yr-long periods were confounded by multiple intercepts in the calibration curve. The analysis indicated that terminal Late Neolithic (4700–4300 cal BC) and “transitional” Proto-Tiszapolgár occupations (4600–4250 cal BC) at tell sites were contemporary with initial Early Copper Age habitations (4450–4250 cal BC). Calibrated dates from small Early Copper Age settlements at Vészto-Bikeri and Körösladány-Bikeri document changes in community and household organization that took place over several decades during the transition to the Copper Age. Bayesian analysis indicated that the small fortified sites were occupied contiguously in phases of 30–50 yr. The younger Körösladány-Bikeri site was established before the older Vészto-Bikeri site was abandoned. When large nucleated Late Neolithic communities dispersed and established small Early Copper Age settlements, the pattern of vertical accretion that had created the Late Neolithic tells gave way to a pattern of horizontal settlement accretion at the smaller settlements.
In recognition of its special interdisciplinary character, IAU Commission 14 is linked directly to the Executive Committee. The Commission’s role is to inform the astronomical community of new developments in the diverse fields of research which involve atoms and molecules. Conversely it endeavors to sensitize the research community active in those fields to the specific needs of astronomy, especially concerning basic data and modeling tools. More generally, Commission 14 tries to foster long term relations and collaborations between the two communities and, when necessary, to alert funding authorities to the specific needs of ground and space based astronomy for specific atomic and molecular data. This report is one of the main contributions of Commission 14 to the information of the astronomical community. Several meetings concerned, at least in part, with the need and availability of atomic and molecular data for astrophysics were also sponsored or co-sponsored. In the last triennium, Commission 14 cosponsored IAU Symposium 194 “Astrochemistry: From Molecular Cloud to Planetary Systems” held in Sogwipo (Korea) from Aug. 23 to 27, 1999 and organized by Commission 34. A Joint Discussion: JD1 on “Atomic and Molecular Data for Astrophysics, New Developments, Case Studies and Future Needs” has been planned for the XXIVth IAU General Assembly in Manchester (Aug. 7-19, 2000) and cosponsored by Commissions 15, 16, 29, 34, 36, 40 and 44. Several other Joint Discussions to be held at the Manchester General Assembly are co-sponsored by this commission.
Research in molecular spectroscopy has continued to grow over the past three years. The spectral range has expanded from the far ultraviolet to millimeter wavelengths. The report has been limited to molecular spectroscopy of relevance to astronomy and has been compiled from edited contributions sent to me in the fall of 1987.
We compare the relative merits of four different types of instrument for tridimensional spectrometry at visible and ultraviolet wavelengths: the echelle and long-slit spectrographs and two types of Fourier transform spectrometer (conventional scanning and fixed tilt spatially heterodyned). Each of these instruments requires different spatial and spectral scanning modes. It is shown that in certain limiting conditions all four are equally efficient, but that they differ in other important characteristics.
The oscillator strengths of two ultraviolet molecular lines expected to be seen in diffuse interstellar clouds have been measured. For the 1290.257 A° line of HC1, f=0.16±0.06. For the 1114.225 A° line of H2O, f=(5.0±2.0)x10−3. These results have been used in conjunction with observational data to compare measured and predicted column densities of these molecules in the ζ Óphiuchi cloud.
We performed a study to determine rates of reinfection in three groups followed for 2 years after successful treatment: American Indian/Alaska Native (AI/AN) persons living in urban (group 1) and rural (group 2) communities, and urban Alaska non-Native persons (group 3). We enrolled adults diagnosed with H. pylori infection based on a positive urea breath test (13C-UBT). After successful treatment was documented at 2 months, we tested each patient by 13C-UBT at 4, 6, 12 and 24 months. At each visit, participants were asked about medication use, illnesses and risk factors for reinfection. We followed 229 persons for 2 years or until they became reinfected. H. pylori reinfection occurred in 36 persons; cumulative reinfection rates were 14·5%, 22·1%, and 12·0% for groups 1, 2, and 3, respectively. Study participants who became reinfected were more likely to have peptic ulcer disease (P = 0·02), low education level (P = 0·04), or have a higher proportion of household members infected with H. pylori compared to participants who did not become reinfected (P = 0·03). Among all three groups, reinfection occurred at rates higher than those reported for other US populations (<5% at 2 years); rural AI/AN individuals appear to be at highest risk for reinfection.
A heuristic greedy algorithm is developed for efficiently tiling spatially dense redshift surveys. In its first application to the Galaxy and MassAssembly (GAMA) redshift survey we find it rapidly improves the spatial uniformity of our data, and naturally corrects for any spatial bias introduced by the 2dF multi-object spectrograph. We make conservative predictions for the final state of the GAMA redshift survey after our final allocation of time, and can be confident that even if worse than typical weather affects our observations, all of our main survey requirements will be met.
The growth of copper, silver and gold thin films on tungsten disulfide has been examined as a model of metal contacts on a layered semiconductor. All three metals were found to grow epitaxially on the WS2. However, Cu appears to form a discontinuous film while Au and Ag grow layer by layer. Such epitaxial growth is somewhat surprising since there is a large lattice mismatch between the metals and the WS2.
Silicon carbide whiskers have excellent mechanical and chemical properties, making them very desirable as a reinforcement for structural ceramic and other composite materials. Los Alamos has developed a laboratoryscale batch process for producing very high quality SiC whiskers by the vapor-liquid-solid (VLS) method which is an active candidate for technology transfer involving significant scale-up. The process, however, involves quite complex chemical/physical and parametric relationships and has not as yet lent itself successfully to modeling. An expert computer system was therefore developed to facilitate the transfer of this technology to industry. Optimum conditions were determined by relating the many process parameters to product results to establish a set of rules for running the process. These are incorporated in a two-phase expert system designed to guide inexperienced users. In Phase I, an expert consultant program provides the user with information that enables him to set up the run. This information is incorporated into the rule base that makes up Phase II- the control system. At present, the operator functions as the controller by responding to the decisions of the expert system; automation can be added later.
In a recent study by Yeung & Parkinson (1997), a wake width was proposed which
allowed the bluff-body potential-flow model by Parkinson & Jandali (1970) to be
extended to include the flow around an oblique flat plate. By incorporating this wake
width in the momentum equation originally derived by Eppler (1954) for separated
flow, the drag of the plate is related to its inclination and base pressure through
a simple analytical condition. It allows the base pressure, which is usually treated
as an empirical input, to be determined theoretically and thus the model becomes
self-contained. Predictions of the base pressure, drag and width of wake are found
to be in reasonable agreement with the experimental data. When applied to the
symmetrical flow around a wedge of arbitrary vertex angle, similar agreement with
experimental measurements is obtained as well. It is also demonstrated that this
condition is compatible with the free-streamline models by Wu (1962) and Wu &
Wang (1964) such that the corresponding predictions are in good agreement with
A theoretical study is presented for the investigation of a potential-flow model for enhancing lift over a flat-plate aerofoil experiencing thin aerofoil stall. Rather than suppressing the leading-edge separation, flow is assumed to separate tangentially at the leading edge and made to reattach smoothly at the tip of a forward-facing fence joining the plate tangentially on its upper surface to avoid any unnecessary stagnated flow. The length of the fence and its location from the leading edge form two geometrical parameters. At any positive angle of attack, the resulting bounding streamline emanating from the leading edge and terminating at the tip of the fence is simulated by using suitable mathematical singularities subject to boundary conditions such as attaining a finite velocity at each critical point of the conformal mapping involved, and the condition of finite pressure gradient at reattachment, when applicable. Computational results from varying these two geometrical parameters indicate that the lift from each model is enhanced, as compared with the attached flow model around a simple flat plate and the original separated flow model by Kirchhoff.
An inviscid analytic model is proposed for the steady
separated flow around an inclined flat plate. With the plate normal
to the stream, the model reduces to the wake-source model of
Parkinson & Jandali originally developed for flow external to a
symmetrical two-dimensional bluff body and its wake. At any other
inclination, the Kutta condition is satisfied at both leading and
trailing edges of the plate, and, in the limit that the angle of
attack approaches zero, classical airfoil theory is recovered. A
boundary condition is formulated based on some experimental results
of Abernathy, but no additional empirical information is required.
The predicted pressure distributions on the wetted surface for a
wide range of angle attack are found to be in good agreement with
experimental data, especially at smaller angles of attack. An
extension to include a leading-edge separation bubble is explored
and results are satisfactory.
Deer experience a period of reduced appetite and growth in winter which has a major impact on venison supply. Photoperiod manipulation has been shown to modify this. The objective of this experiment was to investigate the effect of extended photoperiod and the modifying effect of dietary energy supply in red deer stag calves
Forty red deer stag calves born in May/June 1992 were weaned in mid-September and put indoors on a grass silage-based ration. On 30 September the stag calves were weighed and randomised to four treatments groups on the basis of liveweight.