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Scanning helium microscopy is an emerging form of microscopy using thermal energy neutral helium atoms as the probe particle. The very low energy combined with lack of charge gives the technique great potential for studying delicate systems, and the possibility of several new forms of contrast. To date, neutral helium images have been dominated by topographic contrast, relating to the height and angle of the surface. Here we present data showing contrast resulting from specular reflection and diffraction of helium atoms from an atomic lattice of lithium fluoride. The signature for diffraction is evident by varying the scattering angle and observing sharp features in the scattered distribution. The data indicates the viability of the approach for imaging with diffraction contrast and suggests application to a wide variety of other locally crystalline materials.

The development of a new class of cysteine protease inhibitors utilising the thiosulfonate moiety as an SH specific electrophile is described. This moiety has been introduced into suitable amino acid derived building blocks, which were incorporated into peptidic sequences leading to very potent i.e. sub micromolar inhibitors of the cysteine protease papain in the same range as the vinyl sulfone based inhibitor K11777. Therefore, their inhibitory effect on Schistosoma mansoni, a human blood parasite, that expresses several cysteine proteases, was evaluated. The homophenylalanine side chain containing compounds 27 - 30 and especially 36 showed promising activities compared with K11777 and warrant further investigations of these peptidic thiosulfonate inhibitors as new potential anti-parasitic compounds.

The interfacial behaviour of water remains a central question to fields as diverse as protein folding, friction and ice formation. While the properties of water at interfaces differ from those in the bulk, major gaps in our knowledge limit our understanding at the molecular level. Information concerning the microscopic motion of water comes mostly from computation and, on an atomic scale, is largely unexplored by experiment. Here, we provide a detailed insight into the behaviour of water monomers on a graphene surface. The motion displays remarkably strong signatures of cooperative behaviour due to repulsive forces between the monomers, enhancing the monomer lifetime ( ≈ 3 s at 125 K) in a free-gas phase that precedes the nucleation of ice islands and, in turn, provides the opportunity for our experiments to be performed. Our results give a molecular perspective on a kinetic barrier to ice nucleation, providing routes to understand and control the processes involved in ice formation., The dynamics of water molecules at interfaces controls natural and artificial processes, but experimental investigations have been challenging. Here the authors investigate water molecules on a graphene surface using helium spin-echo spectroscopy, and reveal a regime where freely mobile molecules undergo strong repulsive mutual interactions which inhibit ice nucleation.

The design of a high-efficiency mass spectrometer is described, aimed at residual gas detection of low mass species using low-energy electron impact, with particular applications in helium atom microscopy and atomic or molecular scattering. The instrument consists of an extended ionization volume, where electrons emitted from a hot filament are confined using a solenoidal magnetic field to give a high ionization probability. Electron space charge is used to confine and extract the gas ions formed, which are then passed through a magnetic sector mass filter before reaching an ion counter. The design and implementation of each of the major components are described in turn, followed by the overall performance of the detector in terms of mass separation, detection efficiency, time response, and background count rates. The linearity of response with emission current and magnetic field is discussed. The detection efficiency for helium is very high, reaching as much as 0.5%, with a time constant of (198 ± 6) ms and a background signal equivalent to an incoming helium flux of (8.7 ± 0.2) × 106 s−1. publishedVersion

The adsorption of sodium on Ru(0001) is studied using 3He spin-echo spectroscopy (HeSE), molecular dynamics simulations (MD) and density functional theory (DFT). In the multi-layer regime, an analysis of helium reflectivity, gives an electron-phonon coupling constant of λ = 0.64 ± 0.06. At sub-monolayer coverage, DFT calculations show that the preferred adsorption site changes from hollow site to top site as the supercell increases and the effective coverage, θ, is reduced from 0.25 to 0.0625 adsorbates per substrate atom. Energy barriers and adsorption geometries taken from DFT are used in molecular dynamics calculations to generate simulated data sets for comparison with measurements. We introduce a new Bayesian method of analysis that compares measurement and model directly, without assuming analytic lineshapes. The value of adsorbate-substrate energy exchange rate (friction) in the MD simulation is the sole variable parameter. Experimental data at a coverage θ = 0.028 compares well with the low-coverage DFT result, giving an effective activation barrier Eeff = 46 ± 4 meV with a friction γ = 0.3 ps-1. Better fits to the data can be achieved by including additional variable parameters, but in all cases, the mechanism of diffusion is predominantly on a Bravais lattice, suggesting a single adsorption site in the unit cell, despite the close packed geometry.

Using atom beams to image the surface of samples in real space is an emerging technique that delivers unique contrast from delicate samples. Here, we explore the contrast that arises from multiple scattering of helium atoms, a specific process that plays an important role in forming topographic contrast in scanning helium microscopy (SHeM) images. A test sample consisting of a series of trenches of varying depths was prepared by ion beam milling. SHeM images of shallow trenches (depth/width 1) exhibited an enhanced intensity. The scattered helium signal was modeled analytically and simulated numerically using Monte Carlo ray tracing. Both approaches gave excellent agreement with the experimental data and confirmed that the enhancement was due to localization of scattered helium atoms due to multiple scattering. The results were used to interpret SHeM images of a bio-technologically relevant sample with a deep porous structure, highlighting the relevance of multiple scattering in SHeM image interpretation.

7 pags., 4 figs., In studies of dynamical systems, helium atoms scatter coherently from an ensemble of adsorbates as they diffuse on the surface. The results give information on the co-operative behaviour of interacting adsorbates and thus include the effects of both adsorbate-substrate and adsorbate-adsorbate interactions. Here, we discuss a method to disentangle the effects of interactions between adsorbates from those with the substrate. The result gives an approximation to observations that would be obtained if the scattering was incoherent. Information from the experiment can therefore be used to distinguish more clearly between long-range inter-adsorbate forces and the short range effects arising from the local lattice potential and associated thermal excitations. The method is discussed in the context of a system with strong inter-adsorbate interactions, sodium atoms diffusing on a copper (111) surface., The authors acknowledge use of and support by the Cambridge Atom Scattering Facility (https://atomscattering.phy.cam.ac.uk) and EPSRC award EP/T00634X/1. One of us (AT) acknowledges financial support provided by the FWF (Austrian Science Fund) within the project J3479-N20. One of us (SMA) would like to acknowledge the Ministerio de Ciencia, Universidades e Innovacion (Spain) for the grant with Ref. FIS2017-83473-C2-1-P. We thank the Cavendish Workshop, particularly Rik Balsod, for making the titanium dispenser that was critical for taking the experimental data.

The last comprehensive review of the fossil vertebrates from the Miocene of Calvert Cliffs was published more than 100 years ago. This volume is a collection of papers that updates some of the geological features of Calvert Cliffs and provides reviews of the fossil biota that include representatives from the following taxonomic groups: chondrichthyans (chimaeras, shark, skates, and rays), actinopterygians (ray-finned fishes), crocodilians (crocodiles), and sirenians (sea cows). Peter Vogt, Ralph E. Eshelman, and Stephen J. Godfrey document how the 20–40 m [65–130 ft] high Calvert Cliffs along the western shore of the Chesapeake Bay continue to yield insights into 18–8 mya (Miocene) geology, marine and terrestrial vertebrate fauna, and the origin and evolution of Chesapeake Bay and Calvert Cliffs up to the present. These exposures rank high among the best-known fossiliferous deposits of any age. Bretton W. Kent describes the cartilaginous fish (the chondrichthyan) fauna, consisting of 54 species—3 chimaeras (ratfishes), 39 sharks, and 12 skates and rays—a fauna rich in large macrophagous sharks and large neritic rays. In an addendum to Kent’s chapter, he and David J. Ward describe a new species of giant thresher shark with serrated teeth. Giorgio Carnevale and Stephen J. Godfrey present an account of the 38 actinopterygian taxa known from osteological remains and a diverse otolith assemblage of at least 55 taxa. These actinopterygians show an affinity for well-oxygenated muddy and sandy substrates dominated primarily by shallow-water species characteristic of the inner shelf and secondarily by epipelagic taxa. Robert E. Weems details the crocodilians referable to the tomistomine Thecachampsa. The closest living relative is Tomistoma schlegelii, the false gharial of Southeast Asia. Two species are present: Thecachampsa sericodon and T. antiquus. These tomistomines are found in shallow marine coastal deposits, indicating that they inhabited coastal waters. Daryl P. Domning reports that fossils of the Miocene marine fauna include rare sirenians of the family Dugongidae. Three taxa are known: the halitheriine dugongid Metaxytherium crataegense, the dugongine dugongid Nanosiren sp., and another dugongine, aff. Corystosiren. The St. Marys Formation contains remains that may be referable to Metaxytherium floridanum, but confirmation awaits the discovery of more complete specimens.

We describe a method for obtaining the optimal design of a normal incidence Scanning Helium Microscope (SHeM). Scanning helium microscopy is a recently developed technique that uses low energy neutral helium atoms as a probe to image the surface of a sample without causing damage. After estimating the variation of source brightness with nozzle size and pressure, we perform a constrained optimisation to determine the optimal geometry of the instrument (i.e. the geometry that maximises intensity) for a given target resolution. For an instrument using a pinhole to form the helium microprobe, the source and atom optics are separable and Lagrange multipliers are used to obtain an analytic expression for the optimal parameters. For an instrument using a zone plate as the focal element, the whole optical system must be considered and a numerical approach has been applied. Unlike previous numerical methods for optimisation, our approach provides insight into the effect and significance of each instrumental parameter, enabling an intuitive understanding of effect of the SHeM geometry. We show that for an instrument with a working distance of 1 mm, a zone plate with a minimum feature size of 25 nm becomes the advantageous focussing element if the desired beam standard deviation is below about 300 nm.

Elasmobranchii is a clade of chondrichthyans (cartilaginous fishes) that comprises sharks, skates and rays represented today by approximately 1,200 species. Chondrichthyans have a long evolutionary history dating back to the Late Ordovician (ca. 450 million years ago [Mya]) based on isolated dermal denticles (Janvier 1996). Other remains such as articulated skeletons and teeth are known from the Lower Devonian (ca. 410 Mya: Mader 1986; Miller et al. 2003). The fossil record of modern elasmobranchs (Neoselachii) can be traced back to the Early Permian (ca. 290 Mya) and is represented by isolated teeth (Ivanov 2005), with fossils of crown group sharks and rays appearing in Lower Jurassic (ca. 200 Mya) rocks (e.g., Cappetta 2012). Since their appearance in the geological record, elasmobranchs are mainly represented by isolated teeth, whereas articulated skeletons are very rare and restricted to a small number of fossil localities (e.g., Cappetta 2012). The scarcity of skeletal remains in their fossil record is due to their poorly mineralized cartilaginous skeleton that requires special taphonomical conditions to be preserved. Elasmobranch teeth, in contrast, are composed of highly mineralized tissues (hydroxyapatite) that have a strong preservation potential (Shimada 2006). In addition, elasmobranchs replace their teeth continuously over the course of their life span (polyphyodonty) and therefore shed thousands of teeth in their lifetime (Reif et al. 1978; Schnetz et al. 2016) leading to large numbers of potential fossils. These morphologically highly diverse isolated teeth constitute much of the rich fossil record of elasmobranchs, and largely form the basis of our understanding of elasmobranch diversity and evolution through geological time.

Shark jaws exhibit teeth that are arranged into distinct series and files and display great diversities in shapes and structures, which not only is related to their function (grasping, cutting, crushing) during feeding, but also bear a strong phylogenetic signal. So far, most research on the relationship between shark teeth and feeding ecology and systematics focused on the external tooth morphology only. Although the tooth histology of sharks has been examined since the early 19th century, its functional and systematic implications are still ambiguous. Shark teeth normally consist of either a porous, cellular dentine, osteodentine (in lamniform sharks and some batoids) or a dense layer of orthodentine (known from different sharks). Sharks of the order Carcharhiniformes, comprising ca. 60% of all extant shark species, are known to have orthodont teeth, with a single exception-the snaggletooth shark, Hemipristis elongata. High resolution micro-CT images of jaws and teeth from selected carcharhiniform sharks (including extant and fossil snaggletooth sharks) and tooth sections of teeth of Hemipristis, other carcharhiniform and lamniform sharks, have revealed that (1) Hemipristis is indeed the only carcharhiniform shark filling its pulp cavity with osteodentine in addition to orthodentine, (2) the tooth histology of Hemipristis elongata differs from the osteodont histotype, which evolved in lamniform sharks and conversely represents a modified orthodonty, and (3) this modified orthodonty was already present in extinct Hemipristis species but the mineralization sequence has changed over time. Our results clearly show the presence of a third tooth histotype-the pseudoosteodont histotype, which is present in Hemipristis. The unique tooth histology of lamniform sharks might provide a phylogenetic signal for this group, but more research is necessary to understand the phylogenetic importance of tooth histology in sharks in general.

Spin-echo instruments are typically used to measure diffusive processes and the dynamics and motion in samples on ps and ns time scales. A key aspect of the spin-echo technique is to determine the polarisation of a particle beam. We present two methods for measuring the spin polarisation in spin-echo experiments. The current method in use is based on taking a number of discrete readings. The implementation of a new method involves continuously rotating the spin and measuring its polarisation after being scattered from the sample. A control system running on a microcontroller is used to perform the spin rotation and to calculate the polarisation of the scattered beam based on a lock-in amplifier. First experimental tests of the method on a helium spin-echo spectrometer show that it is clearly working and that it has advantages over the discrete approach, i.e., it can track changes of the beam properties throughout the experiment. Moreover, we show that real-time numerical simulations can perfectly describe a complex experiment and can be easily used to develop improved experimental methods prior to a first hardware implementation.

The phenomenology of zeolite collapse is outlined, drawing on recent synchrotron x-ray diffraction experiments and computer simulations of low density cage structures like zeolite A and zeolite Y. Attention is drawn to the importance of polyamorphism in destabilizing this type of microporous crystal and its role in order-disorder as well as amorphous-amorphous transitions, together with associated differences in entropy and density between polyamorphic phases and the precursor zeolite. Magic angle spinning NMR and inelastic x-ray scattering are used to highlight changes in structural order and mechanical rigidity between the starting zeolite and the final high density polyamorph. In conclusion, two-level systems detected with inelastic neutron scattering are described and their involvement in dictating the dynamics of the collapse of zeolitic cage structures.

The synthesis of water soluble highly pre-organized Tris-tertiary Amine CycloTriVeratrilene (TACTV) derivatives was developed. A semi-orthogonally protected derivative allowed one pot sequential introduction of different peptide loops toward the molecular construction of synthetic antibody protein mimics.

The alignment of ultra-high-vacuum sample transfer systems can be problematic when there is no direct line of sight to assist the user. We present the design of a simple and cheap system which greatly simplifies the alignment of sample transfer devices. Our method is based on the adaptation of a commercial digital camera which provides live views from within the vacuum chamber. The images of the camera are further processed using an image recognition and processing code which determines any misalignments and reports them to the user. Installation has proven to be extremely useful in order to align the sample with respect to the transfer mechanism. Furthermore, the alignment software can be easily adapted for other systems.

The realization of efficient organic electronic devices requires the controlled preparation of molecular thin films and heterostructures. As top-down structuring methods such as lithography cannot be applied to van der Waals bound materials, surface diffusion becomes a structure-determining factor that requires microscopic understanding. Scanning probe techniques provide atomic resolution, but are limited to observations of slow movements, and therefore constrained to low temperatures. In contrast, the helium-3 spin-echo (HeSE) technique achieves spatial and time resolution on the nm and ps scale, respectively, thus enabling measurements at elevated temperatures. Here we use HeSE to unveil the intricate motion of pentacene admolecules diffusing on a chemisorbed monolayer of pentacene on Cu(110) that serves as a stable, well-ordered organic model surface. We find that pentacene moves along rails parallel and perpendicular to the surface molecules. The experimental data are explained by admolecule rotation that enables a switching between diffusion directions, which extends our molecular level understanding of diffusion in complex organic systems.

Delicate structures (such as biological samples, organic films for polymer electronics and adsorbate layers) suffer degradation under the energetic probes of traditional microscopies. Furthermore, the charged nature of these probes presents difficulties when imaging with electric or magnetic fields, or for insulating materials where the addition of a conductive coating is not desirable. Scanning helium microscopy is able to image such structures completely non-destructively by taking advantage of a neutral helium beam as a chemically, electrically and magnetically inert probe of the sample surface. Here we present scanning helium micrographs demonstrating image contrast arising from a range of mechanisms including, for the first time, chemical contrast observed from a series of metal–semiconductor interfaces. The ability of scanning helium microscopy to distinguish between materials without the risk of damage makes it ideal for investigating a wide range of systems., Scanning helium microscopy uses neutral atoms to image traditionally challenging materials (e.g. delicate, insulating and magnetic samples) non-destructively with absolute surface sensitivity. This work reports the first observation of chemical contrast in helium microscopy via inelastic scattering.

Mass transport at a surface is a key factor in heterogeneous catalysis. The rate is determined by excitation across a translational barrier and depends on the energy landscape and the coupling to the thermal bath of the surface. Here we use helium spin−echo spectroscopy to track the microscopic motion of benzene adsorbed on Cu(001) at low coverage (θ ∼ 0.07 ML). Specifically, our combined experimental and computational data determine both the absolute rate and mechanism of the molecular motion. The observed rate is significantly higher by a factor of 3.0 ± 0.1 than is possible in a conventional, point-particle model and can be understood only by including additional molecular (rotational) coordinates. We argue that the effect can be described as an entropic contribution that enhances the population of molecules in the transition state. The process is generally relevant to molecular systems and illustrates the importance of the pre-exponential factor alongside the activation barrier in studies of surface kinetics.

Over the years there has been considerable research investigating the controversial issues of cult recruitment, “mind control” and post-group difficulties of ex-members from a variety of religious groups. However, the less-well-defined phenomenon of “spiritual abuse” is still under-researched as a specific phenomenon. This is particularly evident in the lack of studies exploring the subjective, internal experience. This study reports on the lived experiences of six individuals who left five different religious groups that were essentially Judeo-Christian in their orientation. An Interpretative Phenomenological Analysis (IPA) revealed six core themes throughout the participant narratives. They consist of “Leadership representing God,” “Spiritual bullying,” “Acceptance via performance,” “Spiritual neglect,” “Manifestation of internal states,” and “Expanding external/internal tension.” These are offered as a foundation to answer the question What can be described as the lived experience of spiritual abuse? T...

Description of two new species of macruran decapod crustaceans, Hoploparia uzbekensis and Linuparus dzheirantuiensis, from Late Cretaceous rocks in the Kyzylkum Desert, Uzbekistan, represents the first published record of decapods from that country. Hoploparia is considered to be an intact, integrated genus. Specimens of Hoploparia uzbekensis and Linuparus dzheirantuiensis collected from the Aitym and Bissekty formations, respectively, are preserved as altered cuticular material in a sandy matrix. Specimens of Hoploparia and Linuparus collected from the Uchkuduk and Dzheirantui formations, respectively, are preserved as ironstone replacements, an unusual preservation style for decapods. The cephalothorax on the specimen of Linuparus from the Dzheirantui Formation has been partially broken in a manner suggestive of predation. The lateral thoracic flanks of the holotype of Linuparus dzheirantuiensis bear a raised, ridged area suggestive of a stridulating structure. These genera, although cosmopolit...

We present a simplified design for a scanning helium microscope (SHeM) which utilises almost entirely off the shelf components. The SHeM produces images by detecting scattered neutral helium atoms from a surface, forming an entirely surface sensitive and non-destructive imaging technique. This particular prototype instrument avoids the complexities of existing neutral atom optics by replacing them with an aperture in the form of an ion beam milled pinhole, resulting in a resolution of around 5 microns. Using the images so far produced, an initial investigation of topological contrast has been performed.

We have developed a convenient new method of ageing grasstrees (Xanthorrhoea) and determining their fire history over the last 250 years or more. Grinding off the charred leafbases reveals alternating cream and brown bands that we equate with annual growth cycles and occasional black bands that we equate with the passage of fire. The new method was employed on 159 grasstrees at 50 sites distributed throughout the dry eucalypt forest region of southwestern Australia. In the 80 years prior to European settlement in 1829, and for the next 40 years, fires were recorded on grasstrees at 3–5 year intervals. The ensuing decline in mean fire frequencies and increased variability corresponded with demise of the aboriginal inhabitants and onset of intense wildfires associated with unrestrained logging. Our data show that from 1920 attempts at fire exclusion followed later by prescribed burning programs were only partly successful. Currently recorded intervals on individual trees of 10–20 years are consistent with further changes in fire management practices. Both extremes would have had significant impacts on the biota.

Flowering and fruiting were assessed on 14 populations of the grasstree, Xanthorrhoea preissii Endl., occurring in the Darling Range near Perth, Western Australia. Independent of site, season of burn or year of flowering, there was a strong relationship between plant height, which varied from 0.1 to over 2 m, and the incidence of postfire flowering, which varied from 1% (winter burn) to 75% (summer burn) of grasstrees present. There was no relationship between inflorescence dimensions, or flower or fruit production on a spike basis, and plant size/age (height). When standardized for height, spring-burnt populations produced 40% as many inflorescences as autumn-burnt populations and 20% as many as summer-burnt populations. Inflorescences produced by spring-burnt plants were moderately smaller than those by summer–autumn-burnt plants. Fruit density per spike in autumn-burnt plants was 80% of that in spring–summer-burnt plants. The net effect was an average of 70 000 fruits produced per 100 summer-burnt plants, 22 000 in autumn-burnt plants, and 14 000 in spring-burnt plants. Ecophysiological explanations of these results and their implications for population dynamics have yet to be explored.

The general control of tokamak plasmas has evolved considerably over the past few years with an increase in the plasma pulse length, an increase in the control of additional heating and fueling, and an increase in the degree to which the shape of the plasma can be varied. The Tokamak Configuration Variable (TCV) is specifically designed to explore the operational benefits of plasma shaping over a wide variety of plasma shapes. Consequently, considerable attention has been given to the control of the poloidal field coil currents that impose the desired shape. All aspects of the control of TCV plasmas, from the diagnostic measurements to the power supplies, via particular control algorithms and overall supervision are discussed.

Bondholders and financial analysts have long sought models which will predict financial distress in corporations. Prior research has produced a number of useful models to predict bankruptcy in the short term. This paper looks at four models which predict default based upon public information at the time of issuance of high yield bonds. Multivariate results using logistic regression analysis indicate that high yield issues that default are characterized by having higher asset growth rates, lower operating profit margins, larger levels of collateralizable assets, and larger changes in net working capital. Models using Altman (1968) variables have lower likelihood ratio indexes than models employing alternative explanatory variables. Predictive ability tests of models excluding the traditional variables on a holdout sample are able to correctly predict 73.3 percent of the defaulted bonds and 68.6 percent of the nondefaulted bonds.

This paper investigates the common stock price reaction at the announcement of the issuance of high-yield straight debt. The two-day announcement period abnormal returns are not different from zero for the 164 bond issues in the sample. No difference is found between announcement period abnormal returns of firms with bonds that default and firms with bonds that do not default. Results from statistical tests indicate that the announcement period abnormal returns are not explained by issuance year, bond-rate class, underwriter, issuance size, takeover activity or prior high-yield debt issuance experience. The findings are not consistent with the models by Miller and Rock (1985), Jensen (1986), Myers and Majluf (1984) and Krasker (1986). However, results indicate that existing stockholders are not harmed or helped by the issuance of the high-yield straight debt.

Non-volatile element and volume flux during slaty cleavage formation was determined by mapping major element compositions in hand specimens of slate with variable cleavage intensity due to non-argillaceous interlayers. Intense spaced cleavage zones form where cleavage coalesces within the inner arcs of folded nonargillaceous layers or at the offsets between imbricated non-argillaceous layers. The element distributions in samples from Nova Scotia, Vermont and New Jersey were mapped using an XRFmacroprobe, an energy dispersive XRF with automated spectrum acquisition and a mm-scale collimated beam. Cleavage zones are depleted in quartz and SiO2, and enriched in phyllosilicates, Al2O3, Fe2O3, K2O, MgO and TiO2. CaO and MnO show more variable behavior consistent with simultaneous depletion in carbonates and residual enrichment in silicates. Quartz-rich, weakly cleaved areas adjacent to fold outer arcs or between imbricate offsets are enriched in quartz with respect to probable pre-cleavage compositions, with SiO2 commonly reaching 75–80 wt%. The spaced cleavage zones and their intervening microlithons grade texturally and compositionally into penetrative cleavage with distance from non-argillaceous layering. Average compositions of heterogeneously cleaved beds are quite similar to compositions of homogeneously cleaved beds in the same sample, suggesting balanced, localized element enrichment and depletion adjacent to non-argillaceous layers. The similarities between average macroprobe, slate and shale compositions suggest minimal non-volatile net volume flux during the formation of slaty cleavage. Volume losses of 50% by SiO2 flux would result in a rock with approximately equal SiO2 and Al2O3 wt%, not a slate. Most of the non-volatile element and volume flux in the slates occurred on a hand specimen scale, with quartz depletion in cleavage zones balanced by enrichment in adjoining microlithons.

(1993). Risk and Return in Defaulted Bonds. Financial Analysts Journal: Vol. 49, No. 3, pp. 61-65.

Measurements of the atomic-scale motion of H and D atoms on the Pt(111) surface, above the crossover temperature to deep tunneling, are presented. The results indicate that quantum effects are significant up to the highest temperature studied (250 K). The motion is shown to correspond to nearest neighbor hopping diffusion on a well defined fcc (111) lattice. The measurements provide information on the adiabatic potential of both the adsorption site and the transition state and give strong empirical support for a dissipative transition-state theory description of the quantum contribution to the motion.

The adoption of open source software (OSS) by government has been a topic of interest in recent years. National, regional, and local government are using OSS in increasing numbers, yet the adoption rate is still very low. This study considers if it is possible from an organizational perspective for small to medium-sized cities to provide services and conduct business using only OSS. We examine characteristics of municipal government that may influence the adoption of OSS for the delivery of services and to conduct city business. Three characteristics are considered to develop an understanding of city behavior with respect to OSS: capability, discipline, and cultural affinity. Each of these general characteristics contributes to the successful adoption and deployment of OSS by cities. Our goal was to determine the organizational characteristics that promote the adoption of OSS. We conducted a survey to support this study resulting in 3,316 responses representing 1,286 cities in the Unites States and Canada. We found most cities do not have the requisite characteristics to successfully adopt OSS on a comprehensive scale and most cities not currently using OSS have no future plans for OSS.

Estimating the number of objects in a plane given varying pattern is a problem of practical significance in a number of fields including forestry, ecology, agriculture, geography and microscopy. Historically, foresters have tried two main approaches to the problem - the first involving tree or seedling counts in fixed areas suchs as plots or quadrats, and the second using various interpoint distances such as that from a random point to the nearest tree, or from the nearest tree to its neasrest neighbour. A third approach is now proposed, which combines area and distance, is easy to use in the field, and avoids some problems associated with the previous two approaches. The sides of a triangle formed by three trees around the sample point are measured, and for most forestry purposes pacing is sufficiently accurate. A hand-held computer can be used in the field to give estimates of stems per hectare, and sampling ceases when the cumulative estimate stabilisesw. A short BASIC program for this purpose is appended.

3He spin echo measurements of the atomic scale motion of propane on a Pt(111) surface are presented. The measurements provide both the height of the energy barriers to diffusion and the strength of the frictional coupling of propane to the substrate. We show that both the rate and the nature of the dynamics we measure cannot be reproduced by an existing empirical potential. Using numerical simulation we derive a potential energy surface which is capable of reproducing the main features of our dataset.

We describe a method for text entry based on inverse arithmetic coding that relies on gaze direction and which is faster and more accurate than using an on-screen keyboard. These benefits are derived from two innovations: the writing task is matched to the capabilities of the eye, and a language model is used to make predictable words and phrases easier to write., 3 pages. Final version