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31 pags., 20 figs., Many experiments that utilize beams of incident atoms colliding with surfaces as a probe of surface properties are carried out at large energies, high temperatures and with large mass atoms. Under these conditions the scattering process does not exhibit quantum mechanical properties such as diffraction or single-phonon excitation, but rather can be treated with classical physics. This is a review of work carried out by the authors over a span of several years to develop theoretical frameworks using classical physics for describing the scattering interactions of atom with surfaces., SMA also acknowledges support from Ministerio de Ciencia e Innovacion through a grant with reference FIS2021-125735NB-I00 and from Fundacio´n Humanismo y Ciencia

BACKGROUND: Efficacy of vitamin D supplementation may vary by dosing strategies and adiposity. To address such heterogeneity, we performed a meta-analysis of randomised controlled trials of vitamin D supplementation and total cancer outcomes. METHODS: PubMed and Embase were searched through January 2022. Summary relative risk (SRR) and 95% confidence interval (CI) were estimated using the DerSimonian–Laird random-effects model. RESULTS: For total cancer incidence (12 trials), the SRR for vitamin D supplementation vs. control group was 0.99 (95% CI, 0.94–1.03; P = 0.54; I(2) = 0%). No significant association was observed regardless of whether the supplement was given daily or infrequently in a large-bolus. Yet, among trials testing daily supplementation, a significant inverse association was observed among normal-weight individuals (SRR, 0.76; 95% CI, 0.64–0.90; P = 0.001, I(2) = 0%), but not among overweight or obese individuals (P(heterogeneity) = 0.02). For total cancer mortality (six trials), the SRR was 0.92 (95% CI, 0.82–1.03; P = 0.17; I(2) = 33%). A significant inverse association emerged (SRR, 0.87; 95% CI, 0.78–0.96; P = 0.007; I(2) = 0%) among studies testing daily supplementations but not among studies that testing infrequent large-bolus supplementations (P(heterogeneity) = 0.09). CONCLUSIONS: For vitamin D supplementation, daily dosing, but not infrequent large-bolus dosing, reduced total cancer mortality. For total cancer incidence, bolus dosing did not reduce the risk and the benefits of daily dosing were limited to normal-weight individuals.

20 pags., 10 figs., 1 tab., Helium Atom Scattering (HAS) and Helium Spin-Echo scattering (HeSE), together helium scattering, are well established, but non-commercial surface science techniques. They are characterised by the beam inertness and very low beam energy (

We present here a study of the magnetic properties of the antiferromagnetic dimer material CuVOF$_4$(H$_2$O)$_6\cdot$H$_2$O, in which the dimer unit is composed of two different $S = 1/2$ species, Cu(II) and V(IV). An applied magnetic field of $\mu_0H_{\rm c1} = 13.1(1)~\rm T$ is found to close the singlet-triplet energy gap, the magnitude of which is governed by the antiferromagnetic intradimer, $J_0 \approx 21~\rm K$, and interdimer, $J' \approx 1~\rm K$, exchange energies, determined from magnetometry and electron-spin resonance measurements. The results of density functional theory (DFT) calculations are consistent with the experimental results and predicts antiferromagnetic coupling along all nearest-neighbor bonds, with the magnetic ground state comprising spins of different species aligning antiparallel to one another, while spins of the same species are aligned parallel. The magnetism in this system cannot be accurately described by the overlap between localized V orbitals and magnetic Cu orbitals lying in the Jahn-Teller (JT) plane, with a tight-binding model based on such a set of orbitals incorrectly predicting that interdimer exchange should be dominant. DFT calculations indicate significant spin density on the bridging oxide, suggesting instead an unusual mechanism in which intradimer exchange is mediated through the O atom on the Cu(II) JT axis., Comment: Main - 12 pages, 11 figures. Supplemental Information - 11 pages, 11 figures; V2 - Corrected typo in author list

The change in bending rigidity with temperature κ(T) for 2D materials is highly debated: theoretical works predict both increase and decrease. Here we present measurements of κ(T), for a 2D material: AB-stacked bilayer graphene. We obtain κ(T) from phonon dispersion curves measured with helium atom scattering in the temperature range 320–400 K. We find that the bending rigidity increases with temperature. Assuming a linear dependence over the measured temperature region we obtain κ(T)=[(1.3 ± 0.1) + (0.006 ± 0.001)T/K] eV by fitting the data. We discuss this result in the context of existing predictions and room temperature measurements. publishedVersion

This Festschrift issue for Peter Toennies includes a collection of articles on new horizons in the dynamics of molecules: from gases to surfaces.

Helium-atom scattering (HAS) spectroscopy from conducting surfaces has been shown to provide direct information on the electron&ndash, phonon interaction, more specifically the mass-enhancement factor &lambda, from the temperature dependence of the Debye&ndash, Waller exponent, and the mode-selected electron&ndash, phonon coupling constants &lambda, Q&nu, from the inelastic HAS intensities from individual surface phonons. The recent applications of the method to superconducting ultra-thin films, quasi-1D high-index surfaces, and layered transition-metal and topological pnictogen chalcogenides is briefly reviewed.

11 pags., 3 figs., 1 tab. -- We adknowledge support by the CSIC Open Access Publication Initiative through its Unit Information Resources for Research (URICI), Recent theory has demonstrated that the value of the electron–phonon coupling strength l can be extracted directly from the thermal attenuation (Debye–Waller factor) of helium atom scattering reflectivity. This theory is here extended to multivalley semimetal systems and applied to the case of graphene on different metal substrates and graphite. It is shown that l rapidly increases for decreasing graphene–substrate binding strength. Two different calculational models are considered which produce qualitatively similar results for the dependence of l on binding strength. These models predict, respectively, values of lHAS = 0.89 and 0.32 for a hypothetical flat free-standing single-layer graphene with cyclic boundary conditions. The method is suitable for analysis and characterization of not only the graphene overlayers considered here, but also other layered systems such as twisted graphene bilayers., This work is partially supported by a grant with Ref. FIS2017-83473-C2-1-P from the Ministerio de Ciencia (Spain). We also acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI)

10 pags., 5 figs., 1 tab., Atom scattering is becoming recognized as a sensitive probe of the electron–phonon interaction parameter λ at metal and metal-overlayer surfaces. Here, the theory is developed, linking λ to the thermal attenuation of atom scattering spectra (in particular, the Debye–Waller factor), to conducting materials of different dimensions, from quasi-1D systems such as W(110):H(1 × 1) and Bi(114), to quasi-2D layered chalcogenides, and high-dimensional surfaces such as quasicrystalline 2ML-Ba(0001)/Cu(001) and d-AlNiCo(00001). Values of λ obtained using He atoms compare favorably with known values for the bulk materials. The corresponding analysis indicates in addition, the number of layers contributing to the electron–phonon interaction, which is measured in an atom surface collision., This work was partially supported by a grant with Ref. FIS2017-83473-C2-1-P from the Ministerio de Ciencia, Universidades e Innovación (Spain).

8 pags., 5 figs., 1 tab., He atom scattering has been shown to be a sensitive probe of electron-phonon interaction properties at surfaces. Here it is shown that measurements of the thermal attenuation of the specular He atom diffraction peak (the Debye-Waller effect) can determine the electron-phonon coupling constant, for ultrathin films of metal overlayers on various close-packed metal substrates. Values of obtained for single and multiple monolayers of alkali metals, and for Pb layers on Cu(111), extrapolated to large thicknesses, agree favorably with known bulk values. This demonstrates that He atom scattering can measure the electron-phonon coupling strength as a function of film thickness on a layer-by-layer basis., This work is partially supported by a grant with ref. FIS2014-52172-C2-1- P from the Ministerio de Economia y Competitividad (Spain).

We report Ne atom scattering from clean Ru(0001) and from Ru(0001) covered with a single layer of graphene. For both systems, the quantum and classical regimes are observed and analyzed. The quantum to classical boundary is explored by varying both the surface temperature and the incident Ne kinetic energy. The classical smooth surface model is used to perform theoretical simulations in order to reproduce the angular distributions in the classical regime and determine the effective surface mass and hence allow determination of the Debye temperature. The theoretical calculations, in agreement with experiments, predict angular distributions that are subspecular at low energies and shift to supraspecular with increasing incident energy. The energy-resolved spectra in the classical regime exhibit only a single and somewhat broad multiphonon peak, but this peak persists into the regime where quantum features are also observed; thus care must be taken to avoid misinterpretation of the multiphonon background pea...

The habitat complexity of streams contributes to their biotic diversity and to their overall stream metabolism. Habitat complexity is manifested in several ways. Here we are interested specifically in physical complexity inherent in geomorphologic structures and non-uniform bed substrate at multiple spatial scales; essentially, we are considering the numerous pockets and interstices in the stream caused by both abiotic (stones, pebbles and rocks) and biotic (macro-phytes, organic debris) material. This paper explores the relationship between the dispersive fraction parameter of the Aggregated Dead Zone Model (as a surrogate for physical habitat complexity) and flow rate for streams. Results were obtained by fitting the model to a set of tracer data from several streams in Norway, the United Kingdom and Poland. The results show that while there was no apparent correlation between the dispersive fraction and flow rate, the variance in possible values for the dispersive fraction increases with decreasing flow rate. These results suggest possible estimates of this parameter but crucially also suggest uncertainties to be ascribed along with this estimate. They also suggest that as streams decrease in size the variance in physical habitat complexity increases.

7 pags., 3 figs., 1 tab., He atom scattering has been demonstrated to be a sensitive probe of the electron-phonon interaction parameter λ at metal and metal-overlayer surfaces. Here it is shown that the theory linking λ to the thermal attenuation of atom scattering spectra (the Debye-Waller factor) can be applied to topological semimetal surfaces, such as the quasi-one-dimensional charge-density-wave system Bi(114) and the layered pnictogen chalcogenides. The electron-phonon coupling, as determined for several topological insulators belonging to the class of bismuth chalcogenides, suggests a dominant contribution of the surface quantum well states over the Dirac electrons in terms of λ., This work is partially supported by a grant with ref. FIS2017-83473-C2-1-P from the Ministerio de Ciencia Universidades e Innovacion (Spain). A.R., W.E.E., and ́ A.T. acknowledge financial support provided by the FWF (Austrian Science Fund) within projects J3479-N20 and P29641-N36. G.B. gratefully acknowledges the Italian Ministry of University and Research (MIUR) for financial support through grant “Dipartimenti di Eccellenza-2017 Materials for Energy”.

Aquatic CO2 emissions are expected to increase if warming reduces photosynthesis relative to respiration. An analysis of streams across a 41 °C temperature gradient reveals that the thermal responses of respiration and photosynthesis are similar.

Work on theories of gas–surface interactions received a strong impetus from advances in experimental physics in the early part of the last century, notably from the work of Stern and coworkers on verifying the Maxwell–Boltzmann distribution and the work of Roberts in measuring the energy accommodation coefficient. Much of the subsequent experimental work has involved gases made up of heavy mass atoms with large incident energies and relatively high surface temperatures, which are the conditions under which the scattering can be described with classical physics. In this paper a straightforward theory of classical gas–surface scattering is considered and applied to the analysis of a wide variety of experiments. The theory depends on limited information about the nature of the actual particle–surface interaction potential but does correctly account for the necessary laws of conservation of energy and momentum. Analysis of well-controlled experiments in the classical regime involving rare gases scattering from liquid, metal, and insulator surfaces is shown to yield a great deal of information about the atom–surface interaction and also reveals limitations on what such experiments are capable of revealing about the collision process.

Growing anthropopressure in mountain streams aimed at limiting erosion and flood protection often caused adverse effects on the natural environment. In recent years, great attention has been paid to the restoration and conservation of natural habitats in mountain streams using environmentally friendly solutions such as the Block Ramp (BR) Hydraulic Structures. In this study we investigated the factors responsible for spatial variability in thermal and oxygen conditions at the single BR structure in the growing season, and the relation between water temperature and dissolved oxygen (DO) concentration. This has been done by measurements of hydraulic characteristics along with physicochemical properties of water, such as water temperature and DO concentration, at two different discharges. The redundancy analysis has been applied in order to describe the relationships among hydraulic parameters and physicochemical variables, and extract potential sources of water temperature and DO variability within the BR hydraulic structure. Results have shown that DO and water temperature distributions within the BR hydraulic structure depend on discharge conditions and are associated with the submergence of the block ramp. The highest heterogeneity in hydraulic, DO and water temperature conditions occurs at low flow and is associated with the presence of crevices between protruding cobbles at the block ramp. The lowest variability, in turn, occurs at high discharge, when the block ramp is completely submerged. The results indicated that thermal and oxygen conditions within the BR hydraulic structure are independent of hydraulic parameters at low flow. Moreover, the relation between DO concentration and water temperature is positive at low flow indicating potential impact of biological processes. On the contrary, at high discharge both, the DO concentrations and water temperature within the BR structure, depend on bed shear velocity and maximum Reynolds number.

We investigate the low-temperature magnetic properties of the molecule-based chiral spin chain [Cu(pym)(H_{2}O)_{4}]SiF_{6}·H_{2}O (pym=pyrimidine). Electron-spin resonance, magnetometry and heat capacity measurements reveal the presence of staggered g tensors, a rich low-temperature excitation spectrum, a staggered susceptibility, and a spin gap that opens on the application of a magnetic field. These phenomena are reminiscent of those previously observed in nonchiral staggered chains, which are explicable within the sine-Gordon quantum-field theory. In the present case, however, although the sine-Gordon model accounts well for the form of the temperature dependence of the heat capacity, the size of the gap and its measured linear field dependence do not fit with the sine-Gordon theory as it stands. We propose that the differences arise due to additional terms in the Hamiltonian resulting from the chiral structure of [Cu(pym)(H_{2}O)_{4}]SiF_{6}·H_{2}O, particularly a uniform Dzyaloshinskii-Moriya coupling and a fourfold periodic staggered field.

Global quantitative estimations of ecosystem functions are vital. Among those, ecosystem respiration and photosynthesis contribute to carbon cycling and energy flow to food webs. These can be estimated in streams with the open channel diel oxygen method (single or two stations) essentially relying on a mass balance of oxygen over a defined reach. The method is generally perceived as low cost and easy to apply with new drift free optic sensors. Yet, it remains challenging on several key issues reviewed here: measurements of gas transfer at the air-water interface, appropriate mixing of tracers, uncertainty propagation in the calculations, spatial heterogeneity in oxygen concentrations, the derivation of net primary production (NPP) or autotrophic respiration, and the temperature dependence of photosynthesis and respiration. An extremely simple modeling tool is presented in an Excel workbook recommended for teaching the basic principles of the method. The only method able to deal with stream spatial heterogeneity is the method by Demars et al. Example data, Excel workbook, and R script are provided to run stream metabolism calculations. Direct gas exchange determination is essential in shallow turbulent streams, but modeling may be more accurate in large (deep) rivers. Lateral inflows should be avoided or well characterized. New methods have recently been developed to estimate NPP using multiple diel oxygen curves. The metabolic estimates should not be systematically temperature corrected to compare streams. Other recent advances have improved significantly the open channel diel oxygen method, notably the estimation of respiration during daylight hours.

Measurements of Ne atom scattering from a clean and ordered Ir(111) surface are shown under conditions in which the scattering is nearly classical. The only quantum mechanical manifestation is a small elastic specular diffraction intensity. The energy-resolved intensity spectra exhibit only a single broad peak attributed to multiple phonon excitations. The multiphonon peak is well explained by classical scattering theory. It is shown that the multiphonon peak can mimic the behavior of a single-phonon dispersion curve, however, measurements at different incident energies can be used to identify this false dispersion curve.

Using 25 tracer experiments, parameters of the transient storage model (TSM) were evaluated for a reach of the river Brock in north-west England with the primary aim of investigating their dependence on flow rate. Since only a very few previous studies have considered this issue, these new results aid our understanding on how the TSM could be applied to a reach at flow rates beyond the range of flow rates for which observations of solute transport exist. Velocity increased with increasing flow rate in a manner consistent with current knowledge. In contrast, and unexpectedly, the dispersion coefficient reduced (weakly) with increasing flow rate and the values were rather scattered. The transient storage exchange rate increased with increasing flow rate, which corroborates some of the sparse existing knowledge of this parameter’s behaviour. The ratio of transient storage area to main channel area was essentially constant over the range of flow rates examined, which is consistent with some studies on single reaches.

Specific features of diffractive scattering of H

This work aimed to examine the impact of rapid hydraulic structures on water temperature and dissolved oxygen concentration in the Porebianka mountain stream. This has been achieved by measurements of hydraulic characteristics and physiochemical properties of water such as water temperature and dissolved oxygen concentration. It has been shown that rapid hydraulic structures exhibit a large spatial diversity in morphology and flow paths, that manifests in the spatial heterogeneity of thermal conditions and oxygen concentrations at a single structure scale. The results have demonstrated that pools between the rapid have higher oxygen concentrations when compared to the rapid region. The highest concentrations of oxygen occured in pools located close to the upstream edge of the rapid ramp where the flow undergoes gradual acceleration. Elevated concentrations of dissolved oxygen were also observed in the dissipation basin. The lowest concentrations were observed at stream banks. The results emphasise the relative importance of site-specific characteristics on physiochemical properties of flow, which might help to understand multi-scale processes across rivers and improve future plans of restoration practices in mountain streams.

Сексуальная дисфункция является важной детерминантой здоровья и качества жизни женщин и обычно связана со снижением уровня эстрогенов в период менопаузального перехода. Цель. Определение влияния пероральной и трансдермальной терапии эстрогенами в сравнении с плацебо на сексуальную функцию у женщин в постменопаузе. Дизайн, параметры и участники. Дополнительное исследование Kronos Early Estrogen Prevention Study (KEEPS), четырехлетнее проспективное рандомизированное двойное слепое плацебо-контролируемое исследование менопаузальной гормональной терапии у здоровых женщин в ранней постменопаузе. Из 727 участников KEEPS 670 согласились принять участие в этом многоцентровом вспомогательном исследовании. Включали женщин от 42 до 58 лет в течение 36 месяцев от их последнего менструального цикла. Данные были собраны в период с июля 2005 года по июнь 2008 года и проанализированы с июля 2010 года по июнь 2017 года. Вмешательства. Женщины были рандомизированы на прием либо 0,45 мг/сут конъюгированных лошадиных эстрогенов (o-CEE), либо на 50 мкг/день трансдермального 17β-эстрадиола (t-E2), либо на плацебо. Участники также получали 200 мг перорального микронизированного прогестерона (если они были рандомизированы на o-CEE или t-E2) или плацебо (если принимали плацебо-эстрогены) в течение 12 дней в месяц. Основные результаты и измерения. Аспекты сексуальной функции (желание, возбуждение, смазка, оргазм, удовлетворенность и боль) оценивались с использованием опросника Female Sexual Function Inventory (FSFI, диапазон – 0–36 баллов, более высокие оценки – лучшая сексуальная функция). Низкая сексуальная функция (LSF) была определена как общий балл FSFI менее 26,55. Дисстресс, связанный с низкой оценкой FSFI, не оценивали. Результаты. У 670 участников был средний возраст 52,7 (2,6) года. Прием t-E2 был связан со значительным улучшением общей оценки FSFI во всех временных точках по сравнению с плацебо (средняя эффективность 2,6; 95% ДИ: 1,11–4,10; скорректированная P=0,002). При приеме o-CEE существенной разницы в общем балле FSFI не было по сравнению с плацебо (средняя эффективность 1,4; 95% ДИ: ̶ 0,1 до 2,8; скорректированная Р=0,13). Не было разницы в общем балле FSFI между группами t-E2 и o-CEE в среднем за 48 месяцев (скорректировано P=0,22). В отдельных областях половой функции лечение t-E2 ассоциировалось со значительным улучшением, например увеличением количества смазки (0,61; 95% ДИ: 0,25–0,97; P=0,001) и уменьшенной болью (0,67; 95% ДИ: 0,25–1,09; P=0,002) по сравнению с плацебо. В целом доля женщин с LSF была значительно ниже после лечения t-E2 по сравнению с плацебо (67%; 95% ДИ: 55–77% против 76%; 95% ДИ: 67–83%; Р=0,04). В группе o-CEE существенного снижения LSF не было. Заключение. Лечение t-E2 характеризовалось умеренным улучшением половой функции у женщин в постменопаузе, но неизвестно, облегчило ли это симптомы дисстресса. Регистрация исследования Идентификатор: NCT00154180

© 2018 authors. Published by the American Physical Society. A chemically stable bilayers of SiO2 (2D silica) is a new, wide band gap 2D material. Up till now graphene has been the only 2D material where the bending rigidity has been measured. Here we present inelastic helium atom scattering data from 2D silica on Ru(0001) and extract the first bending rigidity, κ, measurements for a nonmonoatomic 2D material of definable thickness. We find a value of κ=8.8 eV±0.5 eV which is of the same order of magnitude as theoretical values in the literature for freestanding crystalline 2D silica.

Diamond anvil cell techniques, synchrotron-based infrared and Raman spectroscopies, and lattice dynamics calculations are combined with prior magnetic property work to reveal the pressure-temperature phase diagram of Co[N(CN)

Significant disagreement and debate persist regarding several aspects of the optimal surgical management of oesophageal cancer. We address some of these issues based on our consecutive series of 165 patients undergoing oesophageal resection (reported in full elsewhere) and the available literature. The areas considered are controversial but we argue in favour of a ‘traditional’ two-stage open approach (Ivor–Lewis), leaving the pylorus alone, making no attempt to perform a radical lymphadenectomy and fashioning a hand sewn anastomosis.

Specific features of diffractive scattering of H2 from metal surfaces can serve as fingerprints of the reactivity of the metal towards H2, and in principle theory-experiment comparisons for molecular diffraction can help with the validation of semi-empirical functionals fitted to experiments of sticking of H2 on metals. However, a recent comparison of calculated and Debye-Waller (DW) extrapolated experimental diffraction probabilities, in which the theory was done on the basis of a potential energy surface (PES) accurately describing sticking to Ru(0001), showed substantial discrepancies, with theoretical and experimental probabilities differing by factors of 2 and 3. We demonstrate that assuming a particular amount of random static disorder to be present in the positions of the surface atoms, which can be characterized through a single parameter, removes most of the discrepancies between experiment and theory. Further improvement might be achievable by improving the accuracy of the DW extrapolation, the model of the H2 rotational state distribution in the experimental beams, and by fine-tuning the PES. However, the question of whether the DW model is applicable to attenuation of diffractive scattering in the presence of a sizable van der Waals well (depth ≈ 50 meV) should also receive attention, in addition to the question of whether the amount of static surface disorder effectively assumed in the modeling by us could have been present in the experiments.

6 págs.; 2 figs.; 1 tab., A new quantum-theoretical derivation of the elastic and inelastic scattering probability of He atoms from a metal surface, where the energy and momentum exchange with the phonon gas can occur only through the mediation of the surface free-electron density, shows that the Debye-Waller exponent is directly proportional to the electron-phonon mass coupling constant ?. The comparison between the values of ? extracted from existing data on the Debye-Waller factor for various metal surfaces and the ? values known from literature indicates a substantial agreement, which opens the possibility of directly extracting the electron-phonon coupling strength in quasi-2D conducting systems from the temperature or incident energy dependence of the elastic helium atom scattering intensities. © 2016 American Chemical Society, This work is partially supported by a grant with ref. FIS2014- 52172-C2-1-P from the Ministerio de Economia y Competitividad (Spain).

Summary 1. It is becoming increasingly clear that fresh waters play a major role in the global C cycle. Stream ecosystem respiration (ER) and gross primary productivity (GPP) exert a significant control on organic carbon fluxes in fluvial networks. However, little is known about how climate change will influence these fluxes. 2. Here, we used a ‘natural experiment’ to demonstrate the role of temperature and nutrient cycling in whole-system metabolism (ER, GPP and net ecosystem production – NEP), in naturally heated geothermal (5–25 °C) Icelandic streams. 3. We calculated ER and GPP with a new, more accurate method, which enabled us to take into account the additional uncertainties owing to stream spatial heterogeneity in oxygen concentrations within a reach. ER ranged 1–25 g C m−2 day−1 and GPP 1–10 g C m−2 day−1. The median uncertainties (based on 1 SD) in ER and GPP were 50% and 20%, respectively. 4. Despite extremely low water nutrient concentrations, high metabolic rates in the warm streams were supported by fast cycling rates of nutrients, as revealed from inorganic nutrient (N, P) addition experiments. 5. ER exceeded GPP in all streams (with average GPP/ER = 0.6) and was more strongly related to temperature than GPP, resulting in elevated negative NEP with warming. We show that, as a first approximation based on summer investigations, global stream carbon emission to the atmosphere would nearly double from 0.12 Pg C year−1 at 13 °C to 0.21 (0.15–0.33) Pg C year−1 with a 5 °C warming. 6. Compared to previous studies from natural systems (including terrestrial ecosystems), the temperature dependence of stream metabolism was not confounded by latitude or altitude, seasonality, light and nutrient availability, water chemistry, space availability (water transient storage), and water availability. 7. Consequently, stream nutrient processing is likely to increase with warming, protecting downstream ecosystems (rivers, estuaries, coastal marine systems) during the summer low flows from nutrient enrichment, but at the cost of increased CO2 flux back to the atmosphere.

Calculations are carried out for the energy accommodation coefficient at a gas–surface interface using a recently developed classical mechanical theory of atom–surface collisions that includes both direct scattering and trapping–desorption processes in the physisorption well of the interaction potential. Full three-dimensional calculations are compared with the available data for the accommodation of rare gases at a tungsten surface and reasonable agreement is found for the heavier gases for which classical physics is expected to be valid at all measured temperatures.

Stream ecology may be influenced by the temporary trapping of solutes in geomorphologic structures, which is usually quantified by fitting the Transient Storage Model to tracer data. This paper explores the relationships between the parameters of this model and those of two simpler models, namely the Advection-Dispersion Model and the Aggregated Dead Zone model. It is motivated by the possibility of obtaining more reliable transient storage parameter values by correlating them with the parameters of the other models instead of evaluating them directly. Results were obtained by fitting all three models to a set of tracer data from mountain streams, predominantly in Iceland. Some strong correlations were found between some of the parameters of the transient storage model and the advection-dispersion model, but no strong correlations were found between the parameters of the transient storage model and the aggregated dead zone model. For all three models, combinations of the optimized parameters correctly described the bulk movement of the solute cloud, giving confidence in the optimized parameters.

Certain epoxy paints and filled resins were shown to be potentially useful protective coatings for concrete exposed to hot saline media. Since, however, very little information was available about water-polymer interactions at elevated temperatures, a study of permeation and of dielectric and mechanical relaxation was begun. In this part of the study, the permeation of liquid water through an epoxy film (filled with 0, 10, and 20 wt.-% spherical glass beads) was measured at temperatures up to 130°CC. As expected, the filler served to decrease permeation, though to a greater extent than predicted. Arrhenius plots of permeation revealed several other characteristics. In general a discontinuity was observed at Tg, with the apparent energies of activation, Ea, being lower below Tg (4–11 kcal/mole, compared to 19–26 kcal/mole). Both the sharpness of the transition and Ea were sensitive to the history of the specimen. At elevated temperatures, the most highly filled specimen showed an additional relative decrease of permeability in comparison with other specimens. An interpretation of the data is proposed, based on segmental mobility as affected by restrictions due to the presence of filler particles.

A numerical model of the medial open wedge tibial osteotomy based on the finite element method was developed. Two plate positions were tested numerically. In a configuration, (a), the plate was fixed in a medial position and (b) in an anteromedial position. The simulation took into account soft tissues preload, muscular tonus and maximal gait load.The maximal stresses observed in the four structural elements (bone, plate, wedge, screws) of an osteotomy with plate in medial position were substantially higher (1.13-2.8 times more) than those observed in osteotomy with an anteromedial plate configuration. An important increase (1.71 times more) of the relative micromotions between the wedge and the bone was also observed. In order to avoid formation of fibrous tissue at the bone wedge interface, the osteotomy should be loaded under 18.8% (approximately 50 kg) of the normal gait load until the osteotomy interfaces union is achieved.

The majority of approaches for predicting pollutant transport in rivers rely on being able to estimate dispersion coefficients. This paper describes four methods for doing this and argues that in most cases practising engineers would rely on one of numerous predictive equations that have been proposed over the past 30 years or so. The paper reviews these equations and discusses some recent improvements to the theoretical representation of pertinent transport processes that implies that the latest predictors should be more reliable than older ones. Use of seven predictors for a simple test case shows considerable scatter in predictive values, indicating that predicting dispersion coefficients remains a difficult task. Interestingly, theoretically based predictors seem to give reasonably consistent, but possibly low, values while predictors that are heavily reliant on regression to observed values seem to overpredict. The paper will be of interest to practising engineers who use computer models to predict t...