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Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is mainly transmitted via droplets and aerosols. To evaluate the role of transmission by fomites, SARS-CoV-2-specific data on transfer rates from surfaces to hands and from hands to face are lacking. Here, we generated quantitatively controlled transfer rates for SARS-CoV-2 from food items (lettuce, ham, and vegetarian meat alternative [VMA]) and packaging materials (cardboard and plastic) to gloves using a wet, dry, and frozen viral inoculum and from glove to glove using a wet viral inoculum. For biosafety reasons, the transfer from surfaces to hands and hands to face was simulated by using gloves. The cumulative transfer rate was calculated by using the data from the first transfer experiment, food or packaging material to glove, and combined with the transfer rate obtained from the second transfer experiment from glove to glove. The cumulative transfer rates from lettuce (4.7%) and ham (3.4%) were not significantly different (

We present the design and characterization of a large-area Cryogenic PhotoDetector (CPD) designed for active particle identification in rare event searches, such as neutrinoless double beta decay and dark matter experiments. The detector consists of a $45.6$ $\mathrm{cm}^2$ surface area by 1-mm-thick $10.6$ $\mathrm{g}$ Si wafer. It is instrumented with a distributed network of Quasiparticle-trap-assisted Electrothermal feedback Transition-edge sensors (QETs) with superconducting critical temperature $T_c=41.5$ $\mathrm{mK}$ to measure athermal phonons released from interactions with photons. The detector is characterized and calibrated with a collimated $^{55}$Fe X-ray source incident on the center of the detector. The noise equivalent power is measured to be $1\times 10^{-17}$ $\mathrm{W}/\sqrt{\mathrm{Hz}}$ in a bandwidth of $2.7$ $\mathrm{kHz}$. The baseline energy resolution is measured to be $\sigma_E = 3.86 \pm 0.04$ $(\mathrm{stat.})^{+0.23}_{-0.00}$ $(\mathrm{syst.})$ $\mathrm{eV}$ (RMS). The detector also has an expected timing resolution of $\sigma_t = 2.3$ $\mu\mathrm{s}$ for $5$ $\sigma_E$ events., Comment: 6 pages, 5 figures

A major thrust of the work has been an effort to reduce or eliminate aflatoxin contamination by acquiring more information on the biology of the toxin-producing species, Aspergillus flavus and A. parasiticus, as well as on factors affecting fungal infection and the aflatoxin contamination level. Heterogeneity in stored maize may reflect preharvest crop conditions, meteorological events during harvest, or handling technique during and after harvest. Grain entering commercial channels is often intentionally blended to achieve: an average moisture level required for a specific grade, a specific quality level, by blending lower with higher quality grain, and additional storage time, by blending dry grain with high-moisture grain. Effective biological control of aflatoxin-producing fungi in developing maize kernels requires information about the range of fungal species that can effectively compete in the econiche. The laboratory studies of microbial competition with aflatoxin-producing fungi on postharvest maize have produced provocative concepts on nature of the interacting mycoflora on the mature seed.

We present limits on spin-independent dark matter-nucleon interactions using a $10.6$ $\mathrm{g}$ Si athermal phonon detector with a baseline energy resolution of $\sigma_E=3.86 \pm 0.04$ $(\mathrm{stat.})^{+0.19}_{-0.00}$ $(\mathrm{syst.})$ $\mathrm{eV}$. This exclusion analysis sets the most stringent dark matter-nucleon scattering cross-section limits achieved by a cryogenic detector for dark matter particle masses from $93$ to $140$ $\mathrm{MeV}/c^2$, with a raw exposure of $9.9$ $\mathrm{g}\cdot\mathrm{d}$ acquired at an above-ground facility. This work illustrates the scientific potential of detectors with athermal phonon sensors with eV-scale energy resolution for future dark matter searches., Comment: 7 pages, 4 figures, this version includes ancillary files from official data release

Ammonia (R717) is a commonly used refrigerant, often used in food, beverage and chemical industry for example. Recently, R717 is also used in high-temperature heat pumps. Typically, hydrocarbon oils like mineral oil (MO), polyalphaolefine (PAO) and alkyl benzene (AB) are applied for lubricating R717 compressors. In our previous experiments as well as the latest literature it was found that at high temperatures ammonia dissolves in these oils and thus affects the viscosity stronger than expected. The solubility of R717 increases from around 1% at room temperature to more than 10% at temperatures above 100 °C. For this reason, it is necessary to think about generating corresponding viscosity–temperature charts for such systems. The paper deals with measurements of solubility, vapour pressure and viscosity of four different oils mixed with ammonia up to 50 bar and 140 °C. The density was determined based on the bending vibration principle; the pressure of three to five refrigerant–oil-mixtures (90–99% oil) per oil was determined with a static measurement method. With the results from the pressure measurement, the miscibility gap was calculated. To prevent segregation during the viscosity experiment a complex measurement setup was developed. After measuring the viscosity of the pure oils and the mixtures, the viscosity reduction was calculated and data are presented in the form of “Daniel Charts”, a viscosity–temperature chart that is combined with solubility data. For the first time, high temperature behaviour of several types and viscosity grades of hydrocarbon oils with ammonia can be compared by Daniel charts to choose the best oil for high-temperature ammonia heat pump applications.

Regular corn cells have nuclei with 20 chromosomes. Ten of these are derived from the egg cell and ten from the sperm nucleus that fertilizes the egg. Corn cross-pollinates when silks protruding from the ear shoot capture pollen grains from the tassel which germinate on the silk and then releases two sperms, each bearing 10 chromosomes. The nucleus of one sperm fuses with the egg to form the zygote (2n = 20 chromosomes), whereas the other with one of the two polar nuclei, which then fuses with the other polar nucleus, forms a primary endosperm nucleus with 3n cells. The corn kernel is a single fruit constituted by the embryo, endosperm, aleurone, and pericarp. The pericarp is the transformed ovary wall, whereas the single-layered aleurone is part of the endosperm containing 3n cells. The starchy endosperm makes up the greater part of the kernel and the embryo and is actually a dormant young corn plant constituted by the plumule and primary root and the scutellum rich in nutrients necessary for germination. The pedicel serves as the attachment point of the kernel to the cob. The main strategies used to generate new varieties and hybrids are mass selection, random selfed lines, recurrent selection, and single cross and modified single-cross hybridization. Corn kernels can be altered by genetic means to give modifications in quantity and type of starch, protein, oil, and other aspects such as pericarp thickness or kernel hardness. Because of these strategies, many specialty corns have been generated like white, waxy, high-amylose, quality protein, high oil, popcorn, and sweet corns. Certified or registered seed production requires special attention in order to keep the pedigree and assure viability. Seeds are carefully harvested, dried, shelled, cleaned/sized, and treated with pesticides before marketing.

The risk of importing foot and mouth disease, a highly contagious viral disease of livestock, severely restricts trade and investment opportunities in many developing countries where the virus is present. This study was designed to investigate the inactivation of foot and mouth disease virus (FMDV) by heat treatments used in extruded commercial pet food manufacture. If extrusion could be shown to reliably inactivate the virus, this could potentially facilitate trade for FMDV-endemic countries. The authors found that there was no detectable virus following: i) treatment of FMDVspiked meat slurry at 68°C for 300 s; ii) treatment of FMDV-spiked slurry and meal mix at 79°C for 10 or 30 s, or iii) treatment of homogenised bovine tongue epithelium, taken from an FMDV-infected animal, at 79°C for 10 s. This corresponds to an estimated 8 log10 reduction in titre (95% credible interval: 6 log10 -13 log10). Furthermore, the authors found that the pH of the slurry and meal mix was sufficient to inactivate FMDV in the absence of heat treatment. This demonstrates that heat treatments used in commercial pet food manufacture are able to substantially reduce the titre of FMDV in infected raw materials.

In this letter, we present the performance of a $100~\mu\mathrm{m}\times 400~\mu\mathrm{m} \times 40~\mathrm{nm}$ tungsten (W) Transition-Edge Sensor (TES) with a critical temperature of 40 mK. This device has a measured noise equivalent power (NEP) of $1.5\times 10^{-18}\ \mathrm{W}/\sqrt{\mathrm{Hz}}$, in a bandwidth of $2.6$ kHz, indicating a resolution for Dirac delta energy depositions of $40\pm 5~\mathrm{meV}$ (rms). The performance demonstrated by this device is a critical step towards developing a $\mathcal{O}(100)~\mathrm{meV}$ threshold athermal phonon detectors for low-mass dark matter searches., Comment: 5 pages, 6 figures. Accepted for publication at AIP Advances

Palladium was deposited gradually under ultrahigh vacuum onto a well-defined surface of (0001)- oriented n-type GaN, at room temperature. Each deposition step was followed by annealing. Physicochemical proper- ties of the Pd adlayers were in situ investigated prior to and after annealing by the X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, low-energy elec- tron diffraction, scanning tunneling microscopy and atomic force microscopy techniques. Annealing resulted in the formation of GaPd2 and GaPd intermetallic compounds at 550 C and at 800 C. Even for thicker layers, the com- pounds were strongly dispersed, forming 3D nanostruc- tures. The substrate uncovered by the compounds revealed Ga-rich GaN(0001)-(1 9 1) surface. Formation of Ga-Pd- N bonds or Pd nitrides was not detected at the surface. The Ga-Pd intermetallic compound surface engineered on the GaN(0001) substrate can be used as the strongly dispersed catalyst or a model catalyst.

The risk of importing foot and mouth disease, a highly contagious viral disease of livestock, severely restricts trade and investment opportunities in many developing countries where the virus is present. This study was designed to investigate the inactivation of foot and mouth disease virus (FMDV) by heat treatments used in extruded commercial pet food manufacture. If extrusion could be shown to reliably inactivate the virus, this could potentially facilitate trade for FMDV-endemic countries. The authors found that there was no detectable virus following: i) treatment of FMDVspiked meat slurry at 68°C for 300 s; ii) treatment of FMDV-spiked slurry and meal mix at 79°C for 10 or 30 s, or iii) treatment of homogenised bovine tongue epithelium, taken from an FMDV-infected animal, at 79°C for 10 s. This corresponds to an estimated 8 log10 reduction in titre (95% credible interval: 6 log10 -13 log10). Furthermore, the authors found that the pH of the slurry and meal mix was sufficient to inactivate FMDV in the absence of heat treatment. This demonstrates that heat treatments used in commercial pet food manufacture are able to substantially reduce the titre of FMDV in infected raw materials.En raison du risque d’introduction de la fièvre aphteuse, une maladie virale très contagieuse affectant le bétail, les échanges internationaux et les possibilités d’investissement de nombreux pays en développement sont soumis à des restrictions majeures. La présente étude vise à déterminer si les traitements thermiques appliqués lors de la fabrication industrielle d’aliments extrudés destinés aux animaux de compagnie sont efficaces pour inactiver le virus de la fièvre aphteuse dans ces produits. Si la procédure d’extrusion avait pour propriété démontrée d’inactiver le virus de manière fiable, les pays où le virus de la fièvre aphteuse est présent à l’état endémique pourraient accéder plus facilement aux échanges internationaux. Les auteurs n’ont pas trouvé de virus détectable à l’issue des opérations suivantes : i) traitement à 68 °C pendant 300 s d’une bouillie de viandes à laquelle avait été ajoutée une quantité connue de virus de la fièvre aphteuse ; ii) traitement à 79 °C pendant 10 ou 30 s d’un mélange de bouillie et de pâté auquel avait été ajoutée une quantité connue de virus de la fièvre aphteuse ; iii) traitement à 79 °C pendant 10 s d’un échantillon homogénéisé d’épithélium lingual prélevé d’un bovin atteint de fièvre aphteuse. Ces résultats correspondent à une réduction estimée du titre de 8 log10 (intervalle de confiance à 95 % : 6 log10 –13 log10). En outre, les auteurs ont constaté que le pH du mélange de bouillie et de pâté était de nature à inactiver le virus de la fièvre aphteuse, en l’absence de traitement thermique. Ces résultats démontrent que les traitements thermiques utilisés lors de la fabrication industrielle d’aliments pour animaux de compagnie permettent de réduire de manière importante les titres du virus de la fièvre aphteuse dans les matières premières infectées.El riesgo de importar fiebre aftosa, enfermedad vírica muy contagiosa que afecta al ganado vacuno, restringe sobremanera el comercio y las oportunidades de inversión en muchos países en desarrollo en los que el virus está presente. Los autores describen un estudio encaminado a analizar el método de inactivación del virus por calor que se emplea en la fabricación industrial de piensos extrusionados para animales de compañía. Si quedaba demostrado que la extrusión es un método fiable para inactivar el virus de la fiebre aftosa, ello podría abrir perspectivas comerciales a todos aquellos países donde dicho virus es endémico. Los autores observaron que no había presencia detectable de virus después de: i) mantener a 68°C durante 300 segundos una emulsión cárnica enriquecida con virus de la fiebre aftosa; ii) mantener a 79°C durante 10 o 30 segundos una emulsión y una mezcla de harinas enriquecidas con el virus; o iii) mantener a 79°C durante 10 segundos un homogenado de epitelio lingual bovino procedente de un animal infectado por el virus. Ello corresponde a una reducción estimada de la titulación de log10 8 (intervalo de confianza al 95%: log10 6 – log10 13). Además, los autores observaron que, en ausencia de tratamiento térmico, el pH de la emulsión y la mezcla de harinas bastaba para inactivar el virus de la fiebre aftosa, lo que demuestra que los tratamientos térmicos utilizados en la fabricación industrial de piensos pueden reducir sustancialmente el título de virus de la fiebre aftosa en materias primas infectadas.

This work presents the result of the growth of thin zirconium films on the GaN(0 0 0 1) surface under various conditions. In experiment were used the X-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED) techniques, which allowed to investigate the chemical composition, bonding environment and surface reconstruction. It is shown that zirconium forms ZrN, ZrNxOy, ZrOx and ZrO2 compounds, depending on the selected experimental conditions: the pressure and annealing temperature. Such a varied zirconium growth behaviour is explained by the diffusion of oxygen and nitrogen in the created interface region.

Morphology of Ni/GaN contact formed at room temperature (RT) by Ni vapor deposition onto the (0 0 0 1)-oriented n-type GaN surface under ultrahigh vacuum, and morphological changes introduced by annealing were studied. Measurements were carried out in situ using XPS, UPS, LEED and STM. The WF of the Ni film of the mean thickness 1 nm equaled 4.1 eV. For thicker layers (≥2 nm), it increased to 5.1 eV. The Schottky barrier height of the Ni/GaN(0 0 0 1) contact formed at RT amounted to 1.20 eV. Annealing of the Ni/GaN contact at 650 °C resulted in Ga diffusion into the Ni film and Ni–Ga alloying. The dominating alloy phase was Ni3Ga. The alloying was accompanied by coalescence of Ni film grains into 3D islands of a Ni–Ga alloy. Annealing at 800 °C enriched the islands with Ga. The Ga-rich phases of NiGa and/or Ni3Ga2 were dominant in the alloy.

This report concerns the properties of an interface formed between Pd films deposited onto the surface of (0001)-oriented n-type GaN at room temperature (RT) under ultrahigh vacuum. The surface of clean substrate and the stages of Pd-film growth were characterized in situ by X-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM), ultraviolet photoelectron spectroscopy (UPS), and low energy electron diffraction (LEED). As-deposited Pd films are grainy, cover the substrate surface uniformly and reproduce its topography. Electron affinity of the clean n-GaN surface amounts to 3.1 eV. The work function of the Pd-film is equal to 5.3 eV. No chemical interaction has been found at the Pd/GaN interface formed at RT. The Schottky barrier height of the Pd/GaN contact is equal to 1.60 eV.

Atomic force microscopy (AFM) has become an important tool in surface science and nanotechnology. It is obvious that the intrinsic limitations of AFM must be understood in order to get useful information about surface structure of the material under study. The ability to recognize artifacts should assist in reliable evaluation of instrument operation and in reporting of data. In this paper, we discuss the most frequently encountered image artifacts in atomic force microscopy. A variety of artifacts are illustrated by the results obtained with the aid of contact AFM (C-AFM), which can help avoid misinterpretations. It is shown that, despite inaccuracies in AFM image generation, in many cases valuable information can be obtained.

Mechanisms of PTCDI–C 8 adsorption and thin films growth on Si(1 1 0)–(16 × 2) have been studied using a combination of X-ray photoelectron spectroscopy, scanning tunneling microscopy, and density functional theory. Oxygen atoms of the PTCDI–C 8 molecule interact with the substrate increasing substantially the adsorption energy. Adsorbed molecules do not form long-range ordered structures on the surface but local chain-like arrangements. A good agreement between the calculated isosurfaces of electronic charge density and the scanning tunneling microscopy images of the filled electron states of clean and adsorbate-covered surfaces allows to recognize the PTCDI–C 8 molecules adsorbed on Si(1 1 0)–(16 × 2).

Oxygen bombardment is used as the oxidation method to form an insulator on GaN substrate at room temperature. The surface of clean substrate and the Ga2O3/GaN interface are characterized in situ by X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and low-energy electron diffraction (LEED). XPS spectra of the Ga 2p core level show a peak shift of ∼1 eV from Ga O to Ga N bonding, demonstrating an oxide formation of Ga2O3. Electron affinity of the clean GaN surface amounts to 3.65 eV; the electron affinity of the Ga2O3 on GaN(0001) surface is 3.7 eV. Valence band offset (VBO) of the Ga2O3/GaN interface measured using XPS and UPS is 1.15 eV. After annealing the system at 500 °C the electron affinity and the VBO decrease to the values 3.5 and 0.35 eV, respectively.

This research focuses on development of EMG circuit to detect the EMG signal from quadriceps muscle. The circuit used Surface self-adhesive electrodes to capture muscle activity during the knee extension. The two electrodes were placed at a distance of 10mm from each other in the middle rectus femoris muscle. This is the initial effort to investigate the output signal stage by stage from EMG circuit that consists of several circuits specifically amplification, filtering and rectification. Experimental analysis results based on five subjects showed that the output signal from EMG circuit has successfully deliver the voltage output as required for the next analysis stage. The circuit was tested on all five healthy subjects with different leg dominant for data acquisition for further signal analysis.

In this work, the results of the growth of zirconium films deposited under the ultrahigh vacuum at room temperature on the 6H-SiC(0001) and GaN(0001) surfaces were studied. Observed changes in the chemical composition, bonding environment, and surface reconstruction, and the effects of high-temperature annealing of the film are presented and discussed as well. In the performed experiment, the X-ray photoelectron spectroscopy, low-energy electron diffraction, and scanning tunneling microscopy were used. The results show that for both investigated substrates, the grown films have eminently rich and varied compositions. Besides the metallic zirconium, there are also zirconium oxides, zirconium carbides, or zirconium nitrides. The growth process proceeds according to the Volmer–Weber mode. Moreover, the zirconium–semiconductor interface does not form typical Schottky contact, but some paths with a quasi-ohmic conduction character can be observed.

Atomic force microscopy and scanning tunneling microscopy have been used for nanometer scale modi cations of Sb lms deposited on 6H-SiC(0001) surface. The lms are grown in situ by vapor deposition under ultrahigh vacuum. The growth follows the Volmer Weber mode. Ultrathin (up to 3 nm on average) Sb lms which consist of no coalesced islands can be modi ed by moving the island over the substrate surface by the AFM tip. Thicker lms, which are rmer due to the coalescence, can be modi ed by the eld and/or current produced by STM tip. Final result of the modi cations is adsorbate free 6H-SiC(0001) surface restitution over the modi ed area.

The electronic structure of p-type GaN(0001) surfaces and its modi cation by antimony adsorption, and properties of Sb/GaN(0001) interface, are presented in this report. The studies were carried out in situ by ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, and low-energy electron di raction. Thin Sb layers were deposited under ultrahigh vacuum conditions onto the substrate at room temperature. Electron a nity of clean p-GaN surface amounted to 3.0 eV. A small amount of Sb on GaN(0001) surface reduced the electron a nity to 1.9 eV. The work function of the Sb layer was equal to 4.4 eV. For the Schottky barrier height of the Sb/GaN interface, the value of 2.50 eV was obtained.

Atomic-scale structure of the growth of a gold film on (1 1 2) plane of Mo single crystal was investigated by means of low energy electron diffraction (LEED) and scanning tunneling microscopy (STM) up to two monolayers (ML) of gold coverage. Both LEED and STM results establish that Au grows on Mo(1 1 2) in a layer-by-layer mode, for at least the first two monolayers. A number of ordered structures are formed and both the first and second layers adopt the Mo(1 1 2) 1 × 1 surface structure upon completion. For some gold layers on Mo(1 1 2), notably the 1.66 monolayer 3 × 1 and 1.75 monolayer 4 × 1 gold overlayers, we find evidence of a phase transition associated with increasing disorder in gold layers with structural corrugation and anisotropic band structure. The signature of this phase transition, at temperatures in the range of 400–500 K, is a sharp decrease in the overlayer effective Debye temperature.

The electrical properties and interface chemistry of Cr/6H-SiC(0 0 0 1) contacts have been studied by current-sensing atomic force microscopy (CS-AFM) and X-ray photoelectron spectroscopy (XPS). Cr layers were vapor deposited under ultrahigh vacuum onto both ex situ etched in H 2 and in situ Ar + ion-bombarded samples. The Cr/SiC contacts are electrically non-uniform. Both the measured I – V characteristics and the modeling calculations enabled to estimate changes of the Schottky barrier height caused by Ar + bombardment. Formation of ohmic nano-contacts on Ar + -bombarded surfaces was observed.

The topography of the (1 0 0) cleavage surfaces of In4Se3 layered semiconductor crystal was analyzed by atomic force microscopy (AFM) in ultrahigh vacuum. The shape and dimensions of subsequent profiles well correspond to the lattice parameters derived from bulk crystal structure obtained by X-ray diffraction. The local force curves for the cleavage surfaces under different experimental conditions are discussed.

Hydrogen etching was carried out on the (0001)-oriented 6H–SiC wafer at various temperatures in the range from 1450 to 1650 °C. Surface topography and morphology was characterized by the atomic force microscope (AFM). Optimal conditions have been found, under which all scratches due to the polishing process are efficiently removed and the atomically smooth, clean surface of SiC(0001) is achieved. The most characteristic elements observed on the perfectly etched surface were straight-line steps of equal height and nearly the same width. The AFM imaging revealed also intrinsic defects of the samples. Conditions have been found for maintaining the saturation of etching products on the surface at the level enabling the empty core dislocations to be formed during etching. The observed population of the dislocations ranges between 10 7 and 10 8 cm − 2 . Burgers vectors of the dislocations as evaluated on the basis of Frank's model are equal to 2 or 3 lattice constants.

Alq 3 thin layers were vapor deposited onto a single crystal of Si(1 1 1) and the morphology of the surface was investigated by the scanning tunneling microscope under ultrahigh vacuum conditions. The STM imaging showed considerable influence of the thermal processing onto the topography of the sample. Slowly raising the sample temperature to ∼160 °C caused a complete desorption of Alq 3 molecules and uncovering the clean surface of Si(1 1 1). A fast rise of the temperature (flashing) to ∼600 °C led to decomposition of the Alq 3 and resulted in remnants of a carbon-rich surface species. Then heating or flashing this surface to a temperature in excess of 1000 °C brought about the occurrence of regular shape object on the Si(1 1 1) surface.

The Atomic Force Microscope (AFM) with the conducting cantilever has been used as a tool for controlled printing the well-defined shapes of conductive paths on the 6H–SiC(0 0 0 1) surface as well as paths connecting the shapes. For clean 6H–SiC(0 0 0 1) samples the metal-tip/sample contact is of the diode type. The conditions have been found (tip/sample voltage, current) for which the local morphology of the surface is modified during current flow between the tip and the sample. Such a modified surface shows quite a different conduction type of the tip/sample surface contact than that of the unmodified surface.

The adsorption of two very different adsorbates, gold and oxygen, induce the formation of a (3 × 1) surface structure on both W(1 1 2) and Mo(1 1 2). In spite of similar adsorbate unit cells, the surface electronic structure, derived from photoemission, exhibits pronounced differences for the two adsorbates. Indeed, both experiment and simulations indicate substantial changes in electronic structures of (1 × 1) and (3 × 1) gold overlayers supported by highly anisotropic (1 1 2) plane. We speculate that (3 × 1) is a favored periodicity in the atomic rearrangement of the (1 1 2) surfaces of molybdenum and tungsten due in part as a result of the initial state band structure of these surfaces.

Two alkali halide adsorbate–substrate systems were investigated by atomic force microscopy (AFM) working in contact mode. Adsorbate film orientation relative to the substrate was determined from the arrangement of the atomic steps of the substrate and the edges of the forming islands. In this work we present experimental results obtained for systems: NaCl/LiF(0 0 1) and LiF/NaCl(0 0 1), which exhibit a strong tendency of the self-assembly into regular structures.

Early stages of Cr contact formation on 6H-SiC(0001) were investigated using the atomic force microscope (AFM) and current-sensing AFM with conducting tip. Cr layers were vapor deposited under ultrahigh vacuum onto samples cut out of a single crystal of n-type 6H-SiC(0001) that were ex situ hydrogen etched in a tubular flow reactor. Topography of the samples, their local conductance patterns and local current–voltage characteristics of the Cr/SiC contact were examined simultaneously as a function of Cr-adlayer thickness and annealing temperature. The growth of Cr follows the Stranski–Krastanov growth mode. The layers of mean thickness ⩾4.5 nm have a grainy structure. Differences in quality of the electric contact between the grains and the substrate as well as between the grains themselves enable to obtain a good contrast image of the local conductance of the layer. The contact of the as-deposited at room temperature Cr-layer of the thickness from 1.5 to 10 nm is typical of the rectifying junction. Annealing the Cr-SiC contact at temperatures up to 1800 K leads to coalescence of grains and dissolution of Cr in the substrate. The dissolution essentially disturbs the rectifying character of the electric contact Cr/SiC.

Thin layers of alkali halides were investigated by atomic force microscope (AFM). The studied systems were: LiBr/KBr(0 0 1) with −16.7% misfit, LiF/Si(0 0 1) with +4.4% misfit, LiBr/LiF(0 0 1) with +36.8% misfit and NaCl/Si(0 0 1) with +46.5% misfit. The results show that the surface morphology strongly depends on the temperature of layer formation. The alkali halides deposited on the foreign substrate at elevated temperatures or at room temperature and subsequently annealed form preferentially 3D islands leaving uncovered substrate areas between them. It is suggested that Ostwald ripening takes place at elevated temperatures.

We present evidence of coverage-dependent band structure symmetry effects in scanning tunneling microscopy. We find that the symmetry of the Gd induced band located at about 2 eV below the Fermi energy, at the surface Brillouin zone center, appears to be strongly dependent on the atomic structure in the bilayer regime for Gd on W(1 1 2). Light polarization dependent photoemission from this band indicates more d z 2 symmetry character for rectangular Gd structures and rather more d xz d yz character for the quasi hexagonal bilayer structure. Band symmetry changes accompanying the structural phase transition from rectangular to quasi-hexagonal Gd bilayer structures are consistent with arguments used to explain the apparent STM corrugation observed for Gd on W(1 1 2) (Surf Sci 520(2002)43).

In order to investigate to what extent the crystallographic structure of the substrate affects the process of interdiffusion and surface alloy formation in the case of the same components, adsorption systems of Pd on Nb(0 1 1), Nb(0 0 1) and Nb(1 1 1) have been studied by means of low-energy electron diffraction, Auger electron spectroscopy, and contact potential measurement. For all the systems, Pd dissolves in the substrate, when its population on the surface exceeds 1 ML. Kinetics of the mutual solution depends on the amount of deposited Pd, and increases with increasing amount of the adsorbate. Independent of the substrate structure, there was no evidence for a mixing of Pd and Nb in the top-most layer. For the Pd/Nb(0 1 1) system, the lateral interactions inside the Pd adlayer surpass the adsorbate–substrate interaction. The adsorbate–substrate interaction is dominant for the Pd/Nb(0 0 1) and Pd/Nb(1 1 1) systems, and results in the formation of a sandwich-like laminar surface alloy with a Pd layer on top.

To examine by scanning tunnelling microscopy the surface of a W(0 0 1)-oriented sample, it was cleaned either conventionally by heating in an atmosphere of oxygen and flashing to 2300 K or by Ar+-ion bombardment. The changes of the topography of the W(0 0 1) surface caused by bombardment with ions of energy up to 5 kV and doses not higher than 1.4×1017 ions/cm2 are extensive. The extent of the changes upon cleaning does not prevent the sample surface from being used for scanning tunnelling microscope (STM) studies. Details of the atomic structures of the surface, revealed in the STM images at 130 K, allows the cleanness of the surface to be characterised as well as residual impurities to be determined.

Thermally cleaned W(2 1 1) surface with 0.7° miscut consists of (2 1 1) terraces separated by monoatomic steps. When the surface is exposed to oxygen and subsequently annealed at 1100–1900 K, the width of (2 1 1) terraces increases and multilayer steps are formed. Similar step bunching is observed during routine cleaning of the sample by annealing in oxygen and thermal flashing in ultra high vacuum. During such cleaning procedure islands of c(6×4) reconstruction are observed.

Scanning tunneling microscopy is used to obtain images of reconstructed W(111) and W(211) surfaces. The reconstruction is induced by submonolayer coverages of carbon and oxygen.

Changes of the topography and surface structure during hydrogen adsorption and absorption on Ti and Hf ad-crystals epitaxially grown on tungsten field emitters were observed by means of field emission microscopy and the local work function measurements. Hydrogen adsorbs on the surfaces of the investigated metals in two states β− and β+. The observed work function changes correspond to an overlapping of both adsorption states. While the population of the β− increases with exposure, the β+ dominates only at low hydrogen exposures. The presence of terraces and atomic steps reduces the population of the β+ state on the surface. There are some evidences that the densely packed atomic structure of the (0 0 0 1) faces of Ti and Hf better stabilize this state on the surface. Within the temperature range 80–150 K the population of β+ increases with increasing temperature.

Results concerning the morphology of Cu adsorption layers deposited from vapor under ultra-high vacuum on Ir tip and the influence of oxygen on this morphology are reported. The method employed was field electron emission microscopy. It was found that the presence of oxygen decreases the copper wettability of iridium. Preadsorption of oxygen on the Ir surface is followed by an increase in cohesion interaction between atoms of the Cu deposited onto the tip at room temperature. Coadsorption of Cu and O on the Ir tip surface at liquid nitrogen temperature, when followed by gradually heating the adlayer, results in crystallization of the deposit in the temperature range from 430 K to about 700 K. Some evidence indicates the formation of Cu2O with a high degree of crystallinity under these conditions. Cu and O coadsorption on the Ir surface at a temperature higher than 1090 K leads to selective accumulation of Cu on the {111} faces and to formation of epitaxial crystals which are oriented to the substrate in the same manner as the Cu crystals grown at ultrahigh vacuum from Cu flux containing no oxygen. Oxygen incorporated into the Cu beam interact preferentially with {011} and {001} Ir faces, where it can produce oxide layers.

Elastic peak electron spectroscopy (EPES) is based on measurements of elastic electron reflection coefficients. The angular distribution in EPES depends on different parameters such as atomic number of the substrate, the energy of the electron beam and the geometry of the analysis system. In this study, we compare the measured angular distribution of electrons elastically reflected from Pd and In surfaces with Monte-Carlo simulations. We have used a theoretical approach based on knowledge of electron trajectories and interaction effects inside the samples. For the experiments, we have constructed a special rotary energy analyser with a small aperture. The angular distributions of elastically backscattered electrons at 500 eV resulting from Monte-Carlo simulations of electron transport for Pd and In (atomic numbers 46 and 49) compare very well with the corresponding experimental measurements.

Some results of a study of the adsorption and thermal desorption of H 2 O on Pt and Ir surfaces, using field emission methods, are presented. At a substrate temperature of 78 K H 2 O admolecules reduced the total field emission current both from the Pt and Ir tips in a wide range of coverages whereas the local emission current, e.g. from the (001) and (113) faces of Ir, was increased. Water was desorbed from thermally cleaned Pt in the temperature range 140–160 K with an average desorption energy of E des = 54kJ/mol. The possible behavior of H 2 O molecules on the crystallographically diversified surfaces of Pt and Ir under the conditions of field emission is discussed.

Zeins, the major endosperm proteins in maize (Zea mays L.), are deficient in the essential amino acids lysine and tryptophan. Some mutant genes, like opaque-2 (o2) and floury-2 (fl2), reduce the levels of A- and B-zeins, thereby improving maize's nutritional value. Other mutants, such as amylose-extender (ae), floury-1 (fl1), soft starch (h), dull-1 (du), shrunken-1 (sh1), sugary-1 (su1), sugary-2 (su2), and waxy (wx), primarily affect starch composition, but also alter zein composition. We undertook this study to examine the effects of some of these mutant genes on A/B-zein composition and to study the interactions of these genes in double-mutant combinations. Endosperm prolamins were extracted from inbred B37, ten near-isogenic single mutants (ae, du, fl1, fl2, h, o2, sh1, su1, su2, and wx), and most double-mutant combinations. Zeins in these extracts were fractionated by reversed-phase highperformance liquid chromatography (RP-HPLC) into 22-24 peaks. Of the resulting 22 major peaks the areas of 16 (per milligram endosperm) were significantly affected by individual mutant genes relative to the zein composition of the normal inbred. In combination these genes exhibited significant epistatic interactions in regulating the expression of individual A/B zeins. Epistatic interactions were judged to be significant when the amount of a peak in a double mutant differed from the averages for the peak in the two respective single mutants. The o2 gene, alone and in combination with other mutant genes, significantly decreased the amounts of many individual zeins. The effect of the o2 gene was the greatest of all the genes examined. Various clustering techniques were used to see if mutant effects could be grouped; among these was principal component analysis, a multivariate statistical technique that analyzes all peak sizes simultaneously. Three-dimensional scatter graphs were constructed based on the first three principal components. For the single mutants, these showed no relationships to gene actions; for the double mutants, however, this technique showed that four single mutants, o2, sh1, su1 and su2, had the greatest effects on zein composition when combined with each other and with the remaining six single mutants.

Energy loss spectroscopy (ELS) is a source of information on energies of both surface atom excitations and the electron gas collective oscillations — plasmons. According to the theoretical model [1] the plasmon energy depends on the electron gas density. There are two plasma oscillation frequencies ωb and ωs , the latter is attributed to an abrupt change of the electron density at a surface (surface plasmon), while the former is a frequency of the plasma oscillations in the bulk (volume plasmon). Occurrence of the surface and volume plasmons is connected with a free electron gas of density characteristic of a given metal. A metal deposited on a surface of another metal changes the frequency of the substrate plasmons which is a result of mixing of the electron gas from the substrate and adsorbate. When a density of an electron gas of the adsorbate layer reaches a value attributed to a solid also the plasmons with energy characteristic of the adsorbate should appear [2]. So, for thin layers occurrence of both substrate and adsorbate plasmons is expected as long as the penetration depth of the primary electron beam is larger than the adsorbate thickness. for the lowest coverages θ → 0 when the electron gas of the substrate and adsorbate is mixed [2] the adsorbate plasmons should not be expected, however, in some papers [3-7] such features were reported and interpreted as plasmon losses. Our studies concern the appearance of the plasmon losses of the adsorbate and disappearance of the plasmon losses of the substrate during the adsorbate deposition. We chose the aluminium coverage to our study for its relatively simple electronic stucture, for this metal the free electron model is tue without any exceptions and the excitation energy of the electrons from inner shells is 78 eV or

Thin films of TiO 2 were prepared on glass substrates by reactive evaporation of TiO. Properties of the thin films were investigated under ultrahigh vacuum conditions by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). AFM topography exhibits a uniformity structure of the thin films and shows a high quality nanocrystalline structure of TiO 2 with grain size ranging from 28 nm to 35nm. The XPS Ti-2p spectra confirmed the occurrence of the 4+oxidation state of Ti and the O-1s spectra revealed the presence of an O−2 photoelectron peak. The calculated O/Ti ratio in TiO 2 thin films was in the range 1.85–2.15 depending on the samples. Additional analysis of the thin films was carried out by X-ray powder diffraction (XRD).

Es wird untersucht, unter welchen Bedingungen die modifizierte NDF-Methode (neutrale Detergenzfaser) mit Ditalan E bei Einsatz von α-Amylase aus Schweinepankreas auch fur starkereiche Produkte eingesetzt werden kann. Die benotigte Amylasemenge (zwischen 10 und 50 mg je Probe) ist davon abhangig, ob die Starke in freier oder gebundener Form vorliegt. Der Zusatz der Enzymlosung sollte nach der Detergenzienbehandlung erfolgen. Als Inkubationszeit werden mindestens 10 h benotigt. Zur Bestimmung der sauren Detergenzfaser (ADF) mit nachfolgender Fraktionierung (Cellulose, Rohlignin) ist eine enzymatische Behandlung nicht erforderlich. Die beschriebene Methode ist fur die routinemasige Faseranalytik geeignet.