Epidemiological observations on pastern dermatitis in young horses and evaluation of essential fatty acid spot-on applications with or without phytosphingosine as prophylactic treatment

Background - Equine pastern dermatitis (EPD) is a common multifactorial clinical syndrome in horses. Treatment can be difficult;pathogenesis and triggering factors cannot always be determined. Objectives - To assess risk factors for developing EPD in a large group of horses kept under the same conditions and to analyse whether or not a spot-on containing essential fatty acids and antimicrobial agents is able to prevent the development of EPD or accelerate the healing process. Animals - Each year 50 young, privately owned, warmblood horses were prospectively included. Methods - All horses were examined weekly between August and October for the presence of typical EPD skin lesions. Additionally, in the first year, horses were randomly divided into three subgroups of intervention. The pastern areas were treated once weekly either with 0.6 mL of a spot-on containing essential fatty acids and aromatic oils, or a preparation containing additional antibacterial phytosphingosine, or not at all. Results - Nonpigmented pastern areas were affected significantly more often than pigmented pastern areas (P < 0.0001). The interaction between moisture and opportunistic pathogens seemed to be a major triggering factor for EPD. There was no difference in the occurrence of EPD in the three subgroups. The lesion scores of affected limbs in both spot-on groups were significantly lower compared to the control group. Conclusion and clinical importance - Moisture and lack of pigmentation predisposed to EPD. Topical application of the tested spot-on once weekly did not prevent the disease. A positive effect of both spot-on products on the severity of EPD lesions was detected

Understanding atom movement during lateral manipulation with the STM tip using a simple simulation method

Kühnle A, Meyer G, Hla SW, Rieder K-H. Understanding atom movement during lateral manipulation with the STM tip using a simple simulation method. Surface Science. 2002;499(1):15-23.We report on a fast simulation method to investigate the movement of an atom induced by the tip during lateral manipulation with a scanning tunneling microscope. The simulation is based on a model assuming the atom moving in the combined potential of tip and surface. The pathway of the tip is subdivided in small steps, and the atomic position for each step is calculated by an iterative algorithm searching for the closest energetic minimum. The method is demonstrated for manipulation on the (111) surface of an fcc metal. Our model calculations predict which energetic minima of the surface are attained by the atom during manipulation. The details of the modelled manipulation curves allow a precise description of the atomic pathway in dependence on manipulation direction and positioning of the tip relative to the atom. Furthermore, the simulation predicts a transition from the so-called pulling to sliding manipulation mode upon reducing tip-surface distance, well in agreement with general experimental observations. To test our algorithm we present experimental results for the manipulation of iodine on Cu(I 11) along the [211] direction and compare them to simulated manipulation curves. The comparison allows for a complete understanding of all details in atomic movements during manipulation along a complicated path. (C) 2001 Published by Elsevier Science B.V

Controlled lateral manipulation of single diiodobenzene molecules on the Cu(111) surface with the tip of a scanning tunnelling microscope

Hla SW, Kühnle A, Bartels L, Meyer G, Rieder KH. Controlled lateral manipulation of single diiodobenzene molecules on the Cu(111) surface with the tip of a scanning tunnelling microscope. Surface Science. 2000;454:1079-1084.We report on the controlled lateral manipulations of adsorbed single diiodobenzene molecules on the Cu(111) surface with a scanning tunnelling microscope (STM) tip at 20 K. The molecular motions in this experiment are mainly induced by the attractive interaction between the tip and the molecule. Even though the leading manipulation mode is 'pulling', a continuous 'sliding' mode can also be induced if we use higher tip-molecule interaction forces. During the manipulation process, the molecules can follow the tip with hops of single or double copper-atomic-site distances and in some cases 'hop-scotch' type movements can also be observed. (C) 2000 Elsevier Science B.V. All rights reserved

Adsorption of dodecanethiol on Cu(110): Structural ordering upon thiolate formation

Kühnle A, Vollmer S, Linderoth TR, Witte G, Wöll C, Besenbacher F. Adsorption of dodecanethiol on Cu(110): Structural ordering upon thiolate formation. Langmuir. 2002;18(14):5558-5565.The adsorption of dodecanethiol [CH3(CH2)(11)SH] films on Cu(110) by vapor deposition under ultrahigh vacuum conditions has been studied by means of thermal desorption spectroscopy, scanning tunneling microscopy, X-ray photoelectron spectroscopy (XPS), and low-energy electron diffraction with a special emphasis on the structural changes accompanying the transition from a physisorbed monolayer to a chemisorbed saturation structure. Adsorption at 110 K leads to the formation of an ordered physisorbed layer with flat-lying thiol molecules. Upon room-temperature deposition, initially an ordered pinstripe phase is formed which may be a molecular double layer. This layer transforms with time into a stable saturation structure of upright-tilted thiolates in a local c(2 x 2) arrangement that exhibits a long-range c(12 x 16) modulation, attributed to a Moire pattern. The XPS measurements show that the room-temperature saturation structure contains a fraction of sulfide species formed by partial decomposition and desorption of alkyl chains. At 400 K, the thiolate monolayer desorbs dissociatively, eventually resulting in a p(5 x 2) sulfur structure

STM observations of a one-dimensional electronic edge state at steps on Cu(111)

Bartels L, Hla SW, Kühnle A, Meyer G, Rieder K-H, Manson JR. STM observations of a one-dimensional electronic edge state at steps on Cu(111). Physical Review B. 2003;67(20):205416.Scanning tunneling microscopy measurements across isolated straight step edges on a Cu(111) surface were carried out for biases between 100 mV and 5 V. In addition to the well known surface state oscillations, and at lower sample bias than the onset of the two-dimensional surface image state, a sharply defined linear protrusion, was observed at the top of the step faces. This linear feature is interpreted as a one-dimensional image state at the step, with its energy modified by a dipolar potential whose appearance is attributed to Smoluchowski smoothing of the electron density at the step edge

Deposition Order Controls the First Stages of a Metal-Organic Coordination Network on an Insulator Surface

Schüller L, Haapasilta V, Kuhn S, et al. Deposition Order Controls the First Stages of a Metal-Organic Coordination Network on an Insulator Surface. Journal of Physical Chemistry C. 2016;120(27):14730-14735.We report on first stages toward the formation of a surface-confined metal organic coordination network (MOCN) by sequential deposition of biphenyl-4,4'-dicarboxylic acid and iron atoms on the surface of a bulk insulator, calcite (10.4). The influence of the deposition order on the structure formation is studied by noncontact atomic force microscopy operated in ultrahigh vacuum at room temperature. It is found that sequential deposition facilitates MOCN formation when the organic linker molecules are first adsorbed on the surface, followed by iron deposition. This observation is explained by first-principles computations, indicating that the metal molecule interaction dominates over the molecule molecule interaction on the surface. The observed MOCN islands are elongated in the [010] substrate direction, demonstrating a templating effect of the underlying substrate. This experimental finding is confirmed by calculations suggesting that the MOCN network matches the calcite lattice periodicity in the [010] direction but not in the [(42) over bar1] direction. This work, thus, demonstrates the decisive influence of both deposition order and lattice matching on the formation of an extended MOCN on a bulk insulator surface

Diacetylene polymerization on a bulk insulator surface

Richter A, Haapasilta V, Venturini C, et al. Diacetylene polymerization on a bulk insulator surface. Physical Chemistry Chemical Physics. 2017;19(23):15172-15176.Molecular electronics has great potential to surpass known limitations in conventional silicon-based technologies. The development of molecular electronics devices requires reliable strategies for connecting functional molecules by wire-like structures. To this end, diacetylene polymerization has been discussed as a very promising approach for contacting single molecules with a conductive polymer chain. A major challenge for future device fabrication is transferring this method to bulk insulator surfaces, which are mandatory to decouple the electronic structure of the functional molecules from the support surface. Here, we provide experimental evidence for diacetylene polymerization of 3,30-(1,3-butadiyne-1,4-diyl) bisbenzoic acid precursors on the (10.4) surface of calcite, a bulk insulator with a band gap of around 6 eV. When deposited on the surface held at room temperature, ordered islands with a (1 x 3) superstructure are observed using dynamic atomic force microscopy. A distinct change is revealed upon heating the substrate to 485 K. After heating, molecular stripes with a characteristic inner structure are formed that excellently match the expected diacetylene polymer chains in appearance and repeat distance. The corresponding density functional theory computations reveal molecular-level bonding patterns of both the (1 x 3) superstructure and the formed striped structure, confirming the assignment of on-surface diacetylene polymerization. Transferring the concept of using diacetylene polymerization for creating conductive connections to bulk insulator surfaces paves the way towards application-relevant systems for future molecular electronic devices

The weight function for charges-A rigorous theoretical concept for Kelvin probe force microscopy

Söngen H, Rahe P, Neff JL, et al. The weight function for charges-A rigorous theoretical concept for Kelvin probe force microscopy. Journal of Applied Physics. 2016;119(2):25304.A comprehensive discussion of the physical origins of Kelvin probe force microscopy (KPFM) signals for charged systems is given. We extend the existing descriptions by including the openloop operation mode, which is relevant when performing KPFM in electrolyte solutions. We define the contribution of charges to the KPFM signal by a weight function, which depends on the electric potential and on the capacitance of the tip-sample system. We analyze the sign as well as the lateral decay of this weight function for different sample types, namely, conductive samples as well as dielectric samples with permittivities both larger and smaller than the permittivity of the surrounding medium. Depending on the surrounding medium the sign of the weight function can be positive or negative, which can lead to a contrast inversion for single charges. We furthermore demonstrate that the KPFM signal on thick dielectric samples can scale with the sample size-rendering quantitative statements regarding the charge density challenging. Thus, knowledge on the weight function for charges is crucial for qualitative as well as quantitative statements regarding charges beneath the tip. (C) 2016 AIP Publishing LLC

Smooth crack-free targets for nuclear applications produced by molecular plating

Vascon A, Santi S, Isse AA, et al. Smooth crack-free targets for nuclear applications produced by molecular plating. Nuclear Instruments and Methods in Physics Research A. 2013;714:163-175.The production process of smooth and crack-free targets by means of constant current electrolysis in organic media, commonly known as molecular plating, was optimized. Using a Nd salt, i.e., [Nd(NO3)(3)center dot 6H(2)O], as model electrolyte several constant current density electrolysis experiments were carried out to investigate the effects of different parameters, namely the plating solvent (isopropanol and isobutanol mixed together, pyridine, and N,N-dimethylformamide), the electrolyte concentration (0.11, 0.22, 0.44 mM), the applied current density (0.17, 0.3, 0.7, and 1.3 mA/cm(2)), and the surface roughness of the deposition substrates (12 and 24 nm). Different environments (air and Ar) were used to dry the samples and the effects on the produced layers were investigated. The obtained deposits were characterized using gamma-ray spectroscopy for determining Nd deposition yields, X-ray photoelectron spectroscopy for chemical analysis of the produced surfaces, radiographic imaging for surface homogeneity inspection, atomic force microscopy for surface roughness evaluation, and scanning electron microscopy for surface morphology investigation. The results allowed identifying the optimum parameters for the production of smooth and crack-free targets by means of molecular plating. The smoothest layers, which had an average RMS roughness of ca. 20 nm and showed no cracks, were obtained using 0.22 mM [Nd(NO3)(3)center dot 6H(2)O] plated from N,N-dimethylformamide at current densities in the range of 0.3-0.7 mA/cm(2) on the smoothest deposition substrate available. (c) 2013 Elsevier B.V. All rights reserved

Hydration layers at the graphite-water interface: Attraction or confinement

Söngen H, Morais Jaques Y, Zivanovic L, et al. Hydration layers at the graphite-water interface: Attraction or confinement. Physical Review B. 2019;100(20):205410