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Parallel to the massive use of image based computational hemodynamics to study the complex flow establishing in the human aorta the need for suitable experimental techniques and ad hoc cases for the validation and benchmarking of numerical codes has grown more and more. Here we present a study where the 3D pulsatile flow in an anatomically realistic phantom of human ascending aorta is investigated both experimentally and computationally. The experimental study uses 3D particle tracking velocimetry (PTV) to characterize the flow field in vitro while finite volume method is applied to numerically solve the governing equations of motion in the same domain under the same conditions. Our findings show that there is an excellent agreement between computational and measured flow fields during the forward flow phase while the agreement is poorer during the reverse flow phase. In conclusion here we demonstrate that 3D PTV is very suitable for a detailed study of complex unsteady flows as in aorta and for validating computational models of aortic hemodynamics. In a future step it will be possible to take advantage from the ability of 3D PTV to evaluate velocity fluctuations and for this reason to gain further knowledge on the process of transition to turbulence occurring in the thoracic aorta.

The spectral and geometric trends of Ln(trensal) complexes (H(3)trensal = 2,2',2' '-tris(salicylideneimino)triethylamine) along the lanthanide series are analyzed. Low-temperature polarized absorption and luminescence spectra are reported for nine of the complexes with transitions suitable for analysis. Both the angular and radial geometry variations as a function of the lanthanide ion are quantified. The structural parameters are related to the trend in the ligand field found from an analysis of the f-f transitions. The ligand-field analysis is fitted globally across the whole series accounting for the contraction of the f orbitals as a function of atomic number. This study establishes the utility of describing the ligand field of f electrons within the one-electron operator approach of the angular overlap model.

Combined STM/AFM experiments were performed on monolayer islands of Cu-TBPP molecules on Cu(100). Pulling of single molecules on the substrate was observed and the imaging parameters were compared to STM studies. Local frequency shift vs. distance curves reveal three types of curves, which can be related to the interaction of the tip above the Cu(100) substrate, the centre of the molecule and the leg of the molecule. The frequency vs. distance curves above the legs reveal two minima, which are associated with the bending of the legs above a certain threshold value. Quantitative analysis yields force values of about 0.4 nN.

Materials displaying intrinsic optical bistability (IOB), i.e., allowing the coexistence of two stable steadystate excitation rates for a single given excitation power, are of interest for potential technological applications related to optical data switching and manipulation. The properties of the unusual IOB previously observed in Yb-doped CsLuBr and CsCdBr host materials are studied here using absorption and luminescence spectroscopies. The IOB phenomenon is concluded to derive ultimately from laser heating effects. When combined with a strongly increasing and nonlinear dependence of the material's absorbance on internal temperature, laser heating leads to a positive-feedback absorption amplification process showing a hysteresis in both power- and temperature-sweep experiments. A simple model describing this effect in terms of rates of sample heating and cooling in the irradiated volume reproduces the power, temperature, concentration, and excitation-energy dependence of the Yb IOB using only the experimental absorption data as input. The temperature dependence of the absorption cross section is correlated with thermal changes in the monomeric YbBr geometry, which becomes more asymmetric as the temperature is elevated. The IOB observed in Yb-doped CsLuBr and CsCdBr host lattices is therefore a property of the monomeric Yb ion in these materials, and not a dimer property as was previously believed. These results also emphasize the more general conclusion that laser heating may contribute significantly to the shape or slope of an excitation power dependence curve, and may even be the dominant aspect of that curve when absorption cross sections are strongly dependent on temperature.

We show theoretically with the simplest possible model that the intensity of an upconversion luminescence that is excited by the sequential absorption of n photons has a dependence on absorbed pump power P, which may range from the limit of Pn down to the limit of P1 for the upper state and less than P1 for the intermediate states. The two limits are identified as the cases of infinitely small and infinitely large upconversion rates, respectively. In the latter case, the dependence of luminescence intensities from intermediate excited states on pump power changes with the underlying upconversion and decay mechanisms. In certain situations, energy transfer upconversion and excited-state absorption can be distinguished by the measured slopes. The competition between linear decay and upconversion in the individual excitation steps of sequential upconversion can be analyzed. The influence of nonuniform distributions of absorbed pump power or of a subset of ions participating in energy-transfer upconversion is investigated. These results are of importance for the interpretation of excitation mechanisms of luminescent and laser materials. We verify our theoretical results by experimental examples of multiphoton-excited luminescence in Cs3Lu2Cl9:Er3+, Ba2YCl7:Er3+, LiYF4:Nd3+, and Cs2ZrCl6:Re4+.

A detailed study of upconversion processes in Cs3Er2X9 (X = Cl, Br, I) crystals and in the diluted systems Cs3Lu2Cl9:1% Er3+, Cs3Lu2Br9:1% Er3+, and Cs3Y2I9:1% Er3+ is presented. Efficient two-, three-, and four-step upconversion excitation along the sequence 4I15/2 4I13/2 4I9/2 4S3/2 2H9/2 leading to luminescence throughout the visible and near UV is demonstrated using a 1.54-µm excitation wavelength. This stepwise excitation is possible due to the low phonon energies and, consequently, the significantly longer lifetime of the 4I9/2 intermediate state in these systems relative to oxides and fluorides. The absorption and upconversion luminescence intensities increase along the isostructural series X = Cl, Br, I as a result of the decreasing energy of the electric-dipole allowed 4f-5d transitions and, thus, their increasing influence on the parity forbidden 4f-4f transitions. The excitation mechanisms in the chloride systems are investigated by time-resolved spectroscopy and the respective dynamics is studied by a rate-equation model. In the diluted sample 4I9/2 4S3/2 excited-state absorption plays a major role and occurs within 3 cm-1 of the ground-state absorption, whereas the dynamics in the concentrated system is dominated by energy-transfer upconversion (ETU) in all excitation steps. Of the 35 most likely ETU processes, eight are found to contribute significantly to the excitation mechanisms in the concentrated system. The excitation pathways leading to red luminescence from 4F9/2 are also partly resolved.

Energies and intensities of 114, 101, and 76 f–f absorption transitions of Er3+ are determined by high-resolution spectroscopy in the closely related host lattices Cs3Lu2Cl9, Cs3Lu2Br9, and Cs3Y2I9, respectively. The observed trends in the energy-level structure reflect the increasing covalency and the length of the Er3+–X− bond. The decreasing Coulomb repulsion of the 4f electrons, spin–orbit coupling, and crystal-field potential reduces the energy splittings of the SL, SLJ, and SLJMJ states by 0.5%, 0.5%, and 25%, respectively, along the series Cl–Br–I. Energy-level calculations that include crystal-field and correlation crystal-field terms in the effective Hamiltonian, reproduce most of the experimentally found trends. Root-mean-square standard deviations of 18.0, 19.2, and 21.9 cm−1 are reached in least-squares fits to the experimental crystal-field energies. The f–f transition intensities increase along the series Cl–Br–I as a result of the decreasing energy of the f–d bands. In the iodide compound, where the first f–d bands are as low as 30 000 cm−1, this influence is especially pronounced for the f–f absorptions at higher energy. The quality of the wavefunctions obtained in the energy-level calculations is not sufficient to reliably calculate the relative absorption intensities of individual crystal-field components within a given multiplet transition. This deficiency is ascribed to small deviations of the actual coordination geometry of Er3+ from the C3v point group symmetry that was assumed in the calculation. Intensities are analyzed on the level of multiplet-to-multiplet transitions using the Judd–Ofelt formalism.

We report the first observation of intrinsic optical bistability in ${\mathrm{CsCdBr}}_{3}:1%$ ${\mathrm{Yb}}^{3+}$ and show, using site-selective spectroscopy, that only the asymmetric, strongly coupled ${\mathrm{Yb}}^{3+}$ ion-pair minority site gives rise to hysteresis of near-infrared and cooperative up-conversion luminescence as a function of incident laser intensity below 15 K.

Ferroelectric bulk single crystals of tri-glycine sulphate (TGS) have been investigated in ultra-high vacuum (UHV) using dynamic force microscopy (DFM) in the non-contact (nc) mode. Bath chemical contrast from different sub-unit cell cleavage steps, and ferroelectric domains were differentiated by recording the variation in interaction force affecting the excitation amplitude A(exc) applied to the piezo shaker in constant amplitude DFM. No chemical difference was found for steps measuring half the unit cell height b, in contrast to b/4-steps where sulphate ions change the local short-range chemical forces. By varying the bias voltage applied to the TGS counter electrode, the sign of bound surface charge within each ferroelectric domain was determined. Domain walls separating regions with antiparallel polarisation vectors are resolved down to a 9 nm domain wall width. Furthermore, we achieved atomic resolution with nc-DFM on cleaved TGS samples indicating the monoclinic unit cell at the ferroelectric sample surface with a = 1.0 +/- 0.05 nm, c = 0.55 +/- 0.05 nm, and beta = 107 +/- 3 degrees.

We investigate interaction effects which occur in scanning tunneling microscopy (STM) by performing local force spectroscopy with an oscillating tip while imaging Si(111)7 x 7 terraces in the dynamic lever STM mode (constant time-averaged current). It is found that true atomic resolution is achieved close to the minimum of the resonance frequency vs. distance curve and even closer to the sample. On the other hand true atomic resolution in noncontact AFM (constant frequency shift) is expected several nm away from this minimum, in the range where the frequency shift becomes more negative with decreasing distance.

Decision-making logic based on fuzzy logic and an adaptive PI-controller was inserted into the feedback loop of a combined atomic force microscope/scanning tunneling microscope (AFM/STM), which is able to measure the frequency shift Delta f of the cantilever-type spring and the mean tunneling current (I) over bar(t) simultanously. Depending on the conductivity of the surface the fuzzy logic controller decides whether it has to use the AFM feedback or the STM feedback. On conductive regions of the sample STM mode is used, whereas on poorly conducting regions the non-contact AFM mode is preferred. This allows one to scan over heterogenous surfaces avoiding a tip crash.

One way to improve imaging in dynamic force mi- croscopy is to increase the cantilever resonance frequency. Higher frequencies require faster electronics. This work presents fast new digital electronics based on the principle of phase-locked loop techniques. First results show very high frequency resolution and very stable imaging.

Cooperative visible upconversion is reported in crystals of Cs 3 Lu 2 Br 9 : 1% Yb 3+ , Cs 3 Lu 2 Br 9 : 10% Yb 3+ , and Cs 3 Yb 2 Br 9 . The near-infrared emission decays twice as fast as the visible emission as expected from theory. Both, the 10% and the 100% crystals exhibit bistability of the luminescence intensity as a function of the excitation intensity at temperatures below 30 K. The bistable region gets narrower and moves to lower excitation intensities with increasing temperature and concentration. Both trends are in accordance with theoretical models.

In this note we report the first observation of salient features of the Si(111)(7×7) reconstructed surface across monatomic steps by dynamic atomic force microscopy (AFM) in ultrahigh vacuum (UHV). Simultaneous measurements of the resonance frequency shift Δf of the Si cantilever and of the mean tunneling current [Formula: see text] from the cleaned Si tip indicate a restricted range for stable imaging with true atomic resolution. The corresponding characteristics vs. distance reveal why feedback control via Δf is problematic, whereas it is as successful as in conventional STM via [Formula: see text]. Furthermore, local dissipation (energy loss of 10-14 W) through individual atoms is observed and explained by the coupling of the surface atoms to phonons.

Friction force microscopy is implemented in ultrahigh vacuum conditions. Atomic-scale friction is observed on clean surfaces. The onset of atomic-scale stick - slip is observed and discussed in relation to the plucking model. Comparative measurements of AgBr(001) versus NaCl(001) and versus NaCl(001) demonstrate the material-specific contrast of friction. Contrast mechanisms are discussed in relation to these experiments. The role of the chemical nature of the tip is exemplified for the case of Si(111) , where wearless sliding is achieved with a PTFE-coated probing tip.

Scanning force microscopy (SFM) was used to visualize the surface of hard elastic polypropylene (HEPP) film. The surface morphology of unstrained HEPP shows crystalline and noncrystalline rows oriented parallel to the extrusion direction. The crystalline rows are composed of lamellar blocks. The dimensions of crystalline and noncrystalline regions are determined. The structural surface changes induced by stepwise elongation of the film with a home-built stretching device are documented by SFM. Stretching of HEPP perpendicular to the extrusion direction causes cracks advancing through several crystalline rows. During elongation parallel to the extrusion direction the separation of adjacent lamellae by their translatory displacement occurs. Deformation-induced structural changes of HEPP on the nanometer scale are compared with proposed deformation models. Nanostructural changes are correlated with characteristic variations in the force-elongation curve. © 1996 John Wiley & Sons, Inc.

We performed scanning force microscopy (SFM) in ultrahigh vacuum (UHV) on C60 and AgBr thin films deposited on NaCl(001) substrates. The morphology of the initial growth stage and the nanotribological properties of these thin films are characterized and discussed. A novel experimental approach is presented where local friction coefficients are determined: the lateral (frictional) forces are measured as a function of normal load, controlled by an external ramp generator. The local friction coefficient can be extracted by means of the two-dimensional histogram technique. In the low load regime, friction coefficients of 0.15 +/- 0.02, 0.33 +/- 0.07 and > 0.03 were found between probing SiOx tip and C60, AgBr and NaCl, respectively. The two-dimensional histogram reveals significant details about the force regime of wear-less friction and the initial stage of wear on these thin films.

We discuss recent results on atomic friction at clean atomically flat surfaces obtained by atomic-force microscopy in terms of a simple two-dimensional model. Instabilities of the tip position give rise to irreversible jumps which are responsible for the occurrence of friction. The model calculations are in good agreement with the experimental observations. We propose a method for the reconstruction of the lateral atomic force field from measured data.

We performed scanning force microscopy (SFM) in ultrahigh vacuum (UHV) on AgBr thin films which were in situ deposited on NaCl(001) substrates. The morphology of the initial growth stage and the nanotribological properties of these thin films are characterized and discussed. The lateral (frictional) forces are measured as a function of normal load. The local friction coefficients are extracted by means of the two-dimensional histogram technique. In the low load regime, friction coefficients of 0.33 ± 0.07 and

We have applied the non-contact dynamic force microscopy method to investigate soft biological materials such as hexagonally-packed intermediate layers, DNA, and tobacco mosaic virus under ambient conditions. This method, where a stiff cantilever is oscillated close to its resonance frequency with an amplitude of 0.3-1.5 nm above the sample, allows highly reliable investigation of soft organic matter with minimized normal and lateral forces between tip and sample. The vertical and lateral resolution are determined to be

Samples of ultra-thin MoS2 platelets on a mica support were probed for their topography, friction and elasticity by scanning force microscopy. Platelet heights measured in the topographic mode of the instrument indicate the presence of single- and double-layer MoS2. Frictional forces on MoS2 layers are found to be noticeably reduced by a factor of 1.4 as compared with those on mica. Measurements of the elasticity lead to the conclusion that ultra-thin MoS2 is softer than mica. The results are discussed within the more general context of current models of lubrication.

The surfaces of in situ cleaved NaF crystals have been studied by scanning force microscopy (SFM) in ultrahigh vacuum (UHV). Operating the UHV force microscope in the contact mode, the surface structure with extended terraces interrupted by steps of typically 0.25 nm and 0.5 nm in height is revealed. Atomic-scale resolution is achieved on the terraces as well as at monatomic steps of the ionic crystal. The square surface lattice shows a periodicity of 0.45+/-0.04 nm that corresponds well to the spacing between equally charged ions along the [100] directions in the bulk phase. From the SFM data at cleavage steps the imaging area of the sensing tip is estimated to be less than 1 nm2. Some aspects of the contrast mechanism in the lateral and normal force images are discussed. The SFM data are complemented by low-energy-electron-diffraction measurements on NaF(001) carried out in the same compact UHV system.

Scanning force microscopy has been employed to investigate static and dynamic surface structures on ferroelectric crystals of GASH and TGS. On the crystal cleavage faces two sets of complementary results are obtained depending on the operation mode of the force microscope: (1) In the contact mode, static domain structures and superimposed cleavage structures are imaged on GASH(0001), whereas on TGS(010) specific domain erosion due to water adsorption is observed. Additionally, molecular resolution has been achieved on GASH surfaces. (2) In the non-contact mode, domain walls are revealed and the motions of the walls due to heat treatment are documented.

Scanning force microscopy (SFM) has been used to study the (0001) cleavage faces of ferroelectric crystals of GASH (guanidinium aluminium sulfate hexahydrate). For the first time, the surface and domain structures of a ferroelectric material has been imaged directly from the micrometer down to the molecular scale. On the micrometer scale SFM reveals the elementary cleavage structure with typical zig-zag-shaped steps. Superimposed on this topographic structure are ferroelectric domain structures which could be imaged with SFM operating the force microscope in the repulsive contact mode. On the nanometer scale, molecular resolution has been achieved on the atomically flat terraces. The imaged surface lattice with spacings of 0.68 nm reflects the threefold symmetry of the unreconstructed GASH (0001) surface.

A polycrystalline diamond film was etched down to a depth corresponding to the grain size with 193 nm excimer laser radiation. Below a graphitic surface layer (GL) we have observed a highly stable layer (SL) which is conducting. Atomic force microscope measurements were made in order to characterize the topography and microfriction of these two surface layers. Features of the diamond facet structure are still visible in spite of smoothening by the laser etch process. An approximation for the friction coefficient of both surface layers yields values of between 0.01 and 0.1. The friction pictures of the GL show a local period length of about 70 nm, which could be a typical diameter for micrographitic grains. The SL is more disrupted than the GL and the appearance of a period length of about 70 nm has faded discernibly.

The surfaces of corona-treated isotactic polypropylene films have been investigated by atomic force microscopy. The occurrence of droplets on the film surfaces is related to the energy dose of the corona discharge. The sizes of these droplets correlate with the corona dose. The loss of adhesive strength of self-adhered polypropylene films can be explained on the basis of morphology changes during corona treatment. A comparative study of uniaxial and biaxial polypropylene films is presented.

Some examples are selected to demonstrate the variety of possible scanning probe microscopy application in industry. Magnetic and magnetooptical storage media can be investigated by magnetic force microscopy, whereas a conventional scanning force microscope is used to examine surface features of many different materials, such as technical glasses, photosensitive materials, new superconductors, and biomolecules. Some other examples include the modification as well as the observation of liquid crystal devices, and the impact that scanning probe microscopy has on other techniques such as high precision stepping motors and high quality electron beam sources.

Thin films of mixtures of fluorocarbons and hydrocarbons are investigated by friction force microscopy. For a mixture of equal molar parts of arachidic acid and partially fluorinated carboxylic acid, phase separation manifests itself as circular domains. By shortening the length of the hydrocarbon chain, the disorder of the system is increased and phase separation takes on a fractal geometry. The frictional forces are found to be material specific and distinguish between domains of fluorocarbons and hydrocarbons. With higher normal forces hydrocarbon particles are easily sheared away while the fluorocarbon region remains unbroken. The results are discussed in relation to the phenomenon of boundary lubrication.

Within a short time, atomic force microscopy (AFM) has developed into a useful tool in surface science. The ability to image insulating surfaces is demonstrated on epitaxially grown AgBr(100) films and on Langmuir-Blodgett films of Cg-arachidate. In addition to the imaging of surfaces the technique is extended to study dynamic processes. By increasing the force, the onset of plastic deformation is observed. Small nanometer-sized indentations are created. In the case of AgBr these structures are refilled by surface diffusion on a time scale observable by AFM. The results are discussed in relation to other surface-sensitive techniques and compared to theoretical calculations. Another dynamic process which is monitored during the AFM measurements is friction. First results with a bidirectional force sensor are presented, allowing simultaneous acquisition of normal and lateral forces.

Recent developments in the field of scanning-probe methods show increasing demand for controlling and storing many different experimental parameters in addition to topographic information. In order to be able to perform these experiments (e.g. force spectroscopy, surface modification, friction measurements, etc.) we have designed a versatile acquisition system. Up to four different channels can be measured and displayed at the same time. Scan parameters are under software control, and additional output signals can be easily generated to meet experimental requirements. This flexibility allows the straightforward incorporation of new conditions and modes of measurement. We use a PC/386 system based principally on commercially available electronics. As an illustration of its performance we present the application of this system to a bidirectional atomic-force microscope. With this particular microscope it is important to control lateral as well as normal forces independently. Topography and friction information can be acquired and viewed simultaneously. The versatility of this data-acquisition system also makes it well suited for a variety of other tribological/micromechanical experiments such as friction loops, force-distance curves and surface wear.

In the German-speaking countries: Austria, Germany and Switzerland, which have a joint annual conference in psychiatric nursing, the process of academization of nursing has led to a discussion about which adaptations to make in psychiatric nursing in order to develop a profile, which is practicable in the future. Therefore, it was necessary to describe the current duties and activities of psychiatric nurses. With this, the knowledge and abilities of the nurses were to be made more explicit and their identity was to be strengthened. Data were generated by using participant observation and group discussions with the involved nurses to validate the observations and the emerging categories of activities. Participant observation took place in a psychiatric clinic in Switzerland over a period of 11 months on 14 psychiatric wards with different specializations. Data analysis followed a qualitative content analysis. Findings show that by means of descriptions of nursing situations the duties and activities of the nurses can be summarized into 12 categories. Many of the described activities can be found in psychiatric nursing textbooks. This concurrence suggests that there is something like a basic framework of psychiatric nursing. In addition, the findings illustrate how wide the variety of tasks are and how challenging psychiatric nursing is.

A feedback mechanism based on fuzzy logic has been applied to operate a combined atomic force microscope (AFM)/scanning tunneling microscope (STM), which is able to measure the resonance frequency shift Δf of the cantilever-type spring and the mean tunneling current Īt simultaneously. Using a decision making logic, the microscope can be scanned over a heterogeneous surface without tip crash. On the conductive parts of the sample, the STM mode is preferred, whereas the noncontact (nc)-AFM mode is used on the poorly conductive parts of the surface. The transition from the STM mode to nc-AFM mode is performed smoothly with the fuzzy logic feedback.

Huntington's disease is the most prevalent inherited human neurodegenerative disorder worldwide, affecting between 2 to 8 per 100000 inhabitants of Western countries, with an average age of onset close to 40 (range 2-80) and a usually slow progression over 10 to 30 years. Tremendous progress has been made in the understanding of the mechanisms implicated in this disease since the original description by George Huntington in 1872, marked by the identification of the locus in 1983 and the responsible gene in 1993. Clinical features include impaired motor control, manifesting as motor impersistence and inability to perform tasks that require motor sequences, along with abnormal movements such as chorea, athetosis, impaired ocular saccades and characteristic gait disturbances. Psychiatric and cognitive symptoms are also prominent, including depression and psychosis, with a high incidence of suicide, personality changes, aggressive or uncontrolled behaviour, impaired problem-solving abilities and ultimately more diffuse neuropsychological deficits leading to dementia. Genetically, the disease demonstrates fully penetrant autosomal dominant inheritance through a CAG trinucleotide repeat expansion in the protein-coding region of the huntingtin gene. There is an inverse correlation between the number of repeats and the patient's age at onset of the disease. Due to a phenomenon referred to as anticipation, the number of CAG trinucleotide repeats tends to increase when the disease is inherited from the father (paternal transmission), with disease onset at a younger age in the affected children. Despite 10 years of intensive study, the exact route between mutant protein and neurodegenerative illness remains elusive. Protein aggregation, mitochondrial dysfunction, transcriptional dysregulation, calcium homoeostasis and signalling anormalities, and organellar transport defects are leading candidate disease mechanisms. Huntington's disease pathology is characterised by marked atrophy of the caudate and putamen, with involvement of cerebral cortex, thalamus, subthalamus, nucleus accumbens, globus pallidus and substantia nigra pars reticulata. Within the caudate and putamen, the medium spiny GABA-ergic projection neurons are selectively vulnerable. Huntington's disease progresses slowly but irremediably to a state where patients are bedridden and demented, followed by death from secondary complications such as pneumonia. Current disease treatment is limited to pharmacologic management of symptoms, mostly antipsychotics, both for the abnormal movements and some psychiatric symptoms, and antidepressants. Future therapies targeting underlying disease mechanisms are currently under evaluation, raising tremendous hope for the development of curative treatments. They include metabolic support, neurotrophic intervention, cell replacement, transcriptional regulation and reducing the expression of the causative gene using small interfering RNA.

Zusammenfassung Hintergrund: Bei Patienten mit venösen Ulzera liegt die Prävalenz der Faktor-V-Leiden-Mutation bei 23 bis 26%. Wir untersuchten die wichtigsten Thrombophilie-assoziierten Gerinnungsparameter bei Patienten mit venösem Ulkus mit oder ohne postthrombotischem Syndrom. Patienten, Methodik: Fall-Kontroll-Studie mit 73 konsekutiven Patienten mit venösen Ulzera und 45 Kontrollpersonen. Anamnese und duplexsonographische bzw. phlebographische Abklärung. Folgende Gerinnungsparameter wurden bestimmt: Antithrombin III, Protein C und Protein S, Faktor-V-Leiden-Mutation, Prothrombinmutation (G20210A), Lupus Antikoagulans, Antikardiolipin-Antikörper, Homocysteinkonzentration und die Mutation (C677T) der Methylentetrahydrofolat-Reduktase (MTHFR). Ergebnisse: 42 Patienten hatten ein postthrombotisches Syndrom: 52% hatten mindestens einen Thrombophilie-assoziierten Gerinnungsbefund (p = 0,001), 33% eine Zweier-Kombination (p = 0,001) und zusätzlich in 14% eine Dreier-Kombination (p = 0,0002). Die Faktor-V-Leiden-Mutation fand sich in 38% (p = 0,0001). 31 Patienten hatten eine primäre venöse Insuffizienz (kein postthrombotisches Syndrom): 39% hatten mindestens einen Thrombophilie-assoziierten Gerinnungsparameter (p = 0,14), 3% eine Zweier-Kombination (p = 1,0) und 0% eine Dreier-Kombination. Die Faktor-V-Leiden-Mutation fand sich in 16% (p = 0,11). Schlussfolgerung: Patienten mit postthrombotischen venösen Ulzera haben stark gehäuft (52%) Thrombophilie-assoziierte Gerinnungsbefunde. In 47% liegen Kombinationen der „klassischen“ Thrombophilie-Parameter vor. Routinemäßige Abklärungen des Thrombophiliestatus bei venösen Ulzera sind mangels Konsequenzen und wegen der hohen Kosten jedoch nicht angezeigt.

We demonstrate 10 dB gain enhancement in S-band optical parametric amplification, 10 dB net conversion efficiency enhancement, and S/C band wavelength conversion by simultaneous Raman amplification using a highly nonlinear fiber. Numerical simulations support the experimental results.

In this note we report the first observation of salient features of the Si(1 1 1)7×7 reconstructed surface across monatomic steps by dynamic atomic force microscopy (AFM) in ultrahigh vacuum (UHV). Simultaneous measurements of the resonance frequency shift Δf of the Si-cantilever and of the mean tunneling current Ī i from the cleaned Si tip indicate a restricted range for stable imaging with true atomic resolution. The corresponding characteristics vs. distance reveal why feedback control via Δf is problematic, whereas it is as successful as in conventional STM via Ī i .

Using a noncontact atomic-force and scanning-tunneling microscope in ultrahigh vacuum, we have measured the switching energy of a single molecule switch based on the rotation of a di-butyl-phenyl leg in a Cu-tetra-3,5 di-tertiary-butyl-phenyl porphyrin. The mechanics and intramolecular conformation of the switched leg is controlled by the tip apex of the noncontact atomic-force microscope. The comparison between experimental and calculated force curves shows that the rotation of the leg requires an energy less than 100 x 10(-21) J, which is 4 orders of magnitude lower than state-of-the-art transistors.

The tribological properties of C(60) on the mesoscopic scale were investigated with a scanning force microscope, which allowed simultaneous measurements of normal and lateral forces under ultrahigh-vacuum conditions. Islands of C(60), deposited on NaCl(001), could be moved by the action of the probing tip in a controlled way. Different modes of motion, such as translation and rotation, were observed. An extremely small dissipation energy of about 0.25 millielectron volt per molecule and a cohesive energy of 1.5 electron volts were determined in these nanometer-scale experiments. The corresponding shear strength of 0.05 to 0.1 megapascal was smaller by one order of magnitude than typical values of boundary lubricants. For C(60) on graphite, disruption of the islands was observed and collective motion of the islands could not be achieved. These results could find use in the field of nanotechnology; for example, C(60) islands could be developed into a sled-type transport system on the nanometer scale.

Scanning force microscopy (SFM) was employed to characterize C60 island films in an ultra-high vacuum (UHV). The initial growth stage of C60 on NaCl cleavage faces and nanotribological properties of this solid lubricant are investigated. In comparison to the NaCl(001) face, higher friction is measured on the C60 islands, resulting in a ratio of friction of 1∶3 for NaCl∶C60. The friction coefficient of the (111) oriented C60 island is determined to be 0.15±0.05. High-resolution SFM images reveal the hexagonal lattice of the unreconstructed (111) top surfaces and the overgrowth relationships of the C60 islands.

We present a compact 8-port EDFA for banded-channel amplification. The unit comprises an 8-port 980-nm pump source and an 8-port gain block, achieving saturated output powers in excess of 15 dBm/port with excellent port-to-port uniformity.

A scanning force/tunneling microscope (SFM/STM) for remote controlled operation in ultrahigh vacuum (UHV) is described. The lateral forces, normal forces, and tunneling currents between probe tip and sample can all be measured simultaneously. The optical beam deflection detector and the sample position can be adjusted by means of three compact inertial stepping motors. An UHV‐compatible light emitting diode is introduced as a general alternative to the widely used laser diode in the detector. Images, taken at 5×10−11 mbar on Si(111) with STM and noncontact SFM, and on NaF(001) with contact SFM, are presented.

Polarized absorption and emission spectra of trigonal single crystals of an Er(III) complex coordinated to a heptadentate tripodal ligand are reported at temperatures between 8 and 298 K. The assigned energy levels below the onset of ligand absorption (25 000 cm(-1)) are fitted to a parametrized electronic Hamiltonian. The C(3) site symmetry of the Er(III) ion requires eight parameters for a full description of the ligand field within a one-electron operator description. This compound shows unusually large splittings of the multiplets, and the fitted parameters imply that this heptadentate ligand imparts the largest ligand field reported for an Er(III) complex. The ligand field was also interpreted within the angular overlap model (AOM). We derive the AOM matrix to include both sigma and anisotropic pi bonding and show that a useful description of the C(3) ligand field can be made using only five parameters. The success of the AOM description is encouraging for applications on isomorphous complexes within the lanthanide series and in describing the ligand field of low-symmetry complexes with less parameters than in the usual spherical harmonic expansion.

To determine the prevalence of the factor V Leiden mutation in patients with postthrombotic and non-postthrombotic venous ulcers.Case-control study.Department of Dermatology, University Hospital of Zurich, Zurich, Switzerland.Seventy-three consecutive outpatients and inpatients with venous ulcers and 45 age- and sex-matched control subjects (matched to the 42 patients with postthrombotic syndrome).Frequency of postthrombotic and non-postthrombotic findings in patients with venous ulcers. Prevalence of the factor V Leiden mutation in these different subgroups.Postthrombotic syndrome was identified as the cause of 42 (58%; 95% confidence interval [CI], 45%-69%) of 73 venous ulcers, and the remainder were caused by primary valvular insufficiency. In postthrombotic ulcers, the prevalence of the factor V Leiden mutation was 38% (95% CI, 24%-54%) (16/42), which corresponds to an odds ratio of 13.2 (95% CI, 2.8-62.3; P.001). In non-postthrombotic venous ulcers, the prevalence was 16% (95% CI, 5%-34%) (5/31), which corresponds to an odds ratio of 3.2 (95% CI, 1.0-10.0; P =.07).The factor V Leiden mutation is highly prevalent in patients with postthrombotic venous ulcers. Even patients with non-postthrombotic venous ulcers show a moderately elevated prevalence of the factor V Leiden mutation. Some of the latter might be misclassified because of near-to-perfect revascularization after asymptomatic deep venous thrombosis. However, as long as the therapeutic consequences of the factor V Leiden mutation are not established, systematic screening cannot be recommended in patients with venous ulcers.

THE study of chemical phase separation in multicomponent thin organic films typically involves the addition of a dye which is selectively more soluble in one of the phases, thereby making it possible to probe the domain structures by fluorescence microscopy1–4. The resolution of this approach is generally limited to tens of micrometres. The atomic force microscope, on the other hand, has recently proved useful for imaging organic thin films down to the atomic scale5–9, but this technique provides details of the overall film topography, rather than the chemical composition. Here we show that the recently developed friction force microscope10–13, which simultaneously measures both the normal and lateral forces on the scanning tip, can be used to image and identify compositional domains with a resolution of ∼5 A. Although the topography of the individual domains can be imaged with a standard atomic force microscope, it is the additional information provided by the friction measurement that allows them to be chemically differentiated.

We report the first observation of intense visible upconversion luminescence from Cs/sub 3/Lu/sub 2/Cl/sub 9/:Er/sup 3+/ crystals excited by a 1.53-/spl mu/m tunable cw diode laser amplified by an erbium-doped fiber amplifier. Spectral and dynamic properties between 15 and 300 K as well as changes along the chloride sample series are discussed.

The combination of ceftazidime plus aminoglycoside is widely used for the treatment of febrile neutropenic patients but requires multiple daily administration. Because the frequency of Pseudomonas aeruginosa is low in many centers, there is a rationale to test other antibiotic regimens that provide appropriate antibacterial coverage with the advantage of reduced dosing frequency, such as once daily ceftriaxone plus amikacin.Febrile neutropenic children with leukemia, lymphoma or solid tumors after chemotherapy were included in an open, prospective, randomized, multinational study comparing once daily ceftriaxone plus amikacin vs. 8-hourly ceftazidime and amikacin. The response to antimicrobial therapy was defined as complete response, improvement or failure. Assessment of adverse events was supplemented by specific definitions of nephrotoxicity, ototoxicity, hepatotoxicity and hypokalemia. Costs were estimated from published values of acquisition costs, delivery costs and hospitalization costs.Efficacy was evaluable in 364 of 468 episodes in 265 children. Response rates in ceftriaxone and amikacin vs. ceftazidime and amikacin-treated episodes were 119 of 181 (66%) vs. 121 of 183 (66%), 7 of 181 (4%) vs. 9 of 183 (5%) and 55 of 181 (30%) vs. 53 of 181 (29%) for complete response, improvement and failure, respectively. Safety profiles were similar with both treatment regimens. The acquisition and administration costs were lower for the ceftriaxone and amikacin regimen.A once daily regimen of ceftriaxone and amikacin is as safe and clinically effective as that of three times daily ceftazidime and amikacin for the treatment of febrile neutropenic children with cancer and is more cost-effective. The once daily regimen of ceftriaxone and amikacin is suitable for outpatient treatment.

We present an atomic-scale study on friction performed by a bidirectional atomic force microscope operated in ultrahigh vacuum. Experiments on surfaces of in situ cleaved KBr crystals are presented. On a μm scale the cleavage structure with monoatomic steps of 3.5 ± 0.3 A is revealed. On the atomically flat terraces, atomic-scale resolution is achieved. The resolved square lattice shows a periodicity of 4.7 A and corrugations of 0.3–0.7 A and exhibits the cubic symmetry of KBr(001). The lateral (frictional) force map shows all characteristics of the stick-slip movement of the probing tip. From analysis of the friction loops, the kinetic friction force was determined as a function of load. For a load regime of -4 to 10 nN, lateral force corrugations ranging from 1 to 5 nN were found. A comparison with a novel theoretical model is discussed qualitatively.