Search

The investigation of the electronic structure of liquid elements with photoelectron spectroscopy is restricted to some 20 elements of the periodic table. This restriction is mainly due to the high vapour pressures of most elements in the liquid state and the need of ultra high vacuum conditions in the spectrometer. To overcome this limit we introduced the new technique of time-resolved photoemission during pulsed laser heating. This technique allowed us to measure several elements in the liquid state, not accessible by conventional photoemission, of which the early transition metals Ti, V, Zr, Nb, Mo, Hf, Ta and W are presented here. The use of eight subsequent time windows also enabled us to observe the solid–liquid phase transition revealed by the changes in the valence band spectra. These neighbouring elements which nearly cover a square area of the periodic table were chosen to show an overall trend in the liquid state when going from 3d to 5d metals and varying the number of d-electrons. Furthermore a well known solid–solid phase transition (hcp→bcc) could be observed for the elements Ti and Zr.

Photoelectron spectroscopy measurements on liquid transition metals are not feasible by conventional steady state experiments because of the elevated vapor pressures of these metals at the melting point. However, dynamic experiments with surface melting induced by pulsed laser irradiation combined with time resolved photoelectron spectroscopy make these experiments possible for the first time. Valence band spectra of Pd and Mo have been obtained by this method in both the high temperature solid phase and the liquid phase under identical experimental conditions. Both the elements reveal distinct changes in the valence band spectra on melting. The shapes of the 4d bands of the two metals in the liquid phase are in good agreement with the calculated spectra based on the ab initio density of states (DOS) calculations.

The electronic structure of liquid tungsten has been studied by time-resolved photo electron spectroscopy on laser pulse molten surface layers. The valence band spectra reveal distinct changes of the electronic structure across the solid-liquid phase transition which are interpreted by marked changes of the short-range order on melting which change qualitatively the valence electron density of states.

The electronic structure of liquid transition metals has been studied by time resolved photoelectron spectroscopy. Distinct changes in the valence band structure across the solid-liquid phase transitions have been observed for Pd, Mo and W. In the case of Pd the changes on melting are caused by a change in the photoemission process itself. For Nb, Mo, Ta and W we suggest a change in the atomic short range order from the bcc structure to an fcc-like short range order in the liquid state which causes a marked change in the valence band spectra of Mo and W due to the filling up of the pronounced gap in the density of states near the Fermi level. The measurements show that time resolved photoelectron spectroscopy can be used to study high temperature oxidation processes on the microsecond time scale.

BACKGROUND In continuation of our previously published report on initial experience with titanium implants in the middle ear [13], we now present the results of routine use over a three year period. METHODS From November 1994 to November 1997, 661 titanium implants (Dusseldorf model) were implanted in the authors' clinics (355 PORP, 306 TORP). There was no preselection of patients. Five hundred eighty-two follow up examinations were performed with a medium follow up time of 11.6 months. RESULTS The good initial results of the previous study with respect to biocompatibility and functional hearing results were confirmed in the long term follow-up. The average air-bone gap was calculated over the frequencies 0.5, 1, 2, and 4 kHz. Closure to within 20 dB was achieved in 72% of cases. The air-bone gap tended to decrease with increasing time of implantation. Adverse reaction to the prostheses did not occur. Extrusion occurred in one case of complete middle ear atelectasis with resorption of the interposed cartilage. Insufficient improvement of hearing was attributable to a short implant in 12 cases (1.8%). In three cases (0.5%) insufficient stability of the PORP was attributable to eroded stapes suprastructure, and in three others (0.5%) a dislocation was responsible for a poor hearing result. Middle ear fibrosis with impairment of sound transmission was seen in 3 patients (0.5%). CONCLUSION The superior acoustic properties of the delicate yet rigid low-weight titanium implants combined with excellent biocompatibility lead to a good hearing result if a meticulous surgical technique is employed. The easy handling makes it a pleasure to work with these protheses.

The solid - liquid - solid-phase transitions of a alloy have been investigated by means of the recently developed method of time-resolved photoelectron spectroscopy, using dye laser pulses to melt the sample surface on a microsecond scale. Starting at a temperature of the liquid sample just above the melting point (740 K), the laser pulse heating allowed us to obtain, for the first time, valence band spectra of an alloy at temperatures of up to 1620 K, distinctly above the vapour pressure limit of steady-state photoelectron spectroscopy. The photoemission results of the liquid at different temperatures are compared with data from the corresponding amorphous alloy, prepared by vapour condensation at liquid-nitrogen temperature. By increasing the temperature of the disordered phase, the Au 5d band is found to shift continuously toward a lower binding energy, showing a linear behaviour over the whole temperature range. Our measurements confirm earlier results obtained with conventional photoemission within a restricted temperature range. The results presented here clearly show the potential of the new technique to investigate the electronic structure of alloys at conditions under which standard photoemission experiments cannot be performed.

Interface reactions were observed by means of photoelectron spectroscopy during the preparation of Au/Sn bilayers at 77 K. These reactions lead to ultra-thin (0.5–2 nm) amorphous layers with tunable stoichiometry, spanning the same range of compositions as found for the corresponding vapor-quenched amorphous Hume-Rothery alloys. In all cases, structure-induced minima in the electronic density of states at the Fermi level are observed for the intermixed amorphous phases. Since structure-induced minima are a characteristic feature of a Peierls system, the ultra-thin amorphous layers may be discussed as reflecting the transition from a nearly two-dimensional to an isotropic three-dimensional Peierls-distorted system.

Natural type IIb diamond surfaces of (100), (110), and (111) orientation, as well as chemical vapor deposited (CVD) diamond thin films with (100), (110), or mixed orientation are probed by photoelectron spectroscopy in the ultraviolet (UPS) and X-ray (XPS) energy regimes. Dramatic changes can be observed in the valence band and core level spectra of these surfaces upon annealing, hydrogen-plasma exposure, or pulsed dye laser irradiation. The observed changes can be reversed by the exposure of the surfaces to atomic hydrogen (deuterium). The valence band spectra reveal specific surface reconstructions for all three surface preparation methods and moreover a cleaning effect is observed following laser irradiation of CVD diamond surfaces. A comparison to a multitude of theoretical and experimental studies on diamond surface reconstruction is made to elucidate the connection between electronic properties and atomic surface structures.

We report on detailed measurements of the electrical conductivity σ(T) in uncompensated Si:P in a magnetic field B of 6 T between 30 mK and 1 K. The approximate relation σ(T) = σ(0) + mB √T allows a reliable extrapolation of σ(0). The critical behaviour σ(0) ~ (N - Ne)μ' close to the critical P concentration Ne yields a critical exponent μ' ≈ 1.3, with a tendency to smaller values at a crossover concentration which is close to the concentration where mB changes strongly. The implications for the previously proposed solution to the exponent puzzle for B = 0 are discussed.

The electrical conductivity \ensuremath{\sigma} (extrapolated to T=0) of uncompensated Si:P indicates a crossover as a function of P concentration N at ${\mathit{N}}_{\mathrm{cr}}$ slightly above the metal-insulator transition at ${\mathit{N}}_{\mathit{c}}$. For Ng${\mathit{N}}_{\mathrm{cr}}$ the exponent of \ensuremath{\sigma}\ensuremath{\sim}(N-${\mathit{N}}_{\mathit{c}}$${)}^{\mathrm{\ensuremath{\mu}}}$ is \ensuremath{\mu}\ensuremath{\approxeq}0.64, while \ensuremath{\mu}\ensuremath{\approxeq}1.3 for ${\mathit{N}}_{\mathit{c}}$N${\mathit{N}}_{\mathrm{cr}}$. At ${\mathit{N}}_{\mathrm{cr}}$ d\ensuremath{\sigma}/dT changes sign from negative for Ng${\mathit{N}}_{\mathrm{cr}}$ to positive for N${\mathit{N}}_{\mathrm{cr}}$. $sigma--- in a magnetic field also yields \ensuremath{\mu}\ensuremath{\approxeq}1. The apparent discrepancy between uncompensated and compensated semiconductors is traced back to a difference in the (nonuniversal) width of the critical region.

Background Titanium has been a well established implant material for many years. New material processing techniques now permit the manufacture of small implants for ossicular chain reconstruction. Methods Between November 1994 and September 1995, 100 titanium middle ear implants (55 PORP, 45 TORP) were used for reconstruction of the ossicular chain. A range of five different sizes for partial and total protheses suits all implantation needs. The shape of the implants can be altered by bending. Time consuming intraoperative shaping and trimming is avoided. Results At a follow-up time of three months (33 patients) and six months (17 patients), no adverse reactions or extrusions occurred. Biologic fixation between the foot of the partial prothesis and the head of the stapes was found eight months after implantation. A hearing result of 0-20 dB residual air-bone gap was achieved in 79%. Conclusion Titanium middle ear implants show good bio-compatibility and are readily integrated into the ossicular chain. Although delicate in shape, they offer excellent mechanical properties in respect to sound conduction and implantation. Initial results show Titanium to be a perfect implant material for middle ear prostheses, although long-term results are not yet available.

The effect of processing conditions on polysilicon TFT (thin-film transistor) performance is explained. By careful selection of process techniques excellent devices are obtained, independent of processing temperature. It is possible to fabricate polysilicon TFTs at low temperature with performance comparable to that of high-temperature TFTs by replacing the high-temperature steps with low-temperature steps which have the same effect on the material and device structure. These TFTs are used in full-resolution LCDs (liquid crystal displays) for projection television. >

Polysilicon thin-film transistors (TFTs) were fabricated with the maximum processing temperature limited to 650 degrees C. Best results were obtained when the gate oxide was grown by a two-step high-pressure oxidation process, using high-pressure steam and then dry oxygen both at 15 atm and 650 degrees C. The TFTs exhibit a mobility of 34 cm/sup 2//V*s, threshold voltage of 3.5 V, leakage current below 0.01 pA/ mu m, subthreshold slope of 0.18 V/decade, and an ON/OFF ratio of over eight orders of magnitude. These values are comparable to those obtained with conventional polysilicon TFTs using high-temperature thermal oxidation. >

In continuation of our previously published report on initial experience with titanium implants in the middle ear [13], we now present the results of routine use over a three year period.From November 1994 to November 1997, 661 titanium implants (Düsseldorf model) were implanted in the authors' clinics (355 PORP, 306 TORP). There was no preselection of patients. Five hundred eighty-two follow up examinations were performed with a medium follow up time of 11.6 months.The good initial results of the previous study with respect to biocompatibility and functional hearing results were confirmed in the long term follow-up. The average air-bone gap was calculated over the frequencies 0.5, 1, 2, and 4 kHz. Closure to within 20 dB was achieved in 72% of cases. The air-bone gap tended to decrease with increasing time of implantation. Adverse reaction to the prostheses did not occur. Extrusion occurred in one case of complete middle ear atelectasis with resorption of the interposed cartilage. Insufficient improvement of hearing was attributable to a short implant in 12 cases (1.8%). In three cases (0.5%) insufficient stability of the PORP was attributable to eroded stapes suprastructure, and in three others (0.5%) a dislocation was responsible for a poor hearing result. Middle ear fibrosis with impairment of sound transmission was seen in 3 patients (0.5%).The superior acoustic properties of the delicate yet rigid low-weight titanium implants combined with excellent biocompatibility lead to a good hearing result if a meticulous surgical technique is employed. The easy handling makes it a pleasure to work with these protheses.

Titanium has been a well established implant material for many years. New material processing techniques now permit the manufacture of small implants for ossicular chain reconstruction.Between November 1994 and September 1995, 100 titanium middle ear implants (55 PORP, 45 TORP) were used for reconstruction of the ossicular chain. A range of five different sizes for partial and total protheses suits all implantation needs. The shape of the implants can be altered by bending. Time consuming intraoperative shaping and trimming is avoided.At a follow-up time of three months (33 patients) and six months (17 patients), no adverse reactions or extrusions occurred. Biologic fixation between the foot of the partial prothesis and the head of the stapes was found eight months after implantation. A hearing result of 0-20 dB residual air-bone gap was achieved in 79%.Titanium middle ear implants show good bio-compatibility and are readily integrated into the ossicular chain. Although delicate in shape, they offer excellent mechanical properties in respect to sound conduction and implantation. Initial results show Titanium to be a perfect implant material for middle ear prostheses, although long-term results are not yet available.

A two dimensional study of reverse avalanche breakdown in high voltage gated diodes is presented. The numerical method uses the finite difference solution of Poisson's equation with appropriate boundary conditions. A modified two dimensional depletion region approximation is used to take into account the effects of accumulation and inversion near the insulator-semiconductor interface. It has been found that although the effects of surface states and accumulation on the breakdown is small, inversion changes the breakdown characteristics substantially. Breakdown voltage versus gate voltage curves are given for various geometries and doping properties. Good agreement has been achieved between the computed and experimental values of breakdown voltages for a large range of gate potentials.

A nondestructive photoelectronic technique for determining the thickness and minority‐carrier diffusion length of thin epitaxial layers of GaP is described. The method is useful over a thickness range of about one to ten diffusion lengths. The diffusion lengths can be rapidly measured to within 0.25 μm when the diffusion length of the substrate is known. The accuracy of the thickness measurement is about 0.5 μm. The measurements are independent of the supporting substrate thickness.

Zusammenfassend last sich sagen, das vor allem Streptomycin, viel weniger dagegen Kanamycin bei direkter Applikation in das Mittelohr und weniger ausgepragt bei intraperitonealer Injektion, zu einer Schadigung der Sinneszellen der Macula des Sacculus und Utriculus sowie der Cristae der Bogengange fuhrt. Die ausgepragtesten Sinneszellverluste fanden sich in der Macula des Utriculus. Die Schadigungen waren besonders ausgepragt im Zentrum der Macula bzw. der Crista. Am meisten betroffen waren die Typ-I-Zellen im Vergleich zu den Typ-II-Zellen, die sich in allen Abschnitten als wesentlich resistenter gegenuber den toxischen Antibiotica erwiesen. An den Stutzzellen waren keine Zeichen einer Schadigung zu erkennen.

The photoconductivity in cadmium selenide single crystals is investigated to determine if the Klasens picture properly describes the electronic phenomena in this material. It is found that the simple two‐state model is inadequate and at least three recombination centers, and possibly four, are needed for consistency. It is furthermore found that for the model to be acceptable, it must be assumed that activation occurs at impurity levels below that available in the purest material. Some of the limitations of using sintered photoconductors in a study of this type are also described.

Unsere Untersuchungen ergaben eine uberrascbend hohe Kanamycin-konzentration in der Peri- und vor allem audi in der Hndolymphe. Sie enthielten z. B. 12 Stunden post injectionem lOmal mehr Kanamycin als das Bint und 20mal mehr als Herz und Leber. Die Tatsachc, das der Kanamycingehalt des Innenolires uber 100inal so hoch ist wie ini Gehirn, weist darauf hin, das wahrscheinlich ini Innenohr und nicht im ZNS der Schadigungsort zu suchen ist.

Two dimensional analysis has been applied to model the lateral DMOST (LDMOST) transistor in the off condition. This approach predicts breakdown voltages beyond the conventional limit. Using this model, a 400 volt lateral transistor was designed, fabricated, and tested. The design values obtained from the numerical modeling, and the experimental results for a >425 volt LDMOST are presented.

A monochromator system is described which has a constant output energy as a function of wavelength with an accuracy limited by the blackness of a radiation thermocouple. This is accomplished through the variation of the temperature of the radiant source thus providing for independent slit control. The wavelength range considered is from 550 to 1500 mμ. The system is adaptable to other spectral regions for which thermal sources of radiation are available.

They are different methods of medical treatment in Menière's disease. 1. The dehydration of the hydrops by diet, diuretics, hypertonic solutions and glycerol. 2. Improvement of the blood supply by carbon dioxide, by myotropic and neurotropic vasodilators or by decreasing the blood viscosity and by medical or surgical paralysis of the sympathetic nerve. The optimistic results seen by acupuncture or neural therapy are not confirmed. - Experimental and double blind studies with betahistin (vasomotal) showed a significant effect in improving the blood circulation of the inner ear and the symptoms of Menière's disease. 3. Sedatives especially neuroleptics and tranquilizers were successful only by suppressing the symptoms, but are not a causal treatment. The same mechanism is supposed for procain and lidocain. 4. Partial destruction of the inner ear has been produced by local application of anesthetics or ototoxic antibiotics. These methods succeed in relieving vertigo and save the hearing in most cases.