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We present a study on the quantification of energy dissipation of Micro-Electro-Mechanical System (MEMS) resonators. Toroidal Ring Gyroscope (TRG) was used as a platform to conduct the study. The main energy dissipation mechanisms in TRG include viscous air damping, Thermo-Elastic Damping (TED), anchor loss, and surface loss. During our experimental study, these energy dissipation mechanisms were minimized and controlled by venting the encapsulation and actively pumping down to high vacuum, cooling the temperature down to around 123 K, adjusting modal balance by electrostatic tuning, and pre-baking the device at high temperature (425 °C), respectively. At room temperature, the quality factor related to viscous air damping was measured to be 625,000, TED to be 170,000, and anchor loss to be 1,350,000. Finite Element Analysis (FEA) was conducted to support these findings. Relation between the anchor loss and electrostatic tuning was also explored. The effects of moisture-related surface loss have also been demonstrated by monitoring characteristics over a 2-year period of time. High temperature bake-out was proven to be effective in removing the moisture and reducing the surface loss. This paper combines topics that are scattered in literature on identification of energy dissipation mechanisms in kilohertz-range silicon MEMS resonators and presents the topic as a single methodology illustrating how the contribution of each energy dissipation mechanism can be quantified independently. To the best of our knowledge, this study is the first to experimentally quantify all major energy dissipation mechanisms in a kilohertz-range silicon MEMS resonator. [2020-0294]

We present a Lame mode resonator whose limiting damping mechanism depends on its anchor geometry. The device is anchor-limited when the anchors are stiffer and is Akhiezer-limited with more compliant anchors. This result is determined by observing the temperature dependence of the quality factor (Q) for devices with different lateral dimensions and different anchor designs. The total measured Q increases by an order of magnitude with the more compliant anchors and reaches a room temperature fxQ product of $\boldsymbol {2.2\times 10^{13}}$ . We studied the relationship between the device design and the anchor design and the measured Q(T) results to identify the contributions from different dissipation mechanisms. This investigation provides insight into how anchor design affects anchor damping. [2020-0195]

We demonstrate two novel dual-mode ovenized MEMS resonators, each with an in-chip device layer micro-oven that utilizes less than 30mW for resonator temperature control over variations in external temperature from −40°C to +60°C. The device layer micro-oven enables correction for ambient temperature variations and achieves a 1-week frequency stability for the output mode over temperature near 1.5 ppb for the Lame-mode resonator. The devices were built in the Epi-Seal fabrication process and take advantage of the exceptional long-term stability of MEMS resonators built in that process. These results exceed all prior reports for frequency stability over time and temperature for MEMS resonators and have the potential to impact the development of miniature, low-power time references. [2019-0054]

The thermomechanical motion imposes the fundamental noise limit in room-temperature resonant sensors and oscillators. Due to the inherently low sensitivity of capacitive transduction in microelectromechanical (MEM) resonators, its effects are often masked by noise in the subsequent amplifier and measurement stages. In this work, we demonstrate a capacitive transduction scheme for measuring kHz-MHz frequency MEM resonators across 1 $\mu \text{m}$ capacitive gaps with 99.8% thermomechanical-noise-limited resolution. We delineate the transimpedance gain and noise of our custom off-chip differential transimpedance amplifier setup. The thermomechanical noise spectrum can provide estimates of the resonant frequency, quality factor, and electromechanical transduction factor comparable to the commonly used driven response, without the downsides of capacitive feedthrough or nonlinearity. [2019-0115]

This paper demonstrates a post-fabrication technique for creating highly compliant structures inside a hermetic, wafer-scale encapsulation process. Single crystal silicon micro-tethers were fabricated alongside compliant structures to temporarily provide additional anchoring and increased device rigidity during the fabrication process. This technique mitigates in-process stiction for compliant devices by tethering the large, free-moving structures during fabrication. After successful fabrication, the micro-tethers can be selectively removed by two methods. The first method utilizes a potential voltage difference across the device. Joule heating can be concentrated in the micro-tether and the device separated after supplying requisite heat energy. The second method utilizes mechanical fracturing where a large external force is applied to separate the device from the tether. Micro-tethers in this paper were attached to differential resonant beam accelerometers, and were designed for detachment by each method: Joule heating and mechanical fracture. Our results show that the $40\mu \text{m}$ thick device can be successfully detached by both methods, indicated by the device sensitivity increase from ~100 Hz/g to ~400 Hz/g. [2018-0091]

Millions of micro electro mechanical system sensors are fabricated each year using an ultra-clean process that allows for a vacuum-encapsulated cavity. These devices have a multi-layer structure that contains hidden layers with highly doped silicon, which makes common imaging techniques ineffective. Thus, examining device features post-fabrication, and testing, is a significant challenge. Here, we use a combination of micro- and nano-scale x-ray computed tomography to study device features and assess failure mechanisms in such devices without destroying the ultra-clean cavity. This provides a unique opportunity to examine surfaces and trace failure mechanisms to specific steps in the fabrication process.

A systematic experimental and theoretical evaluation of stiction between intermittently contacting silicon surfaces in an ultra-clean encapsulation process is presented, evaluating magnitude of stiction forces, the reversible nature of sidewall contact, and repeatability of results. The uniquely stable environment and the lack of native oxide are leveraged to enable reliable collision and contact models, which confirm the nature of the asperity contact. In addition, we demonstrate a series of dynamic mechanical anti-stiction solutions and the mechanisms by which they mitigate stiction. These devices are shown to reduce susceptibility to stiction-related failure by 50%. [2015-0291]

This paper reports the results of a diffusion doping-based method of controlling the temperature coefficient of frequency (TCf) of MEMS resonators. In this work, a suite of resonators from two different wafers — one with and one without diffusion doping — is characterized and compared. By diffusing dopants through exposed sidewalls of silicon resonators within an epitaxial polysilicon encapsulation process, this technique demonstrates a dramatic reduction in the resonator's frequency-temperature sensitivity, one of the significant disadvantages of silicon as a resonator material. Moreover, because thicker geometries are less affected by lateral diffusion, this method provides capability to independently manipulate frequency-temperature behaviors of different resonant systems fabricated on the same wafer.

We present theoretical and experimental data on instability bands in a low-power resonant pull-in based MEMS vibration detector. The ohmic Silicon-to-Silicon switch was fabricated in a near-vacuum encapsulation epitaxially sealed process. The device requires a static bias (

We present a tunable broadband shoaling mechanical amplifier and a method to extend its operation near the electrostatic pull-in instability. The model has been verified experimentally on a vacuum encapsulated silicon MEMS device. We show that by adding an appropriate mechanical compensation spring, the amplifier can be operated near the pull-in instability in a quasi-linear fashion. Furthermore, electrostatic band-pass region and amplification tuning is shown.

We measure the influence of ambient temperature (from −40 °C to 80 °C) on the threshold current for self-oscillations inathermal-piezoresistively pumped, capacitively sensed resonator. We demonstrate that for our flexural mode self-oscillator, the threshold current decreases with decreasing ambient temperature. We observe the generation of harmonics during self-oscillation with amplitudes that decrease and effective quality factors that increase with each successive mode. Following self-oscillations, we observe that the effective quality factor and amplitude is extremely sensitive to further DC current increases.

In this work, we demonstrate both high-frequency (1.12 MHz) MEMS tuning fork resonators and lower frequency (39kHz) MEMS test devices capable of withstanding large magnitude inertial shocks. These devices reliably continue to function after the application of repeated inertial shocks in excess of 20,000g. The device performance, and the robust, pure silicon encapsulated environment are both preserved. Detailed before/after analysis and high-speed real time measurements confirm the functionality of the devices. High frequency, single anchored devices display no measureable change in properties, and even low frequency devices have high survival rates and only small changes in surface adhesion.

There is significant interest in integration of multiple MEMS functionalities into a single compact device. Our group has developed a wafer-scale encapsulation process that provides an ultraclean, stable environment for operation of MEMS timing references, which has been commercialized by SiTime, Inc. In this paper, we discuss some of the issues associated with incorporation of inertial sensors into this encapsulation process, including design constraints, stiction, pressure, and other issues.

Quality factor (Q) is an important property of micro- and nano-electromechanical (MEM/NEM) resonators that underlie timing references, frequency sources, atomic force microscopes, gyroscopes, and mass sensors. Various methods have been utilized to tune the effective quality factor of MEM/NEM resonators, including external proportional feedback control, optical pumping, mechanical pumping, thermal-piezoresistive pumping, and parametric pumping. This work reviews these mechanisms and compares the effective Q tuning using a position-proportional and a velocity-proportional force expression. We further clarify the relationship between the mechanical Q, the effective Q, and the thermomechanical noise of a resonator. We finally show that parametric pumping and thermal-piezoresistive pumping enhance the effective Q of a micromechanical resonator by experimentally studying the thermomechanical noise spectrum of a device subjected to both techniques. (C) 2018 Author(s).

Energy policy 61, 1556 - 1567 (2013). doi:10.1016/j.enpol.2013.06.095, Published by Elsevier Science, Amsterdam [u.a.]

Background: Mucormycosis has emerged as a rare but frequently fatal invasive fungal disease. Current knowledge on paediatric mucormycosis is based on case reports and small series reported over several decades. Contemporary data on a large cohort of patients is lacking. Methods: Two large international registries (Zygomyco.net and FungiScope™) were searched for mucormycosis cases in ≤19 year-old patients. Cases enrolled between 2005 and 2014 were extracted, and dual entries in the two databases merged. Epidemiology, clinical characteristics, diagnostic procedures, therapeutic management and final outcome were recorded and analysed with SPSS v.12. Results: Sixty-three unique cases (44 proven and 19 probable) were enrolled from 15 countries (54 in European and 9 in non-European countries). Median age was 13 years [Interquartile Range (IQR) 7.7] with a slight predominance (54.1 %) of females. Underlying conditions were haematological malignancies (46 %), other malignancies (6.3 %), haematopoietic stem cell transplantation (15.9 %), solid organ transplantation, trauma/surgery and diabetes mellitus (4.8 % each) and a variety of other diseases (7.9 %); in 9.5%, no underlying medical condition was found. Neutropenia was recorded in 46 % of the patients. The main sites of infection were lungs (19 %), skin and soft tissues (19 %), paranasal sinus/sino-orbital region (15.8 %) and rhino-cerebral region (7.9 %). Disseminated infection was present in 38.1 %. Mucormycosis diagnosis was based on several combinations of methods; culture combined with histology was performed in 31 cases (49.2 %). Fungal isolates included Rhizopus spp. (39.7 %), Lichtheimia spp. (17.5 %), Mucor spp. (12.7 %), Cunninghamella bertholletiae (6.3 %) and unspecified (23.8 %). Treatment comprised amphotericin B (AmB) monotherapy in 31.7 % or AmB in combination with other antifungals in 47.7 % of the cases, while 14.3 % received no antifungals. Surgery alone was performed in 6.3 %, and combined with antifungal therapy in 47.6 %. Crude mortality at last contact of follow-up was 33.3 %. In regression analysis, disseminated disease and prior haematopoietic stem cell transplantation were associated with increased odds of death, whereas the combination of systemic antifungal therapy with surgery was associated with improved survival. Conclusion: Paediatric mucormycosis mainly affects children with malignancies, presents as pulmonary, soft tissue, paranasal sinus or disseminated disease and is highly lethal. Outcome is improved when active antifungal therapy and surgery are combined. © 2016 The Author(s).

This paper introduces a ‘high-frequency’ resonant tri-axial tuning fork gyroscope (TFG) with a single-drive mode of operation. The quad-mass device is implemented on a 2×2 mm2 vacuum-packaged die fabricated using the epi-seal process, making this one of the smallest wafer-level packaged 3-axis gyros. In contrast to conventional resonant TFGs, the resonant frequencies are designed to be relatively high (∼138 kHz) permitting high bandwidth for mode-matched operation and enhancing resistance to shock and vibration. The results show sensitivity to all three axes with mode-matched operation for the Z-axis and mode-split for the X- and Y-axes.

PurposeThere is a stream of literature highlighting the enormous growth potential of emerging markets. This literature forms the basis for strategic investment decisions made by multinational corporations (MNCs). Seeking to question the findings of this literature, this paper aims to undertake a comparison of the BRIC countries with that of Germany as a representative mature market to put into perspective the short to medium‐term market potential of BRIC markets.Design/methodology/approachAn analysis of the geographical investment priorities of 25 DAX multinationals operating in the real economy and a statistical comparison of market size and growth between BRIC countries and Germany are undertaken.FindingsWhile the majority of the DAX companies examined focused their strategic investment priorities on emerging markets, the short‐ to mid‐term revenue potential of the BRIC countries – currently the most important emerging markets – are expected to be lower in absolute terms than those for mature markets such as Germany. This holds true on several levels of granularity, such as GPD per capita, size and growth of high‐income market segments.Research limitations/implicationsThe considerable “hype” surrounding focusing investment on emerging markets needs closer scrutiny. Further research is required to subject the reasons behind the strategic investments of MNCs in BRIC countries to more detailed analysis. This encompasses, for example, a closer consideration of the extent to which messages from the company reports might not reflect true strategic priorities but rather represent a means of public relations or tactical ploys. Next, the impact of real long‐term expectations and potential bandwagon effects require further study. Finally, a comprehensive theoretical model placing emerging market growth into a broader perspective has yet to be developed.Practical implicationsDecision makers in business, government and NGOs should not be misled by the “hype” surrounding emerging markets. In many industries, BRIC countries do and will provide smaller markets when compared to mature markets like Germany.Originality/valueDirect comparison of market growth in the BRIC countries and that in Germany reveals greater short‐ to medium‐term absolute growth potential in Germany, a fact often ignored by current literature on international growth strategies and not reflected in the growth priorities published by German DAX companies.

This paper presents a capacitive X/Y and Z-axis accelerometer, pressure sensor, and resonant thermometer, co-fabricated in a single die using an ultra-clean, high-temperature, wafer-scale, production-compatible encapsulation process. This process is free of bond rings and getter areas, thereby reducing overall die size to a minimum. Utilizing a process that allows for nitride and silicon etch stops, we show that it is possible to design high-sensitivity pressure sensors and accelerometers with very little cross-sensitivity. In addition, remaining sensitivities to environmental effects, such as temperature, can be compensated to reveal a suite of on-chip high-performance sensors that is accurate over temperature. All of this is accomplished in a process similar to current high-volume production processes in industry.

We demonstrate the consistent and manageable nature of surface adhesion and stiction forces in MEMS devices fabricated using the high-temperature epitaxial encapsulation process. In this encapsulation process (commercialized by SiTime), there are no chemical anti-stiction films or getters. Data from more than 2000 test structures with more than 80 design variations from three different fabrication runs were gathered in this study. Surprisingly, the adhesion force is shown to be independent of design geometry. The measured adhesion forces (18–25uN) are small enough for inertial sensors. In addition, we demonstrate anti-stiction bump stops with springs for a sliding contact, which reduce the probability of stiction by over 50%.

Research on MEMS Resonators began over 50 years ago. In just the last 10 years, there has been a series of important technological developments, and (finally!) success at commercialization. The presentation will highlight some key milestones along this path, describe some of the critical technology steps, and outline some of the important non-technological events within SiTime - all of these factors contributed to the successful outcome.

A better knowledge of biochemical and structural properties of human chromosomes is important for cytogenetic investigations and diagnostics. Fluorescence in situ hybridization (FISH) is a commonly used technique for the visualization of chromosomal details. Localizing specific gene probes by FISH combined with conventional fluorescence microscopy has reached its limit. Also, microdissecting DNA from G-banded human metaphase chromosomes by either a glass tip or by laser capture needs further improvement. By both atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM), local information from G-bands and chromosomal probes can be obtained. The final resolution allows a more precise localization compared to standard techniques, and the extraction of very small amounts of chromosomal DNA by the scanning probe is possible. Besides new strategies towards a better G-band and fluorescent probe detection, this study is focused on the combination of biochemical and nanomanipulation techniques which enable both nanodissection and nanoextraction of chromosomal DNA.

Most Sinorhizobium meliloti strains lack several key genes involved in microbial biotin biosynthesis, and it is assumed that this may be a special adaptation which allows the microbe to down-regulate metabolic activities in the absence of a host plant. To further explore this hypothesis, we employed two different strategies. (i) Searches of the S. meliloti genome database in combination with the construction of nine different gusA reporter fusions identified three genes involved in a biotin starvation response in this microbe. A gene coding for a protein-methyl carboxyl transferase ( pcm ) exhibited 13.6-fold-higher transcription under biotin-limiting conditions than cells grown in the presence of 40 nM biotin. Consistent with this observation, biotin-limiting conditions resulted in a significantly decreased survival of pcm mutant cells compared to parental cells or cells grown in the presence of 40 nM biotin. Further studies indicated that the autoinducer synthase gene, sinI , was transcribed at a 4.5-fold-higher level in early stationary phase in biotin-starved cells than in biotin-supplemented cells. Lastly, we observed that open reading frame smc02283 , which codes for a putative copper resistance protein (CopC), was 21-fold down-regulated in response to biotin starvation. (ii) In a second approach, proteome analysis identified 10 proteins which were significantly down-regulated under the biotin-limiting conditions. Among the proteins identified by using matrix-assisted laser desorption ionization-time of flight mass spectrometry were the ϖ subunit of the RNA polymerase and the 50S ribosomal protein L7/L12 (L8) subunit, indicating that biotin-limiting conditions generally affect transcription and translation in S. meliloti .

A large dc bias voltage (tens of volts) is often useful for the operation of capacitive MEMS devices. Charge-biasing techniques have been demonstrated to be able to replace a bias voltage source by trapping an equivalent charge on an electrically floating electrode. This work presents a charge-biased resonator that uses an electrostatically actuated mechanical switch with a pull-in voltage of 36 V to introduce a voltage-equivalent charge of 10-15V onto a resonant body. The switch and resonator are hermetically sealed in a clean vacuum cavity, within an epitaxial polysilicon encapsulation process (epi-seal). No charge leakage has been observed, even at an elevated temperature of 125°C for weeks.

We show that contact between encapsulated MEMS devices and the bare silicon surrounding sidewalls generally results in a reversible adhesion with a consistent adhesion force. This force is small enough (25 mN) to be overcome by the restoring force of the springs in inertial sensors with resonant frequency above 4 kHz. Therefore, it should be possible to design and build stiction-free inertial sensors in this process - a significant advantage over approaches that rely on deposition, tuning and maintenance of chemical coatings for inertial sensors.

WO3 films, either prepared by sputtering or evaporation under high or ultrahigh vacuum conditions, were irradiated with He+ and Ar+ ions (energy range 300–350 keV) at ambient and low temperatures (77–100 K). The resulting ion induced changes of the optical absorption as well as of the electrical conductivity could be determined on one and the same sample, which enables the variable range hopping (VRH) model to be tested under the assumption that the density of irradiation induced color centers is proportional to the electronic density of states contributing to the hopping conductivity. It is found that the data obtained at 300 K for He+ and Ar+ bombardment can be described within the VRH model by one common conductivity versus absorption curve, even though the effectiveness per projectile of the heavier ion for coloration as well as for increasing the conductivity is much higher. This is different at low temperatures. While the ion induced coloration is practically independent of the irradiation temperatu...

Zwischen dem 1. 6. 1990 und 30. 11. 1997 wurden in der Klinik und Poliklinik fur Unfallchirurgie der Universitat Bonn insgesamt 96 Oberarmschaftfrakturen bei 88 Patienten plattenosteosynthetisch versorgt. In 85 Fallen handelte es sich hierbei um frische Frakturen einschlieslich 11 pathologischer Frakturen, in 11 Fallen um revisionspflichtige Pseudarthrosen. Die retrospektive Auswertung der Krankenunterlagen ergab, dass die Frakturen nach durchschnittlich 16,2 Wochen klinisch und radiologisch konsolidiert waren. Postoperativ kam es 3-mal zur Implantatlockerung, 6-mal zur Ausbildung eines Hamatoms oder Seroms, 1-mal zur sekundaren Amputation bei ausgedehntem Weichteilschaden, 1-mal zum Plattenlagerinfekt und 5-mal zu einer passageren Radialisparese, eine dauerhafte Radialisparese wurde nicht beobachtet. During the period from 1 June 1990 to 30 November 1997, a total of 96 humeral shaft fractures, including 11 pathological fractures and 11 pseudarthroses, were treated in the Department of Traumatology of the University of Bonn by open reduction and internal fixation using an AO plate. The medical records and radiographs of these patients were reviewed retrospectively. Bony union was achieved after 16.2 weeks on average. There were 16 significant complications, three instances of implant failure, six instances of developing a hematoma, one deep infection, and five instances of temporary radial nerve palsy. No longterm radial nerve palsy was observed. One secondary amputation had to be performed after extensive soft tissue injury.

Cylindrical diamond columns of 15 nm height and 10 nm diameter have been prepared on a diamond(100) substrate by exploiting the self-organization of metal-loaded diblock copolymers. For this purpose, chemomechanically polished substrates of synthetic (high pressure high temperature) diamond exhibiting extremely low roughness (typical root-mean-square roughness 60 pm) were covered by a monolayer of gold-loaded inverse polystyrene-block-poly(2-vinylpyridine) micelles which self-organize in an hexagonal order on the substrate. After burning off the blockcopolymer in an oxygen plasma, the resulting Au nanoparticles act as a mask during further etching the diamond substrate in this plasma. As a result, Au-capped diamond columns are formed with an approximate size of the former gold particles. After removing the Au caps by evaporation at 1100 °C in ultrahigh vacuum, an array of diamond nanocolumns is obtained. As a consequence of this preparation process, the columns form an hexagonal lattice with a separation of 85 nm reflecting the arrangement of the self-organized micelles. The successive states of sample preparation were characterized by atomic force microscopy, Rutherford backscattering, and in situ scanning tunneling microscopy.

Tungsten trioxide (WO3) films were deposited by electron evaporation as well as rf-magnetron sputtering. To study the effect of medium energy ion bombardment on film properties, the samples were mounted in a UHV chamber allowing RBS measurements in combination with an in situ determination of the optical properties and the electrical resistance. Analysis of the spectral dependence of the reflection and the transmission of the films after various irradiation steps allowed to determine the real and the imaginary part of the refractive index as well as the optical thickness as a function of the ion fluence. Additionally, the area density of the tungsten atoms could be determined by RBS measurements with 700 keV He++-ions after each irradiation step. Thus, the combination of both methods provides the possibility to calculate directly the density of the films. While WO3-films produced by sputtering exhibit bulk density even in the as-prepared state, evaporated films possess an open morphology with a significantly lowered density. As a consequence, the irradiation of evaporated films with Ar+- or He+-ions leads to a significant densification in contrast to sputtered films, for which no further densification could be observed due to ion irradiation, independent of the projectile.

The transformation of crystalline (111) oriented Au50Ni50 thin films produced by ion beam mixing of Au/Ni multilayers was studied under krypton ion irradiation in the temperature range from 4 to 100 K. The volume fraction of the amorphous phase was determined as a function of the ion fluence from in situ resistivity measurements, while ex situ x-ray diffraction was used to analyze the residual crystalline fraction. The experimental results indicate that the total Kr+ fluence necessary for complete amorphization of a metastable Au50Ni50 solid solution exponentially increases with increasing bombardment temperatures up to a critical value Tc of approximately 100 K, above which an ion induced amorphization is no longer possible. Furthermore, within the amorphization regime, two different mechanisms can be distinguished: A direct amorphization process via dense cascades at very low temperatures, while close to Tc overlapping of sequentially damaged regions is required to obtain the amorphous phase. The fact t...

Crystalline films of the intermetallic compounds AuIn2 and In3Pd can be amorphized by irradiation with 350 keV noble gas ions (He, Ar, Kr) at low temperatures. To study this process on a microscopic scale, the γγ-perturbed angular correlation technique (PAC) was applied in combination with resistance measurements both performed in situ. AuIn2 and In3Pd-films were prepared by flash evaporation and implanted with radioactive 111In probe atoms at room temperature. After annealing and recooling the crystalline films to 77 K, complete amorphization of the films can be achieved by stepwise increasing the fluence. From the PAC results as well as from the resistivity data, the amorphous volume fraction is extracted as a function of the ion fluence. The description of the transformation kinetics as obtained by the microscopic PAC-method is found to be in good agreement with that deduced from transport measurements.

Theoretical predictions make the Bi x Pd 1− x system a promising candidate for studying the possibility of amorphization by an enforced extension of the solubility into a metastable regime. By quench-condensation of Bi 30 Pd 70 , the existence of a previously unknown amorphous (a–) phase is proven, which above 520 K crystallizes into the monoclinic Bi 2 Pd 5 phase. Ar + -irradiation of this crystalline phase at low temperatures leads back into the a-phase in accordance with a general amorphization rule. Experimentally, this behaviour is demonstrated by applying in situ resistance measurements and ex situ XRD. A surprising result is found for supersaturated Pd 70 Bi 30 solid solutions, which can be prepared by exploiting interface reactions in Pd/Bi multilayers. Ion irradiation performed on these cubic metastable solid solutions under exactly the same conditions as above, result only in a segregation of the surplus Bi towards the equilibrium solubility limit. No irradiation induced amorphization can be obtained starting with a stable or metastable cubic solid solution.

Background The purpose of this study was to analyze the therapy concept used in the management of severe epistaxis in order to optimize the quality of our treatment and to arrive at an optimal therapeutic concept. Material and methods The study was performed as a retrospective analysis of the charts of all 335 patients treated as inpatients for epistaxis over a period of 6 years. Results An increased rate of complications was found in the following three situations: 1. Age > 65 years, 2. chronic obstructive pulmonary disease, 3. several systemic illnesses. Recurrence was increased with septal perforations and Osler's disease. Conclusions Localization of the site of bleeding is the first priority and allows treatment of bleeding with bipolar electrocautery. If the bleeding vessel is not found, insertion of a Merocel pack is recommended. Patients with persistent or recurrent bleeding are treated in the operating theater under general anesthesia if they are at an elevated risk for complications or have a septal deviation which is clinically significant. The nose is systematically visualized with the endoscope, bleeding vessels are coagulated under endoscopic control, and, where appropriate, a septoplasty is performed. In the remaining cases an epipharynx balloon is inserted, combined with an anterior pack. Angiography with superselective embolization, external ligation of the ethmoidal arteries, and endonasal obliteration of the sphenopalatine artery is reserved for cases where the measures discussed above have failed.

The attenuated total reflection (ATR) technique has been combined with low temperature ion irradiation allowing to study the changes of optical properties of AuIn 2 films under bombardment. For this purpose, crystalline films were irradiated at 80 K with 350 keV Ar + ions resulting in a stepwise amorphization as indicated by accompanying in situ resistance measurements. It is demonstrated that this ion induced amorphization also leads to significant changes of the real and imaginary part of the index of refraction and its dispersion relation, which can be traced back to a disappearance of band structure effects in the amorphous phase. Based on the optical information, a procedure can be developed to extract the amorphous volume fraction, which, as a function of the ion fluence, compares very well with the corresponding results obtained from the resistance data.

By combining optical methods with photoelectron spectroscopy on crystalline ${\mathrm{AuIn}}_{2}$ films, clear evidence is provided for a non-Drude-like behavior of the intraband contribution to the optical response. The deviation from simple Drude theory is related to a non-free-electron-like density of states, which differs from the standard band shape assumed in the calculation of intraband excitations in ordered simple metals. The close connection between intraband optical and electronic properties is supported by results from amorphous ${\mathrm{AuIn}}_{2}$ films, for which a free-electron behavior is consistently observed by both methods.

We present the first ultra-miniature (

Isothermal current-voltage (I - V) characteristics of c-axes oriented YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} films taken in different external magnetic fields {mu}{sub 0}H, exhibit voltage jumps at a well defined current density J{sup *}(T, H) pointing to a specific instability of the vortex system. Interpreted as Larkin- Ovchinnikov (LO)-instability, this behavior allows to extract the inelastic scattering time {tau}{sub in} of quasiparticles. In the present work, the LO-analysis is applied to study the effect of additional defects on {tau}{sub in}. For this purpose, YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} films were irradiated at 77K with increasing fluences {phi} of 350 keV He{sup +} ions. The I - V characteristics were determined in the temperature range 45K < T < 80K and in magnetic fields up to 5 Tesla. While J{sup *} as well as the superconducting transition temperature T{sub c} are significantly decreased by the ion bombardment, the critical vortex velocity as deduced from LO-theory is much less affected. If the temperature dependence of the extracted scattering times {tau}{sub in} is rescaled by plotting versus the reduced temperature t = T/T{sub c}({phi}), the results for all ion fluences fall on one common curve within the error bars. This leads to the conclusion thatmore » a universal quasiparticle density n{sub N}(t) dominates the scattering rate 1/{tau}{sub in}.« less

Experimental data of the temperature dependence of the thermoelectric power S(T) for differently doped HTSC-samples recently found renewed interest in the context of the van Hove scenario as well as the spin gap behavior. Furthermore, a universal relation between S(290K) and the hole concentration p has been reported. On the other hand, ion irradiation of HTSC- films with ions of medium energy (typically 350 ke V) is known to produce defects leading to a strong increase in normal-state resistivity and a depression of the superconducting transition temperature Tc. The idea of the present work is to combine both techniques to test whether the ion-induced defects are predominantly oxygen vacancies within the CuO-chains, reducing p as monitored by S(290K). For this purpose, c-axis oriented YBa2Cu3O7-films on (100)-SrTiO3 substrates were irradiated with 350 ke V He+-ions. After each irradiation step an XRD analysis and an S(T)-measurement for Tc < T < 295 K is performed. It is shown that for small fluences the ioninduced S(T)-changes can be attributed to oxygen displacements destroying the CuO-chains, while for higher fluences additional defects within the CuO2-planes have to be taken into account. The corresponding S(T) behavior is comparable to what has been reported for Zn-substituted underdoped HTSC-samples.

The effect of 350 keV He+ ion irradiation with fluences Φ (ions cm−2) on the anisotropy of the critical current density jc(Θ, H, Φ) of c-axis oriented YBa2Cu3O7−δ thin films is reported. Here, Θ is the angle between the c-axis and the direction of the external magnetic field μ0H ≤ 5 tesla. An almost isotropic decrease of critical current density due to the ion bombardment up to fluences Φ ≤ 4.0 × 1014 cm−2 is observed. This result is different from that found for irradiation with heavy ions at high energies, for which an anisotropic change of the critical current density is obtained with a maximum near the incident direction of the ion beam due to the formation of amorphous columnar defects. The angular dependence of the normalized current densities j c (Θ, H, Φ) j c (0, H, Φ) exhibits a universal relation with a maximum at Θ = 90°. Significant deviations from jc(0, H, Φ) towards larger values, however, occur only for angles above 40° in contrast to the predictions of standard models. Similarly, the field dependence of the normalized current densities j c (Θ, H, Φ) j c (Θ, 0, Φ) is found to be unaffected by the ion bombardment.