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The analysis of the impact crater size-frequency distribution (CSFD) is a well-established approach to the determination of the age of planetary surfaces. Classically, estimation of the CSFD is achieved by manual crater counting and size determination in spacecraft images, which, however, becomes very time-consuming for large surface areas and/or high image resolution. With increasing availability of high-resolution (nearly) global image mosaics of planetary surfaces, a variety of automated methods for the detection of craters based on image data and/or topographic data have been developed. In this contribution a template-based crater detection algorithm is used which analyses image data acquired under known illumination conditions. Its results are used to establish the CSFD for the examined area, which is then used to estimate the absolute model age of the surface. The detection threshold of the automatic crater detection algorithm is calibrated based on a region with available manually determined CSFD such that the age inferred from the manual crater counts corresponds to the age inferred from the automatic crater detection results. With this detection threshold, the automatic crater detection algorithm can be applied to a much larger surface region around the calibration area. The proposed age estimation method is demonstrated for a Kaguya Terrain Camera image mosaic of 7.4 m per pixel resolution of the floor region of the lunar crater Tsiolkovsky, which consists of dark and flat mare basalt and has an area of nearly 10,000 km2. The region used for calibration, for which manual crater counts are available, has an area of 100 km2. In order to obtain a spatially resolved age map, CSFDs and surface ages are computed for overlapping quadratic regions of about 4.4 x 4.4 km2 size offset by a step width of 74 m. Our constructed surface age map of the floor of Tsiolkovsky shows age values of typically 3.2-3.3 Ga, while for small regions lower (down to 2.9 Ga) and higher (up to 3.6 Ga) age values can be observed. It is known that CSFD-derived absolute model ages can exhibit variations although the surface has a constant age. However, for four 10-20 km sized regions in the eastern part of the crater floor our map shows age values differing by several hundred Ma from the typical age of the crater floor, where the same regions are also discernible in Clementine UV/VIS color ratio image data probably due to compositional variations, such that the age differences of these four regions may be real.

Altere Patienten (>75 Jahre) sind oft durch physiologische Veranderungen, die meist von multiplen und komplexen chronischen bzw. degenerativen Erkrankungen des Bewegungsapparats begleitet werden, beeintrachtigt. Die Aufarbeitung der klinischen Symptomatik in dieser Altersgruppe mit modernen zeitgemasen radiologischen Untersuchungsmoglichkeiten wurde anhand des Einsatzes von State-of-the-Art-Technologie in einem Schwerpunktkrankenhaus mit Betreuung eines geriatrischen Zentrums analysiert. Vor allem Untersuchungen des Bewegungsapparats und interzerebraler Prozesse bei alteren Patienten wurden bei der Analyse berucksichtigt. Die Ergebnisse zeigen, dass sowohl die Patientenanamnese als auch eine angemessene radiologische Untersuchung und interdisziplinare Zusammenarbeit fur eine umfassende Diagnose unbedingt erforderlich sind.

Metastatic involvement of the spinal column is frequently seen in various types of cancer. When neoplastic proliferation occurs strictly within the borders of a vertebral body, pain is the major clinical problem. In non-contiguous spinal metastases, however, epidural tumour extension and spinal instability lead to neurological deficit. Both pain and neurological deficit severely interfere with life quality, but rarely with survival, which is mainly determined by the underlying cancer disease. Therefore, the treatment of spinal metastasis primarily aims at preserving neurological function, spinal stability and at reducing pain.

Introduction The aim of this retrospective study was to analyse the short term results after the Weil-procedure for the treatment for metatarsalgia in 30 consecutive patients. Methods 30 patients (69 osteotomies) after the Weil-procedure with an average age of 60 years (range 25 to 78 years) were analysed by clinical and radiological evaluation. The average follow up was 15 months (range 12 to 26 months). Analysis was performed using the patients' records, weight-bearing radiographs and a standardized questionnaire. Results Subjective evaluation revealed 23 very satisfied and satisfied patients. Based on the Lesser-Metatarsal-Interphalangeal-Scale the objective results showed 77.1 points on average. The results were excellent in 17 cases, good in 4, fair in 3 and unsatisfactory in 6 cases respectively. Recurrent metatarsalgia was noted in 5 cases, whereas no transfermetatarsalgia was observed. The average shortening was 4.4 mm. Subluxation of the metatarsophalangeal joint was corrected in 18 out of 22 cases. A restricted plantar flexion of the metatarsophalangeal joint was noted in 14 cases. 2 patients showed loss of movement. Conclusion Our short-term results reveal that the Weil-osteotomy is a sufficient treatment for metatarsalgia. This technique is able to reestablish the alignment of the metatarsals and to correct luxation and subluxation of the metatarsophalangeal joint. Restricted plantarflexion of the metatarsophalangeal joint is a drawback, which may be avoided by intensive physiotherapy.

Introduction Aim of this study is to present the treatment concept and the results of hallux valgus surgery of our department. Patients and methods The criteria for decision making are 1st intermetatarsal angle, congruency of the first metatarsophalangeal joint and sesamoid position. According to our concept we performed between 1993 and 1996 42 Chevron osteotomies for mild, 138 Chevron with lateral soft tissue release (Chevron + LSR) for moderate and 93 basal crescentic (Mann) osteotomies with lateral soft tissue release for severe hallux valgus deformities. Results 31 Chevron, 118 Chevron with lateral soft tissue release and 80 basal crescentic osteotomies (Mann) were seen at an average follow up of 19 months (12-29) after a Chevron, respectively. 16 months (12-43) after Chevron with lateral soft tissue release and 18 months (12-32) after a basal crescentic osteotomy. 83% of all patients classified the results of the surgery as "very satisfactory" and "satisfactory". The average hallux valgus angle was corrected from preoperatively. 25.3 degrees (Chevron), 29.9 degrees (Chevron + LSR) and 41.8 degrees (Mann) to 16.5 degrees (Chevron), 12.1 degrees (Chevron + LSR) and 14.1 degrees (Mann) at final follow up, the average first intermetatarsal angle was corrected from preoperatively 12.1 degrees (Chevron), 14.0 degrees (Chevron + LSR) and 17.4 degrees (Mann) to 7.9 degrees (Chevron), 5.8 degrees (Chevron + LSR) and 7.8 degrees (Mann) at final follow up. Conclusion Our analysis of the three osteotomies revealed that with this differentiated concept we were able to achieve excellent and good results in more than 80% of our patients. Only with a treatment plan that includes different procedures to address the various stages of hallux valgus can one achieve the optimum result for the patient.

INTRODUCTION Aim of this retrospective study was to analyse the long term results after basal closing wedge osteotomy for correction of metatarsus primus varus and hallux valgus in the younger patient. PATIENT AND METHODS 49 patients (70 feet) were operated according to a basal closing wedge osteotomy from 1974 to 1985 at our institution. Age was under 40 years in all patients at the time of surgery. 34 patients (50 feet) were evaluated in respect to their clinical and 26 patients (37 feet) to their radiological outcome. The average age was 26 years (14-39 years). The follow-up was 12 to 22 years (Median: 18 years). Analysis was performed using the patient's record, weight-bearing X-rays, a standardized questionnaire and clinical investigation. RESULTS 82% of the patients had very good and good subjective results. Cosmetics was rated very good and good in 78%, 88% of the patients were painfree. Radiological analysis at follow-up: Hallux valgus-angle 19,3 degrees, intermetatarsal I/II-angle 6 degrees, shortening of first metatarsale 5 mm, at average; dorsal elevation of first metatarsale 38%, degenerative arthritis of the metatarsocuneiforme joint 19%, congruency of first metatarsophalangeal joint 54%,sesamoid subluxation: 46% grade 0, 30% grade I, 14% grade II and 10% grade III. In 14 feet (28%) metatarsalgia was found. DISCUSSION The basal closing wedge osteotomy is rather a technically demanding procedure conjuncted with a higher risk of failure. Satisfactory long term results can be obtained by an ideal operating technique. As undesirable side effects shortening of the first ray and dorsal malangulation of the first metatarsale may occur consecutively leading to metatarsalgia. Lower risk procedures like the crescentic osteotomy according to Mann or chevron osteotomy should be preferred.

Normal-pressure hydrocephalus (NPH) syndrome is treatable by implantation of a cerebrospinal fluid (CSF) shunt. However, diagnosis of NPH by clinical and radiological findings alone is unreliable, and co-existing structural dementia can contribute to low success rates after shunt implantation. The aim of our study was to investigate whether long-term results after shunt implantation in NPH improve when surgical candidates are selected by continuous intraventricular pressure monitoring (CIPM).Ninety-two consecutive patients who were admitted with suspected NPH received CIPM for 48 h including an intraventricular steady-state infusion test to determine the resistance outflow. With positive CIPM, shunt implantation was performed and the patients were prospectively followed up for 1 to 10 years (median 6.5 years).CIPM was negative in 37 patients. Fifty-five patients had a positive CIPM and received CSF shunt. 96.1% of them improved from gait disturbance, 77.1% from cognitive impairment and 75.7% from urinary dysfunction. Clinical improvement remained during long-term follow-up in all but 3 patients who showed a decline at 4, 5 and 7 years, respectively. CIPM-related complications (ventriculitis) occurred in only one patient.CIPM is a safe and valuable tool to establish a reliable diagnosis of NPH and to identify promising surgical candidates.

A systematic calculation of nuclear matter is performed which includes the long-range correlations between nucleons arising from one- and two-pion exchange. Three-body effects from $2\pi$-exchange with excitations of virtual $\Delta(1232)$-isobars are also taken into account in our diagrammatic calculation of the energy per particle $\bar E(k_f)$. In order to eliminate possible high-momentum components from the interactions we introduce at each pion-baryon vertex a form factor of monopole type. The empirical nuclear matter saturation point, $\rho_0 \simeq 0.16 $fm$^{-3}$, $\bar E_0\simeq -16 $MeV, is well reproduced with a monopole mass of $\Lambda \simeq 4\pi f_\pi \simeq 1.16 $GeV. As in the recent approach based on the universal low-momentum $NN$-potential $V_{\rm low-k}$, the inclusion of three-body effects is crucial in order to achieve saturation of nuclear matter. We demonstrate that the dependence of the pion-exchange contributions to $\bar E(k_f)$ on the ''resolution'' scale $\Lambda$ can be compensated over a wide range of $\Lambda$ by counterterms with two ''running'' contact-couplings. As a further application we study the in-medium chiral condensate $(\rho)$ beyond the linear density approximation. For $\rho \leq 1.5 \rho_0$ we find small corrections from the derivative $d \bar E(k_f)/d m_\pi$, which are stable against variations of the monopole regulator mass $\Lambda$., Comment: 13 pages, 6 figures

The present study was carried out to assess the possibility of measuring fecal steroid hormone metabolites as a noninvasive technique for monitoring reproductive function in the three-toed sloth, Bradypus variegatus. Levels of the estradiol (E2) and progesterone (P4) metabolites were measured by radioimmunoassay in fecal samples collected over 12 weeks from 4 captive female B. variegatus sloths. The validation of the radioimmunoassay for evaluation of fecal steroid metabolites was carried out by collecting 10 blood samples on the same day as defecation. There was a significant direct correlation between the plasma and fecal E2 and P4 levels (P < 0.05, Pearson's test), thereby validating this noninvasive technique for the study of the estrous cycle in these animals. Ovulation was detected in two sloths (SL03 and SL04) whose E2 levels reached 2237.43 and 6713.26 pg/g wet feces weight, respectively, for over four weeks, followed by an increase in P4 metabolites reaching 33.54 and 3242.68 ng/g wet feces weight, respectively. Interestingly, SL04, which presented higher levels of E2 and P4 metabolites, later gave birth to a healthy baby sloth. The results obtained indicate that this is a reliable technique for recording gonadal steroid secretion and thereby reproduction in sloths.

Objectives: The aim of this study was to evaluate the influence of total drainage time on the risk of catheter infection, and the predictive value of standard laboratory examinations for the diagnosis of bacteriologically recorded cerebrospinal fluid (CSF) infection during external ventricular drainage. Methods: During a three year period, all patients of the neurosurgical intensive care unit (ICU), who received an external ventricular drain, were prospectivly studied. Daily CSF samples were obtained and examined for cell count, glucose and protein content. Bacteriological cultures were taken three times a week, and serum sepsis parameters were determined. Results: 130 patients received a total of 186 external ventricular drains. The ventricular catheters were in place from one to 25 days (mean 7.1 days). In 1343 days of drainage, the authors recorded 41 positive bacteriological cultures in 21 patients between the first and the 22nd drainage day (mean 6.4). No significant correlation was found between drainage time and positive CSF culture. The only parameter that significantly correlated with the occurrence of a positive CSF culture was the CSF cell count (unpaired t test, p Conclusions: Drainage time is not a significant risk factor for catheter infection. Increasing CSF cell count should lead to the suspicion of bacteriological drainage contamination. Other standard laboratory parameters, such as peripheral leucocyte count, CSF glucose, CSF protein, or serum sepsis parameters, are not reliable predictors for incipient ventricular catheter infection.

AIM A Chevron osteotomy with lateral soft-tissue release was performed at our department in 1993. In 1994 a prospective study to evaluate the temporary Kirschner wire fixation was started. Aim of this prospective study was to analyse the short-term clinical and radiological results with special attention to stability, necroses, and luxation of the first metatarsal head. METHOD Between February 1994 and October 1995 45 patients (55 feet) were treated with a Chevron osteotomy combined with a lateral soft-tissue release and temporary Kirschner wire fixation. The average follow-up was 33.9 months. All patients were seen and evaluated preoperatively and at a minimum follow-up of 24 months using a standardized questionnaire based on the Hallux metatarsophalangeal interphalangeal Scale (HMIS) of the American Foot and Ankle Society. RESULTS Results of the survey of patient satisfaction revealed excellent and good results in 83%, fair in 8%, and poor in 9%. The median HMIS at final follow-up was 86.9 pints of 100 points. The average hallux valgus angle correction was 19.8 (from 28.7 to 8.9) and the average first intermetatarsal angel correction was, 8.2 (from 14.4 to 6.2). No avascular necrosis of the first metatarsal head and no loss of correction were noted. In one case a luxation of the metatarsal head was observed. CONCLUSION Combining the Chevron osteotomy with an excessive lateral soft-tissue release increases the likelihood of instability of the metatarsal head and consecutive loss of correction. The temporary Kirschner wire fixation increases the stability of the Chevron osteotomy and prevents the loss of correction. The disadvantage of this method is, that the wire has to be removed after 6 weeks.

Kinetic energy distributions of muonic hydrogen atoms μp(1S) have been obtained by means of a time-of-flight technique for hydrogen gas pressures between 4 and 64 hPa. A high energy component of ∼900 eV observed in the data is interpreted as the signature of long-lived μp(2S) atoms, which are quenched in a non-radiative process leading to the observed high energy: the collision of a thermalized μp(2S) atom with a hydrogen molecule H2 results in the resonant formation of a {[(ppμ)+]*pee}* molecule. Then the (ppμ)+ complex undergoes Coulomb de-excitation and the ∼1.9 keV excitation energy is shared between a μp(1S) atom and one proton. The preliminary analysis of the time spectra gives a long-lived μp(2S) population of ∼1% of all stopped muons, and a quenching rate of ∼4⋅1011 s−1.

We have measured the neutron electric form factor ${G}_{\mathrm{en}}$ via ${}^{3}\stackrel{\ensuremath{\rightarrow}}{\mathrm{He}}(\stackrel{\ensuremath{\rightarrow}}{e}{,e}^{\ensuremath{'}}n)\mathrm{pp}$ at ${Q}^{2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.67(\mathrm{GeV}/c{)}^{2}$ using the 3-spectrometer facility of the A1 Collaboration at the Mainz Microtron and a dedicated neutron detector. High pressure polarized ${}^{3}\stackrel{\ensuremath{\rightarrow}}{\mathrm{He}}$ gas was used as a target of polarized neutrons. ${G}_{\mathrm{en}}$ is determined from the ratio of the asymmetries ${A}_{\ensuremath{\perp}}{/A}_{\ensuremath{\parallel}}$ measured in quasifree kinematics with the target spin perpendicular and parallel to the momentum transfer. We find ${G}_{\mathrm{en}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.052\ifmmode\pm\else\textpm\fi{}0.011\ifmmode\pm\else\textpm\fi{}0.005$.

The transfer reaction of negative muons from muonic protium to 3 and 4 in binary and triple gas mixtures was studied. In the binary mixtures the transfer rates to the two helium isotopes were determined from the time distribution of the 7-keV X-rays of the intermediate muonic molecule (pµHe)*. The experimental transfer rate to 4 is in good agreement with theoretical predictions, whereas the rate to 3 is a factor 2 to 3 smaller than the predicted ones. Radiative branching ratios of the (pµHe)8 molecular decay were obtained. Muon transfer from excited states of muonic protium gives the main contribution to the total intensity of the µHe Lyman series in the binary mixtures. Values of q 1s He are determined.

We report on the results of an experiment aimed at observing muon-catalyzed d 3He-fusion with a setup previously used for studies of the muon-catalyzed dd-fusion. The basic element of the setup is a high pressure ionization chamber operating as an active target. In this experiment the chamber was filled with an HD + 3He (5.6%) gas mixture at 13.2 bar pressure and 50 K temperature. These conditions were chosen as optimal for formation of the 3Heμd-molecules with a low level of background from the d-μ-d fusion. The chamber was exposed to the negative muon beam at PSI. During a 3-week data-taking period, 9.7 × 108 muon stops have been selected. The analysis of the data was able to determine a new upper limit for the d 3He-fusion rate in the 3Heμd-molecule (λf≤ 6× 104 s-1), which is more than three orders of magnitude lower than the previously existed limit.

We present the results of precision measurements of dμ spin-flip rates in pure D2, in pure HD gas, and in the non-equilibrium and equilibrium H2+D2 gas mixtures. The experiments were performed at PSI in 1994-1996 using the high pressure ionization chamber from Gatchina as a 100% efficient detector of the charged fusion products. The measurements have been carried out in the temperature range 28-300 K, at gas density of 5% of LHD. In pure deuterium, the measured temperature dependence of the spin-flip rate allowed us to separate the two components (resonant and non-resonant) of the spin-flip processes. From the experiments in H/D mixtures we have measured the non-resonant spin-flip rate in collisions of dμ-atoms with HD molecules. Comparison with the theory revealed considerable disagreement in the case of non-resonant spin-flip in collisions of the dμ-atoms with D2 molecules.

The classical methods used in beam cooling are hard to be adapted for a beam of short-lived elementary particles. A novel method, the so-called frictional cooling – that is cooling a beam of low-energy charged particles by moderation in matter and acceleration in an electrostatic field – has been shown to be feasible. In our experiments performed in 1994/1995 a beam of short-lived particles was cooled for the first time ever. Utilizing frictional cooling on a beam of slow negative muons we observed increase in phase space density by about one order of magnitude.

The energy and time distributions of the decay X-rays of excited, metastable, molecular (dµHe)*-resonances were measured. The comparison of the observed energy spectra with calculated ones suggests that decay from the rotational state J = 1 dominates at the investigated conditions. The muon transfer rates from ground state deuterium to the helium isotopes 3He and 4He at low temperatures were determined from the time distributions of these spectra. Additionally, the temperature dependence of the muon transfer rate was clearly established in deuterium / 4He mixtures.

We present the results of an experiment performed at PSI to investigate muon catalyzed fusion in pure deuterium gas of 5% density (LHD) at temperatures ranging from 28 K to 350 K. Using a new high pressure ionization chamber the reactions dd → n + 3He and dd → p+t were observed with 100% detection efficiency. The rates of dμd formation were measured with the absolute precision of 1% and the μd spin-flip rates with 0.5%. The temperature dependence of molecular formation and spin-flip rates display pronounced resonance structures. A preliminary fit based on the Vesman mechanism of resonant muonic molecule formation was carried out yielding a dd fusion rate of 3.5·108 s-1 and a hfs splitting energy \(\delta \varepsilon _{d\mu d} \) of 24.3 meV, both in good agreement with the theory.

The results of an experiment on muon catalyzed dd-fussion in HD gas are presented. The experiment was performed at the muon beam of PSI using a high-pressure ionization chamber filled with pure HD-gas of low D2 concentration on the level 1%, at temperatures 50, 150 and 300 K. The non-resonant character of ddμ-molecule formation on HD molecules was confirmed by measuring the ratio of yields of the two ddμ-fusion channels, R=Y(3He,n)/Y(3H,p), which proved to be close to unity. The ddμ formation rate was found to vary from λddμ-HD=0.05· 106 s-1 at T=50 K to λddμ-HD=0.12· 106 s-1 at T=300 K, in agreement with the theoretical prediction. A prominent peak at t

The muon transfer rate $$(\tilde \lambda _{d{\text{ }}^{\text{3}} {\text{He}}} )$$ from deuterium to 3 at temperatures of 39.5 K and 50.0 K, respectively, has been determined as a by-product of the experiment aimed to search for muon catalyzed d 3He-fusion. The measurements were performed in the muon beam at PSI with a multi-anode high pressure ionization chamber as a target and detector of the incoming muons and the charged reaction products. The chamber was filled with the HD + 3He(5.6%) gas mixture of 9.21% LHD density. The analysis of time distributions of dd-fusion events was able to determine the transfer rates: $$\tilde \lambda _{d{\text{ }}^{\text{3}} {\text{He}}} $$ (50 K)=(2.32± 0.09)× 108 s-1, $$\tilde \lambda _{d{\text{ }}^{\text{3}} {\text{He}}} $$ (39.5 K)=(2.33± 0.16)·108 s-1. These values, normalized to liquid hydrogen density (LHD, 4.25· 1022 atoms/cm3), significantly exceed the transfer rates at room temperature, in agreement with theoretical predictions.

Muon capture on hydrogen gives a unique possibility for a measurement of the pseudo-scalar form factor gp(qc2 = -0.88 mμ2) of the nucleonic weak current, thus providing a sensitive test of the QCD chiral symmetry perturbation theory which predicts the value of this form factor with a precision of Δgp/gp≃ 2%. For adequate comparison with theory, the muon capture rate Λc should be measured with a precision of ΔΛc/Λc ≤ 1%, that is an order of magnitude better than the precision of the present world data. We report on the project of an experiment designed to provide the required precision. Also, we present the final result of our previous experiment on a high precision measurement of the μ3He capture rate and compare this result with the PCAC prediction.

The complex balance of processes occurring at the cascade of exotic H-atoms is usually described by the so-called standard cascade model, but this model neglects variations of the kinetic energy T of the exotic atom during the cascade which are crucial for the analysis of several important experiments. New experimental results on T µp at H2 pressures between 0.063 and 4 hPa demonstrate the importance of acceleration due to Coulomb de-excitation processes at highly excited µp levels n > 9. The data at the lowest density are sensitive to the initial values of the kinetic energy and n-levels at the moment of atomic capture. From the measured low-energy tail of the T µp-distribution it can be concluded that a considerable part of the µp(2s) atoms is metastable at pressures of a few hPa.

The stopping power of gaseous hydrogen for positive and negative muons at energies ranging from 3 to 100 keV has been measured by time-of-flight. A pronounced Barkas effect was observed: the energy loss in hydrogen for negative muons was found to be significantly smaller than that for positive muons.

A new experiment was started at PSI aiming for high-precision and complete studies of dµd fusion in D2, HD and D2/H2 gas mixtures. A high-pressure ionization chamber surrounded by a set of neutron counters is used to observe dd-fusion at temperatures between 25 and 350 K. Here we report preliminary results from the first test run with pure D2 filling.

Very recent results relevant to the planning of laser spectroscopy of the 2s-2p splitting in the µp atom are presented. An experimental configuration providing a sufficiently small muon stopping volume at the lowest pressures has been tested. The first experimental indications for the existence of a long-lived 2s fraction at low pressure are discussed.

In this article we report the results of an experiment performed in 1993 at PSI. The goal was to determine the absolute rate of nuclear muon capture by3He. In the experiment we used a new technique recently developed at Gatchina. As a preliminary result from this experiment we obtainedλ c=(1496±3(stat)-3(syst)) s−1.

Muon transfer from hydrogen isotopes to helium is of importance in muon-catalyzed fusion and serves as a unique tool for the direct observation of the mesomolecular ion (pµHe)*. During two data-taking runs in 1994 and 1995 at PSI, measurements of the transfer from protium to helium were carried out using CCD's and Ge-diodes as independent X-ray detectors to obtain information on the time distribution and intensity of the 7 keV decay X-ray of the mesomolecular ion. Dual1H2 +4 He and triple1H2 + Ne +3,4He gas mixtures at low temperatures were investigated to extract transfer rates. Protium of high purity was available. For the first time a transfer rate from muonic protium to3He was measured. A general survey of our measurements and preliminary analysis is presented.

Frictional cooling — that is cooling a beam of very low-energetic charged particles by moderation in matter and simultaneous acceleration in an electrostatic field — has been shown to be feasible during our experiments in 1994/1995 at PSI. In agreement with our previous closed-form and Monte Carlo calculations we found a significant increase in spectral density and a decrease in the angular spread in the case of a beam of negative muons.

The triton energy spectrum of the muon capture reaction mu(3)He --> t + v(mu), where mu(3)He is the ground state of muonic He-3, has been measured by means of a high-pressure ionization chamber in order to investigate a possible heavy v admixture into the mu flavor with high sensitivity. The upper limit of the mu-heavy v(i) mixing matrix element squared was obtained to be U-mu i((2) less than or equal to 10(-3) for heavy neutrino masses in the range 25 less than or equal to E(ov) less than or equal to 75 MeV.

The rates of the breakup reactions Lambda B(He-3) and Lambda B(He-4) in nuclear muon capture by He-3 and He-4 have been measured. The measurements were performed on the muon beam of PSI with a multi-anode high-pressure ionization chamber filled with isotopically pure He-3 or He-4 at 120 bar. The chamber was used as a target and detector for both the incoming muons and for the charged reaction products (tritons, deuterons and protons) of the breakup reactions mu(-) + He-3 --> d + n + v(mu), p + 2n + v(mu) and mu(-) + He-4 --> t + n + v(mu), d + 2n + v(mu), p + 3n + v(mu). Our statistics, about 5 x 10(5) of breakup events, provides a possibility to improve the precision of evaluated rates. The preliminary results: Lambda(B)(He-3) = 720 +/- 70 s(-1), Lambda B(He-4) = 415 +/- 40 s(-1) are compared to theoretical predictions and to previous experiments.

Two experiments with low-energy muons are described: the determination of the stopping power of C, Si, Ti and Au for muons at energies down to 2 keV and the measurement of the diffusion times for pµ and dµ atoms in low-pressure (0.25–12 hPa) hydrogen gas. A pronounced Barkas effect was found for muons at the Bragg peak (about 10 keV): the stopping power for µ− in C, e.g., is about 30% lower than that for µ+. The mean kinetic energy of pµ atoms at the end of the cascade in 1 hPa hydrogen gas was determined to be (2.6 ± 0.6) eV (preliminary value).

We propose to study a number of open problems in ddµ and pdµ fusion using the new high-pressure ionization chamber for charged particle identification in coincidence with the n-/e-counter array for the detection of neutrons and µ-decay electrons. Our first objective will be a precise measurement of the absolute rates of resonant and non-resonant ddµ formation in D2 and HD-gases and their temperature dependence from 40 to 350 K. Both output channels of the dd-reaction:3He + n and t + p will be observed and their ratio sensitive to contributions of S and P-waves will be determined. Simultaneously, we shall investigate the pdµ-cycle and determine the absolute pd-fusion yields in different molecular H/D compositions, observing tritons from nuclear muon capture in3Heµ: pdµ →3Heµ + γ. We have developed a special system for the preparation of HD-gas with high concentration (96%) of HD and a purity (10−6).

Frictional cooling — that is cooling a beam of very low-energy charged particles by moderation in matter and simultaneous acceleration in an electrostatic field — has been shown to be feasible during our experiments in 1994/1995 at PSI. As indicated by our previous closed-form and Monte-Carlo calculations we found a significant increase in spectral density and a decrease in the angular spread for a beam of negative muons. With the help of the cooled muons we were able to measure the diffusion times for p μ and d μ atoms in low-pressure (0.25 to 12 mbar) hydrogen gas. From this the mean kinetic energy of p μ atoms at the end of the cascade in 1 mbar hydrogen gas was determined to be (2.6 ± 0.6) eV (preliminary value).

In 20 consecutive patients submitted to CT evaluation of a suspected disk protrusion at level L4-5, CT measurements to define entry point and penetration angle for percutaneous diskectomy were performed. It was shown that in order to reach the disk center, the entry point had to be more lateral than recommended by most authors. Body height, weight and body surface area were not significantly correlated to entry point position or penetration angle. In particular, the extension of the intervertebral facet joint determined the route of the probe to the disk center. Therefore, CT-assisted planning of the instrument route prior to percutaneous lumbar diskectomy is helpful in defining the proper entry point and penetration angle for safe and effective instrument positioning.

Pathology at the origin of the vertebral artery may be the cause of incapacitating vertebrobasilar insufficiency (VBI). Preoperative diagnosis is made primarily on angiographic criteria. We compared intraoperative and angiographic findings in 30 patients and found important diagnostic discrepancies in patients with a caudal, ventral or dorsal origin of the vertebral artery. In their angiograms, vessel superimposition led us to over look 3 ostial stenoses and 10 stenoses due to kinking. Angiographic assessment of patients with VBI can be difficult. Adequate visualisation of the origin of the vertebral artery is mandatory for accurate diagnosis.

Internet disruptions such as the Northeast Blackout (2003) and the Taiwan earthquake (2006) highlight the fragility of today's Internet. Our goal in this paper is to investigate the robustness of inter-domain communication at the level of autonomous systems (ASes), taking into account both topological connectivity and compliance to routing policies. To this end, we introduce the concept of k-fault tolerance for Type-of-Relationship (ToR) graphs, which requires that any two nodes (ASes) remain reachable from each other even after removing arbitrary k nodes from the AS graph. Our main contribution is theoretical and concerns the complexity of the k-fault tolerance decision problem. Drawing on strong evidence about the hierarchical structure of the Internet AS graph, we derive sufficient and necessary conditions for determining whether the graph is k-fault tolerant or not in polynomial time. We then apply this theoretical result to study the network-wide resilience properties of AS-level topology instances, as inferred from large-scale experimental data sets. We find that even single-node failures can disconnect up to hundred of ASes and that approximately 1500 ASes do not avail any real redundancy for their global reachability despite having two or more upstream links. Augmenting AS-level graphs for 1-fault tolerance improves overall resilience to failures, but requires a considerable number of AS-level edges (>7000) to be added. Interestingly, such additional upstream links are mainly needed at stub networks rather than at transit ASes, pointing out the need for multi-homing at stub networks. © 2011 Elsevier B.V. All rights reserved.

The “sticking” process dtμ → αμ + n, which constitutes the most severe limit to the number of fusions which a muon can catalyze, is reviewed. Many attempts were made to determine by calculations and measurements the probability for initial stickingω s 0 (immediately after dtμ fusion) and for final stickingω s (after the αμ came to rest). Previous results based on neutron disappearance rates and on the observation of αμ-X-rays were controversial and also in some disagreement with theory. New data are reported from PSI on direct observation of final sticking, using a setup with the St. Petersburg ionization chamber. These data mark a significant improvement in reliability and may clarify questions concerning previous discrepancies. The new results isω s∼(0.56±0.04)%, lower than the theory predictionω s=(0.65±0.03)%, at medium density.