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A large international meta-analysis using primary data from 64 cohorts has quantified the increased risk of fracture associated with a previous history of fracture for future use in FRAX.IntroductionThe aim of this study was to quantify the fracture risk associated with a prior fracture on an international basis and to explore the relationship of this risk with age, sex, time since baseline and bone mineral density (BMD).MethodsWe studied 665,971 men and 1,438,535 women from 64 cohorts in 32 countries followed for a total of 19.5 million person-years. The effect of a prior history of fracture on the risk of any clinical fracture, any osteoporotic fracture, major osteoporotic fracture, and hip fracture alone was examined using an extended Poisson model in each cohort. Covariates examined were age, sex, BMD, and duration of follow-up. The results of the different studies were merged by using the weighted & beta;-coefficients.ResultsA previous fracture history, compared with individuals without a prior fracture, was associated with a significantly increased risk of any clinical fracture (hazard ratio, HR = 1.88; 95% CI = 1.72-2.07). The risk ratio was similar for the outcome of osteoporotic fracture (HR = 1.87; 95% CI = 1.69-2.07), major osteoporotic fracture (HR = 1.83; 95% CI = 1.63-2.06), or for hip fracture (HR = 1.82; 95% CI = 1.62-2.06). There was no significant difference in risk ratio between men and women. Subsequent fracture risk was marginally downward adjusted when account was taken of BMD. Low BMD explained a minority of the risk for any clinical fracture (14%), osteoporotic fracture (17%), and for hip fracture (33%). The risk ratio for all fracture outcomes related to prior fracture decreased significantly with adjustment for age and time since baseline examination.ConclusionA previous history of fracture confers an increased risk of fracture of substantial importance beyond that explained by BMD. The effect is similar in men and women. Its quantitati

Background Duchenne muscular dystrophy (DMD) is a severe, progressive, and rare neuromuscular, X-linked recessive disease. Dystrophin deficiency is the underlying cause of disease; therefore, mutation-specific therapies aimed at restoring dystrophin protein production are being explored. We aimed to assess the efficacy and safety of ataluren in ambulatory boys with nonsense mutation DMD. Methods We did this multicentre, randomised, double-blind, placebo-controlled, phase 3 trial at 54 sites in 18 countries located in North America, Europe, the Asia-Pacific region, and Latin America. Boys aged 7–16 years with nonsense mutation DMD and a baseline 6-minute walk distance (6MWD) of 150 m or more and 80% or less of the predicted normal value for age and height were randomly assigned (1:1), via permuted block randomisation (block size of four) using an interactive voice-response or web-response system, to receive ataluren orally three times daily (40 mg/kg per day) or matching placebo. Randomisation was stratified by age (<9 years vs ≥9 years), duration of previous corticosteroid use (6 months to <12 months vs ≥12 months), and baseline 6MWD (<350 m vs ≥350 m). Patients, parents and caregivers, investigational site personnel, PTC Therapeutics employees, and all other study personnel were masked to group allocation until after database lock. The primary endpoint was change in 6MWD from baseline to week 48. We additionally did a prespecified subgroup analysis of the primary endpoint, based on baseline 6MWD, which is reflective of anticipated rates of disease progression over 1 year. The primary analysis was by intention to treat. This study is registered with ClinicalTrials.gov, number NCT01826487. Findings Between March 26, 2013, and Aug 26, 2014, we randomly assigned 230 patients to receive ataluren (n=115) or placebo (n=115); 228 patients comprised the intention-to-treat population. The least-squares mean change in 6MWD from baseline to week 48 was −47·7 m (SE 9·3

OBJECTIVE: To investigate associations between morbidity and global life satisfaction in postmenopausal women taking into account type and number of diseases. MATERIALS AND METHODS: A total of 11,084 women (age range 57-66 years) from a population-based cohort of Finnish women (OSTPRE Study) responded to a postal enquiry in 1999. Life satisfaction was measured with a 4-item scale. Self-reported diseases diagnosed by a physician and categorized according to ICD-10 main classes were used as a measure of morbidity. Enquiry data on health and lifestyle were used as covariates in the multivariate logistic models. RESULTS: Morbidity was strongly associated with life dissatisfaction. Every additional disease increased the risk of life dissatisfaction by 21.1% (p < .001). The risk of dissatisfaction was strongest among women with mental disorders (OR = 5.26; 95%CI 3.84-7.20) and neurological disorders (OR = 3.62; 95%CI 2.60-5.02) compared to the healthy (each p < .001). Smoking, physical inactivity and marital status were also associated with life dissatisfaction (each p < .001) but their introduction to the multivariate model did not attenuate the pattern of associations. CONCLUSIONS: Morbidity and life dissatisfaction have a disease-specific and dose-dependent relationship. Even if women with mental and neurological disorders have the highest risk for life dissatisfaction, monitoring life satisfaction among aging women regardless of disorders should be undertaken in order to intervene the joint adverse effects of poor health and poor well-being.

Osteoporosis is a serious worldwide epidemic. Increased risk of fractures is the hallmark of the disease and is associated with increased morbidity, mortality and economic burden.FRAX® is a web-based tool developed by the Sheffield WHO Collaborating Center team, that integrates clinical risk factors, femoral neck BMD, country specific mortality and fracture data and calculates the 10 year fracture probability in order to help health care professionals identify patients who need treatment. However, only 31 countries have a FRAX® calculator at the time paper was accepted for publication. In the absence of a FRAX® model for a particular country, it has been suggested to use a surrogate country for which the epidemiology of osteoporosis most closely approximates the index country. More specific recommendations for clinicians in these countries are not available.In North America, concerns have also been raised regarding the assumptions used to construct the US ethnic specific FRAX® calculators with respect to the correction factors applied to derive fracture probabilities in Blacks, Asians and Hispanics in comparison to Whites. In addition, questions were raised about calculating fracture risk in other ethnic groups e.g., Native Americans and First Canadians.In order to provide additional guidance to clinicians, a FRAX® International Task Force was formed to address specific questions raised by physicians in countries without FRAX® calculators and seeking to integrate FRAX® into their clinical practice. The main questions that the task force tried to answer were the following:1.What is the evidence supporting ethnic and sex specific adjustments for fracture incidence rates in Blacks, Hispanics and Asians-2.What data exist for other groups, e.g., Native Americans, First Nations Canadians-3.Are there secular changes in fracture rates-4.What are the requirements for the construction of a FRAX® calculator? And what are the desirable/optimal characteristics of the data-5.What

Osteoporosis is a serious worldwide epidemic. Increased risk of fractures is the hallmark of the disease and is associated with increased morbidity, mortality and economic burden.FRAX® is a web-based tool developed by the Sheffield WHO Collaborating Center team, that integrates clinical risk factors, femoral neck BMD, country specific mortality and fracture data and calculates the 10 year fracture probability in order to help health care professionals identify patients who need treatment. However, only 31 countries have a FRAX® calculator at the time paper was accepted for publication. In the absence of a FRAX® model for a particular country, it has been suggested to use a surrogate country for which the epidemiology of osteoporosis most closely approximates the index country. More specific recommendations for clinicians in these countries are not available.In North America, concerns have also been raised regarding the assumptions used to construct the US ethnic specific FRAX® calculators with respect to the correction factors applied to derive fracture probabilities in Blacks, Asians and Hispanics in comparison to Whites. In addition, questions were raised about calculating fracture risk in other ethnic groups e.g., Native Americans and First Canadians.In order to provide additional guidance to clinicians, a FRAX® International Task Force was formed to address specific questions raised by physicians in countries without FRAX® calculators and seeking to integrate FRAX® into their clinical practice. The main questions that the task force tried to answer were the following:1.What is the evidence supporting ethnic and sex specific adjustments for fracture incidence rates in Blacks, Hispanics and Asians-2.What data exist for other groups, e.g., Native Americans, First Nations Canadians-3.Are there secular changes in fracture rates-4.What are the requirements for the construction of a FRAX® calculator? And what are the desirable/optimal characteristics of the data-5.What

We suggest a new method to compute the spectrum and wave functions of excited states. We construct a stochastic basis of Bargmann link states, drawn from a physical probability density distribution and compute transition amplitudes between stochastic basis states. From such transition matrix we extract wave functions and the energy spectrum. We apply this method to $U(1)_{2+1}$ lattice gauge theory. As a test we compute the energy spectrum, wave functions and thermodynamical functions of the electric Hamiltonian and compare it with analytical results. We find excellent agreement. We observe scaling of energies and wave functions in the variable of time. We also present first results on a small lattice for the full Hamiltonian including the magnetic term., Comment: Lattice 2008 conference

We suggest a new method to compute the spectrum and wave functions of excited states. We construct a stochastic basis of Bargmann link states, drawn from a physical probability density distribution and compute transition amplitudes between stochastic basis states. From such transition matrix we extract wave functions and the energy spectrum. We apply this method to $U(1)_{2+1}$ lattice gauge theory. As a test we compute the energy spectrum, wave functions and thermodynamical functions of the electric Hamiltonian and compare it with analytical results. We find excellent agreement. We observe scaling of energies and wave functions in the variable of time. We also present first results on a small lattice for the full Hamiltonian including the magnetic term., Comment: Lattice 2008 conference

We suggest a new method to compute the spectrum and wave functions of excited states. We construct a stochastic basis of Bargmann link states, drawn from a physical probability density distribution and compute transition amplitudes between stochastic basis states. From such transition matrix we extract wave functions and the energy spectrum. We apply this method to $U(1)_{2+1}$ lattice gauge theory. As a test we compute the energy spectrum, wave functions and thermodynamical functions of the electric Hamiltonian and compare it with analytical results. We find excellent agreement. We observe scaling of energies and wave functions in the variable of time. We also present first results on a small lattice for the full Hamiltonian including the magnetic term., Comment: Lattice 2008 conference

We collected population-based young normal hip and spine BMD data from 17 centres across Europe to assess between centre differences and to compare reference values with the US NHANES-III data. There was strong evidence of between country heterogeneity, but not between centres within countries. Hip BMD mean values were lower in European women, but SD's differed little from the NHANES-III USA results in both sexes. It may be necessary to adjust NHANES-III based T-scores by adding/subtracting a country-specific adjustment factor. INTRODUCTION: It remains unclear whether young normal BMD reference values specific to an American population can be validly used for T-score calculation in Europeans. METHODS: We collected population based BMD data from 1163 men and 329 women aged 19-29 years from 17 centres across Europe to compare mean and SD values with the NHANES-III study USA results. BMD(g/cm2) was measured at the hip and spine using DXA densitometers cross-calibrated with the European Spine Phantom (ESP). The only exclusions were for technically inadequate scans. A linear regression model was used to derive reference values. To allow for direct comparison with published NHANES III study data, the cross-calibrated BMD values were converted using the ESP equations to Hologic QDR 1000 units. RESULTS: In men, the overall mean(SD) BMD values expressed in Hologic-QDR1000 units of measurement, were: femoral neck 0.912(0.132); trochanter 0.793(0.124); and L2-L4 spine 1.027(0.123). The respective estimates in women were: 0.826(0.115); 0.670(0.093); and 0.983(0.107). However the I2 statistic for heterogeneity indicated moderate to strong evidence of between-centre heterogeneity. There was, however, no significant heterogeneity observed between centres within countries, suggesting that this variation arose from national differences. Compared to the NHANES III population-based US data, the mean values in women were significantly lower at both sites due to some lower national Euro

We collected population-based young normal hip and spine BMD data from 17 centres across Europe to assess between centre differences and to compare reference values with the US NHANES-III data. There was strong evidence of between country heterogeneity, but not between centres within countries. Hip BMD mean values were lower in European women, but SD's differed little from the NHANES-III USA results in both sexes. It may be necessary to adjust NHANES-III based T-scores by adding/subtracting a country-specific adjustment factor. INTRODUCTION: It remains unclear whether young normal BMD reference values specific to an American population can be validly used for T-score calculation in Europeans. METHODS: We collected population based BMD data from 1163 men and 329 women aged 19-29 years from 17 centres across Europe to compare mean and SD values with the NHANES-III study USA results. BMD(g/cm2) was measured at the hip and spine using DXA densitometers cross-calibrated with the European Spine Phantom (ESP). The only exclusions were for technically inadequate scans. A linear regression model was used to derive reference values. To allow for direct comparison with published NHANES III study data, the cross-calibrated BMD values were converted using the ESP equations to Hologic QDR 1000 units. RESULTS: In men, the overall mean(SD) BMD values expressed in Hologic-QDR1000 units of measurement, were: femoral neck 0.912(0.132); trochanter 0.793(0.124); and L2-L4 spine 1.027(0.123). The respective estimates in women were: 0.826(0.115); 0.670(0.093); and 0.983(0.107). However the I2 statistic for heterogeneity indicated moderate to strong evidence of between-centre heterogeneity. There was, however, no significant heterogeneity observed between centres within countries, suggesting that this variation arose from national differences. Compared to the NHANES III population-based US data, the mean values in women were significantly lower at both sites due to some lower national Euro

We investigate the dynamics of gravity coupled to a scalar field using a non-canonical form of the kinetic term. It is shown that its singular point represents an attractor for classical solutions and the stationary value of the field may occur distant from the minimum of the potential. In this paper properties of universes with such stationary states are considered. We reveal that such state can be responsible for modern dark energy density., Comment: H. Kroger, invited talk, FFP6, Udine (2004), revised version with corrected author list

We discuss how the concept of the Monte Carlo Hamiltonian can be applied to lattice gauge theories., Comment: "Non-Perturbative Quantum Field Theory: Lattice and Beyond", Guangzhou, China 2004

We show how to construct the measure of the path integral in lattice gauge theory. This measure contains a factor beyond the standard Haar measure. Such factor becomes relevant for the calculation of a single transition amplitude (in contrast to the calculation of ratios of amplitudes). Single amplitudes are required for computation of the partition function and the free energy. For U(1) lattice gauge theory, we present a numerical simulation of the transition amplitude comparing the path integral with the evolution in terms of the Hamiltonian, showing good agreement., Comment: 5 pages, 2 figures

We show how to construct the measure of the path integral in lattice gauge theory. This measure contains a factor beyond the standard Haar measure. Such factor becomes relevant for the calculation of a single transition amplitude (in contrast to the calculation of ratios of amplitudes). Single amplitudes are required for computation of the partition function and the free energy. For U(1) lattice gauge theory, we present a numerical simulation of the transition amplitude comparing the path integral with the evolution in terms of the Hamiltonian, showing good agreement., Comment: 5 pages, 2 figures

We discuss how the concept of the Monte Carlo Hamiltonian can be applied to lattice gauge theories., Comment: "Non-Perturbative Quantum Field Theory: Lattice and Beyond", Guangzhou, China 2004

We discuss how the concept of the Monte Carlo Hamiltonian can be applied to lattice gauge theories., Comment: "Non-Perturbative Quantum Field Theory: Lattice and Beyond", Guangzhou, China 2004

We show how to construct the measure of the path integral in lattice gauge theory. This measure contains a factor beyond the standard Haar measure. Such factor becomes relevant for the calculation of a single transition amplitude (in contrast to the calculation of ratios of amplitudes). Single amplitudes are required for computation of the partition function and the free energy. For U(1) lattice gauge theory, we present a numerical simulation of the transition amplitude comparing the path integral with the evolution in terms of the Hamiltonian, showing good agreement., Comment: 5 pages, 2 figures

Monte Carlo techniques have been widely employed in statistical physics as well as in quantum theory in the Lagrangian formulation. However, in the conventional approach, it is extremely difficult to compute the excited states. Here we present a different algorithm: the Monte Carlo Hamiltonian method, designed to overcome the difficulties of the conventional approach. As a new example, application to the Klein-Gordon field theory is shown., Comment: 3 pages, uses Latex and aipproc.cls

Monte Carlo techniques with importance sampling have been extensively applied to lattice gauge theory in the Lagrangian formulation. Unfortunately, it is extremely difficult to compute the excited states using the conventional Monte Carlo algorithm. Our recently developed approach: the Monte Carlo Hamiltonian method, has been designed to overcome the difficulties of the conventional approach. In this paper, we extend the method to many body systems and quantum field theory. The Klein-Gordon field theory is used as a testing ground., Comment: 12 pages, uses latex and ws-p8-50x6-00.cls

Monte Carlo techniques with importance sampling have been extensively applied to lattice gauge theory in the Lagrangian formulation. Unfortunately, it is extremely difficult to compute the excited states using the conventional Monte Carlo algorithm. Our recently developed approach: the Monte Carlo Hamiltonian method, has been designed to overcome the difficulties of the conventional approach. In this paper, we extend the method to many body systems and quantum field theory. The Klein-Gordon field theory is used as a testing ground., Comment: 12 pages, uses latex and ws-p8-50x6-00.cls

Monte Carlo techniques with importance sampling have been extensively applied to lattice gauge theory in the Lagrangian formulation. Unfortunately, it is extremely difficult to compute the excited states using the conventional Monte Carlo algorithm. Our recently developed approach: the Monte Carlo Hamiltonian method, has been designed to overcome the difficulties of the conventional approach. In this paper, we extend the method to many body systems and quantum field theory. The Klein-Gordon field theory is used as a testing ground., Comment: 12 pages, uses latex and ws-p8-50x6-00.cls

Monte Carlo techniques have been widely employed in statistical physics as well as in quantum theory in the Lagrangian formulation. However, in some areas of application to quantum theories computational progress has been slow. Here we present a recently developed approach: the Monte Carlo Hamiltonian method, designed to overcome the difficulties of the conventional approach., Comment: StatPhys-Taiwan-1999, 6 pages, LaTeX using elsart.cls

At sufficiently high temperature and density, quantum chromodynamics (QCD) is expected to undergo a phase transition from the confined phase to the quark-gluon plasma phase. In the Lagrangian lattice formulation the Monte Carlo method works well for QCD at finite temperature, however, it breaks down at finite chemical potential. We develop a Hamiltonian approach to lattice QCD at finite chemical potential and solve it in the case of free quarks and in the strong coupling limit. At zero temperature, we calculate the vacuum energy, chiral condensate, quark number density and its susceptibility, as well as mass of the pseudoscalar, vector mesons and nucleon. We find that the chiral phase transition is of first order, and the critical chemical potential is $\mu_C =m_{dyn}^{(0)}$ (dynamical quark mass at $\mu=0$). This is consistent with $\mu_C \approx M_N^{(0)}/3$ (where $M_N^{(0)}$ is the nucleon mass at $\mu=0$)., Comment: Final version appeared in Phys. Rev. D

At sufficiently high temperature and density, quantum chromodynamics (QCD) is expected to undergo a phase transition from the confined phase to the quark-gluon plasma phase. In the Lagrangian lattice formulation the Monte Carlo method works well for QCD at finite temperature, however, it breaks down at finite chemical potential. We develop a Hamiltonian approach to lattice QCD at finite chemical potential and solve it in the case of free quarks and in the strong coupling limit. At zero temperature, we calculate the vacuum energy, chiral condensate, quark number density and its susceptibility, as well as mass of the pseudoscalar, vector mesons and nucleon. We find that the chiral phase transition is of first order, and the critical chemical potential is $\mu_C =m_{dyn}^{(0)}$ (dynamical quark mass at $\mu=0$). This is consistent with $\mu_C \approx M_N^{(0)}/3$ (where $M_N^{(0)}$ is the nucleon mass at $\mu=0$)., Comment: Final version appeared in Phys. Rev. D

Monte Carlo techniques have been widely employed in statistical physics as well as in quantum theory in the Lagrangian formulation. However, in some areas of application to quantum theories computational progress has been slow. Here we present a recently developed approach: the Monte Carlo Hamiltonian method, designed to overcome the difficulties of the conventional approach., Comment: StatPhys-Taiwan-1999, 6 pages, LaTeX using elsart.cls

At sufficiently high temperature and density, quantum chromodynamics (QCD) is expected to undergo a phase transition from the confined phase to the quark-gluon plasma phase. In the Lagrangian lattice formulation the Monte Carlo method works well for QCD at finite temperature, however, it breaks down at finite chemical potential. We develop a Hamiltonian approach to lattice QCD at finite chemical potential and solve it in the case of free quarks and in the strong coupling limit. At zero temperature, we calculate the vacuum energy, chiral condensate, quark number density and its susceptibility, as well as mass of the pseudoscalar, vector mesons and nucleon. We find that the chiral phase transition is of first order, and the critical chemical potential is $\mu_C =m_{dyn}^{(0)}$ (dynamical quark mass at $\mu=0$). This is consistent with $\mu_C \approx M_N^{(0)}/3$ (where $M_N^{(0)}$ is the nucleon mass at $\mu=0$)., Comment: Final version appeared in Phys. Rev. D

Monte Carlo techniques have been widely employed in statistical physics as well as in quantum theory in the Lagrangian formulation. However, in some areas of application to quantum theories computational progress has been slow. Here we present a recently developed approach: the Monte Carlo Hamiltonian method, designed to overcome the difficulties of the conventional approach., Comment: StatPhys-Taiwan-1999, 6 pages, LaTeX using elsart.cls

At sufficiently high temperature and density, quantum chromodynamics (QCD) is expected to undergo a phase transition from the confined phase to the quark-gluon plasma phase. In the Lagrangian lattice formulation the Monte Carlo method works well for QCD at finite temperature, however, it breaks down at finite chemical potential. We develop a Hamiltonian approach to lattice QCD at finite chemical potential and solve it in the case of free quarks and in the strong coupling limit. At zero temperature, we calculate the vacuum energy, chiral condensate, quark number density and its susceptibility, as well as mass of the pseudoscalar, vector mesons and nucleon. We find that the chiral phase transition is of first order, and the critical chemical potential is $\mu_C =m_{dyn}^{(0)}$ (dynamical quark mass at $\mu=0$). This is consistent with $\mu_C \approx M_N^{(0)}/3$ (where $M_N^{(0)}$ is the nucleon mass at $\mu=0$)., Comment: Final version appeared in Phys. Rev. D

Monte Carlo techniques have been widely employed in statistical physics as well as in quantum theory in the Lagrangian formulation. However, in some areas of application to quantum theories computational progress has been slow. Here we present a recently developed approach: the Monte Carlo Hamiltonian method, designed to overcome the difficulties of the conventional approach., Comment: StatPhys-Taiwan-1999, 6 pages, LaTeX using elsart.cls

At sufficiently high temperature and density, quantum chromodynamics (QCD) is expected to undergo a phase transition from the confined phase to the quark-gluon plasma phase. In the Lagrangian lattice formulation the Monte Carlo method works well for QCD at finite temperature, however, it breaks down at finite chemical potential. We develop a Hamiltonian approach to lattice QCD at finite chemical potential and solve it in the case of free quarks and in the strong coupling limit. At zero temperature, we calculate the vacuum energy, chiral condensate, quark number density and its susceptibility, as well as mass of the pseudoscalar, vector mesons and nucleon. We find that the chiral phase transition is of first order, and the critical chemical potential is $\mu_C =m_{dyn}^{(0)}$ (dynamical quark mass at $\mu=0$). This is consistent with $\mu_C \approx M_N^{(0)}/3$ (where $M_N^{(0)}$ is the nucleon mass at $\mu=0$)., Comment: Final version appeared in Phys. Rev. D

We study QCD in 2 dimensions using the improved lattice fermionic Hamiltonian proposed by Luo, Chen, Xu and Jiang. The vector mass and the chiral condensate are computed for various $SU(N_C)$ gauge groups. We do observe considerable improvement in comparison with the Wilson quark case., Comment: LATTICE98(improvement)

We study QCD in 2 dimensions using the improved lattice fermionic Hamiltonian proposed by Luo, Chen, Xu and Jiang. The vector mass and the chiral condensate are computed for various $SU(N_C)$ gauge groups. We do observe considerable improvement in comparison with the Wilson quark case., Comment: LATTICE98(improvement)

We study QCD in 2 dimensions using the improved lattice fermionic Hamiltonian proposed by Luo, Chen, Xu and Jiang. The vector mass and the chiral condensate are computed for various $SU(N_C)$ gauge groups. We do observe considerable improvement in comparison with the Wilson quark case., Comment: LATTICE98(improvement)

We measure the propagator length in imaginary time quantum mechanics by Monte Carlo simulation on a lattice and extract the Hausdorff dimension $d_{H}$. We find that all local potentials fall into the same universality class giving $d_{H}=2$ like the free motion. A velocity dependent action ($S \propto \int dt \mid \vec{v} \mid^{\alpha}$) in the path integral (e.g. electrons moving in solids, or Brueckner's theory of nuclear matter) yields $d_{H}=\frac{\alpha }{\alpha - 1}$ if $\alpha > 2$ and $d_{H}=2$ if $\alpha \leq 2$. We discuss the relevance of fractal pathes in solid state physics and in $QFT$, in particular for the Wilson loop in $QCD$., Comment: uuencoded and compressed shell archive file. 8 pages with 7 figures

We measure the propagator length in imaginary time quantum mechanics by Monte Carlo simulation on a lattice and extract the Hausdorff dimension $d_{H}$. We find that all local potentials fall into the same universality class giving $d_{H}=2$ like the free motion. A velocity dependent action ($S \propto \int dt \mid \vec{v} \mid^{\alpha}$) in the path integral (e.g. electrons moving in solids, or Brueckner's theory of nuclear matter) yields $d_{H}=\frac{\alpha }{\alpha - 1}$ if $\alpha > 2$ and $d_{H}=2$ if $\alpha \leq 2$. We discuss the relevance of fractal pathes in solid state physics and in $QFT$, in particular for the Wilson loop in $QCD$., Comment: uuencoded and compressed shell archive file. 8 pages with 7 figures

We measure the propagator length in imaginary time quantum mechanics by Monte Carlo simulation on a lattice and extract the Hausdorff dimension $d_{H}$. We find that all local potentials fall into the same universality class giving $d_{H}=2$ like the free motion. A velocity dependent action ($S \propto \int dt \mid \vec{v} \mid^{\alpha}$) in the path integral (e.g. electrons moving in solids, or Brueckner's theory of nuclear matter) yields $d_{H}=\frac{\alpha }{\alpha - 1}$ if $\alpha > 2$ and $d_{H}=2$ if $\alpha \leq 2$. We discuss the relevance of fractal pathes in solid state physics and in $QFT$, in particular for the Wilson loop in $QCD$., Comment: uuencoded and compressed shell archive file. 8 pages with 7 figures

This is the report of the Workshop on New Research Opportunities in Superconductivity held at Copper Mountain, Colorado on August 19-20,1991. The workshop is a follow-up to two previous meetings to evaluate progress in superconductivity. The first, held at Copper Mountain, Colorado in 1983, focuses on low-temperature superconductors (LTS), while the second-in 1988 examined the progress of low-temperature materials and the potential of the then recently- discovered high-temperature superconductors (HTS). The summaries of these two superconductivity workshops were published in Cryogenics (July 1984, p.378; and November 1988, p.711). This workshop was the first in this series to concentrate largely on high-temperature superconductors. Its objectives were to identify the barriers limiting progress in high-temperature materials and to assess research areas that are ripe for important advances. The workshop was organized in four sessions, with Robert C.Dynes and Victor J. Emery leading the session on Fundamentals, Charles M. Falco and Donald U. Gubser leading the session on Materials, David K. Christen and Harry Kroger leading the session on Thin Films and Devices, and Sungho Jin and David T. Shaw leading the session on Bulk Materials and Large-Scale Applications. The organizational committee for the workshop consisted of David K. Christen, Alan F. Clark, Robert C. Dynes, Donald H. Liebenberg, David L. Nelson, and David T. Shaw (chair).

Semiconductor barriers are investigated as a means of producing NbN-barrier-NbN and NbN-barrier-Nb Josephson devices. Chemical vapor deposition of silicon and germanium polycrystalline barriers onto NbN substrates and sputter deposition of amorphous silicon onto NbN substrates were used to produce the barrier layers. NbN-aSi-Nb tunnel junctions which had a Vm (product of critical current and subgap resistance) as high as 15 mV were fabricated. Phosphorus doped Ge barriers about 60 A thick produced tunnel junctions with Vm = 2-3 mV. Super Schottky diodes were produced with boron doped germanium barriers about 130 A thick. Boron doped germanium barriers about 60-70 A thick were observed to have Josephson coupling with good uniformity as judged by ideal threshold curves, but had non-ideal tunneling characteristics. Nbn-Ge-NbN devices were produced by first depositing the trilayer structure over the entire wafer and then isolating the desired junctions by thermally oxidizing the upper NbN layer between devices, with the device area being protected from oxidization by a patterned SiO2 layer. Some correlation between good tunneling characteristics and the crystal structure and high optical reflectivity of the lower NbN electrode was observed. (Author)

This program is part of an ongoing effort to fabricate all-refractory S-I-S devices for use as mm-wave detectors and mixers in the quantum regime, and operating in the temperature range of 8-10 K. There are four ongoing approaches to achieve this goal: (1) Development of high-quality NbN-barrier-Nb S-I-S junctions as an intermediate goal towards fabricating all-NbN junctions; (2) Actual development of all-NbN junctions using the results of (1) above as a guide; (3) Development of an in-house NbN deposition capability in order to speed the progress on (2) above; and (4) The use of existing all-NB digital circuit fabrication capability to design and fabricate mm-wave mixers to operate at T less than or approx. 4.2 K, thus gaining valuable experience that can be applied to the eventual design of all-NbN mixers. Sputtered NbN-a:Si-NB Josephson tunnel junctions fabricated using SRC's SNAP process (Selective Niobium Anodization Process) have been developed. All-NbN devices using the plain a:Si barrier have been developed to the point where they exhibit S-I-S tunnelling characteristics. Fourteen types of mm-wave mixer chips have been designed in collaboration with the Goddard Institute for Space Studies using the existing all -NB digital circuit fabrication process. Masks were fabricated, and a trial fabrication proved the integrity of the process. The viability of the proposed mounting scheme has been experimentally ascertained., Continuation of work done under Contract N00173-80-C-0159.

Substantial evidence has been accumulated during the course of this program which indicates that the localized states which are present in nonhydrogenated sputtered amorphous silicon barriers contribute to the larger current density observed at biases below the superconducting energy gap of the electrodes. The basic observations and the method of measuring the density of localized states at the Fermi level of the barrier materials are presented in the Appendix which is a reprint of a paper presented at the 1982 Superconductivity Conference (1). More recent observations and theoretical speculations are included in this report.

This program is an effort to achieve the ultimate goal of fabricating refractory superconducting S-I-S mixer devices for operation in mm-wave receivers in the quantum mode and in the 8-10 K temperature range. The following progress has been made toward the above goal: (1) development of in-house capability of depositing niobium carbonitride films (Nb (x) N(y) of device quality with transition temperatures to approx. 16 K; (2) development of NbC(x)N(y):aSi:Nb and NbC(x)N(y):Ge:Nb devices of very high quality; (3) fabrication and successful operation of niobium based S-I-S mixer chips; and (4) fabrication and evaluation of aSi and Ge barrier all-NbC(x)N(y) devices. NbC(x)N(y):Ge:Nb devices have been fabricated with chemical vapor deposited (CVD) polycrystalline arsenic-doped germanium barriers. All-Nb-S-I-S mixer chips were fabricated and sent to Goddard Institute for Space Studies to be evaluated. The noise temperature was approx. 60 K and the conversion loss of 5 dB. These results are comparable to Pb alloy junction results. A second-generation mixer was designed by GISS.

The report describes the design and testing of X-band TRAPATT oscillators and amplifiers. The amplifier circuits were designed to permit, in principle, broadband output by prohibiting 'time-delayed triggering.' A circuit of this type was fabricated and performed with 150 MHz bandwidth at 8.0 GHz. X-band oscillators were fabricated with careful attention paid to reduction of ohmic losses and enhancement in their ease of triggering. Several devices were found which would oscillate at greater than 30% efficiency (one over 40%) at X-band frequencies. (Author)

The report describes the design and development of a wideband TRAPATT amplifier in a microstrip configuration, and is also concerned with the progress being made on the development of cw devices in a ring geometry. Particular emphasis is placed on describing surface degradation effects observed in large periphery devices and the approaches used toward solving these difficulties. An amplifier broadbanding technique based on a lumped element technique is described and preliminary experimental results are presented. A section describing the use of small area diodes as a means of lowering input power thresholds for a TRAPATT amplifier is included. Improvements in amplifier efficiency through the use of a new bias network which permits second harmonic tuning is also described. Finally, a summary of a generalized TRAPATT amplifier design technique is presented. (Author)