Search

Objective Perianal fistulizing disease is a problem in patients with Crohn’s disease (CD) because they often need repetitive surgeries. Among the various available procedures, none of them proves to be superior. In addition, the long-term outcome of fistula Seton drainage is not well described. The aims of this study were to analyze the long-term healing and recurrence rates of perianal fistulas in CD patients, stratified according to the first procedure performed. Methods Database analysis of a prospective Swiss cohort of patients with perianal CD. Results 365 patients with 576 interventions and a median follow-up of 7.5 years (0 - 12.6) were analyzed. 39.7% of patients required more than one surgery. The first surgical interventions were fistulectomies (58.4%), Seton drainage (26.9%), fistula plugs (2.2%) and combined procedures (9.9%). Fistulectomy patients required no more surgery in 67.6%, one additional surgery in 25.4% and more than one additional surgery in 7.7%. In these 3 groups of patients, after a median follow-up of 12.1 years, perianal fistula closure was achieved in 77.1%, 74.1% and 66.7%, respectively. In patients with Seton drainage as index surgery, 50.3% required no more surgery and over 75% achieved fistula closure after 10 years. 49.7% of patients with Seton required one or more surgeries. At median follow up of 7.5 years, closure rates were 64.2% and 60.5% in patients with one and more than one surgeries, respectively. There was no difference in demographics in Seton patients with closed or not closed fistulas. Non-closure patients had a higher Crohn Disease Activity Index (33 vs. 6) and more frequent anti-TNF medication (57.4% vs. 48.1%). Conclusion First line fistulectomies achieved the highest healing rates in perianal CD but 1/3 of patients require additional surgeries and 1/4 patients will remain with a fistula at 10 years. Initial seton drainage and concurrent medical therapy can achieve fistula closure in 75%. However, in 50% of patients more surgeries are performed with a seton staying in place up to 5 years and fistula closure in only 2/3 patients.

In the present paper, the turbulent mixing and structure of decaying stably stratified flows are investigated using direct numerical simulations (DNS). A key quantity for estimating turbulent diapyncal mixing in stably stratified flows is the flux Richardson number Rf (also commonly referred to as the mixing efficiency) which is a measure of the amount of turbulent kinetic energy that is irreversibly converted to background potential energy. Using simulations with varying strengths of density stratification, it is found that when the buoyancy Reynolds number R e b = ϵ / ( ν N 2 ) (where ϵ is the turbulent kinetic energy dissipation rate, ν is the kinematic viscosity, and N is the Brunt–Vaisala frequency), is less than 10, Rf becomes a property of the fluid as strong buoyancy effects inhibit turbulent mixing and hence Rf is influenced by (molecular) Prandtl number effects. On the other hand, for energetic flows at higher buoyancy Reynolds numbers (i.e. Reb > O(10)), Prandtl number effects diminish, indicating that Rf is a property of the flow. Flow visualization of enstrophy structures show the presence of elongated vortex tubes characteristic of classic isotropic turbulence for weakly stratified flows while ‘pancake-like’ structures emerge for strongly stratified flows.

Background Data of large cohort studies on the fate of perianal fistulizing Crohn’s disease (CD) is scarce. We aimed to evaluate the prevalence and natural history of perianal fistulas in adults with Crohn’s disease (CD). Methods Data from the Swiss IBD cohort study were analysed. The Swiss IBD Cohort study includes since 2006 IBD patients, follow-up questionnaires are completed once a year. Patients were recruited from university centres (80%), regional hospitals (19%), and private practices (1%). Results Among 2163 CD patients, 495 (22.9%) ever had perianal fistulas whereas 1668 (77.1%) did not. Patients with perianal fistulas were characterised by the following features when compared with patients without perianal fistulas: younger age at diagnosis (23.4 vs. 25.3 years, p = 0.001), longer disease duration at enrolment (9.6 vs. 4.9 years, p < 0.001), longer disease duration at latest follow-up (17.4 vs. 11.2 years, p < 0.001), less frequenty isolated ileal disease at diagnosis (15.8% vs. 28.6%, p < 0.001), more frequently rectal disease at enrolment (32.5% vs. 14.8%, p < 0.001) and latest follow-up (24.2% vs. 11.7%, p < 0.001), more frequently acne inversa (1.4% vs. 0.1%, p < 0.001), and more frequently intestinal resection (49.5% vs. 35.3%, p < 0.001). The prevalence of extraintestinal manifestations was not different (59.0% vs. 54.4%, p = 0.073). Compared with patients without perianal fistulas, patients with perianal fistulas were more frequently treated with topical 5-ASA (14.8% vs. 8.0%, p < 0.001), systemic steroids (78.2% vs. 70.1%, p < 0.001), azathioprine (82.6% vs. 77%, p = 0.008), methotrexate (28.3% vs. 22.2%, p = 0.005), infliximab (71.9% vs. 50.8%, p < 0.001), adalimumab (36% vs. 27.9%, p < 0.001), certolizumab pegol (18.6% vs. 11.5%, p < 0.001), and antibiotics (69.1% vs. 41.2%, p < 0.001). Regarding fistula anatomy, 321 patients (64.8%) had a low perianal fistula, 82 (16.6%) a high perianal fistula, and 227 (45.9%) a perineal fistula. The following fistula therapies were ever applied: perianal abscess drainage (45.7%), fistulectomy/fistulotomy (39.6%), seton drainage (28.7%), mucosal sliding flap (2%), fistula plug (1.4%), and fibrin glue instillation (1%). Conclusion In our national cohort roughly one-quarter of CD patients was diagnosed with perianal fistulizing disease. Compared with patients without perianal fistulas, patients with perianal fistulizing disease were characterised by several stigmata of complicated disease course such as a higher frequency of intestinal resections and higher prevalence of treatment with biologic agents.

We report on a first measurement of the polarized-target asymmetry of the pion-proton bremsstrahlung cross section ({pi}{sup +}{ital p}{r arrow}{pi}{sup {minus}}{ital p}{gamma}). As in previous cross section measurements the pion energy (298 MeV) and the detector geometry for this experiment was chosen to optimize the sensitivity to the radiation from the magnetic dipole moment of the {Delta}{sup ++}(1232) resonance {mu}{sub {Delta}}. Comparison to a recent isobar model for pion-nucleon bremsstrahlung yields {mu}{sub {Delta}}=(1.62{plus minus}0.18){mu}{sub {ital p}}, where {mu}{sub {ital p}} is the proton magnetic moment. Since the asymmetry depends less than the cross section on the choice of the other input parameters for the model, their uncertainties affect this analysis by less than the experimental error. However the theory fails to represent both the cross section and the asymmetry data at the highest photon energies. Hence further improvements in the calculations are needed before the model dependence of the magnetic moment analysis can be fully assessed. The present result agrees with bag-model corrections to the SU(6) prediction {mu}{sub {Delta}}=2{mu}{sub {ital p}}. As a by-product, the analyzing power for elastic {pi}{sup +}{ital p} scattering at 415 MeV/{ital c} was also measured. This second result is in good agreement with phase shiftmore » calculations.« less

We describe the details of an experiment designed to search for the admixture of massive neutrinos into electron-flavor neutrinos by observation with high resolution of the positron momentum spectrum in {pi}{r arrow}{ital e}+{nu} decay. No indication was found for such an admixture and the corresponding mixing amplitude was constrained below the {ital U}{sub {ital e}{ital i}}{sup 2}{le}10{sup {minus}6} region for neutrinos of {similar to}30 MeV/{ital c}{sup 2} mass.

A precise measurement of the ratio R of the total cross section e+e-hadrons to the pointlike cross section e+e-+- at a center-of-mass energy of 29.0 GeV is presented. The data were taken with the upgraded Mark II detector at the SLAC storage ring PEP. The result is R=3.920.050.09. The luminosity has been determined with three independent luminosity monitors measuring Bhabha scattering at different angular intervals. Recent calculations of higher-order QED radiative corrections are used to estimate the systematic error due to missing higher-order radiative corrections in the Monte Carlo event generators. © 1991 The American Physical Society.

Direct numerical simulations of stably stratified turbulence are used to compare the Thorpe overturn length scale, LT, with other length scales of the flow that can be constructed from large-scale quantities fundamental to shear-free, stratified turbulence. Quantities considered are the turbulent kinetic energy, k, its dissipation rate, e, and the buoyancy frequency, N. Fundamental length scales are then the Ozmidov length scale, LO, the isotropic large scale, Lke, and a kinetic energy length scale, LkN. Behavior of all three fundamental scales, relative to LT, is shown to be a function of the buoyancy strength parameter NTL, where TL = k/e is the turbulence time scale. When buoyancy effects are dominant (i.e., for NTL > 1), LT is shown to be linearly correlated with LkN and not with LO as is commonly assumed for oceanic flows. Agreement between LO and LT is only observed when the buoyancy and turbulence time scales are approximately equal (i.e., for the critical case when NTL ≈ 1). The relative lack of a...

First data are presented for the polarized-target asymmetry in the reaction {pi}{sup +}{ital p}{r arrow}{pi}{sup +}{ital p}{gamma} at an incident pion energy of 298 MeV. The geometry was chosen to maximize the sensitivity to the radiation of the magnetic dipole moment {mu}{sub {Delta}} of the {Delta}{sup ++}(1232 MeV). A fit of the asymmetry in the cross section {ital d}{sup 5}{sigma}/{ital d}{Omega}{sub {pi}} {ital d}{Omega}{sub {gamma}} {ital dk} as a function of the photon energy {ital k} to predictions from a recent isobar-model calculation with {mu}{sub {Delta}} as the only free parameter yields {mu}{sub {Delta}}=1.64({plus minus}0.19exp{Delta},{plus minus}0.14 theor){mu}{sub {ital p}}. Though this value agrees with bag-model corrections to the SU(6) prediction {mu}{sub {Delta}}=2{mu}{sub {ital p}}, further clarifications on the model dependence of the result are needed, in particular since the isobar model fails to describe both the cross section and the asymmetry at the highest photon energies.

The energy spectra of photons following negative muon absorption in $^{12}\mathrm{C}$, $^{16}\mathrm{O}$, $^{27}\mathrm{Al}$, $^{40}\mathrm{Ca}$, $^{\mathrm{nat}}\mathrm{Fe}$, $^{165}\mathrm{Ho}$, and $^{209}\mathrm{Bi}$ have been measured with two NaI spectrometers. The branching ratios for the emission of high energy photons give information on the induced pseudoscalar coupling constant ${g}_{P}$ in nuclear matter. The data for light nuclei are in agreement with the theoretical calculations using the nucleonic value of ${g}_{P}$\ensuremath{\approxeq}7${g}_{A}$ predicted by the partially conserved axial vector current hypothesis, while significantly lower values of ${g}_{P}$ are required to fit the data of the heavier elements with presently existing theoretical predictions. Disregarding the remaining theoretical uncertainties, these results can be interpreted as a further indication of the renormalization of the nucleonic form factors inside the nucleus.

Improved upper limits of generation-mixing amplitudes /b U//sub ie/ are presented for the electron-flavour in the heavy neutrino mass range of 20-70 MeV//b c//sup 2/. In conjunction with astrophysical considerations the new limits tend to exclude together the existence of heavy neutrinos in the investigated mass range.

The cross section and angular distribution for the reaction 13C(π+, γ)13N(g.s.) have been measured from 37 to 85° in the laboratory, at a pion energy of 115.5 MeV. The observed cross section ranges from 320 to 660 nbsr. These results do not show the large magnitude and wide-angle peaking expected if pre-critical effects due to nascent pion condensation were present. In addition, the observed cross section is less than one-half of the predictions of available theoretical calculations which do not include the pre-critical effect. Data on the reaction 1H(π−, γ)n at Tπ = 116.6 MeV were also obtained for calibration purposes. These data agree with expectations based on knowledge of the inverse reaction and previous measurements.

We have measured the fivefold differential cross section ${d}^{5}$\ensuremath{\sigma}/d${\ensuremath{\Omega}}_{\ensuremath{\pi}}$d${\ensuremath{\Omega}}_{\ensuremath{\gamma}}$${\mathrm{dE}}_{\ensuremath{\gamma}}$ for the process ${\ensuremath{\pi}}^{+}$p\ensuremath{\rightarrow}${\ensuremath{\pi}}^{+}$p\ensuremath{\gamma} with incident pions of energy 299 MeV. The angular regions for the outgoing pions (55\ifmmode^\circ\else\textdegree\fi{}\ensuremath{\le}${\ensuremath{\theta}}_{\mathrm{lab}{}^{\ensuremath{\pi}}\mathrm{\ensuremath{\le}}95}$\ifmmode^\circ\else\textdegree\fi{}), and photons (${\ensuremath{\theta}}_{\mathrm{lab}{}^{\ensuremath{\gamma}}=241\mathrm{\ifmmode^\circ\else\textdegree\fi{}}\ifmmode\pm\else\textpm\fi{}10}$\ifmmode^\circ\else\textdegree\fi{}) in coplanar geometry are selected to maximize the sensitivity to the radiation from the magnetic dipole moment of the ${\ensuremath{\Delta}}^{++}$(1232) resonance. At low photon energies, the data agree with the soft-photon approximation to pion-proton bremsstrahlung. At forward pion angles the data agree with older data and with the latest theoretical calculations for 2.3${\ensuremath{\mu}}_{p}$\ensuremath{\le}${\ensuremath{\mu}}_{\ensuremath{\Delta}}$\ensuremath{\le}3.3${\ensuremath{\mu}}_{p}$. However at more backward pion angles where no data existed, the predictions fail.

A large ..mu../sup -/ polarization was achieved in muonic Bi atoms with the help of the strong hyperfine field in a polarized nuclear target. Using /sup 209/Bi nuclei polarized to (59 +- 9)% in ferromagnetic BiMn, we observed a ..mu..-e decay asymmetry of (13.1 +- 3.9)%, which gives ..mu../sup -/ polarization per nuclear polarization equal to -1.07 +- 0.35. This value is almost consistent with -0.792 calculated for nuclei with spin I = (9/2) and a positive magnetic moment under the assumption that the hyperfine interaction becomes effective in the lowest muonic states.

Experimental results for the radiative muon capture branching ratio in several nuclei and the photon-muon spin asymmetry in40Ca are reported. For the measurements a two arm Nalspectrometer was used. Apart from26O and40Ca, where we confirm previous results of our group, new data on12C,26Fe,165Ho and209Bi are presented. No available theoretical models explain all the data consistently. The preliminary results for the asymmetry measurements, obtained using a stroboscopic method are in agreement with previous measurements and with theoretical calculations.

We have searched for events with new-particle topologies in 390 hadronic Z decays with the Mark II detector at the SLAC Linear Collider. We place 95%-confidence-level lower limits of 40.7 GeV/c^2 for the top-quark mass, 42.0 GeV/c^2 for the mass of a fourth-generation charge - 1/3 quark, and 41.3 GeV/c^2 for the mass of an unstable Dirac neutral lepton.

The experimental attempts to exploit the sensitivity of the radiative muon capture (RMC) reaction[1] $$ {\mu^{ - }}N\left( {A,Z} \right) \to N * \left( {A,Z - 1} \right){\nu_{\mu }}\gamma $$ to the induced pseudoscalar coupling g P until now are limited to the two nuclear targets 16 O[2] and 40 Ca [2,3,4]. The observables are the photon energy spectrum above a cutoff energy of 57 MeV, below which the muon decay electron induced bremsstrahlung prohibits the measurement, and the muon spin photon angular correlation. The latter quantity has only been measured with poor statistical accuracy for 40 Ca[3,5,6]. The data are scarce because the low rate (the radiative branch above 57 MeV contributes only 2 * 10-5 to the total muon absorption rate in 40 Ca), the modest resolution attainable for medium energy photons and the high background environment of fast neutrons severely trouble the measurement. But even this limited amount of data has lead to surprising results, when compared to theoretical calculations [7,8,9], which proceed in the impulse approximation with a Hamiltonian derived from the elementary μ - p → nν μ γ reaction and a nuclear response function, adapted to describe the results of other medium energy weak or electromagnetic processes. The interpretation of the integrated photon yield and the photon spectrum in terms of the pseudoscalar coupling yields g P = (4.5±1.5)g A for 40 Ca[4] and g P exceeding 12g A for 16 O [1,2,9].