ABSTRACT
We performed the first simultaneous extraction of the six leading-order proton polarizabilities. We reached this milestone thanks to both new high-quality experimental data and an innovative bootstrap-based fitting method. These new results provide a self-consistent and fundamental benchmark for all future theoretical and experimental polarizability estimates.
Subject(s)
Escherichia coli Infections/microbiology , Extraintestinal Pathogenic Escherichia coli/enzymology , beta-Lactamases/biosynthesis , Aged , Extraintestinal Pathogenic Escherichia coli/drug effects , Extraintestinal Pathogenic Escherichia coli/isolation & purification , Fatal Outcome , Female , Humans , Italy , Male , Middle AgedABSTRACT
Helium ion beams are expected to be available again in the near future for clinical use. A suitable formalism to obtain relative biological effectiveness (RBE) values for treatment planning (TP) studies is needed. In this work we developed a data-driven RBE parameterization based on published in vitro experimental values. The RBE parameterization has been developed within the framework of the linear-quadratic (LQ) model as a function of the helium linear energy transfer (LET), dose and the tissue specific parameter (α/ß)ph of the LQ model for the reference radiation. Analytic expressions are provided, derived from the collected database, describing the RBEα = αHe/αph and Rß = ßHe/ßph ratios as a function of LET. Calculated RBE values at 2 Gy photon dose and at 10% survival (RBE10) are compared with the experimental ones. Pearson's correlation coefficients were, respectively, 0.85 and 0.84 confirming the soundness of the introduced approach. Moreover, due to the lack of experimental data at low LET, clonogenic experiments have been performed irradiating A549 cell line with (α/ß)ph = 5.4 Gy at the entrance of a 56.4 MeV u(-1)He beam at the Heidelberg Ion Beam Therapy Center. The proposed parameterization reproduces the measured cell survival within the experimental uncertainties. A RBE formula, which depends only on dose, LET and (α/ß)ph as input parameters is proposed, allowing a straightforward implementation in a TP system.
Subject(s)
Helium/therapeutic use , Radioisotopes/therapeutic use , Radiotherapy Planning, Computer-Assisted/methods , Algorithms , Cell Line , Cell Survival/radiation effects , Dose-Response Relationship, Radiation , Humans , Linear Energy Transfer , Male , Relative Biological EffectivenessABSTRACT
Information on the size and shape of the neutron skin on (208)Pb is extracted from coherent pion photoproduction cross sections measured using the Crystal Ball detector together with the Glasgow tagger at the MAMI electron beam facility. On exploitation of an interpolated fit of a theoretical model to the measured cross sections, the half-height radius and diffuseness of the neutron distribution are found to be c(n)=6.70±0.03(stat.) fm and a(n)=0.55±0.01(stat.)(-0.03)(+0.02)(sys.) fm, respectively, corresponding to a neutron skin thickness Δr(np)=0.15±0.03(stat.)(-0.03)(+0.01)(sys.) fm. The results give the first successful extraction of a neutron skin thickness with an electromagnetic probe and indicate that the skin of (208)Pb has a halo character. The measurement provides valuable new constraints on both the structure of nuclei and the equation of state for neutron-rich matter.
ABSTRACT
A precision measurement of the differential cross sections dσ/dΩ and the linearly polarized photon asymmetry Σ≡(dσâ¥-dσâ¥)/(dσâ¥+dσâ¥) for the γpâπ0p reaction in the near-threshold region has been performed with a tagged photon beam and almost 4π detector at the Mainz Microtron. The Glasgow-Mainz photon tagging facility along with the Crystal Ball/TAPS multiphoton detector system and a cryogenic liquid hydrogen target were used. These data allowed for a precise determination of the energy dependence of the real parts of the S- and all three P-wave amplitudes for the first time and provide the most stringent test to date of the predictions of chiral perturbation theory and its energy region of agreement with experiment.
ABSTRACT
Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz in the three isospin channels gamma[over -->]p-->pi(+)pi(0)n, gamma[over -->]p-->pi(0)pi(0)p, and gamma[over -->]p-->pi(+)pi(-)p. The circularly polarized photons, produced from bremsstrahlung of longitudinally polarized electrons, were tagged with the Glasgow magnetic spectrometer. Charged pions and the decay photons of pi(0) mesons were detected in a 4pi electromagnetic calorimeter which combined the Crystal Ball detector with the TAPS detector. The precisely measured asymmetries are very sensitive to details of the production processes and are thus key observables in the modeling of the reaction dynamics.
ABSTRACT
We present the first detailed measurement of incoherent photoproduction of neutral pions to a discrete state of a residual nucleus. The 12C(gamma,pi(0))(12)C*(4.4 MeV) reaction has been studied with the Glasgow photon tagger at MAMI employing a new technique which uses the large solid angle Crystal Ball detector both as a pi(0) spectrometer and to detect decay photons from the excited residual nucleus. The technique has potential applications to a broad range of future nuclear measurements with the Crystal Ball and similar detector systems elsewhere. Such data are sensitive to the propagation of the Delta in the nuclear medium and will give the first information on matter transition form factors from measurements with an electromagnetic probe. The incoherent cross sections are compared to two theoretical predictions including a Delta-hole model.
ABSTRACT
A measurement of the helicity dependence of the total inclusive photoabsorption cross section on the deuteron was carried out at MAMI (Mainz) in the energy range 200
ABSTRACT
Helicity-dependent total photoabsorption cross sections on the deuteron have been measured for the first time at ELSA (Bonn) in the photon energy range from 815 to 1825 MeV. Circularly polarized tagged photons impinging on a longitudinally polarized LiD target have been used together with a highly efficient 4pi detector system. The data around 1 GeV are not compatible with predictions from existing multipole analyses. From the measured energy range an experimental contribution to the GDH integral on the neutron of [33.9 +/- 5.5(stat) +/- 4.5(syst)] microb is extracted.
ABSTRACT
For the first time we checked the fundamental Gerasimov-Drell-Hearn (GDH) sum rule for the proton experimentally in the photon energy range from 0.2-2.9 GeV with the tagged photon facilities at MAMI (Mainz) and ELSA (Bonn). New data of the doubly polarized total cross section difference are presented in the energy range from 1.6 to 2.9 GeV. The contribution to the GDH integral from 0.2-2.9 GeV yields [254+/-5(stat)+/-12(syst)] microb with negative contributions in the Regge regime at photon energies above 2.1 GeV. This trend supports the validity of the GDH sum rule.
ABSTRACT
UNLABELLED: The presence of ventricular complex cardiac arrhythmias in coronary patients, both at rest or during physical exercise, is considered a risk factor for future coronary events or sudden death during long time follow up. The meaning of ventricular complex arrhythmias (VCA) in patients with normal ventricular function and without myocardium ischemia has still not been explained. This study aimed to evaluate if patients with normal ventricular function and no evidence of cardiac ischemia (determined by means of Gated SPECT) who developed VCA during stress test show an increase in cardiac events on later monitoring. PATIENTS AND METHODS: All patients were studied by means of an ergometric exercise test using a standard Bruce protocol and Gated SPECT with Methoxyisobutyl Isonitrile-99mTechnetium (99mTC-MIBI). Sixty-seven (67) patients with normal ventricular function and no evidence of cardiac ischemia were included. RESULTS: 13 patients had VCA and 54 had no ventricular arrhythmias during stress test. During the follow up of 681.3 +/- 469 days, none of the 13 patients had sudden death, angina pectoris or myocardium infarction. CONCLUSIONS: In our sample, the appearance of VCA during stress test in patients without myocardium ischemia and normal ventricular function was not associated with an increase of cardiac events during the monitoring which was carried out.
Subject(s)
Arrhythmias, Cardiac/diagnostic imaging , Gated Blood-Pool Imaging/methods , Radiopharmaceuticals , Technetium Tc 99m Sestamibi , Tomography, Emission-Computed, Single-Photon/methods , Arrhythmias, Cardiac/physiopathology , Exercise Test , Female , Humans , Male , Middle Aged , Prognosis , Ventricular DysfunctionABSTRACT
La aparición de arritmias ventriculares complejas, tanto en reposo como durante el ejercicio físico en enfermos con cardiopatía isquémica, se ha considerado un elemento capaz de predecir eventos coronarios y muerte súbita en el seguimiento alejado. La implicancia clínica de este hallazgo en pacientes sin isquemia miocárdica y función ventricular izquierda normal, no ha sido totalmente aclarada. El objetivo del presente trabajo fue evaluar si los pacientes con función ventricular izquierda normal y sin isquemia (definidos mediante el empleo de un estudio de perfusión miocárdica Gated-Spect), que desarrollan taquicardia ventricular no sostenida (TVNS) durante el ejercicio físico presentan, en el seguimiento alejado, un mayor número de eventos cardiovasculares en comparación con aquellos pacientes que no desencadenan dicha arritmia. Material y métodos: A todos los pacientes se les realizó una prueba ergométrica siguiendo el protocolo de Bruce y un estudio de perfusión miocárdica Gated-Spect utilizando como radiotrazador Methoxy Iso Butil Isonitrilo-Tecnecio99m (MIBI-Tc99m). Se incluyeron 67 pacientes con función ventricular normal y sin evidencia de isquemia; fueron divididos en dos grupos de acuerdo a la presencia, Grupo 1(G1), 13 pacientes, o ausencia, Grupo 2(G2), 54 pacientes, de TVNS durante el esfuerzo. Se realizó un seguimiento medio de 681,3 ñ 469 días donde se evaluó la aparición de angina de pecho, necesidad de revascularización miocárdica, muerte o infarto agudo de miocardio. Resultados: En el G1 no se registraron eventos durante el período de seguimiento. En el G2 un paciente necesitó revascularización miocárdica. (p: No Significativa) Conclusión: En nuestro grupo de pacienes sin isquemia miocárdica inducida por el ejercicio y con función ventricular izquierda normal, la presencia de TVNS desarrollada durante la prueba de esfuerzo no demostró incrementar la probabilidad de eventos coronarios en el seguimiento realizado (AU)
Subject(s)
Middle Aged , Male , Female , Humans , Gated Blood-Pool Imaging , Tomography, Emission-Computed, Single-Photon , Radiopharmaceuticals , Technetium Tc 99m Sestamibi , Ventricular Dysfunction , Prognosis , Arrhythmias, Cardiac , Exercise TestABSTRACT
The purpose of this study was to evaluate boron distribution for a safe and effective BNCT (Boron Neutron Capture Therapy) of liver metastases. Samples both from healthy and tumour liver parenchyma were analysed, after i.v. boron administration, by: alpha particles counting under neutron irradiation; morphological analysis by standard haematoxylin-eosin staining; neutron autoradiography. Our method was unaffected by the cytological heterogeneity inside tumour nodules; it demonstrated selective boron distribution in tumour tissue and predicted estimated mean therapeutic doses in tumour and safety doses in healthy tissue. The time interval for efficient BNCT was 2 to 4 hours after i.v. boron administration.
Subject(s)
Boron Neutron Capture Therapy , Boron/pharmacokinetics , Colorectal Neoplasms/pathology , Liver Neoplasms/radiotherapy , Liver Neoplasms/secondary , Animals , Male , Rats , Tissue DistributionABSTRACT
To verify the fundamental Gerasimov-Drell-Hearn (GDH) sum rule for the first time experimentally, we measured the helicity dependent total photoabsorption cross section with circularly polarized real photons and longitudinally polarized nucleons in the photon energy range 0.68-1.82 GeV with the tagged photon facility at ELSA. The experiment was carried out with a 4pi detection system, a circularly polarized tagged photon beam, and a frozen spin polarized proton target. The contribution to the GDH sum rule in this photon energy range is [49.9+/-2.4(stat)+/-2.2(syst)] microb.
ABSTRACT
The helicity dependence of the gamma-->p-->-->ppi(0) reaction has been measured for the first time in the photon-energy range from 550 to 790 MeV. The experiment, performed at the Mainz microtron MAMI, used a 4pi-detector system, a circularly polarized, tagged photon beam, and a longitudinally polarized frozen-spin target. These data are predominantly sensitive to the D13(1520) resonance and are used to determine its helicity amplitudes.
ABSTRACT
The helicity dependence of the single pion photoproduction on the proton has been measured in the energy range from 200 to 450 MeV for the first time. The experiment, performed at the Mainz microtron MAMI, used a 4pi-detector system, a circularly polarized, tagged photon beam, and a frozen-spin target. The data obtained provide new information for multipole analyses of pion photoproduction and determine the main contributions to the Gerasimov-Drell-Hearn sum rule and the forward spin polarizability gamma(0).
ABSTRACT
BACKGROUND: The aim of this study was to assess the ability of clinical and instrumental features to identify patients with left main coronary artery disease (LMCD) compared with a three-vessel coronary artery disease group. METHODS: A cohort of 70 patients with LMCD was matched with another one of 66 patients with three-vessel disease. A history of angina before angiography was similar in both groups; the higher degrees of stable angina and the forms of unstable angina were moderately prevalent in the group with LMCD. RESULTS: In the last subgroup a significantly reduced incidence of previous acute myocardial infarction (AMI) was observed (p < 0.05). The resting electrocardiogram (ECG) showed higher incidence of atrial fibrillation (fa) and left bundle branch block (BBS) in the subjects with LMCD, with a statistic value (p < 0.05). The exercise test performed by a lot of patients appeared equally positive for inducible ischemia in the 2 groups. Significantly higher exercise peak load was achieved by the patients with three-vessel disease (p < 0.05). The coronary angiography showed a prevalence of right dominant circulation in the 2 groups; significantly the collateral circulation was more represented in the subjects with three-vessel disease (p < 0.05). Most patients with LMCD underwent a bypass coronary artery graft surgery (CABG surgery) more frequently than the ones with three-vessel disease (p < 0.01). In the former group the cardiovascular mortality within an average 2-year follow-up proved higher as to the latter group even if without statistic significance. CONCLUSIONS: Nevertheless this retrospective study showed some limitations. Particularly the incidence of clinical and instrumental variables and their capacity to differentiate LMCD patients from those with three-vessel disease were not demonstrated.
Subject(s)
Coronary Disease/diagnostic imaging , Myocardial Infarction/diagnostic imaging , Myocardial Revascularization , Acute Disease , Coronary Angiography , Coronary Disease/surgery , Female , Humans , Male , Myocardial Infarction/surgery , Retrospective StudiesABSTRACT
BACKGROUND: The aim of this study was to determine the role of the ST segment elevation resolution > 50% between the ECG before and 2 hours after thrombolytic therapy as a predictor of acute myocardial infarction (AMI)-related artery patency, assessed by a coronary angiography performed 1 month after AMI. MATERIALS AND METHODS: This study enrolled 95 patients, 75 men and 20 women, 58 years mean aged, admitted to the coronary care unit with diagnosis of AMI. Patients were treated with thrombolysis within 6 hours from the onset of chest pain, according to the GUSTO trial. RESULTS: The findings showed a significant prevalence of ST segment elevation resolution > 50% in inferior AMI (p < 0.01). It has been observed that the ST segment resolution is correlated with lower (p < 0.01) and earlier (p < 0.05) peak in serum creatinekinase (CK) and CK MB release and with less damage of left ventricular ejection fraction assessed by ventriculography (p < 0.01). All these findings indicated a lower extensive myocardial damage. Patients with ST segment resolution presented a prevalence of one or two-coronary vessel disease, with an infarct-related vessel narrowing like that observed in the other patients without ST resolution. Nevertheless a TIMI grade 2 or 3 flow was observed more frequently, but not significantly, in the subjects with ST resolution; a significant prevalence was limited to TIMI 3 grade flow (p < 0.05). In the present study ST segment elevation resolution > 50% represented a highly sensitive and a poor specific predictor of vessel patency in inferior AMI, but with a poor sensitivity and specificity in anterior AMI. CONCLUSIONS: Personal experience suggested that the thrombolytic therapy has a less favourable effect on the artery patency assessed 1 month after AMI, rather than in the acute phase as reported in previous studies. Dynamic changes of flow or a following worsening in atherosclerotic plaque could be probably responsible of reocclusion of an initially reperfused coronary artery.
Subject(s)
Electrocardiography , Myocardial Infarction/diagnosis , Myocardial Reperfusion/methods , Female , Humans , Male , Middle Aged , Myocardial Infarction/therapy , Thrombolytic Therapy , Time FactorsABSTRACT
Biochemical analysis of the soluble hydrogenase from the thermophilic organism Acetomicrobium flavidum revealed that the enzyme is an alpha 2 beta 2 tetramer, with the alpha and beta subunits having a molecular mass of 50 kDa and 25 kDa, respectively. The most important biochemical properties of the enzyme are a specific activity of 77 mumol min-1 (mg protein)-1, a Km for methylviologen of 0.2 mM, a pH optimum of 7.5 and a T50 of about 70 degrees C. In addition, the enzyme is remarkably stable to oxygen inactivation, retaining full activity after 24 h exposure to air. By using oligodeoxynucleotides designed on the basis of the N-terminal sequences of the two subunits, the corresponding genes have been isolated and sequenced. When compared to the other hydrogenases so far characterized, the A. flavidum hydrogenase appears to be a typical [Ni-Fe] enzyme. The hydrogenase was expressed in Escherichia coli at high levels in a soluble form but it was not active. The analysis of the recombinant large subunit showed that it was not post-translationally processed at its C-terminus.
