Extreme particle acceleration in the microquasar Cygnus X-3.

Super-massive black holes in active galaxies can accelerate particles to relativistic energies, producing jets with associated gamma-ray emission. Galactic 'microquasars', which are binary systems consisting of a neutron star or stellar-mass black hole accreting gas from a companion star, also produce relativistic jets, generally together with radio flares. Apart from an isolated event detected in Cygnus X-1, there has hitherto been no systematic evidence for the acceleration of particles to gigaelectronvolt or higher energies in a microquasar, with the consequence that we are as yet unsure about the mechanism of jet energization. Here we report four gamma-ray flares with energies above 100 MeV from the microquasar Cygnus X-3 (an exceptional X-ray binary that sporadically produces radio jets). There is a clear pattern of temporal correlations between the gamma-ray flares and transitional spectral states of the radio-frequency and X-ray emission. Particle acceleration occurred a few days before radio-jet ejections for two of the four flares, meaning that the process of jet formation implies the production of very energetic particles. In Cygnus X-3, particle energies during the flares can be thousands of times higher than during quiescent states.

Terrestrial gamma-ray flashes as powerful particle accelerators.

Strong electric discharges associated with thunderstorms can produce terrestrial gamma-ray flashes (TGFs), i.e., intense bursts of x rays and γ rays lasting a few milliseconds or less. We present in this Letter new TGF timing and spectral data based on the observations of the Italian Space Agency AGILE satellite. We determine that the TGF emission above 10 MeV has a significant power-law spectral component reaching energies up to 100 MeV. These results challenge TGF theoretical models based on runaway electron acceleration. The TGF discharge electric field accelerates particles over the large distances for which maximal voltages of hundreds of megavolts can be established. The combination of huge potentials and large electric fields in TGFs can efficiently accelerate particles in large numbers, and we reconsider here the photon spectrum and the neutron production by photonuclear reactions in the atmosphere.

Gamma-ray localization of terrestrial gamma-ray flashes.

Terrestrial gamma-ray flashes (TGFs) are very short bursts of high-energy photons and electrons originating in Earth's atmosphere. We present here a localization study of TGFs carried out at gamma-ray energies above 20 MeV based on an innovative event selection method. We use the AGILE satellite Silicon Tracker data that for the first time have been correlated with TGFs detected by the AGILE Mini-Calorimeter. We detect 8 TGFs with gamma-ray photons of energies above 20 MeV localized by the AGILE gamma-ray imager with an accuracy of ∼5-10° at 50 MeV. Remarkably, all TGF-associated gamma rays are compatible with a terrestrial production site closer to the subsatellite point than 400 km. Considering that our gamma rays reach the AGILE satellite at 540 km altitude with limited scattering or attenuation, our measurements provide the first precise direct localization of TGFs from space.

Effects of a salt of cholestyramine and 2-[4-(p-chlorobenzoyl)phenoxy]2-methyl propionic acid (alpha-1081) on biliary lipid secretion in rats.

1 Hypolipidaemic agents may increase biliary cholesterol in man, inducing a supersaturated bile. 2 To evaluate this possible side-effect, we have studied bile lipid secretion over a period of 8 h with intact enterohepatic circulation and 4 h with complete interruption in rats treated for two months with a salt of cholestyramine and 2-[4-(p-chlorobenzoyl)-phenoxy]2-methyl propionic acid (alpha-1081, 1.150 g/kg body wt., daily), cholestyramine (1.125 g/kg body wt. daily), procetofenic acid (25 mg/kg body wt. daily) and saline respectively (six rats for each group). 3 Cholesterol saturation index significantly (P less than 0.005) increased (from 0.21 +/- 0.01 to 0.39 +/- 0.09, mean +/- s.d.), in rats fed with procetofenic acid but it did not in alpha-1081- and cholestyramine-treated animals. 4 Procetofenic acid and, to a lesser extent, cholestyramine increased the bile flow. Procetofenic acid increased cholesterol secretion from 0.45 +/- 0.17 to 0.94 +/- 0.19 mumol kg-1 body wt. h-1 (mean +/- s.d.). 5 Cholestyramine increased both serum cholesterol and bile acid secretion from 0.45 +/- 0.17 to 0.68 +/- 0.10 and 25.8 +/- 9.48 to 39.96 +/- 6.68 mumol kg-1 body wt. h-1 respectively; alpha-1081, on the contrary, had no effect on bile lipid secretion. 6 These data suggest that alpha-1081 may be used as a new hypolipidaemic drug without any risk of increasing cholesterol in bile.

Self-control expectancy and postsurgical pain: relationships to previous pain, behavior in past pain, familial pain tolerance models, and personality.

The importance of self-control expectancy on postsurgical pain was studied in 126 patients enrolled in a particular clinical setting. The contribution of previous pain experiences, past behaviors, vicarious experiences, and personality traits to self-control expectancy reported by patients was also investigated. To collect this information, a specific questionnaire and a semistructured interview were given before surgery. Minnesota Multiphasic Personality Inventory (MMPI), Eysenck Personality Inventory (EPI), and State-Trait Anxiety Inventory (STAI) personality tests were also administered. Postsurgical pain was assessed by measuring intensity (Visual Analogue Scale, VAS), latency (hr), and duration (days). Results show that expected emotional coping response is crucially related to the whole pain experience (intensity, latency, and duration). Self-control expectancy is associated with mastery behaviors in previous pains, vicarious experiences, and personality traits. These findings suggest that the knowledge of patients' beliefs about their ability to acquire and maintain control over impending pain is useful in predicting and managing postsurgical pain.

Individual pain history and familial pain tolerance models: relationships to post-surgical pain.

OBJECTIVES: (a) To investigate the influence of previous pain experience and familial pain tolerance models on postsurgical pain; (b) to investigate the effect of personality traits on vicarious learning. DESIGN: Before surgery, the patients completed the Minnesota Multiphasic Personality Inventory (MMPI), Eysenck Personality Inventory (EPI), and State-Trait Anxiety Inventory (STAI) personality tests. They also underwent a semi-structured interview to collect information on familial pain tolerance models and their own pain history. Postthoracotomy pain was assessed by measuring its latency (h), intensity (VAS 0-10), and duration (days). SETTING: A unique protocol to minimize the use of pain killers and encourage the adoption of coping strategies to face postsurgical pain was in use in the Thoracic Department. PATIENTS: A total of 126 patients who were free from chronic pain and undergoing thoracic surgery entered the study. OUTCOME: Most patients recalled a history of surgical or medical pain and good pain tolerance models in their original family. An almost equal number denied pain or had good pain tolerance models in their present family. Only a few patients reported poor tolerance models. RESULTS: Patients who had previously been subjected to medical pain experienced a greater intensity of pain. In addition, those who had reported poor tolerance in the original family experienced both earlier and more severe pain. Some patients' personality traits were related to familial pain tolerance models. CONCLUSIONS: We conclude that knowledge of an individual's pain history and familial pain tolerance models can be useful in predicting and managing post-surgical pain.

Study of the radiation environment on MIR space station with SILEYE-2 experiment.

In this work we present preliminary results of nuclear composition measurements on board space station MIR obtained with SILEYE-2 particle telescope. SILEYE-2 was placed on MIR in 1997 and has been working since then. It consists of an array of 6 active silicon strip detectors which allow nuclear and energetic identification of cosmic rays in the energy range between approximately 30 and 200 MeV/n. The device is attached to an helmet and connected to an eye mask which shields the cosmonaut eyes from light and allow studies of the Light Flashes (LF) phenomenon. In addition to the study of the causes of LF, the device is used to perform real time long term radiation environment monitoring inside the MIR, performing measurements in solar quiet and active days.

Study of cosmic rays and light flashes on board Space Station MIR: the SilEye experiment.

The SilEye experiment aims to study the cause and processes related to the anomalous Light Flashes (LF) perceived by astronauts in orbit and their relation with Cosmic Rays. These observations will be also useful in the study of the long duration manned space flight environment. Two PC-driven silicon detector telescopes have been built and placed aboard Space Station MIR. SilEye-1 was launched in 1995 and provided particles track and LF information; the data gathered indicate a linear dependence of FLF(Hz) ( 4 2) 10(3) 5.3 1.7 10(4) Fpart(Hz) if South Atlantic Anomaly fluxes are not included. Even though higher statistic is required, this is an indication that heavy ion interactions with the eye are the main LF cause. To improve quality and quantity of measurements, a second apparatus, SilEye-2, was placed on MIR in 1997, and started work from August 1998. This instrument provides energetic information, which allows nuclear identification in selected energy ranges; we present preliminary measurements of the radiation field inside MIR performed with SilEye-2 detector in June 1998.

ALTEA: anomalous long term effects in astronauts. A probe on the influence of cosmic radiation and microgravity on the central nervous system during long flights.

The ALTEA project participates to the quest for increasing the safety of manned space flights. It addresses the problems related to possible functional damage to neural cells and circuits due to particle radiation in space environment. Specifically it aims at studying the functionality of the astronauts' Central Nervous Systems (CNS) during long space flights and relating it to the peculiar environments in space, with a particular focus on the particle flux impinging in the head. The project is a large international and multidisciplinary collaboration. Competences in particle physics, neurophysiology, psychophysiology, electronics, space environment, data analyses will work together to construct the fully integrated vision electrophysiology and particle analyser system which is the core device of the project: an helmet-shaped multi-sensor device that will measure concurrently the dynamics of the functional status of the visual system and passage of each particle through the brain within a pre-determined energy window. ALTEA is scheduled to fly in the International Space Station in late 2002. One part of the multi-sensor device, one of the advanced silicon telescopes, will be launched in the ISS in early 2002 and serve as test for the final device and as discriminating dosimeter for the particle fluences within the ISS.

The ALTEA/ALTEINO projects: studying functional effects of microgravity and cosmic radiation.

The ALTEA project investigates the risks of functional brain damage induced by particle radiation in space. A modular facility (the ALTEA facility) is being implemented and will be operated in the International Space Station (ISS) to record electrophysiological and behavioral descriptors of brain function and to monitor their time dynamics and correlation with particles and space environment. The focus of the program will be on abnormal visual perceptions (often reported as "light flashes" by astronauts) and the impact on retinal and brain visual structures of particle in microgravity conditions. The facility will be made available to the international scientific community for human neurophysiological, electrophysiological and psychophysics experiments, studies on particle fluxes, and dosimetry. A precursor of ALTEA (the 'Alteino' project) helps set the experimental baseline for the ALTEA experiments, while providing novel information on the radiation environment onboard the ISS and on the brain electrophysiology of the astronauts during orbital flights. Alteino was flown to the ISS on the Soyuz TM34 as part of mission Marco Polo. Controlled ground experiments using mice and accelerator beams complete the experimental strategy of ALTEA. We present here the status of progress of the ALTEA project and preliminary results of the Alteino study on brain dynamics, particle fluxes and abnormal visual perceptions.

The ALTEA facility on the International Space Station.

The ALTEA project studies the problems related to possible functional damage to the Central Nervous System (CNS) due to particle radiation in space environment. The project is a large international and multi-disciplinary collaboration. The ALTEA instrumentation is an helmet-shaped multi-sensor device that will measure concurrently the dynamics of the functional status of the visual system and the passage of each particle through the brain within a pre-determined energy window. ALTEA is scheduled to fly in the International Space Station in February 2003. One part of the multi-sensor device, one of the advanced silicon telescopes, will be launched in the ISS in early 2002 and serve as test for the final device and as discriminating dosimeter for the particle fluences within the ISS.

Eye light flashes on the Mir space station.

The phenomenon of light flashes (LF) in eyes for people in space has been investigated onboard Mir. Data on particles hitting the eye have been collected with the SilEye detectors, and correlated with human observations. It is found that a nucleus in the radiation environment of Mir has roughly a 1% probability to cause an LF, whereas the proton probability is almost three orders of magnitude less. As a function of LET, the LF probability increases above 10 keV/micrometer, reaching about 5% at around 50 keV/micrometer.

Discovery of powerful gamma-ray flares from the Crab Nebula.

The well-known Crab Nebula is at the center of the SN1054 supernova remnant. It consists of a rotationally powered pulsar interacting with a surrounding nebula through a relativistic particle wind. The emissions originating from the pulsar and nebula have been considered to be essentially stable. Here, we report the detection of strong gamma-ray (100 mega-electron volts to 10 giga-electron volts) flares observed by the AGILE satellite in September 2010 and October 2007. In both cases, the total gamma-ray flux increased by a factor of three compared with the non-flaring flux. The flare luminosity and short time scale favor an origin near the pulsar, and we discuss Chandra Observatory x-ray and Hubble Space Telescope optical follow-up observations of the nebula. Our observations challenge standard models of nebular emission and require power-law acceleration by shock-driven plasma wave turbulence within an approximately 1-day time scale.

Detection of gamma-ray emission from the Vela pulsar wind nebula with AGILE.

Pulsars are known to power winds of relativistic particles that can produce bright nebulae by interacting with the surrounding medium. These pulsar wind nebulae are observed by their radio, optical, and x-ray emissions, and in some cases also at TeV (teraelectron volt) energies, but the lack of information in the gamma-ray band precludes drawing a comprehensive multiwavelength picture of their phenomenology and emission mechanisms. Using data from the AGILE satellite, we detected the Vela pulsar wind nebula in the energy range from 100 MeV to 3 GeV. This result constrains the particle population responsible for the GeV emission and establishes a class of gamma-ray emitters that could account for a fraction of the unidentified galactic gamma-ray sources.

Alterations to the permeability of plant and animal mitochondria submitted to Ca2+ releasing agents.

1. Mitochondria from different rat tissues and from plants were compared as regards their sensitivity towards Ca2+ in the presence of different Ca2+ releasing agents, and the phospholipase A2 activity was evaluated in the different mitochondrial preparations. 2. The mitochondria were exposed to Ca2+ and an oxidant such as t-butylhydroperoxide or diamide or to Ca2+ and inorganic phosphate, and plant mitochondria were seen to be much more resistant than liver, brain or kidney mitochondria of rats to the deleterious effects of these agents. 3. The phospholipase A2 activity is not directly involved in the alterations of the mitochondrial inner membrane permeability within the first 10 min of incubation under our experimental conditions. 4. The protection conferred by ATP and Mg2+ against Ca2+ efflux from mitochondria or the decrease in the mitochondrial transmembrane electrical potential was also observed under our experimental conditions, but cannot be attributed to an enhancement of the reacylation of lysophospholipids resulting from the phospholipase A2 activity.

Serum primary bile acids in Gilbert's syndrome.

We studied some aspects of bile acid metabolism in 25 patients affected by Gilbert's syndrome, 5 patients with hemolytic anemia, and 25 control subjects in order to assess whether bile acids as well as bilirubin are affected in unconjugated hyperbilirubinemic conditions. We measured serum cholic and chenodeoxycholic acid conjugates fasting and postprandially, the plasma disappearance of intravenously injected cholyl[1-14C]glycine, 14CO2 in breath, and 14C in stools after oral administration of the same isotope. Mean serum fasting level of conjugated cholic acid was significantly reduced in hyperbilirubinemic patients (p less than 0.01) in comparison with the controls, while the postprandial elevation was similar. The cholyl[1-14C]glycine hepatic uptake was faster in the patients with Gilbert's syndrome, but no significant difference was found as far as 14CO2 in breath and 14C in stools were concerned. Additional in vitro studies showed that increasing bilirubin concentrations displace glycocholic acid and, to a lesser extent, glycochenodeoxycholic acid from their binding to albumin, the affinity constant of the latter bile acid being 30 times greater than that of the former one. This competition between bilirubin and bile acids explains the faster hepatic uptake of cholic acid conjugates and hence their lower serum levels in unconjugated hyperbilirubinemic conditions. In addition, low levels of cholic acid conjugates, together with normal serum chenodeoxycholic acid conjugate levels, discriminate Gilbert's syndrome from other causes of hyperbilirubinemia.

High plasma levels of atrial natriuretic peptide in preascitic cirrhosis: indirect evidence of reduced natriuretic effectiveness of the peptide.

Controversial results come from spot measurements of plasma atrial natriuretic peptide (ANP) in compensated cirrhotic patients. Moreover, either blunted or exaggerated natriuresis has been described after maneuvers increasing plasma ANP. This does not make it possible to delineate the ANP effectiveness. Plasma ANP, renin activity (PRA) and aldosterone and hematocrit were serially measured (7 AM, 9 AM, 6 PM, and 11 PM) in nine preascitic cirrhotic outpatients and in nine healthy subjects on normal sodium diet (150 mmol/day) and carrying on their usual activities (mobile from 7 AM to 10 PM). Daily natriuresis was monitored the day before and during the study. In both groups, ANP peaked at the end of the recumbence period (7 AM) and declined on the assumption of the upright position, so that both ANP values of the standing period were significantly lower than the mean daily level. These fluctuations were reciprocal to PRA and hematocrit changes. Patients showed steadily elevated plasma ANP and reduced PRA (ANP mean daily level: 33.3 +/- 3.8 vs. 15.5 +/- 3.2 pg/mL, P = .004; PRA: 0.76 +/- 0.23 vs. 1.66 +/- 0.21 ng/mL/hr, P = .003). Aldosterone fluctuations and mean daily level were similar in the two groups (mean daily level: 122 +/- 11 vs. 119 +/- 9 pg/mL). Natriuresis was well adapted to the sodium intake and similar in healthy subjects (day 1: 152 +/- 11 mmol; day 2: 138 +/- 12.5 mmol) and patients (143 +/- 15 mmol; 148 +/- 29 mmol). Preascitic cirrhotic patients on a normal salt intake and carrying on their usual activities develop a new steady state requiring increased ANP levels to maintain a sodium balance.(ABSTRACT TRUNCATED AT 250 WORDS)

[Kinetics of 14C-cholic acid in the baboon under normal conditions and in cholestasis. Description and validity of a multicompartmental model]. / Cinetica dell'acido colico-14C nel barbuino in condizioni fisioloigiche e di colestasi. Descrizione e validita' di un modello multicompartimentale.

A multicompartmental model was applied to the study of the plasmatic and biliary kinetics of the 14C-Cholic acid intravenously injected into a baboon in normal and cholestatic condition. For the evaluation of transfer rates FORTAN IV procedures were used, utilizing Powell method. The degree of fitting was: in normal condition in serum 7% for free and 35% for conjugated Cholic acid, while in bile 5% and 4% respectively; in serum in cholestatic condition 7% for free and 12% for conjugates. The high degree of fitting and reliable estimation of transfer rates suggest that the multicompartmental model applied represents most likely the physio-pathological conditions studied.

Results with six "kit" radioimmunoassays for primary bile acids in human serum intercompared.

We examined six radioimmunoassay procedures for measuring primary bile acids in human serum (two 3H-labeled and four 125I-labeled). A significant (p < 0.01) correlation was observed between measurements in the assay both for cholic acid and chenodeoxycholic acid, at low and high concentrations of serum bile acids. All kits were acceptable with respect to accuracy, precision, stability, and analytical recovery. All six procedures gave similar results for chenodeoxycholic and cholic acid in sera of 80 healthy subjects; the agreement was also close when the two primary bile acids were compared with their sum in serum. Normal values ranged from 0.4 to 2.5 mumol/L for conjugated chenodeoxycholic acid and from 0.3 to 1.5 mumol/L for conjugated cholic acid. The 125I assays do not require liquid-scintillation equipment but 125I induces a decrease in the affinity constant of antibody. The sensitivity of the assays was still adequate for measuring bile acids in the serum of healthy fasting persons and liver-disease patients.