900 resultados para EPITHERMAL NEUTRON-SPECTRUM
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Abstract Background Eating disorder (ED) patients often have comorbidities with other psychiatric disorders, especially with mood disorders. Although recent studies suggest an intimate relationship between ED and bipolar disorder (BD), the study on a broader bipolar spectrum definition has not been done in this population. We aimed to study the occurrence of bipolar spectrum (BS) and comorbidities in eating disorder patients of a tertiary service provider. Methods Sixty-nine female patients diagnosed with anorexia nervosa, bulimia nervosa, or eating disorder not otherwise specified were evaluated. The assessment comprised the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I), clinical criteria for diagnosis of the Zurich bipolar spectrum. Mann–Whitney tests compared means of continuous variables. The association between categorical variables and the groups was described using contingency tables and analyzed using the chi-square or Fisher's exact test. The level of significance alpha was set at 5%. Results The results showed that 68.1% of patients had comorbidity with bipolar spectrum, and this was associated with higher family income, proportion of married people, and comorbidity with substance use. The ED with BS group showed higher rates of substance use comorbidity (40.4%) than the ED without BS group (13.6%). Discussion These results showed that the bipolar spectrum is a common comorbidity in patients with eating disorders and is associated with correlates of clinical importance, notably the comorbidity with substance use. Due to the pattern of similarity between the groups with and without comorbid bipolar spectrum in relation to various outcomes evaluated, the identification of comorbidity can be difficult. However, the precise diagnosis and careful identification of clinical correlates may contribute to future advances in treating these conditions. Further studies are necessary to evaluate the association of other clinical correlates and its possible causal association.
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The complex formed by the tetracycline (TC) molecule with the Mg ion is able to prevent the replication of the genetic material in the bacterial ribosome, making an excellent antibiotic. In general, the absorption and emission spectra of TC are very sensitive to the host ions and the pH of the solvent that the set is immersed. However, the theoretical absorption spectrum available in the literature is scarce and limited to simple models that do not consider the fluctuations of the liquid. Our aim is to obtain the electronic absorption spectrum of TC and the complex Mg:TC in the ratio 1:1 and 2:1. Moreover, we analyze the changes in intensity and shifts of the bands in the systems listed. We performed the simulation using the classical Monte Carlo technique with the Lennard-Jones plus Coulomb potential applied to each atom of the both TC molecule and the Mg:TC complexes in water. The electronic absorption spectrum was obtained from the time-dependent density functional theory using different solvent models. In general, we obtained a good qualitative description of the spectra when compared with the experimental results. The Mg atom shifts the first band by 4 nm in our models, in excellent agreement to the experimental result of 4 nm. The second absorption band is found here to be useful for the characterization of the position where the ion attaches to the TC.
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Single and double strand breaks in DNA can be caused by low-energy electrons, the most abundant secondary products of the interaction of ionizing radiation to the biological matter. Attachment of these electrons to biomolecules lead to the formation of transient negative ions (TNIs) [1], often referred to as resonances, a process that may lead to significant vibrational excitation and dissociation. In the present study, we employ the parallel version [2] of the Schwinger Multichannel Method implemented with pseudopotentials [3] to obtain the shape resonance spectrum of cytosine-guanine (CG) pairs, with special attention to π* transient anion states. Recent experimental studies pointed out a quasi-continuum vibrational excitation spectrum for electron collisions against formic acid dimers [4], suggesting that electron attachment into π* valence orbitals could induce proton transfer in these dimers. In addition, our previous studies on the shape resonance spectra of the hydrogen-bonded complexes comprising formic acid and formamide units indicated interesting electron delocalization (localization) effects arising from the presence (absence) of inversion symmetry centers in the complexes [5]. In the present work, we extend the studies on hydrogen-bonded complexes to the CG pair, where localization of ¼¤ anions would be expected, based on the previous results. References [1]. B. Boudaïffa, P. Cloutier, D. Hunting, M. A. Huels, L. Sanche, Science 287, 1658 (2000). [2]. J. S. dos Santos, R. F. da Costa , M. T. do N. Varella, J. Chem. Phys. 136, 084307 (2012). [3]. M. H. F. Bettega, L. G. Ferreira, M. A. P. Lima, Phys. Rev. A 47, 1111 (1993). [4]. M. Allan, Phys. Rev. Lett. 98, 123201 (2007). [5]. T. C. Freitas, S. dA. Sanchez, M. T. do N. Varella, M. H. F. Bettega, Phys. Rev. A 84, 062714 (2011).
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Context. HD140283 is a nearby (V = 7:7) subgiant metal-poor star, extensively analysed in the literature. Although many spectra have been obtained for this star, none showed a signal-to-noise (S/N) ratio high enough to enable a very accurate derivation of abundances from weak lines. Aims. The detection of europium proves that the neutron-capture elements in this star originate in the r-process, and not in the s-process, as recently claimed in the literature. Methods. Based on the OSMARCS 1D LTE atmospheric model and with a consistent approach based on the spectrum synthesis code Turbospectrum, we measured the europium lines at 4129 Å and 4205 Å, taking into account the hyperfine structure of the transitions. The spectrum, obtained with a long exposure time of seven hours at the Canada-France-Hawaii Telescope (CFHT), has a resolving power of 81 000 and a S/N ratio of 800 at 4100 Å. Results. We were able to determine the abundance A(Eu) =
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Objective To compare autoantibody features in patients with primary biliary cirrhosis (PBC) and individuals presenting antimitochondria antibodies (AMAs) but no clinical or biochemical evidence of disease. Methods A total of 212 AMA-positive serum samples were classified into four groups: PBC (definite PBC, n = 93); PBC/autoimmune disease (AID; PBC plus other AID, n = 37); biochemically normal (BN) individuals (n = 61); and BN/AID (BN plus other AID, n = 21). Samples were tested by indirect immunofluorescence (IIF) on rat kidney (IIF-AMA) and ELISA [antibodies to pyruvate dehydrogenase E2-complex (PDC-E2), gp-210, Sp-100, and CENP-A/B]. AMA isotype was determined by IIF-AMA. Affinity of anti-PDC-E2 IgG was determined by 8 M urea-modified ELISA. Results High-titer IIF-AMA was more frequent in PBC and PBC/AID (57 and 70 %) than in BN and BN/AID samples (23 and 19 %) (p < 0.001). Triple isotype IIF-AMA (IgA/IgM/IgG) was more frequent in PBC and PBC/AID samples (35 and 43 %) than in BN sample (18 %; p = 0.008; p = 0.013, respectively). Anti-PDC-E2 levels were higher in PBC (mean 3.82; 95 % CI 3.36–4.29) and PBC/AID samples (3.89; 3.15–4.63) than in BN (2.43; 1.92–2.94) and BN/AID samples (2.52; 1.54–3.50) (p < 0.001). Anti-PDC-E2 avidity was higher in PBC (mean 64.5 %; 95 % CI 57.5–71.5 %) and PBC/AID samples (66.1 %; 54.4–77.8 %) than in BN samples (39.2 %; 30.9–37.5 %) (p < 0.001). PBC and PBC/AID recognized more cell domains (mitochondria, nuclear envelope, PML/sp-100 bodies, centromere) than BN (p = 0.008) and BN/AID samples (p = 0.002). Three variables were independently associated with established PBC: high-avidity anti-PDC-E2 (OR 4.121; 95 % CI 2.118–8.019); high-titer IIF-AMA (OR 4.890; 2.319–10.314); antibodies to three or more antigenic cell domains (OR 9.414; 1.924–46.060). Conclusion The autoantibody profile was quantitatively and qualitatively more robust in definite PBC as compared with AMA-positive biochemically normal individuals.
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A systematic study of the response of different nuclei to the (18O, 16O) two-neutron transfer reaction at 84 MeV incident energy was pursued at the INFN-LNS in Catania (Italy). The experiments were performed using several solid targets from light (9Bc, 11 B, 12,13C, 16O, 28Si) to heavier ones (58,64Ni, 120Sn, 208Pb). The 16O ejectiles were detected at forward angles by the MAGNEX magnetic spectrometer and identified without the need of time of flight measurements. Exploiting the large momentum (≈ 25%) and angular (50 msr) acceptance of the spectrometer, energy spectra were obtained with a relevant yield up to about 20 MeV excitation energy. A common feature of the light nuclei spectra is the strong population of states with well known configuration of two-particle over a core and the appearance of unknown resonant structures in the continuum. These latter can reveal the excitation of a collective mode connected with the transfer of a pair. For the heavier nuclei as 66Ni a completely different behaviour is observed indicating the presence of more dissipative processes in the reaction mechanisms that hide the spectroscopic information.
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During the last decade advances in the field of sensor design and improved base materials have pushed the radiation hardness of the current silicon detector technology to impressive performance. It should allow operation of the tracking systems of the Large Hadron Collider (LHC) experiments at nominal luminosity (1034 cm-2s-1) for about 10 years. The current silicon detectors are unable to cope with such an environment. Silicon carbide (SiC), which has recently been recognized as potentially radiation hard, is now studied. In this work it was analyzed the effect of high energy neutron irradiation on 4H-SiC particle detectors. Schottky and junction particle detectors were irradiated with 1 MeV neutrons up to fluence of 1016 cm-2. It is well known that the degradation of the detectors with irradiation, independently of the structure used for their realization, is caused by lattice defects, like creation of point-like defect, dopant deactivation and dead layer formation and that a crucial aspect for the understanding of the defect kinetics at a microscopic level is the correct identification of the crystal defects in terms of their electrical activity. In order to clarify the defect kinetic it were carried out a thermal transient spectroscopy (DLTS and PICTS) analysis of different samples irradiated at increasing fluences. The defect evolution was correlated with the transport properties of the irradiated detector, always comparing with the un-irradiated one. The charge collection efficiency degradation of Schottky detectors induced by neutron irradiation was related to the increasing concentration of defects as function of the neutron fluence.
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In this thesis, numerical methods aiming at determining the eigenfunctions, their adjoint and the corresponding eigenvalues of the two-group neutron diffusion equations representing any heterogeneous system are investigated. First, the classical power iteration method is modified so that the calculation of modes higher than the fundamental mode is possible. Thereafter, the Explicitly-Restarted Arnoldi method, belonging to the class of Krylov subspace methods, is touched upon. Although the modified power iteration method is a computationally-expensive algorithm, its main advantage is its robustness, i.e. the method always converges to the desired eigenfunctions without any need from the user to set up any parameter in the algorithm. On the other hand, the Arnoldi method, which requires some parameters to be defined by the user, is a very efficient method for calculating eigenfunctions of large sparse system of equations with a minimum computational effort. These methods are thereafter used for off-line analysis of the stability of Boiling Water Reactors. Since several oscillation modes are usually excited (global and regional oscillations) when unstable conditions are encountered, the characterization of the stability of the reactor using for instance the Decay Ratio as a stability indicator might be difficult if the contribution from each of the modes are not separated from each other. Such a modal decomposition is applied to a stability test performed at the Swedish Ringhals-1 unit in September 2002, after the use of the Arnoldi method for pre-calculating the different eigenmodes of the neutron flux throughout the reactor. The modal decomposition clearly demonstrates the excitation of both the global and regional oscillations. Furthermore, such oscillations are found to be intermittent with a time-varying phase shift between the first and second azimuthal modes.
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Electromagnetic spectrum can be identified as a resource for the designer, as well as for the manufacturer, from two complementary points of view: first, because it is a good in great demand by many different kind of applications; second, because despite its scarce availability, it may be advantageous to use more spectrum than necessary. This is the case of Spread-Spectrum Systems, those systems in which the transmitted signal is spread over a wide frequency band, much wider, in fact, than the minimum bandwidth required to transmit the information being sent. Part I of this dissertation deals with Spread-Spectrum Clock Generators (SSCG) aiming at reducing Electro Magnetic Interference (EMI) of clock signals in integrated circuits (IC) design. In particular, the modulation of the clock and the consequent spreading of its spectrum are obtained through a random modulating signal outputted by a chaotic map, i.e. a discrete-time dynamical system showing chaotic behavior. The advantages offered by this kind of modulation are highlighted. Three different prototypes of chaos-based SSCG are presented in all their aspects: design, simulation, and post-fabrication measurements. The third one, operating at a frequency equal to 3GHz, aims at being applied to Serial ATA, standard de facto for fast data transmission to and from Hard Disk Drives. The most extreme example of spread-spectrum signalling is the emerging ultra-wideband (UWB) technology, which proposes the use of large sections of the radio spectrum at low amplitudes to transmit high-bandwidth digital data. In part II of the dissertation, two UWB applications are presented, both dealing with the advantages as well as with the challenges of a wide-band system, namely: a chaos-based sequence generation method for reducing Multiple Access Interference (MAI) in Direct Sequence UWB Wireless-Sensor-Networks (WSNs), and design and simulations of a Low-Noise Amplifier (LNA) for impulse radio UWB. This latter topic was studied during a study-abroad period in collaboration with Delft University of Technology, Delft, Netherlands.
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The present PhD thesis summarizes the three-years study about the neutronic investigation of a new concept nuclear reactor aiming at the optimization and the sustainable management of nuclear fuel in a possible European scenario. A new generation nuclear reactor for the nuclear reinassance is indeed desired by the actual industrialized world, both for the solution of the energetic question arising from the continuously growing energy demand together with the corresponding reduction of oil availability, and the environment question for a sustainable energy source free from Long Lived Radioisotopes and therefore geological repositories. Among the Generation IV candidate typologies, the Lead Fast Reactor concept has been pursued, being the one top rated in sustainability. The European Lead-cooled SYstem (ELSY) has been at first investigated. The neutronic analysis of the ELSY core has been performed via deterministic analysis by means of the ERANOS code, in order to retrieve a stable configuration for the overall design of the reactor. Further analyses have been carried out by means of the Monte Carlo general purpose transport code MCNP, in order to check the former one and to define an exact model of the system. An innovative system of absorbers has been conceptualized and designed for both the reactivity compensation and regulation of the core due to cycle swing, as well as for safety in order to guarantee the cold shutdown of the system in case of accident. Aiming at the sustainability of nuclear energy, the steady-state nuclear equilibrium has been investigated and generalized into the definition of the ``extended'' equilibrium state. According to this, the Adiabatic Reactor Theory has been developed, together with a New Paradigm for Nuclear Power: in order to design a reactor that does not exchange with the environment anything valuable (thus the term ``adiabatic''), in the sense of both Plutonium and Minor Actinides, it is required indeed to revert the logical design scheme of nuclear cores, starting from the definition of the equilibrium composition of the fuel and submitting to the latter the whole core design. The New Paradigm has been applied then to the core design of an Adiabatic Lead Fast Reactor complying with the ELSY overall system layout. A complete core characterization has been done in order to asses criticality and power flattening; a preliminary evaluation of the main safety parameters has been also done to verify the viability of the system. Burn up calculations have been then performed in order to investigate the operating cycle for the Adiabatic Lead Fast Reactor; the fuel performances have been therefore extracted and inserted in a more general analysis for an European scenario. The present nuclear reactors fleet has been modeled and its evolution simulated by means of the COSI code in order to investigate the materials fluxes to be managed in the European region. Different plausible scenarios have been identified to forecast the evolution of the European nuclear energy production, including the one involving the introduction of Adiabatic Lead Fast Reactors, and compared to better analyze the advantages introduced by the adoption of new concept reactors. At last, since both ELSY and the ALFR represent new concept systems based upon innovative solutions, the neutronic design of a demonstrator reactor has been carried out: such a system is intended to prove the viability of technology to be implemented in the First-of-a-Kind industrial power plant, with the aim at attesting the general strategy to use, to the largest extent. It was chosen then to base the DEMO design upon a compromise between demonstration of developed technology and testing of emerging technology in order to significantly subserve the purpose of reducing uncertainties about construction and licensing, both validating ELSY/ALFR main features and performances, and to qualify numerical codes and tools.
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Zusammenfassung Um zu einem besseren Verständnis des Prozesses der Biomineralisation zu gelangen, muss das Zusammenwirken der verschiedenen Typen biologischer Makromoleküle, die am Keimbildungs- und Wachstumsprozess der Minerale beteiligt sind, berücksichtigt werden. In dieser Arbeit wird ein neues Modellsystem eingeführt, das aus einem SAM (self-assembled monolayer) mit verschiedenen Funktionalitäten und unterschiedlichen, gelösten Makromolekülen besteht. Es konnte gezeigt werden, dass die Kristallisation von Vaterit (CaCO3) sowie Strontianit (SrCO3) Nanodrähten der Präsenz von Polyacrylat in Kooperation mit einer COOH-funktionalisierten SAM-Oberfläche zugeschrieben werden kann. Die Kombination bestehend aus einer polaren SAM-Oberfläche und Polyacrylat fungiert als Grenzfläche für die Struktur dirigierende Kristallisation von Nanodraht-Kristallen. Weiter konnte gezeigt werden, dass die Phasenselektion von CaCO3 durch die kooperative Wechselwirkung zwischen einer SAM-Oberfläche und einem daran adsorbierten hb-Polyglycerol kontrolliert wird. Auch die Funktionalität einer SAM-Oberfläche in Gegenwart von Carboxymethyl-cellulose übt einen entscheidenden Einfluss auf die Phasenselektion des entstehenden Produktes aus. In der vorliegenden Arbeit wurden Untersuchungen an CaCO3 zur homogenen Keimbildung, zur Nukleation in Gegenwart eines Proteins sowie auf Kolloiden, die als Template fungieren, mittels Kleinwinkel-Neutronenstreuung durchgeführt. Die homogene Kristallisation in wässriger Lösung stellte sich als ein mehrstufiger Prozess heraus. In Gegenwart des Eiweißproteins Ovalbumin konnten drei Phasen identifiziert werden, darunter eine anfänglich vorhandene amorphe sowie zwei kristalline Phasen.
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In dieser Arbeit wird zum Erreichen hoher Kernspinpolarisationen die Methode des metastabilen optischen Pumpens benutzt. Das Verfahren beruht auf dem "Ubertrag des Drehimpulses absorbierter Photonen auf das hierbei angeregte Valenzelektron, welches durch Hyperfeinkopplung den Drehimpuls weiter auf den $^3$He-Kern transferiert. Da der Polarisationsprozess nur bei Dr"ucken von ca. 1~mbar effizient funktioniert, f"ur die meisten Anwendungen aber polarisiertes $^3$He bei einem Druck von $geq 1$~bar ben"otigt wird, muss das Gas nach der Aufpolarisation komprimiert werden. In unserer Arbeitsgruppe steht eine Maschine ("`Polarisator"') zur Verf"ugung, die das Gas polarisiert und anschlie"send komprimiert. Ziel dieser Dissertation ist, einerseits die Leistungsf"ahigkeit des Polarisators bez"uglich Maximalpolarisation und Gasfluss zu verbessern und andererseits den metastabilen Pumpprozess selbst genauer zu untersuchen.\ noindent Durch die Verwendung neuer Laser auf Basis der Fasertechnologie sowie einer systematischen Optimierung der optischen Komponenten konnten in abgeschlossenen Pumpzellen Rekord-Polarisationsgrade von $91pm 2$% erzielt werden.\ noindent Mit der Implementierung neuartiger Optiken und Laser am Mainzer Polarisator konnte die Leistungscharakteristik entscheidend verbessert werden. So wurde die erreichbare Polarisation bei identischer Produktionsrate um 20 Prozentpunkte gesteigert. Zurzeit sind maximale Polarisationsgrade von mehr als 75% im optischen Pumpvolumen erreichbar. Eine am Mainzer Triga-Reaktor durchgef"uhrte Polarisationsbestimmung ergab einen Wert von $72.7pm 0.7$%. Dies veranschaulicht die geringen Polarisationsverluste infolge der Gaskompression, des Transports und einer Lagerung "uber mehrere Stunden.\ noindent Zur Dynamik der geschwindigkeitsver"andernden St"o"se sowie zur Bestimmung der mittleren Photonen-Absorptionsrate wurde ein Modell entwickelt, welches auch experimentell best"atigt wurde. Damit konnte erstmalig das gemessene Absorptionsverhalten einer spektral schmalbandigen Laserdiode korrekt beschrieben werden.\ noindent Zudem stimmen die an so genannten abgeschlossenen Pumpzellen gemessenen extrem hohen Polarisationswerte mit theoretischen Vorhersagen "uberein, sofern der Druck im optischen Pumpvolumen geringer als 1~mbar ist und das $^3$He nicht durch Fremdgase verunreinigt ist. Bei derartigen Pumpzellen ist die gemessene Abh"angigkeit der Polarisation von Laserleistung, Metastabilendichte und falscher Zirkularkomponente mit der Theorie kompatibel.\
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Im Jahre 1997 wurden von Tatischeff et al. bei der Reaktion p p -> X p pi+ resonanzartige Zustände im Spektrum der invarianten Masse des fehlenden Nukleons X bei M = 1004, 1044 und 1094 MeV gefunden. In einem zweiten Experiment von Filkov et al. beobachtete man bei der Reaktion p d -> p p X Resonanzstrukturen bei M = 966, 986 und 1003 MeV. Solche exotischen Resonanzen widersprechen etablierten Nukleonenmodellen, die die Delta(1232)-Resonanz als ersten Anregungszustand beschreiben. Zur Deutung der beobachteten Strukturen wurden Quarkcluster-Modelle mit und ohne Farb-Magnet-Wechselwirkungen entwickelt. Lvov et al. zweifelten die experimentellen Ergebnisse an, da keine Strukturen in den Daten zur reellen Comptonstreuung gefunden wurden. Als Gegenargument wurde von Kobushkin vorgeschlagen, dass diese Resonanzen eine total-antisymmetrische Spin-Flavour-Wellenfunktion haben und nur der N-2Gamma-Zerfall erlaubt wäre. In dieser Arbeit wurde die Reaktion g p -> X pi+ -> n g g pi+ zur Suche nach diesen exotischen Resonanzen verwendet. Die Daten wurden parallel zur Messung der Pion-Polarisierbarkeiten am Mainzer Beschleuniger MAMI genommen. Durch Bremsstrahlung der Elektronen an einer Radiatorfolie wurden reelle Photonen erzeugt, deren Energie von der A2-Photonenmarkierungsanlage (Glasgow-Tagger) bestimmt wurde. Als Protontarget wurde ein 10 cm langes Flüssigwasserstoff-Target verwendet. Geladene Reaktionsprodukte wurden unter Vorwärtswinkeln Theta < 20 Grad bezüglich der Strahlachse in einer Vieldraht-Proportionalkammer nachgewiesen, während Photonen im Spektrometer TAPS mit 526 BaF2-Kristallen unter Polarwinkeln Theta > 60 Grad detektiert wurden. Zum Nachweis von Neutronen stand ein Flugzeitdetektor mit insgesamt 111 Einzelmodulen zur Verfügung. Zum Test der Analysesoftware und des experimentellen Aufbaus wurden zusätzlich die Reaktionskanäle g p -> p pi0 und g p -> n pi0 pi+ ausgewertet. Für die Ein-Pion-Produktion wurden differentielle Wirkungsquerschnitte unter Rückwärtswinkeln bestimmt und mit theoretischen Modellen und experimentellen Werten verglichen. Für den Kanal g p -> n pi0 pi+ wurden Spektren invarianter Massen für verschiedene Teilchenkombinationen ermittelt und mit einer Simulation verglichen. Die Daten legen nahe, dass die Reaktion hauptsächlich über eine Anregung der Delta0(1232)-Resonanz verläuft. Bei der Suche nach exotischen Resonanzen wurden keine statistisch signifikanten Strukturen gefunden. Es wurden Obergrenzen für den differentiellen Wirkungsquerschnitt ermittelt.