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Search Results: 1 - 10 of 325237 matches for " S. Sangiorgio "
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Anomalous double peak structure in Nb/Ni superconductor/ferromagnet tunneling DOS
P. SanGiorgio,S. Reymond,M. R. Beasley,J. H. Kwon,K. Char
Physics , 2007, DOI: 10.1103/PhysRevLett.100.237002
Abstract: We have experimentally investigated the density of states (DOS) in Nb/Ni (S/F) bilayers as a function of Ni thickness, $d_F$. Our thinnest samples show the usual DOS peak at $\pm\Delta_0$, whereas intermediate-thickness samples have an anomalous ``double-peak'' structure. For thicker samples ($d_F \geq 3.5$ nm), we see an ``inverted'' DOS which has previously only been reported in superconductor/weak-ferromagnet structures. We analyze the data using the self-consistent non-linear Usadel equation and find that we are able to quantitatively fit the features at $\pm\Delta_0$ if we include a large amount of spin-orbit scattering in the model. Interestingly, we are unable to reproduce the sub-gap structure through the addition of any parameter(s). Therefore, the observed anomalous sub-gap structure represents new physics beyond that contained in the present Usadel theory.
Design and demonstration of a quasi-monoenergetic neutron source
T. H. Joshi,S. Sangiorgio,V. Mozin,E. B. Norman,P. Sorensen,M. Foxe,G. Bench,A. Bernstein
Physics , 2014, DOI: 10.1016/j.nimb.2014.04.008
Abstract: The design of a neutron source capable of producing 24 and 70 keV neutron beams with narrow energy spread is presented. The source exploits near-threshold kinematics of the $^{7}$Li(p,n)$^{7}$Be reaction while taking advantage of the interference `notches' found in the scattering cross-sections of iron. The design was implemented and characterized at the Center for Accelerator Mass Spectrometry at Lawrence Livermore National Laboratory. Alternative filters such as vanadium and manganese are also explored and the possibility of studying the response of different materials to low-energy nuclear recoils using the resultant neutron beams is discussed.
The low-temperature energy calibration system for the CUORE bolometer array
S. Sangiorgio,L. M. Ejzak,K. M. Heeger,R. H. Maruyama,A. Nucciotti,M. Olcese,T. S. Wise,A. L. Woodcraft
Physics , 2009, DOI: 10.1063/1.3292432
Abstract: The CUORE experiment will search for neutrinoless double beta decay (0nDBD) of 130Te using an array of 988 TeO_2 bolometers operated at 10 mK in the Laboratori Nazionali del Gran Sasso (Italy). The detector is housed in a large cryogen-free cryostat cooled by pulse tubes and a high-power dilution refrigerator. The TeO_2 bolometers measure the event energies, and a precise and reliable energy calibration is critical for the successful identification of candidate 0nDBD and background events. The detector calibration system under development is based on the insertion of 12 gamma-sources that are able to move under their own weight through a set of guide tubes that route them from deployment boxes on the 300K flange down into position in the detector region inside the cryostat. The CUORE experiment poses stringent requirements on the maximum heat load on the cryostat, material radiopurity, contamination risk and the ability to fully retract the sources during normal data taking. Together with the integration into a unique cryostat, this requires careful design and unconventional solutions. We present the design, challenges, and expected performance of this low-temperature energy calibration system.
First measurement of the ionization yield of nuclear recoils in liquid argon
T. H. Joshi,S. Sangiorgio,A. Bernstein,M. Foxe,C. Hagmann,I. Jovanovic,K. Kazkaz,V. Mozin,E. B. Norman,S. V. Pereverzev,F. Rebassoo,P. Sorensen
Physics , 2014, DOI: 10.1103/PhysRevLett.112.171303
Abstract: This Letter details a measurement of the ionization yield ($Q_y$) of 6.7 keV $^{40}Ar$ atoms stopping in a liquid argon detector. The $Q_y$ of 3.6-6.3 detected $e^{-}/\mbox{keV}$, for applied electric fields in the range 240--2130 V/cm, is encouraging for the use of this detector medium to search for the signals from hypothetical dark matter particle interactions and from coherent elastic neutrino nucleus scattering. A significant dependence of $Q_y$ on the applied electric field is observed and explained in the context of ion recombination.
First demonstration of a sub-keV electron recoil energy threshold in a liquid argon ionization chamber
S. Sangiorgio,T. H. Joshi,A. Bernstein,J. Coleman,M. Foxe,C. Hagmann,I. Jovanovic,K. Kazkaz,K. Mavrokoridis,V. Mozin,S. Pereverzev,P. Sorensen
Physics , 2013, DOI: 10.1016/j.nima.2013.06.061
Abstract: We describe the first demonstration of a sub-keV electron recoil energy threshold in a dual-phase liquid argon time projection chamber. This is an important step in an effort to develop a detector capable of identifying the ionization signal resulting from nuclear recoils with energies of order a few keV and below. We obtained this result by observing the peaks in the energy spectrum at 2.82 keV and 0.27 keV, following the K- and L-shell electron capture decay of Ar-37, respectively. The Ar-37 source preparation is described in detail, since it enables calibration that may also prove useful in dark matter direct detection experiments. An internally placed Fe-55 x-ray source simultaneously provided another calibration point at 5.9 keV. We discuss the ionization yield and electron recombination in liquid argon at those three calibration energies.
Optimization of Physical Activity as a Countermeasure of Bone Loss: A 5-Year Study of Bikram Yoga Practice in Females  [PDF]
Sophia N. Sangiorgio, Arnob K. Mukherjee, Nicole W. Lau, Apurba Mukherjee, Prithwis Mukhopadhyay, Edward Ebramzadeh
Health (Health) , 2014, DOI: 10.4236/health.2014.611139
Abstract: Over the last decade, the number of people diagnosed with osteoporosis has increased dramatically due to many factors. While it has been asserted that one variable associated with preserving bone health is participation in high-impact exercises, those same exercises are also well documented to damage the hip and knee joints. Therefore, the goal of the present study was to evaluate the potential benefits of a highly regimented, low impact weight-bearing exercise, Bikram Yoga. Specifically, the bone mineral content was measured using DEXA analysis of the proximal femur and lumbar spine of nine female Bikram Yoga instructors between the ages of 30 and 59, who not only participated in a minimum of 3 classes (4.5 hours) a week, but also actively taught Bikram Yoga classes. These same participants, who remained active as instructors and practitioners, were rescanned five years later. The results of the study, which focused on the percent change in individual bone mineral density over the five-year period were as follows: the premenopausal subjects showed a mean increase in BMD of 6.6% at the femoral neck, 2.0% for the total hip, and 1.0% for the total lumbar spine. In contrast, post-menopausal subjects revealed a mean decrease in bone mineral density (BMD) of ﹣6.0%, ﹣8.1%, and ﹣5.6% in the femoral neck, total hip, and total lumbar spine, respectively. Consequently, the results of this study suggest that performing Bikram Yoga may preserve, or even perhaps, increase bone mineral density in pre-menopausal women and hence, may be an effective countermeasure for preventing osteoporosis.
Surface-sensitive macrobolometers for the identification of external charged particles
Luca Foggetta,Andrea Giuliani,Claudia Nones,Marisa Pedretti,Samuele Sangiorgio
Physics , 2009, DOI: 10.1063/1.1894608
Abstract: We report the performance of two prototype TeO2 macrobolometers, operated at ~25 mK, able to identify events due to energy deposited at the detector surface. This capability is obtained by thermally coupling thin Ge active layers to the main energy absorber of the bolometer, and is demonstrated by irradiating the detectors with alpha particles. The temperature variations of the main absorber and of the active layer are measured independently with doped Ge thermistors. These results show clearly that an intrinsic limitation of monolithic low temperature calorimeters, e.g., the impossibility to give information about event position, can be efficiently overcome using composite structures.
Domain-wall free energy in Heisenberg ferromagnets
Boris Sangiorgio,Thomas C. T. Michaels,Danilo Pescia,Alessandro Vindigni
Physics , 2013, DOI: 10.1103/PhysRevB.89.014429
Abstract: We consider Gaussian fluctuations about domain walls embedded in one- or two-dimensional spin lattices. Analytic expressions for the free energy of one domain wall are obtained. From these, the temperature dependence of experimentally relevant spatial scales -- i.e., the correlation length for spin chains and the size of magnetic domains for thin films magnetized out of plane -- are deduced. Stability of chiral order inside domain walls against thermal fluctuations is also discussed.
Spatial analysis of plant detritus processing in a Mediterranean River type: the case of the River Tirso Basin, Sardinia, Italy
Maurizio Pinna,Franca Sangiorgio,Alessio Fonnesu,Alberto Basset,
Maurizio Pinn
,Franca Sangiorgio,Alessio Fonnesu,Alberto Basset

环境科学学报(英文版) , 2003,
Abstract: The river continuum concept represents the most general framework addressing the spatial variation of both structure and function in river ecosystems. In the Mediterranean ecoregion, summer drought events and dams constitute the main sources of local disturbance to the structure and functioning of river ecosystems occurring in the river basin. In this study, we analysed patterns of spatial variation of detritus processing in a 7th order river of the Mediterranean ecoregion (River Tirso, Sardinia-Italy) and in three 4th order sub-basins which were exposed to different summer drought pressures. The study was carried out on Phragmites australis and Alnus glutinosa leaf detritus at 31 field sites in seasonal field experiment. Detritus processing rates were higher for Alnus glutinosa than for Phragmites australis plant detritus. Processing rates of Alnus glutinosa leaves varied among seasons and study sites from 0.006 d(-1) to 0.189 d(-1) and those of Phragmites australis leaves ranged from 0.0008 d(-1) to 0.102 d(-1), with the lowest values occurring at sites exposed to summer drought. Seasons and sites accounted for a significant proportion of such variability. Alder detritus decay rates generally decreased with increasing stream order, while reed detritus decay rates generally increased on the same spatial gradient. Summer drought events affected these spatial patterns of variation by influencing significantly the decay rates of both plant detritus. The comparisons among and within sub-basins showed strong negative influence of summer drought on detritus processing rates. Similarly, in the entire River Tirso basin decay rates were always lower at disturbed than at undisturbed sites for each stream order; decay rates of reed detritus remained lower at those sites even after the end of the disturbance events, while alder decay rates recovered rapidly from the summer drought perturbations. The different recovery of the processing rates of the two leaves could also explain the different patterns of spatial variation observed between the two leaves.
Measurement of Scintillation and Ionization Yield and Scintillation Pulse Shape from Nuclear Recoils in Liquid Argon
H. Cao,T. Alexander,A. Aprahamian,R. Avetisyan,H. O. Back,A. G. Cocco,F. DeJongh,G. Fiorillo,C. Galbiati,L. Grandi,Y. Guardincerri,C. Kendziora,W. H. Lippincott,C. Love,S. Lyons,L. Manenti,C. J. Martoff,Y. Meng,D. Montanari,P. Mosteiro,D. Olvitt,S. Pordes,H. Qian,B. Rossi,R. Saldanha,S. Sangiorgio,K. Siegl,S. Y. Strauss,W. Tan,J. Tatarowicz,S. Walker,H. Wang,A. W. Watson,S. Westerdale,J. Yoo
Physics , 2014, DOI: 10.1103/PhysRevD.91.092007
Abstract: We have measured the scintillation and ionization yield of recoiling nuclei in liquid argon as a function of applied electric field by exposing a dual-phase liquid argon time projection chamber (LAr-TPC) to a low energy pulsed narrow band neutron beam produced at the Notre Dame Institute for Structure and Nuclear Astrophysics. Liquid scintillation counters were arranged to detect and identify neutrons scattered in the TPC and to select the energy of the recoiling nuclei. We report measurements of the scintillation yields for nuclear recoils with energies from 10.3 to 57.3 keV and for median applied electric fields from 0 to 970 V/cm. For the ionization yields, we report measurements from 16.9 to 57.3 keV and for electric fields from 96.4 to 486 V/cm. We also report the observation of an anticorrelation between scintillation and ionization from nuclear recoils, which is similar to the anticorrelation between scintillation and ionization from electron recoils. Assuming that the energy loss partitions into excitons and ion pairs from $^{83m}$Kr internal conversion electrons is comparable to that from $^{207}$Bi conversion electrons, we obtained the numbers of excitons ($N_{ex}$) and ion pairs ($N_i$) and their ratio ($N_{ex}/N_i$) produced by nuclear recoils from 16.9 to 57.3 keV. Motivated by arguments suggesting direction sensitivity in LAr-TPC signals due to columnar recombination, a comparison of the light and charge yield of recoils parallel and perpendicular to the applied electric field is presented for the first time.
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