228 research outputs found
Phonon-induced spin relaxation of conduction electrons in silicon crystals
No full textExperimental works managing electrical injection
of spin polarization in n-type and p-type silicon have been
recently carried out up to room-temperature. In spite of these
promising experimental results, a comprehensive theoretical
framework concerning the influence of transport conditions on
phonon-induced electron spin depolarization in silicon structures,
in a wide range of values of lattice temperature, doping
concentration and amplitude of external fields, is still at a
developing stage. In order to investigate the spin transport of
conduction electrons in lightly doped n-type Si crystals, a set of
semiclassical multiparticle Monte Carlo simulations has been
carried out. The mean spin depolarization time and length of
drifting electrons, heated by an electric field, have been
calculated. A good agreement is found between our numerical
findings and those computed by using different theoretical
approaches and recent experimental results obtained in spin
transport devices. Our Monte Carlo outcomes, in ranges of
temperature and field amplitude yet unexplored, can be used as a
guide for future experimental studies oriented towards a more
effective optimization of room-temperature silicon-based
spintronic devices
ELECTRON SPIN RELAXATION PROCESS IN SILICON CRYSTALS
No full textRecently, electrical injection of spin polarization in n-type and p-type silicon has been experimentally carried out up to room-temperature. Despite of these preliminary but promising experimental results, a comprehensive theoretical framework concerning the influence of transport conditions on the phonon-induced spin depolarization process in silicon structures, in a wide range of values of temperature, doping concentration and amplitude of external fields, is still in a developing stage. In order to elucidate the electron transport and spin dynamics of conduction electrons in lightly doped n-type Si crystals we have performed semiclassical multiparticle Monte Carlo simulations and numerically calculated the spin lifetimes of drifting electrons heated by the electric field. Spin flipping is taken into account through the Elliot-Yafet mechanism, which is dominant in group IV materials. We discuss the influence of different intravalley and intervalley phonon interactions in the spin relaxation process during the spin transport. Our findings are in good agreement with those obtained by using different theoretical approaches and with the most recent experimental results obtained in spin transport devices. Moreover, our Monte Carlo predictions, in ranges of temperature and field amplitude yet unexplored, can be used as a guide for future experimental studies oriented towards a more effective optimization of room-temperature silicon-based spintronic devices
Phonon-induced spin depolarization of conduction electrons in silicon crystals
No full textIn last decade the process of spin relaxation of conduction electrons in semiconductor structures has been widely investigated, in order to use spin polarization as information carrier [1]. However, each initial non-equilibrium orientation decays over time during the transport. Thus, to make feasible the implementation of spin-based electronic devices, the features of spin relaxation at relatively high temperatures, jointly with the influence of transport conditions, should be fully understood [1]. Electrical injection of spin polarization in silicon structures up to room temperature has been experimentally carried out [2]. Despite these promising experimental results, a comprehensive theoretical framework accounting for the spin depolarization process in silicon crystals, in a wide range of temperature values, doping concentration, and amplitude of external fields, is still in a developing stage [3-4].
Here, by using a semiclassical multiparticle Monte Carlo (MC) approach, we simulate spin transport in lightly doped n-type Si samples and calculate the spin lifetimes of conduction electrons. Spin flipping is taken into account through the Elliot-Yafet mechanism, which is dominant in group IV materials
Lettere 1936-1963
No full textAuthor of Architettura del medioevo in Sardegna which won him the Premio Nazionale Olivetti in 1956, Raffaello Delogu was an art historian and Commissioner for Antiquities and Monuments in Sardinia, Abruzzo and Sicily. His correspondence with one of the most eminent Italian writers of the second half of the twentieth century, as transcribed and lavishly annotated here by Monica Graceffa, reveals him not only as a committed intellectual devoted to the study of ancient and modern art, but also as a caustic and playful friend. His dialogue with Giuseppe Dessí commenced in their youth, when Dessí was an amateur painter on the way to maturity, who instead rapidly developed into a mature writer and attentive connoisseur of all forms of art. In addition to their studies and mutual friends (including Claudio Varese and Maria Lai), they also shared an interest in painting and in what Dessí was experiencing (his moves, his political passion) and what he was writing (fiction, drama, essays); important in this regard are the letters touching on the collaboration of both on the Sardinian issue of Pietro Calamandrei's «Il Ponte»
Pathways of Self-Determination: A Constructivist Grounded Theory Study of Slut-shaming Vulnerability in a Group of Young Adults
No full textSlut-shaming is a sexual stigmatization that consists in a form of discrimination
against those who do not respect gender stereotypes of external appearance and/
or sexual behaviors and attitudes. Individuals may also be exposed to slut-shaming
merely due to fortuitous elements unrelated to the sexual dimension. Slut-sham ing is perpetrated through ostracism, rejection and sexual stigmatization and may
have negative efects on psychophysical well-being. The primary aim of the pre sent study is to explore the victimization of young adults through slut-shaming. A
sample of thirty-six participants (aged 19–28) was recruited and focus groups and
interviews were conducted to explore participants’ slut-shaming experiences. Con structivist grounded theory was employed to understand how young adults deal with
slut-shaming and analyze sociocultural factors involved in slut-shaming dynamics.
Several individual, social and cultural factors are involved in sexual stigmatization
processes. A core set of 6 categories related to slut-shaming exposure was identifed:
exposure to slut-shaming, antecedents of slut-shaming, socio-cultural context facili tating slut-shaming, LGBTQIA+and slut-shaming, negative efects of slut-sham ing, and reactions to slut-shaming. Results emphasized that, even if young adults
showed a generally high level of awareness of sexual discrimination and stigmati zation processes, slut-shaming victimization is not uniformly experienced by them.
Young adults’ narratives seem to show conficting feelings and thoughts regarding
the possible strategies that could be employed to deal with slut-shaming exposure and pervasive internal and external forms of oppression
Impressive objective response to nab-paclitaxel plus trastuzumab as fifth line therapy in aelderly her2-positive breast cancer patient
No full textAgent targeting HER-2 pathway plus chemotherapy has represented a major progress in the management of patients with breast cancer. However the role of late-line treatment in heavily pretreated patients is largely unclear. In the last decade nab-paclitaxel has show significant activity and good toxicity profile in metastatic breast cancer. We report the case of a 76-year-old Caucasian woman with metastatic HER-2 positive ductal infiltrating breast carcinoma treated with a combination of weekly nab-paclitaxel and trastuzumab as fifth-line therapy. She had previously received first-line paclitaxel and trastuzumab, second-line vinorelbine and trastuzumab, third-line TDM1 and fourth-line oral capecitabine and lapatinib. Clinical and radiological staging showed progression at bone, skin and soft-Tissue. The patients received weekly nab-paclitaxel plus trastuzumab. Massive objective response was clinically and PET documented which lasted 8 months. Tolerance to treatment was fairly good as well as cardiac safety. To the best of our knowledge, this is the first reported case of efficacy of nab-paclitaxel in combination with trastuzumab as fifth-line of treatment in a patient with metastatic HER-2 positive breast cancer
Lapatinib activity in a patient with encephalic metastases from trastuzumab-resistant her-2 positive breast cancer
No full textA 42-year-old woman with right breast cancer cT4dN2M0 HR +, HER2 +, undergoes mastectomy with axillary lymphadenectomy after neoadjuvant chemotherapy. During adjuvant treatment with trastuzumab and hormone therapy, the patient develops multiple symptomatic encephalic metastases. She undergoes panencephalic radiotherapy and begins chemotherapy with capecitabine and lapatinib. After three months of well tolerated therapy, an important volumetric response of encephalic metastases is observed, with regression of neurological symptoms
Validity of needle core biopsy in the histological characterisation of mammary lesions
No full textOver the last few years, there has been an enormous increase in the use of needle core biopsy (CB) for the histopathological characterisation of suspect lesions of the breast. The aim of this study was to verify the diagnostic reliability of CB by comparing the histological results obtained with the use of this technique with those obtained from the whole of the surgically resected specimen. We studied 198 out of 426 patients with clinically and/or radiologically suspect breast lesions. We found correspondence between the histological examination of the whole of the excised specimen and that of the CB in 94.9% of the cases of infiltrating carcinoma and in 71.4% of those involving ductal carcinomas in situ. The predictive value of CB was 98.9%, sensitivity was 96.1% and specificity 93.3%. These results confirmed that CB is an extremely reliable diagnostic tool in the definition of breast lesions
Verbal working memory deficit in Parkinson's disease subjects
No full textThe aim of the present work was to evaluate verbal working memory in patients affected by Parkinson's disease (PD). In particular, tests that explore the functionality of the Articulatory Loop and of the Central Executive during verbal tasks were given. PD patients displayed normal phonological similarity, word length and word frequency effects in a Word span task, thus demonstrating adequate retention capacity of the phonological store, normal functioning of the articulatory rehearsal mechanism and a normal contribution of lexical-semantic knowledge to verbal immediate recall. In the Brown-Peterson task, PD patients showed abnormal performance decay on the letter recall task when articulatory rehearsal was inhibited by a serial subtraction concurrent task. These data provide evidence for normal functioning of the Articulatory Loop in PD patients. However, when the verbal recall task is more attention demanding, PD patients show deficient performance levels, presumably due to depleted processing resources by the Central Executive
Role of the complement system in rheumatoid arthritis and psoriatic arthritis: Relationship with anti-TNF inhibitors
No full textThe complement system is an essential component of innate immunity and also plays an important role in modulating adaptive immunity. It comprises more than 30 plasma and membrane-bound proteins and can be activated through three pathways: the classical, the alternative and the lectin pathways. Its activation contributes to the pathogenesis of several autoimmune and inflammatory conditions. The evidence of complement activation in synovial fluid of Rheumatoid Arthritis (RA) patients is abundant, while few data exist in Psoriatic Arthritis (PsA) patients. Levels of complement proteins are generally depressed in the synovial fluid of patients with RA, reflecting consumption of complement. On the other hand, elevated levels of several complement cleavage products have been observed in synovial fluid. Involvement of complement in the pathogenesis of RA was also confirmed in animal models of arthritis: mice deficient for complement proteins are protected against the development of collagen-induced arthritis and administration of the anti-C5 monoclonal antibody prevents the onset of this arthritis. In the last decade anti-tumor necrosis factor agents have shown to be effective for the treatment of both RA and PsA and some studies suggest that the interaction between TNF alpha and complement system may contribute to the pathogenesis of these diseases. Reduction of the complement activation could be one of the mechanism by which TNF alpha-inhibitors exert their effectiveness in inflammatory arthritides. Because of these findings, complement could be an attractive therapeutic target both in RA and in PsA. (C) 2011 Elsevier B.V. All rights reserved
- …
