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Fano resonance is a fundamental physical process that strongly affects the electronic transport, optical, and vibronic properties of matter. Here, we provide the first experimental demonstration of its profound effect on spin properties in semiconductor nanostructures. We show that electron spin generation in InAs/GaAs quantum-dot structures is completely quenched upon spin injection from adjacent InGaAs wetting layers at the Fano resonance due to coupling of light-hole excitons and the heavy-hole continuum of the interband optical transitions, mediated by an anisotropic exchange interaction. Using a master equation approach, we show that such quenching of spin generation is robust and independent of Fano parameters. This work therefore identifies spin-dependent Fano resonance as a universal spin loss channel in quantum-dot systems with an inherent symmetry-breaking effect.
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A 66-year-old male patient presented to the ophthalmology department with bilateral blurred vision, which had persisted for 1 week. Due to a pulmonary melanoma metastasis, the patient received a combination treatment with dabrafenib and trametinib. At the first presentation visual acuity was 1.2 on the right and 1.0 on the left. A normotensive intraocular pressure was measured in both eyes. Fundoscopy showed bilateral white, areolar alterations in the choroid and choroid folds and in the left eye a bullous choroidal detachment. Bilateral neurosensory detachment and subretinal fluid were found in optical coherence tomography (OCT). After reduction of the local treatment for pressure reduction and under local and systemic anti-inflammatory treatment, the choroidal swelling was progressive, the visual acuity dropped to 0.5 in the right and to 0.1 in the left eye. A significant regression of the findings occurred only after pausing the treatment with trametinib. Visual acuity rose to 1.0 (left) and 0.8 (right). The OCT showed a dry macula on the right and a small amount of residual subretinal fluid in the left eye.
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Doenças da Coroide , Inibidores de Proteínas Quinases/efeitos adversos , Descolamento Retiniano , Idoso , Corioide , Doenças da Coroide/induzido quimicamente , Angiofluoresceinografia , Humanos , Masculino , Tomografia de Coerência ÓpticaRESUMO
The aim of the European Metrology Research Project MetroBeta is to improve the knowledge of the shapes of beta spectra, both in terms of theoretical calculation and measurement. The precise knowledge of beta spectra is required for the activity standardisation of pure beta emitters. Metallic magnetic calorimeters (MMCs), a type of cryogenic detectors, with the beta emitter embedded in the absorber have proven to be among the best beta spectrometers, in particular for low-energy beta transitions. Within this project, new designs of MMCs optimized for five different beta energy ranges were developed and a new detector module was constructed. The beta spectra of 151Sm, 14C and 99Tc have been measured so far; additional measurements with 36Cl are under preparation. Improved theoretical calculation methods and complementary measurement techniques complete the project.
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Determining stage and anticipating prognosis are the two crucial steps after the diagnosis of a germ-cell cancer that both guide subsequent treatment decisions. This review focuses on metastatic disease, which means germ-cell cancers beyond stage I limited to the testis. In the past, major centers developed separate staging and prognostic classifications for metastatic germ-cell cancer, which heavily impaired communication and comparisons across clinical trials. More recently, the classification system of the International Germ-Cell Cancer Collaborative Group (IGCCCG) has found acceptance worldwide and is currently being updated.
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Neoplasias Embrionárias de Células Germinativas/diagnóstico , Neoplasias Testiculares/diagnóstico , Humanos , Masculino , Estadiamento de Neoplasias , PrognósticoRESUMO
The European Society for Medical Oncology (ESMO) consensus conference on testicular cancer was held on 3-5 November 2016 in Paris, France. The conference included a multidisciplinary panel of 36 leading experts in the diagnosis and treatment of testicular cancer (34 panel members attended the conference; an additional two panel members [CB and K-PD] participated in all preparatory work and subsequent manuscript development). The aim of the conference was to develop detailed recommendations on topics relating to testicular cancer that are not covered in detail in the current ESMO Clinical Practice Guidelines (CPGs) and where the available level of evidence is insufficient. The main topics identified for discussion related to: (1) diagnostic work-up and patient assessment; (2) stage I disease; (3) stage II-III disease; (4) post-chemotherapy surgery, salvage chemotherapy, salvage and desperation surgery and special topics; and (5) survivorship and follow-up schemes. The experts addressed questions relating to one of the five topics within five working groups. Relevant scientific literature was reviewed in advance. Recommendations were developed by the working groups and then presented to the entire panel. A consensus vote was obtained following whole-panel discussions, and the consensus recommendations were then further developed in post-meeting discussions in written form. This manuscript presents the results of the expert panel discussions, including the consensus recommendations and a summary of evidence supporting each recommendation. All participants approved the final manuscript.
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Oncologia/normas , Recidiva Local de Neoplasia/prevenção & controle , Neoplasias Embrionárias de Células Germinativas/terapia , Guias de Prática Clínica como Assunto , Neoplasias Testiculares/terapia , Assistência ao Convalescente/métodos , Assistência ao Convalescente/normas , Sobreviventes de Câncer/psicologia , Quimiorradioterapia Adjuvante/métodos , Quimiorradioterapia Adjuvante/normas , Conferências de Consenso como Assunto , Europa (Continente) , Humanos , Masculino , Oncologia/métodos , Terapia Neoadjuvante/métodos , Terapia Neoadjuvante/normas , Recidiva Local de Neoplasia/epidemiologia , Estadiamento de Neoplasias , Neoplasias Embrionárias de Células Germinativas/diagnóstico , Neoplasias Embrionárias de Células Germinativas/patologia , Orquiectomia/psicologia , Cuidados Paliativos/métodos , Cuidados Paliativos/normas , Prognóstico , Qualidade de Vida , Fatores de Risco , Terapia de Salvação/métodos , Terapia de Salvação/normas , Sociedades Médicas/normas , Sobrevivência , Neoplasias Testiculares/diagnóstico , Neoplasias Testiculares/patologia , Testículo/diagnóstico por imagem , Testículo/patologia , Testículo/cirurgiaRESUMO
We measure the full photon-number distribution emitted from a Bose condensate of microcavity exciton polaritons confined in a micropillar cavity. The statistics are acquired by means of a photon-number-resolving transition edge sensor. We directly observe that the photon-number distribution evolves with the nonresonant optical excitation power from geometric to quasi-Poissonian statistics, which is canonical for a transition from a thermal to a coherent state. Moreover, the photon-number distribution allows one to evaluate the higher-order photon correlations, shedding further light on the coherence formation and phase transition of the polariton condensate. The experimental data are analyzed in terms of thermal-coherent states, which gives direct access to the thermal and coherent fraction from the measured distributions. These results pave the way for a full understanding of the contribution of interactions in light-matter condensates in the coherence buildup at threshold.
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Hepatitis C virus (HCV) genotype 4 (GT4) is genetically diverse with 17 confirmed and 4 provisional subtypes. In this report, HCV GT4-infected patient samples from Phase 2/3 clinical studies were analysed to characterize global demographics and genetic diversity of GT4 infection among patients treated with ombitasvir (OBV, NS5A inhibitor) plus paritaprevir/r (NS3/4A inhibitor codosed with ritonavir). Among 17 subtypes isolated from GT4-infected patients in the PEARL-I and AGATE-I studies, subtype prevalence by country of enrolment and country of origin suggested that subtypes 4a and 4d were likely circulating in Europe, while heterogeneous GT4 subtypes and a portion of GT4a detected in European and North American countries were likely due to immigration of HCV-infected patients from Africa. The distributions of birth cohort and race were also significantly different across GT4 subtypes 4a, 4d, and non-4a/4d. In addition, phylogenetic analyses of NS5A sequences revealed clustering within subtype 4a which segregated by the patient-reported country of origin and the presence of the L30R/S polymorphism. HCV NS5A sequences derived from GT4a-infected patients who originated from Europe and the United States clustered separately from sequences derived from patients who originated from Egypt, suggesting that genetically distinct strains of subtype 4a may be circulating globally. Finally, NS5A baseline polymorphisms were frequently detected at amino acid positions of interest for the inhibitor-class and OBV retained activity against 37 of 39 NS5A GT4 clinical isolates, with no impact on treatment outcome in the PEARL-I and AGATE-I studies.
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Antivirais/administração & dosagem , Variação Genética , Genótipo , Hepacivirus/genética , Hepatite C Crônica/tratamento farmacológico , Hepatite C Crônica/virologia , Proteínas não Estruturais Virais/genética , Adulto , Idoso , Idoso de 80 Anos ou mais , Anilidas/administração & dosagem , Carbamatos/administração & dosagem , Ensaios Clínicos Fase II como Assunto , Ensaios Clínicos Fase III como Assunto , Análise por Conglomerados , Ciclopropanos , Demografia , Europa (Continente)/epidemiologia , Feminino , Hepacivirus/classificação , Hepatite C Crônica/epidemiologia , Humanos , Lactamas Macrocíclicas , Compostos Macrocíclicos/administração & dosagem , Masculino , Pessoa de Meia-Idade , Epidemiologia Molecular , América do Norte/epidemiologia , Filogenia , Prevalência , Prolina/análogos & derivados , Ritonavir/administração & dosagem , Análise de Sequência de DNA , Sulfonamidas , Resultado do Tratamento , ValinaRESUMO
Background: The prognostic score of the International Germ-Cell Cancer Collaborative Group (IGCCCG) in metastatic germ-cell cancers (mGCC) relies on treatments delivered before 1990. It is unclear, if this score is still relevant to contemporary cohorts of patients who receive modern-type chemotherapy and supportive care. Patients and methods: All patients who underwent cisplatin/etoposide-based first-line chemotherapy for mGCC at the University Hospital Zurich (USZ) between 1991 and 2016 were identified retrospectively. Clinical characteristics were extracted from medical charts and patients classified according to the IGCCCG score. International germ cell consensus classification: a prognostic factor-based staging system for metastatic germ cell cancers. J Clin Oncol 1997; 15: 594-603.). Progression-free survival (PFS) and overall survival (OS) probabilities at 5 years served as outcome parameters. Results: The study cohort consisted of 204 patients at a median age of 32 years and a median follow-up of 4.2 years. According to the IGCCCG score, PFS in the contemporary USZ cohort was 71% overall: 83% for good-risk, 69% for intermediate-risk and 30% for poor-risk patients, P < 0.001. OS for the entire cohort was 88%. In respect to OS, we observed no difference between good- and intermediate-risk patients (94% versus 91%, P = 0.62), but a statistically significant difference between those two risk groups and poor-risk patients, who had an OS of only 65%, P < 0.001. Conclusions: Within the contemporary USZ cohort of mGCC patients no improvements in PFS probabilities were observed compared with the ones predicted by the IGCCCG score for any prognostic category, but marked improvements in OS probabilities for intermediate- and poor-risk patients, possibly due to better salvage treatments.
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Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Neoplasias Embrionárias de Células Germinativas/tratamento farmacológico , Neoplasias Embrionárias de Células Germinativas/mortalidade , Adolescente , Adulto , Cisplatino/administração & dosagem , Etoposídeo/administração & dosagem , Humanos , Estimativa de Kaplan-Meier , Masculino , Pessoa de Meia-Idade , Neoplasias Embrionárias de Células Germinativas/patologia , Prognóstico , Intervalo Livre de Progressão , Estudos Retrospectivos , Adulto JovemRESUMO
A non-classical light source emitting pairs of identical photons represents a versatile resource of interdisciplinary importance with applications in quantum optics and quantum biology. To date, photon twins have mostly been generated using parametric downconversion sources, relying on Poissonian number distributions, or atoms, exhibiting low emission rates. Here we propose and experimentally demonstrate the efficient, triggered generation of photon twins using the energy-degenerate biexciton-exciton radiative cascade of a single semiconductor quantum dot. Deterministically integrated within a microlens, this nanostructure emits highly correlated photon pairs, degenerate in energy and polarization, at a rate of up to (234±4) kHz. Furthermore, we verify a significant degree of photon indistinguishability and directly observe twin-photon emission by employing photon-number-resolving detectors, which enables the reconstruction of the emitted photon number distribution. Our work represents an important step towards the realization of efficient sources of twin-photon states on a fully scalable technology platform.
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BACKGROUND: Many testicular germ cell cancers are curable despite metastatic disease, but about 10-15% of patients fail cisplatin-based first-line treatment. Immunotherapy is considered as additional treatment approach for these patients. Inhibition of the interaction between Programmed Death Receptor 1 (PD-1) and Programmed Death Receptor Ligand 1 (PD-L1) enhances T-cell responses in vitro and mediates clinical antitumour activity. We analysed the expression of PD-L1 in testicular germ cell tumours to evaluate its potential as target for immunotherapeutic strategies. METHODS: Immunohistochemistry was performed in 479 formalin-fixed paraffin-embedded specimens using a rabbit monoclonal antibody (E1L3N). The tissue microarray consisted of 208 pure seminomas, 121 non-seminomas, 20 intratubular germ cell neoplasia unclassified (IGCNU) and 20 specimens of non-neoplastic testicular tissue. RESULTS: Programmed Death Receptor Ligand-1 expression was found in 73% of all seminomas and in 64% of all non-seminomas. None of 20 IGCNU and none of 20 normal tissue specimens exhibited PD-L1 expression. PD-L1 positive stromal cells were only detected in seminomas, but not in non-seminomas. The anti PD-L1 antibody showed a pre-dominantly membranous staining pattern in testicular tumour cells, as well as expression in stromal cells. CONCLUSIONS: This frequent expression of PD-L1 in human testicular germ cell tumours suggests that patients with testicular germ cell tumours could profit from immunotherapeutic strategies using anti-PD1 and anti-PDL1 antibodies.
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Antígeno B7-H1/metabolismo , Neoplasias Embrionárias de Células Germinativas/epidemiologia , Neoplasias Embrionárias de Células Germinativas/metabolismo , Neoplasias Testiculares/epidemiologia , Neoplasias Testiculares/metabolismo , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Humanos , Imuno-Histoquímica , Masculino , Pessoa de Meia-Idade , Neoplasias Embrionárias de Células Germinativas/patologia , Seminoma/epidemiologia , Seminoma/metabolismo , Seminoma/patologia , Neoplasias Testiculares/patologia , Testículo/metabolismo , Testículo/patologia , Análise Serial de Tecidos , Adulto JovemRESUMO
Drug abuse is a widespread problem affecting both teenagers and adults. Nitrous oxide is becoming increasingly popular as an inhalation drug, causing harmful neurological and hematological effects. Some gas chromatography-mass spectrometry (GC-MS) methods for nitrous oxide measurement have been previously described. The main drawbacks of these methods include a lack of sensitivity for forensic applications; including an inability to quantitatively determine the concentration of gas present. The following study provides a validated method using HS-GC-MS which incorporates hydrogen sulfide as a suitable internal standard allowing the quantification of nitrous oxide. Upon analysis, sample and internal standard have similar retention times and are eluted quickly from the molecular sieve 5Å PLOT capillary column and the Porabond Q column therefore providing rapid data collection whilst preserving well defined peaks. After validation, the method has been applied to a real case of N2O intoxication indicating concentrations in a mono-intoxication.
Assuntos
Ciências Forenses/métodos , Cromatografia Gasosa-Espectrometria de Massas/métodos , Óxido Nitroso/efeitos adversos , Óxido Nitroso/análise , Calibragem , Dióxido de Carbono/análise , Humanos , Sulfeto de Hidrogênio/análise , Limite de Detecção , Padrões de Referência , Reprodutibilidade dos Testes , Fatores de TempoRESUMO
Testicular cancer (TC) is the most common neoplasm in males aged 15-40 years. The majority of patients have no evidence of metastases at diagnosis and thus have clinical stage I (CSI) disease [Oldenburg J, Fossa SD, Nuver J et al. Testicular seminoma and non-seminoma: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Ann Oncol 2013; 24(Suppl 6): vi125-vi132; de Wit R, Fizazi K. Controversies in the management of clinical stage I testis cancer. J Clin Oncol 2006; 24: 5482-5492.]. Management of CSI TC is controversial and options include surveillance and active treatment. Different forms of adjuvant therapy exist, including either one or two cycles of carboplatin chemotherapy or radiotherapy for seminoma and either one or two cycles of cisplatin-based chemotherapy or retroperitoneal lymph node dissection for non-seminoma. Long-term disease-specific survival is â¼99% with any of these approaches, including surveillance. While surveillance allows most patients to avoid additional treatment, adjuvant therapy markedly lowers the relapse rate. Weighing the net benefits of surveillance against those of adjuvant treatment depends on prioritizing competing aims such as avoiding unnecessary treatment, avoiding more burdensome treatment with salvage chemotherapy and minimizing the anxiety, stress and life disruption associated with relapse. Unbiased information about the advantages and disadvantages of surveillance and adjuvant treatment is a prerequisite for informed consent by the patient. In a clinical scenario like CSI TC, where different disease-management options produce indistinguishable long-term survival rates, patient values, priorities and preferences should be taken into account. In this review, we provide an overview about risk factors for relapse, potential benefits and harms of adjuvant chemotherapy and active surveillance and a rationale for involving patients in individualized decision making about their treatment rather than adopting a uniform recommendation for all.
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Antineoplásicos/uso terapêutico , Técnicas de Apoio para a Decisão , Neoplasias Embrionárias de Células Germinativas/terapia , Participação do Paciente , Autonomia Pessoal , Seminoma/terapia , Neoplasias Testiculares/terapia , Conduta Expectante , Adolescente , Adulto , Antineoplásicos/efeitos adversos , Quimioterapia Adjuvante , Comportamento de Escolha , Progressão da Doença , Humanos , Masculino , Recidiva Local de Neoplasia , Estadiamento de Neoplasias , Neoplasias Embrionárias de Células Germinativas/patologia , Orquiectomia/efeitos adversos , Seleção de Pacientes , Valor Preditivo dos Testes , Radioterapia Adjuvante , Fatores de Risco , Seminoma/patologia , Neoplasias Testiculares/patologia , Fatores de Tempo , Resultado do Tratamento , Adulto JovemAssuntos
Seminoma/diagnóstico , Seminoma/terapia , Neoplasias Testiculares/diagnóstico , Neoplasias Testiculares/terapia , Antineoplásicos/efeitos adversos , Antineoplásicos/uso terapêutico , Europa (Continente)/epidemiologia , Seguimentos , Humanos , Masculino , Recidiva Local de Neoplasia/tratamento farmacológico , Recidiva Local de Neoplasia/cirurgia , Estadiamento de Neoplasias , Orquiectomia , Medição de Risco , Terapia de Salvação , Seminoma/epidemiologia , Neoplasias Testiculares/epidemiologia , Resultado do TratamentoRESUMO
We have previously shown that adeno-associated virus type 2 (AAV2) undergoes anterograde axonal transport in rat and non-human primate brain. We screened other AAV serotypes for axonal transport and found that AAV6 is transported almost exclusively in a retrograde direction and, in the same way as AAV2, it is also neuron-specific in rat brain. Our findings show that axonal transport of AAV is serotype dependent and this has implications for gene therapy of neurological diseases such as Huntington's disease.
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Transporte Axonal , Encéfalo/metabolismo , Dependovirus/genética , Transdução Genética/métodos , Animais , Encéfalo/citologia , Corpo Estriado/citologia , Corpo Estriado/metabolismo , Dependovirus/classificação , Imunofluorescência , Terapia Genética/métodos , Vetores Genéticos/genética , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Humanos , Doença de Huntington/genética , Doença de Huntington/terapia , Doenças Neurodegenerativas/genética , Doenças Neurodegenerativas/terapia , Ratos , Ratos Sprague-Dawley , Sorotipagem , Especificidade da Espécie , Tálamo/citologia , Tálamo/metabolismoRESUMO
In November 2011, the Third European Consensus Conference on Diagnosis and Treatment of Germ-Cell Cancer (GCC) was held in Berlin, Germany. This third conference followed similar meetings in 2003 (Essen, Germany) and 2006 (Amsterdam, The Netherlands) [Schmoll H-J, Souchon R, Krege S et al. European consensus on diagnosis and treatment of germ-cell cancer: a report of the European Germ-Cell Cancer Consensus Group (EGCCCG). Ann Oncol 2004; 15: 1377-1399; Krege S, Beyer J, Souchon R et al. European consensus conference on diagnosis and treatment of germ-cell cancer: a report of the second meeting of the European Germ-Cell Cancer Consensus group (EGCCCG): part I. Eur Urol 2008; 53: 478-496; Krege S, Beyer J, Souchon R et al. European consensus conference on diagnosis and treatment of germ-cell cancer: a report of the second meeting of the European Germ-Cell Cancer Consensus group (EGCCCG): part II. Eur Urol 2008; 53: 497-513]. A panel of 56 of 60 invited GCC experts from all across Europe discussed all aspects on diagnosis and treatment of GCC, with a particular focus on acute and late toxic effects as well as on survivorship issues. The panel consisted of oncologists, urologic surgeons, radiooncologists, pathologists and basic scientists, who are all actively involved in care of GCC patients. Panelists were chosen based on the publication activity in recent years. Before the meeting, panelists were asked to review the literature published since 2006 in 20 major areas concerning all aspects of diagnosis, treatment and follow-up of GCC patients, and to prepare an updated version of the previous recommendations to be discussed at the conference. In addition, â¼50 E-vote questions were drafted and presented at the conference to address the most controversial areas for a poll of expert opinions. Here, we present the main recommendations and controversies of this meeting. The votes of the panelists are added as online supplements.
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Neoplasias Embrionárias de Células Germinativas/patologia , Neoplasias Embrionárias de Células Germinativas/terapia , Europa (Continente) , Seguimentos , Humanos , Metástase Neoplásica , Estadiamento de Neoplasias , Neoplasias Embrionárias de Células Germinativas/classificação , Neoplasias Embrionárias de Células Germinativas/diagnóstico , Taxa de SobrevidaRESUMO
BACKGROUND: An early serum tumor marker (TM) decline during chemotherapy was shown to independently predict survival in patients with poor-prognosis disseminated non-seminomatous germ-cell tumors (NSGCTs). The aim of this study was to assess whether a TM decline (TMD) also correlates with the outcome in the salvage setting. PATIENTS AND METHODS: Data regarding 400 patients with progressive or relapsed disseminated NSGCTs after first-line chemotherapy prospectively accrued onto two phase III clinical trials were obtained. Serum alpha-fetoprotein (AFP) and/or human chorionic gonadotropin (hCG) were assessed at baseline and after 6 weeks of chemotherapy. A total of 297 patients, 185 and 112 in the training and validation sets, with initially abnormal TMs for whom a change from baseline could be established were used for this analysis. RESULTS: An unfavorable decline in either AFP or hCG was predictive of progression-free survival (PFS) [hazard ratio, HR = 2.15, (95% CI 1.48-3.11); P < 0.001; 2-year PFS rate: 50% versus 26%] as was the Lorch prognostic score (LPS). In the multivariate analysis, an unfavorable TMD, stratified based on the LPS, was an independent adverse prognostic factor for PFS and OS. CONCLUSION: An unfavorable TMD during the first 6 weeks after chemotherapy is associated with a poorer outcome in patients with relapsed disseminated NSGCTs.
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Biomarcadores Tumorais/sangue , Gonadotropina Coriônica/sangue , Recidiva Local de Neoplasia/tratamento farmacológico , Neoplasias Embrionárias de Células Germinativas , alfa-Fetoproteínas/análise , Adulto , Carboplatina/uso terapêutico , Cisplatino/uso terapêutico , Ciclofosfamida/uso terapêutico , Intervalo Livre de Doença , Esquema de Medicação , Etoposídeo/uso terapêutico , Feminino , Humanos , Ifosfamida/uso terapêutico , Masculino , Neoplasias Embrionárias de Células Germinativas/tratamento farmacológico , Neoplasias Embrionárias de Células Germinativas/metabolismo , Neoplasias Embrionárias de Células Germinativas/mortalidade , Sobrevida , Neoplasias Testiculares , Resultado do Tratamento , Vimblastina/uso terapêuticoAssuntos
Conservação dos Recursos Naturais , Ecossistema , Pesqueiros , Peixes , Animais , Biodiversidade , Biomassa , Tamanho Corporal , Modelos Biológicos , PolíticasRESUMO
Effects of a longitudinal magnetic field on optical spin injection and detection in InAs/GaAs quantum dot (QD) structures are investigated by optical orientation spectroscopy. An increase in the optical and spin polarization of the QDs is observed with increasing magnetic field in the range 0-2 T, and is attributed to suppression of exciton spin depolarization within the QDs that is promoted by the hyperfine interaction and anisotropic electron-hole exchange interaction. This leads to a corresponding enhancement in spin detection efficiency of the QDs by a factor of up to 2.5. At higher magnetic fields, when these spin depolarization processes are quenched, the electron spin polarization in anisotropic QD structures (such as double QDs that are preferably aligned along a specific crystallographic axis) still exhibits a rather strong field dependence under non-resonant excitation. In contrast, such a field dependence is practically absent in more 'isotropic' QD structures (e.g. single QDs). We attribute the observed effect to stronger electron spin relaxation in the spin injectors (i.e. wetting layer and GaAs barriers) of the lower-symmetry QD structures, which also explains the lower spin injection efficiency observed in these structures.
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Arsenicais/química , Espectroscopia de Ressonância de Spin Eletrônica , Gálio/química , Índio/química , Campos Magnéticos , Pontos Quânticos , Marcadores de Spin , Anisotropia , Simulação por ComputadorRESUMO
The Hanle effect in InAs/GaAs quantum dots (QDs) is studied under optical orientation as a function of temperature over the range of 150-300 K, with the aim of understanding the physical mechanism responsible for the observed sharp increase of electron spin polarization with increasing temperature. The deduced spin lifetime T(s) of positive trions in the QDs is found to be independent of temperature, and is also insensitive to excitation energy and density. It is argued that the measured T(s) is mainly determined by the longitudinal spin-flip time (T(1)) and the spin dephasing time (T(2)*) of the studied QD ensemble, of which both are temperature independent over the studied temperature range and the latter makes a larger contribution. The observed sharply rising QD spin polarization degree with increasing temperature, on the other hand, is shown to be induced by an increase in spin injection efficiency from the barrier/wetting layer and also by a moderate increase in spin detection efficiency of the QD.
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This paper presents the first volume visualization system that scales to petascale volumes imaged as a continuous stream of high-resolution electron microscopy images. Our architecture scales to dense, anisotropic petascale volumes because it: (1) decouples construction of the 3D multi-resolution representation required for visualization from data acquisition, and (2) decouples sample access time during ray-casting from the size of the multi-resolution hierarchy. Our system is designed around a scalable multi-resolution virtual memory architecture that handles missing data naturally, does not pre-compute any 3D multi-resolution representation such as an octree, and can accept a constant stream of 2D image tiles from the microscopes. A novelty of our system design is that it is visualization-driven: we restrict most computations to the visible volume data. Leveraging the virtual memory architecture, missing data are detected during volume ray-casting as cache misses, which are propagated backwards for on-demand out-of-core processing. 3D blocks of volume data are only constructed from 2D microscope image tiles when they have actually been accessed during ray-casting. We extensively evaluate our system design choices with respect to scalability and performance, compare to previous best-of-breed systems, and illustrate the effectiveness of our system for real microscopy data from neuroscience.