Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 975
Filtrar
1.
Nature ; 609(7925): 41-45, 2022 09.
Artigo em Inglês | MEDLINE | ID: mdl-36045235

RESUMO

When protons and neutrons (nucleons) are bound into atomic nuclei, they are close enough to feel significant attraction, or repulsion, from the strong, short-distance part of the nucleon-nucleon interaction. These strong interactions lead to hard collisions between nucleons, generating pairs of highly energetic nucleons referred to as short-range correlations (SRCs). SRCs are an important but relatively poorly understood part of nuclear structure1-3, and mapping out the strength and the isospin structure (neutron-proton (np) versus proton-proton (pp) pairs) of these virtual excitations is thus critical input for modelling a range of nuclear, particle and astrophysics measurements3-5. Two-nucleon knockout or 'triple coincidence' reactions have been used to measure the relative contribution of np-SRCs and pp-SRCs by knocking out a proton from the SRC and detecting its partner nucleon (proton or neutron). These measurements6-8 have shown that SRCs are almost exclusively np pairs, but they had limited statistics and required large model-dependent final-state interaction corrections. Here we report on measurements using inclusive scattering from the mirror nuclei hydrogen-3 and helium-3 to extract the np/pp ratio of SRCs in systems with a mass number of three. We obtain a measure of the np/pp SRC ratio that is an order of magnitude more precise than previous experiments, and find a marked deviation from the near-total np dominance observed in heavy nuclei. This result implies an unexpected structure in the high-momentum wavefunction for hydrogen-3 and helium-3. Understanding these results will improve our understanding of the short-range part of the nucleon-nucleon interaction.

2.
Phys Rev Lett ; 132(16): 162501, 2024 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-38701469

RESUMO

The electromagnetic form factors of the proton and neutron encode information on the spatial structure of their charge and magnetization distributions. While measurements of the proton are relatively straightforward, the lack of a free neutron target makes measurements of the neutron's electromagnetic structure more challenging and more sensitive to experimental or model-dependent uncertainties. Various experiments have attempted to extract the neutron form factors from scattering from the neutron in deuterium, with different techniques providing different, and sometimes large, systematic uncertainties. We present results from a novel measurement of the neutron magnetic form factor using quasielastic scattering from the mirror nuclei ^{3}H and ^{3}He, where the nuclear effects are larger than for deuterium but expected to largely cancel in the cross-section ratios. We extracted values of the neutron magnetic form factor for low-to-modest momentum transfer, 0.6

3.
Ann Vasc Surg ; 2024 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-38942375

RESUMO

OBJECTIVES: Investigate readmission rates, diagnoses associated with readmission, and associations with mortality through 90-days post-operatively after elective endovascular thoracic and thoracoabdominal aortic repair overall and by extent of coverage. METHODS: A cohort of index elective non-traumatic endovascular thoracic and thoracoabdominal aortic cases from 2010-2018 was derived from the Vascular Implant Surveillance and Interventional Outcomes Network. Cohort readmissions within 90-days postoperative were examined both overall and by Crawford extent (CE) of aortic coverage. Postoperative mortality was examined by reason for readmission and CE. RESULTS: The cohort consisted of 2,093 patients who underwent endovascular thoracic and thoracoabdominal aortic repair (1,541 CE 0A/0B; 240 CE 1-3; 312 CE 4-5). Cumulative risk for 90-day readmission was 34.3% in CE 0A/0B repairs, 33.4% in CE4-5 repairs and 47.4% in CE 1-3 repairs. Compared to CE 0A/B, patients with CE 1-3 repairs experienced an increased risk of readmission within 90 days postoperatively after adjusting for preoperative factors (aHR 1.27(1.00,1.61) while the readmission risk for CE 4-5 repairs did not differ significantly (aHR 0.83 (0.64,1.06). Significant risk factors for 90-day readmission included COPD, dialysis dependence, limited ambulation, visceral/spinal ischemia, and in-hospital stroke. Discharge to home was protective against readmission (HR 0.65, CI 0.54-0.79). Patients with a readmission within 90-days had a 7.89-fold increase in 90-day mortality (HR 7.84; 5.17, 11.9) compared to those not readmitted. CONCLUSIONS: Increasing extent of endovascular thoracic and thoracoabdominal aortic repair was associated with higher 90-day readmission rates. Readmission for all CE was associated with near 8-fold increased risk of mortality. Risk factors associated with increased risk for readmission included pulmonary insufficiency, renal disease, and poor functional status. These findings can inform stakeholders about investment of resources to improve processes of care that both target prevention and mitigate risk of readmission after elective endovascular thoracic and thoracoabdominal aortic repair.

4.
BMC Psychiatry ; 23(1): 839, 2023 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-37964300

RESUMO

BACKGROUND: Alcohol use disorder (AUD) belongs to the most burdensome clinical disorders worldwide. Current treatment approaches yield unsatisfactory long-term effects with relapse rates up to 85%. Craving for alcohol is a major predictor for relapse and can be intentionally induced via cue exposure in real life as well as in Virtual Reality (VR). The induction and habituation of craving via conditioned cues as well as extinction learning is used in Cue Exposure Therapy (CET), a long-known but rarely used strategy in Cognitive Behavioral Therapy (CBT) of AUD. VR scenarios with alcohol related cues offer several advantages over real life scenarios and are within the focus of current efforts to develop new treatment options. As a first step, we aim to analyze if the VR scenarios elicit a transient change in craving levels and if this is measurable via subjective and psychophysiological parameters. METHODS: A single-arm clinical study will be conducted including n = 60 patients with AUD. Data on severity of AUD and craving, comorbidities, demographics, side effects and the feeling of presence in VR will be assessed. Patients will use a head-mounted display (HMD) to immerse themselves into three different scenarios (neutral vs. two target situations: a living room and a bar) while heart rate, heart rate variability, pupillometry and electrodermal activity will be measured continuously. Subjective craving levels will be assessed before, during and after the VR session. DISCUSSION: Results of this study will yield insight into the induction of alcohol craving in VR cue exposure paradigms and its measurement via subjective and psychophysiological parameters. This might be an important step in the development of innovative therapeutic approaches in the treatment of patients with AUD. TRIAL REGISTRATION: This study was approved by the Charité-Universitätsmedizin Berlin Institutional Review Board (EA1/190/22, 23.05.2023). It was registered on ClinicalTrials.gov (NCT05861843).


Assuntos
Alcoolismo , Realidade Virtual , Humanos , Consumo de Bebidas Alcoólicas , Alcoolismo/terapia , Alcoolismo/psicologia , Fissura , Sinais (Psicologia) , Recidiva
5.
Artigo em Inglês | MEDLINE | ID: mdl-36646309

RESUMO

Digestion and assimilation of nutrients and energy is central to survival. At its most basic level, investigations of digestion in animals must examine digestive efficiency, or how much of a given meal (i.e., energy) or a specific nutrient an organism can acquire from its food. There are many studies examining this in reptiles, but there is large variation in methodology, and thus, in the conclusions drawn from the gathered data. The majority rely on ratio-based analyses that can jeopardize the reliability of their findings. Therefore, we reviewed the literature to identify common themes in the digestive efficiency data on reptiles. Due to the sheer number of available studies, we largely focused on lizards, but included data on all reptilian groups. As an example of what the current data can reveal, we performed a meta-analysis of digestive efficiency in lizards as a function of temperature using regression analyses. We detected a weak positive trend of soluble carbohydrate digestibility as a function of temperature, but no similar trend in broad-scale digestive efficiency, and propose that these patterns be reevaluated with non-ratio data. We conclude with calls to end conducting analyses on ratios and instead employ covariate methods, for more studies of reptilian digestive efficiency and related processes using consistent methodology, more representation of each population (e.g., many studies focus on males only), and more detailed studies examining the effects of temperature on digestion (since the current data are inconclusive).


Assuntos
Digestão , Lagartos , Masculino , Animais , Digestão/fisiologia , Reprodutibilidade dos Testes , Lagartos/fisiologia , Temperatura , Dieta
6.
Nervenarzt ; 94(1): 27-33, 2023 Jan.
Artigo em Alemão | MEDLINE | ID: mdl-36053303

RESUMO

BACKGROUND: Virtual reality (VR) enables immersion in an interactive digital world with realistic experiences, that can be applied for controlled and personalized interventions. This review summarizes the current research on VR in the treatment of mental disorders. METHODS: Selective literature search in PubMed and Google Scholar. RESULTS: An increasing number of publications report the therapeutic application of VR for the treatment of mental disorders. Most VR applications are based on established therapy approaches, such as exposure therapy. According to meta-analytic data, virtual exposure therapy (VRET) for specific phobia and agoraphobia with panic disorder is as effective as traditional in vivo exposure therapy. VRET for the treatment of social phobia is significantly more effective than waitlist and placebo control groups with, however, currently inconsistent metanalytic results when compared to in vivo exposure therapy. VRET for the treatment of posttraumatic stress disorder (PTSD) is similar in effectiveness compared to active psychotherapy. For psychosis, positive results have been reported for the VR-based treatment of auditory verbal hallucinations. For patients with a substance use disorder, VR can induce craving, with still unverified diagnostic and therapeutic relevance. CONCLUSIONS: VRET can broaden the psychotherapy options for anxiety disorders. Encouraging results of VR-based treatments for psychosis and PTSD indicate the need for further research concerning its effectiveness and safety. In the field of substance use disorders, evaluation of clinical-orientated VR applications is needed.


Assuntos
Transtorno de Pânico , Transtornos Fóbicos , Transtornos de Estresse Pós-Traumáticos , Terapia de Exposição à Realidade Virtual , Realidade Virtual , Humanos , Transtornos Fóbicos/diagnóstico , Transtornos Fóbicos/terapia , Transtornos de Ansiedade/terapia , Transtorno de Pânico/terapia , Transtornos de Estresse Pós-Traumáticos/terapia
7.
Phys Rev Lett ; 128(13): 132003, 2022 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-35426713

RESUMO

The ratio of the nucleon F_{2} structure functions, F_{2}^{n}/F_{2}^{p}, is determined by the MARATHON experiment from measurements of deep inelastic scattering of electrons from ^{3}H and ^{3}He nuclei. The experiment was performed in the Hall A Facility of Jefferson Lab using two high-resolution spectrometers for electron detection, and a cryogenic target system which included a low-activity tritium cell. The data analysis used a novel technique exploiting the mirror symmetry of the two nuclei, which essentially eliminates many theoretical uncertainties in the extraction of the ratio. The results, which cover the Bjorken scaling variable range 0.19

8.
Environ Sci Technol ; 56(2): 928-937, 2022 01 18.
Artigo em Inglês | MEDLINE | ID: mdl-34951307

RESUMO

Chronic exposure to groundwater contaminated with geogenic arsenic (As) poses a significant threat to human health worldwide, especially for those living on floodplains in South and Southeast (S-SE) Asia. In the alluvial and deltaic aquifers of S-SE Asia, aqueous As concentrations vary sharply over small spatial scales (10-100 m), making it challenging to identify where As contamination is present and mitigate exposure. Improved mechanistic understanding of the factors that control groundwater As levels is essential to develop models that accurately predict spatially variable groundwater As concentrations. Here we demonstrate that surface flooding duration and interannual frequency are master variables that integrate key hydrologic and biogeochemical processes that affect groundwater As levels in S-SE Asia. A machine-learning model based on high-resolution, satellite-derived, long-term measures of surface flooding duration and frequency effectively predicts heterogeneous groundwater As concentrations at fine spatial scales in Cambodia, Vietnam, and Bangladesh. Our approach can be reliably applied to identify locations of safe and unsafe groundwater sources with sufficient accuracy for making management decisions by solely using remotely sensed information. This work is important to evaluate levels of As exposure, impacts to public health, and to shed light on the underlying hydrogeochemical processes that drive As mobilization into groundwater.


Assuntos
Arsênio , Água Subterrânea , Poluentes Químicos da Água , Arsênio/análise , Sudeste Asiático , Monitoramento Ambiental , Humanos , Poluentes Químicos da Água/análise
9.
Artigo em Inglês | MEDLINE | ID: mdl-35537602

RESUMO

Abalone around the world are subject to increasing frequency of marine heatwaves, yet we have a limited understanding of how acute high temperature events impact the physiology of these commercially and ecologically important species. This study examines the impact of a 5 °C temperature increase over ambient conditions for six weeks on the metabolic rates, digestive enzyme activities in the digestive gland, and digestive efficiency of Red Abalone (Haliotis rufescens) and Paua (H. iris) on their natural diets. We test the hypothesis that abalone digestive function can keep pace with this increased metabolic demand in two separate experiments, one for each species. H. iris had higher food intake in the heat treatment. Both species had higher metabolic rates in the heat treatment with Q10 = 1.73 and Q10 = 2.46 for H. rufescens and H. iris, respectively. Apparent organic matter digestibility, protein digestibility, and carbohydrate digestibility did not differ between the heat treatment and the ambient (control) treatment in either experiment. H. rufescens exhibited higher maltase, alanine-aminopeptidase, and leucine-aminopeptidase activities in the heat treatment. Amylase, ß-glucosidase, trypsin, and alkaline phosphatase activities in the digestive gland tissue did not differ between temperature treatments. H. iris exhibited lower amylase and ß-glucosidase activities in the heat treatment, while maltase, trypsin, leucine-aminopeptidase, and alkaline phosphatase activities did not differ between treatments. We conclude that over six weeks of moderate heat stress both abalone species were able to maintain digestive function, but achieved this maintenance in species-specific ways.


Assuntos
Celulases , Gastrópodes , Fosfatase Alcalina/metabolismo , Aminopeptidases/metabolismo , Amilases/metabolismo , Animais , Celulases/metabolismo , Gastrópodes/metabolismo , Resposta ao Choque Térmico , Leucina/metabolismo , Tripsina/metabolismo , alfa-Glucosidases/metabolismo
10.
J Endocrinol Invest ; 44(6): 1151-1158, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33111215

RESUMO

CONTEXT: Gender incongruence is defined as disharmony between assigned gender and gender identity. Several interventions are liable in this case including genital affirming surgery among other surgical interventions such as harmonization, and also the use of gonadotropin-releasing hormone agonists (GnRHa) for gonadal shielding. This aids in preventing the development of secondary sexual characteristics related to the genetic sex. OBJECTIVE: Systematically review the treatment of gender incongruity with GnRHa analogues. DATA SOURCES: The data source of this research is from Pubmed-Medline and Embase. STUDY SELECTION: Articles published between 2009 and 2019 which studied transgender adolescents treated with GnRHa were carefully selected. DATA EXTRACTION: Were extracted: design, sample size, study context, targeted subjects of intervention, outcome measures, and results. RESULTS: Eleven studies were included. The use of GnRHa seems to be well tolerated by the studied population. When started in pubertal transition, it was associated with a more distinct resemblance to body shape than to the affirmed sex. In addition to preventing the irreversible phenotypic changes that occur in cross-hormonal therapy, the use of GnRHa can equally contribute to the mental health of these adolescents. LIMITATION: There are few consistent studies on the use of GnRHa for gender incongruence. CONCLUSION: As the population of transgender children and adolescents grows, they acquire knowledge and greater access to the various forms and stages of treatment for sex reassignment. The medical community needs to be adequately prepared to better serve this population and offer the safest resources available.


Assuntos
Disforia de Gênero , Hormônio Liberador de Gonadotropina/agonistas , Puberdade , Adolescente , Disruptores Endócrinos/farmacologia , Disforia de Gênero/metabolismo , Disforia de Gênero/fisiopatologia , Disforia de Gênero/prevenção & controle , Humanos , Puberdade/efeitos dos fármacos , Puberdade/fisiologia , Desenvolvimento Sexual/efeitos dos fármacos , Desenvolvimento Sexual/fisiologia , Pessoas Transgênero
11.
Nervenarzt ; 92(3): 228-233, 2021 Mar.
Artigo em Alemão | MEDLINE | ID: mdl-33245403

RESUMO

BACKGROUND: Genetic risk factors for major mental disorders identified in psychiatric research show a substantial overlap. Therefore, it has been suggested that neurobiological research should focus on intermediate phenotypes that reflect shared aspects of different mental disorders due to overlapping genetic effects and environmental factors. Longitudinal studies are required to assess the interaction between genetic variability and modifying environmental factors and to investigate the effects on intermediate phenotypes and (mediated by them) on the expression of individual mental disorders. OBJECTIVE: Discussion of the possibilities and limitations of longitudinal cohort studies using the IMAGEN study as an example. MATERIAL AND METHODS: The results of the European IMAGEN study are presented with a focus on addiction. RESULTS: The longitudinal assessments of the IMAGEN cohort revealed that neuroimaging data indicating a low activation of the dopaminergic reinforcement system detected at the age of 14 years are predictive for increased drug use. In addition to genetic factors, environmental influences such as maternal smoking during pregnancy were correlated with this low activation. CONCLUSION: Longitudinal neurobiological basic research can validate the effects of candidate genes and reveal relevant environmental factors. Relevant modifiable factors indicated by the IMAGEN study and related datasets include drug use during pregnancy, trauma and other experiences of violence, social disadvantage and exclusion.


Assuntos
Comportamento Aditivo , Transtornos Relacionados ao Uso de Substâncias , Adolescente , Estudos de Coortes , Feminino , Humanos , Estudos Longitudinais , Neuroimagem , Gravidez
12.
J Intern Med ; 288(1): 51-61, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32303118

RESUMO

Given the increasing availability of large data set, small single-institutional series raise decreasing attention. Rapid expansion of technology from electronic medical records to easily accessible internet access, and widespread use and acceptance of registries in the medical world has allowed for research and quality improvement efforts using 'big data'. Big data, although technically not defined, typically refers to large databases that can be used to investigate common or rare disease processes or outcomes, describe variation in clinical practices across and between different specialties at various practice location, whilst allowing important information about trends over time. Big data have allowed investigators to quickly assimilate cohorts of patients and/or procedures to answer current questions, with more complete population representation and improved generalizability whilst decreasing the likelihood of power problems and type II errors. On the other hand, pitfalls still exist with the growing problem of hypothesis fishing, lack of granularity and the fear by many clinicians that registry transparency may have already gone too far, where surgery groups or individual surgeon outcomes are readily available to patients and referring providers. Within vascular surgery specifically, big data have expanded over the last decade and now includes regional, national and global registries that have major benefits of gathering specific clinical and procedural information within vascular surgery. In this review, we highlight the main vascular surgery registries and recap a few success stories of how the registries have been leveraged to benefit discovery, quality improvement and ultimately patient care. Additionally, we outline future directions that will be imperative for continued expansion, acceptance and adoption of 'big data' utilization inpatients with vascular disease.


Assuntos
Big Data , Cooperação Internacional , Melhoria de Qualidade , Sistema de Registros , Procedimentos Cirúrgicos Vasculares , Aneurisma da Aorta Abdominal/cirurgia , Pesquisa Biomédica , Política de Saúde , Humanos , Legislação de Dispositivos Médicos , Garantia da Qualidade dos Cuidados de Saúde
13.
Phys Rev Lett ; 124(21): 212501, 2020 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-32530643

RESUMO

We report the first measurement of the (e,e^{'}p) three-body breakup reaction cross sections in helium-3 (^{3}He) and tritium (^{3}H) at large momentum transfer [⟨Q^{2}⟩≈1.9 (GeV/c)^{2}] and x_{B}>1 kinematics, where the cross section should be sensitive to quasielastic (QE) scattering from single nucleons. The data cover missing momenta 40≤p_{miss}≤500 MeV/c that, in the QE limit with no rescattering, equals the initial momentum of the probed nucleon. The measured cross sections are compared with state-of-the-art ab initio calculations. Overall good agreement, within ±20%, is observed between data and calculations for the full p_{miss} range for ^{3}H and for 100≤p_{miss}≤350 MeV/c for ^{3}He. Including the effects of rescattering of the outgoing nucleon improves agreement with the data at p_{miss}>250 MeV/c and suggests contributions from charge-exchange (SCX) rescattering. The isoscalar sum of ^{3}He plus ^{3}H, which is largely insensitive to SCX, is described by calculations to within the accuracy of the data over the entire p_{miss} range. This validates current models of the ground state of the three-nucleon system up to very high initial nucleon momenta of 500 MeV/c.

14.
World J Urol ; 38(12): 3085-3090, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32103332

RESUMO

INTRODUCTION: Prostate-specific membrane antigen positron emission tomography-computed tomography (PSMA PET/CT) represents the upcoming standard for the staging of prostate cancer (PCa). However, there is still an unmet need for the validation of PSMA PET/CT at primary staging and consecutive histological correlation. Consequently, we decided to analyze the prediction parameter of PSMA PET/CT at primary staging. METHODS: We relied on 90 ≥ intermediate-risk PCa patients treated with radical prostatectomy (RP) and extended pelvic lymph node dissection. All patients were administered to 68Ga-PSMA PET/CT prior to surgery. 68Ga-PSMA PET/CT data were retrospectively reevaluated by a single radiologist and consequently compared to histological results from RP. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for the detection of lymph node metastases were analyzed per-patient (n = 90), per-pelvic side (n = 180), and per-anatomic-region (external iliac artery and vein left/right vs. obturator fossa left/right vs. internal iliac artery left/right) (n = 458), respectively. RESULTS: Sensitivity, specificity, PPV, and NPV per-patient were: 43.8, 96.0, 70.0, and 88.8%, respectively. Sensitivity, specificity, PPV, and NPV per-pelvic-side were: 42.9, 95.6, 56.3, and 92.7%, respectively. Sensitivity, specificity, PPV, and NPV per-anatomic-region were: 47.6, 98.9, 66.7, and 97.5%, respectively. CONCLUSIONS: Negative 68Ga-PSMA PET/CT results were highly reliable in our study. Positive 68Ga-PSMA PET/CT results, however, revealed less reliable results. Larger and ideally prospective trials are justified to clarify the potential role of PSMA PET/CT based primary staging.


Assuntos
Ácido Edético/análogos & derivados , Oligopeptídeos , Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada/métodos , Prostatectomia/métodos , Neoplasias da Próstata/diagnóstico por imagem , Neoplasias da Próstata/patologia , Compostos Radiofarmacêuticos , Idoso , Correlação de Dados , Isótopos de Gálio , Radioisótopos de Gálio , Humanos , Excisão de Linfonodo , Metástase Linfática , Masculino , Pessoa de Meia-Idade , Estadiamento de Neoplasias , Valor Preditivo dos Testes , Neoplasias da Próstata/cirurgia , Estudos Retrospectivos
15.
Pathologe ; 41(3): 230-237, 2020 May.
Artigo em Alemão | MEDLINE | ID: mdl-32239324

RESUMO

Autoimmune enteropathy (AIE) was originally believed to be a pediatric disease until there were increasing numbers of adult cases reported over the last 20 years. AIE is an autoimmune disease that manifests as severe chronic diarrhea.The histological hallmark is villous atrophy. Histology alone is not sufficiently sensitive and consistent. Four different histological patterns are known. There are many differential diagnoses to be considered relating to both histology and symptoms.We present the case of a young woman with fatal AIE and homozygous germline-mutation of the CLEC7A gene. The course of disease is documented in multiple intestinal biopsies, which show a morphological change over time.Histology and symptoms often resemble celiac disease. In order to recognize this rare disease early in its course there is a need for a special awareness among attending physicians and pathologists.


Assuntos
Diarreia/diagnóstico , Poliendocrinopatias Autoimunes/diagnóstico , Adulto , Biópsia , Doença Celíaca , Diagnóstico Diferencial , Diarreia/etiologia , Feminino , Humanos , Mucosa Intestinal/patologia , Poliendocrinopatias Autoimunes/complicações
16.
Phys Rev Lett ; 122(17): 172502, 2019 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-31107086

RESUMO

We measured the triple coincidence A(e,e^{'}np) and A(e,e^{'}pp) reactions on carbon, aluminum, iron, and lead targets at Q^{2}>1.5 (GeV/c)^{2}, x_{B}>1.1 and missing momentum >400 MeV/c. This was the first direct measurement of both proton-proton (pp) and neutron-proton (np) short-range correlated (SRC) pair knockout from heavy asymmetric nuclei. For all measured nuclei, the average proton-proton (pp) to neutron-proton (np) reduced cross-section ratio is about 6%, in agreement with previous indirect measurements. Correcting for single-charge exchange effects decreased the SRC pairs ratio to ∼3%, which is lower than previous results. Comparisons to theoretical generalized contact formalism (GCF) cross-section calculations show good agreement using both phenomenological and chiral nucleon-nucleon potentials, favoring a lower pp to np pair ratio. The ability of the GCF calculation to describe the experimental data using either phenomenological or chiral potentials suggests possible reduction of scale and scheme dependence in cross-section ratios. Our results also support the high-resolution description of high-momentum states being predominantly due to nucleons in SRC pairs.

17.
Phys Rev Lett ; 121(9): 092501, 2018 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-30230869

RESUMO

Short-range correlated (SRC) nucleon pairs are a vital part of the nucleus, accounting for almost all nucleons with momentum greater than the Fermi momentum (k_{F}). A fundamental characteristic of SRC pairs is having large relative momenta as compared to k_{F}, and smaller center of mass (c.m.) which indicates a small separation distance between the nucleons in the pair. Determining the c.m. momentum distribution of SRC pairs is essential for understanding their formation process. We report here on the extraction of the c.m. motion of proton-proton (pp) SRC pairs in carbon and, for the first time in heavier and ansymetric nuclei: aluminum, iron, and lead, from measurements of the A(e,e^{'}pp) reaction. We find that the pair c.m. motion for these nuclei can be described by a three-dimensional Gaussian with a narrow width ranging from 140 to 170 MeV/c, approximately consistent with the sum of two mean-field nucleon momenta. Comparison with calculations appears to show that the SRC pairs are formed from mean-field nucleons in specific quantum states.

18.
Psychol Med ; 48(2): 261-268, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-28637521

RESUMO

BACKGROUND: Negative symptoms significantly contribute to disability and lack of community participation for low functioning individuals with schizophrenia. Cognitive therapy has been shown to improve negative symptoms and functional outcome in this population. Elucidation of the mechanisms of the therapy would lead to a better understanding of negative symptoms and the development of more effective interventions to promote recovery. The objective of this study was to determine (1) whether guided success at a card-sorting task will produce improvement in defeatist beliefs, positive beliefs about the self, mood, and card-sorting performance, and (2) whether these changes in beliefs and mood predict improvements in unguided card-sorting. METHODS: Individuals with schizophrenia having prominent negative symptoms and impaired neurocognitive performance (N = 35) were randomized to guided success (n = 19) or a control (n = 16) condition. RESULTS: Controlling for baseline performance, the experimental group performed significantly better, endorsed defeatist beliefs to a lesser degree, reported greater positive self-concept, and reported better mood than the control condition immediately after the experimental session. A composite index of change in defeatist beliefs, self-concept, and mood was significantly correlated with improvements in card-sorting. CONCLUSIONS: This analogue study supports the rationale of cognitive therapy and provides a general therapeutic model in which experiential interventions that produce success have a significant immediate effect on a behavioral task, mediated by changes in beliefs and mood. The rapid improvement is a promising indicator of the responsiveness of this population, often regarded as recalcitrant, to cognitively-targeted behavioral interventions.


Assuntos
Logro , Afeto/fisiologia , Terapia Cognitivo-Comportamental/métodos , Disfunção Cognitiva/terapia , Função Executiva/fisiologia , Avaliação de Resultados em Cuidados de Saúde , Esquizofrenia/terapia , Autoimagem , Adulto , Disfunção Cognitiva/etiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Esquizofrenia/complicações , Esquizofrenia/fisiopatologia
19.
Faraday Discuss ; 208(0): 395-407, 2018 09 03.
Artigo em Inglês | MEDLINE | ID: mdl-29808189

RESUMO

Bimetallic gold based catalysts have been prepared using a sol immobilisation technique. Despite a very similar metal dispersion, different structures are revealed depending on the second metal, with alloyed systems being preferred in the case of Pd, Pt and Cu, and core-shell in the case of Ru. A positive synergistic effect between the metals has been revealed only in the cases of Pd and Cu in the oxidation of benzyl alcohol. AuPd/C has been also studied in the hydrogenation of benzaldehyde where the bimetallic catalyst revealed a different selectivity compared to the monometallic counterpart.

20.
Acta Psychiatr Scand ; 137(3): 252-262, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29377059

RESUMO

OBJECTIVE: We investigated the potential of computer-based models to decode diagnosis and lifetime consumption in alcohol dependence (AD) from grey-matter pattern information. As machine-learning approaches to psychiatric neuroimaging have recently come under scrutiny due to unclear generalization and the opacity of algorithms, our investigation aimed to address a number of methodological criticisms. METHOD: Participants were adult individuals diagnosed with AD (N = 119) and substance-naïve controls (N = 97) ages 20-65 who underwent structural MRI. Machine-learning models were applied to predict diagnosis and lifetime alcohol consumption. RESULTS: A classification scheme based on regional grey matter attained 74% diagnostic accuracy and predicted lifetime consumption with high accuracy (r = 0.56, P < 10-10 ). A key advantage of the classification scheme was its algorithmic transparency, revealing cingulate, insular and inferior frontal cortices as important brain areas underlying classification. Validation of the classification scheme on data of an independent trial was successful with nearly identical accuracy, addressing the concern of generalization. Finally, compared to a blinded radiologist, computer-based classification showed higher accuracy and sensitivity, reduced age and gender biases, but lower specificity. CONCLUSION: Computer-based models applied to whole-brain grey-matter predicted diagnosis and lifetime consumption in AD with good accuracy. Computer-based classification may be particularly suited as a screening tool with high sensitivity.


Assuntos
Consumo de Bebidas Alcoólicas , Alcoolismo/diagnóstico por imagem , Córtex Cerebral/diagnóstico por imagem , Substância Cinzenta/diagnóstico por imagem , Interpretação de Imagem Assistida por Computador/métodos , Processamento de Imagem Assistida por Computador/métodos , Aprendizado de Máquina , Imageamento por Ressonância Magnética/métodos , Adulto , Idoso , Consumo de Bebidas Alcoólicas/patologia , Alcoolismo/patologia , Atrofia/patologia , Córtex Cerebral/patologia , Feminino , Substância Cinzenta/patologia , Humanos , Masculino , Pessoa de Meia-Idade , Adulto Jovem
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA