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Change history: In this Article, the original affiliation 2 was not applicable and has been removed. In addition, in the Acknowledgements there was a statement missing and an error in a name. These errors have been corrected online.
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An Amendment to this paper has been published and can be accessed via a link at the top of the paper.
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Carbon and other volatiles in the form of gases, fluids or mineral phases are transported from Earth's surface into the mantle at convergent margins, where the oceanic crust subducts beneath the continental crust. The efficiency of this transfer has profound implications for the nature and scale of geochemical heterogeneities in Earth's deep mantle and shallow crustal reservoirs, as well as Earth's oxidation state. However, the proportions of volatiles released from the forearc and backarc are not well constrained compared to fluxes from the volcanic arc front. Here we use helium and carbon isotope data from deeply sourced springs along two cross-arc transects to show that about 91 per cent of carbon released from the slab and mantle beneath the Costa Rican forearc is sequestered within the crust by calcite deposition. Around an additional three per cent is incorporated into the biomass through microbial chemolithoautotrophy, whereby microbes assimilate inorganic carbon into biomass. We estimate that between 1.2 × 108 and 1.3 × 1010 moles of carbon dioxide per year are released from the slab beneath the forearc, and thus up to about 19 per cent less carbon is being transferred into Earth's deep mantle than previously estimated.
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Dióxido de Carbono/análise , Sequestro de Carbono , Sedimentos Geológicos/química , Biomassa , Isótopos de Carbono , Costa Rica , Sedimentos Geológicos/microbiologia , HélioRESUMO
PURPOSE OF REVIEW: In this article, we reviewed 67 reported cases of linezolid optic neuropathy and describe the common characteristics and expectations for recovery with an emphasis on recent findings in the literature. RECENT FINDINGS: Linezolid classically causes a reversible, duration-dependent optic neuropathy. However, in our review, we found only 66.7% of patients recovered complete visual function. Vision loss most commonly affected visual acuity followed by visual field and color vision. We also found patients taking higher doses of linezolid experienced full recovery less often, suggesting a dose-dependent component of linezolid optic neuropathy. Linezolid use has increased in frequency and duration, especially in the treatment of drug-resistant tuberculosis, and data indicate that these patients experience lower rates of complete vision recovery compared with patients taking linezolid for other indications. SUMMARY: Linezolid is an effective medication for treating drug-resistant infections; however, it may result in optic neuropathy. It is reasonable for patients on linezolid to undergo screening examinations, especially those on higher doses or for prolonged duration of therapy.
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Anti-Infecciosos , Doenças do Nervo Óptico , Humanos , Linezolida/efeitos adversos , Doenças do Nervo Óptico/induzido quimicamente , Doenças do Nervo Óptico/diagnóstico , Nervo Óptico , Transtornos da VisãoRESUMO
The nature of inter-group relations among prehistoric hunter-gatherers remains disputed, with arguments in favour and against the existence of warfare before the development of sedentary societies. Here we report on a case of inter-group violence towards a group of hunter-gatherers from Nataruk, west of Lake Turkana, which during the late Pleistocene/early Holocene period extended about 30 km beyond its present-day shore. Ten of the twelve articulated skeletons found at Nataruk show evidence of having died violently at the edge of a lagoon, into which some of the bodies fell. The remains from Nataruk are unique, preserved by the particular conditions of the lagoon with no evidence of deliberate burial. They offer a rare glimpse into the life and death of past foraging people, and evidence that warfare was part of the repertoire of inter-group relations among prehistoric hunter-gatherers.
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Arqueologia , Processos Grupais , Violência/história , Ferimentos e Lesões/história , Adolescente , Adulto , Criança , Pré-Escolar , Comportamento Alimentar , Feminino , História Antiga , Humanos , Quênia , Masculino , Esqueleto , Crânio/lesõesRESUMO
Rust, putatively caused by Puccinia emaculata, is a widespread and potentially damaging disease of switchgrass, a crop produced as feedstock for livestock and bioenergy. Azoxystrobin, chlorothalonil, and myclobutanil were applied at 1-, 2-, 3-, or 4-week intervals for 12 to 14 weeks to the vegetatively propagated switchgrass cultivar Cloud Nine to assess fungicide selection and application interval for the control of rust as well as the impact of this disease on switchgrass biomass yield. Although rust severity significantly differed among study years, azoxystrobin and myclobutanil were often equally and more effective than chlorothalonil at controlling rust, with superior disease control coming at shorter application intervals compared with extended application intervals. Year, product, application interval, and product × interval significantly impacted dry biomass yield, which was greatest in 2016 and lowest in 2014. Dry biomass yield protection was significantly better with azoxystrobin and myclobutanil applications than with chlorothalonil or no fungicide. Linear regression models with the final disease rating, as well as with the area under disease progress curve in each year, were significant, but coefficients of determination were low to moderate (0.21 < R2 < 0.60), indicating that rust response and subsequent disease impact on dry biomass yield were impacted by other factors. From our models, an estimated 3 to 5% biomass decline was calculated for each 10% increment in rust-related leaf necrosis observed at the final September rating date. With rust-related leaf necrosis ≥80% by 1 September in each of 4 study years, biomass yield may be reduced by 24 to 40% if rust problems are not managed in switchgrass crops.
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Panicum , Doenças das Plantas/microbiologia , Puccinia/patogenicidade , Biomassa , Panicum/crescimento & desenvolvimento , Panicum/microbiologiaRESUMO
Infection with human cytomegalovirus (CMV) is common and may have grave consequences in transplant recipients and congenitally infected children. Diagnosis of CMV infection is based on detection of specific antibodies and molecular assays. The incorporation of CMV serological assays into diagnostic algorithms requires careful evaluation and interpretation. Very few serological assays measure CMV infection by a specific strain. We developed an enzyme-linked immunosorbent assay (ELISA) using CMV-encoded UL144 as the antigen. UL144 encodes three major genotypes, A, B, and C, and recombinants. The ELISA was developed with the three UL144 proteins and optimized as a multiplex assay. Sera from 55 positive and 59 negative CMV IgG, determined by the clinical microbiology laboratory, were used for evaluation and optimization. A cutoff optical density (OD) that distinguishes UL144 antibody-positive from antibody-negative sera was established. UL144 A, B, C, and combinations of these antigens were detected in sera. An assay threshold of 0.1 was established and, from a total of 303 sera, the overall sensitivity, specificity, and positive and negative predictive values of the multiplex ELISA were 86.72% (95% confidence interval [CI] 79.59% to 92.07%), 96.57% (92.69% to 98.73%), 94.40% (88.45% to 97.38%), and 91.60% (87.50% to 94.44%), respectively. The inter- and intraassay median coefficients of variation were 0.06 (interquartile range [IQR] 0.56, 0.2) and 0.171 (IQR 0.038, 0.302), respectively. No cross-reactivity was observed with HSV-positive CMV-negative sera. This ELISA gives simple and reproducible results for detection of anti-CMV UL144 IgG. It may assist in differentiating natural infection from CMV vaccines that lack UL144, and may provide an important tool for epidemiological studies of CMV strains.
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Infecções por Citomegalovirus , Citomegalovirus , Anticorpos Antivirais , Criança , Citomegalovirus/genética , Infecções por Citomegalovirus/diagnóstico , Ensaio de Imunoadsorção Enzimática , Humanos , Imunoglobulina G , Glicoproteínas de Membrana , Proteínas ViraisRESUMO
AIM: To quantify the association between behaviour change and weight loss after diagnosis of Type 2 diabetes, and the likelihood of remission of diabetes at 5-year follow-up. METHOD: We conducted a prospective cohort study in 867 people with newly diagnosed diabetes aged 40-69 years from the ADDITION-Cambridge trial. Participants were identified via stepwise screening between 2002 and 2006, and underwent assessment of weight change, physical activity (EPAQ2 questionnaire), diet (plasma vitamin C and self-report), and alcohol consumption (self-report) at baseline and 1 year after diagnosis. Remission was examined at 5 years after diabetes diagnosis via HbA1c level. We constructed log binomial regression models to quantify the association between change in behaviour and weight over both the first year after diagnosis and the subsequent 1-5 years, as well as remission at 5-year follow-up. RESULTS: Diabetes remission was achieved in 257 participants (30%) at 5-year follow-up. Compared with people who maintained the same weight, those who achieved ≥ 10% weight loss in the first year after diagnosis had a significantly higher likelihood of remission [risk ratio 1.77 (95% CI 1.32 to 2.38; p<0.01)]. In the subsequent 1-5 years, achieving ≥10% weight loss was also associated with remission [risk ratio 2.43 (95% CI 1.78 to 3.31); p<0.01]. CONCLUSION: In a population-based sample of adults with screen-detected Type 2 diabetes, weight loss of ≥10% early in the disease trajectory was associated with a doubling of the likelihood of remission at 5 years. This was achieved without intensive lifestyle interventions or extreme calorie restrictions. Greater attention should be paid to enabling people to achieve weight loss following diagnosis of Type 2 diabetes.
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Diabetes Mellitus Tipo 2/epidemiologia , Diabetes Mellitus Tipo 2/terapia , Comportamentos Relacionados com a Saúde/fisiologia , Redução de Peso/fisiologia , Adulto , Idoso , Estudos de Coortes , Diabetes Mellitus Tipo 2/psicologia , Dieta/métodos , Inglaterra/epidemiologia , Exercício Físico/fisiologia , Feminino , Seguimentos , Humanos , Estilo de Vida , Masculino , Pessoa de Meia-Idade , Indução de Remissão/métodos , Comportamento de Redução do RiscoRESUMO
Coxiella burnetii, the causative agent of Q fever, is widely present in dairy products around the world. It has been isolated from unpasteurised milk and cheese and can survive for extended periods of time under typical storage conditions for these products. Although consumption of contaminated dairy products has been suggested as a potential route for transmission, it remains controversial. Given the high prevalence of C. burnetii in dairy products, we sought to examine the feasibility of transmitting the major sequence types (ST16, ST8 and ST20) of C. burnetii circulating in the United States. We delivered three strains of C. burnetii, comprising each sequence type, directly into the stomachs of immunocompetent BALB/c mice via oral gavage (OG) and assessed them for clinical symptoms, serological response and bacterial dissemination. We found that mice receiving C. burnetii by OG had notable splenomegaly only after infection with ST16. A robust immune response and persistence in the stomach and mesenteric lymph nodes were observed in mice receiving ST16 and ST20 by OG, and dissemination of C. burnetii to peripheral tissues was observed in all OG infected mice. These findings support the oral route as a mode of transmission for C. burnetii.
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Coxiella burnetii/crescimento & desenvolvimento , Laticínios/microbiologia , Transmissão de Doença Infecciosa , Ingestão de Alimentos , Doenças Transmitidas por Alimentos , Febre Q/transmissão , Animais , Coxiella burnetii/classificação , Coxiella burnetii/genética , Modelos Animais de Doenças , Genótipo , Masculino , Camundongos Endogâmicos BALB C , Estados UnidosRESUMO
BACKGROUND: Acute hypoxemic respiratory failure (AHRF) and acute respiratory distress syndrome (ARDS) are associated with high in-hospital mortality. However, in cohorts of ARDS patients from the 1990s, patients more commonly died from sepsis or multi-organ failure rather than refractory hypoxemia. Given increased attention to lung-protective ventilation and sepsis treatment in the past 25 years, we hypothesized that causes of death may be different among contemporary cohorts. These differences may provide clinicians with insight into targets for future therapeutic interventions. METHODS: We identified adult patients hospitalized at a single tertiary care center (2016-2017) with AHRF, defined as PaO2/FiO2 ≤ 300 while receiving invasive mechanical ventilation for > 12 h, who died during hospitalization. ARDS was adjudicated by multiple physicians using the Berlin definition. Separate abstractors blinded to ARDS status collected data on organ dysfunction and withdrawal of life support using a standardized tool. The primary cause of death was defined as the organ system that most directly contributed to death or withdrawal of life support. RESULTS: We identified 385 decedents with AHRF, of whom 127 (33%) had ARDS. The most common primary causes of death were sepsis (26%), pulmonary dysfunction (22%), and neurologic dysfunction (19%). Multi-organ failure was present in 70% at time of death, most commonly due to sepsis (50% of all patients), and 70% were on significant respiratory support at the time of death. Only 2% of patients had insupportable oxygenation or ventilation. Eighty-five percent died following withdrawal of life support. Patients with ARDS more often had pulmonary dysfunction as the primary cause of death (28% vs 19%; p = 0.04) and were also more likely to die while requiring significant respiratory support (82% vs 64%; p < 0.01). CONCLUSIONS: In this contemporary cohort of patients with AHRF, the most common primary causes of death were sepsis and pulmonary dysfunction, but few patients had insupportable oxygenation or ventilation. The vast majority of deaths occurred after withdrawal of life support. ARDS patients were more likely to have pulmonary dysfunction as the primary cause of death and die while requiring significant respiratory support compared to patients without ARDS.
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Síndrome do Desconforto Respiratório/etiologia , Insuficiência Respiratória/etiologia , Idoso , Estudos de Coortes , Feminino , Humanos , Hipóxia/fisiopatologia , Masculino , Michigan , Pessoa de Meia-Idade , Estudos Prospectivos , Síndrome do Desconforto Respiratório/epidemiologia , Síndrome do Desconforto Respiratório/mortalidade , Insuficiência Respiratória/epidemiologia , Insuficiência Respiratória/mortalidade , Estudos Retrospectivos , Fatores de RiscoRESUMO
BACKGROUND: Angelman syndrome (AS) is a neurodevelopmental disorder caused by a lack of expression of the maternally inherited UBE3A gene on chromosome 15. Individuals with AS due to a UBE3A mutation are more likely to have siblings who also have AS compared with those with AS due to other cytogenetic/molecular mechanisms, but it is unknown whether the developmental outcome of siblings who have AS is similar. METHODS: Through an ongoing AS Natural History Study, we identified seven pairs of siblings with AS due to a UBE3A mutation. We compared the neurodevelopment of the first-born and second-born siblings with AS participants who have a UBE3A mutation and have either typically developing siblings or no siblings. RESULTS: Second-born AS participants due to a UBE3A mutation were more likely to be diagnosed at an earlier age. With the exception of higher expressive language scores among the second-born participants, no other differences were observed in the developmental and adaptive functioning skills across the different groups. CONCLUSIONS: The presence of an older sibling with the same neurodevelopmental disorder is associated with an earlier age of diagnosis and may be associated with an improvement in expressive language skills; the developmental outcome of siblings with AS due to a UBE3A mutation is otherwise comparable.
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Síndrome de Angelman/diagnóstico , Síndrome de Angelman/fisiopatologia , Ordem de Nascimento , Irmãos , Ubiquitina-Proteína Ligases/genética , Fatores Etários , Síndrome de Angelman/genética , Criança , Pré-Escolar , Diagnóstico Precoce , Feminino , Humanos , Lactente , MasculinoRESUMO
BACKGROUND: Rural, low-income US veterans face additional barriers to accessing food and resources compared to urban veterans. Based on both social-ecological and cultural competence approaches, the Reaching Rural Veterans (RRV) pilot intervention built on the existing infrastructure of food pantries to improve food security and connect rural, low-income veterans with resources. This article describes the process of implementing and evaluating RRV. METHODS: Five rural food pantries within each of two states, Indiana and Kentucky, received training in cultural competence and held monthly outreach events where food and services were offered to veterans. Veteran adult participants completed an assessment at baseline and 3-month follow-up that measured food security using the US Household Food Security Survey Module and self-reported resource enrollment. Repeated measures logistic regression models evaluated the odds of improving food security and resource enrollment from baseline to follow-up (significance P < 0.05). RESULTS: RRV recruited 234 participants; 53% completed the follow-up assessment. At follow-up, the odds of household (P = 0.009) and adult (P = 0.01) food security increased, as did enrollment in one or more of the following resources: Temporary Assistance for Needy Families, Supplemental Security Income, General Assistance or Assistance from the Township Trustee (P = 0.005). CONCLUSIONS: RRV yielded promising preliminary results of improved food security and resource use.
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Abastecimento de Alimentos/métodos , Pobreza , População Rural , Veteranos , Adolescente , Adulto , Idoso , Feminino , Assistência Alimentar , Humanos , Indiana , Kentucky , Masculino , Pessoa de Meia-Idade , Adulto JovemRESUMO
PURPOSE: Studies have found that pomegranate juice (PJ) consumption increases the binding of high-density lipoproteins (HDL) to paraoxonase 1 (PON1), thus increasing the catalytic activity of this enzyme. PON1 is an antioxidant arylesterase synthesized in the liver and transported in plasma in association with HDL. Decreased levels of PON1 are associated with higher levels of cholesterol. We determined the effects of PJ on body weight, cholesterol, and triacylglycerols through 5 months of supplementation. In addition, the effect of PJ on pon1 gene expression in the liver was also measured by RT-qPCR as well as the activity in serum by a semiautomated method using paraoxon as a substrate. METHODS: CD-1 mice were either fed a control diet or were fed a high-fat diet 1.25% (wt/wt) cholesterol, 0.5% (wt/wt) sodium cholate, and 15% (wt/wt) saturated fat. 300 µL of PJ containing 0.35 mmol total polyphenols was administered by oral gavage to half of the high fat mice daily. The rest of the high fat mice and the control mice were administered with 300 µL of water. RESULTS: PJ-supplemented animals had significantly higher levels of expression of pon1 compared to the unsupplemented group. PJ-supplemented animals had twice the PON1 activity of the unsupplemented group. In addition, PJ-supplemented animals had the lowest body weight and significantly reduced cholesterol and triacylglycerol levels, although the tricylglycerol levels were not consistently decreased. CONCLUSIONS: These results suggest that PJ protects against the effects of a high-fat diet in body weight, and cholesterol levels.
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Arildialquilfosfatase/sangue , Arildialquilfosfatase/genética , Dieta Hiperlipídica/efeitos adversos , Sucos de Frutas e Vegetais , Frutas , Lythraceae , Animais , Peso Corporal , Colesterol/sangue , Suplementos Nutricionais , Expressão Gênica , Fígado/química , Camundongos , RNA Mensageiro/análise , Triglicerídeos/sangueRESUMO
Target spot, caused by Corynespora cassiicola, has recently emerged as a problematic foliar disease of cotton. This pathogen causes premature defoliation during boll set and maturation that can subsequently impact yield, and on certain cotton cultivars loss can be substantial. This study sought to better understand target spot epidemics and disease-incited yield losses on cotton. In order to establish a range of disease, varying numbers of fungicide applications were made to each of two cotton cultivars in each of four site-years. Target spot intensity was rated over several dates beginning in late July or early August and continuing into September. Yield of seed plus lint (seed cotton) was recorded at harvest. When analyzed across cultivars, a second or third fungicide application increased yield compared with no treatment. Lack of significant yield response with a single fungicide application may have been due to timing of that application which preceded disease onset. The cultivar PhytoGen 499 WRF had consistently greater defoliation than any of the three Deltapine cultivars grown in each site-year. However, yields of both cultivars responded similarly to the fungicide regimes. Yield loss models based on late August defoliation were only predictive at site-years where conditions favored target spot development, i.e., abundant rain and moderate temperatures. Epidemic development fit the Gompertz growth model better than it did a logistic model. Knowledge of the underlying mathematical character of the epidemiology of target spot will prove useful for development of a predictive model for the disease.
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Ascomicetos/fisiologia , Gossypium/microbiologia , Doenças das Plantas/estatística & dados numéricos , Fungicidas Industriais , Gossypium/crescimento & desenvolvimento , Modelos Estatísticos , Doenças das Plantas/microbiologia , Sementes/crescimento & desenvolvimento , Sementes/microbiologia , Tempo (Meteorologia)RESUMO
1. The aim of this study was to evaluate the effects of phytase and xylanase and their interaction on laying hen performance, egg quality, phosphorus (P) digestibility, phytate breakdown, volatile fatty acid (VFA) production and peptide YY concentration. 2. Two hundred and forty hens were allocated to cages at 22 weeks of age based on a 3 × 2 arrangement with phytase (0, 300 or 1500 FTU/kg) and xylanase (0 or 12 000 BXU/kg) as factors. 3. Phytase increased hen-day production (P < 0.05), daily egg mass (P < 0.05) and P digestibility with increasing levels of phytase (P < 0.001). Phytase fed at 1500 FTU/kg reduced IP6 and IP5 and increased myo-inositol concentration in gizzard digesta (P < 0.05). Phytase fed at 300 FTU/kg reduced IP6 in ileal digesta (P < 0.05); however, IP6 and IP5 were further reduced and myo-inositol increased when phytase was added at 1500 FTU/kg (P < 0.05). 4. Xylanase improved feed efficiency when phytase was fed at 300 FTU/kg (P < 0.05). In the absence of phytase, xylanase reduced dry matter and Ca digestibilities (P < 0.05). 5. Neither phytase nor xylanase had an effect on peptide YY or caecal VFA concentrations.
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6-Fitase/farmacologia , Galinhas/fisiologia , Ovos/normas , Endo-1,4-beta-Xilanases/farmacologia , Aditivos Alimentares/farmacologia , Ração Animal , Fenômenos Fisiológicos da Nutrição Animal/efeitos dos fármacos , Animais , Galinhas/crescimento & desenvolvimento , Dieta , Digestão , Feminino , Fósforo na Dieta/metabolismoRESUMO
As children living with HIV (CLHIV) grow into adolescence and adulthood, caregivers and healthcare providers are faced with the sensitive challenge of when to disclose to a CLHIV his or her HIV status. Despite WHO recommendations for CLHIV to know their status, in countries most affected by HIV, effective resources are often limited, and national guidance on disclosure is often lacking. To address the need for effective resources, gray and scientific literature was searched to identify existing tools and resources that can aid in the disclosure process. From peer-reviewed literature, seven disclosure models from six different countries were identified. From the gray literature, 23 resources were identified including children's books (15), job aides to assist healthcare providers (5), and videos (3). While these existing resources can be tailored to reflect local norms and used to aid in the disclosure process, careful consideration must be taken in order to avoid damaging disclosure practices.
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Cuidadores/psicologia , Comunicação , Infecções por HIV/psicologia , Pessoal de Saúde/psicologia , Revelação da Verdade , Adolescente , Criança , Feminino , Infecções por HIV/diagnóstico , Conhecimentos, Atitudes e Prática em Saúde , Recursos em Saúde , Humanos , Conhecimento , Masculino , Grupo AssociadoRESUMO
BACKGROUND: Patient-reported outcomes (PROs) are of growing importance in research and clinical care and may be used as primary outcomes or as compliments to traditional surgical outcomes. In assessing the impact of surgical and traumatic scars, PROs are often the most meaningful. To assess outcomes from the patient perspective, rigorously developed and validated PRO instruments are essential. METHODS: The authors conducted a systematic literature review to identify PRO instruments developed and/or validated for patients with surgical and/or non-burn traumatic scars. Identified instruments were assessed for content, development process, and validation under recommended guidelines for PRO instrument development. RESULTS: The systematic review identified 6534 articles. After review, we identified four PRO instruments meeting inclusion criteria: patient and observer scar assessment scale (POSAS), bock quality of life questionnaire for patients with keloid and hypertrophic scarring (Bock), patient scar assessment questionnaire (PSAQ), and patient-reported impact of scars measure (PRISM). Common concepts measured were symptoms and psychosocial well-being. Only PSAQ had a dedicated appearance domain. Qualitative data were used to inform content for the PSAQ and PRISM, and a modern psychometric approach (Rasch Measurement Theory) was used to develop PRISM and to test POSAS. Overall, PRISM demonstrated the most rigorous design and validation process, however, was limited by the lack of a dedicated appearance domain. CONCLUSIONS: PRO instruments to evaluate outcomes in scars exist but vary in terms of concepts measured and psychometric soundness. This review discusses the strengths and weaknesses of existing instruments, highlighting the need for future scar-focused PRO instrument development. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to Table of Contents or the online Instructions to Authors www.springer.com/00266 .
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Cicatriz/psicologia , Medidas de Resultados Relatados pelo Paciente , Qualidade de Vida , Ferimentos e Lesões/cirurgia , Cicatriz/epidemiologia , Cicatriz/etiologia , Feminino , Humanos , Masculino , Satisfação do Paciente/estatística & dados numéricos , Psicometria , Ferida Cirúrgica/complicações , Ferida Cirúrgica/psicologia , Ferimentos e Lesões/complicaçõesRESUMO
Blazars are the most extreme active galactic nuclei. They possess oppositely directed plasma jets emanating at near light speeds from accreting supermassive black holes. According to theoretical models, such jets are propelled by magnetic fields twisted by differential rotation of the black hole's accretion disk or inertial-frame-dragging ergosphere. The flow velocity increases outward along the jet in an acceleration and collimation zone containing a coiled magnetic field. Detailed observations of outbursts of electromagnetic radiation, for which blazars are famous, can potentially probe the zone. It has hitherto not been possible to either specify the location of the outbursts or verify the general picture of jet formation. Here we report sequences of high-resolution radio images and optical polarization measurements of the blazar BL Lacertae. The data reveal a bright feature in the jet that causes a double flare of radiation from optical frequencies to TeV gamma-ray energies, as well as a delayed outburst at radio wavelengths. We conclude that the event starts in a region with a helical magnetic field that we identify with the acceleration and collimation zone predicted by the theories. The feature brightens again when it crosses a standing shock wave corresponding to the bright 'core' seen on the images.