Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 274
Filtrar
Mais filtros

Base de dados
Tipo de documento
Intervalo de ano de publicação
1.
Phys Rev Lett ; 130(5): 051802, 2023 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-36800478

RESUMO

The inclusive electron neutrino charged-current cross section is measured in the NOvA near detector using 8.02×10^{20} protons-on-target in the NuMI beam. The sample of GeV electron neutrino interactions is the largest analyzed to date and is limited by ≃17% systematic rather than the ≃7.4% statistical uncertainties. The double-differential cross section in final-state electron energy and angle is presented for the first time, together with the single-differential dependence on Q^{2} (squared four-momentum transfer) and energy, in the range 1 GeV≤E_{ν}<6 GeV. Detailed comparisons are made to the predictions of the GENIE, GiBUU, NEUT, and NuWro neutrino event generators. The data do not strongly favor a model over the others consistently across all three cross sections measured, though some models have especially good or poor agreement in the single differential cross section vs Q^{2}.

2.
Phys Rev Lett ; 127(20): 201801, 2021 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-34860065

RESUMO

This Letter reports results from the first long-baseline search for sterile antineutrinos mixing in an accelerator-based antineutrino-dominated beam. The rate of neutral-current interactions in the two NOvA detectors, at distances of 1 and 810 km from the beam source, is analyzed using an exposure of 12.51×10^{20} protons-on-target from the NuMI beam at Fermilab running in antineutrino mode. A total of 121 of neutral-current candidates are observed at the far detector, compared to a prediction of 122±11(stat.)±15(syst.) assuming mixing only between three active flavors. No evidence for ν[over ¯]_{µ}→ν[over ¯]_{s} oscillation is observed. Interpreting this result within a 3+1 model, constraints are placed on the mixing angles θ_{24}<25° and θ_{34}<32° at the 90% C.L. for 0.05 eV^{2}≤Δm_{41}^{2}≤0.5 eV^{2}, the range of mass splittings that produces no significant oscillations at the near detector. These are the first 3+1 confidence limits set using long-baseline accelerator antineutrinos.

3.
Phys Rev Lett ; 123(15): 151803, 2019 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-31702305

RESUMO

The NOvA experiment has seen a 4.4σ signal of ν[over ¯]_{e} appearance in a 2 GeV ν[over ¯]_{µ} beam at a distance of 810 km. Using 12.33×10^{20} protons on target delivered to the Fermilab NuMI neutrino beamline, the experiment recorded 27 ν[over ¯]_{µ}→ν[over ¯]_{e} candidates with a background of 10.3 and 102 ν[over ¯]_{µ}→ν[over ¯]_{µ} candidates. This new antineutrino data are combined with neutrino data to measure the parameters |Δm_{32}^{2}|=2.48_{-0.06}^{+0.11}×10^{-3} eV^{2}/c^{4} and sin^{2}θ_{23} in the ranges from (0.53-0.60) and (0.45-0.48) in the normal neutrino mass hierarchy. The data exclude most values near δ_{CP}=π/2 for the inverted mass hierarchy by more than 3σ and favor the normal neutrino mass hierarchy by 1.9σ and θ_{23} values in the upper octant by 1.6σ.

4.
Phys Rev Lett ; 118(15): 151802, 2017 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-28452513

RESUMO

This Letter reports new results on muon neutrino disappearance from NOvA, using a 14 kton detector equivalent exposure of 6.05×10^{20} protons on target from the NuMI beam at the Fermi National Accelerator Laboratory. The measurement probes the muon-tau symmetry hypothesis that requires maximal θ_{23} mixing (θ_{23}=π/4). Assuming the normal mass hierarchy, we find Δm_{32}^{2}=(2.67±0.11)×10^{-3} eV^{2} and sin^{2}θ_{23} at the two statistically degenerate values 0.404_{-0.022}^{+0.030} and 0.624_{-0.030}^{+0.022}, both at the 68% confidence level. Our data disfavor the maximal mixing scenario with 2.6σ significance.

5.
Phys Rev Lett ; 118(23): 231801, 2017 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-28644674

RESUMO

Results are reported from an improved measurement of ν_{µ}→ν_{e} transitions by the NOvA experiment. Using an exposure equivalent to 6.05×10^{20} protons on target, 33 ν_{e} candidates are observed with a background of 8.2±0.8 (syst.). Combined with the latest NOvA ν_{µ} disappearance data and external constraints from reactor experiments on sin^{2}2θ_{13}, the hypothesis of inverted mass hierarchy with θ_{23} in the lower octant is disfavored at greater than 93% C.L. for all values of δ_{CP}.

6.
J Appl Microbiol ; 121(2): 577-86, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-27187055

RESUMO

AIMS: High rate algal ponds (HRAPs) have been suggested as replacements for waste stabilization ponds (WSPs) in Community Wastewater Management Systems (CWMS) used in rural South Australian (SA) towns. Treated effluent from CWMS is reused for irrigation. To manage the risk of human exposure to pathogens, the disinfection performance of HRAPs was validated using the common indicators Escherichia coli and F-RNA bacteriophage; aerobic spore-forming bacteria (ASFB) were used as indicators for protozoa. METHODS AND RESULTS: Using standard culture methods, the removal of the indicator organisms F-RNA bacteriophage, E. coli and ASFB by a HRAP at Kingston-on-Murray, SA, was measured. The mean log10 reduction values achieved for the F-RNA bacteriophage was 1·59 ± 0·82 log10 PFU 100 ml(-1) and for E. coli it was 2·13 ± 0·55 log10  E. coli MPN 100 ml(-1) . ASFB numbers in the treated pond effluent often exceeded those of the influent. CONCLUSIONS: The results show that HRAPs are able to remove viral and bacterial indicators to levels acceptable for subsurface irrigation of nonfood crops. Additionally, it was concluded that alternate environmental sources and the potential for regrowth made ASFB unsuitable indicators for pathogenic protozoa in natural pond systems. SIGNIFICANCE AND IMPACT OF THE STUDY: This study shows HRAPs would be suitable replacements for WSPs in CWMS schemes in regard to pathogen disinfection. Such demonstration of the treatment efficacy of HRAPs, together with their smaller land area requirements relative to WSPs, should facilitate their wider adoption in rural and remote communities.


Assuntos
Bactérias/crescimento & desenvolvimento , Clorófitas/fisiologia , Lagoas/microbiologia , Águas Residuárias/microbiologia , Purificação da Água/métodos , Austrália , Bactérias/isolamento & purificação , Viabilidade Microbiana , Lagoas/química , Eliminação de Resíduos Líquidos/métodos
7.
Phys Rev Lett ; 112(6): 061802, 2014 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-24580687

RESUMO

The T2K experiment has observed electron neutrino appearance in a muon neutrino beam produced 295 km from the Super-Kamiokande detector with a peak energy of 0.6 GeV. A total of 28 electron neutrino events were detected with an energy distribution consistent with an appearance signal, corresponding to a significance of 7.3σ when compared to 4.92±0.55 expected background events. In the Pontecorvo-Maki-Nakagawa-Sakata mixing model, the electron neutrino appearance signal depends on several parameters including three mixing angles θ12, θ23, θ13, a mass difference Δm(32)(2) and a CP violating phase δ(CP). In this neutrino oscillation scenario, assuming |Δm(32)(2)|=2.4×10(-3) eV(2), sin(2)θ(23)=0.5, and Δm322>0 (Δm(32)(2)<0), a best-fit value of sin(2)2θ(13)=0.140(-0.032)(+0.038) (0.170(-0.037)(+0.045)) is obtained at δ(CP)=0. When combining the result with the current best knowledge of oscillation parameters including the world average value of θ(13) from reactor experiments, some values of δ(CP) are disfavored at the 90% C.L.

8.
Phys Rev Lett ; 112(18): 181801, 2014 May 09.
Artigo em Inglês | MEDLINE | ID: mdl-24856687

RESUMO

New data from the T2K neutrino oscillation experiment produce the most precise measurement of the neutrino mixing parameter θ23. Using an off-axis neutrino beam with a peak energy of 0.6 GeV and a data set corresponding to 6.57×10(20) protons on target, T2K has fit the energy-dependent νµ oscillation probability to determine oscillation parameters. The 68% confidence limit on sin(2)(θ23) is 0.514(-0.056)(+0.055) (0.511±0.055), assuming normal (inverted) mass hierarchy. The best-fit mass-squared splitting for normal hierarchy is Δm32(2)=(2.51±0.10)×10(-3) eV(2)/c(4) (inverted hierarchy: Δm13(2)=(2.48±0.10)×10(-3) eV(2)/c(4)). Adding a model of multinucleon interactions that affect neutrino energy reconstruction is found to produce only small biases in neutrino oscillation parameter extraction at current levels of statistical uncertainty.

9.
Phys Rev Lett ; 113(24): 241803, 2014 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-25541766

RESUMO

The T2K off-axis near detector ND280 is used to make the first differential cross-section measurements of electron neutrino charged current interactions at energies ∼1 GeV as a function of electron momentum, electron scattering angle, and four-momentum transfer of the interaction. The total flux-averaged ν(e) charged current cross section on carbon is measured to be ⟨σ⟩(ϕ)=1.11±0.10(stat)±0.18(syst)×10⁻³8 cm²/nucleon. The differential and total cross-section measurements agree with the predictions of two leading neutrino interaction generators, NEUT and GENIE. The NEUT prediction is 1.23×10⁻³8 cm²/nucleon and the GENIE prediction is 1.08×10⁻³8 cm²/nucleon. The total ν(e) charged current cross-section result is also in agreement with data from the Gargamelle experiment.

10.
Phys Rev Lett ; 111(21): 211803, 2013 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-24313479

RESUMO

The T2K Collaboration reports a precision measurement of muon neutrino disappearance with an off-axis neutrino beam with a peak energy of 0.6 GeV. Near detector measurements are used to constrain the neutrino flux and cross section parameters. The Super-Kamiokande far detector, which is 295 km downstream of the neutrino production target, collected data corresponding to 3.01×10(20) protons on target. In the absence of neutrino oscillations, 205±17 (syst) events are expected to be detected while only 58 muon neutrino event candidates are observed. A fit to the neutrino rate and energy spectrum, assuming three neutrino flavors and normal mass hierarchy yields a best-fit mixing angle sin2(θ23)=0.514±0.082 and mass splitting |Δm(32)(2)|=2.44(-0.15)(+0.17)×10(-3) eV2/c4. Our result corresponds to the maximal oscillation disappearance probability.

11.
Phys Rev Lett ; 107(4): 041801, 2011 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-21866992

RESUMO

The T2K experiment observes indications of ν(µ) → ν(e) appearance in data accumulated with 1.43×10(20) protons on target. Six events pass all selection criteria at the far detector. In a three-flavor neutrino oscillation scenario with |Δm(23)(2)| = 2.4×10(-3) eV(2), sin(2)2θ(23) = 1 and sin(2)2θ(13) = 0, the expected number of such events is 1.5±0.3(syst). Under this hypothesis, the probability to observe six or more candidate events is 7×10(-3), equivalent to 2.5σ significance. At 90% C.L., the data are consistent with 0.03(0.04) < sin(2)2θ(13) < 0.28(0.34) for δ(CP) = 0 and a normal (inverted) hierarchy.

12.
Scand J Med Sci Sports ; 21(6): e341-50, 2011 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-21518010

RESUMO

The purpose of this study was to examine the effects of exercising at different intensities over 7 weeks on components of physical fitness and CVD risk factors. Forty-seven boys and 10 girls, (16.4±0.7 years of age) were divided into a moderate, high intensity, or a control group. All participants had indices of obesity and blood pressure recorded in addition to four physical performance measures pre- and post-intervention. In addition, the intervention groups repeated the physical performance measures at the 4th week phase of the intervention. Following the intervention, significant improvements (P<0.05) in the high-intensity group were found in the 20 MSFT, agility, CMJ and 10 m sprint post-intervention. Participants in the moderate intensity group displayed significant improvements (P<0.05) in both the CMJ and 20 MSFT post-intervention. Body fat % significantly improved (P<0.01) in the moderate group only post-intervention. Interestingly, Systolic blood pressure significantly improved post-intervention (112±10 vs 106±11 mmHg) (P=0.017) in the high intensity group. In conclusion, high-intensity exercise over 7 weeks is a very time efficient means of improving important components of physical fitness in adolescents.


Assuntos
Exercício Físico/fisiologia , Aptidão Física/fisiologia , Adolescente , Doenças Cardiovasculares/prevenção & controle , Estudos de Coortes , Feminino , Humanos , Masculino , Obesidade/prevenção & controle , Escócia , Inquéritos e Questionários
13.
J Am Coll Cardiol ; 17(6): 1334-42, 1991 May.
Artigo em Inglês | MEDLINE | ID: mdl-2016451

RESUMO

To compare the hemodynamic and gas exchange responses of ramp treadmill and cycle ergometer tests with standard exercise protocols used clinically, 10 patients with chronic heart failure, 10 with coronary artery disease who were asymptomatic during exercise, 11 with coronary artery disease who were limited by angina during exercise and 10 age-matched normal subjects performed maximal exercise using six different exercise protocols. Gas exchange data were collected continuously during each of the following protocols, performed on separate days in randomized order: Bruce, Balke and an individualized ramp treadmill; 25 W/stage, 50 W/stage and an individualized ramp cycle ergometer test. Maximal oxygen uptake was 16% greater on the treadmill protocols combined (21.4 +/- 8 ml/kg per min) versus the cycle ergometer protocols combined (18.1 +/- 7 ml/kg per min) (p less than 0.01), although no differences were observed in maximal heart rate (131 +/- 24 versus 126 +/- 24 beats/min for the treadmill and cycle ergometer protocols, respectively). No major differences were observed in maximal heart rate or maximal oxygen uptake among the various treadmill protocols or among the various cycle ergometer protocols. The ratio of oxygen uptake to work rate, expressed as a slope, was highest for the ramp tests (slope +/- SEE ml/kg per min = 0.80 +/- 2.5 and 0.78 +/- 1.7 for ramp treadmill and ramp cycle ergometer, respectively). The slopes were poorest for the tests with the largest increments in work (0.62 +/- 4.0 and 0.59 +/- 2.8 for the Bruce treadmill and 50 W/stage cycle ergometer, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)


Assuntos
Teste de Esforço/métodos , Idoso , Angina Pectoris/fisiopatologia , Limiar Diferencial , Teste de Esforço/instrumentação , Teste de Esforço/normas , Previsões , Hemodinâmica , Humanos , Masculino , Pessoa de Meia-Idade , Consumo de Oxigênio , Troca Gasosa Pulmonar , Respiração
14.
Am J Clin Nutr ; 32(12): 2439-42, 1979 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-506967

RESUMO

Hepatic microsomal oxidation and glucuronidation were studied in 15 children with kwashiorkor on admission to the hospital and again after 3 weeks of nutritional rehabilitation. Microsomal oxidation as measured by antipyrine half-life and clearance was shown to be depressed in the acute phase of malnutrition (T 1/2 = 7.9 +/- 5.0 hr, clearance = 8.4 +/- 5.1 ml/min) improving with nutritional rehabilitation (T 1/2 = 4.3 +/- 2.3 hr, clearance = 15.5 +/- 8.7 ml/min). Urinary D-glucaric acid excretion increased from 60.6 +/- 42.2 mumoles/24 hr to 121.8 +/- 105.0 mumoles/24 hr over the same time period. Evidence is thus presented that both hepatic microsomal oxidation and glucuronidation are depressed in the acute phase of kwashiorkor but recover with nutritional rehabilitation.


Assuntos
Antipirina/metabolismo , Ácido Glucárico/urina , Kwashiorkor/metabolismo , Microssomos Hepáticos/metabolismo , Açúcares Ácidos/urina , Glucuronatos/metabolismo , Meia-Vida , Humanos , Lactente , Cinética , Kwashiorkor/dietoterapia , Oxirredução
15.
Am J Clin Nutr ; 30(6): 847-50, 1977 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-68676

RESUMO

The binding of chloramphenicol to normal and kwashiorkor sera was investigated in vitro. Chloramphenicol is predominantly albumin bound, although a significant degree of binding to the other major protein fractions occurs. From the clinical view point, a decreased degree of binding of kwashiorkor serum (+/-5%) is not of significance.


Assuntos
Cloranfenicol/metabolismo , Kwashiorkor/sangue , alfa-Globulinas/metabolismo , beta-Globulinas/metabolismo , Criança , Humanos , Ligação Proteica , Albumina Sérica/metabolismo , África do Sul
16.
Am J Clin Nutr ; 32(11): 2233-6, 1979 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-495540

RESUMO

Intravenous penicillin kinetics have been studied in eight children with kwashiorkor on admission to hospital and when rehabilitated. A 75% increase in penicillin clearance was observed with recovery, associated with a fall in half-life; this was probably due to an improvement of both renal plasma flow and tubular function. The present observations and those of other authors working in this area are discussed and an approach to drug dosage of renally excreted drugs in kwashiorkor has been proposed.


Assuntos
Kwashiorkor/metabolismo , Penicilina G/metabolismo , Meia-Vida , Humanos , Lactente , Rim/irrigação sanguínea , Túbulos Renais/fisiopatologia , Cinética , Kwashiorkor/terapia , Ácido p-Aminoipúrico/metabolismo
17.
Am J Med ; 81(2A): 40-3, 1986 Aug 18.
Artigo em Inglês | MEDLINE | ID: mdl-3092653

RESUMO

In healthy human volunteers, a single oral dose of enprostil (35 micrograms) inhibited basal gastric acid output by a mean of 71 percent, pentagastrin-stimulated output by 46 percent, sham-meal-stimulated output by 48 percent, and histamine-stimulated output by 16 percent. In each case, there was a reduction in both the volume and acidity of the gastric juice. Pepsin output was unchanged. Although enprostil increased the gastric pH, it did not induce basal or post-prandial hypergastrinemia. In patients with hypergastrinemia secondary to achlorhydria, enprostil lowered the basal gastrin level and reduced or abolished the post-prandial gastrin rise in a dose-related fashion. Enprostil reduces basal and stimulated gastric acid secretion and inhibits gastrin release.


Assuntos
Anemia Perniciosa/fisiopatologia , Ácido Gástrico/metabolismo , Gastrinas/sangue , Prostaglandinas E Sintéticas/farmacologia , Acloridria/sangue , Acloridria/fisiopatologia , Adulto , Anemia Perniciosa/sangue , Emprostila , Suco Gástrico/metabolismo , Histamina , Humanos , Concentração de Íons de Hidrogênio , Masculino , Pentagastrina , Pepsina A/metabolismo , Prostaglandinas E Sintéticas/administração & dosagem
18.
Mol Biochem Parasitol ; 76(1-2): 31-42, 1996.
Artigo em Inglês | MEDLINE | ID: mdl-8919993

RESUMO

We have investigated whether Trypanosoma brucei can undergo self-fertilisation. A group of 27 metacyclic clones derived from the tsetse transmission of a mixture of two genetically marked stocks was analysed and 22 clones were observed to be of non-hybrid phenotype. A group of 10 clones from this non-hybrid subset were then analysed for one isoenzyme, one restriction fragment length polymorphism and three karyotype markers potentially informative for the detection of self-fertilisation. Five of the 10 clones were found to be recombinant for at least one marker and we interpret these recombination events as indicating the clones to be products of self-fertilisation. We have also analysed a limited number of metacyclic clones from stocks of T. brucei each singly transmitted through tsetse flies but, so far, no evidence of recombination has been detected. We conclude that T. brucei is able to self-fertilise but there may be a requirement for the presence of dissimilar stocks to initiate such an event.


Assuntos
Recombinação Genética , Trypanosoma brucei brucei/fisiologia , Animais , Eletroforese em Gel de Campo Pulsado , Fertilização/genética , Marcadores Genéticos , Insetos Vetores/parasitologia , Cariotipagem , Polimorfismo de Fragmento de Restrição , Infecções por Protozoários/transmissão , Trypanosoma brucei brucei/enzimologia , Trypanosoma brucei brucei/genética
19.
Thromb Haemost ; 77(1): 39-43, 1997 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-9031446

RESUMO

Venous thromboembolic disease remains the commonest cause of maternal death. The management of thromboprophylaxis in high risk women during pregnancy is contentious. Low molecular weight heparins (LMW) have theoretical advantages compared with unfractionated heparin and warfarin but have been poorly studied in pregnancy. We report on the use of LMW heparin (Fragmin) as thromboprophylaxis in thirty four high risk pregnancies. All the women had a previous thrombosis or a thrombosis in their current pregnancy +/- a recognised thrombophilic state (eleven had the antiphospholipid syndrome). Fragmin was given subcutaneously to maintain trough anti-Xa activity of 0.15-0.2 U/ml and 2 h post injection levels of 0.4-0.6 U/ml. The levels were checked monthly during pregnancy. Most women required 5,000U Fragmin once daily during the first trimester unless they were greater than 100 kg at the start of pregnancy. The mean time for dosage increase was 20.5 week (S.D. 8.2). 26/34 pregnancies (76%) required 5,000 twice daily at the end of pregnancy. Epidural anaesthesia was managed by omitting Fragmin dose or inserting the needle 6 hours after the previous Fragmin injection. There were no thromboembolic events thrombocytopenias or excessive haemorrhage. One woman had osteoporotic vertebral collapse post partum, she had no other risk factors for osteoporosis. LWM heparin (Fragmin) appears to be efficacious in preventing recurrent thromboembolic disease in pregnant women at high risk, but it is notable that osteoporotic fractures occurred post partum in one woman. Further trials are required to determine optimal dosage and safety.


Assuntos
Anticoagulantes/administração & dosagem , Dalteparina/administração & dosagem , Complicações Hematológicas na Gravidez/prevenção & controle , Tromboflebite/prevenção & controle , Adulto , Feminino , Humanos , Injeções Subcutâneas , Gravidez , Resultado do Tratamento
20.
Am J Cardiol ; 72(11): 767-9, 1993 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-8213507

RESUMO

To quantitate changes in gas exchange variables that occur after administration of sublingual nitroglycerin in patients with stable angina pectoris, a randomized double-blind 2-period crossover study was performed with continuous expired gas exchange analysis and progressive exercise using individualized ramp treadmill protocols. Significant reductions in minute ventilation and respiratory rate were observed at 5 minutes of exercise during nitroglycerin therapy. Gas exchange variables i.e., minute ventilation, carbon dioxide production and oxygen uptake were significantly increased at the onset of angina after nitroglycerin administration. When techniques for optimizing the assessment of cardiopulmonary function were used, significant improvements in gas exchange variables were demonstrated in stable angina pectoris after administration of sublingual nitroglycerin.


Assuntos
Angina Pectoris/tratamento farmacológico , Teste de Esforço , Nitroglicerina/uso terapêutico , Troca Gasosa Pulmonar/efeitos dos fármacos , Administração Sublingual , Idoso , Angina Pectoris/diagnóstico , Angina Pectoris/fisiopatologia , Método Duplo-Cego , Humanos , Masculino , Pessoa de Meia-Idade , Nitroglicerina/administração & dosagem , Nitroglicerina/farmacologia , Esforço Físico/efeitos dos fármacos
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA