Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 10 de 10
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Phys Rev Lett ; 123(3): 031101, 2019 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-31386438

RESUMO

The Laser Ranging Interferometer (LRI) instrument on the Gravity Recovery and Climate Experiment (GRACE) Follow-On mission has provided the first laser interferometric range measurements between remote spacecraft, separated by approximately 220 km. Autonomous controls that lock the laser frequency to a cavity reference and establish the 5 degrees of freedom two-way laser link between remote spacecraft succeeded on the first attempt. Active beam pointing based on differential wave front sensing compensates spacecraft attitude fluctuations. The LRI has operated continuously without breaks in phase tracking for more than 50 days, and has shown biased range measurements similar to the primary ranging instrument based on microwaves, but with much less noise at a level of 1 nm/sqrt[Hz] at Fourier frequencies above 100 mHz.

2.
TH Open ; 3(1): e2-e9, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31249975

RESUMO

Objectives In patients with suspected venous thromboembolism (VTE), the D-dimer assay is commonly utilized as part of the workup. The assay is primarily used to determine whether to proceed with radiographic imaging. We compared D-dimer levels in patients suspected of having VTE. We hypothesized that higher D-dimer values predict a higher likelihood of subsequent VTE diagnosis. Methods We conducted a secondary analysis of a multinational, prospective observational study of low- to intermediate-risk adult patients presenting to the emergency department with suspicion of VTE. Demographic and clinical data were collected in a structured manner. Advanced imaging including ultrasound, computed tomography (CT) pulmonary angiography, and ventilation/perfusion scanning was obtained at the discretion of the treating physicians. Imaging was evaluated by board-certified radiologists in real time. D-dimer values' bins were evaluated using a logistic regression model. Results We evaluated 1,752 patients for suspected deep vein thrombosis (DVT), with 191 (10.4%) DVT positive. We evaluated 1,834 patients for suspected pulmonary embolism (PE), with 108 (5.9%) PE positive. Higher D-dimer values in both groups were associated with higher likelihood of subsequent VTE diagnosis, with D-dimer values > 3,999 ng/mL in both groups having the highest incidence of VTE. More than 50% of those patients were VTE positive. Conclusions Increasing D-dimer values predict increased likelihood of being found VTE positive in this patient population. Among those in the highest D-dimer category, > 3,999 ng/mL, over half of patients were VTE positive. Further research could determine additional nuance in D-dimer as a tool to work up suspected VTE.

3.
Am J Emerg Med ; 37(1): 33-37, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-29703562

RESUMO

OBJECTIVES: There is growing evidence that venous thromboembolism (VTE) patients with distal clots (distal calf deep vein thrombosis [DVT] and sub-segmental pulmonary embolism [PE]) may not routinely benefit from anticoagulation. We compared the D-dimer levels in VTE patients with distal and proximal clots. METHODS: We conducted a multinational, prospective observational study of low-to-intermediate risk adult patients presenting to the emergency department (ED) with suspected VTE. Patients were classified as distal (calf DVT or sub-segmental PE) or proximal (proximal DVT or non-sub-segmental PE) clot groups and compared with univariate and multivariate analyses. RESULTS: Of 1752 patients with suspected DVT, 1561 (89.1%) had no DVT, 78 (4.4%) had a distal calf DVT, and 113 (6.4%) had a proximal DVT. DVT patients with proximal clots had higher D-dimer levels (3760 vs. 1670 mg/dL) than with distal clots. Sensitivity and negative predictive value (NPV) for proximal DVT at an optimal D-dimer cutoff of 5770 mg/dL were 40.7% and 52.1% respectively. Of 1834 patients with suspected PE, 1726 (94.1%) had no PE, 7 (0.4%) had isolated sub-segmental PE, and 101 (5.5%) had non-sub-segmental PE. PE patients with proximal clots had higher D-dimer levels (4170 vs. 2520 mg/dL) than those with distal clots. Sensitivity and NPV for proximal PE at an optimal D-dimer cutoff of 3499 mg/dL were 57.4% and 10.4% respectively. CONCLUSIONS: VTE patients with proximal clots had higher D-dimer levels than patients with distal clots. However, D-dimer levels cannot be used alone to discriminate between VTE patients with distal or proximal clots.


Assuntos
Anticoagulantes/uso terapêutico , Serviço Hospitalar de Emergência , Produtos de Degradação da Fibrina e do Fibrinogênio/metabolismo , Embolia Pulmonar/metabolismo , Tromboembolia Venosa/metabolismo , Adulto , Idoso , Biomarcadores/metabolismo , Estado Terminal , Processamento Eletrônico de Dados , Feminino , Testes de Hemaglutinação , Humanos , Masculino , Pessoa de Meia-Idade , Valor Preditivo dos Testes , Estudos Prospectivos , Embolia Pulmonar/tratamento farmacológico , Embolia Pulmonar/fisiopatologia , Sensibilidade e Especificidade , Tromboembolia Venosa/tratamento farmacológico , Tromboembolia Venosa/fisiopatologia
4.
Acad Emerg Med ; 25(9): 995-1003, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29757489

RESUMO

BACKGROUND: Hospitalization for low-risk pulmonary embolism (PE) is common, expensive, and of questionable benefit. OBJECTIVE: The objective was to determine if low-risk PE patients discharged from the emergency department (ED) on rivaroxaban require fewer hospital days compared to standard of care (SOC). METHODS: Multicenter, open-label randomized trial in low-risk PE defined by Hestia criteria. Adult subjects were randomized to early ED discharge on rivaroxaban or SOC. Primary outcome was total number of initial hospital hours, plus hours of hospitalization for bleeding or venous thromboembolism (VTE), 30 days after randomization. A 90-day composite safety endpoint was defined as major bleeding, clinically relevant nonmajor bleeding, and mortality. RESULTS: Of 114 randomized subjects, 51 were early discharge and 63 were SOC. Of 112 (98.2%) receiving at least one dose of study drug, 99 (86.8%) completed the study. Initial hospital LOS was 4.8 hours versus 33.6 hours, with a mean difference of -28.8 hours (95% confidence interval [CI] = -42.55 to -15.12 hours) for early discharge versus SOC, respectively. At 90 days, mean total hospital days (for any reason) were less for early discharge than SOC, 19.2 hours versus 43.2 hours, with a mean difference of 26.4 hours (95% CI = -46.97 to -3.34 hours). At 90 days, there were no bleeding events, recurrent VTE, or deaths. The composite safety endpoint was similar in both groups, with a difference in proportions of 0.005 (95% CI = -0.18 to 0.19). Total costs were $1,496 for early discharge and $4,234 for SOC, with a median difference of $2,496 (95% CI = -$2,999 to -$2,151). CONCLUSIONS: Low-risk ED PE patients receiving early discharge on rivaroxaban have similar outcomes to SOC, but fewer total hospital days and lower costs over 30 days.


Assuntos
Inibidores do Fator Xa/uso terapêutico , Tempo de Internação/estatística & dados numéricos , Alta do Paciente/estatística & dados numéricos , Embolia Pulmonar/tratamento farmacológico , Rivaroxabana/uso terapêutico , Adulto , Idoso , Serviço Hospitalar de Emergência/economia , Feminino , Humanos , Tempo de Internação/economia , Masculino , Pessoa de Meia-Idade , Alta do Paciente/economia , Padrão de Cuidado/economia , Adulto Jovem
5.
Acad Emerg Med ; 25(9): 987-994, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29603819

RESUMO

BACKGROUND: It may be possible to safely rule out pulmonary embolism (PE) in patients with low pretest probability (PTP) using a higher than standard D-dimer threshold. The YEARS criteria, which include three questions from the Wells PE score to identify low-PTP patients and a variable D-dimer threshold, was recently shown to decrease the need for imaging to rule out PE by 14% in a multicenter study in the Netherlands. However, the YEARS approach has not been studied in the United States. METHODS: This study was a prospective, observational study of consecutive adult patients evaluated for PE in 17 U.S. emergency departments. Prior to diagnostic testing, we collected the YEARS criteria: "Does the patient have clinical signs or symptoms of DVT?" "Does the patient have hemoptysis?" "Are alternative diagnoses less likely than PE?" with YEARS (+) being any "yes" response. A negative D-dimer was <1000 mg/dL for YEARS (-) patients and <500 mg/dL for YEARS (+) patients. We calculated test characteristics and used Fisher's exact test to compare proportions of patients who would have been referred for imaging and patients who would have had PE "missed." RESULTS: Of 1,789 patients, 84 (4%) had PE, 1,134 (63%) were female, 1,038 (58%) were white, and mean (±SD) age was 48 (±16) years. Using the standard D-dimer threshold, 940 (53%) would not have had imaging, with two (0.2%, 95% confidence interval [CI] = 0.02%-0.60%) missed PE. Using YEARS adjustment, 1,204 (67%, 95% CI = 65%-69%) would not have been referred for imaging, with six (0.5%, 95% CI = 0.18%-1.1%) missed PE, and using "alternative diagnoses less likely than PE" adjustment, 1,237 (69%, 95% CI = 67%-71%) would not have had imaging with six (0.49%, 95% CI = 0.18%-1.05%) missed PE. Sensitivity was 97.6% (95% CI = 91.7%-99.7%) for the standard threshold and 92.9% (95% CI = 85%-97%) for both adjusted thresholds. Negative predictive value (NPV) was nearly 100% for all approaches. CONCLUSIONS: D-dimer adjustment based on PTP may result in a reduced need for imaging to evaluate possible PE, with some additional missed PE but no decrease in NPV.


Assuntos
Serviço Hospitalar de Emergência/normas , Produtos de Degradação da Fibrina e do Fibrinogênio/análise , Embolia Pulmonar/diagnóstico , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Valor Preditivo dos Testes , Estudos Prospectivos
6.
Thromb Res ; 166: 63-70, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29656169

RESUMO

INTRODUCTION: We sought to determine the test characteristics of an automated INNOVANCE D-dimer assay for the exclusion of pulmonary embolism (PE) and deep venous thrombosis (DVT) in emergency department (ED) patients using standard and age-adjusted cut-offs. METHODS: Cross-sectional, international, multicenter study of consecutive patients with suspected DVT or PE in 24 centers (18 USA, 6 Europe). Evaluated patients had low or intermediate Wells PE or DVT scores. For the standard cut-off, a D-dimer result <500 ng/ml was negative. For the age adjusted cut-off, we used the formula: Age (years) ∗ 10. The diagnostic standard was imaging demonstrating PE or DVT within 3 months. We calculated test characteristics using standard methods. We also explored modifications of the age adjustment multiplier. RESULTS: We included 3837 patients and excluded 251. The mean age of patients evaluated for PE (n = 1834) was 48 ±â€¯16 years, with 676 (37%) male, and 1081 (59%) white. The mean age of evaluated for DVT (n = 1752) was 53 ±â€¯16 years, with 710 (41%) male, and 1172 (67%) white. D-dimer test characteristics for PE were: sensitivity 98.0%, specificity 55.4%, negative predictive value (NPV) 99.8%, positive predictive value (PPV) 11.4%, and for DVT were: sensitivity 92.0%, specificity 44.8%, NPV 98.8%, PPV 10.3%. Age adjustment increased specificity (59.6% [PE], 51.1% [DVT]), but increasing the age-adjustment multiplier decreased sensitivity without increasing specificity. CONCLUSIONS: INNOVANCE D-dimer is highly sensitive and can exclude PE and DVT in ED patients with low- and intermediate- pre-test probability. Age-adjustment increases specificity, without increasing false negatives.


Assuntos
Produtos de Degradação da Fibrina e do Fibrinogênio/metabolismo , Tromboembolia Venosa/diagnóstico , Fatores Etários , Bioensaio , Estudos Transversais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Valor Preditivo dos Testes , Tromboembolia Venosa/patologia
7.
Opt Express ; 24(12): 13467-79, 2016 Jun 13.
Artigo em Inglês | MEDLINE | ID: mdl-27410363

RESUMO

The technical embodiment of the Huygens-Fresnel principle, an optical phased array (OPA) is an arrangement of optical emitters with relative phases controlled to create a desired beam profile after propagation. One important application of an OPA is coherent beam combining (CBC), which can be used to create beams of higher power than is possible with a single laser source, especially for narrow linewidth sources. Here we present an all-fiber architecture that stabilizes the relative output phase by inferring the relative path length differences between lasers using the small fraction of light that is back-reflected into the fiber at the OPA's glass-air interface, without the need for any external sampling optics. This architecture is compatible with high power continuous wave laser sources (e.g., fiber amplifiers) up to 100 W per channel. The high-power compatible internally sensed OPA was implemented experimentally using commercial 15 W fiber amplifiers, demonstrating an output RMS phase stability of λ/194, and the ability to steer the beam at up to 10 kHz.

9.
Opt Express ; 22(9): 11351-66, 2014 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-24921832

RESUMO

We experimentally demonstrate an inter-satellite laser link acquisition scheme for GRACE Follow-On. In this strategy, dedicated acquisition sensors are not required-instead we use the photodetectors and signal processing hardware already required for science operation. To establish the laser link, a search over five degrees of freedom must be conducted (± 3 mrad in pitch/yaw for each laser beam, and ± 1 GHz for the frequency difference between the two lasers). This search is combined with a FFT-based peak detection algorithm run on each satellite to find the heterodyne beat note resulting when the two beams are interfered. We experimentally demonstrate the two stages of our acquisition strategy: a ± 3 mrad commissioning scan and a ± 300 µrad reacquisition scan. The commissioning scan enables each beam to be pointed at the other satellite to within 142 µrad of its best alignment point with a frequency difference between lasers of less than 20 MHz. Scanning over the 4 alignment degrees of freedom in our commissioning scan takes 214 seconds, and when combined with sweeping the laser frequency difference at a rate of 88 kHz/s, the entire commissioning sequence completes within 6.3 hours. The reacquisition sequence takes 7 seconds to complete, and optimizes the alignment between beams to allow a smooth transition to differential wavefront sensing-based auto-alignment.

10.
Opt Lett ; 39(18): 5251-4, 2014 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-26466243

RESUMO

The Gravity Recovery and Climate Experiment Follow-On mission will use a phase-locked loop to track changes in the phase of an optical signal that has been transmitted hundreds of kilometers between two spacecraft. Beam diffraction significantly reduces the received signal power, making it difficult to track, as the phase-locked loop is more susceptible to cycle slips. The lowest reported weak-light phase locking is at 40 fW with a cycle slip rate of 1 cycle per second. By selecting a phase-locked loop bandwidth that minimized the signal variance due to shot noise and laser phase fluctuations, a 30 fW signal has been tracked with a cycle slip rate less than 0.01 cycles per second. This is tracking at a power 25% lower with a 100-fold improvement in the cycle slip rate. This capability will enable a new class of missions, opening up new opportunities for space-based interferometry.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA