RESUMO
The filamentation of the femtosecond laser pulse in air with a preformed density hole is studied numerically. The result shows that density-hole-induced defocusing effect can relieve the self-focusing of the pulse, and by changing the length of the density hole and relative delay time, the filamentation length, intensity, spectral energy density and broaden region can be effectively controlled. When a short density hole with millisecond delay time is introduced, a significant elongation of the filamentation and enhancement of supercontinuum intensity can be obtained. This study provides a new method to control filamentation by pulse sequence.
RESUMO
Intense vector supercontinuum (SC) radiation with spatial polarization is obtained by using 800nm femtosecond vector laser beams in the air. The SC generated by azimuthally, radially, cylindrically polarized beams, and higher-order vector beams are investigated, respectively. The results show that the SC generated by vector beams is greatly enhanced compared to that by a Gaussian beam. The energy density of SC radiation reaches the order of 1µJ/nm in a bandwidth of 258 nm from 559 nm to 817 nm and 0.1 µJ/nm from 500 nm to 559 nm. Furthermore, by checking the polarization distribution of SC in different wavelengths from visible to near-infrared bands, we find that the SC maintains nearly the same polarization distribution as pump pulses. This work provides an effective and convenient way to generate powerful SC vector beams which may facilitate potential applications including optical communication, micro/nano-fabrication, and super-resolution microscopy.
RESUMO
BACKGROUND: Sepsis-associated cholestasis is a common problem in neonatal patients. However, there are limited data related to sepsis-associated cholestasis in adults. In this study, the authors assessed the clinical characteristics, risk factors and outcome of adult patients with sepsis-associated cholestasis. METHODS: An observational prospective single-center study was conducted. A total of 608 patients with sepsis (66 patients with cholestasis and 542 without evidence of cholestasis) from January 1, 2005, to December 31, 2011, were included from the infectious disease unit. Demographic, clinical and laboratory information were recorded on admission for all patients. Additional data were also collected on the day of the 1st episode of bacteremia for patients who developed cholestasis. Accordingly, the organ dysfunction scores (Acute Physiology and Chronic Health Evaluation [APACHE] II and Sequential Organ Failure Assessment [SOFA]) were assessed on the same day. RESULTS: The mean age of the 608 patients was 49.3 ± 11.4 years (range, 22-83 years); 312 (51.3%) patients were men, 296 (48.7%) were women. The mean APACHE II and SOFA score were 15.2 ± 6 and 5.6 ± 2.3, respectively. Sepsis-associated cholestasis was strongly associated with older age, biomarkers of organ dysfunction and clinical composite scores (APACHE II and SOFA). Mortality was higher in patients with sepsis-associated cholestasis (10.6%) compared with subjects with sepsis without cholestasis (1.5%) (P < 0.05). CONCLUSIONS: The authors found that sepsis-associated cholestasis affects the outcome of patients with sepsis in the infectious disease unit. Additional clinical studies are necessary to elucidate the pathology and pathophysiology of sepsis-associated cholestasis.
