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Introduction: Although ventilator-associated pneumonia (VAP) mostly has bacterial etiology, many cases have viral etiology. The present study aimed at determining the proportion of viral VAP and any associated factors and identifying the viral isolates in pediatric VAP. Materials and Methods: A descriptive observational study was conducted at pediatric intensive care unit of tertiary referral center including 120 VAP cases aged 1--18 years. Endotracheal aspiration samples from these patients were tested for viral etiology. Results: Most VAP cases were males (66.7%). Virus was isolated in 14.2% of cases of VAP. Human adenovirus (29%), respiratory syncytial virus (29%), and herpes simplex virus (24%) were the most common viruses identified. Viral VAP was significantly associated with age, primary disease, and total leukocyte count. Neutrophil count decreased and lymphocyte count increased significantly after viral VAP. Conclusion: Viral etiology should be considered in VAP patients, especially in patients not responding to antibiotics as proper diagnosis and timely initiation of appropriate antiviral could be lifesaving. Prevalent viruses may vary geographically; hence, hospitals should try to identify the common viruses causing VAP in their settings to guide appropriate battery of tests and antiviral drugs. [ABSTRACT FROM AUTHOR]

Laser-induced breakdown spectroscopy was applied to quantitative analysis of three impurities in Sn alloy. The impurities analysis was based on the internal standard method using the Sn I 333.062-nm line as the reference line to achieve the best reproducible results. Minor-element concentrations (Ag, Cu, Pb) in the alloy were comparatively evaluated by artificial neural networks (ANNs) and calibration curves. ANN was found to effectively predict elemental concentrations with a trend of nonlinear growth due to self-absorption. The limits of detection for Ag, Cu, and Pb in Sn alloy were determined to be 29, 197, and 213 ppm, respectively. [c] 2010 Optical Society of America OCIS codes: 120.6200, 140.3440, 300.2140, 300.6210, 300.6360, 350.5400.

Direct analysis of wet slurry samples with laser induced breakdown spectroscopy (LIBS) is challenging due to problems of sedimentation, splashing, and surface turbulence. Also, water can quench the laser plasma and suppress the LIBS signal, resulting in poor sensitivity. The effect of water on LIBS spectra from slurries was investigated. As the water content decreased, the LIBS signal was enhanced and the standard deviation was reduced. To improve LIBS slurry analysis, dried slurry samples prepared by applying slurry on PVC coated slides were evaluated. Univariate and multivariate calibration was performed on the LIBS spectra of the dried slurry samples for elemental analysis of Mg, Si, and Fe. Calibration results show that the dried slurry samples give a good correlation between spectral intensity and elemental concentration. [c] 2010 Optical Society of America OCIS codes: 140.3440, 300.2140, 300.6210, 120.6200.

A high spectral contrast is expected to be very important when laser-induced fluorescence (LIF) is employed for cancer diagnosis. We developed a LIF optical fiber sensor to achieve a very high spectral contrast between normal and malignant tissues. A comprehensive experimental investigation was carried out to study the role of two critically important parameters for sensor design, namely, the excitation--collection geometry and the excitation wavelength, and their effect on the autofluorescence spectral contrast. An optimum sensing configuration was determined in order to enhance the small, but consistent, spectral difference between the normal and the malignant tissue for improving the accuracy of LIF-based cancer diagnosis. With the optimum sensor configuration, we realized a spectral contrast of more than 22 times between normal and malignant tissue sample spectra. OCIS codes: 060.2370, 060.2310, 300.2530.

Laser-induced breakdown spectroscopy (LIBS) has been applied to measure the equivalence ratio of C[H.sub.4]/air flames using gated detection. In this work, we have developed an ungated, miniature LIBS-based sensor for studying C[H.sub.4]/air and biodiesel flames. We have used this sensor to characterize the biodiesel flame. LIBS spectra of biodiesel flames were recorded with different ethanol concentrations in the biodiesel and also at different axial locations within the flame. The sensor performance was evaluated with a C[H.sub.4]/air flame. LIBS signals of N, O, and H from a C[H.sub.4]/air flame were used to determine the equivalence ratio. A linear relationship between the intensity ratio of H and O lines and the calculated equivalence ratio were obtained with this sensor. OCIS codes: 140.3440, 300.6210, 120.6200, 300.0300, 020.0020, 350.5400.

The utility of laser-induced breakdown spectroscopy (LIBS) for categorizing different types of gallbladder stone has been demonstrated by analyzing their major and minor constituents. LIBS spectra of three types of gallstone have been recorded in the 200-900 nm spectral region. Calcium is found to be the major element in all types of gallbladder stone. The spectrophotometric method has been used to classify the stones. A calibration-free LIBS method has been used for the quantitative analysis of metal elements, and the results have been compared with those obtained from inductively coupled plasma atomic emission spectroscopy (ICP-AES) measurements. The single-shot LIBS spectra from different points on the cross section (in steps of 0.5 mm from one end to the other) of gallstones have also been recorded to study the variation of constituents from the center to the surface. The presence of different metal elements and their possible role in gallstone formation is discussed. OCIS codes: 140.3440, 300.2140, 300.6210, 120.6200, 300.0300, 350.5400.

We present a simple theoretical model for the emission from double pulse laser-induced plasmas that was developed to better understand the processes and factors involved in enhancement of plasma emission. In this model, the plasma emission is directly proportional to the square of plasma density, its volume, and the fraction of second laser pulse absorbed through inverse bremsstrahlung absorption by the plasma plume of the first laser pulse. The electron--ion collision frequency determines the profile and location of the peak of emission enhancement with respect to the delay between the two lasers, whereas the amplitude of the enhancement is mainly dependent on the increase in the mass ablation rate after the second laser pulse. The effects of increase in temperature and in plasma volume after the second laser pulse are also discussed in light of this model. OCIS codes: 300.6365, 140.3440, 300.2140, 300.6210, 300.0300, 350.5400.

A study of aqueous solutions of chromium using single and double pulse laser-induced breakdown spectroscopy (LIBS) is presented. Three atomic emission lines show enhancement in emission under dual pulse LIBS excitation. The temporal evolution of line emission indicates that a shock wave front produced by the first laser pulse plays an important role in determining the decay rate of intensity by excitation transfer in single pulse LIBS and by plasma confinement in double pulse LIBS. The ratio of emission in dual pulse LIBS to single pulse LIBS with time shows a linear increase followed by the onset of saturation. A theoretical calculation of the enhancement is found to be in qualitative agreement with the experimental results, suggesting that material ablation in dual pulse LIBS should be [greater than or equal to] 3.5 times that of single pulse LIBS. There is indication that the increase in ablation and subsequent enhancement in emission may be due to the rarefied gas density inside the region enclosed by the shock wave produced by the first laser pulse. The limit of detection of Cr in aqueous solution has been improved by an order of magnitude with double pulse LIBS. OCIS codes: 300.6365, 140.3440, 300.2140, 300.6210, 300.0300, 350.5400.

The experimental conditions associated with slurry measurements to achieve good precision by using laser-induced breakdown spectroscopy (LIBS) are examined. LIBS analysis was applied to a special waste slurry sample that contains 85.4% water, 2.5% ferric oxide [Fe.sub.2] [O.sub.3], 1.7% alumina [Al.sub.2][O.sub.3], and small quantities of oxides of boron and chromium. While liquids add challenge to LIBS measurements, the analysis was successfully performed on iron and aluminum. Two slurry circulation systems were devised to overcome the major technical problems associated with LIBS measurements of slurry samples, namely, sedimentation and change in the lens-to-sample distance during measurement. LIBS slurry measurements using both circulation systems are compared. The results show that the experimental configuration plays a crucial role for online slurry analysis. OCIS codes: 140.3440, 300.2140, 300.6210, 120.6200.

A spontaneous Raman scattering optical fiber sensor was developed for a specific need of the National Aeronautics and Space Administration (NASA) for long-term detection and monitoring of the purity of liquid oxygen (L[O.sub.2]) in the oxidizer feed line during ground testing of rocket engines. The Raman peak intensity ratios for liquid nitrogen (L[N.sup.2]) and L[O.sub.2] with varied weight ratios (L[N.sup.2]/L[O.sub.2]) were analyzed for their applicability to impurity sensing. The study of the sensor performance with different excitation light sources has helped to design a miniaturized, cost-effective system for this application. The optimal system response time of this miniaturized sensor for L[N.sup.2]/L[O.sub.2] measurement was found to be in the range of a few seconds. It will need to be further reduced to the millisecond range for real-time, quantitative monitoring of the quality of cryogenic fluids in a harsh envioronment. OCIS codes: 0300.6450, 300.6330, 300.0300, 140.3550, 170.5660, 060.2370.