Detection improvement in spatially filtered x-ray fluoroscopy image sequences

The effect of spatial noise-reduction filtering on human observer detection of stationary cylinders mimicking arteries, catheters, and guide wires in x-ray fluoroscopy was investigated in both single image frames and image sequences. Ideal edge-preserving spatial filtering was simulated by filtering of the noise before addition of the target cylinder. This allowed us to separate the effect of edge blurring from those of noise reduction and spatial noise correlation. We used three different center-weighted averagers that reduced pixel noise variance by factors of 0.75, 0.50, and 0.25. As compared with no filtering, the effect of filtering on detection in single images was statistically insignificant. This indicated an adverse effect of spatial noise correlation on detection that countered the effect of noise reduction. By comparison, spatial filtering significantly improved detection in image sequences and yielded potential x-ray dose savings of 26-34%. Comparison of results with two observer models suggested that human observers have an improved detection efficiency in spatially filtered image sequences as compared with white-noise sequences. Pixel noise reduction, a measure commonly used to assess filter performance, overestimated the effect of filtering on detection and was not a good indicator of image quality. We conclude that edge-preserving spatial filtering is more effective in sequences than in single images and that such filtering can be used to improve image quality in noisy image sequences such as x-ray fluoroscopy.     

Performance requirements of physically strenuous occupations: validating minimum standards for muscular strength and endurance

Employment rights legislative mandates passed in the USA over the last three decades emphasize the importance of validating performance standards for physically strenuous occupations. This study validated minimally acceptable standards for the muscular strength and endurance necessary to perform fire suppression activities. Incumbent firefighters (n=153) selected for key demographic characteristics completed a simulated set of firefighting tasks (Fire Suppression Evolution) and then a Predictor Test Battery of physical abilities tests. Regression analysis revealed that three predictor test items (hose drag/high rise pack carry; arm lift; arm endurance) combined to significantly predict performance time of the Fire Suppression Evolution (p < or =0.01). Firefighters (n=41) rating videotaped performance times of the Fire Suppression Evolution determined that more than one-half a standard deviation slower than the mean time established by the incumbents reflected unacceptable performance. Approximately 80% of incumbent firefighters passed the minimally acceptable performance standard. Use of the 3-predictor test battery would correctly identify 89% of successful performers and 72% of unsuccessful performers. This study demonstrates that validation of minimal physical performance standards will identify a cohort of individuals with a high probability of not being able to perform critical fire suppression activities. This finding has important implications for examining the relationship between physical performance standards and medical and economic outcomes.     

The effect of phone design on upper extremity discomfort and muscle fatigue

OBJECTIVE: To compare a small cellular clamshell phone with a traditional office phone in the development of discomfort and muscle fatigue over time during phone use. BACKGROUND: Phone use involves low-level static exertions that may be influenced by phone design. Phone design and its interactions with anthropometry may change shoulder and hand postures assumed during use, which in turn may modify the length-strength relationship and moment arms of the muscles. METHOD: Ten adults participated in a study that simulated phone use using a small clamshell and a traditional office phone. Discomfort information and electromyographic (EMG) muscle activity were monitored on four upper extremity muscles. Discomfort and fatigue data (EMG median frequency shifts) were analyzed to assess differences between phones as well as differing effects attributable to anthropometry. RESULTS: Median frequency shifts supported discomfort claims and indicated muscle fatigue in the deltoid and thenar muscles. Biomechanical measures demonstrated that participants with short limb lengths developed more severe signs of thenar fatigue. Participants with longer arms developed greater discomfort in the neck, shoulder, and back. The deltoid confirmed this occurrence, showing signs of muscle fatigue. CONCLUSION: Phone design and anthropometry influenced the development of discomfort and fatigue during phone use. Phone design dictated grip style, resulting in differing discomfort and fatigue levels. Anthropometry influenced the severity of the discomfort and fatigue present in the shoulder and hand. APPLICATION: Use of small clamshell phones may contribute to a lack of rest and recovery from typical workday exposures. It should be explored from an ergonomic perspective.     

今天工作不规划，明天规划找工作

在日益严峻的就业压力下，从大学刚毕业开始。很多人就认为谈职业生涯规划是件很不现实的事情。衡量工作的标准。也无非“薪水高”、“更轻松”，找到理想兴趣相结合的工作几乎成了一种奢望。以至不少人到了30多岁还在频繁地跳槽，不知道自己究竟应该干什么。     

A method for quantification from composite spectra: application to the determination of isomeric DNA photoproducts by tandem mass spectrometry

Quantification of mixture components from their composite optical or mass spectra is a common need in analytical chemistry. We encountered the need when applying a combination of enzymatic digestion with nuclease P1 and tandem mass spectrometry to a mixture of isomeric photomodified oligodeoxynucleotides. In the procedure, we collisionally activated the [M - H]- or [M + Na - 2H]- ion of trinucleotide triphosphates, which were extricated enzymatically from the larger, damaged oligodeoxynucleotides, and we measured the relative abundances of characteristic fragment ions. The results sometimes yield curved calibrations for plots of the relative fragment ion abundances in the product ion spectra of isomers versus their relative amounts. We developed a normalized linear model, which brings understanding to the nonlinear plots and allows quantification of the mixture components from their composite spectra. The outcome demonstrates a general quantification procedure and shows that different yields for generating fragment ions from different constituents of the mixture cause the curved calibration lines.     

Application of Balanced Detection to Absorption Measurements of Trace Gases with Room-Temperature, Quasi-cw Quantum-Cascade Lasers

Distributed-feedback quantum-cascade (QC) lasers are expected to form the heart of the next-generation mid-IR laser absorption spectrometers, especially as they are applied to measurements of trace gases in a variety of environments. The incorporation of room-temperature-operable, single-mode QC lasers should result in highly compact and rugged sensors for real-world applications. We report preliminary results on the performance of a laser absorption spectrometer that uses a QC laser operating at room temperature in a quasi-cw mode in conjunction with balanced ratiometric detection. We have demonstrated sensitivities for N(2)O [10 parts in 10(6) volume-mixing ratio for a 1-m path (ppmv-m)] and NO [520 parts in 10(9) volume-mixing ratio for a 1-m path (ppbv-m)] at 5.4 mum. System improvements are described that are expected to result in a 2 orders of magnitude increase in sensitivity.     

Two-beam Coupling Modules for Photorefractive Optical Circuits

Modules that perform photorefractive two-beam coupling operations have been built, characterized, and tested. These portable modules, interconnected by fiber optics, dispense with the need for repeated alignment and greatly facilitate the prototyping of complex signal- or image-processing photorefractive circuits. To evaluate the performance of the modules in a photorefractive circuit, we interconnected them in the feature extractor configuration: a ring configuration composed of two modules that selects the strongest signal within the signals presented on its input. With two signals at the input, an output contrast ratio of 45.4 dB is obtained for an input contrast ratio of 5 dB.     

Temperature-dependent optical constants of water ice in the near infrared: new results and critical review of the available measurements

The optical constants of water ice have been determined in the near infrared from 4000 to 7000 cm(-1). Polycrystalline ice films with thickness as great as ~1164 mum were formed by condensation of water vapor on a cold silicon substrate at temperatures of 166, 176, 186, and 196 K. The transmission of light through the ice films was measured during their growth from 0 to 1164 mum over the frequency range of approximately 500-7000 cm(-1). The optical constants were extracted by means of simultaneously fitting the calculated transmission spectra of films of varying thickness to their respective measured transmission spectra with an iterative Kramers-Kronig technique. Equations are presented to account for reflection losses at the interfaces when the sample is held in a cell. These equations are used to reanalyze the transmission spectrum of water ice (358-mum sample at 247 K) recorded by Ockman in 1957 [Philos. Mag. Suppl. 7, 199 (1958)]. Our imaginary indices for water ice are compared with those of Gosse et al. [Appl. Opt. 34, 6582 (1995)], Kou et al. [Appl. Opt. 32, 3531 (1993)], Grundy and Schmitt [J. Geophys. Res. 103, 25809 (1998)], and Warren [Appl. Opt. 23, 1206 (1984)], and with the new indices from Ockman's spectrum. The temperature dependence in the imaginary index of refraction observed by us between 166 and 196 K and that between our data at 196 K and the data of Gosse et al. at 250 K are compared with that predicted by the model of Grundy and Schmitt. On the basis of this comparison a linear interpolation of the imaginary indices of refraction between 196 and 250 K is proposed. We believe that the accuracy of this interpolation is better than 20%.