Photon-counting compressive sensing laser radar for 3D imaging.

We experimentally demonstrate a photon-counting, single-pixel, laser radar camera for 3D imaging where transverse spatial resolution is obtained through compressive sensing without scanning. We use this technique to image through partially obscuring objects, such as camouflage netting. Our implementation improves upon pixel-array based designs with a compact, resource-efficient design and highly scalable resolution.

Reporting of skin cancer risks in the house-building industry: alternative approaches to the analysis of categorical data.

BACKGROUND: Increasing incidence of skin cancer is of concern to public health. Working predominantly outside, construction workers are at increased risk of sunburn and certain forms of skin cancer. The objective of this paper was to explore these concerns via use of alternative approaches to categorical data analysis by considering the relationship between the size of house-building companies, use of risk assessments and the system for reporting sunburn. METHODS: The survey population was speculative house-building companies. A self-administered questionnaire was sent to health and safety advisors in house-building companies. Questions related to the number of house units built, inclusion of adverse weather in the risk assessment, and the presence or absence of a system for reporting sunburn were analysed. Alternative approaches to conventional chi(2) tests were used in order to investigate a multiway data structure. A loglinear model was employed using Statistical Package for Social Sciences to explain data in three-way tables. RESULTS: The questionnaire achieved a response rate of 31% (n=94). A significant association identified in a two-way study of the mechanisms of reporting sunburn also appeared at the sublevels introduced by the inclusion of a third method of categorization. Finally, correspondence analysis was used to present a graphical insight into the study. CONCLUSIONS: In the two-way analysis, the size of house-building company had a significant impact on the presence of a system for reporting sunburn, although this was not translated into the three-way analysis. The establishment of systems within risk assessments to incorporate exposure of construction workers to ultraviolet radiation, and reporting of incidents of sunburn, is essential if this public health issue is to be addressed.

Feasibility of detection and identification of individual bioaerosols using laser-induced breakdown spectroscopy.

The detection and identification of individual bioaerosols using laser-induced breakdown spectroscopy (LIBS) is investigated using aerosolized Bacillus spores. Spores of Bacillus atrophaeous, Bacillus pumilus, and Bacillus stearothemophilus were introduced into an aerosol flow stream in a prescribed manner such that single-particle LIBS detection was realized. Bacillus spores were successfully detected based on the presence of the 393.4- and 396.9-nm calcium atomic emission lines. Statistical analyses based on the aerosol number density, the LIBS-based spore sampling frequency, and the distribution of the resulting calcium mass loadings support the conclusion of individual spore detection within single-shot laser-induced plasmas. The average mass loadings were in the range of 2-3 fg of calcium/Bacillus spore, which corresponds to a calcium mass percentage of approximately 0.5%. While individual spores were detected based on calcium emission, the resulting Bacillus spectra were free from CN emission bands, which has implications for the detection of elemental carbon, and LIBS-based detection of single spores based on the presence of magnesium or sodium atomic emission was unsuccessful. Based on the current instrumental setup and analyses, real-time LIBS-based detection and identification of single Bacillus spores in ambient (i.e., real life) conditions appears unfeasible.

Spontaneous clearance of Chlamydia trachomatis infection in untreated patients.

BACKGROUND AND OBJECTIVES: To assess the spontaneous clearance of untreated Chlamydia trachomatis infections and factors correlated with the process. STUDY DESIGN: Spontaneous clearance was assessed through review of laboratory database, chart review, and laboratory testing using direct immunofluorescence (DFA) and polymerase chain reaction (PCR) tests on C. trachomatis culture transport media from patients with negative chlamydial cultures. Specimens (C. trachomatis culture transport media) were obtained from patients attending a Birmingham, Alabama sexually transmitted diseases clinic. The study group consisted of patients with positive cultures for C. trachomatis who had repeat specimens obtained for culture within 45 days of initial observation and who had not received recommended therapy for chlamydial infection in the interval between the two tests. RESULTS: Of 74 evaluable patients, 24 (32%) had negative follow-up cultures. Culture transport media for these 24 culture-negative patients were tested with DFA or PCR assays for chlamydial infection, and 3 (13%) were positive. Culture positivity rates declined significantly with increasing age and duration of follow-up. Interval treatment with benzathine penicillin resulted in apparent resolution of infection in 9 of 10 patients. Neither a history of a C. trachomatis-associated syndrome nor treatment with cefixime, metronidazole, or antifungal agents was associated with clearance of infection. CONCLUSIONS: These results are consistent with host response-mediated resolution of infection in a minority of patients and have implications regarding public health efforts to control chlamydial infection.

Evaluation of the Biostar Chlamydia OIA assay with specimens from women attending a sexually transmitted disease clinic.

Chlamydia trachomatis infections are the most prevalent sexually transmitted diseases (STDs) in the United States. In acute-care settings such as clinics and emergency rooms, a desirable chlamydia screening assay should exhibit good sensitivity and good specificity and should provide test results while the patient is still present. The Biostar Chlamydia OIA (Biostar, Inc., Boulder, Colo.) is an optical immunoassay (OIA) that provides test results in less than 30 min and that uses a test format that allows office-based testing. This assay is performed entirely at room temperature without the need for rotators or other specialized equipment. The goal of this study was to compare the performance of the Biostar Chlamydia OIA for the detection of C. trachomatis with the performance of cell culture, direct fluorescent-antibody (DFA) assay (Syva MicroTrak; Syva Co., Palo Alto, Calif.), and PCR (Roche Amplicor Chlamydia trachomatis; Roche, Branchburg, N.J.) for the detection of C. trachomatis infections in women attending an urban STD clinic. For calculations of relative test performance (sensitivity, specificity, and positive and negative predictive values), patient specimens that yielded positive results by two or more of the four assays (cell culture, DFA assay, PCR, and OIA) were classified as "true infections." By these criteria, 42 of 306 total specimens were classified as positive for C. trachomatis (positive prevalence, 13.7%), 11 (3.6%; 10 by PCR and 1 by DFA assay) were positive by a single assay, and 253 (82.7%) were negative by all four tests. All culture-positive specimens were also positive by at least one other assay. Among the culture-negative specimens, 14(5%) specimens were positive by two of the three non-culture-based assays used. By using the criterion that positivity by at least two of the tests indicated a true infection,the relative sensitivities were as follows: culture and PCR, 92.9% each; Biostar Chlamydia OIA, 73.8%; and DFA assay, 59.5%.

Ability of the digene hybrid capture II test to identify Chlamydia trachomatis and Neisseria gonorrhoeae in cervical specimens.

The Digene Hybrid Capture II (HCII CT/GC) test is a combination test designed to detect Chlamydia trachomatis and Neisseria gonorrhoeae in a single specimen. It is a nucleic acid hybridization test which uses signal amplification to increase sensitivity. We compared its performance to that of culture on cervical specimens from 1,370 women. Direct fluorescent-antibody assay was used to resolve discrepant results for C. trachomatis. Samples were collected with a proprietary cervical brush or with endocervical swabs. The HCII CT/GC test proved to be sensitive and specific in detecting these organisms. Compared to N. gonorrhoeae culture, it had a sensitivity of 93% (87/94) and a specificity of 98.5% (1,244/1,263). Compared to C. trachomatis culture, the sensitivity was 97.7% (129/132) and specificity was 98.2% (1,216/1,238). Testing of some specimens with discrepant results by PCR suggested that the test would actually prove to be even more specific if it were compared to a nucleic acid amplification test (NAAT). The sensitivity of C. trachomatis culture was somewhat less, at 88.6% (117/132). The endocervical brush appeared to be better than Dacron swabs for collecting specimens. The HCII CT/GC test offers an attractive format that allows simultaneous detection of C. trachomatis and N. gonorrhoeae with a single specimen. An initial positive result is followed by repeat tests with probes to identify chlamydiae or gonococci. This test is more sensitive than C. trachomatis culture and is at least as sensitive as culture for gonococci. It deserves further evaluation and comparison with NAATs and may well offer an attractive alternative for diagnosis and screening of these infections.