A method for extraction and quantification of Ginkgo terpene trilactones

A method was developed for the extraction and quantification of pharmacologically active terpene trilactones (ginkgolides, bilobalide) from the tissues of Ginkgo biloba L. and pharmaceutical ginkgo products by RP-HPLC, based on the theory of terpene trilactones ionization. Four ginkgolides (GA, GB, GC, GJ) and bilobalide (BB) from both the ginkgo leaves and commercially available ginkgo extracts were quantitatively extracted by using this method. The recovery rate of the method was 97.5-100% with RSD of 1.2-2.8%. The detection limit was 0.05-0.1 microg, and the linear range was 0.1-12 microg. This detection limit represents a marked improvement over previously reported methods, suggesting the new method is a viable technique for routine analysis of ginkgo terpene trilactones in natural and commercial samples. The method reported by van Beek et al. in 1991 (van Beek, T. A.; Scheeren, H. A.; Rantio T.; Melger, W. C.; Lelyveld, G. P. J. Chromatogr. 1991, 543, 375-387.) was used as a reference method to monitor the accuracy of extraction and analysis in this study. SSI-MS technique was used to identify isolated target components. Carbohydrase treatment and solubility of terpene trilactones in various solvents were also discussed.     

A solid-phase microextraction device for the analysis of electrochemical reaction products by gas chromatography/mass spectrometry

Presented is a solid-phase microextraction syringe-electrode assembly that may be used to identify electrode reaction products. After an electrochemical experiment, the electrode within this syringe-electrode assembly can be introduced into the injection port of a gas chromatograph. Electrochemical reaction products can be analyzed, provided they adhere to the electrode surface and are amenable to gas chromatographic/mass spectrometric analysis. We highlight the potential usefulness of this device using well-known electrochemical reaction of quinones.     

Optical implementation of the hopfield neural network with matrix gratings

We propose a new method for the optical implementation of the Hopfield neural network with a universal tool. The tool is a matrix grating constituted with a group of element gratings. The algorithms for designing a matrix grating are proposed, and a matrix grating is created to execute recognition experiments by use of the Hopfield neural network. The experimental results demonstrate that the proposed method performs well. The stability of the light efficiencies of different optical components used in optical networks is also considered.     

A non-lensed fiber-optic resonance-enhanced multiphoton ionization probe

We have developed a miniature fiber-optic probe with no focusing optics for in situ analysis of volatile organic compounds (VOCs). The probe uses an optical fiber to transmit a laser pulse to a vapor sample causing it to ionize adjacent to the fiber tip through a resonance-enhanced multiphoton ionization (REMPI) process. The distal end of the optical fiber is contained co-axially within 2-mm-inner-diameter stainless steel tubing that serves as an electrode. The electrode is biased at a high positive potential to collect electrons. The current generated is shown to be proportional over about two orders of magnitude to the concentration of the species ionized. Visible wavelength REMPI spectroscopy is used to determine probe sensitivities of 20 ppb (benzene) and 43 ppb (toluene). Designing the probe without focusing optics specifies an achromatic ionization region constant in size and position as the laser wavelength is scanned, which simplifies data collection and reduction. Focusing achromatic systems are discussed and the potential signal improvement is estimated.     

Risk-based approach to evaluate the public health benefit of additional wastewater treatment

The City of Stockton, CA operates a wastewater treatment facility that discharges tertiary treated effluent during the summer and secondary treated effluent during the winter to the San Joaquin River. Investigations were carried out between 1996 and 2002 to provide insight regarding the potential public health benefit that may be provided by year-round tertiary treatment. A hydraulic model of the San Joaquin River and a dynamic disease transmission model integrated a wide array of disparate data to estimate the level of viral gastroenteritis in the population under the two treatment scenarios. The results of the investigation suggest that risk of viral gastroenteritis attributable to the treatment facility under the existing treatment scheme is several orders of magnitude below the 8-14 illnesses per 1000 recreation events considered tolerable by U.S. EPA, and winter tertiary treatment would further reduce the existing risk by approximately 15-50%. The methodologies employed herein are applicable to other watersheds where additional water treatment is being considered to address public health concerns from recreation in receiving waters.     

Demonstration of a method for the direct determination of polycyclic aromatic hydrocarbons in submerged sediments

We describe the development of a novel method for real-time in situ characterization of polycyclic aromatic hydrocarbons (PAHs) in submerged freshwater sediments. Laser-induced fluorescence (LIF) spectroscopy, a mature technique for PAH characterization in terrestrial sediments, was adapted for shipboard use. A cone penetrometer-type apparatus was designed for probe penetration at a constant rate (1 cm/s) to a depth of 3 m. A field-portable LIF system was used for in situ measurements in which the output of a pulsed excimer laser was transmitted by optical fiber to a sapphire window (6.4-mm o.d.) in the probe wall; fluorescent emission was collected by a separate optical fiber for transmission to the spectrometer on deck. Four wavelengths (340, 390, 440, 490 nm) were selected via optical delay lines, and multiple-wavelength waveforms were created. These multiple-wavelength waveforms contain information on the fluorescence frequency, intensity, and emission decay rate. Field testing was conducted at 10 sites in Milwaukee Harbor (total PAH concentrations ranged from approximately 10 to 650 microg/g); conventional sediment core samples were collected concurrently. The core samples were analyzed by EPA methods 3545 (pressurized fluid extraction, PFE) and 8270C (gas chromatography-mass spectrometry, GC-MS) for PAHs. A partial least-squares regression (PLSR) model wasthen created based on laboratory LIF measurements and PFE-GC-MS of the core samples. The PLSR model was applied to the in situ field test data, and 13 of the 16 EPA-regulated PAHs were quantified with a relative error of <30% overall (the remaining three PAHs were found at levels insufficient to quantify). We additionally describe preliminary source apportionment relationships that were revealed by the PLSR model for the in situ LIF measurements.     

Distribution and fluxes of total and methylmercury in Lake Superior

Despite the importance and size of Lake Superior, little is known regarding the biogeochemical cycling or distribution of mercury within its waters. We present the results from two research cruises on total Hg (HgT) and methylmercury (MeHg) distributions in aqueous and particulate phases, and in offshore sediments. Open waters of Lake Superior are similar in HgT content to Lakes Michigan and Ontario (sub-ng L(-1)), whereas MeHg was only 1% of HgT. Seasonality in aqueous HgT distribution was observed, most likely from tributary inputs during Spring snowmelt. Suspended particles were enriched in MeHg relative to water and surficial sediments, suggesting enhanced particle partitioning followed by demethylation in the water column and in surface sediments. Distribution coefficients for mercury in surficial sediments were lower than those in suspended material, likely due to remineralization. Preliminary estimates of mass balance indicate that air-water exchange processes such as evasion and wet deposition dominate the HgT budget, due to the basin's relatively small watershed area relative to lake area. In contrast, methylmercury cycling within Lake Superior is influenced more strongly by watershed sources, as well as by sedimentary sources and photodemethylation. The Hg cycle in Lake Superior is unique in that it is more similar in many aspects to that in marine systems than in small lakes, where management data for freshwaters typically originates.     

Effects of pH and agitation on the growth of Listeria monocytogenes Scott A in brain heart infusion broth containing combined potassium lactate and sodium diacetate during storage at 4 or 10 degrees C

The objective of this study was to compare the effects of pH on the growth kinetics of Listeria monocytogenes Scott A in static and agitated broths stored at 4 and 10 degrees C with and without a combination of 1.85% potassium lactate (PL) and 0.13% sodium diacetate (SDA) (3.3% of a 60% commercial solution, PURASAL P Opti.Form 4). The pH of brain heart infusion broth without (control) or with 1.85% PL + 0.13% SDA was adjusted to 5.5, 6.0, 6.5, and 7.5. L. monocytogenes Scott A was inoculated (at 10(2) CFU/ml) into pH-adjusted broth, which was stored at 4 or 10 degrees C with or without agitation. At pH 5.5, a listeriostatic effect was observed for the broth containing 1.85% PL + 0.13% SDA at 4 and 10 degrees C both with and without agitation. At pH 6.0, 1.85% PL + 0.13% SDA fully controlled the growth of L. monocytogenes Scott A in static broth at 4 degrees C for up to 20 days and significantly slowed the growth of the pathogen in agitated broth. At 10 degrees C, the growth of L. monocytogenes Scott A was significantly reduced by 1.85% PL + 0.13% SDA in agitated and unagitated broths. At pH 6.5, 1.85% PL + 0.13% SDA significantly suppressed the growth of L. monocytogenes Scott A at both 4 degrees C (P < 0.001) and 10 degrees C (P < 0.01). At pH 7.5, 1.85% PL + 0.13% SDA had a limited effect on the growth of L. monocytogenes Scott A in broth stored at 4 and 10 degrees C. At 4 degrees C, agitation decreased the lag time and increased the growth rate of L. monocytogenes Scott A at all tested pHs. A similar but less obvious trend was observed for broths stored at 10 degrees C. These results indicate that lactate-diacetate combinations effectively acted with low pH and temperature to inhibit the growth of L. monocytogenes Scott A.     

The effects of different viewing conditions on performance in simulated minimal access surgery

This study aimed to assess performance in simulated minimal access surgery (MAS) tasks under a range of viewing conditions. MAS conventionally uses 2d viewing systems which produce a flat image. However, 3d viewing systems which produce stereoscopic depth information should in principle lead to better depth perception, and improve performance on tasks which require appropriate spatial representation of layout and depth. The study compared a novel 3d viewing system with a state of the art 2d viewing system and a direct viewing condition ('open surgery') as a point of reference. Tasks included pulling and cutting of threads using standard surgical instruments. Medical students (n = 16) were allocated to viewing conditions according to a Latin square and carried out 120 tasks each. Assessment was by means of a 3d movement tracking device providing a number of performance parameters (time on task, velocity, number of movements, distance travelled). In addition instrument movement was video-recorded and analysed by four observers to validate the tracking device. Results from tracking data and observer data were highly correlated (r > 0.85). While open surgery naturally scored highest, the key finding was the clearly superior performance in the 3d condition compared to 2d. Thus modern 3d viewing systems can improve performance in a realistic task.     

Validation of biokinetic models of Cs and I using their daily dietary intakes and organ contents in an adult Indian population

The daily dietary intakes and total contents of Cs and I in skeletal muscle and thyroid, respectively, for an average Indian adult were estimated by determining their concentrations in the total cooked diet and tissue samples using instrumental neutron activation analysis. These data were then used to predict the biological half-lives of Cs and I and their radioactive counterparts for the Reference Indian Man. The predicted biological half-lives of Cs and I for Reference Indian Man were found to be comparable with the reported values for the ICRP Reference Man.