A respiratory valve for rapid switching between two gas mixtures.

We have devised a respiratory valve that facilitates rapid and silent breath-to-breath switching between two gas mixtures, under remote control. It utilizes two inspiratory Loven-type valve elements, one for each gas mixture, either of which can be held closed with an electromagnet. Any type of valve element can serve as the expiratory valve. We have used a small respiratory valve with goats and a larger model for both goat and human use.     

Open top chambers for exposing plant canopies to elevated CO2 concentration and for measuring net gas exchange

Open top chamber design and function are reviewed. All of the chambers described maintain CO₂ concentrations measured at a central location within ±30 ppm of a desired target when averaged over the growing season, but the spatial and temporal range within any chamber may be closer to 100 ppm. Compared with unchambered companion plots, open top chambers modify the microenvironment in the following ways: temperatures are increased up to 3°C depending on the chamber design and location of the measurement; light intensity is typically diminished by as much as 20%; wind velocity is lower and constant; and relative humidity is higher. The chamber environment may significantly alter plant growth when compared with unchambered controls, but the chamber effect on growth has not been clearly attributed to a single or even a few environmental factors.A method for modifying an open top chamber for tracking gas exchange between natural vegetation and the ambient air is described. This modification consists of the addition of a top with exit chimney to reduce dilution of chamber CO₂ by external ambient air, is quickly made and permits estimation of the effects of elevated CO₂ and water vapor exchange.The relatively simple design and construction of open top chambers make them the most likely method to be used in the near future for long-term elevated CO₂ exposure of small trees, crops and grassland ecosystems. Improvements in the basic geometry to improve control of temperature, reduce the variation of CO₂ concentrations, and increase the turbulence and wind speed in the canopy boundary layer are desirable objectives. Similarly, modifications for measuring water vapor and carbon dioxide gas exchange will extend the usefulness of open top chambers to include non-destructive monitoring of the responses of ecosystems to rising atmospheric CO₂.     

Apparatus for exposing cell membranes to rapid temperature transients

We seek to determine whether cell membranes contain sensors that trigger a downstream response to temperature excursions. To do this, we have developed a novel apparatus for exposing a cell membrane to an extremely rapid temperature excursion in the nanosecond range. Cells are plated on a gold surface that is back-heated by a pulsed laser and cooled by conduction of heat into the glass substrate and the liquid medium. Analysis using the heat diffusion equation shows that the greatest temperature rise is localized within a region tens of nanometres thick, suitable for specifically heating a cell membrane without heating the remainder of a cell. We refer to this device as a nanosecond hotplate.This paper was submitted as a record of the 2002 Australian Biophysical Society     

A method for the chronic electromagnetic recording of eye and head movements in monkeys

A search-coil method for two-dimensional chronic registration of eye and head movements is described. The method is based on the analysis of the electromotive force induced by a magnetic field in a search coil. The output parameters of the original dual system were measured using both the standard search coil and that implanted into monkey's eye. The precision of eye movement recording was evaluated in real time. Standard deviation of spontaneous noise level for both channels was equal to 0.16 degrees (deg). The same parameters representing eye movement error during gaze fixation in the horizontal (in the range of -20/+20 deg) and vertical (in the range of -13/+13 deg) directions were equal to 0.27-0.38 and 0.23-0.31 deg, respectively. The obtained errors were comparable with the angular size of the peripheral target stimuli (0.20 deg), which had to be traced by an animal with saccadic movements.     

An open-air system for exposing forest-canopy branches to ozone pollution

We developed a chamberless system to expose branches to elevated concentrations of ozone with little alteration of micro-meteorological conditions. In a 35-year-old stand of sugar maple (Acer saccharum Marsh.), scaffolding and a platform (14 m in height) provided access to 10 branches and ten paired controls within the canopy. Ozone was delivered to the canopy through a manifold and an array of loops (38 cm in diameter) of teflon tubing individually fitted to each branch. Ozone-enriched air was discharged through numerous small holes in each loop positioned beneath the exposed foliage. A sampling system controlled by a microcomputer monitored ozone concentrations for each loop by means of composite air samples from 12 leaves, drawn through small teflon tubes (1.65 mm diameter) attached to the petioles. On average, coefficients of variation for ozone concentrations for the sample points within each branch loop were less than 50%. Between 0900 and 1700 h for 68 d of exposure, the mean hourly ozone concentrations among the branches averaged 95nmol mol⁻¹ (±13SD), about twice the ambient mean. Frequency distributions of mean hourly concentrations during exposure were unimodal and approximately log-normal, comparable to ambient ozone concentrations. The open-air loop system enables exposure of branches to gaseous pollutants under relatively natural conditions.     

A field enclosure apparatus for measuring crop photosynthesis

The field enclosure is a transparent box covering a soil area of 1.5 m². It is a semi-closed system in which concentrations of water vapour and carbon dioxide are maintained constant: the required rate of input of carbon dioxide being a measure of the photosynthesis rate, and the rate of condensation of water, on cooling coils, a measure of transpiration. The air within the enclosure is circulated rapidly by fans to decrease concentration gradients, and under steady radiation inputs the air temperature is controlled to ±0.5 °C. Both photosynthesis and transpiration rates are corrected for air exchange with the surroundings, as measured through the injection of the inert gas, nitrous oxide.     

A gas chromatographic mass spectrometric chemical ionization assay for haloperidol with selected ion monitoring

A new gas chromatographic mass spectrometric chemical ionization assay for haloperidol with selectedion monitoring is presented which provides for better combined selectivity and sensitivity than previous assays. Levels of haloperidol in 2 ml of human plasma were reproducibly measured down to subnanogram levels. Both methane and methane--ammonia chemical ionization spectra are presented for haloperidol and the internal standard trifluperidol.     

Hydrocracking of vacuum gas oil-vegetable oil mixtures for biofuels production

Hydrocracking of vacuum gas oil (VGO) - vegetable oil mixtures is a prominent process for the production of biofuels. In this work both pre-hydrotreated and non-hydrotreated VGO are assessed whether they are suitable fossil components in a VGO-vegetable oil mixture as feed-stocks to a hydrocracking process. This assessment indicates the necessity of a VGO pre-hydrotreated step prior to hydrocracking the VGO-vegetable oil mixture. Moreover, the comparison of two different mixing ratios suggests that higher vegetable oil content favors hydrocracking product yields and qualities. Three commercial catalysts of different activity are utilized in order to identify a range of products that can be produced via a hydrocracking route. Finally, the effect of temperature on hydrocracking VGO-vegetable oil mixtures is studied in terms of conversion and selectivity to diesel, jet/kerosene and naphtha.     

Susceptibility of selected winter wheat cultivars produced in Poland to Fusarium head blight

The susceptibility of six winter wheat cultivars toFusarium head blight has beenstudied. The lowest infected plants intensity, mean degree of head damage and fusariosis index exhibited cultivar Grana which also cumulated the lowest amount of trichothecenes (DON and derivatives ). Possibility to produce NIV by Polish strains has been found.in F.graminearum.     

A gas chromatographic assay for carnitine.

A sensitive gas chromatographic method for the measurement of the biologically significant quaternary ammonium compound, carnitine (β-hydroxy-γ-trimethylaminobutyric acid) was developed, based upon decomposition of the compound upon heating at 160°C, in the presence of NaOH and NaBH₄. A derivative, present in the chloroform extract of the acidified reaction mixture, was separated on a column of Carbowax 20M (20%) + 3% H₃PO₄ on Chromosorb W, and measured using a H₂ flame ionization detector. The derivative was identified as 4-butyrolactone, based upon its chromatographic retention time and its mass spectrum. Using the reported method, the carnitine concentration of mature rat caput epididymis was 1.9 ± 0.5 μmole/g wet wt, while that of cauda epididymis was 16.0 ± 1.8 μmole/g wet wt.     

Effects of hyperoxic gas mixtures on energy metabolism during prolonged work.

These experiments were designed to study selected respiratory and metabolic responses to exercise in hyperoxia. Four subjects were examined during 30-min bicycle ergometer rides at both 40% and 80% of their aerobic maximum. The VO2 was significantly increased at both work levels breathing 60% O2 versus 21% O2, while VCO2 showed no significant change during the 40% exercise tests but was significantly decreased during the 80% intensity rides. The average increase in the volume of O2 taken up during 30 min of hyperoxic exercise, compared with normoxia, was 3.3 liters at the 40% exercise level and 5.6 liters at the 80% level. Neither the magnitude of the O2 nor the CO2 storage calculated for the exercise bouts could explain these increases. Steady-state criteria for the gas stores were established by the stable values of PETCO2, VO2, VCO2, and VI from minute 6 through 30 at both work levels. R values decreased during the hyperoxic tests suggesting the possibility of a shift toward increased fatty acid metabolism.