Development of a probabilistic multi-zone multi-source computational model and demonstration of its applications in predicting PM concentrations indoors.

This paper highlights the development and application of the probabilistic model (IAPPEM), which predicts PM10 and PM2.5 concentrations in the indoor environments. A number of features are detailed and justified through simulated comparison, which are shown to be necessary when modelling indoor PM concentrations. A one minute resolution predicts up to 20% higher peak concentrations compared with a 15 min resolution. A modified PM10 deposition method, devised to independently analyse the PM2.5 fraction of PM10, predicts up to 56% higher mean concentrations. The application of the model is demonstrated by a number of simulations. The total PM contribution, from different indoor emission sources, was analysed in terms of both emission strength and duration. In addition, PM concentrations were examined by varying the location of the emission source. A 24-hour sample profile is simulated based on sample data, designed to demonstrate the combined functionality of the model, predicting PM10 and PM2.5 peak concentrations up to 1107±175 and 596±102 µg m(-3) respectively, whilst predicting PM10 and PM2.5 mean concentrations up to 259±21 and 166±11 µg m(-3) respectively.

General stabilizing effects of plant diversity on grassland productivity through population asynchrony and overyielding.

Insurance effects of biodiversity can stabilize the functioning of multispecies ecosystems against environmental variability when differential species' responses lead to asynchronous population dynamics. When responses are not perfectly positively correlated, declines in some populations are compensated by increases in others, smoothing variability in ecosystem productivity. This variance reduction effect of biodiversity is analogous to the risk-spreading benefits of diverse investment portfolios in financial markets. We use data from the BIODEPTH network of grassland biodiversity experiments to perform a general test for stabilizing effects of plant diversity on the temporal variability of individual species, functional groups, and aggregate communities. We tested three potential mechanisms: reduction of temporal variability through population asynchrony; enhancement of long-term average performance through positive selection effects; and increases in the temporal mean due to overyielding. Our results support a stabilizing effect of diversity on the temporal variability of grassland aboveground annual net primary production through two mechanisms. Two-species communities with greater population asynchrony were more stable in their average production over time due to compensatory fluctuations. Overyielding also stabilized productivity by increasing levels of average biomass production relative to temporal variability. However, there was no evidence for a performance-enhancing effect on the temporal mean through positive selection effects. In combination with previous work, our results suggest that stabilizing effects of diversity on community productivity through population asynchrony and overyielding appear to be general in grassland ecosystems.

Modelling stomatal ozone flux and deposition to grassland communities across Europe.

Regional scale modelling of both ozone deposition and the risk of ozone impacts is poorly developed for grassland communities. This paper presents new predictions of stomatal ozone flux to grasslands at five different locations in Europe, using a mechanistic model of canopy development for productive grasslands to generate time series of leaf area index and soil water potential as inputs to the stomatal component of the DO(3)SE ozone deposition model. The parameterisation of both models was based on Lolium perenne, a dominant species of productive pasture in Europe. The modelled seasonal time course of stomatal ozone flux to both the whole canopy and to upper leaves showed large differences between climatic zones, which depended on the timing of the start of the growing season, the effect of soil water potential, and the frequency of hay cuts. Values of modelled accumulated flux indices and the AOT40 index showed a five-fold difference between locations, but the locations with the highest flux differed depending on the index used; the period contributing to the accumulation of AOT40 did not always coincide with the modelled period of active ozone canopy uptake. Use of a fixed seasonal profile of leaf area index in the flux model produced very different estimates of annual accumulated total canopy and leaf ozone flux when compared with the flux model linked to a simulation of canopy growth. Regional scale model estimates of both the risks of ozone impacts and of total ozone deposition will be inaccurate unless the effects of climate and management in modifying grass canopy growth are incorporated.

Time to chill: effects of simulated global change on leaf ice nucleation temperatures of subarctic vegetation.

We investigated the effects of long-term (7-yr) in situ CO(2) enrichment (600 µmol/mol) and increased exposure to UV-B radiation, the latter an important component of global change at high latitudes, on the ice nucleation temperatures of leaves of several evergreen and deciduous woody ericaceous shrubs in the subarctic (68° N). Three (Vaccinium uliginosum, V. vitis-idaea, and Empetrum hermaphroditum) of the four species of shrubs studied showed significantly higher ice nucleation temperatures throughout the 1999 growing season in response to CO(2) enrichment and increased exposure to UV-B radiation relative to the controls. The same species also showed a strong interactive effect when both treatments were applied together. In all cases, leaves cooled to below their ice nucleation temperatures failed to survive the damage resulting from intracellular ice formation. Our results strongly suggest that future global change on a decadal time scale (atmospheric CO(2) increases and polar stratospheric O(3) destruction) will lead to increased foliage damage of subarctic vegetation by severe late spring or early autumnal frosting events. Indeed, in support of our experimental findings, there is now some evidence that increases in atmospheric CO(2) concentration over the past three to four decades may already have acted in this manner on high-elevation arboreal plants in the Swedish Scandes. The implications for vegetation modeling in a future "greenhouse" world and palaeoclimate estimates from high-latitude plant fossils dating to the high-CO(2) environment of the Mesozoic are discussed.

Long-term growth of Ginkgo with CO(2) enrichment increases leaf ice nucleation temperatures and limits recovery of the photosynthetic system from freezing.

The importance of subzero temperature interactions with elevated CO(2) on plant carbon metabolism has received rather little attention, despite their likely role in influencing future vegetation productivity and dynamics. Here we focused on the critical issues of CO(2)-enrichment effects on leaf-freezing temperatures, subsequent membrane damage, and recovery of the photosynthetic system. We show that growth in elevated CO(2) (70 Pa) results in a substantial and significant (P<0.01) increase (up to 4 degrees C) in the ice nucleation temperature of leaves of Maidenhair tree (Ginkgo biloba), which was observed consistently throughout the 1999 growing season relative to their ambient CO(2) (35 Pa) counterparts. We suggest that increased sensitivity of leaves to ice damage after growth in elevated CO(2) provides an explanation for increased photoinhibition observed in the field early and late in the growing season when low nighttime temperatures are experienced. This new mechanism is proposed in addition to the earlier postulated explanation for this phenomenon involving a reduction in the rate of triose-P utilization owing to a decrease in the rate of carbohydrate export from the leaf.

Plant diversity and productivity experiments in european grasslands

At eight European field sites, the impact of loss of plant diversity on primary productivity was simulated by synthesizing grassland communities with different numbers of plant species. Results differed in detail at each location, but there was an overall log-linear reduction of average aboveground biomass with loss of species. For a given number of species, communities with fewer functional groups were less productive. These diversity effects occurred along with differences associated with species composition and geographic location. Niche complementarity and positive species interactions appear to play a role in generating diversity-productivity relationships within sites in addition to sampling from the species pool.

A systematic approach to the diagnosis and treatment of chronic conjunctivitis.

In 58 patients with chronic conjunctivitis of greater than two weeks' duration, examination included obtaining an ocular and general medical history and performing a complete ophthalmic examination of the external eye. Conjunctival smears were obtained for Gram and Giemsa staining, direct immunofluorescent monoclonal antibody staining for Chlamydia trachomatis and herpes simplex virus, and chlamydial culture. Cultures for bacteria and viruses were obtained in 33 patients. The cause of the chronic conjunctivitis based on clinical and laboratory criteria was established in 40 of 58 (69%) patients: chlamydia, 11 (19%); virus, eight (14%); irritant, six (10%); allergen, four (7%); contact lens, four (7%); bacteria, four (7%); acne rosacea, two (3%); and floppy eyelid syndrome, one (2%). In 18 of 58 (31%) patients, no specific cause was detected. We recommend a systematic approach in the investigation of chronic conjunctivitis. Direct immunofluorescent monoclonal antibody staining is an effective and rapid technique for detecting chronic chlamydial conjunctivitis.

Cataract extraction after vitrectomy.

Cataract extractions were performed in 25 patients who had previously undergone pars plana vitrectomy. Posterior chamber IOLs were implanted in 20 of 26 eyes. Modification of the usual surgical technique was often necessary because the zonules and/or posterior capsule were unusually mobile. Lens opacities were nuclear sclerotic in 17 eyes (65%) and posterior subcapsular in nine eyes (35%). Visual acuity improved an average of five lines, and final visual acuity was 20/50 or better in 13 eyes (50%). Visual acuity after cataract extraction closely paralleled the best visual acuity after vitreous surgery in all patients. Complications were tears in the posterior capsule in two eyes and postoperative vitreous hemorrhage in one eye. These complications did not limit final vision.

Complications of semiflexible, closed-loop anterior chamber intraocular lenses.

Anterior chamber intraocular lenses (IOLs) provided good visual rehabilitation of aphakia in a majority of patients. An increasing number of eyes with closed-loop, semiflexible anterior chamber implants are now being seen with decreased vision due to corneal edema and persistent cystoid macular edema. We evaluated 53 such eyes in 52 patients who presented with decreased vision one to 51 months (average, 15 months) after lens implantation. The most frequent lens implanted was the Surgidev Style 10 Leiske IOL. Surgery for IOL removal or exchange with or without penetrating keratoplasty was performed in 34 (64%) of 53 eyes; visual acuity recovery ranged from 20/20 to hand motions (average, 20/80). Despite clear corneal grafts in 24 (92%) of the 26 eyes that underwent corneal transplantation, visual acuity of 20/40 or better was obtained in only nine eyes (26%). Based on the intractable inflammatory sequelae associated with anterior chamber closed-loop IOLs, we strongly urge discontinuation of their use.

Tissue toxicity of laser-damaged intraocular lens implants.

Because of close proximity to the posterior capsule, the posterior chamber intraocular lens is frequently damaged when capsulotomy is performed using the Nd:YAG laser. Damage to the optic or haptics of an intraocular lens may release substances potentially toxic to intraocular tissues. We found that injection molded intraocular lenses experimentally damaged using multiple YAG laser burst at energy levels of 10 mJ or greater released compounds which caused cell death to cultures of human conjunctival epithelial cells, retinal pigment epithelial cells, choroidal cells, and retinoblastoma cells. No cytotoxic effect was seen at energy levels of 2 and 5 mJ.

Improved vision following penetrating keratoplasty for pseudophakic corneal edema--visual results.

We studied prospectively 20 consecutive eyes of 17 patients who underwent penetrating keratoplasty for pseudophakic corneal edema. Copeland intraocular lens implants were retained in all cases initially, although one implant was subsequently removed. The visual results were analyzed at 12 and 24 months. With a minimum of 12 months follow-up, 65% of eyes saw 20/40 or better, while 80% saw 20/80 or better. By 24 months, 80% saw 20/40 or better, while 95% saw 20/80 or better. Post-keratoplasty refractive surgery, consisting of relaxing incisions and/or wedge resections, was performed in six eyes.

Removal of closed-loop anterior chamber lens implants.

A simplified method for removing closed-loop anterior chamber intraocular lenses which have become embedded within the ciliary body is described. The procedure is not difficult to perform, requires no special instrumentation, and minimizes the risk of bleeding.

Neodymium-YAG laser for posterior capsulotomy.

We used the neodymium-YAG laser to perform discission of the posterior capsule in 49 eyes of 47 patients who had undergone previous extracapsular cataract extraction. The visual results were encouraging, with an improvement in visual acuity of one or more Snellen lines in 45 eyes and an improvement of three or more Snellen lines in 33 eyes. The complications included increases in intraocular pressure in 28 eyes. Intraocular pressures between 21 and 40 mm Hg were detected in 21 eyes and exceeded 41 mm Hg in another seven. In 14 of the 16 eyes in which intraocular pressure increased to more than 30 mm Hg, the maximum intraocular pressure was detectable within three hours after treatment. Other complications included damage to the intraocular lens in 12 of 30 eyes with implants and rupture of the anterior hyaloid face with forward displacement of vitreous into the anterior chamber in six of 19 eyes without implants. One of these eyes later developed a rhegmatogenous retinal detachment. A transient laser-induced hemorrhage occurred in one eye.

Rate of incorporation of dietary fat in gold thioglucose obesity in mice.

Gold Thioglucose injections in mice are followed by a rapid accumulation of fat in the carcasses. The incorporation of an oral dose of [3H] glyceroyl tripalmitate in body fat stores showed after GTG-treatment a transient but significant increase and a return to normal values within 6 weeks. The rate of incorporation of dietary fat into the body was estimated from these values as well as from food intake and fat content of the diet (2.5 per cent). The resulting curve showed great similarity with the first differential of the curve of total body fat accumulated during that period. The rate of incorporation of dietary fat into body stores is apparently modified in GTG obesity in mice.

Food and water intake in gold thioglucose-induced obese Charles River mice.

Food and water intake have been measured during the dynamic phase of gold thioglucose-induced obesity in Charles River mice. Regressions of gain in weight with food and water consumption were calculated in young growing animals and in adults fed ad libitum. The influence of fat content in the diet (2.5 and 8% fat) and environmental temperature (68degrees or 79degrees F) was estimated on the regressions. Excessive gain in weight without hyperphagia was observed in growing animals, in adults fed on a fat-enriched diet or maintained within a thermoneutral environment (79degrees F). But a significant hyperphagia was observed in adults fed with a conventional diet and maintained at 68degrees F or in growing animals as a sequela of food deprivation.