Pattern formation and individual-based models: The importance of understanding individual-based movement

This paper demonstrates that while pattern formation can stabilize individual-based models of predator–prey systems, the same individual-based models also allow for stabilization by alternate mechanisms, particularly localized consumption or diffusion limitation. The movement rules of the simulation are the critical feature which determines which of these mechanisms stabilizes any particular predator–prey individual-based model. In particular, systems from well-connected subpopulations, in each of which a predator can attack any prey, generally exhibit stabilization by pattern formation. In contrast, when restricted movement within a (sub-)population limits the ability of predators to consume prey, localized consumption or diffusion limitation can stabilize the system. Thus while the conclusions from differential equations on the role of pattern formation for stability may apply to discrete and noisy systems, it will take a detailed understanding of movement and scales of interaction to examine the role of pattern formation in real systems. Additionally, it will be important to link an understanding of both foraging and inter-patch movement, since by analogy to the models, both would be critical for understanding how real systems are stabilized by being discrete and spatial.     

Toxicity of depleted uranium on isolated liver mitochondria: a revised mechanistic vision for justification of clinical complication of depleted uranium (DU) on liver

Depleted uranium (DU) is widely used in military anti-armor weapons. Recent evidence suggested that oxidative stress and mitochondrial dysfunction may contribute to DU-induced toxicity. However, the underlying mechanisms of DU toxicity in mitochondria are not well understood. In this study, liver mitochondria were obtained from Wistar rats treated with DU in the form of uranyl acetate (UA) (0.5, 1 or 2 mg/kg i.p.) using differential centrifugation. For in vitro experiments, control rat liver mitochondria were incubated with different concentrations of UA (50, 100 or 200 μM) for 1 hr. Mitochondrial reactive oxygen species (ROS) production, collapse of mitochondrial membrane potential, and mitochondrial swelling were examined by flow cytometry. Mitochondrial sources of ROS formation were determined using specific substrates and inhibitors. Extent of lipid peroxidation (LPO) and glutathione (GSH) oxidation, and also complex II and IV activities were detected via spectroscopy. Further, the concentration of ATP and ATP/ADP ratio was measured using luciferase enzyme and release of cytochrome c from mitochondria which was detected by ELISA kit. UA induced succinate-supported mitochondrial ROS production, elevated LPO levels, GSH oxidation, and mitochondrial complex II inhibition. UA also induced mitochondrial permeability transition and increase in cytochrome c release which subsequently disturbed oxidative phosphorylation and reduced the mitochondrial ATP concentration. Data suggest that mitochondrial oxidative stress and uncoupling of oxidative phosphorylation may play key roles in DU-induced hepatic toxicity.     

Toxicity of cigarette smoke on isolated lung,heart, and brain mitochondria: induction of oxidative stress and cytochrome c release

Cigarette smoking is one of the main risk factors for premature human death which is associated with a variety of respiratory and vascular diseases, and cancer due to exposure to hundreds of toxicants. Rat mitochondria were obtained by differential ultracentrifugation and incubated with different concentrations (1%, 10%, or 100%) of standardized cigarette smoke extract (CSE). Our results showed that CSE induced a rise in mitochondrial reactive oxygen species (ROS) formation, lipid peroxidation, and mitochondrial membrane potential (MMP) collapse before mitochondrial swelling ensued in isolated pulmonary mitochondria. Disturbance in oxidative phosphorylation was also confirmed by decrease in ATP concentration in the CSE-treated mitochondria. In addition, collapse of MMP and mitochondrial swelling produced release of cytochrome c via outer membrane rupture or mitochondrial permeability transition (MPT) pore opening. Our results suggested that CSE-induced toxicity in lung tissue is the result of disruptive effect on mitochondrial respiratory chain that leads to ROS formation, lipid peroxidation, MMP decline, and cytochrome c expulsion which results in apoptosis signaling and cell loss.     

An investigation into the socioeconomic aspects of two major earthquakes in Iran

An evaluation of the socioeconomic consequences of earthquakes is an essential part of the development of risk reduction and disaster management plans. However, these variables are not normally addressed sufficiently after strong earthquakes; researchers and relevant stakeholders focus primarily on the physical damage and casualties. The importance of the socioeconomic consequences of seismic events became clearer in Iran after the Bam earthquake on 26 December 2003, as demonstrated by the formulation and approval of various laws and ordinances. This paper reviews the country's regulatory framework in the light of the socioeconomic aspects of two major and destructive earthquakes: in Manjil–Rudbar in 1990, and in Bam in 2003. The results take the form of recommendations and practical strategies for incorporating the socioeconomic dimensions of earthquakes in disaster risk management planning. The results presented here can be applied in other countries with similar conditions to those of Iran in order to improve public preparedness and risk reduction.     

Soil organic carbon sequestration as affected by afforestation: the Darab Kola forest (north of Iran) case study

Following the ratification of the Kyoto Protocol, afforestation of formerly arable lands and/or degraded areas has been acknowledged as a land-use change contributing to the mitigation of increasing atmospheric CO(2) concentration in the atmosphere. In the present work, we study the soil organic carbon sequestration (SOCS) in 21 year old stands of maple (Acer velutinum Bioss.), oak (Quercus castaneifolia C.A. Mey.), and red pine (Pinus brutia Ten.) in the Darab Kola region, north of Iran. Soil samples were collected at four different depths (0-10, 10-20, 20-30, and 30-40 cm), and characterized with respect to bulk density, water content, electrical conductivity, pH, texture, lime content, total organic C, total N, and earthworm density and biomass. Data showed that afforested stands significantly affected soil characteristics, also raising SOCS phenomena, with values of 163.3, 120.6, and 102.1 Mg C ha(-1) for red pine, oak and maple stands, respectively, vs. 83.0 Mg C ha(-1) for the control region. Even if the dynamics of organic matter (OM) in soil is very complex and affected by several pedo-climatic factors, a stepwise regression method indicates that SOCS values in the studied area could be predicted using the following parameters, i.e., sand, clay, lime, and total N contents, and C/N ratio. In particular, although the chemical and physical stabilization capacity of organic C by soil is believed to be mainly governed by clay content, regression analysis showed a positive correlation between SOCS and sand (R = 0.86(**)), whereas a negative correlation with clay (R = -0.77(**)) was observed, thus suggesting that most of this organic C occurs as particulate OM instead of mineral-associated OM. Although the proposed models do not take into account possible changes due to natural and anthropogenic processes, they represent a simple way that could be used to evaluate and/or monitor the potential of each forest plantation in immobilizing organic C in soil (thus reducing atmospheric C concentration), as well as to select more appropriate species during forestation plan management at least in the north of Iran.     

Cumulative effects of developed road network on woodland—a landscape approach

Population growth, during the twentieth century, has increased demand for new farmlands. Accordingly, road networks have rapidly been developed to facilitate and accelerate human access to the essential resources resulted in extensive land use changes. The present study aims at assessing cumulative effects of developed road network on tree cover of Golestan Province in northern Iran. In order to detect changes over the study period of 1987–2002, the LULC map of the study area was initially prepared from the satellite images of Landsat TM (1987) and ETM+ (2002) using maximum likelihood supervised classification method. Afterwards, a total number of seven landscape matrices were selected to detect cumulative effects of the developed road network on woodland cover. The obtained results indicated that the fragile patches are mainly located at a distance of 171–342 m from the roadside. Furthermore, the majority of the patches affected by cumulative effects of development activities are situated at a distance of 342–684 m from the roadside, over an approximate area of 55 ha. The analysis of landscape metrics revealed that the developed road network has increased the landscape metrics of “the number of patches” and “patches perimeter-area ratio”. It has also followed by a decrease in metrics such as “patches area”, “Euclidean nearest neighbor distance”, “patches proximity”, “shape index”, “contiguity”, and “mean patches fractal dimension”. The road network has also increased the “number of patches” and decreased the “mean patches area” representing further fragmentation of the landscape. With identification of highly affected wooldland cover patches, it would be possible to apply adaptive environmental management strategies to preserve and rehabilitate high-priority patches.     

Workstation design in carpet hand-weaving operation: guidelines for prevention of musculoskeletal disorders.

Carpet weavers suffer from musculoskeletal problems mainly attributed to poor working postures. Their posture is mostly constrained by the design of workstations. This study was conducted to investigate the effects of 2 design parameters (weaving height and seat type) on postural variables and subjective experience, and to develop guidelines for workstation adjustments. At an experimental workstation, 30 professional weavers worked in 9 different conditions. Working posture and weavers' perceptions were measured. It was shown that head, neck and shoulder postures were influenced by weaving height. Both design parameters influenced trunk and elbows postures. The determinant factor for weavers' perception on the neck, shoulders and elbows was found to be weaving height, and on the back and knees it was seat type. Based on the results, the following guidelines were developed: (a) weaving height should be adjusted to 20 cm above elbow height; (b) a 10 degrees forward-sloping high seat is to be used at weaving workstations.     

Effect of the water-soluble fraction of diesel exhaust particles on the development and protein patterns of pollen grains in bean plants (Phaseolus vulgaris L.)

Excessive air pollution may adversely affect plant growth and development. The overall objective of this research was to elucidate some microscopic effects of diesel exhaust particles (DEP) on the formation, development, and structure of pollen grains and its proteins in Phaseolus vulgaris L. Bean plants were grown in experimental pots and treated with different concentrations of the water-soluble fraction of DEP. Flowers and young buds were removed, fixed in FAA₇₀ (formalin?:?acetic acid?:?ethanol, 2?:?1?:?17), and subjected to developmental studies. Our results show that DEP cause some abnormalities during pollen development. Pollen grains in normal plants are spherical in equatorial view and triangular in polar view; in DEP-treated plants, they were changed into irregular shapes in equatorial view and asteroidal in polar view. Delay in degeneration of the tapetum layer of the anther, and formation of giant, irregular, and non-fertile pollen grains are other results of DEP treatment. Gel electrophoretic studies revealed that a new protein with a molecular mass of 80?kD was formed in the DEP-treated group. Some pollen proteins may act as allergens, considering the fact that pollen allergy frequency is increased in polluted areas; the possibility arises that DEP could be an effective agent entail formation of detoxifying proteins which, on the other hand, can also act as allergens.     

Geochemical fractions and phytoavailability of Zinc in a contaminated calcareous soil affected by biotic and abiotic amendments

Many studies have conducted to determine the best management practice to reduce the mobility and phytoavailability of the trace metals in contaminated soils. In this study, geochemical speciation and phytoavailability of Zn for sunflower were studied after application of nanoparticles (SiO₂ and zeolite, with an application rate of 200 mg kg^?1) and bacteria [Bacillus safensis FO-036b(T) and Pseudomonas fluorescens p.f.169] to a calcareous heavily contaminated soil. Results showed that the biotic and abiotic treatments significantly reduced the Zn concentration in the aboveground to non-toxicity levels compared to the control treatment, and the nanoparticle treatments were more effective than the bacteria and control treatments. The concentration of CaCl₂-extractable Zn in the treated soils was significantly lower than those of the control treatment. The results of sequential extraction showed that the maximum portion of total Zn belonged to the fraction associated with iron and manganese oxides. On the contrary, the minimum percent belonged to the exchangeable and water-soluble Zn (F₁). From the environmental point of view, the fraction associated with iron and manganese oxides is less bioavailable than the F₁ and carbonated fractions. On the basis of plant growth promotion, simultaneous application of the biotic and abiotic treatments significantly increased the aboveground dry biomass yield and also significantly reduced the CaCl₂-extractable form, uptake by aboveground and translocation factor of Zn compared to the control treatment. Therefore, it might be suggested as an efficient strategy to promote the plant growth and reduce the mobile and available forms of toxic metals in calcareous heavily contaminated soils.     

Models relating individual and population response to contaminants

Even when present at sub‐lethal levels, toxic compounds have an effect on the dynamics of a population, expressed through altered growth and reproduction rates. We explore some of the potential effects of toxicants on populations, using a simple model that considers a generic toxicant and populations of two species, a primary producer, and a consumer living under food‐limited conditions. The toxicant is assumed to affect the consumers only, and it may enter them either directly from the environment or via their food, the latter opening the possibility of biomagnification. The initial response of the consumer to introduction of a toxicant is invariably a decline in its fecundity and density. However, in the longer term, the equilibrium densities of both producer and consumer may increase or decrease, depending on parameter values and ambient toxicant levels. The surprising case of an increased equilibrium in response to the toxicant occurs if, in the absence of toxicant, the consumers held the producers at a very low level, analogous to ‘overfishing’ in fishery studies. If the toxicant enters the consumer via food, multiple, non‐trivial equilibria are possible. The complex, but interpretable, dynamics exhibited by these simple models will be used to guide studies with more realistic models, for whose development this study forms a prelude.