Biocontrol of weeds: Overcoming evolution for efficacy

Abstract

Inundatively used mycoherbicides have been uneconomical and ineffectual, mainly because a large inoculum is required to overcome weeds’ innate defenses, as well as the need for long dew periods to become established. Weed defenses can be suppressed by specific chemical agents, or overcome biologically (using mixed organisms and/or engineering enhanced pathogenicity), and better formulants replace the long dew periods.     

A novel auditory working-memory vigilance task for mental fatigue assessment

An auditory working-memory vigilance task (AWVT), which involves higher mental abilities of a person, like working-memory and decision-making, in addition to vigilance, is presented for measuring human mental fatigue in this paper. A 25-h sleep deprivation study, with hourly testing by AWVT (3 min), PalmPVT (5 min) and self-report of sleepiness, is conducted on eight healthy subjects. The trend of mental fatigue level as measured by a specially proposed score, AWVT Fatigue Index (AFI), during the 25-h study shows very similar pattern to those of PalmPVT lapses and self-report sleepiness. AFI even shows closer correspondence to self-report sleepiness than PalmPVT lapses. This suggests that AWVT is able to measure performance decrement due to sleep deprivation, and it can even provide better measurement of mental fatigue than PalmPVT. AWVT shows a learning curve of less than 3 trials indicating that no skill is required in performing AWVT. Furthermore, repeat studies are done on five of the eight subjects. Pearson’s correlation analysis and other statistical exhibits suggest that AWVT has good test–retest reliability and within subject consistency, which are even better than those of PalmPVT. These results suggest that the AWVT can be used as a reliable objective measure of mental fatigue, and it can even track mental fatigue more accurately than PalmPVT in the real world where most tasks require not just a reaction time type response, but also higher mental abilities.     

Modeling the Impacts of Two Bark Beetle Species Under a Warming Climate in the Southwestern USA: Ecological and Economic Consequences

Predicted climate warming is expected to have profound effects on bark beetle population dynamics in the southwestern United States. Temperature-mediated effects may include increases in developmental rates, generations per year, and changes in habitat suitability. As a result, the impacts of Dendroctonus frontalis and Dendroctonus mexicanus on forest resources are likely subject to amplification. To assess the implications of such change, we evaluated the generations per year of these species under three climate scenarios using a degree-day development model. We also assessed economic impacts of increased beetle outbreaks in terms of the costs of application of preventative silvicultural treatments and potential economic revenues forgone. Across the southwestern USA, the potential number of beetle generations per year ranged from 1–3+ under historical climate, an increase of 2–4+ under the minimal warming scenario and 3–5+ under the greatest warming scenario. Economic benefits of applying basal area reduction treatments to reduce forest susceptibility to beetle outbreaks ranged from 7.75/ha (NM) to7.75/ha (NM) to 95.69/ha (AZ) under historical conditions, and 47.96/ha (NM) to47.96/ha (NM) to 174.58/ha (AZ) under simulated severe drought conditions. Basal area reduction treatments that reduce forest susceptibility to beetle outbreak result in higher net present values than no action scenarios. Coupled with other deleterious consequences associated with beetle outbreaks, such as increased wildfires, the results suggest that forest thinning treatments play a useful role in a period of climate warming.     

改性油页岩灰渣对水中DNBP吸附去除效果

采用PDMDAAC改性方法对油页岩灰渣进行改性，确定最佳改性方案，并研究了环境因素对改性油页岩灰渣吸附DNBP的影响。实验研究结果表明，油页岩灰渣经20 g/L 的PDMDAAC处理时，对DNBP的吸附能力最强。在吸附温度为30℃，初始溶液pH值为4的条件下，0.3 g 的改性油页岩灰渣对30.0 mg/L DNBP溶液50 mL，吸附120 min时，其吸附率达到94.48%以上。在实验条件下，改性油页岩灰渣对DNBP的吸附符合Langmuir和Freundlich等温吸附方程，相关系数分别为0.9985和0.9776，其对DNBP的理论饱和吸附量达到6.196 mg/g。改性油页岩灰渣对DNBP的吸附主要归因于离子交换和表面吸附作用。     

CS-Fe和CS-Fe/Ni的制备及其用于去除钴离子

以氯化铁为铁源，硼氢化钠为还原剂，壳聚糖为稳定剂，采用液相还原法制备壳聚糖稳定纳米铁（CS-Fe）；并以氯化铁为铁源，硫酸镍为镍源，硼氢化钠为还原剂，壳聚糖为稳定剂，采用液相还原共沉淀法制备壳聚糖稳定纳米铁镍（CS-Fe/Ni）。通过SEM、EDS、XRD、FT-IR等表征手段，对所制备的CS-Fe和CS-Fe/Ni的形貌及微观结构进行表征，并以Co²⁺为目标去除物评价CS-Fe和CS-Fe/Ni的反应活性。初步研究表明，制成的CS-Fe含有单质纳米铁，颗粒多数以30~90 nm球形颗粒为主；而CS-Fe/Ni材料中含有纳米铁镍，颗粒多数以30~60 nm球形颗粒为主；在相同的实验条件下，反应60 min，CS-Fe/Ni对Co²⁺的去除率高达100%，但是CS-Fe仅为88%，即CS-Fe/Ni对Co²⁺的去除率比CS-Fe高。     

Examining the temperature dependence of ethanol (E85) versus gasoline emissions on air pollution with a largely-explicit chemical mechanism

The increased use of ethanol in transportation fuels warrants an investigation of its consequences. An important component of such an investigation is the temperature dependence of ethanol and gasoline exhaust chemistry. We use the Master Chemical Mechanism (MCM, version 3.1, LEEDS University) with the SMVGEAR II chemical ordinary differential solver to provide the speed necessary to simulate complex chemistry to examine such effects. The MCM has over 13,500 organic reactions and 4600 species. SMVGEAR II is a sparse-matrix Gear solver that reduces the computation time significantly while maintaining any specified accuracy. Although we use a box model for this study, we determine and demonstrate in a separate study that the speed of the MCM with SMVGEAR II allows the MCM to be modeled in 3-dimensions. We also verified the accuracy of the model in comparison with smog chamber data. We then use the model with species-resolved tailpipe emissions data for E85 (15% gasoline, 85% ethanol fuel blend) and gasoline vehicles to compare the impact of each on nitrogen oxides, organic gases, and ozone as a function of ambient temperature and background concentrations, using Los Angeles in 2020 as a base case. We use two different emissions sets – one is a compilation of exhaust and evaporative data taken near 24 °C and the other from exhaust data taken at ?7 °C – to determine how atmospheric chemistry and emissions are affected by temperature. We include diurnal effects by examining two day scenarios. We find that, accounting for chemistry and dilution alone, the average ozone concentrations through the range of temperatures tested are higher with E85 than with gasoline by ～7 part per billion volume (ppbv) at higher temperatures (summer conditions) to ～39 ppbv at low temperatures and low sunlight (winter conditions) for an area with a high nitrogen oxide (NOx) to non-methane organic gas (NMOG) ratio. The results suggest that E85's effect on health through ozone formation becomes increasingly more significant relative to gasoline at colder temperatures due to the change in exhaust emission composition at lower temperatures. Acetaldehyde and formaldehyde concentrations are also much higher with E85 at cold temperatures, which is a concern because both are considered to be carcinogens. These could have implications for wintertime use of E85. Peroxy acetyl nitrate (PAN), another air pollutant of concern, increases with E85 by 0.3–8 ppbv. The sensitivity of the results to box size, initial background concentrations, background emissions, and water vapor were also examined.     

Experimental investigation and modelling of tritium washout by precipitation in the area of the nuclear power plant of Paks, Hungary

Tritium occurs in nature in trace amounts, but its concentration is changing due to natural and artificial sources. Studies focusing on natural tritium have to take into account the effect of artificial sources. Also, the impact of tritium is an important issue in environmental protection, e.g. in connection with the emissions from nuclear power plants. The present work focuses on the rain washout of tritium emitted from the Paks nuclear power plant in Hungary. Rainwater collectors were placed around the plant and after a period of precipitation, rainwater was collected and analysed for tritium content. Samples were analysed using low-level liquid scintillation counting, with some also subject to the more accurate ³He ingrowth method. The results clearly show the trace of the tritium plume emitted from the plant; however, values are only about one order of magnitude higher than environmental background levels. A washout model was devised to estimate the distribution of tritium around the plant. The model gives slightly higher concentrations than those measured in the field, but in general the agreement is satisfactory. The modelled values demonstrate that the effect of the plant on rainwater tritium levels is negligible over a distance of some kilometres.     

Dietary antioxidants (selenium and N-acetylcysteine) modulate paraoxonase 1 (PON1) in PCB 126-exposed rats

Environmental pollutants polychlorinated biphenyls (PCBs), especially dioxin-like PCBs, cause oxidative stress and associated toxic effects, including cancer and possibly atherosclerosis. We previously reported that PCB 126, the most potent dioxin-like PCB congener, not only decreases antioxidants such as hepatic selenium (Se), Se-dependent glutathione peroxidase, and glutathione (GSH) but also increases levels of the antiatherosclerosis enzyme paraoxonase 1 (PON1) in liver and serum. To probe the interconnection of these three antioxidant systems, Se, GSH, and PON1, we examined the influence of varying levels of dietary Se and N-acetylcysteine (NAC), a scavenger of reactive oxygen species (ROS) and precursor for GSH synthesis, on PON1 in the absence and presence of PCB 126 exposure. Male Sprague–Dawley rats, fed diets with differing Se levels (0.02, 0.2, or 2 ppm) or NAC (1 %), were treated with a single intraperitoneal injection of corn oil or various doses of PCB 126 and euthanized 2 weeks later. PCB 126 significantly increased liver PON1 mRNA, protein level and activity, and serum PON1 activity in all dietary groups but did not consistently increase thiobarbituric acid levels (thiobarbituric acid reactive substances, TBARS), an indicator of lipid oxidation and oxidative stress, in liver or serum. Inadequate (high or low) dietary Se decreased baseline and PCB 126-induced aryl hydrocarbon receptor (AhR) expression but further increased PCB 126-induced cytochrome P450 1A1 (CYP1A1) expression, the enzyme believed to be the cause for PCB 126-induced oxidative stress. In addition, a significant inverse relationship was observed not only between dietary Se levels and PON1 mRNA and PON1 activity but also with TBARS levels in the liver, suggesting significant antioxidant protection from dietary Se. NAC lowered serum baseline TBARS levels in controls and increased serum PON1 activity but lowered liver PON1 activities in animals treated with 1 μmol/kg PCB 126, suggesting antioxidant activity by NAC primarily in serum. These results also show an unexpected predominantly inverse relationship between Se or NAC and PON1 during control and PCB 126 exposure conditions. These interactions should be further explored in the development of dietary protection regimens.     

Faecal pollution loads in the wastewater effluents and receiving water bodies: a potential threat to the health of Sedibeng and Soshanguve communities,South Africa

The discharge of untreated or inadequately treated effluents has been identified among the activities responsible for the spread of a wide range of potentially infectious agents. The aim of this study was to determine whether inadequate treatment of wastewater and the faecal pollution load of effluents and receiving water bodies in Sedibeng District and Soshanguve peri-urban area of the Tshwane Metropolitan Municipality could be a potential threat to the health of the surrounding communities. Variations in the counts of faecal indicator bacteria and pathogenic microorganisms and compliance of the effluents and receiving water bodies with South African and World Health Organization standards were assessed between August 2011 and May 2012 using culture-based methods and molecular techniques. The overall quality of effluents did not comply with the South African special standard of no risk for unrestricted irrigation (zero?Escherichia coli/100 ml). The quality of the receiving water bodies did not comply with South African regulatory limits set for domestic purposes (zero?E.?coli/100 ml, <30 faecal enterococci/100 ml and <1 somatic coliphages/100 ml), for full contact recreation (<20 somatic coliphages/100 ml) and aquaculture (<10?E.?coli/100 ml) and WHO standards for full and intermediate contact recreational use (<1?E.?coli/100 ml and <40 faecal enterococci/100 ml, respectively). The PCR results revealed the prevalence of pathogenic microorganisms; between 0 and 60 % of samples tested positive for Salmonella Typhimurium and Shigella dysenteriae, and between 20 and 60 % of samples tested positive for Vibrio cholerae. These findings demonstrated that potential health risks might be associated with the use of the target river waters for domestic, recreational and irrigation purposes. This study calls for a prompt intervention to improve wastewater management.     

水源区河流非点源污染物入河量计算的水质方程反演方法

以水质一维流方程为基础,建立了水源地区非点源污染物入河量计算的反演模型;计算了浙江省湖州市老虎潭水库水源地区各条支流的非点源污染物入河量;并通过对实测水文水质参数的统计,采用Monte Carlo模拟方法,分析了模型各输入参数的敏感性.由于该模型所有敏感参数都可以实测获得,避免了关键参数取值的人为主观因素的影响,保证了非点源污染过程定量分析的客观性;该模型在计算非点源污染物入河量时不受时间的限制,可以根据研究区域的水文水质监测频率计算任意时段内的非点源污染物入河量.结果表明,该水源区所有溪流中的氮、磷污染物负荷量都与溪流流量呈极显著正相关(r0.90,p0.01),因此,丰水期是非点源污染物入河的集中期;对输入参数的敏感性分析显示,对模型输出结果影响最大的是溪流的流量,其次是段末浓度和背景浓度,综合降解系数和流速的影响较小.