Lack of detectable nepotism in multiple-queen colonies of the fire ant Solenopsis invicta (Hymenoptera: Formicidae)

Multiple-queen (polygyne) colonies of the introduced fire ant Solenopsis invicta present a paradox for kin selection theory. Egg-laying queens within these societies are, on average, unrelated to one another, and the numbers of queens per colony are high, so that workers appear to raise new sexuals that are no more closely related to them than are random individuals in the population. This paradox could be resolved if workers discriminate between related and unrelated nestmate sexuals in important fitness-related contexts. This study examines the possibility of such nepotism using methods that combine the following features: (1) multiple relevant behavioral assays, (2) colonies with an unmanipulated family structure, (3) multiple genetic markers with no known phenotypic effects, and (4) a statistical technique for distinguishing between nepotism and potentially confounding phenomena. We estimated relatedness between interactants in polygyne S. invicta colonies in two situations, workers tending egg-laying queens and workers feeding maturing winged queens. In neither case did we detect a significant positive value of relatedness that would implicate nepotism. We argue that the non-nepotistic strategies displayed by these ants reflect historical selection pressures experienced by native populations, in which nestmate queens are highly related to one another. The markedly different genetic structure in native populations may favor the operation of stronger higher-level selection that effectively opposes weaker individual-level selection for nepotistic interactions within nests. Received: 28 June 1996 / Accepted after revision: 6 October 1996     

Integrating models to predict regional haze from wildland fire

Visibility impairment from regional haze is a significant problem throughout the continental United States. A substantial portion of regional haze is produced by smoke from prescribed and wildland fires. Here we describe the integration of four simulation models, an array of GIS raster layers, and a set of algorithms for fire-danger calculations into a modeling framework for simulating regional-scale smoke dispersion. We focus on a representative fire season (2003) in the northwestern USA, on a 12 km domain, and track the simulated dispersion and concentration of PM_2.5 over the course of the season. Simulated visibility reductions over national parks and wilderness areas are within the ranges of measured values at selected monitoring sites, although the magnitudes of peak events are underestimated because these include inputs other than fire. By linking the spatial and temporal patterns of haze-producing emissions to climatic variability, particularly synoptic weather patterns, and the stochastic nature of fire occurrence across the region, we can provide a robust method for estimating the quantity and distribution of fire-caused regional haze under climate-warming scenarios.     

Estimation of probabilities and likely consequences of a chain of accidents (domino effect) in Manali Industrial Complex

Chains of accidents (the domino effect) have been occurring with ever increasing frequency in chemical process industries. This is reflected in several accidents ‘J Loss Prevent Process Ind 12 (1999a) 361’; the world's worst industrial accident of the 1990s — the Vishakhpatnam disaster — also involved the domino effect ‘J Loss Prevent Process Ind 12 (1999a) 361; and Process Safety Prog 18 (1999b) 135’. Such chains of accidents have a greater propensity to cause damage than stand-alone accidents ‘Process Safety Prog 17(2) (1998a) 107; and J Loss Prevent Process Ind 12 (1999a) 361’.In order to assess the likelihood of occurrence of the domino effect and its damage potential, use of deterministic models in conjunction with probabilistic analysis is required. Recently we have proposed a systematic methodology called ‘domino effect analysis’ (DEA). A computer-automated tool, DOMIFFECT, has also been developed by us based on DEA ‘Process Safety Prog 17(2) (1998a) 107; Environment Model Software 13 (1998b) 163; and Risk assessment in chemical process industries: advanced techniques. Discovery Publishing House (1998c)’.This paper illustrates the application of DEA and DOMIFFECT to an industrial complex comprising 16 different industries. Out of 12 credible accident scenarios envisaged in three different industries — namely Madras Refineries Limited (MRL), UB Petrochemicals (UBP) and Indian Organic Chemicals Limited (IOCL), eight scenarios are likely to cause the domino effect. A further detailed analysis reveals that accidents in the storage of liquified petroleum gas and propylene and in the reflux drum units of MRL may cause domino effects. Similarly, propylene storage of UBP and monoethylene glycol storage of IOCL are also likely to cause domino effects. The impact of various chains of accidents has been forecast which reveals that in several cases the accidents may be catastrophic, harming the entire industrial complex of 16 industries. The study leads to the identification of ‘hot spots’ — units that pose the greatest risk — in turn forewarning the industries concerned and enabling them to prioritize and augment accident-prevention steps.     

Landfill gas - a potential environmental hazard

Methane derived from the decomposition of organic material contained within a landfill may escape beyond the site boundary where it can pose an explosion or fire hazard. Methods are described to prevent die occurrence of such lateral gas migration. Problems due to the accumulation of gas in buildings, erected on landfill sites, have occurred and techniques are now available to overcome these at some sites. However, it is recognized that at other sites, redevelopment should not be allowed to take place on die grounds of safety.     

混凝土高温爆裂性能影响因素及预防措施综述

对混凝土高温爆裂成因进行总结,综述高温下混凝土内部蒸汽压力的测试手段、降低混凝土内部蒸汽压力方法、提高混凝土在高温中的抗高温爆裂性能的方法,以及总结了升温速率对混凝土高温爆裂的影响,并提出了几种预防混凝土高温爆裂的措施,为混凝土高温爆裂研究提供依据。     

飞机防火试验中的燃烧反应动力学模型研究

使用反应路径分析法对Jet-A型航空煤油燃烧的气相燃烧机理进行简化。选用POSF-4658机理作为Jet-A燃烧的详细反应机理,该机理包含1607种燃烧组分、6633个基元反应机理。将飞机防火试验条件作为简化过程的初始条件,得到78种组分,196个反应机理的Jet-A燃烧机理。通过对Jet-A的简化反应机理、详细反应机理和JetA实验数据的比较可以发现,简化反应机理可以较准确地反映Jet-A型航空煤油在防火试验条件下的燃烧特性。利用常用的Jet-A型航空煤油简化机理计算的绝热火焰温度、点火延迟时间及层流火焰速度与本文提出的简化的计算值进行比较。结果表明,提出的简化机理在防火试验条件下具有较高的精确度。得到的Jet-A简化反应机理可为飞机防火试验的仿真研究提供燃烧场的化学反应动力学模型。     

Towards an inherently safer bioprocessing industry: A review

The bioprocessing industry is regarded as one of the fastest growing sectors with an estimated compound annual growth rate of 8.6%. The global market for biopharmaceuticals is projected to rise to a market value of USD 727.1 billion by 2025. Due to the unique nature of bioprocessing industries wherein micro-organisms are employed to manufacture the desired products, these processes are prone to additional hazards such as biological hazards and dust explosion amongst others. This necessitates the need to review the existing research in the fields of biotechnology and bioprocessing to reduce/eliminate these hazards and pave the path towards a safer bioprocessing industry. The study involves developing a framework comprising of studying the recent technologies that reduce/eliminate these hazards involved in the bioprocessing industries that include dust explosions, loss of containment of toxic chemicals, loss of containment of biohazard/active product ingredient, fire, and explosion and mapping these technologies with respect to inherent safety principles that include substitution, minimization, moderation and simplification with an overall objective of minimizing the risk associated with bioprocesses and moving towards an inherently safer bioprocessing industry.     

Short-Term Influence of Tank Tracks on Vegetation and Microphytic Crusts in Shrubsteppe Habitat

Artemisia tridentata Nutt.) habitat within the Idaho Army National Guard Orchard Training Area in southwestern Idaho. The purpose of this study was to determine the short-term (1–2 years) influence of tank tracks on vegetation and microphytic crusts in shrubsteppe habitat. The two types of tank tracks studied were divots (area where one track has been stopped or slowed to make a sharp turn) and straight-line tracks. Divots generally had a stronger influence on vegetation and microphytic crusts than did straight-line tracks. Tank tracks increased cover of bare ground, litter, and exotic annuals, and reduced cover of vegetation, perennial native grasses, sagebrush, and microphytic crusts. Increased bare ground and reduced cover of vegetation and microphytic crusts caused by tank tracks increase the potential for soil erosion and may reduce ecosystem productivity. Reduced sagebrush cover caused by tank tracks may reduce habitat quality for rodents. Tank tracks may also facilitate the invasion of exotic annuals into sagebrush habitat, increasing the potential for wildfire and subsequent habitat degradation. Thus, creation of divots and movement through sagebrush habitat by tanks should be minimized.     

火源功率对竖井负压控烟效果影响的实验研究

基于竖井的烟囱效应原理,利用小尺寸实验台开展了一系列实验,通过改变油盘的尺寸,对竖井内的烟气温度、压力、速度以及通风口处的压力、气流速度进行测量,研究了火源功率对房间利用竖井进行负压控烟效果的影响。实验结果表明:一方面随着火源功率的增大,室内温度升高,热烟气形成的热压增大,使烟气向外膨胀;另一方面,竖井底部的烟气温度升高,竖井底部的负压值增大,烟囱效应增强,排烟速度增大,新鲜空气补入的速度增大,逐渐抑制住烟气从通风口向外溢出,达到了负压控烟的效果。     

细水雾幕衰减热辐射的数值模拟研究

针对现有防火分隔技术的不足,以细水雾幕作为新的防火分隔技术,开展了不同细水雾幕雾特性对衰减热辐射影响的数值模拟研究。通过建立长通道模型,在火源和被保护物体中间设置细水雾幕系统,测量有无细水雾幕及不同细水雾特性条件下被保护侧温度及热辐射强度值,来定性定量研究细水雾幕衰减热辐射的效率。模拟结果表明:细水雾幕可以很好的降低被保护侧空间的温度和热辐射强度;衰减热辐射效率随雾滴粒径的减小,喷雾流量的增大,喷头排数增加而增大;另外,其衰减热辐射效率与喷头布置方式有关,上喷方式明显优于下喷方式。研究结果将对现有防火分隔技术的改善提供帮助和技术支持。