Gendered Spaces of Informal Entrepreneurship in Soweto,South Africa   总被引：1，自引：1，他引：0  

Richard Grant 《Urban geography》2013,34(1):86-108

Abstract

The full diversity of economic activities in the informal economy is not well understood. The apartheid legacy of limiting informal entrepreneurship explains the most obvious geographical patterns in South Africa. After a decade and a half since the end of apartheid, however, knowledge about the places from which informal entrepreneurs operate is incomplete. Retailing is overemphasized and production firm entrepreneurs, both male and female, remain a neglected spatiality. This study reports on a survey of 100 firms in Soweto and in-depth interviews with 30 firm owners. The findings challenge the representations of isolated urban entrepreneurs dependent on inherited social capital and of women's exclusive engagement in retail. Entrepreneurs create their own social capital in work-related realms, but there are important gender differences. More finely tuned conceptualizations of entrepreneurs and of gendered working spaces need to be developed so that policy does not perpetuate unitary myths and incomplete spatial representations. [Key words: entrepreneurship, Soweto, informal economy, gender.]  相似文献   

Discussion of “Challenges in operationalizing the water–energy–food nexus”*     

Olli Varis  Marko Keskinen 《水文科学杂志》2013,58(12):1863-1865

ABSTRACT

We greatly enjoyed reading the paper by Liu et al., which is both timely and rich in insight, as it discusses the challenges in operationalizing the water–energy–food security (WEF) nexus. The nexus approach is gaining increasing attention, both in research and in policy documents, as reflected in the number and content of published documents in the past years and highlighted by the authors.  相似文献   

Chemosynthetic trophic support for the benthic community at an intertidal cold seep site at Mocha Island off central Chile     

Javier Sellanes  Germán Zapata-Hernández  Silvio Pantoja  Gerdhard L. Jessen 《Estuarine, Coastal and Shelf Science》2011

We analyzed C and N stable isotope ratios of benthic fauna and their potential food sources at an intertidal methane seep site and a control site without emanation at Mocha Island (central Chile). The objective was to trace the origin of the main food sources used by the local heterotrophic fauna, based on the hypothesis that chemosynthetic production could be partially fueling the local food web at the seep site. Food sources sampled at both sites included macroalgae, particulate organic matter and bacteria-like filaments found growing over the red algae Gelidium lingulatum within the areas of active methane release.  相似文献   

Trophic functioning of the St. Lucia estuarine lake during a drought phase assessed using stable isotopes     

Natasha Govender  Albertus J. SmitRenzo Perissinotto 《Estuarine, Coastal and Shelf Science》2011

The St. Lucia Estuary is Africa’s largest estuarine system and is currently experiencing the stress of prolonged freshwater deprivation, manifested by extremely low water levels and hypersalinity. These unprecedented conditions have raised questions regarding the trophic functioning of the ecosystem. Despite the substantial amount of research previously undertaken within this system, no studies of food web structure and function have yet been documented. This study therefore aimed to examine the food web structure of the St. Lucia estuary system through the use of carbon and nitrogen stable isotope analysis. Analysis of carbon isotope ratios indicates that benthic carbon sources are most utilised at sites with low water levels and generally higher salinity (Catalina Bay, Charter’s Creek). Conversely, the estuarine region of the mouth and Narrows, with its elevated water levels and lower salinity, still sustains a viable pelagic food web. Analysis of δ¹⁵N ratios indicates that the number of trophic transfers (food chain length) might be related to water levels. Overall, the study provides a greater understanding of the ecological processes of this complex estuarine lake, which may allow for future comparisons of trophic functioning under drought and normal/wet conditions to be made.  相似文献   

Origin of resources and trophic pathways in a large SW Atlantic estuary: An evaluation using stable isotopes     

Florencia Botto  Esteban Gaitán  Hermes Mianzan  Marcelo Acha  Diego Giberto  Agustín Schiariti  Oscar Iribarne 《Estuarine, Coastal and Shelf Science》2011

The Río de la Plata (34° 36′ S, 55° 58′ W; Argentina and Uruguay) estuary, one of the most important South American estuarine environments, is characterized by weak seasonal freshwater discharge, low tidal amplitude (<1 m), a wide and permanent connection to the sea, and a salt-wedge regime. Using stable isotope analysis, we explored the relative importance of the different sources of primary production in the food web. Our results show that phytoplankton and macrodetritus from terrestrial salt and freshwater marshes both contribute to the food web of the Río de la Plata estuary. On the basis of the sampled species, we identified four trophic levels. The clam Mactra isabelleana, the calanoid copepod Acartia tonsa, and the opossum shrimp Neomysis americana are the primary consumers. The rays Atlantoraja castelnaui and Squatina guggenheim and the shark Galeorhinus galeus are the top predators. The Río de la Plata food web shows an important input of nutrients derived from phytoplankton. Rays, sharks, and predatory gastropods reveal an important contribution of C4 plants (likely Spartina spp.). However, production derived from C3 plants is also important for some species. The fishes Brazilian menhaden, Brevoortia aurea; the stripped weakfish Cynoscion guatucupa; and the whitemouth croaker, Micropogonias furnieri, showed differences in their isotopic signatures as juveniles and adults, indicating different food sources, and they were therefore treated as different components of the food web. Our data suggest that detritus from salt and freshwater marshes is reaching the Río de la Plata estuary and can be an important allocthonous source of energy to this environment.  相似文献   

不同饵料对真蛸亲体产罗同量、受精卵孵化率及初孵幼体大小的影响     

刘兆胜  刘永胜  郑小东  曲海波 《海洋科学》2011,35(10):81-85

分别采用文蛤（Meretrix meretrix）、菲律宾蛤仔（Ruditapes philippinarum）、缢蛏（Sinonovacula constrzcta）、许氏平鲌（Sebastodes fuscescens）投喂处于产卵、护卵期的真蛸（Octopus vulgaris）亲体,通过测量亲蛸摄食量、产卵量、...  相似文献   

福建沿岸海域浒苔藻类的营养成分含量与食用安全   总被引：4，自引：0，他引：4  

林建云  陈维芬  贺青  林力斌  汤荣坤  暨卫东 《台湾海峡》2011,30(4):570-576

对福建沿岸海域浒苔（Enteromorpha）样品的主要组成成分、氨基酸、脂肪酸、矿物质含量的研究表明,浒苔属高膳食纤维（49．0％～59．1％）、高蛋白质（19．60％～38．24％）、低脂肪（0．20％～0．55％）的藻类．浒苔中17种氨基酸总量（Ctaa）与蛋白质含量的比值为74．1％～91．0％;其必需氨基酸含量（Ctaa）占C11从的35．4％～40．0％,CⅢ与非必需氨基酸含量（C。Ⅲ）之比为0．55～0．67,且呈味氨基酸的含量丰富（47．1％）,氨基酸组成均衡．浒苔油脂中脂肪酸组成丰富,n一3PUFA含量达油脂总量的20．0％～26．4％,其中含有EPA、DHA．浒苔中矿物质含量较高,尤其富含镁、钙、铁、锌、硒、钾等人体必需矿物元素．有害元素测定结果表明,中、低潮区浒苔的铅、汞、镉、砷含量均能够符合《无公害食品海藻》安全指标的限量要求,养殖区、高潮区部分浒苔的Pb含量超标．研究结果认为,在低污染海区生长的浒苔是一种高蛋白质、高膳食纤维、低脂肪、矿物元素丰富且安全的海洋食品．  相似文献   

基于Faster R-CNN的食品图像检索和分类     

梅舒欢  闵巍庆  刘林虎  段华  蒋树强 《南京气象学院学报》2017,9(6):635-641

面向食品领域的图像检索和分类等方面的研究成为多媒体分析和应用领域越来越受关注的研究课题之一.当前的主要研究方法基于全图提取视觉特征,但由于食品图像背景噪音的存在使得提取的视觉特征不够鲁棒,进而影响食品图像检索和分类的性能.为此,本文提出了一种基于Faster R-CNN网络的食品图像检索和分类方法.首先通过Faster R-CNN检测图像中的候选食品区域,然后通过卷积神经网络（CNN）方法提取候选区域的视觉特征,避免了噪音的干扰使得提取的视觉特征更具有判别力.此外,选取来自视觉基因库中标注好的食品图像集微调Faster R-CNN网络,以保证Faster R-CNN食品区域检测的准确度.在包括233类菜品和49 168张食品图像的Dish-233数据集上进行实验.全面的实验评估表明：基于Faster R-CNN食品区域检测的视觉特征提取方法可以有效地提高食品图像检索和分类的性能.  相似文献   

Analysis of Food Consumption and Its Characteristics in Uzbekistan based on the Emergy Method     

JIA Mengmeng  ZHEN Lin  ZHANG Changshun 《资源与生态学报(英文版)》2022,13(5):842-850

Food resources play a great role in human livelihood, so it is meaningful to investigate their utilization and structural evolution, especially in developing countries. This study takes data from FAOSTAT and the World Bank, and applies the emergy method to analyze Uzbek food consumption changes and characteristics from 1992 to 2019. Two main results were obtained: (1) National food consumption showed a persistent increase and had a remarkable change in stages, with the first stage of low-level repetition, the second stage of speeding up and the third stage of high development. The increase of animal-based food consumption was more notable than that of plant-based food consumption. (2) Per capita annual food consumption had a tendency of change that was similar to that of national food consumption. The proportion of animal-based food in the total per capita annual food consumption usually remained about 2-fold higher than that of plant-based food consumption. The main food consumption pattern was the combination of crops such as wheat and rice with meat such as beef. The fruit and vegetable consumption also increased. With the growing population, various changes in food demand will inevitably happen, so it is necessary to take sustainable measures in time to satisfy the new demand and to protect resources and the environment.  相似文献   

生物土壤结皮：荒漠昆虫食物链的重要构建者   总被引：4，自引：3，他引：1  

李新荣  陈应武  贾荣亮 《中国沙漠》2008,28(2):245-248

干旱荒漠地区由于水分因子的限制,其植被分布以不连续的高等植物斑块与隐花植物及其结皮的斑块镶嵌为其主要特征,构成了独特的荒漠植被景观格局。作为荒漠生态系统的主要组成者,荒漠昆虫与生境的关系,特别是与高等植物之间的食物链关系已得到大量的文献报道。本文基于野外调查和实验室模拟观测,发现了尖尾东鳖甲(Anatolica mucronata)对藓类结皮有取食现象,哈蛃(Haslundichilis sp.)对地衣结皮有取食现象。证实了生物土壤结皮直接参与了荒漠昆虫食物链和食物网的构成,为深入了解生物土壤结皮在荒漠生态系统中的功能和地位提供了实验证据。  相似文献