388 research outputs found
Drifters, Party Boys and Incumbents: The Life Patterns of Male Street-based Sex Workers
This paper is based on a qualitative study of male street-based prostitution. It suggests that the street-based sector is more varied, with sellers adopting a wider range of working practices, than is commonly acknowledged in the literature on male prostitution. Drawing on data from Manchester, England I identify a number of ‘life patterns’ among male street sellers that reflect varied working practices based on issues around rational decision-making and the sex worker’s relationship to place and environment. The discussion has implications for urban policies around street-based sex work but also for a more general understanding of male sex work in international and comparative perspective
Louisville Seamount Trail: implications for geodynamic mantle flow models and the geochemical evolution of primary hotspots
The Louisville Seamount Trail is a 4300 km long volcanic chain that has been built in the past 80 m.y. as the Pacific plate moved over a persistent mantle melting anomaly or hotspot. Because of its linear morphology and its long-lived age-progressive volcanism, Louisville is the South Pacific counterpart of the much better studied Hawaiian-Emperor Seamount Trail. Together, Louisville and Hawaii are textbook examples of two primary hotspots that have been keystones in deciphering the motion of the Pacific plate relative to a set of "fixed" deep-mantle plumes. However, drilling during Ocean Drilling Program (ODP) Leg 197 in the Emperor Seamounts documented a large ~15° southward motion of the Hawaiian hotspot prior to 50 Ma. Is it possible that the Hawaiian and Louisville hotspots moved in concert and thus constitute a moving reference frame for modeling plate motion in the Pacific? Alternatively, could they have moved independently, as predicted by mantle flow models that reproduce the observed latitudinal motion for Hawaii but that predict a largely longitudinal shift for the Louisville hotspot? These two end-member geodynamic models were tested during Integrated Ocean Drilling Program (IODP) Expedition 330 to the Louisville Seamount Trail.
In addition, existing data from dredged lavas suggest that the mantle plume source of the Louisville hotspot has been remarkably homogeneous for as long as 80 m.y. These lavas are predominantly alkali basalts and likely represent a mostly alkalic shield-building stage, which is in sharp contrast to the massive tholeiitic shield-building stage of Hawaiian volcanoes. Geochemical and isotopic data for the recovered lavas during Expedition 330 will provide insights into the magmatic evolution and melting processes of individual Louisville volcanoes, their progression from shield-building to postshield and (maybe) posterosional stages, the temperature and depth of partial melting of their mantle plume source, and the enigmatic long-lived and apparent geochemical homogeneity of the Louisville mantle source. Collectively, this will enable us to characterize the Louisville Seamount Trail as a product of one of the few global primary hotspots, to better constrain its plume-lithosphere interactions, and to further test the hypothesis that the Ontong Java Plateau formed from the plume head of the Louisville mantle plume around 120 Ma.
During Expedition 330 we replicated the drilling strategy of Leg 197, the first expedition to provide compelling evidence for the motion of the Hawaiian mantle plume between 80 and 50 Ma. For that reason we targeted Louisville seamounts that have ages similar to Detroit, Suiko, Nintoku, and Koko Seamounts in the Emperor Seamount Trail. In total, five seamounts were drilled in the Louisville Seamount Trail: Canopus, Rigil, Burton, Achernar, and Hadar Guyots (old to young). By analyzing a large number of time-independent in situ lava flows (and other volcanic eruptive products) from these seamounts using modern paleomagnetic, 40Ar/39Ar geochronological, and geochemical techniques, we will be able to directly compare the paleolatitude estimates and geochemical signatures between the two longest-lived hotspot systems in the Pacific Ocean.
We drilled into the summits of the five Louisville guyots and reached volcanic basement at four of these drilling targets. In two cases we targeted larger seamount structures and drilled near the flanks of these ancient volcanoes, and in the other three cases we selected smaller edifices that we drilled closer to their centers. Drilling and logging plans for each of these sites were similar, with coring reaching 522.0 meters below seafloor (mbsf) for Site U1374 and 232.9, 65.7, 11.5, 182.8, and 53.3 mbsf for Sites U1372, U1373, U1375, U1376, and U1377, respectively. Some Expedition 330 drill sites were capped with only a thin layer of pelagic ooze between 6.6 and 13.5 m thick, and, if present, these were cored by using a low-rotation gravity-push technique with the rotary core barrel to maximize recovery. However, at Sites U1373 and U1376 no pelagic ooze was present, and the holes needed to be started directly into cobble-rich hardgrounds. In all cases, the bulk of the seamount sediment cover comprised sequences of volcanic sandstones and various kinds of basalt breccia or basalt conglomerate, which often were interspersed with basaltic lava flows, the spatter/tephra products of submarine eruptions, or other volcanic products, including auto-brecciated flows or peperites. Also several intervals of carbonate were cored, with the special occurrence of a ~15 m thick algal limestone reef at Site U1376 on Burton Guyot. In addition, some condensed pelagic limestone units were recovered on three of the other seamounts, but these did not exceed 30 cm in thickness. Despite their limited presence in the drilled sediment, these limestones provide valuable insights for the paleoclimate record at high ~50° southern latitudes since Mesozoic times.
Several Louisville sites progressed from subaerial conditions in the top of volcanic basement into submarine eruptive environments, or drilling of the igneous basement immediately started in submarine volcanic sequences, as was the case for Sites U1376 and U1377 on Burton and Hadar Guyots. At three sites we cored >100 m into the igneous basement: 187.3 m at Site U1372, 505.3 m at Site U1374, and 140.9 m at Site U1376. At the other sites we did not core into basement (Site U1375) or we cored only 38.2 m (Site U1377) because of unstable hole conditions. Even so, drilling during Expedition 330 resulted in a large number of in situ lava flows, pillow basalts, or other types of volcanic products such as auto-brecciated lava flows, intrusive sheets or dikes, and peperites. In particular, the three holes on Canopus and Rigil Guyots (the two oldest seamounts drilled in the Louisville Seamount Trail), resulted in adequate numbers of in situ lava flows to average out paleosecular variation, with probable eruption ages estimated at ~78 and 73 Ma, respectively. Remarkably, at all drill sites large quantities of hyaloclastites, volcanic sandstones, and basaltic breccias were also recovered, which in many cases show consistent paleomagnetic inclinations compared to the lava flows bracketing these units. For Site U1374 on Rigil Guyot we also observed a magnetic polarity reversal in the cored sequence. Overall, this is very promising for determining a reliable paleolatitude record for the Louisville Seamounts following detailed postcruise examinations.
The deeper penetrations of several hundred meters required bit changes and reentries using free-fall funnels. Basement penetration rates were 1.8–2.5 m/h depending on drill depth. In total, 1114 m of sediment and igneous basement at five seamounts was drilled, and 806 m was recovered (average recovery = 72.4%). At Site U1374 on Rigil Guyot, a total of 522 m was drilled, with a record-breaking 87.8% recovery. Most outstandingly, nearly all Expedition 330 core material is characterized by low degrees of alteration, providing us with a large quantity of samples of mostly well-preserved basalt, containing, for example, pristine olivine crystals with melt inclusions, fresh volcanic glass, unaltered plagioclase, carbonate, zeolite and celadonite alteration minerals, various micro- and macrofossils, and, in one case, mantle xenoliths and xenocrysts. The large quantity and excellent quality of the recovered sample material allow us to address all the scientific objectives of this expedition and beyond
Humanity Education as a School-Based Intervention for Healing
Violence is a large-scale public health concern that impacts the mental health of people all over the world. There is a critical need for early intervention strategies that prevent violence and foster humanity and well-being. Traditional approaches to violence prevention focus on inhibiting antisocial behavior, overlooking the benefits of promoting positive values, humanity, and prosocial behavior. Aegis Trust is an international organization dedicated to the prevention of future genocides and promotion of humanity globally through education. It developed an educational methodology that has shown evidence of effectiveness in recovering from trauma, promoting humanity, and preventing violence in post-genocide Rwanda and other countries that have experienced conflict. This program, known as Champion Humanity (CH), was found to increase positive behaviors and attitudes. The purpose of this article is to describe the core principles of Humanity Education, the CH program, and propose its utility as a school-based intervention
Mineralogical characterization of rejuvenated magmatism at Burton Guyot, Louisville Seamount trail
Volcaniclastic sequences drilled during IODP Expedition 330 on top of Burton Guyot preserve a unique record of rejuvenated magmatic activity along the Louisville Seamount trail. Geochemical analysis of clinopyroxenes in primary volcaniclastic deposits of this rejuvenated phase allows the reconstruction of magmatic evolution from the shield to post-erosional phases of a Louisville seamount, and to compare this evolution to that of Hawaiian volcanoes. Our results reveal the occurrence of three main types of clinopyroxenes in the rejuvenated volcaniclastic deposits at Burton Guyot, with a Na (and Al)-poor phenocrystic clinopyroxene and two types of Na-rich clinopyroxenes from disaggregated ultramafic xenoliths. The rejuvenated Na-poor phenocrysts have the same compositional range as clinopyroxenes associated with the shield stage of the volcano, indicating an overlap in shield and rejuvenated magma compositions. The dominant type of Na-rich clinopyroxene (Type 1) is very similar to clinopyroxenes in Hawaiian pyroxenitic xenoliths thought to represent high pressure cumulates. Their relatively low Mg/(Mg + Fe), Cr, and Sc contents, similar trace element abundances and high Al(vi):Al(iv) to Hawaiian cumulates indicates that they too are cumulates. This contrasts with lower Al(vi):Al(iv) of the Na-poor phenocrysts that crystallized between 6–7 kbars and 1150–1200 °C. Type 2 clinopyroxenes are Mg-rich, and have major and trace element compositions very similar to clinopyroxenes in Hawaiian peridotites. These clinopyroxenes are interpreted as fragments of mantle xenoliths. They show intermediate amounts of incompatible element depletion, between more enriched Hawaiian peridotites and strongly depleted abyssal peridotites. Some grains exhibit the effects of mantle metasomatism, having spoon-shaped, chondrite-normalized REE patterns like those of Hawaiian peridotite xenoliths. The occurrence of disaggregated pyroxenitic cumulates and metasomatized mantle xenoliths in rejuvenated magmas of both Burton Guyot and Hawaiian islands suggests that the plumbing system of these volcanic systems share significant similarities. However, consistently with previous geochemical studies of the Louisville seamounts, geochemical consistency of shield and rejuvenated clinopyroxenes at Burton Guyot show that this volcano experienced similar alkaline magmatism from shield to rejuvenated stages. This is an important difference with the evolution of Hawaiian volcanoes that includes a dominantly tholeiitic shield stages and alkaline post-shield and rejuvenated stages, which suggests that the model of Hawaiian island formation may not be fully applicable to Louisville seamounts
Using Light to Improve Commercial Value
The plasticity of plant morphology has evolved to maximize reproductive fitness in response to prevailing environmental conditions. Leaf architecture elaborates to maximize light harvesting, while the transition to flowering can either be accelerated or delayed to improve an individual's fitness. One of the most important environmental signals is light, with plants using light for both photosynthesis and as an environmental signal. Plants perceive different wavelengths of light using distinct photoreceptors. Recent advances in LED technology now enable light quality to be manipulated at a commercial scale, and as such opportunities now exist to take advantage of plants' developmental plasticity to enhance crop yield and quality through precise manipulation of a crops' lighting regime. This review will discuss how plants perceive and respond to light, and consider how these specific signaling pathways can be manipulated to improve crop yield and quality
Conducting gender-based analysis of existing databases when self-reported gender data are unavailable: the GENDER Index in a working population
Objectives
Growing attention has been given to considering sex and gender in health research. However, this remains a challenge in the context of retrospective studies where self-reported gender measures are often unavailable. This study aimed to create and validate a composite gender index using data from the Canadian Community Health Survey (CCHS).
Methods
According to scientific literature and expert opinion, the GENDER Index was built using several variables available in the CCHS and deemed to be gender-related (e.g., occupation, receiving child support, number of working hours). Among workers aged 18–50 years who had no missing data for our variables of interest (n = 29,470 participants), propensity scores were derived from a logistic regression model that included gender-related variables as covariates and where biological sex served as the dependent variable. Construct validity of propensity scores (GENDER Index scores) were then examined.
Results
When looking at the distribution of the GENDER Index scores in males and females, they appeared related but partly independent. Differences in the proportion of females appeared between groups categorized according to the GENDER Index scores tertiles (p < 0.0001). Construct validity was also examined through associations between the GENDER Index scores and gender-related variables identified a priori such as choosing/avoiding certain foods because of weight concerns (p < 0.0001), caring for children as the most important thing contributing to stress (p = 0.0309), and ability to handle unexpected/difficult problems (p = 0.0375).
Conclusion
The GENDER Index could be useful to enhance the capacity of researchers using CCHS data to conduct gender-based analysis among populations of workers
Reverse mathematics of matroids
Matroids generalize the familiar notion of linear dependence from linear algebra. Following a brief discussion of founding work in computability and matroids, we use the techniques of reverse mathematics to determine the logical strength of some basis theorems for matroids and enumerated matroids. Next, using Weihrauch reducibility, we relate the basis results to combinatorial choice principles and statements about vector spaces. Finally, we formalize some of the Weihrauch reductions to extract related reverse mathematics results. In particular, we show that the existence of bases for vector spaces of bounded dimension is equivalent to the induction scheme for \Sigma^0_2 formulas
Impact of water quality and irrigation management on organic greenhouse horticulture
Water quality and water supply are essential for organic greenhouse grown crops to prevent soil contaminationby undesirable chemicals and microorganisms, while providing a sufficient amount of water for plant growth.The absence of natural precipitation combined with higher evapotranspiration due to higher temperatureand longer cropping period requires an adequate supply of water. Water quality is commonly defined by itschemical, physical, and biological attributes. It is closely linked to the soil/rock native components, surroundingenvironment and land use. The runoff from urban, industrial, farming, mining, and forestry activities alsosignificantly affects the quality of water available for greenhouse horticulture. High water quality is particularlyimportant in organic greenhouse production in order to prevent soil salinization and ensure optimal soil biologicalactivity. Indeed, unbalanced organic fertilizer inputs may contribute to soil salinity, while soil microbial activitiesresponsible for nutrient mineralization, soil suppressiveness and plant health, are affected by soil pH, ions, andcontaminants. Poor water quality can also result in drip and micro irrigation clogging, plant toxicity, and productcontamination by human pathogen or illicit compounds.To achieve sustainable water management, good knowledge of crops' water requirements is essential as isknowledge of the soil water characteristics that determine the irrigation scheduling. Moreover, the adequacyof the irrigation distribution system determines the accuracy of the water supplied. Crop water needs areoften determined on the basis of daily evapotranspiration and solar radiation levels. Different irrigation controltools such as soil moisture sensors, plant sensors, lysimeters and models contribute to the optimization of theirrigation management of organic greenhouse crops. In addition to determining crop productivity, water qualityand water management also impact on product quality.In this booklet we first illustrate the water flows through different organic greenhouse growing systems. Westate the importance of water quality for organic greenhouse horticulture and give some guidelines regardingthe required water quality attributes in terms of inorganic, organic and microbial loads as well as hazardousmicroorganisms and compounds. We also define advantages and disadvantages of different water resourcesand describe the important drivers for crop and soil water demand. We then report the effects of salinity on soilmineralisation and crop development in organic greenhouse production systems. The main irrigation technologyused for organic greenhouse horticulture is described along with the most important management aspects forirrigation. Because quality attributes of greenhouse products drive consumer demand for organic products, wedefine the impact of water quality and irrigation management on product quality. Organic farming should usecultural practices that maintain land resources and ecological balance, in addition to promoting biodiversity,biological cycles, and soil biological activity. We therefore state the importance of water resources and their usefor organic greenhouse system sustainability. We then conclude by summarizing main aspects of water qualityand irrigation management, and by identifying knowledge gaps.Better prediction of the temporal dynamics of plant and soil microbial water needs in relation to sustainableproductivity and high water use efficiency is needed for greenhouse horticultural crops. It is also importantin terms of reduced attractiveness to pests and susceptibility to diseases. A reduction in spatial and temporalcrop heterogeneity should result from improved growing systems and better water and crop management.Nevertheless, advances in irrigation management for conventional greenhouse crops and development of newcontrol tools can be adapted for use in organic greenhouse horticulture. Similarly, some water treatmentsof drained or collected waters such as thermal, UV, ozone and biological treatments can be used by growersaccording to their organic regulation. Consequently, research is needed in different areas of organic greenhousehorticulture: (i) water quality in terms of relevant thresholds for contaminants and potential risks related toplant and human pathogens; (ii) efficient measures to prevent clogging of the irrigation systems; (iii) alternativewater treatments and system cleaning products; (iv) better knowledge and guidelines for non-leaching systems;(v) affordable and highly efficient control tools to assist growers; and (vi) knowledge about the environmentalimpact of different water management and water sources used for organic greenhouse horticulture to helpgrowers fulfilling the organic principles and improve their sustainability
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