While pathways for exposure to occupant-borne bacteria have mainly focused on touching fomites and on person-to-person direct contact, our results reinforce an understanding that humans may also be exposed to bioaerosol-borne microorganisms originating from other building occupants. These emissions might be produced by direct shedding into air or they might result from shedding followed by deposition and then resuspension. While the relative proportions of these mechanisms are unknown, there is evidence that both mechanisms may be significant. The increase in total particulate matter mass in larger sizes demonstrates a potentially significant role for resuspension. For direct emissions, previous literature indicates that the shedding of desquamated skin is a significant contributor to indoor aerosols . The emission rate of bacteria associated with skin shedding has been reported to range up to 6.8 · 105 culturable colonies per person-hour , which is 12% of the value for total human micro-biota emissions reported here. We note that previous studies that focus on the bacteria shed from skin desquamation have demonstrated that the majority of skin bacteria are associated with particles larger than the 3–5 lm peak observed in our study . We note that the high enrichment of human microflora in larger-size bins of the indoor bioaerosol during occupancy indicates an increase in human bacterial emissions relative to total bacterial emissions in the larger size ranges . The results provided here represent an early inquiry into the impacts of human occupancy on the type and character of biological aerosols present in indoor air. Linking occupant characteristics such as health status, clothing type, and individual activity is an important area of future research to produce directly applicable data on how specific characteristics of human occupancy impact exposure to etiological agents. Environmental parameters, such as season, building materials and furnishings,cannabis grow rack and geographic location also should be considered. Limitations of this study included the restriction to one environment and that biological measurements were made from two indoor and two outdoor impactor samplers.
Future investigations should extend this approach to multiple environments to determine the extent to which results such as these are broadly observed.One aspect is the undefined upper size limit for particles collected on this stage. For analysis in this paper, we have assumed a sharp cut at 20 lm. Irrespective of this assumption, the mass and microbial genome concentration measurements for this upper size section are robust. However, the graphical presentation in Figure 1 would shift with a different upper size limit, with height changing so as to maintain a constant area for that section. More significantly, converting from measured concentrations to emission factors depends on knowing the section-averaged particle deposition rate, k, which in turn depends on particle size. Overall, the literature lacks good empirical data on indoor deposition rates for particles larger than 10 lm. Furthermore, size-resolved deposition rates for bacteria and fungi have not been reported. The lack of microbe-specific deposition data may be a source of additional error owing to differences in shape and density from the olive-oil droplets studied by Thatcher et al. . We based our analysis on empirical measurements reported by Thatcher et al. and extrapolated to cover the largest size section. If we had used gravitational settling as the basis for determining the loss-rate coefficient, then choosing 15 lm as the upper size limit would have reduced the loss-rate coefficient by 29%, whereas choosing 25 lm as the upper size limit would have increased it by 33%. For this range of aerodynamic diameters applied as the upper limit on the largest impactor size stage, there would be a ±20% corresponding uncertainty in emission rates. Errors in estimating the emission rates for other particle size sections are much smaller because of three factors: well-defined upper size limits, stronger basis for the loss-rate coefficient, and less importance of the smaller loss-rate coefficients as compared to ventilation as a particle removal mechanism.Relationship to place is powerful and fundamental to human experience. Each of us was born somewhere and has an ancestral lineage that connects us to that place, or to distant locales, known and imagined.
We crave the experience of travel, and we insert visual notations of our journeys into our everyday lives with bits of natural detritus, mementos and photographs. Each object, relic or image, imbued with the distilled essence of its place of origin, is reframed by and reframes its new surroundings. Although we may appreciate a saved pebble for its essential qualities as a stone, it also holds its own history and has the potential to evoke deeply personal, experiential memories. Artist’s expressions of their relationships to place have long served as important indicators of the shifting formal innovations and philosophical tenor of their times. The Impressionists’ aspiration to capture the transient light and color in a landscape with fleeting brushwork and a subjective palette was central to their desire to represent modernity in the nineteenth century. For the emerging middle class at that time, the rapidly changing urban world had stimulated a desire for scenes of rural landscape and life. Such scenes reassured them there were still places where timeless values could be found. The duality of this situation opened the possibility for a technically and conceptually innovative avantgarde, and as artists expanded the paradigm for modern subject matter throughout the twentieth century, some began to merge formal radicalism with social commentary about the changing landscape. The importance of the relationship between nature and culture intensified during the late 1960s, as artists began to eradicate the boundaries between form, process and meaning, shifting their relationship to the location and presentation of their work. Two major trajectories eventually emerged. Land- or Earthworks artists asserted their relationship to nature with performance-based works or large scale sculpture in remote locations. Minimalists responded to this institutional shift and telluricurge by transporting earth and other natural materials into the white cube of the gallery. As artists embraced this new aesthetic, their work also evolved to incorporate formal eclecticism, performative practice, and the primacy of conceptual expression. The legacy of this period has been a generation of artists who have adapted these methodologies to establish ideational, emotional and aesthetic bridges between the personal and public. Their confrontation of the not-sodelicate balance between nature and culture has compelled many of them to create works that commingle elements of the natural world with personal narrative to showcase issues that might otherwise be overlooked.
Parker’s deep artistic and philosophical connections to the materials of nature is shared by a growing number of contemporary artists involved with liberating natural materials from their utilitarian identities and presenting them for aesthetic, symbolic and scientific contemplation. Among them is Wolfgang Laib,cannabis grower racks whose art is largely concerned with gathering pollen, which he exhibits as material and art object. Laib’s sensibility is similar to Parker’s in that he allows the pollen to retain its own character and meaning. His process of gathering it also mimics the bee’s rites of collection. Laib’s holistic attitude toward his primary material, the creatures that cultivate it, and his reference to nature as “his monastery” have poetic resonance with Parker’s empathy toward the land, its output, and place.2 But Parker also says her “personal hunger to have connection with the land is a form of spirituality.” She speaks of her paintings, which reduce the landscape to geometrically patterned fields of color, as “more about the spirit of the land than a direct replication of it.” The material and pieces that speak most deeply of Parker’s connection to the land are those that are comprised of earth or that tell stories about it. For several years she has been collecting soil samples from various farms, which she uses as subject and medium. “The soil is really the palette, and you can’t make anything if the soil isn’t of quality.” During her exhibition’s opening, Parker glamorized the experience of soil quality by setting small portions of damp soil in wine glasses for people to test its aroma. For “Palette,” she displayed small samples in see-through containers in a box, creating an earth palette of assorted colors and textures. One particularly meaningful soil sample was gathered from her partner’s family farm in France, which “had not been disked or turned over for a hundred years. There was something poignant to me about these people living on their land, who don’t turn some of it over; who don’t impact it in any major way. I loved that soil and the idea that there’s a place where people don’t mess with the earth.” Parker’s personal identification with the soil is distilled in “Clod,” a chunk of earth which fl oats serenely atop a transparent Plexiglass pedestal, as her emblematic alter ego.Numerous observational epidemiologic studies have demonstrated that physical activity is inversely related to cardiovascular morbidity and mortality. Physical activity may contribute up to 20% – 30% reduced risk of coronary heart disease. However, studies have shown that different types of physical activities may have different effects on the risk of cardiovascular disease and may interact together. For example, some leisure time activities such as walking, stair climbing, and cycling provide protection against CVD, whereas others, such as intensive domestic physical activity, may not offer protection against CVD. There are also interactive effects between lack of exercise and sitting at work and between demanding household work and sitting at work on the association with increased risk of acute myocardial infarction. Therefore, if we use a single summary measurement to reflect physical activity, such as METS, the association between physical activity and risk of CVD might be biased because subjects who have the same measured value may have a distinct combination of physical activities. Furthermore, studying different types of physical activity in isolation may not adequately consider any joint and interactive associations on the risk of CVD. Previous models that incorporate one type of physical activity of interest and other types of physical activity for exploring the effects of each type of physical activity on CVD may be problematic because of the concomitant change in total physical activity.
As one type of physical activity increases, total physical activity increases as well, given that the other physical activities are fixed. Hence, the effect estimate of one type of physical activity does not present its pure effect, but includes the effects of total physical activity. In order to overcome these challenges in the analysis of physical activity data, we used the method of principal component analysis to identify physical activity patterns that take into account combinations of physical activities. We used both parametric and semi-parametric regression models to examine the association between derived physical activity patterns and risk of acute myocardial infarction . Data from a population-based, casecontrol study in Costa Rica were utilized for purposes of this investigation.In Costa Rica, CVD has been the country’s leading cause of death since 1970 and the mortality rate for CVD has been declining since 2002 according to 2007 Health in the Americas, a report from World Health Organization. The participants in this study are cases and controls from a case-control study of non-fatal myocardial infarction conducted in the Central Valley in Costa Rica from 1994 to 2004. The study design and population have been described previously. In brief, eligible cases were men and women who were diagnosed as survivors of a first AMI by two independent cardiologists at any of the six recruiting hospitals in the Central Valley of Costa Rica during the period 1994-2004. All cases met the World Health Organization criteria for AMI. Enrollment was carried out while cases were in the hospital’s step-down-unit. One free-living control subject for each case, matched for age , sex, and area of residence , was randomly selected using information available at the National Census and Statistics Bureau of Costa Rica. Participation rates were 98% for cases and 88% for controls. Cases and controls provided informed consent on documents approved by the Human Subjects Committee of the Harvard School of Public Health and the University of Costa Rica.Trained interviewers visited all study participants at their homes for purposes of collecting sociodemographic characteristics, physical activity, lifestyle, medical history, smoking, and dietary data by use of a standardized questionnaire. They visited cases, on average, within 3 weeks of hospital discharge and when possible, by the same interviewer. Identical questionnaires and data collection procedures were used for cases and controls.