Science and sensuality of silk

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Humanities, Program in Writing and Humanistic Studies, 2005.Includes bibliographical references (leaves 43-45).For five thousand years, silk threads have woven through the fabric of human history. Since its accidental discovery in China all that time ago, silk has played roles, major or minor, in many cultures. In both the East and the West, it has cropped up in some rather unexpected places. Silk's molecular structure, unique among natural fibers, imparts equally unique physical and chemical properties. It is these properties that give silk the versatility and functionality of which such staying power is made. Its strength and resilience make silk valuable as a material, whether for body armor or contraceptive devices. Its low conductivity made it an excellent insulator for early electrical applications, and silk's hydrophilic nature make it comfortable to wear in hot weather. The list goes on. Silk's appeal goes far beyond the practical, however. As a luxury good, it wordlessly signals the high economic status of its wearer. But perhaps silk's most profound attractions are aesthetic. The rustling scroop, the rich luster, and the soft hand are all products of science, but they appeal to the senses as well as the mind. It is remarkable that one fiber can do so much.(cont.) To fully grasp just how remarkable requires an appreciation of both the science and sensuality of silk. They are inseparably interwoven.by Jennifer E. Boyce.S.M

The application of S isotopes and S/Se ratios in determining ore-forming processes of magmatic Ni–Cu–PGE sulfide deposits: a cautionary case study from the northern Bushveld Complex

The application of S/Se ratios and S isotopes in the study of magmatic Ni–Cu–PGE sulfide deposits has long been used to trace the source of S and to constrain the role of crustal contamination in triggering sulfide saturation. However, both S/Se ratios and S isotopes are subject to syn- and post-magmatic processes that may alter their initial signatures. We present in situ mineral δ34S signatures and S/Se ratios combined with bulk S/Se ratios to investigate and assess their utility in constraining ore-forming processes and the source of S within magmatic sulfide deposits. Magmatic Ni–Cu–PGE sulfide mineralization in the Grasvally Norite–Pyroxenite–Anorthosite (GNPA) member, northern Bushveld Complex was used as a case study based on well-defined constraints of sulfide paragenesis and local S isotope signatures. A crustal δ34S component is evident in the most primary sulfide assemblage regardless of footwall lithology, and is inferred that the parental magma(s) of the GNPA member was crustally contaminated and sulfide saturated at the time of emplacement. However, S/Se ratios of both the primary and in particular secondary sulfide assemblages record values within or below the mantle range, rather than high crustal S/Se ratios. In addition, there is a wide range of S/Se ratio for each sulfide mineral within individual assemblages that is not necessarily consistent with the bulk ratio. The initial crustal S/Se ratio is interpreted to have been significantly modified by syn-magmatic lowering of S/Se ratio by sulfide dissolution, and post-magmatic lowering of the S/Se ratio from hydrothermal S-loss, which also increases the PGE tenor of the sulfides. Trace element signatures and variations in Th/Yb and Nb/Th ratios support both an early pre-emplacement contamination event as seen by the S isotopes and S/Se ratios, but also a second contamination event resulting from the interaction of the GNPA magma with the local footwall country rocks at the time of emplacement; though this did not add any additional S. We are able to present an integrated emplacement and contamination model for the northern limb of the Bushveld Complex. Although the multitude of processes that affect variations in the δ34S signature and in particular S/Se ratio may be problematic in interpreting ore genesis, they can reveal a wealth of additional detail on a number of processes involved in the genetic history of a Ni–Cu–PGE deposit in addition to crustal contamination. However, a prerequisite for being able to do this is to utilize other independent petrological and mineralogical techniques that provide constraints on both the timing and effect of various ore-forming and modifying processes. Utilizing both bulk and in situ methods in concert to determine the S/Se ratio allows for the assessment of multiple sulfide populations, the partitioning behaviour of Se during sulfide liquid fractionation and also the effects of low temperature fluid alteration. In comparison, S isotopes are relatively more robust and represent a more reliable indicator of the role of crustal S contamination. The addition of trace element data to the above makes for an incredibly powerful approach in assessing the role of crustal contamination in magmatic sulfide systems

The Oxidation State of Sulfur in Lunar Apatite

Lunar apatites contain hundreds to thousands of parts per million of sulfur. This is puzzling because lunar basalts are thought to form in low oxygen fugacity (f(sub O2)) conditions where sulfur can only exist in its reduced form (S2()), a substitution not previously observed in natural apatite. We present measurements of the oxidation state of S in lunar apatites and associated mesostasis glass that show that lunar apatites and glass contain dominantly S2(), whereas natural apatites from Earth are only known to contain S6+. It is likely that many terrestrial and martian igneous rocks contain apatites with mixed sulfur oxidation states. The S6(+)/S2() ratios of such apatites could be used to quantify the f(sub O2) values at which they crystallized, given information on the portioning of S6(+) and S2() between apatite and melt and on the S6(+)/S2() ratios of melts as functions of f(sub O2) and melt composition. Such a well-calibrated oxybarometer based on this the oxidation state of S in apatite would have wide application

Interventions to improve healthcare workers’ hand hygiene compliance: a systematic review of systematic reviews

Objective: To synthesize the existing evidence base of systematic reviews of interventions to improve healthcare worker (HCW) hand hygiene compliance (HHC). Methods: PRISMA guidelines were followed, and 10 information sources were searched in September 2017, with no limits to language or date of publication, and papers were screened against inclusion criteria for relevance. Data were extracted and risk of bias was assessed. Results: Overall, 19 systematic reviews (n=20 articles) were included. Only 1 article had a low risk of bias. Moreover, 15 systematic reviews showed positive effects of interventions on HCW HHC, whereas 3 reviews evaluating monitoring technology did not. Findings regarding whether multimodal rather than single interventions are preferable were inconclusive. Targeting social influence, attitude, self-efficacy, and intention were associated with greater effectiveness. No clear link emerged between how educational interventions were delivered and effectiveness. Conclusions: This is the first systematic review of systematic reviews of interventions to improve HCW HHC. The evidence is sufficient to recommend the implementation of interventions to improve HCW HHC (except for monitoring technology), but it is insufficient to make specific recommendations regarding the content or how the content should be delivered. Future research should rigorously apply behavior change theory, and recommendations should be clearly described with respect to intervention content and how it is delivered. Such recommendations should be tested for longer terms using stronger study designs with clearly defined outcomes

Justice in the Air: Tracking Toxic Pollution from America's Industries and Companies to Add to Our States, Cities, and Neighborhoods

This new environmental justice study examines not only who receives the disproportionate share of toxic air releases -- low-income communities and people of color -- but who is releasing them.Justice in the Air: Tracking Toxic Pollution from America's Industries and Companies to Our States, Cities, and Neighborhoods uses the EPA's Toxic Release Inventory and Risk Screening Environmental Indicators to explore the demographics of those who are most affected by toxic pollution, and then establishes the corporate ownership of the plants responsible. Justice in the Air enhances the data available in PERI's Toxic 100 Report with a new environmental justice scorecard, ranking the Toxic 100 companies by the share of their health impacts from toxic air pollution that falls upon minority and low-income communities. The authors conclude by recommending four ways the right-to-know and environmental justice movements can use these findings in their efforts to protect the health of vulnerable communities

CD11cHi monocyte-derived macrophages are a major cellular compartment infected by Mycobacterium tuberculosis

During tuberculosis, lung myeloid cells have two opposing roles: they are an intracellular niche occupied by Mycobacterium tuberculosis, and they restrict bacterial replication. Lung myeloid cells from mice infected with yellow-fluorescent protein expressing M. tuberculosis were analyzed by flow cytometry and transcriptional profiling to identify the cell types infected and their response to infection. CD14, CD38, and Abca1 were expressed more highly by infected alveolar macrophages and CD11cHi monocyte-derived cells compared to uninfected cells. CD14, CD38, and Abca1 triple positive (TP) cells had not only the highest infection rates and bacterial loads, but also a strong interferon-gamma signature and nitric oxide synthetase-2 production indicating recognition by T cells. Despite evidence of T cell recognition and appropriate activation, these TP macrophages are a cellular compartment occupied by M. tuberculosis long-term. Defining the niche where M. tuberculosis resists elimination promises to provide insight into why inducing sterilizing immunity is a formidable challenge

CD4 T cell help prevents CD8 T cell exhaustion and promotes control of Mycobacterium tuberculosis infection [preprint]

CD4 T cells are essential for immunity to tuberculosis because they produce cytokines including interferon-γ. Whether CD4 T cells act as “helper” cells to promote optimal CD8 T cell responses during Mycobacterium tuberculosis is unknown. Using two independent models, we show that CD4 T cell help enhances CD8 effector functions and prevents CD8 T cell exhaustion. We demonstrate synergy between CD4 and CD8 T cells in promoting the survival of infected mice. Purified helped, but not helpless, CD8 T cells efficiently restrict intracellular bacterial growth in vitro. Thus, CD4 T cell help plays an essential role in generating protective CD8 T cell responses against M. tuberculosis infection in vitro and in vivo. We infer vaccines that elicit both CD4 and CD8 T cells are more likely to be successful than vaccines that elicit only CD4 or CD8 T cells

Design of \u27Iris\u27, a Small Autonomous Surveillance UAV

This paper documents the design process used for a small autonomous surveillance UAV. The most significant requirements for the plane were size (man-packable), endurance (about 1 hour) and cost (essentially disposable). The plane that resulted, named Iris , is a tailless plane with a 45 cm wing span and a total mass of less than 200g. During flight tests, it achieved an endurance of 52 minutes. The estimated cost to manufacture the planes was $343, excluding the autopilot