Oxygen content of the fixative is important in the interpretation of the ultrastructure of ischaemic myocardium

Isolated rat hearts were subjected to 15, 45, or 60 minutes of global ischaemia and then fixed by perfusion at 37°C with glutaraldehyde containing various amounts of oxygen. This either had been bubbled with 100% oxygen (PO₂ 620 mm Hg) or with 100% nitrogen (PO₂ 40 mm Hg) immediately before use, or it had been routinely prepared and stored exposed to atmospheric oxygen (PO₂ 245 mm Hg). The ultrastructure of myocytes and endothelial cells subjected to 15 minutes of ischaemia was not affected by the treatment of the fixative. However, when the tissue subjected to longer periods of ischaemia was fixed with routinely prepared or oxygen-bubbled glutaraldehyde, ultrastructural changes characteristic of reoxygenation damage were uniformly evident in both the microvasculature and myocytes. These qualitatively distinct changes included mitochondrial swelling, cell swelling, endothelial bleb formation, and narrowing of capillary lumina. These abnormalities were not observed in tissue fixed with nitrogen-bubbled glutaraldehyde. These findings indicate that deliberate steps should be taken to reduce or eliminate dissolved oxygen from the fixatives used to study ischaemic tissues. Otherwise artefactual reoxygenation damage in vitro may occur and make valid ultrastructural interpretation difficult or impossible.     

Welfare or Work? Low-Income Working Households' Housing Consumption in the Private Rented Sector in England

This paper is concerned with issues of equity and efficiency in the Housing Benefit (HB) system in the private rented sector (PRS) in England. Using information from a survey of low- income working households (LIWH) and in-depth interviews with LIWH families, it addresses two policy-relevant questions. First, there are mixed findings on whether the current HB system enables HB recipients to consume more housing than is available to otherwise similar non-HB-recipient households in the PRS. HB rules on eligible property size appear not to unduly favour HB claimants compared with LIWH. LIWH, however, tend to pay a rent which is less than the maximum amount an HB recipient could receive. This is particularly true for LIWH families with children who are most likely to be living in properties smaller than allowed by HB regulations. Second, there is no evidence that the HB system incentivises LIWH to give up work or otherwise seek to become eligible for HB.     

Second generation anticoagulant rodenticides in tawny owls (Strix aluco) from Great Britain

Secondary exposure of vertebrate predators to second generation anticoagulant rodenticides (SGARs) is widespread in Britain. Tawny owl (Strix aluco) populations in the UK are thought to have declined since the 1970s, when SGARs were first introduced, and these compounds may have contributed to any decline in owl numbers. Our aims were to conduct the first systematic survey of SGAR exposure in tawny owls and ascertain whether there had been a change in the proportion of exposed birds that was concurrent with the decline in the population. Liver difenacoum, bromadiolone, flocoumafen and brodifacoum concentrations in British tawny owls from two periods (1990-1993 and 2003-2005) were quantified. In total, some 20% of birds contained detectable residues of one or more SGAR. The extent of exposure (% of birds exposed, magnitude of residues) to different SGARs did not change consistently between time periods. Of the raptors analysed to date in Britain, tawny owls had the lowest proportion of individuals that contained detectable liver residues and so appear to be the least vulnerable to exposure and/or assimilation of SGARs. We found no clear evidence to implicate SGARs as a major factor affecting tawny owl numbers in Britain between 1990 and 2005.     

A methodology for optimally designing fibre-reinforced laminated structures with design variable tolerances for maximum buckling strength

A procedure to design symmetrically laminated structures for maximum buckling load with manufacturing uncertainty in the ply angle—which is the design variable, is described. It is assumed that the probability of any tolerance value occurring within the tolerance band, compared with any other, is equal, and thus the technique is aimed at designing for the worst-case scenario. The finite element method is implemented and used to determine the fitness of each design candidate, and so the effects of bending–twisting coupling are accounted for. The methodology is flexible enough to allow any appropriate finite element formulation and search algorithm to be substituted. Three different tolerance scenarios are used for the purposes of illustrating the methodology, and plates with varying aspect and loading ratios, as well as differing boundary conditions, are chosen to demonstrate the technique, and optimally designed and compared.     

AND SO ON,AND

…aporia is not something negative, not something which in fact paralyses us. but on the contrary it is an ordeal, a test, a crucial moment through which we have to go, even if we are stuck, we have to experience this moment of aporia in order to make a decision, in order to take responsibility, in order to have a future, and so on and so forth.¹     

Spatial distribution of lead in human primary teeth as a biomarker of pre- and neonatal lead exposure

Lead remains one of the most hazardous toxins in our environment. Because the toxic effects of lead are most prominent during early development, it is important to develop a suitable biomarker for lead exposure during the pre- and neonatal periods. In the present study, the spatial distribution of lead was measured in the enamel and dentine of ten human primary teeth using laser ablation-inductively coupled plasma-mass spectrometry. The neonatal line, visualized using confocal laser scanning microscopy, was used to demarcate the pre- and postnatal regions of the sample teeth. Lead levels in pre- and postnatally formed enamel and dentine were compared to blood-lead levels measured at birth and one year of age for four of these participants. Mean dentine-lead levels ranged from 0.17+/-0.02 to 5.60+/-1.79 microg/g, and mean enamel-lead levels ranged from 0.04+/-0.01 to 1.47+/-0.20 microg/g. The results of this preliminary study showed that the spatial distribution of lead in dentine reflected the blood-lead levels. The present study demonstrates a methodology where the spatial distribution of lead in the dentine of human primary teeth may be used to obtain temporal information of environmental lead exposure during the pre- and neonatal periods.     

Water and solute mass balance of five small, relatively undisturbed watersheds in the U.S

Geochemical mass balances were computed for water years 1992-1997 (October 1991 through September 1997) for the five watersheds of the U.S. Geological Survey Water, Energy, and Biogeochemical Budgets (WEBB) Program to determine the primary regional controls on yields of the major dissolved inorganic solutes. The sites, which vary markedly with respect to climate, geology, physiography, and ecology, are: Allequash Creek, Wisconsin (low-relief, humid continental forest); Andrews Creek, Colorado (cold alpine, taiga/tundra, and subalpine boreal forest); Río Icacos, Puerto Rico (lower montane, wet tropical forest); Panola Mountain, Georgia (humid subtropical piedmont forest); and Sleepers River, Vermont (humid northern hardwood forest). Streamwater output fluxes were determined by constructing empirical multivariate concentration models including discharge and seasonal components. Input fluxes were computed from weekly wet-only or bulk precipitation sampling. Despite uncertainties in input fluxes arising from poorly defined elevation gradients, lack of dry-deposition and occult-deposition measurements, and uncertain sea-salt contributions, the following was concluded: (1) for solutes derived primarily from rock weathering (Ca, Mg, Na, K, and H(4)SiO(4)), net fluxes (outputs in streamflow minus inputs in deposition) varied by two orders of magnitude, which is attributed to a large gradient in rock weathering rates controlled by climate and geologic parent material; (2) the net flux of atmospherically derived solutes (NH(4), NO(3), SO(4), and Cl) was similar among sites, with SO(4) being the most variable and NH(4) and NO(3) generally retained (except for NO(3) at Andrews); and (3) relations among monthly solute fluxes and differences among solute concentration model parameters yielded additional insights into comparative biogeochemical processes at the sites.     

Theory experiment comparison of the electron backscattering factor from solids at low electron energy (250-5,000 eV)

The electron backscattering factor was measured from 24 different elements at low primary beam energy (250-5,000 eV). The results were compared with Monte Carlo simulations from a variety of freely available programs and an in-house developed program. The results suggest that a thin film of oxide can modify the backscattering factor at low primary energy. In addition, a number of problems have been identified with the freely available programs.     

Processing of 1-3 Piezoelectric Ceramic/Polymer Composites

Several methods of forming fine-scale 1–3 piezoelectric ceramic/polymer composites for possible transducer applications were demonstrated. These methods include tape casting, honeycomb dicing, and ceramic fiber weaving. In the tape casting technique, laminated structures were formed using thin PZT tapes. The tapes were stacked, with spacers separating the layers, and the stack embedded in polymer. Dicing the stack resulted in a composite with 1–3 connectivity. The thin tape technique can be used to develop composites with ceramic or polymer volume fraction gradients and multifunctional ceramics. Dicing of PZT honeycombs yields 1–3 composites with uniquely shaped rods. Shapes included +, T, and L. In the ceramic fiber weaving technique, green PZT fibers were woven through a PZT honeycomb support structure. The structure was fired to sinter the PZT fibers, and embedded with polymer to yield 1–3 composites. All 1–3 composites showed high and uniform piezoelectric coefficients across the electroded area.