Residual stress evaluation in composites using a modified layer removal method

The layer removal method is often used for measurement of internal stresses in homogeneous polymeric materials. In order to extend the use of this method to laminated composites certain refinements are needed. These include: (i) use of varying material properties (elastic moduli) through the thickness of the composite plate; (ii) use of geometric non-linear analysis to account for large deformations; and (iii) measurement not only of curvatures but also of strains. These refinements are necessary because a non-symmetric laminate is created when layers are removed, which shows large curvatures. The modified layer removal method was theoretically validated on a typical compression-moulded continuous-fibre laminate (PEI/glass) and a typical injection-moulded short-fibre-reinforced laminate (PC/glass). The modified method produced good results and the need to use the modified layer removal analysis is clearly demonstrated

Managing inter-organizational knowledge sharing

Corporate knowledge is considered a crucial determinant of sustainable competitive advantages. Recent resource-leveraging strategies emphasize inter-firm collaboration and knowledge sharing across firm boundaries, however. This strategic paradox of protecting versus sharing knowledge suggests the need for new paradigms that reconcile intra- and inter-organizational knowledge sharing. Building on organizational collaboration and control theory, this paper investigates contingencies of inter-organizational knowledge sharing and proposes four configurations of inter-organizational knowledge sharing for managing the paradox. It concludes with a critical review, suggestions for further conceptual and empirical research, and implications for research and practice

Long-term stress-strain response of chalk:a micro-mechanical interpretation

A long-term laboratory test programme of conventional compression and extension tests was carried out with test durations from 8 to 22-months, in a purpose built environmentally controlled facility, with specially designed loading frames and modified triaxial cells. In addition, Scanning Electron Microscope (SEM) techniques were employed in an effort to investigate the micro-mechanical res-ponse. Creep strains appeared to trigger an ageing process that produces elevated post-creep strength and stiffness irrespective of the ap-plied stress path

Galectin-3 deficiency in pregnancy increases the risk of fetal growth restriction (FGR) via placental insufficiency.

Fetal growth restriction (FGR) is the most common pregnancy complication in developed countries. Pregnancies affected by FGR, frequently concur with complications and high risk of neonatal morbidity and mortality. To date, no approved treatment is available for pregnant women affected with FGR. The objective of this study was to investigate the contribution of galectin-3 (gal-3), a β-galactoside binding protein involved in pregnancy, placental function and fetal growth. We demonstrated that lack of gal-3 during mouse pregnancy leads to placental dysfunction and drives FGR in the absence of a maternal preeclampsia syndrome. Analysis of gal-3 deficient dams revealed placental inflammation and malperfusion, as well as uterine natural killer cell infiltration with aberrant activation. Our results also show that FGR is associated with a failure to increase maternal circulating gal-3 levels during the second and third trimester in human pregnancies. Placentas from human pregnancies affected by FGR displayed lower gal-3 expression, which correlated with placental dysfunction. These data highlight the importance of gal-3 in the promotion of proper placental function, as its absence leads to placental disease and subsequent FGR

The vulnerabilities of agricultural land and food production to future water scarcity

Rapidly increasing populations coupled with increased food demand requires either an expansion of agriculturalland or sufficient production gains from current resources. However, in a changing world, reduced wateravailability might undermine improvements in crop and grass productivity and may disproportionately affectdifferent parts of the world. Using multi-model studies, the potential trends, risks and uncertainties to land useand land availability that may arise from reductions in water availability are examined here. In addition, theimpacts of different policy interventions on pressures from emerging risks are examined.Results indicate that globally, approximately 11% and 10% of current crop- and grass-lands could be vul-nerable to reduction in water availability and may lose some productive capacity, with Africa and the MiddleEast, China, Europe and Asia particularly at risk. While uncertainties remain, reduction in agricultural land areaassociated with dietary changes (reduction of food waste and decreased meat consumption) offers the greatestbuffer against land loss and food insecurity

Field Measurements of Terrestrial and Martian Dust Devils

Surface-based measurements of terrestrial and martian dust devils/convective vortices provided from mobile and stationary platforms are discussed. Imaging of terrestrial dust devils has quantified their rotational and vertical wind speeds, translation speeds, dimensions, dust load, and frequency of occurrence. Imaging of martian dust devils has provided translation speeds and constraints on dimensions, but only limited constraints on vertical motion within a vortex. The longer mission durations on Mars afforded by long operating robotic landers and rovers have provided statistical quantification of vortex occurrence (time-of-sol, and recently seasonal) that has until recently not been a primary outcome of more temporally limited terrestrial dust devil measurement campaigns. Terrestrial measurement campaigns have included a more extensive range of measured vortex parameters (pressure, wind, morphology, etc.) than have martian opportunities, with electric field and direct measure of dust abundance not yet obtained on Mars. No martian robotic mission has yet provided contemporaneous high frequency wind and pressure measurements. Comparison of measured terrestrial and martian dust devil characteristics suggests that martian dust devils are larger and possess faster maximum rotational wind speeds, that the absolute magnitude of the pressure deficit within a terrestrial dust devil is an order of magnitude greater than a martian dust devil, and that the time-of-day variation in vortex frequency is similar. Recent terrestrial investigations have demonstrated the presence of diagnostic dust devil signals within seismic and infrasound measurements; an upcoming Mars robotic mission will obtain similar measurement types

A systematic review of physical activity promotion strategies

This article was first published in:British Journal of Sports Medicine:1996:30:84-89We have reviewed randomised controlled trials of physical activity promotion to provide recent and reliable information on the effectiveness of physical activity promotion. Computerised databases and references of references were searched. Experts were contacted and asked for information about existing work. Studies assessed were randomised controlled trials of healthy, free living, adult subjects, where exercise behaviour was the dependent variable. Eleven trials were identified. No United Kingdom based studies were found. Interventions that encourage walking and do not require attendance at a facility are most likely to lead to sustainable increases in overall physical activity. Brisk walking has the greatest potential for increasing overall activity levels of a sedentary population and meeting current public health recommendations. The small number of trials limits the strength of any conclusions and highlights the need for more research