Heterogeneity and risk sharing in village economies

We show how to use panel data on household consumption to directly estimate households' risk preferences. Specifically, we measure heterogeneity in risk aversion among households in Thai villages using a full risk-sharing model, which we then test allowing for this heterogeneity. There is substantial, statistically significant heterogeneity in estimated risk preferences. Full insurance cannot be rejected. As the risk-sharing as-if-complete-markets theory might predict, estimated risk preferences are unrelated to wealth or other characteristics. The heterogeneity matters for policy: Although the average household would benefit from eliminating village-level risk, less-risk-averse households that are paid to absorb that risk would be worse off by several percent of household consumption

Wood-Based Carbon Storage in the Mackenzie River Delta: The World\u27s Largest Mapped Riverine Wood Deposit

The Mackenzie River Delta (MRD) has been recognized as an important host of river-derived wood deposits, and Mackenzie River wood has been found across the Arctic Ocean. Nevertheless, we lack estimates of the amount of carbon stored as wood and its age in the delta, representing a gap in carbon cycle estimates. Here, we use very high-resolution satellite imagery and deep learning to map wood deposits in the MRD, combining this with field data to measure the stock and age of wood-based carbon. We find \u3e400,000 individual large wood deposits, collectively storing 3.1 × 1012 g-C, equating to 2 × 106 g-C ha−1 across the delta. Sampled wood pieces date from 690 AD to 2015 AD but are mostly young with ∼40% of the wood samples formed after 1955 AD. These estimates represent a minimum bound on an important surficial, potentially reactive, carbon pool compared to other deeper carbon stocks in permafrost zones

Blue Light Second Harmonic Generation In The Organic Crystal Ortho-Dicyanovinyl-Anisole

Type I phase matched second harmonic generation (SHG) in the organic crystal ortho-Dicyanovinyl-anisole (DIVA) has been measured for a range of near infrared fundamental wavelengths (855-960 nm). Turning curves for type I phase matched SHG were derived from measured refractive index values and show noncritical phase matching at 860. Measured type I phase matched SHG is in close agreement with the calculated results and gives effective SHG coefficients ranging from 1.9 to 5.9 times as large as d(32) Of potassium niobate. (C) 1997 American Institute of Physics

Heterogeneity and Risk Sharing in Village Economies

We measure heterogeneity in risk aversion among households in Thai villages using a full risk-sharing model and complement the results with a measure based on optimal portfolio choice. Among households with relatives living in the same village, full insurance cannot be rejected, suggesting that relatives provide something close to a complete-markets consumption allocation. There is substantial heterogeneity in risk preferences estimated from the full-insurance model, positively correlated in most villages with portfolio-choice estimates. The heterogeneity matters for policy: Although the average household would benefit from eliminating village-level risk, less-risk-averse households who are paid to absorb that risk would be worse off.

Laser Ablation Surface Preparation of Ti-6A1-4V for Adhesive Bonding

Adhesive bonding offers many advantages over mechanical fastening, but requires certification before it can be incorporated in primary structures for commercial aviation without disbond-arrestment features or redundant load paths. Surface preparation is widely recognized as the key step to producing robust and predictable bonds. Laser ablation imparts both topographical and chemical changes to a surface which can lead to increased bond durability. A laser based process provides an alternative to chemical-dip, manual abrasion and grit blast treatments which are expensive, hazardous, polluting, and less precise. This report documents preliminary testing of a surface preparation technique using laser ablation as a replacement for the chemical etch and abrasive processes currently applied to Ti-6Al-4V alloy adherends. Failure mode, surface roughness, and chemical makeup were analyzed using fluorescence enhanced visualization, microscopy, and X-ray photoelectron spectroscopy, respectively. Single lap shear tests were conducted on bonded and aged specimens to observe bond strength retention and failure mode. Some promising results showed increasing strength and durability of lap shear specimens as laser ablation coverage area and beam intensity increased. Chemical analyses showed trends for surface chemical species which correlated with improved bond strength and durability. Combined, these results suggest that laser ablation is a viable process for inclusion with or/and replacement of one or more currently used titanium surface treatments. On-going work will focus on additional mechanical tests to further demonstrate improved bond durability

Directly observed antiretroviral therapy: a systematic review and meta-analysis of randomised clinical trials.

BACKGROUND: Directly observed therapy has been recommended to improve adherence for patients with HIV infection who are on highly active antiretroviral therapy, but the benefit and cost-effectiveness of this approach has not been established conclusively. We did a systematic review and meta-analysis of randomised trials of directly observed versus self-administered antiretroviral treatment. METHODS: We did duplicate searches of databases (from inception to July 27, 2009), searchable websites of major HIV conferences (up to July, 2009), and lay publications and websites (March-July, 2009) to identify randomised trials assessing directly observed therapy to promote adherence to antiretroviral therapy in adults. Our primary outcome was virological suppression at study completion. We calculated relative risks (95% CIs), and pooled estimates using a random-effects method. FINDINGS: 12 studies met our inclusion criteria; four of these were done in groups that were judged to be at high risk of poor adherence (drug users and homeless people). Ten studies reported on the primary outcome (n=1862 participants); we calculated a pooled relative risk of 1.04 (95% CI 0.91-1.20, p=0.55), and noted moderate heterogeneity between the studies (I(2)= 53.8%, 95% CI 0-75.7, p=0.0247) for directly observed versus self-administered treatment. INTERPRETATION: Directly observed antiretroviral therapy seems to offer no benefit over self-administered treatment, which calls into question the use of such an approach to support adherence in the general patient population. FUNDING: None

Designer molecular probes for phosphonium ionic liquids

Investigations into the extent of structuring present in phosphonium based ionic liquids (ILs) have been carried out using photochromic molecular probes. Three spiropyran derivatives containing hydroxyl (BSP-1), carboxylic acid (BSP-2) and aliphatic chain (C14H29) (BSP-3) functional groups have been analysed in a range of phosphonium based ionic liquids and their subsequent physico-chemical interactions were reported. It is believed that the functional groups locate the probe molecules into specific regions based upon the interaction of the functional groups with particular and defined regions of the ionic liquid. This structuring results in thermodynamic, kinetic and solvatochromic parameters that are not predictable from classical solvent models. BSP-1 and BSP-2 exhibit generally negative entropies of activation ranging from -50 J K-1 mol-1 to -90 J K-1 mol-1 implying relatively low solvent–solute interactions and possible anion interactions with IL polar functional groups. Higher than expected activation energies of 60 kJ mol-1 to 100 kJ mol-1 obtained for polar probes maybe be due to IL functional groups competing with the charged sites of the merocyanine (MC) isomer thus reducing MC stabilisation effects. Differences in thermal relaxation rate constants (2.5 × 10-3 s-1 in BSP-1 and 3 × 10-4 s-1 in BSP-2 in [P6,6,6,14][dbsa]) imply that while the polar probe systems are primarily located in polar/charged regions, each probe experiences slightly differing polar domains. BSP-3 entropies of activation are positive and between 30 J K-1 mol-1 to 66 J K-1 mol-1. The association of the non-polar functional group is believed to locate the spiropyran moiety in the interfacial polar and non-polar regions. The thermal relaxation of the MC form causes solvent reorientation to accommodate the molecule as it reverts to its closed form. Slow thermal relaxation rate constants were obserevd in contrast to high activation energies (5 × 10-4 s-1 and 111.91 kJ mol-1 respectively, for BSP-3 in [P6,6,6,14][dbsa]). This may be due to steric effects arising from proposed nano-cavity formation by the alkyl chains in phosphonium based ILs

Opt-out HIV testing in prison: informed and voluntary?

HIV testing in prison settings has been identified as an important mechanism to detect cases among high-risk, underserved populations. Several public health organizations recommend that testing across healthcare settings, including prisons, be delivered in an opt-out manner. However, implementation of opt-out testing within prisons may pose challenges in delivering testing that is informed and understood to be voluntary. In a large state prison system with a policy of voluntary opt-out HIV testing, we randomly sampled adult prisoners in each of seven intake prisons within two weeks after their opportunity to be HIV tested. We surveyed prisoners’ perception of HIV testing as voluntary or mandatory and used multivariable statistical models to identify factors associated with their perception. We also linked survey responses to lab records to determine if prisoners’ test status (tested or not) matched their desired and perceived test status. Thirty eight percent (359/936) perceived testing as voluntary. The perception that testing was mandatory was positively associated with age less than 25 years (adjusted relative risk [aRR]: 1.45, 95% CI: 1.24, 1.71) and preference that testing be mandatory (aRR: 1.81, 95% CI: 1.41, 2.31), but negatively associated with entry into one of the intake prisons (aRR: 0.41 95% CI: 0.27, 0.63). Eighty-nine percent of prisoners wanted to be tested, 85% were tested according to their wishes, and 82% correctly understood whether or not they were tested. Most prisoners wanted to be HIV tested and were aware that they had been tested, but less than 40% understood testing to be voluntary. Prisoners’ understanding of the voluntary nature of testing varied by intake prison and by a few individual-level factors. Testing procedures should ensure that opt-out testing is informed and understood to be voluntary by prisoners and other vulnerable populations

Predictors of Unrecognized HIV Infection Among Poor and Ethnic Men Who Have Sex with Men in Los Angeles

This study evaluates associations between unrecognized HIV infection and demographic factors, internalized homonegativity, drug use, and sexual behaviors among HIV positive men who have sex with men (MSM). We analyzed data from 347 HIV positive participants from the Los Angeles site for NIDA’s Sexual Acquisition and Transmission of HIV-Cooperative Agreement Program. Participants were HIV positive MSM and MSM/W and predominantly African American (36.0%) or Latino (38.7%), and unemployed (82.8%). Results from a multivariate logistic regression suggest that, compared to HIV positive participants who correctly reported their HIV positive status, being African-American (OR: 9.81, CI: 1.2–77.9) or Latino (OR: 10.92, CI: 1.3–88.4) rather than White, MSM/W rather than MSM (OR: 3.24, CI: 1.09–9.62), and having higher homonegativity scores (OR: 1.22, CI: 1.02–1.4) is associated with unrecognized HIV infection, controlling for age, education, and homelessness. Findings provide some immediate evidence to help craft HIV prevention interventions

The social meaning of social indicators

While new modes of data processing have provided reams of data, there has been relatively less effort in seeking to comprehend the social meaning of results of empirical work. A set of previously developed indicators of urban social structure is here examined for its link to theory, and to the social structure of the city itself. The original indicators (size, social class, racial composition and community maturity) were empirically derived. In this paper, each is taken in turn, and explored with respect to several possible social meanings. Size, for example, is considered to be itself an indicator, and an imperfect one, for system complexity; percent non-white is seen to be itself an indicator for a slowdown in the mobility process, or a slower social metabolism. These and other results are suggestions, with illustrations, but not conclusive support, from other than the original data. While it is hoped that the theoretical suggestions may themselves be of interest, it is also hoped that approach itself can indicate the fertility and usefulness of going back to theory once empirical measures have been developed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43687/1/11205_2004_Article_BF00304121.pd