On Peres' statement "opposite momenta lead to opposite directions", decaying systems and optical imaging

We re-examine Peres' statement ``opposite momenta lead to opposite directions''. It will be shown that Peres' statement is only valid in the large distance or large time limit. In the short distance or short time limit an additional deviation from perfect alignment occurs due to the uncertainty of the location of the source. This error contribution plays a major role in Popper's orginal experimental proposal. Peres' statement applies rather to the phenomenon of optical imaging, which was regarded by him as a verification of his statement. This is because this experiment can in a certain sense be seen as occurring in the large distance limit. We will also reconsider both experiments from the viewpoint of Bohmian mechanics. In Bohmian mechanics particles with exactly opposite momenta will move in opposite directions. In addition it will prove particularly usefull to use Bohmian mechanics because the Bohmian trajectories coincide with the conceptual trajectories drawn by Pittman et al. In this way Bohmian mechanics provides a theoretical basis for these conceptual trajectories.Comment: 20 pages, 3 figures, LaTex, to be published in Found. Phy

Genes, Economics, and Happiness

We explore the influence of genetic variation on subjective well-being by employing a twin design and genetic association study. In a nationally-representative twin sample, we first show that about 33% of the variation in life satisfaction is explained by genetic variation. Although previous studies have shown that baseline happiness is significantly heritable, little research has considered molecular genetic associations with subjective well-being. We study the relationship between a functional polymorphism on the serotonin transporter gene (5-HTTLPR) and life satisfaction. We initially find that individuals with the longer, transcriptionally more efficient variant of this genotype report greater life satisfaction (n=2,545, p=0.012). However, our replication attempts on independent samples produce mixed results indicating that more work needs to be done to better understand the relationship between this genotype and subjective well-being. This work has implications for how economists think about the determinants of utility, and the extent to which exogenous shocks might affect individual well-being.life satisfaction, twin study, genetic association, serotonin transporter gene, 5-HTTLPR, rs2020933

Genes, Economics and Happiness

A major finding from research into the sources of subjective well-being is that individuals exhibit a "baseline" level of happiness. We explore the influence of genetic variation by employing a twin design and genetic association study. We first show that about 33% of the variation in happiness is explained by genes. Next, using two independent data sources, we present evidence that individuals with a transcriptionally more efficient version of the serotonin transporter gene (SLC6A4) report significantly higher levels of life satisfaction. These results are the first to identify a specific gene that is associated with happiness and suggest that behavioral models benefit from integrating genetic variation.wellbeing, socio-demographics, happiness, genetics, life satisfaction

Assessing the influence of rice roots and root exudates on nitrogen mineralization using a novel protocol

Classical nitrogen (N) mineralization experiments are done using uncropped soil, thus completely neglecting the influence of roots and root exudates. Therefore, experiments were conducted at two field sites in Bangladesh during ‘boro’ season (winter rice), using two rice cultivars (BRRI Dhan 29 and BINA Dhan6) to investigate the influence of rice roots and root exudates on N mineralization. Rice cultivars were transplanted in three replicated plots maintaining 25 x 15cm spacing along with three replicated uncropped plots as control. A novel method was used to identify the most suitable location to assess N mineralization in soil having actively growing rice plants. For this purpose, soil samples were collected from three locations in soil namely; 1) rhizosphere (0cm, at the rhizosphere), 2) middle of the two plants (7.5cm apart from rhizosphere) and 3) middle of two rows (12.5cm apart from rhizosphere). There was significant stimulatory effect of rice roots and root exudates on N mineralization at both filed sites. Significant influences of rice varieties were also observed, with BINA Dhan 6 having greater influence on N mineralization than BRRI Dhan 29. Sampling location also had a significant effect on measured N mineralization. The highest stimulatory effects of rice roots and root exudates were recorded when soil was sampled from rhizosphere. Sampling between the plants and between the rows had similar effects. In conclusion, rice roots and root exudates had a large influence on N mineralization and the best sampling location to determine the effects of actively growing rice roots and root exudates on N mineralization, was the rice rhizosphere

Community structure and intertidal zonation of the macrobenthos on a macrotidal, ultra-dissipative sandy beach: summer-winter comparison

Community structure and intertidal zonation of the macrobenthos on a macrotidal, ultra-dissipative beach were studied. On the beach of De Panne, Belgium, six transects perpendicular to the waterline (each with five stations) were sampled in September 1995 (summer) and March 1996 (winter). The 30 stations were distributed across the continuum from mean high water spring to mean low water spring in order to sample the macrobenthos at different levels of elevation. The 39 species found had total densities up to 5,500 ind m-2 in summer and 1,400 ind m-2 in winter. The highest densities were found in the spionid polychaetes Scolelepis squamata and Spio filicornis, the nephtyid polychaete Nephtys cirrosa, the cirolanid isopod Eurydice pulchra, and the haustorid amphipods Bathyporeia spp. Based on species composition, specific densities, and biomass, two species associations were defined: a relatively species-poor, high intertidal species association, dominated by S. squamata and with an average density of 1,413 ind m-2 and biomass of 808 mg AFDW m-2 (summer); and a relatively species-rich, low intertidal species association, dominated by N. cirrosa, and with an average density of 104 ind m-2 and biomass of 162 mg AFDW m-2 in summer. For both seasons, the high intertidal species association was restricted in its intertidal distribution between the mean tidal and the mean high-water spring level, whereas the low intertidal species association was found from the mean tidal level to the subtidal. The latter showed good affinities with the subtidal N. cirrosa species association, occurring just offshore of De Panne beach, confirming the existence of a relationship between the low intertidal and subtidal macrobenthic species associations. Summer-winter comparison revealed a strong decrease in densities and biomass in the high intertidal zone during winter. Habitat continuity of the low intertidal zone with the subtidal allows subtidal organisms to repopulate the low intertidal zone

Happiness predicts compliance with preventive health behaviours during Covid-19 lockdowns

To combat the public health crisis of Covid-19, governments and public health officials have been asking individuals to substantially change their behaviours for prolonged periods of time. Are happier people more willing to comply with such measures? Using independent, large-scale surveys covering about 79,000 adult respondents across 29 countries, including longitudinal data from the UK, we find that life satisfaction predicts compliance with preventive health behaviours during Covid-19 lockdowns, especially the number of weekdays stood at home (β = 0.02, p 0.10, 2 on a 0-to-10 scale). We explore risk-avoidance and pro-social motivations for this relationship, and find suggestive evidence that people who are older or have certain medical preconditions seem to be behave in line with risk-avoidance, whereas motivations of people who are less at risk of Covid-19 seem more mixed. While it is difficult to estimate the relationship between life satisfaction and compliance behaviour due to potential confounders and unobserved heterogeneity, our findings suggest that life satisfaction is important, both for complying with preventive health measures and as a policy end in itself

Length of secondary schooling and risk of HIV infection in Botswana: evidence from a natural experiment

Background An estimated 2·1 million individuals are newly infected with HIV every year. Cross-sectional and longitudinal studies have reported confl icting evidence for the association between education and HIV risk, and no randomised trial has identifi ed a causal eff ect for education on HIV incidence. We aimed to use a policy reform in secondary schooling in Botswana to identify the causal eff ect of length of schooling on new HIV infection. Methods Data for HIV biomarkers and demographics were obtained from the nationally representative household 2004 and 2008 Botswana AIDS Impact Surveys (N=7018). In 1996, Botswana reformed the grade structure of secondary school, expanding access to grade ten and increasing educational attainment for aff ected cohorts. Using exposure to the policy reform as an instrumental variable, we used two-stage least squares to estimate the causal eff ect of years of schooling on the cumulative probability that an individual contracted HIV up to their age at the time of the survey. We also assessed the cost-eff ectiveness of secondary schooling as an HIV prevention intervention in comparison to other established interventions. Findings Each additional year of secondary schooling caused by the policy change led to an absolute reduction in the cumulative risk of HIV infection of 8·1 percentage points (p=0·008), relative to a baseline prevalence of 25·5% in the pre-reform 1980 birth cohort. Eff ects were particularly large in women (11·6 percentage points, p=0·046). Results were robust to a wide array of sensitivity analyses. Secondary school was cost eff ective as an HIV prevention intervention by standard metrics (cost per HIV infection averted was US$27 753). Interpretation Additional years of secondary schooling had a large protective eff ect against HIV risk in Botswana, particularly for women. Increasing progression through secondary school could be a cost-eff ective HIV prevention measure in HIV-endemic settings, in addition to yielding other societal benefi ts. Funding Takemi Program in International Health at the Harvard T.H.Chan School of Public Health, Belgian American Educational Foundation, Fernand Lazard Foundation, Boston University, National Institutes of Health

On the uniqueness of paths for spin-0 and spin-1 quantum mechanics

The uniqueness of the Bohmian particle interpretation of the Kemmer equation, which describes massive spin-0 and spin-1 particles, is discussed. Recently the same problem for spin-1/2 was dealt with by Holland. It appears that the uniqueness of boson paths can be enforced under well determined conditions. This in turn fixes the nonrelativistic particle equations of the nonrelativistic Schrodinger equation, which appear to correspond with the original definitions given by de Broglie and Bohm only in the spin-0 case. Similar to the spin-1/2 case, there appears an additional spin-dependent term in the guidance equation in the spin-1 case. We also discuss the ambiguity associated with the introduction of an electromagnetic coupling in the Kemmer theory. We argue that when the minimal coupling is correctly introduced, then the current constructed from the energy-momentum tensor is no longer conserved. Hence this current can not serve as a particle probability four-vector.Comment: 19 pages, no figures, LaTex, shortened version for Phys. Lett.

Nitrogen mineralization dynamics of different valuable organic amendments commonly used in agriculture

Published online: 27 February 2016This is an open access article under the CC BY-NC-ND licenseSustainable agriculture requires the careful optimization of the use of organic amendments to improve soil fertility while minimizing any harmful environmental effects. To understand the events that occur in soil after the addition of different organic amendments, we evaluated the nitrogen (N) mineralization dynamics in soil after adding organic amendments, and evaluated changes in the microbial population. The four organic amendments were fresh dairy cattle manure, fresh white clover, vegetable, fruit, and yard waste compost, and poplar tree compost. The N mineralization potential of each organic amendment was determined by analyzing total mineral nitrogen during a 97-day laboratory incubation experiment. Soils amended with clover released 240 μg N g−1 soil during the 97-day incubation, more than twice as much as that released from soils amended with manure or composts (76–100 μg N g−1 soil). At the end of the incubation, the net N mineralization in clover-amended soils was 54%, more than five times higher than that in soils amended with composts or manure (4%–9%). Nitrogen was mineralized faster in clover-amended soil (1.056 μg N g−1 soil day−1) than in soil amended with composts (0.361–0.417 μg N g−1 soil day−1). The microbial biomass carbon content was higher in clover-amended soil than in the soils amended with manure or composts. We monitored changes in the microbial population in amended soils by a phospholipid fatty acid (PLFA) analysis. On day 97, there were higher concentrations of total PLFAs in soils with organic amendments (e.g., 14.41 nmol g−1 in clover-amended soil) than in control soil without amendments (9.84 nmol g−1). Bacteria (Gram-positive and Gram-negative), actinomycetes, and fungi were more abundant in clover-amended soils than soils amended with manure or composts. The N mineralization potential varied among the four organic amendments. Therefore, the timing of application and the type of organic amendment should be matched to the nutrient needs of the crop