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Study of the morphology of individual root systems growing with those of associated plants is facilitated by washing a monolith of soil containing roots of plants whose tops were treated with C^1^4 applied as urea. The roots thus extracted are pressed and dried. X-ray film is applied and the labeled roots can be detected clearly on the resulting autograph. A method of measuring root length for quantitative analysis is suggested.

Will summer pruning of young apple trees bring the trees into bearing earlier or affect the growth of the tree? In order to obtain this information Prof. J. W. Crow, Department of Horticulture, Ontario Agricultural College, started a series of experiments on summer pruning...

Los nazis no sólo quisieron volver a una época supuestamente signada por la pureza racial del pueblo alemán; los más entusiastas también aspiraron a restaurar el paganismo precristiano. Pese a sus pretensiones científicas, los comunistas rusos buscaron retornar a los tiempos precapitalistas, los del viejo mir eslavo, cuando, según imaginaban, los hombres compartían todo e imperaba la armonía. En la mitad inicial del siglo XX, los japoneses hicieron un esfuerzo enorme por encarnar nuevamente los valores de sus antepasados guerreros. Incluso en la Argentina, los seducidos por la consigna \"vivir con lo nuestro\" ven detrás de ella un reflejo tenue del sueño de poder regresar a un mítico hogar ancestral. A diferencia de Europa, Japón y, últimamente, China y la India, los países árabes, Irán y Paquistán, no han conseguido reconciliarse con el mundo cada vez más globalizado de nuestros días. Además, en la Unión Europea, la mayoría de los veinte millones de musulmanes es pobre y en los colegios sus hijos suelen rendir llamativamente menos que sus coetáneos de origen chino, hindú y sij, para no hablar de los autóctonos \"blancos\".

Two-dimensional perovskites have emerged as more intrinsically stable materials for solar cells. Chemical tuning of spacer organic cations has attracted great interest due to their additional functionalities. However, how the chemical nature of the organic cations affects the properties of two-dimensional perovskites and devices is rarely reported. Here we demonstrate that the selection of spacer cations (i.e., selective fluorination of phenethylammonium) affects the film properties of two-dimensional perovskites, leading to different device performance of two-dimensional perovskite solar cells (average n = 4). Structural analysis reveals that different packing arrangements and orientational disorder of the spacer cations result in orientational degeneracy and different formation energies, largely explaining the difference in film properties. This work provides key missing information on how spacer cations exert influence on desirable electronic properties and device performance of two-dimensional perovskites via the weak and cooperative interactions of these cations in the crystal lattice. Two dimensional halide perovskites solar cells have attracted research interest due to their higher stability compared to three dimensional counterparts. Here Hu et al. show that fine tuning of the chemical structure of the spacer cations leads to different packing arrangements and device efficiency.

Women with twin pregnancy are at high risk for spontaneous preterm delivery. Progesterone seems to be effective in reducing preterm birth in selected high-risk singleton pregnancies, albeit with no significant reduction in perinatal mortality and little evidence of neonatal benefit. We investigated the use of progesterone for prevention of preterm birth in twin pregnancy. In this double-blind, placebo-controlled trial, 500 women with twin pregnancy were recruited from nine UK National Health Service clinics specialising in the management of twin pregnancy. Women were randomised, by permuted blocks of randomly mixed sizes, either to daily vaginal progesterone gel 90 mg (n=250) or to placebo gel (n=250) for 10 weeks from 24 weeks' gestation. All study personnel and participants were masked to treatment assignment for the duration of the study. The primary outcome was delivery or intrauterine death before 34 weeks' gestation. Analysis was by intention to treat. Additionally we undertook a meta-analysis of published and unpublished data to establish the efficacy of progesterone in prevention of early (<34 weeks' gestation) preterm birth or intrauterine death in women with twin pregnancy. This study is registered, number ISRCTN35782581. Three participants in each group were lost to follow-up, leaving 247 analysed per group. The combined proportion of intrauterine death or delivery before 34 weeks of pregnancy was 24·7% (61/247) in the progesterone group and 19·4% (48/247) in the placebo group (odds ratio [OR] 1·36, 95% CI 0·89–2·09; p=0·16). The rate of adverse events did not differ between the two groups. The meta-analysis confirmed that progesterone does not prevent early preterm birth in women with twin pregnancy (pooled OR 1·16, 95% CI 0·89–1·51). Progesterone, administered vaginally, does not prevent preterm birth in women with twin pregnancy. Chief Scientist Office of the Scottish Government Health Directorate.

Climate change threatens to shift vegetation, disrupting ecosystems and damaging human well-being. Field observations in boreal, temperate and tropical ecosystems have detected biome changes in the 20th century, yet a lack of spatial data on vulnerability hinders organizations that manage natural resources from identifying priority areas for adaptation measures. We explore potential methods to identify areas vulnerable to vegetation shifts and potential refugia. Global vegetation biomes. We examined nine combinations of three sets of potential indicators of the vulnerability of ecosystems to biome change: (1) observed changes of 20th-century climate, (2) projected 21st-century vegetation changes using the MC1 dynamic global vegetation model under three Intergovernmental Panel on Climate Change (IPCC) emissions scenarios, and (3) overlap of results from (1) and (2). Estimating probability density functions for climate observations and confidence levels for vegetation projections, we classified areas into vulnerability classes based on IPCC treatment of uncertainty. One-tenth to one-half of global land may be highly (confidence 0.80-0.95) to very highly (confidence ≥ 0.95) vulnerable. Temperate mixed forest, boreal conifer and tundra and alpine biomes show the highest vulnerability, often due to potential changes in wildfire. Tropical evergreen broadleaf forest and desert biomes show the lowest vulnerability. Spatial analyses of observed climate and projected vegetation indicate widespread vulnerability of ecosystems to biome change. A mismatch between vulnerability patterns and the geographic priorities of natural resource organizations suggests the need to adapt management plans. Approximately a billion people live in the areas classified as vulnerable.

Assessment of risk factors for preterm birth in a population with high incidence of preterm birth and HIV infection. Secondary analysis of data for 2,149 women included in a community based randomized placebo controlled trial for the prevention of preterm birth (APPLe trial (ISRCTN84023116) with gestational age at birth determined through ultrasound measurement in early pregnancy. Multivariate Logistic Regression analyses to obtain models for three outcome variables: all preterm, early preterm, and late preterm birth. No statistical differences were noted for the prevalence of HIV infection (p = 0.30) or syphilis (p = 0.12) between women who delivered preterm versus term. BMI (Adjusted OR 0.91 (0.85-0.97); p = 0.005) and weight gain (Adjusted OR 0.89 (0.82-0.97); p = 0.006) had an independent, protective effect. Previous preterm birth doubled the odds of preterm birth (Adjusted OR 2.13 (1.198-3.80); p = 0.01). Persistent malaria (despite malaria prophylaxis) increased the risk of late preterm birth (Adjusted OR 1.99 (1.05-3.79); p = 0.04). Age <20 (Adjusted OR 1.73 (1.03-2.90); p = 0.04) and anemia (Adjusted OR 1.95 (1.08-3.52); p = 0.03) were associated with early preterm birth (<34 weeks). Despite claims that HIV infection is an important cause of preterm birth in Africa, we found no evidence of an association in this population (unexposed to anti-retroviral treatment). Persistent malaria was associated with late preterm birth. Maternal undernourishment and anemia were independently associated with early preterm birth. The study did not assess whether the link was direct or whether a common precursor such as chronic infection was responsible for both maternal effects and early labour.