The social roots of Einstein's theory of relativity

In its infancy the British Association for the Advancement of Science derived a good deal of its inspiration from the writings of Francis Bacon. But the pursuit of Baconian policies brought with it attendant dangers which critics from Charles Dickens to the Times were not slow to magnify. Although the situation was further complicated by the sensitiveness of institutional Christianity at the start of Victoria's reign, some of the hazards which the Association endured had to be accepted simply as consequences of the attempt to provide a secure platform for British science.     

Status of Descurainia torulosa (Brassicaceae)

Descurainia torulosa was established in 1983 based on material collected in northwestern Wyoming. The species is now known from 2 disjunct populations in southwestern Wyoming, and recent collections have expanded the known distribution within the northern portion of its range. The north-south disjunct distribution and apparent habitat differences have stimulated questions concerning the degree of relatedness between the disjunct elements to the point that the southern populations have been suggested to be a distinct taxon. Recognition of D. torulosa as a distinct species has also been questioned. This paper is based on field examination of D. torulosa populations, study of all known D. torulosa herbarium specimens, and analysis of nucleotide sequence from the internal transcribed spacer regions 1 and 2 of nuclear ribosomal DNA (ITS-1 & 2) from population exemplars. Cladistic analysis of the sequence data support our conclusion, based on morphological analysis. Northern and southern populations of D. torulosa are conspecific. Western North American Descurainia is in need of modern, critical taxonomic revision.     

Mourning dove numbers on different seral communities in the Chihuahuan Desert

Mourning Doves are the most commonly hunted game bird in New Mexico based on hunter harvest data collected by New Mexico Department of Game and Fish. Research is limited on the influence of rangeland ecological condition on Mourning Dove ( Zenaida macroura ) populations in the Chihuahuan Desert of New Mexico. Mourning Dove numbers were evaluated periodically (1988-1989) on ranges in late- and mid-seral conditions in south central New Mexico based on the Dyksterhuis quantitative climax procedure. Strip transect procedures were used to estimate Mourning Dove populations. Concurrently, vegetation canopy cover was determined by line intercept. On the basis of percent cover, grasses were the most abundant group on late-seral range while shrubs dominated mid-seral range. Mourning Dove sightings did not differ ( P > 0.05) between late- and mid-seral ranges, nor did they differ ( P > 0.05) among grassland, shrubland, and shrub-grass mosaic communities. Mourning Dove populations showed seasonal differences ( P < 0.05), with numbers highest in summer and fall and lowest in winter and spring. Data from our study indicate that Chihuahuan Desert ranges in either mid- or late-seral stages provide equally suitable habitat for Mourning Doves.     

Forecasting time series which are inherently discontinuous

Commonly used forecasting methods often produce meaningless forecasts when time series display abrupt changes in level. Measuring and accounting for the effect of discontinuities can have a significant impact on forecasting accuracy. In addition, if discontinuities are considered non-random and their cause is known, then adjustments can be made to more reliably represent the trend, seasonal and random component. This paper concerns a computational method used in forecasting inherently discontinuous time series. The method provides screening to determine the locations and types of discontinuities. The paper includes analyses of actual time series which are typical of certain types of inherently discontinuous processes.     

Short-latency drinking and increased Na appetite after intracerebral microinjections of NGF in rats

NERVE GROWTH FACTOR (NGF) is a polypeptide trophic factor for peripheral sympathetic and sensory neurones(1,2). Apparent NGF(3-5) and NGF receptors(6,7) have also been identified in the brain, and intracerebral administration of NGF in the adult rat produces marked biochemical(8) and morphologica(9,10) changes in brain tissue. These findings, taken together with the observations that central injections of NGF facilitate behavioural recovery from brain damage(11,12), indicate that this polypeptide may have an important role in brain function. It has been observed that rats given intraventricular injections of up to 2.3 microg NGF drink copiously (M.E.L. and G. Guroff, unpublished observations). Perkins et al.(13) reported that diencephalic application of crystalline NGF (1-15 microg) resulted in an intense polydipsia. The present report confirms the observations of M.E.L. and Guroff, and extends the findings of Perkins et al.(13) by using solutions of NGF instead of crystals. It also describes for the first time a second phenomenon produced by intracranial administration of NGF, namely an intense appetite for aversive concentrations of sodium solutions.     

Extensive halogen-mediated ozone destruction over the tropical Atlantic Ocean

Increasing tropospheric ozone levels over the past 150 years have led to a significant climate perturbation; the prediction of future trends in tropospheric ozone will require a full understanding of both its precursor emissions and its destruction processes. A large proportion of tropospheric ozone loss occurs in the tropical marine boundary layer and is thought to be driven primarily by high ozone photolysis rates in the presence of high concentrations of water vapour. A further reduction in the tropospheric ozone burden through bromine and iodine emitted from open-ocean marine sources has been postulated by numerical models, but thus far has not been verified by observations. Here we report eight months of spectroscopic measurements at the Cape Verde Observatory indicative of the ubiquitous daytime presence of bromine monoxide and iodine monoxide in the tropical marine boundary layer. A year-round data set of co-located in situ surface trace gas measurements made in conjunction with low-level aircraft observations shows that the mean daily observed ozone loss is approximately 50 per cent greater than that simulated by a global chemistry model using a classical photochemistry scheme that excludes halogen chemistry. We perform box model calculations that indicate that the observed halogen concentrations induce the extra ozone loss required for the models to match observations. Our results show that halogen chemistry has a significant and extensive influence on photochemical ozone loss in the tropical Atlantic Ocean boundary layer. The omission of halogen sources and their chemistry in atmospheric models may lead to significant errors in calculations of global ozone budgets, tropospheric oxidizing capacity and methane oxidation rates, both historically and in the future.     

Control of segment number in vertebrate embryos

The vertebrate body axis is subdivided into repeated segments, best exemplified by the vertebrae that derive from embryonic somites. The number of somites is precisely defined for any given species but varies widely from one species to another. To determine the mechanism controlling somite number, we have compared somitogenesis in zebrafish, chicken, mouse and corn snake embryos. Here we present evidence that in all of these species a similar 'clock-and-wavefront' mechanism operates to control somitogenesis; in all of them, somitogenesis is brought to an end through a process in which the presomitic mesoderm, having first increased in size, gradually shrinks until it is exhausted, terminating somite formation. In snake embryos, however, the segmentation clock rate is much faster relative to developmental rate than in other amniotes, leading to a greatly increased number of smaller-sized somites.     

The draft genome of the transgenic tropical fruit tree papaya (Carica papaya Linnaeus)

Papaya, a fruit crop cultivated in tropical and subtropical regions, is known for its nutritional benefits and medicinal applications. Here we report a 3x draft genome sequence of 'SunUp' papaya, the first commercial virus-resistant transgenic fruit tree to be sequenced. The papaya genome is three times the size of the Arabidopsis genome, but contains fewer genes, including significantly fewer disease-resistance gene analogues. Comparison of the five sequenced genomes suggests a minimal angiosperm gene set of 13,311. A lack of recent genome duplication, atypical of other angiosperm genomes sequenced so far, may account for the smaller papaya gene number in most functional groups. Nonetheless, striking amplifications in gene number within particular functional groups suggest roles in the evolution of tree-like habit, deposition and remobilization of starch reserves, attraction of seed dispersal agents, and adaptation to tropical daylengths. Transgenesis at three locations is closely associated with chloroplast insertions into the nuclear genome, and with topoisomerase I recognition sites. Papaya offers numerous advantages as a system for fruit-tree functional genomics, and this draft genome sequence provides the foundation for revealing the basis of Carica's distinguishing morpho-physiological, medicinal and nutritional properties.