Proposal for a Universal Particle Detector Experiment

The Universal Particle Detector Experiment (UPDE), which consists of parallel planes of two diode laser beams of different wavelengths and a large surface metal oxide semiconductor (MOS) impact detector, is proposed. It will be used to perform real-time monitoring of contamination particles and meteoroids impacting the spacecraft surface with high resolution of time, position, direction, and velocity. The UPDE will discriminate between contaminants and meteoroids, and will determine their velocity and size distribution around the spacecraft environment. With two different color diode lasers, the contaminant and meteroid composition will also be determined based on laboratory calibration with different materials. Secondary particles dislodged from the top aluminum surface of the MOS detector will also be measured to determine the kinetic energy losses during energetic meteoroid impacts. The velocity range of this instrument is 0.1 m/s to more than 14 km/s, while its size sensitivity is from 0.2 microns to millimeter-sized particles. The particulate measurements in space of the kind proposed will be the first simultaneous multipurpose particulate experiment that includes velocities from very slow to hypervelocities, sizes from submicrometer- to pellet-sized diameters, chemical analysis of the particulate composition, and measurements of the kinetic energy losses after energetic impacts of meteroids. The experiment will provide contamination particles and orbital debris data that are critically needed for our present understanding of the space environment. The data will also be used to validate contamination and orbital debris models for predicting optimal configuration of future space sensors and for understanding their effects on sensitive surfaces such as mirrors, lenses, paints, and thermal blankets

Intrasexual competition facilitates the evolution of alternative mating strategies in a colour polymorphic fish

<p>Abstract</p> <p>Background</p> <p>Intense competition for access to females can lead to males exploiting different components of sexual selection, and result in the evolution of alternative mating strategies (AMSs). Males of <it>Poecilia parae</it>, a colour polymorphic fish, exhibit five distinct phenotypes: drab-coloured (immaculata), striped (parae), structural-coloured (blue) and carotenoid-based red and yellow morphs. Previous work indicates that immaculata males employ a sneaker strategy, whereas the red and yellow morphs exploit female preferences for carotenoid-based colours. Mating strategies favouring the maintenance of the other morphs remain to be determined. Here, we report the role of agonistic male-male interactions in influencing female mating preferences and male mating success, and in facilitating the evolution of AMSs.</p> <p>Results</p> <p>Our study reveals variation in aggressiveness among <it>P. parae </it>morphs during indirect and direct interactions with sexually receptive females. Two morphs, parae and yellow, use aggression to enhance their mating success (i.e., number of copulations) by 1) directly monopolizing access to females, and 2) modifying female preferences after winning agonistic encounters. Conversely, we found that the success of the drab-coloured immaculata morph, which specializes in a sneak copulation strategy, relies in its ability to circumvent both male aggression and female choice when facing all but yellow males.</p> <p>Conclusions</p> <p>Strong directional selection is expected to deplete genetic variation, yet many species show striking genetically-based polymorphisms. Most studies evoke frequency dependent selection to explain the persistence of such variation. Consistent with a growing body of evidence, our findings suggest that a complex form of balancing selection may alternatively explain the evolution and maintenance of AMSs in a colour polymorphic fish. In particular, this study demonstrates that intrasexual competition results in phenotypically distinct males exhibiting clear differences in their levels of aggression to exclude potential sexual rivals. By being dominant, the more aggressive males are able to circumvent female mating preferences for attractive males, whereas another male type incorporates subordinate behaviours that allow them to circumvent male aggression and female mating preferences. Together, these and previous results indicate that exploiting different aspects of social interactions may allow males to evolve distinct mating strategies and thus the long term maintenance of polymorphisms within populations.</p

INDEPENDENT OBSERVATIONS OF PHAEOMELANIC MALES OF THE VARIABLE SEEDEATER (SPOROPHILA CORVINA) WITH COMMENTS ABOUT ITS POTENTIAL FOR EVOLUTIONARY DIVERGENCE

Plumage coloration largely depends on the type and concentration of pigments present in feathers. Therefore, changes in pigment deposition may result in aberrant colorations, which, in turn, will likely interfere with the plumage color’s function (e.g., signaling, protection). Published records of aberrant plumage colors underestimate the type and frequency of these phenotypes, especially in the tropics. Here, we report five independent observations of phaeomelanic males of the Variable Seedeater (Sporophila corvina), in which typically white feathers were instead chestnut-red, likely due to the deposition of phaeomelanin. Our observations add to previous reports of aberrant melanin-based coloration in this species, suggesting that genomic region(s) influencing the expression of phaeomelanin are a biased target for mutations. Because mutations affecting the regulation of melanin deposition result in novel plumage phenotypes, we discuss aberrant phenotypes as an important source of variation fueling rapid divergence among populations of this avian clade

Difference in Plumage Color Used in Species Recognition between Incipient Species Is Linked to a Single Amino Acid Substitution in the Melanocortin‐1 Receptor

This is the publisher's version, also available electronically from http://www.jstor.org/stable/10.1086/600084Many studies demonstrate that differences in mating signals are used by incipient species in recognizing potential mates or sexual competitors (i.e., species recognition). Little is known, however, about the genetic changes responsible for these differences in mating signals. Populations of the Monarcha castaneiventris flycatcher vary in plumage color across the Solomon Islands, with a subspecies on Makira Island having chestnut bellies and blue‐black upper parts (Monarcha castaneiventris megarhynchus) and a subspecies on neighboring satellite islands being entirely blue‐black (melanic; Monarcha castaneiventris ugiensis). Here we show that a single nonsynonymous point mutation in the melanocortin‐1 receptor (MC1R) gene is present in all melanic birds from one island (Santa Ana) but absent in all chestnut‐bellied birds from Makira Island, implicating this mutation in causing melanism. Birds from a second satellite island (Ugi) do not show the same perfect association between this MC1R variant and plumage color, suggesting an alternative mechanism for melanism on this island. Finally, taxidermic mount presentation experiments in Makira (chestnut) and Santa Ana (melanic) suggest that the plumage difference mediates species recognition. Assuming that the signals used in species recognition are also used in mutual mate choice, our results indicate that a single amino acid substitution contributes to speciation

Geography of hospital admissions for multiple sclerosis in England and comparison with the geography of hospital admissions for infectious mononucleosis: a descriptive study

Objective It is well recognised that variation in the geographical distribution of multiple sclerosis (MS) exists. Early studies in England have shown the disease to have been more common in the North than the South. However, this could be an artefact of inaccurate diagnosis and ascertainment, and recent data on MS prevalence are lacking. In the present study, data were analysed to provide a more contemporary map of the distribution of MS in England and, as infectious mononucleosis (IM) has been shown to be associated with the risk of MS, the geographical distribution of IM with that of MS was compared.Methods Analysis of linked statistical abstracts of hospital data for England between 1999 and 2005.Results There were 56 681 MS patients. The admission rate for MS was higher in females (22/10(5); 95% CI 21.8 to 22.3) than males (10.4/10(5); 95% CI 10.2 to 10.5). The highest admission rate for MS was seen for residents of Cumbria and Lancashire (North of England) (20.1/10(5); 95% CI 19.3 to 20.8) and the lowest admission rate was for North West London residents (South of England) (12.4/10(5); 95% CI 11.8 to 13.1). The geographical distributions of IM and MS were significantly correlated (weighted regression coefficient (r (w))=0.70, p<0.0001). Admission rates for MS were lowest in the area quintile with the highest level of deprivation and they were also lowest in the area quintile with the highest percentage of population born outside the UK. A significant association between northernliness and MS remained after adjustment for deprivation and UK birthplace.Conclusions The results show the continued existence of a latitude gradient for MS in England and show a correlation with the distribution of IM. The data have implications for healthcare provision, because lifetime costs of MS exceed 1 pound million per case in the UK, as well as for studies of disease causality and prevention

The orbital debris detector consortium: Suppliers of instruments for in-situ measurements of small-particles in the space environment

Industry and university participants have joined together to form the IMPA:Ct consortium (In-situ Monitors of the Particulate Ambient: Circumterrestrial) which offers a broad range of flight qualified instruments for monitoring the small particle (0.1 micron to 10 cm) environment in space. Instruments are available in 12 months or less at costs ranging from 0.5 to 1.5 million dollars (US) for the total program. Detector technologies represented by these groups are: impact-induced capacitor-discharge (MOS, metal-oxide-silicon), cratering or penetration of electroactive thin film (polyvinylidene fluoride (PVDF)), impact-plasma detection, acoustic detection, CCD tracking of optical scatter of sunlight, and photodiode detection of optical scatter of laser light. The operational characteristics, general spacecraft interface and resource requirements (mass/power/telemetry), cost and delivery schedules, and points of contact for seven different instruments are presented

Selective sweeps on different pigmentation genes mediate convergent evolution of island melanism in two incipient bird species

Insular organisms often evolve predictable phenotypes, like flightlessness, extreme body sizes, or increased melanin deposition. The evolutionary forces and molecular targets mediating these patterns remain mostly unknown. Here we study the Chestnut-bellied Monarch (Monarcha castaneiventris) from the Solomon Islands, a complex of closely related subspecies in the early stages of speciation. On the large island of Makira M. c. megarhynchus has a chestnut belly, whereas on the small satellite islands of Ugi, and Santa Ana and Santa Catalina (SA/SC) M. c. ugiensis is entirely iridescent blue-black (i.e., melanic). Melanism has likely evolved twice, as the Ugi and SA/SC populations were established independently. To investigate the genetic basis of melanism on each island we generated whole genome sequence data from all three populations. Non-synonymous mutations at the MC1R pigmentation gene are associated with melanism on SA/SC, while ASIP, an antagonistic ligand of MC1R, is associated with melanism on Ugi. Both genes show evidence of selective sweeps in traditional summary statistics and statistics derived from the ancestral recombination graph (ARG). Using the ARG in combination with machine learning, we inferred selection strength, timing of onset and allele frequency trajectories. MC1R shows evidence of a recent, strong, soft selective sweep. The region including ASIP shows more complex signatures; however, we find evidence for sweeps in mutations near ASIP, which are comparatively older than those on MC1R and have been under relatively strong selection. Overall, our study shows convergent melanism results from selective sweeps at independent molecular targets, evolving in taxa where coloration likely mediates reproductive isolation with the neighboring chestnut-bellied subspecies

Coherent control of enrichment and conversion of molecular spin isomers

A theoretical model of nuclear spin conversion in molecules controlled by an external electromagnetic radiation resonant to rotational transition has been developed. It has been shown that one can produce an enrichment of spin isomers and influence their conversion rates in two ways, through coherences and through level population change induced by radiation. Influence of conversion is ranged from significant speed up to almost complete inhibition of the process by proper choice of frequency and intensity of the external field.Comment: REVTEX, 13 pages + 6 eps figure

Theory of nuclear spin conversion in ethylene

First theoretical analysis of the nuclear spin conversion in ethylene molecules (13^CCH4) has been performed. The conversion rate was found equal approx. 3x10^{-4} 1/s*Torr, which is in qualitative agreement with the recently obtained experimental value. It was shown that the ortho-para mixing in 13^CCH4 is dominated by the spin-rotation coupling. Mixing of only two pairs of ortho-para levels were found to contribute significantly to the spin conversion.Comment: 20 pages, 5 eps figure