Preservation of glaciochemical time-series in snow and ice from the Penny Ice Cap, Baffin Island

A detailed investigation of major ion concentrations of snow and ice in the summit region of Penny Ice Cap (PIC) was performed to determine the effects of summer melt on the glaciochemical time-series. While ion migration due to meltwater percolation makes it difficult to confidently count annual layers in the glaciochemical profiles, time-series of these parameters do show good structure and a strong one year spectral component, suggesting that annual to biannual signals are preserved in PIC glaciochemical records

Laser optical separation of chiral molecules

The optical trapping of molecules with an off-resonant laser beam involves a forward-Rayleigh scattering mechanism. It is shown that discriminatory effects arise on irradiating chiral molecules with circularly polarized light; the complete representation requires ensemble-weighted averaging to account for the influence of the trapping beam on the distribution of molecular orientations. Results of general application enable comparisons to be drawn between the results for two limits of the input laser intensity. It emerges that, in a racemic mixture, there is a differential driving force whose effect, at high laser intensities, is to produce differing local concentrations of the two enantiomers

Conjugative transfer of ICESde3396 between three β-hemolytic streptococcal species

Background: Integrative conjugative elements (ICEs) are mobile genetic elements (MGEs) that possess all genes necessary for excision, transfer and integration into recipient genome. They also carry accessory genes that impart new phenotypic features to recipient strains. ICEs therefore play an important role in genomic plasticity and population structure. We previously characterised ICESde 3396, the first ICE identified in the β-hemolytic Streptococcus dysgalactiae subsp equisimilis (SDSE) and demonstrated its transfer to single isolates of Streptococcus pyogenes (group A streptococcus, GAS) and Streptococcus agalactiae (group B streptococcus, GBS). While molecular studies found the ICE in multiple SDSE and GBS isolates, it was absent in all GAS isolates examined. Results: Here we demonstrate that ICESde 3396:km is transferable from SDSE to multiple SDSE, GAS and GBS isolates. However not all strains of these species were successful recipients under the same growth conditions. To address the role that host factors may have in conjugation we also undertook conjugation experiments in the presence of A549 epithelial cells and DMEM. While Horizontal Gene Transfer (HGT) occurred, conjugation efficiencies were no greater than when similar experiments were conducted in DMEM. Additionally transfer to GAS NS235 was successful in the presence of DMEM but not in Todd Hewitt Broth suggesting that nutritional factors may also influence HGT. The GAS and GBS transconjugants produced in this study are also able to act as donors of the ICE. Conclusion: We conclude that ICEs are major sources of interspecies HGT between β-hemolytic streptococci, and by introducing accessory genes imparting novel phenotypic characteristics, have the potential to alter the population structure of these species

Electromagnetic trapping of chiral molecules: orientational effects of the irradiating beam

The photonic interaction generally responsible for the electromagnetic trapping of molecules is forward-Rayleigh scattering, a process that is mediated by transition electric dipoles connecting the ground electronic state and virtual excited states. Higher order electric and magnetic multipole contributions to the scattering amplitude are usually negligible. However, on consideration of chiral discrimination effects (in which an input light of left-handed circular polarization can present different observables compared to right-handed polarization, or molecules of opposite enantiomeric form respond differently to a set circular polarization), the mechanism must be extended to specifically accommodate transition magnetic dipoles. Moreover, it is important to account for the fact that chiral molecules are necessarily non-spherical, so that their interactions with a laser beam will have an orientational dependence. Using quantum electrodynamics, this article quantifies the extent of the energetic discrimination that arises when chiral molecules are optically trapped, placing particular emphasis on the orientational effects of the trapping beam. An in-depth description of the intricate ensemble-weighted method used to incorporate the latter is presented. It is thus shown that, when a mixture of molecular enantiomers is irradiated by a continuous beam of circularly polarized light, a difference arises in the relative rates of migration of each enantiomer in and out of the most intense regions of the beam. In consequence, optical trapping can be used as a means of achieving enantiomer separation

Spatial Clustering of Dark Matter Halos: Secondary Bias, Neighbor Bias, and the Influence of Massive Neighbors on Halo Properties

We explore the phenomenon commonly known as halo assembly bias, whereby dark matter halos of the same mass are found to be more or less clustered when a second halo property is considered, for halos in the mass range $3.7 \times 10^{11} \; h^{-1} \mathrm{M_{\odot}} - 5.0 \times 10^{13} \; h^{-1} \mathrm{M_{\odot}}$. Using the Large Suite of Dark Matter Simulations (LasDamas) we consider nine commonly used halo properties and find that a clustering bias exists if halos are binned by mass or by any other halo property. This secondary bias implies that no single halo property encompasses all the spatial clustering information of the halo population. The mean values of some halo properties depend on their halo's distance to a more massive neighbor. Halo samples selected by having high values of one of these properties therefore inherit a neighbor bias such that they are much more likely to be close to a much more massive neighbor. This neighbor bias largely accounts for the secondary bias seen in halos binned by mass and split by concentration or age. However, halos binned by other mass-like properties still show a secondary bias even when the neighbor bias is removed. The secondary bias of halos selected by their spin behaves differently than that for other halo properties, suggesting that the origin of the spin bias is different than of other secondary biases.Comment: 14 pages, LaTeX; minor revisions, and added references; results unchange

Determination of plutonium in seawater using co-precipitation and inductively coupled plasma mass spectrometry with ultrasonic nebulisation1

A flow injection–inductively coupled plasma–mass spectrometric (FI–ICP–MS) procedure, utilising ultrasonic nebulisation with membrane desolvation (USN/MD), has been developed for the determination of plutonium (Pu) in seawater at fg l−1 concentration levels. Seawater samples (1 l), after filtration, were subjected to co-precipitation with NdF3, followed by ion exchange to enrich Pu and to reject seawater matrix ions and co-existing uranium. The seawater concentrate (1.0 ml) was then analysed by FI–ICP–MS. The limit of detection for in seawater based on an enrichment factor of 1000 was 5 fg l−1, and precision at the 0.80 pg l−1 level was 12% RSD. Accuracy was verified via recovery experiments, and by comparing survey data for the Irish Sea with that derived by standard methodology based on co-precipitation and α-spectrometry. Concentrations for dissolved in the Irish Sea were in the range of 0.267–0.941 pg l−1 (0.614–2.164 mBq l−1) and 0.051–0.196 pg l−1 (0.428–1.646 mBq l−1), respectively

Individual, Neighborhood, and Situational Factors Associated with Violent Victimization and Offending

The criminological literature presents substantial evidence that victims and offenders in violent crimes share demographic characteristics, engage in similar lifestyles and activities, and reside in socially disorganized neighborhoods. However, research has examined these relationships separately using either victimization or offending data, and prior studies have not examined these relationships by comparing victims and offenders within the same incidents. This limits the effect of examining whether these factors are associated with victimization and offending in similar or distinct ways. Using a law enforcement database of victims (n = 1,248) and offenders (n = 1,735) involved within the same aggravated battery incidents (n = 1,015) in Bernalillo County, New Mexico, this research explores whether victims and offenders involved in non-lethal violence share certain individual, neighborhood and situational characteristics. Results suggest that victims and offenders live in socially disorganized neighborhoods and engage in risky lifestyles and violent offending behaviors in similar proportions. These findings highlight the overlapping factors associated with victimization and offending in non-lethal violent personal crimes. The implications of these findings are discussed

Movement patterns of Pacific crown-of-thorns starfish (Acanthaster cf. solaris) linked to habitat structure and prey availability

Patterns of movement and habitat use by adult crown-of-thorns starfishes (Acanthaster spp.) will have a major bearing on their distribution, reproductive capacity, and impacts on coral assemblages and reef ecosystems. The spatial and temporal scales over which crown-ofthorns starfish move will also have important implications for the scales at which they will be most effectively managed. Movement patterns of crown-of-thorns starfish have been studied previously, though mostly over small distances (metres) and limited timeframes (minutes to hours). This study reports on explicit studies that measured the movement rates and movement patterns of Pacific crown-of-thorns starfish (Acanthaster cf. solaris) at a range of temporal and spatial scales. In the first instance, we measured the instantaneous movement rates of starfish (n = 218) across different substrates; sand, coral rubble and consolidated carbonate pavement. This study was conducted in a large (5m diameter) tank, using video recordings that were then analysed to determine the mean and maximum rates of movement over successive 15-second intervals. To assess movement patterns of A. cf. solaris in the field, short-term tagging and movement studies were undertaken at Rib Reef, in the central GBR. All starfish (n = 357) recorded on semi-permanent transects were individually tagged using numbered pieces of flagging tape. The precise position of each starfish (where detected) was then recorded during successive surveys during day and night for up to 4 days. To further scale-up movement studies for crownof-thorns starfish we tagged 50 crown-of-thorns starfish using V7 (69KHZ) acoustic transmitters, at Lodestone Reef or Big Broadhurst Reef. The position of these starfish relative to acoustic receivers deployed 50-200m along the edge of the reef was recorded (at 3-minute intervals) for up to 8 months. Passive acoustic monitoring was intended to provide greater insights into longer-term (weeks to months) and larger-scale (kilometres) patterns of movement for crown-of-thorns starfish, but provided much less resolution regarding fine-scale movements of individual starfish. Instantaneous measures of movement capacity for A. cf. solaris (in aquaria) showed that these starfish are capable of moving at 20-35 cm per minute, and move fastest over sand. Despite their capacity for movement, field-based studies suggested that crown-of-thorns starfish actually move very little at scales of days to weeks, and even months. For starfish that were tagged with temporary visual markers, the minimum displacement distance recorded for the majority of starfish (88.0%) was <2m throughout the course of the study. Moreover, starfish that did move to feed (mostly at night) often returned to the same resting location between feeding bouts. Similarly, starfish tagged with acoustic transmitters for up to 6 months were only ever detected on adjacent receivers with large overlap in their ranges, suggesting that all starfish remained within 50-100m of where they were initially found and tagged for up to 6- months. The frequency and duration of passive detections varied greatly among individual starfish tagged with transmitters, with detections peaking in early hours of the morning. While this study shows that it is possible to effectively tag crown-of-thorns starfish, both over short and longer time-frames, there were considerable logistical challenges to documenting occasional large-scale, and presumably quite rapid, displacement of individual starfish. It is clear that crown-of-thorns starfish generally move very little and remain within localised areas (even returning to the same sheltering location between successive feeding bouts) of moderate to high coral cover. However, Acanthaster spp. are also capable of moving large distances when necessary, presumably when coral prey are locally depleted. It will be important to understand the nature and scale of both modes of movement to effectively manage population irruptions of crown-of-thorns starfish. Documenting the incidence and rates of movement during these infrequent events remains a priority for future research

Preliminary evidence of increased striatal dopamine in a nonhuman primate model of maternal immune activation.

Women exposed to a variety of viral and bacterial infections during pregnancy have an increased risk of giving birth to a child with autism, schizophrenia or other neurodevelopmental disorders. Preclinical maternal immune activation (MIA) models are powerful translational tools to investigate mechanisms underlying epidemiological links between infection during pregnancy and offspring neurodevelopmental disorders. Our previous studies documenting the emergence of aberrant behavior in rhesus monkey offspring born to MIA-treated dams extends the rodent MIA model into a species more closely related to humans. Here we present novel neuroimaging data from these animals to further explore the translational potential of the nonhuman primate MIA model. Nine male MIA-treated offspring and 4 controls from our original cohort underwent in vivo positron emission tomography (PET) scanning at approximately 3.5-years of age using [18F] fluoro-l-m-tyrosine (FMT) to measure presynaptic dopamine levels in the striatum, which are consistently elevated in individuals with schizophrenia. Analysis of [18F]FMT signal in the striatum of these nonhuman primates showed that MIA animals had significantly higher [18F]FMT index of influx compared to control animals. In spite of the modest sample size, this group difference reflects a large effect size (Cohen's d = 0.998). Nonhuman primates born to MIA-treated dams exhibited increased striatal dopamine in late adolescence-a hallmark molecular biomarker of schizophrenia. These results validate the MIA model in a species more closely related to humans and open up new avenues for understanding the neurodevelopmental biology of schizophrenia and other neurodevelopmental disorders associated with prenatal immune challenge