The effect of transport apertures on relay-imaged, sharp-edged laser profiles in photoinjectors and the impact on electron beam properties.

In a photoinjector electron source, the initial transverse electron bunch properties are determined by the spatial properties of the laser beam on the photocathode. Spatial shaping of the laser is commonly achieved by relay imaging an illuminated circular mask onto the photocathode. However, the Gibbs phenomenon shows that recreating the sharp edge and discontinuity of the cut profile at the mask on the cathode is not possible with an optical relay of finite aperture. Furthermore, the practical injection of the laser into the photoinjector results in the beam passing through small or asymmetrically positioned apertures. This work uses wavefront propagation to show how the transport apertures cause ripple structures to appear in the transverse laser profile even when effectively the full laser power is transmitted. The impact of these structures on the propagated electron bunch has also been studied with electron bunches of high and low charge density. With high charge density, the ripples in the initial charge distribution rapidly wash-out through space charge effects. However, for bunches with low charge density, the ripples can persist through the bunch transport. Although statistical properties of the electron bunch in the cases studied are not greatly affected, there is the potential for the distorted electron bunch to negatively impact machine performance. Therefore, these effects should be considered in the design phase of accelerators using photoinjectors.

Inclusive fitness forces of selection in an age-structured population.

Hamilton's force of selection acting against age-specific mortality is constant and maximal prior to the age of first reproduction, before declining to zero at the age of last reproduction. The force of selection acting on age-specific reproduction declines monotonically from birth in a growing or stationary population. Central to these results is the assumption that individuals do not interact with one another. This assumption is violated in social organisms, where an individual's survival and/or reproduction may shape the inclusive fitness of other group members. Yet, it remains unclear how the forces of selection might be modified when inclusive fitness, rather than population growth rate, is considered the appropriate metric for fitness. Here, we derive such inclusive fitness forces of selection, and show that selection on age-specific survival is not always constant before maturity, and can remain above zero in post-reproductive age classes. We also show how the force of selection on age-specific reproduction does not always decline monotonically from birth, but instead depends on the balance of costs and benefits of increasing reproduction to both direct and indirect fitness. Our theoretical framework provides an opportunity to expand our understanding of senescence across social species.

Bumblebees retrieve only the ordinal ranking of foraging options when comparing memories obtained in distinct settings.

Are animals' preferences determined by absolute memories for options (e.g. reward sizes) or by their remembered ranking (better/worse)? The only studies examining this question suggest humans and starlings utilise memories for both absolute and relative information. We show that bumblebees' learned preferences are based only on memories of ordinal comparisons. A series of experiments showed that after learning to discriminate pairs of different flowers by sucrose concentration, bumblebees preferred flowers (in novel pairings) with (1) higher ranking over equal absolute reward, (2) higher ranking over higher absolute reward, and (3) identical qualitative ranking but different quantitative ranking equally. Bumblebees used absolute information in order to rank different flowers. However, additional experiments revealed that, even when ranking information was absent (i.e. bees learned one flower at a time), memories for absolute information were lost or could no longer be retrieved after at most 1 hr. Our results illuminate a divergent mechanism for bees (compared to starlings and humans) of learned preferences that may have arisen from different adaptations to their natural environment.

Separation of Azeotropic Hydrofluorocarbon Refrigerant Mixtures: Thermodynamic and Kinetic Modeling for Binary Adsorption of HFC-32 and HFC-125 on Zeolite 5A.

Hydrofluorocarbons (HFCs) have been used extensively as refrigerants over the past four decades; however, HFCs are currently being phased out due to large global warming potentials. As the next generation of hydrofluoroolefin refrigerants are phased in, action must be taken to responsibly and sustainably deal with the HFCs currently in circulation. Ideally, unused HFCs can be reclaimed and recycled; however, many HFCs in circulation are azeotropic or near-azeotropic mixtures and must be separated before recycling. Previously, pure gas isotherm data were presented for both HFC-125 (pentafluoroethane) and HFC-32 (difluoromethane) with zeolite 5A, and it was concluded that this zeolite could separate refrigerant R-410A (50/50 wt % HFC-125/HFC-32). To further investigate the separation capabilities of zeolite 5A, binary adsorption was measured for the same system using the Integral Mass Balance method. Zeolite 5A showed a selectivity of 9.6-10.9 for HFC-32 over the composition range of 25-75 mol % HFC-125. Adsorbed phase activity coefficients were calculated from binary adsorption data. The Spreading Pressure Dependent, modified nonrandom two-liquid, and modified Wilson activity coefficient models were fit to experimental data, and the resulting activity coefficient models were used in Real Adsorbed Solution Theory (RAST). RAST binary adsorption model predictions were compared with Ideal Adsorbed Solution Theory (IAST) predictions made using the Dual-Site Langmuir, Tóth, and Jensen and Seaton pure gas isotherm models. Both IAST and RAST yielded qualitatively accurate predictions; however, quantitative accuracy was greatly improved using RAST models. Diffusion behavior of HFC-125 and HFC-32 was also investigated by fitting the isothermal Fickian diffusion model to kinetic data. Molecular-level phenomena were investigated to understand both thermodynamic and kinetic behaviors.

Discrimination of edge orientation by bumblebees.

Simple feature detectors in the visual system, such as edge-detectors, are likely to underlie even the most complex visual processing, so understanding the limits of these systems is crucial for a fuller understanding of visual processing. We investigated the ability of bumblebees (Bombus terrestris) to discriminate between differently angled edges. In a multiple-choice, "meadow-like" scenario, bumblebees successfully discriminated between angled bars with 7° differences, significantly exceeding the previously reported performance of eastern honeybees (Apis cerana, limit: 15°). Neither the rate at which bees learned, nor their final discrimination performance were affected by the angular orientation of the training bars, indicating a uniform performance across the visual field. Previous work has found that, in dual-choice tests, eastern honeybees cannot reliably discriminate between angles with less than 25° difference, suggesting that performance in discrimination tasks is affected by the training regime, and doesn't simply reflect the perceptual limitations of the visual system. We used high resolution LCD monitors to investigate bumblebees' angular resolution in a dual-choice experiment. Bumblebees could still discriminate 7° angle differences under such conditions (exceeding the previously reported limit for Apis mellifera, of 10°, as well as that of A. cerana). Bees eventually reached similar levels of accuracy in the dual-choice experiment as they did under multiple-choice conditions but required longer learning periods. Bumblebees show impressive abilities to discriminate between angled edges, performing better than two previously tested species of honeybee. This high performance may, in turn, support complex visual processing in the bumblebee brain.

Individual variation explains ageing patterns in a cooperatively breeding bird, the long-tailed tit Aegithalos caudatus.

Alloparental care in cooperatively breeding species may alter breeder age-specific survival and reproduction and subsequently senescence. The helping behaviour itself might also undergo age-related change, and decisions to help in facultative cooperative breeders are likely to be affected by individual condition. Helpers in long-tailed tits Aegithalos caudatus assist relatives after failing to raise their own brood, with offspring from helped nests being more likely to recruit into the breeding population. Using data collected over 25 years, we examined the age trajectories of survival and reproduction in adult long-tailed tits to determine how these were affected by the presence or absence of helpers and how helper behaviour changed with age. There was evidence for increased reproductive performance with breeder age, but no effect of age on the probability of survival. We found no evidence of significant senescent decline in survival or reproductive performance, although individuals accrued less inclusive fitness in their last year of life. Lifetime reproductive success was positively related to both reproductive life span and body mass. Within a season, breeders that were assisted by helpers enjoyed greater reproductive success through enhanced offspring recruitment in the following year. We found no evidence that age affected an individual's propensity to help, or the amount of indirect fitness accrued through helping. We found a positive correlation between life span and multiple components of reproductive success, suggesting that individual variation in quality underpins age-related variation in fitness in this species. Helping decisions are driven by condition, and lifetime inclusive fitness of immigrants was predicted by body mass. These findings further support individual heterogeneity in quality being a major driver for fitness gains across the life course of long-tailed tits.

Senescence: why and where selection gradients might not decline with age.

Patterns of ageing across the tree of life are much more diverse than previously thought. Yet, we still do not adequately understand how, why and where across the tree of life a particular pattern of ageing will evolve. An ability to predict ageing patterns requires a firmer understanding of how and why different ecological and evolutionary factors alter the sensitivity of fitness to age-related changes in mortality and reproduction. From this understanding, we can ask why and where selection gradients might not decline with age. Here, we begin by summarizing the recent breadth of literature that is unearthing, empirically and theoretically, the mechanisms that drive variation in patters of senescence. We focus on the relevance of two key parameters, population structure and reproductive value, as key to understanding selection gradients, and therefore senescence. We discuss how growth form, individual trade-offs, stage structure and social interactions may all facilitate differing distributions of these two key parameters than those predicted by classical theory. We argue that these four key aspects can help us understand why patterns of negligible and negative senescence can actually be explained under the same evolutionary framework as classical senescence.

Inherent Ethyl Acetate Selectivity in a Trianglimine Molecular Solid.

Ethyl acetate is an important chemical raw material and solvent. It is also a key volatile organic compound in the brewing industry and a marker for lung cancer. Materials that are highly selective toward ethyl acetate are needed for its separation and detection. Here, we report a trianglimine macrocycle (TAMC) that selectively adsorbs ethyl acetate by forming a solvate. Crystal structure prediction showed this to be the lowest energy solvate structure available. This solvate leaves a metastable, "templated" cavity after solvent removal. Adsorption and breakthrough experiments confirmed that TAMC has adequate adsorption kinetics to separate ethyl acetate from azeotropic mixtures with ethanol, which is a challenging and energy-intensive industrial separation.

High-Speed Videography Reveals How Honeybees Can Turn a Spatial Concept Learning Task Into a Simple Discrimination Task by Stereotyped Flight Movements and Sequential Inspection of Pattern Elements.

Honey bees display remarkable visual learning abilities, providing insights regarding visual information processing in a miniature brain. It was discovered that bees can solve a task that is generally viewed as spatial concept learning in primates, specifically the concept of "above" and "below." In these works, two pairs of visual stimuli were shown in the two arms of a Y-maze. Each arm displayed a "referent" shape (e.g., a cross, or a horizontal line) and a second geometric shape that appeared either above or below the referent. Bees learning the "concept of aboveness" had to choose the arm of the Y-maze in which a shape-any shape-occurred above the referent, while those learning the "concept of belowness" had to pick the arm in which there was an arbitrary item beneath the referent. Here, we explore the sequential decision-making process that allows bees to solve this task by analyzing their flight trajectories inside the Y-maze. Over 368 h of high-speed video footage of the bees' choice strategies were analyzed in detail. In our experiments, many bees failed the task, and, with the possible exception of a single forager, bees as a group failed to reach significance in picking the correct arm from the decision chamber of the maze. Of those bees that succeeded in choosing correctly, most required a close-up inspection of the targets. These bees typically employed a close-up scan of only the bottom part of the pattern before taking the decision of landing on a feeder. When rejecting incorrect feeders, they repeatedly scanned the pattern features, but were still, on average, faster at completing the task than the non-leaners. This shows that solving a concept learning task could actually be mediated by turning it into a more manageable discrimination task by some animals, although one individual in this study appeared to have gained the ability (by the end of the training) to solve the task in a manner predicted by concept learning.

Grasshopper DCMD: An Undergraduate Electrophysiology Lab for Investigating Single-Unit Responses to Behaviorally-Relevant Stimuli.

Avoiding capture from a fast-approaching predator is an important survival skill shared by many animals. Investigating the neural circuits that give rise to this escape behavior can provide a tractable demonstration of systems-level neuroscience research for undergraduate laboratories. In this paper, we describe three related hands-on exercises using the grasshopper and affordable technology to bring neurophysiology, neuroethology, and neural computation to life and enhance student understanding and interest. We simplified a looming stimuli procedure using the Backyard Brains SpikerBox bioamplifier, an open-source and low-cost electrophysiology rig, to extracellularly record activity of the descending contralateral movement detector (DCMD) neuron from the grasshopper's neck. The DCMD activity underlies the grasshopper's motor responses to looming monocular visual cues and can easily be recorded and analyzed on an open-source iOS oscilloscope app, Spike Recorder. Visual stimuli are presented to the grasshopper by this same mobile application allowing for synchronized recording of stimuli and neural activity. An in-app spike-sorting algorithm is described that allows a quick way for students to record, sort, and analyze their data at the bench. We also describe a way for students to export these data to other analysis tools. With the protocol described, students will be able to prepare the grasshopper, find and record from the DCMD neuron, and visualize the DCMD responses to quantitatively investigate the escape system by adjusting the speed and size of simulated approaching objects. We describe the results from 22 grasshoppers, where 50 of the 57 recording sessions (87.7%) had a reliable DCMD response. Finally, we field-tested our experiment in an undergraduate neuroscience laboratory and found that a majority of students (67%) could perform this exercise in one two-hour lab setting, and had an increase in interest for studying the neural systems that drive behavior.

Insect Bio-inspired Neural Network Provides New Evidence on How Simple Feature Detectors Can Enable Complex Visual Generalization and Stimulus Location Invariance in the Miniature Brain of Honeybees.

The ability to generalize over naturally occurring variation in cues indicating food or predation risk is highly useful for efficient decision-making in many animals. Honeybees have remarkable visual cognitive abilities, allowing them to classify visual patterns by common features despite having a relatively miniature brain. Here we ask the question whether generalization requires complex visual recognition or whether it can also be achieved with relatively simple neuronal mechanisms. We produced several simple models inspired by the known anatomical structures and neuronal responses within the bee brain and subsequently compared their ability to generalize achromatic patterns to the observed behavioural performance of honeybees on these cues. Neural networks with just eight large-field orientation-sensitive input neurons from the optic ganglia and a single layer of simple neuronal connectivity within the mushroom bodies (learning centres) show performances remarkably similar to a large proportion of the empirical results without requiring any form of learning, or fine-tuning of neuronal parameters to replicate these results. Indeed, a model simply combining sensory input from both eyes onto single mushroom body neurons returned correct discriminations even with partial occlusion of the patterns and an impressive invariance to the location of the test patterns on the eyes. This model also replicated surprising failures of bees to discriminate certain seemingly highly different patterns, providing novel and useful insights into the inner workings facilitating and limiting the utilisation of visual cues in honeybees. Our results reveal that reliable generalization of visual information can be achieved through simple neuronal circuitry that is biologically plausible and can easily be accommodated in a tiny insect brain.

Feasibility of a call-in centre to deliver colorectal cancer screening in primary care.

OBJECTIVE: To evaluate the feasibility of a call-in centre to deliver colorectal cancer (CRC) screening in primary care through self-administered fecal occult blood testing (FOBT). DESIGN: Four-month intervention study (September 2010 to January 2011) with randomly selected follow-up interviews. SETTING: The family medicine clinics of 3 hospitals in Montreal, Que. PARTICIPANTS: Letters from doctors invited their patients to contact the call-in centre (N = 761). Eligible patients agreeing to FOBT were sent testing kits that could be returned by mail (N = 100). Randomly selected patients (N = 36) were interviewed to explore the reasons why they did not contact the call-in centre, or why they did or did not adhere to FOBT. MAIN OUTCOME MEASURES: Feasibility was assessed by the proportions of patients who contacted the call-in centre, who were eligible for FOBT, and who adhered to FOBT; and by the time between invitation mail-out and contact with the call-in centre, initial telephone contact and receipt of the signed consent form, and FOBT kit mail-out and receipt of the kit by the laboratory. Hierarchical logistic regression evaluated the effect of patient characteristics on feasibility indicators, adjusting for clustering by physician and centre. RESULTS: Of 761 patients (61.6% female, mean age 61.0 years), 250 (32.9%) contacted the call-in centre, of whom 100 (40.0%) were eligible for and consented to FOBT; 62 (62.0%) of these patients adhered to FOBT. Median (interquartile range) time from invitation mail-out to call-in centre contact was 21 (7 to 29) days, from initial telephone contact to receipt of the signed consent form was 24 (10 to 38) days, and from FOBT kit mail-out to receipt at the laboratory was 23 (18 to 32) days. With the exception of previous cancer diagnosis, patient characteristics were not associated with feasibility indicators. Of the 115 (46.0%) patients determined to be ineligible for FOBT screening, 111 (96.5%) were up to date with or already scheduled for screening. CONCLUSION: Feasibility of the call-in centre was demonstrated. Targeting screening-eligible individuals or coupling a call-in service with another evidence-based CRC screening improvement strategy might further improve uptake of fecal testing.

Optimal care for rheumatoid arthritis: a focus group study.

Our study sought to identify barriers to optimal care for individuals with rheumatoid arthritis (RA). Our study was set in a population with universal access to comprehensive health care in the context of a university hospital health network. Using purposive sampling, we invited RA patients, health professionals, and decision makers from urban and rural regions to participate in structured focus group interviews. Content analysis was performed to determine themes emerging from the data. We identified four general themes. First, initial barriers to optimal care for people begin before primary care contact, at the level of the general population and/or related to primary care access. Second, many factors (at the patient, physician, and system level) influenced how quickly a patient is referred from primary to specialty care. Third, after referral, multiple comanagement issues influence patient outcomes. Fourth, optimizing RA care requires adequate resources. Participants emphasized the need for more education (of patients, of health care providers, and within the general community), better communication between and among patients and health care providers, and more efficient use of existing resources. Our work provides insights regarding barriers to and facilitators of optimal care in RA. Further work with these stakeholder groups in our health care region will examine potential solutions and the feasibility of their implementation. Our work provides an example of how research can assist stakeholder leaders in creating structured and incremental plans to improve health care delivery for persons with chronic diseases like RA.

Methylthiolate on Au(111): adsorption and desorption kinetics.

Low energy electron diffraction, Auger electron spectroscopy, X-ray photoelectron spectroscopy and line of sight mass spectrometry have been used to study the adsorption and desorption of dimethyldisulfide (DMDS) on Au(111). At 300 K adsorption is dissociative, forming a chemisorbed adlayer of methylthiolate with a 1/3 ML, (sq rt 3 x sq rt 3)R30 degrees, structure. At 100 K adsorption is molecular, with dissociation to form the 1/3 ML (sq rt 3 x sq rt 3)R30 degrees methylthiolate structure occurring at 138-160 K. A physisorbed DMDS layer, with a coverage of 1/6 ML of DMDS, forms on top of the (sq rt 3 x sq rt 3)R30 degrees chemisorbed MT surface for T < or = 180 K, with multilayers forming for T < or = 150 K. In temperature programmed desorption, multilayers of DMDS desorbed with zero order kinetics and an activation energy of 41 kJ mol(-1); the physisorbed layer desorbed with first order kinetics, exhibiting repulsive lateral interactions with an activation energy which varied from 63 kJ mol(-1) (theta = 0) to 51 kJ mol(-1) (theta = 1); the chemisorbed methylthiolate layer desorbed associatively as DMDS via the physisorbed layer, the activation energy for the reaction, 2 methylthiolate --> physisorbed DMDS, exhibiting repulsive lateral interactions with an activation energy which varied from 65 kJ mol(-1) (theta = 0) to 61 kJ mol(-1) (theta = 1). The physisorbed disulfide layer explains the pre-cursor state adsorption kinetics observed in sticking probability measurement, while its relatively facile formation provides a mechanism by which thiolate self-assembled monolayers can become mobile at room temperature.

Do physician recommendations for colorectal cancer screening differ by patient age?

Colorectal cancer screening is underutilized, resulting in preventable morbidity and mortality. In the present study, age-related and other disparities associated with physicians' delivery of colorectal cancer screening recommendations were examined. The present cross-sectional study included 43 physicians and 618 of their patients, aged 50 to 80 years, without past or present colorectal cancer. Of the 285 screen-eligible patients, 45% received a recommendation. Multivariate analyses revealed that, compared with younger nondepressed patients, older depressed patients were less likely to receive fecal occult blood test recommendations, compared with no recommendation (OR=0.31, 95% CI 0.09 to 1.02), as well as less likely to receive colonoscopy recommendations, compared with no recommendation (OR=0.14; 95% CI 0.03 to 0.66). Comorbidity and marital status were associated with delivery of fecal occult blood test and colonoscopy recommendations, respectively, compared with no recommendation. In summary, patient age and other characteristics appeared to influence physicians' delivery of colorectal cancer screening and choice of modality.

Colorectal cancer screening: physicians' knowledge of risk assessment and guidelines, practice, and description of barriers and facilitators.

BACKGROUND: Physician nonadherence to colorectal cancer (CRC) screening recommendations contributes to underuse of screening. OBJECTIVE: To assess physicians' knowledge of CRC screening guidelines for average-risk individuals, perceived barriers to screening and practice behaviours. METHODS: Between October 2004 and March 2005, staff physicians working in three university-affiliated hospitals in Montreal, Quebec, were surveyed. Self-administered questionnaires assessed knowledge of risk classification and current guidelines for average-risk individuals, as well as perceptions of barriers to screening and practice behaviours. RESULTS: All 65 invited physicians participated in the survey, including 46 (70.8%) family medicine physicians and 19 (29.2%) general internists. Most physicians knew that screening should begin at 50 years of age, all knew to screen men and women and 92% said they screened average-risk patients. Fifty-seven (87.7%) physicians correctly identified three common characteristics associated with high risk for developing CRC. Physicians who screened average-risk patients preferred fecal occult blood testing (88.3%) and colonoscopy (88.3%) to flexible sigmoidoscopy (10.0%) and double-contrast barium enema (30.0%). Most physicians knew the correct screening periodicity for fecal occult blood testing (87.6%), but only 40% or fewer could identify correct screening periodicities for the other modalities. Barriers and facilitators focused on health care delivery system improvements, better evidence on which to base recommendations and development of practical screening modalities. CONCLUSIONS: Physicians lacked knowledge of the recommended screening modalities and periodicities to appropriately screen average-risk individuals. Because CRC screening can reduce mortality, efforts to improve physician delivery should focus on physician knowledge and changes to the health care delivery system.

Direct observation of thiolate displacement reactions on Au(111): the role of physisorbed disulfides.

Line-of-sight mass spectroscopy (LOSMS) has been used to study the displacement reaction of ( radical3x radical3)R30 degrees methylthiolate on Au(111) by butylthiolate. The reaction was carried out at room temperature and constant saturation coverage, by exposing the methylthiolate-covered surface to dibutyl disulfide gas. The adsorbed methylthiolate was desorbed as dimethyl disulfide and the cross product methylbutyl disulfide, both identified by LOSMS. This shows that reaction occurs between adsorbed thiolates of different chain length at room temperature, while the kinetics indicate that a rapid equilibrium is established between immobile, chemisorbed thiolates, and highly mobile, physisorbed disulfides.