Simple Wave-Optical Superpositions as Prime Number Sieves.

We encode the sequence of prime numbers into simple superpositions of identical waves, mimicking the archetypal prime number sieve of Eratosthenes. The primes are identified as zeros accompanied by phase singularities in a physically generated wave field for integer valued momenta. Similarly, primes are encoded in the diffraction pattern from a simple single aperture and in the harmonics of a single vibrating resonator. Further, diffraction physics connections to number theory reveal how to encode all Gaussian primes, twin primes, and how to construct wave fields with amplitudes equal to the divisor function at integer spatial frequencies. Remarkably, all of these basic diffraction phenomena reveal that the naturally irregular sequence of primes can arise from trivially ordered wave superpositions.

Robotic vs. laparoscopic ventral mesh rectopexy for external rectal prolapse and rectal intussusception: a systematic review.

BACKGROUND: Laparoscopic ventral mesh rectopexy (LVR) is a treatment with promising results in external rectal prolapse, rectal intussusception, and rectocele. Because of the emergence of robotic-assisted surgery and the technical advantage it provides, we examined the potential role and place of robotic surgery in ventral rectopexy. METHODS: MEDLINE, PubMed, and other databases were searched, by two independent reviewers, to identify studies comparing robotic to laparoscopic ventral mesh rectopexy. The primary outcome was the rate of unplanned conversion to open. The secondary outcomes were morbidity, length of hospital stay and recurrence rate. RESULTS: Five studies (4% male, n = 259) met the inclusion criteria. All 5 studies reported on conversion rate and showed no significant difference between the conversion rate of robotic and laparoscopic groups [OR 0.58 (95% CI 0.09-3.77)]. Robotic surgery was also similar to laparoscopic surgery for both morbidity [OR 0.71 (95% CI 0.34-1.48)] and recurrence rate [OR 0.56 (95% CI 0.18-1.75)]. Operative time was longer in the robotic group with a MWD of 22.88 minutes (CI 5.73-40.04, p < 0.0007). There was a statistically significant reduction in length of stay with robotic surgery [mean difference - 0.36 days (95% CI - 0.66 to - 0.07)]. CONCLUSIONS: This systematic review shows that robotic-assisted ventral rectopexy requires longer operative time with no significant added benefit over laparoscopic ventral rectopexy. The conversion rate was low in both groups and the trends to benefit did not reach statistical significance. More studies are required to clarify whether the potential technical advantage of robotic surgery in ventral rectopexy translates to an improvement in clinical outcome.

Laparoscopic ventral rectopexy for rectal prolapse and rectal intussusception using a biological mesh.

AIM: Laparoscopic ventral rectopexy (LVR) is a nerve-sparing technique for the treatment of rectal prolapse. Concerns about the use of synthetic meshes in the pelvis and the associated risk of erosion have led to the recent use of biological meshes in some colorectal units. This retrospective study aims to assess the outcomes of patients undergoing LVR using a noncross-linked nondermal biological mesh. METHOD: The medical notes of all patients who underwent LVR between 1 December 2011 and 31 May 2014 were reviewed. The rate of obstructed defaecation before surgery was retrospectively determined from medical records using the Rome III criteria. The rates of obstructed defaecation and faecal incontinence following surgery were determined using a self-reported questionnaire. RESULTS: A total of 51 patients had LVR between 1 December 2011 and 31 May 2014. Their mean age was 57.3 ± 2.5 years and the mean follow-up was 23 ± 1 months. There were seven (13.7%) postoperative complications. In total, 45 (88%) patients completed the functional outcome questionnaires. Before surgery, 33 (73.3%) patients complained of symptoms of obstructed defaecation. At the end of follow-up, 22 (48.8%, P = 0.001) patients continued to have some symptoms of obstructed defaecation. Before surgery, 12 (26.7%) patients complained of faecal incontinence. At the end of follow-up, only three (6.7%, P = 0.004) patients reported faecal incontinence. At the end of follow-up, recurrence of symptoms had occurred in six (13.3%) patients. CONCLUSION: LVR using a biological mesh is safe and results in significant reduction in symptoms associated with external rectal prolapse and rectal intussusception.

Effect of specimen orientation on the accuracy of vector field electron tomography.

Vector field electron tomography (VFET) reconstructs vector fields based on phase maps recorded from two or more orthogonal tilt series. The tomographic reconstruction of vector fields involves considerations beyond those involved in the reconstruction of scalar fields. Here we examine the effect of initial magnetization orientation on reconstruction errors. The orientation of a magnetic particle affects the contrast in the phase maps. This, in turn, affects the accuracy of the reconstructed vector fields. We derive expressions that model the dependence of reconstruction errors on initial specimen orientation when using a filtered backprojection algorithm to reconstruct a vector potential from two tilt series. We compare these analytical results with those from numerical simulations. Our results can inform experimental procedures, such as sample preparation techniques and the choice of tilt series orientations. Specimen orientation can be a significant source of error in VFET, and our results can provide the means to minimize these errors.

Impulsivity as a Multifaceted Construct Related to Excessive Drinking Among UK Students.

AIMS: A substantial number of university students exceed alcohol guidelines. Impulsivity has been repeatedly implicated in heavy alcohol use, yet despite knowledge that impulsivity is multifaceted, there have previously been few studies applying multiple measures of self-report and behavioural impulsivity to examine the relationship with excessive student drinking. This results in a limited understanding of the relationship of various facets of impulsivity to student drinking. METHODS: Participants completed a comprehensive battery of impulsivity measures: the Barratt Impulsiveness Scale as a self-report index and the Stop Signal Task, Information Sampling Task and Monetary Choice Questionnaire as behavioural measures of three facets of impulsivity. Participants who exceeded UK drinking guidelines were compared to those who did not on measures of impulsivity. Hierarchical linear regression was then employed to test whether indices of impulsivity were associated with the average units consumed per week. RESULTS: Participants who exceeded UK guidelines reported increased impulsivity in facets of self-report impulsivity. They also displayed performance deficits in normal adjustment of Go responses on the Stop Signal Task. In the regression model, nonplanning impulsivity on the Barratt Impulsiveness Scale was seen to predict quantity of alcohol consumed per month. CONCLUSIONS: The study applies a comprehensive selection of behavioural and self-report measures of impulsivity and indicates that excessive drinkers are more impulsive in some but not all aspects. The results indicate that the wide range of deficits apparent in alcohol-dependent individuals are not evident in this younger, heavy drinking population, but that specific performance and self-identified deficits are already apparent.

Depth and temperature associations of haddock Melanogrammus aeglefinus off southern Newfoundland.

Using data collected as part of offshore surveys conducted during 1972-2013, haddock Melanogrammus aeglefinus association patterns with depth and temperature in southern Newfoundland waters, the northern extremity of the species' range in the western Atlantic Ocean, were quantified. They were typically concentrated in the deep warm waters along the narrow shelf slope in North-west Atlantic Fisheries Organization Divisions 3O and 3P with individuals moving seasonally into the shallow waters of the banks as they warmed. While M. aeglefinus were found over a range of depths and temperatures, they were primarily located at depths deeper and temperatures warmer than the median sampled. Analyses demonstrated that of the two hydrographic variables assessed, temperature was most influential in structuring distribution, with individuals appearing to change depth in order to maintain similar temperature throughout the year. Melanogrammus aeglefinus were found predominantly in temperatures of c. 4-8° C which often represented some of the warmest waters available. Differences in fish-habitat association patterns in relation to sex or maturity status were not readily apparent from the analyses. Warming conditions off Newfoundland and Labrador in recent years might be predicted to improve local M. aeglefinus productivity.

Rapid eye movements to a virtual target are biased by illusory context in the Poggendorff figure.

In order to determine the influence of perceptual input upon oculomotor responses, we examined rapid saccadic eye movements made by healthy human observers to a virtual target defined by the extrapolated intersection of a pointer with a distant landing line. While corresponding perceptual judgments showed no evidence of systematic bias, eye movements showed a strong bias, in the direction of assimilation of the saccade trajectory to the shortest path between the end of the pointer and the landing line. Adding an abutting vertical inducing line to make an angle of 45 deg with the pointer led to a larger bias in the same direction as the classical Poggendorff illusion. This additional Poggendorff effect was similar in direction and magnitude for the eye movements and the perceptual responses. Latency and dynamics of the eye movements were closely similar to those recorded for a control task in which observers made a saccade from the start fixation to an explicit target on the landing line. Further experiments with inducing lines presented briefly at various times during the saccade latency period showed that the magnitude of the saccade bias was affected by inducer presentation during the saccade planning process, but not during the saccade itself. We conclude that the neural mechanisms for extrapolation can feed into the control of eye movements without obvious penalties in timing and accuracy and that this information can instantaneously modify motor response throughout the planning phase, suggesting close association between perceptual and motor mechanisms in the process of visuo-spatial extrapolation.

High-density aggregations of rodlet cells in the gonads of Greenland halibut Reinhardtius hippoglossoides, a deep-water marine flatfish.

Large aggregations of rodlet cells in the gonads of male and female Greenland halibut Reinhardtius hippoglossoides are reported for the first time. These rodlet cells were not arranged epithelially but rather were found throughout the connective tissue between oocytes (females) or within lymphatic spaces between testicular lobules (males). The reason for large aggregations of rodlet cells in the gonads and not other tissues of this species is uncertain.

A texture-processing model of the 'visual sense of number'.

It has been suggested that numerosity is an elementary quality of perception, similar to colour. If so (and despite considerable investigation), its mechanism remains unknown. Here, we show that observers require on average a massive difference of approximately 40% to detect a change in the number of objects that vary irrelevantly in blur, contrast and spatial separation, and that some naive observers require even more than this. We suggest that relative numerosity is a type of texture discrimination and that a simple model computing the contrast energy at fine spatial scales in the image can perform at least as well as human observers. Like some human observers, this mechanism finds it harder to discriminate relative numerosity in two patterns with different degrees of blur, but it still outpaces the human. We propose energy discrimination as a benchmark model against which more complex models and new data can be tested.

Fate of Salmonella Senftenberg in broiler chickens evaluated by challenge experiments.

Experimental and epidemiological evidence has indicated the respiratory route to be a potential portal of entry for salmonellas in poultry. The purpose of this study was to evaluate and compare the infectivity of Salmonella enterica serovar Senftenberg following oral gavage, intratracheal or intravenous challenge in chickens. Seven-day-old chicks were challenged with either 10(4) or 10(6) colony-forming units of S. Senftenberg per chick by oral gavage, intratracheal or intravenous challenge, respectively, in two independent trials. Chickens were humanely killed 24 h post challenge and S. Senftenberg was cultured and enumerated from caecal contents, caecal tissue-caecal tonsils and liver and spleen. In both trials, intratracheal delivery of S. Senftenberg was the only route that allowed colonization of the caeca of chickens when compared with oral gavage or intravenous challenge in a dose response fashion (P < 0.05). Liver and spleen samples yielded no S. Seftenberg after the lower dose challenge by the oral or intratracheal route and only low levels following the high-dose administration by these routes, whereas intravenous challenge resulted in recovery of the organisms after both doses. The results of the present study suggest that S. Senftenberg entering the blood is likely to be cleared and will not be able to colonize caeca to the same extent as compared with intratracheal challenge. Clarification of the potential importance of the respiratory tract for transmission of salmonellas under field conditions may be of critical importance to develop intervention strategies to reduce the transmission in poultry.

A bias-free measure of retinotopic tilt adaptation.

The traditional method of single stimuli for measuring perceptual illusions and context effects confounds perceptual effects with changes in the observer's decision criterion. By deciding consciously or unconsciously to select one of the two response alternatives more than the other when unsure of the correct response, the observer can shift his or her psychometric function in a manner indistinguishable from a genuine perceptual shift. Here, a spatial two-alternative forced-choice method is described to measure a perceptual aftereffect by its influence on the shape of the psychometric function rather than the mean. The method was tested by measuring the effect of motion adaptation on the apparent Vernier offset of stationary Gabor patterns. The shift due to adaptation was found to be comparable in size to the internal noise, estimated from the slope of the psychometric function. By moving the eyes between adaptation and test, it was determined that adaptation is retinotopic rather than spatiotopic.

Evaluation of germination, distribution, and persistence of Bacillus subtilis spores through the gastrointestinal tract of chickens.

Spores are popular as direct-fed microbials, though little is known about their mode of action. Hence, the first objective of the present study was to evaluate the in vitro germination and growth rate of Bacillus subtilis spores. Approximately 90% of B. subtilis spores germinate within 60 min in the presence of feed in vitro. The second objective was to determine the distribution of these spores throughout different anatomical segments of the gastrointestinal tract (GIT) in a chicken model. For in vivo evaluation of persistence and dissemination, spores were administered to day-of-hatch broiler chicks either as a single gavage dose or constantly in the feed. During 2 independent experiments, chicks were housed in isolation chambers and fed sterile corn-soy-based diets. In these experiments one group of chickens was supplemented with 10(6) spores/g of feed, whereas a second group was gavaged with a single dose of 10(6) spores per chick on day of hatch. In both experiments, crop, ileum, and cecae were sampled from 5 chicks at 24, 48, 72, 96, and 120 h. Viable B. subtilis spores were determined by plate count method after heat treatment (75°C for 10 min). The number of recovered spores was constant through 120 h in each of the enteric regions from chickens receiving spores supplemented in the feed. However, the number of recovered B. subtilis spores was consistently about 10(5) spores per gram of digesta, which is about a 1-log10 reduction of the feed inclusion rate, suggesting approximately a 90% germination rate in the GIT when fed. On the other hand, recovered B. subtilis spores from chicks that received a single gavage dose decreased with time, with only approximately 10(2) spores per gram of sample by 120 h. This confirms that B. subtilis spores are transiently present in the GIT of chickens, but the persistence of vegetative cells is presently unknown. For persistent benefit, continuous administration of effective B. subtilis direct-fed microbials as vegetative cells or spores is advisable.

Evaluation of the respiratory route as a viable portal of entry for Salmonella in poultry via intratracheal challenge of Salmonella Enteritidis and Salmonella Typhimurium.

Experimental and epidemiological evidence suggests that primary infection of Salmonella is by the oral-fecal route for poultry. However, the airborne transmission of Salmonella and similar enteric zoonotic pathogens has been historically neglected. Increasing evidence of Salmonella bioaerosol generation in production facilities and studies suggesting the vulnerabilities of the avian respiratory architecture together have indicated the possibility of the respiratory system being a potential portal of entry for Salmonella in poultry. Presently, we evaluated this hypothesis through intratracheal (IT) administration of Salmonella Enteritidis and Salmonella Typhimurium, as separate challenges, in a total of 4 independent trials, followed by enumeration of cfu recovery in ceca-cecal tonsils and recovery incidence in liver and spleen. In all trials, both Salmonella Enteritidis and Salmonella Typhimurium, challenged IT colonized cecae to a similar or greater extent than oral administration at identical challenge levels. In most trials, chickens cultured for cfu enumeration from IT-challenged chicks at same dose as orally challenged, resulted in an increase of 1.5 log higher Salmonella Enteritidis from ceca-cecal tonsils and a much lower dose IT of Salmonella Enteritidis could colonize ceca to the same extent than a higher oral challenge. This trend of increased cecal colonization due to IT challenge was observed with all trails involving week-old birds (experiment 2 and 3), which are widely considered to be more difficult to infect via the oral route. Liver-spleen incidence data showed 33% of liver and spleen samples to be positive for Salmonella Enteritidis administered IT (10(6) cfu/chick), compared with 0% when administered orally (experiment 2, trial 1). Collectively, these data suggest that the respiratory tract may be a largely overlooked portal of entry for Salmonella infections in chickens.

Electron vortex production and control using aberration induced diffraction catastrophes.

An aberration corrected electron microscope is used to create electron diffraction catastrophes, containing arrays of intensity zeros threading vortex cores. Vortices are ascribed to these arrays using catastrophe theory, scalar diffraction integrals, and experimentally retrieved phase maps. From measured wave function phases, obtained using focal-series phase retrieval, the orbital angular momentum density is mapped for highly astigmatic electron probes. We observe vortex rings and topological reconnections of nodal lines by tracking the vortex cores using the retrieved phases.

Linking hypotheses underlying Class A and Class B methods.

Class A psychophysical observations are based on the linking hypothesis that perceptually distinguishable stimuli must correspond to different brain events. Class B observations are related to the appearance of stimuli not their discriminability. There is no clear linking hypothesis underlying Class B observations, but they are necessary for studying the effects of context on appearance, including a large class of phenomena known as "illusions." Class B observations are necessarily measures of observer bias (Fechner's "constant error") as opposed to Class A measures of sensitivity (Fechner's "variable error"). It is therefore important that Class B observations distinguish between response biases, decisional biases, and perceptual biases. This review argues that the commonly used method of single stimuli fails to do this, and that multiple-alternative forced choice (mAFC) methods can do a better job, particularly if combined with a roving pedestal.

Perceived pattern regularity computed as a summary statistic: implications for camouflage.

Why do the equally spaced dots in figure 1 appear regularly spaced? The answer 'because they are' is naive and ignores the existence of sensory noise, which is known to limit the accuracy of positional localization. Actually, all the dots in figure 1 have been physically perturbed, but in the case of the apparently regular patterns to an extent that is below threshold for reliable detection. Only when retinal pathology causes severe distortions do regular grids appear perturbed. Here, we present evidence that low-level sensory noise does indeed corrupt the encoding of relative spatial position, and limits the accuracy with which observers can detect real distortions. The noise is equivalent to a Gaussian random variable with a standard deviation of approximately 5 per cent of the inter-element spacing. The just-noticeable difference in positional distortion between two patterns is smallest when neither of them is perfectly regular. The computation of variance is statistically inefficient, typically using only five or six of the available dots.

The role of an early Salmonella Typhimurium infection as a predisposing factor for necrotic enteritis in a laboratory challenge model.

Necrotic enteritis (NE) caused by Clostridium perfringens (CP) in poultry is an important bacterial disease in terms of economic implications. The disease is multifactorial and is invariably associated with predisposing factors. In the present experiments, we investigated the potential predisposing role of neonatal Salmonella Typhimurium (ST) infection for NE-associated mortality in a laboratory challenge model. In two experiments, day-of-hatch chicks were randomly assigned to four groups: Group 1, nonchallenged control; Group 2, chickens received Eimeria maxima (EM) and CP; Group 3, chickens received EM and CP and were also challenged with ST at day 1 of age; Group 4, chickens received EM and CP and were also challenged with ST at day 17 of age. Challenged groups received an oral dose of EM at 18 days of age and CP (10(8) colony-forming units/chick) at 22-23 days of age. When compared to EM and CP, chicks challenged with ST (day 1) had increased NE-associated mortality and CP-associated lesion scores (P < 0.05) in both experiments. Furthermore, body weight and body weight gain were lower (P < 0.05) in chicks infected with ST (day 1) in the first experiment, even though no differences (P > 0.05) were observed in weight gain in the second experiment. Chicks challenged with ST (day 17) were similar to the EM and CP group in all of the above-mentioned parameters, indicating that a paratyphoid infection in younger chicks remarkably alters the susceptibility to secondary bacterial infections. Based on this work, the authors suggest that an ST infection early in the age of a chick may be important for altering susceptibility to NE, an observation that may be useful from the perspective of experimental reproduction of this disease and, perhaps, as an economically important reason to address the problem of paratyphoid Salmonella infections in young chicks.

Evaluation of Bacillus species as potential candidates for direct-fed microbials in commercial poultry.

Increasing sociopolitical concerns with antibiotic use have led to investigations of potential alternatives for food safety and growth promotion. Direct-fed microbials (DFM) including spore-based probiotics are amenable to feed inclusion and are extremely stable. We isolated several Bacillus spp. from environmental and poultry sources and tested them for their ability to reduce Salmonella in vitro. In a preliminary in vivo trial, day-of-hatch chicks and poults were randomly assigned to the following treatments (24 birds/treatment): control and one of 8 DFM candidates at 10(6) spores/g of feed. Chicks and poults were tagged, weighed, and orally challenged with Salmonella Typhimurium (ST). Body weight gain and ST recovery were measured 11 d posthatch. Total percentages of ST-positive crop and ceca were significantly lower (P < 0.05) in at least 3 DFM candidates compared with control. Additionally, beneficial effects on BW gain were observed in at least 5 DFM candidates (P < 0.05) compared with control. In a second study, birds treated with NP122 (identified as Bacillus subtilis) had significantly lower (P < 0.05) cecal ST than control and benefitted BW gain irrespective of the presence or absence of a Salmonella challenge. In conclusion, NP122 markedly reduced ST recovery and increased BW gain in both chicks and poults. This provides preliminary evidence that this isolate may have potential use as a DFM in poultry.

Evaluation of selected direct-fed microbial candidates on live performance and Salmonella reduction in commercial turkey brooding houses.

As effective probiotic Bacillus isolates that can increase BW gain (BWG) are identified, they may offer advantages in terms of stability, cost, and feed application over probiotics limited to drinking water application. Additionally, an effective direct-fed microbial (DFM) may offer an effective alternative to antibiotic growth promoters. Previously, 4 Bacillus isolates were identified and evaluated in our laboratory as potential DFM candidates. These isolates were shown to significantly increase BWG as well as reduce recovery of Salmonella after experimental infection. In the first experiment, isolates PHL-MM65 (a Bacillus laterosporus) and PHL-NP122 (a Bacillus subtilis) were evaluated using poults raised under commercial conditions. After 7 d of conventional brooding, poults were tagged, weighed, and placed in 1 of 4 replicate pens for each treatment group [negative control, 0.019% nitarsone, PHL-MM65 (10(6) spores/g of feed), or PHL-NP122 (10(6) spores/g of feed)] within the commercial turkey barn. At 23 d, poults were weighed and BW was calculated. Treatment with PHL-NP122 (853 g) or nitarsone (852 g) increased BW (P ≤ 0.05) compared with control (784 g), whereas treatment with PHL-MM65 (794 g) did not significantly improve BW. Also on d 23 of the trial, ceca were aseptically removed from 10 poults per pen and cultured for recovery of Salmonella. Both Bacillus isolates PHL-NP122 and PHL-MM65 resulted in a significant reduction (P ≤ 0.05) in the frequency of Salmonella by more than 25% compared with the controls. In a second experiment on a different farm, isolates PHL-NP122, PHL-RW33 (a B. subtilis), and PHL-B1 (a Bacillus licheniformis) were evaluated. None of the candidate Bacillus DFM or the group fed nitarsone had significantly different BW or BWG than untreated control. These data suggest that isolate PHL-NP122, when added as a DFM to turkey diets, may increase BW gain as well as nitarsone during the brooding phase of commercial turkey production.