The unexpected narrowness of eccentric debris rings: a sign of eccentricity during the protoplanetary disc phase

This paper shows that the eccentric debris rings seen around the stars Fomalhaut and HD 202628 are narrower than expected in the standard eccentric planet perturbation scenario (sometimes referred to as 'pericentre glow'). The standard scenario posits an initially circular and narrow belt of planetesimals at semi-major axis a, whose eccentricity is increased to e _f after the gas disc has dispersed by secular perturbations from an eccentric planet, resulting in a belt of width 2ae _f . In a minor modification of this scenario, narrower belts can arise if the planetesimals are initially eccentric, which could result from earlier planet perturbations during the gas-rich protoplanetary disc phase. However, a primordial eccentricity could alternatively be caused by instabilities that increase the disc eccentricity, without the need for any planets. Whether these scenarios produce detectable eccentric rings within protoplanetary discs is unclear, but they nevertheless predict that narrow eccentric planetesimal rings should exist before the gas in protoplanetary discs is dispersed. PDS 70 is noted as a system hosting an asymmetric protoplanetary disc that may be a progenitor of eccentric debris ring systems.

Inactivation of the bacterial pathogens Staphylococcus pseudintermedius and Acinetobacter baumannii by butanoic acid

AIMS

This study was performed to evaluate the efficacy of butanoic acid against bacterial pathogens including Acinetobacter baumannii and Staphylococcus pseudintermedius.

METHODS AND RESULTS

Vegetative bacteria were exposed to butanoic acid in vitro and log reduction was quantified using viable count assays. The maximum (8 and 9) log inactivation was determined by qualitatively assaying for growth/no-growth after a 48-h incubation (37°C). Membrane integrity after exposure to butanoic acid was determined by propidium iodide staining, scanning electron microscopy, membrane depolarization and inductively coupled plasma analysis. Cytosolic pH was measured by 5-(6-)carboxyfluorescein succinimidyl ester.

CONCLUSIONS

Inhibitory concentrations of butanoic acid ranged between 11 and 21 mmol l^-1 for Gram-positive and Gram-negative species tested. The maximum log reduction of A. baumannii was achieved with a 10-s exposure of 0·50 mol l^-1 of butanoic acid. Staphylococcus pseudintermedius required 0·40 mol l^-1 of butanoic acid to achieve the same level of reduction in the same time period. Inactivation was associated with membrane permeability and acidification of the cytosol.

SIGNIFICANCE AND IMPACT OF THE STUDY

Antibiotic resistance among bacterial pathogens necessitates the utilization of novel therapeutics for disinfection and biological control. These results may facilitate the development of butanoic acid as an effective agent against a broad-spectrum of antibiotic-resistant bacterial pathogens.

The transiting dust clumps in the evolved disc of the Sun-like UXor RZ Psc

RZ Psc is a young Sun-like star, long associated with the UXor class of variable stars, which is partially or wholly dimmed by dust clumps several times each year. The system has a bright and variable infrared excess, which has been interpreted as evidence that the dimming events are the passage of asteroidal fragments in front of the host star. Here, we present a decade of optical photometry of RZ Psc and take a critical look at the asteroid belt interpretation. We show that the distribution of light curve gradients is non-uniform for deep events, which we interpret as possible evidence for an asteroidal fragment-like clump structure. However, the clumps are very likely seen above a high optical depth midplane, so the disc's bulk clumpiness is not revealed. While circumstantial evidence suggests an asteroid belt is more plausible than a gas-rich transition disc, the evolutionary status remains uncertain. We suggest that the rarity of Sun-like stars showing disc-related variability may arise because (i) any accretion streams are transparent and/or (ii) turbulence above the inner rim is normally shadowed by a flared outer disc.

A prospective study of bile leaks after laparoscopic cholecystectomy

Since laparoscopic cholecystectomy rapidly became the gold standard, there is an increased morbidity of 1% to 3% for clinically significant bile leaks with this procedure, as compared with open cholecystectomy (<1%). The identification of subclinical bile leaks using cholescintigraphy occurs in the range from 31.4% to 40% after elective open cholecystectomy. At this writing, no studies exist that document the rate of subclinical bile leaks after elective laparoscopic cholecystectomy. In this study, 71 patients were evaluated using cholescintigraphy after elective laparoscopic cholecystectomy. This study represents the first prospective look at the rate of subclinical bile leaks after laparoscopic cholecystectomy in elective cases, and the findings show an overall incidence of 7.3%, as compared with historical reports of 30% to 44% for open cholecystectomy.

Paraduodenal hernia: a report of two cases

Paraduodenal hernias are uncommon congenital herniations into the mesentery of the colon that present as small bowel obstruction. The diagnosis is elusive but may be made by CT scan or upper gastrointestinal series. There are three types: left, right, and transverse. The repair involves reduction of the hernia and closure of the mesenteric defect in accordance with the anatomy of the hernia. We present two cases of paraduodenal hernia that are representative of this unusual class of internal herniation.

Diagnosis of CMT1A duplications and HNPP deletions by interphase FISH: implications for testing in the cytogenetics laboratory

Charcot-Marie-Tooth (CMT) disease type 1A is an inherited peripheral neuropathy characterized by slowly progressive distal muscle wasting and weakness, decreased nerve conduction velocities, and genetic linkage to 17p12. Most (> 98%) CMT1A cases are caused by a DNA duplication of a 1.5-Mb region in 17p12 containing the PMP22 gene. The reciprocal product of the CMT1A duplication is a 1.5-Mb deletion which causes hereditary neuropathy with liability to pressure palsies (HNPP). The most informative current diagnostic testing requires pulsed-field gel electrophoresis to detect DNA rearrangement-specific junction fragments. We investigated the use of interphase FISH for the detection of duplications and deletions for these disorders in the clinical molecular cytogenetics laboratory. Established cell lines or blood specimens from 23 individuals with known molecular diagnoses and 10 controls were obtained and scored using a two-color FISH assay. At least 70% of CMT1A cells displayed three signals consistent with duplications. Using this minimum expected percentile to make a CMT1A duplication diagnosis, all patients with CMT1A showed a range of 71-92% of cells displaying at least three signals. Of the HNPP cases, 88% of cells displayed only one hybridization signal, consistent with deletions. The PMP22 locus from normal control individuals displayed a duplication pattern in approximately 9% of cells, interpreted as replication of this locus. The percentage of cells showing replication was significantly lower than in those cells displaying true duplications. We conclude that FISH can be reliably used to diagnose CMT1A and HNPP in the clinical cytogenetics laboratory and to readily distinguish the DNA rearrangements associated with these disorders from individuals without duplication or deletion of the PMP22 locus.

Natural-Image Discrimination in the Periphery: The Importance of Phase and Amplitude Information

Previous studies with simplified stimuli such as combinations of sinusoidal gratings have revealed phase identification losses in the periphery that are not eliminated by a scaling factor. How do these phase processing problems influence our ability to discriminate natural images in the periphery?

In this study the ability of an observer to identify the ‘odd-image-out’ when there is either an amplitude-only, phase-only, or amplitude and phase change in one out of three stimuli is compared. Pairs of Fourier-manipulated black-and-white digitised photographs of natural images were used and phase and amplitude spectral exchanges of varying proportions were made between two different images. Measurements were made to determine the smallest phase change needed in order for the observer to reliably discriminate the manipulated image, compared to two reference stimuli, at eccentricities of 0°, 2.5°, 5°, and 10°. This was compared to discrimination thresholds found when amplitude and phase, and amplitude alone were exchanged.

The ability to discriminate images on the basis of phase information alone did fall off quickly with eccentricity (comparable to phase and amplitude discriminations). However, there was a much more rapid decline in amplitude-only discrimination. It appears that phase information in natural scenes remains a relatively more important visual cue in the periphery than amplitude.

Use of expanded polytetrafluoroethylene in the repair of the difficult hernia

Hernias that are not correctable by primary approximation require a prosthetic material to provide a tension-free repair. We report the results of 121 consecutive ventral (40) and inguinal (81) herniorrhaphies in 112 patients using the 2.0-mm expanded polytetrafluoroethylene (ePTFE) soft tissue patch. All follow-up was conducted by physical examination by the surgical team. Average follow-up was 49 months. Five patients (4%) experienced complications: there was 1 inguinal recurrence, 1 ventral recurrence, 1 seroma, 1 wound infection, and 1 prolonged gastrocutaneous fistula. The cause of one of the recurrences is unknown because the patient refused further surgery. The seroma resolved spontaneously after two aspirations. The remaining three complications were considered to be unrelated to the implantation of the prosthetic patch. There were no complications due to adhesions, bowel erosion, or bowel obstruction in the ventral repairs. On the basis of our clinical experience, we believe that ePTFE is an acceptable mode of treatment for all difficult hernias.