Artificial neural network discovery of a switchable metasurface reflector.

Optical materials engineered to dynamically and selectively manipulate electromagnetic waves are essential to the future of modern optical systems. In this paper, we simulate various metasurface configurations consisting of periodic 1D bars or 2D pillars made of the ternary phase change material Ge2Sb2Te5 (GST). Dynamic switching behavior in reflectance is exploited due to a drastic refractive index change between the crystalline and amorphous states of GST. Selectivity in the reflection and transmission spectra is manipulated by tailoring the geometrical parameters of the metasurface. Due to the immense number of possible metasurface configurations, we train deep neural networks capable of exploring all possible designs within the working parameter space. The data requirements, predictive accuracy, and robustness of these neural networks are benchmarked against a ground truth by varying quality and quantity of training data. After ensuring trustworthy neural network advisory, we identify and validate optimal GST metasurface configurations best suited as dynamic switchable mirrors depending on selected light and manufacturing constraints.

Effects of clarithromycin, azithromycin and rifampicin on terbutaline-induced sweating in foals.

BACKGROUND: Erythromycin (ERY) induces anhidrosis in foals. Azithromycin (AZI) and clarithromycin (CLA), often combined with rifampicin (RIF), are commonly used to treat Rhodococcus equi infections, but effects on sweating have not been investigated. OBJECTIVE: To determine the effects of AZI, CLA and RIF on sweat responses in normal foals. STUDY DESIGN: Each experiment was a blinded, duplicated, six foal × three period counterbalanced within subjects design (12 foals/experiment). METHODS: Antimicrobials were given orally for 5 days. In Experiment 1, ERY, AZI and CLA were given. In Experiment 2, ERY, RIF and ERY/RIF combination were used. Quantitative intradermal terbutaline sweat tests were performed daily for 3 days before and 1, 2, 5, 9, 24, and 39 days after treatment. Data were analysed by repeated measures analysis of variance procedures. Significance was P≤0.05. RESULTS: In Experiment 1, all macrolides suppressed sweating although CLA and AZI were less potent than ERY. In Experiment 2, significant sweat suppression occurred in foals given ERY with or without RIF, but there was no effect of RIF alone. Rifampicin reduced sweat suppression by ERY on Day 1 of treatment but not thereafter. MAIN LIMITATIONS: Because ERY blood concentrations were not measured, effects of RIF on ERY-induced anhidrosis could not definitively be ascribed to altered ERY bioavailability. CONCLUSIONS: All macrolides commonly used to treat R. equi pneumonia, i.e. ERY, AZI and CLA, induce anhidrosis in foals. The potent anti-sudorific effect of ERY is delayed, but not substantially affected by concurrent RIF administration.

The use of the Podotrack in forensic podiatry for collection and analysis of bare footprints using the Reel method of measurement.

This small-scale study examined the role that bare footprint collection and measurement processes have on the Reel method of measurement in forensic podiatry and its use in the Criminal Justice System. Previous research indicated that the Reel method was a valid and reliable measurement system for bare footprint analysis but various collection systems have been used to collect footprint data and both manual and digital measurement processes were utilized in forensic podiatry and other disciplines. This study contributes to the debate about collecting bare footprints; the techniques employed to quantify various Reel measurements and considered whether there was asymmetry between feet and footprints of the same person. An inductive, quantitative paradigm used the Podotrack gathering procedure for footprint collection and the subsequent dynamic footprints subjected to Adobe Photoshop techniques of calculating the Reel linear variables. Statistical analyses using paired-sample t tests were conducted to test hypotheses and compare data sets. Standard error of mean (SEM) showed variation between feet and the findings provide support for the Reel study and measurement method.

Macrolide-induced hyperthermia in foals: Role of impaired sweat responses.

REASONS FOR PERFORMING STUDY: The mechanism of hyperthermia, a potentially fatal adverse effect of erythromycin treatment of foals, is unknown. OBJECTIVES: To determine the cause of erythromycin-associated hyperthermia. It was hypothesised that the normal sweat response of foals is impaired by treatment with erythromycin. STUDY DESIGN: Blinded, crossover study in 10 healthy pony foals. METHODS: Foals kept in stalls were given either erythromycin (25 mg/kg bwt orally, 3 times daily) or control for 10 days then turned out for a further 10 days. Quantitative intradermal terbutaline sweat tests were performed on Days 1 (baseline), 3, 10 and 20. The effects on terbutaline-induced sweating of erythromycin, terbutaline concentration and treatment day were analysed by repeated-measures ANOVA with Bonferroni-corrected pairwise post hoc comparisons. Peak temperatures were compared by Wilcoxon's signed rank test and proportions by McNemar's related samples test. Significance was set at P<0.05. RESULTS: There were significant 2-factor interactions for treatment × terbutaline after baseline, treatment × day at every terbutaline concentration, and day × terbutaline for erythromycin (P<0.001) but not control (P = 0.9) treatment. Sweating was significantly reduced from baseline in erythromycin-treated foals at all subsequent days. Erythromycin-treated foals produced less sweat at all time-points than did control-treated foals (P<0.05). Peak rectal temperatures of erythromycin-treated foals were significantly higher (P = 0.02) than those of controls. During the first 3 days outside more erythromycin-treated than control-treated foals required treatment for hyperthermia (6 vs. 0; P = 0.03). CONCLUSIONS: We believe drug-induced anhidrosis is the likely cause of hyperthermia in some foals treated with erythromycin.

Consensus guidelines for the investigation and management of encephalitis in adults and children in Australia and New Zealand.

Encephalitis is a complex neurological syndrome caused by inflammation of the brain parenchyma. The management of encephalitis is challenging because: the differential diagnosis of encephalopathy is broad; there is often rapid disease progression; it often requires intensive supportive management; and there are many aetiologic agents for which there is no definitive treatment. Patients with possible meningoencephalitis are often encountered in the emergency care environment where clinicians must consider differential diagnoses, perform appropriate investigations and initiate empiric antimicrobials. For patients who require admission to hospital and in whom encephalitis is likely, a staged approach to investigation and management is preferred with the potential involvement of multiple medical specialties. Key considerations in the investigation and management of patients with encephalitis addressed in this guideline include: Which first-line investigations should be performed?; Which aetiologies should be considered possible based on clinical features, risk factors and radiological features?; What tests should be arranged in order to diagnose the common causes of encephalitis?; When to consider empiric antimicrobials and immune modulatory therapies?; and What is the role of brain biopsy?

Systemic, renal, and colonic effects of intravenous and enteral rehydration in horses.

BACKGROUND: Intravenous (IV) and intragastric (IG) administration of fluid therapy are commonly used in equine practice, but there are limited data on the systemic, renal, and enteric effects. HYPOTHESIS: IV fluid administration will increase intestinal and fecal hydration in a rate-dependent manner after hypertonic dehydration, but will be associated with significant urinary water and electrolyte loss. Equivalent volumes of IG plain water will result in comparatively greater intestinal hydration with less renal loss. ANIMALS: Six Thoroughbred geldings. METHODS: Experimental study. 6 by 6 Latin square design investigating constant rate IV administration at 50, 100, and 150 mL/kg/d over 24 hours in horses dehydrated by water deprivation. Equivalent volumes of IG plain water were administered by 4 bolus doses over 24 hours. RESULTS: Water deprivation resulted in a significant decrease in the percentage of fecal water, and increases in serum and urine osmolality. IV fluids administered at 100 and 150 mL/kg/d restored fecal hydration, but increasing the rate from 100 to 150 mL/kg/d did not confer any additional intestinal benefit, but did result in significantly greater urine production and sodium loss. Equivalent 24-hour volumes of plain water resulted in greater intestinal water and less urine output. CONCLUSIONS AND CLINICAL IMPORTANCE: IV polyionic isotonic fluids can be used to hydrate intestinal contents in situations where enteral fluids are impractical. IV fluids administered at three times maintenance are no more efficacious and might be associated with adverse physiological findings after withdrawal. Bolus dosing of IG water can be used to restore intestinal water with minimal adverse effects.

The relationship between relapse, impairment and disability in multiple sclerosis.

OBJECTIVE: To describe the spatial relationship between relapse and disability in multiple sclerosis (MS). METHODS: 141 relapse onset MS patients were studied. For each patient an examination was performed and a relapse history obtained. Multivariate logistic regression examined whether there was an association between localizing clinical signs and a history of relevant relapse in order to explore the spatial relationship between relapse and subsequent disability. RESULTS: The presence of impaired vision or sensation was independently associated with a history of one or more anatomically related relapses. The presence of weakness or cerebellar ataxia in a limb was not associated with a single relevant relapse but was associated with multiple relevant relapses. A history of multiple episodes of weakness or ataxia in the same limb was uncommon. CONCLUSIONS: Our data suggest that motor pathways are relatively resistant to chronic impairment from acute relapse, whereas afferent pathways are more susceptible. This, in combination with prominent usage of the Expanded Disability Status Scale, which is dependent on mobility and motor function at higher scores, may explain the paradox between natural history studies that suggest relapses are irrelevant to long-term disability and shorter studies at lower disability levels suggesting relapses are responsible for disability accumulation.

The efficiency of an air filtration system in the hospital ward.

A study was conducted to ascertain the efficiency and effectiveness of an air filtration system (Electromedia Model 100C, Clean Air UK, UK) in the hospital ward. The sampling was conducted using a portable Surface Air Sampler (Cherwell Laboratories, Bicester, UK) in conjunction with settle plates. Samples were taken two days before and two days following activation of the filtration system and results compared. A clear, demonstrable, statistically significant reduction in microbial organisms following the activation of the filtration systems is evident (81% settle plates; 24% Surface Air Sampler). This study has implications for the improved health and welfare of patients and healthcare workers who may benefit through the implementation of such a system.

Pits and fissures: relative space contribution in fissures from sealants, prophylaxis pastes and organic remnants.

BACKGROUND: Previous studies by the authors have looked at the nature of the fissure system of human permanent molars and premolars, and has provided evidence for the presence of a prismless layer of enamel. It was noted during these studies that the fissure spaces were often occupied by material other than the fissure sealant. The aim of this study was to define these materials and to look at the percentage contribution of each to the sealed fissure space. METHODS: A sample of teeth, both molars and premolars, were sealed with an unfilled fissure sealant after prophylaxis with a coloured prophylaxis paste. In one group, the crown of the tooth was removed by dissolution in hydrochloric acid following placement of the sealant. This revealed a negative image of the fissure system and its contents. The second group of teeth was sectioned following sealing, and the contents of the fissure space were analyzed. RESULTS: The negative image of the fissure system displayed the fissure contents by colour and the sectioned teeth were able to be computer analyzed to establish the relative contribution of sealant, prophylaxis paste and organic material to the fissure space. CONCLUSIONS: Sealant contribution was in the range of 14-96 per cent, prophylaxis paste from 0-50 per cent and organic remnants 0-55 per cent. The presence of these last two components could contribute to sealant loss.

Effect of GastroGard and three compounded oral omeprazole preparations on 24 h intragastric pH in gastrically cannulated mature horses.

REASONS FOR PERFORMING STUDY: Ulceration of the squamous gastric mucosa is commonly associated with intensive training programmes in horses, but only one compound ('Gastrogard') has been subjected to controlled scrutiny as to therapeutic efficacy. OBJECTIVES: To compare the gastric acid inhibitory efficacy of one manufactured ('GastroGard') and 3 generic pharmacy-compounded preparations of the proton pump inhibitor omeprazole (OME) in the mature horse. HYPOTHESIS: All OME preparations tested would induce a clinically acceptable effect. METHODS: Six healthy mature gastrically cannulated horses of various breeds, 3 mares and 3 geldings, were used. Each product was administered per os once daily (0730 h) at an equivalent dose of 4 mg OME/kg bwt, in a randomised complete repeated measures design for sequence of individual preparation treatment per horse. There was a minimum of 14 days between treatment regimens. A portable unit that recorded pH continuously was attached to a recording electrode fixed within the gastric lumen via the gastric cannula. Three 24 h recordings were made one day before and during Days 2 and 7 after commencement of a 7 day treatment with each of the 4 individual preparations. The horses were fed as usual throughout the study. RESULTS: Only the GastroGard and one other preparation induced a significant increase over baseline in mean percentage of time that the pH was > 4.0 and mean median intragastric pH, during the first 14 and 12 h post treatment respectively, for both Days 2 and 7 post treatment. Both these products had a vehicle pH > 8.0, in contrast to the 2 less effective products, where the vehicle pH was < 6.0. CONCLUSIONS: OME at 4 mg/kg per os s.i.d. can effectively maintain intragastric pH at an accepted anti-ulcerogenic level for at least 12 h post administration in mature horses. In contrast to GastroGard, it should not be expected that all compounded preparations of OME are equally effective in achieving this performance. It appears that vehicle pH might play an important part in determining preparation efficacy. POTENTIAL RELEVANCE: Optimal timing for daily dosing of athletic horses with an effective OME preparation, in order to suppress gastric squamous ulceration, might be 4-8 h prior to a training session.

Pits and fissures: etch resistance in prismless enamel walls.

BACKGROUND: In a previous study to examine the nature of etching on the walls of fissures, there was a consistent result of resistance to deep etching on parts of the walls and a zone of lesser etching on part of the walls as evidenced by the uptake of stain. The staining had been used to examine the nature of the etch pattern. The aims of this study were to define the nature of this etch resistant area. METHODS: A sample of 55 teeth, both molars and premolars, were divided into three groups. In the first group the wetting of fissures by the etchant was examined; the second group tested for the effects of pellicle-cuticle-debris or air entrapment on the etching process. The final group looked at alternative mechanical treatments of the fissure prior to etching. RESULTS: The specimens split along the fissures showed clearly that the etch resistant zone was not due to lack of contact with the etchant or the presence of a pellicle-cuticle-debris covering, but to the presence of a prismless enamel structure. This study showed that this zone inhibited tag development on the fissure walls. CONCLUSIONS: The mechanical removal of this prismless layer of enamel within the fissure system should result in an improved bonding of a fissure sealant through better tag development, in turn leading to a reduction in the failure rate of a sealant used to prevent caries.

Endemic melioidosis in tropical northern Australia: a 10-year prospective study and review of the literature.

In a prospective study of melioidosis in northern Australia, 252 cases were found over 10 years. Of these, 46% were bacteremic, and 49 (19%) patients died. Despite administration of ceftazidime or carbapenems, mortality was 86% (43 of 50 patients) among those with septic shock. Pneumonia accounted for 127 presentations (50%) and genitourinary infections for 37 (15%), with 35 men (18%) having prostatic abscesses. Other presentations included skin abscesses (32 patients; 13%), osteomyelitis and/or septic arthritis (9; 4%), soft tissue abscesses (10; 4%), and encephalomyelitis (10; 4%). Risk factors included diabetes (37%), excessive alcohol intake (39%), chronic lung disease (27%), chronic renal disease (10%), and consumption of kava (8%). Only 1 death occurred among the 51 patients (20%) with no risk factors (relative risk, 0.08; 95% confidence interval, 0.01-0.58). Intensive therapy with ceftazidime or carbapenems, followed by at least 3 months of eradication therapy with trimethoprim-sulfamethoxazole, was associated with decreased mortality. Strategies are needed to decrease the high mortality with melioidosis septic shock. Preliminary data on granulocyte colony-stimulating factor therapy are very encouraging.

Effect of pyloric blockade and infusion of histamine or pentagastrin on gastric secretion in horses.

OBJECTIVE: To determine the origin of the nonacid (nonparietal) component of gastric secretions in horses induced by pentagastrin infusion. ANIMALS: 6 horses. PROCEDURE: A Latin square design was used, involving 6 horses, 3 treatments, and 2 duodenal intubation conditions (catheter with balloon to obstruct pylorus [B] or without balloon allowing movement of contents between stomach and duodenum [NB]). Each horse had an indwelling gastric cannula and a catheter positioned in the duodenum. Gastric and duodenal contents were collected during 15-minute periods. Each experiment consisted of serial collection periods: baseline; infusion of pyrilamine maleate (1 mg/kg of body weight, IV); not treated; and IV infusion of saline (0.9% NaCl) solution alone, saline solution containing pentagastrin (6 microg/kg x h), or saline solution containing histamine (30 microg/kg x h). Volume of samples was recorded, and electrolyte concentrations were measured. RESULTS: Pentagastrin and histamine stimulated maximal acid output; however, during NB conditions, pentagastrin-induced concentration of hydrogen ions was significantly less than during histamine or pentagastrin infusions during B conditions. The large volume produced in response to pentagastrin during NB conditions was accompanied by increased sodium ion output that was greater than for pentagastrin during B conditions, but both values were significantly greater than values for histamine during B or NB conditions. CONCLUSIONS AND CLINICAL RELEVANCE: Nonparietal secretions collected during IV infusion of pentagastrin are duodenal in origin. Reflux of duodenal contents into the stomach of horses is enhanced by pentagastrin. Flow of duodenal contents into the stomach could have implications in the pathogenesis of ulcers in horses.

The epidemiology of melioidosis in Australia and Papua New Guinea.

Melioidosis was first described in Australia in an outbreak in sheep in 1949 in north Queensland (22 degrees S). Human melioidosis was first described from Townsville (19 degrees S) in 1950. Melioidosis is hyperendemic in the Top End of the Northern Territory (NT) and as in parts of northeastern Thailand it is the commonest cause of fatal community-acquired septicemic pneumonia. In the 9 years since 1989 the prospective NT melioidosis study at Royal Darwin Hospital (12 degrees S) has documented 206 culture confirmed cases of melioidosis, with an average annual incidence of 16.5/100,000. Melioidosis is also seen in the north of Western Australia and north Queensland, including the Torres Strait Islands, but is uncommon in adjacent Papua New Guinea. Serological studies suggest that infection is rare in the Port Moresby region, but there is emerging evidence of melioidosis from Western Province. The NT study has documented inoculating events in 52 (25%) of cases, with an incubation period of 1-21 days (mean 9 days); 84% of cases had acute disease from presumed recent acquisition and 13% had chronic disease (sick, > 2 months). In 4% there was evidence of possible reactivation from a latent focus; 28 of 153 (18%) males had prostatic abscesses. The overall mortality was 21% (43 cases), with a mortality rate in septicemic cases (95) of 39% and in non-septicemic cases (103) of 4%. Pneumonia was the commonest presentation in both groups and, in addition, eight patients (two deaths) presented with melioidosis encephalomyelitis. Melioidosis clusters in temperate Australia are attributed to animals imported from the north. Molecular typing of Burkholderia pseudomallei isolates from temperate southwest Western Australia showed clonality over 25 years. In this outbreak and in studies from the NT, some soil isolates are molecularly identical to epidemiologically related animal and human isolates. Molecular typing has implicated the water supply in two clonal outbreaks in remote aboriginal communities in northern Australia. Further prospective collaborative studies are required to evaluate whether there are truly regional differences in clinical features of melioidosis and to better understand how B. pseudomallei is acquired from the environment.

Neurological melioidosis.

Neurological abnormalities have long been recognised in animals with melioidosis, including laboratory rodents and sheep in the first Australian outbreak in 1949. Autopsies in animals have shown microabscesses and lymphocytic infiltration to be present on occasion in the same animal, but Burkholderia pseudomallei is usually able to be grown from central nervous system (CNS) tissue. In humans CNS melioidosis is unusual, but both macroscopic brain abscesses and encephalitis occur. There has been a recently recognised syndrome of meningoencephalitis with varying involvement of brainstem, cerebellum and spinal cord. The prospective melioidosis study at Royal Darwin Hospital has documented 12 cases of CNS melioidosis over 9 years out of a total of 232 cases of melioidosis (5%). Prominent features on presentation were unilateral limb weakness (6), predominant cerebellar signs (2), mixed cerebellar and brainstem features with peripheral weakness (2) and flaccid paraparesis (2). Eight patients had unilateral VIIth nerve palsy and six bulbar palsy, with five requiring prolonged ventilation. Brain CT scans are usually normal initially, but MRI shows dramatic changes. Three patients died and only three made a full recovery. In two patients with predominant mononuclear CSF pleocytosis, B. pseudomallei was cultured from CSF and autopsy in one of these showed necrotising encephalitis with microabscesses. Although it has been postulated that a neurotropic exotoxin may account for melioidosis encephalomyelitis, the recent findings and comparison with the animal data suggest that direct organism spread within the CNS may be primarily responsible. Preliminary molecular typing of isolates shows no evidence of a specific strain of B. pseudomallei responsible for CNS melioidosis end further studies are required to determine if the apparent higher rate of CNS disease in Australia is due to true regional differences or is from increased ascertainment.

Comparison of the antisecretory effects of omeprazole when administered intravenously, as acid-stable granules and as an oral paste in horses.

The antisecretory activity of omeprazole on gastric acid when administered i.v., intragastrically or per os, was evaluated in 2 female and 3 castrated male horses. Each horse had been prepared with a chronic indwelling gastric cannula. A single i.v. administration of omeprazole (1.5 mg/kg bwt) was effective in abolishing basal and pentagastrin (PG)-stimulated acid secretion. Once daily, nasogastric administration of omeprazole in acid-stable granules for 5 days inhibited acid secretion in a dose-dependent manner: 57% (1.5 mg/kg bwt) and 98% (5.0 mg/kg bwt) reduction of PG-stimulated acid secretion. The degree of inhibition was maintained over a 19 day treatment period with once daily dosing. A prototype oral paste formulation containing either acid-stable omeprazole granules or uncoated omeprazole powder was equipotent when compared to a similar dosage of acid-stable omeprazole granules administered by nasogastric tube. A dose-dependent inhibition was seen with the oral paste formulation containing omeprazole powder: 55% (1.5 mg/kg bwt) and 77% (3.0 mg/kg bwt) reduction of PG-stimulated acid secretion after 5 days. Therefore, a paste formulation of omeprazole powder may offer an effective, easily administered, once daily acid inhibitory treatment for gastric ulcer disease in horses.