Does Maintenance of Pulmonary Blood Flow Pulsatility at the Time of the Fontan Operation Improve Hemodynamic Outcome in Functionally Univentricular Hearts?

It is unclear whether residual anterograde pulmonary blood flow (APBF) at the time of Fontan is beneficial. Pulsatile pulmonary flow may be important in maintaining a compliant and healthy vascular circuit. We, therefore, wished to ascertain whether there was hemodynamic evidence that residual pulsatile flow at time of Fontan promotes clinical benefit. 106 consecutive children with Fontan completion (1999-2018) were included. Pulmonary artery pulsatility index (PI, (systolic pressure-diastolic pressure)/mean pressure)) was calculated from preoperative cardiac catheterization. Spectral analysis charted PI as a continuum against clinical outcome. The population was subsequently divided into three pulsatility subgroups to facilitate further comparison. Median PI prior to Fontan was 0.236 (range 0-1). 39 had APBF, in whom PI was significantly greater (median: 0.364 vs. 0.177, Mann-Whitney p < 0.0001). There were four early hospital deaths (3.77%), and PI in these patients ranged from 0.214 to 0.423. There was no correlation between PI and standard cardiac surgical outcomes or systemic oxygen saturation at discharge. Median follow-up time was 4.33 years (range 0.0273-19.6), with no late deaths. Increased pulsatility was associated with higher oxygen saturations in the long term, but there was no difference in reported exercise tolerance (Ross), ventricular function, or atrioventricular valve regurgitation at follow-up. PI in those with Fontan-associated complications or the requiring pulmonary vasodilators aligned with the overall population median. Maintenance of pulmonary flow pulsatility did not alter short-term outcomes or long-term prognosis following Fontan although it tended to increase postoperative oxygen saturations, which may be beneficial in later life.

First-order wedge wetting revisited.

We consider a fluid adsorbed in a wedge made from walls that exhibit a first-order wetting transition and revisit the argument as to why and how the pre-filling and pre-wetting coexistence lines merge when the opening angle is increased approaching the planar geometry. We clarify the nature of the possible surface phase diagrams, pointing out the connection with complete pre-wetting, and show that the merging of the coexistence lines lead to new interfacial transitions. These occur along the side walls and are associated with the unbinding of the thin-thick interface, rather than the liquid-gas interface (meniscus), from the wedge apex. When fluctuation effects, together with the influence of dispersion forces are included, these transitions display strong non-universal critical singularities that depend on the opening angle itself. Similar phenomena are also shown to occur for adsorption near an apex tip.

Challenging cognitive cases among physician populations: case vignettes and recommendations.

BACKGROUND: Physicians are not immune to cognitive impairment. Because of the risks created by practising doctors with these issues, some have suggested developing objective, population-specific measures of evaluation and screening guidelines to assess dysfunction. However, there is very little published information from which to construct such resources. AIMS: To highlight the presentation characteristics and provide evaluation recommendations specific to the needs of physicians with actual or presumed cognitive impairment. METHODS: A retrospective database and chart review of cognitively impaired doctors who presented to a physician health programme (PHP). Complex cases were highlighted using simple descriptives and clinical vignettes. RESULTS: A total of 124 cases were included. Clients presented with a variety of issues other than cognitive concerns. We identified four principal domains of impairment: (i) diseases of (or in) the brain (48%); (ii) mood/ anxiety disorders or treatment side effects (28%); (iii) substance use (9%) and (iv) traumatic brain injury (7%). Age was not a good predictor of impairment and brief screening using the Montreal Cognitive Assessment demonstrated a ceiling effect with this cohort. Although many clients underwent some type of professional or personal transition, impairment did not necessarily indicate worse functioning after care. CONCLUSIONS: Physician cognitive evaluations should consider a variety of secondary sources of information, particularly vocational performance reports. It may take time before cognitive impairment can be diagnosed or ruled-out in this population. Prior assumptions, especially for non-cognitive referrals, can lead to inaccurate diagnosis and referrals. PHPs must manage cognitive cases carefully, not only in their clinical complexity but also in their psychosocial aspects.

Capillary contact angle in a completely wet groove.

We consider the phase equilibria of a fluid confined in a deep capillary groove of width L with identical side walls and a bottom made of a different material. All walls are completely wet by the liquid. Using density functional theory and interfacial models, we show that the meniscus separating liquid and gas phases at two phase capillary coexistence meets the bottom capped end of the groove at a capillary contact angle θ(cap)(L) which depends on the difference between the Hamaker constants. If the bottom wall has a weaker wall-fluid attraction than the side walls, then θ(cap) > 0 even though all the isolated walls are themselves completely wet. This alters the capillary condensation transition which is now first order; this would be continuous in a capped capillary made wholly of either type of material. We show that the capillary contact angle θ(cap)(L) vanishes in two limits, corresponding to different capillary wetting transitions. These occur as the width (i) becomes macroscopically large, and (ii) is reduced to a microscopic value determined by the difference in Hamaker constants. This second wetting transition is characterized by large scale fluctuations and essential critical singularities arising from marginal interfacial interactions.

Double outlet right atrium in a dog.

Double outlet right atrium is a rare congenital cardiac abnormality that has been previously reported in humans and cats, but not in dogs. A double outlet right atrium is typically characterized by the presence of a leftward deviation of the interatrial septum and atrial septal defect. Therefore, the right atrium drains into both ventricles. The unique features consistent with double outlet right atrium were identified by transthoracic echocardiography and computed tomography in a puppy. This case report describes the clinical, echocardiographic, and tomographic findings of a five-month-old Cocker Spaniel diagnosed with this rare congenital abnormality.

Capillary emptying and short-range wetting.

We consider a liquid trapped in a narrow horizontal capillary, under the influence of gravity. As the slit is widened, the meniscus, separating the capillary liquid from gas, deforms and develops a long tongue extending along the bottom wall. As a critical slit width is approached, the length of the tongue diverges continuously, leading to the emptying of the capillary. We show that the critical singularities characterizing emptying are the same as those at short-ranged wetting transitions, but at a scale set by the capillary length rather than the bulk correlation length. These meso- or macroscopic versions of both complete and critical wetting are observable in the laboratory and are studied here using a colloid-polymer mixture.

Knowledge and attitudes towards TB among healthcare workers in Yogyakarta, Indonesia.

SETTING: Healthcare workers (HCWs) are at an increased risk of TB worldwide. Individual knowledge and attitudes may influence HCW behaviour, and subsequently, TB risk. Indonesia has the second highest case-load globally. OBJECTIVE: To measure TB knowledge and attitudes among a subsection of HCWs in Yogyakarta, Indonesia, and to explore factors associated with knowledge. DESIGN: A cross-sectional study using an online survey targeting all HCW staff was conducted among HCWs from four pre-selected healthcare facilities in Yogyakarta. Descriptive analysis and a multivariable linear regression were undertaken. RESULTS: Of 792 HCWs, 290 (37%) completed the survey; 64% (n = 185) were medical staff, 33% (n = 95) reported previously being tested for active TB and 8% (n = 24) for latent TB. The mean knowledge score was 7.2/11 (SD 1.5): this was higher among medical staff and those with university education (average score increase: 0.53, 95% CI 0.15 to 0.90; and 0.38, 95% CI 0.01 to 0.74, respectively). Participants agreed that free access to TB screening (93%) and treatment (93%) should be available, and 57% of medical and 77% of non-medical staff would take preventive therapy if eligible. CONCLUSION: Participants had practical understanding of TB; however, gaps were identified in knowledge about TB disease progression and prevention. Prevention programmes were viewed positively. We suggest further TB education and engagement programmes for HCWs.

CONTEXTE: Les travailleurs de la santé (HCW) sont exposés à un risque accru de TB dans le monde entier. Les connaissances et les attitudes individuelles peuvent influencer le comportement des HCW et, par conséquent, le risque de TB. L'Indonésie a le deuxième plus grand nombre de cas dans le monde. OBJECTIF: Mesurer les connaissances et les attitudes à l'égard de la TB parmi un sous-groupe de HCW à Yogyakarta, en Indonésie, et explorer les facteurs associés aux connaissances de la TB. MÉTHODE: Une étude transversale a été menée à l'aide d'un sondage en ligne ciblant tous les HCW de quatre établissements de santé présélectionnés à Yogyakarta. Une analyse descriptive et une régression linéaire multivariable ont été effectuées. RÉSULTATS: Sur 792 HCW, 290 (37%) ont répondu à l'enquête ; 62% (n = 181) étaient des membres du personnel médical, 33% (n = 95) ont déclaré avoir déjà été testés pour la TB active et 8% (n = 24) pour la TB latente. Le score moyen de connaissances était de 7,2/11 (SD 1,5) : il était plus élevé parmi le personnel médical et les personnes ayant une formation universitaire (augmentation moyenne du score : 0,53 ; IC 95% 0,11­0,93 et 0,38 ; IC 95% 0,01­0,74, respectivement). Les participants étaient d'accord pour dire que l'accès au dépistage (93%) et au traitement (93%) de la TB devrait être gratuit, et 57% du personnel médical et 77% du personnel non médical suivraient un traitement préventif s'ils étaient éligibles. CONCLUSION: Les participants avaient une compréhension pratique de la TB ; cependant, des lacunes ont été identifiées dans les connaissances sur la progression de la maladie et la prévention de la TB. Les programmes de prévention ont été perçus positivement. Nous suggérons d'autres programmes d'éducation et d'engagement sur la TB pour les HCW.

Solution self-assembly and adsorption at the air-water interface of the monorhamnose and dirhamnose rhamnolipids and their mixtures.

The self-assembly in solution and adsorption at the air-water interface, measured by small-angle neutron scattering, SANS, and neutron reflectivity, NR, of the monorhamnose and dirhamnose rhamnolipids (R1, R2) and their mixtures, are discussed. The production of the deuterium-labeled rhamnolipids (required for the NR studies) from a Pseudomonas aeruginosa culture and their separation into the pure R1 and R2 components is described. At the air-water interface, R1 and R2 exhibit Langmuir-like adsorption isotherms, with saturated area/molecule values of about 60 and 75 Å(2), respectively. In R1/R2 mixtures, there is a strong partitioning of R1 to the surface and R2 competes less favorably because of the steric or packing constraints of the larger R2 dirhamnose headgroup. In dilute solution (<20 mM), R1 and R2 form small globular micelles, L(1), with aggregation numbers of about 50 and 30, respectively. At higher solution concentrations, R1 has a predominantly planar structure, L(α) (unilamellar, ULV, or bilamellar, BLV, vesicles) whereas R2 remains globular, with an aggregation number that increases with increasing surfactant concentration. For R1/R2 mixtures, solutions rich in R2 are predominantly micellar whereas solutions rich in R1 have a more planar structure. At an intermediate composition (60 to 80 mol % R1), there are mixed L(α)/L(1) and L(1)/L(α) regions. However, the higher preferred curvature associated with R2 tends to dominate the mixed R1/R2 microstructure and its associated phase behavior.

Mixing behavior of the biosurfactant, rhamnolipid, with a conventional anionic surfactant, sodium dodecyl benzene sulfonate.

The use of small angle neutron scattering, SANS, neutron reflectivity, NR, and surface tension to study the mixing properties of the biosurfactant rhamnolipid with a conventional anionic surfactant, sodium dodecyl 6-benzene sulfonate, LAS, is reported. The monorhamnose rhamnolipid, R1, mixes close to ideally with LAS at the air-water interface, whereas for mixtures of LAS with the dirhamnose rhamnolipid, R2, the LAS strongly partitions to the air-water interface relative to R2, probably because of the steric hindrance of the larger R2 headgroup. These trends in the binary mixtures are also reflected in the ternary R1/R2/LAS mixtures. However, for these ternary mixtures, there is also a pronounced synergy in the total adsorption, which reaches a maximum for a LAS/rhamnolipid mole ratio of about 0.6 and a R1/R2 mol ratio of about 0.5, an effect which is not observed in the binary mixtures. In solution, the R1/LAS mixtures form relatively small globular micelles, L(1), at low surfactant concentrations (<20 mM), more planar structures (lamellar, L(α), unilamellar/multilamellar vesicles, ulv/mlv) are formed at higher surfactant concentrations for R1 and LAS rich compositions, and a large mixed phase (L(α)/L(1) and L(1)/L(α)) region forms at intermediate surfactant compositions. In contrast, for the R2/LAS mixtures, the higher preferred curvature of R2 dominates the phase behavior. The predominant microstructure is in the form of small globular micelles, except for solution compositions rich in LAS (>80 mol % LAS) where more planar structures are formed. For the ternary mixtures, there is an evolution in the resulting phase behavior from one dominated by L(1) (R2 rich) to one dominated by planar structures, L(α), (R1, LAS rich), and which strongly depends upon the LAS/rhamnolipid and R1/R2 mole ratio.

An interpretation of covariance relations for wetting and wedge filling transitions.

Recent studies have shown that there exist precise connections (or covariance relations) between adsorption properties for substrates with different shapes. This occurs, for example, when a fluid is adsorbed in a linear wedge. In this case, the influence of the geometry is to shift effectively the contact angle from theta to theta-alpha, where alpha is the tilt angle. Despite the fact that these relations are obeyed both at mean-field level and also exactly in two dimensions (when fluctuation effects dominate), their fundamental origin has been unclear. Here, we show that they can be traced to a symmetry present in interfacial Hamiltonian models, and further relate this to surface thermodynamics and the nonlocal nature of interfacial interactions in systems with short-ranged forces.

The 3D anatomy of the cervical articular process joints in the horse and their topographical relationship to the spinal cord.

UNLABELLED: REASONS FOR STUDY: Detailed anatomy of the equine cervical articular process joints (APJs) has received little attention in the literature and yet disorders of this joint have been linked to spinal cord compression resulting in severe clinical signs such as ataxia and weakness. This study aimed to describe the 3D anatomy of the APJ in relation to the spinal cord in the horse. HYPOTHESIS: Artificial distension of the APJ causes the joint pouches to extend into the vertebral canal, with the potential for APJ effusion to cause spinal cord compressive disease. METHODS: Six cadaveric necks (C1-C7) of clinically normal horses were used in this study. Computed tomography scans of the cervical APJ were acquired after injection of a negative contrast agent to maximal distension. The resulting images were semi-automatically segmented using greyscale thresholding and reconstructed in 3D by polygonal surface meshing. The 3D reconstructions were used to assess the topographic anatomy of the APJ in relation to the spinal cord and to measure joint volume at each cervical vertebra in relation to vertebrae size. RESULTS: Joint volume varied significantly between joint location (P<0.0001) and was positively correlated to the vertebral site (from cranial to caudal) (r = 0.781, P<0.0001). After distension, the medial outpouch of the APJ extended towards the vertebral canal from a dorsolateral location but in none of the 6 horses was there apparent compression of the dura mater surrounding the spinal cord. There was no significant difference in the extent of medial outpouch at any vertebral level (P = 0.104). Flexion of the neck resulted in minor changes to the shape of the APJ but did not result in the medial outpouch encroaching any closer to the spinal cord. CONCLUSIONS: From this study, it appears that in the absence of any other soft tissue or bony changes an effusion of the APJ is unlikely to cause spinal cord compression. However, given that the APJ and spinal cord are in close approximation, in the presence of other anatomical changes, an effusion may have the potential to cause compression. POTENTIAL RELEVANCE: This study confirms that the APJ extend into the dorsolateral aspect of the vertebral canal in a ventromedial direction, suggesting that oblique myelographic views are recommended for the diagnosis of spinal cord compression when pathology of the APJ is suspected.

[Sensory ataxic neuromyelopathy in acquired copper deficiency]. / Ataxie proprioceptive et carence en cuivre masquée.

INTRODUCTION: Neurological involvement associated with copper deficiency has been reported recently in humans and may be under-recognized. CASE REPORT: A 65-year-old patient, with past history of gastrectomy 40 years earlier, developed a myelodysplastic syndrome and then subacute onset of progressive gait ataxia and paresthesias in the lower extremities. Serum vitamin B12 level was low but neurological deterioration persisted, despite vitamin replacement therapy and normal cobalamin level. Further diagnostic investigations revealed severe copper deficiency. Copper supplementation led to hematologic improvement and neurological stabilization. CONCLUSION: Copper and vitamin B12 deficiency, due to malabsorption as a cause of progressive neuromyelopathy and hematologic manifestations, may coexist.

Classification of portosystemic shunts entering the caudal vena cava at the omental foramen in dogs.

OBJECTIVE: To re-evaluate the anatomy and classification of congenital extrahepatic portosystemic shunts entering the caudal vena cava at the level of the omental foramen. MATERIAL AND METHODS: A retrospective review of a consecutive series of dogs undergoing CT angiography as part of the diagnostic work-up for a congenital extrahepatic portosystemic shunt. RESULTS: In total, 53 dogs met the inclusion criteria revealing four anatomically distinct omental foramen shunt types; one of which (32 of 53 dogs) showed no shunting blood flow through the right gastric vein and three of which (21 of 53 dogs) involved shunting flow through this vessel. The anatomy of these four distinct shunt types, as defined by CT angiography, was found to be highly consistent. In all cases, regardless of the tributary vessels, the left gastric vein was the final vessel that communicated with the caudal vena cava. Using these findings, a more accurate naming classification for congenital portosystemic shunts entering the caudal vena cava at the level of the omental foramen was proposed. CLINICAL SIGNIFICANCE: A precise pre-treatment anatomical classification of congenital extrahepatic portosystemic shunts entering the caudal vena cava at the level of the omental foramen is important for a more complete understanding of the severity of clinical signs and prognosis, and for the better communication between clinicians and researchers in this clinical field.

A search for new MRI criteria for dissemination in space in subjects with a clinically isolated syndrome.

The International Panel on the Diagnosis of Multiple Sclerosis (MS) incorporated the Barkhof/Tintoré (B/T) magnetic resonance criteria into their diagnostic scheme to provide evidence of dissemination in space of central nervous system lesions, a prerequisite for diagnosing MS in patients who present with clinically isolated syndromes (CIS). Although specific for MS, the B/T criteria were criticised for their low sensitivity and relative complexity in clinical use. We used lesion characteristics at onset from 349 CIS patients in logistic regression and recursive partitioning modelling in a search for simpler and more sensitive criteria, while maintaining current specificity. The resulting models, all based on the presence of periventricular and deep white matter lesions, performed roughly in agreement with the B/T criteria, but were unable to provide higher diagnostic accuracy based on information from a single scan. Apparently, findings from contrast-enhanced and follow-up magnetic resonance scans are needed to improve the diagnostic algorithm.

Effect of short-term exercise training on aerobic fitness in patients with abdominal aortic aneurysms: a pilot study.

BACKGROUND: Patients with abdominal aortic aneurysms (AAA) represent a high-risk surgical group. Despite medical optimization and radiological stenting interventions, mortality remains high and it is difficult to improve fitness. The aim of this pilot study was to evaluate the effect of a 6 week, supervised exercise programme (30 min continuous moderate intensity cycle ergometry, twice weekly) on anaerobic threshold (AT) in subjects with AAA. METHODS: Thirty participants with an AAA under surveillance were randomized to either the supervised exercise intervention (n=20) or a usual care control group (n=10). AT was measured using cardiopulmonary exercise testing, at baseline (AT1), week 5 (AT2), and week 7 (AT3). The change in AT (AT3-AT1) between the groups was compared using a mixed model ancova, providing the mean effect together with the standard deviation (sd) for individual patient responses to the intervention. The minimum clinically important difference (MCID) was defined as an improvement in AT of 2 ml O(2) kg(-1) min(-1). RESULTS: Of the 30 participants recruited, 17 of 20 (exercise) and eight of 10 (control) completed the study. The AT in the intervention group increased by 10% (equivalent to 1.1 ml O(2) kg(-1) min(-1)) compared with the control (90% confidence interval 4-16%; P=0.007). The sd for the individual patient responses to the intervention was 8%. The estimated number needed to treat (NNT) for benefit was 5 patients. CONCLUSIONS: The small mean benefit was lower than the MCID. However, the marked variability in the individual patient responses revealed that a proportion of patients did benefit clinically, with an estimated NNT of 5.

Reliability of the anaerobic threshold in cardiopulmonary exercise testing of patients with abdominal aortic aneurysms.

Anaerobic threshold (AT), determined by cardiopulmonary exercise testing (CPET), is a well-documented measure of pre-operative fitness, although its reliability in patient populations is uncertain. Our aim was to assess the reliability of AT measurement in patients with abdominal aortic aneurysms. Eighteen patients were recruited. CPET was performed four times over a 6-week period. We examined shifts in the mean AT to evaluate systematic bias with random measurement error assessed using typical within-patient error and intraclass correlation coefficient (ICC, 3,1) statistics. There was no significant or clinically substantial change in mean AT across the tests (p = 0.68). The typical within-patient error expressed as a percentage coefficient of variation was 10% (95% CI, 8-13%), with an ICC of 0.74 (95% CI, 0.55-0.89). We consider the reliability of the AT to be acceptable, supporting its clinical validity and utility as an objective marker of pre-operative fitness in this population.

Correlation-function structure in square-gradient models of the liquid-gas interface: Exact results and reliable approximations.

In a recent article, we described how the microscopic structure of density-density correlations in the fluid interfacial region, for systems with short-ranged forces, can be understood by considering the resonances of the local structure factor occurring at specific parallel wave vectors q [Nat. Phys. 15, 287 (2019)1745-247310.1038/s41567-018-0361-z]. Here we investigate this further by comparing approximations for the local structure factor and pair correlation function against three new examples of analytically solvable models within square-gradient theory. Our analysis further demonstrates that these approximations describe the pair correlation function and structure factor across the whole spectrum of wave vectors, encapsulating the crossover from the Goldstone mode divergence (at small q) to bulklike behavior (at larger q). As shown, these approximations are exact for some square-gradient model potentials and never more than a few percent inaccurate for the others. Additionally, we show that they describe very accurately the correlation function structure for a model describing an interface near a tricritical point. In this case, there are no analytical solutions for the correlation functions, but the approximations are nearly indistinguishable from the numerical solutions of the Ornstein-Zernike equation.

Microscopic determination of correlations in the fluid interfacial region in the presence of liquid-gas asymmetry.

In a recent article, we showed how the properties of the density-density correlation function and its integral, the local structure factor, in the fluid interfacial region, in systems with short-ranged forces, can be understood microscopically by considering the resonances of the local structure factor [A. O. Parry and C. Rascón, Nat. Phys. 15, 287 (2019)NPAHAX1745-247310.1038/s41567-018-0361-z]. Here, we illustrate, using mean-field square-gradient theory and the more microscopic Sullivan density functional model, and how this approach generalizes when there is liquid-gas asymmetry, i.e., when the bulk correlation lengths of the coexisting liquid and gas phases are different. In particular, we are able to express the correlation function exactly as a simple average of contributions arising from two effective Ising-symmetric systems referred to as the symmetric gas and symmetric liquid. When combined with our earlier results, this generates analytical approximations for the correlation function and the local structure factor, which are near indistinguishable from the numerical solution to the Ornstein-Zernike equations over the whole range of wave vectors. Our results highlight how asymmetry affects the correlation function structure and describes the crossover from a long-ranged Goldstone mode to short-ranged properties determined by the local density as the wave vector increases.

Effect of caffeinated gum on a battery of rugby-specific tests in trained university-standard male rugby union players.

BACKGROUND: Caffeine has been shown to enhance strength, power and endurance, characteristics that underpin performance in rugby. Caffeinated gum has attracted interest as a novel vehicle for delivering caffeine, because absorption of caffeine from gum is quick. Rapid absorption of caffeine may be useful during rugby matches when there is limited time for supplementation such as at half-time or when substitutes enter play. The purpose of this study was to determine whether a low dose of caffeine in gum improves performance in a battery of rugby-specific tests. METHODS: In a double-blind, randomized, placebo-controlled, crossover design, 17 male university-standard rugby players (mass: 85.6 ± 6.3 kg; height: 179.4 ± 6.2 cm; age: 20.4 ± 1.2 years) chewed caffeinated gum (200 mg caffeine) or a placebo gum on two occasions separated by a week. After a standardized warm-up, gum was chewed for 5 min. Subsequently, participants performed three countermovement jumps, followed by an Illinois agility test, 6 × 30 m repeated sprints, and the Yo-Yo IR-2 test; each test was separated by short rest periods. RESULTS: Caffeinated gum enhanced countermovement jump by 3.6% (caffeine: 43.7 ± 7.6 cm vs. placebo: 42.2 ± 6.2 cm; d = 0.22, 95% CI [0.006, 0.432]; p = 0.044). There was a greater resistance to fatigue during the 6 × 30 m repeated sprint test (fatigue index caffeine: 102.2 ± 0.9% vs. placebo: 103.3 ± 1.2%; d = 1.03, 95% CI [0.430, 1.613]; p = 0.001), and performance on the Yo-Yo IR2 was improved by 14.5% (caffeine: 426 ± 105 m, placebo: 372 ± 91 m; d = 0.55, 95% CI [0.130, 0.957]; p = 0.010). Caffeine gum had no significant effect on the Illinois agility test (caffeine 16.22 ± 1.08 s vs. placebo 15.88 ± 1.09 s; d = - 0.31, 95% CI [- 0.855, 0.240]; p = 0.271). CONCLUSIONS: In university-standard rugby players, a low dose of caffeine (200 mg) supplied in chewing gum enhanced performance on the Yo-Yo IR-2 test and the countermovement jump test and reduced fatigue index during repeated sprints. These improvements in a battery of rugby-specific tests may transfer to enhanced performance in rugby matches.

A cost-effective colourimetric assay for quantifying hydrogen peroxide in honey.

Honey is a natural product with many beneficial properties including antimicrobial action. Production of hydrogen peroxide (H2O2) in diluted honey is central to this action. Here, we describe an optimized method for measuring levels of H2O2 in honey. This method is based on established methods, with the level of dilution, the time between dilution and reading the assay, and aeration of the samples during the assay identified as critical points for ensuring reliability and reproducibility. The method is cost-effective and easy to perform using common laboratory equipment. Using this method, we quantified the hydrogen peroxide content of five different, unprocessed polyfloral honeys collected in NC, USA. Our results show that H2O2 production by these honeys varies greatly, with some samples producing negligible levels of H2O2. We assessed the effect of colour on the assay by measuring the recovery of spiked H2O2 from light and dark honey and from serially diluted dark corn syrup, and found the amount of H2O2 that could be detected was lower in dark corn syrup and darker honey samples.