Spin-density wave Fermi surface reconstruction in underdoped YBa2Cu3O6+x

We consider the reconstruction expected for the Fermi surface of underdoped YBa2Cu3O6+x in the case of a collinear spin-density wave with a characteristic vector Q=(pi[1+/-2 delta],pi), assuming an incommensurability delta~0.06 similar to that found in recent neutron scattering experiments. A Fermi surface possibly consistent with the multiple observed quantum oscillation frequencies is obtained. From the low band masses expected using this model as compared with experiment, a uniform enhancement of the quasiparticle effective mass over the Fermi surface by a factor of ~7 is indicated. Further predictions of the Fermi surface topology are made, which may potentially be tested by experiment to indicate the relevance of this model to underdoped YBa2Cu3O6+x.Comment:

The challenges of control groups, placebos and blinding in clinical trials of dietary interventions

High-quality placebo-controlled evidence for food, nutrient or dietary advice interventions is vital for verifying the role of diet in optimising health or for the management of disease. This could be argued to be especially important where the benefits of dietary intervention are coupled with potential risks such as compromising nutrient intake, particularly in the case of exclusion diets. The objective of the present paper is to explore the challenges associated with clinical trials in dietary research, review the types of controls used and present the advantages and disadvantages of each, including issues regarding placebos and blinding. Placebo-controlled trials in nutrient interventions are relatively straightforward, as in general placebos can be easily produced. However, the challenges associated with conducting placebo-controlled food interventions and dietary advice interventions are protean, and this has led to a paucity of placebo-controlled food and dietary advice trials compared with drug trials. This review appraises the types of controls used in dietary intervention trials and provides recommendations and nine essential criteria for the design and development of sham diets for use in studies evaluating the effect of dietary advice, along with practical guidance regarding their evaluation. The rationale for these criteria predominantly relate to avoiding altering the outcome of interest in those delivered the sham intervention in these types of studies, while not compromising blinding.</jats:p

Band-structure topologies of graphene: spin-orbit coupling effects from first principles

The electronic band structure of graphene in the presence of spin-orbit coupling and transverse electric field is investigated from first principles using the linearized augmented plane-wave method. The spin-orbit coupling opens a gap at the $K(K')$-point of the magnitude of 24 $\mu$eV (0.28 K). This intrinsic splitting comes 96% from the usually neglected $d$ and higher orbitals. The electric field induces an additional (extrinsic) Bychkov-Rashba-type splitting of 10 $\mu$eV (0.11 K) per V/nm, coming from the $\sigma$-$\pi$ mixing. A 'mini-ripple' configuration with every other atom is shifted out of the sheet by less than 1% differs little from the intrinsic case.Comment: 4 pages, 4 figure

Analysis of the use of tapered graded-index polymer optical fibers for refractive-index sensors

The behavior of tapered graded-index polymer optical fibers is analyzed computationally for different refractive indices of the surrounding medium. This serves to clarify the main parameters affecting their possible performance as refractive-index sensors and extends an existing study of similar structures in glass fibers. The ray-tracing method is employed, its specific implementation is explained, and its results are compared with experimental ones, both from our laboratory and from the literature. The results show that the current commercial graded-index polymer optical fibers can be used to measure a large range of refractive indices with several advantages over glass fibers

Perceived acceptability of partial enteral nutrition (PEN) using oral nutritional supplement drinks in adolescent and adult Crohn’s Disease outpatients: a feasibility study

BACKGROUND AND AIMS: Studies, mainly in Japanese cohorts, have shown that partial enteral nutrition (PEN) including oral nutritional supplement (ONS) drinks can prolong disease remission and increase drug effectiveness in Crohn’s disease (CD). Acceptability is a key feasibility parameter to determine whether PEN is a viable treatment option in UK CD patients. We report the results of a single centre cross-sectional feasibility study carried out to investigate perceived acceptability of PEN using ONS drinks and whether ONS preference varies with sex, nutritional status or phenylthiocarbamide (PTC) sensitivity. METHODS: Patients with a confirmed CD diagnosis were recruited using convenience sampling from an adult and adolescent gastroenterology outpatient clinic over 3 years. Blind taste testing of 5 polymeric ONS drinks was conducted using a validated 9-point hedonic rating scale followed by completion of the acceptability questionnaire based on the preferred ONS drink. A subset of patients took home the preferred ONS for a 7-day study. RESULTS: 105 CD patients (55 males), aged 34.9 (±15.4) years were recruited and 28 patients completed the 7-day ONS study. Overall impression scores did not significantly vary with nutritional status, sex, BMI, handgrip strength (HGS), mid-upper arm circumference (MUAC) or PTC sensitivity. Ensure plus™ milkshake rated highest for overall impression (6.5, p=<0.0001) and all other organoleptic properties (p<0.0001). The main perceived benefits of using ONS drinks as PEN related to assurance of nutrient intake (89.3%), convenience (85.7%), and improvement of gut symptoms (84.6%). The main perceived barriers related to reduction in pleasure from eating and drinking (55.6%), struggle with drink storage (53.6%) and increased tiredness than if eating 3 solid meals daily (52%%). 64.8% of patients would consider using PEN as a maintenance treatment option. 81.0% of patients felt confident about consuming ONS drinks daily as PEN for three months but this dropped to 63.8% and 37.1% at 6 and 12 months, respectively. There was a significant drop in perceived ease of use as PEN after the 7-day ONS study (P=0.01). CONCLUSION: Use of ONS drinks as PEN have high perceived benefits and appear to be a feasible option for short-term use of 3-6 months in CD patients. However, confidence in long-term use of ONS drinks as PEN is low mainly due to the perceived social impact. Future studies should assess longer trial periods and volume of ONS drinks to increase the validity of these findings

Faecal and urine metabolites, but not gut microbiota, may predict response to low FODMAP diet in irritable bowel syndrome

BackgroundThe low FODMAP diet (LFD) leads to clinical response in 50%-80% of patients with irritable bowel syndrome (IBS). It is unclear why only some patients respond.AimsTo determine if differences in baseline faecal microbiota or faecal and urine metabolite profiles may separate clinical responders to the diet from non-responders allowing predictive algorithms to be proposed.MethodsWe recruited adults fulfilling Rome III criteria for IBS to a blinded randomised controlled trial. Patients were randomised to sham diet with a placebo supplement (control) or LFD supplemented with either placebo (LFD) or 1.8 g/d B-galactooligosaccharide (LFD/B-GOS), for 4 weeks. Clinical response was defined as adequate symptom relief at 4 weeks after the intervention (global symptom question). Differences between responders and non-responders in faecal microbiota (FISH, 16S rRNA sequencing) and faecal (gas-liquid chromatography, gas-chromatography mass-spectrometry) and urine (1 H NMR) metabolites were analysed.ResultsAt 4 weeks, clinical response differed across the 3groups with adequate symptom relief of 30% (7/23) in controls, 50% (11/22) in the LFD group and 67% (16/24) in the LFD/B-GOS group (p = 0.048). In the control and the LFD/B-GOS groups, microbiota and metabolites did not separate responders from non-responders. In the LFD group, higher baseline faecal propionate (sensitivity 91%, specificity 89%) and cyclohexanecarboxylic acid esters (sensitivity 80%, specificity 78%), and urine metabolite profile (Q2 0.296 vs. randomised -0.175) predicted clinical response.ConclusionsBaseline faecal and urine metabolites may predict response to the LFD

Successful fiber sensing technologies and hot topics for the near future

Inside the Photonics field Optical Fiber Sensors (OFS) are currently being used and will still be used in the future in a wide number of applications because its properties present technical advantages over traditional techniques or, sometimes, is practically the only feasible solution. In this paper, the more successful techniques will be reviewed. Then a prospective for the near future of the market and hot topics in which invest research resources will be suggested

The low FODMAP diet in the management of irritable bowel syndrome:an evidence-based review of FODMAP restriction, reintroduction and personalisation in clinical practice

Dietary restriction of fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs) is effective in the management of functional gastrointestinal symptoms that occur in irritable bowel syndrome (IBS). Numerous reviews have been published regarding the evidence for their restriction in the low FODMAP diet; however, few reviews discuss the implementation of the low FODMAP diet in practice. The aim of this review is to provide practical guidance on patient assessment and the implementation and monitoring of the low FODMAP diet. Broadly speaking, the low FODMAP diet consists of three stages: FODMAP restriction; FODMAP reintroduction; and FODMAP personalisation. These stages can be covered in at least two dietetic appointments. The first appointment focuses on confirmation of diagnosis, comprehensive symptom and dietary assessment, detailed description of FODMAPs and their association with symptom induction, followed by counselling regarding FODMAP restriction. Dietary counselling should be tailored to individual needs and appropriate resources provided. At the second appointment, symptoms and diet are re-assessed and, if restriction has successfully reduced IBS symptoms, education is provided on FODMAP reintroduction to identify foods triggering symptoms. Following this, the patient can follow FODMAP personalisation for which a less restrictive diet is consumed that excludes their personal FODMAP triggers and enables a more diverse dietary intake. This review provides evidence and practice guidance to assist in delivering high-quality clinical service in relation to the low FODMAP diet