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Introduction Measurement of breath hydrogen (H2) and methane (CH4) excretion after ingestion of test‐carbohydrates is used for different diagnostic purposes. There is a lack of standardization among centers performing these tests and this, together with recent technical developments and evidence from clinical studies, highlight the need for a European guideline. Methods This consensus‐based clinical practice guideline defines the clinical indications, performance, and interpretation of H2‐CH4‐breath tests in adult and pediatric patients. A balance between scientific evidence and clinical experience was achieved by a Delphi consensus that involved 44 experts from 18 European countries. Eighty eight statements and recommendations were drafted based on a review of the literature. Consensus (≥80% agreement) was reached for 82. Quality of evidence was evaluated using validated criteria. Results The guideline incorporates new insights into the role of symptom assessment to diagnose carbohydrate (e.g., lactose) intolerances and recommends that breath tests for carbohydrate malabsorption require additional validated concurrent symptom evaluation to establish carbohydrate intolerance. Regarding the use of breath tests for the evaluation of oro‐cecal transit time and suspected small bowel bacterial overgrowth, this guideline highlights confounding factors associated with the interpretation of H2‐CH4‐breath tests in these indications and recommends approaches to mitigate these issues. Conclusion This clinical practice guideline should facilitate pan‐European harmonization of diagnostic approaches to symptoms and disorders, which are very common in specialist and primary care gastroenterology practice, both in adult and pediatric patients. In addition, it identifies areas of future research needs to clarify diagnostic and therapeutic approaches.

BackgroundConstipation is one of the most common gastrointestinal complaints. Although the causes of constipation are varied, dietary habits have a significant influence. Excessive fat intake is suggested as one of the main causes of constipation; however, the exact mechanism is unknown.AimsTo investigate whether a high-fat diet (HFD) causes constipation in mice and to clarify the underlying mechanism, focusing on the amount of colonic mucus.MethodsSix-week-old male C57BL/6 mice were randomly divided into two groups: mice fed with HFD and those with normal chow diet (NCD). Fecal weight, water content, total gastrointestinal transit time, and colon transit time were measured to determine whether the mice were constipated. The colonic mucus was evaluated by immunostaining and quantified by spectrometry. Malondialdehyde (MDA) was measured using the thiobarbituric acid (TBA) test as a marker for oxidative stress.ResultsCompared to the NCD group, the weight of feces was less in the HFD group. In the functional experiment, the total gastrointestinal transit time and colon transit time were longer in the HFD group. Furthermore, HFD significantly reduced the amount of colonic mucus. In addition, the reduction in colonic mucus caused by surfactant resulted in constipation in the NCD group.ConclusionsHFD causes constipation with delayed colon transit time possibly via the reduction in colonic mucus in mice.

Continuous blood pressure (BP) monitoring is of great significance for the real-time monitoring and early prevention of cardiovascular diseases. Recently, wearable BP monitoring devices have made great progress in the development of daily BP monitoring because they adapt to long-term and high-comfort wear requirements. However, the research and development of wearable continuous BP monitoring devices still face great challenges such as obvious motion noise and slow dynamic response speeds. The pulse wave transit time method which is combined with photoplethysmography (PPG) waves and electrocardiogram (ECG) waves for continuous BP monitoring has received wide attention due to its advantages in terms of excellent dynamic response characteristics and high accuracy. Here, we review the recent state-of-art wearable continuous BP monitoring devices and related technology based on the pulse wave transit time; their measuring principles, design methods, preparation processes, and properties are analyzed in detail. In addition, the potential development directions and challenges of wearable continuous BP monitoring devices based on the pulse wave transit time method are discussed.

•Konjac oligo-glucomannan (KOG) has both laxative and prebiotic effects to prevent and relieve constipation.•KOG increased the defecation frequency and fecal water content in constipated mice.•KOG decreased gut transit time in constipated mice.•KOG recovered colonic smooth muscle contraction and motility in constipated mice.•KOG promoted the growth of bifidobacteria but suppressed the growth of Bacteroides. Konjac oligo-glucomannan (KOG) is a non-digestible dietary fiber that is resistant to digestion and absorption in gastrointestinal (GI) tract. Thus, it might be used as an alternative management for constipation. The aim of this study was to evaluate the effects of KOG on gut motility and microbiota to relieve constipation in mice. Mice received Bifidobacterium animalis, lactulose, konjac glucomannan (KGM), or KOG for 14 d. Constipation was induced by 5 mg/kg loperamide days 12 through 14 in all groups except the control. Defecation frequency, small intestinal transit, and total gut transit time were indicated by counting the number of feces, and using charcoal meal and Evans blue as markers, respectively. Smooth muscle (SM) contraction and gut motility were evaluated by organ bath and GI motility monitor system. Gut microbiota were measured by fluorescence in situ hybridization technique. KOG significantly (P < 0.01) increased defecation frequency and small intestinal transit but decreased total gut transit time when compared with the constipation-without-treatment group. These results were similar to the effects of Bifidobacterium animalis, lactulose, and KGM. KOG ameliorated the effect of loperamide on contraction frequency of distal colonic circular SM. The motility patterns were changed in the KOG group from non-propagation to propagation contraction. KOG significantly inhibited the effects of loperamide on gut microbiota by increasing the numbers of Bifidobacterium spp. and decreasing the numbers of Clostridium spp. and Bacteroides spp. These results suggest that KOG acts as a prebiotic and stimulant laxative for relief and prevention of constipation. [Display omitted]

Elevated nitrogen (N) concentrations have detrimental effects on aquatic ecosystems worldwide, calling for effective management practices. However, catchment-scale annual mass-balance estimates often exhibit N deficits and time lags between the trajectory of net N inputs and that of N riverine export. Here, we analyzed 40-year time series of N surplus and nitrate-N loads in 16 mesoscale catchments (104-10 135 km2) of a temperate agricultural region, with the aim to (1) investigate the fate of the 'missing N', either still in transit through the soil-vadose zone-groundwater continuum or removed via denitrification, and (2) estimate the transit time distribution of N by convoluting the input signal with a lognormal model. We found that apparent N retention, the 'missing N', ranged from 45%-88% of then N net input, and that topsoil N accumulation alone accounted for ca. two-thirds of this retention. The mode of the nitrate-N transit time distribution ranged from 2-14 years and was negatively correlated with the estimated retention. Apparent retention was controlled primarily by average runoff, while the transit time mode was controlled in part by lithology. We conclude that the fate of the soil 'biogeochemical legacy', which represents much of the catchment-scale 'missing N', is in our hands, since the N accumulated in soils can still be recycled in agroecosystems.

In trees, the use of nonstructural carbon (NSC) under limiting conditions impacts the age structure of the NSC pools. We compared model predictions of NSC ages and transit times for Pinus halepensis, Acer rubrum and Pinus taeda, to understand differences in carbon (C) storage dynamics in species with different leaf phenology and growth environments. We used two C allocation models from the literature to estimate the NSC age and transit time distributions, to simulate C limitation, and to evaluate the sensitivity of the mean ages to changes in allocation fluxes. Differences in allocation resulted in different NSC age and transit time distributions. The simulated starvation flattened the NSC age distribution and increased the mean NSC transit time, which can be used to estimate the age of the NSC available and the time it would take to exhaust the reserves. Mean NSC ages and transit times were sensitive to C fluxes in roots and allocation of C from wood storage. Our results demonstrate how trees with different storage traits are expected to react differently to starvation. They also provide a probabilistic explanation for the ‘last-in, first-out’ pattern of NSC mobilization from well-mixed C pools.

Most current land models approximate terrestrial hydrological processes as one‐dimensional vertical flow, neglecting lateral water movement from ridges to valleys. Such lateral flow is fundamental at catchment scales and becomes crucial for finer‐scale land models. To test the effect of incorporating lateral flow toward three‐dimensional representations of hydrological processes in the next generation land models, we integrate a water tracer model into the WRF‐Hydro framework to track water movement from precipitation to discharge and evapotranspiration. This hydrologic‐tracer integrated system allows us to identify the key mechanisms by which lateral flow affects the flow paths and transit times in WRF‐Hydro. By comparing modeling experiments with and without lateral routing in two contrasting catchments, we determine the impacts of lateral flow on the transit times of precipitation event‐water. Results show that with limited hydrologic connectivity, lateral flow extends the transit times by reducing (increasing) event‐water drainage loss (accumulation) in ridges (valleys) and allowing reinfiltration of infiltration‐excess flow, which is missing in most land models. On the contrary with high hydrologic connectivity, lateral flow can effectively accelerate the water release to streams and reduce the transit time. However, the transit times are substantially underestimated by the model compared with isotope‐derived estimates, indicating model limitations in representing flow paths and transit times. This study provides some insights on the fundamental differences in terrestrial hydrology simulated by land models with and without lateral flow representation. Key Points A water tracer model has been integrated with WRF‐Hydro to examine the role of lateral flow in terrestrial hydrological processes Accounting for lateral flow lengthens the transit times of precipitation in conditions with limited hydrology connectivity and vice versa Modeled results underestimate transit times compared to isotope‐derived estimates in the H.J. Andrews Experimental Forest

The question of whether the construction of the highway network is economical and can produce positive economic benefits has been a hot topic of discussion in recent years. Previous scholars have explored the impact from multiple perspectives. Our paper draws the “trade potential” model proposed by Armstrong, based on the universal gravity model and the principle of space interaction, which is different from the traffic accessibility, market potential, and market access used in most of the literature. We argue that it is more appropriate to consider both the size impact and the time distance or trade cost impact of the two cities. The paper constructs a conceptual framework and theoretical model for the impact of highways on regional economic growth, measures the “minimum transit time” of highways between prefecture-level cities in China, and calculates the trade potential of prefecture-level cities. Through corresponding empirical model testing, we have obtained some meaningful conclusions. First published online 17 September 2024

This study reports the room temperature testing of an InGaAs/InP photodetector, biased under linear sweep and/or parametric bias voltage for both modulated, and unmodulated 1550 nm wavelength illuminations. Charge transport of the photo-generated carriers is probed under absorber’s electric field manipulations via parametric control of applied bias, readout element, and light intensity. The device exhibits three different illumination intensity dependent current signatures. Speed of the employed device is enhanced under relatively stronger electric fields ensuring higher drift, and reduced transit times. A three order reduction in the gain setting of the readout element results in ∼ 235 times large peak-current under 20 times smaller pulsed illumination of 0.2 μ W . This electric field enhancement decreases rise, and fall times under pulsed illumination from 225 ns to 115 ns , and 1.553 μ s to 1.143 μ s , respectively. But, the large photodetection plausibility, and reduced transit times ensuring relatively fast speed comes at the expense of ~ 5 order high noise activity in the device. It is also inferred that, overall noise spectrum of the device is not decided by simple generational processes in the absorber, but through the actual proportion of photo-generated carriers taking part in the real charge transport.

The assessment of resting perfusion measures (mean transit time, cerebral blood flow, and cerebral blood volume) with magnetic resonance imaging currently requires the presence of a susceptibility contrast agent such as gadolinium. Here, we present an initial comparison between perfusion measures obtained using hypoxia‐induced deoxyhemoglobin and gadolinium in healthy study participants. We hypothesize that resting cerebral perfusion measures obtained using precise changes of deoxyhemoglobin concentration will generate images comparable to those obtained using a clinical standard, gadolinium. Eight healthy study participants were recruited (6F; age 23–60). The study was performed using a 3‐Tesla scanner with an eight‐channel head coil. The experimental protocol consisted of a high‐resolution T1‐weighted scan followed by two BOLD sequence scans in which each participant underwent a controlled bolus of transient pulmonary hypoxia, and subsequently received an intravenous bolus of gadolinium. The resting perfusion measures calculated using hypoxia‐induced deoxyhemoglobin and gadolinium yielded maps that looked spatially comparable. There was no statistical difference between methods in the average voxel‐wise measures of mean transit time, relative cerebral blood flow and relative cerebral blood volume, in the gray matter or white matter within each participant. We conclude that perfusion measures generated with hypoxia‐induced deoxyhemoglobin are spatially and quantitatively comparable to those generated from a gadolinium injection in the same healthy participant. The exploration of hypoxia‐induced dOHb as a noninvasive contrast agent for cerebral perfusion imaging with magnetic resonance imaging.