Transit Time Research Articles

Modeling the diffusion and depletion capacitances of a silicon pn diode in forward bias with impedance spectroscopy

We investigated the capacitance of a forward-biased silicon pn diode using impedance spectroscopy. Despite extensive research spanning decades, no single model in the literature adequately describes the impedance behavior for bias up to the built-in voltage. By employing the 1N4007 diode as a case study, we analyzed the impedance over a wide frequency range, from 1 Hz to 1 MHz. Our analysis reveals that impedance can be effectively studied by combining two models. In both models, the depletion capacitance is assumed to be an ideal capacitor with a value independent of frequency. One model accounts for diffusion processes, while the other addresses interfacial effects, as well as potential and capacitance distributions across the junction. This approach offers valuable insights into the complex capacitance behavior of pn junctions as a function of the bias voltage. Measurements of depletion and diffusion capacitances, as well as of the diode transit time can be achieved from a set of impedance spectroscopy data.

Determinants of cerebral blood flow and arterial transit time in healthy older adults.

Cerebral blood flow (CBF) and arterial transit time (ATT), markers of brain vascular health, worsen with age. The primary aim of this cross-sectional study was to identify modifiable determinants of CBF and ATT in healthy older adults (n = 78, aged 60-81 years). Associations between cardiorespiratory fitness and CBF or ATT were of particular interest because the impact of cardiorespiratory fitness is not clear within existing literature. Secondly, this study assessed whether CBF or ATT relate to cognitive function in older adults. Multiple post-labelling delay pseudo-continuous arterial spin labelling estimated resting CBF and ATT in grey matter. Results from multiple linear regressions found higher BMI was associated with lower global CBF (β = -0.35, P = 0.008) and a longer global ATT (β = 0.30, P = 0.017), global ATT lengthened with increasing age (β = 0.43, P = 0.004), and higher cardiorespiratory fitness was associated with longer ATT in parietal (β = 0.44, P = 0.004) and occipital (β = 0.45, P = 0.003) regions. Global or regional CBF or ATT were not associated with processing speed, working memory, or attention. In conclusion, preventing excessive weight gain may help attenuate age-related declines in brain vascular health. ATT may be more sensitive to age-related decline than CBF, and therefore useful for early detection and management of cerebrovascular impairment. Finally, cardiorespiratory fitness appears to have little effect on CBF but may induce longer ATT in specific regions.

Effect of dephasing on modulation transfer in potassium

In this work, experimental studies on the effect of dephasing on modulation transfer are reported. Here Potassium D1 transition, i.e., 39K 4S1/2(F) → 4P1/2(F/), is used as the medium. The 4 S→4P connection is modified by introducing two independent lasers. The separation between ground hyperfine states 4S1/2(F = 2,1) is almost half of Doppler width (~ 815 MHz). Hence, the two-level connections satisfied by respective lasers are overlapping in nature. In such cases, the existing optical pumping for particular F = 1, 2→ F/ channel influences each other. Further, the D1 transition itself is an open transition, i.e., it does not have any cyclic decay route. Hence, decay from each of the F/=2,1 states can also influence the population in the other F/state. Our pump-probe spectroscopy results clearly show the presence of Four Wave Mixing due to degenerate two-level and Vee (V) coupling, Electromagnetically Induced Transparency (EIT) signals due to single Lambda (Λ) and Double Λ connections. We have studied these signals as a function of dephasing, which is mainly contributed by transit time broadening for two different regimes of pump laser intensities: (i) below and (ii) above saturation intensity level of 4S1/2(F) → 4P1/2(F/) transition. The pump laser is current modulated, and phase-sensitive detection is performed on the probe transmission to study modulation transfer under different values of coherent dephasing. For this purpose, the beam size of the pump laser is varied systematically. This study provides a scope to explore the modulation transfer as a function of transit time broadening, and it may find applications in photonics technology where potassium vapor is used as a medium.

Influence from highways on regional economic growth – based on the trade potential in China

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.

The impact of managed aquifer recharge on the fate and transport of pesticides in agricultural soils

Groundwater aquifers worldwide experience unsustainable depletion, compounded by population growth, economic development, and climate forcing. Managed aquifer recharge provides one tool to alleviate flood risk and replenish groundwater. However, concerns grow that intentional flooding of farmland for groundwater recharge, a practice known as Ag-MAR, may increase the leaching of pesticides and other chemicals into groundwater. This study employs a physically based unsaturated flow model to determine the fate and transport of residues of four pesticide in three vadose zone profiles characterized by differing fractions of sand (41 %, 61 %, and 84 %) in California's Central Valley. Here, we show that the complex heterogeneity of alternating coarse and fine-grain hydrogeologic units controls the transit times of pesticides and their adsorption and degradation rates. Unsaturated zones that contain a higher fraction of sand are more prone to support preferential flow, higher recharge rates (+8 %), and faster (42 %) water flow and pesticide transport, more flooding-induced pesticide leaching (about 22 %), as well as more salt leaching correlating with increased risks of groundwater contamination. Interestingly, considering preferential flow predicted higher degradation and retention rates despite shorter travel times, attributed to the trapping of pesticides in immobile zones where they degrade more effectively. The findings underscore the importance of considering soil texture and structure in Ag-MAR practices to minimize environmental risks while enhancing groundwater recharge. The study also highlights that selecting less mobile pesticides can reduce leaching risks in sandy areas.

Can temperature be a low-cost tracer for modelling water age distributions in a karst catchment?

To investigate the feasibility of using temperature for tracking rainfall-runoff processes in karst catchments, this study developed a tracer-aided conceptual model using temperature as a tracer by coupling water and heat transport processes at the catchment scale. The model was calibrated and validated using hourly hydrometeorological and temperature data from a 1.25 km2 karst catchment in south-western China. The results showed that the model was able to capture the water flux and temperature dynamics of different landscape units in the karst catchment. Utilizing this framework, the model delineated the flux age distribution within different landscape units, as well as the overall water transit times through the catchment. The average flux ages were determined to be approximately 80 days for the hillslope unit, 452 days for the slow flow system, and 260 days for the fast flow regime within the depression areas. These estimations align broadly with those acquired using stable isotopes as tracers. Comparative analysis revealed that the flux age distributions derived from both temperature and isotopic tracers exhibited analogous patterns at the catchment outlet and across the hillslope compartments. However, the simulations based on temperature hinted at a heightened proportion of exceedingly young and decidedly old water in the outflow, alluding to a potential overestimation of these extreme age classes by the temperature-tracer model. From the temperature-simulated transit time distribution, about 31 % of the precipitation entering during the study period have left the catchment within 3 years, and a notable proportion of rain water was either stored in the aquifer or lost through evapotranspiration. The general characteristics of the transit time distribution simulated using temperature was similar with that simulated using isotopes, though a higher proportion of precipitation being drained by fast flows was inferred from the transit time distribution simulated using temperature. Collectively, our study demonstrated that temperature can serve as a cost-effective tracer for modelling of water age distributions and associated hydrological processes in karst catchments.

New Transit Timing Observations of WASP-12b from TESS Sectors 71 and 72

I present new transit and occultation timing measurements for the hot Jupiter WASP-12b using data from TESS Sectors 71 and 72, observed in 2023. Using full-phase curve fitting for the first time, I precisely locate both transits and occultations. I report 34 new transit times and sector-specific occultation times, updating the orbital decay rate to −26.310 ± 0.901 ms yr−1. My analysis strongly favors the orbital decay model over constant period and apsidal precession models.

An adapted savings algorithm for planning heterogeneous logistics with uncrewed aerial vehicles

This paper proposes a new extension to the Sustainable Specimen Collection Problem (SSCP), where medical specimens are transported by vans, bikes, and uncrewed aerial vehicles (UAVs, or drones) from local medical practices/offices to a central hospital laboratory for analysis, employing a two-echelon collection approach. Time restrictions from existing operations and literature are also introduced, with the study being formulated as a weighted multi-objective problem seeking to minimise (i) operating costs; (ii) transit times; and (iii) energy/environmental impacts. A new adaptation of the Clarke and Wright Savings Algorithm is subsequently presented to create collection rounds that leverage each mode’s strengths. Subsequently, routes are compiled into workable fixed shifts using a modified bin-packing algorithm in each iteration.The approach of this study is based on a case study of the UK’s National Health Service (NHS), involving the collection of pathology samples using traditional vans operating within fixed time slots. Using case study data from the Solent region (England), a novel test instance generation methodology was also developed, whereby realistic site positioning and origin-destination travel data are captured to enable effective algorithm experimentation. The findings from applying the proposed algorithm to a set of test instances based on this methodology are subsequently discussed, where it was found that the adapted savings and bin-packing approach produced effective solutions quickly, with 90% of all large instances (200 sites) being solved within 15 min. Further algorithm developments and the application of the devised problem/methodologies are also discussed.

Photovoltage-Driven Photoconductor Based on Horizontal p-n-p Junction.

The photoconductive gain theory demonstrates that the photoconductive gain is related to the ratio of carrier lifetime to carrier transit time. Theoretically, to achieve higher gain, one can either prolong the carrier lifetime or select materials with high mobility to shorten the transit time. However, the former slows the response speed of the device, while the latter increases the dark current and degrades device sensitivity. To address this challenge, a horizontal p-n-p junction-based photoconductor is proposed in this work. This device utilizes the n-region as the charge transport channel, with the charge transport direction perpendicular to the p-n-p junction. This design offers two advantages: (i) the channel is depleted by the space charge layer generated by the p and n regions, enabling the device to maintain a low dark current. (ii) The photovoltage generated in the p-n junction upon light absorption can compress the space charge layer and expand the conductive path in the n-region, enabling the device to achieve high gain and responsivity without relying on long carrier lifetimes. By adopting this device structure design, a balance between responsivity, dark current, and response speed is achieved, offering a new approach to designing high-performance photodetectors based on both traditional materials and emerging nanomaterials.

Signal Quality Classification of Impedance Plethysmogram and Ballistocardiogram for Pulse Transit Time Measurement

Signal Quality Classification of Impedance Plethysmogram and Ballistocardiogram for Pulse Transit Time Measurement

Measurement of blood-brain barrier water exchange rate using diffusion-prepared and multi-echo arterial spin labelling: Comparison of quantitative values and age dependence.

Water exchange rate (Kw) across the blood-brain barrier (BBB) is an important physiological parameter that may provide new insight into ageing and neurodegenerative disease. Recently, two non-invasive arterial spin labelling (ASL) MRI methods have been developed to measure Kw, but results from the different methods have not been directly compared. Furthermore, the association of Kw with age for each method has not been investigated in a single cohort. Thirty participants (70% female, 63.8 ± 10.4years) were scanned at 3T with Diffusion-Prepared ASL (DP-ASL) and Multi-Echo ASL (ME-ASL) using previously implemented acquisition and analysis protocols. Grey matter Kw, cerebral blood flow (CBF) and arterial transit time (ATT) were extracted. CBF values were consistent; approximately 50 ml/min/100 g for both methods, and a strong positive correlation in CBF from both methods across participants (r = 0.82, p < 0.001). ATT was significantly different between methods (on average 147.7ms lower when measured with DP-ASL compared to ME-ASL) but was positively correlated across participants (r = 0.39, p < 0.05). Significantly different Kw values of 106.6±19.7min-1 and 306.8±71.7min-1 were measured using DP-ASL and ME-ASL, respectively, and DP-ASL Kw and ME-ASL Kw were negatively correlated across participants (r = -0.46, p < 0.01). Kw measured using ME-ASL had a significant linear relationship with age (p < 0.05). In conclusion, DP-ASL and ME-ASL provided estimates of Kw with significantly different quantitative values and inconsistent dependence with age. We propose future standardisation of modelling and fitting methods for DP-ASL and ME-ASL, to evaluate the effect on Kw quantification. Also, sensitivity and bias analyses should be performed for both approaches, to assess the effect of varying acquisition and fitting parameters. Lastly, comparison with independent measures of BBB water transport, and with physiological and clinical biomarkers known to be associated with changes in BBB permeability, are essential to validate the ASL methods, and to demonstrate their clinical utility.

Antecedent Hydrologic Conditions Reflected in Stream Lithium Isotope Ratios During Storms

AbstractAntecedent hydrological conditions are recorded through the evolution of dissolved lithium isotope signatures (Li) by juxtaposing two storm events in an upland watershed subject to a Mediterranean climate. Discharge and Li are negatively correlated in both events, but mean Li ratios and associated ranges of variation are distinct between them. We apply a previously developed reactive transport model (RTM) for the site to these event‐scale flow perturbations, but observed shifts in stream Li are not reproduced. To reconcile the stability of the subsurface solute weathering profile with our observations of dynamic stream Li signatures, we couple the RTM to a distribution of fluid transit times that evolve based on storm hydrographs. The approach guides appropriate flux‐weighting of fluid from the RTM over a range of flow path lengths, or equivalently fluid residence times. This flux‐weighted RTM approach accurately reproduces dynamic storm Li‐discharge patterns distinguished by the antecedent conditions of the watershed.

The Light Switch and the Dimmer: Qualitative Observations to Improve Diagnostic Lacrimal Irrigation

ABSTRACT Purpose To emphasise the importance of “soft” observations during lacrimal irrigation in diagnosing lacrimal outflow dysfunction and reporting outcomes of soft factors post-DCR. Methods A retrospective study of patients with ≤ 20% of regurgitation on lacrimal irrigation who underwent DCR surgery. A comparative analysis of percentage reflux of saline (RFX), initial mucus in reflux (IMR), patient-reported transit time of saline (PR-TTS), and resistance encountered (RES) during LS was performed. Validated TEARS score was used. Subjective success was defined as ≥ 2-point improvement in T subscale of TEARS score. Objective success, as a decrease in RFX, RES, PR-TTS and absence of IMR, post-operatively. Results From a total of 253 patients who underwent DCR surgery, 8 patients met the inclusion criteria. All patients were T4 (wiping >10× daily) indoors and outdoors. TEARS score improved after surgery with a mean reduction of T = 2.62, E = 1.63 and A = 1.35 (p < .05) with no significant change in R scores (p = .10). A mean reduction in RFX of 11.75 ± 6.74% and a median improvement of 1 point in PR-TTS and 2 point in RES was observed (p < .05). No significant changes of these parameters occurred in the contralateral side during this period. Subjective and objective success of DCR was 75% and 100%, respectively. Conclusions This study is the first to attempt to combine qualitative “soft” observations during lacrimal irrigation such as IMR, RES and PR-TTS for identifying nasolacrimal outflow dysfunction and reporting outcomes using these parameters of DCR in patients with epiphora and ≤ 20% of fluid regurgitation. These parameters were greater in the more symptomatic side and successfully improved after DCR, making them a valuable tool to reach a provisional diagnosis.

Peculiarities of cerebral blood flow and vascular reactivity in patients with large and giant tumors of the cerebello-pontine angle

Background. Vestibular schwannomas and posterior fossa meningiomas are one of the most difficult tumors for surgical treatment. The mortality rate after their removal reaches 13,5 %. The main causes of death are hemorrhagic and ischemic complications. There are no studies in the literature on tissue perfusion of brainstem structures and cerebellum and reactivity of vertebral and basilar arteries in patients with extraaxial tumors of the posterior cranial fossa. Therefore, the study of the blood supply of the brainstem structures and cerebellum, as well as the functional characteristics of the vertebral and basilar arteries in these patients is of considerable interest.Aim. To evaluate tissue perfusion of the pons and cerebellum, as well asthe reactivity of the vertebral and basilar arteries in patients with large and giant vestibular schwannomas and posterior fossa meningiomas.Materials and methods. Eighty-two patients with large and giant extraaxial tumors of the base of the posterior cranial fossa were examined. The median age was 54 [44; 61] years. Vestibular schwannomas were diagnosed in 52.4 % of patients, and meningiomas of the posterior cranial fossa were diagnosed in 47.6 %. All patients underwent duplex scanning of the basilar and vertebral arteries. We evaluated linear blood flow and coefficients of reactivity and index of vasomotor reactivity. We investigated the metabolic reactivity of cerebral blood flow by conducting hyper- and hypocapnic tests. Computed tomography perfusion imaging was performed in 18 patients. We detected cerebral blood volume, cerebral blood flow, mean transit time of contrast agent and time to peak of contrast agent. Measurements were carried out in six regions of interest located symmetrically on the pons and in the white matter of the cerebellar hemispheres on the side of the tumor and on the opposite side.Results. Linear blood flow rates in the intracranial segments of the vertebral and the basilar arteries in patients with tumors were higher than in the comparison group (p&lt;0.05). These patients are characterized by a decrease of reactivity coefficients in the vertebral and basilar arteries, especially when performing hypercapnic tests (p &lt;0.05). Paradoxical reactivity and areactivity were diagnosed in 34.9 % of patients with vestibularschwannomas and 25.6 % with meningiomas. In the pons on the side of the tumor in patients with vestibularschwannomas, a decrease in cerebral blood flow by 19.3 %, an increase in cerebral blood volume by 33.3 % and an increase in mean transit time of contrast agent and in time to peak of contrast agent by 48.1 % and 71.1 % (p &lt;0.05) were found. In patients with meningiomas in the pons on the side of the tumor, all perfusion parameters were higher (p&lt;0.05). In the deep regions of the cerebellar hemisphere on the side of the tumor in patients with tumors, all perfusion parameters were higher compared to the opposite side.Conclusion. The results of the study made it possible to quantify cerebral blood flow in patients with large and giant vestibular schwannomas and meningiomas of the posterior cranial fossa base. The revealed changes indicate the risk of developing pathological vascular reactions and disorders of cerebral blood flow in the postoperative period.

A new method of intraoperative assessment of the dynamics of cortical blood flow using imaging photoplethysmography

Background. Intraoperative assessment of changes in cerebral blood flow is an important component of objective quality control of surgical treatment of cerebral artery aneurysms. Various techniques have been tried to solve this task, but they all have their drawbacks, which forces us to look for new ways of blood flow monitoring. We propose to use the technology of imaging photoplethysmography (IPPG) – a technically simple, contactless, safe and cheap optical method for assessing the perfusion of biological tissues.Aim. To demonstrate the possibility of using IPPG to assess the dynamics of cerebral blood flow parameters during aneurysm clipping surgery, as well as to identify early changes in blood supply to the cerebral cortex.Materials and methods. The study was carried out during six surgeries of clipping aneurysms of the anterior part of the Willis’s circle, both in the acute stage of rupture (n = 1) and in a planned manner (n = 5). The IPPG system, which is an LED illuminator in a single unit with a digital video camera, was located on a tripod 25 cm from the intervention zone. During each operation, two one-minute recordings of the illuminated surface of the cerebral cortex were performed: after dissection of the dura mater and before its suturing at the end of the main stage of the intervention. To improve the measurement accuracy, video frames of the studied area were recorded synchronously with the registration of an electrocardiogram. After recording, two IPPG parameters were calculated and compared: the amplitude of the pulsatile component and the pulse wave transit time. Thereafter, the obtained data were compared with the results of computed tomography. Statistical analysis was performed using pairwise comparison tests in the GraphPad Prism software package.Results. Clipping of cerebral vessel aneurysms are accompanied by significant changes in the parameters of cerebral blood flow. Analysis of the data for all patients revealed significant differences in IPPG parameters before and after surgery, namely, statistically significant increase in amplitude of the pulsatile component (n = 3) and decrease in pulse wave transit time (n = 5). The absence of significant changes in both parameters was found only in one patient who had mechanical damage in the cortex in the region of video recording.Conclusion. The IPPG system is capable to quantify changes in blood supply to the cortex during surgical treatment of cerebral artery aneurysms and to identify areas with either increased or decreased blood supply. In-depth studies are required to obtain additional markers of the postoperative state of cerebral blood flow.

Perfusion-weighted MRI patterns in neuropsychiatric systemic lupus erythematosus: a systematic review and meta-analysis.

Neuropsychiatric Systemic Lupus Erythematosus (NPSLE) is a complex manifestation of Systemic Lupus Erythematosus (SLE) characterized by a wide range of neurological and psychiatric symptoms. This study aims to elucidate the patterns of Perfusion-Weighted MRI (PWI) in NPSLE patients compared to SLE patients without neuropsychiatric manifestations (non-NPSLE) and healthy controls (HCs). A systematic search was conducted in PubMed/Medline, Embase, Web of Science, and Scopus for studies utilizing PWI in NPSLE patients published through April 14, 2024. Cerebral blood flow (CBF) data from NPSLE, non-NPSLE patients, and HCs were extracted for meta-analysis, using standardized mean difference (SMD) as an estimate measure. For studies lacking sufficient data for inclusion, CBF, cerebral blood volume (CBV), and mean transit time (MTT) were reviewed qualitatively. Our review included eight observational studies employing PWI techniques, including dynamic susceptibility contrast (DSC) and arterial spin labeling (ASL). The meta-analysis of NPSLE compared to non-NPSLE incorporated four studies, encompassing 104 NPSLE patients and 90 non-NPSLE patients. The results revealed an SMD of -1.42 (95% CI: -2.85-0.00, I2: 94%) for CBF in NPSLE compared to non-NPSLE. PWI reveals informative patterns of cerebral perfusion, showing a significant reduction in mean CBF in NPSLE patients compared to non-NPSLE patients. Our qualitative synthesis highlights these changes, particularly in the frontal and temporal lobes. However, the existing data exhibits considerable heterogeneity and limitations.

Sink location problems in dynamic flow grid networks

A dynamic flow network consists of a directed graph, where nodes called sources represent locations of evacuees, and nodes called sinks represent locations of evacuation facilities. Each source and each sink are given supply representing the number of evacuees and demand representing the maximum number of acceptable evacuees, respectively. Each edge is given capacity and transit time. Here, the capacity of an edge bounds the rate at which evacuees can enter the edge per unit time, and the transit time represents the time which evacuees take to travel across the edge. The evacuation completion time is the minimum time at which each evacuee can arrive at one of the evacuation facilities. Given a dynamic flow network without sinks, once sinks are located on some nodes or edges, the evacuation completion time for this sink location is determined. We then consider the problem of locating sinks to minimize the evacuation completion time, called the sink location problem. The problems have been given polynomial-time algorithms only for limited networks such as paths [1–3], cycles [1], and trees [4–6], but no polynomial-time algorithms are known for more complex network classes. In this paper, we prove that the 1-sink location problem can be solved in polynomial-time when an input network is a grid with uniform edge capacity and transit time.

Searching for tidal orbital decay in hot Jupiters

ABSTRACT We study transits of several ‘hot Jupiter’ systems, including WASP-12 b, WASP-43 b, WASP-103 b, HAT-P-23 b, KELT-16 b, WD 1856+534 b, and WTS-2 b, with the goal of detecting tidal orbital decay and extending the baselines of transit times. We find no evidence of orbital decay in any of the observed systems except for that of the extensively studied WASP-12 b. Although the orbit of WASP-12 b is unequivocally decaying, we find no evidence for acceleration of said orbital decay, with measured $\ddot{P} = (-7 \pm 8) \times 10^{-14} \, \rm s^{-1}$, against the expected acceleration decay of $\ddot{P} \approx -10^{-23} \, \rm s^{-1}$. In the case of WD 1856+534 b, there is a tentative detection of orbital growth with $\dot{P} = (5.0 \pm 1.5) \times 10^{-10}$. While statistically significant, we err on the side of caution and wait for longer follow-up observations to consider the measured $\dot{P}$ real. For most systems, we provide a 95 per cent confidence lower limit on the tidal quality factor, $Q_\star ^{\prime }$. The possibility of detecting orbital decay in hot Jupiters via long-term radial velocity (RV) measurements is also explored. We find that ${\sim} 1 \rm \, m \, s^{-1}$ precision in RVs will be required to detect orbital decay of WASP-12 b with only 3 yr of observations. Currently available RV measurements and precision are unable to detect orbital decay in any of the systems studied here.

The effect of fiber supplementation with agave fructans or psyllium plantago in symptoms of constipation and its relation with whole and regional transit time and pH.

Supplementation with the Agave tequilana Weber blue variety fructans is a feasible treatment option for functional constipation (FC). However, its effects on colonic function have not yet been studied. This study assessed whole gut transit time (WGTT) and regional transit time using a wireless motility capsule (WMC) before and after supplementation with different fiber treatments in patients with FC. A secondary analysis was performed on data collected from a randomized, double-blind clinical trial comparing agave fructans with psyllium plantago. WGTT, regional transit time, contractility, and pH were measured using WMC before and after fiber supplementation. Comparisons were performed using nonparametric tests. Twenty patients with FC were evaluated, with a median age of 39 (25-54 years), and 18 (90%) were women. Five patients were included in each intervention group. There were no changes in WGTT or regional transit times between the groups (p > 0.05). Similarly, there were no differences in the changes experienced by regional or general contractility among the groups (p > 0.05). The cecal pH profile did not differ between the groups before and after fiber supplementation (p > 0.05). The percentages of clinical responses and consistency of bowel movements between the groups were similar. FC presents a clinical response to a fiber challenge, regardless of the administered intervention. However, this response was not associated with improvement in contractility or regional transit time. We speculate that there are other mechanisms by which fiber consumption may improve FC.

Competitive flow of bilateral internal thoracic artery Y-graft: Insights from hemodynamics and transit time flow measurement parameters

Recent studies have demonstrated the superior efficacy of bilateral internal thoracic artery (BITA) grafts compared to other graft methods in treating coronary artery disease. Competitive flow (CF) is a primary factor contributing to graft failure in the long term. For the first time, the CF of the BITA-Y graft has undergone rigorous numerical analysis. Through the application of transit time flow measurement (TTFM) and hemodynamic parameters, this study provides a new perspective on graft performance. Simulation results indicate that average flow, TTFM, and hemodynamic parameters fall within the critical range for stenosis severities below 90%. Specifically, at 80% stenosis, the mean graft flow (MGF) and pulsatility index (PI) of the left internal thoracic artery (LITA) were 0.071 cc/s and 27, respectively, while those of the right internal thoracic artery (RITA) were 0.211 cc/s and 11. With increasing stenosis severity, TTFM parameters remained within the clinical permissible limit (MGF &amp;gt; 0.34 cc/s and PI &amp;lt; 5). At 95% stenosis severity, the MGF and PI for LITA were 0.526 cc/s and 1.2, respectively, while those for RITA were 0.790 cc/s and 0.9. The results indicate the presence of competitive flow within the BITA-Y graft for stenosis severities below 90% area reduction, suggesting a potential risk of graft failure in the long term. Additionally, the results indicated that when there are significant differences in stenosis severity between the two native arteries, the BITA-Y graft is not optimal due to CF, characterized by low MGF and high reverse flow.