Conduit Diameter Research Articles

Optimizing the technical results of robotic esophagectomy: conduit creation and esophagogastric anastomoses

The esophagectomy, first done over a century ago, has evolved from open procedures to minimally invasive techniques. As minimally invasive surgery has progressed in both safety and efficiency since its inception, it is becoming increasingly favored and continues to demonstrate advantageous outcomes over open techniques. In terms of operative decisions, conduit diameter choice is crucial in esophagectomy. Narrower conduits (≤ 3 cm) seem to be more efficacious, and less prone to stricture than their wider counterparts (> 5 cm). Perfusion assessment, notably with indocyanine green (ICG), is still a topic of debate among surgeons with conflicting opinions on ICG’s impact. There are varying results in leak rates; however, the use of ICG in determining anastomotic site seems to exert some influence on surgical decision-making. Anastomotic techniques, such as circular stapling and linear stapling, have shown to be preferred over more traditional hand-sewn methods. At our institution, a completely robotic approach is used with creation of a 3-4 cm wide conduit and hybrid-type anastomosis. ICG is used to guide conduit transection and gastrotomy for anastomosis. Our experience shows that this approach offers an excellent combination of safety and reproducibility.

542. POST-ESOPHAGECTOMY PARACONDUIT HIATAL HERNIA DEVELOPMENT AND RECURRENCE

Abstract Background Hiatal hernia post esophagectomy is a delayed postoperative complication. Historically, in open surgery, the incidence is rare. The increased utilization of minimally invasive methods has increased the incidence of hiatal hernias. Current literature is limited to case series. There is even less on frequency and management of re-recurrent cases. Our objectives were to identify the incidence of hiatal hernia post esophagectomy and the outcomes of the recurrent cases. Methods A retrospective analysis of prospective data at a single center was conducted on esophagectomies performed 2017 to 2022. Non-gastric conduit reconstructions were excluded. Baseline patient demographics including comorbidities, type of tumor, neoadjuvant therapy, surgical approach (open versus minimally invasive [MIE]), and conduit construction were recorded. Radiographic presence of non-gastric conduit abdominal contents was defined as hiatal hernia. Time of hiatal hernia occurrence, details of the repair and timing re-recurrence was recorded. Associated factors described in literature including baseline demographics, neoadjuvant therapy, operative technique, conduit diameter and use of pexy techniques were analyzed with univariate analysis. P<0.05 was considered significant. Results A total of 565 esophagectomies met inclusion criteria, 78% (439/565) were MIE. Robotic-assisted comprised 33% (143/439) of the MIE cohort. A hiatal hernia was identified in 3% of patients (15/565). All had malignancy and were Ivor Lewis (11/15, 73%) or 3-hole (4/15, 27%). The majority had an MIE (13/15, 86%), one had open esophagectomy (6%), and one had hybrid (1/15, 6%). There was no difference in risk factors between the hernia and non-hernia groups. Median time to hernia was 5 months (IQR: 4, 12). All underwent repair. Recurrent hernia occurred in 33% of patients (5/15), all within the robotic-assisted MIE. Conclusion Hiatal hernia post esophagectomy occurred in 3% of cases, and most cases occurred within the MIE group. Recurrence of hernias occurred in robotic-assisted esophagectomy patients. Analysis of patient-specific factors such as prior hiatal hernia, body-mass index, neoadjuvant therapy, operative technique, conduit pexy technique all did not reveal significant correlation with hiatal hernia development. The recurrence of hiatal hernia all required redo repairs. Though we had no deaths in the hiatal hernia cohort, repeat surgeries affect morbidity in esophagectomy patients. Further analysis is needed to identify ways to minimize hernia recurrence in minimally invasive esophagectomy.

Durability of Aortic Homografts in Pulmonary Atresia and Major Aortopulmonary Collateral Arteries.

Objectives: It is well-known that right ventricle-to-pulmonary artery homograft conduit durability is worse for smaller conduits and smaller/younger patients. However, there is limited literature on age and conduit-size specific outcomes, or on the role of conduit oversizing. Methods: Patients diagnosed with tetralogy of Fallot and major aortopulmonary collateral arteries undergoing right ventricular outflow tract (RVOT) reconstruction with a valved aortic homograft conduit from November 2001 through March 2023, at our institution were included. Conduits were grouped and evaluated by diameter, diameter Z-score, and patient age at implant. The primary time-related outcome was freedom from RVOT reintervention. Factors associated with freedom from time-related outcomes were assessed with univariable Cox regression analysis. Results: A total of 863 RVOT conduits were implanted in 722 patients. On multivariable analysis, younger age, male sex, Alagille syndrome, smaller diameter of the conduit, and smaller Z-score were associated with shorter freedom from reintervention. Among patients with smaller diameter conduits, larger Z-scores were associated with longer freedom from conduit reintervention (P < .001). Transcatheter interventions were commonly used to extend conduit lifespan across ages and conduit sizes. Conclusions: Larger conduit diameter, older age, and higher conduit Z-score were associated with longer freedom from reintervention in patients undergoing RVOT reconstruction in this cohort. Oversizing of conduits, even beyond a Z-score of 4, is generally appropriate.

Numerical study on the efficiency of an electrostatic precipitator having the shape of a truncated cone

This paper presents a comprehensive numerical study of a truncated conical precipitator. The main objective was to enhance the efficiency of the precipitator by exploring the influence of several parameters on particle trajectories and the evolution of the collection efficiency. The studied parameters include the cone coefficient ( D), flow velocity, applied voltage, conduit diameter and length, as well as relative permeability. For each parameter, analyses were conducted on the evolution of the collection efficiency for particles with various diameters, ranging from 0.01 to 10 μm. The results obtained from the numerical simulation on COMSOL Multiphysics® indicate that, regardless of the value of D, the precipitator exhibits optimal efficiency in collecting particles with extreme diameters (0.01 and 10 μm) due to the dominance of the electrical force. In contrast, particles with intermediate diameters (0.1–1 μm) present a challenge, as the drag and electric forces are too weak to ensure effective particle collection. The study highlights that a sharper tip at the top of the precipitator significantly enhances its efficiency. Increasing the applied voltage and selecting lower inner radii of the collecting electrode reinforce the electrical force and enhance particle collection. Furthermore, increasing the height of the precipitator directs particle trajectories more effectively toward the collecting electrode. The results provide valuable insights for the design of more efficient precipitators and propose practical guidelines for improving their effectiveness. These contributions are particularly important for air pollution control technologies, offering significant advancements in this field.

Seasonal plasticity of stem embolism resistance and its potential driving factors in six temperate woody species.

The seasonal plasticity of resistance to xylem embolism has been demonstrated in leaves of some tree species, but is controversial in stems. In this study, we investigated the seasonality of stem xylem resistance to embolism in six temperate woody species (four deciduous and two evergreen tree species) that were grown at the same site. The xylem conduit anatomy, the concentrations, and ratios of the main cation in the xylem sap, as well as the content of nonstructural carbohydrates (including soluble sugars and starch) were measured in each species under each season to reveal the potential mechanisms of seasonal change in embolism resistance. The stem of all species showed increasing resistance to embolism as seasons progressed, with more vulnerable xylem in spring, but no significant adjustment in the other three seasons. The seasonal plasticity of stem embolism resistance was greater in deciduous species than in evergreen. On a seasonal scale, conduit diameter and conduit implosion resistance, the ratios of K+/Ca2+ and K+/Na+, and starch content were generally not correlated with embolism resistance, suggesting that these are probably not the main drivers of seasonal plasticity of stem embolism resistance. The seasonality of embolism resistance provides critical information for better understanding plant hydraulics in response to seasonal environments, especially under climate change.

Melody transcatheter pulmonary valve replacement: a single-center case series in Southeast Asia

BackgroundStudies of transcatheter pulmonary valve replacement (TPVR) with the Melody valve have demonstrated good clinical and hemodynamic outcomes. Our study analyzes the midterm clinical and hemodynamic outcomes for patients who underwent Melody valve implantation in Southeast Asia.MethodsPatients with circumferential conduits or bioprosthetic valves and experiencing post-operative right ventricular outflow tract (RVOT) dysfunction were recruited for Melody TPVR.ResultsOur cohort (n = 14) was evenly divided between pediatric and adult patients. The median age was 19 years (8–38 years), a male-to-female ratio of 6:1 with a median follow-up period of 48 months (16–79 months), and the smallest patient was an 8-year-old boy weighing 18 kg. All TPVR procedures were uneventful and successful with no immediate mortality or conduit rupture. The primary implant indication was combined stenosis and regurgitation. The average conduit diameter was 21 ± 2.3 mm. Concomitant pre-stenting was done in 71.4% of the patients without Melody valve stent fractures (MSFs). Implanted valve size included 22-mm (64.3%), 20-mm (14.3%), and 18-mm (21.4%). After TPVR, the mean gradient across the RVOT was significantly reduced from 41 mmHg (10–48 mmHg) to 16 mmHg (6–35 mmHg) at discharge, p < 0.01. Late follow-up infective endocarditis (IE) was diagnosed in 2 patients (14.3%). Overall freedom from IE was 86% at 79 months follow-up. Three patients (21.4%) developed progressive RVOT gradients.ConclusionFor patients in Southeast Asia with RVOT dysfunction, Melody TPVR outcomes are similar to those reported for patients in the US in terms of hemodynamic and clinical improvements. A pre-stenting strategy was adopted and no MSFs were observed. Post-implantation residual stenosis and progressive stenosis of the RVOT require long term monitoring and reintervention. Lastly, IE remained a concern despite vigorous prevention and peri-procedural bacterial endocarditis prophylaxis.

Robust hydraulic traits correlation in woody species despite large trait variation along natural and experimental environmental gradients

Abstract Hydraulic traits are major determinants of plant fitness, thus exerting control over vegetation structure, function and distribution. Yet it remains unclear whether and how hydraulic traits respond to environmental stimuli (i.e. phenotypic variation of hydraulic traits; PVHT) and if the coordination between different hydraulic traits and the trait–climate relationship are affected by PVHT. Here, we synthesized data of PVHT (maximum hydraulic conductivity and water potential inducing 50% loss of hydraulic conductivity) and potentially related morphological and anatomical traits (e.g. sapwood density, branch Huber value, mean and hydraulic weighted conduit diameter). We analysed the magnitude, direction and source of variation of the plastic response, as well as the influence of environmental factors on trait coordination. Additionally, we compared the intra‐ and inter‐specific variation between key hydraulic traits and climate metrics (mean annual precipitation and mean annual temperature) at the site of growth, as well as across the population range. PVHT was highly variable in both magnitude and direction, which was contingent on the environmental factor. The variation in PVHT mainly occurred at high taxonomic levels (i.e. family and genus), whereas phenology explained little variation for PVHT. Despite the high variability, trait correlation remained robust in the presence of environmental stimuli. Moreover, trait–climate relationships differed at inter‐specific and intra‐specific levels. The intra‐specific variation of hydraulic traits in most species showed no correlation with climate metrics compared with the high correlation of hydraulic traits with climate metrics across species. Our findings suggest that the high variability of PVHT does not affect the trait correlation which may be valuable in predicting vegetation dynamics under varying environments. The distinct trait–climate relationships highlight the need to unravel the driving force of PVHT, as well as the adaptive strategy across populations. Read the free Plain Language Summary for this article on the Journal blog.

Which contributes more in predictor of desert shrubs traits: Intra-annual or inter-annual precipitation change?

Considering the implications of future climatic shifts, mid-latitude desert ecosystems will experience pronounced changes in precipitation dynamics, as evidenced by the elevated inter-annual variability and escalated annual incidence of extreme rainfall events. Despite considerable research on vegetation response to intricate precipitation patterns at the community level, the physiological adaptations of individual plants within these assemblages are not well defined. This investigation employed simulations of diverse precipitation scenarios, utilising varying precipitation amounts (to simulate inter-annual variability) and intervals (to simulate intra-annual variability). A field-manipulated experiment was conducted to assess the responses of the leaf and stem hydraulic functional traits of Artemisia ordosica under different precipitation regimes. The results demonstrated that 1) the magnitude of inter-annual precipitation, rather than the intra-annual redistribution of precipitation, dominated the variability in the functional traits of A. ordosica, with diminished inter-annual precipitation inducing an array of functional trait alterations (e.g., specific leaf area, stomatal conductance, water use efficiency, and conduit diameter) to enhance water-use safety. Reallocating precipitation to low-frequency but high-intensity events during years with less inter-annual precipitation was more advantageous for the survival of A. ordosica. 2) A reduction in annual precipitation fostered a correlation between stem and leaf functional traits in A. ordosica (e.g., hydraulic conductance with photosynthetic rate, stomatal conductance, conduit diameter with transpiration rate, and water use efficiency), suggesting that under decreased precipitation, A. ordosica strengthens the coupling between hydraulics and photosynthesis to prevent hydraulic failure, demonstrating a safer survival strategy. Overall, the impact of global changes in precipitation patterns on the individual survival of A. ordosica primarily depended on the variation in inter-annual precipitation rather than the within-year redistribution. This study enhanced our understanding of the adaptability of dominant shrub species within desert shrub communities to altered precipitation patterns under climate change.

BRACHIAL, FEMORAL, AND SKIN HAEMODYNAMIC RESPONSES TO WALKING IN HOT CONDITIONS: COMPARISON BETWEEN MALES AND FEMALES

INTRODUCTION &amp; AIMS Heat exposure induces acute changes in arterial function, but sex differences have not been fully addressed. METHODS Participants walked (5km/h; 2% incline) in a climate chamber (42°C;50%RH) for 120mins. Cutaneous microvascular function (laser doppler flowmetry), conduit artery haemodynamics (Doppler ultrasound) and core temperature were measured at baseline, and every 30min. RESULTS 14♂ and 15♀ completed 120min. At baseline, differences in core temperature (Tc) between males and females were not significant (37.2±0.1 vs 37.0±0.1°C; P=0.06). Across all 5 timepoints, females exhibited larger Tc than males (P=0.019). At baseline, males had larger brachial (3.89±0.11 vs 3.13±0.09mm, P&amp;lt;0.001) and femoral (6.22±0.16 vs 5.29±0.14mm, P=0.001) diameters than females. A significant interaction (P=0.047) indicated that brachial diameter increased more in response to heat exertion than in males, whereas no sex difference was apparent in femoral diameter change. Males and females had similar baseline brachial flows (♂80.1±11.2 vs ♀57.0±7.09ml/min, P=0.087), but males had larger baseline femoral flows (♂263.0±23.9 vs ♀151.5±18.6 ml/min, P=0.010). No sex differences were apparent in the terms of the increases in brachial or femoral flows. Finally, at baseline males and females had similar skin blood flux (♂22.6±2.7 vs ♀18.3±2.9PU), but males demonstrated larger increases during heat exertion (P=0.029). CONCLUSIONS Males exhibit larger baseline artery diameters and flows in vessel beds feeding active (femoral) and inactive (brachial) limbs. In response to heat exertion, men and women exhibit similar increases in conduit diameter and flow to active muscle beds (femoral responses). In the inactive forearms, which reflect thermoregulatory responses, females had larger brachial artery diameter changes, but blood flow responses were similar between the sexes and men demonstrated larger increases in skin perfusion. These data indicate that responses to heat exertion differ in the upper and lower limbs, with sex-differences apparent in each of these territories, and at distinct levels of the arterial hierarchy.

Heat-related changes in the velocity and kinetic energy of flowing blood influence the human heart's output during hyperthermia.

Passive whole-body hyperthermia increases limb blood flow and cardiac output ( ), but the interplay between peripheral and central thermo-haemodynamic mechanisms remains unclear. Here we tested the hypothesis that local hyperthermia-induced alterations in peripheral blood flow and blood kinetic energy modulate flow to the heart and . Body temperatures, regional (leg, arm, head) and systemic haemodynamics, and left ventricular (LV) volumes and functions were assessed in eight healthy males during: (1) 3h control (normothermic condition); (2) 3h of single-leg heating; (3) 3h of two-leg heating; and (4) 2.5h of whole-body heating. Leg, forearm, and extracranial blood flow increased in close association with local rises in temperature while brain perfusion remained unchanged. Increases in blood velocity with small to no changes in the conduit artery diameter underpinned the augmented limb and extracranial perfusion. In all heating conditions, increased in association with proportional elevations in systemic vascular conductance, related to enhanced blood flow, blood velocity, vascular conductance and kinetic energy in the limbs and head (all R2≥0.803; P<0.001), but not in the brain. LV systolic (end-systolic elastance and twist) and diastolic functional profiles (untwisting rate), pulmonary ventilation and systemic aerobic metabolism were only altered in whole-body heating. These findings substantiate the idea that local hyperthermia-induced selective alterations in peripheral blood flow modulate the magnitude of flow to the heart and through changes in blood velocity and kinetic energy. Localised heat-activated events in the peripheral circulation therefore affect the human heart's output. KEY POINTS: Local and whole-body hyperthermia increases limb and systemic perfusion, but the underlying peripheral and central heat-sensitive mechanisms are not fully established. Here we investigated the regional (leg, arm and head) and systemic haemodynamics (cardiac output: ) during passive single-leg, two-leg and whole-body hyperthermia to determine the contribution of peripheral and central thermosensitive factors in the control of human circulation. Single-leg, two-leg, and whole-body hyperthermia induced graded increases in leg blood flow and . Brain blood flow, however, remained unchanged in all conditions. Ventilation, extracranial blood flow and cardiac systolic and diastolic functions only increased during whole-body hyperthermia. The augmented with hyperthermia was tightly related to increased limb and head blood velocity, flow and kinetic energy. The findings indicate that local thermosensitive mechanisms modulate regional blood velocity, flow and kinetic energy, thereby controlling the magnitude of flow to the heart and thus the coupling of peripheral and central circulation during hyperthermia.

Scaling of leaf area with biomass in trees reconsidered: constant metabolically active sapwood volume per unit leaf area with height growth.

Hypoallometric (slope<1) scaling between metabolic rate and body mass is often regarded as near-universal across organisms. However, there are compelling reasons to question hypoallometric scaling in woody plants, where metabolic rate is directly proportional to leaf area. This leaf area must provide carbon to the volume of the metabolically active sapwood (VMASW). Within populations of a species, variants in which VMASW increases per unit leaf area with height growth (e.g. ⅔ or ¾ scaling) would have proportionally less carbon for growth and reproduction as they grow taller. Therefore, selection should favor individuals in which, as they grow taller, leaf area scales isometrically with shoot VMASW (slope=1). Using tetrazolium staining, we measured total VMASW and total leaf area (LAtot) across 22 individuals of Ricinus communis and confirmed that leaf area scales isometrically with VMASW, and that VMASW is much smaller than total sapwood volume. With the potential of the LAtot-VMASW relationship to shape factors as diverse as the crown area-stem diameter relationship, conduit diameter scaling, reproductive output, and drought-induced mortality, our work indicates that the notion that sapwood increases per unit leaf area with height growth requires revision.

Exploring optimal deep tunnel sewer systems to enhance urban pluvial flood resilience in the gangnam region, South Korea

Urban pluvial flooding is becoming a global concern, exacerbated by urbanization and climate change, especially in rapidly developing areas where existing sewer systems lag behind growth. In order to minimize a system's functional failures during extreme rainfalls, localized engineering solutions are required for urban areas chronically suffering from pluvial floods. This study critically evaluates the Deep Tunnel Sewer System (DTSS) as a robust grey infrastructure solution for enhancing urban flood resilience, with a case study in the Gangnam region of Seoul, South Korea. To do so, we integrated a one-dimensional sewer model with a rapid flood spreading model to identify optimal routes and conduit diameters for the DTSS, focusing on four flood-related metrics: the total flood volume, the flood duration, the peak flooding rate, and the number of flooded nodes. Results indicate that, had the DTSS been in place, it could have reduced historical flood volumes over the last decade by 50.1–99.3%, depending on the DTSS route. Regarding the conduit diameter, an 8 m diameter was found to be optimal for minimizing all flood-related metrics. Our research also developed the Intensity-Duration-Frequency (IDF) surfaces in three dimensions, providing a correlation between simulated flood-related metrics and design rainfall characteristics to distinguish the effect of DTSS on flood risk reduction. Our findings demonstrate how highly engineered solutions can enhance urban flood resilience, but they may still face challenges during extreme heavy rainfalls with a 80-year frequency or above. This study contributes to rational decision-making and emergency management in the face of increasing urban pluvial flood risks.

In Situ Rainwater Harvesting System Slows Forest Decline through Increasing Soil Water Content, Fine-Root Traits, and Plant Hydraulic Conductivity

Large-scale vegetation restoration campaigns have been implemented on the Chinese Loess Plateau, which have resulted in higher soil moisture deficits in this region. This, in turn, has hampered the healthy growth of planted trees, leading to a decline and, in severe cases, mortality of trees. Therefore, the rational regulation and utilization of rainwater, the primary water source in this region, may alleviate drought stress, ensuring the sustainability of the ecosystem. In this study, we investigated the impact of in situ rainwater collection and infiltration systems (IRCISs) on soil water, fine-root distribution, xylem vascular, and hydraulic conductivity characteristics in declining Robinia pseudoacacia forests. The results demonstrated that the application of an IRCIS can effectively increase plant available moisture content (0–5.0 m) of declining Robinia pseudoacacia forests. In particular, IRCIS treatment significantly increased xylem conduit diameter and plant hydraulic conductivity while substantially reducing the percentage loss of hydraulic conductivity in both roots and branches. Furthermore, IRCIS treatment significantly reduced the root biomass and distribution depth of Robinia pseudoacacia during both wet and dry years. This implies that IRCISs are beneficial for plant growth and survival. The findings of this study are significant for devising strategic methodologies for the planning and management of rainwater resources.

"Fontan Conduit Stent-Angioplasty and Progression of Fontan-Associated Liver Disease".

Patients with Fontan circulation insidiously develop congestive hepatopathy related to chronically reduced cardiac output and central venous hypertension, also known as Fontan-associated liver disease (FALD). Fontan pathway obstruction is increasingly detected and may accelerate FALD. The impact of conduit stent angioplasty on FALD is unknown. Retrospective, single-center review of patients with Fontan circulation who underwent conduit stent angioplasty at cardiac catheterization over 5-year period. Demographics and cardiac histories were reviewed. Labs, liver ultrasound elastography, echocardiogram, hemodynamic and angiographic data at catheterization were recorded pre- and post-stent angioplasty. Primary outcome was change in hepatic function via MELD-XI scores and liver stiffness (kPa), with secondary outcomes of ventricular function, BNP, and repeat catheterization hemodynamics. 33 patients underwent Fontan conduit stent angioplasty, 19.3 ± 7.0years from Fontan operation. Original conduit diameter was 19.1 ± 1.9mm. Prior to angioplasty, conduit size was reduced to a cross-sectional area 132 (91, 173)mm2 and increased to 314 (255, 363)mm2 post-stent. Subjects' baseline median MELD-XI of 11 (9, 12) increased to 12 (9, 13) at 19 ± 15.5months post-angioplasty (n = 22, p = 0.053). There was no significant change in liver stiffness at 12.1 ± 8.9months post-angioplasty (n = 15, p = 0.13). Median total bilirubin significantly increased (1.4 [0.9, 1.8]), from baseline 1.1 [0.7, 1.5], p = 0.04), as did median BNP (41 [0, 148] from baseline 34 [15, 79]; p = 0.02). There were no significant changes in ventricular function or repeat invasive hemodynamics (n = 8 subjects). Mid-term follow-up of Fontan subjects post-conduit stent angioplasty did not show improvements in non-invasive markers of FALD.

Evaluating physical controls on conduit flow contribution to spring discharge

The physical controls on the contribution of conduit to spring discharge, quantified as the ratio of conduit flow to spring discharge (Qc/Q), are evaluated through numerical simulations using MODFLOW-Conduit Flow Process. The controlling factors include the ratio of conduit surface roughness to conduit diameter (ε/D), the hydraulic conductivity ratio between the conduit wall and the porous matrix (Kc/K), the ratio of groundwater recharge to the hydraulic conductivity of the porous matrix, and conduit density (Cd) defined as the ratio of total conduit length to springshed area. For a single conduit, Qc/Q increases with Kc/K when flow in the conduit is laminar. When flow is turbulent, Qc/Q is stable and then decreases with ε/D, increases with Kc/K, and decreases with R/K due to the limited exchange capacity between matrix and conduit (i.e., small Kc/K). The results of hypothetical conduit networks show that Qc/Q increases with Cd but is not sensitive to the two sets of network structure evaluated. The sensitivity analysis for the Silver Springs in Florida shows that the spatial heterogeneity of conduit diameter causes higher Qc/Q, and Qc/Q is most sensitive to the conduit density, followed by R/K, and then Kc/K.

Comparison of Xylem Anatomy and Hydraulic Properties in Black Locust Trees at Two Growth Stages in Semiarid China

Tree species transitioning between different developmental phases requires homeostatic adjustments in order to maintain the integrity of the tree hydraulic system. Hence, adjustments related to hydraulic traits (e.g., xylem conduit diameter) are of key functional significance. However, critical information on the differences between different developmental stages is rare. Using sapwood samples from 36 black locust trees with different growth stages (actively growing and declining stages) and a soil water gradient along a hillslope, xylem conduits at stem apexes and breast height (1.3 m above ground) stems were measured. The results showed marked differences in vascular traits between actively growing and declining trees. In contrast to actively growing trees, declining trees exhibited a reduction in conduit diameters accompanied by increased frequency with a positively skewed distribution and a subsequent decline in cumulative theoretical hydraulic conductivity. Across all sampled trees, the hydraulically weighted mean conduit diameter tapered acropetally from breast height to the stem apex. The extent of conduit tapering in actively growing trees (0.244, 95% CI 0.201–0.287) aligned with predictions from the hydraulic optimality model. Conversely, trees in a declining status displayed significantly reduced conduit tapering (0.175, 95% CI 0.146–0.198), indicating an elevation in hydraulic resistance with increasing tree height. Variations in hydraulic properties predominantly resulted from differences in tree height rather than variations in stem diameter or soil water content. The correlation between conduit diameter and soil water content in both actively growing and declining trees stemmed indirectly from variations in tree height rather than presenting a direct response to drought stress.

Outcomes after Biventricular Repair Using a Conduit between the Right Ventricle and Pulmonary Artery in Infancy.

This study investigated the outcomes of biventricular repair using right ventricle to pulmonary artery (RV-PA) conduit placement in patients aged <1 year. Patients aged <1 year who underwent biventricular repair using an RV-PA conduit between 2011 and 2020 were included in this study. The outcomes of interest were death from any cause, conduit reintervention, and conduit dysfunction (peak velocity of ≥3.5 m/sec or moderate or severe regurgitation). In total, 141 patients were enrolled. The median age at initial conduit implantation was 6 months. The median conduit diameter z-score was 1.3. The overall 5-year survival rate was 89.6%. In the multivariable analysis, younger age (p=0.006) and longer cardiopulmonary bypass time (p=0.001) were risk factors for overall mortality. During follow-up, 61 patients required conduit reintervention, and conduit dysfunction occurred in 68 patients. The 5-year freedom from conduit reintervention and dysfunction rates were 52.9% and 45.9%, respectively. In the multivariable analysis, a smaller conduit z-score (p<0.001) was a shared risk factor for both conduit reintervention and dysfunction. Analysis of variance demonstrated a nonlinear relationship between the conduit z-score and conduit reintervention or dysfunction. The hazard ratio was lowest in patients with a conduit z-score of 1.3 for reintervention and a conduit z-score of 1.4 for dysfunction. RV-PA conduit placement can be safely performed in infants. A significant number of patients required conduit reintervention and had conduit dysfunction. A slightly oversized conduit with a z-score of 1.3 may reduce the risk of conduit reintervention or dysfunction.

Effects of Geometry on Artificial Tracer Dispersion in Synthetic Karst Conduit Networks

This paper presents the modeling results of tracer test simulations performed using COMSOL Multiphysics (version 6.1), a powerful software for multiphysics simulation. The simulations consist of the propagation of artificial tracers injected into different model configurations. This study is based on computational fluid dynamics (CFDs), which allows us to take into consideration the turbulent regime of the water flow in conduits. The objective of this contribution is to identify the relationship between the tracer dynamics and the geometric parameters of synthetic karstic systems via a systematic investigation of the occurrence of dual-peaked breakthrough curves (BTCs) in tracer tests. Various conduit structures were proposed by modifying five key factors: conduit diameter, presence of pools, connection angle between conduits, distance of the outlet from the inlet, and number of branches. The next step will be to confront these computational experiments with real-world tracer test experiments.

Transvaginal Natural Orifice Specimen Extraction (NOSE) in Laparoscopic Colorectal Cancer Surgery With New Insights on Technique and Patient Selection.

Following laparoscopic colorectal surgery, transabdominal specimen extraction requires a mini-laparotomy or Pfannenstiel incision, associated with increased postoperative pain and wound complications. The vagina has several unique properties that make natural orifice specimen extraction (NOSE) ideal. We report our experience with transvaginal NOSE for colorectal cancer surgery. A transvaginal sizer allows the posterior vagina to be incised under tension. A transverse or cruciate incision is made, followed by the insertion of a double-ring wound protector. The external ring is opened against the perineum to shorten the length of the conduit for specimen delivery. Vaginotomy closure is performed via laparoscopy using a barbed suture. Seventeen consecutive female patients underwent elective colorectal cancer surgery with attempted transvaginal NOSE. Median age and body mass index was 67 (range: 50 to 82) years and 26.5 (range: 19.7 to 35.8)kg/m2, respectively. Fourteen patients (82%) underwent left-sided resections and 3 (18%) underwent right-sided resections. Median operating time, blood loss, and length of hospital stay was 245 (range: 155 to 360) minutes, 30 (range: 10 to 500)mL, and 3 (range: 2 to 9) days, respectively. Transvaginal extraction was unsuccessful in 1 (6%) patient. Two (12%) patients experienced early postoperative morbidity, neither attributable to the extraction procedure. Median tumor circumferential diameter was 3.3 (range: 2.2 to 7.0)cm. Median follow-up duration was 17 (range: 8 to 27) months. There was no instance of sexual dysfunction. Transvaginal NOSE for colorectal cancer surgery is feasible and safe in selected patients. Overall specimen diameter, inclusive of tumor and mesentery, relative to pelvic outlet and conduit diameter is the most important consideration for transvaginal NOSE.

Trade-Off between Hydraulic Safety and Efficiency in Plant Xylem and Its Influencing Factors

Forests are vital ecosystems that are increasingly threatened by environmental stress; exploring the possible trade-off between hydraulic safety and efficiency in plant xylem is crucial to understanding their environmental adaptation strategies. However, to date, there is no consensus whether such trade-offs exist among and within species. To better comprehend the mechanism of xylem water transport, in this review, we summarized previously published work on xylem hydraulic safety and efficiency trade-off from the inter-species, intra-species, and intra-tree perspectives and its influencing factors. We gathered data on xylem hydraulic safety and efficiency and their related anatomical traits, i.e., conduit diameter and inter-conduit pit membrane thickness, from a total of 653 plant species analyzed in 80 published papers. At the inter-species level, we confirmed that there is a weak hydraulic safety and efficiency trade-off. For gymnosperms and herbaceous species, the observed trade-off is stronger. At the intra-species level, the hydraulic safety and efficiency trade-off was found in individuals of the same species investigated in the literature. At the intra-tree level, there is a trade-off between hydraulic safety and efficiency for leaves, stems, and roots, and we confirmed the vessel widening hypothesis, i.e., vessel diameter in the outer wood increases from the top to the bottom of the tree. Additionally, pit membrane thickness increases as the tree height decreases, thus increasing the xylem hydraulic efficiency and affecting the trade-off. Finally, we discussed the environmental factors affecting the trade-off between hydraulic safety and efficiency in the xylem, such as plant habitats, temperature, rainfall, altitude, and soil. Further investigations of the bordered pit membrane from the three-dimensional perspective would be useful to understand the hydraulic safety and efficiency trade-off at the nanoscale.