Total Conductance Research Articles

Quantification and Interpretation of Nitric Oxide-Dependent Cutaneous Vasodilation During Local Heating.

Human cutaneous microdialysis approaches for assessing nitric oxide (NO)-dependent blood flow include local heating (LH) of the skin until a plateau is reached, followed by infusion of a NO synthase inhibitor such as L-NAME; however, varied methods of quantifying and expressing NO-dependent vasodilation can obfuscate data interpretation and reproducibility. We retrospectively assessed NO-dependent vasodilation during LH to 39°C or 42°C, calculated as the: (1) absolute contribution of the NO-dependent component (along with baseline and the non-NO-dependent component) to the total cutaneous vascular conductance (CVC) response to LH, normalized to maximal CVC (%CVCmax); (2) difference in %CVCmax (∆%CVCmax) between the LH plateau and post-NO inhibition (L-NAME plateau; ∆%CVCmax=LH plateau-L-NAME plateau); (3) percentage of the LH plateau attributable to ∆%CVCmax (%Plateau = ∆%CVCmax/LH plateau*100); and (4) %Plateau when correcting for baseline. The LH plateaus during 39°C and 42°C were 48±17 %CVCmax (9±5% baseline; 2±4% non-NO-dependent; 36±15% NO-dependent) and 88±10 %CVCmax (15±8% baseline; 9±10% non-NO-dependent; 64±13% NO-dependent), respectively. The absolute contributions of the non-NO-dependent and NO-dependent components of the response (p<0.0001) and the ∆%CVCmax (66±14% vs. 38±15%) were greater during 42°C compared with 39°C (all p≤0.02); however, there were no differences between the two protocols in %Plateau (75±13% vs. 80±10%; p=0.57) or %PlateauBL (88±14% vs. 95±8%; p=0.31). For both protocols, the values were greater for %PlateauBL versus ∆%CVCmax and %Plateau (p≤0.0001), and for %Plateau versus ∆%CVCmax (p≤0.05). Quantification of NO-dependent skin vasodilation responses to LH is dependent upon the mathematical approach and verbal description, which can meaningfully impact data interpretation and reproducibility.

A Multiple-physics coupled model for nanoconfined CO2-CH4 mixture transport behavior: Implications for CO2 geological storage in ultra-tight formation

Considerable efforts have been made to examine the feasibility of CO2-enhanced gas recovery (CO2-EGR), a promising approach for improving gas recovery by using CO2 to displace in-situ CH4 in ultra-tight gas reservoirs rich in nanopores. However, most research has focused on either single-component gas flow physics or competitive adsorption of multiple gas components in nanopores. The flow behavior of nanoconfined CO2-CH4 mixtures remains an area of knowledge gap. This work establishes a theoretical framework for CO2-CH4 mixture flow capacity by coupling mixture flow in the bulk region with surface diffusion in the adsorption area. Results indicate that: a) Total mixture flow conductance increases rapidly at pressures below ∼10 MPa, with CO2 contributing over 99 % to surface diffusion conductance; b) Increasing CO2 molar ratio from 0.2 to 0.8 can lead to a 167 % enhancement in total mixture conductance; c) Variations in CO2-CH4 competitive adsorption characteristics have little impact on total conductance.

Binge Alcohol Consumption Elevates Sympathetic Transduction to Blood Pressure: A Randomized Controlled Trial.

Alcohol consumption is associated with cardiovascular disease, and the sympathetic nervous system is a suspected mediator. The present study investigated sympathetic transduction of muscle sympathetic nerve activity to blood pressure at rest and in response to cold pressor test following evening binge alcohol or fluid control, with the hypothesis that sympathetic transduction would be elevated the morning after binge alcohol consumption. Using a randomized, fluid-controlled (FC) crossover design, 26 healthy adults (12 male, 14 female, 25±6 years, 27±4 kg/m2) received an evening binge alcohol dose and a FC. All participants underwent next-morning autonomic-cardiovascular testing consisting of muscle sympathetic nerve activity, beat-to-beat blood pressure, and heart rate during a 10-minute rest period and a 2-minute cold pressor test. Sympathetic transduction was assessed at rest and during the cold pressor test in both experimental conditions. Evening alcohol increased heart rate (FC: 60±9 versus alcohol: 64±9 bpm; P=0.010) but did not alter resting mean arterial pressure (FC: 80±6 versus alcohol: 80±7 mm Hg; P=0.857) or muscle sympathetic nerve activity (FC: 18±9 versus alcohol: 20±8 bursts/min; P=0.283). Sympathetic transduction to mean arterial pressure (time×condition; P=0.003), diastolic blood pressure (time×condition; P=0.010), and total vascular conductance (time×condition; P=0.004) was augmented after alcohol at rest. Sympathetic transduction during the cold pressor test was also elevated after evening binge alcohol consumption (P=0.002). These findings suggest that evening binge alcohol consumption leads to augmented morning-after sympathetic transduction of muscle sympathetic nerve activity to blood pressure, highlighting a new mechanism whereby chronic or excessive alcohol consumption contributes to cardiovascular disease progression via altered end-organ responsiveness to sympathetic neural outflow. URL: https://clinicaltrials.gov/study/NCT03567434; Unique identifier: NCT03567434.

Somatostatin peptides prevent increased human colonic epithelial permeability induced by hypoxia.

Mesenteric ischemia increases gut permeability and bacterial translocation. In human colon, chemical hypoxia induced by 2,4-dinitrophenol (DNP) activates basolateral intermediate conductance K+ (IK) channels (designated KCa3.1 or KCNN4) and increases paracellular shunt conductance/permeability (GS), but whether this leads to increased macromolecule permeability is unclear. Somatostatin (SOM) inhibits IK channels and prevents hypoxia-induced increases in GS. Thus, we examined whether octreotide (OCT), a synthetic SOM analog, prevents hypoxia-induced increases GS in human colon and hypoxia-induced increases in total epithelial conductance (GT) and permeability to FITC-dextran 4000 (FITC) in rat colon. The effects of serosal SOM and OCT on increases in GS induced by 100 µM DNP were compared in isolated human colon. The effects of OCT on DNP-induced increases in GT and transepithelial FITC movement were evaluated in isolated rat distal colon. GS in DNP-treated human colon was 52% greater than in controls (P = 0.003). GS was similar when 2 µM SOM was added after or before DNP treatment, in both cases being less (P < 0.05) than with DNP alone. OCT (0.2 µM) was equally effective preventing hypoxia-induced increases in GS, whether added after or before DNP treatment. In rat distal colon, DNP significantly increased GT by 18% (P = 0.016) and mucosa-to-serosa FITC movement by 43% (P = 0.01), and 0.2 µM OCT pretreatment completely prevented these changes. We conclude that OCT prevents hypoxia-induced increases in paracellular/macromolecule permeability and speculate that it may limit ischemia-induced gut hyperpermeability during abdominal surgery, thereby reducing bacterial/bacterial toxin translocation and sepsis.NEW & NOTEWORTHY Somatostatin (SOM, 2 µM) and octreotide (OCT, 0.2 µM, a long-acting synthetic analog of SOM) were equally effective in preventing chemical hypoxia-induced increases in paracellular shunt permeability/conductance in isolated human colon. In rat distal colon, chemical hypoxia significantly increased total epithelial conductance and transepithelial movement of FITC-dextran 4000, changes completely prevented by 0.2 µM OCT. OCT may prevent or limit gut ischemia during abdominal surgery, thereby decreasing the risk of bacterial/bacterial toxin translocation and sepsis.

Reduced diffusional limitations in carnation stems facilitate higher photosynthetic rates and reduced photorespiratory losses compared with leaves.

Green stem photosynthesis has been shown to be relatively inefficient but can occasionally contribute significantly to the carbon budget of desert plants. Although the possession of green photosynthetic stems is a common trait, little is known about their photosynthetic characteristics in non-desert species. Dianthus caryophyllus is a semi-woody species with prominent green stems, which show similar photosynthetic anatomy with leaves. In the present study, we used a combination of gas exchange and chlorophyll fluorescence measurements, some of which were taken under varying O2 and CO2 partial pressures, to investigate whether the apparent anatomical similarities between the species' leaves and stems translate into similar photosynthetic physiology and capacity for CO2 assimilation. Both organs displayed high photosynthetic electron transport rates (ETR) and similar values of steady-state non-photochemical quenching (NPQ), albeit leaves could attain them faster. The analysis of OJIP transients showed that the quantum efficiencies and energy fluxes along the photosynthetic electron transport chain are largely similar between leaves and stems. Stems displayed higher total conductance to CO2 diffusion, similar biochemical properties, significantly higher photosynthetic rates and lower water use efficiency than leaves. Leaf ETR was more sensitive to sub-ambient O2 and super-ambient CO2 partial pressures, while leaves also displayed a higher relative rate of Rubisco oxygenation. We conclude that the highly responsive NPQ and the enhanced photorespiration and WUE in leaves represent photoprotective and water-conserving adaptations to the high incident light intensities they experience naturally, at the expense of higher CO2 assimilation rates, which the vertically orientated stems can readily attain.

Atomistic simulations of coherent thermoelectric transport in ultrathin pristine and decorated noble metals nanowires

Nanowires (NWs) are envisioned to be an important component of novel nanoscale electronic devices. Here, we perform atomistic simulations of coherent thermoelectric (TE) transport in free-standing ultrathin NWs of noble metals (viz. Au, Ag, Cu, Pt) cut along the [111] crystallographic direction using a non-equilibrium Greens function based first principles approach. Effect of decorating these NWs with Au or Pt atoms in an fcc environment, is also explored. Results of the calculated electronic structure show that all considered NWs, except the Pt and Pt-decorated NWs, are metallic and non-magnetic. Interestingly, Cu@Pt NW is found to be a magnetic semiconductor with an unequal band gap in ↑− and ↓−spin energy bands, while Pt NW and other Pt-decorated NWs (viz. Ag@Pt and Au@Pt) behave like a magnetic half-metal. To explore the TE potential of as-considered NWs, electrical conductance G, thermal conductance κT, and thermopower S are computed in the linear response regime. Notably, the metallic NWs exhibit a quantized G. Among these, pristine NWs show a quantized value 3G0 up to a temperature of 200 K, while Cu@Au NW preserves its quantized value 5G0 even at T exceeding 300 K. In thermal transport, valence electrons make a dominant contribution to the room-temperature κT of pristine NWs. The phononic contribution κph, however, goes up following decoration, with Pt-decorated NWs showing a pronounced increment (by a factor of ∼2). But, these NWs undergo a simultaneous reduction in the electronic contribution κel owing to half-metallic conduction, resulting in a net suppression of total thermal conductance κT. Moreover, Pt-decorated NWs show a manifold enhancement in zero-bias S, with Ag@Pt exhibiting the highest value ∼119μV/K. However, S can be augmented considerably by adjusting the chemical potential μ of electrodes, and an overall best S∼−890μV/K is found in Au NW for μ=0.575eV. In this way, TE figure of merit ZT is tunable in pristine NWs over the range 1−3.7. Correspondingly, the decorated NWs exhibit somewhat smaller S and ZT. Furthermore, spin-asymmetric electronic transport in Pt and Pt-decorated NWs results in net spin conductance Gs and spin thermopower Ss. It is found that the spin figure of merit ZsT, as high as 3.5, can be attained in Pt NW by controlling μ. Thus, noble metals NWs can be tailored for both thermoelectric and spin-thermoelectric applications. We have also investigated TE transport for the pristine NWs in the [110] direction, and found S and ZT to be comparatively much smaller. Such NWs may be useful as interconnects for low noise applications.

Optimizing thermoelectric performance in molecular junction: The role of van der Waals interface coupling with boron-doped electrodes

The key prerequisite for fully rationalizing and optimizing thermoelectric performance of molecular devices is to effectively overcome the inherent mismatch between electrode molecular orbital energy and Fermi level (FL). Two structures were formed by stacking bis-phenylethynyl-anthrancene (BPA-molecule) with B-doped armchair/zigzag graphene nanoribbon (AGNR@B/ZGNR@B) electrodes. Optimal distance between the molecule and these two B-doped graphene nanoribbons was related to interfacial stacking mode (BPA-AGNR@B optimization distance is 3.387\\AA for the case of top-site stacking, and it is 3.472\\AA for malposed stacking of BPA-ZGNR@B). Thermal conductivities of both the two B-doped systems based on mass mismatch mechanism are greatly improved at FL. The role of mass matching effect on total thermal conductance of BPA-AGNR@B system is pivotal to result in significant enhancements, but it is not the case for BPA-ZGNR@B, because large layer spacing weakens mass matching effect. In addition, boron-doped molecular junctions (BPA-AGNR@B and BPA-ZGNR@B) show an excellent thermoelectric quality factor (ZT) of 3.5/3.3 near FL.

Application of Electrical Resistivity Sounding Method for Groundwater Exploration in Ugboshi-Afe, Akoko-Edo, Southwestern Nigeria

Schlumberger configuration of Vertical Electrical Sounding (VES) was deplored for groundwater exploration in Ugboshi-Afe study location. A total of nine (9) vertical electrical sounding (VES) locations, spread across the community were occupied to gain insights on the hydrogeological settings within the area. Quantitative computer interpretation of the data yielded three to six geoelectrical layers. The geoelectrical interpretation models were geologically interpreted as: clayey sand/sandy topsoil with resistivity values ranging from 54 Ohm-m to 424 Ohm-m, this is underlain by a relatively high resistivity layer (228-868 Ohm-m) interpreted as lateritic sand, and below this the low resistivity (21.38 Ohm-m – 42.4 Ohm-m) interpreted as clay, then the fractured/weathered geoelectric layer (95Ohm-m to 385Ohm-m), while the fresh basement has resistivity greater than 400 Ohm-m. Several maps such as fractured window thickness map, isoresistivity map of the fractured interval, overburden map were generated to investigate trends that may hold prospects for groundwater exploitation. Furthermore, hydro-resistivity parameters such as Total Transverse Resistance, Total Longitudinal Conductance, Resistivity Reflection Co-efficient and Resistivity Contrast values were calculated for further screening of the study site for groundwater development. The VES1, VES2, VES6 and VES7 locations were concluded as holding prospects for groundwater potentials in the study area.

Interspecific variation in Rubisco CO2/O2 specificity along the leaf economic spectrum across 23 woody angiosperm plants in the Pacific islands.

The coordinated interspecific variation in leaf traits and leaf lifespan is known as the leaf economic spectrum (LES). The limitation of CO2 diffusion to chloroplasts within the lamina is significant in C3 photosynthesis, resulting in a shortage of CO2 for Rubisco. Although Rubisco CO2/O2 specificity (SC/O) should be adaptively adjusted in response to the interspecific variation in CO2 concentrations [CO2] associated with Rubisco, SC/O variations across species along the LES remain unknown. We investigated the coordination among leaf traits, including SC/O, CO2 conductance, leaf protein content, and leaf mass area, across 23 woody C3 species coexisting on an oceanic island through phylogenetic correlation analyses. A high SC/O indicates a high CO2 specificity of Rubisco. SC/O was negatively correlated with [CO2] at Rubisco and total CO2 conductance within lamina, while it was positively correlated with leaf protein across species, regardless of phylogenetic constraint. A simulation analysis shows that the optimal SC/O for maximizing photosynthesis depends on both [CO2] at Rubisco sites and leaf protein per unit leaf area. SC/O is a key parameter along the LES axis and is crucial for maximizing photosynthesis across species and the adaptation of woody plants.

Accurate photosynthetic parameter estimation at low stomatal conductance: effects of cuticular conductance and instrumental noise

Accurate estimation of photosynthetic parameters is essential for understanding plant physiological limitations and responses to environmental factors from the leaf to the global scale. Gas exchange is a useful tool to measure responses of net CO2 assimilation (A) to internal CO2 concentration (Ci), a necessary step in estimating photosynthetic parameters including the maximum rate of carboxylation (Vcmax) and the electron transport rate (Jmax). However, species and environmental conditions of low stomatal conductance (gsw) reduce the signal-to-noise ratio of gas exchange, challenging estimations of Ci. Previous works showed that not considering cuticular conductance to water (gcw) can lead to significant errors in estimating Ci, because it has a different effect on total conductance to CO2 (gtc) than does gsw. Here we present a systematic assessment of the need for incorporating gcw into Ci estimates. In this study we modeled the effect of gcw and of instrumental noise and quantified these effects on photosynthetic parameters in the cases of four species with varying gsw and gcw, measured using steady-state and constant ramping techniques, like the rapid A/Ci response method. We show that not accounting for gcw quantitatively influences Ci and the resulting Vcmax and Jmax, particularly when gcw exceeds 7% of the total conductance to water. The influence of gcw was not limited to low gsw species, highlighting the importance of species-specific knowledge before assessing A/Ci curves. Furthermore, at low gsw instrumental noise can affect Ci estimation, but the effect of instrumental noise can be minimized using constant-ramping rather than steady-state techniques. By incorporating these considerations, more precise measurements and interpretations of photosynthetic parameters can be obtained in a broader range of species and environmental conditions.

A comprehensive evaluation of different responses of supplementary light qualities on physiological and biochemical mechanisms of ‘Kyoho’ grape

Grape is an economically important fruit crop worldwide, for which light qualities play a diverse role in vineyard growth and development. However, the regulatory mechanisms between different light qualities and the quality of plant growth at the morphophysiological and pomological levels remain unknown. Therefore, in the current study, we studied plant physiological, biochemical and genetical analysis to investigate the response of all seven light qualities, including red (R), blue (B), white (W), 1-red, 1 blue (1R1B), 2-red, 1-blue (2R1B), 1-red, 2-blue (1R2B), and natural (N, was used as control group) to evaluate ‘Kyoho'grape (Vitis labrusca L. × V. vinifera) morphophysiological, pomological traits at light responsive transcriptional pathway, which revealed the possible networking metabolism controlling fruit quality and quantity of grape plant. Our results showed that photosynthetic indicators such as leaf stomata, number of stomata, and longitudinal and transverse diameter of stomata improved under red and blue light qualities as compared to white light. Leaf gas exchange indicators showed that net photosynthetic rate, transpiration rate, intercellular CO2 concentration rate, total conductance to CO2, stomatal conductance, conductance to water vapor, maximal quantum yield of PS (II), actual photochemical quantum efficiency, electron transfer chain, and non-photochemical quantum efficiency improve under blue and red light. Photosynthetic pigments showed that chlorophyll a and b, carotenoid, and total pigment contents improved under blue and red light. Nutrient elements showed that potassium, phosphorous, magnesium, calcium, iron, and zinc contents improved under blue and red light. Morphological and organic acid indicators such as the appearance of fruit shape, firmness, and titratable acidity improved under blue and light. However, there was a notable increment in the total soluble sugar under blue and red light as compared to natural light. The composition of sugar including (sucrose, fructose, glucose) and organic acids (tartaric acid, citric acid, and malic acid) improved under blue and red light (fruits) and showed notable reductions for tartaric acid under blue and red light (leaves) as compared to natural light. Aromatic compounds showed that esters, aldehydes, acetaldehyde, 2-hexenal, ethyl acetate, n-propyl acetate, butanoic acid, ethyl ester, 1-hexanol, 2-ethyl, 2-propanone, and 1‑hydroxyl, improved under blue and red light. Further, changes in enhanced expression of light-responsive genes including VvCRYI, VvCRY2, VvPHYA, VvPHYB, VvCOP1, VvHY5, VvHYH, and VvPIF4 upregulated under blue and red light, while VvPIF3.1 down-regulated as compared to natural light. Also, chlorophyll synthesis-related genes including VvSGR, VvPAO, and VvCHLH upregulated under blue and red light, while VvNYC1, VvPPH, and VvPOR showed noticeable changes under blue and red light as compared to natural light. Interestingly, most of the relative genes were highly expressed in fruits as compared to leaves. Finally, we have established correlation and principal component analysis for indicators in grapes. Current findings provide novel mechanisms by which different responses of supplementary light control the plant fruit quality of grapes.

Sympathetic Transduction to Blood Pressure in Patients with Chronic Kidney Disease

Chronic kidney disease (CKD) is a major health problem affecting more than 35 million Americans. Notably, more patients with CKD die of cardiovascular complications than progress to end-stage renal disease. An overactive sympathetic nervous system is a well-known cardiovascular risk factor. Previous research has suggested elevated resting sympathetic nerve activity and a heightened α-adrenergic receptor sensitivity in patients with CKD, both of which may predispose this population to greater sympathetic transduction. Therefore, we tested the hypothesis that patients with stage III CKD have an augmented sympathetic transduction to blood pressure (BP) compared to controls without CKD. In 7 patients with stage III CKD and 8 controls muscle sympathetic nerve activity (MSNA; peroneal microneurography) and beat-to-beat BP (finometer) were continuously recorded during 10 minutes of quiet supine rest. Modelflow was used to estimate stroke volume and calculate total vascular conductance (TVC). Sympathetic transduction was quantified as the peak change in mean arterial pressure (MAP) and the nadir reduction of TVC over 10 cardiac cycles following spontaneous MSNA bursts using signal averaging. Patients with CKD and controls had similar resting MAP (CKD: 102 ± 14 mmHg; CON: 95 ± 8 mmHg; P = 0.27), MSNA burst frequency (CKD: 33 ± 10 bursts/min; CON: 31 ± 14 bursts/min; P = 0.78) and MSNA burst incidence (CKD: 53 ± 15 bursts/100 heartbeats; CON: 47 ± 24 bursts/100 heartbeats; P = 0.60). Peak increases in MAP following all bursts of MSNA were not different between patients with CKD and controls (CKD: 2.1 ± 0.7 mmHg; CON: 2.2 ± 0.9 mmHg; P = 0.83). Likewise, nadir reductions in TVC following all bursts of MSNA were not different in patients with CKD (CKD: -1.2 ± 0.6 ml/min/mmHg; CON: -1.4 ± 0.5 ml/min/mmHg; P = 0.46). Similar results were observed when considering burst patterning. MSNA bursts occurring in multiples (adjacent to other bursts) produced comparable peak MAP (CKD: 2.6 ± 0.6 mmHg; CON: 2.8 ± 1.2 mmHg; P = 0.67) and nadir TVC (CKD: -1.5 ± 0.7 ml/min/mmHg; CON: -1.9 ± 0.7 ml/min/mmHg; P = 0.25) responses between groups. There were also no differences in peak MAP and nadir TVC responses following single bursts of MSNA (bordered by cardiac cycles lacking bursts; both P &gt; 0.30). These preliminary data suggest that, in contrast to our hypothesis, sympathetic transduction to BP is not augmented in patients with stage III CKD. This project was supported by the National Heart, Lung, and Blood Institute R01 HL-127071 (PJF). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Carbon Dioxide Toxicity to Zebra Mussels (Dreissena polymorpha) is Dependent on Water Chemistry.

Carbon dioxide (CO2) is gaining interest as a tool to combat aquatic invasive species, including zebra mussels (Dreissena polymorpha). However, the effects of water chemistry on CO2 efficacy are not well described. We conducted five trials in which we exposed adult zebra mussels to a range of CO2 in water with adjusted total hardness and specific conductance. We compared dose-responses and found differences in lethal concentration to 50% of organisms (LC50) estimates ranging from 108.3 to 179.3 mg/L CO2 and lethal concentration to 90% of organisms (LC90) estimates ranging from 163.7 to 216.6 mg/L CO2. We modeled LC50 and LC90 estimates with measured water chemistry variables from the trials. We found sodium (Na+) concentration to have the strongest correlation to changes in the LC50 and specific conductance to have the strongest correlation to changes in the LC90. Our results identify water chemistry as an important factor in considering efficacious CO2 concentrations for zebra mussel control. Additional research into the physiological responses of zebra mussels exposed to CO2 may be warranted to further explain mode of action and reported selectivity. Further study could likely develop a robust and relevant model to refine CO2 applications for a wider range of water chemistries. Environ Toxicol Chem 2024;43:1312-1319. Published 2024. This article is a U.S. Government work and is in the public domain in the USA. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Temperature coefficient of resistance and thermal boundary conductance determination of ruthenium thin films by micro four-point probe

Accurate characterization of the temperature coefficient of resistance (α TCR) of electrically conductive materials is pertinent for reducing self-heating in electronic devices. In-situ non-destructive measurements of α TCR using the micro four-point probe (M4PP) technique have previously been demonstrated on platinum (Pt) thin films deposited on fused silica, assuming the thermal conductivity of the substrate as known. In this study, we expand the M4PP method to obtain the α TCR on industrially relevant stacks, comprising ruthenium (Ru) thin films (3.3 nm and 5.2 nm thick) deposited on bulk silicon (Si), separated by a 90 nm SiO2 spacer. The new M4PP methodology allows simultaneous determination of both α TCR and the total thermal boundary conductance (G TBC) between the metallic film and its substrate. We measured the α TCR and the G TBC to be 542 ± 18 ppm K−1 and 15.6 ± 1.3 MW m−2K−1 for 3.3 nm Ru, and 982 ± 46 ppm K−1 and 19.3 ± 2.3 MW m−2K−1 for 5.2 nm Ru. This is in good agreement with independent measurements of α TCR. Our methodology demonstrates the potential of M4PP to characterize thermal properties of metallic thin films used in semiconductor technology.

Ifanosine: Olea europaea L. and Hyphaene thebaica L. combination, from traditional utilization to rational formulation: Preclinical and clinical efficacy on hypertensives patients

Ethnopharmacological relevanceOlea europaea L. and Hyphaene thebaica L. are commonly employed by traditional healers in Africa for treating and preventing hypertension, either individually or in a polyherbal preparation (Ifanosine). Aim of the studyThe primary aim was to assess the antihypertensive effects of Olea europaea L. leaves aqueous extract (OEL), Hyphaene thebaica L. mesocarp extract (HT), and the Ifanosine on isolated rat aorta rings. The secondary objective was to evaluate the clinical benefits of a new oral formulation of Ifanosine. Materials and methodsIn vitro studies using an isometric transducer examined the antihypertensive effects of HT, OEL, and Ifanosine on rat aorta. Ussing chambers technic were employed to measure mucosal to serosal fluxes and total transepithelial electrical conductance (Gt) to assess the intestinal bioavailability of HT, OEL, and Ifanosine. HPLC was utilized to determine the phytochemical composition of OEL and HT extracts. Subchronic toxicity investigations involved two groups of rats, treated with either water (control) or Ifanosine at 5 g/kg for 28 days. Clinical benefits of the new Ifanosine formulation were evaluated in an observational study with 32 hypertensive patients receiving a fixed oral dose of 3.5 mg three times a day for 30 days. ResultsAqueous extracts induced dose-dependent relaxation of rat aorta rings, with HT and OEL having higher IC50 values than Ifanosine (IC50 = 44.76 ± 1.35 ng/mL, 58.67 ± 1.02 ng/mL, and 29.46 ± 0.26 ng/mL, respectively). The pA2 values of OEL and HT were 1 and 0.6, respectively, while Ifanosine was 0.06. Intestinal bioavailability studies revealed better Prazosin bioavailability than plant extracts. Toxicological studies demonstrated the safety of Ifanosine, supported by histological examinations and biochemical parameters in rat blood. Biochemical analyses indicated flavonoids and phenolic acids as dominant active constituents. Clinical benefits in humans included reduced SBP, DBP, LDL-c, VLDL-c, and TAG, and increased HDL-c without overt adverse effects. ConclusionThis study validates the traditional use of OEL and HT for hypertension and advocates for alternative and combinatorial polyphytotherapy (ACP) to enhance traditional remedies.

Amphistomy increases leaf photosynthesis more in coastal than montane plants of Hawaiian 'ilima (Sida fallax).

The adaptive significance of amphistomy (stomata on both upper and lower leaf surfaces) is unresolved. A widespread association between amphistomy and open, sunny habitats suggests the adaptive benefit of amphistomy may be greatest in these contexts, but this hypothesis has not been tested experimentally. Understanding amphistomy informs its potential as a target for crop improvement and paleoenvironment reconstruction. We developed a method to quantify "amphistomy advantage" ( ) as the log-ratio of photosynthesis in an amphistomatous leaf to that of the same leaf but with gas exchange blocked through the upper surface (pseudohypostomy). Humidity modulated stomatal conductance and thus enabled comparing photosynthesis at the same total stomatal conductance. We estimated and leaf traits in six coastal (open, sunny) and six montane (closed, shaded) populations of the indigenous Hawaiian species 'ilima (Sida fallax). Coastal 'ilima leaves benefit 4.04 times more from amphistomy than montane leaves. Evidence was equivocal with respect to two hypotheses: (1) that coastal leaves benefit more because they are thicker and have lower CO2 conductance through the internal airspace and (2) that they benefit more because they have similar conductance on each surface, as opposed to most conductance being through the lower surface. This is the first direct experimental evidence that amphistomy increases photosynthesis, consistent with the hypothesis that parallel pathways through upper and lower mesophyll increase CO2 supply to chloroplasts. The prevalence of amphistomatous leaves in open, sunny habitats can partially be explained by the increased benefit of amphistomy in "sun" leaves, but the mechanistic basis remains uncertain.

Sex Differences in Sympathetic Responses to Lower-Body Negative Pressure.

Trauma-induced hemorrhage is a leading cause of death in prehospital settings. Experimental data demonstrate that females have a lower tolerance to simulated hemorrhage (i.e., central hypovolemia). However, the mechanism(s) underpinning these responses are unknown. Therefore, this study aimed to compare autonomic cardiovascular responses during central hypovolemia between the sexes. We hypothesized that females would have a lower tolerance and smaller increase in muscle sympathetic nerve activity (MSNA) to simulated hemorrhage. Data from 17 females and 19 males, aged 19-45 yr, were retrospectively analyzed. Participants completed a progressive lower-body negative pressure (LBNP) protocol to presyncope to simulate hemorrhagic tolerance with continuous measures of MSNA and beat-to-beat hemodynamic variables. We compared responses at baseline, at two LBNP stages (-40 and -50 mmHg), and at immediately before presyncope. In addition, we compared responses at relative percentages (33%, 66%, and 100%) of hemorrhagic tolerance, calculated via the cumulative stress index (i.e., the sum of the product of time and pressure at each LBNP stage). Females had lower tolerance to central hypovolemia (female: 561 ± 309 vs male: 894 ± 304 min·mmHg [time·LBNP]; P = 0.003). At LBNP -40 and -50 mmHg, females had lower diastolic blood pressures (main effect of sex: P = 0.010). For the relative LBNP analysis, females exhibited lower MSNA burst frequency (main effect of sex: P = 0.016) accompanied by a lower total vascular conductance (sex: P = 0.028; main effect of sex). Females have a lower tolerance to central hypovolemia, which was accompanied by lower diastolic blood pressure at -40 and -50 mmHg LBNP. Notably, females had attenuated MSNA responses when assessed as relative LBNP tolerance time.

A novel approach for optimizing the natural gas liquefaction process

The conversion of natural gas into liquefied natural gas (LNG) requires substantial energy consumption. This study proposes a deterministic mathematical model to find the optimal operation conditions for an LNG plant to minimize the energy consumption for turbomachinery and the total thermal conductance of the heat exchangers. General Algebraic Modeling System (GAMS) linked to a Dynamic Link Library was used to calculate the thermodynamic properties of the working fluids. A derivative-based optimization algorithm is used. Results indicate that the novel optimization approach allows the satisfactory management of the model nonlinearities associated, for example, with the bilinear terms involved in the energy balances and the mathematical functions used to calculate the thermodynamic properties. A preprocessing phase for initializing process variables is developed to facilitate model convergence. In comparison to an optimal design reported in the literature, which was obtained by integrating a well-established evolutionary optimization approach with the Aspen HYSYS simulator, the results indicated that the net electrical power could be reduced by up to 10% when the derivative-based optimization algorithm is used. The proposed deterministic approach, consisting of a mathematical model, an initialization phase, and an optimization algorithm, can help process engineers overcome the challenges associated with LNG process optimization.

RESEARCH ON FRACTAL HEAT FLOW CHARACTERIZATION OF FINGER SEAL CONSIDERING THE HEAT TRANSFER EFFECT OF CONTACT GAPS ON ROUGH SURFACES

Finger seal is a new flexible dynamic sealing technology, and its heat transfer characteristics and seepage characteristics are one of the main research hotspots. In this paper, based on the fractal theory, a fractal model of the total thermal conductance of the finger seal considering the heat transfer effect of the contact gap of the rough surface is established, a fractal model of the effective gas permeability of the adjacent finger seals annulus considering the gas slip effect and the temperature change is established, and a finite element calculation method of the two-way thermo-mechanical coupling for the finger seal is proposed. The results show that the solid-phase thermal conductance decreases with the increase of the scale coefficient. When the axial pressure difference is greater than 0.4[Formula: see text]MPa, the rotor speed is greater than 11,000[Formula: see text]r/min, the radial displacement excitation is [0.03[Formula: see text]mm, 0.09[Formula: see text]mm], and the temperature is less than 600[Formula: see text]K, the gas-phase thermal conductance between the finger seal and the rotor shows an increasing trend. The gas-phase thermal conductance of the finger seal and the rotor is always the main position under different working conditions. Under different fractal dimensions, the solid-phase thermal conductance gradually occupies the dominant position. Temperature has a certain effect on the effective gas permeability, and fractal dimension, scale coefficient, and axial pressure difference have less effect on the effective gas permeability. At an axial pressure difference of 0.08[Formula: see text]MPa, the numerical calculation results of the two-way thermo-mechanical coupling calculation method for finger seal are closer to the experimental results, with a maximum error rate of 1.96%. The above results further improve the theoretical research system of the heat transfer characteristics of the finger seal.

Exaggerated Peripheral and Systemic Vasoconstriction During Trauma Recall in Posttraumatic Stress Disorder: A Co-Twin Control Study

BackgroundIndividuals with posttraumatic stress disorder (PTSD) face an increased risk of cardiovascular disease, but the mechanisms linking PTSD to cardiovascular disease remain incompletely understood. We used a co-twin control study design to test the hypothesis that individuals with PTSD exhibit augmented peripheral and systemic vasoconstriction during a personalized trauma recall task. MethodsIn 179 older male twins from the Vietnam Era Twin Registry, lifetime history of PTSD and current (last month) PTSD symptoms were assessed. Participants listened to neutral and personalized trauma scripts while peripheral vascular tone (Peripheral Arterial Tone ratio) and systemic vascular tone (e.g., total vascular conductance) were measured. Linear mixed-effect models were used to assess the within-pair relationship between PTSD and vascular tone indices. ResultsThe mean age of participants was 68 years, and 19% had a history of PTSD. For the Peripheral Arterial Tone ratio analysis, 32 twins were discordant for a history of PTSD, and 46 were discordant for current PTSD symptoms. Compared with their brothers without PTSD, during trauma recall, participants with a history of PTSD had greater increases in peripheral (β = −1.01, 95% CI [−1.72, −0.30]) and systemic (total vascular conductance: β = −1.12, 95% CI [−1.97, −0.27]) vasoconstriction after adjusting for cardiovascular risk factors. Associations persisted after adjusting for antidepressant medication use and heart rate and blood pressure during the tasks. Analysis of current PTSD symptom severity showed consistent results. ConclusionsPTSD is associated with exaggerated peripheral and systemic vasoconstrictor responses to traumatic stress reminders, which may contribute to elevated risk of cardiovascular disease.