Buffer Response Research Articles

Coping with seasonality: dynamics of adult body mass and survival in an alpine hibernator

Alpine mammals are highly vulnerable to current and projected climate change because they are confined to a certain elevation range. Physiological and behavioural adaptations in burrowing species, such as finding shelter in burrows when the summer conditions are unfavorable and hibernating in winter during the stressful period of resource shortage, could partly buffer the negative impacts of these forecasted changes. We studied the links between environmental factors and annual variations in adult mass and survival over 14 years in hoary marmots. We hypothesized that annual variation in seasonal environmental factors determines individual mass and survival through direct effects on food quality and availability, expecting greater survival when marmots reach higher mass before hibernation. We found that harsh winters decreased mass at emergence from hibernation by 47% compared with mild winters. Nonetheless, adult marmots had a greater mass gain in summers following harsh winters and reached a similar mass at the end of the summer compared with summers following mild winters. This suggests individuals can adopt a resource allocation strategy that allows maximizing summer mass gain to survive hibernation. Earlier springs also increased summer mass gain by 15 g day−1, and tended to increase apparent adult survival by 23%, compared with late springs. While these findings suggest a warming climate could have positive effects on summer mass gain and survival, survival also tended to decrease by 24% in summers with more precipitation. This suggests the forecasted changes in precipitation extremes could also trigger considerable negative effects on the demography of burrowing species in the long term. Our study shows that, although burrowing and hibernating behaviours could buffer responses to environmental changes, these behaviours are not an indefectible shield against climate change.

A New Approach to Bicarbonate Addition During Hemodialysis: Testing Model Predictions in a Patient Cohort

In this study, we present a new protocol for kidney replacement therapy (hemodialysis), based on an explicitly solvable mathematical model. With current protocols, the high and constant level of bath bicarbonate (HCO₃^&#x2212;) used to prevent metabolic acidosis leads to very rapid delivery of HCO₃^&#x2212; into the patient during the first part of the therapy. This rapid alkalinization elicits a robust buffer response that, paradoxically, consumes more HCO₃^&#x2212; than is added during the remainder of the treatment. In previous studies, we developed an analytical model that allows one to quantify these events and tested alternative protocols manipulating the rate of rise in blood bicarbonate concentration (HCO₃^&#x2212;). The protocol tested in this paper enforces a more gradual increase in blood HCO₃^&#x2212;, by means of a model-based staircase adjustment of bath HCO₃^&#x2212;. Model equations predict a reduction of buffer response and rate of organic acid production. These predictions are tested in 20 stable outpatients receiving hemodialysis. We find that the proposed protocol achieves the desired profile of blood HCO₃^&#x2212; with good accuracy and reduces the total buffer response by 1/3 and the rate of lactic acid production by at least 1/4, as compared to conventional therapy. Although more studies are needed, we believe that our work will pave the way for a more rational approach to correction of acidosis during hemodialysis. Article Highlights <list list-type="bullet"><list-item><label>&#x2022;</label> Our study tests an analytic model designed to enforce a more gradual rate of bicarbonate delivery during hemodialysis. </list-item><list-item><label>&#x2022;</label> Using our model, we show that we can reduce the excessive buffer response and lactic acid production that occur with the conventional approach. </list-item><list-item><label>&#x2022;</label> We demonstrate that our model can provide a rational approach to bicarbonate addition during treatment. </list-item> </list>

Ultrasound Demonstration of Hepatic Arterial Buffer Response for Blood Flow Regulation

This is observation analytical case control study deal with assessment of hepatic arterial buffer response for blood flow regulation using ultrasonography taking 300 subjects. 150 normal control group and 150 patients with chronic liver diseases. Several previous studies in various setting has support ultrasound scanning as non-invasive, cost effected, reliable, and accurate tool for measuring portal vein diameter and flow comparing with hepatic artery diameter for assess hepatic artery buffer response for blood flow regulation in chronic liver diseases. The Aim: Importance of the study to help in diagnosis impairment of HABR for blood flow regulation in chronic liver diseases in early stage to avoid the complication. As well as to reduce the cost and time of other examination. Method: The data was collected, analyzed by using Statistical Packaged for Social Studies (SPSS). Ultrasound examinations were performed in Tropical Diseases Teaching Hospital. Omdurman, Khartoum State during the period) from January 2021to August 2022(on 150 patients as study group (85 male and 65 female) and 150 control group with normal abdominal scan (Patient who had previous abdominal surgery was excluded). The Result: In result we found significant correlation (P=0.00) between hepatic artery diameter, liver craniocaudal length CCL\cm, caudate lobe size and portal vein diameter, with direction of flow. Highly significant correlation (r=-0.222; P=0.006) was noticed between portal vein diameter and hepatic artery diameter of patient under investigation. In patient with cirrhosis found dilated portal vein associated with Hepatofugal flow away from liver combined with dilated hepatic artery to compensate the liver supply. In case of fatty liver infiltration, the portal vein decrease diameter and flow associated with increase liver size and hepatic artery diameter to supply the liver. In liver tumor HCC the portal vein decrease diameter and flow associated with increase liver size and hepatic artery diameter. In hepatitis both portal vein and hepatic artery dilated to increase supply to the liver. These were expected and goes with previous study. The study also found that there was significant correlation between Sudanese HABR and international standard. The study recommended further study to measure HABR routinely with chronic liver diseases ultrasound scan

Preliminary Results of Hepatic Blood Flow Modulation in an Experimental Model of Hepatectomy – Implications for Hepatic Artery Buffer Response Modulation

Introduction: Portal hyperperfusion of the remnant liver has been implicated in post hepatectomy liver failure (PHLF) following major hepatectomy by inducing arterial vasoconstriction, also called Hepatic Artery Buffer Response (HABR). We aimed to compare the effect of a selective A2Aadenosine receptor agonist Regadenoson to a porto-caval (P-C) shunt in an experimental model of hepatectomy in piglets on hepatic blood flow modulation. Methods: A cohort study with cross-over design of serial doppler measurements in landrace pigs weighing 25-30 Kg was performed; all subjects underwent laparotomy and baseline measurements were taken. Thereafter extended left hepatectomy with P-C shunt was performed and measurements were repeated. Finally, the P-C shunt was occluded and all animals were administered intra-arterially 400mcg of regadenoson, prior repeating measurements. Results: The baseline portal vein and hepatic artery flow were 28.5 ± 7.47 ml/sec and 118.66 ± 19.28 ml/sec respectively. After hepatectomy a significant increase of the portal vein flow by 91.8% while the hepatic artery flow increase only by 26.4%, signifying activation of the HABR. Opening of the P-C shunt decreased the portal vein flow by 24.69% and a more pronounced decrease of hepatic artery flow (34.22%). After occlusion of the portocaval shunt and administration of regadenoson there was a minor decrease of the portal flow by 13.71% while there was a significant drop of the hepatic artery flow by 55.33%, thus more effectively decreasing arterial vasoconstriction (p<0.005). Conclusion: Regadenoson can more effectively decrease hepatic artery flow than PC shunt, thus signifying a potential role in the management of PHLF.

Hepatic pseudolesions caused by alterations in intrahepatic hemodynamics

Hepatic pseudolesion may occur in contrast-enhanced computed tomography and magnetic resonance imaging due to the unique haemodynamic characteristics of the liver. The concept of hepatic arterial buffer response (HABR) has become mainstream for the understanding of the mechanism of the reciprocal effect between hepatic arterial and portal venous flow. And HABR is thought to be significantly related to the occurrence of the abnormal imaging findings on arterial phase of contrast enhanced images, such as hepatic arterial-portal vein shunt and transient hepatic attenuation difference, which mimic hypervascular tumor and may cause clinical problems. Third inflow to the liver also cause hepatic pseudolesion, and some of the cases may show histopathologic change such as focal hyperplasia, focal fatty liver, and focal sparing of fatty liver, and called pseudotumor. To understand these phenomena might be valuable for interpreting the liver imaging findings.

Saline-polyethylene glycol blends preserve in vitro annulus fibrosus hydration and mechanics: An experimental and finite-element analysis

Precise control of tissue water content is essential for ensuring accurate, repeatable, and physiologically relevant measurements of tissue mechanics and biochemical composition. While previous studies have found that saline and polyethylene glycol (PEG) blends were effective at controlling tendon and ligament hydration levels, this work has yet to be extended to the annulus fibrosus (AF). Thus, the first objective of this study was to determine and validate an optimal buffer solution for targeting and maintaining hydration levels of tissue-level AF specimens in vitro. This was accomplished by measuring the transient swelling behavior of bovine AF specimens in phosphate-buffered saline (PBS) and PEG buffers across a wide range of concentrations. Sub-failure, failure, and post-failure mechanics were measured to determine the relationship between changes in tissue hydration and tensile mechanical response. The effect of each buffer solution on tissue composition was also assessed. The second objective of this study was to assess the feasibility and effectiveness of using multi-phasic finite element models to investigate tissue swelling and mechanical responses in different external buffer solutions.A solution containing 6.25%w/v PBS and 6.25%w/v PEG effectively maintained tissue-level AF specimen hydration at fresh-frozen levels after 18 h in solution. Modulus, failure stress, failure strain, and post-failure toughness of specimens soaked in this solution for 18 h closely matched those of fresh-frozen specimens. In contrast, specimens soaked in 0.9%w/v PBS swelled over 100% after 18 h and exhibited significantly diminished sub-failure and failure properties compared to fresh-frozen controls. The increased cross-sectional area with swelling contributed to but was not sufficient to explain the diminished mechanics of PBS-soaked specimens, suggesting additional sub-tissue scale mechanisms. Computational simulations of these specimens generally agreed with experimental results, highlighting the feasibility and importance of including a fluid-phase description when models aim to provide accurate predictions of biological tissue responses. As numerous previous studies suggest that tissue hydration plays a central role in maintaining proper mechanical and biological function, robust methods for controlling hydration levels are essential as the field advances in probing the relationship between tissue hydration, aging, injury, and disease.

Two sexes respond equally to food restriction in a sexually dimorphic but not body mass dimorphic jumping spider.

Natural selection favors animals that evolve developmental and behavioral responses that buffer the negative effects of food restrictions. These buffering responses vary both between species and within species. Many studies have shown sex‐specific responses to environmental changes, usually in species with sexual size dimorphism (SSD), less found in species with weak or no SSD, which suggests that sizes of different sexes are experiencing different selections. However, previous studies usually investigated development and behavior separately, and the balanced situation where males and females of sexually dimorphic species respond in the same way to food restriction remains little known. Here, we investigated this in Phintelloides versicolor (Salticidae) that presents sexual dimorphism in color and shape but weak SSD. We examined whether food restriction induced the same responses in males and females in development duration, adult body size and weight, daily time allocated to foraging, and hunting. We found food restriction induced similar responses in both sexes: both exhibited longer development duration, smaller adult body size and weight, higher probability of staying outside nests and noticing prey immediately, and higher hunting success. However, there were sexual differences regardless of food condition: females showed faster development, smaller adult body size, higher probability of staying outside of nests, and higher hunting success. These indicated the differential selection on male and female sizes of P. versicolor could be under a balanced situation, where males and females show equal developmental and behavioral plasticity to environmental constraints.

A K/Ka/V Triband Single-Signal-Path Receiver With Variable-Gain Low-Noise Amplifier and Constant-Gain Phase Shifter in 28-nm CMOS

This article presents a single-signal-path tri (K/Ka/V)-band receiver (RX) featuring area/cost-effective support for various millimeter-wave phased-array applications. A triple-coupling transformer (TCT) at the common-gate input stage of the RX low-noise amplifier (LNA) is proposed for triband impedance matching and g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> -boosting. By augmenting each low-parasitic pMOS switched inductor load with a pMOS variable resistor in parallel, the variable-gain functionality is merged into this LNA to cover a wide input-signal range in a low-overhead manner. An active single-balanced mixer (SBM) for radio frequency (RF)-intermediate frequency (IF) downconversion is adopted to eliminate a wideband balun. Poor RF-IF and local-oscillator (LO)-IF isolations and low IIP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> normally inherited in an SBM are avoided by setting the IF particularly. The wideband response of an on-chip LO buffer is realized through input resistor coupling and output inductor peaking. Furthermore, a constant-gain phase shifter (CGPS) at IF is proposed to benefit the orthogonal gain-and-phase control preferred by beam steering. This CGPS uses an amplitude-only feedback loop to retain the gain without baseband equalization. Fabricated in a 28-nm bulk CMOS technology, this RX exhibits variable power gains of 12.5-33.2 dB (at 24 GHz), 13.4-34.6 dB (at 33 GHz), and 3.1-32 dB (at 50 GHz) with respective minimum noise figures of 4.78, 5.12, and 6.15 dB. The respective RX 3-dB bandwidths are 20-27, 30-34.6, and 42-55.5 GHz. The measured CGPS gain variation at IF (2-4 GHz) is within 0.94 dB. This RX consumes 131 mW and occupies 1.22 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with pads in a silicon area.

Media coverage of a pandemic's impacts on farmers and implications for agricultural resilience and adaptation

The COVID-19 crisis has revealed weaknesses and placed great stress on the agri-food system in the U.S. Many believe that it could be a catalyst event that leads to structural changes to improve the food system’s resilience. We use a sample of 220 articles published in prominent national newspapers and agricultural trade journals from March to May 2020 to explore the extent to which farmer responses to COVID-19 covered in the media represent examples of resistant, adaptive, or transformative strategies. The pandemic disrupted the U.S. food system and impacted farmers by reducing access to markets, lowering commodity prices, restricting access to farmworker labor, and shifting consumer demand. Media coverage of farmer responses to these stressors were coded into three alternative pathways: (i) reactive or buffering responses, (ii) adaptive responses; and (iii) transformative responses. Most news media coverage focused on the pandemic’s disruptive impacts on the U.S. food system, related negative impacts on farmers, and short-term responses by institutional actors, including policy-makers and food supply chain industry actors. Farmer responses to pandemic stressors were mentioned less frequently than farmer impacts and responses by institutional actors. The most common examples of farmer responses highlighted in the media reflected farmer reactive and buffering behaviors, which were mentioned significantly more frequently than adaptive or transformative responses. National newspapers were more likely to cover farmer responses and present examples of adaptive and transformative strategies compared to agricultural trade journals. Our findings suggest that news media coverage in the early months of the pandemic largely characterized the event as a rapid onset ‘natural’ disaster that created severe negative impacts. Media devoted more attention to short-term policy responses designed to mitigate these impacts than to farmer responses (in general) or to discussion of the deeper structural causes of and potential solutions to the vulnerabilities revealed by the pandemic. In this way, both national newspaper and agricultural trade journal coverage seems to promote frames that reduce the likelihood of the pandemic becoming the seed of a more resilient system.

Hepatic Arterial Buffer Response in Liver Radioembolization and Potential Use for Improved Cancer Therapy.

Simple SummaryRadioembolization of hepatic tumors is performed by injecting 90Y or 166Ho loaded spheres into the hepatic artery. A twofold tumor to normal liver absorbed dose ratio is commonly obtained. In order to improve tumoral cell killing while preserving lobule function, co-injection of arterial vasoconstrictor has been proposed, but without success: the hepatic arterial buffer response quickly inhibits the arterioles vasoconstriction. The aim of the study is to investigate whether it is possible to take benefit from this buffer response, by co-infusing a mesenteric arterial vasodilator in order to dump the hepatic lobules arterial flow. Animal studies evidencing such mechanism are reviewed. Some potential mesenteric vasodilators are identified and their safety profile discussed. A four to sixfold improvement of the tumoral to normal tissue dose ratio is expected, pushing the therapy towards a real curative intention, especially in hepatocellular carcinoma (HCC), more frequent in obese subjects, and where ultra-selective spheres delivery is often not possible.Liver radioembolization is a treatment option for unresectable liver cancers, performed by infusion of 90Y or 166Ho loaded spheres in the hepatic artery. As tumoral cells are mainly perfused via the liver artery unlike hepatic lobules, a twofold tumor to normal liver dose ratio is commonly obtained. To improve tumoral cell killing while preserving lobules, co-infusion of arterial vasoconstrictor has been proposed but with limited success: the hepatic arterial buffer response (HABR) and hepatic vascular escape mechanism hamper the arterioles vasoconstriction. The proposed project aims to take benefit from the HABR by co-infusing a mesenteric arterial vasodilator: the portal flow enhancement inducing the vasoconstriction of the intra sinusoids arterioles barely impacts liver tumors that are mainly fed by novel and anarchic external arterioles. Animal studies were reviewed and dopexamine was identified as a promising safe candidate, reducing by four the hepatic lobules arterial flow. A clinical trial design is proposed. A four to sixfold improvement of the tumoral to normal tissue dose ratio is expected, pushing the therapy towards a real curative intention, especially in HCC where ultra-selective spheres delivery is often not possible.

The polymeric glyco-linker controls the signal outputs for plasmonic gold nanorod biosensors due to biocorona formation.

Gold nanorods (GNRs) are a promising platform for nanoplasmonic biosensing. The localised surface plasmon resonance (LSPR) peak of GNRs is located in the near-infrared optical window and is sensitive to local binding events, enabling label-free detection of biomarkers in complex biological fluids. A key challenge in the development of such sensors is achieving target affinity and selectivity, while both minimizing non-specific binding and maintaining colloidal stability. Herein, we reveal how GNRs decorated with galactosamine-terminated polymer ligands display significantly different binding responses in buffer compared to serum, due to biocorona formation, and how biocorona displacement due to lectin binding plays a key role in their optical responses. GNRs were coated with either poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA) or poly(N-hydroxyethyl acrylamide) (PHEA) prepared via reversible addition–fragmentation chain-transfer (RAFT) polymerisation and end-functionalised with galactosamine (Gal) as the lectin-targeting unit. In buffer Gal-PHEA-coated GNRs aggregated upon soybean agglutinin (SBA) addition, whereas Gal-PHPMA-coated GNRs exhibited a red-shift of the LSPR spectrum without aggregation. In contrast, when incubated in serum Gal-PHPMA-coated nanorods showed no binding response, while Gal-PHEA GNRs exhibited a dose-dependent blue-shift of the LSPR peak, which is the opposite direction (red-shift) to what was observed in buffer. This differential behaviour was attributed to biocorona formation onto both polymer-coated GNRs, shown by differential centrifugal sedimentation and nanoparticle tracking analysis. Upon addition of SBA to the Gal-PHEA coated nanorods, signal was generated due to displacement of weakly-bound biocorona components by lectin binding. However, in the case of Gal-PHPMA which had a thicker corona, attributed to lower polymer grafting densities, addition of SBA did not lead to biocorona displacement and there was no signal output. These results show that plasmonic optical responses in complex biological media can be significantly affected by biocorona formation, and that biocorona formation itself does not prevent sensing so long as its exact nature (e.g. ‘hard versus soft’) is tuned.

Short-term Effects of Hepatic Arterial Buffer Responses Induced by Partial Splenic Embolization on the Hepatic Function of Patients with Cirrhosis According to the Child-Pugh Classification.

Objective This study primarily aimed to investigate the short-term effects of partial splenic embolization (PSE) on the Child-Pugh score and identify predictive factors for changes in the score caused by PSE. The secondary aim was to analyze changes in various parameters at one month postoperatively using these identified factors. Methods Between September 2007 and December 2019, 118 patients with cirrhosis and hypersplenism underwent PSE at our hospital. Testing was conducted preoperatively and at one month after PSE. Results Overall, the Child-Pugh score was not significantly changed postoperatively. The Child-Pugh score before PSE was identified as the strongest independent predictor of ameliorated and deteriorated Child-Pugh scores after PSE. Higher pretreatment Child-Pugh scores were correlated with higher posttreatment amelioration rates of the score. A significant decrease in the portal vein diameter and a significant increase in the common hepatic artery diameter were evident at the same level postoperatively in 64 patients with Child-Pugh class A (group A) and in 54 patients with Child-Pugh class B or C (group B/C) preoperatively. According to Murray's Law, PSE resulted in decreased portal venous flow and increased hepatic arterial flow, suggesting a hepatic arterial buffer response (HABR) induced by the procedure. Despite equivalent splenic infarction rates and similar posttreatment changes in hepatic hemodynamics, PSE significantly increased the Child-Pugh score of group A; however, the procedure significantly decreased the score of group B/C. Conclusion Considering original portal venous-hepatic arterial hemodynamics, PSE is expected to produce HABR-mediated hepatic functional improvements in cirrhosis patients with Child-Pugh class B/C.

Care in Tarlabaşı amidst heightened inequalities, urban transformation and Coronavirus

Istanbul’s Tarlabaşı neighborhood has been undergoing state-led urban transformation for over a decade, without an end date in sight. Experiencing authoritarianism as a protracted process, Tarlabaşı residents brought to life care as a long-term process in response. Through Tarlabaşı Solidarity Network, a network of care (ihtimam) as they conceptualize it, to navigate uncertainty, maintain community, and hold onto their properties through interpersonal and horizontal relationships. And care, as I show in this piece, has become a buffering response to the eruption of the COVID-19 crises, the effects of which have been exacerbated by authoritarian urban politics already in motion. Repertoires of care present alternatives to uneven impacts of crises, and Tarlabaşı Solidarity Network shows us the important of putting care to work in urban spaces we inhabit.

Haemodynamic changes in cirrhosis following terlipressin and induction of sepsis\u2014a preclinical study using caval subtraction phase-contrast and cardiac MRI

ObjectivesEffects of liver disease on portal venous (PV), hepatic arterial (HA), total liver blood flow (TLBF), and cardiac function are poorly understood. Terlipressin modulates PV flow but effects on HA, TLBF, and sepsis/acute-on-chronic liver failure (ACLF)-induced haemodynamic changes are poorly characterised. In this study, we investigated the effects of terlipressin and sepsis/ACLF on hepatic haemodynamics and cardiac function in a rodent cirrhosis model using caval subtraction phase-contrast (PC) MRI and cardiac cine MRI.MethodsSprague-Dawley rats (n = 18 bile duct–ligated (BDL), n = 16 sham surgery controls) underwent caval subtraction PCMRI to estimate TLBF and HA flow and short-axis cardiac cine MRI for systolic function at baseline, following terlipressin and lipopolysaccharide (LPS) infusion, to model ACLF.ResultsAll baseline hepatic haemodynamic/cardiac systolic function parameters (except heart rate and LV mass) were significantly different in BDL rats. Following terlipressin, baseline PV flow (sham 181.4 ± 12.1 ml/min/100 g; BDL 68.5 ± 10.1 ml/min/100 g) reduced (sham − 90.3 ± 11.1 ml/min/100 g, p < 0.0001; BDL − 31.0 ± 8.0 ml/min/100 g, p = 0.02), sham baseline HA flow (33.0 ± 11.3 ml/min/100 g) increased (+ 92.8 ± 21.3 ml/min/100 g, p = 0.0003), but BDL baseline HA flow (83.8 ml/min/100 g) decreased (− 34.4 ± 7.5 ml/min/100 g, p = 0.11). Sham baseline TLBF (214.3 ± 16.7 ml/min/100 g) was maintained (+ 2.5 ± 14.0 ml/min/100 g, p > 0.99) but BDL baseline TLBF (152.3 ± 18.7 ml/min/100 g) declined (− 65.5 ± 8.5 ml/min/100 g, p = 0.0004). Following LPS, there were significant differences between cohort and change in HA fraction (p = 0.03) and TLBF (p = 0.01) with BDL baseline HA fraction (46.2 ± 4.6%) reducing (− 20.9 ± 7.5%, p = 0.03) but sham baseline HA fraction (38.2 ± 2.0%) remaining unchanged (+ 2.9 ± 6.1%, p > 0.99). Animal cohort and change in systolic function interactions were significant only for heart rate (p = 0.01) and end-diastolic volume (p = 0.03).ConclusionsCaval subtraction PCMRI and cardiac MRI in a rodent model of cirrhosis demonstrate significant baseline hepatic haemodynamic/cardiac differences, failure of the HA buffer response post-terlipressin and an altered HA fraction response in sepsis, informing potential translation to ACLF patients.Key PointsCaval subtraction phase-contrast and cardiac MRI demonstrate:• Significant differences between cirrhotic/non-cirrhotic rodent hepatic blood flow and cardiac systolic function at baseline.• Failure of the hepatic arterial buffer response in cirrhotic rodents in response to terlipressin.• Reductions in hepatic arterial flow fraction in the setting of acute-on-chronic liver failure.

Covid-19 and rapid adoption and improvisation of online teaching: curating resources for extensive versus intensive online learning experiences

ABSTRACT The COVID-19 pandemic closed university campuses forcing rapid improvisation and adoption of online teaching. This paper explores the experience of converting three modules from proximate to online learning delivery in March and May 2020. This process was facilitated by reflective practice to support a process of improvisation as a buffering response to the pandemic. This paper distinguishes between the development of Distance Learning programmes compared to rapid adoption of online learning. Shifting to complete online teaching involves a process by which the lecturer’s role transitions towards the curation of online and offline student experiences. This includes facilitating and blending extensive and intensive online learning experiences. Extensive involves the selection and curation of online learning support bundles. This requires the creation of learning roadmaps to facilitate student learning. Intensive revolves around online engagement between academics and students and takes two forms: shallow as involving a limited dialogue with students and deep which involves a co-creation process between students and lecturers. Online learning provides opportunities to adapt learning experiences in real-time. The paper evaluates the shift to online practice from the students’ and academics’ perspectives.

Sulfamethizole-imprinted polymer on screen-printed electrodes: Towards the design of a portable environmental sensor

As the demand for portable, selective yet sensitive environmental pollutants monitoring devices increases, electrochemical sensors specifically screen-printed electrodes (SPEs) integrated with molecularly imprinted polymer layers are gaining unprecedented attention. The work reported herein demonstrates a successful adaptation of an antibiotic imprinted polymer from one platform to another of different sensing principles, without compromising its performance. Specifically, sulfamethizole-MIP (SMZ-MIP) previously optimized on a surface acoustic wave (SAW) platform is redesigned on SPE with necessary upgrade to achieve a portable and highly-performing cost-effective electrochemical sensor for detecting sulfamethizole (SMZ) in water. Sensor performance, as analysed by differential pulse voltammetry (DPV) electrochemical technique indicates rapid response, good sensitivity as represented by an LOD of 0.9 nM, and LOQ of 3 nM; excellent selectivity, as well as concentration dependent responses both in buffer and tap water samples. This study indicates a significant step towards achieving the desired commercially viable small molecule detection platform that combines important peculiarity of low cost, ease of operation, portability and on-site utilization in environmental water.

The Efficacy Of Individualizing Sodium Bicarbonate Supplementation Strategies On Elite-level Rowing Performance

A recent review has addressed a number of practical issues associated with traditional sodium bicarbonate (NaHCO3) supplementation approaches, identifying ingestion timing as critical to maximising the potential of this ergogenic medium. Furthermore, contemporary empirical studies have also suggested that adjusting the start of exercise to commensurate with an individual’s peak blood buffering response may result in better outcomes in terms of GI distress and exercise performance, however this concept has yet to be investigated in international level athletes. PURPOSE: The following study addressed the question of whether or not ingestion timing is critical to time-trial performance (2,000 m rowing time-trial) in elite-level rowers including Pan American, World Champion and Olympic team members) adhering to their own individualised pre-race strategies (e.g. nutrition, warm-up, etc.). METHODS: Twenty three (n = 23) elite rowers across two research centres (Canadian Sport Institute Pacific and the New South Wales Institute of Sport) completed three trials (one NaHCO3 loading profile to determine the individual’s time-to-peak blood buffering capacity followed by two randomized experimental trials (Consensus Standard (CON): 2,000 m rowing time trial (TT) performed 60 min post 0.3 g·kgBW-1 NaHCO3 ingestion; and Individualised Peak (IP): 2,000 m rowing TT performed at the rower’s individual peak bicarbonate concentration [HCO3-] (determined from the profiling trial) after ingesting 0.3 g·kgBW-1 NaHCO3)). RESULTS: Significant interaction effects and post hoc comparisons revealed differences between CON and IP at pre-warm up for HCO3- (mean difference of 2.9 ± 0.4 mmol·L-1 (95% CI 2.0 to 3.8 mmol·L-1); p = 0.02) but not at pre-TT. Performance times were significantly different between CON (369.0 ± 10.3 s) and IP (367 ± 10.5 s) (mean difference 1.5 ± 2.4 s (95% CI 0.5 to 2.6 s); p = 0.007), however given the effect size this difference was likely trivial. CONCLUSIONS: The findings of the present study do not support the recent claims that targeting the onset of exercise to commence with an individual’s peak blood buffering capacity after NaHCO3 supplementation is essential to maximise the erogenicity of this supplement.

Stimulation of the hepatic arterial buffer response using exogenous adenosine: hepatic rest/stress perfusion imaging.

The hepatic arterial buffer response is a mechanism mediated by adenosine whereby hepatic arterial perfusion (HAP) increases when portal flow decreases, and is implicated in liver disease. The first study aim was to measure HAP in patients undergoing myocardial perfusion imaging (MPI), thus developing hepatic arterial rest/stress perfusion imaging (HAPI). The second aim was to compare adenosine-induced changes in splenic perfusion (SP) and HAP with corresponding changes in myocardial blood flow (MBF). Patients had MPI with 82Rb PET/CT using adenosine (n = 45) or regadenoson (n = 33) for stressing. SP and HAP were measured using a first-pass technique that gives HAP rather than total hepatic perfusion. Renal perfusion (RP) was also measured. Mean MBF and HAP increased after both adenosine ([stress-rest]/rest 1.1 and 0.8) and regadenoson (1.4 and 0.6), but the respective changes did not correlate. After adenosine, SP (- 0.48) and RP (- 0.26) both decreased. The change in SP correlated positively with the change in MBF (r = 0.36; p = 0.015) but did not correlate with change in HAP. After regadenoson, SP (0.2) and RP (0.2) both increased. The changes in SP correlated with the changes in MBF (r = 0.39; p = 0.025) and HAP (r = 0.39; p = 0.02). Changes in RP correlated with changes in HAP (r = 0.51; p = 0.0008) but not MBF. Resting SP (r = 0.32; p = 0.004), but not resting HAP, correlated with hepatic fat burden. Adenosine-induced change in HAP also correlated with hepatic fat (r = 0.29; p = 0.05). HAPI could be a useful new hepatic function test. Neither splenic 'switch-off' nor hepatic arterial 'switch-on' identifies adequacy of stress in MPI. • This article describes a new method for assessing arterial perfusion of the liver and its capacity to respond to an infusion of adenosine, a substance that normally 'drives' hepatic arterial flow. • Hepatic arterial flow increased in response to adenosine, sometimes dramatically. Adenosine is already used clinically to stimulate myocardial blood flow in patients with suspected coronary disease, but the increase in flow did not correlate with the corresponding increase in hepatic arterial flow. • Analogous to the use of adenosine in the myocardium, the increase in hepatic arterial flow in response to adenosine has the potential to be a new clinically useful method for the evaluation of hepatic arterial haemodynamics in liver disease.

The axonal actin-spectrin lattice acts as a tension buffering shock absorber.

Axons span extreme distances and are subject to significant stretch deformations during limb movements or sudden head movements, especially during impacts. Yet, axon biomechanics, and its relation to the ultrastructure that allows axons to withstand mechanical stress, is poorly understood. Using a custom developed force apparatus, we demonstrate that chick dorsal root ganglion axons exhibit a tension buffering or strain-softening response, where its steady state elastic modulus decreases with increasing strain. We then explore the contributions from the various cytoskeletal components of the axon to show that the recently discovered membrane-associated actin-spectrin scaffold plays a prominent mechanical role. Finally, using a theoretical model, we argue that the actin-spectrin skeleton acts as an axonal tension buffer by reversibly unfolding repeat domains of the spectrin tetramers to release excess mechanical stress. Our results revise the current viewpoint that microtubules and their associated proteins are the only significant load-bearing elements in axons.

Hypoxia and oxidative stress: The role of the anaerobic gut, the hepatic arterial buffer response and other defence mechanisms of the liver

Hypoxia and oxidative stress: The role of the anaerobic gut, the hepatic arterial buffer response and other defence mechanisms of the liver