An Experiential Learning Opportunity in Norway: Computation for Bioengineering and Mechanical Engineering Students.

The global learning initiative at Northeastern University is focused on fostering intercultural communication skills. The Dialogue of Civilization (DOC) program serves as a mechanism to achieve such a goal by offering faculty-led international experiences. In this paper, we have presented a detailed account of a DOC program that took place in Norway. The primary objective of the program was to teach mechanical engineering and bio-engineering students computational skills while stimulating critical thinking about the cultural and social aspects of technology and engineering in Norway. The program focused on two courses: a technical course and a special topics course. The technical course introduced students to finite element analysis, with practical applications and site visits in Norway to enhance experiential learning. In the special topics course, the interplay between modern technologies, like green energy, state policies, and the rights and traditions of the indigenous Sámi people was explored. The course highlighted both the progressive social policies in Norway and the historical discrimination against the Sámi. Student feedback was positive and experiential learning components such as guest lectures and site visits were particularly appreciated. Additional surveys showed that students' self-confidence was higher following the DOC program. In addition, female-identifying students had higher confidence in their future success after completion of this program as compared to their male-identifying counterparts. Our paper is expected to serve as a resource for educators seeking to integrate technical education with intercultural experiences and discussions on social and cultural impacts in engineering.

Vascular Remodeling During Late-Gestation Pregnancy: An In-Vitro Assessment of the Murine Ascending Thoracic Aorta.

Maternal mortality due to cardiovascular disease is a rising concern in the U.S. Pregnancy triggers changes in the circulatory system, potentially influencing the structure of the central vasculature. Evidence suggests a link between a woman's pregnancy history and future cardiovascular health, but our understanding remains limited. To fill this gap, we examined the passive mechanics of the murine ascending thoracic aorta during late gestation. By performing biaxial mechanical testing on the ascending aorta, we were able to characterize the mechanical properties of both control and late-gestation tissues. By examining mechanical, structural, and geometric properties, we confirmed that remodeling of the aortic wall occurred. Morphological and mechanical properties of the tissue indicated an outward expansion of the tissue, as reflected in changes in wall thickness (∼12% increase) and luminal diameter (∼6% increase) at its physiologically loaded state in the pregnant group. With these geometric adaptations and despite increased hemodynamic loads, pregnancy did not induce significant changes in the tensile wall stress at the similar physiological pressure levels of the pregnant and control tissues. The alterations also included reduced intrinsic stiffness in the circumferential direction (∼18%) and reduced structural stiffness (∼26%) in the pregnant group. The observed vascular remodeling maintained the elastic stored energy of the aortic wall under systolic loads, indicating preservation of vascular function. Data from our study of pregnancy-related vascular remodeling will provide valuable insights for future investigations of maternal cardiovascular health.

Meta Data Analysis of Sex Distribution of Study Samples Reported in Summer Biomechanics, Bioengineering, & Biotransport Annual Conference Abstracts.

The biased use of male subjects in biomedical research has created limitations, underscoring the importance of including women to enhance the outcomes of evidence-based medicine and to promote human health. While federal policies (e.g., the 1993 Revitalization Act and the 2016 Sex as a Biological Variable Act) have aimed to improve sex balance in studies funded by the National Institutes of Health (NIH), data on sex inclusivity in non-NIH funded research remain limited. The objective of this study was to analyze the trend of sex inclusion in abstracts submitted to the Summer Biomechanics, Bioengineering, & Biotransport Conference (SB3C) over seven years. We scored every abstract accepted to SB3C and the findings revealed that approximately 20% of total abstracts included sex-related information, and this trend remained stable. Surprisingly, there was no significant increase in abstracts including both sexes or those with balanced male and female samples. The proportion of abstracts with balanced sexes was notably lower than those including both sexes. Additionally, we examined whether the exclusion of one sex from the corresponding studies was justified by the research questions. Female-only studies had a 50% justification rate, while male-only studies had only 2% justification. Disparity in sex inclusion in SB3C abstracts was apparent, prompting us to encourage scientists to be more mindful of the sex of the research samples. Addressing sex inclusivity in biomechanics and mechanobiology research is essential for advancing medical knowledge and for promoting better healthcare outcomes for everyone.

The Effect of Posterior Fossa Decompression Surgery on Brainstem and Cervical Spinal Cord Dimensions in Adults with Chiari Malformation Type 1.

OBJECTIVE: Posterior fossa decompression (PFD) surgery creates more space at the skull base, reduces the resistance to the cerebrospinal fluid motion, and alters craniocervical biomechanics. In this paper, we retrospectively examined the changes in neural tissue dimensions following PFD surgery on Chiari malformation type 1 adults. METHODS: Measurements were performed on T2-weighted brain magnetic resonance images acquired before and 4 months after surgery. Measurements were conducted for neural tissue volume and spinal cord/brainstem width at 4 different locations; 2 width measurements were made on the brainstem and 2 on the spinal cord in the midsagittal plane. Cerebellar tonsillar position (CTP) was also measured before and after surgery. RESULTS: Twenty-five adult patients, with a mean age of 38.9 ± 8.8 years, were included in the study. The cervical cord volume increased by an average of 2.3 ± 3.3% (P = 0.002). The width at the pontomedullary junction increased by 2.2 ± 3.5% (P < 0.01), while the width 10 mm caudal to this junction increased by 4.2 ± 3.9% (P < 0.0001). The spinal cord width at the base of second cervical vertebra and third cervical vertebra did not significantly change after surgery. The CTP decreased by 60 ± 37% (P < 0.0001) after surgery, but no correlation was found between CTP change and dimension change. CONCLUSIONS: The brainstem width and cervical cord volume showed a modest increase after PFD surgery, although standard deviations were large. A reduction in compression after PFD surgery may allow for an increase in neural tissue dimension. However, clinical relevance is unclear and should be assessed in future studies with high-resolution imaging.

Biomechanical remodeling of the murine descending thoracic aorta during late-gestation pregnancy.

With the rise in maternal mortality rates and the growing body of epidemiological evidence linking pregnancy history to maternal cardiovascular health, it is essential to comprehend the vascular remodeling that occurs during gestation. The maternal body undergoes significant hemodynamic alterations which are believed to induce structural remodeling of the cardiovascular system. Yet, the effects of pregnancy on vascular structure and function have not been fully elucidated. Such a knowledge gap has limited our understanding of the etiology of pregnancy-induced cardiovascular disease. Towards bridging this gap, we measured the biaxial mechanical response of the murine descending thoracic aorta during a normotensive late-gestation pregnancy. Non-invasive hemodynamic measurements confirmed a 50% increase in cardiac output in the pregnant group, with no changes in peripheral blood pressure. Pregnancy was associated with significant wall thickening ( ∼14%), an increase in luminal diameter ( ∼6%), and material softening in both circumferential and axial directions. This expansive remodeling of the tissue resulted in a reduction in tensile wall stress and intrinsic tissue stiffness. Collectively, our data indicate that an increase in the geometry of the vessel may occur to accommodate for the increase in cardiac output and blood flow that occurs in pregnancy. Similarly, wall thickening accompanied by increased luminal diameter, without a change in blood pressure may be a necessary mechanism to decrease the tensile wall stress, and avoid pathophysiological events following late gestation.

Differences in physiological and biochemical responses to short-term flooding among the three avocado (Persea americana Mill.) races.

Avocado (P. americana Mill.) trees are classified into three botanical races, Mexican (M), Guatemalan (G), and West Indian (WI), each distinguished by their geographical centers of origin. While avocados are considered highly sensitive to flooding stress, comparative responses of the different races to short-term flooding are not known. This study assessed the differences in physiological and biochemical responses among clonal, non-grafted avocado cultivars of each race to short-term (2-3 days) flooding. In two separate experiments, each with different cultivars of each race, container-grown trees were divided into two treatments: 1) flooded and 2) non-flooded. Net CO2 assimilation (A), stomatal conductance (gs), and transpiration (Tr) were measured periodically over time beginning the day before treatments were imposed, through the flooding period, and during a recovery period (after unflooding). At the end of the experiments, concentrations of sugars in leaves, stems, and roots, and reactive oxygen species (ROS), antioxidants, and osmolytes in leaves and roots were determined. Guatemalan trees were more sensitive to short-term flooding than M or WI trees based on decreased A, gs, and Tr and survival of flooded trees. Guatemalan trees generally had less partitioning of sugars, particularly mannoheptulose, to the roots of flooded compared to non-flooded trees. Principal component analysis showed distinct clustering of flooded trees by race based on ROS and antioxidant profiles. Thus, differential partitioning of sugars and ROS and antioxidant responses to flooding among races may explain the greater flooding sensitivity of G trees compared to M and WI trees.

Cell cycle-dependent endocytosis of DNA-wrapped single-walled carbon nanotubes by neural progenitor cells.

While exposure of C17.2 neural progenitor cells (NPCs) to nanomolar concentrations of carbon nanotubes (NTs) yields evidence of cellular substructure reorganization and alteration of cell division and differentiation, the mechanisms of NT entry are not understood. This study examines the entry modes of (GT)20 DNA-wrapped single-walled carbon nanotubes (SWCNTs) into NPCs. Several endocytic mechanisms were examined for responsibility in nanomaterial uptake and connections to alterations in cell development via cell-cycle regulation. Chemical cell-cycle arrest agents were used to synchronize NPCs in early G1, late G1/S, and G2/M phases at rates (>80%) aligned with previously documented levels of synchrony for stem cells. Synchronization led to the highest reduction in SWCNT internalization during the G1/S transition of the cell cycle. Concurrently, known inhibitors of endocytosis were used to gain control over established endocytic machineries (receptor-mediated endocytosis (RME), macropinocytosis (MP), and clathrin-independent endocytosis (CIE)), which resulted in a decrease in uptake of SWCNTs across the board in comparison with the control. The outcome implicated RME as the primary mechanism of uptake while suggesting that other endocytic mechanisms, though still fractionally responsible, are not central to SWCNT uptake and can be supplemented by RME when compromised. Thereby, endocytosis of nanomaterials was shown to have a dependency on cell-cycle progression in NPCs.

Sap flow, xylem anatomy and photosynthetic variables of three Persea species in response to laurel wilt.

Laurel wilt, a lethal vascular wilt disease caused by the fungus Raffaelea lauricola, affects several tree species in the Lauraceae, including three Persea species. The susceptibility to laurel wilt of two forest tree species native to the southern USA, Persea borbonia and Persea palustris, [(Raf.) Sarg.] and avocado, Persea americana (Mill.) cv Waldin, was examined and related to tree physiology and xylem anatomy. Net CO2 assimilation (A), stomatal conductance (gs), leaf chlorophyll index (LCI), leaf chlorophyll fluorescence (Fv/Fm), xylem sap flow, theoretical stem hydraulic conductivity (Kh) and xylem vessel anatomy were assessed in trees of each species that were inoculated with R. lauricola and in control trees. Laurel wilt caused a reduction in A, gs, LCI, Fv/Fm and blockage of xylem vessels by tyloses formation that negatively impacted Kh and sap flow in all Persea species. However, disease susceptibility as indicated by canopy wilting and sapwood discoloration was less pronounced in P. americana cv Waldin than in the two forest species. Xylem vessel diameter was significantly smaller in P. borbonia and P. palustris than in P. americana cv Waldin. Differences in laurel wilt susceptibility among species appear to be influenced by physiological and anatomical tree responses.

Plant water uptake from soil through a vapor pathway.

Water uptake from the soil via a vapor pathway was tested. Viburnum suspensum L. plants were divided into: (1) irrigated, (2) drought with vapor and (3) drought without vapor treatments. Each plant was placed into a larger bucket containing deuterium-labeled water as a vapor source (vapor treatment) or no water (drought and irrigation treatments). We also tested whether uptake via a vapor pathway could mitigate drought effects. Net CO2 assimilation (A), transpiration (E) and stomatal conductance (gs) were measured daily until the first visible signs of stress. Soil water content, stem water potential (Ψ) and the stable hydrogen isotope ratio (δ2 H) of soil and plant xylem water were then measured in all treatments. We show that water is taken up by plants through the vapor phase in dry soils. The δ2 H values of the soil water in the vapor treatment were highly enriched compared to the background isotope ratios of the non-vapor exposed irrigated and drought treatments. Stem water δ2 H values for the vapor treatment were significantly greater than those for irrigation and drought treatments not exposed to isotopically enriched vapor. In this experiment, movement of water to the plant via the vapor phase did not mitigate drought effects. A, E, plant Ψ and gs significantly decreased in the drought and vapor treatments relative to the controls, with no significant differences between vapor and drought treatments.

Effectiveness of a micronutrient delivery system fertilizer in jatropha plants is related to enhanced photosynthesis, gas exchange and biomass allocation / Eficácia de um sistema de fornecimento de micronutrientes em plantas de jatropha está relacionado com incrementos na fotossíntese, troca gasosa e alocação de biomassa

This study aimed at comparing the growth and physiological changes in Jatropha curcas L. (jatropha or physic nut) young plants fertilized or not with a commercial product based on a micronutrient delivery system (MDS), under different doses of NPK. Measurements of growth, chlorophyll content, and leaf gas exchange were performed in the greenhouse, where plants were arranged in a split-split plot design. Plants were grown for 120 days in 3.9 L pots containing local soil, with or without MDS (main plot), combined with NPK doses (0; 1.8; 4.7 and 7.4 g L-1) in subplots. Dose-response curves showed that most variables were positively responsive to NPK doses in plants growing without MDS, whereas slight responses or even opposite behavior was observed in MDS-fertilized plants. MDS application under low NPK doses resulted in higher biomass allocation in leaves and roots, increases in number of leaves and chlorophyll content, plant height, stem diameter, shoot and root dry weight, stomatal conductance, photosynthesis, leaf transpiration, and water use efficiency, as well as decreases in intercellular CO2 in the leaf and vapor-pressure deficit. The enhanced biomass allocation, photosynthesis and gas exchange in MDS-supplemented plants indicates the relevant role played by this fertilizer in jatropha metabolism, resulting in more vigorous plants.

Este estudo teve como objetivo comparar o crescimento e as mudanças fisiológicas em plantas jovens de Jatropha curcas L. (pinhão manso), fertilizadas ou não, com um produto comercial baseado em um sistema de fornecimento de micronutrientes (MDS), sob diferentes doses de NPK. Medidas de crescimento, teor de clorofila e troca gasosa foliar foram realizados em casa de vegetação, onde as plantas foram arranjadas em um delineamento de blocos casualizados com parcela subdividida. As plantas foram cultivadas por 120 dias em potes de 3,9 L contendo solo local, com ou sem MDS (parcela principal), combinado com doses de NPK (0; 1,8; 4,7 e 7,4 g L-1) nas subparcelas. Curvas doseresposta mostraram que a maioria das variáveis responderam positivamente às doses de NPK em plantas crescendo sem MDS, enquanto respostas fracas ou mesmo comportamento oposto foi observado em plantas fertilizadas com MDS. A aplicação de MDS em doses baixas de NPK resultaram em maior alocação de biomassa nas folhas e raízes, aumento no número de folhas e teor de clorofila, altura da planta, diâmetro do caule, pesos secos da parte aérea e raiz, condutância estomatal, fotossíntese, transpiração foliar e eficiência no uso da água, bem como na redução do CO2 intercelular na folha e déficit de pressão de vapor. O aumento na alocação de biomassa, fotossíntese e troca gasosa em plantas suplementadas com MDS indica o papel relevante deste fertilizante no metabolismo de pinhão manso, resultando em plantas mais vigorosas.

Testing plant use of mobile vs immobile soil water sources using stable isotope experiments.

We tested for isotope exchange between bound (immobile) and mobile soil water, and whether there is isotope fractionation during plant water uptake. These are critical assumptions to the formulation of the 'two water worlds' hypothesis based on isotope profiles of soil water. In two different soil types, soil-bound water in two sets of 19-l pots, each with a 2-yr-old avocado plant (Persea americana), were identically labeled with tap water. After which, one set received isotopically enriched water whereas the other set received tap water as the mobile phase water. After a dry down period, we analyzed plant stem water as a proxy for soil-bound water as well as total soil water by cryogenic distillation. Seventy-five to 95% of the bound water isotopically exchanged with the mobile water phase. In addition, plants discriminated against 18 O and 2 H during water uptake, and this discrimination is a function of the soil water loss and soil type. The present experiment shows that the assumptions for the 'two water worlds' hypothesis are not supported. We propose a novel explanation for the discrepancy between isotope ratios of the soil water profile and other water compartments in the hydrological cycle.

Impact of Laurel Wilt, Caused by Raffaelea lauricola, on Leaf Gas Exchange and Xylem Sap Flow in Avocado, Persea americana.

Laurel wilt, caused by Raffaelea lauricola, is a destructive disease of avocado (Persea americana). The susceptibility of different cultivars and races was examined previously but more information is needed on how this host responds to the disease. In the present study, net CO2 assimilation (A), stomatal conductance of H2O (gs), transpiration (E), water use efficiency (WUE), and xylem sap flow rates were assessed in cultivars that differed in susceptibility. After artificial inoculation with R. lauricola, there was a close relationship between symptom development and reductions in A, gs, E, WUE, and mean daily sap flow in the most susceptible cultivar, 'Russell', and significantly greater disease and lower A, gs, E, WUE, and sap flow rates were usually detected after 15 days compared with the more tolerant 'Brogdon' and 'Marcus Pumpkin'. Significant differences in preinoculation A, gs, E, and WUE were generally not detected among the cultivars but preinoculation sap flow rates were greater in Russell than in Brogdon and Marcus Pumpkin. Preinoculation sap flow rates and symptom severity for individual trees were correlated at the end of an experiment (r=0.46), indicating that a plant's susceptibility to laurel wilt was related to its ability to conduct water. The potential management of this disease with clonal rootstocks that reduce sap flow rates is discussed.