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  Numerical modeling of the hydrodynamic behavior of MgO– water nanofluid in plate-fin heat exchangers under varying operating conditions

  (Nature Publishing Group, 2026) Sultan, Abbas J.; Yahya, Ali A.; Faraj, Fadhl H.; Sawaran Singh, Narinderjit Singh; Jasim, Dheyaa J.; Sabri, Laith S.; Aljaafari, Haydar A. S.; Taner, Mahmut; Hasanabad, Ali Mohammadi

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  This research examined the ability of an artificial neural network to predict flow behavior, defined by Reynolds number and pressure drop as functions of volume fraction and temperature, at fixed flow rates of 5, 8, and 11 LPM. The proposed framework was developed to address the nonlinear, interrelated thermo-compositional effects that influence flow inertia and pressure losses, without relying on predefined empirical relationships. The model's reliability and predictive performance were evaluated through 5-fold cross-validation, monitoring of learning errors, regression diagnostics, error quantification, and sensitivity analysis. Results from cross-validation indicated stable Reynolds number predictions at low and moderate flow rates, with mean RMSE values of 6.39 at 5 LPM and 6.16 at 8 LPM. At 11 LPM, the mean RMSE rises to 13.87, highlighting the greater sensitivity and complexity of inertia-dominated flow regimes. Conversely, predictions of pressure drop remained consistently accurate across all operating conditions, achieving mean RMSE values of 2.68 mbar, 0.56 mbar, and 0.94 mbar at 5, 8, and 11 LPM, respectively. Regression analysis confirmed a strong linear relationship between predicted and reference values for both outputs, with correlation coefficients exceeding 0.99 at low and moderate flow rates and remaining above 0.96 at the highest flow rate. Further analysis of relative and absolute errors indicated high predictive accuracy, with mean relative errors below 5% for Reynolds number and below 1.3% for pressure drop across all scenarios. Sensitivity analysis consistently identified temperature as the primary source of predictive variability, with volume fraction being the secondary contributor. Pressure drop showed significantly lower sensitivity than Reynolds number, suggesting a smoother, less nonlinear relationship with the governing inputs.

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  Post-exercise auricular vagus nerve stimulation modulates autonomic and recovery responses in physically inactive young adults: a randomized controlled trial

  (Nature Publishing Group, 2026) Ertürk, Çağıl; Mutuş, Rıfat

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  Efficient post-exercise recovery largely depends on rapid parasympathetic reactivation of the autonomic nervous system. Auricular transcutaneous vagus nerve stimulation (taVNS) has emerged as a non-invasive neuromodulatory approach with the potential to facilitate autonomic recovery following physical exertion. This study aimed to investigate the acute effects of auricular transcutaneous vagus nerve stimulation applied immediately after exercise on autonomic nervous system activity and recovery-related physiological, metabolic, and perceptual parameters in healthy young adults. This cross-sectional study with an acute intervention bout included sixty physically inactive healthy young adults (18-35 years) who were randomly allocated to an exercise + taVNS group (n = 30) or an exercise-only control group (n = 30). All participants completed a standardized 30-minute treadmill walking protocol. Immediately after exercise, the intervention group received 20 min of bilateral taVNS, while the control group underwent a matched recovery period. Autonomic function was assessed using heart rate variability indices, including the root mean square of successive differences (RMSSD), a time-domain indicator of parasympathetic activity, and the low-frequency/high-frequency (LF/HF) ratio, which reflects sympathovagal balance, together with cardiovascular, metabolic, and perceptual recovery markers. Both groups demonstrated recovery-related improvements following exercise. However, the taVNS group showed greater reductions in systolic and diastolic blood pressure compared with the control group (p = .003 and p = .004). The parasympathetic nervous system index increased significantly more in the taVNS group (p = .009). Blood lactate concentration decreased more markedly in the taVNS group (- 4.90 ± 3.02 mmol·L⁻¹) than in the control group (- 1.38 ± 0.97 mmol·L⁻¹; p < .001). Participants receiving taVNS also demonstrated a greater reduction in perceived fatigue scores (p < .001). In contrast, heart rate variability parameters such as heart rate, RMSSD, and LF/HF ratio showed comparable recovery patterns between groups (p > .05). Auricular transcutaneous vagus nerve stimulation applied immediately after exercise appears to enhance parasympathetic reactivation and improve cardiovascular, metabolic, and perceptual recovery beyond spontaneous post-exercise recovery. These findings suggest that taVNS may represent a feasible non-invasive strategy to support acute post-exercise recovery in healthy young adults when applied under appropriate stimulation parameters (ClinicalTrials.gov: NCT07371676).

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  Innovative upper extremity rehabilitation methods in stroke patients: a comparison of robotic rehabilitation and action observation therapy-a randomized trial

  (Frontiers Research Foundation, 2026) Şenocak, Emre; Korkut, Elif; Aktürk, Adem; Yıldız Özer, Aysel

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  Introduction: After a stroke, difficulties with arm and hand movement most affect daily life. To overcome these difficulties, research is ongoing to find the most effective treatment approaches. This study investigated which of two different technology-based rehabilitation approaches improved upper extremity motor function, independence, and quality of life in stroke. Methods: Thirty patients were randomized into two groups: robotic rehabilitation (RR) and action observation therapy (AOT). Upper extremity movements were repeated with active participation using the Houston Bionics ExoRehab X device in the RR group. On the other hand, the AOT group focused on watching and practicing functional movements through 31 first-person perspective videos. Motor functions, independence, and quality of life were assessed by the Wolf Motor Function Test (WMFT), Box-Block Test (BBT), Barthel Index (BI), and Stroke-Specific Quality of Life Questionnaire (SS-QoL). Results: The WMFT, BBT, BI, and SS-QoL scores of both groups improved from baseline. However, neither group was superior to the other in the first 4 weeks' results. At the end of 8 weeks, the RR group demonstrated significantly greater improvements in all parameters compared with the AOT group (p < 0.05 for all) except SS-QoL (p = 0.136). Discussion: While both treatment methods showed similar short-term improvements, the RR group demonstrated greater improvements in motor function and independence than the AOT group at the end of 8 weeks. The fact that AOT gains slow down after the 4th week raises the question of which week these gains will stop. Clinical trial registration: Name: Effects of the Action Observation Therapy and Robotic Rehabilitation on the Upper-Limb Motor Function in Stroke. ID: NCT05590156 (18.04.2024). URL: https://register.clinicaltrials.gov/prs/beta/studies/S000CKXO00000049/recordSummary.

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  A social cognitive theory and theory of planned behavior-based serial multiple mediation model of social media-related factors and eating behaviors among sports science students

  (Frontiers Media S. A., 2026) Bayazıtlı, Erhayat Özgür; Çakır, Ayşe Sena; Turan, Mehmet Behzat; Caba, Uğur; Karaoğlu, Barış; Pepe, Osman; Pekel, Aydın; Hanik Sevim, İncinur; Dalbudak, İbrahim

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  Background/objectives: Social media has become a pervasive digital environment closely associated with individuals' dietary preferences, eating attitudes, and consumption behaviors. Although prior research has documented associations between social media use and eating behaviors, the underlying cognitive, attitudinal, and psychological mechanisms remain insufficiently clarified, particularly among university students. Accordingly, this study examines the serial mediating roles of digital healthy nutrition literacy, attitudes toward functional foods, food craving acceptance, and emotional eating in the relationship between social media use and eating behaviors.Methods: This cross-sectional study was conducted with 1,576 sports sciences students from 38 public universities in Türkiye. Sports science students were selected because of their high engagement with health-related content, intensive social media exposure, and potential future role in promoting healthy lifestyle behaviors. Data were collected using validated instruments. The proposed serial multiple mediation model was tested using PROCESS Macro (Model 6) with 5,000 bootstrap resamples.Results: Social media-related factors were significantly associated with e-healthy diet literacy (β = 0.31, p < 0.001), attitudes toward functional foods (β = 0.31, p < 0.001), food craving acceptance (β = -0.12, p < 0.001), and emotional eating (β = 0.12, p < 0.001). In turn, e-healthy diet literacy (β = 0.27, p < 0.001), attitudes toward functional foods (β = 0.21, p < 0.001), food craving acceptance (β = 0.29, p < 0.001), and emotional eating (β = 1.32, p < 0.001) were all significantly associated with eating attitudes. The model explained 50% of the variance in eating attitudes (R2 = 0.50). The full serial pathway was statistically significant, although the indirect effect size was small (B = 0.01, 95% CI [0.01, 0.01]). The total indirect effect was statistically significant (B = 0.51, SE = 0.04, 95% CI [0.44, 0.58]), while the full serial mediation pathway also reached significance (B = 0.01, 95% CI [0.01, 0.01]).Conclusion: The findings indicate that the relationship between social media use and eating behaviors involves a sequence of cognitive, attitudinal, and emotional processes rather than a single direct pathway. Digital healthy nutrition literacy and acceptance-based regulation processes appear to play key roles within this framework. Given their intensive social media use and potential role-model status, sports sciences students represent an important target group for such approaches.

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  Eco-friendly design inspired by nature: examining adolescents' perceptions of biomimicry

  (Frontiers Research Foundation, 2026) Öz Tatacak, Sena; Bingöl, Hatice Zelal; Gürsoy, Figen

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  Introduction: Interest in biomimicry education has grown recently, yet little is known about how high-achieving science high school students conceptualize biomimicry and translate biological knowledge into sustainable design ideas across disciplines. Methods: Using a qualitative case study design, data were collected from 29 ninth-grade students via a written semi-structured form and analyzed through content analysis using the Biology-to-Design Spiral as the analytical framework. Results: Students were familiar with biomimicry and successfully transformed biological knowledge into design logic, but their conception of "living things" remained predominantly animal-centric and the range of inspiration organisms was narrow despite daily contact with the school grove. Designs centered on structural and functional traits and were linked to technology-based, sustainability-oriented solutions. Discussion: Everyday contact with nature alone does not appear sufficient to broaden biomimicry thinking; structured learning environments connecting ecological experience with scientific and design reasoning are needed. Biomimicry education shows strong interdisciplinary potential to integrate biology, engineering, and sustainability and to foster ecological thinking among gifted adolescents.

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