Sources of stress, coping strategies and associated factors among Vietnamese first-year medical students.

OBJECTIVES: This study aims to examine the sources of stress among first-year medical students; the frequency of their coping strategies; the factors associated with specific stressors and specific coping strategies adopted by the participants. METHODS: We conducted a cross-sectional study with 409 first-year students at the University of Medicine and Pharmacy, Vietnam. The Vietnamese versions of the Higher Education Stress Inventory (V_HESI) and Brief Coping Orientation to Problems Experienced (V_Brief COPE) were validated and were used as measurement instruments for participants' sources of stress and coping strategies frequencies. The survey comprised questions of socioeconomic status, stress-related issues, the six sources of stress (using the V_HESI), and the nine coping strategies (using the V_Brief COPE). RESULTS: Among the six sources of stress, "Worries about future competence/endurance" had the highest mean score (3.02±0.64), while "Mismatch in professional role expectations" had the lowest score (1.60±0.53). "Financial concerns" and "Academic workloads" were also significant sources of stress. Regarding coping strategies, Self-distraction was most frequently adopted by the participants (2.80 ± 0.68). Problem-solving (2.72±0.53) and seeking Social support (2.62±0.70) were also common adaptive strategies. Avoidance (1.87±0.55) and substance-use (1.27±0.55) were the least frequent strategies. Students who experienced acute stress event were more likely to have financial concerns compared to others. Substance use was positively associated with stressors from "Mismatch in professional role expectations", "Non-supportive educational environment", "Having physical issues" and "Having part-time job". Self-blame was more frequent among students with "Worries about future competence/endurance", "Financial concerns", and "Academic workload". Male student tended to adopt humor strategy (ß = 0.19, p = 0.02), while less likely to utilize religious practices (ß = -0.21, p = 0.01). CONCLUSIONS: Two-thirds of the participants reported moderate to high levels of stress. "Worries about future competence/endurance" was the most concerned stressor, followed by "Academic workload", and "Financial concerns". The first-year medical students reported high frequency of utilization "Self-distraction", "Problem-solving" and "Social support" when confronting stress. The findings may help inform the school management to better support students' well-being.

Comparative genomics sheds new light on the convergent evolution of infrared vision in snakes.

Infrared vision is a highly specialized sensory system that evolved independently in three clades of snakes. Apparently, convergent evolution occurred in the transient receptor potential ankyrin 1 (TRPA1) proteins of infrared-sensing snakes. However, this gene can only explain how infrared signals are received, and not the transduction and processing of those signals. We sequenced the genome of Xenopeltis unicolor, a key outgroup species of pythons, and performed a genome-wide analysis of convergence between two clades of infrared-sensing snakes. Our results revealed pervasive molecular adaptation in pathways associated with neural development and other functions, with parallel selection on loci associated with trigeminal nerve structural organization. In addition, we found evidence of convergent amino acid substitutions in a set of genes, including TRPA1 and TRPM2. The analysis also identified convergent accelerated evolution in non-coding elements near 12 genes involved in facial nerve structural organization and optic nerve development. Thus, convergent evolution occurred across multiple dimensions of infrared vision in vipers and pythons, as well as amino acid substitutions, non-coding elements, genes and functions. These changes enabled independent groups of snakes to develop and use infrared vision.

A new record and a novel morph description of Boigastoliczkae (Squamata, Colubridae) from China.

Background: The Asian Cat Snake genus Boiga Fitzinger, 1826 includes 37 species, with high species diversity. Five species of Boiga have been recorded in China including B.multomaculata (Boie, 1827), B.kraepelini (Stejneger, 1902), B.cyanea (Duméril, Bibron & Duméril, 1854), B.guangxiensis (Wen, 1998) and B.siamensis (Nutaphand, 1971). Previously, the validity of the species Boigastoliczkae (Wall, 1909) was controversial. B.stoliczkae was considered in synonymy with B.ochracea. Currently, the taxonomy of B.multomaculata and B.ochracea (Theobald, 1868) was revised so that B.multomaculata and B.ochracea actually represent a single species and B.stoliczkae was recognised as a valid species. B.stoliczkae was previously known to be found in the west from central Nepal through Darjeeling, Sikkim and Bhutan to Arunachal Pradesh and Assam in north-eastern India. New information: One adult female specimen of the Asian Cat Snake was collected from Gyirong County, near the China-Nepal border, Tibet, China during fieldwork on August 2023. We compared morphology and mitochondrial DNA sequence data with all the species of the genus Boiga. Both datasets strongly supported referring the Chinese specimens to B.stoliczkae (Wall, 1909) due to the 21 mid-dorsal scale rows and the uncorrected p-distance (mitochondrial DNA gene cytochrome b) between this specimen and B.stoliczkae which is 1.7%. We further described morphological characters of the Chinese specimen in detail and compared these with the specimens that had been previously described. The dorsal ground colour of the Chinese specimen is dark brown, with a black stripe distributed almost evenly across the tail. This is a novel morph of the species B.stoliczkae. The newly-collected Chinese specimen expands the distribution of the species on the Himalaya range.

Take-out food enhances the risk of MPs ingestion and obesity, altering the gut microbiome in young adults.

Young people are consuming large amounts of microplastics (MPs) due to the booming development of the take-out industry. To investigate the association between MPs exposure and obesity, 121 volunteers were divided into high MPs exposure (HME) and low MPs exposure (LME) according to the frequency of take-out food consumption. Fecal samples were collected for MPs detection using Raman spectra analysis, and identification of the gut microbiota was based on 16 S rDNA/ITS, while metabolite analysis was performed by LC-MS/MS. High levels of MPs and body mass index (BMI) were observed in the HME group (P < 0.05). Both the multiple linear regression (MLR) model and the binary logistic regression (BLR) (OR: 1.264, 95 % CI: 1.108-1.441, P < 0.001) analysis showed a positive correlation between MPs content and BMI. Microbial community analysis revealed that Veillonella, Alistipes and Dothideomycotes (pathogenic fungi) increased in HME participants, whereas Faecalibacterium and Coprococcus decreased. Meanwhile, analysis of stool metabolites showed that vancomycin resistance, selenocompound metabolism and drug metabolism pathways were enhanced in HME participants. These findings indicate that frequent consumption of take-out food may elevate the intake of microplastics, consequently modifying the gut microbiota and metabolites of young adults, and could represent a potential risk factor for obesity.

Portal Venous and Hepatic Arterial Coefficients Predict Post-Hepatectomy Overall and Recurrence-Free Survival in Patients with Hepatocellular Carcinoma: A Retrospective Study.

Background: The dominant artery blood supply is a characteristic of hepatocellular carcinoma (HCC). However, it is not known whether the blood supply can predict the post-hepatectomy prognosis of patients with HCC. This retrospective study investigated the prognostic value of the portal venous and arterial blood supply estimated on triphasic liver CT (as a portal venous coefficient, PVC, and hepatic arterial coefficient, HAC, respectively) in patients with HCC following hepatectomy. Methods: HCC patients who were tested by triphasic liver CT 2 weeks before hepatectomy and received R0 hepatectomy at the Second Affiliated Hospital, Kunming Medical University between January 1, 2016 and December 31, 2020, were retrospectively screened. Their PVC and HAC, and other variables were analyzed for the prediction of overall survival (OS) and recurrence-free survival (RFS) using the least absolute shrinkage and selection operator and Cox proportional hazard regression models. Results: Four hundred and nineteen patients (53.2 ± 10.6 years of age and 370 men) were evaluated. A shorter OS was independently associated with higher blood albumin and total bilirubin grade [hazard ratio (HR) 2.020, 95% confidence interval (CI) 1.534-2.660], higher Barcelona Clinic Liver Cancer (BCLC) stage (HR 1.514, 95% CI 1.290-1.777), PVC ≤ 0.386 (HR 1.628, 95% CI 1.149-2.305), and HAC > 0.029 (HR 1.969, 95% CI 1.380-2.809). A shorter RFS was independently associated with male (HR 1.652, 95% CI 1.005-2.716), higher serum α-fetoprotein ≥ 400 ng/mL (HR 1.672, 95% CI 1.236-2.263), higher BCLC stage (HR 1.516, 95% CI 1.300-1.768), tumor PVC ≤ 0.386 (HR 1.641, 95% CI 1.198-2.249), and tumor HAC > 0.029 (HR 1.455, 95% CI 1.060-1.997). Conclusion: Tumor PVC or HAC before hepatectomy is valuable for independently predicting postoperative survival of HCC patients.

A new species of the genus Hebius (Squamata, Natricidae) from Yunnan, China.

A new species of the genus Hebius Thompson, 1913 is described from Yingjiang County, Dehong Dai and Jingpo Autonomous Prefecture, Yunnan Province, China, based on molecular and morphological evidence. It can be distinguished from its congeners by the following set of characters: (1) dorsal scale rows 19-17-17, feebly keeled; (2) ventrals 146-151; (3) nasal complete, nostril in the middle of the nasal; (4) supralabials 9, the fourth to sixth in contact with the eye; (5) infralabials 10-11, the first 5 touching the first pair of chin shields; (6) preoculars 2; (7) postoculars 3; (8) temporals 3, arranged in two rows (1+2); (9) maxillary teeth 31, the last 4 slightly enlarged, without diastema; (10) tail comparatively long, TAL/TL ratio 0.334 in the male; (11) dorsolateral series of irregular orange or ochre yellow blotches, extending from the neck to the posterior part of the tail; and (12) venter pale orange, tips of ventrals with subrectangular black blotches. All Hebius specimens were strongly recovered as monophyletic, in which Hebiustaronensis (Smith, 1940) and Hebiusvenningi (Wall, 1910) were monophyletic as sister to the Yingjiang County specimens. According to the p-distance of cytochrome b, the new species differs from its congeners by 9.7-15.4%.

Molecular Bridging Induced Anti-salting-out Effect Enabling High Ionic Conductive ZnSO4-based Hydrogel for Quasi-solid-state Zinc Ion Batteries.

Hydrogel electrolytes (HEs) hold great promise in tackling severe issues emerging in aqueous zinc-ion batteries, but the prevalent salting-out effect of kosmotropic salt causes low ionic conductivity and electrochemical instability. Herein, a subtle molecular bridging strategy is proposed to enhance the compatibility between PVA and ZnSO4 from the perspective of hydrogen-bonding microenvironment re-construction. By introducing urea containing both an H-bond acceptor and donor, the broken H-bonds between PVA and H2O, initiated by the SO42--driven H2O polarization, could be re-united via intense intermolecular hydrogen bonds, thus leading to greatly increased carrying capacity of ZnSO4. The urea-modified PVA-ZnSO4 HEs featuring a high ionic conductivity up to 31.2 mS cm-1 successfully solves the sluggish ionic transport dilemma at the solid-solid interface. Moreover, an organic solid-electrolyte-interphase can be derived from the in-situ electro-polymerization of urea to prohibit H2O-involved side reactions, thereby prominently improving the reversibility of Zn chemistry. Consequently, Zn anodes witness an impressive lifespan extension from 50 h to 2200 h at 0.1 mA cm-2 while the Zn-I2 full battery maintains a remarkable Coulombic efficiency (>99.7%) even after 8000 cycles. The anti-salting-out strategy proposed in this work provides an insightful concept for addressing the phase separation issue of functional HEs.

Stable zinc anode solid electrolyte interphase via inner Helmholtz plane engineering.

The inner Helmholtz plane and thus derived solid-electrolyte interphase (SEI) are crucial interfacial structure to determine the electrochemical stability of Zn-ion battery (ZIB). In this work, we demonstrate that introducing ß-cyclodextrins (CD) as anion-receptors into Zn(OTf)2 aqueous electrolyte could significantly optimize the Zn anode SEI structure for achieving stable ZIB. Specifically, ß-CD with macrocyclic structure holds appropriate cavity size and charge distribution to encase OTf- anions at the Zn metal surface to form ß-CD@OTf- dominated inner Helmholtz structure. Meanwhile, the electrochemically triggered ß-CD@OTf- decomposition could in situ convert to the organic-inorganic hybrid SEI (ZnF2/ZnCO3/ZnS‒(C-O-C/*CF/*CF3)), which could efficiently hinder the Zn dendrite growth with maintain the proper SEI mechanical strength stability to guarantee the long-term stability. The thus-derived Zn | |Zn pouch cell (21 cm2 size) with ß-CD-containing electrolyte exhibits a cumulative capacity of 6450 mAh-2 cm-2 at conditions of 10 mAh cm-2 high areal capacity. This work gives insights for reaching stable ZIB via electrolyte additive triggered SEI structure regulation.

High-resolution and highly-multiplexed option for fiber-fed spectrograph of the wide field MUltiplexed Survey Telescope (MUST).

In recent decades, rapid advances in astronomical imaging campaigns have generated an urgent need for detailed spectroscopic surveys with increased speed and efficiency. The 6.5 m MUltiplexed Survey Telescope (MUST) aims to address these current demands. The performance of the multi-object fiber-fed spectrograph (MOFS) plays a critical role for spectroscopic survey telescopes, directly influencing the realization of scientific aims. In this paper, we demonstrate a high-resolution and highly-multiplexed option for MOFS of MUST. The system is believed to be first to apply a 92 mm × 92 mm large-size detector in a Schmidt-like camera and reduces the average central obscuration to 14%. Thanks to the F/1.25 camera design with excellent image quality, the spectrograph achieves up to 800 150µm-large-core optical fibers integration. It can obtain the broadband spectral information (395 nm-435 nm, 520 nm-570 nm, 610 nm-680 nm) of 800 objects with a high resolution of >16,000 within one exposure. The spectrograph theory, design method, and final system scheme of the MOFS can offer good reference and guidance for the spectrograph design in the spectroscopic survey.

Optimized optical system with a 1.65 m wide-field corrector for the 6.5 m high-performance MUltiplexed Survey Telescope.

The development of modern large-scale spectroscopic survey telescopes responds to the urgent demand for spectral information in astronomical research. Tsinghua University has previously proposed a 6.5 m MUltiplexed Survey Telescope consisting of a Ritchey-Chretien configuration and a 1.8 m multi-element wide-field corrector, achieving excellent performance and world-leading survey efficiency. However, an optimized 1.65 m multi-element corrector with five lenses is proposed to overcome the constraints on glass uniformity and verification in fabrication of the previous corrector design. It maintains outstanding image quality, with the 80% enclosed energy diameter not more than 0.559 arcsec within 3° FoV over up to a 55° zenith angle. The optimized optical system does not revise the working mode of the ADC or the curvature of the primary mirror while ensuring the reasonability and accuracy of manufacturing of large corrector elements. It provides a more feasible reference optical design for the MUltiplexed Survey Telescope in subsequent iterations and communications with manufacturers.

Combined impact of sleep and obesity on female infertility in the NHANES 2017-2020.

BACKGROUND: Sleep health and obesity may affect the risk of female infertility. However, few studies focused on the interaction of obesity and sleep health on the female infertility risk. This study aimed to evaluate the combined impact of trouble sleeping / sleep duration and overweight/obesity/ abdominal obesity on the risk of female infertility. METHODS: The data for this cross-sectional study was obtained from National Health and Nutritional Examination Survey, which provided information on trouble sleeping, sleep duration, overweight/obesity, abdominal obesity, and confounding factors. Adopted weighted univariate and multivariate logistic regression models to explore the relationship between trouble sleeping, sleep duration, overweight/obesity, abdominal obesity, and the risk of infertility, respectively, and the combined effect of trouble sleeping and overweight/obesity, trouble sleeping and abdominal obesity, sleep duration and overweight/obesity, sleep duration and abdominal obesity, on the female infertility risk. RESULTS: This study included a total of 1,577 women, and 191 were diagnosed with infertility. Women with infertility had a higher proportion of people with overweight/obesity, abdominal obesity, sleep duration ≤ 7 h and trouble sleeping than those with non-infertility. The result indicated that trouble sleeping [odds ratio (OR) = 2.25, 95% confidence intervals (CI): 1.49-3.39], sleep duration ≤ 7 h (OR = 1.59, 95% CI: 1.03-2.48), and the combined impact of abdominal obesity and trouble sleeping (OR = 2.18, 95% CI: 1.28-3.72), abdominal obesity and sleep duration ≤ 7 h (OR = 2.00, 95% CI: 1.17-3.40), overweight/obesity and trouble sleeping (OR = 2.29, 95% CI: 1.24-4.26), and overweight/obesity and sleep duration ≤ 7 h (OR = 1.88, 95% CI: 1.01-3.49) were associated with increased odds of infertility, respectively. CONCLUSION: There was combined effects of trouble sleeping/sleep duration ≤ 7 h and overweight/obesity/ abdominal obesity on increased odds of female infertility.

High-Entropy Transition Metal Phosphorus Trichalcogenides for Rapid Sodium Ion Diffusion.

High-entropy strategies are regarded as a powerful means to enhance performance in energy storage fields. The improved properties are invariably ascribed to entropy stabilization or synergistic cocktail effect. Therefore, the manifested properties in such multicomponent materials are usually unpredictable. Elucidating the precise correlations between atomic structures and properties remains a challenge in high-entropy materials (HEMs). Herein, atomic-resolution scanning transmission electron microscopy annular dark field (STEM-ADF) imaging and four dimensions (4D)-STEM are combined to directly visualize atomic-scale structural and electric information in high-entropy FeMnNiVZnPS3. Aperiodic stacking is found in FeMnNiVZnPS3 accompanied by high-density strain soliton boundaries (SSBs). Theoretical calculation suggests that the formation of such structures is attributed to the imbalanced stress of distinct metal-sulfur bonds in FeMnNiVZnPS3. Interestingly, the electric field concentrates along the two sides of SSBs and gradually diminishes toward the two-dimensional (2D) plane to generate a unique electric field gradient, strongly promoting the ion-diffusion rate. Accordingly, high-entropy FeMnNiVZnPS3 demonstrates superior ion-diffusion coefficients of 10-9.7-10-8.3 cm2 s-1 and high-rate performance (311.5 mAh g-1 at 30 A g-1). This work provides an alternative way for the atomic-scale understanding and design of sophisticated HEMs, paving the way for property engineering in multi-component materials.

Establishment of a human nasal epithelium model of histamine-induced inflammation to assess the activity of fexofenadine as an inverse agonist and its link to clinical benefit.

Background: Fexofenadine (FEX) is an antihistamine that acts as an inverse agonist against histamine (HIS) receptor 1 (H1R), which mediates the allergic reaction. Inverse agonists may be more potent than neutral antagonists, as they bind the same receptor as the agonist (HIS) but stabilize the inactive form and induce an opposite pharmacological response, suppressing the basal activity of H1R and preventing HIS from binding. This study aims to establish and validate a model of HIS-induced inflammation based on fully reconstituted human nasal epithelial tissue to assess the activity of FEX as an inverse agonist in this model and explore its link to clinical benefit. Methods: The model was developed using nasal MucilAir™ (Epithelix) in vitro epithelium challenged by HIS. Two conditions were assessed in a side-by-side comparison: tissue was exposed to HIS + FEX with or without FEX pre-treatment (one-hour prior to HIS challenge). Tissue functionality, cytotoxicity, H1R gene expression, and inflammatory cytokines were assessed. Results: HIS at 100 µM induced significant 3.1-fold and 2.2-fold increases for inflammatory biomarkers interleukin (IL)-8 and IL-6, respectively (p < 0.0001), as well as rapid upregulation of H1R mRNA. Inflammatory biomarkers were inhibited by FEX and H1R expression was significantly reduced (p < 0.0001). FEX alone decreased H1R expression at all doses tested. With one-hour FEX pre-treatment, there was significantly higher downregulation of IL-8 (p < 0.05) and further downregulation of H1R expression and IL-6 versus without FEX pre-treatment; the effects of FEX were improved from 22% to 40%. Conclusion: A model of HIS-induced airway inflammation was established based on IL-8, IL-6 and H1R gene expression and was validated with FEX. FEX works as an inverse agonist, with a higher effect when used before+during versus only during the HIS challenge. Taking FEX before+during allergen exposure, or when symptoms first occur, may reduce basal activity and H1R gene expression, providing stronger protection against the worsening of symptoms upon allergen exposure.

A molecular sheaf: doubly threaded [6]rotaxane.

We report that the use of a hydrogen-bonded pyrimidine-macrocycle complex can efficiently facilitate the threading of two bispyridinium ethylenes into four rings, as evidenced by X-ray crystallography of its precursor, offering a rare example of a doubly threaded [6]rotaxane in 91% yield. The unusual architecture is found to be stable with no dethreading despite the large ring size of the macrocycle with respect to the stopper.

Gingerenone A Attenuates Ulcerative Colitis via Targeting IL-17RA to Inhibit Inflammation and Restore Intestinal Barrier Function.

Ulcerative colitis (UC) is a complicated and recurrent intestinal disease. Currently available drugs for UC treatment are scarce, therefore, novel therapeutic drugs for the UC are urgently to be developed. Gingerenone A (GA) is a phenolic compound known for its anti-inflammatory effect, but its effect on UC remains unknown. Here, it is shown that GA protects mice against UC, which is closely associated with inhibiting intestinal mucosal inflammation and enhancing intestinal barrier integrity in vivo and in vitro. Of note, RNA sequencing analysis demonstrates an evident correlation with IL-17 signaling pathway after GA treatment, and this effect is further corroborated by Western blot. Mechanistically, GA directly interacts with IL-17RA protein through pull-down, surface plasmon resonance analysis and molecular dynamics simulation. Importantly, lentivirus-mediated IL-17RA/Act1 knock-down or GA co-treatment with brodalumab/ixekizumab significantly impairs the protective effects of GA against DSS-induced inflammation and barrier dysfunction, suggesting a critical role of IL-17RA signaling for GA-mediated protection against UC. Overall, these results indicate that GA is an effective agent against UC mainly through the direct binding of IL-17RA to inhibit inflammatory signaling activation.

Numerical simulation of ultrawideband supercontinuum generation covering a 2-20 µm waveband in cascaded all-soft-glass fiber.

We designed a cascaded all-soft-glass fiber structure and simulate midinfrared 2-20 µm ultrawideband supercontinuum (SC) generation numerically. The cascaded fiber structure consists of a 1.5 m I n F 3 fiber, a 0.2 m chalcogenide photonic crystal fiber, and a 0.2 m tellurium-based chalcogenide photonic crystal fiber. Using a 2 µm pulse pumping this cascaded structure, the generated SC covering the wavelengths longer than 20 µm has been demonstrated theoretically. The 30 dB bandwidth reaches 20.87 µm from 1.44 to 22.31 µm. The effect of different pulse widths on SC generation is considered. With the increase of peak power and the decrease of pulse width, the energy of SC in the 15-20 µm waveband increases gradually. The mechanism of SC broadening process has also been analyzed. The SC generation of more than 20 µm in this cascade structure is caused by the self-phase modulation, soliton effects, four-wave mixing, and redshifted dispersive wave. This method demonstrates the possibility of generating ultrawide bandwidth SCs up to a 20 µm waveband by a commercial 2 µm pump source and all-fiber structure.

Inefficient antiviral response in reconstituted small-airway epithelium from chronic obstructive pulmonary disease patients following human parainfluenza virus type 3 infection.

Chronic obstructive pulmonary disease (COPD) affects over 250 million individuals globally and stands as the third leading cause of mortality. Respiratory viral infections serve as the primary drivers of acute exacerbations, hastening the decline in lung function and worsening the prognosis. Notably, Human Parainfluenza Virus type 3 (HPIV-3) is responsible for COPD exacerbations with a frequency comparable to that of Respiratory Syncytial Virus and Influenza viruses. However, the impact of HPIV-3 on respiratory epithelium within the context of COPD remains uncharacterized.In this study, we employed in vitro reconstitution of lower airway epithelia from lung tissues sourced from healthy donors (n = 4) and COPD patients (n = 5), maintained under air-liquid interface conditions. Through a next-generation sequencing-based transcriptome analysis, we compared the cellular response to HPIV-3 infection.Prior to infection, COPD respiratory epithelia exhibited a pro-inflammatory profile, notably enriched in canonical pathways linked to antiviral response, B cell signaling, IL-17 signaling, and epithelial-mesenchymal transition, in contrast to non-COPD epithelia. Intriguingly, post HPIV-3 infection, only non-COPD epithelia exhibited significant enrichment in interferon signaling, pattern recognition receptors of viruses and bacteria, and other pathways involved in antiviral responses. This deficiency could potentially hinder immune cell recruitment essential for controlling viral infections, thus fostering prolonged viral presence and persistent inflammation.

Enhancing the Cooling Efficiency of Aluminum-Filled Epoxy Resin Rapid Tool by Changing Inner Surface Roughness of Cooling Channels.

In low-pressure wax injection molding, cooling time refers to the period during which the molten plastic inside the mold solidifies and cools down to a temperature where it can be safely ejected without deformation. However, cooling efficiency for the mass production of injection-molded wax patterns is crucial. This work aims to investigate the impact of varying surface roughness on the inner walls of the cooling channel on the cooling efficiency of an aluminum-filled epoxy resin rapid tool. It was found that the cooling time for the injection-molded products can be determined by the surface roughness according to the proposed prediction equation. Employing fiber laser processing on high-speed steel rods allows for the creation of microstructures with different surface roughness levels. Results demonstrate a clear link between the surface roughness of cooling channel walls and cooling time for molded wax patterns. Employing an aluminum-filled epoxy resin rapid tool with a surface roughness of 4.9 µm for low-pressure wax injection molding can save time, with a cooling efficiency improvement of approximately 34%. Utilizing an aluminum-filled epoxy resin rapid tool with a surface roughness of 4.9 µm on the inner walls of the cooling channel can save the cooling time by up to approximately 60%. These findings underscore the significant role of cooling channel surface roughness in optimizing injection molding processes for enhanced efficiency.

Effect of Zinc and Severe Plastic Deformation on Mechanical Properties of AZ61 Magnesium Alloy.

This study investigates the effects of zinc (4 wt.%) and severe plastic deformation on the mechanical properties of AZ61 magnesium alloy through the stir-casting process. Severe plastic deformation (Equal Channel Angular Pressing (ECAP)) has been performed followed by T4 heat treatment. The microstructural examinations revealed that the addition of 4 wt.% Zn enhances the uniform distribution of ß-phase, contributing to a more uniformly corroded surface in corrosive environments. Additionally, dynamic recrystallization (DRX) significantly reduces the grain size of as-cast alloys after undergoing ECAP. The attained mechanical properties demonstrate that after a single ECAP pass, AZ61 + 4 wt.% Zn alloy exhibits the highest yield strength (YS), ultimate compression strength (UCS), and hardness. This research highlights the promising potential of AZ61 + 4 wt.% Zn alloy for enhanced mechanical and corrosion-resistant properties, offering valuable insights for applications in diverse engineering fields.

Enhancing the Weld Quality of Polylactic Acid Biomedical Materials Using Rotary Friction Welding.

Polylactic acid (PLA) stands out as a biomaterial with immense potential, primarily owing to its innate biodegradability. Conventional methods for manufacturing PLA encompass injection molding or additive manufacturing (AM). Yet, the fabrication of sizable medical devices often necessitates fragmenting them into multiple components for printing, subsequently requiring reassembly to accommodate the constraints posed by the dimensions of the AM platform. Typically, laboratories resort to employing nuts and bolts for the assembly of printed components into expansive medical devices. Nonetheless, this conventional approach of jointing is susceptible to the inherent risk of bolts and nuts loosening or dislodging amid the reciprocating movements inherent to sizable medical apparatus. Hence, investigation into the joining techniques for integrating printed components into expansive medical devices has emerged as a critical focal point within the realm of research. The main objective is to enhance the joint strength of PLA polymer rods using rotary friction welding (RFW). The mean bending strength of welded components, fabricated under seven distinct rotational speeds, surpasses that of the underlying PLA substrate material. The average bending strength improvement rate of welding parts fabricated by RFW with three-stage transformation to 4000 rpm is about 41.94% compared with the average bending strength of PLA base material. The average surface hardness of the weld interface is about 1.25 to 3.80% higher than the average surface hardness of the PLA base material. The average surface hardness of the weld interface performed by RFW with variable rotational speed is higher than the average surface hardness of the weld interface performed at a fixed rotating friction speed. The temperature rise rate and maximum temperature recorded during RFW in the X-axis of the CNC turning machine at the outer edge of the welding part surpassed those observed in the internal temperature of the welding part. Remarkably, the proposed method in this study complies with the Sustainable Development Goals due to its high energy efficiency and low environmental pollution.