Current Science

Dynamic Analysis of Milling and Burr Morphology in 6061 Aluminum Alloy

2026-03-25T14:09:43+00:00

6061 aluminum alloy is a common aluminum alloy material with good machinability and mechanical properties, which has been widely used in high-end manufacturing fields such as aerospace; Thin wall features are particularly common in the machining process of parts. This article uses a universal tool milling force mechanical model to model the dynamics of the machining process. Firstly, the cutting process is analyzed mechanically, and then the cutting force coefficient is identified through cutting experiments to obtain the milling dynamics model. The calculation results of the model are compared with the cutting experiment results, verifying the effectiveness of the model. The morphology of fine burrs in the machining process of parts was analyzed, and the relationship between machining parameters and burr morphology characteristics was experimentally studied, providing a certain reference for suppressing the formation of fine burrs in the machining of thin-walled aluminum alloy parts.

Nonlinear Association between Serum Folate and Zinc Concentrations in Children with Rickets: A Retrospective Cross-Sectional Study

2026-04-04T00:54:53+00:00

Abstract

Objective: Micronutrient interactions in disease states remain poorly understood. This study evaluated the association between serum folate (exposure) and zinc concentrations (outcome) in children with rickets.

Methods: This retrospective cross-sectional study enrolled 1,440 children with rickets from Shenzhen Children's Hospital (January 2022–December 2024). Serum folate (chemiluminescence immunoassay) and zinc (atomic absorption spectrophotometry) were measured. Covariates included sex and age. We employed multivariable linear regression with progressive covariate adjustment, generalized additive models for nonlinearity testing, and threshold effect analysis using two-piecewise linear regression.

Results: Participants' mean age was distributed across tertiles, with 64.0% males. In adjusted models, each unit increase in folate was associated with a 12.5 nmol/L decrease in zinc (β=-12.5; 95% CI: -17.8 to -7.1; P<0.001). Threshold analysis identified a critical inflection point at folate 18.4 μmol/L. Below this threshold, each unit increase in folate corresponded to a 56.4 nmol/L decrease in zinc (β=-56.4; 95% CI: -67.9 to -44.9; P<0.001); above the threshold, the relationship reversed, with each unit increase in folate associated with an 18.7 nmol/L increase in zinc (β=18.7; 95% CI: 9.8 to 27.7; P<0.001). The two-piecewise model significantly outperformed the linear model (LRT P<0.001). The association was more pronounced in females (β=-19.9 vs. -9.5 in males; interaction P<0.05).

Conclusion: A nonlinear, biphasic relationship exists between folate and zinc in children with rickets, with a threshold at 18.4 μmol/L. These findings suggest precision nutrition strategies should consider baseline folate status when managing zinc homeostasis in rickets.

Design, Optimisation and Evaluation of Orally Disintegrating Tablets of Nicardipine Hydrochloride Prepared with a Natural Sweetener

2026-05-31T04:33:03+00:00

Nicardipine hydrochloride, a dihydropyridine calcium channel blocker used in hypertension and angina, is limited by an intensely bitter taste, poor aqueous solubility and a short half-life. This study aimed to design, optimise and evaluate orally disintegrating tablets (ODTs) of nicardipine hydrochloride using high-purity rebaudioside A as a natural taste-masking sweetener. ODTs were prepared by direct compression and optimised using a three-factor three-level Box–Behnken design with crospovidone, croscarmellose sodium and rebaudioside A as factors and disintegration time, wetting time, hardness and drug release at five minutes as responses. All models were significant (p < 0.0001, R² > 0.98). The optimised formulation (crospovidone 5.62%, croscarmellose sodium 5.48%, rebaudioside A 1.84%) showed disintegration time 13.9 ± 0.4 s, wetting time 17.5 ± 0.6 s, hardness 28.2 ± 0.8 N, friability 0.46%, drug content 99.4 ± 1.6% and 90.4% release within five minutes. Taste-panel scores were significantly higher than placebo (p < 0.001). The formulation was stable under accelerated and long-term conditions. In rats, it achieved higher and earlier Cmax (174.6 ng/mL at 0.86 h vs 148.2 ng/mL at 1.42 h), relative bioavailability 106.3% and a faster antihypertensive onset than the reference. A natural-sweetener-based ODT of nicardipine is thus a feasible, palatable and robust patient-friendly dosage form.

Keywords: Nicardipine hydrochloride; orally disintegrating tablet; rebaudioside A; natural sweetener; taste masking; Box–Behnken design.