中老年人群血小板计数与腰椎骨密度的相关性

背景:近年研究发现,血小板计数与骨密度之间可能具有内在联系,但对于二者内在联系的结论不一。目的:研究中老年人群腰椎骨密度与血小板计数的相关性。方法:研究对象来自美国NHANES数据库,共纳入2571名男性和2929名女性,对样本加权后采用加权多元线性回归模型和平滑曲线拟合,评估腰椎骨密度与血小板计数之间的关联。结果与结论:①加权多元线性回归模型结果显示,总人群腰椎骨密度与血小板计数呈负相关;将腰椎骨密度4分组后与血小板计数仍呈负相关;按性别分层后在男性中仍呈现负相关关系,男性β=-0.0002,95%CI(-0.0003,<-0.0001),按种族分层后只有其他种族美国人的3个模型呈现正相关关系[模型1:β=0.0002,95%CI(<0.0001,0.0004);模型2:β=0.0001,95%CI(-0.0001,0.0003);模型3:β=0.0001,95%CI(-0.0001,0.0003)],而西班牙裔、非西班牙裔白人和非西班牙裔黑人3个模型呈现负相关关系;②采用平滑曲线拟合解决血小板计数与腰椎骨密度之间的非线性关系,发现男性正常范围内的血小板计数与腰椎骨密度存在2个拐点,使用二分段线性回归模型找出这2个拐点,结果显示2个拐点分别是141×10^(9) L^(-1)和246×10^(9) L^(-1);③结果显示,中老年人群男性腰椎骨密度与血小板计数呈负相关,且正常范围内血小板计数<141×10^(9) L^(-1)时腰椎骨密度与血小板计数正相关,血小板计数在(141-246)×10^(9) L^(-1)时腰椎骨密度与血小板计数负相关,血小板计数>246×10^(9) L^(-1)时腰椎骨密度与血小板计数正相关;女性腰椎骨密度与血小板计数可能呈正相关。

A NURBS Fitting Optimization Method for High⁃Speed Five⁃Axis NC Machining Path Based on Curvature Smoothing Preset Point Constraint

Existing curve fitting algorithms of NC machining path mainly focus on the control of fitting error,but ignore the problem that the original discrete cutter position points are not enough in the high curvature area of the tool path.It may cause a sudden change in the drive force of the feed axis,resulting in a large fluctuation in the feed speed.This paper proposes a new non-uniform rational B-spline(NURBS)curve fitting optimization method based on curvature smoothing preset point constraints.First,the short line segments generated by the CAM software are optimally divided into different segment regions,and then the curvature of the short line segments in each region is adjusted to make it smoother.Secondly,a set of characteristic points reflecting the change of the curvature of the fitted curve is constructed as the control apex of the fitted curve,and the curve is fitted using the NURBS curve fitting optimization method based on the curvature smoothing preset point constraint.Finally,the curve fitting error and curve volatility are analyzed with an example,which verifies that the method can significantly improve the curvature smoothness of the high-curvature tool path,reduce the fitting error,and improve the feed speed.

IgA肾病患者血清C3与肾功能进展的相关性分析

目的探讨IgA肾病血清C3水平与肾功能进展的关系。方法本研究为单中心回顾性队列研究,选取2011年1月至2020年6月在深圳市第二人民医院住院、经肾活检证实为IgA肾病并随访至2021年1月的患者。排除继发性IgA肾病、基线估算肾小球滤过率(eGFR)<30 ml·min^(-1)·(1.73 m^(2))^(-1)、基线血清C3或血肌酐缺乏和随访时间<6个月的患者。收集患者的临床、实验室检查、肾脏病理等资料。采用阈值效应分析获取转折点,并采用计算机模拟重采样技术(bootstrapping resampling technique)计算拐点及95%可信区间。根据转折点将患者分为血清C3<0.97 g/L组和C3≥0.97 g/L组,比较两组之间的基线资料。采用Cox回归模型分析血清C3水平与肾功能进展的关系。结果共纳入414例患者,男性145例(35.0%);年龄(35.15±9.18)岁。基线eGFR为77.80(46.67,106.10)ml·min^(-1)·(1.73 m^(2))^(-1),血清C3为(1.04±0.19)g/L。患者血清C3<0.97 g/L组153例,血清C3≥0.97 g/L组261例。与血清C3≥0.97 g/L组相比,C3<0.97 g/L组患者年龄较小,女性比例较多,基线的血红蛋白和eGFR水平均较高,平均动脉压、总胆固醇、三酰甘油、血尿酸、血肌酐、24 h尿蛋白量、IgA和C4水平均较低(均P<0.05)。平滑曲线拟合发现血清C3与肾功能进展呈现“U”形曲线关系。阈值效应及多因素Cox回归分析结果显示,在校正了年龄、性别、平均动脉压、血尿酸、24 h尿蛋白量和肾脏病理指标(MESTC)等混杂因素后,当血清C3<0.97 g/L时,C3每增加0.1 g/L,肾功能进展风险下降40%(HR=0.60,95%CI 0.39~0.94,P=0.024);当血清C3≥0.97 g/L时,C3每增加0.1 g/L,肾功能进展风险增加27%(HR=1.27,95%CI 1.03~1.57,P=0.027);拐点为0.97(95%CI 0.92~1.01)g/L。结论IgA肾病患者血清C3与肾功能进展呈现曲线相关,血清C3水平维持在0.92~1.01 g/L与患者较好的肾脏预后相关。