Testing linearity in cointegrating smooth transition regressions

Summary This paper develops statistical tests that can be used to test linearity in cointegrating smooth transition regression models. These tests extend previous similar tests by considering I(1) regressors instead of stationary or mixing regressors and they also allow for more general transition mechanisms than in previous studies. As is typical in cointegrating regressions, the regressors and errors of the model can be serially and contemporaneously correlated. In order to allow for this feature, an endogeneity correction based on a leads‐and‐lags approach is employed. The proposed tests are very simple to use because ordinary least squares techniques and standard chi‐square limiting distributions apply. Simulation experiments indicate that the tests have reasonable finite sample properties. Empirical applications to a U.K. money demand function illustrate the practical usefulness of the tests.     

Astigmatism of the mammalian cornea: Evolutionary and perceptive significance

Astigmatism enables spatial, linear and directional discrimination. These faculties are demonstrated by astigmatic photographic experiments.Comparative anatomic deductions lead to the assumption that the eyes of early mammals were astigmatic. Thereby these animals, lacking binocularity and accommodation, could achieve visual spatial information. This assumption is supported by the fact that features of astigmatic refraction, specially straight linearity, have been adopted by various intra-ocular structures, and by the neuronal structuralisation of receptive fields in the visual cortex of mammals.     

顶空气相色谱法测定原料药中正丁醇和乙酸乙酯含量的方法验证

验证是实施GMP的基础。在验证工作中，分析方法的验证是其他验证的基础，也是验证工作中的难点。笔者一直从事质量标准的制订和分析方法的优化。通过自己对工作经验的总结，希望为其他分析工作者提供借鉴。     

Linearity and dissociative antigen noise analyses of competitive microfluidic heterogeneous immunoadsorption

Presently, microfluidic heterogeneous immunoadsorption (MHI) has been regarded as an effective and efficient on-chip sample preparation method for various clinical diagnoses. In this work, adsorption performances of an electroosmosis flow (EOF)-based competitive MHI under saturated status are studied numerically. Along with the well-known flow and surface reaction control modes, the diffusion control mode specified in the fluidic configuration is scrutinized to characterize the MHI performance. The numerical results indicate that only in the surface reaction or the diffusion control mode can saturated EOF-based MHI obtain a linear dose-response along with a perfect assay signal without so-called dissociative antigen noise. Considering the tunable assay time and realizable flow velocity required by chip applications, the diffusion controlled MHI is recommended in this work.     

Temporal and spatial frequencies interact in the contrast transfer function of the pattern electroretinogram

The contrast transfer function (CTF) of the pattern electroretinogram (PERG) depends on temporal frequency. For transient stimulation it is fully linear; at faster stimulation rates it becomes strongly non-linear with an accelerated shape. In this study we investigated a range of stimulus parameters with the aim of studying the influence of temporal and spatial frequencies, as well as contrast levels, on the CTF; effects were quantified via an "index of linearity" IL. Both reversal rate and check size influenced linearity (p<.001), examples: At a constant check size of 0.8 degrees, 7.7 rps: IL=1.0; 0.8 degrees/24 rps: IL=0.5; at a constant reversal rate of 19 rps, IL was 0.5 for 0.8 degrees, but rose to 0.8 both for 0.2 degrees and 18 degrees. The reason for this complex response surface remains a puzzle, it cannot be explained by varying parvo/magnocellular contributions, and its possible influences on recordings in patients merit further studies.     

A comparison of two dual-energy X-ray absorptiometry systems for spinal bone mineral measurement

Summary Two dual-energy X-ray absorptiometry (DEXA) systems—the Hologic QDR-1000 and the Norland XR-26 bone densitometers—were evaluated in terms of precision, accuracy, linearity of response, X-ray exposure, and correlation of in vivo spinal measurements. In vitro precision and accuracy studies were performed using the Hologic anthropomorphic spine phantom; linearity of response was determined with increasing thicknesses of aluminum slabs and concentrations of Tums E-X in a constant-level water bath. Both systems were comparable in precision, achieving coefficients of variation (CVs) of less than 1% in bone mineral content (BMC, g), bone area (cm²), and bone mineral density (BMD, g/cm²). Both were accurate in their determination of BMC, bone area, and BMD with reference to the Hologic spine phantom. Both systems also showed good BMC and BMD linearity of response. Measured X-ray skin surface exposures for the Hologic and the Norland systems were 3.11 and 3.02 mR, respectively. In vivo spinal measurements (n=65) on the systems were highly correlated (BMC: r=0.993, SEE=1.770 g; area: r=0.984, SEE=1.713 cm²; BMD: r=0.990, SEE=0.028 g/cm²). In conclusion, both systems are comparable in terms of precision, accuracy, linearity of response, and exposure efficiency.     

血细胞分析仪CRP测定性能的评价

目的了解血细胞分析仪CRP测定的性能特点。方法对ABXMicrosCRP血细胞分析仪系统测定CRP的精密度、携带污染率、线性、稳定性和相关性等指标进行测试。结果ABXMicrosCRP仪器测定CRP的精密度批内变异系数（CV）〈5．1％、批间CV〈10％及日间CV〈4．3％，均在临床可接受范围内。携带污染率小于1．20％；室温或4℃冷藏条件下保存的抗凝血标本48h内，CRP结果稳定性较好，相对偏差小于6．0％。线性范围1．0—70．0mg／L，检测低限可达1．0mg／L。该仪器测试的CRP结果和BNII仪器测试的结果（0—219．0mg／L范围）高度相关，相关系数r2=0．9659（血清）、回归方程Y=0．9967X-0．3985；r^2=0．9594（全血）、Y=0．9088X-0．1382；仪器测定的血清CRP结果与全血CRP结果也高度相关，相关系数r^2=0．9527、Y=1．0017X-0．8982。通过测试溶血标本和高脂血症标本，发现对MicrosCRP测试方法无明显干扰。结论ABXMicrosCRP仪器测定的CRP结果准确、可靠，可在临床使用。     

低场磁共振机SE线性扫描弥散加权成像对超急性期脑梗死的诊断价值

目的探讨低场磁共振机SE线性扫描弥散加权成像（DWI）序列对超急性期脑梗死的诊断价值。方法对发病2~6小时内临床疑诊脑梗死患者18例进行常规MRI和线性扫描DWI序列成像检查,其中6例同时进行了CT检查,并进行对照分析。结果18例超急性期脑梗死中常规MRI 13例阴性,CT检查6例均为阴性,SE线性扫描DWI序列对超急性期脑梗死敏感度高（100%）,均表现为高信号。结论SE线性扫描DWI序列对超急性期脑梗死敏感,能显示常规MRI和CT不能显示的超急性期脑死塞。     

深圳迈瑞BS-300全自动生化分析仪临床使用评估

BS-300是深圳迈瑞公司自主研发的全自动生化分析仪，为评估其临床使用性能，我们选择了临床测试项目丙氨酸氨基转移酶（ALT），白蛋白（ALB），磷（P），GLU（葡萄糖，氧化酶法），尿素（Urea）在BS-300全自动生化分析仪上进行精密度、线性、交叉污染率等指标的评价试验。     

拜耳ADVIA2400全自动生化仪性能评价

目的对拜耳ADVIA2400全自动生化仪主要性能进行初步评价。方法以美国临床实验室标准化委员会（NCCLS）制定的评价标准，通过一系列试验设计，在拜耳ADVIA2400全自动生化仪上对实验室常用的生化检验项目以及电解质部分（Na^＋、K^＋、Cl^-1）进行检测，评价其精密度、准确度、线性、可比性、抗干扰性等。结果ADVIA2400生化仪精密度良好，批内精密度CV在0．18％～2．94％，日间CV为0．25％～3．78％；准确度高，与控制血清靶值相对偏差在5．0％以内（除总胆红素6．38％）；丙氨酸氨基转移酶（ALT）、尿酸（UA）、总蛋白（TP）、载脂蛋白A1（apoAl）线性良好，高胆红素和脂血对检测项目尿素、尿酸、肌酐、葡萄糖、丙氨酸氨基转移酶、天冬氨酸氨基转移酶、碱性磷酸酶、γ-谷氨酰转移酶、总蛋白、白蛋白、肌酸激酶、乳酸脱氢酶、α-羟丁酸脱氢酶、无机磷、总胆固醇、载脂蛋白A1、载脂蛋白B无干扰（P〉0．05），电解质部分在与AVL988对比实验中，K^＋、Na^＋、Cl^-相关系数分别为0．9940、0．9870、0．9819，相关性良好，高低值标本间携带污染率〈0．001％。结论ADVIA2400各方面性能良好，测定样本快速、准确；精密可靠、微量吸样、污染少，是大中型医院实验室较为理想的一种生化分析仪。