Development of needle retention in Scots pine (Pinus sylvestris) in 1957–1991 in northern and southern Finland

The needle trace method was used to study retrospectively the long-term latitudinal variation in needle retention in Scots pine (Pinus sylvestris L.) in Finland. The mean annual summer needle retention (ANR) along the main stem varied from 3.4 to 6.0 needle sets during the period 1957–1991. The lowest values were observed in southern and the highest in northern Finland. The length of the growing season, expressed as the thermal sum (threshold value +5 °C), was negatively correlated with the mean ANR (r=-0.96). The geographical needle retention pattern (NRP) for the period 1957–1991 showed a clearly increasing trend from 1957 to 1969 (southern Finland) and to 1975 (northern Finland); thereafter, the NRP tended to decrease close to its minimum value recorded in 1991. The general level of the NRP was approximately 5.0 needle sets in northern Finland and 3.5–4.0 needle sets in southern Finland. The NRP, with its 6–12 year cycle for southern Finland, was clearly periodical. Differences in the NRP among the ten stands in southern Finland were small, whereas the said periodicity was missing and the differences were high among the stands in northern Finland. The results indicate that variation in the number of needle sets, viz. defoliation of pines, is a normal phenomenon. The role of net carbon assimilation as a regulator of the number of needle sets is discussed.     

Formation of glycine conjugate and (-)-(R)-enantiomer from (+)-(S)-2-phenylpropionic acid suggesting the formation of the CoA thioester intermediate of (+)-(S)-enantiomer in dogs.

It has been proposed that the chiral inversion of the 2-arylpropionic acids is due to the stereospecific formation of the (-)-R-profenyl-CoA thioesters which are putative intermediates in the inversion. Accordingly, amino acid conjugation, for which the CoA thioesters are obligate intermediates, should be restricted to those optical forms which give rise to the (-)-R-profenyl-CoA, i.e., the racemates and the (-)-(R)-isomers. We have examined this problem in dogs with respect to 2-phenylpropionic acid(2-PPA). Regardless of the optical configuration of 2-phenylpropionic acid administered, the glycine conjugate was the major urinary metabolite and this was shown to be exclusively the (+)-(S)-enantiomer by chiral HPLC. Both (-)-(R)- and (+)-(S)-2-phenylpropionic acid were present in plasma after the administration of either antipode, and further evidence of the chiral inversion of both enantiomers was provided by the presence of some 25% of the opposite enantiomer in the free 2-phenylpropionic acid and its glucuronide excreted in urine after administration of (-)-(R)- and (+)-(S)-2-phenylpropionic acid. The (+)-(S)-enantiomer underwent chiral inversion to the (-)-(R)-antipode when incubated with dog hepatocytes. These data suggests that both enantiomers of 2-phenylpropionic acid are substrates for canine hepatic acyl CoA ligase(s) and thus undergo chiral inversion, but that the CoA thioester of only (+)-(S)-2-phenylpropionic acid is a substrate for the glycine N-acyl transferase. These studies are presently being extended to the structure and species specificity of the reverse inversion and amino acid conjugation of profen NSAIDs.     

水相中氢气浓度检测方法的建立

近年来,研究表明氢分子具有广泛的生物学效应,饮用富氢水（hydrogen-rich water,HRW）是其主要的摄取方法,但目前对于水相中氢气浓度检测方法的研究甚少。为了建立适用于测定水相中氢气浓度的检测方法,利用纯水氢气发生器制备饱和富氢水。然后,利用氢气微电极直接测定水相中的氢气浓度,结果表明,在不同氢气浓度范围内（0～1.620 0 mg·L-1和0～0.202 5 mg·L-1）,氢气浓度与微电极信号值均呈现良好的线性关系,方法检出限（method detection limit,MDL）为4.3×10-3 mg·L-1。同时,采用顶空方式将水相中的氢气转移到气相中,通过气相色谱法测定氢气的浓度,结果表明,在不同氢气浓度范围内（0～1.620 0 mg·L-1和0～0.202 5 mg·L-1）,氢气浓度与气相色谱峰面积均具有良好的线性关系,MDL为8.7×10-4 mg·L-1。研究结果表明,氢微电极法和气相色谱法均可用于水相中氢气浓度的精确定量,即成功建立了采用氢气微电极及顶空气相色谱测定水相中氢气含量的检测方法。     

蒙特卡罗模拟多束光辐照下生物组织中的光吸收分布

用蒙特卡罗方法模拟了均匀分布光和高斯分布光在生物组织内的传播。通过比较单束以及多束均匀分布光和高斯分布光照射下组织内的光子能量分布规律,分析了不同光源和光斑大小对光吸收分布的影响。结果表明:与均匀光束比较,高斯光束辐照时,激光能量较为集中,但侧向传播范围较窄。在总功率相同的情况下,使用单束大功率宽光源与多束功率较小的小光斑光源均能明显地增大光的侧向传播距离,但使用多束功率较小的小光斑光辐照时生物组织中的最大光吸收率增大。多束组合光源光束间距对光吸收分布影响很大。     

不同全血过滤方法用于去白细胞血液制备的临床对照研究

目的:观察不同全血过滤方法用于去白细胞血液制备的效果。方法:采用两种全血过滤方法进行对比研究,对照组采用常规法,将采集后全血混匀后直接与白细胞滤器连接直接过滤;实验组采用湿润滤盘法,血液采集完成混匀后静置,先用上层血清10～20 m L湿润滤盘,再混匀与白细胞滤器连接后进行过滤。比较两组制备方法所用的过滤时间、血液回收率、过滤前后血液指标情况及24小时内溶血的发生情况。结果:两组全血过滤方法过滤前后白细胞、红细胞、血红蛋白、血小板及血浆游离血红蛋白水平比较差异均无明显统计学意义(P0.05)。而实验组过滤时间短于对照组,血液回收率高于对照组,且24小时内溶血比例明显低于对照组(P0.05)。结论:常规法与湿润滤盘法均能达到去白细胞血液标准,但湿润滤盘法较常规法能有效的降低过滤时间、增加血液回收率,减少去白细胞悬浮红细胞因溶血造成的血液不合格率,值得临床推广应用。     

一种改良的植物基因组DNA通用提取方法

高质量的基因组DNA是分子生物学研究的基础,而从富含糖类和次生代谢物且异质性强的植物材料中分离DNA相对困难。本方法在CTAB法和商业DNA提取试剂盒的基础上,在裂解细胞之前,对植物材料进行预处理．去除干扰DNA提取的代谢物,并在后续步骤中进行了一些优化。该方法适于多种不同的植物种类,所提取的基因组DNA质量较好,能满足下一步基因操作的要求,是一种通用的植物基因组DNA提取方法。     

飞行质谱鉴定临床分离真菌准确度的Meta分析

目的基于循证医学系统性评价飞行质谱鉴定临床分离真菌的准确度,并与常规方法准确度进行比较。方法检索主要英文数据库PubMed、Cochrane、Web of Science,以及中文数据库CBM、万方、维普、知网数据库,检索飞行质谱鉴定临床分离真菌的原始文献。结果经筛选后纳入19篇文献(6609株真菌),Meta分析结果显示飞行质谱鉴定真菌至种水平正确率为0.9368(95%CI=0.9091～0.9598),常规方法鉴定真菌至种水平正确率为0.9104(95%CI=0.8874～0.9340);对结果进行了亚组分析,主要包括:菌株类型、研究类型、样本处理方法、金标准检测范围、鉴定阈值等;敏感性分析表明结果稳定可靠,Begg和Egger’s结果表明飞行质谱鉴定真菌不存在发表偏倚,常规方法鉴定真菌存在一定发表偏倚。结论基质辅助激光解吸电离-飞行时间质谱系统(MALDI-TOF MS)方法对鉴定临床致病性真菌准确率较高,是临床常规方法的可靠替代方法。     

Nanosecond dynamics of a mimicked membrane-water interface observed by time-resolved stokes shift of LAURDAN

We studied the dipolar relaxation of the surfactant-water interface in reverse micelles of AOT-water in isooctane in the nanosecond and subnanosecond time ranges by incorporating the amphipathic solvatochromic fluorescent probes LAURDAN and TOE. A negative component was observed in the fluorescence decays in the red edge of the emission spectrum-the signature of an excited state reaction-with LAURDAN but not for TOE. The deconvolution of the transient reconstructed spectra of LAURDAN based on a model constructed by adding together three log-normal Gaussian equations made it possible to separate the specific dynamic solvent response from the intramolecular excited state reactions of the probe. The deconvoluted spectrum of lowest energy displayed the largest Stokes shift. This spectral shift was described by unimodal kinetics on the nanosecond timescale, whereas the relaxation kinetics of water-soluble probes have been reported to be biphasic (on the subnanosecond and nanosecond timescales) due to the heterogeneous distribution of these probes in the water pool. Most of this spectral shift probably resulted from water relaxation as it was highly sensitive to the water to surfactant molar ratio (w(0)) (60-65 nm at w(0) = 20-30). A small part of this spectral shift (9 nm at w(0) = 0) probably resulted from dipolar interaction with the AOT polar headgroup. The measured relaxation time values were in the range of the rotational motion of the AOT polar headgroup region as assessed by LAURDAN and TOE fluorescence anisotropy decays.     

落叶阔叶林反照率的时间变化与影响因素

反照率原位测量对生态系统能量收支及其遥感应用至关重要,但目前坡面地形反照率的测量方式有局限且可见光与近红外波段反照率时间变化的差异尚不清楚。本研究以东北地区帽儿山森林生态站的落叶阔叶林为例,探究入射和反射太阳辐射(SR,300～2800 nm)、光合有效辐射(PAR,400～700 nm)、近红外辐射(NIR,700～2800 nm)的反照率时间变化特征及其影响因子,同时分析了两种辐射表安装方式反照率的差异。结果表明: 晴天SR和NIR反照率日变化呈上下午不对称的U型曲线,但PAR从早到晚递增;阴天反照率均先急剧下降后趋于稳定。平行于坡面测量增大了反照率的日均值,但缓和了SR、NIR反照率日不对称的现象。从整个生长季来看,SR、NIR与PAR反照率水平测量时最大值分别为0.16、0.27和0.11,最小值分别为0.07、0.11和0.03。SR和NIR反照率季节变化均为先增大后减小(7月为峰值),PAR则相反,SR反照率主要受NIR而不是PAR控制。各波段反照率季节变化的影响因子按照贡献率排序为宽带归一化植被指数(61.7%～78.5%,可表征叶面积指数)>太阳高度角(15.4%～36.9%)>晴空指数(0.4%～36.9%)。     

Finite elements/Taguchi method based procedure for the identification of the geometrical parameters significantly affecting the biomechanical behavior of a lumbar disc

The aim of this work is to show a quick and simple procedure able to identify the geometrical parameters of the intervertebral disc that strongly affect the behavior of the FEM model. First, we allocated a selection criterion for the minimum number of geometrical parameters that describe, with a good degree of approximation, a healthy human vertebra. Next, we carried out a sensitivity analysis using the ‘Taguchi orthogonal array’ to arrive at a quick identification of the parameters that strongly affect the behavior of the Fem model.