近红外光谱结合共识模型快速检测果酒的总酚含量

果酒发酵中的多酚是引起果酒口感、颜色变化的重要因素。为保证果酒品质,有必要开发一种快速监测发酵过程中多酚含量变化的技术。收集不同批次成熟期的蓝莓、桑葚为原料,分别碾压成汁,同时按比例混合二者,于小型发酵罐进行发酵。通过离线收集不同发酵时段的发酵液于离心管,高速离心后取上清液置于棕色瓶保存,共计得到48个果酒发酵样本。将上清液置于三个平行样比色皿,以傅里叶快速变换近红外光谱仪(FT-NIR)采集其透射光谱,取平均值作为该样本的光谱信号。然后将棕色瓶内的发酵液以国标法(即以标准液的吸光度值制定标准曲线)测定各样品的总酚含量,以duplex法计算样本光谱之间的距离且按2∶1的比例划分为训练集和预测集。采用间隔偏最小二乘法(iPLS)将训练集样本的透射光谱与总酚含量之间构建定量模型,间隔数从2依次变化到60个。该研究创新之处是使用共识方法融合多个已构建好的iPLS成员模型,按一定的共识规则分配权系数。通过各成员模型交互验证的残差及其残差之间的相关性来优化各成员模型的线性组合,以拉格朗日乘数法求解各成员模型的权系数,使间隔偏最小二乘-共识模型(consensual iPLS,CiPLS)的交互验证均方根误差最小。相比于全局PLS模型、划分不同间隔数量时的iPLS模型,CiPLS均具有较小的预测误差。当划分39个间隔时由三个iPLS成员模型(即14th,16th,18th)组成的共识模型误差最小为124.2,交互验证相关系数为0.944,对预测集样本的预测均方根误差为163.4,预测相关系数为0.931,预测性能均优于PLS和iPLS模型。另外,作为对比选用连续投影算法与无信息变量剔除法来优化光谱模型,其预测性能均不及本文提出的共识模型。分析各iPLS模型预测残差之间的相关性,发现共识模型主要是融合那些具有较高预测性能且模型间较低相关性的成员模型。结果表明,光谱分析结合共识方法可提高回归模型的预测精度、减少建模所需变量数,能够用于果酒总酚含量的离线快速检测。     

Surface passivation in n-type silicon and its application in silicon drift detector

Based on the surface passivation of n-type silicon in a silicon drift detector(SDD), we propose a new passivation structure of SiO2/Al2O3/SiO2 passivation stacks. Since the SiO2 formed by the nitric-acid-oxidation-of-silicon(NAOS)method has good compactness and simple process, the first layer film is formed by the NAOS method. The Al2O3 film is also introduced into the passivation stacks owing to exceptional advantages such as good interface characteristic and simple process. In addition, for requirements of thickness and deposition temperature, the third layer of the SiO2 film is deposited by plasma enhanced chemical vapor deposition(PECVD). The deposition of the SiO2 film by PECVD is a low-temperature process and has a high deposition rate, which causes little damage to the device and makes the SiO2 film very suitable for serving as the third passivation layer. The passivation approach of stacks can saturate dangling bonds at the interface between stacks and the silicon substrate, and provide positive charge to optimize the field passivation of the n-type substrate.The passivation method ultimately achieves a good combination of chemical and field passivations. Experimental results show that with the passivation structure of SiO2/Al2O3/SiO2, the final minority carrier lifetime reaches 5223 μs at injection of 5×10¹⁵ cm^-3. When it is applied to the passivation of SDD, the leakage current is reduced to the order of nA.     

Determining the Zn Content of Cherry in Field Using VNIR Spectroscopy

Visible and near-infrared(VNIR)spectroscopy is an eco-friendly method used for estimating plant nutrient deficiencies.The aim of this study was to investigate the possibility of using VNIR method for estimating Zn content in cherry orchard leaves under field conditions.The study was conducted in 3different locations in Isparta region of Turkey.Fifteen cherry orchards containing normal and Zn deficient plants were chosen,and 60 leaf samples were collected from each location.The reflectance spectra of the leaves were measured with an ASD FieldSpec HandHeld spectroradiometer and a plant probe.The Zn contents of leaf samples were predicted through laboratory analysis.The spectral reflectance measurements were used to estimate the Zn levels using stepwise multiple linear regression analysis method.Prediction models were created using the highest coefficient of determination value.The results show that Zn content of cherry trees can be estimated using the VNIR spectroscopic method(87.5相似文献   

IPr3Si3Cl5+: A Highly Reactive Cation with Silanide Character

The reaction of a metastable SiCl₂ solution with the sterically less‐demanding carbene N,N‐diisopropylimidazo‐2‐ylidene (IPr) yields the salt [(IPr₃Si₃Cl₅)⁺]Cl^? ( 1 ‐Cl), containing a silyl cation with a Si₃ backbone. Salt 1 is highly reactive, but it can be used as a reagent in deuterated dichloromethane, whereby dehalogenation with Me₃SiOTf (OTf=O₃SCF₃) gives the dicationic silyl halide [(IPr₃Si₃Cl₄)]²⁺ 2 . Quantum chemical calculations show that the HOMO is localized at the negatively charged central silicon atom of 1 and 2 , and thus although both compounds are cations they are better described as silanides, which was also corroborated by NMR investigations.     

A Lysosome‐Compatible Near‐Infrared Fluorescent Probe for Targeted Monitoring of Nitric Oxide

The requirement for nitric oxide (NO) of lysosomes has motivated the development of a sophisticated fluorescent probe to monitor the distribution of this important biomolecule at the subcellular level in living cells. A near‐infrared (NIR) fluorescent Si‐rhodamine (SiRB)‐NO probe was designed based on the NO‐induced ring‐opening process of Si‐rhodamine. The probe exhibits fast chromogenic and fluorogenic responses, and high sensitivity and selectivity toward trace amounts of NO. Significantly, the spirolactam in Si‐rhodamine exhibits very good tolerance to H⁺, which in turn brings extremely low background fluorescence not only in the physiological environment but also under acidic conditions. The stability of the highly fluorescent product in acidic solution provides persistent fluorescence emission for long‐term imaging experiments. To achieve targeted imaging with improved spatial resolution and sensitivity, an efficient lysosome‐targeting moiety was conjugated to a SiRB‐NO probe, affording a tailored lysosome‐targeting NIR fluorescent Lyso‐SiRB‐NO probe. Inheriting the key advantages of its parent SiRB‐NO probe, Lyso‐SiRB‐NO is a functional probe that is suited for monitoring lysosomal NO with excellent lysosome compatibility. Imaging experiments demonstrated the monitoring of both exogenous and endogenous NO in real time by using the Lyso‐SiRB‐NO probe.     

A Hydrosilylation Approach to Silicon‐Bridged Functional Dipyrromethanes: Introducing Silicon to A New Arena

Two silylene‐spaced ((E)‐vinylsilyl)anthracene‐dipyrromethane dyads have been designed and synthesized by RhCl(PPh₃)₃‐catalyzed hydrosilylation reactions of 5‐methyl‐5′‐(ethynylaryl)dipyrromethanes with (9‐Anthryl)‐dimethylsilane. The complexation studies of dyads toward different anions have also been performed, which reveal that dyads exhibit a highly selective response towards fluoride anion attributable to both hydrogen‐bonding and pentacoordination phenomena. This dual‐mode fluoride recognition event is unprecedented and may pave the way for future developments in the areas of porphyrinoids, organosilicon, polymer, and supramolecular chemistry.