Model selection based on Lorenz and concentration curves,Gini indices and convex order

In order to determine an appropriate amount of premium, statistical goodness-of-fit criteria must be supplemented with actuarial ones when assessing performance of a given candidate pure premium. In this paper, concentration curves and Lorenz curves are shown to provide actuaries with effective tools to evaluate whether a premium is appropriate or to compare two competing alternatives. The idea is to compare the premium income for sub-portfolios gathering low risks (identified as low by means of the premiums under consideration) to the true one, or equivalently, to the actual losses. Numerical illustrations performed on hypothetical data and real ones demonstrate the usefulness of the proposed approach.     

A note on uniqueness of the ground state for nonlinear Schrödinger equations

We are concerned with the following nonlinear Schrödinger equation $-{\epsilon }^2\Delta u+V\left(x\right)u={\left|u\right|}^{p-2}u,u\in H^1\left({\mathbb{R}}^N\right),$where $N\ge 3$, $2<p<\frac{2N}{N-2}$. For $\epsilon$ small enough and a class of $V\left(x\right)$, we show the uniqueness of the positive ground state under certain assumptions on asymptotic behavior of $V\left(x\right)$ and its first derivatives. Here our results are suitable for a kind of $V\left(x\right)$ which has different increasing rates at different directions.     

Aggregation-Induced Emission by Molecular Design: A Route to High-Performance Light-Emitting Electrochemical Cells

The emission efficiency of organic semiconductors (OSCs) often suffers from aggregation caused quenching (ACQ). An elegant solution is aggregation-induced emission (AIE), which constitutes the design of the OSC so that its morphology inhibits quenching π–π interactions and non-radiative motional deactivation. The light-emitting electrochemical cell (LEC) can be sustainably fabricated, but its function depends on motion of bulky ions in proximity of the OSC. It is therefore questionable whether the AIE morphology can be retained during LEC operation. Here, we synthesize two structurally similar OSCs, which are distinguished by that 1 features ACQ while 2 delivers AIE. Interestingly, we find that the AIE-LEC significantly outperforms the ACQ-LEC. We rationalize our finding by showing that the AIE morphology remains intact during LEC operation, and that it can feature appropriately sized free-volume voids for facile ion transport and suppressed non-radiative excitonic deactivation.     

Frenkel Defect-modulated Anti-thermal Quenching Luminescence in Lanthanide-doped Sc2(WO4)3

Although large amount of effort has been invested in combating thermal quenching that severely degrades the performance of luminescent materials particularly at high temperatures, not much affirmative progress has been realized. Herein, we demonstrate that the Frenkel defect formed via controlled annealing of Sc₂(WO₄)₃:Ln (Ln=Yb, Er, Eu, Tb, Sm), can work as energy reservoir and back-transfer the stored excitation energy to Ln³⁺ upon heating. Therefore, except routine anti-thermal quenching, thermally enhanced 415-fold downshifting and 405-fold upconversion luminescence are even obtained in Sc₂(WO₄)₃:Yb/Er, which has set a record of both the Yb³⁺-Er³⁺ energy transfer efficiency (>85 %) and the working temperature at 500 and 1073 K, respectively. Moreover, this design strategy is extendable to other hosts possessing Frenkel defect, and modulation of which directly determines whether enhanced or decreased luminescence can be obtained. This discovery has paved new avenues to reliable generation of high-temperature luminescence.     

Low Concentration Sulfolane-Based Electrolyte for High Voltage Lithium Metal Batteries

Electrolyte engineering is crucial for the commercialization of lithium metal batteries. Here, lithium metal is stabilized in the highly reactive sulfolane-based electrolyte under low concentration (0.25 M) for the first time. Inorganic-polymer hybrid solid electrolyte interphase (SEI) with high ionic conductivity, low bonding with lithium and high flexibility enables dense chunky lithium deposition and high plating/stripping efficiency. Low concentration electrolyte (LCE) also enables excellent cycling stability of LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523)/Li cells at 1 C (90.7 % retention after 500 cycles) and 0.3 C (83.3 % retention after 1000 cycles). With a low N/P ratio (≈2), the capacity retention for NCM523/Li cells can achieve 94.3 % after 100 cycles at 0.3 C. Exploring the LCE is of paramount significance because it provides more possibilities of the lithium salt selections, especially reviving some lithium salts that are excluded before due to their low solubility. More importantly, LCE has the significant advantage of commercialization due to its cost-effectiveness.     

Electrospray ionization stability and concentration sensitivity in capillary electrophoresis-mass spectrometry using a flow-through microvial interface

Concentration sensitivity is a key performance indicator for analytical techniques including for capillary electrophoresis-mass spectrometry (CE–MS) with electrospray ionization (ESI). In this study, a flow-through microvial interface was used to couple CE with MS and improve the ESI stability and detection sensitivity. By infusing a peptide mixture through the interface into an MS detector at a typical flow rate for CE-MS analysis, the spatial region near the interface was mapped for MS signal intensity. When the sprayer tip was within a 6 × 6.5 × 5 mm region in front of the MS inlet, the ESI was stable with no significant loss of signal intensity for ions with m/z 239. Finite element simulations showed that the average electric field strength at the emitter tip did not change significantly with minor changes in emitter tip location. Experiments were conducted with four different mass spectrometer platforms coupled to CE via the flow-through microvial interface. Key performance indicators, that is, limit of detection (LOD) and linearity of calibration curves were measured for nine amino acids and five peptides. Inter- and intraday reproducibility were also tested. The results were shown to be suitable for quantification when internal standards were used.     

Modulating ion current rectification generating high energy output in a single glass conical nanopore channel by concentration gradient

Inspired by biological systems that have the inherent skill to generate considerable bioelectricity from the salt content in fluids with highly selective ion channels and pumps on cell membranes,herein,a fully abiotic,single glass conical nanopores energy-harvesting is demonstrated.Ion current rectification(ICR)in negatively charged glass conical nanopores is shown to be controlled by the electrolyte concentration gradient depending on the direction of ion diffusion.The degree of ICR is enhanced with the increasing forward concentration difference.An unusual rectification inversion is observed when the concentration gradient is reversely applied.The maximum power output with the individual nanopore approaches10~4pW.This facile and cost-efficient energy-harvesting system has the potential to power tiny biomedical devices or construct future clean-energy recovery plants.     

Ca9Al(PO4)7∶Eu2+的发光、浓度猝灭及温度稳定性

采用高温固相法制备了Ca9Al(PO4)7∶Eu2+蓝色荧光粉,研究了Ca9Al(PO4)7∶Eu2+的发光、浓度猝灭及温度稳定性.Ca9Al(PO4)7∶Eu2+的激发光谱覆盖200～350 nm紫外区;发射光谱为一主峰位于445 nm的宽谱,对应Eu2+的4f6 5d1--→4f特征跃迁.研究发现,随Eu2+掺杂量的增大,Ca9Al(PO4)7∶Eu2+的发射强度呈现先增大、后减小的变化趋势,最大发射强度对应的Eu2+掺杂量为0.01,即存在浓度猝灭效应,对应的机理为电偶极-电偶极相互作用;依据晶格常数,得出临界距离为2.297 nm.在25～300℃范围内改变光谱测量温度,发现温度升高到150℃时,Ca9Al(PO4)7∶Eu2+的发射强度变为25℃时的81.0％,对应的激活能为0.268 eV,说明材料具有较好的温度稳定性.     

量子点CdSe／ZnS的浓度对其荧光的影响研究

影响量子点荧光特性除了量子点尺寸因素外,其溶液浓度也会对其荧光特性起很重要的作用。但到目前,还未见到有关量子点 CdSe／ZnS 在溶液中浓度对其荧光影响的详细报道。为了掌握影响量子点CdSe／ZnS荧光特性的因素及其物理机制,利用紫外-可见吸收光谱仪和荧光光谱仪测量了尺寸为4 nm的量子点CdSe／ZnS在氯仿中不同浓度下的吸收光谱和荧光光谱,并侧重研究了量子点CdSe／ZnS的浓度对其发光特性的影响并分析了其物理机制。结果表明量子点对光谱的吸收随其浓度的增加而增大,但其发光却具有一个最佳浓度2μmol·L－1。当量子点的浓度＞2μmol·L－1时,量子点的荧光强度随着量子点浓度的增加而降低,而当量子点的浓度＜2μmol·L－1时,量子点的发光强度则随其浓度的降低而降低。其原因主要有两个：（1）荧光猝灭效应;（2）荧光发射与光吸收的竞争效应。当量子点的浓度＞2μmol·L－1时,由于量子点之间相距太近（仅为94 nm）而引起了荧光猝灭效应,且其荧光猝灭效应随量子点间距的减小而增大,且因为吸收过大,导致受激的量子点并未增加,因此,其荧光随浓度的增加而降低。而当量子点的浓度＜2μmol·L－1时,因为量子点之间的距离足够大,不再引起荧光猝灭效应,其荧光强度取决于单位体积内的量子点的个数,单位体积内量子点的个数越多,其发光强度越强。因此其发光强度随量子点溶液的浓度降低而降低。     

用浓度调制光谱法测量水汽辉光放电中OH和H2O的布居数变化

本文使用波长为2.8 μm的分布式反馈激光器来测量水汽辉光放电产生的物种. 使用浓度调制光谱仅观察到OH自由基和瞬态H₂O分子的吸收光谱. 吸收峰的强度和方向随解调相位而变化，但是H₂O的一个吸收峰的方向始终与其它峰相反. OH和H₂O的不同光谱取向反映了能级中粒子数量的增加或减少. 如果在放电过程中可以检测到更多的瞬态物种，则可以更好地研究H₂O的激发、电离和分解动力学. 研究表明，浓度调制光谱的解调相位关系可以用来研究分子能级的布居数变化.