Tree spanners on chordal graphs: complexity and algorithms

A tree t-spanner T in a graph G is a spanning tree of G such that the distance in T between every pair of vertices is at most t times their distance in G. The T t-S problem asks whether a graph admits a tree t-spanner, given t. We substantially strengthen the hardness result of Cai and Corneil (SIAM J. Discrete Math. 8 (1995) 359–387) by showing that, for any t4, T t-S is NP-complete even on chordal graphs of diameter at most t+1 (if t is even), respectively, at most t+2 (if t is odd). Then we point out that every chordal graph of diameter at most t−1 (respectively, t−2) admits a tree t-spanner whenever t2 is even (respectively, t3 is odd), and such a tree spanner can be constructed in linear time.

The complexity status of T 3-S still remains open for chordal graphs, even on the subclass of undirected path graphs that are strongly chordal as well. For other important subclasses of chordal graphs, such as very strongly chordal graphs (containing all interval graphs), 1-split graphs (containing all split graphs) and chordal graphs of diameter at most 2, we are able to decide T 3-S efficiently.     

Layered Aggregation with Steric Effect: Morphology‐Homogeneous Semiconductor MoS2 as an Alternative 2D Probe for Visual Immunoassay

Liquid‐phase exfoliation routes unavoidably generate 2D nanostructures with inhomogeneous morphologies. Herein, thickness‐dependent sorting of exfoliated nanostructures is achieved via a treatment of differential‐zone centrifugation in the surfactant aqueous phase. With this approach, homogeneous MoS₂ nanosheets are obtained, and due to the intrinsic semiconducting characteristics, those 2D nanosheets are endowed with desired optical properties, rivaling classic gold nanoparticles in sensing applications. Furthermore, MoS₂ nanosheets with high uniformity and chemical inertness are coupled with proteins, exhibiting high performance in stability and anti‐interferences for bioanalysis. As a consequence of aggregation‐induced steric effect, distinguishing running shifts of antibody‐anchored conjugates in gel electrophoresis are visually responsive to those specific antigens. This assay enables the easy and fast monitoring of tumor biomarkers just according to “naked‐eye” identification of band location in electrophoresis results, which are presented by an alternative visual probe of 2D MoS₂‐protein conjugates. The developed visual immunoassay with the synergistic effect of gel electrophoresis techniques and 2D semiconductors pushes significant progress in “home‐made” tests for disease early diagnosis.     

Attitudes toward stress and coping among primary caregivers of patients undergoing hemodialysis: A Q‐methodology study

Introduction Hemodialysis (HD) causes many life changes, not only for patients undergoing it but also for their families by allowing them to rely on this lifesaving equipment unless they receive a kidney transplant. The stress of the primary caregivers, who spends the most time in the family taking care of the patient undergoing HD, is quite high. This study was to identify attitudes about stress and coping among primary caregivers of HD patients. Methods Q‐methodology was undertaken because it integrates quantitative and qualitative research methods. A convenience sample of 33 primary caregivers of HD patients participated. Forty selected Q‐samples were obtained from each participant and were classified into a forced normal distribution using a nine‐point grid. Data was analyzed using a pc‐QUANL program. Findings Three discrete factors emerged as follows: Factor I (they reduced their stress by participating in religious activities; religious sublimation), Factor II (they always worried about the caregiving situations and about the patients' conditions; nervousness), and Factor III (they thought it better to accept their stressful situations; leading handler). Three factors accounted for 44.5% of all the variance, including Factor I (26.0%), Factor II (10.1%), and Factor III (8.4%). The eigenvalues were 8.58, 3.34, and 2.79, respectively. Discussion The subjectivities of the three factors that were identified can be applied during the planning stages of effective interventions for stress and coping. Healthcare workers in clinical practices should consider assesses primary caregivers' attitudes about stress and coping and approaches their situation to cope with it and to adapt to lifestyle changes.     

A modification of UniGrow 2‐parameter driving force model for short fatigue crack growth

In this paper, a modification of the UniGrow model is proposed to predict total fatigue life with the presence of a short fatigue crack by incorporating short crack propagation into the UniGrow crack growth model. The UniGrow model is modified by 2 different methods, namely the “short crack stress intensity correction method” and the “short crack data‐fitting method” to estimate the total fatigue life including both short and long fatigue crack propagations. Predicted fatigue lives obtained from these 2 methods were compared with experimental data sets of 2024‐T3, 7075‐T56 aluminium alloys, and Ti‐6Al‐4V titanium alloy. Two proposed methods have shown good fatigue life predictions at relatively high maximum stresses; however, they provide conservative fatigue life predictions at lower stresses corresponding high cycle fatigue lives where short crack behaviour dominates total fatigue life at lower stress levels.     

Adaptive nonlinear control using input normalized neural networks

An adaptive feedback linearization technique combined with the neural network is addressed to control uncertain nonlinear systems. The neural network-based adaptive control theory has been widely studied. However, the stability analysis of the closed-loop system with the neural network is rather complicated and difficult to understand, and sometimes unnecessary assumptions are involved. As a result, unnecessary assumptions for stability analysis are avoided by using the neural network with input normalization technique. The ultimate boundedness of the tracking error is simply proved by the Lyapunov stability theory. A new simple update law as an adaptive nonlinear control is derived by the simplification of the input normalized neural network assuming the variation of the uncertain term is sufficiently small.     

基于DEM的入库洪水预报模型研究及系统开发

基于数字高程模型,考虑流域空间的变异性,建立数字高程流域水系模型,在此基础上对流域空间进行离散化,划分出产汇流计算子单元并计算各子单元面积权重。将构建好的数字高程流域水系模型与集总式流域水文模型-新安江模型相耦合,建立了基于数字高程模型的数字水文模型。采用客户服务器方式将该理论模型实现为水文预报计算机软件系统,并将该系统应用于全球能量与水循环亚洲季风试验强化观测区-淮河史灌河流域,对流域内梅山水库与鲇鱼山水库进行入库洪水预报实例研究。结果表明:构建的数字水文模型可以很好地模拟水库入库洪水过程,满足实时洪水预报精度的要求。这对充分利用现有空间技术和空间数据进行降雨-径流模拟并改进水文预报方法提供了研究途径。     

Diagnosis and therapy of macrophage cells using dextran-coated near-infrared responsive hollow-type gold nanoparticles

We describe the development of hollow-type gold nanoparticles (NPs) for the photonic-based imaging and therapy of macrophage cells. The strong light-absorption and light-scattering properties of gold NPs render them to be useful as molecular imaging agents as well as therapeutic moieties. By controlling the geometry of the gold NPs, the optical resonance peak was shifted to around the near-infrared (NIR) region, where light transmission through biological tissue is known to be fairly high. Hollow-type gold NPs modified with dextran were phagocytosed by macrophage cells. Using dark-field microscopy, it was possible to image macrophage cells targeted with NPs. After NIR irradiation, macrophages labeled with NPs were selectively destroyed by the photothermal effect. FACS analysis revealed that the photothermal effect caused principally late apoptosis-related cell death or secondary necrosis. The experimental results showed that hollow-type gold NPs conjugated with dextran could be used not only as optical imaging contrast agents but also as a component of a novel anti-macrophage therapeutic strategy.     

Preparation of a polymer surface coated with a gradient of quantum dots

In the present study, we generated a polyethylene surface coated with a gradient of quantum dots for use in imaging experiments. The polyethylene surface was first treated with increasing coronal discharge along its length. Next, the surface was reacted with branched polyethyleneimine followed by biotin to produce a polyethylene surface with a gradient of biotin. Finally, the biotin-coated surface was reacted with streptavidin-coated quantum dots. Fluorescent imaging showed that the fluorescence intensity from the quantum dots gradually increased along its length. Such quantum-dot-modified gradient polyethylene surfaces may be useful in biomedical analyses.     

Effects of working pressure on the electrical and optical properties of aluminum-doped zinc oxide thin films

Zinc oxide films have been actively investigated as transparent electrode materials for optical displays. We report the effect of the working pressure on the electrical and optical properties of Al-doped ZnO thin films deposited by D.C. magnetron sputtering. The films were deposited in working pressures ranging from 1 mTorr to 10 mTorr. The effect of the working pressure was determined and the mechanism of the electrical and optical properties was explained. To understand the relationship between the electrical and optical properties of the films and film structure, the film density, resistivity, carrier concentration, carrier mobility, mean free path and optical band-gap in the films were measured as a function of the working pressure.     

软土的振动排水固结特性试验研究

以江苏镇江某现场软土为研究对象,室内利用自主设计的动态固结渗透仪模拟饱和软土在振动荷载作用下的响应。在不同排水条件、围压、静荷载、振动荷载和频率下进行排水固结试验,并同单一的静压排水固结试验进行对比,重点分析试验过程中的动应变和固结排水效应,探讨软土的动力固结排水机理。试验结果表明,振动作用可以明显地提高排水速度,增加排水量;固结压力、振动荷载和频率对软土的振动排水效应产生显著的影响。试验结果和振动排水的机理分析,对当前软土地基处理及其施工工艺设计具有重要的实用价值和指导意义。