Postponement in New Product Introduction

Agility has now been a main research topic in the l it erature. There is much written on agility mainly focusing on manufacturing p rocess and strategic processes. However, we argue that new product introduction should call for agility as well due to uncertainty about technological advances and customers‘ demand. A technological superiority alone may not guarantee succe ss for new product introduction. We focus on the role of postponement for two ma in processes in new product introduction: new product ...     

Three-dimensional numerical modeling of geoacoustic scattering from seafloor topography

A three-dimensional (3-D), second-order finite-difference method was used to create synthetic seismograms for wave propagation in heterogeneous media in order to investigate the scattering of elastic and acoustic energy due to topography on the seafloor. The method uses a fully staggered grid in Cartesian coordinates as developed by Virieux [Geophysics 51, 889-901 (1986)]. Numerical results were generated for two models: a linear fault scarp on the seafloor, and a flat seafloor containing a rectangular channel. Wave-front snapshots allow the scattering and focusing of different wave modes with direction to be visualized. Compressional and shear wave backscattering from the sides of the features can be seen together with the trapped compressional wave energy propagating inside the channel. The results illustrate the effects of out of the plane scattering due to simple seafloor topographic features.     

Instrumental neutron activation analysis of high-purity gallium,arsenic, and gallium arsenide

Instrumental neutron activation analysis (INAA) has been applied to obtain useful data on impurity concentrations in ultra-pure materials whose matrix elements are strongly activated and create severe interference for several weeks after irradiation. An analytical procedure has been developed and used to determine Sc, Fe, Co, Zn, Se, Zr, Ag, In, Sn, Sb, Te, and Hg in high-purity gallium, arsenic, and gallium arsenide. Detection limits ranged from 50 ng/g for iron to 0.001 ng/g for scandium. Problems of contamination control, blank level, and standardization are discussed.     

Enantioselective Synthesis of Spiroindenes by Enol‐Directed Rhodium(III)‐Catalyzed C?H Functionalization and Spiroannulation

Chiral cyclopentadienyl rhodium complexes promote highly enantioselective enol‐directed C(sp²)‐H functionalization and oxidative annulation with alkynes to give spiroindenes containing all‐carbon quaternary stereocenters. High selectivity between two possible directing groups, as well as control of the direction of rotation in the isomerization of an O‐bound rhodium enolate into the C‐bound isomer, appear to be critical for high enantiomeric excesses.     

Selective Permeability of Uranyl Peroxide Nanocages to Different Alkali Ions: Influences from Surface Pores and Hydration Shells

The precise guidance to different ions across the biological channels is essential for many biological processes. An artificial nanopore system will facilitate the study of the ion‐transport mechanism through nanosized channels and offer new views for designing nanodevices. Herein we reveal that a 2.5 nm‐sized, fullerene‐shaped molecular cluster Li_48+mK₁₂(OH)_m[UO₂(O₂)(OH)]_60?(H₂O)_n (m≈20 and n≈310) ( U₆₀ ) shows selective permeability to different alkali ions. The subnanometer pores on the water–ligand‐rich surface of U₆₀ are able to block Rb⁺ and Cs⁺ ions from passing through, while allowing Na⁺ and K⁺ ions, which possess larger hydrated sizes, to enter the interior space of U₆₀ . An interestingly high entropy gain during the binding process between U₆₀ and alkali ions suggests that the hydration shells of Na⁺/K⁺ and U₆₀ are damaged during the interaction. The ion selectivity of U₆₀ is greatly influenced by both the morphologies of the surface nanopores and the dynamics of the hydration shells.     

抗坏血酸和尿酸在甘氨酸-壳聚糖修饰玻碳电极上的电化学行为及测定

制备了甘氨酸-壳聚糖复合膜修饰玻碳电极(Gly-CTS/GCE),研究了抗坏血酸(AA)和尿酸(UA)在该修饰电极上的电化学行为。结果表明在pH=5.59的磷酸盐缓冲溶液中,AA、UA在Gly-CTS/GCE上均产生灵敏的不可逆氧化峰,其峰电流与浓度在一定范围内呈良好的线性关系。对AA和UA混合溶液平行测定7次,相对标准偏差分别为4.6%、2.9%,表明该电极重现性和稳定性良好。AA、UA在Gly-CTS/GCE电极上的氧化峰峰电位相差340mV,据此可实现对二者的同时检测,并可应用于实际样品测定。     

Ultrasonic frequency analysis of antibody-linked hydrogel biosensors for rapid point of care testing

Analyte quantification in highly scattering media such as tissue, blood, and other biological fluids is challenging using conventional spectroscopic methods. Ultrasound easily penetrates these opaque samples, yet currently provides little chemical information. We have developed a general approach for creating hydrogel biosensors based on antibody-linked cellulose polymers. Target recognition induces changes to the sensor stiffness and size, which is accompanied by characteristic changes to a measured ultrasonic frequency profile. Using this technique, nM sensitivity for acetaminophen is demonstrated in a series of biofluids including whole blood, blood plasma, saliva, and urine. Likewise, this methodology is attractive for point of care diagnostics due to the short measurement time, simple methodology which excludes pretreatment of samples, and has minimal chemical or buffer requirements.