A simple static circuit model for low-high junctions

A simple circuit model for low-high junctions is developed by using basic charge-control concepts. The model is valid in the low-level injection regime. The junction current is expressed as a function of the quasi-Fermi level separation in the space-charge region, and contains linear and non-linear terms. It is shown that the linearity of the junction depends on which of the two terms dominates at a given applied voltage. Calculated static V-J characteristics are given for an n-n⁺ device with donor concentration, N_D, on n-side as a parameter and that on n⁺-side equal to 10¹⁹ cm^?3. For N_D ≦ 10¹³cm^?3, the device is non-linear, for N_D = 10¹⁴ and 10¹⁵ cm^?3, the device is linear in low-level injection regime, and for $\text{N}{}_{\mathrm{D}}\text{≧ 10}{}^{16}\text{cm}{}^{\mathrm{?3}}$, the device is linear over a practically realizable range of applied voltages. The proposed model is expected to be useful in integrated circuit modeling.     

图像导引介入治疗中可视化3D的2D/3D图像数据分析

三维成像对许多医学过程(根本上是对患者的健康)来说,是非常关键的。本文探讨了三维成像方法的与众不同之处,以及作为一种不断发展创新的技术,临床医生们对它的需求和期待。     

Highly selective SERS probe for Hg(II) detection using tryptophan-protected popcorn shaped gold nanoparticles

Contamination of the environment with toxic Hg(II) is becoming a huge concern throughout the world now. Driven by the need, this communication reports for the first time a tryptophan protected popcorn shaped gold nanomaterials based SERS probe for rapid, easy and highly selective recognition of Hg(II) ions in the 5 ppb level from aqueous solution, with high sensitivity and selectivity over competing analytes. We demonstrate that our SERS assay is capable of measuring the amount of Hg(II) in alkaline battery.     

Well-defined air-stable palladium HASPO complexes for efficient Kumada-Corriu cross-couplings of (hetero)aryl or alkenyl tosylates

Palladium complexes of representative heteroatom-substituted secondary phosphine oxide (HASPO) preligands were synthesized and fully characterized, including X-ray crystal structure analysis. Importantly, these well-defined complexes served as highly efficient catalysts for Kumada-Corriu cross-coupling reactions of aryl, alkenyl, and even heteroaryl tosylates. Particularly, an air-stable catalyst derived from inexpensive PinP(O)H displayed a remarkably high catalytic efficacy, which resulted in cross-couplings at low catalyst loadings under exceedingly mild reaction conditions with ample scope.     

Side-Chain Chemistry Governs Hierarchical Order of Charge-Complementary β-sheet Peptide Coassemblies

Self-assembly of proteinaceous biomolecules into functional materials with ordered structures that span length scales is common in nature yet remains a challenge with designer peptides under ambient conditions. This report demonstrates how charged side-chain chemistry affects the hierarchical co-assembly of a family of charge-complementary β-sheet-forming peptide pairs known as CATCH(X+/Y−) at physiologic pH and ionic strength in water. In a concentration-dependent manner, the CATCH(6K+) (Ac-KQKFKFKFKQK-Am) and CATCH(6D−) (Ac-DQDFDFDFDQD-Am) pair formed either β-sheet-rich microspheres or β-sheet-rich gels with a micron-scale plate-like morphology, which were not observed with other CATCH(X+/Y−) pairs. This hierarchical order was disrupted by replacing D with E, which increased fibril twisting. Replacing K with R, or mutating the N- and C-terminal amino acids in CATCH(6K+) and CATCH(6D−) to Qs, increased observed co-assembly kinetics, which also disrupted hierarchical order. Due to the ambient assembly conditions, active CATCH(6K+)-green fluorescent protein fusions could be incorporated into the β-sheet plates and microspheres formed by the CATCH(6K+/6D−) pair, demonstrating the potential to endow functionality.     

Room-Temperature Dialkylamination of Chloroheteroarenes Using a Cu(II)/PTABS Catalytic System

The dimethylamino functionality has significant importance in industrially relevant molecules and methodologies to install these efficiently are highly desirable. We report herein a highly efficient, room-temperature dimethylamination of chloroheteroarenes performed via the in-situ generation of dimethylamine using N,N-dimethylformamide (DMF) as precursor wiith a large substrate scope that includes various heteroarenes, purines as well as commercially relevant drugs such as altretamine, ampyzine and puromycin precursor.