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Abstract We have developed an expression system ( Salmonella ‐based pPro system) containing the Salmonella enterica prpBCDE promoter (P prpB ) and prpR encoding the positive transcriptional regulator of this promoter. In this study, the transcriptional efficiency of the pPro expression system was measured by placing the gene encoding the green fluorescent protein ( gfp ) under the control of P prpB and growing cells containing this construct in minimal medium supplemented with glucose or glycerol as a sole carbon source. In wild‐type Escherichia coli ( E. coli ) BL21, the system exhibited high induced expression as well as high background expression; however, in E. coli JSB, a sbm ‐ ygfDGHI deletion mutant of E. coli BL21(DE3), the system showed low background expression and high induced expression. The system exhibited homogeneous expression at the single‐cell level, highly regulatable expression over a wide range of propionate concentrations, and fully induced expression at a low propionate concentration relative to that needed to induce the system in rich, undefined medium. The expression system is comparable to the widely used T7 promoter‐driven expression systems in glucose or glycerol minimal medium.
The main difficulty in implementing cellular automata on the Cellular Neural Network Universal Machine (CNNUM) is the need to perform arbitrary logic functions of the input neighborhood. Since the architecture computes weighted sums of this neighborhood, by using a "B-template," it is limited to threshold logic, i.e., a logical operation to be computed by a single transient must be in the class of linearly separable Boolean functions. It was shown previously how a general logic function can be implemented on the CNNUM by cascading component functions from this class-namely by the direct implementation of the minterm or maxterm formulation of the desired function. However, for functions of a 3/spl times/3 input neighborhood this method may require up to 256 stages. We propose a more efficient method for implementing general logic functions on the CNNUM and other hardwares capable of performing a threshold logic function of an input neighborhood. The class of considered component functions is a superset of the minterms and maxterms but, for purposes of searchability, ease of implementation, and robustness, a subset of the general linearly separable Boolean functions. We have formulated an algorithm that will find a sequence of weight-restricted threshold logic functions (B-templates with weights from {-1, 0, +1} and a bias) that, when cascaded together using two-input logical operations, will result in the desired Boolean function. Two examples are given to exhibit the algorithm.
Alles dreht sich um Kupfer: Die kupferkatalysierte α-Arylierung von Carbonylverbindungen verläuft über eine oxidative Addition von Iodarenen an die C-gebundene CuI-Enolatspezies 1 unter Bildung einer Aryl/CuIII-Zwischenstufe. Computerstudien bieten Einblick in den Ursprung der relativen Reaktivitäten verschiedener CuI-Enolatkomplexe in den Reaktionen mit Iodarenen.
The strength and toughness of ceramic-metal joints is often controlled by the propagation path selected by stress-induced cracks. Against a background of recent linear elastic mechanics studies, experimental results from fracture tests on ceramic/metal/ceramic sandwich geometries are described which determine both the selection of crack path and the corresponding crack extension rates. It is found that crack path selection is controlled by the path of low microstructural resistance and the driving force directionality, which itself is a function of the far-field loading and the elastic compliance mismatch across the ceramic-metal interface. However, there are instances where the compliance mismatch takes the crack off the weak microstructural path, or where cracking occurs at, or near, both interfaces (crack jumping). Such cracking configurations can be tortuous and high toughness joints result. This paper discusses the potential for predicting and engineering, interfaces with enhanced toughness.
