Showing papers in "Scopus in 1992"

Carnivorous plants: Phylogeny and structural evolution

Abstract: The carnivorous habit in flowering plants represents a grade of structural organization. Different morphological features associated with the attraction, trapping, and digestion of prey characterize a diversity of specialized forms, including the familiar pitcher and flypaper traps. Phylogenetic analysis of nucleotide sequence data from the plastic rbcL gene indicates that both carnivory and stereotyped trap forms have arisen independently in different lineages of angiosperms. Furthermore, these results demonstrate that flypaper traps share close common ancestry with all other trap forms. Recognition of these patterns of diversification may provide ideal, naturally occurring systems for studies of developmental processes underlying macromorphological evolution in angiosperms.

Hydride Effect On The Kinetics Of The Hydrogen Evolution Reaction On Nickel Cathodes In Alkaline Media

Abstract: The time-dependent hydrogen evolution reaction (HER) on Ni electrodes shows a large increase in electrode over-potential with time. This is ascribed to hydride formation at active Ni cathode surfaces. Hydride formation was detected by x-ray diffraction, morphological changes at the electrode surfaces, and resulting changes in secondary electron emissivities. Nickel electrodes annealed for 2 h in an argon atmosphere at 1000 o C after HER did not show x-ray lines assigned to hydride

History-less checking of dynamic integrity constraints

Abstract: An efficient implementation method is described for dynamic integrity constraints formulated in past temporal logic. Although the constraints can refer to past states of the database, their checking does not require that the entire database history be stored. Instead, every database state is extended with auxiliary relations that contain the historical information necessary for checking constraints. Auxiliary relations can be implemented as materialized relational views. The author analyzes the computational cost of the method and outlines how it can be implemented by using existing database technology. Related work on dynamic integrity constraints is surveyed. >

Transesterification of a phosphate diester by divalent and trivalent metal ions

Abstract: The transesterification of the 2-(4-nitrophenyl phosphate) ester of propylene glycol (1) was promoted by La 3+ , Nd 3+ , Eu 3+ , Gd 3+ , Tb 3+ , Yb 3+ , Lu 3+ , Pb 2+ , Zn 2+ , Cu 2+ , Ni 2+ , Co 2+ , Mn 2+ , Mg 2+ , and Ca 2+ at 37 o C in 0.01 M Hepes ethyl)piperazine-N'-ethanesulfonic acid), pH 6.85

The mtrAB operon of Bacillus subtilis encodes GTP cyclohydrolase I (MtrA), an enzyme involved in folic acid biosynthesis, and MtrB, a regulator of tryptophan biosynthesis

Abstract: mtrA of Bacillus subtilis was shown to be the structural gene for GTP cyclohydrolase I, an enzyme essential for folic acid biosynthesis. mtrA is the first gene in a bicistronic operon that includes mtrB, a gene involved in transcriptional attenuation control of the trp genes. mtrA of B. subtilis encodes a 20-kDa polypeptide that is 50% identical to rat GTP cyclohydrolase I. Increased GTP cyclohydrolase I activity was readily detected in crude extracts of B. subtilis and Escherichia coli in which MtrA was overproduced. Biochemical evidence indicating that MtrA catalyzes dihydroneopterin triphosphate and formic acid formation from guanosine triphosphate is presented. It was also shown that mtrB of B. subtilis encodes a 6-kDa polypeptide. Expression of mtrB is sufficient for transcriptional attenuation control of the B. subtilis trp gene cluster in Escherichia coli. Known interrelationships between genes involved in folic acid and aromatic amino acid biosynthesis in B. subtilis are described.

Characterization of protonated trans-bis(dioxime)ruthenium complexes: Crystal structures of trans-Ru(DPGH)2(NO)Cl, trans -[Ru(DMGH)(DMGH2)(NO)Cl]Cl, and trans-Ru(DMGH)2(NO)Cl

Abstract: Single-crystal X-Ray diffraction studies were carried out on trans-Ru(DPGH) 2 (NO)Cl (1), trans-[Ru(DMGH)(DMGH 2 ) (NO)Cl]Cl (2), and trans-Ru(DMGH) 2 (NO)Cl (3) (DMGH=dimethylglyoxime monoanion, DPGH=diphenylglyoxime monoanion). These represent the first crystal structures of trans-bis(dioxime) complexes containing ruthenium

Effect of weak foundation on the seismic response of core wall type buildings

Abstract: This paper investigates the seismic behaviour of a typical wall-type reinforced concrete building with a footing that is unable to develop the flexural wall capacity. Nonlinear dynamic analysis is ...

Non-contacted bases affect the affinity of synthetic P22 operators for P22 repressor

Abstract: The affinity of synthetic P22 operators for P22 repressor varies with the base sequence at the operator's center. At 100 mM KCl, the affinity of these operators for P22 repressor varies over a 10-fold range. Dimethylsulfate protection experiments indicate that the central bases of the P22 operator are not contacted by the repressor. The KD for the complex of P22 repressor with an operator bearing central T-A bases (9T) increases less than 2-fold between 50 and 200 mM KCl, whereas the KD for the complex of repressor with an operator bearing central C-G bases (9C) increases 10-fold in the same salt range. The DNase I cleavage patterns of both bound and unbound P22 operators also vary with central base sequence. The DNase I pattern of the repressor-9C operator complex changes markedly with salt concentration, whereas that of the 9T operator-repressor complex does not. These changes in nuclease digestion pattern thereby mirror the salt-dependent changes in the P22 operator's affinity for repressor. P22 repressor protects the central base pair of the 9T operator from cleavage by the intercalative cleavage reagent Cu(I)-phenanthroline, while repressor does not protect the central bases of the 9C operator. Together these data indicate that central base pairs affect P22 operator strength by altering the structure of the unbound operator and the repressor-operator complex.

Regression approach to combination of decisions by multiple character recognition algorithms

Abstract: A regression method is proposed to combine decisions of multiple character recognition algorithms. The method computes a weighted sum of the rank scores produced by the individual classifiers and derive a consensus ranking. The weights are estimated by a logistic regression analysis. Two experiments are discussed where the method was applied to recognize degraded machine-printed characters and handwritten digits. The results show that the combination outperforms each of the individual classifiers.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A constraint satisfaction approach to the resolution of uncertainty in image interpretation

Abstract: A technique for image interpretation based on the constraint satisfaction methodology is described. The technique uses an intelligent backtracking algorithm to solve the constraint satisfaction problem and also analyzes failures of the backtracking routine to suggest modifications to help locate a solution. This technique is able to overcome uncertainties in image interpretation by generating partial solutions and inferring values for the missing objects. An outline of this processing is presented and an application of this technique is also given. The technique is compared to another approach in the same domain. Preliminary results on over 1000 test images are included. >

Synthesis and muscarinic receptor activity of ester derivatives of 2-substituted 2-azabicyclo[2.2.1]heptan-5-ol and -6-ol

Abstract: Radioligand binding affinities of four new muscarinic antagonists and six potential muscarinic agonists which possess the 2-alkyl-2-azabicyclo[2.2.1]heptane ring system have been determined in rat heart, rat brain, and m1- or m3-transfected CHO cell membrane preparations to examine the selectivity for subtypes of muscarinic receptor. The efficacies of the potential muscarinic agonists were determined by the ratio of binding affinities against [3H]QNB and [3H]Oxo-M. Four muscarinic antagonists which have the 2,2-diphenylpropionate side chain at either the C5 (5-endo or 5-exo) or the C6 (6-endo or 6-exo) positions did not discriminate between the subtypes of muscarinic receptors. The 2,2-diphenylpropionate 5-endo substituted compound was the most potent, showing affinities between 4.23 x 10(-10) and 1.18 x 10(-9) M in rat heart, rat brain, and m1- or m3-transfected CHO cell membrane preparations. The rank order of ester potency was 5-endo greater than 5-exo greater than 6-endo greater than 6-exo. A molecular modeling study based on the pharmacophore developed for azaprophen was used to account for the relative potency of these antagonists. Six potential muscarinic agonists which have acetoxy groups in the C5 or C6 position with an N-methyl or N-benzyl substituent did not discriminate subtypes of muscarinic receptors and had affinities between 6.63 x 10(-6) and 4.76 x 10(-5) M in rat heart, rat brain, and m1- or m3-transfected CHO cell membrane preparations. exo-2-Methyl-5-acetoxy-2-azabicyclo[2.2.1]heptane was the most efficacious partial agonist.

A programmable analog CMOS synapse for neural networks

Abstract: This paper presents a programmable analog synapse for use in both feedforward and feedback neural networks. The synapse consists of two complementary floating-gate MOSFETs which are programmable in both directions by Fowler-Nordheim tunneling. The P-transistor and the N-transistor are programmable independently with pulses of different amplitude and duration, and hence finer weight adjustment is made possible. An experimental 4×4 synapse array has been designed, which in addition has 32 analog CMOS switches and x−y decoders to select a synapse cell for programming. It has been fabricated using a standard 2-μm, double-polysilicon CMOS technology. Simulation results confirm that output current of synapse is proportional to the product of the input voltage and weight and also shows both inhibitory and excitatory current. Current summing effect has been observed at the input of a neuron. This array is designed using modular and regular structured elements, and hence is easily expandable to larger networks.

The Industrial Safety Professionals: A Comparative Analysis From World War I Until The 1980s

Abstract: The birth of industrial society produced demand for the services of professionals specialized in matters related to industrial safety. Three professions—safety engineering, industrial medicine, and...

Pharmacologic and radioligand binding studies of 1,4-dihydropyridines in rat cardiac and vascular preparations: Stereoselectivity and voltage dependence of antagonist and activator interactions

Abstract: The pharmacologic and radioligand-binding properties of 1,4-dihydropyridines in an activator (Bay K 8644) and an antagonist (nifedipine) series were studied in rat tail artery, heart membrane, and neonatal rat ventricular myocytes. The S-enantiomers of the activator series contracted rat tail artery in the presence of 15 mM K+ (EC50 values of 10(-8) to 10(-5) M). (S)-Bay K 8644 (I) and its o-difluoromethoxy analog (III) were the most potent members of the activator series examined. The abilities of the activators to stimulate maximum tension response of the artery differed with structure; thus, the efficacy of (S)-Bay K 8644 was 70% that of the analog lacking the 3-carbomethoxy group. The R-enantiomers of the activator series and a series of achiral nifedipine analogs were inhibitory in the same tissue. The intact-cell binding assay revealed the binding affinities of 1,4-dihydropyridine antagonists in depolarized cells (50 mM K+) to be higher than those in polarized cells (5 mM K+). The ratio KD (polarized)/KD (depolarized) was 77 for nifedipine (IC50 = 5.4 x 10(-9) M) but was only 2.9 for the weak 3-methoxy nifedipine analog (IC50 = 4.8 x 10(-6) M); an approximately linear relationship exists between this ratio and the antagonist potency. In marked contrast, and in confirmation of previous work [Mol. Pharmacol. 35:541-552 (1989)], the binding affinities of activators were not significantly affected by membrane potential, regardless of potency. We conclude that the S-enantiomers of Bay K 8644 analogs are activators with different potency and efficacy and that the R-enantiomers are antagonists, that the binding of 1,4-dihydropyridine antagonists is voltage dependent, whereas binding of the activators is not, and that the voltage-dependence of binding of the antagonists is correlated with the potency of the antagonist.