Identification of two Escherichia coli pseudouridine synthases that show multisite specificity for 23S RNA

Several putative Escherichia coli pseudouridine (Psi) synthases have been identified by iterative searching of genomic databases for ORFs homologous to known Psi synthases [Gustafsson et al. (1996) Nucleic Acids Res. 24, 3756-3762]. Of these, yceC and yfiI were proposed to encode Psi synthases which modify 23S rRNA. In the present work, yceC and yfiI were cloned and overexpressed in E. coli, and the encoded enzymes, YceC and YfiI, were purified to homogeneity. Both proteins converted Urd residues of rRNA to Psi, thus confirming their identities as Psi synthases. However, in in vitro experiments both enzymes extensively modified Urd residues of both 23S rRNA and 16S rRNA. Gene-disruption of yceCresulted in the absence of Psi modification at positions U955, 2504, and 2580 of 23S RNA, thus identifying these sites as in vivo targets for YceC. Likewise, yfiI disruption resulted in the absence of Psi modification at positions U1911, 1917, and possibly 1915 of 23S RNA. Disruption of yceC did not affect the growth under the conditions tested, whereas yfiI-disrupted cells showed a dramatic decrease in growth rate. Since YceC and YfiI hypermodify RNA in vitro, factors in addition to ribonucleotide sequence must contribute to the in vivo specificity of these enzymes.     

The solubility of heavy metal soaps in co-solvent mixtures of chloroform and propylene glycol

Summary The solubilities of the myristates, laurates, palmitates, and stearates of magnesium, lead, calcium, barium, and zinc have been measured at 25° C. in chloroform and in propylene glycol and in their mixtures. Even where they are sparingly soluble in the solvents separately, they dissolve freely in mixtures of the two. For each metal the solubility is greatest for laurate and least for stearate and it is very low for zinc soaps, particularly zinc stearate. Heavy metal soaps may be directly titrated with acid in mixtures of propylene glycol and chloroform using thymol blue as indicator (yellow to pink).     

Rapid prototyping of digital controls for power electronics

The process for designing digital controls for power electronics is typically quite convoluted and affords many opportunities for errors to occur. We present here a new and complete method for rapid prototyping of digital controls that allows rapid realization of new designs. The approach uses a collection of tools that include both software (the virtual test bed (VTB) and Matlab/Simulink) and hardware (dSpace DSP). An example application of the methodology completes the discussion.     

Nutritive value of cashewnut extraction meal

Chemical analysis has shown that cashewnut meal extracted from whole kernels contains about 42% crude protein, about 1% crude lipid, a low content of crude fibre and 0.5 and 0.2% calcium and phosphorus, respectively. The meal has good quality protein containing 4.6% lysine, 1.3% tryptophan, about 2% cystine, and 1.6% methionine. The content of sulphur-containing amino acids is higher than that of soyabean and groundnut meals. The meal from cashewnut is shown to be superior to that of soyabean meal, judging from the weight gains obtained and‘protein score’calculated at 97 for cashew and 93 for soyabean meal.     

Anionic polymerization of butadiene with organosodium soluble catalysts and structure of the resulting polymers

The structure of liquid polybutadienes prepared by anionic catalysts with toluene as transfer agent was studied by ¹³C n.m.r. and information concerning initiation, propagation and transfer mechanism was obtained. A complete characterization of the fractions obtained by high vacuum distillation is also reported.     

A Windows computer application for long term data acquisition, storage and presentation of biological signals

We developed a windows application dedicated to recording, displaying and storing large amounts of biological signals on a standard PC. The application works in Matlab and uses an A/D-converter interface that enables a user to run the same software for signal acquisition, display and processing with different A/D-converter boards. The software program consists of three integrated modules, for setting the protocol for signal acquisition; for commands that can be accessed during data acquisition and for software routines that enable off-line viewing, pre-processing and processing of recorded data. It adapts to different computer hardware configurations by enabling the user to define file size, data resolution and file storage on local and network hard disks during signal acquisition.     

The k-Neighbors Approach to Interference Bounded and Symmetric Topology Control in Ad Hoc Networks

Topology control, wherein nodes adjust their transmission ranges to conserve energy and reduce interference, is an important feature in wireless ad hoc networks. Contrary to most of the literature on topology control which focuses on reducing energy consumption, in this paper we tackle the topology control problem with the goal of limiting interference as much as possible, while keeping the communication graph connected with high probability. Our approach is based on the principle of maintaining the number of physical neighbors of every node equal to or slightly below a specific value k. As we will discuss in this paper, having a nontrivially bounded physical node degree allows a network topology with bounded interference to be generated. The proposed approach enforces symmetry on the resulting communication graph, thereby easing the operation of higher layer protocols. To evaluate the performance of our approach, we estimate the value of k that guarantees connectivity of the communication graph with high probability both theoretically and through simulation. We then define k-Neigh, a fully distributed, asynchronous, and localized protocol that uses distance estimation. k-Neigh guarantees logarithmically bounded physical degree at every node, is the most efficient known protocol (requiring 2n messages in total, where n is the number of nodes in the network), and relies on simpler assumptions than existing protocols. Furthermore, we verify through simulation that the network topologies produced by k-Neigh show good performance in terms of node energy consumption and expected interference.     

Experimental investigation on the breakage of hard rock by the PDC cutters with combined action modes

To verify the feasibility and efficiency of rotary-percussive drilling assisted by waterjets in very hard rocks, experiments on the performance of polycrystalline diamond compact (PDC) cutters resisting different combined loads of static thrust, impact, cutting and waterjets on Missouri red granite and Halston limestone were investigated. The experiments were conducted by means of a drop hammer and linear cutting-impact table. The effects of static thrust (WOB), impact energy, impact spacing and waterjets on the rate of penetration in hard rocks are described and the results are analyzed by measuring the depth of the craters or cuts penetrated by PDC cutters. Results from the study confirmed that the combined mode of cutting-impact is very effective in very hard rocks.     

Modeling and performance analysis of networking and collaborative systems

The special issue on Modeling and Performance Analysis of Networking and Collaborative Systems by leveraging current networks and collaborative applications. In addition, the incorporation of the latest and powerful technologies, based on distributed infrastructure, is also explored for the enhancement of these applications, resulting in complex and entangled systems that pose new issues and challenges, in terms of efficiency, security, mobility, and so on. The goal is to respond to the need for methods and tools for performance analysis and evaluation of current complex collaborative and networking systems and applications. To this direction, this special issue provides latest research on modeling and performance analysis of networking and collaborative systems from different perspectives.