THE DEVICE OF THE ELECTRO-JIGSAW. EXPERIMENTAL STUDY OF THE CHARACTERISTICS OF THE ELECTRO-JIGSAW.

Lobzik (from German Laubsäge) is a tool for curvilinear sawing of materials. Manual mechanical Jigsaw includes an arched frame with a handle and clamps for mounting the saw blade. The saw blade is thin and narrow, thanks to which it is possible to change the direction of sawing. The frame has a large clearance between the canvas and its top, so it can bypass the edges of the workpiece. Manual jigsaw is usually used for processing of wood and its derivatives (in particular, plywood), and also in jeweller practice for processing nonferrous metals. Electric Jigsaw is a hand-held power tool for sawing of various materials with reciprocating movement of saw blade (Fig. 1). The manual electric Jigsaw includes a hull with a flat platform at the bottom and a handle at the top. Inside is an electric motor and a mechanism that transforms the rotational motion of the engine shaft into the reciprocating movement of the guide. For fastening of cloths the shank with a clamping screw or a spring clamp is used

Characterization of Shewanella oneidensis MtrC: a cell-surface decaheme cytochrome involved in respiratory electron transport to extracellular electron acceptors

MtrC is a decaheme c-type cytochrome associated with the outer cell membrane of Fe(III)-respiring species of the Shewanella genus. It is proposed to play a role in anaerobic respiration by mediating electron transfer to extracellular mineral oxides that can serve as terminal electron acceptors. The present work presents the first spectropotentiometric and voltammetric characterization of MtrC, using protein purified from Shewanella oneidensis MR-1. Potentiometric titrations, monitored by UV–vis absorption and electron paramagnetic resonance (EPR) spectroscopy, reveal that the hemes within MtrC titrate over a broad potential range spanning between approximately +100 and approximately -500 mV (vs. the standard hydrogen electrode). Across this potential window the UV–vis absorption spectra are characteristic of low-spin c-type hemes and the EPR spectra reveal broad, complex features that suggest the presence of magnetically spin-coupled low-spin c-hemes. Non-catalytic protein film voltammetry of MtrC demonstrates reversible electrochemistry over a potential window similar to that disclosed spectroscopically. The voltammetry also allows definition of kinetic properties of MtrC in direct electron exchange with a solid electrode surface and during reduction of a model Fe(III) substrate. Taken together, the data provide quantitative information on the potential domain in which MtrC can operate

Quantum dynamics in strong fluctuating fields

A large number of multifaceted quantum transport processes in molecular systems and physical nanosystems can be treated in terms of quantum relaxation processes which couple to one or several fluctuating environments. A thermal equilibrium environment can conveniently be modelled by a thermal bath of harmonic oscillators. An archetype situation provides a two-state dissipative quantum dynamics, commonly known under the label of a spin-boson dynamics. An interesting and nontrivial physical situation emerges, however, when the quantum dynamics evolves far away from thermal equilibrium. This occurs, for example, when a charge transferring medium possesses nonequilibrium degrees of freedom, or when a strong time-dependent control field is applied externally. Accordingly, certain parameters of underlying quantum subsystem acquire stochastic character. Herein, we review the general theoretical framework which is based on the method of projector operators, yielding the quantum master equations for systems that are exposed to strong external fields. This allows one to investigate on a common basis the influence of nonequilibrium fluctuations and periodic electrical fields on quantum transport processes. Most importantly, such strong fluctuating fields induce a whole variety of nonlinear and nonequilibrium phenomena. A characteristic feature of such dynamics is the absence of thermal (quantum) detailed balance.Comment: review article, Advances in Physics (2005), in pres

Solvent Effects on Ionization Potentials of Guanine Runs and Chemically Modified Guanine in Duplex DNA: Effect of Electrostatic Interaction and Its Reduction due to Solvent

We examined the ionization potential (IP) corresponding to the free energy of a hole on duplex DNA by semiempirical molecular orbital theory with a continuum solvent model. As for the contiguous guanines (a guanine run), we found that the IP in the gas phase significantly decreases with the increasing number of nucleotide pairs of the guanine run, whereas the IP in water (OP, oxidation potential) only slightly does. The latter result is consistent with the experimental result for DNA oligomers in water. This decrease in the IP is mainly due to the attractive electrostatic interaction between the hole and a nucleotide pair in the duplex DNA. This interaction is reduced in water, which results in the small decrease in the IP in water. This mechanism explains the discrepancy between the experimental result and the previous computational results obtained by neglecting the solvent. As for the chemically modified guanine, the previous work showed that the removal of some solvent (water) molecules due to the attachment of a neutral functional group to a guanine in a duplex DNA stabilizes the hole on the guanine. One might naively have expected the opposite case, since a polar solvent usually stabilizes ions. This mechanism also explains this unexpected stabilization of a hole as follows. When some water molecules are removed, the attractive electrostatic interaction stabilizing the hole increases, and thus, the hole is stabilized. In order to design the hole energetics by a chemical modification of DNA, this mechanism has to be taken into account and can be used. 1