Synthesis of masked 2-amino-6-methyl-4-oxo-4H-pyran-3-carbaldehydes

Acetoacetylation of (1,3-dimethylbenzimidazol-2-ylidene)-, (3-methylbenzothiazol-2-ylidene)-, and (3,4-dimethylthiazol-2-ylidene)acetonitriles with 2,2,6-trimethyl-4H-1,3-dioxin-4-one was found to yield appropriate C-acylation products. Treatment of the obtained products with perchloric acid afforded 2-(2-amino-6-methyl-4H-pyran-4-one-3-yl)substituted quaternary azolium salts. Their reduction with sodium borohydride yielded the corresponding dihydro (in the case of benzoazoles) or tetrahydro (in the case of thiazole) derivatives, which were shown to be synthetic equivalents of the title aldehyde

Laser-directed hierarchical assembly of liquid crystal defects and control of optical phase singularities

Topological defect lines are ubiquitous and important in a wide variety of fascinating phenomena and theories in many fields ranging from materials science to early-universe cosmology, and to engineering of laser beams. However, they are typically hard to control in a reliable manner. Here we describe facile erasable “optical drawing” of self-assembled defect clusters in liquid crystals. These quadrupolar defect clusters, stabilized by the medium's chirality and the tendency to form twisted configurations, are shaped into arbitrary two-dimensional patterns, including reconfigurable phase gratings capable of generating and controlling optical phase singularities in laser beams. Our findings bridge the studies of defects in condensed matter physics and optics and may enable applications in data storage, singular optics, displays, electro-optic devices, diffraction gratings, as well as in both optically- and electrically-addressed pixel-free spatial light modulators

Merlin controls the repair capacity of Schwann cells after injury by regulating Hippo/YAP activity

Loss of the Merlin tumor suppressor and activation of the Hippo signaling pathway play major roles in the control of cell proliferation and tumorigenesis. We have identified completely novel roles for Merlin and the Hippo pathway effector Yes-associated protein (YAP) in the control of Schwann cell (SC) plasticity and peripheral nerve repair after injury. Injury to the peripheral nervous system (PNS) causes a dramatic shift in SC molecular phenotype and the generation of repair-competent SCs, which direct functional repair. We find that loss of Merlin in these cells causes a catastrophic failure of axonal regeneration and remyelination in the PNS. This effect is mediated by activation of YAP expression in Merlin-null SCs, and loss of YAP restores axonal regrowth and functional repair. This work identifies new mechanisms that control the regenerative potential of SCs and gives new insight into understanding the correct control of functional nerve repair in the PNS

Second Generation Leptoquark Search in p\bar{p} Collisions at s\sqrt{s} = 1.8 TeV

We report on a search for second generation leptoquarks with the D\O\ detector at the Fermilab Tevatron $p\bar{p}$ collider at $\sqrt{s}$ = 1.8 TeV. This search is based on 12.7 pb$^{-1}$ of data. Second generation leptoquarks are assumed to be produced in pairs and to decay into a muon and quark with branching ratio $\beta$ or to neutrino and quark with branching ratio $(1-\beta)$. We obtain cross section times branching ratio limits as a function of leptoquark mass and set a lower limit on the leptoquark mass of 111 GeV/c$^{2}$ for $\beta = 1$ and 89 GeV/c$^{2}$ for $\beta = 0.5$ at the 95%\ confidence level.Comment: 18 pages, FERMILAB-PUB-95/185-

Spatial reorientation of the carriage of a CNC lathe when reversing

The process of machining on CNC machines of parts of a complex profile with multi-pass shaping schemes is accompanied by multiple changes in the direction of movement of the working bodies (reverse) during cutting and at idle. In this case, the formation of processing errors associated with the spatial reorientation of the carriage during reversal is possible, the cause of which is the mismatch of the vector of the traction force acting along the axis of the lead screw and the resulting resistance forces associated with cutting forces and friction in the guides. Based on the analysis of the forces acting on the carriage, a design and mathematical model is proposed for guides with prismatic and flat guides. Approbation of the proposed calculation method showed a good level of agreement between the calculated and experimental results. The regularities of the influence of the cutting forces, the location of the center of gravity of the support group, its mass and speed after the reverse on the value of the spatial reorientation have been established

Impact of manufacturing errors of ball screw system on performance characteristics

To convert rotary motion into translational motion in modern metal-cutting machine tools, screw-nut rolling transmissions are widely used. Special requirements are placed on the stability of the operational characteristics of the screw-nut rolling transmission. The influence of the accuracy of manufacturing screw-nut transmission on the main transmission characteristics: axial stiffness and the moment of idling is considered. When analyzing the quality of the manufacture of the transmission, the following manufacturing errors were taken into account: the pitch errors of the screw and nut threads; errors in thread diameter of screw and nut; deviation of the thread profile of the screw and nut; the error of the diameter of the ball. Since these errors are independent random variables, on the basis of the basic propositions of the theory of probability, analytical dependencies were obtained to determine the coefficients connecting the variances of the design parameters and the variance of the probabilistic distribution of the axial force and the idling torque. Based on the calculation results from the obtained dependencies, it was concluded that the errors in the thread pitch of the screw and nut have a prevailing influence on the dispersion of the probabilistic distribution of the axial force (and, consequently, the axial stiffness) and the idling torque. The results obtained allow us to outline further ways of improving the transmission of the screw-nut rolling

Informativity of the Vibration Signal of the Spindle Unit of the Metal Cutting Machine

Monitoring the condition of the spindle units of modern metal-cutting machines by methods of non-selective diagnostics involves the possibility of installing monitoring sensors in places with maximum vibration information. In this regard, the assessment of the informative value of the vibration field of the spindle unit, which can be carried out in advance, taking into account the design features, geometric and dimensional characteristics, is an urgent task. Based on the energy approach, a computational model based on the median planes of the walls is proposed using the example of a universal lathe spindle unit. On the basis of the calculated model, the energy balance equations are drawn up taking into account the conditions for the transmission of vibration power between the walls of the housing. The dependences that allow us to calculate the coefficients that take into account the absorption of vibration energy by the walls of the housing are given. The solution of the energy balance equations made it possible, based on the level of the vibration power flow, to rank the walls of the spindle unit body by information content,. The resulting model of the vibration field can be used to determine the reference values of vibration velocities that are formed from sources in the absence of defects. This will allow for non-selective diagnostics to detect the occurrence of a defect at an early stage, and in the presence of a defect to assess the level of its development

Simulation of a Contact Pseudo-Environment in Calculating Thermal Resistance

The use of the temperature criterion in the design of metal-cutting machines, determined on the basis of models that take into account the contact thermal resistances, is an objective necessity. These models should take into account to the maximum extent the actual conditions of contact of parts in the design under consideration, determined by the deviations of the mating surfaces from the ideal shape. The article presents the results of numerical modeling based on the finite element method of the formation of the contact thermal resistance and the evaluation of the influence of the parameters of the intermediate layer (pseudo-environment) that occurs in the contact zone of surfaces with macro-deviations on the passage of the heat flow. The obtained results allowed us to identify the most significant of the considered parameters. It is established that when modeling a pseudo-environment, it is necessary to take into account the coefficient of its thermal conductivity, the size, location and integrity of the actual contact zone