Singlet VA \tilde V correlator within the instanton vacuum model

The correlator of singlet axial-vector and vector currents in the external electromagnetic field is studied within the instanton liquid model of QCD vacuum. In the chiral limit we calculate the longitudinal w_L^0 and transversal w_T^0 with respect to axial-vector index invariant amplitudes at arbitrary momentum transfer q. It is demonstrated how the anomalous longitudinal part of the correlator is renormalized at low momenta due to the presence of the U_A(1) anomaly.Comment: 9 pages, 4 figure

Millisecond accuracy video display using OpenGL under Linux

To measure people’s reaction times to the nearest millisecond, it is necessary to know exactly when a stimulus is displayed. This article describes how to display stimuli with millisecond accuracy on a normal CRT monitor, using a PC running Linux. A simple C program is presented to illustrate how this may be done within X Windows using the OpenGL rendering system. A test of this system is reported that demonstrates that stimuli may be consistently displayed with millisecond accuracy. An algorithm is presented that allows the exact time of stimulus presentation to be deduced, even if there are relatively large errors in measuring the display time

Chromatographic Separation Apparatus

An apparatus for the monitoring of a column chromatography separation process includes a segmented column with a seal positioned at the joint defined by the segments of the column. A connector is provided for connecting the segments of the column together. The apparatus further includes a sensor for monitoring an analyte in an eluant within a separation zone of the column. The sensor includes a mesh grid made of optical fibers or metal wires which is placed so as to extend through the separation zone of the column. The metal wires or optical fibers extend through the seal of the joint in the segmented column and connect to signal processing and data analysis equipment for purposes of monitoring the movements and concentration of an analyte in an eluant at various locations within the column. Certain segments of the optical fibers or metal wires which make up the mesh grid are coated so as to be desensitized and other segments are uncoated for sensing the analyte. This provides an effective apparatus to monitor in detail the cross-section of a column chromatography process in-situ