A Versatile Pseudo-Random Noise Generator

A detailed design is presented for a digital pseudo-random noise generator. The instrument is built with standard integrated circuits. It produces both binary noise (pseudo-random binary sequences) and white Gaussian noise of variable bandwidth. By setting front panel switches to match tabulated octal codes, one may select a vast number of independent noise programs

The time resolved measurement of ultrashort THz-band electric fields without an ultrashort probe

The time-resolved detection of ultrashort pulsed THz-band electric field temporal profiles without an ultrashort laser probe is demonstrated. A non-linear interaction between a narrow-bandwidth optical probe and the THz pulse transposes the THz spectral intensity and phase information to the optical region, thereby generating an optical pulse whose temporal electric field envelope replicates the temporal profile of the real THz electric field. This optical envelope is characterised via an autocorrelation based FROG measurement, hence revealing the THz temporal profile. The combination of a narrow-bandwidth, long duration, optical probe and self-referenced FROG makes the technique inherently immune to timing jitter between the optical probe and THz pulse, and may find particular application where the THz field is not initially generated via ultrashort laser methods, such as the measurement of longitudinal electron bunch profiles in particle accelerators.Comment: 7 pages, 3 figures, submitted to AP

Quinine blocks 5-HT and 5-HT3 receptor mediated peristalsis in both guinea pig and mouse ileum tissue

Introduction. Quinine is commonly used to treat malaria; however one of the principal side effects is gastrointestinal disturbances (White, 1992). 5-HT3 receptors modulate gut peristalsis (Chetty et al., 2006), and, as quinine has been shown to act as a 5-HT3 receptor antagonist (Thompson and Lummis, 2008) it is possible that these side effects result from actions at gut 5-HT3 receptors. To address this question, we examined the ability of quinine to antagonise 5-HT and 5-HT3 mediated peristalsis in guinea pig and mouse ileum. Methods. Ileum was excised from male guinea pigs (200-300g) and C57BL/6 mice (25-35g) following cervical dislocation. Ileum segments (3-5 cm) were mounted in 50 ml organ baths containing Tryode’s solution at 35-37 °C. Concentration-response curves were constructed for 5-HT and the selective 5-HT3 agonist 2-Me-5-HT (non-cumulative doses). Quinine was pre-applied for 10 min and inhibition measured using agonist concentrations that elicited a submaximal response. Results. Concentration-dependent contractions produced by 5-HT (pEC50 = 5.45 ± 0.17, n = 8) and the selective 5-HT3 agonist 2-Me-5-HT (5.01 ± 0.17, n = 11) were not significantly different (Student’s t-test, t = 0.619, df = 17, p = 0.544) in guinea pig ileum. Increasing concentrations of quinine were able to antagonise the activities of both 5-HT (pIC50 = 5.03 ± 0.2, n = 6) and 2-Me-5HT (pIC50 = 4.59 ± 0.26, n = 4). At mouse ileum, 5-HT (pEC50 = 7.57 ± 0.33, n = 9) was more potent (Student’s t-test, t = 3.6, df = 12, p = 0.004) than 2-Me-5-HT (pEC50 = 5.45 ± 0.58, n = 5). Quinine antagonised both the 5-HT (pIC50 = 4.87 ± 0.31, n = 7) and 2-Me-5-HT-induced (pIC50 = 6.18 ± 1.14, n = 4) contractions. Conclusions. These results support previous electrophysiological studies that identified quinine as an antagonist at recombinant 5-HT3 receptors with IC50 values comparable with those reported here (pIC50 = 4.87, Thompson et al., 2007). Further, we found that quinine completely blocked 5-HT induced contractions in mouse and guinea pig, raising the possibility that quinine targets other 5-HT receptors in the gut (e.g., 5-HT4 receptors) and may influence intestinal function

Collision of High Frequency Plane Gravitational and Electromagnetic Waves

We study the head-on collision of linearly polarized, high frequency plane gravitational waves and their electromagnetic counterparts in the Einstein-Maxwell theory. The post-collision space-times are obtained by solving the vacuum Einstein-Maxwell field equations in the geometrical optics approximation. The head-on collisions of all possible pairs of these systems of waves is described and the results are then generalised to non-linearly polarized waves which exhibit the maximum two degrees of freedom of polarization.Comment: Latex file, 17 pages, accepted for publication in International Journal of Modern Physics