Alkaloids and carboxylic acids from Piper nigrum

Detailed chemical studies were carried out on the roots of Piper nigrum. Six alkaloids and four carboxylic acids were isolated and identified from this study. The alkaloids were piperolactam A (1), piperolactam D (2), cepharadione A (3), piperine (4), sylvamide (5) and 2,4-tetradecadienoic acid isobutyl amide (6). The carboxylic acids were tetracosanoic acid, p-hydroxy-m-methoxycinnamate ester (7), 3,4-methylenedioxycinnamic acid (8), 2-butenedioic acid, mono-(2-methylpropyl) ester (9) and 3,4-methylenedioxy benzoic acid (10). Larvicidal assays on Aedes aegypti were carried out on the crude extracts of these plants as well as the pure compounds. The larvae were found to be susceptible to some of these extracts and compounds. This paper reports the isolation and characterization of these compounds as well as bioassay data. This is the first report on the presence of piperolactam A (1), piperolactam D (2) cepharadione A (3) and sylvamide (5) in Piper nigrum

Low pressure plasma focus for deuteron Beam generation / Lim Lian Kuang

The thesis presented an experimental investigations performed on the radiation (ion beam, neutrons and X-rays) emitted from a 2.7 kJ plasma focus device. With the aim to optimize for ion beam emission, the system has been modified with long electrode configuration operated at low pressures. Work has been carried out to find the best parameters while matching characteristic time of plasma focus. Diagnostics techniques including Faraday cup, biased ion collector and solid state nuclear track detectors were employed for the study of ion beams emission in terms of beam energies, their fluence (ions/m2), number of ions and angular distribution of the emissions. Lee model code was configured to according to the system parameters and generate outputs at the experimental conditions. The results were compared with the experimental data. The study suggested that multiple current dips and prolong duration in the drop of discharge current signals corresponded to anomalous resistance played an important role in the ion beam emission. Significant ion beam emission with good reproducibility was obtained at operating pressure in the range of 0.1 – 0.5 mbar. The best condition is 0.2 mbar deuterium filling. Ion beams with energies in the range of 18 – 350 keV have been measured, while the discharge voltage was 13.5 kV. Ion beam fluence is estimated in the order of 1015 ions/m2. The emission was highly anisotropic in the forward direction and spread out to about 30o. The density of ion tracks measured to be 6.3 x 1010 ions/m2 while in the velocity space they are in Maxwell-Boltzmann distribution. Electron temperature of the deuterium plasma was estimated as 3 – 5 keV. Correlation between the radiation emissions and pinch dynamics gave a clear picture that the ion beams were emitted at different instances during the pinch phase

Enhancement of the ion beam emission in a low energy plasma focus / Lim Lian Kuang

The characteristic of the plasma focus device as efficient source of ion beam generation as well as X-ray source is particularly an appealing subject of study. In this work, we optimized a plasma focus to work at low pressure as an ion beam source. The plasma focus used is of Mather type which is powered by a low inductance capacitor (15 kV, 30 F). At the discharge voltage of 15 kV, maximum energy supplied to the system is 3.3 kJ. The primary objective of the current project is to to find an optimum condition for ion beam production in deuterium filling. The geometry of the electrodes employed is meant for low pressure operation. Experiments are conducted with deuterium as the working gas at pressure of less than 1 mbar. Operation at this low pressure regime is found to produce much more significant ion beam than at normal pressure of several mbar. The axial current sheath velocity of up to 10 cm/s is achieved, which is near to the speed limit recommended for good focusing discharge. Intense focusing discharge with good reproducibility has been obtained at operating pressure in the range of 0.05 – 0.5 mbar. The energy of the ion beam has been determined using time of flight technique by employing three biased ion collectors installed at the end on direction. Intense ion beam emissions with good reproducibility have been obtained. Optimum operating pressure for the ion beam production is around 0.1 mbar, where the average ion beam energy registered was 80 keV. The average total deuteron flux per shot is estimated to be 2.1 x 1018 cm-2 at 0.1 mbar. The deuteron beam with average energy for the pressure of 0.05 – 0.5 mbar was determined to be in the range of 25 – 80 keV. Correlation of ion beam and X-ray emission as well as other discharge parameters with operating pressures has been investigated. X-ray emission was measured by a filtered 5-channel windowless BPX-65 photodiode array. Soft X-ray production from the plasma focus was also found to be pressure dependent and exhibit similar trend to the ion beam emission. The highest Xray emission is also observed at pressure of 0.1 mbar which implies that high temperature plasma column has been formed. A reliable plasma focus device with consistent high production of ion beam or X-ray emission could be used as ion beam source or light source in various technological fields

Dynamics of ion beam emission in a low pressure plasma focus device

The plasma that accelerates and compresses in the formation of the pinch in dense plasma focus devices has been found to be an abundant source of multiple radiations like ion beams and x-rays. In this work, the ion beam and x-ray emissions from a 2.7 kJ (13.5 kV, 30 µF) plasma focus device operated at pressure below 1 mbar were investigated. The time profile of the ion beam emission was analysed from the simultaneously measured ion beam, soft and hard x-ray signals using biased ion collectors, BPX 65 silicon PIN diode and a scintillator-photomultiplier tube assembly. Time resolved analysis of the emissions revealed that the emission of the ion beam corresponded to several different pinching instances. Two components of the ion beam were identified. An ion beam of lower energy but higher intensity was emitted followed by an ion beam of higher energy but lower intensity in the first plasma pinch. The ion beam emitted from the first plasma pinch also has higher energy than subsequent plasma pinches. The emission was found to be associated with the amplitude of voltage spike. The results from ion beam and electron beams suggest that they were emitted by the same localized electric field induced in the pinched plasma. The strongest plasma focus discharge indicated by sharp voltage spike of high amplitude and highest ion beam energy were both observed at 0.2 mbar. The average energy of the ion beam obtained is (53 ± 13) keV. At this optimum condition, the ions beam with the highest energy also led to the highest hard x-ray emission

Schematic of the plasma focus device equipped with diagnostics of a Faraday cup, biased ion collectors and CR-39 SSNTDs.

<p>Schematic of the plasma focus device equipped with diagnostics of a Faraday cup, biased ion collectors and CR-39 SSNTDs.</p

Discharge voltage and current signal at 0.2 mbar deuterium.

<p>Discharge voltage and current signal at 0.2 mbar deuterium.</p

Typical discharge voltage and Faraday cup signal at 0.2 mbar deuterium.

<p>Typical discharge voltage and Faraday cup signal at 0.2 mbar deuterium.</p

Optical microscope images (1000X) of CR-39 SSNTDS exposed at various angular positions, at 0.2 mbar deuterium.

<p>Optical microscope images (1000X) of CR-39 SSNTDS exposed at various angular positions, at 0.2 mbar deuterium.</p

Average deuteron-beam fluence per shot at different operating pressure.

<p>Average deuteron-beam fluence per shot at different operating pressure.</p

Low-Energy Plasma Focus Device as an Electron Beam Source

A low-energy plasma focus device was used as an electron beam source. A technique was developed to simultaneously measure the electron beam intensity and energy. The system was operated in Argon filling at an optimum pressure of 1.7 mbar. A Faraday cup was used together with an array of filtered PIN diodes. The beam-target X-rays were registered through X-ray spectrometry. Copper and lead line radiations were registered upon usage as targets. The maximum electron beam charge and density were estimated to be 0.31 μC and 13.5×1016/m3, respectively. The average energy of the electron beam was 500 keV. The high flux of the electron beam can be potentially applicable in material sciences