Reduction Of Ionization Research Articles

Ionosphere of Mars during the consecutive solar minima 23/24 and 24/25 as seen by MARSIS-Mars Express

The Mars' ionospheric behavior during two consecutive solar minima (23/24 and 24/25) is investigated with the same dataset. In particular, we use the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) on board Mars Express to investigate the total electron content behavior of the whole atmosphere in relation to the solar irradiance (EUV and X-ray fluxes), the solar zenith angle and the heliocentric distance. The topside variability of the electron density profiles is also investigated through variations in the peak density and neutral scale height. Moreover, the equations of the NeMars empirical model of the Martian ionosphere for low solar activity are tested for both minima. We have found that the topside ionosphere of Mars behaved similarly at both solar minima. However, when considering the bottomside, a pronounced reduction in ionization in particular cases is suggested. In addition, larger TEC values are found during the solar minimum 24/25 in the nightside sector that may indicate possible larger plasma transport than during the minimum 23/24. Finally, this study confirms that the ionospheric empirical NeMars model equations derived by Sanchez-Cano et al. (2016) for the low solar activity period during the solar minimum 23/24 are also valid and accurate for the solar minimum 24/25. The long duration of Mars Express is a critical factor for determining the long-term Martian ionospheric variability, which in turn, is essential for understanding the global evolution of the planet's atmosphere.

Nanoengineering of strong field processes in solids

We present a theoretical investigation of the effect of quantum confinement on high harmonic generation in semiconductor materials by systematically varying the confinement width along one or two directions transverse to the laser polarization. Our analysis shows a growth in high harmonic efficiency concurrent with a reduction of ionization. This decrease in ionization comes as a consequence of an increased band gap resulting from the confinement. The increase in harmonic efficiency results from a restriction of wave packet spreading, leading to greater recollision probability. Consequently, nanoengineering of one and two-dimensional nanosystems may prove to be a viable means to increase harmonic yield and photon energy in semiconductor materials driven by intense laser fields.

Enhancing High Harmonic Output in Solids through Quantum Confinement

We investigate theoretically the effect of quantum confinement on high harmonic generation (HHG) in semiconductors by systematically varying the width of a model quantum nanowire. Our analysis reveals a reduction in ionization and a concurrent growth in HHG efficiency with increasing confinement. The drop in ionization results from an increase in the band gap due to stronger confinement. The increase in harmonic efficiency comes as a result of the confinement restricting the spreading of the transverse wave packet. As a result, intense laser driven 1D and 2D nanosystems present a potential pathway to increasing yield and photon energy of HHG in solids.

Position of chromatographic techniques in screening for detection of drugs or poisons in clinical and forensic toxicology and/or doping control

This paper reviews chromatographic screening procedures for simultaneous detection of several drug classes relevant to clinical and forensic toxicology or doping control in urine or blood using gas chromatography-mass spectrometry (GC-MS), liquid chromatography coupled with a diode-array detector (LC-DAD) or a mass spectrometer (LC-MS). The pros and cons of the different techniques and procedures are discussed leading to the following conclusions and perspectives. GC-MS, especially in the electron ionization full-scan mode, is still the method of choice for comprehensive screening providing best separation power, specificity and universality, although requiring derivatization. LC-DAD is also often used for screening, but its separation power and its specificity are still inferior to those of GC-MS. Finally, LC-MS has shown to be an ideal supplement, especially for the detection of more polar, thermolabile and/or low-dose drugs, especially in blood plasma. It may become the gold standard in clinical and forensic toxicology and doping control if, at a later date, the costs of the apparatus will be markedly reduced, the current disadvantages like irreproducibility of fragmentation, reduction of ionization by matrix, etc. will be overcome, and finally if one of the increasing number of quite different techniques will become the apparatus standard.

An investigation of the influence of applied voltage on ionization due to electrons in free-air ionization-chambers

Secondary electrons, produced in a free-air ionization-chamber, gain or lose energy (i.e., accelerate or decelerate) due to the electric field and, hence, cause an enhancement or reduction in ionization. In order to estimate this effect computer calculations were performed. These calculations showed that when exposure is measured, for example for X-rays generated at a tube voltage of 300 kV and at an electric field strength of 20 kV / m, the output charge of the chamber is increased by 0.8% due to the gain in energy of the secondary electrons. At the same time, the output charge is decreased by a similar amount due to the loss in energy of the secondary electrons. The net increase in the output signal charge is estimated to be 0.05%. However, the effect of acceleration and/or deceleration of high-energy secondary electrons emitted by X-rays, is relatively more significant than that of the gas multiplication at low electric field strengths.

The equatorial total electron content and shape factor

The diurnal variations of electron content NT and shape factor ℱ observed at an equatorial station during sunspot minimum are shown to be consistent with the electron density profiles Ne(h), observed at Jicamarca during sunspot minimum. The rapid increase in NT and ℱ at sunrise results from the EUV production of ionization in the E and F regions. Day‐to‐day variations in daytime NT are observed to be quite small at the equator. The evening decrease in ℱ results from an upward drift of the F region at sunset and the evening decay of the E and bottomside F regions. The nighttime peak or plateau in ℱ is produced by the slow downward drift of the electron density profile. The deep predawn dip in ℱ is caused by the main peak of the F layer reaching low altitudes where high loss rates cause a large reduction in ionization below 300 km and a very flat Ne(h) profile.

Ionization Loss near the Origin of an Electron Pair of Very High Energy

Ionization loss of negatron-positron pair is calculated as a function of their distance. This resudt will be usefud to measure the energy of a gamma ray above 10/sup 10/ ev from the reduction of ionization near the origin of the created pair. The reduction is due to the interference between the electromagnetic field of negatron and that of positron. A method similar to that of Fermi who had treated the energy loss of single electron taking into account the polarizability of the medium was adopted. (auth)

The effect of a solar eclipse on the Earth's magnetic field

Summary—The reduction of ionization in the E‐layer, at a point on the track of the total eclipse of August 31, 1932, has been measured by Henderson; the effect of this on electron‐currents flowing in the layer is here examined, and the corresponding magnetic effects are inferred. If this layer is the seat of the currents which produce the solar diurnal magnetic variation (S), the magnetic effects of an eclipse should, it is inferred, be apparent, and their nature is described. If, however, S is produced in the upper (F) ionized layer, the eclipse‐effects are likely to be too small for detection with certainty. The magnetic observations during eclipses are discussed, and the opinion is expressed that they show no regular magnetic effect of the type here predicted, and that therefore 5 is probably not produced in the E‐layer; but a final decision must await further observations.

RADIO OBSERVATIONS ON THE UPPER IONIZED LAYER OF THE ATMOSPHERE AT THE TIME OF THE TOTAL SOLAR ECLIPSE OF AUGUST 31, 1932

This report contains the results from one of the three stations set up by the National Research Council of Canada to take observations on radio reflections from the ionized layers in the upper atmosphere during the total solar eclipse of August 31, 1932. The station concerned was located at Kingston, Ontario, and was approximately under the centre of totality for the upper or Appleton layer. Hence observations at this station were limited to the upper layer. The results from the other two stations at Corner Brook, Newfoundland, and at Vankleek Hill, Ontario, are reported in the paper immediately preceding (8).The method was that developed by Breit and Tuve, in which a short pulse is transmitted, the reflection being received and its time delay recorded by means of a cathode ray oscillograph.The results indicate that the ionization of the upper layer is caused by radiation (presumably ultra-violet light) from the sun. Whether or not this is the sole cause is uncertain because of the time lag in recombination of ions in the layer. A reduction in ionization of over 30% was noted.A magnetic storm which occurred a few days before the eclipse made the results more difficult to interpret but gave some information of the effect of such a storm on the upper layer. It appeared to cause considerable instability in the layer and a somewhat lower ion content.