Terahertz optically pumped silicon lasers

Stimulated terahertz (THz) emission from silicon single crystals doped by group-V donors has been obtained by optical excitation with pulsed infrared lasers. Pumping by a conventional TEA CO2 laser results in lasing on discrete lines between 1.3 and 7 THz (see figure). Laser thresholds can be as low as 10 kW/cm2. They depend on the donors species and the laser mechanism. Intracentre population inversion is realized between particular excited states which are large-spaced due to the chemical shift of the donor binding energy. The lifetime of an electron in an excited state (up to ~70 ps) is determined by the efficiency of phonon-assisted nonradiative relaxation. Optical excitation by the emission of a frequency-tunable free electron laser results in two different types of lasing. At relatively low pump intensities (~1 kW/cm2) the intracentre mechanism of lasing is dominating. At pump intensities above ~100 kW/cm2 stimulated scattering of pump photons on transverse acoustic intervalley phonons can occur in the vicinity of an impurity atom. This results in laser emission in the frequency range from 4.6 to 5.8 THz. In this case the laser frequency can be tuned proportionally to the pump frequency

Terahertz lasers based on intracentre transitions of group V donors in uniaxially deformed silicon

This paper presents a brief overview of available experimental data on the characteristics of stimulated terahertz emission (4.9 – 6.4 THz) from optically excited neutral group V donors (phosphorus, antimony, arsenic and bismuth) in crystalline silicon subjected to uniaxial compressive strain along the [100] axis. Strain is shown to have a significant effect on the characteristics in question. Optimal strain depends on the dopant and may reduce the threshold pump intensity and improve lasing efficiency. We discuss possible mechanisms behind this effect and estimate the limiting output emission parameters

The evolution of epilepsy surgery between 1991 and 2011 in nine major epilepsy centers across the United States, Germany, and Australia.

OBJECTIVE: Epilepsy surgery is the most effective treatment for select patients with drug-resistant epilepsy. In this article, we aim to provide an accurate understanding of the current epidemiologic characteristics of this intervention, as this knowledge is critical for guiding educational, academic, and resource priorities. METHODS: We profile the practice of epilepsy surgery between 1991 and 2011 in nine major epilepsy surgery centers in the United States, Germany, and Australia. Clinical, imaging, surgical, and histopathologic data were derived from the surgical databases at various centers. RESULTS: Although five of the centers performed their highest number of surgeries for mesial temporal sclerosis (MTS) in 1991, and three had their highest number of MTS surgeries in 2001, only one center achieved its peak number of MTS surgeries in 2011. The most productive year for MTS surgeries varied then by center; overall, the nine centers surveyed performed 48% (95% confidence interval [CI] -27.3% to -67.4%) fewer such surgeries in 2011 compared to either 1991 or 2001, whichever was higher. There was a parallel increase in the performance of surgery for nonlesional epilepsy. Further analysis of 5/9 centers showed a yearly increase of 0.6 ± 0.07% in the performance of invasive electroencephalography (EEG) without subsequent resections. Overall, although MTS was the main surgical substrate in 1991 and 2001 (proportion of total surgeries in study centers ranging from 33.3% to 70.2%); it occupied only 33.6% of all resections in 2011 in the context of an overall stable total surgical volume. SIGNIFICANCE: These findings highlight the major aspects of the evolution of epilepsy surgery across the past two decades in a sample of well-established epilepsy surgery centers, and the critical current challenges of this treatment option in addressing complex epilepsy cases requiring detailed evaluations. Possible causes and implications of these findings are discussed

Analysis of the MBE&MBD Integration as a Tool for Value Creation in Industries

The thesis explores the current state of Model-based Enterprise (MBE) and Model-based Definition (MBD) in the industrial sector. The study consists of two main parts. The first part is a literature-based study on MBE and MBD's modern principles and market situation in the industrial sector. The second part of the thesis includes original data collected through a survey addressed to different manufacturing companies. It was designed to obtain real-world experience, perceived benefits, and current levels of implementation of MBE/MBD technologies in practice. The responses were analyzed, and conclusions were made about trends and future expectations. Both parts of the thesis aim to give a clear picture of the present and future role of MBE and MBD in modern manufacturing

Currently important pathogenic Listeria species affecting animals and birds (review)

Listeriosis is one of the most severe gastrointestinal diseases in the world. Listeria affect different groups of animals and birds. The pathogen has been detected in meat, milk, fish and fish products. The disease shows spring and autumn seasonality. It has been reliably established that Listeria monocytogenes is ubiquitous  in the environment. Listeria monocytogenes is a facultative intracellular pathogen. Infection with Listeria monocytogenes causes an invasive disease in animals and humans, which is transmitted via the fecal-oral route from an animal to a human, from a mother to a fetus. The pathogenesis of Listeria infection has been well studied. The gastrointestinal tract is the site of the pathogenic Listeria species transit and spread. The infection incubation period is 20–30 days in animals and humans. The clinical course in different animal species, including birds, has a number of specific features. Listeria can cross the intestinal, placental and blood-brain barriers. The manifestations of listeriosis include encephalitis, meningitis, gastritis, meningoencephalitis, mastitis, abortions, endometritis, etc. Pathogenic Listeria species show hemolytic activity which non-pathogenic species (except Listeria seeligeri) lack. The review presents the up-to-date information on the classification of Listeria, the pathogenicity factors of Listeria monocytogenes as the major pathogen, the mechanisms of Listeria infection development in different animal species

Terahertz emission from lithium doped silicon under continuous wave interband optical excitation

We report on experimental observation and study of terahertz emission from lithium doped silicon crystals under continuous wave band-to-band optical excitation. It is shown that radiative transitions of electrons from 2P excited states of lithium donor to the 1S(A1) donor ground state prevail in the emission spectrum. The terahertz emission occurs due to capture of nonequilibrium electrons to charged donors, which in turn are generated in the crystal as a result of impurity assisted electron-hole recombination. Besides the intracentre radiative transitions the terahertz emission spectrum exhibits also features at about 12.7 and 15.27 meV, which could be related to intraexciton transitions and transitions from the continuum to the free exciton ground state

Prospects of the application of curable decontamination solutions in problems of impact improving of nuclear power plants

The technology of power generation from nuclear power is accompanied by the formation of radioactive waste, which has significant potential environmental hazards. This paper proposes new methods of decontamination of NPP equipment with fluids that immediately after use can be converted into an environmentally safe condition - curing methods of decontamination solutions. A characteristic feature of curable solutions decontamination methods is that the composition of the decontamination solution, and also processes in the solution during deactivation, affect the subsequent transfer of this solution to a solid state, as well as on the properties of the matrix, which will be "sealed" removed radionuclides. The main factor determining the course of the process of decontamination methods can be divided into contact, acid-abrasive, ultrasound and combined. Concerning the main component of the decontamination solution (slurry) methods can be subdivided into solutions with hydraulic binders, clay slurry (with conventional clay and a clay with a high alumina content) suspension of diatomite and combined. The means of transfer of the solutions used in the solid state methods are divided into "self-curing" heat treatable and cemented. Application of methods of the curing solution allows us to reduce the number of operations to deactivate air conditioning that provides economic benefits and allows us to create a whole class of portable equipment and to reduce the amount ongoing to dump 4-6 times in comparison with cemented. © 2014 WIT Press.International Journal of Safety and Security Engineering;International Journal of Sustainable Development and Planning;WIT Transactions on Ecology and the Environmen