Many-electron transport in Aharonov-Bohm interferometers: Time-dependent density-functional study

We apply time-dependent density-functional theory to study many-electron transport in Aharonov-Bohm interferometers in a non-equilibrium situation. The conductance properties in the system are complex and depend on the enclosed magnetic flux in the interferometer, the number of interacting particles, and the mutual distance of the transport channels at the points of encounter. Generally, the electron-electron interactions do not suppress the visibility of Aharonov-Bohm oscillations if the interchannel distance -- determined by the positioning of the incompressible strips through the external magnetic field -- is optimized. However, the interactions also impose an interesting Aharonov-Bohm phase shift with channel distances below or above the optimal one. This effect is combined with suppressed oscillation amplitudes. We analyze these effects within different approximations for the exchange-correlation potential in time-dependent density-functional theory.Comment: to appear in Eur. J. Phys. B (2013

Post-harvest technology change in cassava processing: a choice paradigm

Open Access Article; Available online: 27 Jan 2020This study employed a choice model to examine the factors influencing the choice of post-harvest technologies in cassava starch processing, using a sample of five hundred and seventy (570) processors in the forest and guinea savanna zones of Nigeria. In addition, the profitability of various post-harvest technologies in the study area was assessed using the budgetary technique while the impact of improved post-harvest technology on processors’ revenue and output was analysed using the average treatment effect model. Sex of the processor, processing experience, income, and cost of post-harvest technology, the capacity of post-harvest technology and access to credit amongst others significantly influence the choice of post-harvest technologies. Although the use of improved post-harvest technology comes with a high cost, the net income from its use was higher than the other types of post-harvest technologies, suggesting that the use of improved techniques was more beneficial and profitable. In addition, using improved post-harvest technology had a positive and significant effect on output and income. These findings shows that investment in improved post-harvest technologies by cassava starch processors and other stakeholders would increase income, thus, improving welfare

On the Propagation of Whistler-Mode Waves in the 2 Magnetic Ducts

This paper studies extremely-low frequency (ELF) whistler-mode waves’ behavior within small-scale magnetic field irregularities in the Earth’s magnetosphere, known as magnetic ducts. Based on the magnetic fields’ magnitude inside and outside these ducts, they are categorized as high-magnetic ducts (HBD) and low-magnetic ducts (LBD). Using the whistler-mode dispersion relation analysis, our primary focus is to show that LBDs are prone to leak electromagnetic energy outside the duct. We further investigate the hypothesis that whistlers can propagate within LBDs without any signal loss when the width of the duct corresponds to an integer multiple of the perpendicular wavelengths of the waves inside it. This condition offers a straightforward and effective method for identifying non-leaking eigenmodes of LBDs. Our analysis of this non-leaking condition reveals that every LBD possesses a finite number of non-leaking eigenmodes directly proportional to the duct’s width and the magnitude of the ambient magnetic field within it. The analytical results are then validated using two-dimensional, time-dependent simulations of the electron-Magnetohydrodynamics (EMHD) model. Also, we model the non-leaking propagation of an ELF whistler-mode wave observed inside the LBD by the NASA Magnetospheric Multiscale mission (MMS) satellite

Whistler-Mode Waves in Magnetic Ducts

Observations from the NASA MMS satellites show packages of ELF whistler-mode waves localized inside the small-scale irregularities of the magnetic field. These irregularities are formed by the narrow field-aligned channels where the magnitude of the background magnetic field inside the channel is greater or less than outside. By analogy with the classical density ducts, we introduce the high-B duct (HBD), where the magnitude of the field inside the channel is greater than the outside, and the low-B duct (LBD), where the magnitude of the field inside the channel is less than the outside. We investigate the guiding of the ELF whistler-mode waves by high-B and low-B ducts. We derive the analytical criteria for the wave ducting by these ducts and confirm them with two-dimension, time-dependent simulations of the electron-MHD model. Also, we model ELF whistler mode waves observed inside the high-B and low-B ducts by MMS satellites

A Brief History of Web Crawlers

Web crawlers visit internet applications, collect data, and learn about new web pages from visited pages. Web crawlers have a long and interesting history. Early web crawlers collected statistics about the web. In addition to collecting statistics about the web and indexing the applications for search engines, modern crawlers can be used to perform accessibility and vulnerability checks on the application. Quick expansion of the web, and the complexity added to web applications have made the process of crawling a very challenging one. Throughout the history of web crawling many researchers and industrial groups addressed different issues and challenges that web crawlers face. Different solutions have been proposed to reduce the time and cost of crawling. Performing an exhaustive crawl is a challenging question. Additionally capturing the model of a modern web application and extracting data from it automatically is another open question. What follows is a brief history of different technique and algorithms used from the early days of crawling up to the recent days. We introduce criteria to evaluate the relative performance of web crawlers. Based on these criteria we plot the evolution of web crawlers and compare their performanc

University Students Perceptions Of Two Countries: Turkey And U.S.A.

This study was generated to understand how Turkish university students perceive their country and the U.S.A. and how U.S.A. university students perceive their country and Turkey. Perceptions are people's realities, and they use their perceptions to make decisions, form opinions and behave based on them. Perceptions may have tremendous impacts on the economic and political future relations for both countries. The paper was conceived and conducted by university faculty from both Turkey (Bahcesehir University, Istanbul Turkey) and the U.S.A. (Robert Morris University, Pittsburgh, PA). The authors would like to thank their colleagues who had their students complete the surveys

Fecundity of the common cuttlefish, Sepia officinalis L. (Cephalopoda, Sepiida): a new look at the old problem

The potential fecundity (PF) of advanced maturing and mature pre-spawning cuttlefish S. officinalis in the Aegean Sea varies from 3,700 to 8,000 (mean 5,871) oocytes, whereas the number of large yolk oocytes increases with mantle length from 130 to 839. Small oocytes predominate at all maturity stages. Spawning animals have a PF of some 1,000-3,000 eggs below that of pre-spawning females. This shows that intermittent spawning, which occurs in captivity, is a normal process in natural habitats. Empty follicular sheaths are resorbed very rapidly, and their number does not represent the number of eggs laid by the female prior to sampling. Regulative oocyte resorption was observed at early maturation in some cuttlefishes