Atomic theory of the scanning tunneling microscope

Ankara : The Department of Physics and the Institute of Graduate Studies of Bilkent Univ. , 1988.Thesis (Master's) -- Bilkent University, 1988.Includes bibliographical references leaves 93-99.The Scanning Tunneling Microscope is proven to be one of the most powerful tools for surface structure determination. Present theories are able to explain the operation of the microscope when the tip is far from the surface. For the small tip height case the atomic-scale interaction of the tip and the surface has to be included in the theory. The electronic structure of the combined system of the tip and the surface is calculated with an Empirical Tight Binding approach for graphite. It is found that in the vicinity of the tip some Tip Induced Localized States are formed. These states play an important role in the tunneling phenomenon. The contribution of these states to the tunneling current is calculated.Tekman, Ahmet ErkanM.S

Examination of "our country and cultural values" theme in the primary education turkish textbooks

The main aim of the Turkish course is to help students gain language skills. Besides language skills, teaching cultural values and transferring them to the next generation are also important. The material and moral values ​​of a society are carried from the past to the present through language. For this reason, not only the activities that develop the language skills but also the elements of the culture of that society must be included in the Turkish textbooks. The aim of this study is to examine to what extent the elements of the culture of the Turkish Cypriot community are included in the Turkish textbooks published by the TRNC Ministry of National Education. In order to collect data, by using document analysis method and scanning technique, in the "our country and cultural values" theme in the Turkish textbook which is used by TRNC Primary Education for 2.-8. grade levels, the findings related to the culture of Turkish Cypriot community, traditions and customs, works of art, folk dances, food and beverage were determined by content analysis. According to the findings, it was found out that the most intense cultural elements were in the Geography/Places and Food and Beverage category, and the least cultural elements were in the Folk Dances / Sports, Children's Games and Religion-Faith categories. In the other categories, a weak content was found out

Marine Debris Floating in Arctic and Temperate Northeast Atlantic Waters

Floating marine debris is ubiquitous in marine environments but knowledge about quantities in remote regions is still limited. Here, we present the results of an extensive survey of floating marine debris by experts, trained scientists from fields other than pollution or non-professional citizen scientists. A total of 276 visual ship-based surveys were conducted between 2015 and 2020 in the Northeast (NE) Atlantic from waters off the Iberian Peninsula to the Central Arctic, however, with a focus on Arctic waters. Spatiotemporal variations among regional seas (Central Arctic, Barents Sea, Greenland Sea, Norwegian Sea, North Sea) and oceanic regions (Arctic waters and the temperate NE Atlantic) were explored. The overall median debris concentration was 11 items km-2, with considerable variability. The median concentration was highest in the North Sea with 19 items km-2. The Nordic seas, except the Central Arctic showed median concentrations ranging from 9 to 13 items km-2. Plastic accounted for 91% of all floating items. Miscellaneous fragments, films, ropes and nets, packaging materials, expanded polystyrene and straps were the most frequently observed plastic types. Although the median debris concentration in the Central Arctic was zero, this region was not entirely free of floating debris. The variations between regional seas and oceanic regions were statistically not significant indicating a continuous supply by a northward transportation of floating debris. The data show a slight annual decrease and clear seasonal differences in debris concentrations with higher levels observed during summer. A correlation between debris concentrations and environmental and spatial variables was found, explaining partly the variability in the observations. Pollution levels were 500 times lower than those recorded on the seafloor indicating the seafloor as a sink for marine debris. The Arctic was characterised by similar pollution levels as regions in temperate latitudes highlighting that Arctic ecosystems face threats from plastic pollution, which add to the effects of rapid climate change

Critical study of perturbative approaches to tunneling

One of the long-lasting objectives of the theory of tunneling is to express the transmission probability in terms of the wave functions of infinitely separated electrodes. This can be achieved by the application of a perturbative approach to tunneling; in this context the transfer Hamiltonian method has been developed and used. In cases such as scanning tunneling microscopy operating at small tip-sample separation, however, it becomes necessary to go beyond the original transfer Hamiltonian method. In this study we examine the modified forms of the transfer Hamiltonian method using exactly solvable one-dimensional tunneling systems. We find that it is possible to calculate the transmission probability approximately by choosing appropriate boundary conditions for the wave functions used in the transition matrix element expression. However, for low and thin barriers these modified methods still fail to give the correct results. On the other hand, Green's-function techniques which extend the perturbation to all orders yield exact results irrespective of the boundary condition chosen at the interface. © 1992 The American Physical Society

Citizen scientists reveal: marine litter pollutes Arctic beaches and affects wild life

Recent data indicate accumulation areas of marine litter in Arctic waters and significant increases over time. Beaches on remote Arctic islands may be sinks for marine litter and reflect pollution levels of the surrounding waters particularly well. We provide the first quantitative data from surveys carried out by citizen scientists on six beaches of Svalbard. Litter quantities recorded by cruise tourists varied from 9-524 g m-2 and were similar to those from densely populated areas. Plastics accounted for >80% of the overall litter, most of which originated from fisheries. Photographs provided by citizens show deleterious effects of beach litter on Arctic wildlife, which is already under strong pressure from global climate change. Our study highlights the potential of citizen scientists to provide scientifically valuable data on the pollution of sensitive remote ecosystems. The results stress once more that current legislative frameworks are insufficient to tackle the pollution of Arctic ecosystems

LITTERBASE - Online Portal for Marine Litter & Microplastics and their Implications for Marine Life

Contamination of the oceans with anthropogenic litter is a global environmental problem which currently receives increasing attention by scientists, policy makers, public authorities, media and the general public. Although research efforts have been intensified, they often do not provide stakeholders with easily understandable information about the dimensions and the extent of the problem. We have developed an online portal to provide easily digestible and continuously updated information on marine litter and microplastics to stakeholders based on scientific literature on a global scale. LITTERBASE gives insight about the distribution of marine litter and its effects on marine biota. Data from 1,420 scientific studies (status 09/10/2017) have been compiled into global maps and real-time graphs to make scientific knowledge accessible to the public. Bibliometric data of all publications were entered, as were metadata pertaining to litter type, litter size, litter quantity unit, aquatic system, biome and total litter quantity. Litter quantities were standardised to the most frequently used units to achieve comparability. Data on biological interactions with litter were also extracted: location of field records, number of species affected, percentage of individuals affected, type of interaction, effects on biota, litter type, litter size, aquatic system and biome. Currently, 1,441 species (status 09/10/2017) have been found to interact with marine litter resulting in mortality in almost 20% of the cases. Web statistics reveal that the information displayed in the LITTERBASE online portal is continuously being retrieved by users from all over the world

Tackling Marine Litter - LITTERBASE

Anthropogenic litter contamination of the oceans is a global problem of growing concern and currently receives strongly increasing attention by policy makers, public authorities, media and the general public. Unlike many other pollutants, marine litter on beaches and its deleterious effects on marine mammals, birds and turtles have attracted much attention as they can be directly observed by stakeholders