Kondo effect of Co adatoms on Ag monolayers on noble metal surfaces

The Kondo temperature $T_K$ of single Co adatoms on monolayers of Ag on Cu and Au(111) is determined using Scanning Tunneling Spectroscopy. $T_K$ of Co on a single monolayer of Ag on either substrate is essentially the same as that of Co on a homogenous Ag(111) crystal. This gives strong evidence that the interaction of surface Kondo impurities with the substrate is very local in nature. By comparing $T_K$ found for Co on Cu, Ag, and Au (111)-surfaces we show that the energy scale of the many-electron Kondo state is insensitive to the properties of surface states and to the energetic position of the projected bulk band edges.Comment: 4 pages, 3 figure

Local pressure-induced metallization of a semiconducting carbon nanotube in a crossed junction

The electronic and vibrational density of states of a semiconducting carbon nanotube in a crossed junction was investigated by elastic and inelastic scanning tunneling spectroscopy. The strong radial compression of the nanotube at the junction induces local metallization spatially confined to a few nm. The local electronic modifications are correlated with the observed changes in the radial breathing and G-band phonon modes, which react very sensitively to local mechanical deformation. In addition, the experiments reveal the crucial contribution of the image charges to the contact potential at nanotube-metal interfaces

Application of hydrogenation to low-temperature cleaning of the Si(001) surface in the processes of molecular-beam epitaxy: Investigation by STM, RHEED and HRTEM

Structural properties of the clean Si(001) surface obtained as a result of low-temperature (470--650C) pre-growth annealings of silicon wafers in a molecular-beam epitaxy chamber have been investigated. To decrease the cleaning temperature, a silicon surface was hydrogenated in the process of a preliminary chemical treatment in HF and NH_4F aqueous solutions. It has been shown that smooth surfaces composed by wide terraces separated by monoatomic steps can be obtained by dehydrogenation at the temperatures > 600C, whereas clean surfaces obtained at the temperatures < 600C are rough. It has been found that there exists a dependence of structural properties of clean surfaces on the temperature of hydrogen thermal desorption and the process of the preliminary chemical treatment. The frequency of detachment/attachment of Si dimers from/to the steps and effect of the Ehrlich-Schwoebel barrier on ad-dimer migration across steps have been found to be the most probable factors determining a degree of the resultant surface roughness.Comment: 8 pages, 8 figures; version accepted to J. Appl. Phy

Quantum Coherence of Image-Potential States

The quantum dynamics of the two-dimensional image-potential states in front of the Cu(100) surface is measured by scanning tunneling microscopy (STM) and spectroscopy (STS). The dispersion relation and the momentum resolved phase-relaxation time of the first image-potential state are determined from the quantum interference patterns in the local density of states (LDOS) at step edges. It is demonstrated that the tip-induced Stark shift does not affect the motion of the electrons parallel to the surface.Comment: Submitted to Phys. Rev. Lett., 4 pages, 4 figures; corrected typos, minor change

Comparative analysis of sustainable development environmental indicators between worldwide, Portugal and Brasil and between two universities within these countries

Measuring the environmental performances by indicators is considered as a crucial step to keep track of progress towards sustainability. This study compares trends in environmental sustainability indicators worldwide, Portugal, Brazil and two universities in these countries. The data collection is done based on findings from the Organisation for Economic Co-operation and Development (OECD) between 2007 and 2017, and reports from both universities between 2010 and 2018. As a result, it can be seen that global Carbon Dioxide (CO2) emissions decreased (10.6 to 9 ton/capita). Portugal also reduced its CO2 till 2014 (5.2 to 4.6 ton/capita) but experienced a raise in its rates in the following years. Brazil experienced a growth in its CO2 (1.7 to 2 ton/capita), as did the Portuguese university (0.85 to 0.87ton/alumnus). World municipal waste decreased (541.8 to 524.4 kg/capita), as well as in Portugal until 2013 (513.7 to 436.7 kg/capita), but in the following years increased. Similarly, Brazil reduced the indexes until 2011 (271.9 to 266.8 kg/capita) and increased in 2012. In the Portuguese university, the rates increased until 2014 (4.02 to 9.02 kg/student) and reduced in 2015, as in the Brazilian university that increased until 2018 (19.53 to 25.08kg/student). Portugal, Brazil, and the two universities pointed out a trend of increasing emissions and waste while the world data a reduction. The Brazilian university had higher municipal waste rates than Portugal. The consumption of water and energy in the Portuguese university decreased while it increased the Brazilian university. Actions have already been undertaken at universities to lower the environmental burden by improving the energy efficiency of buildings through the use of cleaner energy, setting up mobility studies, and campaigns to reduce consumption and cut down waste generation.The authors acknowledge the CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) for its financial support for this study

Positive education: Learning and teaching for wellbeing and academic mastery

Over the past decade, positive education has emerged as a rapidly growing arm of positive psychology that has attracted both interest and critique. Through a case study, we show that positive education can positively impact students, teachers, and others within the educational community, but success is not immediate nor imminent. We suggest that successful positive education programs blend evidence-based learning from the science of positive psychology, best practices in learning and teaching, whole school strategy, and evaluation, and consider pedagogy, philosophical assumptions, and the school’s culture. Positive education must be studied, applied, and managed responsibly, as there is also potential that attempts are ineffective or do harm. Finally, we consider implications for training, teaching, and professional practice. Positive education has made significant progress, but future research and application will benefit from a unified theoretical framework that adequately incorporates educational knowledge and pedagogical practice

Kondo temperature of magnetic impurities at surfaces

Based on the experimental observation, that only the close vicinity of a magnetic impurity at metal surfaces determines its Kondo behaviour, we introduce a simple model which explains the Kondo temperatures observed for cobalt adatoms at the (111) and (100) surfaces of Cu, Ag, and Au. Excellent agreement between the model and scanning tunneling spectroscopy (STS) experiments is demonstrated. The Kondo temperature is shown to depend on the occupation of the d-level determined by the hybridization between adatom and substrate with a minimum around single occupancy.Comment: 4 pages, 2 figure

Lethal Parasites in Oysters from Coastal Georgia with Discussion of Disease and Management Implications

Extensive mortalities of oysters, Crassostrea virginica, occurred from 1985 through 1987 in coastal waters of Georgia. Fluid thioglycolate cultures of oysters collected from 16 of 17 locations revealed infections by the apicomplexan parasite Perkinsus marinus. An ascetosporan parasite, Haplosporidium nelsoni, was also observed in histopathological examination of oysters from 4 of the locations. While the range of H. nelsoni currently is recognized as the east coast of the United States from Maine to Florida, this is the first report of the parasite in Georgia waters. This paper documents the occurrence of these two lethal parasites in oysters from coastal waters of Georgia, along with potential disease and management implications. Results of an earlier independent and previously unpublished survey are also discussed which document the presence of P. marinus in Georgia as early as 1966