Surface and Step Conductivities on Si(111) Surfaces

Four-point measurements using a multi-tip scanning tunneling microscope (STM) are carried out in order to determine surface and step conductivities on Si(111) surfaces. In a first step, distance-dependent four-point measurements in the linear configuration are used in combination with an analytical three-layer model for charge transport to disentangle the 2D surface conductivity from non-surface contributions. A termination of the Si(111) surface with either Bi or H results in the two limiting cases of a pure 2D or 3D conductance, respectively. In order to further disentangle the surface conductivity of the step-free surface from the contribution due to atomic steps, a square four-probe configuration is applied as function of the rotation angle. In total this combined approach leads to an atomic step conductivity of $\sigma_\mathrm{step} = (29 \pm 9)$ $\mathrm{\Omega}^{-1} \mathrm{m}^{-1}$ and to a step-free surface conductivity of $\sigma_\mathrm{surf} = (9 \pm 2) \cdot 10^{-6}\,\mathrm{\Omega}^{-1}/\square$ for the Si(111)-(7$\times$7) surface.Comment: Main paper: 5 pages, 4 figures, Supplemental material: 6 pages, 3 figures. The Supplemental Material contains details on the sample preparation and measurement procedure, additional experimental results for Si(111) samples with different doping levels, and the description of the three-layer conductance mode

Photothermal heterodyne imaging of individual nonfluorescent nanoclusters and nanocrystals

We introduce a new, highly sensitive, and simple heterodyne optical method for imaging individual nonfluorescent nanoclusters and nanocrystals. A 2 order of magnitude improvement of the signal is achieved compared to previous methods. This allows for the unprecedented detection of individual small absorptive objects such as metallic clusters (of 67 atoms) or nonluminescent semiconductor nanocrystals. The measured signals are in agreement with a calculation based on the scattering field theory from a photothermal-induced modulated index of refraction profile around the nanoparticle

A Master equation approach to modeling an artificial protein motor

Linear bio-molecular motors move unidirectionally along a track by coordinating several different processes, such as fuel (ATP) capture, hydrolysis, conformational changes, binding and unbinding from a track, and center-of-mass diffusion. A better understanding of the interdependencies between these processes, which take place over a wide range of different time scales, would help elucidate the general operational principles of molecular motors. Artificial molecular motors present a unique opportunity for such a study because motor structure and function are a priori known. Here we describe use of a Master equation approach, integrated with input from Langevin and molecular dynamics modeling, to stochastically model a molecular motor across many time scales. We apply this approach to a specific concept for an artificial protein motor, the Tumbleweed.Comment: Submitted to Chemical Physics; 9 pages, 7 figure

Sustainability Reporting - A Challenge for Serbian Companies

The purpose of this paper is to point out that sustainability reporting is also important for companies which are operating in developing countries, such as Serbia, but they have a lot of challenges on the road to sustainability reporting. The aim of the conducted research is to determine the level of sustainability reporting by the companies based in Serbia, to consider to which extent they are familiar with the sustainability reporting guidelines and to identify the application level of the Global Reporting Initiative (GRI) Guidelines in the preparation of sustainability reports. The research is realized by the method of descriptive statistics and correlation analysis. The results of the study show that the level of sustainability reporting by Serbian companies included in the sample is low and not satisfactory

Carbon Accounting in the Public Sector - Challenges, Approaches and Perspectives for Municipalities

Nowadays, combating climate change and its effects due to the anthropogenic greenhouse effect is one of the central challenges for society and politics in order to prevent further increase of greenhouse gases in the atmosphere and thus become climate neutral. An indispensable prerequisite for the selection, implementation and monitoring of the effectiveness of measures to reduce greenhouse gas emissions is the measurement and accounting of emissions through the implementation of a carbon accounting system. Compared to companies, the topic of carbon accounting at the municipality level has so far received less public attention. Therefore, this paper deals with the specific challenges, the approaches and the perspectives of municipal carbon accounting

Structure of DNA-Functionalized Dendrimer Nanoparticles

Atomistic molecular dynamics simulations have been carried out to reveal the characteristic features of ethylenediamine (EDA) cored protonated poly amido amine (PAMAM) dendrimers of generation 3 (G3) and 4 (G4) that are functionalized with single stranded DNAs (ssDNAs). The four ssDNA strands that are attached via alkythiolate [-S (CH2)6-] linker molecule to the free amine groups on the surface of the PAMAM dendrimers observed to undergo a rapid conformational change during the 25 ns long simulation period. From the RMSD values of ssDNAs, we find relative stability in the case of purine rich ssDNA strands than pyrimidine rich ssDNA strands. The degree of wrapping of ssDNA strands on the dendrimer molecule was found to be influenced by the charge ratio of DNA and the dendrimer. As G4 dendrimer contains relatively more positive charge than G3 dendrimer, we observe extensive wrapping of ssDNAs on the G4 dendrimer. The ssDNA strands along with the linkers are seen to penetrate the surface of the dendrimer molecule and approach closer to the center of the dendrimer indicating the soft sphere nature of the dendrimer molecule. The effective radius of DNA-functionalized dendrimer nanoparticle was found to be independent of base composition of ssDNAs and was observed to be around 19.5 {\AA} and 22.4 {\AA} when we used G3 and G4 PAMAM dendrimer as the core of the nanoparticle respectively. The observed effective radius of DNA-functionalized dendrimer molecule apparently indicates the significant shrinkage in the structure that has taken place in dendrimer, linker and DNA strands. As a whole our results describe the characteristic features of DNA-functionalized dendrimer nanoparticle and can be used as strong inputs to design effectively the DNA-dendrimer nanoparticle self-assembly for their active biological applications.Comment: 13 pages, 10 figures, 3 Table

EFFECT OF KINESIO TAPING ON PERFORMANCE IN COUNTER-MOVEMENT JUMP

The purpose of this study was to identify the influence of taping with a flexible tape on jumping performance and its effects on the impulse in a stretch-shortening cycle movement. 23 subjects were divided in control group and intervention group. The subjects participated in two trials of vertical counter-movement jumps. In the trial, the knee extensors of the subjects in the intervention group were taped with an activating taping technique. Reaction forces of the jump were measured with an AMTI-force plate. Results showed no significant differences (ANOVA,

Influence of start temperature on tensile stress testing of restrained asphalt concrete specimens

U ovom se radu prikazuju rezultati ispitivanja vlačnog naprezanja pridržanih uzoraka obavljenog na uzorcima asfaltbetona AC 8 s bitumenom 50/70, pri čemu su korištene dvije početne temperature +10 °C i +20 °C. Analiza rezultata pokazuje da je razlika između tih dviju početnih temperatura beznačajna te da su rezultati u okviru standardnih zahtjeva točnosti. S druge strane, uočena je razlika između rezultata ispitivanja dobivenih u dva laboratorija: TU Beč i ZAG Ljubljana, gdje su ispitivanja obavljena u skladu s EN 12697-46 pri početnoj temperaturi od +20 °C.This paper presents the result of the Tensile Stress Restrained Specimen Tests on specimens of asphalt concrete AC 8 with bitumen 50/70 depending on two starting temperatures of +10 °C and +20 °C. The analysis of the results shows that there is only a non significant difference between these two start temperatures and the results are within the limit of standard precision. On the other hand, there is a difference between the results of two laboratory TU Wien and ZAG Ljubljana, who carried out the tests in accordance with EN 12697-46 at start temperature +20 °C