First-principles calculations and bias-dependent STM measurements at the alpha-Sn/Ge(111) surface: a clear indication for the 1U2D configuration

The nature of the alpha-Sn/Ge(111) surface is still a matter of debate. In particular, two possible configurations have been proposed for the 3x3 ground state of this surface: one with two Sn adatoms in a lower position with respect to the third one (1U2D) and the other with opposite configuration (2U1D). By means of first-principles quasiparticle calculations we could simulate STM images as a function of bias voltage and compare them with STM experimental results at 78K, obtaining an unambiguous indication that the stable configuration for the alpha-Sn/Ge(111) surface is the 1U2D. The possible inequivalence of the two down Sn adatoms is also discussed.Comment: Submitted to PR

Observation of Buried Phosphorus Dopants near Clean Si(100)-(2x1) with Scanning Tunneling Microscopy

We have used scanning tunneling microscopy to identify individual phosphorus dopant atoms near the clean silicon (100)-(2x1) reconstructed surface. The charge-induced band bending signature associated with the dopants shows up as an enhancement in both filled and empty states and is consistent with the appearance of n-type dopants on compound semiconductor surfaces and passivated Si(100)-(2x1). We observe dopants at different depths and see a strong dependence of the signature on the magnitude of the sample voltage. Our results suggest that, on this clean surface, the antibonding surface state band acts as an extension of the bulk conduction band into the gap. The positively charged dimer vacancies that have been observed previously appear as depressions in the filled states, as opposed to enhancements, because they disrupt these surface bands.Comment: 4 pages, 3 figures. TeX for OSX from Wierde

Analysis of infected human mononuclear cells by atomic force microscopy

The surfaces of the human lymphoid cells of the line H9 chronically infected with the Human Immunodeficiency Virus HIV-1, and of human monocytes acutely infected in vitro with Mycobacterium Tuberculosis (MTB) were dried, fixed and imaged with atomic force microscopy (AFM). These images were compared with those of non-infected samples. Dried and fixed samples of infected cells can be distinguished from non-infected ones by AFM technology due to their different surface structures and by the presence of pathogenic (viz al or mycobacterial) agents on the cell surface

Atomic Force Microscopy of Neuron Networks

We imaged uncoated neuron networks by an atomic force microscope in the repulsive regime of contact mode. Images of granule cells and their axons have been clearly revealed with details smaller than 20 nm. The good stability of the sample and the mechanical reproducibility of the microscope allowed the imaging of a neuron culture area of several square microns. By combining tens of images, we were able to reconstruct a highly defined neuronal network. Furthermore, the images were very reproducible over repeated scanning acquisition, demonstrating the mechanical and thermal stability of the instrument-sample system

Effect of polyoxometalates on synaptic plasma membrane structure

12-tungstosilicic acid (SiW12) and decavanadate (V10) are polyoxometalate compounds (POMs) exhibiting biological activity. In vitro studies of the influence SiW12 and V10 on synaptic plasma membrane (SPM) acetylcholinesterase (AChE) and Na,K-ATPase, respectively, showed that these POMs inhibit the enzyme activities in submicromolar concentrations. As Na,K-ATPase and AChE are membrane associated enzymes, the inhibition of their activities can result from the membrane changes induced by the inhibitor binding. Thus, the effect of SiW12 and V10 on the membrane structure was investigated by using Atomic Force Microscopy (AFM) technique. The obtained results demonstrated that the calculated average roughness values for SiW12 and V10 treated SPM were significantly higher (about 6 and 1.5 times, respectively), compared to untreated SPM preparation. The obtained changes indicate that both investigated POMs bind to the plasma membranes, and consequently their approved strong inhibitory potencies toward the membrane bound enzymes might be assigned to the induced membrane modifications.14th international conference on fundamental and applied aspects of physical chemistry; 24-28 September 2018, Belgrade, Serbia

Roughness of the plasma membrane as an independent morphological parameter to study RBCs: A quantitative atomic force microscopy investigation

AbstractA novel approach to the study of RBCs based on the collection of three-dimensional high-resolution AFM images and on the measure of the surface roughness of their plasma membrane is presented. The dependence of the roughness from several parameters of the imaging was investigated and a general rule for a trustful analysis and comparison has been suggested. The roughness of RBCs is a morphology-related parameter which has been shown to be characteristic of the single cells composing a sample, but independent of the overall geometric shape (discocyte or spherocyte) of the erythrocytes, thus providing extra-information with respect to a conventional morphology study. The use of the average roughness value as a label of a whole sample was tested on different kinds of samples. Analyzed data revealed that the quantitative roughness value does not change after treatment of RBCs with various commonly used fixation and staining methods while a drastic decrease occurs when studying cells with membrane–skeletal alteration both naturally occurring or artificially induced by chemical treatments. The present method provides a quantitative and powerful tool for a novel approach to the study of erythrocytes structure through an ultrastructural morphological analysis with the potential to give information, in a non-invasive way, on the RBCs function

A Pilot Trial of Social Media in a Technical Area

This paper reports on a project undertaken to trial social networking with Telecommunications students and staff from Swinburne University of Technology. Web 2:0 technologies including social networking sites can encourage informal conversation, dialogue, collaborative content generation, and knowledge sharing, giving students access to a wide range of ideas. A Ning was used with the intention of engaging students and staff in informal discussions relating to the Telecommunications industry in general, rather than course material directly. Although staff contributed enthusiastically and a large number of students enrolled, student participation was low. Follow-up surveys and informal discussions revealed reasons for the low student participation included the risk of appearing foolish in front of peers and teachers, and an intention to use the Ning in a passive manner by seeing what others are doing without necessarily contributing themselves. We conclude that social media in education may be useful but needs some incentive for it to be adopted by students

Gender differences in internet addiction: A study on variables related to its possible development

Internet addiction and its related variables (i.e., internet gaming addiction, social media addiction, fear of missing out, phubbing) have mostly been investigated in the general population without considering possible gender differences. The present study aimed to investigate the specific characteristics of men and women in the possible development of pathological behaviors related to internet addiction. A total of 276 participants (of ages ranging from 18 to 30 years old) were recruited in the study (46.7% were males) and responded to online questionnaires on variables related to internet addiction and psychological traits. The results showed that gender represents a key factor in explaining why individuals are addicted to the internet in different ways. Stepwise linear regression analyses showed that both genders shared social media addiction as the primary predictor of internet addiction but also exclusive predictors for each gender. Knowing the variables underlying the development of internet Addiction can be useful for both prevention and treatment and tailoring intervention for this addictive behavior