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

A novel procedure for the immediate reconstruction of severely resorbed alveolar sockets for advanced periodontal disease

Background. Several clinical techniques and a variety of biomaterials have been introduced over the years in an effort to overcome bone remodeling and resorption after tooth extraction. However, the predictability of these procedures in sockets with severely resorbed buccal/lingual plate due to periodontal disease is still unknown. Case Description. A patient with advanced periodontitis underwent extraction of upper right lateral and central incisors. The central incisor exhibited complete buccal bone plate loss and a 9 mm vertical bone deficiency on its palatal side. The alveolar sockets were filled with collagen sponge and covered with a nonresorbable high-density PTFE membrane. Primary closure was not attained and any rigid scaffold material was not used. Histologic analysis provided evidence of new bone formation. At 12 months a cone-beam computed tomographic scan revealed enough bone volume to insert two conventional dental implants in conjunction with minor horizontal bone augmentation procedures. Clinical Implications. This case report would seem to support the potential of the proposed reconstructive approach in changing the morphology of severely resorbed alveolar sockets, minimizing the need for advanced bone regeneration procedures during implant placement

Biological applications of synchrotron radiation infrared spectromicroscopy.

Extremely brilliant infrared (IR) beams provided by synchrotron radiation sources are now routinely used in many facilities with available commercial spectrometers coupled to IR microscopes. Using these intense non-thermal sources, a brilliance two or three order of magnitude higher than a conventional source is achievable through small pinholes (<10 mu m) with a high signal to-noise ratio. IR spectroscopy is a powerful technique to investigate biological systems and offers many new imaging opportunities. The field of infrared biological imaging covers a wide range of fundamental issues and applied researches such as cell imaging or tissue imaging. Molecular maps with a spatial resolution down to the diffraction limit may be now obtained with a synchrotron radiation IR source also on thick samples. Moreover, changes of the protein structure are detectable in an IR spectrum and cellular molecular markers can be identified and used to recognize a pathological status of a tissue. Molecular structure and functions are strongly correlated and this aspect is particularly relevant for imaging. We will show that the brilliance of synchrotron radiation IR sources may enhance the sensitivity of a molecular signal obtained from small biosamples, e.g., a single cell, containing extremely small amounts of organic matter. We will also show that SR IR sources allow to study chemical composition and to identify the distribution of organic molecules in cells at submicron resolution is possible with a high signal-to-noise ratio. Moreover, the recent availability of two-dimensional IR detectors promises to push forward imaging capabilities in the time domain. Indeed, with a high current synchrotron radiation facility and a Focal Plane Array the chemical imaging of individual cells can be obtained in a few minutes. Within this framework important results are expected in the next years using synchrotron radiation and Free Electron Laser (FEL) sources for spectro-microscopy and spectral-imaging, alone or in combination with Scanning Near-field Optical Microscopy methods to study the molecular composition and dynamic changes in samples of biomedical interest at micrometric and submicrometric scales, respectively. (c) 2012 Elsevier Inc. All rights reserved

Sustainability-Based Framework Development and Specification for Coal Phase-out Policy: Just Transition and Sustainability Requirements in the Canadian Context

Following the Paris Agreement and the commitment to the NDCs (Nationally Determined Contributions) by its members, Canada has reinforced the engagement with a decrease of fossil fuel consumption through a federal policy to phase-out coal by 2030. This thesis analyzes the necessary sustainability criteria reliant on socio-ecological and economic aspects to assess national coal phase-out policy with particular attention to the Canadian case. The research discusses the specification of essential sustainability-based criteria for national coal phase-out policy with just transition and sustainability requirements and integrates other specific sustainability criteria, illuminated by the Canadian case study. The proposed sustainability framework for coal phase-out policy instruments brings to light the necessity of an integrative approach, embedding essential issues for sustainable national climate change policy such as equity and just transition principles in alliance with environmental requirements. This research identifies the benefits of an integrative and robust sustainability framework to promote environmental progress and equity for transition processes to a low carbon economy. This thesis work aims to answer three central research questions: Firstly, what specific requirements are needed to ensure a coal phase-out policy is aligned with contributions to sustainability, with particular attention to climate change mitigation and just transition? Secondly, what can be learned from coal phase-out experiences already implemented globally in terms of strategies and tools applied, challenges, barriers, and drivers for coal phase-out? Thirdly, how can the characteristics of the Canadian design and implementation of coal phase-out policy inform the development and specification of a sustainability-based framework for informing national coal phase-out policies? To address these questions, the thesis builds on Gibson et al.'s (2005) sustainability assessment framework and adapts it to coal phase-out policies. The resulting framework comprises five key categories: socio-ecological system integrity and compliance with fundamental climate change mitigation objectives, livelihood sufficiency, affordability, equity, and opportunity, social dialogue, participatory decision-making, and democratic governance, Adaptability, precaution, and monitoring for long-term sustainability, and Governance accountability, inter-jurisdictional collaboration, and government support. The framework is tested through application to the Canadian case study, which not only validates and enhances its criteria but also provides context-specific insights. The study emphasizes multi-level governance, inclusive engagement, transition fuel challenges, community vulnerability, and establishment of governance bodies as crucial aspects in coal phase-out policy. In conclusion, this research contributes a holistic sustainability-based framework for assessing and guiding coal phase-out policies. Its application to the Canadian case underscores its practical value while acknowledging the need for context-specific adaptation. By promoting an integrated approach that encompasses social, economic, and environmental dimensions, the framework offers a pathway towards sustainable and equitable coal phase-out, essential for a low carbon future

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

Cloud-Enhanced Robotic System for Smart City Crowd Control

Cloud robotics in smart cities is an emerging paradigm that enables autonomous robotic agents to communicate and collaborate with a cloud computing infrastructure. It complements the Internet of Things (IoT) by creating an expanded network where robots offload data-intensive computation to the ubiquitous cloud to ensure quality of service (QoS). However, offloading for robots is significantly complex due to their unique characteristics of mobility, skill-learning, data collection, and decision-making capabilities. In this paper, a generic cloud robotics framework is proposed to realize smart city vision while taking into consideration its various complexities. Specifically, we present an integrated framework for a crowd control system where cloud-enhanced robots are deployed to perform necessary tasks. The task offloading is formulated as a constrained optimization problem capable of handling any task flow that can be characterized by a Direct Acyclic Graph (DAG).We consider two scenarios of minimizing energy and time, respectively, and develop a genetic algorithm (GA)-based approach to identify the optimal task offloading decisions. The performance comparison with two benchmarks shows that our GA scheme achieves desired energy and time performance. We also show the adaptability of our algorithm by varying the values for bandwidth and movement. The results suggest their impact on offloading. Finally, we present a multi-task flow optimal path sequence problem that highlights how the robot can plan its task completion via movements that expend the minimum energy. This integrates path planning with offloading for robotics. To the best of our knowledge, this is the first attempt to evaluate cloud-based task offloading for a smart city crowd control system

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