bluuebunny/crossref_metadata_2025 huggingface dataset:
Les réseaux sociaux dans le canal de distribution traditionnel au Maroc : l’exemple des Souassa
Authors: Balambo Mohammed Amine , Elbaz Jamal
Published: May 2016

Plusieurs recherches constatent le contrôle des Amazighs du commerce de détail au Maghreb. Au Maroc, les Souassa 1 sont réputés maîtriser et contrôler le canal de distribution traditionnel. Cet article a pour objectif de comprendre la nature et les bases de développement de la confiance dans les réseaux sociaux liés à ce canal de distribution traditionnel. Il vise ainsi à démontrer que la nature de la confiance développée obéît aux caractéristiques culturelles du réseau dans lequel les acteurs sont encastrés. Pour étudier le contexte du canal de distribution traditionnel au Maroc, cet article se fondera sur la théorie de l’échange social, celle de l’encastrement dans les réseaux sociaux, et la théorie de la culture. En adoptant une approche exploratoire, nous nous baserons sur des entretiens semi-directifs avec guide d’entretien, qui feront l’objet d’une analyse thématique de contenu. Classification JEL : L22
Philosopher après les EMI
Authors: Flipo Yann
Published: May 2016

Les expériences de mort imminente se sont multipliées avec les techniques de réanimation. La masse considérable de témoignages déborde désormais le cadre du mysticisme ou de l’ésotérisme et fait du phénomène EMI une sorte d’hypothèse de grande ampleur qu’il convient au philosophe d’explorer, qu’il prenne ou non position sur la question de savoir si les EMI sont ou non une émanation du cerveau. Les témoignages seuls ont sans doute déjà modifié notre philosophie de la mort, et notre philosophie tout court.
« Le boudoir de la mort » : le couloir de la mort…
Authors: Pierre Étienne
Published: May 2016

Si la mort n’est qu’un « accident de la vie », selon le mot de Bichat, chez Sade elle s’en détache pour devenir un médiateur du plaisir. Et comme le plaisir est chez le divin marquis pluriel, la mort elle-même prend une multitude de figures dont la finalité est de réduire l’Homme à l’état de chose érotique, et ainsi de provoquer Dieu à travers la négation de l’acte majeur de la Création.
Quelles garanties pour la procédure d’engagements en droit de la concurrence de l’Union européenne ?
Authors: Marty Frédéric , Mezaguer Mehdi
Published: May 2016

Les procédures négociées constituent avec l’approche par les effets l’un des deux piliers de la modernisation de la politique européenne de la concurrence. Cette modernisation cherche à accroître la sécurité juridique de l’ensemble des parties prenantes, en limitant à la fois le risque de faux-positifs et le risque d’annulation de décisions dans le cadre du contrôle juridictionnel, et à permettre de réaliser des gains d’efficience, notamment en termes procéduraux. Le recours à ces procédures, très significatif dans le secteur de l’énergie et dans celui des industries logicielles, a cependant suscité de nombreuses critiques. Celles-ci tiennent notamment au risque de voir s’imposer des remèdes disproportionnés ou imparfaitement reliés au problème de concurrence ou encore de priver les parties prenantes de certains de leurs droits fondamentaux, au travers notamment de la limitation de la portée du contrôle juridictionnel. Cet article analyse ces risques et propose quelques voies de maîtrise de ces derniers.
Effect of Rotational Component Alignment on Clinical Outcome 5 to 7 Years After TKA With the Columbus Knee System
Authors: Thielemann Friedrich W. , Konstantinids Lukas , Herget Georg W. , Knothe Dagmar , Helwig Peter , Sudkamp Norbert P. , Hauschild Oliver
Published: May 2016

The aim of the study was to examine the effects of rotational component alignment on outcome after total knee arthroplasty (TKA) with a minimum follow-up of 5 years. For this study, 96 patients were available for follow-up at a mean of 5.7 years after TKA. Computed tomography scans were available in 55 patients. Outcome (Oxford Knee Score [KSS], Knee Injury and Osteoarthritis Outcome Score [KOOS], 36-item Short Form Health Survey) was correlated with postoperative femoral and tibial component malrotation or femorotibial rotational alignment mismatch. Results showed that femoral or tibial component malrotation or femorotibial mismatch were present in 15.5%, 38.2%, and 29.1% of patients, respectively. Although femoral componoent malrotation was associated with significantly poorer, KSS and KOOS scores, outcome was comparable for patients with or without tibial component malrotation or femorotibial mismatch. In conclusion, both internal and external rotational femoral malalignment exceeding 3° is associated with significantly poorer subjective and objective outcome 5 to 7 years after TKA. Tibial component malrotation and femorotibial mismatch were more common, but did not significantly compromise outcome. [
Orthopedics
. 2016; 39(3):S50–S55.]
Economics of All-Polyethylene Versus Metal-Backed Tibial Prosthesis Designs
Authors: Chambers Monique C. , El-Othmani Mouhanad M. , Sayeed Zain , Anoushiravani Afshin , Schnur Anne-Kathrin , Mihalko William M. , Saleh Khaled J.
Published: May 2016

With the large number of total knee arthroplasties being performed and expectations that these numbers will be on the rise over the coming decades, efforts to provide cost-efficient care are of greater interest. The preferred design of knee arthroplasty implants has changed over time, with the original all-polyethylene tibial (APT) design being replaced by metal-backed tibial (MBT) components, as well as more recent considerations of newer APT designs. Modern APT components have been shown to have similar or superior outcomes than MBT components. Despite their limitations, APT components can be used to reduce the economic burden to the provider, medical institution, and health care system as a whole. There is a paucity of evidence-based literature directly comparing the cost associated with APT and MBT components. The purpose of this report is to review the literature to assess the available data regarding direct and indirect costs of both designs so that orthopedic surgeons can account for economic differences in everyday practice. [
Orthopedics
. 2016; 39(3):S61–S66.]
Assessing Tibial Tray Rotation in TKA: A Cadaveric Study
Authors: Hakki Sam , El-Othmani Mouhanad M. , Gabriel Christian , Mihalko William M. , Saleh Khaled J.
Published: May 2016

Tibial anatomical landmarks for transverse plane rotation of the tibial tray have not been validated. The current authors propose aligning the tibial tray with both the anterior tibial center point of rotation (ATCPR) and the femoral trochlear groove (FTG) to establish the ideal tibial tray rotation in total knee arthroplasty (TKA). When the tibial tray centerline was aligned with ATCPR and FTG lines, the mean range of motion (ROM) was 144.3° (preoperatively 145°) and tibial rotation range was 22.8 mm (preoperatively, 24.9 mm). When the tibial component was rotated 5 mm medially to the ATCPR, the knee ROM decreased in flexion with patellar subluxation, while it decreased in extension when rotated 5 mm laterally. This method identifies the ideal tibial tray rotation in TKA, at which maximal range of tibial rotation and knee ROM are achieved without obvious overriding of components. [
Orthopedics
, 2016; 39(3):S67–S71.]
Development of Network Interactive Teaching Materials and Empirical in "Management" Courses
Authors: JIA Xiaobo , HUANG Juying
Published: May 2016

network interactive teaching material utilizes multimedia technology for digital processing of traditional paper content and makes the teaching material suitable for various electronic terminals. Network interactive teaching material making is closely related to the development of distance teaching. This paper mainly takes Human Resource Management as the experimental course, utilizes teaching resource cloud platform of augmented reality interactive teaching materials for empirical study on the application of network interactive teaching material in Human Resource Management course, discusses the application effect of new distance education and teaching resources, offers theoretical and data support for development of network interactive teaching material and distance education and exploits potential development direction of future course construction.
Contributions of Collaborative and Immersive Environments in Development a Remote Access Laboratory
Authors: Zamora Ronald , Vélez Jeimy , Villa Jose L.
Published: May 2016

The implementation of remote access laboratories by universities is a growing tendency. Worldwide its implementation has been carried out in different disciplines using different technologies, interfaces and protocols. In this sense, it is logical to conclude that there is no fixed methodology or standard for its implementation, which leads researchers to question its effectiveness and differentiation for learning purposes during lab work. It is equally necessary to mention the importance of using collaborative and immersive environment tools to perform lab exercises with remote access since they complement its use and application. In this chapter, is presented the contributions by the implementation of collaborative and immersive environments in the development of laboratory with remote access from the point of view of its effectiveness and differentiation in learning.
Personalisation of 3D Virtual Spaces for Enhanced Ubiquitous Learning
Authors: Saleeb Noha , Dafoulas Georgios A. , Loomes Martin
Published: May 2016

This study explores, using experiments, the effects of different architectural design features of 3D virtual educational buildings on higher-education learners during online e-learning sessions. Architectural features tested include shape, lighting, dimensions, colours and textures. Learners are divided into three groups: under-graduates, post-graduates, and adult learners. Results are demonstrated comprising charts and statistics capturing the extent of learners' enjoyment, information retention, and participation from being inside different 3D virtual spaces with different design characteristics. Consequently, design characteristics causing highest student retention, participation and contentment are established for design of a better 3D virtual learning environment (VLE). These provide guidelines for customised design practices inside 3DVLEs to create 3D virtual educational spaces best suited for ubiquitous “any-time” “any-place” e-learning of each individual student. This will aid in guiding the otherwise current ad-hoc design approach to building educational facilities in 3DVLEs.
Architectures for 3D Virtual Environments
Authors: Rique Thiago Pereira , Nascimento Samara Martins , Fujioka Rodrigo da Cruz , da Fonseca de Souza Fernando
Published: May 2016

A very important aspect in the development of systems that allow access to virtual environments is their architecture, along with both the requirements and the type of offered services, once they significantly affect the design of an application. The concept of architecture refers to how the components that constitute a software system are arranged, their interfaces and relationships. Thus, this chapter aims to present and discuss different architectures that can be used in the development of 3D virtual environments. The first architecture addresses issues about the design of virtual environments for educational purposes with the goal of making collaborative e-learning services available. The second architecture proposes a modular structure for the development of 3D virtual environments that support collaboration, remote experiments and content adaptation. Lastly, the third architecture presents issues related to the sharing and management of 3D virtual environments, making use of software reuse techniques combined with web services.
Reviewing the Effectiveness and Learning Outcomes of a 3D Virtual Museum
Authors: Jones Greg , Alba Adriana D.
Published: May 2016

This comparative descriptive mixed methods pilot study reports results of a joint research pilot study between the University of North Texas (UNT) and the Autonomous University of the State of Mexico (UAEM). Data was collected and analyzed for effectiveness, usability, and knowledge acquisition in the Leopoldo Flores Museum located in Mexico, and its online 3dimensional replica. The primary results of this research show a) students using the virtual environment first and then visiting the museum exhibited better knowledge acquisition about the museum and had higher level of discourse when on the guided tour, and b) the virtual museum experience, when used alone, was a comparable experience to the actual museum guided tour in both knowledge gained and satisfaction.
Content Personalized Recommendation Engine to Support an Informal Learning Environment in the Health Context
Authors: Lima da Costa Alisson Alan , Neto Francisco Milton Mendes , Sombra Enio Lopes , Moreira Jonathan Darlan Cunegundes , Castro de Souza Rafael , Dutra Jerffeson Gomes
Published: May 2016

People with chronic diseases suffer with limitations imposed by their health condition and learn more about the disease helps in improving the quality of life. This is possible because the use in mass of mobile devices and the advent of Web 2.0 tools, which gave rise to the Health 2.0 concept. This search for the construction of knowledge by stimulating citizens to be active and responsible for their health. However, provide contextualized knowledge at the right time, it is not a trivial task due to the diversity of content and user's profiles. The solution to this is to provide informal learning through personalized recommendation of content by providing relevant content to users related to their health. This chapter proposes a personalized recommendation system of content, which includes the union of different recommendation techniques and genetic algorithm, seeking efficacy on the recommendation of the contents to people with chronic diseases aiming informal learning in health.
Education and Leadership in Social Networks
Authors: İli Kenan , Menteşe Mehmet
Published: May 2016

Social networks which play an important role in individuals', many of whom are youngsters, daily life got the opportunity to be used as educational tools and seem to have many features to improve educational organizations and the educational processes. Organizations exist in the very complex and chaotic environments rather than the stable and steady environments. This affects the role of administrator and especially the leader within the organization. The task of the 21st century educators is to be compromising social media leadership with media, mass media instruments and information technologies and the values of the school, and preparing the youngsters for the future by building common living environments. Within the scope of research, some explanations from literature about the concept of social networks and the use of social networks in education were given first. For conclusion, comments, conclusions and suggestions about the usability of social networks in education were presented.
Complexity of School Leadership in the Wake of Teacher Insularity
Authors: Bisaso Ssali Muhammadi
Published: May 2016

The interest to all actors and observers within educational arena denotes a long-term trend of expansion of educational professionalism accompanied by a continuous debate about its desirability, and a perennial instability or dynamic of the structures within education systems. Over the years, however, the emphasis placed on shape of professionalism in education systems has varied substantially to reflect the complexity contained therein from a purely managerial and leadership perspective. Moreover, we observe considerable changes of ‘'views and controversies'' concerning the most desirable quality and structure of teacher interaction and professionalism in educational institutions. This chapter explores the state of teacher interaction and collaboration in educational institutions as well as dissecting implications of same for management and leadership in schools. The study is deemed an eye opener to managers, leaders in schools to ‘mind the gap' that is teacher insularity if they are to effectively achieve the very best out of them.
Decision Making and Problem Solving in Higher Educational Institutions
Authors: Kaweesi Muhamadi , Miiro Farooq
Published: May 2016

As it is stated that the economy of a country can never be greater than the education of its people, today parents and several organizations are investing a lot of money in education to better the future of their children and also meet the demands of the several generations to come. Through this process, the level of competition among higher education institutions is too high for them to survive and continuously attract parents, citizens and funders to meet demands of both institutional and community challenges. The aim of this paper, therefore, is to explore the concept of decision making, factors that determine the decision making process, the effectiveness of decision making and problem solving in higher education institutions deemed to be largely chaotic and complex. World over, government and states are investing in higher education to transform their communities in terms of knowledge, skills, culture and economic development.
Big Data in the Field of Civil Security Research
Authors: Gonschorek Julia , Langer Anja , Bernhardt Benjamin , Räbiger Caroline
Published: May 2016

This article gives insight in a running dissertation at the University in Potsdam. Point of discussion is the spatial and temporal distribution of emergencies of German fire brigades that have not sufficiently been scientifically examined. The challenge is seen in Big Data: enormous amounts of data that exist now (or can be collected in the future) and whose variables are linked to one another. These analyses and visualizations can form a basis for strategic, operational and tactical planning, as well as prevention measures. The user-centered (geo-) visualization of fire brigade data accessible to the general public is a scientific contribution to the research topic 'geovisual analytics and geographical profiling'. It may supplement antiquated methods such as the so-called pinmaps as well as the areas of engagement that are freehand constructions in GIS. Considering police work, there are already numerous scientific projects, publications, and software solutions designed to meet the specific requirements of Crime Analysis and Crime Mapping. By adapting and extending these methods and techniques, civil security research can be tailored to the needs of fire departments. In this paper, a selection of appropriate visualization methods will be presented and discussed.
Sensitivity Analysis of Spatial Autocorrelation Using Distinct Geometrical Settings
Authors: Rodrigues António Manuel , Tenedório José António
Published: May 2016

Inferences based on spatial analysis of areal data depend greatly on the method used to quantify the degree of proximity between spatial units - regions. These proximity measures are normally organized in the form of weights matrices, which are used to obtain statistics that take into account neighbourhood relations between agents. In any scientific field where the focus is on human behaviour, areal datasets are greatly relevant since this is the most common form of data collection (normally as count data). The method or schema used to divide a continuous spatial surface into sets of discrete units influences inferences about geographical and social phenomena, mainly because these units are neither homogeneous nor regular. This article tests the effect of different geometrical data aggregation schemas - administrative regions and hexagonal surface tessellation - on global spatial autocorrelation statistics. Two geographical variables are taken into account: scale (resolution) and form (regularity). This is achieved through the use of different aggregation levels and geometrical schemas. Five different datasets are used, all representing the distribution of resident population aggregated for two study areas, with the objective of consistently test the effect of different spatial aggregation schemas.
Applications of Social Media in Academic Library Services
Authors: San Kong Elaine Wei , Chiu Dickson K. W. , Ho Kevin K.W.
Published: May 2016

In recent years, social media have had a vast number of users and attracted academic libraries to use this new media to connect with their user communities. It allows librarians to communicate and share information with, and even provide services to users. This study examines the Pao Yue-kong Library at the Hong Kong Polytechnic University (PolyUL) that has been using social media to promote their information resources and services. However, throughout websites observations and tracking records on Facebook, Twitter, and YouTube of the PolyUL, it was found users are not as numerous as other commercial organizations. Some recommendations were suggested to the PolyUL for enhancing communication with its users.
Talking about NSA Wiretapping and Guantanamo
Authors: Merola Linda M.
Published: May 2016

Following the attacks of September 11, 2001, American leaders confronted difficult dilemmas involving civil liberties in the context of terrorism. Previous scholarship has made clear that exposure to threatening information may result in significant decreases in the public's willingness to support expansive civil liberties guarantees, yet relatively few researchers have systematically examined the content of information transmitted to the public during these debates. This study employs a computerized content analysis to investigate differences in broadcast media coverage following the reporting of significant post-9/11 security/rights dilemmas. The analysis focuses on two key periods: the reporting of President Bush's authorization of warrantless NSA wiretapping in late 2005 and the coverage of President Obama's 2009 proposal to close the detention facility at Guantanamo Bay, Cuba. Findings suggest that broadcast sources diverged significantly in the amount of threatening information conveyed to the public during the reporting of key security/rights dilemmas.
Pattern-Based Requirements Engineering of New Online Social Networks
Authors: Bouraga Sarah , Jureta Ivan , Faulkner Stéphane
Published: May 2016

Online Social Networks (OSNs), such as Facebook and LinkedIn, are now widely used. They count users in the hundreds of millions. This paper surveys popular OSNs in order to identify and present a pattern of recurring requirements, and a model of that pattern in the i-star requirements modelling language. The pattern can serve as a starting point for requirements engineering of new OSNs.
Fixation System Design in Ipsilateral Proximal Femur and Diaphyseal Fractures in Elderly Patients
Authors: Ene Razvan , Nica Mihai , Panti Zsombor , Pleniceanu Marian , Ene Patricia , Cîrstoiu Monica , Antoniac Iulian Vasile , Cirstoiu Catalin
Published: May 2016

Ipsilateral proximal femur combined with diaphyseal fracture is a rare and problematic combination of injuries with serious potential complications first reported in the literature by Delaney and Street in 1953. This paper offers a retrospective view of 21 cases involving ipsilateral, proximal and diaphyseal fractures in elderly patients who were treated in our department, in order to emphasize the challenges of managing these pathological entities in elderly patients and the need for improvement of implant design. A number of 21 patients treated in our department, over a five year period for ipsilateral, combined proximal (intertrochanteric or femoral neck fractures) and femoral shaft fractures was selected. The cases were the result of various types of trauma as follows: 8 patients injured in motor vehicle accidents, 11 falls from standing position and 2 falls from more than own height. No open fractures or pathological fractures were recorded for this study. The patients were grouped according to treatment approach as group A (n=13), managed using intramedullary fixation devices and group B (n=8), treated with plating. All 21 patients were followed-up for 1 to 2 years after surgery. The data was analysed using Student's t-test and a comparison between the two groups was devised. None of the available fixation methods has shown clear superiority for addressing this fracture association. The multitude of variables affecting the management of this injury pattern is complemented by the poor local biomechanical environment provided by the low bone mineral density characteristic for the elderly patients. This raises the challenge of improving the design of the implants to better suit the biomechanical requirements, which sometimes are dictated by the age of the patients.
The Gephi Network Visualisation of the Guided Bone Regeneration Process Induced with Tissue Engineered Grafts
Authors: Lucaciu Ondine , Băciuţ Mihaela , Băciuţ Grigore , Câmpian Radu Septimiu , Ionel Anca
Published: May 2016

The goal of this study was to create a Gephi network visualisation of the guided bone regeneration induced by tissue-engineered grafts using a histological score. Bioengineered bone grafts were obtained using CD 1 mice mesenchymal stem cells seeded on red deer antler scaffolds. Both basal and complex osteogenic media were used as osteogenic inducers of mesenchymal stem cells in the bioengineering process.Bone defects (5 mm in diameter) in the cranial bone of CD1 mice were surgically induced. Bone reconstruction was not performed in surgically induced bone defects in the control group, consisting of 30 subjects. In the study group, consisting of 60 subjects, bone reconstruction was performed using tissue engineered bone grafts. Subjects were sacrificed 2 and 4 months after surgery. Bone regeneration was assessed using a histological record.Comparative analysis of the bone regeneration process between the groups was performed using SPSS (Statistical Package for the Social Sciences) , network analysis and the visual results were performed using Gephi software.The created Gephi network indicates a more advanced bone regeneration stage for subjects in the study group sacrificed after 4 months.The Gephi networks reveal the time evolution of the bone regeneration process, the nodes size and edges complexity increasing from subjects sacrificed at 2 months to those sacrificed at 4 months.At each stage, two and four months after surgery, bone regeneration was more advanced in the study group than in the control group and it was different for the two osteogenic media. We conclude that bone regeneration in critical size defects, as in our research, cannot be obtained without bone reconstruction.
Evaluation Methods of Bone Graft Materials
Authors: Manolea Horia Octavian , Crăițoiu Monica , Ciucă Eduard , Fronie Adrian , Rîcă Radu , Obădan Florian
Published: May 2016

Bone graft substitute materials play an important role in oral rehabilitation and understanding the biological effects of these materials is important for an optimum use. Many bone graft substitutes have been approved for clinical use but this large variability make it hard to select a graft materials. The present study aimed to evaluate the methods that we can today use to assess the degree of osseointegration of the synthetic bone augmentation materials.For this study we made three study groups, each of them consisting of six laboratory rats. On the maxilla of this animals 3-mm diameter experimental cavities were carried out. For the first study group the cavities were augmented with the collagen fleece Alveoprotect, for the second group with the synthetic bone graft Ossceram nano, and in the third group the experimental cavities were left unaugmented. The obtained samples were subjected to three examination methods: clinical and radiological examination, Optical Coherence Tomography (OCT), and a histological study.The evaluation methods of bone graft materials may be divided in two categories: in vivo and in vitro methods. In vivo methods include clinical evaluation and imagistic such as radiological or computer tomography (CT) evaluation. Even a minimal but careful direct clinical observation allows observing the appearance of the bone defect healing at its different stages. CBCT scan is the imaging method of choice in the graft materials repairment of the osseous defects because provides 3D volumetric measurements of newly formed hard tissues.Optical Coherence Tomography (OCT) is a constantly growing imaging method characterized by high spatial resolution and noninvasive subsurface detection. The OCT allowed us to evaluate the surface and subsurface of the ongoing healing bone defects in a non-destructive manner.For the in vitro methods histological methods represents the classical evaluation of the bone graft materials biological integration. On the histological samples we generally noticed the experimental defects filling with connective tissuewith various bone ingrowths from the surrounding bone tissue.However new emerging methods give new opportunities to a more accurate research of this materials. The microcomputed tomography analysis may determine the relationships and differences in three-dimensional bone mineral density and microtrabecular structures between bone grafts and their adjacent native boneTo design and produce an efficient bone graft, the researchers and clinicians should have sufficient knowledge of the characteristics of grafts such as osteogenesis, osteoinductivity, and osteoconductivity, and their other advantages and disadvantages.
Histologic Evaluation of Tertiary Dentine after Indirect Pulp Capping Procedures
Authors: Monea Monica , Pop Mihai , Stoica Alexandra , Ștefănescu Teodora
Published: May 2016

Early carious lesions induce odontoblast stimulation in tertiary dentine formation even before the lesion reaches the dentine. The most used material for these procedures was calcium hydroxide, which was recently replaced by Mineral Trioxide Aggregate (MTA).The purpose of our study was to assess the histological characteristics of tertiary dentine induced by these materials in permanent molar teeth.We used 23 molars scheduled for extraction due to orthodontic reasons, in patients of 17-24 years of age. In a time interval of 4-8 weeks prior to extraction, occlusal cavities were prepared and filled with MTA or calcium hydroxide and glass ionomer cement.In teeth filled with MTA we noticed an early development of tertiary dentin layer, with a tubular structure, similar to secondary dentine. In the case of calcium hydroxide, the process of new dentine deposition was delayed and diffuse calcification, with formation of pulp stones was noticed.MTA proved to be superior to calcium hydroxide in inducing tertiary dentine formation, which appeared early after treatment. In time the differences in the amount of tertiary dentine between these materials are reduced, but there is a tendency of diffuse mineralization induced by calcium hydroxide.
The Potential of NDPs-Loaded Fish Gelatin Fibers as Reinforcing Agent for Fish Gelatin Hydrogels
Authors: Cecoltan Sergiu , Serafim Andrada , Dragusin Diana Maria , Lungu Adriana , Lagazzo Alberto , Barberis Fabrizio , Stancu Izabela Cristina
Published: May 2016

In this work we report the potential of nanostructured fibers consisting of nanodiamond particles (NDPs) and fish gelatin (FG) to modulate the mechanical properties of fish gelatin hydrogels, in the aim of developing bioinspired ECM analogues. NDPS-loaded FG fibers were obtained by electrospinning. The biocomposites were obtained through the enzymatic crosslinking of gelatin in the presence of NDPs-loaded FG fibers. The mechanical behavior was assessed at different preparative stages (precursors, fibrous mesh, biocomposite scaffolds).
Naturally Derived Matrix for Controlled Selenium Nanoparticles Delivery
Authors: Cavalu Simona , Laslo Vasile , Banica Florin , Vicas Simona Ioana
Published: May 2016

The aim of this study is to develop a lyophilized matrix (microspheres) as a controlled delivery system for nanoselenium particles, using different formulation based on alginate or agar. Elemental selenium is considered as the least toxic of all selenium forms and in the same time supplementation with its nanosize particles has the same or better bioavailability compared to its salts. In our study, nanosized elemental selenium was obtained by fermentation technology using probiotic lactic acid bacteria (Lactobacillus casei). The microspheres have been characterized from structural point of view by using different techniques: FTIR spectroscopy, X-ray Diffraction and SEM. Each individual natural polymer has its own characteristic advantages and disadvantages; it is commonly accepted that naturally derived matrix often show an excellent balance between the mechanical properties, swelling and dissolution capacity. The optimized formulation was proposed upon in vitro dissolution study using Diferential Pulsed Voltammetry in order to measure the concentration of selenium released in simulated gastric fluid (pH=1.2) and simulated intestinal fluid (pH=8.1). The cumulative release of selenium from different formulations showed large differences with respect to matrix composition. We demonstrated that both alginate and agarose-based formulations are suitable to be used in basic environment such as small or large intestine. The results might be of high importance as absorption of selenium occurs mainly in the duodenum, caecum and colon (more than 85%).
Zirconia Neck Implants vs Bone Augmentation
Authors: Ratiu Cristian , Cavalu Simona
Published: May 2016

Different graft materials and techniques are suggested based on the number of bony walls that remain after the tooth is removed. If the implant can’t be inserted within the bone contours, bone augmentation must be performed, and the graft must be stabilized with a membrane or a thin bone block graft. In the present study, two cases are presented both with small bone defects on the buccal plate. Bone augmentation with autogenous bone graft was performed in one case, respectively titanium implants with zirconia necks were used in the second case. It was demonstrated that titanium implants with zirconia necks are a good choice in some cases where small parts of the buccal plate are missing.
Solar Driven Energy Conversion Applications Based on 3C-SiC
Authors: Sun Jian Wu , Jokubavicius Valdas , Gao Lu , Booker Ian , Jansson Mattias , Liu Xin Yu , Hofmann Jan P. , Hensen Emiel J.M. , Linnarsson Margareta K. , Wellmann Peter J. , Ramiro Iñigo , Martí Antonio , Yakimova Rositza , Syväjärvi Mikael
Published: May 2016

There is a strong and growing worldwide research on exploring renewable energy resources. Solar energy is the most abundant, inexhaustible and clean energy source, but there are profound material challenges to capture, convert and store solar energy. In this work, we explore 3C-SiC as an attractive material towards solar-driven energy conversion applications: (i) Boron doped 3C-SiC as candidate for an intermediate band photovoltaic material, and (ii) 3C-SiC as a photoelectrode for solar-driven water splitting. Absorption spectrum of boron doped 3C-SiC shows a deep energy level at ~0.7 eV above the valence band edge. This indicates that boron doped 3C-SiC may be a good candidate as an intermediate band photovoltaic material, and that bulk like 3C-SiC can have sufficient quality to be a promising electrode for photoelectrochemical water splitting.
History and Recent Developments of Packaging Technology for SiC Power Devices
Authors: Dohnke Karl Otto , Guth Karsten , Heuck Nicolas
Published: May 2016

Packaging plays an important role to allow the full potential of silicon carbide devices to be realised. The physical properties of silicon carbide will allow devices to operate with junction temperatures well above 200 °C, but today standard-packaged SiC products are limited to a maximum junction temperature of 175 °C. The limitation lies in the packaging, because a power device package is a complex structure consisting of many components of different materials and with correspondingly different thermal properties. As such, the assembly technologies define both the performance and lifetime of discrete packages and power modules. In this paper we give an insight of packaging technology for SiC devices from the beginning in the mid-1980s through to the state-of-the-art of today. In addition, new packaging technologies to enable power SiC devices to operate up to 200 °C are discussed.
Reliability Evaluation of SiC Power Device Package Used Heat-Resistant Molding Plastic by Power Cycle Test
Authors: Funaki Tsuyoshi , Yasui Akihiro
Published: May 2016

SiC power device can operate in temperature higher than 200°C, where conventional Si power device cannot operate normally. The heat-resistant package is required to ensure the reliability in high temperature operation of SiC power device. This study evaluates the reliability of developed package for high temperature operation in power cycle test. The given power cycle condition is ΔTj=170°C with Tj=200°C for high temperature and Tj=30°C for low temperature. The device in the package with Al2O3-ceramic fails for 3387 power cycle test, but it is necessary to further analyze failure mechanism
Synchrotron X-Ray Topography Analysis of Double Shockley Stacking Faults in 4H-SiC Wafers
Authors: Yang Yu , Guo Jian Qiu , Goue Ouloide , Raghothamachar Balaji , Dudley Michael , Chung Gil Yong , Sanchez Edward , Quast Jeffrey , Manning Ian , Hansen Darren
Published: May 2016

Synchrotron white beam X-ray topography studies carried out on 4H-SiC wafers characterized by locally varying doping concentrations reveals the presence of overlapping Shockley stacking faults generated from residual surface scratches in regions of higher doping concentrations after the wafers have been subjected to heat treatment. The fault generation process is driven by the fact that in regions of higher doping concentrations, a faulted crystal containing double Shockley faults is more stable than perfect 4H–SiC crystal at the high temperatures (>1000 °C) that the wafers are subject to during heat treatment. We have developed a model for the formation mechanism of the rhombus shaped stacking faults, and experimentally verified it by characterizing the configuration of the bounding partials of the stacking faults on both surfaces. Using high resolution transmission electron microscopy, we have verified that the enclosed stacking fault is a double Shockley type.
Impact of Package Parasitics on Switching Performance
Authors: Kostov Konstantin , Lim Jang Kwon , Zhang Ya Fan , Bakowski Mietek
Published: May 2016

The package parasitics are a serious obstacle to the high-speed switching, which is necessary in order to reduce the switching power losses or reduce the size of power converters. In order to design new packages suitable for Silicon Carbide (SiC) power transistors, it is necessary to extract the parasitics of different packages and be able to predict the switching performance of the power devices placed in these packages. This paper presents two ways of simulating the switching performance in a half-bridge power module with SiC MOSFETs. The results show that the parasitic inductances in the power module slow down the switching, lead to poor current sharing, and together with the parasitic capacitances lead to oscillations. These negative effects can cause failures, increased losses, and electromagnetic compatibility issues.
Investigation of Pressure Dependent Thermal Contact Resistance between Silver Metallized SiC Chip and Molybdenum Substrate and between Molybdenum Substrate and Bulk Copper
Authors: Toth-Pal Zsolt , Zhang Ya Fan , Nee Hans Peter , Bakowski Mietek
Published: May 2016

– Thermal contact resistances between a silver metallized SiC chip and a Molybdenum substrate and between the Molybdenum substrate and bulk Copper were measured in a heat transfer experiment. An experimental method to separate thermal contact resistances in a multilayer heat transfer path was used to extract the layer-specific contact resistances. The experimental results were compared with analytical calculations and also with 3-D computational fluid dynamics (CFD) simulation results. The results show significant pressure dependence of the thermal contact resistance and the results show higher thermal contact resistance per unit area between the bulk SiC chip and Molybdenum than between Molybdenum and bulk Copper.
Cascode Configuration of SiC-BGSIT and Si-MOSFET with Low On-Resistance and High Transconductance
Authors: Yamamoto Masayuki , Tanaka Yasunori , Yatsuo Tsutomu , Yano Koji
Published: May 2016

We investigate a cascode configuration of a normally-on SiC-Buried Gate Static Induction Transistor (SiC-BGSIT) and Si-MOSFET as an alternative switching device of the SiC-MOSFET. It is shown that the transconductance of our cascode device is much higher than that of commercial SiC-MOSFETs while the switching speed is much faster than that of normally-off SiC-BGSITs. The origin of the fast switching speed in this cascode configuration is discussed in terms of a simulated reverse transfer capacitance.
Wafer-Scale Graphene on 4-Inch SiC
Authors: Yu Wan Cheng , Chen Xiu Fang , Hu Xiao Bo , Xu Xian Gang
Published: May 2016

Wafer-scale graphene on SiC with uniform structural features was grown on semi-insulating 4 inch on-axis 4H-SiC (0001) face. Growth was carried out in a conventional physical vapor transport (PVT) growth system. Atmospheric pressure graphitization and a “face-down” orientation were account for the high uniformity of graphene. Atomic force microscopy, electrostatic force microscopy and Raman spectroscopy were used to confirm the uniformity of surface morphology and layer number. Electrical properties were also characterized by Hall measurements on 15×15mm2 samples sawed from the wafer. An average Hall mobility of about 2000cm2/Vs was obtained.
Graphene-Silicon Heterojunction Infrared Photodiode at 1.3/1.55 μm
Authors: Ou Tzu Min , Borsa Tomoko , Van Zeghbroeck Bart J.
Published: May 2016

A novel infrared photodiode based on a graphene/n-type silicon heterojunction is explored. The heterojunction photodiode of interest has a large Schottky barrier that results in a low dark current. Graphene serves as the absorbing medium at a wavelength for which silicon is transparent. Under infrared illumination, photo-excited electrons in the graphene gain energy and thus have a greater probability to overcome the barrier and contribute to the photocurrent. We have demonstrated photodiode operation of a graphene/n-Si heterojunction at 1.3 and 1.55 μm wavelength, with 14% internal quantum efficiency and 1.5 pW/Hz1/2 noise-equivalent power, for potential use in silicon photonics.
Homoepitaxial Chemical Vapor Deposition of up to 150 μm Thick 4H-SiC Epilayers in a 10×100 mm Batch Reactor
Authors: Thomas Bernd , Zhang Jie , Chung Gil Yong , Bowen Willie , Torres Victor , Adams Daniel , Hansen Darren , Sanchez Edward
Published: May 2016

In this paper we present results on the growth of low-doped thick epitaxial layers on 4° off-oriented 4H-SiC using a warm-wall multi-wafer CVD system (Aixtron VP2800WW). Statistical data on doping and thickness of 25 μm to 40 μm layer growth show results similar to standard epilayer growth (5-15 μm). Improvements in thickness and doping uniformity as well as the reduction of epitaxial defects has boosted the quality of 25 μm to 40 μm thick epilayers. Laser light scattering measurements resulted in projected device yields with median values of 83% and 96% for 5×5 mm2 and 2×2 mm2 die size, respectively. This corresponds to a low epitaxial defect density of < 0.75 cm-2 in 25-40 μm thick epilayers. This paper also presents results of 60 μm to 150 μm thick epitaxial layer growth. Excellent results for doping, thickness and carrier lifetime were achieved. As an example results of a fully loaded 10×100mm run with 150 μm thick epilayers are presented. Wafer-to-wafer doping and thickness values of 3.7 % and 3.4% for sigma/mean were accomplished, respectively. Typical average lifetime values of 5 μs to 6 μs were measured on the 150 μm thick layers without post-epi treatments.
Stacking Fault Analysis of Epitaxial 3C-SiC on Si(001) Ridges
Authors: Meduňa Mojmír , Kreiliger Thomas , Prieto Ivan , Mauceri Marco , Puglisi Marco , Mancarella Fulvio , La Via Francesco , Crippa Danilo , MIGLIO Leo , von Känel Hans
Published: May 2016

The stacking faults (SFs) in 3C-SiC epitaxially grown on ridges deeply etched into Si (001) substrates offcut towards [110] were quantitatively analyzed by electron microscopy and X-ray diffraction. A significant reduction of SF density with respect to planar material was observed for the {111} planes parallel to the ridges. The highest SF density was found in the (-1-11) plane. A previously observed defect was identified as twins by electron backscatter diffraction.
3C-SiC Epitaxy on Deeply Patterned Si(111) Substrates
Authors: Kreiliger Thomas , Mauceri Marco , Puglisi Marco , Mancarella Fulvio , La Via Francesco , Crippa Danilo , Kaplan Wlodek , Schöner Adolf , Marzegalli Anna , MIGLIO Leo , von Känel Hans
Published: May 2016

The growth morphology of epitaxial 3C-SiC crystals grown on hexagonal pillars deeply etched into Si (111) substrates is presented. Different growth velocities of side facets let the top crystal facet evolve from hexagonal towards triangular shape during growth. The lateral size and separation between Si pillars determine the onset of fusion between neighboring crystals during growth at a height tailoring of which is crucial to reduce the stacking fault (SF) density of the coalesced surface. Intermediate partial fusion of neighboring crystals is shown as well as a surface of fully coalesced crystals.
Identifying Performance Limiting Defects in Silicon Carbide pn-Junctions: A Theoretical Study
Authors: Cottom Jonathon , Gruber Gernot , Pobegen Gregor , Aichinger Thomas , Shluger Alexander L.
Published: May 2016

Dopant implantation is a high energy process which causes a significant damage to the crystal lattice and is usually accompanied by a post implantation anneal to repair the structure. Defects created in these processes may also persist in fully processed devices. Previous electron paramagnetic resonance (EPR) and EDMR studies have identified a series of nitrogen related defect complexes in N implanted silicon carbide (SiC) wafers.[1–3] This study examines the formation energy, charge transition levels and barriers to interconversion of two such defects: NCVSi and the NSiVC. The NCVSi center is favoured in a variety of charge states for a wide range of Fermi level positions. We found, however, that for Fermi level positions close to the valence band of 4H-SiC the NCVSi center is a favoured conformation with barriers to rearrangement of +1.2 eV and +3.8 eV in the neutral and +2 charge states, respectively.
Magnetic Field Sensing with Atomic Scale Defects in SiC Devices
Authors: Cochrane Corey J. , Blacksberg Jordana , Lenahan Patrick M. , Anders Mark A.
Published: May 2016

Silicon carbide (SiC) is well known by the semiconductor industry to have significant potential for electronics used in high temperature environments due to its wide bandgap. It is not so well-known, however, that SiC also has great potential in the area of magnetic field sensing. Using the recently demonstrated zero-field spin dependent recombination (SDR) phenomenon that naturally arises in SiC based devices, near-zero magnetic field measurements can be made with moderately high sensitivity.