The stability of stratified layers within ventilated enclosures

The project consists of experimental and numerical investigation of buoyancy-dominated flow leading to thermal stratification in ventilated spaces for the range of Re from 4,000 to 50,000 and Rio below 40. In the evolution of turbulence in stratified shear flows, solving for the primitive variables both in time and space is most important. Steady-state Reynolds Averaged Navier Stokes (RANS) simulations have shown in the past to model adequately the flows that become eventually steady-state. Therefore, three-dimensional steady-state CFD models were used to simulate the flow. The experimental set-up used an Environmental Test Chamber to investigate the stratification in buildings. Temperature differential was created by introducing cold air through a terminal at floor level and hot air through a diffuser pointing vertically downwards at the ceiling level. An extract point was located opposite to the inlets at the rear wall. Different combinations of inlet velocities/flow rates, temperatures as well as different arrangements of the exhaust height were studied to evaluate its effect on velocity and temperature distribution and the effect of jet flow interaction with the stratified layers. The experimental data obtained in this work were also used to validate the predictions from the numerical simulations so that CFD was used to perform more parametric simulations. To model turbulence in the flow field, the appropriateness of several eddy-viscosity based turbulence models was evaluated. The turbulence models used were the standard k-c model, the k-e Chen-Kim modified model, a Low- Re modification and the RNG k -c model. All models are in close agreement with each other. The buoyancy extended standard k-e model gives a sharper prediction of mixing in the interface. The physics of the flow are well predicted. The hot jet from the ceiling is buoyed up when it reaches the height of the interface where buoyancy forces dominate gravitational forces marking its appearance on the temperature gradient. From the simulations made at this stage, the characteristics of stratified layers are revealed. It is also shown that the interface height is proportional to the exhaust height for certain room temperatures and velocities. In a comparison between experimental results and numerical simulation, the differences are attributed on the non-adiabatic effects such as heat losses and radiation. A correlation is found between inlet parameters and stratified flow in buildings obtained both experimentally and computationally

Multitasking, education, and unemployment as determinants of work-related mental health

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The personal and professional benefits and challenges for Saudi academics after postgraduate study abroad: Implications for higher education reform in the Kingdom of Saudi Arabia

The King Abdullah Scholarships Program commenced in 2005 and replaced all previous government scholarship programs in Saudi Arabia. This led to a dramatic increase in the number of Saudi citizens studying abroad, with over 200,000 Saudis, male and female, receiving their bachelor’s, master’s and doctoral degrees from overseas universities through this program. Currently, the United States of America, the United Kingdom, Canada, and Australia, respectively, host the largest numbers of sponsored Saudi students. This study focuses on Saudi academics who completed their postgraduate studies abroad and returned to work at public universities in Saudi Arabia. Its purpose is to broaden current knowledge of the personal and professional benefits and challenges experienced by Saudi academics after postgraduate study abroad and the implications of these for the project of higher education reform in Saudi Arabia. The data for this qualitative study were drawn from in-depth interviews with nine Saudi academics, five males and four females. This study examines both etic and emic perspectives and provides a detailed and oftentimes privileged analysis of participants’ experiences before, during and after postgraduate study abroad. The gains of study abroad for participants included: increased independence and confidence, particularly for females; intercultural competence; higher salaries and rapid promotions; improved English language skills; improved pedagogical awareness and practice; and, increased research knowledge and skills. Challenges for participants included: reverse culture shock; obstacles to producing quality research; and, resistance to change. Based on the findings, implications for the way forward in Saudi higher education are discussed to assist the Kingdom’s Ministry of Higher Education and public-sector universities to further capitalise on the knowledge and skills that sponsored academics bring home from abroad. The study also contributes to a growing body of research related to the use and efficacy of postgraduate study abroad to improve higher education in emerging economies

Untersuchungen der raumzeitlichen Entwicklung des Großen Heiligen Meeres im Kreis Steinfurt auf hydrochemischer und vegetationsökologischer Basis

The presented dissertation follows up on hydrochemical and vegetation ecology issues that were started during the previous bachelor and master studies at Leibniz Universität Hannover in the form of study and research projects as well as the respective final theses and are to be investigated in depth and purposefully as part of the doctorate. The focus is on spatio-temporal variable processes within a limnic ecosystem, which is exemplarily represented by the "Großes Heiliges Meer" in the nature reserve "Heiliges Meer" in the district of Steinfurt, Germany. The long-term development of the vegetation zonation of the Großes Heiliges Meer from a spatiotemporal perspective is investigated as well as the comparatively short-term hydrochemical diurnal processes of selected parameters. After this summarizing overview, in which the goal of this work is formulated, compact conceptions of the investigation area as well as the vegetation-scientific and hydrochemical-analytical investigation methodology follow. In addition, the concept of space-time dynamics is explanatorily differentiated into its spatial and temporal components in view of its importance for this work. The two large main parts contain the results and analyses of the hydrochemical diurnal dynamics in the annual cycle as well as the presentation of the vegetation composition of the present water body. Finally, the discussion of the results and a conclusion with an outlook are given. The aim of this dissertation is to present a comprehensive overview of the diurnal and annual cycles of selected hydrochemical parameters such as oxygen content for a stillwater of the North German Plain and to contrast these dynamics with spatiotemporal long-term processes such as vegetation development. In addition, however, both dynamics are highlighted in isolation with respect to their contribution to the limnetic ecosystem. Thus, this work is intended to be a complementary component for the Großes Heiliges Meer that has been intensively investigated and described from a natural science perspective by numerous works

Extended platelet-rich fibrin.

Platelet-rich fibrin (PRF) has been characterized as a regenerative biomaterial that is fully resorbed within a typical 2-3 week period. Very recently, however, a novel heating process was shown to extend the working properties of PRP/PRF from a standard 2-3 week period toward a duration of 4-6 months. Numerous clinicians have now utilized this extended-PRF (e-PRF) membrane as a substitute for collagen barrier membranes in various clinical applications, such as guided tissue/bone regeneration. This review article summarizes the scientific work to date on this novel technology, including its current and future applications in periodontology, implant dentistry, orthopedics and facial aesthetics. A systematic review was conducted investigating key terms including "Bio-Heat," "albumin gel," "albumin-PRF," "Alb-PRF," "extended-PRF," "e-PRF," "activated plasma albumin gel," and "APAG" by searching databases such as MEDLINE, EMBASE and PubMed. Findings from preclinical studies demonstrate that following a simple 10-min heating process, the transformation of the liquid plasma albumin layer into a gel-like injectable albumin gel extends the resorption properties to at least 4 months according to ISO standard 10 993 (subcutaneous animal model). Several clinical studies have now demonstrated the use of e-PRF membranes as a replacement for collagen membranes in GTR/GBR procedures, closing lateral windows in sinus grafting procedures, for extraction site management, and as a stable biological membrane during recession coverage procedures. Furthermore, Alb-PRF may also be injected as a regenerative biological filler that lasts extended periods with advantages in joint injections, osteoarthritis and in the field of facial aesthetics. This article highlights the marked improvement in the stability and degradation properties of the novel Alb-PRF/e-PRF technology with its widespread future potential use as a potential replacement for collagen membranes with indications including extraction site management, GBR procedures, lateral sinus window closure, recession coverage among others, and further highlights its use as a biological regenerative filler for joint injections and facial aesthetics. It is hoped that this review will pioneer future opportunities and research development in the field, leading to further progression toward more natural and less costly biomaterials for use in medicine and dentistry

Clinical treatment of postoperative infection following sinus augmentation

Purpose: The aim of this case report is to present the successful clinical treatment of two cases of postoperative infection following maxillary sinus augmentation. Methods: In the two cases of postoperative infection, immediate total removal of the grafted material from the sinus was conducted to stop the spread of the infection, after which a high dose of antibiotics was administrated. Re-augmentation procedures were then conducted after the infection subsided. Results: No further complications occurred after sinus re-augmentation. The dental implants placed in the re-augmented sinus were clinically osseointegrated, and the implant-supported restorations in the two cases of postoperative infection have been functioning very well for over 2 years. Conclusions: In the case of infection of the grafted sinuses, it is necessary to completely remove the graft materials and then administer a high dose of antibiotics to treat the acute infection, after which sinus re-augmentation is suggested. ?? 2010 Korean Academy of Periodontology

Quantitative Comparison of Cone Beam Computed Tomography and Microradiography in the Evaluation of Bone Density after Maxillary Sinus Augmentation: A Preliminary Study

Purpose Cone beam computed tomography ( CBCT ) and microradiographic analyses were comparatively performed in maxillary sinus augmentation to preliminarily verify the diagnostic potential of CBCT on the evaluation of bone regeneration. Materials and Methods A two‐stage protocol was conducted in 19 consenting patients, all having the crestal bone ≤2 mm, in private dental office. Mineralized human bone allograft particles were used to augment sinus using lateral window approach. A succession of CBCT scans of the maxilla was taken before surgery, after sinus augmentation, and immediately after implant insertion. Using virtual probes, CBCT data were processed by medical imaging software and expressed as gray level ( GL ). A bone core biopsy was taken at implant placement, 6 months after surgery. Microradiography of transverse sections, taken 6, 8, and 10 mm from the crestal surface, of methacrylate‐embedded biopsies was performed to analyze and to evaluate the mineralized material amount ( MM %). Results A total of 21 sinus augmentations were performed. CBCT (mean GL : 646–693) data were not statistically different when comparing 6‐, 8‐, and 10‐mm sites to after grafting/implant‐insertion values. Furthermore, microradiographic (mean MM %: 45.3–48.3) data were not statistically different comparing 6‐, 8‐, and 10‐mm sites, due to variation of values among patients. A GL and MM % parallelism was identified considering each patient, instead. A significant correlation ( p  < .001) between GL and MM % was found after both W ilcoxon test for paired data and simple linear regression analysis. Conclusions The preliminary result clearly demonstrated the predictability of the CBCT analysis. Due to the limited sample and great variations of the MM % recorded in patients, further clinical and morphometric studies are needed to fulfill diagnostic expectations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/108331/1/cid12016.pd

Complications associated with implant migration into the maxillary sinus cavity

Background Migration of dental implants into the maxillary sinus is an uncommon, but increasingly reported complication. Implant migration may result from initial lack of primary stability, intrasinusal and nasal pressure changes, autoimmune reaction to the implant or incorrect distribution of occlusal forces. This retrospective study aims at analyzing the factors that may influence implant migration into the maxillary sinus cavity. Material and methods Fourteen patients presenting a total 15 implants that migrated into the maxillary sinus were recruited. Diagnosis of this complication was based on imaging techniques, such as cone beam computerized tomography scan and panoramic radiography. Clinical data were recorded in all cases and processed for statistical analysis. Results ABH was below 6 mm in the majority of cases. However, almost 50% of the patients did not receive any site preparation treatment prior to implant insertion. Five patients (33.3%) were treated by osteotome techniques, but only one of them had bone grafting. Therefore, 73.3% of sites did not receive any biomaterial to increase available bone height. The most common complication‐associated factors found on this study were related to implant design (cylindrical), implant dimension (diameter), implant restoration/rehabilitation method (partial removable denture), site‐specific anatomy (initial residual bone height between 5 and 6.9 mm), demographics (age), and biomaterials. Conclusion Patient selection and proper treatment planning, as well as the application of the appropriate sinus augmentation technique, are critical aspects that should be controlled to minimize the risk of implant migration into the maxillary sinus cavity. [Correction added after online publication August 17 2011: The Conclusion was revised to provide better clarity to the reader.]Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/93739/1/clr2278.pd

Introduction of Risk Management into Municipal Offices Across Poland as an Example of Organizational Change

Purpose: The aim of this paper is to determine the factors that influence the process of implementation of risk management process into municipal offices across Poland. Methodology: The Polish Public Finance Act requires public sector entities to put in place a risk management system within the framework of management control. The author conducted in-depth interviews with key personnel responsible for risk management in public administration units. Findings: The results of the research show that public sector organizations face certain problems in the process of implementing a risk management system. Employees seem to resist change. As a result of the project, four factors that influence the process of introducing risk management have been identified. Implication: Public sector organizations are mostly large, bureaucratic organizations, governed by numerous regulations, which all in all tends to hinder efficient management. The results of the discussed research are to support public entities in the process of implementing change. Value: The paper explores the importance of overcoming barriers to the process of implementing risk management in the public sector