On optimal design and applications of linear transforms

Linear transforms are encountered in many fields of applied science and engineering. In the past, conventional block transforms provided acceptable answers to different practical problems. But now, under increasing competitive pressures, with the growing reservoir of theory and a corresponding development of computing facilities, a real demand has been created for methods that systematically improve performance. As a result the past two decades have seen the explosive growth of a class of linear transform theory known as multiresolution signal decomposition. The goal of this work is to design and apply these advanced signal processing techniques to several different problems. The optimal design of subband filter banks is considered first. Several design examples are presented for M-band filter banks. Conventional design approaches are found to present problems when the number of constraints increases. A novel optimization method is proposed using a step-by-step design of a hierarchical subband tree. This method is shown to possess performance improvements in applications such as subband image coding. The subband tree structuring is then discussed and generalized algorithms are presented. Next, the attention is focused on the interference excision problem in direct sequence spread spectrum (DSSS) communications. The analytical and experimental performance of the DSSS receiver employing excision are presented. Different excision techniques are evaluated and ranked along with the proposed adaptive subband transform-based excises. The robustness of the considered methods is investigated for either time-localized or frequency-localized interferers. A domain switchable excision algorithm is also presented. Finally, sonic of the ideas associated with the interference excision problem are utilized in the spectral shaping of a particular biological signal, namely heart rate variability. The improvements for the spectral shaping process are shown for time-frequency analysis. In general, this dissertation demonstrates the proliferation of new tools for digital signal processing

CD81 interacts with the T cell receptor to suppress signaling

CD81 (TAPA-1) is a ubiquitously expressed tetraspanin protein identified as a component of the B lymphocyte receptor (BCR) and as a receptor for the Hepatitis C Virus. In an effort to identify trans-membrane proteins that interact with the T-cell antigen receptor (TCR), we performed a membrane yeast two hybrid screen and identified CD81 as an interactor of the CD3delta subunit of the TCR. We found that in the absence of CD81, in thymocytes from knockout mice, TCR engagement resulted in stronger signals. These results were recapitulated in T cell lines that express low levels of CD81 through shRNA mediated silencing. Increased signaling did not result from alterations in the levels of TCR on the surface of T lymphocytes. Although CD81 is not essential for normal T lymphocyte development, it plays an important role in regulating TCR and possibly pre-TCR signal transduction by controlling the strength of signaling. CD81 dependent alterations in thymocyte signaling are evident in increased CD5 expression on CD81 deficient double positive (DP) thymocytes. We conclude that CD81 interacts with the T cell receptor to suppress signaling

RasGEF1A and RasGEF1B are guanine nucleotide exchange factors that discriminate between Rap GTP-binding proteins and mediate Rap2-specific nucleotide exchange

The highly conserved RasGEF1 family of proteins contain a C-terminal CDC25-Ras exchange motif domain and an N-terminal RasGEF-N domain, and are of unknown function and specificity. Using purified RasGEF1A and RasGEF1B proteins, as well as Ras family proteins, we established that RasGEF1A and RasGEF1B function as very specific exchange factors for Rap2, a member of the Rap subfamily of Ras-like G-proteins. They do not act on Rap1 or other members of the Ras subfamily. Although Rap2 was implicated in the regulation of cell adhesion, the establishment of cell morphology, and the modulation of synapses in neurons, no specific guanine nucleotide exchange factor for Rap2 was previously identified. Using reciprocal site-directed mutagenesis, we analyzed residues that allow RasGEF1 proteins to discriminate between Rap1 and Rap2, and we were able to identify Phe39 in the switch I region of Rap2 as a specificity residue. Mutation of the corresponding Ser39 in Rap1 changed the specificity and allowed the nucleotide exchange of Rap1(S39F) to be stimulated by RasGEF1B. © 2009 FEBS

Texturing of titanium (Ti6Al4V) medical implant surfaces with MHz-repetition-rate femtosecond and picosecond Yb-doped fiber lasers

Cataloged from PDF version of article.We propose and demonstrate the use of short pulsed fiber lasers in surface texturing using MHz-repetition-rate, microjoule- and sub-microjoule-energy pulses. Texturing of titanium-based (Ti6Al4V) dental implant surfaces is achieved using femtosecond, picosecond and (for comparison) nanosecond pulses with the aim of controlling attachment of human cells onto the surface. Femtosecond and picosecond pulses yield similar results in the creation of micron-scale textures with greatly reduced or no thermal heat effects, whereas nanosecond pulses result in strong thermal effects. Various surface textures are created with excellent uniformity and repeatability on a desired portion of the surface. The effects of the surface texturing on the attachment and proliferation of cells are characterized under cell culture conditions. Our data indicate that picosecond-pulsed laser modification can be utilized effectively in low-cost laser surface engineering of medical implants, where different areas on the surface can be made cell-attachment friendly or hostile through the use of different patterns. (C) 2011 Optical Society of Americ

Landscape approaches for ecosystem management in Mediterranean Islands

This book presents a series of essays, drawing on the twm concepts of ecosystem management and landscape approaches, to elucidate and reflect on the present situation and future evolution of Mediterranean islands. This publication brings together contributions from Mediterranean individuals, non-Mediterranean individuals, islanders and non-islanders there is, after all, no geographical limit on who and what we can learn from. The essays presented here each contribute a specific perspective on the future evolution of Mediterranean islands. This book presents a series of essays, drawing on the twin concepts of ecosystem management and landscape approaches, to elucidate and reflect on the present situation and future evolution of Mediterranean islands. This publication brings together contributions from Mediterranean individuals, non-Mediterranean individuals, islanders and non-islanders; there is, after all, no geographical limit on who and what we can learn from. The essays presented here each contribute a specific perspective on the future evolution of Mediterranean islands. Following this introductory chapter, the first section of the book focuses on the contributions that can be made by the discipline of landscape ecology. loannis Vogiatzakis and Geoffrey Griffiths first explain the concepts and relevance of landscape ecology, also presenting and discussing a range of applied tools that can facilitate landscape planning in Mediterranean islands. Louis F. Cassar then reviews the 'offshoot' discipline of restoration ecology, making a strong case for offsetting the environmental damage inflicted on natural ecosystems over millennia of human occupation, with constructive efforts to effectively restore and/or rehabilitate ecosystems. The two following chapters bring the socio-economic dimension into the discussion. Godfrey Baldacchino first presents two contrasting paradigms for the development of island territories, reviewing the dual influences of ecological and economic factors, and exploring ways in which the two can be brought together in successful development strategies. Gordon Cordina and Nadia Farrugia then address the demographic dimension of development, presenting a model to explain the economic costs of high population densities on islands. The third block of chapters expands on the relevance of social and cultural dynamics to the management of Mediterranean Islands. Isil Cakcï, Nur Belkayali and Ilkden Tazebay explain the evolution of the concept of a 'cultural landscape', focusing on the challenges of managing change in landscapes with strong heritage values. The chapter concludes with a case study on the Turkish island of Gökçeada (lmbros), which is experiencing major challenges in balancing the conservation of a cultural landscape on the one hand, and the management of inevitable change, on the other. Elisabeth Conrad then discusses the role of social capital in managing the landscape resources of Mediterranean islands, reviewing the potential for this intangible social fabric to facilitate or impede the sustainable evolution of island territories. The fourth section includes four chapters, each of which addresses a different aspect relevant to policy development and implementation in Mediterranean islands. Salvino Busuttil presents an essay outlining the political influences on the management of coastal landscapes, the latter so relevant to Mediterranean island territories. The essay derives from the author's professional experience in various policy-related institutions for environmental management within the Mediterranean region. Maggie Roe then reflects on issues of landscape sustainability, focusing on the neglected aspect of intelligence. She discusses ways in which landscape research, knowledge and understanding can feed directly into frameworks for 'sustainable' landscape planning. In the subsequent chapter, Adrian Phillips takes from his substantial experience with international landscape policy, reviewing the gradual emergence of international and national landscape 'tools', to draw out lessons for application in Mediterranean islands. In the final chapter of this section, Riccardo Priore and Damiano Galla present a comprehensive discussion of the European Landscape Convention, the first international instrument to focus exclusively on landscape. The authors explain the innovative character of this convention, and discuss its potential implementation in Mediterranean islands. The publication concludes with a series of case studies, highlighting specific constraints, experiences and opportunities in different Mediterranean islands. Theano Terkenli explores the landscapes of tourism in Mediterranean islands - perhaps no other industry has played such a fundamental role in shaping the evolution of Mediterranean landscapes in recent years. The author reviews the theoretical relationship between landscape and tourism across Mediterranean islands, before focusing on the specific case of the Greek Cycladic islands. In the following chapter, Alex Camilleri, Isabella Colombini and Lorenzo Chelazzi present an in-depth review of the context and challenges being faced on a number of minor Mediterranean islands, namely those of the Tuscan archipelago (Elba, Giglio, Capraia, Montecristo, Pianosa, Gorgona and Giannutri), and Comino, the latter forming part of the Maltese archipelago. The comparison between these various islands enables an appreciation of both commonalities across these islands, as well as considerations that are specific to the context of each in dividual island. JeremyBoissevain then adopts an anthropological lens to review the cautionary tale of landscape change in Malta, exploring underlying causes of landscape destruction and limited civil engagement. In the subsequent chapter, Jala Makhzoumi outlines the richness of Mediterranean islands' rural landscapes, focusing on olive landscapes in Cyprus. Her research demonstrates the economic and ecological robustness of various olive cultivation practices, and whilst warning of several threats to such sustainable regimes, she outlines strategies for reconfiguring our approach to rural heritage, in order to integrate such assets into sustainable development strategies. Finally, Stephen Morse concludes the section with an evaluation of sustainable development indicators, and the contribution that these can make towards enhancing the management of Mediterranean island territories. He illustrates his arguments with reference to the two island states of Malta and Cyprus. To conclude, in the final chapter of this publication, we review key insights emerging from the various chapters, and summarize considerations for ecosystem management and sustainable development in Mediterranean Islands. We truly hope that this publication makes some contribution towards safeguarding the "magic' of Mediterranean islands, whilst embracing their dynamic characteristics.Published under the patronage of UNESCO and with the support of the Maltese National Commission for UNESCOpeer-reviewe

Coiled-Coil Domain Containing Protein 124 Is a Novel Centrosome and Midbody Protein That Interacts with the Ras-Guanine Nucleotide Exchange Factor 1B and Is Involved in Cytokinesis

Cytokinetic abscission is the cellular process leading to physical separation of two postmitotic sister cells by severing the intercellular bridge. The most noticeable structural component of the intercellular bridge is a transient organelle termed as midbody, localized at a central region marking the site of abscission. Despite its major role in completion of cytokinesis, our understanding of spatiotemporal regulation of midbody assembly is limited. Here, we report the first characterization of coiled-coil domain-containing protein-124 (Ccdc124), a eukaryotic protein conserved from fungi-to-man, which we identified as a novel centrosomal and midbody protein. Knockdown of Ccdc124 in human HeLa cells leads to accumulation of enlarged and multinucleated cells; however, centrosome maturation was not affected. We found that Ccdc124 interacts with the Ras-guanine nucleotide exchange factor 1B (RasGEF1B), establishing a functional link between cytokinesis and activation of localized Rap2 signaling at the midbody. Our data indicate that Ccdc124 is a novel factor operating both for proper progression of late cytokinetic stages in eukaryotes, and for establishment of Rap2 signaling dependent cellular functions proximal to the abscission site. © 2013 Telkoparan et al

Cd81 Interacts with the T Cell Receptor to Suppress Signaling

CD81 (TAPA-1) is a ubiquitously expressed tetraspanin protein identified as a component of the B lymphocyte receptor (BCR) and as a receptor for the Hepatitis C Virus. In an effort to identify trans-membrane proteins that interact with the T-cell antigen receptor (TCR), we performed a membrane yeast two hybrid screen and identified CD81 as an interactor of the CD3delta subunit of the TCR. We found that in the absence of CD81, in thymocytes from knockout mice, TCR engagement resulted in stronger signals. These results were recapitulated in T cell lines that express low levels of CD81 through shRNA mediated silencing. Increased signaling did not result from alterations in the levels of TCR on the surface of T lymphocytes. Although CD81 is not essential for normal T lymphocyte development, it plays an important role in regulating TCR and possibly pre-TCR signal transduction by controlling the strength of signaling. CD81 dependent alterations in thymocyte signaling are evident in increased CD5 expression on CD81 deficient double positive (DP) thymocytes. We conclude that CD81 interacts with the T cell receptor to suppress signaling. © 2012 Cevik et al