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Cellular Systems (cellular + system)
Selected AbstractsPerformance analysis of microcell/macrocell with reuse partitioning in TDMA-based cellular systemsINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 9 2008Jane Y. Yu Abstract System capacity and grade of service (GoS) are both important for the rapid growth of cellular communication services. In this paper, we propose a two-tier TDMA-based cellular system with macrocell overlaid on microcell clusters by implementing fixed channel assignment (FCA) scheme and fixed reuse partitioning (FRP) scheme in microcell layer and macrocell layer, respectively, named FCA,FRP overlay scheme. Improvement can be achieved in both system capacity and GoS. Theoretical analysis based on the overlay scheme without overflow and with overflow is first presented. It shows that the simulation results are agreed with the analytical results. Then, simulation results, obtained from the overlay scheme with and without overflow, show that the performance in terms of the call blocking probability, the call dropping probability and system capacity of such a system can be greatly improved compared with a conventional one-tier cellular system deployed with FCA or FRP scheme. Copyright © 2008 John Wiley & Sons, Ltd. [source] Practical performance of digital cellular system in mass rapid transit environmentsINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 2 2005Y. P. ZhangArticle first published online: 13 DEC 200 Abstract Leaky coaxial cables have found applications in the creation of network infrastructures for mobile and personal communication services in underground and enclosed spaces. A digital cellular system based on the GSM 900 standard and using radiated mode leaky coaxial cables has been implemented in an underground mass rapid transit environment. This paper presents the practical performance evaluation of the system. First, we start with a brief introduction of a radiated mode leaky coaxial cable and the digital cellular system GSM 900, and then we move into a full description of the measurement campaign; next we focus on an analysis of the measured performance data about received signal level, received signal quality, speech quality index and grade of service. The results show that the system performance is generally good; however, the poor system performance often occurs at the terminals of the leaky coaxial cable. In addition, it is found that the system performance is highly correlated with the density of train passenger. The higher train passenger density degrades the system performance. Copyright © 2004 John Wiley & Sons, Ltd. [source] Design of the ATM-based interconnecting network of the access segment of future cellular systemsINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 2 2001P. P. Demestichas Abstract An important issue in future cellular communication systems is the design of the interconnecting network of their access segment. This problem aims at finding the minimum-cost configuration of cell site switches (CSSs) and local exchanges (LEs) given the base transceiver station (BTS) layout. An extended version of the problem may also comprise the deployment of mobility and service control points-access (MSCPs-A), based on the assumption that CSSs and LEs are not fully capable of handling the logic of the cellular system. In this paper we solve the extended problem, under the additional assumption that the communication among the network elements is based on the ATM technique. The problem is formally defined, optimally formulated, and solved by computationally efficient heuristics. Finally, results are provided and subsequent conclusions are drawn. Copyright © 2001 John Wiley & Sons, Ltd. [source] N, -carboxymethyllysine-modified proteins are unable to bind to RAGE and activate an inflammatory responseMOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 3 2008Timo M. Buetler Abstract Advanced glycation endproducts (AGEs) containing carboxymethyllysine (CML) modifications are generally thought to be ligands of the receptor for AGEs, RAGEs. It has been argued that this results in the activation of pro-inflammatory pathways and diseases. However, it has not been shown conclusively that a CML-modified protein can interact directly with RAGE. Here, we have analyzed whether beta-lactoglobulin (bLG) or human serum albumin (HSA) modified chemically to contain only CML (10,40% lysine modification) can (i) interact with RAGE in vitro and (ii) interact with and activate RAGE in lung epithelial cells. Our results show that CML-modified bLG or HSA are unable to bind to RAGE in a cell-free assay system (Biacore). Furthermore, they are unable to activate pro-inflammatory signaling in the cellular system. Thus, CML probably does not form the necessary structure(s) to interact with RAGE and activate an inflammatory signaling cascade in RAGE-expressing cells. [source] 1950,MHz IMT-2000 field does not activate microglial cells in vitroBIOELECTROMAGNETICS, Issue 2 2010Hideki Hirose Abstract Given the widespread use of the cellular phone today, investigation of potential biological effects of radiofrequency (RF) fields has become increasingly important. In particular, much research has been conducted on RF effects on brain function. To examine any biological effects on the central nervous system (CNS) induced by 1950,MHz modulation signals, which are controlled by the International Mobile Telecommunication-2000 (IMT-2000) cellular system, we investigated the effect of RF fields on microglial cells in the brain. We assessed functional changes in microglial cells by examining changes in immune reaction-related molecule expression and cytokine production after exposure to a 1950,MHz Wideband Code Division Multiple Access (W-CDMA) RF field, at specific absorption rates (SARs) of 0.2, 0.8, and 2.0,W/kg. Primary microglial cell cultures prepared from neonatal rats were subjected to an RF or sham field for 2,h. Assay samples obtained 24 and 72,h after exposure were processed in a blind manner. Results showed that the percentage of cells positive for major histocompatibility complex (MHC) class II, which is the most common marker for activated microglial cells, was similar between cells exposed to W-CDMA radiation and sham-exposed controls. No statistically significant differences were observed between any of the RF field exposure groups and the sham-exposed controls in percentage of MHC class II positive cells. Further, no remarkable differences in the production of tumor necrosis factor-, (TNF-,), interleukin-1, (IL-1,), and interleukin-6 (IL-6) were observed between the test groups exposed to W-CDMA signal and the sham-exposed negative controls. These findings suggest that exposure to RF fields up to 2,W/kg does not activate microglial cells in vitro. Bioelectromagnetics 31:104,112, 2010. © 2009 Wiley-Liss, Inc. [source] Effects of W-CDMA 1950,MHz EMF emitted by mobile phones on regional cerebral blood flow in humansBIOELECTROMAGNETICS, Issue 7 2009Yoko Mizuno Abstract Use of the third generation mobile phone system is increasing worldwide. This is the first study to investigate the effects of the third generation system on regional cerebral blood flow (rCBF) in humans. We compared effects of the electromagnetic field (EMF) emitted from the Wideband Code Division Multiple Access (W-CDMA) cellular system versus sham control exposure on rCBF in humans. Nine healthy male volunteers participated in this study. Positron emission tomography (PET) scans were obtained before, during, and after unilateral 30,min EMF exposure. The subtraction analysis revealed no significant rCBF changes caused by the EMF conditions compared with the sham exposure, suggesting that EMF emitted by a third generation mobile phone does not affect rCBF in humans. Bioelectromagnetics 30:536,544, 2009. © 2009 Wiley-Liss, Inc. [source] Mobile phone base station-emitted radiation does not induce phosphorylation of Hsp27BIOELECTROMAGNETICS, Issue 2 2007H. Hirose Abstract An in vitro study focusing on the effects of low-level radiofrequency (RF) fields from mobile radio base stations employing the International Mobile Telecommunication 2000 (IMT-2000) cellular system was conducted to test the hypothesis that modulated RF fields act to induce phosphorylation and overexpression of heat shock protein hsp27. First, we evaluated the responses of human cells to microwave exposure at a specific absorption rate (SAR) of 80 mW/kg, which corresponds to the limit of the average whole-body SAR for general public exposure defined as a basic restriction in the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines. Second, we investigated whether continuous wave (CW) and Wideband Code Division Multiple Access (W-CDMA) modulated signal RF fields at 2.1425 GHz induced activation or gene expression of hsp27 and other heat shock proteins (hsps). Human glioblastoma A172 cells were exposed to W-CDMA radiation at SARs of 80 and 800 mW/kg for 2,48 h, and CW radiation at 80 mW/kg for 24 h. Human IMR-90 fibroblasts from fetal lungs were exposed to W-CDMA at 80 and 800 mW/kg for 2 or 28 h, and CW at 80 mW/kg for 28 h. Under the RF field exposure conditions described above, no significant differences in the expression levels of phosphorylated hsp27 at serine 82 (hsp27[pS82]) were observed between the test groups exposed to W-CDMA or CW signal and the sham-exposed negative controls, as evaluated immediately after the exposure periods by bead-based multiplex assays. Moreover, no noticeable differences in the gene expression of hsps were observed between the test groups and the negative controls by DNA Chip analysis. Our results confirm that exposure to low-level RF field up to 800 mW/kg does not induce phosphorylation of hsp27 or expression of hsp gene family. Bioelectromagnetics © 2006 Wiley-Liss, Inc. [source] A systems biology approach to understanding atherosclerosisEMBO MOLECULAR MEDICINE, Issue 3 2010Stephen A. Ramsey Abstract Atherosclerosis, a chronic inflammatory disease of the vascular system, presents significant challenges to developing effective molecular diagnostics and novel therapies. A systems biology approach integrating data from large-scale measurements (e.g. transcriptomics, proteomics and genomics) is successfully contributing to deciphering regulatory networks underlying the response of many different cellular systems to perturbations. Such a network analysis strategy using pathway information and data from multiple measurement platforms, tissues and species is a promising approach to elucidate the mechanistic underpinnings of complex diseases. Here, we present our views on the contributions that a systems approach can bring to the study of atherosclerosis, propose ways to tackle the complexity of the disease in a systems manner and review recent systems-level studies of the disease. [source] Optimization and Control of Industrial Microbial Cultivation ProcessesENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 2 2006M. Jenzsch Abstract Compared to the immense achievements in fundamental molecular biological sciences, the improvements in the fermentation and downstream processing technologies used in industry have been less spectacular over the last decade. Hence, there is a misbalance between new cellular systems and production technologies, resulting in a decreasing annual rate of approved production processes. In its PAT initiative the U.S. Food and Drug Administration identifies the potential for continuous improvement and makes concrete suggestions how this can be achieved. Here, some of these suggestions were applied to recombinant protein production with Escherichia coli and Pichia pastoris cultures. Concretely, the development of process operational procedures is discussed that allow a more tight supervision of the processes and the automatic control in cases where processes deviate from their set-point profiles. [source] Limits of life in MgCl2 -containing environments: chaotropicity defines the windowENVIRONMENTAL MICROBIOLOGY, Issue 3 2007John E. Hallsworth Summary The biosphere of planet Earth is delineated by physico-chemical conditions that are too harsh for, or inconsistent with, life processes and maintenance of the structure and function of biomolecules. To define the window of life on Earth (and perhaps gain insights into the limits that life could tolerate elsewhere), and hence understand some of the most unusual biological activities that operate at such extremes, it is necessary to understand the causes and cellular basis of systems failure beyond these windows. Because water plays such a central role in biomolecules and bioprocesses, its availability, properties and behaviour are among the key life-limiting parameters. Saline waters dominate the Earth, with the oceans holding 96.5% of the planet's water. Saline groundwater, inland seas or saltwater lakes hold another 1%, a quantity that exceeds the world's available freshwater. About one quarter of Earth's land mass is underlain by salt, often more than 100 m thick. Evaporite deposits contain hypersaline waters within and between their salt crystals, and even contain large subterranean salt lakes, and therefore represent significant microbial habitats. Salts have a major impact on the nature and extent of the biosphere, because solutes radically influence water's availability (water activity) and exert other activities that also affect biological systems (e.g. ionic, kosmotropic, chaotropic and those that affect cell turgor), and as a consequence can be major stressors of cellular systems. Despite the stressor effects of salts, hypersaline environments can be heavily populated with salt-tolerant or -dependent microbes, the halophiles. The most common salt in hypersaline environments is NaCl, but many evaporite deposits and brines are also rich in other salts, including MgCl2 (several hundred million tonnes of bischofite, MgCl2·6H2O, occur in one formation alone). Magnesium (Mg) is the third most abundant element dissolved in seawater and is ubiquitous in the Earth's crust, and throughout the Solar System, where it exists in association with a variety of anions. Magnesium chloride is exceptionally soluble in water, so can achieve high concentrations (> 5 M) in brines. However, while NaCl-dominated hypersaline environments are habitats for a rich variety of salt-adapted microbes, there are contradictory indications of life in MgCl2 -rich environments. In this work, we have sought to obtain new insights into how MgCl2 affects cellular systems, to assess whether MgCl2 can determine the window of life, and, if so, to derive a value for this window. We have dissected two relevant cellular stress-related activities of MgCl2 solutions, namely water activity reduction and chaotropicity, and analysed signatures of life at different concentrations of MgCl2 in a natural environment, namely the 0.05,5.05 M MgCl2 gradient of the seawater : hypersaline brine interface of Discovery Basin , a large, stable brine lake almost saturated with MgCl2, located on the Mediterranean Sea floor. We document here the exceptional chaotropicity of MgCl2, and show that this property, rather than water activity reduction, inhibits life by denaturing biological macromolecules. In vitro, a test enzyme was totally inhibited by MgCl2 at concentrations below 1 M; and culture medium with MgCl2 concentrations above 1.26 M inhibited the growth of microbes in samples taken from all parts of the Discovery interface. Although DNA and rRNA from key microbial groups (sulfate reducers and methanogens) were detected along the entire MgCl2 gradient of the seawater : Discovery brine interface, mRNA, a highly labile indicator of active microbes, was recovered only from the upper part of the chemocline at MgCl2 concentrations of less than 2.3 M. We also show that the extreme chaotropicity of MgCl2 at high concentrations not only denatures macromolecules, but also preserves the more stable ones: such indicator molecules, hitherto regarded as evidence of life, may thus be misleading signatures in chaotropic environments. Thus, the chaotropicity of MgCl2 would appear to be a window-of-life-determining parameter, and the results obtained here suggest that the upper MgCl2 concentration for life, in the absence of compensating (e.g. kosmotropic) solutes, is about 2.3 M. [source] Functional estrogen receptors alpha and beta are expressed in normal human salivary gland epithelium and apparently mediate immunomodulatory effectsEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 5 2009Maria Tsinti Salivary gland epithelial cells (SGECs) have been shown to participate in immunological responses and have been implicated in the pathogenesis of Sjögren's syndrome (SS). Experimental evidence from animal models indicates that estrogen deficiency may also participate in SS pathogenesis. However, the expression and functionality of the estrogen receptors alpha (ER,) and beta (ER,) in normal human salivary epithelium is unknown. To investigate these points, formalin-fixed, paraffin-embedded specimens and cultured non-neoplastic SGEC lines derived from nine minor salivary gland (MSG) biopsies with normal histology were studied. Immunohistochemical analyses detected the epithelial expression of ER,, ER,1, and ER,2 protein isoforms both in MSG tissues and in cultured SGECs. Such epithelial expression was verified by immunoblotting of various ER proteins in cellular extracts of cultured SGECs (full-length-ER,, ER,-,3, ER,1-long, ER,1-short, and ER,2-long isoforms). Estrogens did not induce growth or apoptosis in cultured SGECs. However, similarly to other cellular systems, treatment of cultured SGECs with estrogens (17,-estradiol and the ER,- and ER,-selective agonists propylpyrazole-triol and diarylpropiolnitrile, respectively) inhibited the interferon-,-inducible expression of intercellular adhesion molecule-1. This finding corroborated the functionality of ER expressed by SGEC. Our results suggest that salivary epithelium expresses constitutively functional ER, and ER, proteins that apparently mediate immunomodulatory effects. [source] Bacitracin is not a specific inhibitor of protein disulfide isomeraseFEBS JOURNAL, Issue 11 2010Anna-Riikka Karala To successfully dissect molecular pathways in vivo, there is often a need to use specific inhibitors. Bacitracin is very widely used as an inhibitor of protein disulfide isomerase (PDI) in vivo. However, the specificity of action of an inhibitor for a protein-folding catalyst cannot be determined in vivo. Furthermore, in vitro evidence for the specificity of bacitracin for PDI is scarce, and the mechanism of inhibition is unknown. Here, we present in vitro data showing that 1 mm bacitracin has no significant effect on the ability of PDI to introduce or isomerize disulfide bonds in a folding protein or on its ability to act as a chaperone. Where bacitracin has an effect on PDI activity, the effect is relatively minor and appears to be via competition of substrate binding. Whereas 1 mm bacitracin has minimal effects on PDI, it has significant effects on both noncatalyzed protein folding and on other molecular chaperones. These results suggest that the use of bacitracin as a specific inhibitor of PDI in cellular systems requires urgent re-evaluation. [source] Access to immunology through the Gene OntologyIMMUNOLOGY, Issue 2 2008Ruth C. Lovering Summary The Gene Ontology (GO) is widely recognized as the premier tool for the organization and functional annotation of molecular aspects of cellular systems. However, for many immunologists the use of GO is a very foreign concept. Indeed, as a controlled vocabulary, GO can almost be considered a new language, and it can be difficult to appreciate the use and value of this approach for understanding the immune system. This review reflects on the application of GO to the field of immunology and explains the process of GO annotation. Finally, this review hopes to inspire immunologists to invest time and energy in improving both the content of the GO and the quality of GO annotations associated with genes of immunological interest. [source] Performance analysis of a reuse partitioning technique for multi-channel cellular systems supporting elastic services,INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 3 2009Gábor Fodor Abstract For multi-cell systems employing intra-cell orthogonal communication channels, inter-cell interference mitigation techniques are expected to be one of the key radio resource management functions. In this paper we propose and analyze a simple reuse partitioning technique (with random and coordinated resource block allocation in neighbor cells) that is able to reduce inter-cell interference. We propose a model that is able to take into account that sessions dynamically enter and leave the system. Rigid sessions require a class-specific fixed number of resource blocks, while elastic sessions can enter the system if a minimum number of resources are allocated to them. In this rather general setting (and using the example of a system employing frequency division for multiple access) we analyze the system performance in terms of the expected number of channel collisions, the session-blocking probabilities, the signal-to-interference-and-noise ratio (SINR) and packet error rate performance. We present numerical results on the various trade-offs between these measures (including the trade-off between the reuse factor and the SINR performance) that provide insight into the behavior of multi-channel cellular systems and help dimensionalize the parameters of a reuse partitioned system. Copyright © 2008 John Wiley & Sons, Ltd. [source] Performance analysis of microcell/macrocell with reuse partitioning in TDMA-based cellular systemsINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 9 2008Jane Y. Yu Abstract System capacity and grade of service (GoS) are both important for the rapid growth of cellular communication services. In this paper, we propose a two-tier TDMA-based cellular system with macrocell overlaid on microcell clusters by implementing fixed channel assignment (FCA) scheme and fixed reuse partitioning (FRP) scheme in microcell layer and macrocell layer, respectively, named FCA,FRP overlay scheme. Improvement can be achieved in both system capacity and GoS. Theoretical analysis based on the overlay scheme without overflow and with overflow is first presented. It shows that the simulation results are agreed with the analytical results. Then, simulation results, obtained from the overlay scheme with and without overflow, show that the performance in terms of the call blocking probability, the call dropping probability and system capacity of such a system can be greatly improved compared with a conventional one-tier cellular system deployed with FCA or FRP scheme. Copyright © 2008 John Wiley & Sons, Ltd. [source] New centralized automatic vehicle location communications software system under GIS environmentINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 9 2005Omar Al-Bayari Abstract Recent advances in wireless communications and networks have integrated relatively new technologies such as Global Positioning System (GPS), to the popular Global System for Mobile Communication (GSM), second generation cellular systems and the Geographic Information Systems (GIS) technologies. Automatic Vehicle Location (AVL) is based on a combination of GPS, GIS and telecommunication technologies. Automatic Vehicle Tracking systems are more and more used for different purposes, especially those related to tracking one vehicle or a fleet of vehicles. In this work, we introduce a new AVL system, which is based and developed under GIS software environment. The centralized software at the control station offers a new technology of transferring the intelligence of tracking system from the car unit, into the control office PC software. Centralized software will reduce the programming efforts in the car unit and will offer better fleet management. Moreover, the core of our system is based on the objects or the controllers of the GIS software, which reduces dramatically the overall system cost. Our system provides an easy access to change the functions of the system, with great possibility to satisfy the local needs. The design of our software will be presented with an explanation of the new supporting technologies that were to create the system. Finally, our software system has been validated using data from local road networks. Copyright © 2005 John Wiley & Sons, Ltd. [source] Power allocation in the context of dimensioning the air-interface of third generation W-CDMA-based cellular systemsINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 5 2002P. Demestichas Abstract The adoption of W-CDMA as an essential component of the air-interface of third-generation cellular systems brings to the foreground the need for new planning methodologies and software tools. In this perspective, this paper addresses planning problems that are important to the dimensioning of W-CDMA-based cellular networks. The problems aim at finding the optimal feasible allocation of transmission power to the sets of uplink and downlink connections that should be supported by the system, so as to cope with a corresponding traffic load scenario. The problems are concisely defined, mathematically formulated and solved by means of two computationally efficient, novel algorithms. The solutions of the problems may be seen as operating points at which the system performance should be driven. Finally, numerical results are presented and concluding remarks are drawn. Copyright © 2002 John Wiley & Sons, Ltd. [source] Performance evaluation of LIBTA/hybrid time-slot selection algorithm for cellular systems,INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 6 2001Jyh-Horng Wen Abstract This paper studies the performance of radio assignment algorithms for portable access in cellular systems. Several channel access procedures are proposed and simulated using block oriented network simulator (BONeS) simulation of a model 36-port system. Simulation results exhibit that load-sharing system with LIBTA algorithm is better than directed retry system with the same algorithm by around 0.9 erlangs while better than quasi-fixed channel assignment (QFCA) system by around 2 erlangs if the grade of service (GOS) is constrained to less than 10 per cent. Plus, a hybrid time-slot selection procedure is proposed to enhance the system performance. It is observed that systems with hybrid time-slot selection perform better than those with LIBTA algorithm in GOS under heavy load. It is also observed that load sharing system with hybrid time-slot selection algorithm is better than directed retry system with the same algorithm by around 0.7 erlangs and better than QFCA system by around 2 erlangs. Copyright © 2001 John Wiley & Sons, Ltd. [source] Design of the ATM-based interconnecting network of the access segment of future cellular systemsINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 2 2001P. P. Demestichas Abstract An important issue in future cellular communication systems is the design of the interconnecting network of their access segment. This problem aims at finding the minimum-cost configuration of cell site switches (CSSs) and local exchanges (LEs) given the base transceiver station (BTS) layout. An extended version of the problem may also comprise the deployment of mobility and service control points-access (MSCPs-A), based on the assumption that CSSs and LEs are not fully capable of handling the logic of the cellular system. In this paper we solve the extended problem, under the additional assumption that the communication among the network elements is based on the ATM technique. The problem is formally defined, optimally formulated, and solved by computationally efficient heuristics. Finally, results are provided and subsequent conclusions are drawn. Copyright © 2001 John Wiley & Sons, Ltd. [source] An adaptive resource reservation for vehicular mobile networksINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 5 2009I. Ben Hamida This paper presents the time-based bandwidth reservation (TBR) algorithm, suitable for handoff management in cellular systems. TBR is based on real-time measurements of mobile stations (position, velocity and acceleration). The scheme consists in sending reservation requests to the neighboring cells based on an extrapolation of the user's motion. The originality of our approach lies in dynamically adjusting the amount of time for which bandwidth has to be allocated and reserved in a cell. In addition, we propose an optimal channel requests arrangement (CRA) algorithm in order to improve the performance of TBR in terms of resource utilization. Finally, we propose VTBR, an adapted and extended version of TBR for better support of vehicular network specificities where service degradation or forced call termination may occur owing to frequent handoffs. Detailed simulation results for TBR and VTBR schemes and a comparison with the guard channel scheme are presented. The results show that TBR and VTBR can efficiently improve the flow dropping probability. Copyright © 2008 John Wiley & Sons, Ltd. [source] A simple approach for optimum channel reservation for hand-over calls in cellular systemsINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 4 2006Mohamed Laith In cellular mobile communication systems, while an active subscriber is moving from one cell to another, the service of his call needs to be handed over to the base station of the new cell. In such a case, cutting the service, due to all channels being busy at the new base station, would be more annoying to subscribers than normal congestion at the first initiation of calls. This paper is concerned with providing a simple approach for choosing the optimum set of channels that need to be reserved for hand-over calls, while maintaining an acceptable overall system performance. The approach evaluates channel reservation at the cell level, taking into account the offered traffic, that is both the newly initiated original traffic and the hand-over traffic. The approach produces a simple mathematical solution based on Erlang-B formula. It uses the concept of ,Combined Failure Rate' to evaluate the required reservation. The approach is supported by a simulation study that verifies its validity. Applications of the approach to illustrate its use are also presented.,Copyright © 2006 John Wiley & Sons, Ltd. [source] IDENTIFICATION AND COMPARATIVE GENOMIC ANALYSIS OF SIGNALING AND REGULATORY COMPONENTS IN THE DIATOM THALASSIOSIRA PSEUDONANA,JOURNAL OF PHYCOLOGY, Issue 3 2007Anton Montsant Diatoms are unicellular brown algae that likely arose from the endocytobiosis of a red alga into a single-celled heterotroph and that constitute an algal class of major importance in phytoplankton communities around the globe. The first whole-genome sequence from a diatom species, Thalassiosira pseudonana Hasle et Heimdal, was recently reported, and features that are central to diatom physiology and ecology, such as silicon and nitrogen metabolism, iron uptake, and carbon concentration mechanisms, were described. Following this initial study, the basic cellular systems controlling cell signaling, gene expression, cytoskeletal structures, and response to stress have been cataloged in an attempt to obtain a global view of the molecular foundations that sustain such an ecologically successful group of organisms. Comparative analysis with several microbial, plant, and metazoan complete genome sequences allowed the identification of putative membrane receptors, signaling proteins, and other components of central interest to diatom ecophysiology and evolution. Thalassiosira pseudonana likely perceives light through a novel phytochrome and several cryptochrome photoreceptors; it may lack the conserved RHO small-GTPase subfamily of cell-polarity regulators, despite undergoing polarized cell-wall synthesis; and it possesses an unusually large number of heat-shock transcription factors, which may indicate the central importance of transcriptional responses to environmental stress. The availability of the complete gene repertoire will permit a detailed biochemical and genetic analysis of how diatoms prosper in aquatic environments and will contribute to the understanding of eukaryotic evolution. [source] Cover Picture: (Mol. Inf.MOLECULAR INFORMATICS, Issue 8-9 20108-9/2010) Molecular Informatics publishes research that will deepen our understanding about information storage and processing on the molecular level, signaling and regulation of biological and chemical systems including cellular systems and macromolecular assemblies, modeling of molecular interactions and networks, and the design of molecular modulators that exhibit desired biochemical and pharmacological effects. Various aspects of this transdisciplinary scientific area are depicted on the cover: Cells with their nuclei and membranes (image courtesy of Dr. A. Schreiner and E. Resch), models of receptor-ligand interactions, and an artistic representation of "biological information" as multiple bit-codes presented on a right-handed helix. [source] Cover Picture: (Mol. Inf.MOLECULAR INFORMATICS, Issue 6-7 20107/2010) Molecular Informatics publishes research that will deepen our understanding about information storage and processing on the molecular level, signaling and regulation of biological and chemical systems including cellular systems and macromolecular assemblies, modeling of molecular interactions and networks, and the design of molecular modulators that exhibit desired biochemical and pharmacological effects. Various aspects of this transdisciplinary scientific area are depicted on the cover: Cells with their nuclei and membranes (image courtesy of Dr. A. Schreiner and E. Resch), models of receptor-ligand interactions, and an artistic representation of "biological information" as multiple bit-codes presented on a right-handed helix. [source] Cover Picture: (Mol. Inf.MOLECULAR INFORMATICS, Issue 5 20105/2010) Molecular Informatics publishes research that will deepen our understanding about information storage and processing on the molecular level, signaling and regulation of biological and chemical systems including cellular systems and macromolecular assemblies, modeling of molecular interactions and networks, and the design of molecular modulators that exhibit desired biochemical and pharmacological effects. Various aspects of this transdisciplinary scientific area are depicted on the cover: Cells with their nuclei and membranes (image courtesy of Dr. A. Schreiner and E. Resch), models of receptor-ligand interactions, and an artistic representation of "biological information" as multiple bit-codes presented on a right-handed helix. [source] Cover Picture: (Mol. Inf.MOLECULAR INFORMATICS, Issue 4 20104/2010) Molecular Informatics publishes research that will deepen our understanding about information storage and processing on the molecular level, signaling and regulation of biological and chemical systems including cellular systems and macromolecular assemblies, modeling of molecular interactions and networks, and the design of molecular modulators that exhibit desired biochemical and pharmacological effects. Various aspects of this transdisciplinary scientific area are depicted on the cover: Cells with their nuclei and membranes (image courtesy of Dr. A. Schreiner and E. Resch), models of receptor-ligand interactions, and an artistic representation of "biological information" as multiple bit-codes presented on a right-handed helix. [source] Cover Picture: (Mol. Inf.MOLECULAR INFORMATICS, Issue 3 20103/2010) Molecular Informatics publishes research that will deepen our understanding about information storage and processing on the molecular level, signaling and regulation of biological and chemical systems including cellular systems and macromolecular assemblies, modeling of molecular interactions and networks, and the design of molecular modulators that exhibit desired biochemical and pharmacological effects. Various aspects of this transdisciplinary scientific area are depicted on the cover: Cells with their nuclei and membranes (image courtesy of Dr. A. Schreiner and E. Resch), models of receptor-ligand interactions, and an artistic representation of "biological information" as multiple bit-codes presented on a right-handed helix. [source] Cover Picture: (Mol. Inf.MOLECULAR INFORMATICS, Issue 1-2 20101-2/2010) Molecular Informatics publishes research that will deepen our understanding about information storage and processing on the molecular level, signaling and regulation of biological and chemical systems including cellular systems and macromolecular assemblies, modeling of molecular interactions and networks, and the design of molecular modulators that exhibit desired biochemical and pharmacological effects. Various aspects of this transdisciplinary scientific area are depicted on the cover: Cells with their nuclei and membranes (image courtesy of Dr. A. Schreiner and E. Resch), models of receptor-ligand interactions, and an artistic representation of "biological information" as multiple bit-codes presented on a right-handed helix. [source] Protease-activated receptors: novel central role in modulation of gastric functionsNEUROGASTROENTEROLOGY & MOTILITY, Issue 4 2010K. N. Browning Abstract, Protease-activated receptors (PARs) are members of a subfamily of G-protein-coupled receptors that regulate diverse cell functions in response to proteolytic cleavage of an anchored peptide domain that acts as a ,tethered' receptor-activating ligand. PAR-1 and PAR-2 in particular are present throughout the gastrointestinal (GI) tract and play prominent roles in the regulation of GI epithelial function, motility, inflammation and nociception. In a recent article in Neurogastroenterology and Motility, Wang et al. demonstrate, for the first time, that PAR-1 and PAR-2 are present on preganglionic parasympathetic neurons within the rat brainstem. As in other cellular systems, proteases such as thrombin and trypsin activate PAR-1 and PAR-2 on neurons of the dorsal motor nucleus of the vagus (DMV), leading to an increase in intracellular calcium levels via signal transduction mechanisms involving activation of phospholipase C and inositol triphosphate (IP3). The authors also report that the level of PAR-1 and PAR-2 transcripts in DMV tissue is increased following experimental colitis, suggesting that inflammatory conditions may modulate neuronal behavior or induce plasticity within central vagal neurocircuits. It seems reasonable to hypothesize, therefore, that the activity and behavior of vagal efferent motoneurons may be modulated directly by local and/or systemic proteases released during inflammation. This, in turn, may contribute to the increased incidence of functional GI disorders, including gastric dysmotility, delayed emptying and gastritis observed in patients with inflammatory bowel diseases. [source] Low temperature-induced systems failure in Escherichia coli: Insights from rescue by cold-adapted chaperonesPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 1 2006Massimo Strocchi Abstract The growth of Escherichia coli cells is impaired at temperatures below 21°C and stops at 7.5°C; however, growth of a transgenic strain producing the cold-adapted chaperones Cpn60 and Cpn10 from the psychrophilic bacterium Oleispira antarctica is good at low temperatures. The E.,coli,cpn+ transgene offers a novel opportunity for examining the essential protein for cell viability at low temperatures. By screening a large-scale protein map (proteome) of cells of K-12 and its Cpn+ transgene incubated at 4°C, we identified 22,housekeeping proteins involved in systems failure of E.,coli when confronted with low temperature. Through co-immunoprecipitation of Cpn60, Northern blot, and in vitro refolding, we systematically identified that protein,chaperone interactions are key determinants of their protein functions at low temperatures. Furthermore, chromosomal gene deletion experiments suggest that the mechanism of cold-induced systems failure in E.,coli is cold-induced inactivation of the GroELS chaperonins and the resulting failure to refold cold-inactivated Dps, ClpB, DnaK and RpsB proteins. These findings: (1),indicate the potential importance of chaperones in cold sensitivity, cold adaptation and cold tolerance in cellular systems, and (2),suggest the identity of a few key cold-sensitive chaperone-interacting proteins that get inactivated and ultimately cause systems failure in E.,coli cells at low temperatures. [source] | |||||||||||||||||||