Cellular system

The non-homologous end-joining (NHEJ) pathway is a mechanism to repair DNA double strand breaks, which can introduce mutations at repair sites. We constructed new cellular systems to specifically analyze sequence modifications occurring at the repair site. In particular, we looked for the presence of telomeric repeats at the repair junctions, since our previous work indicated that telomeric sequences could be inserted at break sites in germ-line cells during primate evolution. To induce specific DNA breaks, we used the I-SceI system of Saccharomyces cerevisiae or digestion with restriction enzymes. We isolated human and hamster cell lines containing the I-SceI target site integrated in a single chromosomal locus and we exposed the cells to a continuous expression of the I-SceI endonuclease gene. Additionally, we isolated human cell lines that expressed constitutively the I-SceI endonuclease and we introduced the target site on an episomal plasmid stably transfected into the cells. These strategies allowed us to recover repair junctions in which the I-SceI target site was modified at high frequency (100% in hamster cells and about 70% in human cells). Finally, we analyzed junctions produced on an episomal plasmid linearized by restriction enzymes. In all the systems studied, sequence analysis of individual repair junctions showed that deletions were the most frequent modifications, being present in more than 80% of the junctions. On the episomal plasmids, the average deletion length was greater than at intrachromosomal sites. Insertions of nucleotides or deletions associated with insertions were rare events. Junction organization suggested different mechanisms of formation. To check for the insertion of telomeric sequences, we screened plasmid libraries representing about 3.5 × 10 5 junctions with a telomeric repeat probe. No positive clones were detected, suggesting that the addition of telomeric sequences during double strand break repair in somatic cells in culture is either a very rare event or does not occur at all.

We consider blind channel estimation in a single-input single-output full-duplex communication system, where both the self-interference and the communication channels need to be accurately estimated. In this context, blind estimators are attractive as they improve bandwidth efficiency but they suffer from the phase ambiguity problem. In this paper, we first formally define and analyse this ambiguity and then develop a general framework for testing and designing modulation sets for blind estimation of channel parameters. We mathematically show that simply shifting the mean of the $M$-PSK modulation resolves the ambiguity problem. We also show how this can be extended to more general modulation sets. Finally, we propose an expectation maximization (EM) iterative estimator and a closed form minimum mean square error (MMSE) estimator for use with the shifted modulation set. Since the non-data aided Cram\'er-Rao lower bound (CRLB) or the Bayesian CRLB (BCRLB) are intractable, we deri...

We consider the problem of finding optimal, fair and distributed power-rate strategies to achieve the sum capacity of the Gaussian multiple-access block-fading channel. In here, the transmitters have access to only their own fading coefficients, while the receiver has global access to all the fading coefficients. Outage is not permitted in any communication block. The resulting average sum-throughput is also known as ‘power-controlled adaptive sum-capacity’, which appears as an open problem in literature. This paper presents the power-controlled adaptive sum-capacity of a wide-class of popular MAC models. In particular, we propose a power-rate strategy in the presence of distributed channel state information (CSI), which is throughput optimal when all the users have identical channel statistics. The proposed scheme also has an efficient implementation using successive cancellation and rate-splitting. We propose an upperbound when the channel laws are not identical. Furthermore, the ...

In this paper blockwise decoded convolutional encoding is used and evaluated for the design of an error protection coding scheme matched with the characteristics of a variable-rate speech coder's output bit-stream. The performance is evaluted for a symmetrical, interference limited, cellular system. Both microcellular and macrocellular propagation models are used. Different reuse factors are taken into consideration. *This work has been partially supported by MURST "ex-quota 4 0 % , Italy.

Neuroblastoma is one of the most common extracranial solid tumours in childhood with a poor prognosis in its advanced stage. Treatment failure is often associated to the occurrence of drug resistance. To date, treatment of paediatric neuroblastoma is still dismal, and therefore novel effective drugs are awaited. In recent years, an increasing interest has concentrated on camptothecin analogues. Topotecan and irinotecan, the only two clinically relevant camptothecin derivatives to date, have entered clinical trials in neuroblastoma but so far the results have been disappointing. Gimatecan (ST1481, LBQ707; 7-t-butoxyiminomethylcamptothecin), is a novel lipophilic camptothecin derivative that was selected from a series of lipophilic analogues rationally designed and synthesized in order to overcome some of the main drawbacks of conventional camptothecins, limiting their clinical efficacy. Gimatecan is endowed with potent antitumour activity, strong topoisomerase I inhibition, stable drug-target interactions and a better pharmacological profile. The present study deals with the comparative evaluation of cellular pharmacology features of gimatecan, topotecan and SN38 in neuroblastoma cell lines. We show that, despite the lowest intracellular accumulation, gimatecan was the most active among the camptothecin analogues studied. Our findings suggest that the high activity of gimatecan in neuroblastoma is related to the ability of this novel analogue to cause a very high number of DNA breaks as assessed by the Comet assay in both cellular or sub-cellular systems. We propose that DNA strand breaks efficiency as measured by the Comet assay might provide important information about the stability of the ternary complexes induced by camptothecin compounds.

The combination of CDMA and space time block coding (STBC) has been proposed for indoor environment where the delay spreads are very small and the channel is flat fading. However, these schemes are not valid for the outdoor situation where the delay spreads are significantly large and the channel is frequency selective fading. Therefore, in our paper, we propose CDMA with space-time block coding with three transmit antennas for frequency selective fading channels (outdoor situation) without loss of diversity order. In the proposed scheme, Orthogonal Frequency Division Multiplexing (OFDM) technique is used to mathematically change the frequency selective fading channel to multi flat fading channels. It is worthy of noting that our scheme provides very low decoding complexity compared to CDMA with space time trellis coding. Also, the proposed scheme provides high performance and high bandwidth efficiency. Simulation results are provided to show the significant improvement in the perfo...

Ž . The number of reports on the effects induced by radiofrequency RF electromagnetic fields and microwave MW radiation in various cellular systems is still increasing. Until now no satisfactory mechanism has been proposed to explain the biological effects of these fields. One of the current theories is that heat generation by RFrMW is the cause, in spite of the fact that a great number of studies under isothermal conditions have reported significant cellular changes after exposure to RFrMW. Therefore, this study was undertaken to investigate which effect MW radiation from these fields in combination with a significant change of temperature could have on cell w proliferation. The experiments were performed on the same cell line, and with the same exposure system as in a previous work S. Kwee, P. Raskmark, Changes in cell proliferation due to environmental non-ionizing radiation: 2. Microwave radiation, Bioelectrochem. Ž . x Bioenerg., 44 1998 , pp. 251-255 . The field was generated by signal simulation of the Global System for Mobile communications Ž . GSM of 960 MHz. Cell cultures, growing in microtiter plates, were exposed in a specially constructed chamber, a Transverse Ž . Ž . Electromagnetic TEM cell. The Specific Absorption Rate SAR value for each cell well was calculated for this exposure system. However, in this study the cells were exposed to the field at a higher or lower temperature than the temperature in the field-free incubator i.e., the temperature in the TEM cell was either 39 or 35 " 0.18C. The corresponding sham experiments were performed under exactly the same experimental conditions. The results showed that there was a significant change in cell proliferation in the exposed cells in Ž . comparison to the non-exposed control cells at both temperatures. On the other hand, no significant change in proliferation rate was found in the sham-exposed cells at both temperatures. This shows that biological effects due to RFrMW cannot be attributed only to a change of temperature. Since the RFrMW induced changes were of the same order of magnitude at both temperatures and also comparable to our previous results under isothermal conditions at 378C, cellular stress caused by electromagnetic fields could initiate the changes in cell cycle reaction rates. It is widely accepted that certain classes of heat-shock proteins are involved in these stress reactions.

Insulin resistance is an important feature of type 2 diabetes and obesity. The underlying mechanisms of insulin resistance are still unclear and may involve pathological changes in multiple tissues. Mitochondrial dysfunction, including mitochondrial loss and over-production of oxidants, has been suggested to be involved in the development of insulin resistance. Increasing evidence suggests that targeting mitochondria to protect mitochondrial function as a unique measure, i.e. mitochondrial medicine, could prevent and ameliorate various diseases associated with mitochondrial dysfunction. In this review, we have summarized recent progress in pharmaceutical and nutritional studies of drugs and nutrients to targeting mitochondria by stimulating mitochondrial metabolism (biogenesis and degradation) to improve mitochondrial function and decrease oxidative stress for preventing and ameliorating insulin resistance. We have focused on nutrients from natural sources to stimulating mitochondrial biogenesis in cellular systems and in animal models. The in vitro and in vivo studies, especially our own work on the effects and mechanisms of mitochondrial targeting nutrients or their combinations, may help us to understand the importance and mechanisms of mitochondrial biogenesis in insulin resistance, and provide hope for developing mitochondria-targeting agents for preventing and treating insulin resistance in type 2 diabetes and obesity.

Insulin resistance is an important feature of type 2 diabetes and obesity. The underlying mechanisms of insulin resistance are still unclear and may involve pathological changes in multiple tissues. Mitochondrial dysfunction, including mitochondrial loss and over-production of oxidants, has been suggested to be involved in the development of insulin resistance. Increasing evidence suggests that targeting mitochondria to protect mitochondrial function as a unique measure, i.e. mitochondrial medicine, could prevent and ameliorate various diseases associated with mitochondrial dysfunction. In this review, we have summarized recent progress in pharmaceutical and nutritional studies of drugs and nutrients to targeting mitochondria by stimulating mitochondrial metabolism (biogenesis and degradation) to improve mitochondrial function and decrease oxidative stress for preventing and ameliorating insulin resistance. We have focused on nutrients from natural sources to stimulating mitochondrial biogenesis in cellular systems and in animal models. The in vitro and in vivo studies, especially our own work on the effects and mechanisms of mitochondrial targeting nutrients or their combinations, may help us to understand the importance and mechanisms of mitochondrial biogenesis in insulin resistance, and provide hope for developing mitochondria-targeting agents for preventing and treating insulin resistance in type 2 diabetes and obesity.

The location of base stations (BS) and the allocation of channels are of paramount importance for the performance of cellular radio networks. Also cellular service providers are now being driven by the goal to enhance performance, particularly as it relates to the receipt and transmission of emergency crash notification messages generated by automobile telematics systems. In this paper, a mixed integer-programming (MIP) problem is proposed, which integrates into the same model the base station location problem, the frequency channel assignment problem and the emergency notification problem. The purpose of unifying these three problems in the same model is to treat the tradeoffs among them, providing a higher quality solution to the cellular system design. Some properties of the formulation are proposed that give us more insight into the problem structure. An instance generator is developed that randomly creates test problems. A few greedy heuristics are proposed to obtain quick solutions that turn out to be very good in some cases. To further improve the optimality gap, we develop a Lagrangean Heuristic technique that builds on the solution obtained by the greedy heuristics. Finally, the performance of these methods is analyzed by extensive numerical tests and a sample case study is presented.

The location of base stations (BS) and the allocation of channels are of paramount importance for the performance of cellular radio networks. Also cellular service providers are now being driven by the goal to enhance performance, particularly as it relates to the receipt and transmission of emergency crash notification messages generated by automobile telematics systems. In this paper, a mixed integer-programming (MIP) problem is proposed, which integrates into the same model the base station location problem, the frequency channel assignment problem and the emergency notification problem. The purpose of unifying these three problems in the same model is to treat the tradeoffs among them, providing a higher quality solution to the cellular system design. Some properties of the formulation are proposed that give us more insight into the problem structure. An instance generator is developed that randomly creates test problems. A few greedy heuristics are proposed to obtain quick solutions that turn out to be very good in some cases. To further improve the optimality gap, we develop a Lagrangean Heuristic technique that builds on the solution obtained by the greedy heuristics. Finally, the performance of these methods is analyzed by extensive numerical tests and a sample case study is presented.

This paper describes experiments in cell systems that have helped clarify intracellular mechanisms leading to apoptosis. Using the cellular systems described (rat retinal whole mount, rat retinal cell line E1A-NR3, and rat neuronal cell line NG 108-15), it has been possible to demonstrate that intracellular pH change may be the mechanism through which carbonic anhydrases modulate vasodilation and act on retinal blood flow. Intracellular pH can also be used to monitor intracellular changes that precede and occur during apoptosis. The findings also show the potential significance of advanced glycation end products (AGEs) in the glaucomatous process, and the potential for brimonidine and memantine to rescue neuroretinal cells from AGE-induced retinal damage.

This paper describes experiments in cell systems that have helped clarify intracellular mechanisms leading to apoptosis. Using the cellular systems described (rat retinal whole mount, rat retinal cell line E1A-NR3, and rat neuronal cell line NG 108-15), it has been possible to demonstrate that intracellular pH change may be the mechanism through which carbonic anhydrases modulate vasodilation and act on retinal blood flow. Intracellular pH can also be used to monitor intracellular changes that precede and occur during apoptosis. The findings also show the potential significance of advanced glycation end products (AGEs) in the glaucomatous process, and the potential for brimonidine and memantine to rescue neuroretinal cells from AGE-induced retinal damage.

Polychlorinated biphenyls (PCBs) are ubiquitous, persistent environmental contaminants that affect a number of cellular systems, including neutrophils. Among the effects caused by the noncoplanar PCB 2,2′,4,4′,-tetrachlorobiphenyl (2244-TCB) in granulocytic HL-60 cells are increases in superoxide anion production, activation of phospholipase A 2 with subsequent release of arachidonic acid (AA), and upregulation of the inflammatory gene cyclooxygenase-2 (COX-2). The objective of this study was to determine the signal transduction pathways involved in the upregulation of COX-2 by 2244-TCB. Treatment of HL-60 cells with 2244-TCB led to increased expression of COX-2 mRNA. This increase was prevented by the transcriptional inhibitor actinomycin D in cells pretreated with 2244-TCB for 10 minutes. The increase in COX-2 mRNA was associated with release of 3 H-AA, phosphorylation of p38 and extracellular signal-regulated kinase (ERK) mitogen-activated protein (MAP) kinases, increased levels of nuclear NF-κB and increased superoxide anion production. Bromoenol lactone, an inhibitor of the calcium-independent phospholipase A 2 , reduced 3 H-AA release but had no effect on COX-2 mRNA, protein or activity. Pretreatment with SB-202190 or SB-203580, inhibitors of the p38 MAP kinase pathway, prevented the 2244-TCBmediated induction of COX-2 and phosphorylation of p38 and ERK MAP kinases. These inhibitors did not alter 3 H-AA release. Treatment with PD 98059 or U 0126, inhibitors of the MAP/ERK (MEK) pathway, prevented the 2244-TCB-mediated activation of ERK but had no effect on COX-2 induction or p38 phosphorylation. 2244-TCB treatment did not affect c-Jun N-terminal kinase (JNK) phosphorylation. 2244-TCB exposure increased the amount of nuclear NF-κB. This increase was prevented by pretreatment with p38 MAP kinase inhibitors, but not by pretreatment with MEK inhibitors. Pretreatment with inhibitors of NF-κB prevented the 2244-TCB-mediated induction of COX-2 mRNA. 2244-TCB-mediated increases in superoxide anion were prevented by the NADPH oxidase inhibitor apocynin or the free radical scavenger 4-hydroxy TEMPO, but neither of these inhibitors affected the 2244-TCB-induced changes in COX-2 mRNA levels or 3 H-AA release. Taken together these data suggest that p38 MAP kinase-dependent activation of NF-κB is critical for the 2244-TCB-mediated upregulation of COX-2 mRNA.

In this work we investigate the information theoretic capacity of the uplink of a cellular system. Assuming centralised processing for all Base Stations, we consider a power-law path loss model along with variable cell size (variable density of Base Stations) and we formulate an average path-loss approximation. Considering a realistic Rician flat fading environment, the analytical result for the per-cell capacity is derived for a large number of users distributed over each cell. We extend this general approach to model the uplink of sectorized cellular system. To this end, we assume that the user terminals are served by perfectly directional receiver antennas, dividing the cell coverage area into perfectly non-interfering sectors. We show how the capacity is increased (due to degrees of freedom gain) in comparison to the single receiving antenna system and we investigate the asymptotic behaviour when the number of sectors grows large. We further extend the analysis to find the capacity when the multiple antennas used for each Base Station are omnidirectional and uncorrelated (power gain on top of degrees of freedom gain). We validate the numerical solutions with Monte Carlo simulations for random fading realizations and we interpret the results for the real-world systems.

We previously established a role for HSP27 as a predictive marker for therapeutic response towards gemcitabine in pancreatic cancer. Here, we investigate the underlying mechanisms of HSP27-mediated gemcitabine sensitivity. Utilizing a pancreatic cancer cell model with stable HSP27 overexpression, cell cycle arrest and apoptosis induction were analysed by flow cytometry, nuclear staining, immunoblotting and mitochondrial staining. Drug sensitivity studies were performed by proliferation assays. Hyperthermia was simulated using mild heat shock at 41.8°C. Upon gemcitabine treatment, HSP27-overexpressing cells displayed an early S-phase arrest subsequently followed by a strongly increased sub-G1 fraction. Apoptosis was characterized by PARP-, CASPASE 3-, CASPASE 8-, CASPASE 9-and BIM-activation along with a mitochondrial membrane potential loss. It was reversible through chemical caspase inhibition. Importantly, gemcitabine sensitivity and PARP cleavage were also elicited by heat shock-induced HSP27 overexpression, although to a smaller extent, in a panel of pancreatic cancer cell lines. Finally, HSP27overexpressing pancreatic cancer cells displayed an increased sensitivity also towards death receptor-targeting agents, suggesting another proapoptotic role of HSP27 along the extrinsic apoptosis pathway. Taken together, in contrast to the well-established anti-apoptotic properties of HSP27 in cancer, our study reveals novel pro-apoptotic functions of HSP27-mediated through both the intrinsic and the extrinsic apoptotic pathways-at least in pancreatic cancer cells. HSP27 could represent a predictive marker of therapeutic response towards specific drug classes in pancreatic cancer and provides a novel molecular rationale for current clinical trials applying the combination of gemcitabine with regional hyperthermia in pancreatic cancer patients.

Accommodating the needs of a large number of diverse users in the Internet of Things (IoT), notably managing how the users access the common channel, has posed unique challenges to the network designers. In this paper, we study a heterogeneous IoT network consisting of multiple classes of users who may have different service requirements. For this network, we consider the application of irregular repetition slotted ALOHA (IRSA) that is shown to offer large throughput for single-class networks. Then, we focus on finding the network performance boundaries by studying the set of feasible throughput values for each class, called the capacity region. To this end, we first introduce the concept of dual network of a multi-class network meaning a homogeneous network with the same number of users. We then prove that finding the capacity region of the assumed multi-class network boils down to finding the maximum achievable throughput of its dual network. Using this finding, we then discuss how any given point of the capacity region can be achieved. Further, a delay performance study is conducted to evaluate the average and maximum packet transmission delay experienced by the users of each class.

Accommodating the needs of a large number of diverse users in the Internet of Things (IoT), notably managing how the users access the common channel, has posed unique challenges to the network designers. In this paper, we study a heterogeneous IoT network consisting of multiple classes of users who may have different service requirements. For this network, we consider the application of irregular repetition slotted ALOHA (IRSA) that is shown to offer large throughput for single-class networks. Then, we focus on finding the network performance boundaries by studying the set of feasible throughput values for each class, called the capacity region. To this end, we first introduce the concept of dual network of a multi-class network meaning a homogeneous network with the same number of users. We then prove that finding the capacity region of the assumed multi-class network boils down to finding the maximum achievable throughput of its dual network. Using this finding, we then discuss ho...

The reinitiation of the synthesis of major RNA species has been studied in 37 RC cells after maximal inhibition of RNA synthesis by actinomycin D (AMD). During the period of recovery from AMD, resynthesized RNA (rec-RNA) is initially composed of almost exclusively light (4-14S) heterogeneous RNA species. All normal species of RNA can be detected in the rec-RNA spectrum as early as 3 h after AMD removal. The synthesis of low molecular weight methylated RNA species increases slightly during the early period after AMD removal, while the increase of low molecular weight unmethylated species is more significant during the same period. Much of the radioactivity in the polyribosomal fraction is EDTA and puromycin sensitive. Since polysomal, puromycin-sensitive RNA is polyadenylated (as evidenced by the binding of poly-U filters), and is heterogenous in size, it belongs to the m-RNA class. The synthesis of m-RNA increases immediately after AMD removal, whereas the reinitiation of the r-RNA ...

In the downlink of an Orthogonal Frequency Division Multiplexing (OFDM) system, pilot symbols are transmitted across the time-frequency plane for the receiving device to estimate the channel's response. The density of such pilot is often designed to accommodate the devices under most extreme channel conditions. This worst case scenario design results in unnecessary overhead that could have been used for data transmission otherwise. In this paper, we propose an adaptive pilot allocation scheme that, in addition to a low-rate periodically transmitted pilot symbols, sends device associated pilot adaptively only when called for by the channel condition, thereby reducing the overall pilot overhead. Furthermore, the placement of signaling channel and reduced complexity channel estimator required to facilitate this adaptive operation are also addressed.

Optical wireless communications in space are degraded by atmospheric turbulence, light attenuation, and detector noise. In this paper, we develop a neural network (NN) channel estimator that is optimized across a wide range of signal-to-noise ratio levels during the training stage. In addition, we propose a novel autoencoder (AE) model to develop a complete physical layer communication system in space optical communications (SOC). The AE is designed to work with both perfect and imperfect channel state information (CSI), providing a flexible and versatile solution for SOC. Batch normalization and multipledecoders are incorporated into the proposed AE, which improves receiver learning capabilities by allowing the use of more than one path to update encoder and decoder weights. This novel approach can reduce the error in detection relative to state-of-the-art models. Using the system tool kit simulator, we examine our system's performance in a downlink SOC channel that connects a geostationary satellite to a ground station in Log-normal fading channel. Furthermore, we evaluate the performance of our system in a downlink channel that establishes a connection between a Low Earth Orbit satellite and a ground station, operating in Gamma-Gamma fading channel. The numerical results show that the proposed channel estimator NN is superior to state-of-the-art learning-based frameworks and achieves the same level of performance as the minimum mean square error estimator. Additionally, with no fading and for both perfect and imperfect CSI with different code rates and fading channels, the proposed AE-based detection outperforms both benchmark learning frameworks and most popular convolutional codes.

The cytotoxic activity of ecteinascidin 743 (ET-743), a natural product derived from the marine tunicate Ecteinascidia turbinata that exhibits potent anti-tumor activity in pre-clinical systems and promising activity in phase I and II clinical trials, was investigated in a number of cell systems with well-defined deficiencies in DNA-repair mechanisms. ET-743 binds to N2 of guanine in the minor groove, but its activity does not appear to be related to DNA-topoisomerase I poisoning as the drug is equally active in wild-type yeast and in yeast with a deletion in the DNA-topoisomerase I gene. Defects in the mismatch repair pathway, usually associated with increased resistance to methylating agents and cisplatin, did not affect the cytotoxic activity of ET-743. However, ET-743 did show decreased activity (from 2-to 8-fold) in nucleotide excision repair (NER)-deficient cell lines compared to NER-proficient cell lines, from either hamsters or humans. Restoration of NER function sensitized cells to ET-743 treatment. The DNA double-strand-break repair pathway was also investigated using human glioblastoma cell lines MO59K and MO59J, respectively, proficient and deficient in DNA-dependent protein kinase (DNA-PK). ET-743 was more effective in cells lacking DNA-PK; moreover, pre-treatment of HCT-116 colon carcinoma cells with wortmannin, a potent inhibitor of DNA-PK, sensitized cells to ET-743. An increase in ET-743 sensitivity was also observed in ataxia telangiectasia-mutated cells. Our data strongly suggest that ET-743 has a unique mechanism of interaction with DNA.

When the systems evolved from analog to digital, the performance was improved by the use of power control on the one hand and different modulations and coding schemes on the other. Condensing the available information we are able to propose a new concept of power control. The concept is applicable to real systems, since it uses the available measurements for

It is well known that continuous phase modulation (CPM) serially concatenated with convolutional codes provides powerful error correction through iterative decoding. CPM also has the inherent benefits of being bandwidth efficient and compatible with non-linear amplifiers. A disadvantage of CPM is its relatively poor performance over ISI channels. In this paper we compare two methods of iteratively equalizing CPM. The first is the optimal method that combines the memory of the CPM with the memory of the channel such that decoding is performed over the resulting "super-trellis". The second method is the parallel interference cancellation method using the Laurent signal model. The two methods are compared through Monte Carlo simulations and EXIT chart analysis.

Cellular materials (dense emulsions, foams, and vesicles) made out of two different phases, one being dispersed in the other, may coarsen in time through coalescence or rupturing events of the thin liquid domains that separate adjacent cells. In this Letter we study the destruction through coalescence of a model cellular material: A monodisperse dense emulsion. We show that the frequency of rupturing events is proportional to the surface of contact between the droplets, and we measure the activation energy and the natural frequency associated with coalescence. We point out that this process of destruction remarkably preserves monodispersity throughout the growth. [S0031-9007(98)

3GPP LTE is the evolution of the UMTS which will make possible to deliver next generation high quality multimedia services according to the users' expectations. Since Radio Resource Management (RRM) has been recognized as a key point to successfully accomplish this target, the performance evaluation of a multi-cell resource allocation scheme applied to LTE downlink (DL) is presented in this paper. A semidistributed and a fully-distributed RRM framework are compared on the basis of the obtained system throughput. Detailed link level simulations have also been carried out to properly back up the system level results.

Iterative joint detection of random CDMA is considered in conjunction with error control coding, in particular using low-density parity-check (LDPC) codes. The spreading sequences are partitioned into sections, called "partitioned spreading (PS)", creating an artificial repetition code which interfaces the LDPC code with the multiple access channel. A suboptimal, but efficient cancelation processor is used at the multiple access processing node in the factor graph describing the overall system. This system is then analyzed using Gaussian density evolution and it is shown that partitioned spreading conditions the channels such that the efficiency of the code is increased substantially. A comparison between direct application of LDPC coding (without partition spreading) to a two- stage decoding procedure and a full iterative decoding schedule of PS-CDMA reveals that gains of over 100% in spectral efficiencies can be achieved with regular LDPC codes.

Wireless communication is a emerging field of evolution in modern era of technology, and every day it is giving new technology to facilitate human being. The new facilities always need a QoS i.e. directly user satisfaction. For satisfaction of wireless users is to give efficient and reliable technology, so that sharing of information is made easier. In the same context the channel of wireless communication system need extra attention for efficient delivery of information from one place to another wirelessly. In this paper we are trying to estimate the channel using MMSE-Kalman Estimator in OFDM system with median filtering to enhance the performance of the system. The proposed methodology is implemented and figure of merits are calculated as BER and MSE, and we have found that the use of median filter with MMSE-Kalman estimator is good.

Errors causd by IF amplifier and phase detector imbal ance and asymmetry are overcome in a phase interfer ometer radar receiver by ultimate application of the respective antenna inputs to different IF amplifier/li miter channels. The output of the IF amplifier chan nels are cross coupled and fed to a phase detector em ploying a quadrature hybrid. The output of the phase detector is switched in synchronism with the IF ampli fier input and the non-linearities resulting from cross coupling are linearized. 4 Claims, 5 Drawing Figures

The designers of a mobile cellular system must evaluate the possible configurations of the system components and their characteristics in order to develop a system with greater efficiency. The useful parameters to estimate performances of the system are voice quality, frequency spectrum efficiency and grade of service (GOS). In this study, a scheme proposed to reduce the lost calls and interruptions due to the outage channels is tested in the traffic dependent outage rate wireless cellular system. In this scheme no call is dropped but could be delayed. The performance parameters considered for this study is the probability of delay and the mean waiting time for priority and nonpriority calls for non-preemptive type. The system is evaluated for different conditions and the results are discussed.

The traffic characteristic of mobile cellular systems is rather distinct from that of a fixed telephone network. However the system planning and design are still carried out with the tools of conventional traffic theory. In the recent days much work is being done in the performance evaluation of mobile or cellular communication systems in order to develop a system with greater efficiency. The useful parameters to estimate the performance of the system are voice quality, frequency spectrum efficiency and Grade of Service (GOS). The grade of service will be affected due to outage of channels. In this study, a new scheme is proposed to reduce lost calls due to channel outage in the fixed rate outage cellular system. In this proposed scheme the call will never dropped but may be delayed. The system performance is evaluated for different conditions and the results are discussed.

andoff is a process of transferring a mobile station (MS) from one base station (BS) or channel to another. The channel change due to handoff may be through a time slot, frequency band, codeword, or combination of these for time-division multiple access (TDMA), frequency-division multiple access (FDMA), code-division multiple access (CDMA), or a hybrid scheme, respectively [1]. This article includes four major topics. Topic 1: Deployment Scenarios and Handoff-Topic 1 describes different system deployment scenarios and their constraints on the handoff procedure. Handoff algorithms with a specific set of parameters cannot perform uniformly well in different communication system deployment scenarios since these scenarios are characterized by specific environments. Examples of different system structures include macrocells, microcells, overlays, integrated cellular systems, integrated cordless and cellular systems, and integrated terrestrial and satellite systems. Note that these system structures are expected to coexist in future wireless communication systems and warrant closer study. Topic 2: Resource Management in Cellular Systems-Topic 2 views handoff and other resource management tasks and details handoff-related system performance improvement. Prioritizing handoff is one way to improve handoffrelated system performance. Several handoff prioritization schemes (e.g., guard channels and queuing) are discussed. Handoff represents one of the radio resource management tasks carried out by cellular systems. Some other resource management functions include admission control, channel assignment, and power control. If some of the resource management tasks are treated in an integral manner, better overall performance can be obtained in a global sense by making appropriate trade-offs. Topic 3: Implementation of Handoff-Topic 3 describes how handoff procedure is implemented. The decision making process of handoff may be centralized or decentralized (i.e., the handoff decision may be made at the MS, BS, or mobile switching center, MSC). Different systems use different approaches to execute the process of handoff, and handoff protocols characterize these approaches. Topic 4: Analysis of Handoff Algorithms-Three basic mechanisms have been used to evaluate the performance of handoff algorithms, and these mechanisms-the analytical approach, simulation approach, and emulation approachare described in topic 4.

In this paper we propose a two-step distributed scheduling algorithm for relay-assisted cellular networks where a given user can be either served by the base station or by a relay, in a opportunistic way. Such a distributed approach allows a reduced feedback signaling with respect to the centralized case, especially when a simple scalar feedback is not sufficient for estimating the channel quality. As a result of the reduced feedback signaling requirements the system becomes more scalable, as new relays can be deployed where required without need of a careful network planning. We study the effectiveness of the proposal by means of a multicell simulator.

The Erlang capacity per cell and per unit area in urban code-division multiple-access (CDMA) microcellular environments is evaluated. Special emphasis is given to the effect of breakpoint distance and cell size on the system Erlang capacity. Two different cell plans are considered in which the communication between the base station (BS) and the mobile unit always occurs in a line-of-sight (LOS) condition: the full-and half-square cell plans. Our main result has been to obtain analytical expressions for the Erlang capacity, which are evaluated through a cell radius-normalization procedure, as a function of the breakpoint to the cell radius ratio (). This has allowed us to notice some important facts not previously reported in the literature. In particular, we observe that the Erlang capacity is a monotonically decreasing function of and that close to the highest reuse efficiency is achieved for 0 7. Thus, given a breakpoint distance, higher Erlang capacity per cell can be achieved with greater cell radius. Or, equivalently, given a cell radius, higher system capacity can be achieved with smaller breakpoint distances; that is, with smaller base-station antenna heights and/or smaller frequencies. Also, we show that the capacity increase due to the BSs doubling or cell radius-reduction depends on the antenna heights, frequency of operation, and distance between streets. It ranges from 64 to 100%.

The capacity-achieving coding scheme for the multiple-input multiple-output (MIMO) broadcast channel is dirty-paper coding. With this type of transmission scheme the optimal number of active users that receive data and the optimal power allocation strategy are highly dependent on the structure of the channel matrix and on the total transmit power available. In the context of packet-data access with adaptive transmission where mobile users are equipped with a single receive antenna and the base station has multiple transmit antennas, we study the optimal number of active users and the optimal power allocation. In the particular case of two transmit antennas, we prove that the optimal number of active users can be a non-monotonic function of the total transmit power. Thus not only the number of users that should optimally be served simultaneously depends on the user channel vectors but also on the power available at the base station transmitter. The expected complexity of optimal scheduling algorithms is thus very high. Yet we then prove that at most as many users as the number of transmit antennas are allocated a large amount of power asymptotically in the high-power region in order to achieve the sum-capacity. Simulations confirm that constraining the number of active users to be no more than the number of transmit antennas incurs only a marginal loss in spectral efficiency. Based on these observations, we propose low-complexity scheduling algorithms with sub-optimal transmission schemes that can approach the sum-capacity of the MIMO broadcast channel by taking advantage of multiuser diversity. The suitability of known antenna selection algorithms is also demonstrated. We consider the cases of complete and partial channel knowledge at the transmitter. We provide simulation results to illustrate our conclusions.

This work improves channel decoder performance on the code-division multiple-access (CDMA) forward link through more accurate calculation of the channel code trellis path metrics used to decode convolutional and turbo codes. This is achieved by performing the metric calculations with better channel state estimates. Channel state estimation involves determining desired signal amplitude and interference plus noise variance at the channel decoder input. Two options are presented for performing this estimation. Standard estimation is a simple scheme that results from assuming all CDMA forward link interference and noise can be lumped into a single additive white Gaussian noise process. Improved estimation is a new and more accurate technique that separately accounts for the intracell interference and intercell interference plus thermal noise processes. Simulations show that the decoding of convolutional and turbo codes is significantly improved by the more accurate channel state information provided by improved estimation.

Motivation: Proteome-wide prediction of protein–protein interaction is a difficult and important problem in biology. Although there have been recent advances in both experimental and computational methods for predicting protein–protein interactions, we are only beginning to see a confluence of these techniques. In this paper, we describe a very general, high-throughput method for predicting protein–protein interactions. Our method combines a sequence-based description of proteins with experimental information that can be gathered from any type of protein–protein interaction screen. The method uses a novel description of interacting proteins by extending the signature descriptor, which has demonstrated success in predicting peptide/protein binding interactions for individual proteins. This descriptor is extended to protein pairs by taking signature products. The signature product is implemented within a support vector machine classifier as a kernel function. Results: We have applied ...

Background Quantitative models of biochemical and cellular systems are used to answer a variety of questions in the biological sciences. The number of published quantitative models is growing steadily thanks to increasing interest in the use of models as well as the development of improved software systems and the availability of better, cheaper computer hardware. To maximise the benefits of this growing body of models, the field needs centralised model repositories that will encourage, facilitate and promote model dissemination and reuse. Ideally, the models stored in these repositories should be extensively tested and encoded in community-supported and standardised formats. In addition, the models and their components should be cross-referenced with other resources in order to allow their unambiguous identification. Description BioModels Database http://www.ebi.ac.uk/biomodels/ is aimed at addressing exactly these needs. It is a freely-accessible online resource for storing, viewi...

The application of mathematical analysis to the study of wireless ad hoc networks has met with limited success due to the complexity of mobility, traffic models and the dynamic topology. A scenario based UMTS TDD opportunistic cellular system with an ad hoc behaviour that operates over UMTS FDD licensed cellular network is considered. In this paper, we describe how ad hoc opportunistic radio can be modeled as a game and how we apply game theory based Power Control in ad-hoc opportunistic radio.

Cytomics aims to determine the molecular phenotype of single cells. Within the context of the-omics, cytomics allows the investigation of multiple biochemical features of the heterogeneous cellular systems known as the cytomes. Cytomics can be considered as the science of single cell-based analyses that links genomics and proteomics with the dynamics of cell and tissue function, as modulated by external inXuences. Inherent to cytomics are the use of sensitive, scarcely invasive, Xuorescence-based multiparametric methods and the event-integrating concept of individual cells to understand the complexity and behaviour of tissues and organisms. Among cytomic technologies, Xow cytometry, confocal laser scanning microscopy and laser capture microdissection are of great relevance. Other recent technologies based on single cell bioimaging and bioinformatic tools become important in drug discovery and toxicity testing, because of both highcontent and high-troughput. The multiparametric capacity of cytomics is very useful for the identiWcation, characterization and isolation of stem cell populations. In our experience, Xow cytometry is a powerful and versatile tool that allows quantitative analysis of single molecules, prokaryotic and eukaryotic cells for basic, biotechnological, environmental and clinical studies. The dynamic nature of cytomic assays leads to a real-time kinetic approach based on sequential examination of diVerent single cells from a population undergoing a dynamic process, the in Xuxo level. Finally, cytomic technologies may provide in vitro methods alternative to laboratory animals for toxicity assessment.

In recent years, LTE-Advanced (LTE-A) networks can be classified as the most viable wireless broadband technology. LTE-A supports Quality of Service (QoS) by using Admission Control (AC) and Packet Scheduling (PS). Quality of Service (QoS) has many requirements, such as average throughput, fairness, used energy per bit and spectral efficiency. To efficiently improve the network performance, we should pick a powerful and faired scheduling algorithm. One of the most used scheduling algorithms in LTE-A is Proportional Fair (PF). In this paper, a quadratic proportional fairness algorithm is proposed, by using the root mean square value to compute the average throughput. The proposed algorithm is implemented and evaluated using the Vienna system level simulator with various numbers of users and users speed. It is also compared with the original PF and some of its modifications. The results reveal that, the proposed algorithm exceeds the other algorithms in terms of Average UE throughput,...