Redirecting NK cells mediated tumor cell lysis by a new recombinant bifunctional protein

Natural killer (NK) cells are at the crossroad between innate and adaptive immunity and play a major role in cancer immunosurveillance. NK cell stimulation depends on a balance between inhibitory and activating receptors, such as the stimulatory lectin-like receptor NKG2D. To redirect NK cells against tumor cells, we designed bifunctional proteins able to specifically bind tumor cells and to induce their lysis by NK cells, after NKG2D engagement. To this aim, we used the 'knob into hole' heterodimerization strategy, in which 'knob' and 'hole' variants were generated by directed mutagenesis within the CH3 domain of human IgG1 Fc fragments fused to an anti-CEA or anti-HER2 scFv or to the H60 murine ligand of NKG2D, respectively. We demonstrated the capacity of the bifunctional proteins produced to specifically coat tumor cells surface with H60 ligand. Most importantly, we demonstrated that these bifunctional proteins were able to induce an NKG2D-dependent and antibody-specific tumor cell lysis by murine NK cells. Overall, the results show the possibility to redirect NK cytotoxicity to tumor cells by a new format of recombinant bispecific antibody, opening the way of potential NK cell-based cancer immunotherapies by specific activation of the NKG2D receptor at the tumor site.     

Capacity limits of spectrum‐sharing systems over hyper‐fading channels

Cognitive radio (CR) with spectrum‐sharing feature is a promising technique to address the spectrum under‐utilization problem in dynamically changing environments. In this paper, the achievable capacity gain of spectrum‐sharing systems over dynamic fading environments is studied. To perform a general analysis, a theoretical fading model called hyper‐fading model that is suitable to the dynamic nature of CR channel is proposed. Closed‐form expressions of probability density function (PDF) and cumulative density function (CDF) of the signal‐to‐noise ratio (SNR) for secondary users (SUs) in spectrum‐sharing systems are derived. In addition, the capacity gains achievable with spectrum‐sharing systems in high and low power regions are obtained. The effects of different fading figures, average fading powers, interference temperatures, peak powers of secondary transmitters, and numbers of SUs on the achievable capacity are investigated. The analytical and simulation results show that the fading figure of the channel between SUs and primary base‐station (PBS), which describes the diversity of the channel, does not contribute significantly to the system performance gain. Copyright © 2011 John Wiley & Sons, Ltd.     

Single-frequency Sb-based distributed-feedback lasers emitting at 2.3 microm above room temperature for application in tunable diode laser absorption spectroscopy

GaInAsSb/GaAlAsSb/GaSb distributed-feedback (DFB) laser diodes based on a type I active region were fabricated by molecular beam epitaxy at the Centre d'Electronique et de Micro-Optoélectronique de Montpellier (CEM2). The DFB processing was done by Nanoplus Nanosystems and Technologies GmbH. The devices work in the continuous-wave regime above room temperature around an emission wavelength of 2.3 microm with a side-mode suppression ratio greater than 25 dB and as great as 10 mW of output power. The laser devices are fully characterized in terms of optical and electrical properties. Their tuning properties made them adaptable to tunable diode laser absorption spectroscopy because they exhibit more than 220 GHz of continuous tuning by temperature or current. The direct absorption of CH4 is demonstrated to be possible with high spectral selectivity.     

Local mean signal estimation over Nakagami‐m fading channels

Accurate and fast algorithms for the local mean signal level estimation are very important for the successful implementation of many wireless communication enabling techniques such as handoff, power control, and adaptive gain control schemes. In this paper, we present on‐line simple‐to‐implement (i) minimum variance unbiased and (ii) maximum likelihood estimators for the local mean signal power estimation in the decibel domain. We consider a generalized Nakagami‐m fading environment and show that these estimators are asymptotically efficient in the number of samples and in the fading parameter m. Numerical and simulation results confirm that these estimators outperform the sample mean estimator and quickly approach the Cramer–Rao lower bounds. Copyright © 2006 John Wiley & Sons, Ltd.     

Average probability of packet error with diversity reception over arbitrarily correlated fading channels

Closed form expressions for the average probability of packet error (PPE) are presented for no diversity, maximum ratio combining (MRC), selection combining (SC) and switch and stay combining (SSC) diversity schemes. The average PPE for the no diversity case is obtained in two alternative expressions assuming arbitrarily correlated Nakagami and Rician fading channels. For the MRC case, L diversity branches are considered and the channel samples are assumed to follow Nakagami distribution and to be arbitrarily correlated in both time and space. For the SC diversity scheme with L diversity branches, two bounds on the average PPE are derived for both slow and fast fading channels. The average PPE in this case is obtained in an infinite integral form for Nakagami channels while it is reduced to a closed form expression for the Rayleigh case. The average PPE is also derived in the case of SSC diversity with dual branches for both slow and fast Rayleigh fading channels. The new formulas are applicable for all modulation schemes where the conditional probability of error has an exponential dependence on the signal‐to‐noise ratio. The average PPE is then used to obtain a modified expression for the throughput for network protocols. In general, the diversity gain exhibits a little diminishing effect as the number of diversity branches increases. In addition, the system is found to be more sensitive to the space correlation than to the time correlation. The effects of different system parameters and diversity schemes are studied and discussed. Specific figures about the system performance are also provided. Copyright © 2004 John Wiley & Sons, Ltd.     

Performance analysis of single carrier and multicarrier DS‐CDMA systems over generalized fading channels

Using a recently developed moment generating function‐based approach for the performance evaluation of digital communications over fading channels, we present a unified approach for the exact performance analysis of binary direct‐sequence code division multiple access (DS‐CDMA) systems operating over generalized frequency‐selective fading channels. The results are applicable to single carrier systems employing RAKE reception as well as to multicarrier DS‐CDMA systems with frequency diversity. Aside from simplifying previous results both analytically and computationally, the proposed approach also gives a solution for many situations which heretofore defied a simple form. Copyright © 2001 John Wiley & Sons, Ltd.     

Color Edge Detection Using Multidirectional Sobel Filter and Fuzzy Fusion

A new model is proposed in this paper on color edge detection that uses the second derivative operators and data fusion mechanism. The second-order neighborhood shows the connection between the current pixel and the surroundings of this pixel. This connection is for each RGB component color of the input image. Once the image edges are detected for the three primary colors: red, green, and blue, these colors are merged using the combination rule. Then, the final decision is applied to obtain the segmentation. This process allows different data sources to be combined, which is essential to improve the image information quality and have an optimal image segmentation. Finally, the segmentation results of the proposed model are validated. Moreover, the classification accuracy of the tested data is assessed, and a comparison with other current models is conducted. The comparison results show that the proposed model outperforms the existing models in image segmentation.     

Effect of Silicon (Si) Seed Priming on Germination and Effectiveness of its Foliar Supplies on Durum Wheat (Triticum turgidum L. ssp. durum) Genotypes under Semi-Arid Environment

Silicon - Silicon (Si), a nutrient that currently arousing more and more interest from researchers, particularly in relation to water deficit resistance for durum wheat (Triticum turgidum L. ssp....     

Performance analysis of switch‐based multiuser scheduling schemes with adaptive modulation in spectrum sharing systems

This paper focuses on the development of multiuser access schemes for spectrum sharing systems whereby secondary users are allowed to share the spectrum with primary users under the condition that the interference observed at the primary receiver is below a predetermined threshold. In particular, two scheduling schemes are proposed for selecting a user among those that satisfy the interference constraint and achieve an acceptable signal‐to‐noise ratio level. The first scheme focuses on optimizing the average spectral efficiency by selecting the user that reports the best channel quality. In order to alleviate the relatively high feedback required by the first scheme, a second scheme based on the concept of switched diversity is proposed, where the base station (BS) scans the secondary users in a sequential manner until a user whose channel quality is above an acceptable predetermined threshold is found. We develop expressions for the statistics of the signal‐to‐interference and noise ratio as well as the average spectral efficiency, average feedback load, and the delay at the secondary BS. We then present numerical results for the effect of the number of users and the interference constraint on the optimal switching threshold and the system performance and show that our analysis results are in perfect agreement with the numerical results. Copyright © 2014 John Wiley & Sons, Ltd.     

Surface modification of MWCNT to improve the mechanical and thermal properties of natural rubber nanocomposites

In this study, we focused on the synergistic effect between carbon black (CB) and multiwall carbon nanotube (MWCNT) hybrid fillers. In particular, the surface modification of pristine MWCNT (P-MWCNT) via an acid (oxidation) treatment was used to improve their dispersion, as well as the mechanical and thermal properties of their corresponding natural rubber (NR)-based nanocomposites. Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were carried out to determine the presence of functional groups on the oxidized MWCNT (O-MWCNT). After vulcanization, dynamic mechanical analysis (DMA), tensile properties, hardness, thermal conductivity, swelling behaviour in toluene and SEM characterizations were performed on both NR/CB/P-MWCNT- and NR/CB/O-MWCNT-based nanocomposites. The results showed the positive effect of MWCNT surface oxidation on the fillers' dispersion and nanocomposites' properties.