242 research outputs found
High-Efficiency Gene Transfer into Adult Fish : a New Tool to Study Fin Regeneration
No full textZebrafish represents an excellent model to study the function of vertebrate genes (e.g., well-developed genetics, large number of mutants, and genomic sequencing in progress), inasmuch as we have tools to manipulate gene expression. Recent use of injected morpholinos in eggs provides a good method to " knockdown " gene expression in early development (Nasevicius and Ekker, 2000), and the "caged" RNA injected in eggs allows to overexpress a gene in a specific set of cells (Ando et al., 2001). However, a method to specifically modify gene expression in the juvenile or in the adult is still missing. Such a method would be a very powerful tool to understand gene function in differentiated tissues. We describe here an electroporation-based approach, which allows gene transfer in adult tissues. Its efficiency was assessed using a GFP (green fluorescent protein) dependent assay. We then used this method to disrupt the Fgf signalling pathway during the process of regeneration
Erratum: High-efficiency gene transfer into adult fish: A new tool to study fin regeneration (Genesis (January 2002) 32 (27-31))
No full textA simple multiband printed bowtie antenna
No full textThis letter presents a new approach for the design of a multiresonant printed bowtie antenna. Several techniques were attempted to obtain one antenna which is operational in the 2, 3, and 5 GHz bands corresponding to many wireless applications. The idea of creating different slot configurations on different parts of a single antenna is the basic principle. A prototype of the final antenna design was fabricated tested and a good agreement was found between simulated and tested results. © 2008 IEEE.Balanis C. A., 2005, ANTENNA THEORY ANAL; Birch M, 2002, P SOC PHOTO-OPT INS, V4758, P573, DOI 10.1117-12.462195; Eldek AA, 2005, IEEE T ANTENN PROPAG, V53, P3067, DOI 10.1109-TAP.2005.851870; James J.R., 1989, IEE ELECTROMAGNETIC, V28; Karacolak T, 2006, IEEE ANTENN WIREL PR, V5, P446, DOI 10.1109-LAWP.2006.885013; Kiminami K, 2004, IEEE ANTENN WIREL PR, V3, P152, DOI 10.1109-LAWP.2004.832126; Lin YD, 1998, IEEE T ANTENN PROPAG, V46, P459; Nedil M., 2003, P CAN C EL COMP ENG, V3, P1433; Nishioka Y, 1999, IEEE T ANTENN PROPAG, V47, P970, DOI 10.1109-8.777119; TAWK Y, 2007, THESIS AM U BEIRUT L; Uduwawala D, 2004, IEEE T GEOSCI REMOTE, V42, P732, DOI 10.1109-TGRS.2003.819442; Yazdandoost K. Y., 2005, P IEEE WIRELESS COMM, P21282
A low-cost microstrip antenna for 3G-WLAN-WiMAX and UWB applications
No full textThis paper presents a low-cost ultra-wideband microstrip antenna for wireless communications. Printed on a 40×50×1.83 mm3 Isola Gigaver 210 substrate, the antenna features a microstrip feed line with two 45° bends and a tapered section for size reduction and matching, respectively. The ground plane is partial and comprises a rectangular part and a trapezoidal part. The patch is a half ellipse, where the cut is made along the minor axis. Several slots are incorporated into the patch. The placement and sizes of the slots are assisted by the knowledge of fractal geometries . The return loss, input impedance, gain, efficiency and radiation characteristics of the antenna are presented. It is shown that the antenna can operate in the bands used for UMTS, WLAN, WiMAX, and UWB applications. © 2009 IEEE.*AG TECHN, ADS MOM 2006; Al-Husseini M., 2008, 2008 INT WIR COMM MO; ALHUSSEINI M, 2009, 26 NAT RAD SCI C NRS; Balanis C. A., 2005, ANTENNA THEORY ANAL; El-Khamy S. E., 2004, 21 NAT RAD SCI C NRS, P1; Kumar G., 2003, BROADBAND MICROSTRIP; Low ZN, 2005, IEEE ANTENN WIREL PR, V4, P237, DOI 10.1109-LAWP.2005.852577; Werner DH, 2003, IEEE ANTENN PROPAG M, V45, P38, DOI 10.1109-MAP.2003.1189650; Zhang JP, 2008, IEEE T ANTENN PROPAG, V56, P241, DOI 10.1109-TAP.2007.91316510
Study of impact on helicopter blade
No full textThis article presents a study of damage in structures that are similar to helicopter blade sections, subjected to an impact. These complex composite structures were impacted by a steel ball of 125 g at impact speed ranging from 30 to 130 m/s. This led to properly highlight the kinematics of the impact and to define the sequence of the damage’s mechanisms. An explicit FE model is also presented. The damage modelling of the roving is performed through a scale change. It allows a good representation of observed experimental behaviour. As the mesh density is low, it can be used for the modelling of a real structure
THE STAPHYLOCOCCAL PANTON AND VALENTINE LEUKOCIDIN AND gamma-HAEMOLYSIN HLGC/HLGB SHARE C5AR AS A RECEPTOR, BUT OPERATE DIVERSE INTRACELLULAR ACTIVITIES IN HUMAN POLYMORPHONUCLEAR NEUTROPHILS
No full textOccurrence and characterization of penicillium species isolated from post-harvest apples in lebanon
No full textThe apple is one of the most important fruit tree crops in the Mediterranean region. Lebanon, in particular, is among the top apple producer countries in the Middle East; however, recently, several types of damage, particularly rot symptoms, have been detected on fruits in cold storage. This study aims to identify the causal agents of apple decay in Lebanese post-harvest facilities and characterize a set of 39 representative strains of the toxigenic fungus Penicillium. The results demonstrated that blue mould was the most frequent fungal disease associated with apples showing symptoms of decay after 3–4 months of storage at 0◦C, with an average frequency of 76.5% and 80.6% on cv. Red and cv. Golden Delicious apples, respectively. The morphological identification and phylogenetic analysis of benA gene showed that most Penicillium strains (87.2%) belong to P. expansum species whereas the remaining strains (12.8%) belong to P. solitum. Furthermore, 67.7% of P. expansum strains produced patulin when grown on apple puree for 14 days at 25◦C with values ranging from 10.7 mg kg−1 to 125.9 mg kg−1, whereas all P. solitum did not produce the mycotoxin. This study highlights the presence of Penicillium spp. and their related mycotoxin risk during apple storage and calls for the implementation of proper measures to decrease the risk of mycotoxin contamination of apple fruit products
La régénération des appendices chez les vertébrés: un modèle expérimental ancien pour étudier les cellules souches chez l’adulte
No full textLa recherche sur les cellules souches laisse entrevoir d’extraordinaires possibilités de traitement des maladies dégénératives. En effet, la capacité de pouvoir dériver des cellules totipotentes à partir d’embryons humains donne la possibilité de développer une médecine régénérative, mais pose également le problème du statut de l’embryon qui, dans ce cas, est considéré comme matériel thérapeutique. Une alternative à l’utilisation des cellules souches embryonnaires humaines est l’utilisation de cellules souches prélevées chez l’adulte. Mais, dans un cas comme dans l’autre, nos connaissances sur les cellules totipotentes ou pluripotentes sont insuffisantes et de nombreuses questions doivent être résolues avant que l’on ne maîtrise la sélection et la différenciation de ces cellules dans un type cellulaire donné. Quelles sont les caractéristiques moléculaires d’une cellule souche adulte? Quels sont les mécanismes sous-jacents à la re-programmation d’une cellule? Quels sont les signaux qui contrôlent la multiplication et la différenciation des cellules souches? Un travail de recherche fondamentale est nécessaire pour éclaircir ces différents points. Dans ce contexte, la régénération des appendices chez les vertébrés offre un terrain d’investigation intéressant. Cet article se propose de faire le point sur nos connaissances concernant la régénération des pattes chez les tétrapodes et des nageoires chez les poissons.The application of stem cell therapy to cure degenerative diseases offers immense possibilities, but the research in this field is the subject of ethical debates raised by the question of destructive research on early human embryos. Stem cells taken in the adult constitute an alternative to human embryonic stem cells, but our knowledge on totipotent or pluripotent cells is currently insufficient. Furthermore, many questions must be solved before selection and differentiation of these cells in a given cellular type can be controlled on a routine basis. What are the molecular characteristics of an adult stem cell? What are the mechanisms involved in cell reprogramming? Which signals control stem cell replication and differentiation? Basic research activities must be carried out in order to clarify all these points. In this context, the regeneration of vertebrate appendages provides a model for this type of research. The regeneration process is defined by both the morphological and functional reconstruction of a part of a living organism, which has previously been destroyed. But why are some vertebrates able to regenerate complex structures and others apparently not? Among most vertebrates, the capacity to regenerate is limited to some tissues. It is however possible to observe the regeneration of appendages (limb, tail, fin, jaw, etc.) among several amphibians and fish. This regeneration leads to re-forming of the amputated part with a complete restoration of its shape, segmentation and function. Why is the amputation of limbs not followed by regeneration in mammals and birds: absence of stem cells, absence of recruitment signals for these cells, or absence of signal receptivity? This review constitutes a report on the current understanding of the basis of on regeneration of legs in tetrapods and of fins in fish with an emphasis in the role of the nervous system in this process
Frequency-tunable and pattern diversity antennas for cognitive radio applications
No full textFrequency-tunable microstrip antennas, for cognitive radio applications, are proposed herein. The approach is based on tuning the operating frequency of a bandpass filter that is incorporated into a wideband antenna. The integration of an open loop resonator- (OLR-) based adjustable bandpass filter into a wideband antenna to transform it into a tunable filter-antenna is presented. The same technique is employed to design a cognitive radio pattern diversity tunable filter-antenna. A good agreement between the simulated and measured results for the fabricated prototypes is obtained. The radiation characteristics of each designed tunable filter-antenna are included herein. © 2014 A. H. Ramadan et al.Acampora A., 2010, P IEEE INT MICR WORK, P1; Al-Husseini M, 2011, IEEE ANTENNAS PROP, P2212; [Anonymous], SMV1405 SMV1419 HYP; Carey-Smith B. E., 2005, EURASIP Journal on Wireless Communications and Networking, V2005, DOI 10.1155-WCN.2005.354; Hong JS, 1997, IEEE T MICROW THEORY, V45, P2358; Lourandakis E, 2012, IEEE MICROW MAG, V13, P111, DOI 10.1109-MMM.2011.2173987; Marques R, 2008, WILEY MICRO, P1; Perruisseau-Carrier J., 2010, P R SOC B, P1; Razavi B, 2009, IEEE CUST INTEGR CIR, P391; Yucek T, 2009, IEEE COMMUN SURV TUT, V11, P116, DOI 10.1109-SURV.2009.0901091
Design and ground plane optimization of a CPW-fed ultra-wideband antenna
No full textIn this paper, an ultra-wideband antenna based on an egg-shaped conductor and a co-planar waveguide (CPW) feed is presented. The ground plane incorporates an egg-shaped slot with parametrized center and dimensions. By resizing the slot and moving its center, a slotted or a partial ground can be obtained. Based on this configuration, a parametric study that aims at achieving the best ultra-wideband (UWB) response of the antenna is done. The study shows that an excellent UWB response is achieved for a certain ground slot size, beyond which the response starts to degrade. However, as the slot size tends to infinity, thus leading to a partial rectangular ground plane, the UWB property again emerges. A second parametric study is done to find the length of the partial rectangular ground plane that gives the best UWB profile. As a result, two optimal designs are generated. Prototypes of the two are fabricated and their return loss is measured. Other characteristics are computed using a Finite-Element-based EM solver. The radiation patterns, peak gain, and radiation efficiency of both optimal configurations are presented and compared. The results show that the design with the slotted ground yields better omni-directional patterns and higher gains in the principal planes. The second design has slightly larger radiation efficiency and larger peak gains at high frequencies. © tüb ítak.ALHUSSEINI M, 2009, 2009 INT C EL EL ENG, P151; Angelopoulos ES, 2006, IEEE ANTENN WIREL PR, V5, P294, DOI 10.1109-LAWP.2006.878882; [Anonymous], ANS HFSS; Balanis C. A., 2005, ANTENNA THEORY ANAL; Bhobe AU, 2004, IEEE T ANTENN PROPAG, V52, P2545, DOI 10.1109-TAP.2004.834425; Chang DC, 2008, IEEE T ANTENN PROPAG, V56, P3630, DOI 10.1109-TAP.2008.2007279; Chen ME, 2008, ELECTRON LETT, V44, P613, DOI 10.1049-el:20080505; *FCC, 2002, FCC 1 REP ORD ULT TE; JAN JY, 2006, 2006 IEEE AP S INT S, P1697; Li PC, 2006, IEEE T ANTENN PROPAG, V54, P1670, DOI 10.1109-TAP.2006.875499; Liang J, 2005, IEE P-MICROW ANTEN P, V152, P520, DOI 10.1049-ip-map:20045179; ZHAO L, 2006, 2006 IEEE AP S INT S, P258333
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