19 research outputs found
A 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
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
Análisis de la resiliencia frente a la variación de ventas y continuidad del negocio en clientes PYME de una agencia bancaria en tiempos de Covid - Arequipa 2020
No full textEl presente trabajo de investigación tiene como objetivo principal analizar la resiliencia frente a la variación del nivel de ventas y continuidad del negocio en clientes Pyme de una agencia bancaria en tiempos de COVID - Arequipa 2020. La importancia de la investigación se justifica en la resiliencia organizacional y su papel en el proceso de reactivación económica ya que un alto nivel de resiliencia en empresarios puede disminuir el nivel de vulnerabilidad de los negocios frente a riesgos esperados e inesperados. Por lo que es un tema importante en la recesión económica, la cual atraviesa nuestro país y el mundo. Asimismo, la investigación corresponde a un trabajo de campo con enfoque de tipo cuantitativo, descriptivo-correlacional; con un diseño no experimental, transversal, correlacional. Para llevar a cabo dicha investigación se planteó como hipótesis principal la existencia de una correlación entre el nivel de resiliencia frente a la variación del nivel de ventas y continuidad del negocio en los clientes Pyme de una agencia bancaria en tiempos de COVID - Arequipa 2020. Finalmente, al analizar las variables se pudo encontrar que la correlación de Pearson tiene un valor de 0.070. Por lo que se aceptó la hipótesis nula (HO), la cual manifiesta que no existe una correlación entre el nivel de resiliencia frente a la variación de ventas y continuidad del negocio en los clientes pyme de una agencia bancaria en tiempos de covid - Arequipa 2020. Estos resultados son corroborados por Deb, Furceri, D. ostry, y Tawk, (2020) quienes en su investigación señalan que las medidas que se emplean para tratar de controlar el nuevo coronavirus hacen efectos en la economía, observando los indicadores económicos de política fiscal y monetaria tanto en la producción reflejada en el índice porcentual del PBI como a los diversos índices económicos generados por el efecto de la no movilidad de las personas y el resultado del manejo respecto al trabajo no presencial y los diversos impactos que conllevan la inamovilidad. Por lo que podemos concluir que la variación en el nivel de ventas y la continuidad del negocio de la población en estudio estaría relacionado a factores externos como las medidas tomadas por el gobierno para frenar la pandemia
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
Phosphatidylinositol 3-Phosphate, an Essential Lipid in Plasmodium, Localizes to the Food Vacuole Membrane and the Apicoplast
No full textABSTRACT
Phosphoinositides are important regulators of diverse cellular functions, and phosphatidylinositol 3-monophosphate (PI3P) is a key element in vesicular trafficking processes. During its intraerythrocytic development, the malaria parasite
Plasmodium falciparum
establishes a sophisticated but poorly characterized protein and lipid trafficking system. Here we established the detailed phosphoinositide profile of
P. falciparum
-infected erythrocytes and found abundant amounts of PI3P, while phosphatidylinositol 3,5-bisphosphate was not detected. PI3P production was parasite dependent, sensitive to a phosphatidylinositol-3-kinase (PI3-kinase) inhibitor, and predominant in late parasite stages. The
Plasmodium
genome encodes a class III PI3-kinase of unusual size, containing large insertions and several repetitive sequence motifs. The gene could not be deleted in
Plasmodium berghei
, and
in vitro
growth of
P. falciparum
was sensitive to a PI3-kinase inhibitor, indicating that PI3-kinase is essential in
Plasmodium
blood stages. For intraparasitic PI3P localization, transgenic
P. falciparum
that expressed a PI3P-specific fluorescent probe was generated. Fluorescence was associated mainly with the membrane of the food vacuole and with the apicoplast, a four-membrane bounded plastid-like organelle derived from an ancestral secondary endosymbiosis event. Electron microscopy analysis confirmed these findings and revealed, in addition, the presence of PI3P-positive single-membrane vesicles. We hypothesize that these vesicles might be involved in transport processes, likely of proteins and lipids, toward the essential and peculiar parasite compartment, which is the apicoplast. The fact that PI3P metabolism and function in
Plasmodium
appear to be substantially different from those in its human host could offer new possibilities for antimalarial chemotherapy.
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Genetic and transcriptional analysis of phosphoinositide-specific phospholipase C in Plasmodium
No full textAbstractPhosphoinositide-specific phospholipase C (PI-PLC) is a major regulator of calcium-dependent signal transduction, which has been shown to be important in various processes of the malaria parasite Plasmodium. PI-PLC is generally implicated in calcium liberation from intracellular stores through the action of its product, inositol-(1,4,5)-trisphosphate, and is itself dependent on calcium for its activation. Here we describe the plc genes from Plasmodium species. The encoded proteins contain all domains typically found in PI-PLCs of the δ class but are almost twice as long as their orthologues in mammals. Transcriptional analysis by qRT-PCR of plc during the erythrocytic cycle of P. falciparum revealed steady expression levels that increased at the late schizont stages. Genetic analysis in the P. berghei model revealed that the plc locus was targetable but that plc gene knock-outs could not be obtained, thereby strongly indicating that the gene is essential during blood stage development. Alternatively, we attempted to modify plc expression through a promoter exchange approach but found the gene to be refractory to over-expression indicating that plc expression levels might additionally be tightly controlled
Toxoplasmosis: Current and Emerging Parasite Druggable Targets
No full textToxoplasmosis is a prevalent disease affecting a wide range of hosts including approximately one-third of the human population. It is caused by the sporozoan parasite Toxoplasma gondii (T. gondii), which instigates a range of symptoms, manifesting as acute and chronic forms and varying from ocular to deleterious congenital or neuro-toxoplasmosis. Toxoplasmosis may cause serious health problems in fetuses, newborns, and immunocompromised patients. Recently, associations between toxoplasmosis and various neuropathies and different types of cancer were documented. In the veterinary sector, toxoplasmosis results in recurring abortions, leading to significant economic losses. Treatment of toxoplasmosis remains intricate and encompasses general antiparasitic and antibacterial drugs. The efficacy of these drugs is hindered by intolerance, side effects, and emergence of parasite resistance. Furthermore, all currently used drugs in the clinic target acute toxoplasmosis, with no or little effect on the chronic form. In this review, we will provide a comprehensive overview on the currently used and emergent drugs and their respective parasitic targets to combat toxoplasmosis. We will also abridge the repurposing of certain drugs, their targets, and highlight future druggable targets to enhance the therapeutic efficacy against toxoplasmosis, hence lessening its burden and potentially alleviating the complications of its associated diseases
A Key Role for Plasmodium Subtilisin-like SUB1 Protease in Egress of Malaria Parasites from Host Hepatocytes
No full textInternational audienceIn their mammalian host, Plasmodium parasites have two obligatory intracellular development phases, first in hepatocytes and subsequently in erythrocytes. Both involve an orchestrated process of invasion into and egress from host cells. The Plasmodium SUB1 protease plays a dual role at the blood stage by enabling egress of the progeny merozoites from the infected erythrocyte and priming merozoites for subsequent erythrocyte invasion. Here, using conditional mutagenesis in P. berghei, we show that SUB1 plays an essential role at the hepatic stage. Stage-specific sub1 invalidation during prehepatocytic development showed that SUB1-deficient parasites failed to rupture the parasitophorous vacuole membrane and to egress from hepatocytes. Furthermore, mechanically released parasites were not adequately primed and failed to establish a blood stage infection in vivo. The critical involvement of SUB1 in both pre-erythrocytic and erythrocytic developmental phases qualifies SUB1 as an attractive multistage target for prophylactic and therapeutic anti-Plasmodium intervention strategies
Lipid kinases are essential for apicoplast homeostasis inToxoplasma gondii
No full textPhosphoinositides regulate numerous cellular processes by recruiting cytosolic effector proteins and acting as membrane signalling entities. The cellular metabolism and localization of phosphoinositides are tightly regulated by distinct lipid kinases and phosphatases. Here, we identify and characterize a unique phosphatidylinositol 3 kinase (PI3K) in Toxoplasma gondii, a protozoan parasite belonging to the phylum Apicomplexa. Conditional depletion of this enzyme and subsequently of its product, PI(3)P, drastically alters the morphology and inheritance of the apicoplast, an endosymbiotic organelle of algal origin that is a unique feature of many Apicomplexa. We searched the T. gondii genome for PI(3)P-binding proteins and identified in total six PX and FYVE domain-containing proteins including a PIKfyve lipid kinase, which phosphorylates PI(3)P into PI(3,5)P2. Although depletion of putative PI(3)P-binding proteins shows that they are not essential for parasite growth and apicoplast biology, conditional disruption of PIKfyve induces enlarged apicoplasts, as observed upon loss of PI(3)P. A similar defect of apicoplast homeostasis was also observed by knocking down the PIKfyve regulatory protein ArPIKfyve, suggesting that in T. gondii, PI(3)P-related function for the apicoplast might mainly be to serve as a precursor for the synthesis of PI(3,5)P2. Accordingly, PI3K is conserved in all apicomplexan parasites whereas PIKfyve and ArPIKfyve are absent in Cryptosporidium species that lack an apicoplast, supporting a direct role of PI(3,5)P2 in apicoplast homeostasis. This study enriches the already diverse functions attributed to PI(3,5)P2 in eukaryotic cells and highlights these parasite lipid kinases as potential drug targets
