606 research outputs found
Architectures for ku-band broadband airborne satellite communication antennas
This paper describes different architectures for a broadband antenna for satellite communication on aircraft. The antenna is a steerable (conformal) phased array antenna in Ku-band (receive-only). First the requirements for such a system are addressed. Subsequently a number of potential architectures are discussed in detail: a) an architecture with only optical true time delays, b) an architecture with optical phase shifters and optical true time delays and c) an architecture with optical true time delays and RF phase\ud
shifters (or RF true time delays). The last two architectures use sub-arrays to reduce complexity of the antenna system. The advantages and disadvantages of the different architectures are evaluated and an optimal architecture is selected
Loading a Bose-Einstein Condensate onto an Optical Lattice: an Application of Optimal Control Theory to The Non Linear Schr\"odinger Equation
Using a set of general methods developed by Krotov [A. I. Konnov and V. A.
Krotov, Automation and Remote Control, {\bf 60}, 1427 (1999)], we extend the
capabilities of Optimal Control Theory to the Nonlinear Schr\"odinger Equation
(NLSE). The paper begins with a general review of the Krotov approach to
optimization. Although the linearized version of the method is sufficient for
the linear Schr\"odinger equation, the full flexibility of the general method
is required for treatment of the nonlinear Schr\"odinger equation. Formal
equations for the optimization of the NLSE, as well as a concrete algorithm are
presented. As an illustration, we consider a Bose-Einstein condensate initially
at rest in a harmonic trap. A phase develops across the BEC when an optical
lattice potential is turned on. The goal is to counter this effect and keep the
phase flat by adjusting the trap strength. The problem is formulated in the
language of Optimal Control Theory (OCT) and solved using the above
methodology. To our knowledge, this is the first rigorous application of OCT to
the Nonlinear Schr\"odinger equation, a capability that is bound to have
numerous other applications.Comment: 11 pages, 4 figures, A reference added, Some typos correcte
The aquatic ecosystem, a good environment for the horizontal transfer of antimicrobial resistance and virulence-associated factors among extended spectrum Ă-lactamases producing E. coli
One of the main public health problems nowadays is the increase of antimicrobial resistance,
both in the hospital environment and outside it (animal environment, food and aquatic ecosystems,
among others). It is necessary to investigate the virulence-associated factors and the ability of
horizontal gene transfer among bacteria for a better understanding of the pathogenicity and the
mechanisms of dissemination of resistant bacteria. Therefore, the objective of this work was to
detect several virulence factors genes (fimA, papC, papG III, cnf1, hlyA and aer) and to determine the
conjugative capacity in a wide collection of extended-spectrum ÎČ-lactamases-producing E. coli isolated
from different sources (human, food, farms, rivers, and wastewater treatment plants). Regarding
virulence genes, fimA, papC, and aer were distributed throughout all the studied environments, papG
III was mostly related to clinical strains and wastewater is a route of dissemination for cnf1 and hlyA.
Strains isolated from aquatic environments showed an average conjugation frequencies of 1.15 Ă 10â1
± 5 Ă 10â1
, being significantly higher than those observed in strains isolated from farms and food
(p < 0.05), with frequencies of 1.53 Ă 10â4 ± 2.85 Ă 10â4 and 9.61 Ă 10â4 ± 1.96 Ă 10â3
, respectively. The
reported data suggest the importance that the aquatic environment (especially WWTPs) acquires for
the exchange of genes and the dispersion of resistance. Therefore, specific surveillance programs of
AMR indicators in wastewaters from animal or human origin are needed, in order to apply sanitation
measures to reduce the burden of resistant bacteria arriving to risky environments as WWTPs
Novel ring resonator-based integrated photonic beamformer for broadband phased array receive antennas - part I: design and performance analysis
A novel optical beamformer concept is introduced that can be used for seamless control of the reception angle in broadband wireless receivers employing a large phased array antenna (PAA). The core of this beamformer is an optical beamforming network (OBFN), using ring resonator-based broadband delays, and coherent optical combining. The electro-optical conversion is performed by means of single-sideband suppressed carrier modulation, employing a common laser, Mach-Zehnder modulators, and a common optical sideband filter after the OBFN. The unmodulated laser signal is then re-injected in order to perform balanced coherent optical detection, for the opto-electrical conversion. This scheme minimizes the requirements on the complexity of the OBFN, and has potential for compact realization by means of full integration on chip. The impact of the optical beamformer concept on the performance of the full receiver system is analyzed, by modeling the combination of the PAA and the beamformer as an equivalent two-port RF system. The results are illustrated by a numerical example of a PAA receiver for satellite TV reception, showing thatâwhen properly designedâthe beamformer hardly affects the sensitivity of the receiver
The aquatic ecosystem, a good environment for the horizontal transfer of antimicrobial resistance and virulence-associated factors among extended spectrum beta-lactamases producing E. coli
One of the main public health problems nowadays is the increase of antimicrobial resistance,
both in the hospital environment and outside it (animal environment, food and aquatic ecosystems,
among others). It is necessary to investigate the virulence-associated factors and the ability of
horizontal gene transfer among bacteria for a better understanding of the pathogenicity and the
mechanisms of dissemination of resistant bacteria. Therefore, the objective of this work was to
detect several virulence factors genes (fimA, papC, papG III, cnf1, hlyA and aer) and to determine the
conjugative capacity in a wide collection of extended-spectrum ÎČ-lactamases-producing E. coli isolated
from different sources (human, food, farms, rivers, and wastewater treatment plants). Regarding
virulence genes, fimA, papC, and aer were distributed throughout all the studied environments, papG
III was mostly related to clinical strains and wastewater is a route of dissemination for cnf1 and hlyA.
Strains isolated from aquatic environments showed an average conjugation frequencies of 1.15 Ă 10â1
± 5 Ă 10â1
, being significantly higher than those observed in strains isolated from farms and food
(p < 0.05), with frequencies of 1.53 Ă 10â4 ± 2.85 Ă 10â4 and 9.61 Ă 10â4 ± 1.96 Ă 10â3
, respectively. The
reported data suggest the importance that the aquatic environment (especially WWTPs) acquires for
the exchange of genes and the dispersion of resistance. Therefore, specific surveillance programs of
AMR indicators in wastewaters from animal or human origin are needed, in order to apply sanitation
measures to reduce the burden of resistant bacteria arriving to risky environments as WWTPs
Adaptation to Variable Environments, Resilience to Climate Change: Investigating Land, Water and Settlement in Indus Northwest India
This paper explores the nature and dynamics of adaptation and resilience in the face of a diverse and varied environmental and ecological context using the case study of South Asiaâs Indus Civilization (ca. 3000â1300 BC). Most early complex societies developed in regions where the climatic parameters faced by ancient subsistence farmers were varied but rain falls primarily in one season. In contrast, the Indus Civilization developed in a specific environmental context that spanned a very distinct environmental threshold, where winter and summer rainfall systems overlap. There is now evidence to show that this region was directly subject to climate change during the period when the Indus Civilization was at its height (ca. 2500â1900 BC). The Indus Civilization, therefore, provides a unique opportunity to understand how an ancient society coped with diverse and varied ecologies and change in the fundamental environmental parameters. This paper integrates research carried out as part of the Land, Water and Settlement project in northwest India between 2007 and 2014. Although coming from only one of the regions occupied by Indus populations, these data necessitate the reconsideration of several prevailing views about the Indus Civilization as a whole and invigorate discussion about human-environment interactions and their relationship to processes of cultural transformation
Multidrug-Resistant Bacteria Isolated from Different Aquatic Environments in the North of Spain and South of France
Due to the global progress of antimicrobial resistance, the World Health Organization
(WHO) published the list of the antibiotic-resistant âpriority pathogensâ in order to promote research
and development of new antibiotics to the families of bacteria that cause severe and often deadly
infections. In the framework of the One Health approach, the surveillance of these pathogens in
different environments should be implemented in order to analyze their spread and the potential risk
of transmission of antibiotic resistances by food and water. Therefore, the objective of this work was
to determine the presence of high and critical priority pathogens included in the aforementioned list
in different aquatic environments in the POCTEFA area (North SpainâSouth France). In addition to
these pathogens, detection of colistin-resistant Enterobacteriaceae was included due its relevance
as being the antibiotic of choice to treat infections caused by multidrug resistant bacteria (MDR).
From the total of 80 analyzed samples, 100% of the wastewater treatment plants (WWTPs) and
collectors (from hospitals and slaughterhouses) and 96.4% of the rivers, carried antibiotic resistant
bacteria (ARB) against the tested antibiotics. Fifty-five (17.7%) of the isolates were identified as target
microorganisms (high and critical priority pathogens of WHO list) and 58.2% (n = 32) of them came
from WWTPs and collectors. Phenotypic and genotypic characterization showed that 96.4% were
MDR and resistance to penicillins/cephalosporins was the most widespread. The presence of bla genes,
KPC-type carbapenemases, mcr-1 and vanB genes has been confirmed. In summary, the presence
of clinically relevant MDR bacteria in the studied aquatic environments demonstrates the need to
improve surveillance and treatments of wastewaters from slaughterhouses, hospitals and WWTPs,
in order to minimize the dispersion of resistance through the effluents of these areas
Improving broiler performance at market age regardless of stocking density by using a pre-starter diet
Altres ajuts: Centro para el Desarrollo TecnolĂłgico Industrial CDTI project IDI-20180885Broiler early nutrition has caught the attention of nutritionists due to the positive correlation between early growth rate and market weight. Early nutrition strategies such as low Ca levels or the use of highly digestible ingredients (e.g., spray-dried porcine plasma [SDPP]) have been reported to improve gut and muscle development, immunity, and overall growth of the bird. On the other hand, recent works suggested that stocking density represents the main constrain for modern chickens to express their full genetic potential. The current study aimed to elucidate the potential effects of pre-starter feeding strategies on contrasting livestock stocking densities. The study followed a factorial design of 2 contrasting starter programs (standard [0-11d] vs. pre-starter [0-4 d] + standard [4-11 d]) by 3 stocking densities (low, medium, and high, 27, 33, and 39 kg/BW/m, respectively). Birds placed at low stocking density showed higher BW and better FCR than those at high stocking density (P < 0.05) being this evident only after d 28. On the other hand, birds fed on pre-starter diet led to higher BW at 4 d (P < 0.001) and the effects on BW were maintained until market age (+2.54%; P < 0.05). The pre-starter diet also led to heavier carcasses (+2.2%; P < 0.05), improved uniformity (P < 0.10) and showed a lower incidence of lameness at high stocking densities (P < 0.05) compared to birds fed the standard starter diet. Results of the current study confirm that, regardless of the stocking density used, pre-starter diets (0-4 d) could lead to a better early growth and market weight
Prevalence of integrons and insertion sequences in ESBL-producing E-coli isolated from different sources in Navarra, Spain
Mobile genetic elements play an important role in the dissemination of antibiotic resistant
bacteria among human and environmental sources. Therefore, the aim of this study was to determine
the occurrence and patterns of integrons and insertion sequences of extended-spectrum ÎČ-lactamase
(ESBL)-producing Escherichia coli isolated from different sources in Navarra, northern Spain. A total
of 150 isolates coming from food products, farms and feeds, aquatic environments, and humans
(healthy people and hospital inpatients), were analyzed. PCRs were applied for the study of class
1, 2, and 3 integrons (intI1, intI2, and intI3), as well as for the determination of insertion sequences
(IS26, ISEcp1, ISCR1, and IS903). Results show the wide presence and dissemination of intI1 (92%),
while intI3 was not detected. It is remarkable, the prevalence of intI2 among food isolates, as well
as the co-existence of class 1 and class 2 (8% of isolates). The majority of isolates have two or
three IS elements, with the most common being IS26 (99.4%). The genetic pattern IS26âISEcp1
(related with the pathogen clone ST131) was present in the 22% of isolates (including human isolates).
In addition, the combination ISEcp1âIS26âIS903âISCR1 was detected in 11 isolates being, to our
knowledge, the first study that describes this genetic complex. Due to the wide variability observed,
no relationship was determined among these mobile genetic elements and ÎČ-lactam resistance.
More investigations regarding the genetic composition of these elements are needed to understand
the role of multiple types of integrons and insertion sequences on the dissemination of antimicrobial
resistance genes among different environments
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