Fully-Metallic Additively Manufactured Monolithic Double-Ridged Waveguide Rotman Lens in the K/Ka-Band.

This paper reports on the design and experimental validation of a fully-metallic double-ridged waveguide 10 × 10 Rotman lens additively manufactured as a single part. The wide band operation of this quasi-optical beamformer enables us to cover the uplink and downlink frequencies allocated to satellite communications in the K/Ka-band, from 17.3 GHz to 30 GHz. The feeding port design was adjusted to enable vertical printing, thus minimizing the use of supporting structures. A prototype was manufactured and tested. The reported results indicate losses in the range of 0.5 dB in the lower-frequency band and 0.8 dB in the upper-frequency band, including the waveguide transitions added for test purposes. The measured reflection and coupling coefficients remain below -11.5 dB over the operating band. The standard deviation of the residual phase error across the array ports is below 5° in simulation and below 10° in measurements. Array factors synthesized using the scattering parameters confirm the good stability of the beamforming functionality over the wide frequency band analyzed. This monolithic design is a promising step toward more integrated antenna systems, such as a compact dual-stack configuration for planar array design.

HERAS: A Modular Matlab Tool Using Physical Optics for the Analysis of Reflector Antennas.

HERAS is a tool developed in Matlab for the analysis of reflector antennas using physical optics (PO) theory. Its graphical user interface (GUI) and source code are freely available for educational and research purposes. It has the necessity of being a flexible tool to provide adaptability to system engineering requirements and can also be of interest to antenna engineers working on the design of reflector antennas. Due to the increasing demand of broadband services, satellite communications systems are becoming highly complex in order to meet connectivity requirements. To fully exploit the benefits of these systems, multidimensional optimisations are crucial, which call for an efficient estimation of the coverage characteristics. Reflector-based solutions are one of the preferred architectures for very high-throughput satellite (VHTS) systems. A detailed description of HERAS is presented in this paper which has been validated with available commercial software packages. In addition, some examples are described in which the tool has been used for the efficient estimation of VHTS systems performance.

Very Compact Waveguide Orthomode Transducer in the K-Band for Broadband Communication Satellite Array Antennas.

A very compact waveguide orthomode transducer (OMT) is described in this paper. The design is characterized with a twofold rotationally symmetric cross-section in the probing area, adapted from a side-coupling OMT design, simultaneously enabling low port-to-port coupling and high cross-polarization discrimination (XPD) over a fractional bandwidth of about 15-20%. Compared to previously reported compact waveguide OMTs, the proposed design is simpler, thus facilitating its manufacture at millimeter-wave frequencies. The concept is demonstrated with a design in the K-band for a broadband communication satellite downlink over the frequency band of 17.3-20.2 GHz. For test purposes, transitions to standard waveguide WR42 are included, and the OMT is assembled with a conical horn antenna. The measured reflection and coupling coefficients are below -19.5 dB and -22.9 dB, respectively, over the nominal bandwidth, and they are in good agreement with the simulation's results. The on-axis XPD, measured in an anechoic chamber, is better than 30 dB over the nominal bandwidth, which is also in line with simulations. The proposed waveguide OMT may be designed to fit in a lattice below one wavelength at the highest operating frequency, which is desirable for dual-polarized closely spaced array antennas in low and medium Earth orbit communication satellite systems. The simple mechanical design of the proposed OMT makes it particularly appealing for additive manufacturing techniques, as demonstrated with a variant of the design having folded single-mode waveguides, which preserves the RF properties of the original design.

Synthesis of multi-band reflective polarizing metasurfaces using a generative adversarial network.

Electromagnetic linear-to-circular polarization converters with wide- and multi-band capabilities can simplify antenna systems where circular polarization is required. Multi-band solutions are attractive in satellite communication systems, which commonly have the additional requirement that the sense of polarization is reversed between adjacent bands. However, the design of these structures using conventional ad hoc methods relies heavily on empirical methods. Here, we employ a data-driven approach integrated with a generative adversarial network to explore the design space of the polarizer meta-atom thoroughly. Dual-band and triple-band reflective polarizers with stable performance over incident angles up to and including 30°, corresponding to typical reflector antenna system requirements, are synthesized using the proposed method. The feasibility and performance of the designed polarizer is validated through measurements of a fabricated prototype.

Model-Based Reinforcement Learning with Automated Planning for Network Management.

Reinforcement Learning (RL) comes with the promise of automating network management. However, due to its trial-and-error learning approach, model-based RL (MBRL) is not applicable in some network management scenarios. This paper explores the potential of using Automated Planning (AP) to achieve this MBRL in the functional areas of network management. In addition, a comparison of several integration strategies of AP and RL is depicted. We also describe an architecture that realizes a cognitive management control loop by combining AP and RL. Our experiments evaluate on a simulated environment evidence that the combination proposed improves model-free RL but demonstrates lower performance than Deep RL regarding the reward and convergence time metrics. Nonetheless, AP-based MBRL is useful when the prediction model needs to be understood and when the high computational complexity of Deep RL can not be used.

Space-Air-Ground Integrated 6G Wireless Communication Networks: A Review of Antenna Technologies and Application Scenarios.

A review of technological solutions and advances in the framework of a Vertical Heterogeneous Network (VHetNet) integrating satellite, airborne and terrestrial networks is presented. The disruptive features and challenges offered by a fruitful cooperation among these segments within a ubiquitous and seamless wireless connectivity are described. The available technologies and the key research directions for achieving global wireless coverage by considering all these layers are thoroughly discussed. Emphasis is placed on the available antenna systems in satellite, airborne and ground layers by highlighting strengths and weakness and by providing some interesting trends in research. A summary of the most suitable applicative scenarios for future 6G wireless communications are finally illustrated.

Double-layer geodesic and gradient-index lenses.

A double-layer lens consists of a first gradient-index/geodesic profile in an upper waveguide, partially surrounded by a mirror that reflects the wave into a lower guide where there is a second profile. Here, we derive a new family of rotational-symmetric inhomogeneous index profiles and equivalent geodesic lens shapes by solving an inverse problem of pre-specified focal points. We find an equivalence where single-layer lenses have a different functionality as double-layer lenses with the same profiles. As an example, we propose, manufacture, and experimentally validate a practical implementation of a geodesic double-layer lens that is engineered for a low-profile antenna with a compact footprint in the millimeter wave band. Its unique double-layer configuration allows for two-dimensional beam scanning using the same footprint as an extension of the presented design. These lenses may find applications in future wireless communication systems and sensing instruments in microwave, sub-terahertz, and optical domains.

Closed-Form Power Normalization Methods for a Satellite MIMO System.

The paper proposes a new set of normalization techniques for precoding/beamforming matrices applicable to broadband multiuser multiple-input multiple-output (MIMO) satellite systems. The proposed techniques adapt known normalization methods to account for the signal attenuation experienced by users due to the degradation of antenna gain and free space losses towards the edge of the coverage. We use, as an example, an array-fed reflector (AFR) antenna onboard a satellite in geosynchronous orbit (GEO), which provides a favorable trade-off between high-directivity, reconfigurability, and the requirement for digital processing, but suffers from high scan losses away from broadside due to optical aberrations when considered for global coverage applications. Three different precoding/beamforming techniques are employed, namely zero forcing (ZF), minimum mean squared error (MMSE), and matched filtering (MF). Low-complexity power normalization techniques digitally applied after the beamformer are introduced that, in the absence of any atmospheric effects, lead to iso-flux-like characteristics whilst satisfying the power constraint per feed. In comparison with other methods reported in the literature, mainly based on iterative algorithms, the proposed techniques consist in closed-form expressions to provide uniform signal-to-noise ratio (SNR) and signal-to-noise plus interference ratio (SNIR) across the users without significant impact on the payload sum rate. Numerical results are presented to comparatively demonstrate the achieved performance in terms of total capacity and distribution of SNR and SNIR at various noise and interference scenarios.

Cognitive Control-Loop for Elastic Optical Networks with Space-Division Multiplexing.

This paper introduces a new solution to improve network performance by decreasing spectrum fragmentation, crosstalk interference, blocking of virtual networks, cost, and link load imbalance. These problems degrade the performance of Elastic Optical Networks with Space-Division Multiplexing. The proposed solution, called Cognitive control loop (CO-OP), is capable of identifying a set of problems and creating plans to mitigate these problems. The CO-OP comprises four functions that employ learning algorithms to identify problems and plan a series of actions to reduce or eliminate them. The results show that the CO-OP can effectively decrease up to 30% the blocking of requests and up to 50% the crosstalk occurrence compared to existing algorithms.

On the Location of Fog Nodes in Fog-Cloud Infrastructures.

In the fog computing paradigm, fog nodes are placed on the network edge to meet end-user demands with low latency, providing the possibility of new applications. Although the role of the cloud remains unchanged, a new network infrastructure for fog nodes must be created. The design of such an infrastructure must consider user mobility, which causes variations in workload demand over time in different regions. Properly deciding on the location of fog nodes is important to reduce the costs associated with their deployment and maintenance. To meet these demands, this paper discusses the problem of locating fog nodes and proposes a solution which considers time-varying demands, with two classes of workload in terms of latency. The solution was modeled as a mixed-integer linear programming formulation with multiple criteria. An evaluation with real data showed that an improvement in end-user service can be obtained in conjunction with the minimization of the costs by deploying fewer servers in the infrastructure. Furthermore, results show that costs can be further reduced if a limited blocking of requests is tolerated.

Costos hospitalarios directos de la neumonía asociada al ventilador / Hospital direct costs of ventilator-associated pneumonia

Objetivo: el objetivo del estudio fue determinar los costos directos de tratar a los pacientes mecánicamente ventilados que desarrollan un episodio de neumonía asociada al ventilador desde la perspectiva del hospital. Diseño: entre junio 1° de 2011 y junio 1° de 2012, 90 pacientes en ventilación mecánica por más de 48 horas en tres unidades de cuidados intensivos medicoquirúrgicas fueron evaluados para la presencia de neumonía asociada al ventilador. Se determinaron los costos de estancia en la unidad, antibióticos, estudios imagenológicos y microbiológicos. Se determinó el costo total en ventilación mecánica con neumonía asociada al ventilador y sin neumonía. Se estableció el costo incremental de un episodio de neumonía. Los costos se tasaron en pesos colombianos del año 2011 y se convirtieron a dólares 2012. Resultados: 90 pacientes, 33 pacientes tuvieron neumonía asociada al ventilador. El costo promedio por paciente en ventilación mecánica fue 7950 dólares. El costo promedio por paciente en ventilación mecánica con neumonía asociada al ventilador fue 21 217 dólares. El costo incremental fue 14 328 dólares (p<0.001). La fuente de los costos fue 69% en estancia, 21% en el tratamiento antibiótico, 6% en estudios de laboratorio e imagenológicos, y 1% en estudios microbiológicos. En el análisis multivariado por regresión lineal múltiple la presencia de neumonía asociada al ventilador se asoció significativamente con los costos totales (p=0.0001). Conclusiones: la neumonía asociada al ventilador incrementó los costos totales. Los pacientes conneumonía asociada al ventilador tuvieron un costo adicional de 14 328 dólares.

Objective: the aim of the study was to determine the direct costs of treating mechanically ventilated patients who develop an episode of ventilator-associated pneumonia from the hospital perspective. Design: between June 1, 2011 and June 1, 2012, 90 patients on mechanical ventilation for more than 48 hours in 3 medical-surgical units of intensive care were evaluated for the presence of ventilator-associated pneumonia. Costs of unit stay, antibiotics, imaging and microbiological studies were determined. The total cost of mechanical ventilation with ventilator-associated pneumonia and without pneumonia was determined. The incremental cost of an episode of pneumonia was established. Costs were calculated according to the value of Colombian pesos in 2011 and converted to dollars valued in 2012. Results: from a total of 90 patients, 33 had ventilator-associated pneumonia. The average cost per patient on mechanical ventilation was $ 7950. The average cost per patient on mechanical ventilation with ventilator-associated pneumonia was $ 21 217. The incremental cost was $ 14 328 (p < 0.001). The source of the costs was 69% in hospital stay, 21% in antibiotic treatment, 6% in laboratory studies and imaging, and 1% in microbiological studies. In the multivariate analysis by multiple linear regression, the presence of ventilator-associated pneumonia was significantly associated with the total costs (p = 0.0001). Conclusions: ventilator-associated pneumonia increased total costs. Patients with ventilator-associated pneumonia had an additional cost of $ 14 328.

Estrategias y obstáculos para el desarrollo de la investigación en programas de anestesiología: documento de consenso en Colombia / Strategies and obstacles to research development in anesthesiology programs: consensus document in Colombia

La práctica clínica perioperatoria en Latinoamérica está influenciada por investigación generada y publicada en países desarrollados. Afortunadamente, las condiciones económicas cada vez más favorables para la ciencia en los países en vías de desarrollo, sumado al incremento en la visibilidad de nuestras publicaciones científicas, han desencadenado un incremento en el interés por mejorar los estándares de la calidad de la investigación local y a su vez en los trabajos de grado que se generan durante los estudios de posgrado en anestesiología. El presente documento es el resultado de la participación y discusión activa de los expositores y asistentes al evento: «Simposio de investigaciones en Anestesia: El camino para participar en la sociedad del conocimiento¼, organizado por la Sociedad Antioqueña de Anestesiología y Reanimación (SADEA) y la Sociedad Colombiana de Anestesiología y Reanimación (SCARE) en el año 2011. El objetivo del documento es plantear estrategias para ajustar, planificar y mejorar los procesos de investigación, así como la creación y la divulgación del conocimiento generado en anestesiología, medicina del dolor y cuidado intensivo para Colombia y países afines. Incluimos recomendaciones para los programas de posgrado, las instituciones prestadoras de salud y sociedades de anestesiología.

Perioperative clinical practice in Latin America is influenced by research developed and published in developed countries. Fortunately, the increasingly favorable economic conditions for science in the developing countries, in addition to the heightened visibility of our scientific publications has triggered greater interest in improving the quality standards of local research and of the graduate theses generated in the course of graduate studies in anesthesiology. This document is the result of the active participation and discussion among the speakers attending the «Symposium on Research in Anesthesia: the path to participation in the society of knowledge¼, organized by the Society of Anesthesiology and Resuscitation of Antioquia (SADEA) and the Colombian Society of Anesthesiology and Resuscitation (SCARE) in 2011. The purpose of the document is to discuss the strategies to adjust, plan and improve the research processes, as well as the creation and dissemination of knowledge generated in Anesthesiology, Pain Medicine and Intensive Care in Colombia and other developing countries. Recommendations have been included for graduate programs, health care providers and the societies of anesthesiology.

Estádios de desenvolvimento de mudas de umbuzeiros propagadas por enxertia / Developmental stages of umbu fruit seedlings propagated by grafting

O reconhecido potencial econômico das Spondias (como o umbuzeiro) e o crescente interesse dos mercados internacionais em razão da demanda de frutos com sabores exóticos utilizados no preparo de sucos, doces e sorvetes têm despertado o interesse de pesquisadores e produtores por essa fruteira. Os objetivos do trabalho foram avaliar o desenvolvimento de mudas de umbuzeiro e indicar a melhor idade da muda e do garfo para a realização da enxertia. A semeadura foi realizada em canteiros de madeira de 1,5m de largurax10,0m de comprimento x 0,15m de altura, contendo areia lavada, sendo as sementes colocadas juntas e alinhadas em fileiras espaçadas de 5,0 cm uma da outra. Avaliou-se a altura da muda a partir do colo da planta, do número de folhas, do diâmetro do caule a 5, 10 e 15cm do colo, da matéria fresca e seca da parte aérea e das raízes no dia do transplante e após 60, 120, 180 e 240 dias após o transplantio. Avaliou-se também a sobrevivência das mudas com 180 dias após o transplantio, por meio da enxertia, pelo método de garfagem em fenda cheia ao topo com material propagativo (garfos) de umbuzeiros de várias procedências e idades. O delineamento utilizado foi o inteiramente casualizado, e as repetições foram compostas por seis plantas por parcela. Conclui-se que, a partir de seis meses depois da repicagem, as mudas do umbuzeiro podem ser enxertadas pelo método de garfagem em fenda cheia ao topo. Houve uma sobrevivência de 80 por cento das mudas enxertadas, estando estas prontas para o plantio em campo depois de dois meses após a enxertia. O índice de pegamento diminuiu de forma gradual ao serem usados garfos oriundos de plantas com idade acima de seis anos.

The economic importance of Spondias umbuzeiro has been increased in international market due to its exotic flavor and the ability to be used in juices, ice creams and other food preparation. For this reason, the knowledge of many aspects of this species is has been investigated by many researchers and also attracted the farmers interest. The aim of this research was to evaluate the development of umbu seedlings and to indicate the best stage of the seedling and also the more appropriate stage of the fork for grafting. Seeds were sown in wood beds with 1.5m wide10.0m long0.15m high, washed sand, and placed together and aligned in rows spaced 5.0cm apart. The following characteristics were evaluated: seedling size, leaves number, stem diameter at 5, 10 and 15cm from the soil, canopy and root fresh weight in the transplant date and also after 60, 120, 180 and 240 days after transplanting. The grafting technique studied consisted in a top bench grafting with seedlings from different origins and development stages. The efficiency of grafting technique was evaluated after 180 days after transplanting by observing the surviving plants. The experiments were carried out in a completely casualized design and the replicates made up of six plants per plot. It was concluded that from six months after transplanting the umbuzeiro seedlings can be grafted by using top cleft grafting. The efficiency of grafting technique reached 80 percent of all genotypes tested. The same results were observed considering plants after two months when the plants were already planting in a definitive place. The survival index decreased gradually when forks from plants older than six years were used.

C-H...O hydrogen bonding in 4-phenyl-benzaldehyde: a comprehensive crystallographic, spectroscopic and computational study.

The crystal structure of 4-phenyl-benzaldehyde reveals the presence of a dimer linked by the C=O and C9-H groups of adjacent molecules. In the liquid phase, the presence of C-H...O bonded forms is revealed by both vibrational and NMR spectroscopy. A DeltaH value of -8.2 +/- 0.5 kJ mol(-1) for the dimerisation equilibrium is established from the temperature-dependent intensities of the bands assigned to the carbonyl-stretching modes. The NMR data suggest the preferential engagement of the C(2,6)-H and C(10/12)/C(11)-H groups as hydrogen bond donors, instead of the C(9)-H group. While ab initio calculations for the isolated dimers are unable to corroborate these NMR results, the radial distribution functions obtained from molecular dynamics simulations show a preference for C(2,6)-H and C(10/12)/C(11)-H...O contacts relative to the C(9)-H...O ones.

On the modeling of snake venom serine proteinase interactions with benzamidine-based thrombin inhibitors.

Pit viper venoms contain a number of serine proteinases that exhibit one or more thrombin-like activities on fibrinogen and platelets, this being the case for the kinin-releasing and fibrinogen-clotting KN-BJ from the venom of Bothrops jararaca. A three-dimensional structural model of the KN-BJ2 serine proteinase was built by homology modeling using the snake venom plasminogen activator TSV-PA as a major template and porcine kallikrein as additional structural support. A set of intrinsic buried waters was included in the model and its behavior under dynamic conditions was molecular dynamics simulated, revealing a most interesting similarity pattern to kallikrein. The benzamidine-based thrombin inhibitors alpha-NAPAP, 3-TAPAP, and 4-TAPAP were docked into the refined model, allowing for a more insightful functional characterization of the enzyme and a better understanding of the reported comparatively low affinity of KN-BJ2 toward those inhibitors.

Alternativas no transfusionales

Por numerosas razones existe la necesidad de contar con soluciones diferentes a la sangre y sus derivados durante la práctica clínica diaria. Se necesitan soluciones que restauren la volemia pero también sustancias que tengan la posibilidad de transportar oxígeno para así sobrepasar las dificultades y riesgos de la terapia transfusional. Contamos con soluciones cristaloiedes y coloides que tienen características, ventajas y desventajas diferentes, para hacer restituciones iniciales del líquido vascular: A pesar de que en las últimas décadas se ha hecho gran inversión en búsqueda de un transportador de oxígeno diferente al glóbulo rojo, las sustancias con lasque contamos hoy en día, es decir, las soluciones de hemoglobina y las perflourocarbonados, aún no reúnen los requisitos suficientes para ser unos adecuados sustitutos de la sangre