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

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 that—when properly designed—the beamformer hardly affects the sensitivity of the receiver

Prehospital risk stratification in patients with chest pain

OBJECTIVES: The History, ECG, Age, Risk Factors and Troponin (HEART) Score is a decision support tool applied by physicians in the emergency department developed to risk stratify low-risk patients presenting with chest pain. We assessed the potential value of this tool in prehospital setting, when applied by emergency medical services (EMS), and derived and validated a tool adapted to the prehospital setting in order to determine if it could assist with decisions regarding conveyance to a hospital. METHODS: In 2017, EMS personnel prospectively determined the HEART Score, including point-of-care (POC) troponin measurements, in patients presenting with chest pain, in the north of the Netherlands. The primary endpoint was a major adverse cardiac event (MACE), consisting of acute myocardial infarction or death, within 3 days. The components of the HEART Score were evaluated for their discriminatory value, cut-offs were calibrated for the prehospital setting and sex was substituted for cardiac risk factors to develop a prehospital HEART (preHEART) Score. This score was validated in an independent prospective cohort of 435 patients in 2018. RESULTS: Among 1208 patients prospectively recruited in the first cohort, 123 patients (10.2%) developed a MACE. The HEART Score had a negative predictive value (NPV) of 98.4% (96.4-99.3), a positive predictive value (PPV) of 35.5% (31.8-39.3) and an area under the receiver operating characteristic curve (AUC) of 0.81 (0.78-0.85). The preHEART Score had an NPV of 99.3% (98.1-99.8), a PPV of 49.4% (42.0-56.9) and an AUC of 0.85 (0.82-0.88), outperforming the HEART Score or POC troponin measurements on their own. Similar results were found in a validation cohort. CONCLUSIONS: The HEART Score can be used in the prehospital setting to assist with conveyance decisions and choice of hospitals; however, the preHEART Score outperforms both the HEART Score and single POC troponin measurements when applied by EMS personnel in the prehospital setting

Computational aspects of 2D-quasi-periodic-green-function computations for scattering by dielectric objects via surface integral eEquations

We describe a surface integral-equation (SIE) method suitable for computation of electromagnetic fields scattered by 2D-periodic high-permittivity and plasmonic scatterers. The method makes use of fast evaluation of the 2D-quasi-periodic Green function (2D-QPGF) and its gradient using a tabulation technique in combination with tri-linear interpolation. In particular we present a very efficient technique to create the look-up tables for the 2D-QPGF and its gradient where we use to our advantage that it is very effective to simultaneously compute the QPGF and its gradient, and to\u3cbr/\u3esimultaneously compute these values for the case in which the role of source and observation point are interchanged. We use the Ewald representation of the 2D-QPGF and its gradient to construct the tables with pre-computed values. Usually the expressions for the Ewald representation of the 2D-QPGF\u3cbr/\u3eand its gradient are presented in terms of the complex complementary error function but here we give the expressions in terms of the Faddeeva function enabling efficient use of the dedicated algorithms to compute the Faddeeva function. Expressions are given for both lossy and lossless medium parameters\u3cbr/\u3eand it is shown that the expression for the lossless case can be evaluated twice as fast as the expression for the lossy case. Two case studies are presented to validate the proposed method and to show that the time required for computing the method of moments (MoM) integrals that require evaluation of the 2D-QPGF becomes comparable to the time required for computing the MoM integrals that require evaluation of the aperiodic Green function. We describe a surface integral-equation (SIE) method suitable for computation of electromagnetic fields scattered by 2D-periodic high-permittivity and plasmonic scatterers. The method makes use of fast evaluation of the 2D-quasi-periodic Green function (2D-QPGF) and its gradient using a tabulation technique in combination with tri-linear interpolation. In particular we present a very efficient technique to create the look-up tables for the 2D-QPGF and its gradient where we use to our advantage that it is very effective to simultaneously compute the QPGF and its gradient, and to simultaneously compute these values for the case in which the role of source and observation point are interchanged. We use the Ewald representation of the 2D-QPGF and its gradient to construct the tables with pre-computed values. Usually the expressions for the Ewald representation of the 2D-QPGF and its gradient are presented in terms of the complex complementary error function but here we give the expressions in terms of the Faddeeva function enabling efficient use of the dedicated algorithms to compute the Faddeeva function. Expressions are given for both lossy and lossless medium parameters and it is shown that the expression for the lossless case can be evaluated twice as fast as the expression for the lossy case. Two case studies are presented to validate the proposed method and to show that the time required for computing the method of moments (MoM) integrals that require evaluation of the 2D-QPGF becomes comparable to the time required for computing the MoM integrals that require evaluation of the aperiodic Green function.\u3cbr/\u3

A multilevel Green function interpolation method to efficiently construct the EFIE MoM-matrix for 2D-periodic PEC structures in 3D space

For scattering by perfectly conducting objects in a two-dimensionally periodic setup we employ a surface-integral equation, the Ewald representation of the Green function, and the Method of Moments (MoM). For moderate-size matrices, we observe that the computation time is dominated by the computation of the matrix elements. By employing a multi-level decomposition of the Green function based on Lagrange interpolation on a Chebyshev grid, we demonstrate that the overall computation time can be reduced by 73% compared to the original MoM computation

Utility of an intraoperabive gamma probe in the surgical management of secondary or tertiary hyperparathyroidism

BACKGROUND: In primary hyperparathyroidism the gamma probe is effective, but its role in secondary hyperparathyroidism is unclear. We investigated the utility of the probe in the surgical management of secondary and tertiary hyperparathyroidism. METHODS: The value of the probe in guiding resection of parathyroids was determined prospectively in 29 patients with secondary or tertiary hyperparathyroidism. Resected tissues with radioactivity of greater than 20% as compared with the wound bed was considered hyperfunctional parathyroid and was confirmed histologically. RESULTS: The probe was helpful in guiding resection in 13% of the hyperplastic glands, including ectopic glands and those not detected preoperatively. The gamma probe confirmed the presence of hyperfunctional parathyroid after resection with a sensitivity and specificity of 97% and 92%, respectively. CONCLUSIONS: The probe is particularly useful in confirming the presence of hyperfunctional parathyroids after resection. It also is useful in identifying ectopic localizations, but its value is limited in guiding surgery for secondary or tertiary disease. (c) 2008 Elsevier Inc. All rights reserved

Public-private partnership in Poland. A cosmological journey

A language barrier prevents us from understanding how other cultures look at public administration, as "semantic fields" differ between languages. These differences can never be fully grasped, but what we can do is study what happens when a particular concept crosses the border. In this article we select a concept, public-private partnership, that in recent times migrated from one administrative order, the United States, to another, Poland. We follow this concept on its migration to see how it changes and to find out what these shifts in meaning tell us about the differences between the two social realities involved. © 2010 SAGE Publications

Value of I-123-subtraction and single-photon emission computed tomography in addition to planar Tc-99m-MIBI scintigraphy before parathyroid surgery

Purpose. To find out if single-photon emission computed tomography (SPECT) and I-123-subtraction can enhance the findings of Tc-99-methoxyisobutylisonitrile (MIBI) scintigraphy for the preoperative localization of parathyroid (PT) tumors. Methods. Among the 111 consecutive patients who underwent preoperative planar Tc-99-MIBI scintigraphy for hyperparathyroidism (HPT), 64 underwent delayed SPECT, and 17 underwent I-123-subtraction. Two independent blinded experts scored the topographical localization, diagnostic confidence, and impact of each diagnostic modality on the surgical strategy. Results. For adenomas, Tc-99-MIBI scintigraphy had a sensitivity of 77% with a positive predictive value (PPV) of 83%. SPECT did not affect the sensitivity or PPV, but it increased the diagnostic confidence and changed the surgical strategy in 21% of the patients. I-123-subtraction increased the sensitivity from 64% to 82%, but decreased the PPV from 88% to 82%. In hyperplastic glands, Tc-99-MIBI scintigraphy had a sensitivity of 47% and a PPV of 95%. When Tc-99-MIBI scintigraphy was combined with SPECT and I-123-subtraction, the results were 44%/10% and 52%/92%, respectively. Both SPECT and I-123-subtraction decreased the diagnostic confidence. Conclusions. Adding SPECT to Tc-99-MIBI scintigraphy improved the surgical decision for parathyroid adenomas. The addition of I-123-subtraction was of limited value. For hyperplastic glands, Tc-99-MIBI scintigraphy was relatively ineffective, even with the addition of SPECT or I-123-subtraction