On the numerical solution of Volterra integral equations on equispaced nodes

In the present paper, a Nystrom-type method for second kind Volterra integral equations is introduced and studied. The method makes use of generalized Bernstein polynomials, defined for continuous functions and based on equally spaced points. Stability and convergence are studied in the space of continuous functions. Numerical tests illustrate the performance of the proposed approach

Combining Nyström methods for a fast solution of Fredholm integral equations of the second kind

In this paper, we propose a suitable combination of two different Nyström methods, both using the zeros of the same sequence of Jacobi polynomials, in order to approximate the solution of Fredholm integral equations on [−1, 1]. The proposed procedure is cheaper than the Nyström scheme based on using only one of the described methods . Moreover, we can successfully manage functions with possible algebraic singularities at the endpoints and kernels with different pathologies. The error of the method is comparable with that of the best polynomial approximation in suitable spaces of functions, equipped with the weighted uniform norm. The convergence and the stability of the method are proved, and some numerical tests that confirm the theoretical estimates are given

Product integration rules by the constrained mock-Chebyshev least squares operator

In this paper we consider the problem of the approximation of definite integrals on finite intervals for integrand functions showing some kind of "pathological" behavior, e.g. "nearly" singular functions, highly oscillating functions, weakly singular functions, etc. In particular, we introduce and study a product rule based on equally spaced nodes and on the constrained mock-Chebyshev least squares operator. Like other polynomial or rational approximation methods, this operator was recently introduced in order to defeat the Runge phenomenon that occurs when using polynomial interpolation on large sets of equally spaced points. Unlike methods based on piecewise approximation functions, mainly used in the case of equally spaced nodes, our product rule offers a high efficiency, with performances slightly lower than those of global methods based on orthogonal polynomials in the same spaces of functions. We study the convergence of the product rule and provide error estimates in subspaces of continuous functions. We test the effectiveness of the formula by means of several examples, which confirm the theoretical estimates

unfixed and fixed human chromosomes show different staining patterns after restriction endonuclease digestion

Restriction endonucleases (REs) have been widely used to produce banding patterns on chromosomes, but it remains uncertain to what extent the patterns are due to the sequence specificity of the enzymes, and to what extent chromatin structure influences the pattern of digestion. To throw light on this question, we have digested with restriction endonucleases unfixed chromosomes prepared in two different ways (isolated, and whole metaphase cells spread with a cytocentrifuge) and compared the results with those obtained on conventionally fixed chromosomes. Unfixed isolated chromosomes are easily destroyed by REs; after fixation with cold methanol, which produced minimal alteration to the chromatin structure, the chromosomes are resistant to the action of REs, and conventional methanol-acetic acid fixation is required to permit the induction of banding patterns by REs. Unfixed cytocentrifuge preparations, in which the chromosomes are still surrounded by cytoplasm, are much more resistant to the action of REs, and again banding patterns were only induced after methanol-acetic acid fixation. We conclude that the action of restriction endonucleases on chromosomes is strongly influenced by chromatin organisation, and that methanol-acetic acid fixation is required to permit the induction of conventional banding patterns on chromosomes

Low-Noise Ku-Band Receiver Frontend with Switchable SIW Filters for Cubesat Applications

This paper proposes a low-noise receiver frontend for nanosatellite and Cubesat platforms. The frontend is composed by a Low-Noise Amplifier (LNA) and two Substrate Integrated Waveguide (SIW) filters, providing a frequency reconfigurability to the system. The two filters operate in the 13 and in the 14 GHz uplink bands, and are selected by means of a pair of solid-state SPDT switches. As a results, 15.5 dB gain with 2.4 dB noise figure for the 13 GHz configuration and 17.8 dB gain with 2.3 dB noise figure for the 14 GHz configuration are obtained. This work is important since demonstrates a low-cost solution for satellite radio apparatuses based on commercial components on a standard PCB

Low-Noise Block Downconverter based on COTS and SIW Filters for Ku-band Cubesat Transponders

This paper proposes a Low-Noise Block (LNB) downconverter operating in the Ku-band for Cubesat transponders. The frontend is composed by a Low-Noise Amplifier (LNA) and two switchable Substrate Integrated Waveguide (SIW) filters, providing a frequency reconfigurability to the system. The LNB is completed by a downconversion unit, constituted by a mixer, a PLL frequency synthesizer and an IF amplifier. A first breadboard features an overall gain of 54 dB with a 2.3 dB noise figure. The worst case linearity performance indicates an input-referred 1 dB compression point (P1dB) and a third-order intercept point (IIP3) equal to -27 dBm and -16 dBm respectively. This work is important since demonstrates a low-cost solution for satellite radio apparatuses based on commercial components and standard PCB

Community Survey Results Show that Standardisation of Preclinical Imaging Techniques Remains a Challenge

Abstract Purpose To support acquisition of accurate, reproducible and high-quality preclinical imaging data, various standardisation resources have been developed over the years. However, it is unclear the impact of those efforts in current preclinical imaging practices. To better understand the status quo in the field of preclinical imaging standardisation, the STANDARD group of the European Society of Molecular Imaging (ESMI) put together a community survey and a forum for discussion at the European Molecular Imaging Meeting (EMIM) 2022. This paper reports on the results from the STANDARD survey and the forum discussions that took place at EMIM2022. Procedures The survey was delivered to the community by the ESMI office and was promoted through the Society channels, email lists and webpages. The survey contained seven sections organised as generic questions and imaging modality-specific questions. The generic questions focused on issues regarding data acquisition, data processing, data storage, publishing and community awareness of international guidelines for animal research. Specific questions on practices in optical imaging, PET, CT, SPECT, MRI and ultrasound were further included. Results Data from the STANDARD survey showed that 47% of survey participants do not have or do not know if they have QC/QA guidelines at their institutes. Additionally, a large variability exists in the ways data are acquired, processed and reported regarding general aspects as well as modality-specific aspects. Moreover, there is limited awareness of the existence of international guidelines on preclinical (imaging) research practices. Conclusions Standardisation of preclinical imaging techniques remains a challenge and hinders the transformative potential of preclinical imaging to augment biomedical research pipelines by serving as an easy vehicle for translation of research findings to the clinic. Data collected in this project show that there is a need to promote and disseminate already available tools to standardise preclinical imaging practices. </jats:sec

Multimodal imaging of hair follicle bulge-derived stem cells in a mouse model of traumatic brain injury

Traumatic brain injury (TBI) is a devastating event for which current therapies are limited. Stem cell transplantation may lead to recovery of function via different mechanisms, such as cell replacement through differentiation, stimulation of angiogenesis and support to the microenvironment. Adult hair follicle bulge-derived stem cells (HFBSCs) possess neuronal differentiation capacity, are easy to harvest and are relatively immune-privileged, which makes them potential candidates for autologous stem cell-based therapy. In this study, we apply in vivo multimodal, optical and magnetic resonance imaging techniques to investigate the behavior of mouse HFBSCs in a mouse model of TBI. HFBSCs expressed Luc2 and copGFP and were examined for their differentiation capacity in vitro. Subsequently, transduced HFBSCs, preloaded with ferumoxytol, were transplanted next to the TBI lesion (cortical region) in nude mice, 2 days after injury. Brains were fixed for immunohistochemistry 58 days after transplantation. Luc2- and copGFP-expressing, ferumoxytol-loaded HFBSCs showed adequate neuronal differentiation potential in vitro. Bioluminescence of the lesioned brain revealed survival of HFBSCs and magnetic resonance imaging identified their localization in the area of transplantation. Immunohistochemistry showed that transplanted cells stained for nestin and neurofilament protein (NF-Pan). Cells also expressed laminin and fibronectin but extracellular matrix masses were not detected. After 58 days, ferumoxytol could be detected in HFBSCs in brain tissue sections. These results show that HFBSCs are able to survive after brain transplantation and suggest that ce

Wireless power transmission: R&D activities within Europe

Wireless power transmission (WPT) is an emerging technology that is gaining increased visibility in recent years. Efficient WPT circuits, systems and strategies can address a large group of applications spanning from batteryless systems, battery-free sensors, passive RF identification, near-field communications, and many others. WPT is a fundamental enabling technology of the Internet of Things concept, as well as machine-to-machine communications, since it minimizes the use of batteries and eliminates wired power connections. WPT technology brings together RF and dc circuit and system designers with different backgrounds on circuit design, novel materials and applications, and regulatory issues, forming a cross disciplinary team in order to achieve an efficient transmission of power over the air interface. This paper aims to present WPT technology in an integrated way, addressing state-of-the-art and challenges, and to discuss future R&D perspectives summarizing recent activities in Europe.The work of N. Borges Carvalho and A. J. S. Soares Boaventura was supported by the Portuguese Foundation for Science and Technology (FCT) under Project CREATION EXCL/EEI-TEL/0067/2012 and Doctoral Scholarship SFRH/BD/80615/2011. The work of H. Rogier was supported by BELSPO through the IAP Phase VII BESTCOM project and the Fund for Scientific Research-Flanders (FWO-V). The work of A. Georgiadis and A. Collado was supported by the European Union (EU) under Marie Curie FP7-PEOPLE-2009-IAPP 251557 and the Spanish Ministry of Economy and Competitiveness Project TEC 2012-39143. The work of J. A. García and M. N. Ruíz was supported by the Spanish Ministries MICINN and MINECO under FEDER co-funded Project TEC2011-29126-C03-01 and Project CSD2008-00068. The work of J. Kracek and M. Mazanek was supported in part by the Czech Ministry of Education Youth and Sports under Project OC09075–Novel Emerging Wireless Systems