450 research outputs found
Correction: Ntakolia et al. An Explainable Machine Learning Approach for COVID-19’s Impact on Mood States of Children and Adolescents during the First Lockdown in Greece. Healthcare 2022, 10, 149
No full textExclusion of an Author Argyris Stringaris was initially included as an author in the original publication [1]. However, due to his personal decision, we have excluded him from the authors and we added his contribution to the acknowledgments section. The corrected Author Contributions and Acknowledgments are shown below. Author Contributions: Conceptualization, C.N.; methodology, C.N.; software, C.N.; validation, C.N.; formal analysis, C.N., I.R., I.G., A.S. and E.L.; data curation, C.N., D.P., K.M., I.G., K.K., A.S., E.T., A.G., K.L., I.K., N.S. and G.O.; writing—original draft prepara-tion, C.N., D.P., I.R., A.S., E.L. and M.C.-T.; writing—review and editing, C.N., I.R., I.G. and M.C.-T.; visualization, C.N.; supervision, E.L.; project administration, E.L. All authors have read and agreed to the published version of the manuscript. © 2022 by the authors. Licensee MDPI, Basel, Switzerland
Mesenteric artery stenosis presenting as severe erosive gastroduodenitis: A rare case report with long-term follow-up
No full textClinical, angiographic profile and endovascular management of Takayasu's arteritis – Single center prospective study
No full textUltra Linear Low-loss Varactors & Circuits for Adaptive RF Systems
No full textWith the evolution of wireless communication, varactors can play an important role in enabling adaptive transceivers as well as phase-diversity systems. This thesis presents various varactor diode-based circuit topologies that facilitate RF adaptivity. The proposed varactor configurations can act as variable capacitors with high tuning range, low losses and ultra-low distortion, while being continuously tunable and facilitating fast modulation. Making use of these special components, we dealt with various RF applications that can benefit from their unique features, like power and impedance control in the mobile systems and multiple-standard modulators for transceivers and phase diversity systems. Chapter 1 provides an overview of challenges associated with the evolution of wireless communication. Through several case studies, it has been addressed how linear variable reactors (varactors) can enable RF reconfigurability for future telecommunication systems. The challenges on varactors for these applications are brought out, which suggests an urgent need for high-performance varactors. This chapter ends with a descriptive and flow-graph-like outline of the thesis. Chapter 2 presents an overview of the state-of-the-art tunable elements such as BST varactors, MEMS based switches and varactors, and currently available semiconductor switches and varactors. Their advantages and drawbacks are extensively discussed. These surveys clarify the motivation and goal of this thesis, and can at the same time be used as a reference to place this research with respect to the existing literature. To overcome the limitations of currently available tunable elements, Chapter 3 deals with the theory of two novel extremely linear varactor diode configurations with complementary linearity properties in a single varactor diode technology. Both varactor configurations use anti-series varactor diode configurations, where the diodes share the same exponential C(VR) depletion capacitance relation. However, the proposed structures differ in their harmonic terminations and varactor area ratios, resulting in a fundamentally different linearity behavior versus tone spacing. It is this feature that makes it possible to address different requirements of transmit and receive chains in one single technology. In Chapter 4, all varactor configurations, aiming for the cancellation of third-order intermodulation distortion, are summarized and their performance are compared. It is shown that the unique feature of the narrow tone-spacing varactor stack, compared to other “infinite” impedance center-tapped varactor stacks and MEMS varactors, is its high modulation frequency for operation and high linearity for signals with low tone spacing, making it perfectly suitable for many dynamic RF modulation applications. The wide tone-spacing varactor stack, which can be implemented in the same process technology as the narrow tone-spacing varactor stack, offers a complementary linearity behavior in terms of tone spacing and it can be regarded as a bonus, provided that the use of the narrow tone-spacing varactor stack is compulsory. In addition, their exponential C(VR) relationship generally yields larger tuning range compared to the uniformly doped varactors, i.e., the distortion-free varactor stack. When the multi-stack topology is used to further improve the IM5 dominated linearity and power handling capability, it turns out that this stacking yields a linearity improvement that is the double of what is generally found for IM3 dominated devices. The system-level responses of the different varactor configurations are investigated under different bandwidth or data-rate conditions. It reveals that the narrow tone-spacing varactor stack is suitable for both moderate and high data-rate applications, while varactor configurations with linearity limitations at low tone spacings, like the distortion-free varactor stack, may raise some in-band distortion when the bandwidth under consideration is relatively small. Chapter 5 discusses the technology implementation issues and provides the experimental verification of the proposed varactor configurations. The measurement results provide the experimental evidence for the predicted IM3 cancellation, as well as, for the complementary linearity behavior of the narrow tone-spacing varactor stack and wide tone-spacing varactor stack. Their usability in practical circuit conditions was demonstrated through source-pull simulations and measurements, illustrating that high linearity can be maintained in all cases. The multi-stack topology is used to further reduce the IM5 dominated nonlinearity of the narrow tone-spacing varactor stack, yielding a record high linearity for continuously tunable capacitances. Using the ability to adjust the C-VR relationship through the doping profile, the desired capacitance control range and related control voltage are achieved for various practical applications. In particular, the measured data of Skyworks’ pre-production GaAs varactors represent the current state-of-the-art in tuning range, linearity and quality factor among all existing continuously tunable elements. As two application examples of the novel varactors, the adaptive matching networks for mobile handsets are demonstrated in Chapter 6, while a phase shifter and amplitude modulator are given in Chapter 7. The demonstrated adaptive matching networks in Chapter 6 are focused on the efficiency enhancement of the power amplifier in the presence of antenna mismatch. Making use of a varactor-based approach, the resulting networks are capable of dynamically correcting the antenna mismatch with the VSWR of 10 over the whole Smith-chart. For all these conditions, an optimum loading for a power level between 0.5 W and 1 W is offered to the power amplifier stage along with a relatively high operating power gain. The proposed “whole Smith-chart” solution will ease the design of the RF frontend and antennas, yielding a significant reduction in the time-to-market of mobile phones. As another application example, given in Chapter 7, ultra linear low-loss varactors are applied for the implementation of amplitude and phase modulators, which can be used in phase diversity systems. The designed structures allow rapid amplitude and phase modulation with a very low distortion. These components can not only improve the performance of existing RF systems, like phased-array antennas and active load-pull system, but also facilitate other new circuit implementations or RF applications. As a demonstration, a novel polar modulator is proposed that can considerably simplify the structure of the traditional transmitter architecture, while being capable of generating the complex signals, which are typically in use in wireless communication systems. Chapter 8 presents the conclusions and recommendations of this research. The most important conclusion is that the linearization techniques proposed in this thesis has enabled the implementation of ultra linear low-loss varactors. Making use of these varactors, various adaptive circuits can be designed for adaptive RF systems.Microelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
Technical improvement of arthroscopic techniques
No full textMechanical Maritime and Materials Engineerin
Finding cancer genes in copy number data and insertional mutagenesis data
No full textCancer is a genetic disease. Step-wise alteration of genes that have a normal function in the cell can lead to the transformation of a healthy cell into a malignant cancer cell. Cancer genes provide several traits to the cell that allow it to become malignant. These traits have been researched for many years, and currently one knows quite well what has to change in a normal cell before a tumor can be formed. For example, cells must divide continuously, escape the immune system and cause the growth of new blood vessels among others. There are many genes that can cause these processes when deregulated, and each individual tumor alters a different combination of genes to acquire its tumorigenic traits. Knowing which combination of mutations was sustained by a tumor is important as this might make the tumor susceptible or resistant to certain treatments. There are many ways in which cancer genes get mutated. This thesis studies two ways in which cancer genes are mutated. The first way of mutation comes from gains and losses of gene DNA called DNA copy number alterations (CNAs). These alterations occur due to the fact that tumors generally lose their ability to correctly repair damage to their DNA. CNAs can alter the expression of cancer genes and thereby cause cancer. Not only cancer-related genes will be affected by CNAs, also non-related DNA can be damaged. The challenge is to separate the truly oncogenic CNAs from the non-oncogenic passenger CNAs, as these oncogenic CNAs point to novel cancer genes that can be new drug targets. This thesis introduces two methods of finding cancer genes by examining DNA copy number alterations. Multiple comparable tumor samples are used to detect regions in the DNA that are altered significantly more often than other regions, indicating that they are more important for tumor development and therefore probably causative. Analogously, a novel method is introduced to find pairwise regions in the DNA that are preferentially lost or gained together (co-occurring) or preferentially not together (mutually exclusive). It is shown that co-occurring CNAs primarily target genes that are highly similar in function. A detailed analysis of a group of three mutually exclusive CNAs made it possible to associate a novel function to a known cancer gene. The second source of mutations concerns insertions of viral or transposon DNA. These agents insert their DNA in the host genome, which can cause activation or inactivation of host genes. Occasionally they can perturb genes that allow the cell to acquire cancer-related traits. In the end these insertions will cause a tumor. By carefully examining the tumor DNA one is able to reconstruct which genes caused the cancer. Of course, not all insertions were instrumental in the development of the cancer, so also in this case the passenger events and truly causal events have to be separated. This thesis used a novel approach called Shear-Splink that allows determination of the relative number of integrations in a single tumor. Each tumor will present a variety of insertions, each with its own abundance. By examining this abundance it is possible to distinguish between insertions that happened early in tumor development (and are therefore highly abundant) and insertions that are simple passengers or only essential for a small number of cells in the tumor (who will be lowly abundant). In this thesis this has been applied to a study of mouse mammary tumor virus (MMTV), a retrovirus that causes breast cancer in mice through insertion of its DNA in the mouse genome. Results show that by examining the insertion abundance a model through which the tumor has developed can be recovered. Overall this thesis contributes to the analysis of tumor-causing events and especially to the determination of which combination of events is necessary to cause a tumor.Pattern Recognition and BioinformaticsElectrical Engineering, Mathematics and Computer Scienc
Figure 13 from: Seregin AP (2021) Contribution to the "Atlas of the Russian Flora": Twelve local floras of European Russia. Biodiversity Data Journal 9: e73013. https://doi.org/10.3897/BDJ.9.e73013
No full textFigure 13 Typical plant communities of the Patakino local flora (Vladimir Oblast, Russia): broadleaved forest (Querco-Fagetea) dominated by Pteridium pinetorum C.N. Page & R.R. Mill. Photo by the author (2013)
Prognostic value of the SYNTAX score in predicting in-hospital mortality in coronary artery bypass patients – An Indian perspective
No full textAssociation of VKORC1 gene polymorphism (1639G>A and 1173C>T) and acenocoumarol maintenance dosage in patients with mechanical heart valve
No full textIncidence and patterns of valvular heart disease in a tertiary care high-volume cardiac center: A single center experience
No full textAbstractBackgroundDiseases of the heart valves constitute a major cause of cardiovascular morbidity and mortality worldwide with rheumatic heart disease (RHD) being the dominant form of valvular heart disease (VHD) in developing nations. The current study was undertaken at a tertiary care cardiac center with the objective of establishing the incidence and patterns of VHD by Echocardiography (Echo).MethodsAmong the 136,098 first-time Echocardiograms performed between January 2010 and December 2012, an exclusion criterion of trivial and functional regurgitant lesions yielded a total of 13,289 cases of organic valvular heart disease as the study cohort.ResultsIn RHD, the order of involvement of valves was mitral (60.2%), followed by aortic, tricuspid and pulmonary valves. Mitral stenosis, predominantly seen in females, was almost exclusively of rheumatic etiology (97.4%). The predominant form of isolated MR was rheumatic (41.1%) followed closely by myxomatous or mitral valve prolapse (40.8%). Isolated AS, more common in males, was the third most common valve lesion seen in 7.3% of cases. Degenerative calcification was the commonest cause of isolated AS (65.0%) followed by bicuspid aortic valve (BAV) (33.9%) and RHD (1.1%). Multiple valves were involved in more than a third of all cases (36.8%). The order of involvement was MS + MR > MS + AR > MR + AR > AS + AR > MR + AS > MS + AS. Overall, 9.7% of cases had organic tricuspid valve disease.ConclusionRHD contributed most to the burden of VHD in the present study with calcific degeneration, myxomatous disease and BAV being the other major forms of VHD. Multiple valves were affected in more than a third of all cases
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