Methods for Model Complexity Reduction for the Nonlinear Calibration of Amplifiers Using Volterra Kernels

Volterra models allow modeling nonlinear dynamical systems, even though they require the estimation of a large number of parameters and have, consequently, potentially large computational costs. The pruning of Volterra models is thus of fundamental importance to reduce the computational costs of nonlinear calibration, and improve stability and speed, while preserving accuracy. Several techniques (LASSO, DOMP and OBS) and their variants (WLASSO and OBD) are compared in this paper for the experimental calibration of an IF amplifier. The results show that Volterra models can be simplified, yielding models that are 4–5 times sparser, with a limited impact on accuracy. About 6 dB of improved Error Vector Magnitude (EVM) is obtained, improving the dynamic range of the amplifiers. The Symbol Error Rate (SER) is greatly reduced by calibration at a large input power, and pruning reduces the model complexity without hindering SER. Hence, pruning allows improving the dynamic range of the amplifier, with almost an order of magnitude reduction in model complexity. We propose the OBS technique, used in the neural network field, in conjunction with the better known DOMP technique, to prune the model with the best accuracy. The simulations show, in fact, that the OBS and DOMP techniques outperform the others, and OBD, LASSO and WLASSO are, in turn, less efficient. A methodology for pruning in the complex domain is described, based on the Frisch–Waugh–Lovell (FWL) theorem, to separate the linear and nonlinear sections of the model. This is essential because linear models are used for equalization and cannot be pruned to preserve model generality vis-a-vis channel variations, whereas nonlinear models must be pruned as much as possible to minimize the computational overhead. This methodology can be extended to models other than the Volterra one, as the only conditions we impose on the nonlinear model are that it is feedforward and linear in the parameters

A power efficient frequency divider with 55 GHz self-oscillating frequency in SiGe BiCMOS

A power efficient static frequency divider in commercial 55 nm SiGe BiCMOS technology isreported. A standard Current Mode Logic (CML)-based architecture is adopted, and optimizationof layout, biasing and transistor sizes allows achieving a maximum input frequency of 63 GHz anda self-oscillating frequency of 55 GHz, while consuming 23.7 mW from a 3 V supply. This resultsin high efficiency with respect to other static frequency dividers in BiCMOS technology presentedin the literature. The divider topology does not use inductors, thus optimizing the area footprint:the divider core occupies 60×65μm2on silicon

Proton Radiography for a Small-Animal Irradiation Platform Based on a Miniaturized Timepix Detector

Pre-treatment proton radiography and computed tomography can improve precision of proton therapy. A compact imaging setup for small-animal proton radiography, based on a miniaturized Timepix detector is presented along with results from proof-of-concept experiments. The MiniPIX detector was placed behind a µ-CT calibration phantom with 10 different tissue-equivalent inserts. The intensity of the 70 MeV proton beam was adjusted such that pixel signal clusters from individual protons on the detector could be resolved. Analysis and event filtering on various cluster properties were used to suppress unwanted events. The energy deposition of the selected clusters was converted to water-equivalent thickness (WET) of the traversed material using a conversion curve based on Monte Carlo simulations and measured clusters of protons after traversing PMMA slabs of known thickness. Despite a systematic underestimation of up to 3%, retrieved WET values are in good agreement with ground truth values from literature. The achieved spatial resolution ranges from 0.3 to 0.7 mm for phantom-detector-distances of 1 to 5 cm. Applicability to living animals is currently limited by the relatively long acquisition time of up to 20 minutes per radiography. This obstacle can however be overcome with the latest detector generation Timepix3, allowing to handle higher particle rates and thus requiring shorter irradiation times

HPV as a marker for molecular characterization in head and neck oncology: Looking for a standardization of clinical use and of detection method(s) in clinical practice

Background: A consensus about the most appropriate diagnostic method(s) for head and neck human papillomavirus (HPV)\u2010induced carcinogenesis is still lacking because most of the commercially available assays have been designed for the cervix. Methods: This article summarizes current data and trends concerning HPV diagnostic strategies in oropharyngeal squamous cell carcinoma (OPSCC). Six main approaches are described. Results: The diagnostic gold standard for HPV\u2010related OPSCC, focusing on E6/E7 mRNA detection, requires fresh samples. Because most frequently available samples are formalin\u2010fixed paraffin\u2010embedded (FFPE), the pros and cons of the different approaches were analyzed. Conclusions: In the FFPE samples, the immunohistochemistry of p16, which is considered appropriate to assess HPV\u2010driven carcinogenesis in OPSCC according to the 8th American Joint Committee on Cancer TNM classification, may not be specific enough to become the diagnostic standard in the perspective of treatment deintensification. p16 may play a safer role in combination with another highly sensible assay. Other promising approaches are based on DNA detection through real\u2010time polymerase chain reaction and RNAscope

Low power class-AB VCII with extended dynamic range

voltage swing both at the X terminal and at the Z terminal. The VCII consists of a regulated common gate configuration at the Y current input terminal and a class-AB complementary-MOS closed loop output voltage follower that ensures the voltage buffering action between the voltage input X and the voltage output Z terminals. Spice simulation results using AMS 0.35 μm with a ±0.9 V supply voltage are provided to demonstrate the validity of the proposed topology. With a total power consumption of 28 μW, the VCII achieves a voltage swing at the X terminal of ±0.8 V, whereas a ±0.72 V is achieved on the Z terminal. Simulation results for DC and AC voltage and current gains are given, as well as harmonic distortions and noise figures. A final comparison table is also presented, where the proposed VCII is compared with other solutions presented in the literature

Impact of operator experience and wiring technique on procedural efficacy of trans-radial percutaneous chronic total occlusion recanalization performed by dedicated radialists

The efficacy of trans-radial approach (TRA) in chronic total occlusions (CTO) percutaneous coronary interventions (PCI) is not well established. Thus, we sought to review the feasibility and long-term results of TRA for CTO PCI performed by dedicated TRA operatorsof our center

Beam characterization and feasibility study for a small animal irradiation platform at clinical proton therapy facilities

A deeper understanding of biological mechanisms to promote more efficient treatment strategies in proton therapy demands advances in preclinical radiation research. However this is often limited by insufficient availability of adequate infrastructures for precision image guided small animal proton irradiation. The project SIRMIO aims at filling this gap by developing a portable image-guided research platform for small animal irradiation, to be used at clinical facilities and allowing for a precision similar to a clinical treatment, when scaled down to the small animal size. This work investigates the achievable dosimetric properties of different lowest energy clinical proton therapy beams, manipulated by a dedicated portable beamline including active focusing after initial beam energy degradation and collimation. By measuring the lateral beam size in air close to the beam nozzle exit and the laterally integrated depth dose in water, an analytical beam model based on the beam parameters of the clinical beam at the Rinecker Proton Therapy Center was created for the lowest available clinical beam energy. The same approach was then applied to estimate the lowest energy beam model of different proton therapy facilities, Paul Scherrer Institute, Centre Antoine Lacassagne, Trento Proton Therapy Centre and the Danish Centre for Particle Therapy, based on their available beam commissioning data. This comparison indicated similar beam properties for all investigated sites, with emittance values of a few tens of mm·mrad. Finally, starting from these beam models, we simulated propagation through a novel beamline designed to manipulate the beam energy and size for precise small animal irradiation, and evaluated the resulting dosimetric properties in water. For all investigated initial clinical beams, similar dosimetric results suitable for small animal irradiation were found. This work supports the feasibility of the proposed SIRMIO beamline, promising suitable beam characteristics to allow for precise preclinical irradiation at clinical treatment facilities