Calibration of pipeline ADC with pruned Volterra kernels

A Volterra model is used to calibrate a pipeline ADC simulated in Cadence Virtuoso using the STMicroelectronics CMOS 45 nm process. The ADC was designed to work at 50 MSps, but it is simulated at up to 125 MSps, proving that calibration using a Volterra model can significantly increase sampling frequency. Equivalent number of bits (ENOB) improves by 1-2.5 bits (6-15 dB) with 37101 model parameters. The complexity of the calibration algorithm is reduced using different lengths for each Volterra kernels and performing iterative pruning. System identification is performed by least squares techniques with a set of sinusoids at different frequencies spanning the whole Nyquist band. A comparison with simplified Volterra models proposed in the literature shows better performance for the pruned Volterra model with comparable complexity, improving linearity by as much as 1.5 bits more than the other techniques

Nonlinear models and algorithms for RF systems digital calibration

Focusing on the receiving side of a communication system, the current trend in pushing the digital domain ever more closer to the antenna sets heavy constraints on the accuracy and linearity of the analog front-end and the conversion devices. Moreover, mixed-signal implementations of Systems-on-Chip using nanoscale CMOS processes result in an overall poorer analog performance and a reduced yield. To cope with the impairments of the low performance analog section in this "dirty RF" scenario, two solutions exist: designing more complex analog processing architectures or to identify the errors and correct them in the digital domain using DSP algorithms. In the latter, constraints in the analog circuits' precision can be offloaded to a digital signal processor. This thesis aims at the development of a methodology for the analysis, the modeling and the compensation of the analog impairments arising in different stages of a receiving chain using digital calibration techniques. Both single and multiple channel architectures are addressed exploiting the capability of the calibration algorithm to homogenize all the channels' responses of a multi-channel system in addition to the compensation of nonlinearities in each response. The systems targeted for the application of digital post compensation are a pipeline ADC, a digital-IF sub-sampling receiver and a 4-channel TI-ADC. The research focuses on post distortion methods using nonlinear dynamic models to approximate the post-inverse of the nonlinear system and to correct the distortions arising from static and dynamic errors. Volterra model is used due to its general approximation capabilities for the compensation of nonlinear systems with memory. Digital calibration is applied to a Sample and Hold and to a pipeline ADC simulated in the 45nm process, demonstrating high linearity improvement even with incomplete settling errors enabling the use of faster clock speeds. An extended model based on the baseband Volterra series is proposed and applied to the compensation of a digital-IF sub-sampling receiver. This architecture envisages frequency selectivity carried out at IF by an active band-pass CMOS filter causing in-band and out-of-band nonlinear distortions. The improved performance of the proposed model is demonstrated with circuital simulations of a 10th-order band pass filter, realized using a five-stage Gm-C Biquad cascade, and validated using out-of-sample sinusoidal and QAM signals. The same technique is extended to an array receiver with mismatched channels' responses showing that digital calibration can compensate the loss of directivity and enhance the overall system SFDR. An iterative backward pruning is applied to the Volterra models showing that complexity can be reduced without impacting linearity, obtaining state-of-the-art accuracy/complexity performance. Calibration of Time-Interleaved ADCs, widely used in RF-to-digital wideband receivers, is carried out developing ad hoc models because the steep discontinuities generated by the imperfect canceling of aliasing would require a huge number of terms in a polynomial approximation. A closed-form solution is derived for a 4-channel TI-ADC affected by gain errors and timing skews solving the perfect reconstruction equations. A background calibration technique is presented based on cyclo-stationary filter banks architecture. Convergence speed and accuracy of the recursive algorithm are discussed and complexity reduction techniques are applied

Evaluation of estimated glomerular filtration rate and clinical variables in systemic sclerosis patients

Objectives: The most important renal complication of systemic sclerosis (SSc) is scleroderma renal crisis (SRC). Many patients demonstrate less severe renal complications, most likely associated with reduced renal blood flow and a consequent reduction in glomerular filtration rate (GFR). The mechanism of this slowly progressive form of chronic renal disease is unclear. The aim of this study was to evaluate GFR by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and the 7-variable Modification of Diet and Renal Disease (MDRD) equations in SSc patients and to correlate estimated GFR (eGFR) with clinical variables of the disease. Methods: 105 unselected and consecutive patients with SSc were enrolled. Serum creatinine was measured in all patients and GFR was estimated by 7-variable MDRD and CKD-EPI equations. Nailfold videocapillaroscopy was performed in all patients. Results: The mean value of eGFR evaluated by both 7-variable MDRD and CKD-EPI was significantly different (p < 0.0001) in the three capillaroscopic groups and correlated negatively with the severity of capillaroscopic damage (early: 95 ± 16 mL/min and 101 ± 12 mL/min, active: 86 ± 25 mL/min and 95 ± 17 mL/min, late: 76 ± 21 mL/min and 82 ± 21 mL/min). The mean value of eGFR evaluated by 7-variable MDRD (97 ± 23 mL/min vs. 74 ± 15 mL/min, p < 0.0001) and CKD-EPI (0.83 ± 0.20 mL/min vs. 0.68 ± 0.10 mL/min, p < 0.0001) was significantly higher in SSc patients without history of digital ulcers than in those with. Conclusion: We can conclude that in SSc patients without renal involvement, eGFR decreases with the progression of digital vascular damag

Three-dimensional echocardiography and 2D-3D speckle tracking imaging in chronic pulmonary hypertension. diagnostic accuracy in detecting hemodynamic signs of RV failure

Background and objective. Our aim was to compare three-dimensional (3D) and 2D and 3D speckle tracking (2D-STE, 3D-STE) echocardiographic parameters with conventional right ventricular (RV) indexes in patients with chronic pulmonary hypertension (PH), and investigate whether these techniques could result in better correlation with hemodynamic variables indicative of heart failure. Methods. Seventy-three adult patients (mean age, 53±13 years; 44% male) with chronic PH of different etiologies were studied by echocardiography and cardiac catheterization (25 precapillary PH from pulmonary arterial hypertension, 23 obstructive pulmonary heart disease, and 23 postcapillary PH from mitral regurgitation). Thirty healthy subjects (mean age, 54±15 years; 43% male) served as controls. Standard 2D measurements (RV-FAC -fractional area change-, TAPSE -tricuspid annular plane systolic excursion-) and mitral and tricuspid tissue Doppler annular velocities were obtained. RV 3D volumes, and global and regional ejection fraction (3D-RVEF) were determined. RV strains were calculated by 2D-STE and 3D-STE. Results. RV 3D global-free-wall longitudinal strain (3DGFW-RVLS), 2D global-free-wall longitudinal strain (GFW-RVLS), apical-free-wall longitudinal strain (AFW-RVLS), basal-free-wall longitudinal strain (BFW-RVLS), and 3D-RVEF were lower in patients with pre-capillary PH (p<0.0001) and post-capillary PH (p<0.01) compared to controls. 3DGFW-RVLS (HR 4.6, 95% CI 2.79-8.38, p=0.004) and 3D-RVEF (HR 5.3, 95% CI 2.85-9.89, p=0.002) were independent predictors of mortality. ROC curves showed that the thresholds offering an adequate compromise between sensitivity and specificity for detecting hemodynamic signs of RV failure were 39% for 3D-RVEF (AUC 0.89), -17% for 3DGFW-RVLS (AUC 0.88), -18% for GFW-RVLS (AUC 0.88), -16% for AFW-RVLS (AUC 0.85), 16mm for TAPSE (AUC 0.67), and 38% for RV-FAC (AUC 0.62). Conclusions. In chronic PH, 3D, 2D-STE and 3D-STE parameters indicate global and regional RV dysfunction that is associated with RV failure hemodynamics better than conventional echo indices

2030 Agenda and sustainable business models in tourism: A bibliometric analysis

Starting in 2015, 169 states launched a series of initiatives aimed at pursuing achievement of the 2030 Agenda. In particular, one of the main sector interested by 2030 Agenda is represented by the Tourism sector. The centrality of Tourism enterprises is related to the considerable impacts on the landscapes in which they operate. On the point, academics and policy makers have started to discuss about the difficult for Tourism enterprises to adopt business model based on sustainable paradigms such as the circular economy. According to this evidence, this paper aims to analyze the scientific debate that has characterized the first 5 years after the introduction of the 2030 Agenda. Bibliometric analysis has been conducted on 101 articles about the relationship between SDGs and Tourism published during the period 2015–2019. The analysis reveals the existence of three independent clusters of research regarding the impacts on society (Red Cluster), business models (Blue Cluster) and policy implications (Green Cluster). An interpretative framework to evaluate the strategies adopted by tourism enterprises to contribute to the SDGs is then developed and discussed

Regional diastolic function by tissue Doppler echocardiography in systemic sclerosis: correlation with clinical variables

The incidence of left ventricular (LV) diastolic dysfunction is increased in systemic sclerosis (SSc), while systolic dysfunction is present in a small percentage of patients. The aim of this study was to asses the LV "regional" diastolic abnormalities in SSc patients by the mean of Doppler tissue imaging (DTI). Echocardiographic echo-Doppler (DE) and DTI parameters were analyzed for 67 SSc patients: abnormal E/A ratio at DE was detected in 24, while abnormal e/a at DTI was observed in 41. A significant prevalence of DTI diastolic abnormalities in the segments reflecting longitudinal versus those reflecting radial LV motion was found. The segments of the basal regions of LV myocardium were significantly more involved than those of the middle portion. Linear correlation was observed between the extent of the diastolic abnormalities and the duration of disease. Longitudinal myocardial systolic velocities were significantly reduced in patients with abnormal e/a DTI

Disordini immunoematologici

I disordini immunoematologici comprendono un esteso gruppo di entità nosologiche nell'ambito delle quali le malattie ematologiche, solitamente citopenie, sono caratterizzate da un'eziopatogenesi di natura immunologica. Le reazioni immunitarie conducono allo sviluppo di anemia emolitica, trombocitopenia, o neutropenia, isolate o associate. Immunodeficienze, malattie autoimmuni sistemiche e reazioni avverse a farmaci possono essere i meccanismi immunitari alla base di queste patologie. Anche il trasferimento di anticorpi materni per via transplacentare può causare fenomeni di citopenia nel feto e nel neonato. Altri disordini immunoematologici includono la presenza di anticorpi diretti contro fattori emocoagulativi, con possibile sviluppo di trombosi o emorragie, e reazioni emolitiche e non emolitiche in seguito alla somministrazione di emoderivat

Raynaud Phenomenon of the Tongue in a Patient With Scleroderma

[No abstract available

Immunity, autoimmunity and autoimmune diseases in older people

Immunosenescence is defined as all the changes occurring in the immune system in the aged. Recent studies suggest that in older patients the immune system undergoes a functional remodelling. Two contrasting phenomena coexist in immunosenescence: the decreasing of immune response and the autoantibody production. Possible consequences are an increase of autoimmune phenomenon, neoplasia incidence, and predisposition to infections. The study of autoimmune manifestations in the elderly population should be considered as a priority for future medical research because of the increase in life expectancy, especially in developed countries. This review analyzes the clinical expression of systemic autoimmune diseases in older patients. Copyright © by BIOLIFE, s.a.s