Modeling and simulation of a digital control design approach for power supply systems

Electronic designers need to model and simulate system features as close as possible to its effective behaviour. Moreover, today, electronics systems are often composed of mixed analog and digital components. The increasing complexity has led to the use of different simulation softwares, each one specific for a particular level of abstraction: mathematical, circuital, behavioural, etc. In order to simulate the entire system these softwares should work together: co-simulation is necessary for digitally controlled power electronics systems. In this paper, the modeling of a digitally controlled switching power supply system using MATLAB/Simulink, ALDEC Active-HDL and Powersys PSIM is presented. The power converter is modelled in PSIM, the digital control is described in VHDL by using Active-HDL, and the complete system is simulated in MATLAB/Simulink environment. This design approach presents all the advantages of each used software and all its features will be discussed. The comparison between simulation and experimental results of the digitally controlled step-down converter prototype are reported

Influence of TiO2 nanometric filler on the behaviour of a composite membrane for applications in direct methanol fuel cells

Composite Nafion membranes containing various amounts of TiO2 (3 wt%, 5 wt% and 10 wt%) were investigated for operation in high temperature Direct Methanol Fuel Cells (DMFCs). Maximum power density of 350 mW cm -2 was achieved in the presence of oxygen feed at 145°C for the composite membranes containing 3-5 wt% TiO2; whereas, the maximum power density with air feed was about 210 mW cm-2. Moreover, an investigation of the influence of titanium oxide particle size on the electrochemical behaviour of the composite membranes for high temperature operation has been carried out. The DMFC performance increases as the mean particle size of the TiO2 filler decreases. This indicates an influence of the filler morphology on the electrochemical properties of the composite membranes. © J. New. Mat. Electrochem. Systems

Research Directions in the Study of Gaming-Related Escapism: a Commentary to Melodia, Canale, and Griffiths (2020)

Escapism motivations and related processes (e.g., avoidance, dissociation, relaxation, and emotion dysregulation) have been identified as risk factors for problematic gaming. However, the escapism construct has often been poorly conceptualized and operationalized in assessment instruments. In their systematic review, Melodia et al. (2020) proposed that conceptualizing escapism as an avoidant coping strategy could provide a sound basis for further study of problematic gaming. In this commentary, we critically examine some terminological and conceptual issues in relation to escapism to guide future research

Examining bi-directionality between Fear of Missing Out and problematic smartphone use. A two-wave panel study among adolescents

Background: In recent years, the Fear of Missing Out (FoMO) construct has been the object of growing attention in digital technology research with previous studies finding support for the relationship between FoMO and problematic smartphone use (PSU) among adolescents and young adults. However, no previous studies clarified the causal link between FoMO and PSU using a longitudinal design. Methods: An auto-regressive, cross-lagged panel design was tested by using a longitudinal dataset with two waves of data collection (T0 and T1, one year apart). Participants included two hundred and forty-two adolescents (109 males and 133 females), with a mean age of 14.16 years, who filled out the Fear of Missing Out scale (FoMOs) and the Smartphone Addiction Scale (SAS). Moreover, participants filled out the Difficulties in Emotion Regulation Scale (DERS), at the first time-point of data collection. Results: The findings of the study show that FoMO (both FoMO-Fear and FoMO-Control subscales) and PSU are positively related at both time-points (i.e. at a cross-sectional level). However no cross-lagged associations between them were longitudinally supported. Females and older adolescents show higher FoMO-Fear at T1. Conclusions: The findings of the present study suggest caution when causal links between FoMO and PSU are inferred

Congenital scoliosis associated with agenesis of the uterine cervix. Case report

BACKGROUND: Alterations in the normal sequence of development of müllerian ducts lead to a wide spectrum of reproductive tract abnormalities. A rare form of lack of development, regarding a short tract of the müllerian ducts, leads to the isolated agenesis of the uterine cervix. Anomalies identified among patients with müllerian agenesis include skeletal deformities (i.e., scoliosis of the spine and Klippel-Feil anomaly). CASE PRESENTATION: A 46 years old woman presenting cyphoscoliosis and very low stature (120 cm – 3,93 feet), came to our observation for acute pelvic pain; she also reported primary amenorrhoea associated with cyclic pelvic pain. Clinical and imaging evaluation, evidenced a blind vaginal duct of normal length, left cystic adnexal mass, and enlarged uterus with hematometra. FSH, LH, 17β estradiol and CA-125, karyotype and radiographic study of limbs and vertebral column were also evaluated. At laparotomy, a left ovarian cyst was found. Uterus ended at the isthmus; under this level a thin fibrous tissue band was found, joining the uterus to the vagina. Uterine cervix was replaced by fibrous tissue containing some dilated glands lined with müllerian epithelium. Karyotype resulted 46, XX. The described skeletal deformity, were consistent with Klippel-Feil syndrome. CONCLUSION: We report a case of congenital scoliosis associated with müllerian agenesis limited to uterine cervix, association thus far seen only among patients with Mayer-Rokitansky-Kuster-Hauser syndrome (utero-vaginal agenesis). This case report supports the necessity to evaluate, for accompanying müllerian anomalies, all cases of congenital structural scoliosis in view of the possibility for many müllerian development abnormalities, if timely diagnosed, to be surgically corrected

Effect of indacaterol on lung deflation improves cardiac performance in hyperinflated COPD patients : an interventional, randomized, double-blind clinical trial

BACKGROUND: COPD is often associated with cardiovascular comorbidity. Treatment guidelines recommend therapy with bronchodilators as first choice. We investigated the acute effect of single-dose indacaterol on lung hyperinflation in COPD subjects, for the first time evaluating the potential effects on right heart performance. METHODS: In this Phase IV, randomized, interventional, double-blind, crossover clinical study, we recruited 40 patients (50-85 years of age) with stable COPD. Patients were treated with 150 \u3bcg indacaterol or placebo and after 60 minutes (T60) and 180 minutes (T180) the following tests were performed: trans-thoracic echocardiography (TTE), plethysmography, diffusing capacity of the lung for carbon monoxide, saturation of peripheral oxygen, and visual analog scale dyspnea score. Patients underwent a crossover re-challenge after a further 72 hours of pharmacological washout. All TTE measurements were conducted blindly by the same operator and further interpreted by two different blinded operators. Consensus decisions were taken on every value and parameter. The primary outcome was the effect of the reduction of residual volume and functional residual capacity on right heart systolic and diastolic function indexes evaluated by TTE in patients treated with indacaterol, as compared to placebo. RESULTS: Vital capacity, inspiratory capacity, and forced expiratory volume in 1 second were significantly increased by indacaterol, when compared with placebo, while residual volume, intrathoracic gas volume, and specific airway resistance were significantly reduced in patients treated with indacaterol. Tricuspid annular plane systolic excursion was significantly increased versus placebo, paralleled by an increase of tricuspid E-wave deceleration time. The cardiac frequency was also significantly reduced in indacaterol-treated patients. CONCLUSION: Indacaterol significantly reduces lung hyperinflation in acute conditions, with a clinically relevant improvement of dyspnea. These modifications are associated with a significant increase of the right ventricular compliance indexes and may have a role in improving left ventricular preload leading to a reduction in cardiac frequency

THE VALUE OF DIAGNOSTIC ULTRASOUND FOR DETECTING OCCULT INGUINAL HERNIA IN PATIENTS WITH GROIN PAIN

Aims: chronic groin pain caused by an occult hernia can be a difficult clinical diagnosis and may require additional investiga- tive modalities. The aim of this study was to demonstrate the accuracy of ultrasound in diagnosing occult hernia in patients with recurrent inguinal pain and a negative clinical examination. Patients and methods: over a period of three years, a total of 76 patients were referred for ultrasound examination with clini- cally suspected occult inguinal hernia. Patients with positive US scans were offered surgery, while those with negative US findings were offered further imaging or other diagnostic tests. The ultrasound examination of the inguinal region was conducted using a 5- 10 MHz linear probe. The scan was performed with the patient in the supine and erect positions, in a relaxed state, as well as during coughing and during a Valsalva manoeuvre. Results: overall, ultrasound diagnosed 31 inguinal hernias and all 31 patients with positive scans underwent surgery. Surgery confirmed the ultrasound diagnosis in 30 patients, having only 1/31 no hernia at operation (100% ultrasound sensitivity and 96.9% specificity). Patients undergoing surgery showed complete symptom resolution at a three-month follow-up. Conclusions: this study confirms that ultrasound is capable of accurately diagnosing groin hernia and this may justify its use in patients with chronic groin pain due to a suspected occult herni

Regulation of mGlu4 metabotropic glutamate receptor signaling by type-2 G-protein coupled receptor kinase (GRK2

ABSTRACT We examined the role of G-protein coupled receptor kinase-2 (GRK2) in the homologous desensitization of mGlu4 metabotropic glutamate receptors transiently expressed in human embryonic kidney (HEK) 293 cells. Receptor activation with the agonist L-2-amino-4-phosphonobutanoate (L-AP4) stimulated at least two distinct signaling pathways: inhibition of cAMP formation and activation of the mitogen-activated protein kinase (MAPK) pathway [assessed by Western blot analysis of phosphorylated extracellular signal-regulated kinase (ERK) 1 and 2]. Activation of both pathways was attenuated by pertussis toxin. Overexpression of GRK2 (but not GRK4) largely attenuated the stimulation of the MAPK pathway by L-AP4, whereas it slightly potentiated the inhibition of FSK-stimulated cAMP formation. Transfection with a kinase-dead mutant of GRK2 (GRK2-K220R) or with the C-terminal fragment of GRK2 also reduced the mGlu4-mediated stimulation of MAPK, suggesting that GRK2 binds to the G␤␥ subunits to inhibit signal propagation toward the MAPK pathway. This was confirmed by the evidence that GRK2 coimmunoprecipitated with G␤␥ subunits in an agonist-dependent manner. Finally, neither GRK2 nor its kinase-dead mutant had any effect on agonist-induced mGlu4 receptor internalization in HEK293 cells transiently transfected with GFP-tagged receptors. Agonist-dependent internalization was instead abolished by a negative-dominant mutant of dynamin, which also reduced the stimulation of MAPK pathway by L-AP4. We speculate that GRK2 acts as a "switch molecule" by inhibiting the mGlu4 receptor-mediated stimulation of MAPK and therefore directing the signal propagation toward the inhibition of adenylyl cyclase. Metabotropic glutamate (mGlu) receptors, which belong to the third class of the G protein-coupled receptor (GPCR) superfamily, modulate excitatory synaptic transmission and are implicated in different aspects of central nervous system physiology, including motor control, motor coordination, sensory perception and pain transmission, learning and memory processes, and developmental plasticity Homologous desensitization of GCPRs is mediated by a family of enzymes called G-protein coupled receptor kinases (GRKs). This family includes GRK1, which corresponds to rhodopsin kinase, GRK2, and -3, which are ubiquitous and are activated by G-protein ␤␥ subunits, and GRK4, -5, and -6

CO2 gasification of chars prepared from wood and forest residue

The CO2 gasification of chars prepared from Norway spruce and its forest residue was investigated in a thermogravimetric analyzer (TGA) at slow heating rates. The volatile content of the samples was negligible; hence the gasification reaction step could be studied alone, without the disturbance of the devolatilization reactions. Six TGA experiments were carried out for each sample with three different temperature programs in 60 and 100% CO2. Linear, modulated, and constant-reaction rate (CRR) temperature programs were employed to increase the information content available for the modeling. The temperatures at half of the mass loss were lower in the CRR experiments than in the other experiments by around 120 degrees C. A relatively simple, well-known reaction kinetic equation described the experiments. The dependence on the reacted fraction as well as the dependence on the CO2, concentration were described by power functions (n-order reactions). The evaluations were also carried out by assuming a function of the reacted fraction that can mimic the various random pore/random capillary models. These attempts, however, did not result in an improved fit quality. Nearly identical activation energy values were obtained for the chars made from wood and forest residues (221 and 218 kJ/mol, respectively). Nevertheless, the forest residue char was more reactive; the temperatures at half of the mass loss showed 20-34 degrees C differences between the two chars at 10 degrees C/min heating rates. The assumption of a common activation energy, E, and a common reaction order, v, on the CO2, concentration for the two chars had only a negligible effect on the fit quality