Slowly varying function method applied to quartz crystal oscillator transient calculation.

By using an approach based on the full nonlinear Barkhausen criterion, it is possible to describe oscillator behavior under the form of a nonlinear characteristic polynomial whose coefficients are functions of the circuit components and of the oscillation amplitude. Solving the polynomial in the frequency domain leads to the steady state oscillation amplitude and frequency. In the time domain, the characteristic polynomial represents a nonlinear differential equation whose solution gives the oscillator signal transient. It is shown how symbolic manipulation capabilities of commercially available softwares can be used to automatically generate the coding of the oscillator characteristic polynomial from the SPICE description netlist. The numerical processing of such an equation in the time domain leads to unacceptable computer time because of the high quality factor of the oscillator circuits involved. Nevertheless, by using the slowly varying amplitude and phase method, it is possible to transform the initial nonlinear differential equation into a nonlinear first order differential equation system in the amplitude and phase variables. The solution of this system directly gives the designer the most relevant features of the oscillation; that is, the amplitude, phase, or frequency transients which can be accurately obtained within a short computer time by using classical numerical algorithms.

Analysis of noise in quartz crystal oscillators by using slowly varying functions method.

By using formal manipulation capability of commercially available symbolic calculation code, it is possible to automatically derive the characteristic polynomial describing the conditions for oscillation of a circuit. The analytical expression of the characteristic polynomial is obtained through an encapsulation process starting from the SPICE netlist description of the circuit: by using a limited number of simple transformations, the initial circuit is progressively transformed in a simplified standard form. In this method, the nonlinear component is described by its large signal admittance parameters obtained from a set of SPICE transient simulations of larger and larger amplitude. The encapsulation process involving linear and nonlinear components as well as noise sources leads to a perturbed characteristic polynomial. In the time domain, the perturbed characteristic polynomial becomes a nonlinear nonautonomous differential equation. By using an extension of the slowly varying functions method, this differential equation is transformed into a nonlinear differential system with perturbation terms as the right-hand side. Eventually, solving this system with classical algorithms allows one to obtain both amplitude and phase noise spectra of the oscillator.

[A rare complication of chronic pancreatitis: pancreatico-pleural fistula]. / Une complication rare d'une pancréatite chronique: la fistule pancréatico-pleurale.

Pleural effusion is a rare complication of chronic pancreatitis. We report a case observed in a 39-year-old patient hospitalized for dyspnea and pain in the lower left thorax. Chest x-ray revealed left pleural effusion. The exudative pleural fluid contained a very high amylase level. CT-scan revealed a pseudo-cyst of the tail of the pancreas extending into contact with the diaphragm and the chronic pancreatitis lesions. Medical treatment associating thoracic drainage, somatostatin analog, and antibiotics was unsuccessful. Thoracoscopic pleural decortication was performed. The patient then developed pneumonia involving the left base. A new antibiotic regimen was delivered and the pseudocyst was drained percutaneously under CT guidance. The clinical course was favorable at six months with partial involution of the pseudocyst and regression of the pulmonary images.

Nutrient intake of elite sailors during a solitary long-distance offshore race.

The purpose of the present study was to determine the nutritional intake of 11 skippers during the four stages of a solitary long-distance offshore race. Body weight significantly decreased during the race (-1.31 +/- 0.32 kg, range 3.5 to 0.1 kg, p <.01). Total daily energy intake was 18.53 +/- 0.71 MJ x day-1 during the race, and it correlated negatively with the rate duration of each leg. Energy intake during the race was 19% greater than that determined for a subgroup of 5 sailors during a control period 2 months after the race. Nutrient intake expressed as percentage calories of total energy was estimated at 50%, 35%, and 15% for carbohydrate, fat, and protein, respectively. Voluntary fluid intake decreased with increasing race duration (p<.001). Despite high energy intakes, sailors lost body weight during the solitary offshore race. It was not possible to conclude that this change in body weight was related to fluid loss and/or a discrepancy between energy intake and energy expenditure.