78 research outputs found
Diffuse Interface Models for Metal Foams
le interest because of their potential
applications in many fields of the industry. To
produce a metal foam, a well-established process
is starting with a molten metal, then introducing
blowing agents to create gas bubbles inside the
metal. In this work we use COMSOL
Multiphysics® and apply the diffuse interface
methods of the phase field technique, in order to
model the properties of metal foams and describe
the movement of the gas-liquid interfaces. A
metal foam represented by a number of bubbles
moving in a laminar flow is modeled and
simulated. Surface tension effects are considered
and repulsive forces between neighboring
bubbles are expressed through the disjoining
pressure. The numerical results show that diffuse
interface methods are effective to model this
kind of complex phenomena and that
fundamental mechanisms due to surface tension
effects an
Spring diet of the pine marten in Sardinia, Italy
Alimentación primaveral de la marta en Cerdeña, ItaliaEl conocimiento del comportamiento de alimentación de un carnÃvoro es esencial para entender su ecologÃa. La marta Martes martes se define comúnmente como un depredador generalista oportunista, porque su dieta en Europa incluye mamÃferos, frutas, aves y invertebrados. A partir del análisis de las heces, hemos descrito los hábitos alimenticios en primavera y la amplitud del nicho trófico de la marta en ambiente mediterráneo en Cerdeña (Italia central). Los pequeños mamÃferos (sobre todo Apodemus sylvaticus, Mus musculus y Eliomys quercinus) representan la fuente más importante de alimentación de la marta, ya que constituyen aproximadamente el 52% del volumen medio. Otra fuente importante de alimentos secundarios la constituyen los invertebrados (especialmente escarabajos y larvas de insectos) y las aves (paseriformes casi exclusivamente), mientras que los grandes mamÃferos, los lagomorfos, los reptiles y las frutas están poco representados en la dieta. La composición de la dieta y el valor del Ãndice de Levins indican que la marta en Cerdeña es un depredador especialista facultativo, con una especialización en la depredación de los micromamÃferos.Knowledge of a carnivore’s foraging behaviour is essential to understand its ecology. The pine marten Martes martes is commonly defined as an opportunistic generalist predator since its diet in Europe includes mammals, fruits, birds and invertebrates. Based on faecal analyses, we evaluated spring feeding habits and trophic niche breadth of the pine marten in a Mediterranean landscape on the island of Sardinia (Central Italy). The most important source of food for the pine marten was small mammals (mainly Apodemus sylvaticus, Mus musculus and Eliomys quercinus), accounting for 52% of the percent mean volume. Important secondary foods were invertebrates (mainly beetles and insect larvae) and birds (almost exclusively passerines), whereas large mammals, lagomorphs, reptiles and fruits made little contribution to the diet. The diet composition and the Levins’ index value suggest that the pine marten in Sardinia behaves as a facultative specialist predator, with a specialization towards small mammals.Alimentación primaveral de la marta en Cerdeña, ItaliaEl conocimiento del comportamiento de alimentación de un carnÃvoro es esencial para entender su ecologÃa. La marta Martes martes se define comúnmente como un depredador generalista oportunista, porque su dieta en Europa incluye mamÃferos, frutas, aves y invertebrados. A partir del análisis de las heces, hemos descrito los hábitos alimenticios en primavera y la amplitud del nicho trófico de la marta en ambiente mediterráneo en Cerdeña (Italia central). Los pequeños mamÃferos (sobre todo Apodemus sylvaticus, Mus musculus y Eliomys quercinus) representan la fuente más importante de alimentación de la marta, ya que constituyen aproximadamente el 52% del volumen medio. Otra fuente importante de alimentos secundarios la constituyen los invertebrados (especialmente escarabajos y larvas de insectos) y las aves (paseriformes casi exclusivamente), mientras que los grandes mamÃferos, los lagomorfos, los reptiles y las frutas están poco representados en la dieta. La composición de la dieta y el valor del Ãndice de Levins indican que la marta en Cerdeña es un depredador especialista facultativo, con una especialización en la depredación de los micromamÃferos
Bronchoscopic techniques in the management of patients with tuberculosis
Tuberculosis (TB) is one of the leading causes of morbidity and mortality worldwide. Early diagnosis and treatment are key to prevent Mycobacterium tuberculosis transmission. Bronchoscopy can play a primary role in pulmonary TB diagnosis, particularly for suspected patients with scarce sputum or sputum smear negativity, and with endobronchial disease. Bronchoscopic needle aspiration techniques are accurate and safe means adopted to investigate hilar and mediastinal lymph nodes in cases of suspected TB lymphadenopathy. Tracheobronchial stenosis represents the worst complication of endobronchial tuberculosis. Bronchoscopic procedures are less invasive therapeutic strategies than conventional surgery to be adopted in the management of TB-related stenosis. We conducted a non-systematic review aimed at describing the scientific literature on the role of bronchoscopic techniques in the diagnosis and therapy of patients with TB. We focused on three main areas of interventions: bronchoscopic diagnosis of smear negative/sputum scarce TB patients, endobronchial TB diagnosis and treatment and needle aspiration techniques for intrathoracic TB lymphadenopathy. We described experiences on bronchoalveolar lavage, bronchial washing, and biopsy techniques for the diagnosis of patients with tracheobronchial and pulmonary TB; furthermore, we described the role played by conventional and ultrasound-guided transbronchial needle aspiration in the diagnosis of suspected hilar and mediastinal TB adenopathy. Finally, we assessed the role of the bronchoscopic therapy in the treatment of endobronchial TB and its complications, focusing on dilation techniques (such as balloon dilation and airway stenting) and ablative procedures (both heat and cold therapies)
Smith-Magenis sindrome and growth hormone deficiency
Smith-Magenis syndrome (SMS) is a multiple congenital anomaly/mental retardation syndrome including physical and neurobehavioural features. The disease is commonly associated with a ca. 3.7 Mb interstitial deletion of chromosome 17p11.2, while a 1.1 Mb critical region has been identified, containing about 20 genes expressed in multiple tissues. Haploinsufficiency of one of them, RAI1, seems to be responsible for the neurobehavioural, craniofacial and otolaryngological features of the syndrome, but not for short stature, commonly seen in SMS patients with chromosome deletion, implying the role of other genes in the 17p11.2 region. Growth failure is a final result of several different mechanisms involving decreased growth hormone (GH) production, reduced tissue response to GH, or impaired activity of epistatic factors. To our knowledge, the association of GH deficiency with SMS has never been reported and rarely investigated, despite the very short stature of SMS patients. We describe a girl with a full SMS phenotype and a typical 3.7 Mb deletion of 17p11.2 who also has GH deficiency. After starting replacement therapy, growth has significantly improved, her stature being now above both the 10th percentile and her genetic target. CONCLUSION: we suggest that an investigation of both growth hormone secretion and function is carried out in patients with Smith-Magenis syndrome and 17p11.2 deletion
Retinal blood flow in senile macular degeneration. A Blue Field study [STUDIO DEL MICROCIRCOLO RETINICO CON LA TECNICA DEL BLUE FIELD IN PAZIENTI AFFETTI DA DEGENERAZIONE MACULARE SENILE]
The technique of the "Blue Field" simulation is based on an endo-optic phenomenon obtained by means of gazing a dark-blue and uniform light, of a 430 nanometers wave lenght. This phenomenon is due to the presence, in the retinal capillaries of 7-10 micrometers diameter, of red blood cells with some leucocytes among them, while the red blood cells do not allow the light to reach the retinal photoreceptors, the leucocytes are crossed by it, so being perceived as shining bodies.In order to obtain that, the patient is request to compare and balance the number of the perceived leucocytes,their velocity and rythm, by means of simulating with the help of a computer the presence of the leucocytes in a video display. This procedure is repeated five times.The Authors report the results obtained by using this technique in a group of 10 patients suffering from senile macular degeneration in prediskiform stage.In this way we pointed out that the circulation in the macular retinal capillaries in this patients is changed, in relation to the alterations of the visus from near
A CMOS Sub-Harmonic Architecture for Signal Down-Converion at Ka-Band
Quadrature Sub-Harmonic mixing to DC or low-IF can be attractive for signal processing at Ka-band. Frequency translation is performed without the need for a local oscillator at the received signal frequency. A lower frequency reference takes advantage of the higher quality of tuning elements and avoids high frequency, powerhungry dividers in the synthesizer. Moreover DC offsetand second-order inter-modulation distortion, due to poor LO-RF isolation, are mitigated by the LO running at lower frequency. This paper presents the receiver IC architecture and experiments from a quadrature demodulator realized in 65nm CMOS
A 24 GHz Subharmonic Direct Conversion Receiver in 65 nm CMOS
Scaled CMOS proves to be suitable for the design of transceiver ICs at micro- and millimeter-waves. The effort is presently toward compact and low-power solutions in view of integrating several transceivers on the same chip enabling phased array systems. In this paper we present a 24 GHz receiver, based on a subharmonic direct conversion architecture, designed in a 65 nm node. The local oscillator takes advantage of the half frequency operation proving significantly lower power consumption when compared to conventional solutions running at received frequency. Stacked switches for subharmonic down-conversion are passive to save voltage room, current driven and loaded by a transresistance amplifier. Optimum biasing of the switches allows maximizing linearity while saving power in the baseband. The integrated LNA matching network is the bottleneck toward low sensitivities. The LNA design trades-off power consumption, gain and sensitivity. Detailed insights into implementation issues, critical in a single-ended topology where both forward and return signal paths have to be supported, are provided. The chip consumes 78 mW and occupies 1.4 mm2 of active area. Experiments show: 30.5 dB gain, 6.7 dB NF, -13 dBm IIP3
Planar Models of Reconfigurable MEMS Circuits
Abstract—This paper presents a general procedure for the electromagnetic modeling of arbitrarily shaped reconfigurable planar circuits using RF microelectromechanical systems switches. In this model, the reconfigurable structure is represented by a linear time-invariant planar multiport, which is connected through internal ports to as many variable lumped-element circuits as the switches. Unlike conventional equivalent circuits, in this technique, the lumped elements represent only a small portion of the switch, and their values are not affected by the proximity of the switch to line discontinuities or to other switches. For this reason, the same values can be reused, with no substantial constraint, in the modeling of very different reconfigurable structures. For any type of switch, the lumped elements are deduced from the experimental or simulated frequency response of a simple prototype. The (arbitrarily shaped) environment of the switches is taken into account in the planar multiport, which is modeled by using very efficient 2-D electromagnetic simulators. Therefore, a lot of different geometries can be easily experimented and the corresponding frequency responses can be readily calculated for any set of the switch states
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