We present a study of an impacting descent probe that increases the science return of spacecraft orbiting or passing an atmosphere-less planetary bodies of the solar system, such as the Galilean ...moons of Jupiter. The descent probe is a carry-on small spacecraft (<100 kg), to be deployed by the mother spacecraft, that brings itself onto a collisional trajectory with the targeted planetary body in a simple manner. A possible science payload includes instruments for surface imaging, characterisation of the neutral exosphere, and magnetic field and plasma measurement near the target body down to very low-altitudes (~1 km), during the probe’s fast (~km/s) descent to the surface until impact. The science goals and the concept of operation are discussed with particular reference to Europa, including options for flying through water plumes and after-impact retrieval of very-low altitude science data. All in all, it is demonstrated how the descent probe has the potential to provide a high science return to a mission at a low extra level of complexity, engineering effort, and risk. This study builds upon earlier studies for a Callisto Descent Probe for the former Europa-Jupiter System Mission of ESA and NASA, and extends them with a detailed assessment of a descent probe designed to be an additional science payload for the NASA Europa Mission.
Piezoceramic material with anisotropic graded porosity Piazza, D.; Capiani, C.; Galassi, C.
Journal of the European Ceramic Society,
2005, 2005-1-00, 20050101, Letnik:
25, Številka:
12
Journal Article, Conference Proceeding
Recenzirano
Porous PZT ceramics were produced at increasing porosity content to a maximum of 40
vol.%. Anisotropic porosity was obtained by adding lamellar graphite as pore forming agent. The ...elasto-piezo-dielectric properties of the samples with uniform porosity were correlated to the increasingly higher degree of anisotropy introduced as the total pore volume increases. Higher anisotropy enhances the decoupling of the longitudinal to transverse effect. A piezoelectric bending actuator with functionally graded microstructure (FGM) was produced by stacking layer by layer, in the green state, the PZT powder at increasing graphite content, followed by die pressing and co-firing. The final pore distribution measured across the section and the performance of the porosity graded material arise from the combination of the properties of the homogeneous layers. This makes it possible to precisely tailor the performance of the porosity graded material.
Un jeu de piste à base de « géocaches » a été conçu par une équipe de chercheurs et appliqué au territoire du Vercors. Il s'agit à la fois de valoriser les travaux de recherche menés sur le ...changement climatique à Grenoble et de sensibiliser les publics par le biais d'une activité de loisir.
•MCLEA with highest enzymatic activity at low temperatures near to 37 °C.•MCLEA with a high enzyme loading efficiency of 90%.•Magnetic nanoparticles enhanced activity of cross-linked cellulase ...aggregates.•High values of frequency and AMF amplitude decrease MCLEA activity.•Frequency have more significant effects on MCLEA activity than the AMF amplitude.
A magnetic cross-linked enzyme aggregate (MCLEA) of cellulases and a non-magnetic analogue (CLEA) were synthesized and further investigated. The obtained MCLEA and CLEA showed a high enzyme loading efficiency of 90% and 88%, respectively. However, the MCLEA presented an activity 33% higher than the CLEA one, suggesting a catalytic enhancement effect as a result of magnetic nanoparticle presence in cross-linked cellulase aggregates structure. In addition, MCLEA shows an unusual behavior with highest enzymatic activity at low temperatures near to 37 °C. Lastly, a full factorial design (2x2) with two variables at two levels, frequency (203–420 kHz) and amplitude (3–6 kA m−1), was used in order to better investigate the effects of an alternating magnetic field (AMF) on MCLEA activity. AMF application decreased MCLEA activity, particularly in the highest values of frequency and amplitude, when compared to condition field free. In addition, frequency implied in more significant effects on MCLEA activity when compared to AMF amplitude.
The interaction between galactomannans, guar gum (GG) with sodium lauryl ether sulphate (SLES) was demonstrated using conductometric, tensiometric, pyrene probe and 1H NMR analyses. SLES and GG ...formed aggregates and reduced the surface tension at a critical aggregation concentration. The interaction was attributed to the presence of surfactant ethoxyl (EO) groups, since in conductometric, tensiometry and pyrene probe analyses using the non-ethoxylated form, sodium lauryl sulphate – SLS, no aggregation was observed. The aggregates formed between SLES and GG presented a negative zeta potential indicating that the polymer is surrounded by SLES and according to the dynamic light scattering analysis (DLS), presented a size of approximately 26 nm. The determination of the thermodynamic parameters showed that the aggregation occurs spontaneously and is a driven-enthalpy and entropy process. SLES and GG interaction could be explored to produce formulations with lower concentrations of surfactants, using commonly used thickeners as GG.
•Galactomannans and SLES interaction were demonstrated using different techniques.•Galactomannans and SLES interacts forming aggregated structures.•The GG and SLES aggregates presented interfacial properties.•The aggregates are stable and presented a size of approximately 26 nm.•The interaction is non-ionic and may involve SLES EO groups.
In this letter, we demonstrate the performance achievable with a highly reconfigurable leaky-wave antenna (RLWA) when used as a building block of a wideband multiple-input-multiple-output (MIMO) ...communication system. The antenna design consists of a periodic structure, composed of cascaded composite right/left-hand (CRLH) microstrip unit cells with tunable electrical characteristics, that is capable of steering its radiation beam over a wide angular range. Field measurements collected in an indoor environment employing an array of dipoles at the transmitter and the RLWA and an array of dipoles at the receiver are used to measure the RLWA achievable gains. We show that the proposed antenna is capable of providing significant gains, with respect to a traditional array of dipoles, while reducing the space occupied by the antenna on the communication device.
Herniation of a gravid uterus through an incisional hernia of the anterior abdominal wall is a rare but serious condition due to the potentially severe maternal and foetal risks. Because of the ...rarity of the condition, no consensus exists regarding the optimal treatment. The component separation technique (CST) has proven to be effective for the treatment of those giant abdominal hernias in which prosthetic material utilisation is not indicated. We report the case of a woman who presented at 38 weeks of gestation with non-reducible herniation of the pregnant uterus through an anterior abdominal wall incisional hernia treated with CST immediately after caesarean section. Review of the existing literature is performed to further underline the efficacy of CST and the need for the practising surgeons to be familiar with this technique and the scenarios when it may become extremely valuable.
A novel design for a gridless two-stage ion mirror, or reflectron, for time-of-flight mass spectrometry (TOFMS) will be presented. The development of this novel design was driven by the stringent ...engineering requirements for the ion mirror's utilization by the reflectron time-of-flight (RTOF) sensor in the Rosetta orbiter spectrometer for ion and neutral analysis (ROSINA) instrument package of the Rosetta cometary mission launched by the European Space Agency in March 2004.
The reflectron consists of ceramic and titanium alloy components joined by brazing and welding processes. The device serves as both the mechanical structure and as an ultra-high-vacuum (UHV) enclosure for the TOFMS system. The electrostatic fields of the reflectron are generated along two individually adjustable sections of a resistor helix applied to the inner surface of a ceramic cylinder. This design allows for increased homogeneity of the electrostatic fields, and minimizes fringe fields close to the cylindrical boundary of the reflectron structure. Thus, the usable inner diameter of ion flight path for a given outer diameter is maximized; a feature required by spacecraft constraints. An additional electrostatic lens in front of the reflectron allows the geometrical alteration of the shape of the ion beam, and its direction with regard to the ion optical axis. This makes it possible to switch the operation of the TOFMS system between a single-reflection and a triple-reflection mode, the latter using an additional ion mirror. Typically, mass resolutions of up to 5000 at full width at half maximum (FWHM) have been achieved in the triple-reflection mode for an overall sensor dimension of 1
m. Experimental results in the single-reflection mode and in the triple-reflection mode will be presented. Environmental constraints for space applications will also be discussed.
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