The bryoflora of Fernando de Noronha, Brasil

Twenty-two species of bryophytes are reported from Fernando de Noronha. One of these, Fissidens veracruzensis Pursell, has not been reported previously from Brasil

Autocostruzioni

Il volume raccoglie, in occasione di una presentazione pubblica all'interno del programma della Biennale di Venezia, una serie di lavori condotti nell'ambito dell'aucostruzion

Le immagini verranno

Il testo rappresenta il saggio introduttivo propedeutico alla lettura degli scritti che compongono l'antologi

Stable orbits in the proximity of an asteroid: solutions for the Hayabusa 2 mission

This thesis studies the dynamics that arise in the surroundings of a small asteroid with the objective of identifying feasible trajectories for use in the Japanese mission Hayabusa 2. Hayabusa 2, which is expected to be launched at the end of year 2014, will travel to near earth asteroid 1999 JU3 and rendezvous with it. The main purpose of the mission is to collect a sample of the asteroid’s rock and carry it back to the earth for a detailed analysis. The spacecraft, however, will remain close to the asteroid for approximately 1.5 years, and it will perform several other types of scientific observations. All of the operations will be carried out from a controlled hovering position, that is, a fixed point between the earth the asteroid, close to the latter. This study aims at finding orbital strategies, different from hovering, that can enhance the scientific returns of this phase. In particular, orbits passing repeatedly close to the asteroid would provide a wealth of information on the gravitational field, and thus the internal structure, that would not be available through simple hovering. A first part of this work is focused on the circular augmented Hill’s 3–body problem, a formulation similar to the restricted 3-body problem that well describes the asteroidal environment, including solar radiation pressure. In this system we perform a grid search that results in a collection of several periodic orbits. We study a group of these orbits in detail, constructing their whole families with numerical continuation and analyzing their stability properties. The orbit families are also subject to a comparison on the basis of the characteristics most appropriate to Hayabusa 2. The result of this part is the identification of a type of orbit that is most feasible for the Japanese mission. Not treated in the above part are the two other important properties of the dynamical system, that is, the inhomogeneity of the asteroid’s mass and the ellipticity of its orbit around the sun. These are considered in the second part as perturbations, and a linear quadratic regulator (LQR) is set up in order to actively eliminate them. We show that the LQR is capable of stabilizing the periodic orbits against these and other effects, using thrusts attainable, in theory, with electric propulsion. The final part of this thesis addresses the need for trajectories that are stable in the elliptic Hill’s problem without any control. Rather then looking for periodic orbits in this more complex system, we use the results from the circular case to identify non-periodic repetitive trajectories that are nonetheless stable. The result in a map of the space of initial conditions containing a wide group of trajectories that neither impact nor escape from the asteroids for long periods of time. Among these trajectories, some are especially suitable for the purposes and instrument requirements of Hayabusa 2

Correction of deep bite in adults using the Invisalign system

[No abstract available

Reliability of Early Fetal Echocardiography for Congenital Heart Disease Detection: A Preliminary Experience and Outcome Analysis of 102 Fetuses to Demonstrate the Value of a Clinical Flow-Chart Designed for At-Risk Pregnancy Management

Early fetal echocardiography (EFEC) is a fetal cardiac ultrasound analysis performed between the 12th and 16th week of pregnancy (compared with the usual 18-22 weeks). In the last 10 years, the introduction of “aneuploidy sonographic markers” in screening for cardiac defects has led to a shift from late second to end of the first trimester or beginning of the second trimester of pregnancy for specialist fetal echocardiography. In this prospective study, early obstetric screening was performed between January 2014 and October 2015, using “aneuploidy sonographic markers” following SIEOG Guidelines 2014. These parameters were then collected and strategically combined in an evaluation score to select the group of pregnancies for performing EFEC, in accordance with the American Society of Echocardiography guidelines for fetal Echocardiography. All second-level examinations were performed transabdominally using a 3D convex volumetric probe with frequency range of 4-8 MHz (Accuvix – Samsung). The outcome data included transabdominal fetal echocardiography from 18 weeks to term and after birth. Overall, 99 pregnant women in the first trimester underwent EFEC (95 singleton and 4 twin pregnancies). Specifically, 30 fetuses were evaluated for extra-cardiac anomalies evidenced by obstetric screening (30%), 25 for family history of congenital heart diseases (25%), 8 for family history of genetic-linked diseases (8%), 4 for heart diseases suspected by obstetric screening (4%) and 19 by normal screening (19%). Was detected 11 (10.7%) CHD, when EFEC detected CHD, were compared to those performed later in pregnancy (18 weeks GA-term), a high degree of diagnosis correspondence was evidenced. The higher sensitivity value of EFEC vs late-FE, in comparison with the post-natal value, coupled with the high EFEC specificity shown vs both the end points, enabled us to consider it as a really reliable diagnostic technology, at least in perienced hands. The introduction of a key combination of the more sensitive obstetric and cardiologic variables should facilitate the formulation of a possible flow-chart as a guide for CHD at-risk pregnancies

Experimental Investigation Of A New Low-Approach Evaporator With Reduced Refrigerant Charge

The impact of the refrigerant charge is growing more and more due to the high cost of the new synthetic refrigerants (HFO) and the increasing cost of the older refrigerants. In the field of the air conditioning, for the centrifugal systems using flooded evaporators it is useful to find alternative heat exchangers with lower refrigerant charge but the same performance. Namely, it is desired a low temperature approach between the water outlet and the evaporating refrigerant, both for increasing the COP of the machine and for reaching low pressure ratios, typically required in the centrifugal compressors. Nowadays, falling film or spray evaporators start to be considered and used. In general they require a complicated distribution system for the liquid inlet and for the flash gas dissipation, and a big volume of the shell in order to avoid liquid flowing to the compressor. Moreover, the performance at partial loads is problematic, as in general it is difficult to maintain wet all the tubes when varying the operating conditions. The present work describes a shell-and-tube evaporator with a completely new design, named “Hybrid Film Evaporator”, where the refrigerant evaporates on the external of the tubes, and the water is cooled flowing inside the tubes. In it there is a combination of a falling down motion of the liquid to be evaporated and a flooding of all the rows of tubes. The liquid is automatically redistributed on each row, and all the surface is always involved in the heat transfer. Two prototypes are investigated, one with four passes and one with six passes on the water side, in a oil-free centrifugal chiller. Both are 1 m long, and their shell diameter is 610 mm. The experimental analysis consists on the measurement of the capacity (ranging from 250 to 450 kW) in conjunction with the evaporating temperature (ranging from 5.5 to 6.5 °C) with R134a as refrigerant fluid. The water outlet temperature is kept at a constant value of 7 °C, and two different sets of experimental data are obtained, keeping constant either the water inlet temperature (at 12 °C) or the water flowrate (at 50 or 65 m³/h). The heat transfer coefficients (both global and external) are then studied. In addition, a flooded evaporator with the same overall geometry is experimentally studied and all the performance parameters are compared to the above ones. The conclusion is that the hybrid film evaporator reaches the same average heat transfer coefficient, and then the same temperature approach at a given heat flux, of a flooded evaporator with the same surface area, saving the refrigerant charge of a quantity between 30 and 40 %