Experimental and Numerical Dynamic Investigation of an ORC System for Waste Heat Recovery Applications in Transportation Sector

ORC power units represent a promising technology for the recovery of waste heat in Internal Combustion Engines (ICEs), allowing to reduce emissions while keeping ICE performance close to expectations. However, the intrinsic transient nature of exhaust gases represents a challenge since it leads ORCs to often work in off-design conditions. It then becomes relevant to study their transient response to optimize performance and prevent main components from operating at inadequate conditions. To assess this aspect, an experimental dynamic analysis was carried out on an ORC-based power unit bottomed to a 3 L Diesel ICE. The adoption of a scroll expander and the control of the pump revolution speed allow a wide operability of the ORC. Indeed, the refrigerant mass flow rate can be adapted according to the exhaust gas thermal power availability in order to increase thermal power recovery from exhaust gases. The experimental data confirmed that when the expander speed is not regulated, it is possible to control the cycle maximum pressure by acting on the refrigerant flow rate. The experimental data have also been used to validate a model developed to extend the analysis beyond the experimental operating limits. It was seen that a 30% mass flow rate increase allowed to raise the plant power from 750 W to 830 W

A Simple Model for the Absorption of Starlight by Dust in Galaxies

We present a new model to compute the effects of dust on the integrated spectral properties of galaxies, based on an idealized prescription of the main features of the interstellar medium (ISM). The model includes the ionization of HII regions in the interiors of the dense clouds in which stars form and the influence of the finite lifetime of these clouds on the absorption of radiation. We compute the production of emission lines and the absorption of continuum radiation in the HII regions and the subsequent transfer of line and continuum radiation in the surrounding HI regions and the ambient ISM. This enables us to interpret simultaneously all the observations of a homogeneous sample of nearby UV-selected starburst galaxies, including the ratio of far-IR to UV luminosities, the ratio of Halpha to Hbeta luminosities, the Halpha equivalent width, and the UV spectral slope. We show that the finite lifetime of stellar birth clouds is a key ingredient to resolve an apparent discrepancy between the attenuation of line and continuum photons in starburst galaxies. In addition, we find that an effective absorption curve proportional to lambda^-0.7 reproduces the observed relation between the ratio of far-IR to UV luminosities and the UV spectral slope. We interpret this relation most simply as a sequence in the overall dust content of the galaxies. The shallow wavelength dependence of the effective absorption curve is compatible with the steepness of known extinction curves if the dust has a patchy distribution. In particular, we find that a random distribution of discrete clouds with optical depths similar to those in the Milky Way provides a consistent interpretation of all the observations. Our model for absorption can be incorporated easily into any population synthesis model. (abridged)Comment: To appear in the 2000 July 20 issue of the Astrophysical Journal; 19 pages with 13 embedded PS figures (emulateapj5.sty

BioGlue® is not associated with polypropylene suture breakage after aortic surgery

Objective: We have encountered broken or damaged polypropylene sutures (Prolene®) at the anastomotic sites during aortic reoperations. Because a surgical sealant, bovine serum albumin-glutaraldehyde (BioGlue®), was used in previous aortic surgery in some of these cases, we undertook this in vitro study to evaluate whether the use of BioGlue® was associated with breakage of polypropylene sutures at the aortic anastomosis. Materials and methods: The broken polypropylene sutures, anastomotic sites and aortic tissue at the location of suture breakage were visually inspected and evaluated intraoperatively. Six human cadaveric aortic samples were incised circumferentially and anastomosed proximally to a valved conduit with running 4–0 polypropylene sutures (Prolene®). In the test group (n = 3), BioGlue® was applied directly to the Prolene® sutures at the anastomotic sites, while in the control group (n = 3) the anastomoses were not sealed with any surgical adhesive. The six samples were immersed in Dulbecco's phosphate buffered saline solution and mounted on a M-6 Six Position Heart Valve Durability Testing System and tested up to 120 million cycles for a 2-year period. During and upon completion of the testing, the integrity of Prolene® sutures, the anastomosis and aortic tissues was regularly assessed by visual inspection. Results: Intraoperative findings included a stretched and thin aortic wall (some with thrombus), a small cleft between the aortic tissue and the Dacron vascular graft. An excessive amount of BioGlue® was often found around the anastomosis, with cracking material, but no signs of mechanical damage were observed in these cases. Upon visual inspection during and after in vitro testing, there was no apparent damage to the polypropylene sutures on the interior or exterior of the aortic anastomoses in any of the samples. No difference was observed in the physical integrity of the polypropylene sutures at anastomotic lines, the anastomoses and aortic tissues between the test and control samples. Conclusions: The results of this study suggest that the use of BioGlue® was not associated with breakage of the polypropylene sutures at the anastomotic sites after aortic dissection repair

Constraints on the Universal Contact Interaction

Forces beyond those of the standard model may manifest themselves at low energies as four-fermion contact interactions. If these new forces are independent of colour and flavour quantum numbers including baryon and lepton number, then all low energy constraints, arising from quark-lepton universality, flavour-changing neutral currents and atomic parity violation are evaded. This is due to the global U(45) symmetry which the standard model exhibits in the limit of vanishing gauge and Yukawa couplings. The corresponding contact interaction is a unique current-current interaction. Constraints from LEP2 imply that this universal contact interaction cannot be the origin of the recently observed high-$Q^2$ events at HERA.Comment: 6 pages Latex, no figure

Use of the frozen elephant trunk technique for type B aortic dissection and aberrant right subclavian artery: an anatomic repair of the “arteria lusoria”

Retrograde extension into the aortic arch occurs in 16.5% of patients with type B aortic dissection (TBAD) (1). This cohort of patients may be eligible for a radical repair using the frozen elephant trunk (FET) technique. The combination of surgical replacement of the aortic arch and deployment of the stent graft allows complete exclusion of the false lumen in aortic dissections. In the case of aneurysm or residual dissection, patients undergoing FET are ready for subsequent endovascular or surgical treatment (2)

Acquiring, archiving, analyzing and exchanging seismic data in real time at the Seismological Research Center of the OGS in Italy

After the 1976 Friuli earthquake (Ms = 6.5) in north-eastern Italy that caused about 1,000 casualties and widespread destruction in the Friuli area, the Italian government established the Centro di Ricerche Sismologiche (CRS). This is now a department of the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), and it is specifically devoted to the monitoring of the seismicity of north-eastern Italy. Since its inception, the North-East Italy Seismic Network has grown enormously. Currently, it consists of 14 broad-band and 20 short-period seismic stations, all of which are telemetered to and acquired in real time at the OGS-CRS data center in Udine. Data exchange agreements in place with other Italian, Slovenian, Austrian and Swiss seismological institutes lead to a total number of 94 seismic stations acquired in real time, which confirms that the OGS is the reference institute for seismic monitoring of north-eastern Italy. Since 2002, CRS has been using the Antelope software suite as the main tool for collecting, analyzing, archiving and exchanging seismic data. SeisComP is also used as a real-time data exchange server tool. A customized web accessible server is used to manually relocate earthquakes, and automatic procedures have been set-up for moment-tensor determination, shaking-map computation, web publishing of earthquake parametric data, waveform drumplots, state-of-health parameters, and quality checks of the station by spectra analysis. Scripts for email/SMS/fax alerting to public institutions have also been customized. Recently, a real-time seismology website was designed and set-up (http://rts.crs.inogs.it/)

Transcatheter Mitral Valve-in-Valve Dislocation: A Rescue Strategy

In the transcatheter aortic valve replacement era, transapical valve-in-valve mitral valve implantation is considered an alternative treatment for high-risk patients with degenerated mitral bioprosthesis. We report an unusual strategy to remedy the potentially fatal complication of the mitral prosthesis migration into the aortic arch. The dislocated prosthesis was successfully stabilized in the aortic arch with a bare aortic stent, ensuring adequate perfusion of epiaortic vessels. \ua9 2018 The Society of Thoracic Surgeon

ACQUIRING SEISMIC DATA IN THE NORTH-EAST OF ITALY: THE OGS-CRS EXPERIENCE IN USING THE ANTELOPE SOFTWARE SUITE

N

Field emission from two-dimensional GeAs

GeAs is a layered material of the IV–V groups that is attracting growing attention for possible applications in electronic and optoelectronic devices. In this study, exfoliated multilayer GeAs nanoflakes are structurally characterized and used as the channel of back-gate field-effect transistors. It is shown that their gate-modulated p-type conduction is decreased by exposure to light or electron beam. Moreover, the observation of a field emission (FE) current demonstrates the suitability of GeAs nanoflakes as cold cathodes for electron emission and opens up new perspective applications of two-dimensional GeAs in vacuum electronics. FE occurs with a turn-on field of ~80 Vum-1 and attains a current density higher than 10 Acm-2, following the general Fowler–Nordheim model with high reproducibility