Numerical model of a multi-turn Closed Loop Pulsating Heat Pipe: Effects of the local pressure losses due to meanderings

A numerical code has been developed to investigate the thermal performances of Closed Loop Pulsating Heat Pipes (CLPHP). The model takes into account the effects of the local pressure losses due to the presence of turns which have always been neglected by previous models; it can simulate CLPHPs working with different fluids (ethanol, R123 and FC-72 are shown), different number of turns, various inclination angles as well as different input heat fluxes at the evaporator. Numerical results show that the local pressure losses influence the device behavior in particular for high input heat fluxes and when the CLPHP is working in the horizontal position. The trends of the total liquid momentum, maximum tube temperatures, and equivalent thermal resistances, reveal good qualitative and quantitative accordance with the experimental data available in literature. Further direct experimental validations are mandatory to confirm whether this model can be used as a preliminary CLPHP thermal design tool.     

Epileptic discharge of cortical, subcortical and spinal neurons in penicillin induced experimental epilepsy

The sensitivity and electrophysiological patterns of paroxysmal activity induced in different brain structures by topical application of penicillin-G were evaluated in the rat. Recordings were carried out in five groups of animals, in telencephalon, diencephalon, mesencephalon, rombencephalon and spinal cords. The following analysis were carried out: frequency distribution histograms, latency and time course duration of paroxysmal activity, duration and amplitude of epileptic bursts. The results obtained showed that the nervous structures tested with penicillin-G had a different epileptogenic sensitivity and response pattern which significantly changed along the cerebral cortex-spinal cord axis. The highest epileptic sensitivity was observed in somatosensory cortex (SI) at 500-600 microns depth; in the other cortical layers, a significant lenghtening in latency was observed. Among the other structures, the spinal cord seemed to be the most sensitive target to the epileptogenic action of penicillin-G, whereas in the remaining structures, sensitivity significantly decreased in rostro-caudal direction. As far as the features of the paroxysmal activity are concerned, significant differences among tested structures were observed. In particular, within the SI cortex, the main differences were represented by the gradual increase in burst frequency and voltage from the surface to the IVth layer and by their subsequent decrease in deeper layers (V-VI). In the diencephalon, the paroxysmal activity was similar to that observed in more superficial and deeper cortical layers even though epileptic bursts showed a lower amplitude. Mesencephalon and rombencephalon displayed a paroxysmal activity with a distinctive feature, characterized by long lasting bursts of low amplitude, although bulbar outbursts showed a shorter duration than the mesencephalic ones. In the spinal cord, the epileptiform activity displayed a different paroxysmal pattern, characterized by the longest duration and the highest amplitude. The different sensitivities of the investigated brain structures to penicillin-G and the characteristics of the induced paroxysmal activity have been extensively discussed.     

CR-39 detector based thermal neutron flux measurements, in the photo neutron project

PhoNeS (photo neutron source) is a project aimed at the production and moderation of neutrons by exploiting high energy linear accelerators, currently used in radiotherapy. A feasibility study has been carried out with the scope in mind to use the high energy photon beams from these accelerators for the production of neutrons suitable for boron neutron capture therapy (BNCT). Within these investigations, it was necessary to carry out preliminary measurements of the thermal neutron component of neutron spectra, produced by the photo-conversion of X-ray radiotherapy beams supplied by three LinAcs: 15 MV, 18 MV and 23 MV. To this end, a simple passive thermal neutron detector has been used which consists of a CR-39 track detector facing a new type of boron-loaded radiator. Once calibrated, this passive detector has been used for the measurement of both the thermal neutron component and the cadmium ratio of different neutron spectra. In addition, bubble detectors with a response highly sensitive to thermal neutrons have also been used. Both thermal neutron detectors are simple to use, very compact and totally insensitive to low-ionizing radiation such as electrons and X-rays. The resultant thermal neutron flux was above 10⁶ n/cm²s and the cadmium ratio was no greater than 15 for the first attempt of photo-conversion of X-ray radiotherapy beams.     

Hypertrophic cardiomyopathy during adrenocorticotrophic hormone administration in infants: a case report

We report a 2-month-old child with infantile myoclonic seizures, who developed congestive heart failure secondary to hypertrophic cardiomyopathy while receiving adrenocorticotropic hormone (ACTH) therapy. Treatment with propranolol and withdrawal of ACTH led to the resolution of cardiac hypertrophy as determined by two-dimensional echocardiography. Possible links between ACTH therapy and the development of hypertrophic cardiomyopathy are examined. Our report confirms that a careful monitoring is required to detect cardiac abnormalities during ACTH administration.     

Organic field effect transistors for textile applications.

In this paper, several issues concerning the development of textiles endowed with electronic functions will be discussed. In particular, issues concerning materials, structures, electronic models, and the mechanical constraints due to textile technologies will be detailed. The idea starts from an already developed organic field-effect transistor that is realized on a flexible film that can be applied, after the assembly, on whatever kind of substrate, in particular, on textiles. This could pave the way to a variety of applications aimed to conjugate the favorable mechanical properties of textiles with the electronic functions of transistors. Furthermore, a possible perspective for the developments of organic sensors based on this structure are described.     

Edge distributed admission control in MPLS networks

This paper proposes a novel approach for admission control in traffic engineered data networks, which applies at network edges by means of dynamic thresholds evaluated on the basis of network status. The proposed method is described with focus on IP/MPLS networks, but it actually applies as well to a variety of scenarios, such as ATM or generalized MPLS. The proposed solution allows more efficient usage of network resources, especially at medium/high load, and increased robustness of the network.     

Mastering the complexity of an Ultrasonic Sealing System: The port-Hamiltonian approach

This paper deals with the problem of simulating an Ultrasonic Sealing System (USS). The USS is a complex electromechanical system used to seal aseptic packages for liquid foods that is the core of the most advanced filling machines. Since the overall device is the result of the interconnection of several sub-systems that belong to different physical domains, the problem is tackled within the port-Hamiltonian framework, which is naturally multi-domain and multi-scale. On the other hand, the simulation of the whole sealing process is not a trivial task due to the presence of a Compact Transducer (CT) that can be modeled only by means of commercial finite-element software. Then, only extremely high-order models are available, which makes the simulation of the complete system impractical. Consequently, a novel model reduction procedure for port-Hamiltonian systems has been developed. The method is able to preserve the frequency behavior of the original system in a neighborhood of a predefined set of frequencies of interest. In this way, simulation times have been drastically shortened without loosing the essential dynamical information. The reduced order model can be adopted to test the validity of the controller, and to simulate and perform the diagnosis of the entire sealing process. The results of the model reduction algorithm have been experimentally validated. Moreover, also the complete USS model has been derived.     

Contrasting decay of historical building stone: relationships between petrophysical features and frontal polymerization treatment suitability on medieval buildings of north Sardinia,Italy

Bulletin of Engineering Geology and the Environment - Textural, physical–mechanical, and mineralogical–chemical properties influence the degradation of building stone. These properties...     

Total intravenous anaesthesia in Charcot-Marie-Tooth disease. Case report

A Total Intravenous Anaesthesia (TIVA) protocol in a case of hereditary motor-sensory neuropathy Charcot-Marie-Tooth disease in three consecutive orthopaedic surgical procedures is described. History, physical examination and sural nerve fascicular biopsy findings are reported. Problems related to the perioperative anaesthesiological management in peripheral neuropathies are discussed. Propofol and fentanyl without muscle relaxants, proved to be a safe technique, fast at reaching the level of surgical anaesthesia required, manageable for maintenance and rapidly reversible.     

Numerical Investigation of the Effects of Orientation and Gravity in a Closed Loop Pulsating Heat Pipe

The Closed Loop Pulsating Heat Pipe (CLPHP) is a very promising passive two-phase heat transfer device for relatively high heat fluxes (up to 30 W/cm²) patented by Akachi (1990, 1993). Although the CLPHP has a simple structure, its working principles are very complex compared to the standard heat pipe with a porous wick. One of the most debated issues deals on how the thermal performance is affected by the inclination and by the action of different gravity fields (terrestrial, lunar, martian and microgravity). Even if the internal tube diameter satisfies the conventional slug flow regime requirement on the Bond number, gravity force still plays an important role on the PHP behaviour. Heat input and the number of turns are two of the most important indirect parameters linked to the gravity issue. A complete numerical campaign has been performed by means of a FORTRAN code at different inclination angles and gravity levels on various PHP. The numerical model is able to estimate both the hydrodynamic and the thermal performance of a CLPHP with different working fluids. The analysis shows that the effect of local pressure losses due to bends is important and must be taken into account, in particular in the horizontal operation which is the reference point for space applications. Numerical results are matched with the experimental data quoted in literature and both good qualitative and quantitative agreement have been found.