Gas gain on single wire chambers filled with pure isobutane at low pressure

The gas gain of single-wire chambers filled with isobutane, with cell cross-section 12x12 mm and wire diameters of 15, 25, 50 and 100 $\mu$m, has been measured at pressures ranging 12-92 Torr. Contrary to the experience at atmospheric pressure, at very low pressures the gas gain on thick wires is higher than that on thin wires at the same applied high voltage as was recently shown. Bigger wire diameters should be used in wire chambers operating at very low pressure if multiple scattering on wires is not an issue.Comment: 9 pages, 6 figure

The Prehistoric Fishers and Gatherers of the Northern and Western Coasts of the Arabian Sea

This chapter is a review of the prehistory of the fisher-gatherers who settled along the coasts of the Arabian Sea and the Gulf of Oman. Previous research and studies have been centred mainly on the western coasts of the Indian Ocean. They have presented and discussed the general patterns and chronological frame of the coastal human adaptation since the early Holocene, and the recurrent presence of shell middens located close to mangrove environments. More recent research has been focussed on the northern shores of the Arabian Sea. From this region we have new evidence of the presence of fisher-gatherers communities that seasonally settled along the ancient coastline and islands of south-western Sindh and Las Bela (Balochistan) since the end of the eighth millennium BP indicating that early navigation already took place in that period. According to the archaeological evidence, the subsistence activities of these human groups were varied though seasonally based mainly on fishing and shellfish gathering. Broadly speaking marine and mangrove resources were widespread exploited along the two coasts of the Arabian Sea during favourable, well-defined periods of coastal adaptation following the varied environmental conditions and sea-level changes that took place since the beginning of the Holocene

Blind fractionally spaced channel equalization for shallow water PPM digital communications links

Underwater acoustic digital communications suffer from inter-symbol interference deriving from signal distortions caused by the channel propagation. Facing such kind of impairment becomes particularly challenging when dealing with shallow water scenarios characterized by short channel coherence time and large delay spread caused by time-varying multipath effects. Channel equalization operated on the received signal represents a crucial issue in order to mitigate the effect of inter-symbol interference and improve the link reliability. In this direction, this contribution presents a preliminary performance analysis of acoustic digital links adopting pulse position modulation in severe multipath scenarios. First, we show how the spectral redundancy offered by pulse position modulated signals can be fruitfully exploited when using fractional sampling at the receiver side, which is an interesting approach rarely addressed by the current literature. In this context, a novel blind equalization scheme is devised. Specifically, the equalizer is blindly designed according to a suitably modified Bussgang scheme in which the zero-memory nonlinearity is replaced by a M-memory nonlinearity, M being the pulse position modulation order. Numerical results not only confirm the feasibility of the technique described here, but also assess the quality of its performance. An extension to a very interesting complex case is also provided

On the Impact of Channel State Information Quantization and Feedback in Practical OFDM Implementation

In Orthogonal Frequency Division Multiplexing (OFDM), channel knowledge can be exploited to implement adaptive solutions based on bit-loading to improve the communication performance. Typically, channel estimation is performed at the receiver, with the resulting information being sent back to the transmitter to drive bit-loading. However, feedback information is subject to quantization, with the related errors potentially causing unreliable OFDM adaptation. Therefore, we investigate the impact of information quantization on the transmission efficiency, considering different strategies for feedback signaling. Performance are evaluated by referring to four propagation scenarios, that are radio-frequency, optical, powerline and underwater acoustic channels

Sport and dental traumatology: Surgical solutions and prevention

Trauma is a worldwide cause of millions of deaths and severe injuries every year, all over the world. Despite the limited extension of the oral region compared to the whole body, dental and oral injuries account for a fairly high percentage of all body traumas. Among head and neck traumas, dental and facial injuries are highly correlated to sport activities, and their management can be a real challenge for practitioners of any specialty. In case of trauma directed to periodontal structures, restorative and endodontic solutions may not be sufficient to achieve a definitive and long-lasting treatment. This article aims to illustrate surgical options and appliances to prevent dental injuries that may be available to the clinicians treating dental trauma involving oral soft and hard tissues

Hard macrocells for DC/DC converter in automotive embedded mechatronic systems

A novel configurable DC/DC converter architecture, to be integrated as hard macrocell in automotive embedded systems, is proposed in the paper. It aims at realizing an intelligent voltage regulator. With respect to the state of the art, the challenge is the integration into an automotive-qualified chip of several advanced features like dithering of switching frequency, nested control loops with both current and voltage feedback, asynchronous hysteretic control for low power mode, slope control of the power FET gate driver, and diagnostic block against out-of-range current or voltage or temperature conditions. Moreover, the converter macrocell can be connected to the in-vehicle digital network, exchanging with the main vehicle control unit status/diagnostic flags and commands. The proposed design can be configured to work both in step-up and step-down modes, to face a very wide operating input voltage range from 2.5 to 60 V and absolute range from −0.3 to 70 V. The main target is regulating all voltages required in the emerging hybrid/electric vehicles where, besides the conventional 12 V DC bus, also a 48 V DC bus is present. The proposed design supports also digital configurability of the output regulated voltage, through a programmable divider, and of the coefficients of the proportional-integrative controller inside the nested control loops. Fabricated in 0.35 μm CMOS technology, experimental measurements prove that the IC can operate in harsh automotive environments since it meets stringent requirements in terms of electrostatic discharge (ESD) protection, operating temperature range, out-of-range current, or voltage condition

Conservative non-surgical management of horizontal root-fractured maxillary incisors in a young male with angle class ii, division 2, malocclusion

Horizontal root fractures are a rare emergency in a dental office. The injury involves periodontal ligament, cementum, dentine and pulp. The healing is influenced by the location of the root fracture, the displacement of the fragments and the status of the pulp. This report presents a clinical case of horizontal fractures to both maxillary central incisors due to an act of violence. The type of occlusion has avoided a severe diastasis of the coronal parts with a subsequent damage to the pulp and periodontum. The fractures were treated with an orthodontic splint without any further therapy and hard tissue healing was observed. A careful diagnosis and well-timed treatment planning usually allow a cost-efficient and biologically-oriented therapy with a favorable outcome

SEISMO-ELECTROMAGNETIC PHENOMENA IN TECTONICALLY ACTIVE REGIONS

This work presents a research plan that aims to monitor seismo-electromagnetic signals in seismic active regions. Two effects will be considered: electromagnetic field emissions and radio broadcastings. Our study will be focused in the analysis of low magnitude earthquakes almost completely disregarded in literature. We aim to collect novel seismo-electromagnetic emission data emerging from seismic activity. We expect to address the time variation of electromagnetic properties of the crust in relation with the strain field and complement it with the development of proper models. Experimental studies based on the electrical properties of rocks will also be done aiming the understanding of pressure stimulated currents and voltages that produce detectable electromagnetic radiation and can be a cause for seismo-electromagnetic signals

On the Effect of Channel Knowledge in Underwater Acoustic Communications: Estimation, Prediction and Protocol

Underwater acoustic communications are limited by the following channel impairments: time variability, narrow bandwidth, multipath, frequency selective fading and the Doppler effect. Orthogonal Frequency Division Modulation (OFDM) is recognized as an effective solution to such impairments, especially when optimally designed according to the propagation conditions. On the other hand, OFDM implementation requires accurate channel knowledge atboth transmitter and receiver sides. Long propagation delay may lead to outdated channel information. In this work, we present an adaptive OFDM scheme where channel state information is predicted through a Kalman-like filter so as to optimize communication parameters, including the cyclic prefix length. This mechanism aims to mitigate the variability of channel delay spread. This is cast in a protocol where channel estimation/prediction are jointly considered, so as to allow efficiency. The performance obtained through extensive simulations using real channels and interference show the effectiveness of the proposed scheme, both in terms of rate and reliability, at the expense of an increasing complexity. However, this solution is significantly preferable to the conventional mechanism, where channel estimation is performed only at the receiver, with channel coefficients sent back to the transmit node by means of frequent overhead signaling