Underwater Sound Characteristics of a Ship with Controllable Pitch Propeller

The time-dependent spectral characteristics of underwater sound radiated by an oceanic vessel have complex dependencies on ship machinery, propeller dynamics, and the hydrodynamics of the ship exhaust and motion, as well as onboard activities. Here, the underwater sound radiated by a ship equipped with a controllable pitch propeller (CPP) is analyzed and quantified via its (i) power spectral density for signal energetics, (ii) temporal coherence for machinery tonal sound, and (iii) spectral coherence for propeller amplitude-modulated cavitation noise. Frequency-modulated (FM) tonal signals are also characterized in terms of their frequency variations. These characteristics are compared for different propeller pitch ratios, ranging from 20% to 82% at a fixed number of propeller revolutions per minute (RPM). The efficacy and robustness of ship parameter estimation at different pitches are discussed. Finally, an analysis of one special measurement is provided: propeller pitch and RPM over the duration of the measurement when the ship changes speed. The 50% pitch was found to be a crucial point for this ship, around which the tonal characteristics of its underwater radiated sound attain their peak values while broadband sound and associated spectral coherences are at a minimum. The findings here elucidate the effects of pitch variation on underwater sound radiated by ships with controllable pitch propellers and has applications in ship design and underwater noise mitigation

Sheep predation : characteristics and risk factors

Predation has always been an important problem in extensive sheep farms, causing serious economic losses to the farmers. Official predation reports have recently been decreasing in the District of Pisa, in spite of the presence of two wolf packs in the area. The aim of the present research was to obtain reliable information on the characteristics of predation and to estimate the effectiveness of existing prevention methods in sheep farms of the southern District of Pisa, in order to set up predictive models for an improved and more focused prevention plan and support interventions by public authorities. On-farm surveys were carried out in 73 semi-extensive sheep farms. Predation events were reported by 75.3% of the farmers. Wolves seemed to be responsible for most of those events, although their actual role could be confirmed only in 34% of cases. Most of the events occurred in spring and 85.1% of them were concentrated during night time. The average number of sheep killed during each attack was 7.05. In 22.3% of cases, the number of sheep killed was 65 10. Proximity to protected areas and the presence of thick vegetation cover significantly affected the probability of a farm being subjected to chronic predation. Farm size was significantly higher in those cases. No clear indication about the effectiveness of prevention methods could be obtained from our survey. The results of this investigation highlighted the impact of predation in the Southern District of Pisa and emphasized the need for finding technical and political solutions to this problem. Attention should be focused on large farms, with thick vegetation cover and located close to protected areas. Further investigations should be carried out in order to test the effectiveness of suitable prevention methods in these farms

Enfermedad de Chagas congénita de segunda generación en Santiago, Chile. Relato de dos casos

La enfermedad de Chagas congénita ha sido reportada en diferentes países, en su gran mayoría de Latinoamérica. En 1987 un caso fatal de enfermedad de Chagas congénita de segunda generación fue publicado. En 1989-1990 dos casos de enfermedad de Chagas congénita de segunda generación fueron diagnosticados y estudiados en la ciudad de Santiago. Dos recién nacidos prematuros, hijos de dos hermanas, con moderado aumento del hígado y del bazo, presentaron serología para enfermedad de Chagas y xenodiagnósticos positivos. Las madres, residentes urbanas toda su vida, sin antecedentes de contacto con triatominos ni transfusiones de sangre presentaron serología y xenodiagnósticos positivos. La madre de ellas (abuela de los niños) nació y vivió 20 años en una localidad rural de endemia chagásica, en una casa infestada con triatominos. Posteriormente, se trasladó a vivir a Santiago, donde se casó y ha residido hasta el presente; su serología y xenodiagnóstico fueron positivos. Todas las personas infectadas con Trypanosoma cruzi fueron tratadas exitosamente con nifurtimox.Congenital Chagas disease (CChD) has been reported in different countries, mostly in Latin America. In 1987 a fatal case of CChD of second generation (CChDSG) was published. Within a period of six months - 1989-1990 - two cases of CChDSG were diagnosed and studied in the city of Santiago. Two premature newborns, sons of two sisters, with moderate liver and spleen enlargement, were found to have positive serology for Chagas disease and xenodiagnoses. The mothers, urban residents all their lives, without antecedents of triatomine bugs contact or blood transfusions, showed positive serology and xenodiagnoses. Their mother (grandmother of the infants), lived 20 years in a Northern rural Chagas disease endemic locality, in a triatomine infested house. Afterwards, she moved to Santiago, where she married and has resided up to now. Serology and xenodiagnoses were also positive. All the Trypanosoma cruzi infected individuals were successfully treated with nifurtimox

Assessment of different methods for the prediction of marine propellers induced pressures

This paper addresses the problem of the prediction of propellers induced pressures; to this aim numerical and experimental results (both in model and full scale) in correspondence to different functioning conditions for a fast twin screw ship are reported. Numerical results were obtained by means of two different BEM codes and, only for specific cases, of a RANSE solver. Experiments were carried out both in model scale at cavitation tunnel and in full scale

Airborne Sound Power Levels and Spectra of Noise Sources in Port Areas

Airborne port noise has historically suffered from a lack of regulatory assessment compared to other transport infrastructures. This has led to several complaints from citizens living in the urban areas surrounding ports, which is a very common situation, especially in countries facing the Mediterranean sea. Only in relatively recent years has an effort been made to improve this situation, which has resulted in a call for and financing of numerous international cooperation research projects, within the framework of programs such as EU FP7, H2020, ENPI-CBC MED, LIFE, and INTERREG. These projects dealt with issues and aspects of port noise, which is an intrinsically tangled problem, since several authorities and companies operate within the borders of ports, and several different noise sources are present at the same time. In addition, ship classification societies have recently recognized the problem and nowadays are developing procedures and voluntary notations to assess the airborne noise emission from marine vessels. The present work summarizes the recent results of research regarding port noise sources in order to provide a comprehensive database of sources that can be easily used, for example, as an input to the noise mapping phase, and can subsequently prevent citizens' exposure to noise

Health related quality of life in COVID-19 survivors discharged from acute hospitals: results of a short-form 36-item survey [version 1; peer review: awaiting peer review]

Background: Health-related quality of life (HRQL) is important for evaluating the impact of a disease in the longer term across the physical and psychological domains of human functioning. The aim of this study is to evaluate HRQL in COVID-19 survivors in Italy using the short form 36-items questionnaire (SF-36). Methods: This is an observational study involving adults discharged home following a coronavirus disease 2019 (COVID-19)-related hospital admission. Baseline demographic and clinical data including the Cumulative Illness Rating Scale (CIRS) and the Hospital Anxiety and Depression Scale (HADS) were collected. The validated Italian version of SF-36 was administered cross-sectionally. The SF-36 contains eight scales measuring limitations in physical and social functioning, the impact on roles and activities, fatigue, emotional wellbeing, pain and general health perception. Results: A total of 35 patients, with a mean age of 60 years, completed the SF-36. The results showed difficulties across the physical and psychological domains, particularly affecting the return to previous roles and activities. A higher burden of co-morbidities as well as a more severe muscle weakness was associated to a lower physical functioning. Younger age, rather than older, correlated to a perceived greater limitation in physical functioning and vitality. Conclusions: COVID-19 survivors particularly the ones of working age may need support for resuming their premorbid level of functioning and returning to work