Hydrostatic equilibrium and stellar structure in f(R)-gravity

We investigate the hydrostatic equilibrium of stellar structure by taking into account the modi- fied La\'e-Emden equation coming out from f(R)-gravity. Such an equation is obtained in metric approach by considering the Newtonian limit of f(R)-gravity, which gives rise to a modified Poisson equation, and then introducing a relation between pressure and density with polytropic index n. The modified equation results an integro-differential equation, which, in the limit f(R) \rightarrow R, becomes the standard La\'e-Emden equation. We find the radial profiles of gravitational potential by solving for some values of n. The comparison of solutions with those coming from General Relativity shows that they are compatible and physically relevant.Comment: 9 pages, 1 figur

Sudden hearing loss as an early detector of multiple sclerosis: a systematic review

To evaluate whether Sudden Sensorineural Hearing Loss (S-SNHL) may be an early symptom of Multiple Sclerosis (MS). A systematic review was conducted using the following keywords: "Multiple sclerosis, hearing loss, sudden hearing loss, vertigo, tinnitus, magnetic resonance imaging, otoacoustic emission, auditory brainstem responses, white matter lesions, sensorineural hearing loss, symptoms of MS and otolaryngology, nerve disease and MS". Only the articles that included results of at least one auditory test and MRI were considered. We evaluated the prevalence of SNHL in patients with MS, the presence of different forms of SNHL (S-SNHL and Progressive SNHL (P-SNHL)) and their correlation with the stage of MS, the results of electrophysiological tests, and the location (if any) of MS lesions as detected by white matter hyperintensities in the MRI. We reviewed a total of 47 articles, which included 29 case reports, 6 prospective studies, 6 cohort studies, 4 case-control studies, and 2 retrospective studies. 25% of patients suffered from SNHL. S-SNHL typically occurred in the early stage of the disease (92% of patients) and was the only presenting symptom in 43% of female subjects. Instead, P-SNHL occurred in the late stage of MS (88% of patients). Auditory Brainstem Responses (ABR) were abnormal in all MS patients with S-SNHL. When S-SNHL appeared during the early stage of the disease, MS lesions were found in the brain in 60% of patients and in the Internal Auditory Canal in 40% of patients. ABR remained abnormal after recovery. S-SNHL can be an early manifestation of MS and should always be considered in the differential diagnosis of this condition, especially in women. The pathophysiology can be explained by the involvement of microglia attacking the central and/or peripheral auditory pathways as indicated by WMHs

Scanning and data extraction from crop collecting mission documents

Poster presented at TDWG 2009, Montpellier (France). 9 - 13 Nov 2009

Investigating the performance of medical students in anatomy examinations 2002-07

Medical students are examined four times in anatomy over two years. There is a progress test in January each year (formative) and a final summative examination in June. The purpose of this study was to examine the performance of undergraduate medical students of the University of Malta in anatomy over 4 semesters. We were specifically interested in the ways in which students’ results in the final anatomy exam could be predicted by their performance in the previous anatomy exams. We also investigated whether the strength of this correlation and the students’ actual performance were affected by their gender or nationality.peer-reviewe

The Newtonian Limit of F(R) gravity

A general analytic procedure is developed to deal with the Newtonian limit of $f(R)$ gravity. A discussion comparing the Newtonian and the post-Newtonian limit of these models is proposed in order to point out the differences between the two approaches. We calculate the post-Newtonian parameters of such theories without any redefinition of the degrees of freedom, in particular, without adopting some scalar fields and without any change from Jordan to Einstein frame. Considering the Taylor expansion of a generic $f(R)$ theory, it is possible to obtain general solutions in term of the metric coefficients up to the third order of approximation. In particular, the solution relative to the $g_{tt}$ component gives a gravitational potential always corrected with respect to the Newtonian one of the linear theory $f(R)=R$. Furthermore, we show that the Birkhoff theorem is not a general result for $f(R)$-gravity since time-dependent evolution for spherically symmetric solutions can be achieved depending on the order of perturbations. Finally, we discuss the post-Minkowskian limit and the emergence of massive gravitational wave solutions.Comment: 16 page

Underwater acoustic channel properties in the Gulf of Naples and their effects on digital data transmission

In this paper we studied the physical properties of the Gulf of Naples (Southern Italy) for its use as a commu- nication channel for the acoustic transmission of digital data acquired by seismic instruments on the seafloor to a moored buoy. The acoustic link will be assured by high frequency acoustic modems operating with a central frequency of 100 kHz and a band pass of 10 kHz. The main operational requirements of data transmission con- cern the near horizontal acoustic link, the maximum depth of the sea being about 300 m and the planned hori- zontal distance between seismic instruments and buoy 2 km. This study constructs the signal-to-noise ratio maps to understand the limits beyond which the clarity of the transmission is no longer considered reliable. Using ray- theory, we compute the amplitudes of a transmitted signal at a grid of 21×12 receivers to calculate the transmis- sion loss at each receiver. The signal-to-noise ratio is finally computed for each receiver knowing also the trans- mitter source level and the acoustic noise level in the Gulf of Naples. The results show that the multipath effects predominate over the effects produced by the sound velocity gradient in the sea in the summer period. In the case of omnidirectional transmitters with a Source Level (SL) of 165 dB and a baud rate of 2.4 kbit/s, the results al- so show that distances of 1400-1600 m can be reached throughout the year for transmitter-receiver connections below 50 m depth in the underwater acoustic channel

Basic ideas and tools for projection-based model reduction of parametric partial differential equations

We provide first the functional analysis background required for reduced order modeling and present the underlying concepts of reduced basis model reduction. The projection-based model reduction framework under affinity assumptions, offline-online decomposition and error estimation is introduced. Several tools for geometry parametrizations, such as free form deformation, radial basis function interpolation and inverse distance weighting interpolation are explained. The empirical interpolation method is introduced as a general tool to deal with non-affine parameter dependency and non-linear problems. The discrete and matrix versions of the empirical interpolation are considered as well. Active subspaces properties are discussed to reduce high-dimensional parameter spaces as a pre-processing step. Several examples illustrate the methodologies

Pedagogic research in anatomical sciences: a best practice guide

This article explores the background of anatomical educational research. It draws together research and our own personal experiences to propose a best practice piece for novice researchers in anatomical education. The article explores the domains of both qualitative, and quantitative methods as applied to anatomy pedagogy. It takes into consideration validity and what might be undertaken to increase validity and reliability. The article explores how both qualitative and quantitative data can be analysed and recommends top tips including: Identify your research questions and theoretical framework. Map out how you are going to answer your research questions. Consider collaborating with like-minded researchers in other countries: multi-centre studies have a better chance of getting published and carefully consider your target journal and suggestions for peer review, taking into consideration individuals expertise and potential conflicts of interests. This article is designed to be a guide to anyone starting anatomical research or experienced researchers looking for new methods and ideas

Recruiting urban Latina adolescents and their families: Challenges and lessons learned in suicide attempts research

Recruiting samples with unique characteristics dispersed across services and geography is hard to identify because of legal status and stigma create research challenges. Public health, however, requires sustained recruitment efforts. We describe challenges and solutions in recruiting urban adolescent Latinas who had attempted suicide. Procedures for recruitment and human subject protections were established, yet logistic obstacles emerged. Program directors failed to support the research; therapists were slow to identify subjects and to meet inclusionary criteria; numbers of prospective participants were lower than originally calculated; girls and parents were hard to reach; and interview appointments were missed. From challenges came solutions: to use fewer agencies, do better participant surveillance, monitor staff participation, and build rapport and relationships with staff. In-service research training to develop agency research infrastructure generated support among providers and administrators. Our experience may be helpful to other researchers conducting studies with similar populations