OPA1-related auditory neuropathy: site of lesion and outcome of cochlear implantation.

Hearing impairment is the second most prevalent clinical feature after optic atrophy in Dominant Optic Atrophy associated with mutations in the OPA1 gene. In this study we characterized the hearing dysfunction in OPA1-linked disorders and provided effective rehabilitative options to improve speech perception. We studied two groups of OPA1 subjects, one comprising 11 patients (7 males; age range 13-79 years) carrying OPA1 mutations inducing haploinsufficiency, the other, 10 subjects (3 males; age range 5-58 years) carrying OPA1 missense mutations. Both groups underwent audiometric assessment with pure tone and speech perception evaluation, and otoacoustic emissions and auditory brainstem response recording. Cochlear potentials were recorded through transtympanic electrocochleography from the group of patients harboring OPA1 missense mutations and were compared to recordings obtained from 20 normally-hearing controls and from 19 subjects with cochlear hearing loss. Eight patients carrying OPA1 missense mutations underwent cochlear implantation. Speech perception measures and electrically-evoked auditory nerve and brainstem responses were obtained after one year of cochlear implant use. Nine out of 11 patients carrying OPA1 mutations inducing haploinsufficiency had normal hearing function. In contrast, all but one subject harboring OPA1 missense mutations displayed impaired speech perception, abnormal brainstem responses and presence of otoacoustic emissions consistent with auditory neuropathy. In electrocochleography recordings, cochlear microphonic had enhanced amplitudes while summating potential showed normal latency and peak amplitude consistent with preservation of both outer and inner hair cell activities. After cancelling the cochlear microphonic, the synchronized neural response seen in both normally-hearing controls and subjects with cochlear hearing loss was replaced by a prolonged, low-amplitude negative potential that decreased in both amplitude and duration during rapid stimulation consistent with neural generation. The use of cochlear implant improved speech perception in all but one patient. Brainstem potentials were recorded in response to electrical stimulation in five subjects out of six, whereas no compound action potential was evoked from the auditory nerve through the cochlear implant. These findings indicate that underlying the hearing impairment in patients carrying OPA1 missense mutations is a disordered synchrony in auditory nerve fiber activity resulting from neural degeneration affecting the terminal dendrites. Cochlear implantation improves speech perception and synchronous activation of auditory pathways by by-passing the site of lesion

Ultrastable lasers based on vibration insensitive cavities

We present two ultra-stable lasers based on two vibration insensitive cavity designs, one with vertical optical axis geometry, the other horizontal. Ultra-stable cavities are constructed with fused silica mirror substrates, shown to decrease the thermal noise limit, in order to improve the frequency stability over previous designs. Vibration sensitivity components measured are equal to or better than 1.5e-11 per m.s^-2 for each spatial direction, which shows significant improvement over previous studies. We have tested the very low dependence on the position of the cavity support points, in order to establish that our designs eliminate the need for fine tuning to achieve extremely low vibration sensitivity. Relative frequency measurements show that at least one of the stabilized lasers has a stability better than 5.6e-16 at 1 second, which is the best result obtained for this length of cavity.Comment: 8 pages 12 figure

Computational Analysis of a Radiofrequency Knee Coil for Low-Field MRI Using FDTD

Magnetic resonance imaging (MRI) is essential for the diagnosis and treatment of musculoskeletal conditions. Low-field (< 0.5T) imaging is a cost-effective alternative to more expensive high-field strength imaging due to the inexpensive setting, greater patient comfort and better safety profile. On the other hand, if compared with high-field body scanners, the low-field scanners produce poor-quality images with lower signal-to-noise ratio. Especially in low-field MR, receiver coil performance plays a significant role in image quality. Coil performance is generally evaluated using classical electromagnetic theory, but when the coil is loaded with a sample, an analytical solution is extremely difficult to derive, so that a trial-and-error approach is often followed. Numerical methods have been proposed in literature as good alternatives to predict MRI coil performance. In this study the performance of a knee coil for low-field (0.5 T) MR scanners is analyzed using workbench tests and numerical simulation with a software program based on the finite difference time domain method. Parameter performances measured using the classical workbench test are compared with those obtained using numerical simulations. Finally, the knee coil performance is validated with images acquired in a commercial low-field MR system. RI Positano, Vincenzo/A-6953-2008 OI Positano, Vincenzo/0000-0001-6955-957

Recent developments in maleic acid synthesis from bio-based chemicals

This review paper presents the current state of the art on maleic acid synthesis from biomass-derived chemicals over homogeneous or heterogeneous catalysts. It is based on the most recent publications on the topic, which are discussed in details with respect to the observed catalytic performances. The recent developments and the technical drawbacks in the gas and the liquid phases are also reported. In addition, recent results on the mechanistic aspect are discussed giving insights into the probable reaction mechanisms depending on the starting molecule (furan, furfural and 5-hydroxymethylfurfural)

Propagation and interaction of ultrashort electromagnetic pulses in nonlinear media with a quadratic-cubic nonlinearity

Propagation of extremely short unipolar pulses of electromagnetic field ("videopulses") is considered in the framework of a model in which the material medium is represented by anharmonic oscillators (approximating bound electrons) with quadratic and cubic nonlinearities. Two families of exact analytical solutions (with positive or negative polarity) are found for the moving solitary pulses. Direct simulations demonstrate that the pulses are very robust against perturbations. Two unipolar pulses collide nearly elastically, while collisions between pulses with opposite polarities and a small relative velocity are inelastic, leading to emission of radiation and generation of a small-amplitude additional pulse.Comment: 12 pages, 10 figure