923 research outputs found
The Raggy Fox Trot
Checkerboard design in the centerhttps://scholarsjunction.msstate.edu/cht-sheet-music/13843/thumbnail.jp
Optical guiding in meter-scale plasma waveguides
We demonstrate a new highly tunable technique for generating meter-scale low
density plasma waveguides. Such guides can enable electron acceleration to tens
of GeV in a single stage. Plasma waveguides are imprinted in hydrogen gas by
optical field ionization induced by two time-separated Bessel beam pulses: The
first pulse, a J_0 beam, generates the core of the waveguide, while the delayed
second pulse, here a J_8 or J_16 beam, generates the waveguide cladding. We
demonstrate guiding of intense laser pulses over hundreds of Rayleigh lengths
with on axis plasma densities as low as N_e0=5x10^16 cm^-3
Developmental specialization of the left parietal cortex for the semantic representation of Arabic numerals: an fMR-adaptation study
The way the human brain constructs representations of numerical symbols is poorly understood. While increasing evidence from neuroimaging studies has indicated that the intraparietal sulcus (IPS) becomes increasingly specialized for symbolic numerical magnitude representation over developmental time, the extent to which these changes are associated with age-related differences in symbolic numerical magnitude representation or with developmental changes in non-numerical processes, such as response selection, remains to be uncovered. To address these outstanding questions we investigated developmental changes in the cortical representation of symbolic numerical magnitude in 6- to 14-year-old children using a passive functional magnetic resonance imaging adaptation design, thereby mitigating the influence of response selection. A single-digit Arabic numeral was repeatedly presented on a computer screen and interspersed with the presentation of novel digits deviating as a function of numerical ratio (smaller/larger number). Results demonstrated a correlation between age and numerical ratio in the left IPS, suggesting an age-related increase in the extent to which numerical symbols are represented in the left IPS. Brain activation of the right IPS was modulated by numerical ratio but did not correlate with age, indicating hemispheric differences in IPS engagement during the development of symbolic numerical representation
Air hydrodynamics of the ultrafast laser-triggered spark gap
We present space and time resolved measurements of the air hydrodynamics
induced by ultrafast laser pulse excitation of the air gap between two
electrodes at high potential difference. We explore both plasma-based and
plasma-free gap excitation. The former uses the plasma left in the wake of
femtosecond filamentation, while the latter exploits air heating by
multiple-pulse resonant excitation of quantum molecular wavepackets. We find
that the cumulative electrode-driven air density depression channel initiated
by the laser plays the dominant role in the gap evolution leading to breakdown
Unique type of isolated cardiac valvular amyloidosis
BACKGROUND: Amyloid deposition in heart is a common occurrence in systemic amyloidosis. But localised valvular amyloid deposits are very uncommon. It was only in 1922 that the cases of valvular amyloidosis were reported. Then in 1980, Goffin et al reported another type of valvular amyloidosis, which he called the dystrophic valvular amyloidosis. We report a case of aortic valve amyloidosis which is different from the yet described valvular amyloidosis. CASE PRESENTATION: A 72 years old gentleman underwent urgent aortic valve replacement. Intraoperatively, a lesion was found attached to the inferior surface of his bicuspid aortic valve. Histopathology examination of the valve revealed that the lesion contained amyloid deposits, identified as AL amyloidosis. The serum amyloid A protein (SAP) scan was normal and showed no evidence of systemic amyloidosis. The ECG and echocardiogram were not consistent with cardiac amyloidosis. CONCLUSION: Two major types of cardiac amyloidosis have been described in literature: primary-myelomatous type (occurs with systemic amyolidosis), and senile type(s). Recently, a localised cardiac dystrophic valvular amyloidosis has been described. In all previously reported cases, there was a strong association of localised valvular amyloidosis with calcific deposits. Ours is a unique case which differs from the previously reported cases of localised valvular amyloidosis. In this case, the lesion was not associated with any scar tissue. Also there was no calcific deposit found. This may well be a yet unknown type of isolated valvular amyloidosis
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