The monopole-source solution was used to calculate the three-dimensional complex acoustic pressure field for one-dimensional focused rectangular apertures in a medium having homogeneous acoustic and thermal properties. For each of six frequencies (1, 3, 5, 7, 9 and 12 MHz) and three focuses (f/1, f/2 and f/4), 33 rectangular aperture cases were investigated, for a total of 594 cases. For these ...

The fractional transmission as a function of wavelength for stellar objects is measured for clear apertures by comparing count rates through small apertures to open aperture count rates in STIS first order modes. Because OTA "breathing" causes the throughput of the smallest apertures to vary on short time scales, the best estimate of the aperture throughputs is a theoretical model that is based...

Accurate recognition of airborne pollen taxa is crucial for understanding and treating allergic diseases, which affect an important proportion of the world population. Modern computer vision techniques enables the detection of discriminant characteristics. Apertures is one of these characteristic that has been little explored up to now. In this paper, a flexible method of detection, localizatio...

We characterize the acceptance angles of small circular apertures for light collection by simulations and experimental measurements. By examining the full width half maximum acceptance angle as a function of the aperture size, we show that the acceptance angle of a circular aperture reaches a minimum of 67 deg before rebounding around the transition between single mode and multimode transmissio...

*Correspondence: Laurent Talon, CNRS, FAST, Université de Paris-Sud, Bât. 502, Campus University, Orsay, F–91405, France e-mail: [email protected] We derive the volumetric flow rate vs. pressure drop of a Bingham fluid in one-dimensional channels of variable apertures in the lubrication approximation. A characteristic length scale, a∗ characterizing the flow is introduced in order to disting...

The optical diffraction limit has been the dominant barrier to achieving higher optical resolution in the fields of microscopy, photolithography, and optical data storage. We present here an approach toward imaging below the diffraction barrier. Through the exposure of photosensitive films placed a finite and known distance away from nanoscale, zero-mode apertures in thin metallic films, we sho...

Functional MRI was used to test whether instructing subjects to attend to one or another location in a visual scene would affect neural activity in human primary visual cortex. Stimuli were moving gratings restricted to a pair of peripheral, circular apertures, positioned to the right and to the left of a central fixation point. Subjects were trained to perform a motion discrimination task, att...

Nanoscale bowtie aperture antennas can be used to focus light well below the diffraction limit with extremely high transmission efficiencies. This paper studies the spectral dependence of the transmission through nanoscale bowtie apertures defined in a silver film. A realistic bowtie aperture is numerically modeled using the Finite Difference Time Domain (FDTD) method. Results show that the tra...

Precise knowledge of the area of apertures used in high precision radiometry is extremely important. A method is presented here for the determination of the area of round and irregularly shaped apertures by comparison to a standard aperture which has been measured by other means to high accuracy. The method presented here is quick and has no physical contact with the fragile edge of the apertur...

The designer surface plasmons (DSPs) are studied by the use of a kind of metamaterial with a structure of double sets of circular holes: subwavelength apertures, and indentations. The diameter and spacing of the indentations are smaller at least one order of magnitude than those of the apertures. A theoretical model is built to analyze the DSPs sustained by the indentations by using effective d...