The information capacities of two-dimensional optical low-pass channels are discussed. Coherent and incoherent systems operating under finite optical power and area constraints are characterized in terms of two criteria:spacebandwidth product (SBP; the number of pixels required for achieving maximum information capacity) and resolution (G(min); the smallest spot size capable of supporting posit...

Polarization properties of transmission volume holographic phase gratings recorded in a photopolymerizable glass modified with high refractive index species are reported. The gratings are recorded by the interference of two parallel s-polarized writing beams with orthogonal propagation directions. High optical quality, low scattering, and diffraction efficiency of 99.4% are achieved. Degrees of...

Three studies relating perception of motion to stimulus uncertainty are reported. Generally, detectability declines when the observer is uncertain about the direction in which a target will move, but the visibility loss associated with direction uncertainty can be attenuated if the observer has adequate practice. This attenuation seems to depend upon the observer's ability to switch among direc...

Previous studies have suggested that face identification is more sensitive to variations in spatial frequency content than object recognition, but none have compared how sensitive the 2 processes are to variations in spatial frequency overlap (SFO). The authors tested face and object matching accuracy under varying SFO conditions. Their results showed that object recognition was more robust to ...

The study was designed to examine the possibility that vocal frequency and vocal intensity influence the perception of sppech rate. One 30-second segment of spontaneous speech was used to produce nine stimulus segments that factorially varied three levels of vocal frequency and three levels of vocal intensity but were identical in speech rate. The segments were recorded backwards in pairs such ...

Disturbance is key to maintaining species diversity in plant communities. Although the effects of disturbance frequency and extent on species diversity have been studied, we do not yet have a mechanistic understanding of how these aspects of disturbance interact with spatial structure of disturbance to influence species diversity. Here we derive a novel pair approximation model to explore compe...

The Convention on Biological Diversity’s (2010) target to reduce the rate of biodiversity loss was achieved by very few countries. Why? We use the theory of conservation implicit in the Hotelling model of non-renewable resource pricing to analyze the problem, distinguishing between the benefits to countries where conservation takes place, and to other countries. We estimate models for three tax...

When two moving sinusoidal gratings, with similar spatial frequency, contrast, phase, but different orientation are combined to form a plaid, their perceived direction of motion has been predicted by the intersection of constraints rule (IOC) (Adelson & Movshon, Nature, 300, 523-525, 1982). However, at short durations (60 msec) the direction of perceived motion has been predicted by the vector ...

The growing need for baseline data against which efforts to reduce the rate of biodiversity loss can be judged highlights the importance of long-term datasets, some of which are as old as ecology itself. We review methods of evaluating change in biodiversity at the community level using these datasets, and contrast whole-community approaches with those that combine information from different sp...