The effective indices of the cladding modes of optical fibers depend on the refractive index of the medium surrounding the fiber. We show experimentally and theoretically that while cladding modes with similar effective indices normally have similar refractometric sensitivities, the addition of a 50 nm thick gold sheath enhances the sensitivity of some EH modes by more than one order of magnitude while nearly completely suppressing the sensitivity of neighbouring HE modes (by three orders of magnitude, down to insignificant levels). A differential sensitivity of ∼1000 nm/(refractive index unit) is experimentally reported between adjacent EH and HE grating resonances.
Silica-based thin-film multilayers are investigated as a means to enhance the effective second-order nonlinearity induced in silica glass structures by corona poling. Structures consisting of phosphorus-doped and undoped silica glass layers exhibit second harmonic generation (SHG) that is higher by an order of magnitude compared to the SHG in bulk silica glass poled under the same conditions. When the poled structure consists of two multilayered stacks separated in space, the stacks exhibit comparable poling-induced nonlinearities. This result suggests that the poling voltage is divided between the two stacks such that simultaneous poling of multiple regions within the sample is realized.
The conformal coating of a 50 nm-thick layer of copper nanoparticles deposited with pulse chemical vapor deposition of a copper (I) guanidinate precursor on the cladding of a single mode optical fiber was monitored by using a tilted fiber Bragg grating (TFBG) photo-inscribed in the fiber core. The pulse-per-pulse growth of the copper nanoparticles is readily obtained from the position and amplitudes of resonances in the reflection spectrum of the grating. In particular, we confirm that the real part of the effective complex permittivity of the deposited nano-structured copper layer is an order of magnitude larger than that of a bulk copper film at an optical wavelength of 1550 nm. We further observe a transition in the growth behavior from granular to continuous film (as determined from the complex material permittivity) after approximately 20 pulses (corresponding to an effective thickness of 25 nm). Finally, despite the remaining granularity of the film, the final copper-coated optical fiber is shown to support plasmon waves suitable for sensing, even after the growth of a thin oxide layer on the copper surface.
We prove that, for every simple polygon P having k ≥ 1 reflex vertices, there exists a point q ε P such that every half-polygon that contains q contains nearly 1/2(k + 1) times the area of P. We also give a family of examples showing that this result is the best possible.
Conventional training simulators commonly use a hexapod configuration to provide motion cues. While widely used, studies have shown that hexapods are incapable of producing the range of motion required to achieve high fidelity simulation required in many applications. A novel alternative is the Atlas motion platform. This paper presents a new generalized kinematic model of the platform which can be applied to any spherical platform actuated by three omnidirectional wheels. In addition, conditions for slip-free and singularity-free motions are identified. Two illustrative examples are given for different omnidirectional wheel configurations.
Oral narrative skills are assumed to develop through parent-child interactive routines. One such
routine is shared reading. A causal link between shared reading and narrative knowledge,
however, has not been clearly established. The present research tested whether an 8-week
shared-reading intervention enhanced the fictional narrative skills of children entering formal
education. Dialogic reading, a shared reading activity that involves elaborative questioning
techniques, was used to engage children in oral interaction during reading and to emphasize
elements of story knowledge. Forty English-speaking five- and six-year-olds were assigned to
either the dialogic-reading or an alternative-treatment group. ANCOVA results found that the
dialogic-reading children’s post-test narratives were significantly better on structure and context
measures than those for the alternative-treatment children, but results differed for produced or
retold narratives. The dialogic-reading children also showed expressive vocabulary gains.
Overall, this study concretely determined that aspects of fictional narrative construction
knowledge can be learned from interactive book reading.
The researcher conducted a content analysis and literature review of papers written from 2000-2010 that focused on university biology students, faculty, and their papers. Scholarly articles were divided into the library research domains. The largest number of papers was from the Education domain, followed closely by Collections. Only two papers were categorized as Reference/Enquiries, and no papers were found in Management and Professional Issues. This research will enable science librarians to better understand what has already been written about biology subjects in a university setting. Gaps in the literature can help other librarians who are interested in pursuing more research with biology subjects.