88 research outputs found
The asymmetric lossy near-perfect lens
No full textWe extend the ideas of the perfect lens recently proposed [J.B. Pendry, Phys. Rev. Lett. 85, 3966 (2000)] to an alternative structure. We show that a slab of a medium with negative refractive index bounded by media of different positive refractive index also amplifies evanescent waves and can act as a near-perfect lens. We examine the role of the surface states in the amplification of the evanescent waves. The image resolution obtained by this asymmetric lens is more robust against the effects of absorption in the lens. In particular, we study the case of a slab of silver, which has a negative dielectric constant, with air on one side and other media such as glass or GaAs on the other side as an ‘asymmetric’ lossy near-perfect lens for p-polarized waves. It is found that retardation has an adverse effect on the imaging due to the positive magnetic permeability of silver, but we conclude that subwavelength image resolution is possible in spite of it
Bird & Squirrel On The Run! by J. Burks
No full textBurks, James. Bird & Squirrel On The Run! New York: Scholastic Graphix, 2012. Print. After years as an artist in the hallways of the animation industry, author/illustrator James Burks takes an unlikely duo on an adventure of discovered friendship. Timid Squirrel, complete with winter food preparations and a fear of almost everything (“Don’t you know that cats are responsible for 47 percent of all squirrel deaths each year?”), suddenly loses his winter safety net in dramatic fashion, catching the hungry eye of a determined and ferocious cat. Squirrel has no choice but to grudgingly pair himself with the animal responsible for his loss, an adventurous Bird who brazenly lives in the moment (“The world is our oyster!”) but who attracts trouble with every swoop of his wing. Together they venture south to find warmth and food, dodging their persistently predatory cat and other natural hazards but find help along the way from a kind family of moles. A few shared life and death adventures later, Bird and Squirrel begin to appreciate and learn from each other’s ways, discovering new aspects of their own personalities while becoming true friends in the process. Burks uses clean lines and brightly coloured characters against more neutral backgrounds to frame clear and simple facial expressions that will appeal to younger readers. The fast paced story is presented with minimal change in perspective and timeline which makes this an ideal introduction to graphic novels for younger readers. Recommended: 3 out of 4 stars Reviewer: Annabelle Pendry Annabelle Pendry loves her job as Teacher Librarian at Mount Pleasant Elementary in Vancouver, BC
Van der Waals Force Assisted Heat Transfer
No full textPhonons (collective atomic vibrations in solids) are more effective in transporting heat than photons. This is the reason why the conduction mode of heat transport in nonmetals (mediated by phonons) is dominant compared to the radiation mode of heat transport (mediated by photons). However, since phonons are unable to traverse a vacuum gap (unlike photons), it is commonly believed that two bodies separated by a gap cannot exchange heat via phonons. Recently, a mechanism was proposed [J. B. Pendry, K. Sasihithlu, and R. V. Craster, Phys. Rev. B 94, 075414 (2016)] by which phonons can transport heat across a vacuum gap – through the Van der Waals interaction between two bodies with gap less than the wavelength of light. Such heat transfer mechanisms are highly relevant for heating (and cooling) of nanostructures; the heating of the flying heads in magnetic storage disks is a case in point. Here, the theoretical derivation for modelling phonon transmission is revisited and extended to the case of two bodies made of different materials separated by a vacuum gap. Magnitudes of phonon transmission, and hence the heat transfer, for commonly used materials in the micro- and nano-electromechanical industry are calculated and compared with the calculation of conduction heat transfer through air for small gaps as well as the heat transfer calculation due to photon exchange
Photon number conservation in time dependent systems
No full textTime dependent systems in general do not conserve photons nor do they conserve energy. However when parity-time symmetry holds Maxwell’s equations can sometimes both conserve photon number and energy. Here we show that photon conservation is the more widely applicable law which can hold in circumstances where energy conservation is violated shedding further light on an amplification mechanism identified in previous papers as a process of conserved photons climbing a frequency ladder
Negative refraction makes a perfect lens
No full textWith a conventional lens sharpness of the image is always limited by the wavelength of light. An unconventional alternative to a lens, a slab of negative refractive index material, has the power to focus all Fourier components of a 2D image, even those that do not propagate in a radiative manner. Such super lenses can be realised in the microwave band with current technology and a version operating at the frequency of visible light, but at short distances of a few nanometres, can be realised in the form of a thin slab of silver as our simulations show
- …
