Frozen light in photonic crystals with degenerate band edge

Consider a plane monochromatic wave incident on a semi-infinite periodic structure. What happens if the normal component of the transmitted wave group velocity vanishes? At first sight, zero normal component of the transmitted wave group velocity simply implies total reflection of the incident wave. But we demonstrate that total reflection is not the only possible outcome. Instead, the transmitted wave can appear in the form of a frozen mode with very large diverging amplitude and either zero, or purely tangential energy flux. The field amplitude in the transmitted wave can exceed that of the incident wave by several orders of magnitude. There are two qualitatively different kinds of frozen mode regime. The first one is associated with a stationary inflection point of electromagnetic dispersion relation. This phenomenon has been analyzed in our previous publications. Now, our focus is on the frozen mode regime related to a degenerate photonic band edge. An advantage of this new phenomenon is that it can occur in much simpler periodic structures. This spectacular effect is extremely sensitive to the frequency and direction of propagation of the incident plane wave. These features can be very attractive in a variety practical applications, such as higher harmonic generation and wave mixing, light amplification and lasing, highly efficient superprizms, etc

Gigantic transmission band edge resonance in periodic stacks of anisotropic layers

We consider Fabry-Perot cavity resonance in periodic stacks of anisotropic layers with misaligned in-plane anisotropy at the frequency close to a photonic band edge. We show that in-plane dielectric anisotropy can result in a dramatic increase in field intensity and group delay associated with the transmission resonance. The field enhancement appears to be proportional to forth degree of the number N of layers in the stack. By contrast, in common periodic stacks of isotropic layers, those effects are much weaker and proportional to N^2. Thus, the anisotropy allows to drastically reduce the size of the resonance cavity with similar performance. The key characteristic of the periodic arrays with the gigantic transmission resonance is that the dispersion curve omega(k)at the photonic band edge has the degenerate form Delta(omega) ~ Delta(k)^4, rather than the regular form Delta(omega) ~ Delta(k)^2. This can be realized in specially arranged stacks of misaligned anisotropic layers. The degenerate band edge cavity resonance with similar outstanding properties can also be realized in a waveguide environment, as well as in a linear array of coupled multimode resonators, provided that certain symmetry conditions are in place.Comment: To be submitted to Phys. Re

The Impact of Interactivity on Truth Claims in Life Stories

Autobiographies, biographies, and documentary life stories all claim to tell a ‘true life story’. Yet each life story genre highlights different aspects of the truth. In autobiography, the personal subjective truth of self-identity is foregrounded. In biography, it is the seemingly objective truth about someone’s life asserted by another person, whose mediation introduces an element of subjectivity. In a documentary life story testimonial, the credibility of the objective truth presented is of utmost importance, but so is the subjective life experience that undergirds it. In this article we ask: How is interactivity exploited to construct the truth claims in interactive life stories across genres? By comparing three interactive nonfiction life stories – an autobiography, Fitting the Pattern (Wilks 2008), the biographical docugame The Cat and the Coup (Brinson / ValaNejad 2011), and the documentary Alma (Fougère / Dewever-Plana 2012) –, we explore how the aspects of truth most relevant to each life story genre are foregrounded using interactivity

Tropism, Cytotoxicity, and Inflammatory Properties of Two Envelope Genes of Murine Leukemia Virus Type-Endogenous Retroviruses of C57BL/6J Mice

Envelope (env) proteins of certain endogenous retroviruses (ERVs) participate in various pathophysiological processes. In this study, we characterized pathophysiologic properties of two murine leukemia virus-type ERV (MuLV-ERV) env genes cloned from the ovary of C57BL/6J mice. The two env genes (named ENVOV1 and ENVOV2), with 1,926 bp coding region, originated from two MuLV-ERV loci on chromosomes 8 and 18, respectively. ENVOV1 and ENVOV2 were ~75 kDa and predominantly expressed on the cell membrane. They were capable of producing pseudotype murine leukemia virus virions. Tropism trait and infectivity of ENVOV2 were similar to the polytropic env; however, ENVOV1 had very low level of infectivity. Overexpression of ENVOV2, but not ENVOV1, exerted cytotoxic effects and induced expression of COX-2, IL-1β, IL-6, and iNOS. These findings suggest that the ENVOV1 and ENVOV2 are capable of serving as an env protein for virion assembly, and they exert differential cytotoxicity and modulation of inflammatory mediators

Slow wave resonance in periodic stacks of anisotropic layers

We consider transmission band edge resonance in periodic layered structures involving birefringent layers. Previously we have shown that the presence of birefringent layers with misaligned in-plane anisotropy can dramatically enhance the performance of the photonic-crystal Fabry-Perot resonator. It allows to reduce its size by an order of magnitude without compromising on its performance. The key characteristic of the enhanced photonic-crystal cavity is that its Bloch dispersion relation displays a degenerate photonic band edge, rather than only regular ones. This can be realized in specially arranged stacks of misaligned anisotropic layers. On the down side, the presence of birefringent layers results in the Fabry-Perot resonance being coupled only with one (elliptic) polarization component of the incident wave, while the other polarization component is reflected back to space. In this paper we show how a small modification of the periodic layered array can solve the above fundamental problem and provide a perfect impedance match regardless of the incident wave polarization, while preserving the giant transmission resonance, characteristic of a degenerate photonic band edge. Both features are of critical importance for a variety of practical applications, including antennas, light amplification, optical and microwave filters, etc.Comment: To be submitted to Phys. Rev.

Genome-wide expression profiles of endogenous retroviruses in lymphoid tissues and their biological properties

AbstractEndogenous retroviruses (ERVs) constitute approximately 8–10% of the human and mouse genome. Some autoimmune diseases are attributed to the altered expression of ERVs. In this study, we examined the ERV expression profiles in lymphoid tissues and analyzed their biological properties. Tissues (spleen, thymus, and lymph nodes [axillary, inguinal, and mesenteric]) from C57BL/6J mice were analyzed for differential murine ERV (MuERV) expression by RT-PCR examination of polymorphic U3 sequences. Each tissue had a unique profile of MuERV expression. A genomic map identifying 60 putative MuERVs was established using 22 unique U3s as probes and their biological properties (primer binding site, coding potential, transcription regulatory element, tropism, recombination event, and integration age) were characterized. Interestingly, 12 putative MuERVs retained intact coding potentials for all three polypeptides essential for virus assembly and replication. We suggest that MuERV expression is differentially regulated in conjunction with the transcriptional environment of individual lymphoid tissues

Genome-wide changes in expression profile of murine endogenous retroviruses (MuERVs) in distant organs after burn injury

<p>Abstract</p> <p>Background</p> <p>Previous studies have shown that burn-elicited stress signals alter expression of certain murine endogenous retroviruses (MuERVs) in distant organs of mice. These findings suggest that MuERVs may participate in a network of pathophysiologic events during post-burn systemic response. To gain a better understanding of the biological roles of MuERVs in post-burn systemic response, we examined the genome-wide changes in the MuERV expression profiles in distant organs and the biological properties of the putative-burn related MuERVs were characterized.</p> <p>Results</p> <p>Female C57BL/6J mice were subjected to an approximately 18 % total body surface area flame burn and tissues (liver, lung, and kidney) were harvested at 3 hours and 24 hours after injury. The changes in the MuERV expression profiles in these tissues were examined by RT-PCR using a primer set flanking the non-ecotropic MuERV U3 promoter region within the 3' long terminal repeat. There were differential changes in the expression profiles of MuERV U3 regions after injury in all three tissues examined. Subsequently, a total of 31 unique U3 promoter sequences were identified from the tissues of both burn and no burn mice. An analysis of viral tropisms revealed that putative MuERVs harboring these U3 promoter sequences were presumed to be either xenotropic or polytropic. Some putative transcription regulatory elements were present predominantly in U3 promoter sequences isolated from burn and no burn mice, respectively. In addition, <it>in silico </it>mapping using these U3 sequences as a probe against the mouse genome database identified 59 putative MuERVs. The biological properties (coding potentials for retroviral polypeptides, primer binding sites, tropisms, branching ages, recombination events, and neighboring host genes) of each putative MuERV were characterized. In particular, 16 putative MuERVs identified in this study retained intact coding potentials for all three retroviral polypeptides (<it>gag, pol</it>, and <it>env</it>). None of the putative MuERVs identified in this study were mapped to the coding sequences of host genes.</p> <p>Conclusion</p> <p>In this study, we identified and characterized putative MuERVs whose expression might be altered in response to burn-elicited systemic stress signals. Further investigation is needed to understand the role of these MuERVs in post-burn systemic pathogenesis, in particular, via characterization of their interaction with host genes, MuERV gene products, and viral activities.</p

Neural Active Learning on Heteroskedastic Distributions

Models that can actively seek out the best quality training data hold the promise of more accurate, adaptable, and efficient machine learning. State-of-the-art active learning techniques tend to prefer examples that are the most difficult to classify. While this works well on homogeneous datasets, we find that it can lead to catastrophic failures when performed on multiple distributions with different degrees of label noise or heteroskedasticity. These active learning algorithms strongly prefer to draw from the distribution with more noise, even if their examples have no informative structure (such as solid color images with random labels). To this end, we demonstrate the catastrophic failure of these active learning algorithms on heteroskedastic distributions and propose a fine-tuning-based approach to mitigate these failures. Further, we propose a new algorithm that incorporates a model difference scoring function for each data point to filter out the noisy examples and sample clean examples that maximize accuracy, outperforming the existing active learning techniques on the heteroskedastic datasets. We hope these observations and techniques are immediately helpful to practitioners and can help to challenge common assumptions in the design of active learning algorithms

Prevalent de novo somatic mutations in superantigen genes of mouse mammary tumor viruses in the genome of C57BL/6J mice and its potential implication in the immune system

<p>Abstract</p> <p>Background</p> <p>Superantigens (SAgs) of mouse mammary tumor viruses (MMTVs) play a crucial role in T cell selection in the thymus in a T cell receptor (TCR) Vβ-specific manner and SAgs presented by B cells activate T cells in the periphery. The peripheral T cell repertoire is dynamically shaped by the steady induction of T cell tolerance against self antigens throughout the lifespan. We hypothesize that <it>de novo </it>somatic mutation of endogenous MMTV SAgs contributes to the modulation of the peripheral T cell repertoire.</p> <p>Results</p> <p>SAg coding sequences were cloned from the genomic DNAs and/or cDNAs of various tissues of female C57BL/6J mice. A total of 68 unique SAg sequences (54 translated sequences) were identified from the genomic DNAs of liver, lungs, and bone marrow, which are presumed to harbor only three endogenous MMTV loci (<it>Mtv-8</it>, <it>Mtv-9</it>, and <it>Mtv-17</it>). Similarly, 69 unique SAg sequences (58 translated sequences) were cloned from the cDNAs of 18 different tissues. Examination of putative TCR Vβ specificity suggested that some of the SAg isoforms identified in this study have Vβ specificities different from the reference SAgs of <it>Mtv-8</it>, <it>Mtv-9</it>, or <it>Mtv-17</it>.</p> <p>Conclusion</p> <p>The pool of diverse SAg isoforms, generated by <it>de novo </it>somatic mutation, may play a role in the shaping of the peripheral T cell repertoire including the autoimmune T cell population.</p