An update on retinal prostheses

Retinal prostheses are designed to restore a basic sense of sight to people with profound vision loss. They require a relatively intact posterior visual pathway (optic nerve, lateral geniculate nucleus and visual cortex). Retinal implants are options for people with severe stages of retinal degenerative disease such as retinitis pigmentosa and age-related macular degeneration. There have now been three regulatory-approved retinal prostheses. Over five hundred patients have been implanted globally over the past 15 years. Devices generally provide an improved ability to localize high-contrast objects, navigate, and perform basic orientation tasks. Adverse events have included conjunctival erosion, retinal detachment, loss of light perception, and the need for revision surgery, but are rare. There are also specific device risks, including overstimulation (which could cause damage to the retina) or delamination of implanted components, but these are very unlikely. Current challenges include how to improve visual acuity, enlarge the field-of-view, and reduce a complex visual scene to its most salient components through image processing. This review encompasses the work of over 40 individual research groups who have built devices, developed stimulation strategies, or investigated the basic physiology underpinning retinal prostheses. Current technologies are summarized, along with future challenges that face the field

Scheduling science on television: A comparative analysis of the representations of science in 11 European countries

While science-in-the-media is a useful vehicle for understanding the media, few scholars have used it that way: instead, they look at science-in-the-media as a way of understanding science-in-the-media and often end up attributing characteristics to science-in-the-media that are simply characteristics of the media, rather than of the science they see there. This point of view was argued by Jane Gregory and Steve Miller in 1998 in Science in Public. Science, they concluded, is not a special case in the mass media, understanding science-in-the-media is mostly about understanding the media (Gregory and Miller, 1998: 105). More than a decade later, research that looks for patterns or even determinants of science-in-the-media, be it in press or electronic media, is still very rare. There is interest in explaining the media’s selection of science content from a media perspective. Instead, the search for, and analysis of, several kinds of distortions in media representations of science have been leading topics of science-in-the-media research since its beginning in the USA at the end of the 1960s and remain influential today (see Lewenstein, 1994; Weigold, 2001; Kohring, 2005 for summaries). Only a relatively small amount of research has been conducted seeking to identify factors relevant to understanding how science is treated by the mass media in general and by television in particular. The current study addresses the lack of research in this area. Our research seeks to explore which constraints national media systems place on the volume and structure of science programming in television. In simpler terms, the main question this study is trying to address is why science-in-TV in Europe appears as it does. We seek to link research focussing on the detailed analysis of science representations on television (Silverstone, 1984; Collins, 1987; Hornig, 1990; Leon, 2008), and media research focussing on the historical genesis and current political regulation of national media systems (see for instance Hallin and Mancini, 2004; Napoli, 2004; Open Society Institute, 2005, 2008). The former studies provide deeper insights into the selection and reconstruction of scientific subject matters, which reflect and – at the same time – reinforce popular images of science. But their studies do not give much attention to production constraints or other relevant factors which could provide an insight into why media treat science as they do. The latter scholars inter alia shed light on distinct media policies in Europe which significantly influence national channel patterns. However, they do not refer to clearly defined content categories but to fairly rough distinctions such as information versus entertainment or fictional versus factual. Accordingly, we know more about historical roots and current practices of media regulation across Europe than we do about the effects of these different regimes on the provision of specific content in European societies

Jet Shapes and Jet Algorithms in SCET

Jet shapes are weighted sums over the four-momenta of the constituents of a jet and reveal details of its internal structure, potentially allowing discrimination of its partonic origin. In this work we make predictions for quark and gluon jet shape distributions in N-jet final states in e+e- collisions, defined with a cone or recombination algorithm, where we measure some jet shape observable on a subset of these jets. Using the framework of Soft-Collinear Effective Theory, we prove a factorization theorem for jet shape distributions and demonstrate the consistent renormalization-group running of the functions in the factorization theorem for any number of measured and unmeasured jets, any number of quark and gluon jets, and any angular size R of the jets, as long as R is much smaller than the angular separation between jets. We calculate the jet and soft functions for angularity jet shapes \tau_a to one-loop order (O(alpha_s)) and resum a subset of the large logarithms of \tau_a needed for next-to-leading logarithmic (NLL) accuracy for both cone and kT-type jets. We compare our predictions for the resummed \tau_a distribution of a quark or a gluon jet produced in a 3-jet final state in e+e- annihilation to the output of a Monte Carlo event generator and find that the dependence on a and R is very similar.Comment: 62 pages plus 21 pages of Appendices, 13 figures, uses JHEP3.cls. v2: corrections to finite parts of NLO jet functions, minor changes to plots, clarified discussion of power corrections. v3: Journal version. Introductory sections significantly reorganized for clarity, classification of logarithmic accuracy clarified, results for non-Mercedes-Benz configurations adde

Direct photon production with effective field theory

The production of hard photons in hadronic collisions is studied using Soft-Collinear Effective Theory (SCET). This is the first application of SCET to a physical, observable cross section involving energetic partons in more than two directions. A factorization formula is derived which involves a non-trivial interplay of the angular dependence in the hard and soft functions, both quark and gluon jet functions, and multiple partonic channels. The relevant hard, jet and soft functions are computed to one loop and their anomalous dimensions are determined to three loops. The final resummed inclusive direct photon distribution is valid to next-to-next-to-leading logarithmic order (NNLL), one order beyond previous work. The result is improved by including non-logarithmic terms and photon isolation cuts through matching, and compared to Tevatron data and to fixed order results at the Tevatron and the LHC. The resummed cross section has a significantly smaller theoretical uncertainty than the next-to-leading fixed-order result, particularly at high transverse momentum.Comment: 42 pages, 9 figures; v2: references added, minor changes; v3: typos; v4: typos, corrections in (16), (47), (72

An effective theory for jet propagation in dense QCD matter: jet broadening and medium-induced bremsstrahlung

Two effects, jet broadening and gluon bremsstrahlung induced by the propagation of a highly energetic quark in dense QCD matter, are reconsidered from effective theory point of view. We modify the standard Soft Collinear Effective Theory (SCET) Lagrangian to include Glauber modes, which are needed to implement the interactions between the medium and the collinear fields. We derive the Feynman rules for this Lagrangian and show that it is invariant under soft and collinear gauge transformations. We find that the newly constructed theory SCET$_{\rm G}$ recovers exactly the general result for the transverse momentum broadening of jets. In the limit where the radiated gluons are significantly less energetic than the parent quark, we obtain a jet energy-loss kernel identical to the one discussed in the reaction operator approach to parton propagation in matter. In the framework of SCET$_{\rm G}$ we present results for the fully-differential bremsstrahlung spectrum for both the incoherent and the Landau-Pomeranchunk-Migdal suppressed regimes beyond the soft-gluon approximation. Gauge invariance of the physics results is demonstrated explicitly by performing the calculations in both the light-cone and covariant $R_{\xi}$ gauges. We also show how the process-dependent medium-induced radiative corrections factorize from the jet production cross section on the example of the quark jets considered here.Comment: 52 pages, 15 pdf figures, as published in JHE

Changes in synaptic transmission and protein expression in the brains of adult offspring after prenatal inhibition of the kynurenine pathway

During early brain development, N-methyl-d-aspartate (NMDA) receptors are involved in cell migration, neuritogenesis, axon guidance and synapse formation, but the mechanisms which regulate NMDA receptor density and function remain unclear. The kynurenine pathway of tryptophan metabolism includes an agonist (quinolinic acid) and an antagonist (kynurenic acid) at NMDA receptors and we have previously shown that inhibition of the pathway using the kynurenine-3-monoxygenase inhibitor Ro61-8048 in late gestation produces rapid changes in protein expression in the embryos and effects on synaptic transmission lasting until postnatal day 21 (P21). The present study sought to determine whether any of these effects are maintained into adulthood. After prenatal injections of Ro61-8048 the litter was allowed to develop to P60 when some offspring were euthanized and the brains removed for examination. Analysis of protein expression by Western blotting revealed significantly reduced expression of the GluN2A subunit (32%) and the morphogenetic protein sonic hedgehog (31%), with a 29% increase in the expression of doublecortin, a protein associated with neurogenesis. No changes were seen in mRNA abundance using quantitative real-time polymerase chain reaction. Neuronal excitability was normal in the CA1 region of hippocampal slices but paired-pulse stimulation revealed less inhibition at short interpulse intervals. The amount of long-term potentiation was decreased by 49% in treated pups and recovery after low-frequency stimulation was delayed. The results not only strengthen the view that basal, constitutive kynurenine metabolism is involved in normal brain development, but also show that changes induced prenatally can affect the brains of adult offspring and those changes are quite different from those seen previously at weaning (P21). Those changes may be mediated by altered expression of NMDAR subunits and sonic hedgehog

A human mitochondrial poly(A) polymerase mutation reveals the complexities of post-transcriptional mitochondrial gene expression

The p.N478D missense mutation in human mitochondrial poly(A) polymerase (mtPAP) has previously been implicated in a form of spastic ataxia with optic atrophy. In this study, we have investigated fibroblast cell lines established from family members. The homozygous mutation resulted in the loss of polyadenylation of all mitochondrial transcripts assessed; however, oligoadenylation was retained. Interestingly, this had differential effects on transcript stability that were dependent on the particular species of transcript. These changes were accompanied by a severe loss of oxidative phosphorylation complexes I and IV, and perturbation of de novo mitochondrial protein synthesis. Decreases in transcript polyadenylation and in respiratory chain complexes were effectively rescued by overexpression of wild-type mtPAP. Both mutated and wild-type mtPAP localized to the mitochondrial RNA-processing granules thereby eliminating mislocalization as a cause of defective polyadenylation. In vitro polyadenylation assays revealed severely compromised activity by the mutated protein, which generated only short oligo(A) extensions on RNA substrates, irrespective of RNA secondary structure. The addition of LRPPRC/SLIRP, a mitochondrial RNA-binding complex, enhanced activity of the wild-type mtPAP resulting in increased overall tail length. The LRPPRC/SLIRP effect although present was less marked with mutated mtPAP, independent of RNA secondary structure. We conclude that (i) the polymerase activity of mtPAP can be modulated by the presence of LRPPRC/SLIRP, (ii) N478D mtPAP mutation decreases polymerase activity and (iii) the alteration in poly(A) length is sufficient to cause dysregulation of post-transcriptional expression and the pathogenic lack of respiratory chain complexe

Non--global logs and clustering impact on jet mass with a jet veto distribution

There has recently been much interest in analytical computations of jet mass distributions with and without vetos on additional jet activity [1-6]. An important issue affecting such calculations, particularly at next-to-leading logarithmic (NLL) accuracy, is that of non-global logarithms as well as logarithms induced by jet definition, as we pointed out in an earlier work [3]. In this paper, we extend our previous calculations by independently deriving the full jet-radius analytical form of non-global logarithms, in the anti-\kt jet algorithm. Employing the small-jet radius approximation, we also compute, at fixed-order, the effect of jet clustering on both \CF^{2} and \CF\CA colour channels. Our findings for the \CF\CA channel confirm earlier analytical calculations of non-global logarithms in soft-collinear effective theory [5]. Moreover, all of our results, as well as those of [3], are compared to the output of the numerical program \texttt{EVENT2}. We find good agreement between analytical and numerical results both with and without final state clustering.Comment: 33 pages, 15 figures. Version accepted by JHE

Beyond the looking glass: recent advances in understanding the impact of environmental exposures on neuropsychiatric disease

The etiologic pathways leading to neuropsychiatric diseases remain poorly defined. As genomic technologies have advanced over the past several decades, considerable progress has been made linking neuropsychiatric disorders to genetic underpinnings. Interest and consideration of nongenetic risk factors (e.g., lead exposure and schizophrenia) have, in contrast, lagged behind heritable frameworks of explanation. Thus, the association of neuropsychiatric illness to environmental chemical exposure, and their potential interactions with genetic susceptibility, are largely unexplored. In this review, we describe emerging approaches for considering the impact of chemical risk factors acting alone and in concert with genetic risk, and point to the potential role of epigenetics in mediating exposure effects on transcription of genes implicated in mental disorders. We highlight recent examples of research in nongenetic risk factors in psychiatric disorders that point to potential shared biological mechanisms—synaptic dysfunction, immune alterations, and gut–brain interactions. We outline new tools and resources that can be harnessed for the study of environmental factors in psychiatric disorders. These tools, combined with emerging experimental evidence, suggest that there is a need to broadly incorporate environmental exposures in psychiatric research, with the ultimate goal of identifying modifiable risk factors and informing new treatment strategies for neuropsychiatric disease

Do current and magnetic helicities have the same sign?

Current helicity, H c , and magnetic helicity, H m , are two main quantities used to characterize magnetic fields. For example, such quantities have been widely used to characterize solar active regions and their ejecta (magnetic clouds). It is commonly assumed that H c and H m have the same sign, but this has not been rigorously addressed beyond the simple case of linear force-free fields. We aim to answer whether H m H c ≥ 0 in general, and whether it is true over some useful set of magnetic fields. This question is addressed analytically and with numerical examples. The main focus is on cylindrically symmetric straight flux tubes, referred to as flux ropes (FRs), using the relative magnetic helicity with respect to a straight (untwisted) reference field. Counterexamples with H m H c < 0 have been found for cylindrically symmetric FRs with finite plasma pressure, and for force-free cylindrically symmetric FRs in which the poloidal field component changes direction. Our main result is a proof that H m H c ≥ 0 is true for force-free cylindrically symmetric FRs where the toroidal field and poloidal field components are each of a single sign, and the poloidal component does not exceed the toroidal component. We conclude that the conjecture that current and magnetic helicities have the same sign is not true in general, but it is true for a set of FRs of importance to coronal and heliospheric physics