382 research outputs found
Extension of Bethe's diffraction model to conical Geometry: application to near field optics
The generality of the Bethe's two dipole model for light diffraction through
a subwavelength aperture in a conducting plane is studied in the radiation zone
for coated conical fiber tips as those used in near field scanning optical
microscopy. In order to describe the angular radiated power of the tip
theoretically, we present a simple, analytical model for small apertures
(radius < 40 nm) based on a multipole expansion. Our model is able to reproduce
the available experimental results. It proves relatively insensitive to cone
angle and aperture radius and contains, as a first approximation, the empirical
two-dipole model proposed earlier
Theory of imaging a photonic crystal with transmission near-field optical microscopy
While near-field scanning optical microscopy (NSOM) can provide optical
images with resolution much better than the diffraction limit, analysis and
interpretation of these images is often difficult. We present a theory of
imaging with transmission NSOM that includes the effects of tip field,
tip/sample coupling, light propagation through the sample and light collection.
We apply this theory to analyze experimental NSOM images of a nanochannel glass
(NCG) array obtained in transmission mode. The NCG is a triangular array of
dielectric rods in a dielectric glass matrix with a two-dimensional photonic
band structure. We determine the modes for the NCG photonic crystal and
simulate the observed data. The calculations show large contrast at low
numerical aperture (NA) of the collection optics and detailed structure at high
NA consistent with the observed images. We present calculations as a function
of NA to identify how the NCG photonic modes contribute to and determine the
spatial structure in these images. Calculations are presented as a function of
tip/sample position, sample index contrast and geometry, and aperture size to
identify the factors that determine image formation with transmission NSOM in
this experiment.Comment: 28 pages of ReVTex, 14 ps figures, submitted to Phys. Rev.
Local Optical Spectroscopy in Quantum Confined Systems: A Theoretical Description
A theoretical description of local absorption is proposed in order to
investigate spectral variations on a length scale comparable with the extension
of the relevant quantum states. A general formulation is derived within the
density-matrix formalism including Coulomb correlation, and applied to the
prototypical case of coupled quantum wires. The results show that excitonic
effects may have a crucial impact on the local absorption with implications for
the spatial resolution and the interpretation of near-field optical spectra.Comment: To appear in Phys. Rev. Lett. - 11 pages, 3 PostScript figures (1
figure in colors) embedded. Uses RevTex, and psfig style
Quantitative expression profiling of highly degraded RNA from formalin-fixed, paraffin-embedded breast tumor biopsies by oligonucleotide microarrays.
Microarray-based gene expression profiling is well suited for parallel quantitative analysis of large numbers of RNAs, but its application to cancer biopsies, particularly formalin-fixed, paraffin-embedded (FFPE) archived tissues, is limited by the poor quality of the RNA recovered. This represents a serious drawback, as FFPE tumor tissue banks are available with clinical and prognostic annotations, which could be exploited for molecular profiling studies, provided that reliable analytical technologies are found. We applied and evaluated here a microarray-based cDNA-mediated annealing, selection, extension and ligation (DASL) assay for analysis of 502 mRNAs in highly degraded total RNA extracted from cultured cells or FFPE breast cancer (MT) biopsies. The study included quantitative and qualitative comparison of data obtained by analysis of the same RNAs with genome-wide oligonucleotide microarrays vs DASL arrays and, by DASL, before and after extensive in vitro RNA fragmentation. The DASL-based expression profiling assay applied to RNA extracted from MCF-7 cells, before or after 24 h stimulation with a mitogenic dose of 17b-estradiol, consistently allowed to detect hormone-induced gene expression changes following extensive RNA degradation in vitro. Comparable results where obtained with tumor RNA extracted from FFPE MT biopsies (6 to 19 years old). The method proved itself sensitive, reproducible and accurate, when compared to results obtained by microarray analysis of RNA extracted from snap-frozen tissue of the same tumor
Anomalous Couplings in Double Higgs Production
The process of gluon-initiated double Higgs production is sensitive to
non-linear interactions of the Higgs boson. In the context of the Standard
Model, studies of this process focused on the extraction of the Higgs trilinear
coupling. In a general parametrization of New Physics effects, however, an even
more interesting interaction that can be tested through this channel is the
(ttbar hh) coupling. This interaction vanishes in the Standard Model and is a
genuine signature of theories in which the Higgs boson emerges from a
strongly-interacting sector. In this paper we perform a model-independent
estimate of the LHC potential to detect anomalous Higgs couplings in
gluon-fusion double Higgs production. We find that while the sensitivity to the
trilinear is poor, the perspectives of measuring the new (ttbar hh) coupling
are rather promising.Comment: 22 pages, 9 figures. v2: plots of Figs.8 and 9 redone to include
experimental uncertainty on the Higgs couplings, references adde
C/EBPd gene targets in human keratinocytes
C/EBPs are a family of B-Zip transcription factors -TFs- involved in the regulation of differentiation in several tissues. The two most studied members -C/EBP\u3b1 and C/EBP\u3b2- play important roles in skin homeostasis and their ablation reveals cells with stem cells signatures. Much less is known about C/EBP\u3b4 which is highly expressed in the granular layer of interfollicular epidermis and is a direct target of p63, the master regular of multilayered epithelia. We identified C/EBP\u3b4 target genes in human primary keratinocytes by ChIP on chip and profiling of cells functionally inactivated with siRNA. Categorization suggests a role in differentiation and control of cell-cycle, particularly of G2/M genes. Among positively controlled targets are numerous genes involved in barrier function. Functional inactivation of C/EBP\u3b4 as well as overexpressions of two TF targets -MafB and SOX2- affect expression of markers of keratinocyte differentiation. We performed IHC on skin tumor tissue arrays: expression of C/EBP\u3b4 is lost in Basal Cell Carcinomas, but a majority of Squamous Cell Carcinomas showed elevated levels of the protein. Our data indicate that C/EBP\u3b4 plays a role in late stages of keratinocyte differentiation
How do we get there? Effects of cognitive aging on route memory
© 2017 The Author(s) Research into the effects of cognitive aging on route navigation usually focuses on differences in learning performance. In contrast, we investigated age-related differences in route knowledge after successful route learning. One young and two groups of older adults categorized using different cut-off scores on the Montreal Cognitive Assessment (MoCA), were trained until they could correctly recall short routes. During the test phase, they were asked to recall the sequence in which landmarks were encountered (Landmark Sequence Task), the sequence of turns (Direction Sequence Task), the direction of turn at each landmark (Landmark Direction Task), and to identify the learned routes from a map perspective (Perspective Taking Task). Comparing the young participant group with the older group that scored high on the MoCA, we found effects of typical aging in learning performance and in the Direction Sequence Task. Comparing the two older groups, we found effects of early signs of atypical aging in the Landmark Direction and the Perspective Taking Tasks. We found no differences between groups in the Landmark Sequence Task. Given that participants were able to recall routes after training, these results suggest that typical and early signs of atypical aging result in differential memory deficits for aspects of route knowledge
Medical error in the portuguese press: when patients are part of the news
Esta investigação aborda a qualidade da produção noticiosa sobre o erro médico, como um fator essencial na construção do conhecimento público sobre o tema, com o objetivo de compreender que caracterÃsticas definem tal produção e até que ponto poderão ser explicadas pela periodicidade e orientação editorial dos jornais; que conceito de erro médico é veiculado pela produção noticiosa sobre o tema; e quais são os protagonistas no discurso jornalÃstico sobre o erro médico. Foram analisadas as edições de três jornais portugueses, de 2008 a 2011, resultando num corpus de 266 (4,2%) artigos, que foram classificados de acordo com as seguintes variáveis: as fontes de informação citadas (o seu estatuto e especialidade, no caso dos médicos); os temas que são tratados; as caracterÃsticas de enquadramento da informação publicada (tom, género jornalÃstico; e a presença e número de fontes de informação). Pela análise de conteúdo quantitativa, apurou-se que esse tema está em crescimento, essencialmente com notÃcias de tom negativo e fontes de informação habitualmente identificadas. Não há evidência para afirmar que a periodicidade e a orientação editorial expliquem as variações dessas caracterÃsticas, a não ser relativamente ao número de fontes citadas. Vigoram as notÃcias centradas nos resultados dos erros (mortes ou lesões), provocados por "erros de omissão" e por "erros de comissão", envolvendo uma diversidade de protagonistas: são, tal como acontece na informação sobre saúde em geral, fontes oficiais e especializadas do campo da saúde. Destacam-se os médicos e os juristas e é dado relevo aos pacientes.This research addresses the quality of news production on medical error, as an essential factor in building public knowledge on the subject, in order to understand which characteristics define the news production of medical error and to what extent can they be explained by the periodicity and editorial orientation of the newspaper; which concept of medical error is transmitted by the news production on the subject; and who are the main actors in the journalistic discourse about medical error. The editions of three Portuguese newspapers were analyzed, from 2008 to 2011, resulting in a corpus of 266 (4.2%) articles, which were classified according to the following variables: the sources of information quoted (their status and specialty, in the case of doctors); the issues covered; and characteristic framework of the published information (tone, journalistic style, and the presence and number of information sources). Through quantitative content analysis, it was found that this topic is growing, essentially with negative news and information sources usually being identified. There is no evidence to support that periodicity and editorial orientation explain the variations in these characteristics, except for the number of cited sources. News focused on the results of errors (death or injury), caused by "errors of omission" and "commission errors", prevail, involving a variety of actors: they are, such as it happens in health information, in general, official sources and experts in health. Doctors and lawyers stand out, and special attention is given to patients
Estrogen-dependent dynamic profile of eNOS-DNA associations in prostate cancer
In previous work we have documented the nuclear translocation of endothelial NOS (eNOS) and its participation in combinatorial complexes with Estrogen Receptor Beta (ERβ) and Hypoxia Inducible Factors (HIFs) that determine localized chromatin remodeling in response to estrogen (E2) and hypoxia stimuli, resulting in transcriptional regulation of genes associated with adverse prognosis in prostate cancer (PCa). To explore the role of nuclear eNOS in the acquisition of aggressive phenotype in PCa, we performed ChIP-Sequencing on chromatin-associated eNOS from cells from a primary tumor with poor outcome and from metastatic LNCaP cells. We found that: 1. the eNOS-bound regions (peaks) are widely distributed across the genome encompassing multiple transcription factors binding sites, including Estrogen Response Elements. 2. E2 increased the number of peaks, indicating hormone-dependent eNOS re-localization. 3. Peak distribution was similar with/without E2 with ≈ 55% of them in extragenic DNA regions and an intriguing involvement of the 5′ domain of several miRs deregulated in PCa. Numerous potentially novel eNOS-targeted genes have been identified suggesting that eNOS participates in the regulation of large gene sets. The parallel finding of downregulation of a cluster of miRs, including miR-34a, in PCa cells associated with poor outcome led us to unveil a molecular link between eNOS and SIRT1, an epigenetic regulator of aging and tumorigenicity, negatively regulated by miR-34a and in turn activating eNOS. E2 potentiates miR-34a downregulation thus enhancing SIRT1 expression, depicting a novel eNOS/SIRT1 interplay fine-tuned by E2-activated ER signaling, and suggesting that eNOS may play an important role in aggressive PCa
Global Analysis of the Higgs Candidate with Mass ~ 125 GeV
We analyze the properties of the Higgs candidate with mass ~ 125 GeV
discovered by the CMS and ATLAS Collaborations, constraining the possible
deviations of its couplings from those of a Standard Model Higgs boson. The
CMS, ATLAS and Tevatron data are compatible with Standard Model couplings to
massive gauge bosons and fermions, and disfavour several types of composite
Higgs models unless their couplings resemble those in the Standard Model. We
show that the couplings of the Higgs candidate are consistent with a linear
dependence on particle masses, scaled by the electroweak scale ~ 246 GeV, the
power law and the mass scale both having uncertainties ~ 20%.Comment: 22 pages, 9 figures, v2 incorporates experimental data released
during July 2012 and corrected (and improved) treatment of mass dependence of
coupling
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