375 research outputs found
Beam-Size Invariant Spectropolarimeters Using Gap-Plasmon Metasurfaces
Metasurfaces enable exceptional control over the light with surface-confined
planar components, offering the fascinating possibility of very dense
integration and miniaturization in photonics. Here, we design, fabricate and
experimentally demonstrate chip-size plasmonic spectropolarimeters for
simultaneous polarization state and wavelength determination.
Spectropolarimeters, consisting of three gap-plasmon phase-gradient
metasurfaces that occupy 120{\deg} circular sectors each, diffract normally
incident light to six predesigned directions, whose azimuthal angles are
proportional to the light wavelength, while contrasts in the corresponding
diffraction intensities provide a direct measure of the incident polarization
state through retrieval of the associated Stokes parameters. The
proof-of-concept 96-{\mu}m-diameter spectropolarimeter operating in the
wavelength range of 750-950nm exhibits the expected polarization selectivity
and high angular dispersion. Moreover, we show that, due to the circular-sector
design, polarization analysis can be conducted for optical beams of different
diameters without prior calibration, demonstrating thereby the beam-size
invariant functionality. The proposed spectropolarimeters are compact,
cost-effective, robust, and promise high-performance real-time polarization and
spectral measurements
Analysis of interference to cable television due to mobile usage in the Digital Dividend
The start of use of mobile applications in the 800 MHz band, which forms part of the ‘Digital Dividend’, will cause interference to TV signals under certain conditions. The new mobile applications (called LTE, Long Term Evolution) use frequencies also used in cable TV networks. This report examines how much interference may occur when providing digital television over cable networks
Mitoxantrone and Analogues Bind and Stabilize i-Motif Forming DNA Sequences
YesThere are hundreds of ligands which can interact with G-quadruplex DNA, yet very few which target i-motif. To appreciate an understanding between the dynamics between these structures and how they can be affected by intervention with small molecule ligands, more i-motif binding compounds are required. Herein we describe how the drug mitoxantrone can bind, induce folding of and stabilise i-motif forming DNA sequences, even at physiological pH. Additionally, mitoxantrone was found to bind i-motif forming sequences preferentially over double helical DNA. We also describe the stabilisation properties of analogues of mitoxantrone. This offers a new family of ligands with potential for use in experiments into the structure and function of i-motif forming DNA sequences
Bounds and optimisation of orbital angular momentum bandwidths within parametric down-conversion systems
The measurement of high-dimensional entangled states of orbital angular
momentum prepared by spontaneous parametric down-conversion can be considered
in two separate stages: a generation stage and a detection stage. Given a
certain number of generated modes, the number of measured modes is determined
by the measurement apparatus. We derive a simple relationship between the
generation and detection parameters and the number of measured entangled modes.Comment: 6 pages, 4 figure
Shannon dimensionality of quantum channels and its application to photon entanglement
We introduce the concept of Shannon dimensionality D as a new way to quantify
bipartite entanglement as measured in an experiment. This is applied to
orbital-angular-momentum entanglement of two photons, using two state analyzers
composed of a rotatable angular-sector phase plate that is lens-coupled to a
single-mode fiber. We can deduce the value of D directly from the observed
two-photon coincidence fringe. In our experiment, D varies between 2 and 6,
depending on the experimental conditions. We predict how the Shannon
dimensionality evolves when the number of angular sectors imprinted in the
phase plate is increased and anticipate that D = 50 is experimentally within
reach.Comment: 4 pages, 3 figures, accepted for Physical Review Letter
The dual-acting chemotherapeutic agent Alchemix induces cell death independently of ATM and p53
YesTopoisomerase inhibitors are in common use as chemotherapeutic agents although they can display reduced efficacy in chemotherapy-resistant tumours, which have inactivated DNA damage response (DDR) genes, such as ATM and TP53. Here, we characterise the cellular response to the dual-acting agent, Alchemix (ALX), which is a modified anthraquinone that functions as a topoisomerase inhibitor as well as an alkylating agent. We show that ALX induces a robust DDR at nano-molar concentrations and this is mediated primarily through ATR- and DNA-PK- but not ATM-dependent pathways, despite DNA double strand breaks being generated after prolonged exposure to the drug. Interestingly, exposure of epithelial tumour cell lines to ALX in vitro resulted in potent activation of the G2/M checkpoint, which after a prolonged arrest, was bypassed allowing cells to progress into mitosis where they ultimately died by mitotic catastrophe. We also observed effective killing of lymphoid tumour cell lines in vitro following exposure to ALX, although, in contrast, this tended to occur via activation of a p53-independent apoptotic pathway. Lastly, we validate the effectiveness of ALX as a chemotherapeutic agent in vivo by demonstrating its ability to cause a significant reduction in tumour cell growth, irrespective of TP53 status, using a mouse leukaemia xenograft model. Taken together, these data demonstrate that ALX, through its dual action as an alkylating agent and topoisomerase inhibitor, represents a novel anti-cancer agent that could be potentially used clinically to treat refractory or relapsed tumours, particularly those harbouring mutations in DDR genes
Onderzoek naar storing op kabeltelevisie door mobiel gebruik in het Digitaal Dividend
De introductie van het gebruik van mobiele toepassingen in de 800 MHz band, die onderdeel vormt van het zogenaamde digitaal dividend, leidt onder bepaalde omstandigheden tot een verstoring van tv-signalen. De nieuwe (LTE) mobiele toepassingen gebruiken frequenties die ook worden toegepast in kabel-tv-netwerken. Dit rapport gaat in op de mate waarin deze storing kan plaatsvinden in het (digitale) televisie aanbod van de kabel.\u
The dual-acting chemotherapeutic agent Alchemix induces cell death independently of ATM and p53
YesTopoisomerase inhibitors are in common use as chemotherapeutic agents although they can display reduced efficacy in chemotherapy-resistant tumours, which have inactivated DNA damage response (DDR) genes, such as ATM and TP53. Here, we characterise the cellular response to the dual-acting agent, Alchemix (ALX), which is a modified anthraquinone that functions as a topoisomerase inhibitor as well as an alkylating agent. We show that ALX induces a robust DDR at nano-molar concentrations and this is mediated primarily through ATR- and DNA-PK- but not ATM-dependent pathways, despite DNA double strand breaks being generated after prolonged exposure to the drug. Interestingly, exposure of epithelial tumour cell lines to ALX in vitro resulted in potent activation of the G2/M checkpoint, which after a prolonged arrest, was bypassed allowing cells to progress into mitosis where they ultimately died by mitotic catastrophe. We also observed effective killing of lymphoid tumour cell lines in vitro following exposure to ALX, although, in contrast, this tended to occur via activation of a p53-independent apoptotic pathway. Lastly, we validate the effectiveness of ALX as a chemotherapeutic agent in vivo by demonstrating its ability to cause a significant reduction in tumour cell growth, irrespective of TP53 status, using a mouse leukaemia xenograft model. Taken together, these data demonstrate that ALX, through its dual action as an alkylating agent and topoisomerase inhibitor, represents a novel anti-cancer agent that could be potentially used clinically to treat refractory or relapsed tumours, particularly those harbouring mutations in DDR genes
Metamaterial Polarization Converter Analysis: Limits of Performance
In this paper we analyze the theoretical limits of a metamaterial converter
that allows for linear-to- elliptical polarization transformation with any
desired ellipticity and ellipse orientation. We employ the transmission line
approach providing a needed level of the design generalization. Our analysis
reveals that the maximal conversion efficiency for transmission through a
single metamaterial layer is 50%, while the realistic re ection configuration
can give the conversion efficiency up to 90%. We show that a double layer
transmission converter and a single layer with a ground plane can have 100%
polarization conversion efficiency. We tested our conclusions numerically
reaching the designated limits of efficiency using a simple metamaterial
design. Our general analysis provides useful guidelines for the metamaterial
polarization converter design for virtually any frequency range of the
electromagnetic waves.Comment: 10 pages, 11 figures, 2 table
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