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"Antonov, A."
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Space race archaeologies : photographs, biographies, and design
As the byproduct of the Cold War, the space race produced a considerable number of objects disseminated in networks, not only in the East and West but also in the Global South ? rockets, launching pads, satellite tracking stations, astronomical observatories, and several other pieces of design, machineries, and infrastructures. As they stand today, these objects are remnants of a modernity tied to secrecy, war deterrence, and mass media associated to outer space politics. By bringing together the work of architect Philipp Meuser, photographer Petr Antonov, designer Hugo Palmarola, and historian of science Asif Siddiqi, this book comes from a conference held at the Princeton University School of Architecture in March 2016 on technology and the Cold War, contesting the historiographical status of these objects in order to give value to the manner in which they came to construct current modes of subjectivity and social relations.
Book
Too little, too late, and in the wrong place: Alpha band activity does not reflect an active mechanism of selective attention
Selective attention focuses visual processing on relevant stimuli in order to allow for adaptive behaviour despite an abundance of distracting information. It has been proposed that increases in alpha band (8–12 Hz) amplitude reflect an active mechanism for distractor suppression. If this were the case, increases in alpha band amplitude should be succeeded by a decrease in distractor processing. Surprisingly, this connection has not been tested directly; specifically, studies that have investigated changes in alpha band after attention-directing cues have not directly assessed the neuronal processing of distractors. We concurrently recorded alpha activity and steady-state visual evoked potentials (SSVEPs) to assess the processing of target and distractor stimuli. In two experiments, participants covertly shifted attention to one of two letter streams (left or right) to detect infrequent target letters ‘X’ while ignoring the other stream. In line with previous findings, alpha band amplitudes contralateral to the unattended location increased compared to a pre-cue baseline. However, there was no suppression of SSVEP amplitudes elicited by unattended stimuli, while there was a pronounced enhancement of SSVEPs elicited by attended stimuli. Furthermore, and crucially, changes in alpha band amplitude during attention shifts did not precede those in SSVEPs and hit rates in both experiments, indicating that changes in alpha band amplitudes are likely to be a consequence of attention shifts rather than the other way around. We conclude that these findings contradict the notion that alpha band activity reflects mechanisms that have a causal role in the allocation of selective attention.
•Alpha brain waves supposedly represent an active mechanism of selective attention.•Tested via EEG recordings of steady-state visual evoked potentials and alpha waves.•Alpha-enhancement did not lead to the suppression of distractor stimulus processing.•Stimulus processing and task performance changes were not preceded by alpha changes.•Selective attention shifts might lead to changes in alpha, not vice-versa.
Journal Article
Unlocking the out-of-plane dimension for photonic bound states in the continuum to achieve maximum optical chirality
The realization of lossless metasurfaces with true chirality crucially requires the fabrication of three-dimensional structures, constraining experimental feasibility and hampering practical implementations. Even though the three-dimensional assembly of metallic nanostructures has been demonstrated previously, the resulting plasmonic resonances suffer from high intrinsic and radiative losses. The concept of photonic bound states in the continuum (BICs) is instrumental for tailoring radiative losses in diverse geometries, especially when implemented using lossless dielectrics, but applications have so far been limited to planar structures. Here, we introduce a novel nanofabrication approach to unlock the height of individual resonators within all-dielectric metasurfaces as an accessible parameter for the efficient control of resonance features and nanophotonic functionalities. In particular, we realize out-of-plane symmetry breaking in quasi-BIC metasurfaces and leverage this design degree of freedom to demonstrate an optical all-dielectric quasi-BIC metasurface with maximum intrinsic chirality that responds selectively to light of a particular circular polarization depending on the structural handedness. Our experimental results not only open a new paradigm for all-dielectric BICs and chiral nanophotonics, but also promise advances in the realization of efficient generation of optical angular momentum, holographic metasurfaces, and parity-time symmetry-broken optical systems.
We unlock the height as accessible parameter of all-dielectric metasurfaces, allowing polarization-selective interaction of their high-Q eigenstates with light of different helicity and promoting ultra-narrow maximally chiral optical resonances.
Journal Article
Superconducting phase transitions in disordered NbTiN films
Suppression of superconductivity in disordered systems is a fundamental problem of condensed matter physics. Here we investigate superconducting niobium-titanium-nitride (Nb
1−
x
Ti
x
N) thin films grown by the atomic layer deposition (ALD) with slightly different growth process parameters. We observe a smooth crossover from the disorder-driven superconductor-normal metal transition (SMT) to the superconductor-insulator transition (SIT) via the intermediate Bose metal state detected by the low-temperature saturation of the temperature dependence of the sheet resistance. We demonstrate that the SIT via the intervening Bose metal state occurs if the sheet resistance of the film in the maximum,
R
max
prior to the superconducting drop of
R
(
T
), exceeds
R
q
=
h
/4
e
2
.
Journal Article
A Mass Analyzer Based on a Magnetic Mirror
An ion optical analysis of a static mass analyzer, based on a second-order focusing magnetic mirror, was conducted while accounting for aberrations caused by the movement of ions outside the mean plane of the mass analyzer. As part of this study, an optimization algorithm was developed for the four-dimensional acceptance of the mass analyzer at a fixed resolution, formulated within the framework of the inverse problem.
Journal Article
Edge Matrices of Magnetic Sector in a Static Mass Spectrometer
The first-order input and output edge transfer matrix elements of the magnetic sector in a static mass spectrometer are derived based on the conservation law of the generalized momentum of ions in a magnetic field. The structure of the edge matrix is shown to be ambiguous and dependent on the effective model, which considers the displacement of ion trajectories in the edge field. A comparison of the results obtained with traditional methods, such as expanding the edge field components and trajectory equations into asymptotic series and integrating successive approximations, reveals significant differences in the first-order edge matrix elements in the effective model of the magnetic sector, where the ideal uniform field is bounded by Herzog boundaries, compared to the published data. Algorithms for matching the input and output axes of the magnetic sector, taking into account the action of the edge fields, are given.
Journal Article
p73 regulates serine biosynthesis in cancer
Activation of serine biosynthesis supports growth and proliferation of cancer cells. Human cancers often exhibit overexpression of phosphoglycerate dehydrogenase (PHGDH), the metabolic enzyme that catalyses the reaction that diverts serine biosynthesis from the glycolytic pathway. By refueling serine biosynthetic pathways, cancer cells sustain their metabolic requirements, promoting macromolecule synthesis, anaplerotic flux and ATP. Serine biosynthesis intersects glutaminolysis and together with this pathway provides substrates for production of antioxidant GSH. In human lung adenocarcinomas we identified a correlation between serine biosynthetic pathway and p73 expression. Metabolic profiling of human cancer cell line revealed that TAp73 activates serine biosynthesis, resulting in increased intracellular levels of serine and glycine, associated to accumulation of glutamate, tricarboxylic acid (TCA) anaplerotic intermediates and GSH. However, at molecular level p73 does not directly regulate serine metabolic enzymes, but transcriptionally controls a key enzyme of glutaminolysis, glutaminase-2 (GLS-2). p73, through GLS-2, favors conversion of glutamine in glutamate, which in turn drives the serine biosynthetic pathway. Serine and glutamate can be then employed for GSH synthesis, thus the p73-dependent metabolic switch enables potential response against oxidative stress. In knockdown experiment, indeed, TAp73 depletion completely abrogates cancer cell proliferation capacity in serine/glycine-deprivation, supporting the role of p73 to help cancer cells under metabolic stress. These findings implicate p73 in regulation of cancer metabolism and suggest that TAp73 influences glutamine and serine metabolism, affecting GSH synthesis and determining cancer pathogenesis.
Journal Article
Acoustically induced transparency for synchrotron hard x-ray photons
The induced transparency of opaque medium for resonant electromagnetic radiation is a powerful tool for manipulating the field-matter interaction. Various techniques to make different physical systems transparent for radiation from microwaves to x-rays were implemented. Most of them are based on the modification of the quantum-optical properties of the medium under the action of an external coherent electromagnetic field. Recently, an observation of acoustically induced transparency (AIT) of the
57
Fe absorber for resonant 14.4-keV photons from the radioactive
57
Co source was reported. About 150-fold suppression of the resonant absorption of photons due to collective acoustic oscillations of the nuclei was demonstrated. In this paper, we extend the AIT phenomenon to a novel phase-locked regime, when the transmitted photons are synchronized with the absorber vibration. We show that the advantages of synchrotron Mössbauer sources such as the deterministic periodic emission of radiation and controlled spectral-temporal characteristics of the emitted photons along with high-intensity photon flux in a tightly focused beam, make it possible to efficiently implement this regime, paving the way for the development of the acoustically controlled interface between hard x-ray photons and nuclear ensembles.
Journal Article
Human EHMT2/G9a activates p53 through methylation-independent mechanism
p53 is a critical tumor suppressor in humans. It functions mostly as a transcriptional factor and its activity is regulated by numerous post-translational modifications. Among different covalent modifications found on p53 the most controversial one is lysine methylation. We found that human G9a (hG9a) unlike its mouse orthologue (mG9a) potently stimulated p53 transcriptional activity. Both ectopic and endogenous hG9a augmented p53-dependent transcription of pro-apoptotic genes, including Bax and Puma, resulting in enhanced apoptosis and reduced colony formation. Significantly, shRNA-mediated knockdown of hG9a attenuated p53-dependent activation of Puma. On the molecular level, hG9a interacted with histone acetyltransferase, p300/CBP, resulting in increased histone acetylation at the promoter of Puma. The bioinformatics data substantiated our findings showing that positive correlation between G9a and p53 expression is associated with better survival of lung cancer patients. Collectively, this study demonstrates that depending on the cellular and organismal context, orthologous proteins may exert both overlapping and opposing functions. Furthermore, this finding has important ramifications on the use of G9a inhibitors in combination with genotoxic drugs to treat p53-positive tumors.
Journal Article
Identities Relating the Angular and Coordinate Components of Axial Aberration in the Fringing Field of the Magnetic Sector of Static Mass Analyzer
AbstractWe derived identities that relate the angular and coordinate elements of the 2nd order transfer matrix, which determine the axial aberration of static mass analyzers in the fringing field of the magnetic sector with an arbitrary entrance of ions. These identities can be used as criteria for the correct calculation of the axial aberration of the mass analyzer and its resolution.
Journal Article