A large-scale continuous detonation combustor (CDC) has been designed, fabricated and tested to study the effect of different design elements on the operation process and CDC propulsion performance. ...It has been shown experimentally that widening of the air-inlet slit in the annular combustion chamber from 2 to 15 mm leads to a decrease in the number of detonation waves (DWs) simultaneously circulating in the combustor from four to one and, finally, to transition to the operation mode with intermittent (pulse) longitudinal reaction waves resembling pulse detonations. The number of DWs and the thrust produced by the CDC can be increased by installing a shaped obstacle at the CDC exit nozzle providing the blockage of the combustor cross section. The maximum net thrust produced by the CDC attained 6 kN at the total mass flow rate of fuel components of 7.5 kg/s, whereas the maximum fuel-based specific impulse attained ∼3000 s.
•We conduct experiments in a large-scale continuous-detonation combustor operating on hydrogen–air mixture.•We vary a size of air-inlet slit to observe changes in operation process and propulsion performance.•Widening of slit from 2 to 15 mm leads to decrease in a number of rotating detonation waves and to detonation failure.•Maximum fuel-based specific impulse obtained in experiments is 3000 s.
Time-Resolved Holography with Photoelectrons Huismans, Y; Rouzée, A; Gijsbertsen, A ...
Science (American Association for the Advancement of Science),
01/2011, Letnik:
331, Številka:
6013
Journal Article
Recenzirano
Odprti dostop
Ionization is the dominant response of atoms and molecules to intense laser fields and is at the basis of several important techniques, such as the generation of attosecond pulses that allow the ...measurement of electron motion in real time. We present experiments in which metastable xenon atoms were ionized with intense 7-micrometer laser pulses from a free-electron laser. Holographic structures were observed that record underlying electron dynamics on a sublaser-cycle time scale, enabling photoelectron spectroscopy with a time resolution of almost two orders of magnitude higher than the duration of the ionizing pulse.
The transverse voltage generated by a temperature gradient in a perpendicularly applied magnetic field, termed the Nernst effect, has promise for thermoelectric applications and for probing ...electronic structure. In magnetic materials, an anomalous Nernst effect (ANE) is possible in a zero magnetic field. We report a colossal ANE in the ferromagnetic metal UCo
Ru
Al, reaching 23 microvolts per kelvin. Uranium's 5
electrons provide strong electronic correlations that lead to narrow bands, a known route to producing a large thermoelectric response. In addition, uranium's strong spin-orbit coupling produces an intrinsic transverse response in this material due to the Berry curvature associated with the relativistic electronic structure. Theoretical calculations show that in UCo
Ru
Al at least 148 Weyl nodes, and two nodal lines, exist within 60 millielectron volt of the Fermi level. This work demonstrates that magnetic actinide materials can host strong Nernst and Hall responses due to their combined correlated and topological nature.
Multimodal nonlinear microscopy combining third-harmonic generation (THG) with two- and three-photon-excited fluorescence (2PEF and 3PEF) is shown to provide a powerful resource for high-fidelity ...imaging of nucleoli and nucleolar proteins. We demonstrate that, with a suitably tailored genetically encoded fluorescent stain, the 2PEF/3PEF readout from specific nucleolar proteins can be reliably detected against the extranucleolar 2PEF/3PEF signal, enabling high-contrast imaging of the key nucleolar ribosome biogenesis components, such as fibrillarin. THG is shown to provide a versatile readout for unstained nucleolus imaging in a vast class of biological systems as different as neurons in brain slices and cultured HeLa cells.
The present review is focused on the main transformation routes of sp
2
- and sp
3
-hybridized carbanions derived from the compounds containing two or more fused N,O,S-heterocycles. The rearrangement ...and fragmentation reactions and their applications in the synthesis of poorly available organic compounds are discussed. In the review, separate consideration is given to the reactions leading to a decrease, retention, and increase in the number of annulated heterocycles.
Electrons in two-dimensional hexagonal materials have an extra degree of freedom, the valley pseudospin, that can be used to encode and process quantum information. Valley-selective excitations, ...governed by the circularly polarized light resonant with the material’s bandgap, are the foundation of valleytronics. It is often assumed that achieving valley selective excitation in pristine graphene with all-optical means is not possible due to the inversion symmetry of the system. Here, we demonstrate that both valley-selective excitation and valley-selective high-harmonic generation can be achieved in pristine graphene by using a combination of two counter-rotating circularly polarized fields, the fundamental and its second harmonic. Controlling the relative phase between the two colors allows us to select the valleys where the electron–hole pairs and higher-order harmonics are generated. We also describe an all-optical method for measuring valley polarization in graphene with a weak probe pulse. This work offers a robust recipe to write and read valley-selective electron excitations in materials with zero bandgap and zero Berry curvature.
Sediment samples from 53 stations of the southwestern Chukchi sea were investigated to the spatial distributions and assess the state of trace metals contamination using ecological indices. The mean ...concentrations (mg kg−1) in sediments were: Cr (70.5), Ni (41.0), Cu (16.5), Zn (82.7), As (15.90), Cd (0.27), Pb (15.96), Hg (32.0 μg kg−1). The spatial distribution pattern of trace metals was similar with maximum values in the northern of the Chukchi Sea in the outer shelf sediments, while the high values of Cd were noted at stations located in the southern part of the sea where a strong influence of the Pacific waters penetrating through the Bering Strait. The ecological indices indicated no signs of anthropogenic pollution in the study sediments of the Chukchi Sea. Received data are of value for detecting and tracking future chemical changes in the sediments of the Chukchi sea, particularly in light of environmental changes.
•Trace metals were examined in sediments from the southwestern Chukchi sea.•Baseline data for the surface sediments of the Chukchi Sea•Geochemical data highlight enrichments in Cd in in the southern part of the sea.•All trace metals showed a low ecological risk index.
Background
Cognitive impairment is an irreversible, aging-associated condition that robs people of their independence. The purpose of this study was to investigate possible causes of this condition ...and propose preventive options.
Methods
We assessed cognitive status in long-living adults aged 90+ (
n
= 2,559) and performed a genome wide association study using two sets of variables: Mini-Mental State Examination scores as a continuous variable (linear regression) and cognitive status as a binary variable (> 24, no cognitive impairment; <10, impairment) (logistic regression).
Results
Both variations yielded the same polymorphisms, including a well-known marker of dementia, rs429358in the APOE gene. Molecular dynamics simulations showed that this polymorphism leads to changes in the structure of alpha helices and the mobility of the lipid-binding domain in the APOE protein.
Conclusion
These changes, along with higher LDL and total cholesterol levels, could be the mechanism underlying the development of cognitive impairment in older adults. However, this polymorphism is not the only determining factor in cognitive impairment. The polygenic risk score model included 45 polymorphisms (ROC AUC 69%), further confirming the multifactorial nature of this condition. Our findings, particularly the results of PRS modeling, could contribute to the development of early detection strategies for predisposition to cognitive impairment in older adults.
3-
tert
-Butyl-8-nitro-7-R-pyrazolo5,1-
c
1,2,4triazin-4(6
H
)-ones (R = H, Cl, Br, NO
2
, N
3
) were prepared by nitration with HNO
3
/H
2
SO
4
of the corresponding 7-R-substituted 8-carboxylic ...acids or their analogs with a vacant C
8
position. The latter were synthesized by diazotization of 7-amino-3-
tert
-butyl-4-oxo-4,6-dihydropyrazolo5,1-
c
1,2,4triazin-8-carboxylic acid. The electrophilic halogenation and cycloaddition of the 7-azido and 7-nitro derivatives of the synthesized compounds were considered. The structures of the products were confirmed by IR, heteronuclear NMR spectroscopy, HRMS, and single-crystal XRD.
This article uses Deep Learning technologies to safeguard DNA sequencing against Bio-Cyber attacks. We consider a hybrid attack scenario where the payload is encoded into a DNA sequence to activate a ...Trojan malware implanted in a software tool used in the sequencing pipeline in order to allow the perpetrators to gain control over the resources used in that pipeline during sequence analysis. The scenario considered in the paper is based on perpetrators submitting synthetically engineered DNA samples that contain digitally encoded IP address and port number of the perpetrator's machine in the DNA. Genetic analysis of the sample's DNA will decode the address that is used by the software Trojan malware to activate and trigger a remote connection. This approach can open up to multiple perpetrators to create connections to hijack the DNA sequencing pipeline. As a way of hiding the data, the perpetrators can avoid detection by encoding the address to maximise similarity with genuine DNAs, which we showed previously. However, in this paper we show how Deep Learning can be used to successfully detect and identify the trigger encoded data, in order to protect a DNA sequencing pipeline from Trojan attacks. The result shows nearly up to 100% accuracy in detection in such a novel Trojan attack scenario even after applying fragmentation encryption and steganography on the encoded trigger data. In addition, feasibility of designing and synthesizing encoded DNA for such Trojan payloads is validated by a wet lab experiment.
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