435 research outputs found
Prospects for direct cosmic ray mass measurements through the Gerasimova-Zatsepin effect
The Solar radiation field may break apart ultra high energy cosmic nuclei,
after which both remnants will be deflected in the interplanetary magnetic
field in different ways. This process is known as the Gerasimova-Zatsepin
effect after its discoverers. We investigate the possibility of using the
detection of the separated air showers produced by a pair of remnant particles
as a way to identify the species of the original cosmic ray primary directly.
Event rates for current and proposed detectors are estimated, and requirements
are defined for ideal detectors of this phenomenon. Detailed computational
models of the disintegration and deflection processes for a wide range of
cosmic ray primaries in the energy range of 10^16 to 10^20 eV are combined with
sophisticated detector models to calculate realistic detection rates. The
fraction of Gerasimova-Zatsepin events is found to be of the order of 10^-5 of
the cosmic ray flux, implying an intrinsic event rate of around 0.07 km^-2
sr^-1 yr^-1 in the energy range defined. Event rates in any real experiment,
however, existing or under construction, will probably not exceed 10^-2 yr^-1.Comment: 4 pages, 4 figure
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COVID-19 and Other Challenges: A Case Study of Certified Organic Green Tea Producers in China
Funder: Renmin University of China; FundRef: https://doi.org/10.13039/501100004260 This article explores how the western concept of “organic agriculture” has been applied in the traditional Chinese tea industry and how it has been tested during the COVID-19 pandemic. Using in-depth interviews and observations made during 2017–2020, we analyzed different meanings of organic agriculture and values that were given by Chinese farmers who are certified organic producers. Although organic agriculture, particular certified by international certification standards, is a foreign concept, producers invested efforts that go beyond the commercial pursuit for profit. Most importantly, the combination of the reiterated cultural meaning and health benefits of the certified organic tea with the visionary strategy has allowed these producers to shift in a timely manner from export to domestic markets and adapt to the pandemic’s barriers presented to the global trade. </jats:p
Dynamics of a ring of three unidirectionally coupled Duffing oscillators with time-dependent damping
We study dynamics of a ring of three unidirectionally coupled double-well
Duffing oscillators for three different values of the damping coefficient:
fixed dumping, proportional to time, and inversely proportional to time. The
dynamics in all cases is analyzed through time series, Fourier and Hilbert
transforms, Poincar\'e sections, as well as bifurcation diagrams and Lyapunov
exponents with respect to the coupling strength. In the first case, we observe
a well-known route from a stable steady state to hyperchaos through Hopf
bifurcation and a series of torus bifurcations, as the coupling strength is
increased. In the second case, the system is highly dissipative and converges
into one of stable equilibria. Finally, in the third case, transient toroidal
hyperchaos takes place
Hanbury Brown and Twiss interferometry at a free-electron laser
We present measurements of second- and higher-order intensity correlation
functions (so-called Hanbury Brown and Twiss experiment) performed at the
free-electron laser (FEL) FLASH in the non-linear regime of its operation. We
demonstrate the high transverse coherence properties of the FEL beam with a
degree of transverse coherence of about 80% and degeneracy parameter of the
order 10^9 that makes it similar to laser sources. Intensity correlation
measurements in spatial and frequency domain gave an estimate of the FEL
average pulse duration of 50 fs. Our measurements of the higher-order
correlation functions indicate that FEL radiation obeys Gaussian statistics,
which is characteristic to chaotic sources.Comment: 19 pages, 6 figures, 1 table, 40 reference
Mechanisms of hydrogen sulfide (H<inf>2</inf>S) action on synaptic transmission at the mouse neuromuscular junction
© 2015 IBRO. Hydrogen sulfide (H2S) is a widespread gasotransmitter also known as a powerful neuroprotective agent in the central nervous system. However, the action of H2S in peripheral synapses is much less studied. In the current project we studied the modulatory effects of the H2S donor sodium hydrosulfide (NaHS) on synaptic transmission in the mouse neuromuscular junction using microelectrode technique. Using focal recordings of presynaptic response and evoked transmitter release we have shown that NaHS (300μM) increased evoked end-plate currents (EPCs) without changes of presynaptic waveforms which indicated the absence of NaHS effects on sodium and potassium currents of motor nerve endings. Using intracellular recordings it was shown that NaHS increased the frequency of miniature end-plate potentials (MEPPs) without changing their amplitudes indicating a pure presynaptic effect. Furthermore, NaHS increased the amplitude of end-plate potentials (EPPs) without influencing the resting membrane potential of muscle fibers. l-cysteine, a substrate of H2S synthesis induced, similar to NaHS, an increase of EPC amplitudes whereas inhibitors of H2S synthesis (β-cyano-l-alanine and aminooxyacetic acid) had the opposite effect. Inhibition of adenylate cyclase using MDL 12,330A hydrochloride (MDL 12,330A) or elevation of cAMP level with 8-(4-chlorophenylthio)-adenosine 3′,5′-cyclic monophosphate (pCPT-cAMP) completely prevented the facilitatory action of NaHS indicating involvement of the cAMP signaling cascade. The facilitatory effect of NaHS was significantly diminished when intracellular calcium (Ca2+) was buffered by 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid tetrakis acetoxymethyl ester (BAPTA-AM) and ethylene glycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid acetoxymethyl ester (EGTA-AM). Activation of ryanodine receptors by caffeine or ryanodine increased acetylcholine release and prevented further action of NaHS on transmitter release, likely due to an occlusion effect. Inhibition of ryanodine receptors by ryanodine or dantrolene also reduced the action of NaHS on EPC amplitudes. Our results indicate that in mammalian neuromuscular synapses endogenously produced H2S increases spontaneously and evoked quantal transmitter release from motor nerve endings without changing the response of nerve endings. The presynaptic effect of H2S appears mediated by intracellular Ca2+ and cAMP signaling and involves presynaptic ryanodine receptors
Cytokine Level Changes in Schizophrenia Patients with and without Metabolic Syndrome Treated with Atypical Antipsychotics
The present study aims at comparing the change in cytokine levels in schizophrenia patients treated with atypical antipsychotics, with or without metabolic syndrome (MetS). The study included 101 patients with schizophrenia, 38 with and 63 without MetS, who received risperidone, quetiapine, olanzapine or aripiprazole for six weeks. We analyzed the concentration of 21 cytokines in the serum patients. The treatment with atypical antipsychotics changed some proinflammatory cytokine levels. It led to increased IFN-alpha 2 (p = 0.010), IL-1 alpha (p = 0.024) and IL-7 (p = 0.017) levels in patients with MetS, whereas the same treatment led to decreased levels of IFN-gamma (p = 0.011), IL-1 beta (p = 0.035), IL-12p40 (p = 0.011), IL-17A (p = 0.031), IL-6 (p = 0.043) and TNF-alpha (p = 0.012) in individuals without MetS. Our results demonstrated the effects of atypical antipsychotics on the immune-inflammatory parameters, depending on the metabolic disturbances in schizophrenia patients
Optimal Radio Window for the Detection of Ultra-High-Energy Cosmic Rays and Neutrinos off the Moon
When high-energy cosmic rays impinge on a dense dielectric medium, radio
waves are produced through the Askaryan effect. We show that at wavelengths
comparable to the length of the shower produced by an Ultra-High Energy cosmic
ray or neutrino, radio signals are an extremely efficient way to detect these
particles. Through an example it is shown that this new approach offers, for
the first time, the realistic possibility of measuring UHE neutrino fluxes
below the Waxman-Bahcall limit. It is shown that in only one month of observing
with the upcoming LOFAR radio telescope, cosmic-ray events can be measured
beyond the GZK-limit, at a sensitivity level of two orders of magnitude below
the extrapolated values.Comment: Submitted to Astroparticle Physic
Holographic recording in a photopolymer by optically induced detachment of chromophores
We demonstrate holographic recording in a new photopolymer system. The recording material is created by copolymerization of an optically inert monomer, methyl methacrylate, and a second monomer that is optically sensitive. On exposure of the recording material to light, a portion of the optically sensitive component detaches from the polymer matrix and causes hologram amplification through diffusion of the free molecules. We measured postrecording grating amplifications as high as 170% by this process. The recorded holograms are persistent at room temperature under continuous illumination at the recording wavelength
Transformation of the reproduction of human capital in the context of the digital economy
The goal of the article is to study transformation processes and to identify the main characteristics of the reproduction of human capital in the context of digital and technological transformatio
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