Antiparticles account for a small fraction of cosmic rays and are known to be produced in interactions between cosmic-ray nuclei and atoms in the interstellar medium, which is referred to as a ...'secondary source'. Positrons might also originate in objects such as pulsars and microquasars or through dark matter annihilation, which would be 'primary sources'. Previous statistically limited measurements of the ratio of positron and electron fluxes have been interpreted as evidence for a primary source for the positrons, as has an increase in the total electron+positron flux at energies between 300 and 600 GeV (ref. 8). Here we report a measurement of the positron fraction in the energy range 1.5-100 GeV. We find that the positron fraction increases sharply over much of that range, in a way that appears to be completely inconsistent with secondary sources. We therefore conclude that a primary source, be it an astrophysical object or dark matter annihilation, is necessary.
A new measurement of the cosmic-ray antiproton-to-proton flux ratio between 1 and 100 GeV is presented. The results were obtained with the PAMELA experiment, which was launched into low-Earth orbit ...on-board the Resurs-DK1 satellite on June 15th 2006. During 500 days of data collection a total of about 1000 antiprotons have been identified, including 100 above an energy of 20 GeV. The high-energy results are a tenfold improvement in statistics with respect to all previously published data. The data follow the trend expected from secondary production calculations and significantly constrain contributions from exotic sources, e.g., dark matter particle annihilations.
The paper presents some processing and interpretation results of the very-high-resolution seismic data, acquired during the
RV
Academic Mstislav Keldysh cruise to Bennett island in the Russian ...Arctic. The purpose of investigations was to study underwater geological structures around the island, presence or absence of their connection to the ancient rocks on the surface of the island. Interpretation of the seismic data gives some clues to these questions.
•The possibility of forming PVDF+20% Al2O3 composites by explosive pressing is shown.•The dependence of the structure and properties of PVDF on the pressure applied during EP was studied.•The ...dependence of the structure and properties of PVDF+20% Al2O3 composites on the pressure during EP was studied.•Partial destruction and interaction of the composite components at pressure 3 GPa is revealed.
The possibility of forming PVDF composites with 20% Al2O3 content by explosive pressing in a cylindrical ampoule is shown. It has been established that a change in pressure when using this pressing method leads to the implementation of various compaction mechanisms for PVDF and its composites. A change in pressure affects almost all characteristics of the polymer and the composites being formed, up to their partial destruction.
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In order to develop methods for space weather forecasting, the dynamics of galactic cosmic ray fluctuations during the events of intense geomagnetic storms in February and March 2023 are studied. To ...study the properties of galactic cosmic ray fluctuations in the frequency range
Hz spectral analysis is used. It is shown that the maximum values of the coherence coefficient can serve for the purposes of forecasting intense geomagnetic storms. The obtained results are in good agreement with the physical picture of the occurrence of cosmic ray fluctuations that we have previously constructed.
The authors describe a compact analog-to-digital converter for high-resolution seismoacoustic studies and provide its technical characteristics. The converter has a capacity of 24 bits and 16 ...channels with the possibility of increasing their number by combining converters into a network. A local Ethernet network is used to exchange data with the control computer, which provides high speed (100 Mbit/s) and interface versatility. Distributed data acquisition systems based on the transducer can be used in surface, borehole, or marine seismic acoustics, as well as in hydroacoustics.
We present the space spectrometer PAMELA observations of proton and helium fluxes during the 2006 December 13 and 14 solar particle events. This is the first direct measurement of the solar energetic ...particles in space with a single instrument in the energy range from ~80 MeV n--1 up to ~3 GeV n--1. For the December 13 event, measured energy spectra of solar protons and helium are compared with results obtained by neutron monitors and other detectors. Our measurements show a spectral behavior different from those derived from the neutron monitor network. No satisfactory analytical fitting was found for the energy spectra. During the first hours of the December 13 event, solar energetic particles spectra were close to the exponential form, demonstrating rather significant temporal evolution. Solar He with energy up to 1 GeV n--1 was recorded on December 13. For the December 14 event, energy of solar protons reached 600 MeV, whereas the maximum energy of He was below 100 MeV n--1. The spectra were slightly bent in the lower energy range and preserved their form during the second event. Differences in the particle flux appearance and temporal evolution of these two events may argue for special conditions leading to the acceleration of solar particles up to relativistic energies.
Antimicrobial properties are traditionally evaluated by the seeding technique, which is laborious, time-consuming, and rather imprecise. We studied the possibility of using microscopy and ...spectrophotometry methods for evaluation of cytotoxic activity of breast milk serum against opportunistic microbes. Activity of 50 breast milk samples obtained from healthy women at different lactation stages was tested against opportunistic yeast
C. albicans
. Microscopy showed that incubation of cell suspension with lactoserum led to destruction of cell walls and cytoplasmic membranes with the formation of vesicular debris that absorbed the dye from the medium. Spectrophotometric measurement of the dye remained in the medium revealed a dose-depended effect of the lactoserum on
C. albicans
cells and strong inverse correlation between the lactation period and cytotoxic activity of the lactoserum (
r
=-0.948). These methods can be used in veterinary and food processing for estimation of biological activity of milk.
A study of MHD waves in solar wind plasma during two geoeffective space weather events in February–March 2023 is reported. At that time, various geophysical phenomena were observed on Earth: intense ...magnetic storms, decreases in the intensity of galactic cosmic rays, auroras, and a number of other manifestations of space weather. To study the situation in near-Earth outer space, we used data from direct measurements of the parameters of the interplanetary medium with the
DSCOVR
and
ACE
spacecraft. The application of spectral analysis methods to the data of direct measurements of the solar wind parameters onboard the
DSCOVR
spacecraft made it possible to study the characteristics and dynamics of Alfén, fast, and slow magnetosonic waves in the inertial frequency range (from ∼0.0001 to ∼0.01 Hz) of the observed solar wind turbulence spectrum during these events.
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