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The magnetic and density models were constructed for the Earth's crust and upper mantle of the Taragai area located in the northeastern part of the Sutar Range (Lesser Khingan). The deep structure of the area is determined by the inclined crust–mantle high-density zone subsiding to the SSE at angle of ∼ 60°. In the Earth's crust, the area of the elevated density is related to the Proterozoic–Cambrian metamorphic rocks and mafic intrusions of the Birobidzhan complex. The magnetic features of the upper crust are mainly determined by horizons of hematite and magnetite–hematite ores in Vendian–Cambrian rocks. Joint analysis of the density section passing through the Taragai explosion pipe and magnetic petrology data suggest the presence of two magmatic paleochambers: at mantle depths of 40–70 km and at crustal depths of 12–25 km. Paleomagnetic data indicate that the gabbrodolerites of the Birobidzhan complex were formed within a latitude band of ±16°, which likely points to their Paleozoic age. [ABSTRACT FROM AUTHOR]

The paper presents the results of comprehensive (microprobe, paleomagnetic and magnetic) studies on peats from the Tyapka peat section (Russian Far East). Radiocarbon dating placed the start of peat formation at ∼11.7 ky B.P. The principle carriers of magnetization were found to be magnetite, to a lesser extent hematite and, possibly, greigite. The relative paleointensity values obtained through calculations are in good agreement with the literature data. Intervals with negative inclinations of the magnetization vector were identified in peats, which most likely correspond to geomagnetic excursions in the Holocene. The research constrained the duration of the geomagnetic excursions, as well as the geomagnetic field intensity behavior not typical for such variations. [ABSTRACT FROM AUTHOR]

The SimMechanics software module for three-dimensional simulation of multibody mechanical systems of the Simulink package, written in the MATLAB environment, can be used to assess the manipulation capabilities of positioning manipulators in working environments when interacting with elastic objects whose movement is partially constrained by contact with one or several objects. The present article discusses the design of a three-dimensional manipulator model as a block structure with feedback. The block structure of the model operates not via signals, but on the basis of mechanical forces arising within the mathematical model. The automation of massage therapy procedures is addressed as an operating environment for a manipulator. The object being manipulated is biological soft tissue. [ABSTRACT FROM AUTHOR]

When ultra-short unipolar pulses overlap in a resonant medium, the formation of a dynamic “microcavity”, i.e. a burst of the population difference, is feasible. This paper presents, first, the relations allowing to calculate the parameters of such a microcavity using the analytical solution of the equations for the density matrix of a two-level medium, and second, the dependence of the microcavities’ parameters on the pulse form using the numerical solution of Maxwell–Bloch equations. [ABSTRACT FROM AUTHOR]

A comparison of the generation efficiency of short pulses with coherent and standard passive (incoherent) mode locking with a saturable absorber is made on the basis of numerical simulations. The advantage of the coherent mode locking in comparison to the standard mode locking in lasers with a saturable absorber is shown. Coherent mode locking in two-section lasers is based on the coherent interaction of the radiation with the absorbing and amplifying media. It allows the generation of ultrashort laser pulses with a duration shorter than the polarisation relaxation time T2 of the absorbing and amplifying media. In conventional lasers with standard (incoherent) passive mode locking with a saturable absorber, the interaction of the laser pulses with the absorbing and amplifying media is incoherent and the duration of the generated pulses is always limited by the polarization relaxation time T2 of the absorber and amplifier. [ABSTRACT FROM AUTHOR]

This paper addresses the scientific and technical prospects and potential directions for the development of subterahertz astronomy in the Russian Federation. The concept of creating subterahertz instruments in the form of a universal compact antenna array for placement on the territory of the Russian Federation is proposed. It is possible to implement several space projects in the subterahertz range using such an antenna array, including a space interferometer and a telescope on the surface of the Moon. Ground-based compact antenna arrays will be able to act as a support for the very long baseline interferometer mode of the Millimetron observatory. [ABSTRACT FROM AUTHOR]

The validity issues of some approximations widely used to describe subcycle pulse propagation in various non-magnetic media are addressed. As the validity criteria we apply the fundamental electric area conservation rule, which directly follows from Maxwell's equations in the 1D case. The general relations are derived for the possible values of the electric area in different media. It is shown that several theoretical models do not in general comply with the electric area conservation rule, which implies their limited applicability to correctly describe the subcycle pulse interaction with media. Therefore, any results obtained using such models cannot be taken as scientifically valid and meaningful. [ABSTRACT FROM AUTHOR]

The results of petro- and paleomagnetic studies of phase-I gabbrodiorites from the Lower Amur Complex of the Zhuravlevka-Amur terrane (Poni massif, Poni-Mulinsky ore cluster) are presented. They were used to determine that during the formation of the Lower Amur intrusive complex (Cenomanian-Turonian) the Amur River zone was located approximately 10° north of its current position between the Central Sikhote-Alin fault in the east and the Priamursky fault in the west. It is shown that starting from the middle of the Cenomanian there were no latitudinal movements of the Amur River zone of the Zhuravlevka-Amur terrane relative to the Eurasian continent. However, a more than 20°-counterclockwise rotation of the zone relative to the continent was recorded, which is easily explained within the ball-bearing tectonic model under the impact of the Amur and Central Sikhote-Alin en echelon left-lateral strike-slip faults. The left-lateral strike-slip fault systems were likely to be the channels for mantle material supply during the formation of the largest Malmyzh porphyry copper deposit, which, along with the Poni-Mulinsky ore cluster, is part of the Lower Amur mineragenic zone. [ABSTRACT FROM AUTHOR]

The results of structural, petrogeochemical, petro- and paleomagnetic studies of Mesozoic rocks from the Nilan terrane, which from the north adjoin the Paleozoic rocks of the Paukan block (52.0° N, 135.6° E), are presented. Jurassic and Triassic (?) complexly dislocated deposits of terrane are found to be fragments of the Middle–Late Jurassic accretionary complex with different concentration of older oceanic rocks and the oceanic plate with completely destroyed stratigraphy. Basic and intermediate volcanic rocks hosted within Jurassic and Triassic (?) sedimentary rocks of the terrane are of oceanic origin. Based on geochemical and paleomagnetic data, it is assumed that the volcanic rocks formed near the equator in geodynamic settings of the mid-ocean ridge and intraplate ocean islands. [ABSTRACT FROM AUTHOR]

In recent years, significant progress has been made in generating ultrashort electromagnetic pulses of single-cycle and subcycle duration. Unipolar pulses contain one half-cycle of the field and have a nonzero electric area. The conventional concepts of interaction of electromagnetic radiation with matter (in particular, interference) used in the case of multicycle pulses are not applicable to unipolar ones. This minireview discusses the latest results on the effects of extremely short low-amplitude pulses (when the perturbation theory is valid) on resonant media and individual quantum systems (atoms, molecules, and nanostructures) from the viewpoint of the recently introduced concept of "interference" of the areas of short light pulses (electric and envelope areas). We provide a simple relation showing that in order to compare the effects of multicycle bipolar and subcycle unipolar pulses on micro-objects, one should compare their areas, not energies. By numerically solving the Maxwell–Bloch equations, we study the features of area interference are studied beyond the limits of perturbation theory. It is shown that, after the collision of a pair of π-like ultrashort pulses, polarization structures and population difference gratings with nonharmonic multipeak structures are formed inside the medium. The possibility of experimentally determining the electric area of unipolar pulses through interference of their areas is discussed for the first time. [ABSTRACT FROM AUTHOR]

This paper presents the results of microprobe, paleomagnetic, and rock magnetic studies on peats from the Tyapka peat section (Khabarovsk krai) up to the turn of 4 ka BP. The alternating field demagnetization of peats yielded a horizon of 57–109 cm (1833–3083 cal. BP) with negative inclination values of the magnetization vector corresponding to the geomagnetic Etrussia excursion. The relative paleointensity estimates obtained for peats for the first time are consistent with the literature archeomagnetic data on the western part of Eurasia. According to the results of this study, the Etrussia excursion took place against the background of increased values of the Earth's magnetic field and lasted for ~1200 years. [ABSTRACT FROM AUTHOR]

Results of experiments on the observation of frequency locking by resonant transitions of cesium vapor, a cell with which was placed in the cavity of a titanium–sapphire laser, are reported. The radiation frequency of the titanium–sapphire laser was tuned near the DII absorption line of Cs at 852 nm. In this case, simultaneous generation on the absorption line in the coherent mode locking regime and generation at the frequency specified by the spectral selector were demonstrated. Passive losses of the laser cavity at the selector frequency were less than the losses at the frequency of the Cs absorption transition. This unusual result was discussed from the viewpoint of the effect of intracavity narrow-band absorption on the emission spectra of broadband lasers and the effect of spectrum condensation. [ABSTRACT FROM AUTHOR]

Photons have zero rest mass and always travel at the speed of light in a vacuum, but have no dipole moment. Atoms and molecules, which may have a constant or variable dipole moment, have mass and therefore cannot move at or above the speed of light. As a result, the radiation from such systems moving at the velocity of light was not considered. However, it is possible to create many artificial objects (light spots, effective charges, current pulses, etc.) that can travel at the speed of light and even exceed it. In this case, they become a source of electromagnetic radiation. In this work, the radiation of a solitary polarization pulse that travels at the speed of light and has a variable or constant amplitude is discussed. It is shown that if the amplitude does not change, then such an object does not radiate outward; i.e., the field emitted by it remains completely localized inside the moving polarization pulse. If the amplitude changes over time, then it begins to radiate backwards. In this case, unipolar pulses of an unusual shape, such as a rectangular one, can be obtained. [ABSTRACT FROM AUTHOR]

Using the solution of the time-dependent Schrödinger equation, the features of the excitation of a bound state of a particle in a one-dimensional rectangular quantum well of small depth by an extremely short light pulse are studied. The case of a shallow well with only one energy level is considered. In this case, the system is excited by an attosecond pulse whose duration is shorter than the characteristic time associated with the energy of the bound state of the particle in the well. It is shown that in this case the population of the bound state and the ionization probability are determined by the ratio of the electric area of the pulse to its atomic scale, which is inversely proportional to the well width. The calculation results showed that unipolar subcycle pulses with nonzero electric area can excite the system faster and more efficiently than bipolar pulses with zero area. The possibility of using unipolar gamma-ray pulses of zeptosecond duration for deuteron excitation is discussed, and numerical estimates of the required duration and electric area of the pulse are given. [ABSTRACT FROM AUTHOR]

A brief review of the authors' latest work in the field of extremely short electromagnetic pulses, including unipolar pulses, is presented. [ABSTRACT FROM AUTHOR]

Obtaining unipolar half-cycle optical pulses of femto- and attosecond duration with a large electrical area is an urgent but difficult task. The reason for the emerging difficulties lies in the existence of the rule of conservation of the electrical area of the pulse, which does not allow converting a bipolar pulse into a unipolar one. In this work, it is shown that in a resonant medium a few-cycle pulse can be converted into two unipolar pulses separated in time by a distance that is an order of magnitude or more longer than the duration of the initial pulse. This allows in a number of problems to consider such pulses separately as unipolar. The estimation of the electric area value relative to its "atomic scale" is carried out. [ABSTRACT FROM AUTHOR]

Using the numerical solution of the system of equations for the amplitudes of bound states, together with the wave equation, we theoretically consider stopped polarization pulse superradiance upon excitation by a pair of half-period attosecond pulses in a thin layer of a five-level resonant medium, the parameters of which are the same as in a hydrogen atom. It is shown that in the case of a multilevel medium, at certain parameters of the exciting field, the superradiance pulse near the medium is also a single-cycle pulse, the shape of which is determined by the first time derivative of the stopped polarization pulse, as in the case when approximate low-level and classical models were used to describe the response of the medium. [ABSTRACT FROM AUTHOR]

In the case of coherent interaction with a medium of extremely short light pulses (ESPs) having a carrier frequency and harmonic shape (when the pulse durations are shorter than the population relaxation times T1 and polarization relaxation time T2 of the medium), electromagnetically induced gratings (EMIGs) of the population difference, which have a pronounced harmonic dependence on the coordinates, may appear in it. These structures can occur when pulses do not overlap or overlap in the medium. Recently, the possibility of obtaining unipolar electromagnetic pulses in the optical and adjacent ranges of non-harmonic shape, for example, rectangular and triangular, with a duration less or comparable to the duration of the extremely-short pulse in this range, has attracted interest. In this work, using the numerical solution of the system of Maxwell–Bloch equations, we study EMIG formation by rectangular attosecond pulses in a two-level resonant medium. The possibility of inducing an EMIG of a non-harmonic shape in the form of light-induced channels microresonators (microcavities) with a size of the order of the wavelength of the resonant transition of the medium, whose parameters can be controlled, for example, by the amplitude of the incident pulses, is shown. It has been suggested that it is possible to create an EMIG of a predetermined non-harmonic shape only in the general case of using unipolar pulses. [ABSTRACT FROM AUTHOR]

A physical situation is proposed and theoretically analyzed, in which, in our opinion, it is possible to generate unipolar terahertz pulses with a large electric area. In this case, the gas in the tube is excited by a femtosecond IR laser pulse. In this case, the tube with gas is placed in a constant external electric field. The generation of a unipolar pulse is based on "three-step scheme"—ionization of gas atoms by a femtosecond pulse, subsequent acceleration of a free electron in a dc external field and subsequent annihilation of an electron upon collision with a tube wall or another atom (ion). [ABSTRACT FROM AUTHOR]

It is shown that not only multicycle resonant pulses with zero electric area, but also nonresonant unipolar pulses can be used to efficiently excite quantum transitions in a medium. Arguments are presented in favor of the advantages of unipolar pulses for excitation of quantum systems in comparison with resonant radiation. A simple relationship has been found showing that in order to compare the effects of unipolar half-cycle and resonant multicycle pulses on atomic systems. It shows that it is necessary to compare the electric area of a unipolar pulse and the area of the envelope of a bipolar pulse, rather than their energies. [ABSTRACT FROM AUTHOR]

With the coherent interaction of a sequence of extremely short light pulses with a resonant medium (when the duration of the pulses and the delays between them are shorter than the relaxation times of the population difference T1 and polarization T2 of the medium), it is possible to create spatial electromagnetically induced gratings (EMIG) of polarization and population difference in the medium, as well as their ultrafast control. The dynamics of such gratings is of interest in connection with the possibility of ultrafast control over the properties of a medium at times of the order of the pulse duration and their influence on the stability of generation of extremely short pulses in a laser with a short linear cavity. In this paper, based on the numerical solution of the system of Maxwell-Bloch equations, an unusual and interesting possibility of the appearance of narrow and alternating sections in the medium is shown and studied in detail, in which harmonic polarization waves of the medium are formed, propagating in opposite directions relative to neighboring sections. This situation occurs when two extremely short attosecond pulses collide in a two-level resonant medium. [ABSTRACT FROM AUTHOR]

In recent years, progress has been made in obtaining extremely short electromagnetic pulses up to single-cycle and unipolar half-cycle pulses. For pulses with such a dependence of the electric field strength on time, the behavior and properties of such radiation and its interaction with matter acquires a number of new features. For extremely short unipolar pulses an important role in the interaction with matter is played by the electric pulse area (the integral of the electric field strength over time at a given point in space). The review presents the latest theoretical and experimental results in the field of obtaining and interaction of extremely short pulses with extended resonant media and individual microobjects (atoms, molecules, nanostructures). The results of new publications are discussed, in which phenomena are predicted that arise during the coherent propagation of extremely short pulses in resonant media—self-compression and self-stopping of a pulse in a homogeneous medium. Particular attention is paid to the effect of ultrashort pulses on microobjects from the point of view of the recently introduced concept of "interference" of pulse areas (electrical area and envelope area). The research results presented in the review relate to a new direction in modern optics that has emerged recently—"Optics of unipolar and subcycle light," which is becoming an actively developing area of modern physics. [ABSTRACT FROM AUTHOR]

Attosecond pulses can be used to create and control coherence in resonant media, since their duration is shorter than the population relaxation times T1 and medium polarization T2. Previously, the possibility of creating and ultrafast control of electromagnetically induced gratings (EMIG) of atomic populations in a resonant medium was shown using a sequence of extremely short light pulses, when the pulses coherently interact with the medium and do not simultaneously overlap in the medium. These studies were carried out in various approximations, when a finite number of energy levels of the medium is taken into account, or when the pulse amplitude is small. In this paper, based on a direct numerical solution of the time dependent Schrödinger equation without the indicated approximations, we study the possibility of ultrafast coherent control of populations and the creation of an EMIG by a pair of attosecond pulses in a multilevel resonant medium with a low density of particles. The medium is modeled using a one-dimensional rectangular potential well with infinitely high walls. The studies performed show the possibility of ultrafast coherent control of the properties of resonant media based on quantum wells using attosecond pulses. [ABSTRACT FROM AUTHOR]

A geochronological study of detrital zircons from sedimentary rocks of the Gorinskaya (91 zircons with concordant ages), Pionerskaya (117 zircons with concordant ages), and Pivanskaya (115 zircons with concordant ages) formations of the Komsomolskaya Group has been carried out. It was found that the 206Pb/238U age of the youngest zircon population is consistent with the stratigraphic age only for the Pivanskaya Formation. For the other two formations, the youngest zircon populations turned out to be significantly younger than their upper stratigraphic limits. New evidence shows that: (1) the age of the "Berriasian–Valanginian" sediments of the Pionerskaya Formation is not older than the Barremian and (2) the age of the "Tithonian–Berriasian" deposits of the Gorinskaya Formation is not older than the Hauterivian. The subdivision of the Komsomolskaya Group into formations is based primarily on lithological criteria. However, since the composition of the formations is very similar, the identical deposits in other Lower Cretaceous sequences of the region could be assigned to other stratigraphic units. Thus, the above conclusion is valid only for the sections we studied. [ABSTRACT FROM AUTHOR]

An Erratum to this paper has been published: https://doi.org/10.1134/S0021364022330013 [ABSTRACT FROM AUTHOR]

Here we demonstrate an unusual type of superradiance in an extended layer of a two-level medium excited by a pair of unipolar pulses. It is shown that, due to the interference of secondary waves emitted by the resonant medium, the response of such a layer in reflection represents a pair of half-cycle unipolar pulses of different polarity. They follow with a time delay proportional to the layer thickness. The source of such superradiance is a monopolar half-cycle pulse of the stopped polarization induced by the first excitation pulse and switched off by the second excitation pulse. The predicted effect can be used to control the shape of few- and subcycle pulses in resonant media. [ABSTRACT FROM AUTHOR]

The results of petromagnetic and paleomagnetic studies of rocks from mafic dykes of the Sergeevka Terrane that intruded the basement rocks and are widespread in coastal outcrops of the eastern part of Peter the Great Bay of the Sea of Japan between the Anna and Priboinaya bays in the southern part of Primorskii krai are reported. The structural information allows us to conclude that dykes of both the eastern (Srednyaya Bay–Priboinaya Bay) and western (Anna Bay–Cape De Livron) clusters intruded from the igneous feeding channels of the same orientation. Rocks of the dykes were subjected to significant secondary alterations. Inverse magnetic fabric in the dykes is due to high-temperature decomposition and granulation of primary titanomagnetites upon postmagmatic deformations and metamorphism, traces of which are clearly visible in the microscopic and microprobe study of secondary alteration products. This provides evidence for a significant secondary change in rocks of the dykes after their intrusion. This is the secondary heating of the dykes above the temperature of 600°C, i.e., above the Curie point of magnetite (578°C). The nature of the isolated high-temperature NRM component of the dykes is not primary, but secondary, that is, metachronous. The paleomagnetic data constrained the time of the metamorphic event leading to the remagnetization of mafic dykes of the Sergeevka Terrane to about 250 Ma. The calculated paleolatitude of the Sergeevka Terrane at the time of acquisition of the metachronous NRM component by mafic dykes (21.8° ± 4.2° N) is consistent with the paleolatitudes of the northeastern edge of the North China Craton at the Late Permian/Early Triassic boundary. [ABSTRACT FROM AUTHOR]

The Migdal sudden perturbation approximation is used to solve the problem of excitation and ionization particles in a one-dimensional potential of zero radius with an extremely short pulse. There is only one energy level in such a one-dimensional the delta-shaped potential well. It is shown that for pulse durations shorter than the characteristic period of oscillations of the wave function of the particle in the bound state, the population of the level (and the probability of ionization) is determined by the ratio of the electric area of the pulse to the characteristic "scale" of the area inversely proportional to the size of localization of the particle in a bound state. [ABSTRACT FROM AUTHOR]

Energy, pulse duration, and frequency of the spectral maximum are important characteristics of pulsed terahertz radiation. The unipolarity of radiation is another characteristic that is paid less attention to. This paper demonstrates possible ways how to determine the presence of unipolarity in the radiation of pulsed terahertz sources. The first approach is based on integrating the time dependence of the field strength in the far zone obtained experimentally. The second approach uses radio-technical equipment by means of recording low-frequency components of pulses, which exist in the unipolar terahertz radiation. The results of experiments are presented with recording the unipolar component of THz pulses by both methods. The existence of unipolarity is shown for pulses from some types of terahertz radiation sources. Estimations are made for the electric area and the degree of unipolarity of the pulsed radiation for the first time. [ABSTRACT FROM AUTHOR]

The basic principles of operation of the PRU 2000/750 overspeed protection device developed and manufactured by the Sensors, Modules, Systems Innovation and Research Company are considered. Devices of this class are designed for safe shutdown of hydraulic turbines even with complete loss of automatic control. [ABSTRACT FROM AUTHOR]

An Erratum to this paper has been published: https://doi.org/10.1134/S002136402234001X [ABSTRACT FROM AUTHOR]

In this letter, excitation of discrete levels in a quantum system is considered, when the duration of the driving pulse is changed from multicycle to ultrashort half-cycle regime. It is shown that, as the number of optical cycles decreases, the system passes from the periodic-driven regime to the "kick-driven" action. In both cases the effect depends on the pulse area. However for subcycle pulses the area is equal to the time integral of the field strength, whereas for multicycle pulses it is determined by the time integral of the pulse envelope. The interference of the envelope pulse area and the electric pulse area and its possible manifestations in experiments are discussed. [ABSTRACT FROM AUTHOR]

New data are reported on the age, composition, and formation conditions of the Late Triassic granitoids of minor intrusions from the eastern part of the Bureya continental massif of the Central Asian fold belt, and their geodynamic interpretation is given. U–Pb geochronological zircon studies indicate that the rocks of the Altakhta syenite–leucogranite complex were formed in two phases within 235–224 Ma. The first phase (235.3 ± 2.9–230 Ma) was responsible for the formation of magmatic rocks that are similar to the А1-type intraplate granitoids in terms of geochemistry and resemble subduction- and collision- related granitoids in terms of REE composition. The second phase (226–224 Ma) produced granites similar to А2-type and А2 + I and S-types. A combination of within-plate and subduction signatures and the presence of A, I, and S-type rocks of similar ages in this complex supports their formation in a transform continental margin setting. [ABSTRACT FROM AUTHOR]

We study the possibility of creating gratings of populations in a gas of hydrogen atoms using a pair of UV attosecond pulses that do not overlap in the medium. In this case, the central frequency of the pulses can either coincide with the frequency of the 1–2 resonant transition from the ground state to the first excited state (the main line of the Lyman series), or be detuned from it. The values of numerically calculated quantities agree with those obtained analytically from the solution of an approximate Schrödinger equation in perturbation theory. We show that, upon resonant excitation, the greatest creation efficiency of gratings is achieved with increasing pulse duration. In the case of nonresonant excitation, on the contrary, the system is excited more efficiently by short quasi-unipolar subcycle pulses than by bipolar multicycle once. The obtained results can be applied to coherent excitation of a single atom (thin layer) using a pair of UV pulses. We show that the modulation depth of gratings can be controlled by changing the carrier envelope phase (CEP) of UV attosecond pulses. [ABSTRACT FROM AUTHOR]

The paper presents the first findings of paleomagnetic studies on Middle Jurassic sedimentary rocks of the Elgon Formation of the Ulban Terrane from the coastal outcrops along the Ulban Bay (53.5° N, 137.7° E). Demagnetization yielded a ChRM component of the pre-folding age. No inclination shallowing effect for the ChRM vector was revealed in sandstone specimens of the Elgon Formation. The paleomagnetic pole coordinates and the paleolatitude at which the studied rocks deposited were calculated: Plat = –34.3 (34.3)°; Plong = 161.2 (341.2)°; dm = 2.7, dp = 5.3, paleolatitude = 0.1° (+2.7°/–2.6°) S. The acquired paleomagnetic data are evidence of the deposition of the rocks of the Ulban Terrane in the Middle Jurassic at the boundary between the Asian paleocontinent and the Paleo-Pacific, which later formed part of the Sikhote Alin Orogenic Belt. [ABSTRACT FROM AUTHOR]

Our recent theoretical studies of generation of ultrashort pulses based on collective spontaneous emission from a thin resonant medium layer excited by a pair of high-frequency (compared to the transition frequency of the medium) pulses are reviewed. The source of generated radiation is a resonant polarization pulse in the medium ("stopped polarization pulse"), which is excited and switched off by a pair of light pump pulses. This method allows obtaining attosecond pulses in the optical and ultraviolet ranges, as well as femtosecond terahertz pulses. The effect of the superradiance in generation is discussed. The use of coherent and collective processes makes it possible to achieve a high efficiency of the generation of terahertz radiation. The proposed method is an alternative method of obtaining ultrashort pulses compared to the currently well-developed methods such as the high-harmonic generation method. [ABSTRACT FROM AUTHOR]

The possibility of selective population of the energy levels of quantum systems using a single unipolar subcycle pulse and a pair of pulses has been studied. The possibility of selective population of quantum levels has been clearly illustrated based on the numerical solution of a system of equations for the density matrix of a three-level medium that interacts with a pair of subcycle attosecond and terahertz pulses. The possibility of creating a population inversion in a three-level medium using a pair of such pulses has been shown. The dynamics of population gratings in a three-level medium exposed to the action of a pair of Gaussian pulses of large amplitude on the system is studied. Whereas the shape of the gratings in a weak field is harmonic, according to analytical calculations performed by the perturbation theory, in the case of a strong field, the spatial profile of the gratings may differ from the sinusoidal profile and may have a complex structure of peaks. [ABSTRACT FROM AUTHOR]

We analyze and generalize new data inferred from the geological, geochronological, and metallogenic studies performed in recent decades on igneous rocks of the Iorokhan gold-bearing complex in the eastern Bureya Massif. It is shown that four phases are determinative of the structure of the Iorokhan complex of minor intrusions whose rocks are referred to hypabyssal and subvolcanic intrusive facies. Specific features of their rock composition and structural tectonic conditions of localization are described and geological and geochronological (103 ± 1.0-97.4 ± 6.5 Ma) data on their Late Albian–Early Cenomanian age are presented. Based on the alumina, calcium, and alkali ratio, the major part of their compositions corresponds to the I-type (A/CNK < 1.1) high-alumina magnesia and magnesia–ferruginous varieties with decreased HFSE concentrations, including HREE. Melts formed due to amphibolite source melting might have been the deep sources of the Iorokhan diorites. The Noni deposit is briefly described and the main localization factors of the gold-ore mineralization are considered. The Iorokhan magmatite areals of the East Bureya Volcano–Plutonic Zone may be considered as one of the fragments of the structure bordering between the continental margin of the Bureya Massif and the accretionary prisms of the Sikhote Alin Orogenic Belt. The Iorokhan complex of minor intrusions is assumed to be a small fragment of an extensive band of Late Albian–Early Cenomanian magmatites developed in southern Far East Russia that originated under the transform continental marginal setting, and a combination of synstrike–slip compression and extension zones typical of such margins with further development of the pull-apart depressions. [ABSTRACT FROM AUTHOR]

The deployment kinematics of a petal reflector is considered. An engineering approach to solving the partial problem of determining the sole rotation axis of the petal that provides for deployment of the reflector is proposed. The results of a numerical simulation of the deployment kinematics and the results of tests of the full-scale mockup are presented. [ABSTRACT FROM AUTHOR]

A method of coherent controlling the polarization of a medium has been proposed recently for the generation of extremely short pulses. The method is based on the excitation of atomic polarization oscillations and their subsequent stop using a pair of ultrashort pulses. The so-called stopped pulse of the polarization of a medium, which arises in the interval between its excitation and deexcitation, can be a source of an extremely short radiation pulse. In this work, the above-indicated possibility of generation of an isolated attosecond ultraviolet pulse in a three-level resonant medium whose parameters correspond to a hydrogen atom excited by a pair of unipolar X-ray pulses is considered theoretically. In this case, the generation mechanism is of the antenna-type, that is, it is caused by the collective spontaneous emission of pre-phased atoms in the absence of a noticeable decay of their free polarization. [ABSTRACT FROM AUTHOR]

The scientific and technical fundamentals of physical modeling of "ideal agroecosystems" characterized by a high degree of controllability of the matter and energy flows between the environment and plants with accompanying biota are presented. In these systems, it becomes possible to maximize the genetically determined potential of any agricultural crop, creating ecologically harmonious optimized highly efficient microclimate–variety (hybrid)–technology complexes for obtaining consistently high yields of quality plant production. It was shown that the creation of such agroecosystems is possible with a comprehensive approach, including optimization of the light, air, and root-inhabited environments in accordance with the requirements of a particular crop. The creation of the agroecosystem requires the production or selection of hybrids and varieties providing high yields of high-quality plant products in a regulated agroecosystem, as well as monitoring the physiological state of plants and detecting stress at the early stages using noninvasive physical methods. The use of high-quality seeds based on the results of a nondamaging express assessment of internal defects by X-ray in combination with morphometric analysis. Development and application of highly effective environmentally friendly growth and metabolism regulators is also needed for such agroecosystem. [ABSTRACT FROM AUTHOR]

New petrogeochemical data were used to determine the conditions of the formation and tectonic setting of volcanic rocks of the Lake Udyl' area. These rocks were compared with similar rocks in the region. The volcanic rocks of the Lake Udyl' area are subdivided into two genetic types: (1) within-plate oceanic volcanic rocks ascribed to the accretionary volcanogenic–siliceous complex (Tithonian–Valanginian–Hauterivian–Barremian) similar to accretionary complexes in other segments of the Kiselevka–Manoma Terrane, and (2) suprasubduction-zone volcanic rocks from the island-arc volcanogenic-terrigenous complex (Valanginian–Hauterivian–Aptian–Albian–Cenomanian). A synthesis of new geological and petrogeochemical data, as well as previous geochronological and paleomagnetic data indicates the co-occurrence of genetically diverse complexes in the Udyl' segment. [ABSTRACT FROM AUTHOR]

A new plant growth stimulant was developed according to the technology engineered by the scientists of ITMO and SPBGAU Universities. The biological effectiveness of the preparation was assessed by measuring 20 wheat productivity parameters and 16 parameters of various types of pathogenesis formed during the progress of root rot caused by Helminthosporium, different types of rust, powdery mildew, and wheat leaf blotch. Application of the stimulant promoted a potential yield increase in 64% of samples (statistically significant at P < 0.05 in 28% of samples). Among the essential parameters of the yield formula, the preparation exerted the most remarkable action on spike length, the number of spikelets per spike, number of grains per spike, and weight of grains in one spike. Foliar spraying of plants with the protein growth stimulant promoted an increase in total nitrogen content of wheat leaves by an average of 84.6% in 92% of samples. Wheat grains exhibited better characteristics with the application of the protein stimulant compared to the control according to the results of microfocus X-ray radiography and optical analysis. The use of the protein growth stimulant delayed the progress rate of Helminthosporium root rot by an average of 60%, powdery mildew by 5% (based on the number of spots and their area by 36 and 52%, respectively), brown rust by 2.9% (based on the number of pustules per leaf by 76.8% and pustule area by 79.7%), and wheat leaf blotch by 15.9% compared with the control. The stimulant effectiveness has been found to depend strongly on wheat variety. Thus, the prospects of using the new, effective plant-growth stimulant to increase wheat productivity and protect against diseases have been shown experimentally. Further research is necessary due to the heterogeneity of outcomes in experiment variations. [ABSTRACT FROM AUTHOR]

A variant of the experiment to observe the optical Aharonov—Bohm effect has been discussed. In the experiment, a unipolar subcycle light pulse has been proposed as a source of the vector potential acting on electrons and having zero electric field strength in the region of a nonzero vector potential. Such a relation between the field and potential appears because the unipolar pulse has a nonzero electric area. An unusual situation where the fact of the passage of the pulse in one of the arms of two-beam interferometer is stored for a very long time after the passage and can be recorded in a two-beam electronic interferometer by a shift of fringes has been discussed. Detailed analysis of the phase shift under the influence of the vector potential created by the inhomogeneous unipolar pulse removes this contradiction and shows the equality of phase incursions in both arms that is unobvious at first glance. [ABSTRACT FROM AUTHOR]

Petrogeochemical and geochronological studies were conducted on the main varieties of granitoids from the Sedelga and Berezovsky batholiths in the eastern Bureya continental Massif of the Central Asian Fold Belt. SHRIMP-II U–Pb zircon dating of granitoids constrained the time of formation to the Late Triassic and Early Jurassic between 208 to 193 Ma. Our studies revealed that the batholiths contain peraluminous granitoids of high K calc-alkaline series clearly enriched in Rb, K, Th, U, and Pb and relatively depleted in Nb, Ta, Y, HREE, Sr, Ba, Ti, and P and belong to I-type granites. Synthesis of the U–Pb geochronological data indicates that magmatism of tectonic blocks constituting the Bureya Massif at 213–183 Ma was accompanied by the emplacement of granitoid rocks of the Khara Complex. Strike-slip tectonics as a reflection of oblique collision of continental blocks and transform movement might have been an important mechanism of granitoid derivation in the Bureya Massif. Strike-slip faults were likely to penetrate deep into the crust initiating the ascent of an asthenospheric diapir and its fluids into the higher crustal levels thus transferring the heat and triggering melting with appreciable concentrations of Th, U, Rb, Pb and losses of Sr, P, Ba, and Ti. The depletion in Nb, Ta, Ti, and P and the enrichment in Pb make these granitoids similar to those of subduction zones. Granitoids of the Khara Complex display subduction-related (associated with the preceding subduction) and within-plate (associated with an asthenospheric diapir and its fluids) geochemical features, which is characteristic of transform margin environments. The most likely settings for granitoid magmatism to occur throughout the eastern margin of the Bureya Massif in the Late Triassic and Early Jurassic were transform settings associated with asthenospheric diapirism following the cessation of subduction. [ABSTRACT FROM AUTHOR]

Conventionally, attosecond pulses are obtained using generation of high-order optical harmonics upon excitation of various media by femtosecond laser pulses with the central frequency in the infrared range. Here, we consider theoretically an alternative possibility of obtaining an isolated extreme ultraviolet (XUV) attosecond pulse in a thin layer of helium atoms excited by a pair of half-cycle (quasi-unipolar) X-ray pulses. The approach is based on the free polarization decay of an atomic medium. An analogy of the processes under consideration with the phenomenon of superradiance is discussed. [ABSTRACT FROM AUTHOR]

The article by R. M. Feshchenko (J. Exp. Theor. Phys. 136, 406 (2023)) is devoted to an important issue concerning general properties of electromagnetic field pulses and contains, in particular, critical remarks on our publications (R. M. Arkhipov et al. Quant. Electronics 50, 801 (2020); R. Arkhipov et al., Laser Field Lett. 19, 043001 (2022), and M. V. Arkhipov et al., JETP Lett. 115, 1 (2022)). We reply to these critical remarks and indicate a number of inaccuracies in the aforementioned article. [ABSTRACT FROM AUTHOR]

The article discusses the conservation of the electric area of an electromagnetic pulse during its unidirectional propagation. The authors analyze a recent statement that contradicts previous works, including their own studies. They explain that the conservation law of the electric area is valid under certain conditions and can be derived from Maxwell's equations. The article emphasizes that the conservation law is exact and applicable in the described conditions, and the violation of the conservation law in the unidirectional propagation approximation leads to an inaccurate description of the pulse's evolution. The article concludes by mentioning that experimental verification of the conservation law is challenging but will be conducted in the future. [Extracted from the article]

Under the pulses with non-harmonic waveform, propagate in free space, the time dependence of the field strength changes. In the far field or when the radiation is focused on the focal point, the field strength becomes proportional to the time derivative of the source field. If the field in any near zone is unipolar, then differentiation will lead to unipolarity lost. Based on these considerations, it is usually concluded that the practical use of radiation from unipolar sources is extremely limited. Since any propagation and attempts to focusing will lead to the loss of radiation unipolarity. However, this limitation does not effect situations when the field is depended on time in a near zone having a special form. In this note, conditions are given when it is possible to obtain unipolar pulses in the far field zone. [ABSTRACT FROM AUTHOR]

Modern hardware solutions used to obtain digital X-ray images of seeds are characterized. The main visualization methods and techniques for analyzing digital X-ray images of seeds are described. We revealed and assessed hidden defects of seed samples of the studied species such as Siberian cedar pine (Pinus sibirica Du Tour), Korean cedar pine (P. koraiensis Siebold & Zucc.), sugar corn (Zea mays L.), cucumber (Cucumis sativum L.), and pepper (Capsicum annuum L.) by microfocus X-ray radiography in combination with automatic analysis of digital X-ray images. Empty-grain and partially full-grain seeds have lower values of the "average brightness" of X-ray diffraction patterns. A comparative assessment of X-ray indicators and germination capacity of seedlings as integrated indicators for assessing the biological usefulness of seeds is performed. [ABSTRACT FROM AUTHOR]