Early visual experience and its role in the development of a child

The function of the visual analyzer plays one of the leading roles in the development of the child. From the first days of a child’s life, vision is closely associated with touch, hearing, smell and other types of sensitivity. As a result, complex dynamic systems of connections are formed, which are the sensory basis of all mental activity and orientation of the child in space. Understanding the processes and creating optimal conditions for early neuro-sensory development is important both for caring for a healthy newborn and young child, and for organizing developmental care for premature and sick children in a hospital setting. The newborn is able to recognize contrasting images (faces and eyes), which are rounded and easier to observe, since their eye muscles have not yet had much practice in making sudden movements. The visual apparatus of a premature newborn has additional functional limitations and points of vulnerability. The article discusses aspects of the visual system in the neonatal period, with a more detailed analysis of the features associated with prematurity, describes the mechanisms explaining the negative impact on the processes of visual development of intense direct light, the absence of objects and patterns in focus, lack of attention (for example, sedation), lack of changes in the environment, lack of movement, complete darkness, or lack of adequate lighting on waking. A long period of nursing a premature baby in a hospital in the intensive care unit, in an incubator microclimate in compliance with a protective regime, the impossibility of full maternal care, and therefore in the absence of sensitive stimuli, falls on the most important period of the development of the nervous system. It is at this age that an adequate and timely start of neurosensory development is very important, in connection with which the need for research is increasing to determine the optimal start dates and methodology for early developmental care

Field-aligned currents in Saturn's magnetosphere: local time dependence of southern summer currents in the dawn sector between midnight and noon

We examine and compare the magnetic field perturbations associated with field-aligned ionosphere-magnetosphere coupling currents at Saturn, observed by the Cassini spacecraft during two sequences of highly inclined orbits in 2006/2007 and 2008 under late southern summer conditions. These sequences explore the southern currents in the dawn-noon and midnight sectors, respectively, thus allowing investigation of possible origins of the local time (LT) asymmetry in auroral Saturn kilometric radiation (SKR) emissions, which peak in power at ~8 h LT in the dawn-noon sector. We first show that the dawn-noon field data generally have the same four-sheet current structure as found previously in the midnight data and that both are similarly modulated by “planetary period oscillation” (PPO) currents. We then separate the averaged PPO-independent (e.g., subcorotation) and PPO-related currents for both LT sectors by using the current system symmetry properties. Surprisingly, we find that the PPO-independent currents are essentially identical within uncertainties in the dawn-dusk and midnight sectors, thus providing no explanation for the LT dependence of the SKR emissions. The main PPO-related currents are, however, found to be slightly stronger and narrower in latitudinal width at dawn-noon than at midnight, leading to estimated precipitating electron powers, and hence emissions, that are on average a factor of ~1.3 larger at dawn-noon than at midnight, inadequate to account for the observed LT asymmetry in SKR power by a factor of ~2.7. Some other factors must also be involved, such as a LT asymmetry in the hot magnetospheric auroral source electron population

Field-aligned currents in Saturn's northern nightside magnetosphere: Evidence for interhemispheric current flow associated with planetary period oscillations

We investigate the magnetic perturbations associated with field-aligned currents observed on 34 Cassini passes over the premidnight northern auroral region during 2008. These are found to be significantly modulated not only by the northern planetary-period oscillation (PPO) system, similar to the southern currents by the southern PPO system found previously, but also by the southern PPO system as well, thus providing the first clear evidence of PPO-related interhemispheric current flow. The principal field-aligned currents of the two PPO systems are found to be co-located in northern ionospheric colatitude, together with the currents of the PPO-independent (subcorotation) system, located between the vicinity of the open-closed field boundary and field lines mapping to ~9 Saturn radius (Rs) in the equatorial plane. All three systems are of comparable magnitude, ~3 MA in each PPO half-cycle. Smaller PPO-related field-aligned currents of opposite polarity also flow in the interior region, mapping between ~6 and ~9 Rs in the equatorial plane, carrying a current of ~ ±2 MA per half-cycle, which significantly reduce the oscillation amplitudes in the interior region. Within this interior region the amplitudes of the northern and southern oscillations are found to fall continuously with distance along the field lines from the corresponding hemisphere, thus showing the presence of cross-field currents, with the southern oscillations being dominant in the south, and modestly lower in amplitude than the northern oscillations in the north. As in previous studies, no oscillations related to the opposite hemisphere are found on open field lines in either hemisphere

Nonperturbative contributions to the quark form factor at high energy

The analysis of nonperturbative effects in high energy asymptotics of the electomagnetic quark form factor is presented. It is shown that the nonperturbative effects determine the initial value for the perturbative evolution of the quark form factor and find their general structure with respect to the high energy asymptotics. Within the Wilson integral formalism which is natural for investigation of the soft, IR sensitive, part of the factorized form factor, the structure of the instanton induced effects in the evolution equation is discussed. It is demonstrated that the instanton contributions result in the finite renormalization of the subleading perturbative result and numerically are characterized by small factor reflecting the diluteness of the QCD vacuum within the instanton liquid model. The relevance of the IR renormalon induced effects in high energy asymptotic behaviour is discussed. The consequences of the various analytization procedures of the strong coupling constant in the IR domain are considered.Comment: REVTeX, 12 pages, 1 figure. Important references and discussions added, misprints corrected, minor changes in tex

The use of computer vision technologies for an objective assessment of indicators of concentration of attention in newborns and infants with visual stimulation for the purpose of developmental care

Assessment of visual function in the first few days after birth is mainly limited to the study of eye movements, the ability to fix a gaze and follow an object. In order to determine how the child's gaze moves when looking at an object, how long it is fixed on the object, techniques are needed to record the movements of the eyeballs and determine the trajectory of the gaze. THE AIM OF THE study is to develop a method based on machine learning technology and computer vision for the automated analysis of eye movement and fixation of the gaze of a newborn and an infant during visual stimulation. MATERIAL AND METHODS: The proposed method includes video filming of newborns and children of the first year of life in hospital and outpatient. Video recordings from mobile phone cameras with a length of 15 s to 3 min were used as the initial data. Of the 150 videos of newborns, 73 videos were selected, of which 61 recordings of sufficient quality were selected, in which the child was recognized in at least 30% of frames. For each recording, a track was recorded of the state of the newborn during visual stimulation. Facial recognition was implemented using a widely used pre-trained model based on machine learning and ultra-precise networks. The algorithm for the study of eye movement includes searching for a face, determining the position of the head by the location of the eyes, nose, lips, searching for the eye zone, searching for the pupil, determining the relative and absolute direction of gaze. RESULTS AND DISCUSSION: A neural network was developed and trained for recognizing facial images of newborns and babies and for locating the eyes on a child's face. The method made it possible to obtain data on the direction of the child's gaze in real time using the camera of an ordinary smartphone or a simple web camera. Depending on the size of the displayed image and the distance to it, the system calculates the total time of concentration on the image, and also detects moments when the child is not interested in the image. CONCLUSION: The proposed method can be used to analyze the effectiveness of early visual stimulation in children, in the context of long-term effects on psychomotor and cognitive development, as well as to objectify data from various programs for early assessment of visual function in newborns and infants

Integer and half-integer flux-quantum transitions in a niobium/iron-pnictide loop

The recent discovery of iron-based superconductors challenges the existing paradigm of high-temperature superconductivity. Owing to their unusual multi-orbital band structure, magnetism, and electron correlation, theories propose a unique sign reversed s-wave pairing state, with the order parameter changing sign between the electron and hole Fermi pockets. However, because of the complex Fermi surface topology and material related issues, the predicted sign reversal remains unconfirmed. Here we report a novel phase-sensitive technique for probing unconventional pairing symmetry in the polycrystalline iron-pnictides. Through the observation of both integer and half-integer flux-quantum transitions in composite niobium/iron-pnictide loops, we provide the first phase-sensitive evidence of the sign change of the order parameter in NdFeAsO0.88F0.12, lending strong support for microscopic models predicting unconventional s-wave pairing symmetry. These findings have important implications on the mechanism of pnictide superconductivity, and lay the groundwork for future studies of new physics arising from the exotic order in the FeAs-based superconductors.Comment: 23 pages, including 4 figures and supplementary informatio

Field-aligned currents in Saturn's southern nightside magnetosphere: Subcorotation and planetary period oscillation components

We investigate magnetic data showing the presence of field‐aligned magnetosphere‐ionosphere coupling currents on 31 Cassini passes across Saturn's southern postmidnight auroral region. The currents are strongly modulated in magnitude, form, and position by the phase of the southern planetary period oscillations (PPOs). PPO‐independent currents are separated from PPO‐related currents using the antisymmetry of the latter with respect to PPO phase. PPO‐independent downward currents ~1.1 MA per radian of azimuth flow over the polar open field region indicative of significant plasma subcorotation are enhanced in an outer plasma sheet layer of elevated ionospheric conductivity carrying ~0.8 MA rad−1 and close principally in an upward directed current sheet at ~17°–19° ionospheric colatitude carrying ~2.3 MA rad−1 that maps to the outer hot plasma region in Saturn's magnetosphere (equatorial range ~11–16 Saturn radii (RS)) colocated with the UV oval. Subsidiary downward and upward currents ~0.5 MA rad−1 lie at ~19°–20.5° colatitude mapping to the inner hot plasma region, but no comparable currents are detected at larger colatitudes mapping to the cool plasma regime inside ~8 RS. PPO‐related currents at ~17.5°–20° colatitude overlap the main upward and subsidiary downward currents and carry comparable rotating upward and downward currents peaking at ~1.7 MA rad−1. The overall current layer colatitude is also modulated with 1° amplitude in the PPO cycle, maximum equatorward adjacent to the peak upward PPO current and maximum poleward adjacent to peak downward PPO current. This phasing requires the current system to be driven from the planetary atmosphere rather than directly from the magnetosphere

Giant Superfluorescent Bursts from a Semiconductor Magnetoplasma

Currently, considerable resurgent interest exists in the concept of superradiance (SR), i.e., accelerated relaxation of excited dipoles due to cooperative spontaneous emission, first proposed by Dicke in 1954. Recent authors have discussed SR in diverse contexts, including cavity quantum electrodynamics, quantum phase transitions, and plasmonics. At the heart of these various experiments lies the coherent coupling of constituent particles to each other via their radiation field that cooperatively governs the dynamics of the whole system. In the most exciting form of SR, called superfluorescence (SF), macroscopic coherence spontaneously builds up out of an initially incoherent ensemble of excited dipoles and then decays abruptly. Here, we demonstrate the emergence of this photon-mediated, cooperative, many-body state in a very unlikely system: an ultradense electron-hole plasma in a semiconductor. We observe intense, delayed pulses, or bursts, of coherent radiation from highly photo-excited semiconductor quantum wells with a concomitant sudden decrease in population from total inversion to zero. Unlike previously reported SF in atomic and molecular systems that occur on nanosecond time scales, these intense SF bursts have picosecond pulse-widths and are delayed in time by tens of picoseconds with respect to the excitation pulse. They appear only at sufficiently high excitation powers and magnetic fields and sufficiently low temperatures - where various interactions causing decoherence are suppressed. We present theoretical simulations based on the relaxation and recombination dynamics of ultrahigh-density electron-hole pairs in a quantizing magnetic field, which successfully capture the salient features of the experimental observations.Comment: 21 pages, 4 figure