Colloquium: Comparison of Astrophysical and Terrestrial Frequency Standards

We have re-analyzed the stability of pulse arrival times from pulsars and white dwarfs using several analysis tools for measuring the noise characteristics of sampled time and frequency data. We show that the best terrestrial artificial clocks substantially exceed the performance of astronomical sources as time-keepers in terms of accuracy (as defined by cesium primary frequency standards) and stability. This superiority in stability can be directly demonstrated over time periods up to two years, where there is high quality data for both. Beyond 2 years there is a deficiency of data for clock/clock comparisons and both terrestrial and astronomical clocks show equal performance being equally limited by the quality of the reference timescales used to make the comparisons. Nonetheless, we show that detailed accuracy evaluations of modern terrestrial clocks imply that these new clocks are likely to have a stability better than any astronomical source up to comparison times of at least hundreds of years. This article is intended to provide a correct appreciation of the relative merits of natural and artificial clocks. The use of natural clocks as tests of physics under the most extreme conditions is entirely appropriate; however, the contention that these natural clocks, particularly white dwarfs, can compete as timekeepers against devices constructed by mankind is shown to be doubtful.Comment: 9 pages, 2 figures; presented at the International Frequency Control Symposium, Newport Beach, Calif., June, 2010; presented at Pulsar Conference 2010, October 12th, Sardinia; accepted 13th September 2010 for publication in Reviews of Modern Physic

Anharmonic vs. relaxational sound damping in glasses: II. Vitreous silica

The temperature dependence of the frequency dispersion in the sound velocity and damping of vitreous silica is reanalyzed. Thermally activated relaxation accounts for the sound attenuation observed above 10 K at sonic and ultrasonic frequencies. Its extrapolation to the hypersonic regime reveals that the anharmonic coupling to the thermal bath becomes important in Brillouin-scattering measurements. At 35 GHz and room temperature, the damping due to this anharmonicity is found to be nearly twice that produced by thermally activated relaxation. The analysis also reveals a sizeable velocity increase with temperature which is not related with sound dispersion. This suggests that silica experiences a gradual structural change that already starts well below room temperature.Comment: 13 pages with 8 figure

The Vega Debris Disk -- A Surprise from Spitzer

We present high spatial resolution mid- and far-infrared images of the Vega debris disk obtained with the Multiband Imaging Photometer for Spitzer (MIPS). The disk is well resolved and its angular size is much larger than found previously. The radius of the disk is at least 43" (330 AU), 70"(543 AU), and 105" (815 AU) in extent at 24, 70 and 160 um, respectively. The disk images are circular, smooth and without clumpiness at all three wavelengths. The radial surface brightness profiles imply an inner boundary at a radius of 11"+/-2" (86 AU). Assuming an amalgam of amorphous silicate and carbonaceous grains, the disk can be modeled as an axially symmetric and geometrically thin disk, viewed face-on, with the surface particle number density following an r^-1 power law. The disk radiometric properties are consistent with a range of models using grains of sizes ~1 to ~50 um. We find that a ring, containing grains larger than 180 um and at radii of 86-200 AU from the star, can reproduce the observed 850 um flux, while its emission does not violate the observed MIPS profiles. This ring could be associated with a population of larger asteroidal bodies analogous to our own Kuiper Belt. Cascades of collisions starting with encounters amongthese large bodies in the ring produce the small debris that is blown outward by radiation pressure to much larger distances where we detect its thermal emission. The dust production rate is >~10^15 g/s based on the MIPS results. This rate would require a very massive asteroidal reservoir for the dust to be produced in a steady state throughout Vega's life. Instead, we suggest that the disk we imaged is ephemeral and that we are witnessing the aftermath of a large and relatively recent collisional event, and subsequent collisional cascade.Comment: 13 pages, 17 figures, accepted for publication in ApJ. (Figures 2, 3a, 3b and 4 have been degraded to lower resolutions.

Hard loss of stability in Painlev\'e-2 equation

A special asymptotic solution of the Painlev\'e-2 equation with small parameter is studied. This solution has a critical point $t_*$ corresponding to a bifurcation phenomenon. When $t<t_*$ the constructed solution varies slowly and when $t>t_*$ the solution oscillates very fast. We investigate the transitional layer in detail and obtain a smooth asymptotic solution, using a sequence of scaling and matching procedures

Generation of small-scale structures in the developed turbulence

The Navier-Stokes equation for incompressible liquid is considered in the limit of infinitely large Reynolds number. It is assumed that the flow instability leads to generation of steady-state large-scale pulsations. The excitation and evolution of the small-scale turbulence is investigated. It is shown that the developed small-scale pulsations are intermittent. The maximal amplitude of the vorticity fluctuations is reached along the vortex filaments. Basing on the obtained solution, the pair correlation function in the limit $r\to 0$ is calculated. It is shown that the function obeys the Kolmogorov law $r^{2/3}$.Comment: 18 page

Anharmonicity, vibrational instability and Boson peak in glasses

We show that a {\em vibrational instability} of the spectrum of weakly interacting quasi-local harmonic modes creates the maximum in the inelastic scattering intensity in glasses, the Boson peak. The instability, limited by anharmonicity, causes a complete reconstruction of the vibrational density of states (DOS) below some frequency $\omega_c$, proportional to the strength of interaction. The DOS of the new {\em harmonic modes} is independent of the actual value of the anharmonicity. It is a universal function of frequency depending on a single parameter -- the Boson peak frequency, $\omega_b$ which is a function of interaction strength. The excess of the DOS over the Debye value is $\propto\omega^4$ at low frequencies and linear in $\omega$ in the interval $\omega_b \ll \omega \ll \omega_c$. Our results are in an excellent agreement with recent experimental studies.Comment: LaTeX, 8 pages, 6 figure

The role of neurophysiological assessments during the combined treatment of patients with malignant brain tumors

The aim of the study was to assess the reliability of the transcranial magnetic stimulation technique as a tool for neurophysiological monitoring in patients with malignant brain tumorsЦелью исследования явилась оценка достоверности методики транскраниальной магнитной стимуляции в качестве инструмента нейрофизиологического мониторинга у пациентов со злокачественными опухолями головного мозга

Unfinished History and Paradoxes of Quantum Potential. II. Relativistic Point of View

This is the second of the two related papers analysing origins and possible explanations of a paradoxical phenomenon of the quantum potential (QP). It arises in quantum mechanics'(QM) of a particle in the Riemannian $n$-dimensional configurational space obtained by various procedures of quantization of the non-relativistic natural Hamilton systems. Now, the two questions are investigated: 1)Does QP appear in the non-relativistic QM generated by the quantum theory of scalar field (QFT) non-minimally coupled to the space-time metric? 2)To which extent is it in accord with quantization of the natural systems? To this end, the asymptotic non-relativistic equation for the particle-interpretable wave functions and operators of canonical observables are obtained from the primary QFT objects. It is shown that, in the globally-static space-time, the Hamilton operators coincide at the origin of the quasi-Euclidean space coordinates in the both altenative approaches for any constant of non-minimality $\tilde\xi$, but a certain requirement of the Principle of Equivalence to the quantum field propagator distinguishes the unique value $\tilde\xi = 1/6$. Just the same value had the constant $\xi$ in the quantum Hamiltonians arising from the traditional quantizations of the natural systems: the DeWitt canonical, Pauli-DeWitt quasiclassical, geometrical and Feynman ones, as well as in the revised Schr\"{o}dinger variational quantization. Thus, QP generated by mechanics is tightly related to non-minimality of the quantum scalar field. Meanwhile, an essential discrepancy exists between the non-relativistic QMs derived from the two altenative approaches: QFT generate a scalar QP, whereas various quantizations of natural mechanics, lead to PQs depending on choice of space coordinates as physical observables and non-vanishing even in the flat space if the coordinates are curvilinear.Comment: 15 pages, based on the plenary talk at the A. Z. Petrov Centenary Memorial International Symposium, 1-7.11.2010, Kazan, Russia. Few errors are corrected and minor improving changes are introduced into Chapters 4 -

Оценка физического развития и питания детей в возрасте 1–3 лет, проживающих в г. Москве

Irrational feeding can lead to a child’s physical and intellectual development disorders, a decrease in the body’s ability to resist aggressive environmental factors.Aim: to evaluate the physical development and nutrition of children aged 1–3 years living in Moscow.Methods: 106 children aged 1–3 years were examined: group 1 (n = 59) was comprised of children aged 1–2 years, group 2 — children aged 2–3 years (n = 47). Anthropometric data was evaluated using AntroPlus (WHO software). The following Z-score figures were calculated: WAZ (body mass for age), HAZ (height for age) and BAZ (body mass index for age). Nutrition was evaluated by reproducing a 3-day food allowance (actual nutrition) using the Dietplan 6 software. Figures analyzed: the volume of consumed food, daily caloricity, the amount of consumed proteins, fats and carbohydrates.Results: for the majority (76.4%) of examined children BAZ was between -2 and +1. 20% of children had an excessive body mass and obesity (BAZ &gt; 1). Children with an excessive body mass demonstrated exceeding volumes of food consumption (by about 200–300g. per day, p &lt; 0.001), protein consumption by 47.5%, fat consumption — 36.7% and caloricity by 21.3% (p &lt; 0.001) as compared with the recommended consumption norms.Conclusion: the revealed nutrition disorders in children aged 1–3 years (overeating and unbalanced diet) lead to an increased body mass and obesity. Children with high body mass indexes at birth and Z-score and BAZ at the time of the study can be attributed to the obesity risk group. The BAZ index is the most informative one in terms of evaluating the child’s nutritive status.Нерациональное питание может привести к нарушениям физического и интеллектуального развития ребенка, снижению сопротивляемости организма к агрессивным факторам внешней среды.Цель исследования: оценить физическое развитие и питание детей в возрасте 1–3 лет, проживающих в г. Москве.Методы: обследовано 106 детей в возрасте от 1 до 3 лет: I группу (n = 59) составили дети 1–2 лет, II группу — дети 2–3 лет (n = 47). Антропометрические данные оценивались с использованием программы WHO AnthroPlus: расчитывались показатели Z-score — массы тела для возраста (WAZ), длины тела для возраста (HAZ), а также индекс массы тела/возраст (BAZ). Оценка питания проводилась методом воспроизведения 3-дневного рациона (фактического питания) с использованием программы Dietplan 6. Анализировались объем съеденной пищи, суточная калорийность питания, количество потребляемых белков, жиров, углеводов.Результаты: для большинства (76,4%) обследованных детей были характерны средневозрастные показатели физического развития и нутритивного статуса (BAZ от -2 до +1). У 1/5 детей были выявлены избыточная масса тела и ожирение (BAZ &gt; 1). При избыточной массе тела, особенно у детей 1–2 лет, было установлено превышение потребляемых объемов пищи на 200–300 г/сут, белка — на 47,5%, жира — на 36,7% и энергетической ценности — на 21,3% (p &lt; 0,001) по сравнению с рекомендуемыми нормами потребления.Заключение: выявленные нарушения питания у детей в возрасте 1–3 лет (переедание и разбалансированный рацион) приводят к развитию у них избыточной массы тела вплоть до ожирения. Детей с высокими показателями веса при рождении и Z-score BAZ на момент исследования можно отнести к группе риска по развитию ожирения. Наиболее информативным для оценки нутритивного статуса ребенка является показатель BAZ

Опыт дистанционного температурно-влажностного зондирования атмосферы в период дрейфа НЭС «Академик Трешников»

For the first time experience was gained with the operation of Russian equipment for water content and temperature remote sensing of the lower atmosphere in the Arctic. The comparison the results of measurements by radiometric systems with data of radiosoundings in wide range of meteorological conditions had been executed. It is shown that mean difference between integral atmospheric water content, measured by water vapor radiometer WVR, and calculated from radiosoundings data does not exceed 6 % with standard deviation 0.54 kg/m2 and significant correlation coefficient 0,92. Analysis the data of meteorological temperature profiler MTR-5 allows to conclude that in general its adequately reproduce air temperature profiles in the atmospheric lower 1000 m layer. Some deviations take place only in cases of large temperature gradients. Preliminary analysis of WVR data showed that monthly mean value of integral atmospheric water content in area under study in April 2019 year practically coincides with calculated from radiosoundings, performed in 1983—1988 years at the polar station Barentsburg, nearest to the drift region, 3.61 and 3.62 kg/m2 respectively. Same time hourly mean values of integral atmospheric water content during drift varied from 2 to 10 kg/m2, with extreme values recorded between April 15 and April 20, probably due to intensive transport of air masses of the Atlantic origin. Based on MTR-5 data it was concluded that despite differences in sounding technology, the place and time of observations, the statistics of inversions registered during drift correspond well to statistics of inversions, recorded on the Arctic coastal stations and over sea ice cover of the Weddell Sea in winter.Приведено описание работы комплекса аппаратуры влажностно-температурного дистанционного зондирования нижнего слоя атмосферы (радиометр РВП и метеорологический профилемер МТР-5РЕ) в условиях Арктики. Выполнено сравнение результатов измерений радиометрических систем с данными аэрологического зондирования в широком спектре метеорологических условий. Получены оценки интегрального влагосодержания атмосферы и характеристик инверсий в нижнем 1000-метровом слое атмосферы в период дрейфа НЭС «Академик Трёшников» в северной части Баренцева моря