Markov Process of Muscle Motors

We study a Markov random process describing a muscle molecular motor behavior. Every motor is either bound up with a thin filament or unbound. In the bound state the motor creates a force proportional to its displacement from the neutral position. In both states the motor spend an exponential time depending on the state. The thin filament moves at its velocity proportional to average of all displacements of all motors. We assume that the time which a motor stays at the bound state does not depend on its displacement. Then one can find an exact solution of a non-linear equation appearing in the limit of infinite number of the motors.Comment: 10 page

A Search for Pulsed and Bursty Radio Emission from X-ray Dim Isolated Neutron Stars

We have carried out a search for radio emission from six X-ray dim isolated neutron stars (XDINSs) observed with the Robert C. Byrd Green Bank Radio Telescope (GBT) at 820 MHz. No bursty or pulsed radio emission was found down to a 4sigma significance level. The corresponding flux limit is 0.01-0.04 mJy depending on the integration time for the particular source and pulse duty cycle of 2%. These are the most sensitive limits yet on radio emission from these objects.Comment: 3 pages, 3 figures, to be appeared in the Proceedings of the conference "40 Years of Pulsars: Millisecond Pulsars, Magnetars, and More" held on August 12-17, 2007, McGill University, Montreal, Canad

Pulsar Science with the Green Bank 43m Telescope

The 43m telescope at the NRAO site in Green Bank, WV has recently been outfitted with a clone of the Green Bank Ultimate Pulsar Processing Instrument (GUPPI \cite{Ransom:2009}) backend, making it very useful for a number of pulsar related studies in frequency ranges 800-1600 MHz and 220-440 MHz. Some of the recent science being done with it include: monitoring of the Crab pulsar, a blind search for transient sources, pulsar searches of targets of opportunity, and an all-sky mapping project. For the Crab monitoring project, regular observations are searched for giant pulses (GPs), which are then correlated with $\gamma$-ray photons from the \emph{Fermi} spacecraft. Data from the all-sky mapping project are first run through a pipeline that does a blind transient search, looking for single pulses over a DM range of 0-500 pc~cm$^{-3}$. These projects are made possible by MIT Lincoln Labs.Comment: 2 pages, 1 figure, to appear in AIP Conference Proceedings of Pulsar Conference 2010 "Radio Pulsars: a key to unlock the secrets of the Universe", Sardinia, October 201

Correlation of Chandra photons with the radio giant pulses from the Crab pulsar

No apparent correlation was found between giant pulses (GPs) and X-ray photons from the Crab pulsar during 5.4 hours of simultaneous observations with the Green Bank Telescope at 1.5 GHz and Chandra X-Ray Observatory primarily in the energy range 1.5-4.5 keV. During the Crab pulsar periods with GPs the X-ray flux in radio emission phase windows does not change more than by +-10% for main pulse (MP) GPs and +-30% for interpulse (IP) GPs. During giant pulses themselves, the X-ray flux does not change more than by two times for MP GPs and 5 times for IP GPs. All limits quoted are compatible with 2-sigma fluctuations of the X-ray flux around the sets of false GPs with random arrival times. The results speak in favor of changes in plasma coherence as the origin of GPs. However, the results do not rule out variations in the rate of particle creation if the particles that emit coherent radio emission are mostly at the lowest Landau level.Comment: 7 pages, 5 figures; to appear in The Astrophysical Journal, 201

Instantaneous Radio Spectra of Giant Pulses from the Crab Pulsar from Decimeter to Decameter Wavelengths

The results of simultaneous multifrequency observations of giant radio pulses from the Crab pulsar, PSR B0531+21, at 23, 111, and 600 MHz are presented and analyzed. Giant pulses were detected at a frequency as low as 23 MHz for the first time. Of the 45 giant pulses detected at 23 MHz, 12 were identified with counterparts observed simultaneously at 600 MHz. Of the 128 giant pulses detected at 111 MHz, 21 were identified with counterparts observed simultaneously at 600 MHz. The spectral indices for the power-law frequency dependence of the giant-pulse energies are from -3.1 to -1.6. The mean spectral index is -2.7 +/- 0.1 and is the same for both frequency combinations (600-111 MHz and 600-23 MHz). The large scatter in the spectral indices of the individual pulses and the large number of unidentified giant pulses suggest that the spectra of the individual giant pulses do not actually follow a simple power law. The observed shapes of the giant pulses at all three frequencies are determined by scattering on interstellar plasma irregularities. The scatter broadening of the pulses and its frequency dependence were determined as tau_sc=20*(f/100)^(-3.5 +/- 0.1) ms, where the frequency f is in MHz.Comment: 13 pages, 1 figure, 1 table (originally published in Russian in Astronomicheskii Zhurnal, 2006, vol. 83, No. 7, pp. 630-637), translated by Georgii Rudnitski

Phase transitions and quantum effects in anharmonic crystals

The most important recent results in the theory of phase transitions and quantum effects in quantum anharmonic crystals are presented and discussed. In particular, necessary and sufficient conditions for a phase transition to occur at some temperature are given in the form of simple inequalities involving the interaction strength and the parameters describing a single oscillator. The main characteristic feature of the theory is that both mentioned phenomena are described in one and the same setting, in which thermodynamic phases of the model appear as probability measures on path spaces. Then the possibility of a phase transition to occur is related to the existence of multiple phases at the same values of the relevant parameters. Other definitions of phase transitions, based on the non-differentiability of the free energy density and on the appearance of ordering, are also discussed

Simulation-based model course to demonstrate seafarers' competence for deck officers' discipline

Postprint (published version

Soliton dual comb in crystalline microresonators

We present a novel compact dual-comb source based on a monolithic optical crystalline MgF$_2$ multi-resonator stack. The coherent soliton combs generated in two microresonators of the stack with the repetition rate of 12.1 GHz and difference of 1.62 MHz provided after heterodyning a 300 MHz wide radio-frequency comb. Analogous system can be used for dual-comb spectroscopy, coherent LIDAR applications and massively parallel optical communications.Comment: 5 pages, 5 figure