The Radiation Transfer at a Layer of Magnetized Plasma With Random Irregularities

The problem of radio wave reflection from an optically thick plane monotonous layer of magnetized plasma is considered at present work. The plasma electron density irregularities are described by spatial spectrum of an arbitrary form. The small-angle scattering approximation in the invariant ray coordinates is suggested for analytical investigation of the radiation transfer equation. The approximated solution describing spatial-and-angular distribution of radiation reflected from a plasma layer has been obtained. The obtained solution has been investigated numerically for the case of the ionospheric radio wave propagation. Two effects are the consequence of multiple scattering: change of the reflected signal intensity and anomalous refraction.Comment: 22 pages, 4 figure

Beam Dynamics of the 50 MeV Preinjector for the Berlin Synchrotron BESSY II

A turn key 50 MeV linac is under construction, in order to inject electrons into the booster of BESSY II synchrotron in replacement of the existing microtron. The linac will deliver electron beams according to two operation modes a Short Pulse Mode 1 to 5 pulses 0.35nC each and a Long Pulse Mode 40 to 300 ns 3nC . We have calculated the beam dynamics, using our in house code, PRODYN [1], from the gun to the end of the linac. This code has been previously used for the beam dynamics of the SOLEIL and ALBA linacs [2] [3]. The beam behaviour, such as the radial control, the bunching process, the energy spread and emittance are analyzed

Identical Particle Scattering From A Weakly Coupled Bose-Einstein Condensed Gas

We calculate the scattering states and cross sections for a Bose-Einstein condensed dilute gas trapped in a spherical square well of finite depth. The interactions are treated in the scattering length approximation. We solve the Gross-Pitaevskii equation and the Bogoliubov equations for bound and scattering states. The results show that there are transparency effects reminiscent of those conjectured to occur for strongly coupled systems. When incident particle wavelengths λ are comparable to the well size a, exchange induced transparency enhancement is dramatic only for particular combinations of well depth, interaction strength, and particle number. For particles with large momenta (a/λ≫1),however, exchange with the condensate results in enhanced transmission for all coupling strengths. We calculated the rate of decay of the scattering states to leading order in anharmonic corrections to the Bogoliubov approximation and found the corresponding inelastic cross sections to be extremely small

Distributed Space Traffic Management Solutions with Emerging New Space Industry

Day-to-day services, from weather forecast to logistics, rely on space-based infrastructures whose integrity is crucial to stakeholders and end-users worldwide. Current trends point towards congestion of the near-Earth space environment increasing at a rate greater than existing systems support, and thus demand novel cost-efficient approaches to traffic detection, characterization, tracking, and management to ensure space remains a safe, integral part of societies and economies worldwide. Whereas machine-learning (ML) and artificial intelligence (AI) have been extensively proposed to address congestion and alleviate big-data problems of the future, little has been done so far to tackle the need for transnational coordination and conflict-resolution in the context of space traffic management (STM). In STM, there is an ever-growing need for distributing information and coordinating actions (e.g., avoidance manoeuvres) to reduce the operational costs borne by individual entities and to decrease the latencies of actionable responses taken upon the detection of hazardous conditions by one-to-two orders of magnitude. However, these needs are not exclusive to STM, as evidenced by the widespread adoption of solutions to distributing, coordinating, and automating actions in other industries such as air traffic management (ATM), where a short-range airborne collision avoidance system (ACAS) automatically coordinates evasive manoeuvres whenever a conjunction is detected. Within this context, this paper aims at establishing a roadmap of promising technologies (e.g., blockchain), protocols and processes that could be adapted from different domains (railway, automotive, aerial, and maritime) to build an integrated traffic coordination and communication architecture to simplify and harmonise stakeholders’ satellite operations. This paper is organised into seven sections. First, Section 1 introduces the problem of STM, highlighting its complexity. Following this introduction, Section 2 discusses needs and requirements of various stakeholders such as commercial operators, space situational awareness (SSA) service providers, launch-service providers, satellite and constellation owners, governmental agencies, regulators, and insurance companies. Then, Section 3 addresses existing gaps and challenges in STM, focusing on globally coordinated approaches. Next, Section 4 reviews technologies for distributed, secure, and persistent communications, and proposed solutions to address some of these challenges from non-space sectors. Thereafter, Section 5 briefly covers the history of STM proposals and presents the state-of-the-art solution being proposed for modern STM. Following this review, Section 6 devises a step-by-step plan for exploiting and deploying some of the identified technologies within a five-to-ten-year timeline to close several existing gaps. Finally, Section 7 concludes the paper

Natural history of endometriosis in pregnancy: ultrasound study of morphology of deep endometriosis and ovarian endometrioma

Objective: To assess the morphological appearance of deep endometriosis and ovarian endometrioma in pregnancy using pelvic ultrasound examination. Methods: This was a prospective observational cohort study conducted over 3 years at University College London Hospital, which is a tertiary level referral unit for early pregnancy complications and an accredited endometriosis center. All women who participated provided written consent and were invited for surveillance ultrasound examination at the time of their routine scans in pregnancy. All scans were performed by a single operator to eliminate interobserver variability. The change in size of ovarian endometrioma and nodules was reported as change in their mean diameter. Ovarian endometrioma with irregular thick inner walls, hyperechoic papillary projections and/or high vascularity and hyperechoic nodules with moderate to high vascularity were reported as decidualized. Results: Sixty-five women with a live, normally sited pregnancy and concomitant ultrasound features of deep and/or ovarian endometriosis were included in the study. The median age of the study population was 34 (range, 23–44) years, and the median gestational age at presentation was 7 + 6 (range, 3 + 6 to 18 + 0) weeks. From the cohort, 47/65 (72%) were nulliparous, 48/65 (74%) had a previous diagnosis of endometriosis and 19/65 (29%) conceived via in-vitro fertilization. There were 10/65 (15% (95% CI, 7–24%)) women with ovarian endometrioma alone, 28/65 (43% (95% CI, 31–55%)) with endometriotic nodules alone and the remaining 27/65 (42% (95% CI, 30–54%)) had both. Of the women with ovarian endometrioma who underwent follow-up, 29/34 (85% (95% CI, 73–97%)) experienced cyst regression, 2/34 (6% (95% CI, 0–14%)) experienced cyst growth, and in 3/34 (9% (95% CI, 0.0–18%)) women, cyst size was unchanged. In 10/34 (29% (95% CI, 14–45%)), there was complete resolution of all cysts. Of the women with nodules who underwent follow-up, 43/51 (84% (95% CI, 74–94%)) experienced nodule regression, 2/51 (4% (95% CI, 0–9%)) experienced nodule growth and, in 6/51 (12% (95% CI, 3–21%)) women, nodule size was unchanged. In 4/51 (8% (95% CI, 0–15%)) women, there was complete resolution of all nodules. In 5/37 (14% (95% CI, 3–25%)) women who attended postnatal follow-up, complete resolution of all endometriotic lesions occurred during pregnancy. In 10/34 (29% (95% CI, 14–45%)) women with ovarian endometrioma and 27/51 (53% (95% CI, 39–67%)) women with nodules, a pattern of growth was observed in the first and second trimesters, followed by regression later in pregnancy. Features of decidualization were observed in 17/34 (50% (95% CI, 33–67%)) women with ovarian endometrioma, most commonly in the first trimester, and in 25/51 (49% (95% CI, 35–63%)) women with nodules, most commonly in the second trimester. Conclusions: For the majority of women, despite features of decidualization being common in the first and second trimesters, ovarian endometrioma and deep nodules regress during pregnancy. Morphological changes of endometriosis in pregnancy are difficult to differentiate from characteristics of malignant lesions. Better understanding of the appearance of endometriosis in pregnancy is vital to minimize intervention and help counsel women regarding their condition. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology

Anomalous attenuation of extraordinary waves in the ionosphere heating experiments

Multiple scattering of radio waves by artificial random irregularities HF-induced in the ionosphere F region may cause significant attenuation of both ordinary and extraordinary waves together with common anomalous absorption of ordinary waves due to their non-linear conversion into plasma waves. To demonstrate existence and strength of this effect, direct measurements of attenuation of both powerful pump wave and weak probing waves of extraordinary polarization have been carried out during an experimental campaign on September 6, 7 and 9, 1999 at the Sura heating facility. The attenuation magnitude of extraordinary waves reaches of 1-10 dB over a background attenuation caused by natural irregularities. It is interpreted in the paper on the base of the theory of multiple scattering from the artificial random irregularities with characteristic scale lengths of 0.1-1 km. Simple procedure for determining of irregularity spectrum parameters from the measured attenuation of extraordinary waves has been implemented and some conclusions about the artificial irregularity formation have been obtained.Comment: 17 pages, 9 figure

Identical particle scattering from a weakly coupled Bose-Einstein condensed gas

We calculate the scattering states and cross sections for a Bose-Einstein condensed dilute gas trapped in a spherical square well of finite depth. The interactions are treated in the scattering length approximation. We solve the Gross-Pitaevskii equation and the Bogoliubov equations for bound and scattering states. The results show that there are transparency effects reminiscent of those conjectured to occur for strongly coupled systems. When incident particle wavelengths λ are comparable to the well size a, exchange induced transparency enhancement is dramatic only for particular combinations of well depth, interaction strength, and particle number. For particles with large momenta (a/λ≫1),however, exchange with the condensate results in enhanced transmission for all coupling strengths. We calculated the rate of decay of the scattering states to leading order in anharmonic corrections to the Bogoliubov approximation and found the corresponding inelastic cross sections to be extremely small

Quantum sticking, scattering and transmission of 4He atoms from superfluid 4He surfaces

We develop a microscopic theory of the scattering, transmission, and sticking of 4He atoms impinging on a superfluid 4He slab at near normal incidence, and inelastic neutron scattering from the slab. The theory includes coupling between different modes and allows for inelastic processes. We find a number of essential aspects that must be observed in a physically meaningful and reliable theory of atom transmission and scattering; all are connected with multiparticle scattering, particularly the possibility of energy loss. These processes are (a) the coupling to low-lying (surface) excitations (ripplons/third sound) which is manifested in a finite imaginary part of the self energy, and (b) the reduction of the strength of the excitation in the maxon/roton region