Polarization Study of Gamma-ray Binary Systems

The polarization of X-ray emission is a unique tool used to investigate the magnetic field structure around astrophysical objects. In this paper, we study the linear polarization of X-ray emissions from gamma-ray binary systems based on pulsar scenarios. We discuss synchrotron emission from pulsar wind particles accelerated by a standing shock. We explore three kinds of axisymmetric magnetic field structures: (i) toroidal magnetic fields, (ii) poloidal magnetic fields, and (iii) tangled magnetic fields. Because of the axisymmetric structure, the polarization angle of integrated emission is oriented along or perpendicular to the shock-cone axis projected on the sky and swings around 360° in one orbit. For the toroidal case, the polarization angle is always directed along the shock-cone axis and smoothly changes along the orbital phase. For the poloidal/tangled magnetic field, the direction of the polarization angle depends on the system parameters and orbital phase. In one orbit, the polarization degree for the toroidal case can reach the maximum value of the synchrotron radiation (∼70%), while the maximum polarization degree for poloidal/tangled field cases is several 10%. We apply our model to bright gamma-ray binary LS 5039 and make predictions for future observations. With the expected sensitivity of the Imaging X-ray Polarimetry Explorer, linear polarization can be detected by an observation of several days if the magnetic field is dominated by the toroidal magnetic field. If the magnetic field is dominated by the poloidal/tangled field, significant detection is expected with an observation longer than 10 days.

Radiation characteristics of sharply directed conical waveguide-slot antenna arrays

Currently, much attention is paid to antenna arrays, the emitters of which can be located in the bow of unmanned aerial vehicles (UAVs). Emitters can be longitudinal, transverse or oblique slots located along the generatrix of the cone on the conducting surface. A number of specific requirements are imposed on such ARs used in on-board radar systems (radars) of UAVs, among which we can note the need to form a highly directional total-difference directional pattern (DP) with a maximum of the total DP and a minimum of a difference DP in the direction of the UAV flight axis, as well as high gain and slope of the difference characteristic. The aim of this work was to study the radiation of a waveguide-slot antenna array (WASAA) installed on a conical surface and providing linear polarization of the emitted field in the direction of the cone axis. For this, electrodynamic modeling of various configurations of WASAA, located both in free space and on a conical surface, was carried out. For the developed models of antennas, the directivity characteristics and their dependence on the geometry and dimensions of the WASAA are determined. The results of an experimental study of the characteristics of a model of a conical antenna emitting a field of linear polarization in the direction of the cone axis are presented. The experimental results are compared with the results of electrodynamic modeling. The results obtained are of practical interest for the development of airborne antenna UAVs.

Collapse of conical granular columns

This paper experimentally analyzes the collapse of conical granular columns made out of non-cohesive granular materials. Dimensionless run-out lengths were found, as a function of the aspect ratio a, similar to those occurring in the collapse of cylindrical columns, although in the case of conical columns of high aspect ration, at the end of the collapse, a layer of grains that rotates around the cone axis appears and it affects the final profiles of the mounds.

Understanding the cone scale in Cupressaceae: insights from seed-cone teratology in Glyptostrobus pensilis

Both wild-type and teratological seed cones are described in the monoecious conifer Glyptostrobus pensilis and compared with those of other Cupressaceae sensu lato and other conifers. Some Cupressaceae apparently possess a proliferation of axillary structures in their cone scales. In our interpretation, in Glyptostrobus each bract of both typical and atypical seed cones bears two descending accessory shoots, interpreted here as seed scales (ovuliferous scales). The primary seed scale is fertile and forms the ovules, the second is sterile and forms characteristic tooth-like structures. The bract and the two axillary seed scales are each supplied with a single distinct vascular bundle that enters the cone axis as a separate strand; this vasculature also characterises the descending accessory short shoots in the vegetative parts of the crown. In wild-type seed cones, the fertile seed scale is reduced to its ovules, and the ovules are always axillary. In contrast, the ovules of some of the teratological seed cones examined were located at the centre of the cone scale. An additional tissue found on the upper surface of the sterile lower seed scale is here interpreted as the axis of the fertile seed scale. Thus, the central position of the ovules can be explained by recaulescent fusion of the upper fertile and lower sterile seed scales. In several teratological cone scales, the ovules were enveloped by an additional sterile tissue that is uniseriate and represents an epidermal outgrowth of the fertile seed scale. Close to the ovules, the epidermis was detached from lower tissue and surrounded the ovule completely, except at the micropyle. These teratological features are potentially significant in understanding seed-cone homologies among extant conifers.

The conical conformal MEMS quasi-end-fire array antenna

The microelectromechanical system (MEMS) quasi-end-fire array antenna based on a liquid crystal polymer (LCP) substrate is designed and fabricated in this paper. The maximum radiation direction of the antenna tends to the cone axis forming an angle less than 90[Formula: see text], which satisfies the proximity detection system applied at the forward target detection. Furthermore, the proposed antenna is fed at the ended side in order to save internal space. Moreover, the proposed antenna takes small covering area of the proximity detection system. The proposed antenna is fabricated by using the flexible MEMS process, and the measurement results agree well with the simulation results. This is the first time that a conical conformal array antenna is fabricated by the flexible MEMS process to realize the quasi-end-fire radiation. A pair of conformal MEMS array antennas resonates at 14.2 GHz with its mainlobes tending to the cone axis forming a 30[Formula: see text] angle and a 31[Formula: see text] angle separately, and the gains achieved are 1.82 dB in two directions, respectively. The proposed antenna meets the performance requirements for the proximity detection system which has vast application prospects.

Regarding the structure and possible function of the columella in seed cones of Callitroideae (Cupressaceae): a morpho-anatomical approach

‘Columella’-named structures in seed cones of callitroid Cupressaceae were investigated. In the past, the term columella was used for different structures, which should not be summarised and treated under the same name. We suggest that all apices should be called columella, which exclusively represent the prolonged tip of the cone axis and do not reach the periphery of the seed cone and do not take part in it. The three distal lobes in Fitzroya Lindl. represent a sterile, strongly reduced, distal whorl of cone scales and not naked nucelli or resin glands as suggested in former studies. They should not be termed columella. The columellae and also the three lobes in Fitzroya may play a role within the pollination process and possibly in the chemical defence against pathogens. The columella, as it is defined here, is not restricted to the Callitroideae and is also present in other Cupressaceae, including Cupressus L. and Thujopsis Siebold & Zucc.

The pollination mechanism of Abies amabilis

The development and function of the pollination mechanism were studied in Abies amabilis (Dougl. ex Loud.) Dougl. ex J. Forbes growing in clonal seed orchards. Two adaxial ovules developed on each scale after dormancy and each ovule formed a funnel-like integument tip with a nucellus at the base of the shallow funnel. At receptivity, the seed cones were erect and the ovules inverted. No pollination drop was observed in fresh specimens but lipid microdrops were secreted on the rim and inner surface of the funnel. Water applied as spray beaded on all cone surfaces except where microdrops were present. Surfaces of the cone were observed using scanning electron microscopy to determine the presence and ultrastructure of the waxy cuticle. All surfaces that were not wettable with water were covered with epicuticular wax. Pollen did not adhere firmly to cone surfaces having epicuticular wax but adhered to the microdrops on the funnel. Drops of water picked up pollen as they moved over the waxy surfaces toward the cone axis. There, the inverted ovules were arranged in a tight helix around the cone axis. Beads of water, often containing pollen, settled on the scale surface just below the funnels and then touched and wetted the inside of the funnels, forming a column of water from the scale surface below to the funnel above. The saccate, buoyant pollen then floated up and into the funnel. Experiments were done to determine the effect of pollen application on pollen uptake into the ovule: without water, with water applied before or after pollen was applied, or as a pollen–water mix. Results support the hypothesis that A. amabilis, and likely other Abies species, lacks a conspicuous pollination drop and water as rain or dew substitutes for a pollination drop.

Factors affecting seed and cone development in Pacific silver fir (Abies amabilis)

The reproductive development from pollination until seed maturity for Pacific silver fir (amabilis fir; Abies amabilis (Dougl. ex Loud.) Dougl. ex J. Forbes) was studied at two sites in British Columbia. Ten trees growing at varying elevations at each site were flagged and two or more cones were collected from each tree every 1 or 2 weeks. Following size measurements, cones were dissected and 20 ovules from each cone were sampled, fixed, embedded in paraffin, sectioned, and stained for anatomical study. Ovule, megagametophyte, and embryo size was measured and stage of ovule or seed and embryo was determined. At both sites the phenology and details of development were similar. The major causes of cone loss were frost at pollination and insect damage following pollination. The seed potential per cone was 359-408, but the filled seeds per cone based on cutting tests and X-raying was only 18-22%. The major causes of seed loss were insect damage (32-39%) during ovule and seed development and failure of ovules to be pollinated (26-31%). Although the amount of insect damage was similar at both sites, damage at Site 1 was primarily caused by Megastigmus sp. larvae in the seeds whereas at Site 2, damage was to seeds, scales, and the cone axis and due to Earomyia abietum larvae. Megagametophyte and embryo development is described and the time and causes of the seed loss are related to development. Anomalous types of development are described and possible causes discussed.

Reduction of Droplet Density onto Hydroxyapatite Films Grown by Pulsed Laser Deposition from Concave-Shaped Targets

A new deposition method, inspired from the crossed fluxes technique, which employs a concave, conic-shaped target is presented here. The rectangular excimer laser beam used for ablation was focused so that the middle of the spot laid exactly on the tip of the concave-shaped target. Each half of the laser spot created a plasma plume on one side of the concave target which was the symmetrical image across the cone axis of that created by the other half of the laser spot. The heavy droplets passed through the plasma interaction region without collisions and, maintaining their direction of motion, moved away from the system axis. The majority of the ablated ions and atoms emitted from one side of the spot collided with those emitted from the other side and, because of the symmetry of the concave-shaped target, acquired a velocity component along the system axis, moving towards the substrate. Scanning electron microscopy investigations showed a significant reduction of droplet density onto the surface of hydroxyapatite layers grown from such concave-shaped targets as compared to films grown from the usual cylindrical targets.