Controlling polarization direction in epitaxial Pb(Zr0.2Ti0.8)O3 films through Nb (n-type) and Fe (p-type) doping

Fe (acceptor) and Nb (donor) doped epitaxial Pb(Zr0.2Ti0.8)O3 (PZT) films were grown on single crystal SrTiO3 substrates and their electric properties were compared to those of un-doped PZT layers deposited in similar conditions. All the films were grown from targets produced from high purity precursor oxides and the doping was in the limit of 1% atomic in both cases. The remnant polarization, the coercive field and the potential barriers at electrode interfaces are different, with lowest values for Fe doping and highest values for Nb doping, with un-doped PZT in between. The dielectric constant is larger in the doped films, while the effective density of charge carriers is of the same order of magnitude. An interesting result was obtained from piezoelectric force microscopy (PFM) investigations. It was found that the as-grown Nb-doped PZT has polarization orientated upward, while the Fe-doped PZT has polarization oriented mostly downward. This difference is explained by the change in the conduction type, thus in the sign of the carriers involved in the compensation of the depolarization field during the growth. In the Nb-doped film the majority carriers are electrons, which tend to accumulate to the growing surface, leaving positively charged ions at the interface with the bottom SrRuO3 electrode, thus favouring an upward orientation of polarization. For Fe-doped film the dominant carriers are holes, thus the sign of charges is opposite at the growing surface and the bottom electrode interface, favouring downward orientation of polarization. These findings open the way to obtain p-n ferroelectric homojunctions and suggest that PFM can be used to identify the type of conduction in PZT upon the dominant direction of polarization in the as-grown films.

Kepadatan populasi dan waktu efektif pelepasan tungau predator Neoseiulus longispinosus Evans untuk pengendalian Tetranychus kanzawai Kishida

Kanzawa spider mite, Tetranychus kanzawai Kishida (Tetranychidae) is one of the most important pest mite in Indonesia. This mite is known as the pest of many crops, including cassava. Neoseiulus longispinosus Evans (Phytoseiidae) is a predatory mite commonly found on plant infested by kanzawa spider mite. This predatory mite has high potential to be developed as biological control agent of T. kanzawai. The aim of this research is to elucidate the effective density and release time of N. longispinosus to control T. kanzawai on cassava. The research was conducted in the greenhouse, using cassava of Mentega cultivar. T. kanzawai were introduced into the cassava plants two weeks after planting, with density 5 female adults/plants. N. longispinosus were introduced 1, 2, and 3 weeks after T. kanzawai introduction with predator:prey ratio of 0:5, 1:5, 2:5, dan 3:5, respectively. Population of T. kanzawai and N. longispinosus, and also plant damage were observed at 6 weeks after planting. N. longispinosus could suppress T. kanzawai population and the highest suppression occurred at the interaction between 3:5 ratio and the release time at one week after T. kanzawai infestation. There was no significant effect of N. longispinosus release at various release ratio and time on attack intensity of T. kanzawai.

Ecological and morphological features of Rhodiola rosea L. in natural populations in the Altai Mountains

The paper presents the results of the comprehensive study of Rhodiola rosea L. in natural populations in the Altai Mountains. The phytocoenotic confinement, demographic structure, and morphological characters of coenopopulations of Rh. rosea were studied in different ecological and coenotic conditions in the Chemal and Kosh-Agach regions of the Republic of Altai. Correlation between the morphometric parameters and their calculated values for the shoot and sex of the studied individuals, as well as environmental factors, was revealed. Rhodiola rosea L. is a valuable medicinal plant used for functional diseases of the central nervous system. At present, the natural reserves and areas of natural growth of the golden root have decreased significantly. The species is included in the Red Data Book of the Russian Federation (2008) and many regional Red Data Books of Siberia. In the Altai Mountains, Rh. rosea is widespread throughout the highlands, where it has occupied a wide range of habitats. The study showed that the highest values of ecological and effective density are characteristic of coenopopulations which are part of various hygrophytic variants of alpine and subalpine miscellaneous herbs with a high total projective cover of the herbaceous layer (CP 1, 2, 3, 4). The lowest values were found for coenopopulations growing in communities with a scarce herbaceous layer or dense shrub layer, and on steep gravelly slopes with crumbling soil and nonuniform moisture distribution (CP 5, 6, 8, 9). The studied coenopopulations are normal, full-membered, or incomplete-membered (some of them lack postgenerative individuals). In terms of the ontogenetic spectra, they are mainly left-sided, with a predominance of young generative individuals (CP 4, 5, 7) or bimodal, with an additional peak for old generative individuals (CP 2, 3, 6, 8). Male and female individuals Rh. rosea differ in many morphometric characters of the generative shoots. In some coenopopulations (CP 2, 3, 6, 9), male and female individuals show multidirectional deviation of characters compared to the totality, which indicates that in different environmental conditions these characters are not only genetically determined but can also be related to the sex of individuals.

Some rare plant species in the Aktolagay cretaceous massif (Republic of Kazakhstan): the characteristics of populations

Cretaceous massifs of the Eurasian continent is unique not only for its geological features, but also for the peculiar flora, therefore, identification and study of the biodiversity of these unique objects is currently an urgent task. Comprehensive studies of the flora and vegetation of the Aktolagay cretaceous massif (Republic of Kazakhstan) were carried out in 2019. One aspect was the consideration of the ecological and biological features of several plant species characteristic for this territory. The research is devoted to the study of 5 plant species: Astragalus lasiophyllus Lеdеb., Astragalus vulpinus Willd., Matthiola tatarica (Pall.) DC., Eremurus inderiensis (M. Bieb.) Regel, Tragopogon ruber S.G. Gmel. on the territory of the Cretaceous massif Aktolagai. The coenopopulations of the species are located in the lower parts of the slopes, as well as aligned areas at the foot on cretaceous substrates, and on sandstone soils. The arithmetic density of the studied CPs varies from 2.2 to 6.6 ind./m2, the effective density varies from 1.6 to 4.9 ind./m2. The studied coenopopulations belong to normal incomplete ones. The most typical feature is the absence of seedlings, juvenile and senile individuals in the spectrum, while the peak falls on mature generative individuals, in the Mattiolla tatarica coenopopulations - on virginile individuals. Coenopopulations are heterogeneous in their type ("delta-omega" criterion): the Matthiola tatarica one is young, the CP of Astragalus lasiophyllus is transitional, the CPs of Astragalus vulpinus and Eremurus inderiensis are maturing, and the CP of Tragogon ruber is mature. The recruitment index in the studied populations is rather high (0.36–3.05), the agting index is equal or close to zero. Most morphometric features show low levels of variability and plasticity.

Effects of recycling neutral on density shoulder formation in tokamak plasmas

Towards the physical understanding on the formation of flattened upstream scrape-off-layer (SOL) density profiles, namely ‘density shoulders’, a self-consistent one-dimensional radial transport model has been developed to estimate the upstream profiles covering both core plasma and SOL region at tokamak midplane. For the SOL region, the effective density and temperature profiles for the ionization process are obtained by weighted averaging of the upstream and downstream profiles, which can distinguish the open target operation (OTO) from the closed target operation (CTO) by a weighting factor. Compared with the enhanced turbulent convective transport, it is complementary for the model to study the competition between the effective source Seff and the parallel particle loss LSOL . It indicates that: (1) an appropriate Seff intensity controlled by the neutral pressure due to divertor or wall recycling and (2) an appropriate Seff peak position in a far SOL region adjusted by the plasma current as well as the weighting factor could offset the damping effect of LSOL on density profile. Then Seff over LSOL in a far SOL region could be the sole process involved in bringing about SOL density shoulders.

Effect of density and mixed culture of largemouth bass (Micropterus salmoides) and pikeperch (Sander lucioperca) on growth, survival and feed conversion rate in intensive culture

In this study, two experiments were performed with the aim to optimize intensive aquaculture of largemouth bass (Micropterus salmoides). In the first 140-day experiment the effect of the initial fish density was assessed at three levels: low density (LD) 23 kg/m³, medium density (MD) 35 kg/m³ and high density (HD) 46 kg/m³. All three densities provided the same final Fulton’s condition coefficient (FC = 1.24–1.28), specific growth rate (SGR = 0.22–0.24%/day) and survival rate (97–100%). No cannibalism was observed at all tested densities. Feed conversion ratio (FCR = 1.39 ± 0.21 g/g) was the lowest for LD and the highest (1.61 ± 0.08 g/g) for MD. The highest fish biomass (25.7 ± 2.7 kg/m³) was obtained at HD and this density was considered as the most effective density of all tested ones during the intensive culture of largemouth bass. The second 60-day experiment tested the effect of largemouth bass and pikeperch (Sander lucioperca) monoculture and biculture of both species on production efficiency. Higher size heterogeneity was obtained in both (mono- and bicultural) groups of pikeperch (308.91–314.56‰/day) compared to the groups of largemouth bass (279.26–284.05 ‰/day). The higher FC (1.09) was found in both types of culture in largemouth bass compared to both methods of culture in pikeperch (0.74–0.78). The lowest SGR was evident in both types of largemouth bass cultures (1.20–1.28%/day). In contrast, the highest SGR was achieved in the bicultural pikeperch (1.88%/day). Similar results like for SGR were also assessed for FCR, where the highest value of FCR was in both cultures of largemouth bass (1.44–1.48 g/g) compared to the lowest FCR in the bicultural of pikeperch (0.73 g/g). Largemouth bass in both tested types of culture had higher survival rates (99.95–99.99%) compared to pikeperch (98.61–98.63%).

Topological flocking models in spatially heterogeneous environments

Flocking models with metric and topological interactions are supposed to exhibit distinct features, as for instance the presence and absence of moving polar bands. On the other hand, quenched disorder (spatial heterogeneities) has been shown to dramatically affect large-scale properties of active systems with metric interactions, while the impact of quenched disorder on active systems with metric-free interactions has remained, until now, unexplored. Here, we show that topological flocking models recover several features of metric ones in homogeneous media, when placed in a heterogeneous environment. In particular, we find that order is long-ranged even in the presence of spatial heterogeneities, and that the heterogeneous environment induces an effective density-order coupling facilitating emergence of traveling bands, which are observed in wide regions of parameter space. We argue that such a coupling results from a fluctuation-induced rewiring of the topological interaction network, strongly enhanced by the presence of spatial heterogeneities.