Two Electrons in a Quantum Dot: A Unified Approach

Low-lying energy levels of two interacting electrons confined in a two-dimensional parabolic quantum dot in the presence of an external magnetic field have been revised within the frame of a novel model. The present formalism, which gives closed algebraic solutions for the specific values of magnetic field and spatial confinement length, enables us to see explicitly individual effects of the electron correlation.Comment: 14 page

Pauli principle and chaos in a magnetized disk

We present results of a detailed quantum mechanical study of a gas of $N$ noninteracting electrons confined to a circular boundary and subject to homogeneous dc plus ac magnetic fields $(B=B_{dc}+B_{ac}f(t)$, with $f(t+2\pi/\omega_0)=f(t)$). We earlier found a one-particle {\it classical} phase diagram of the (scaled) Larmor frequency $\tilde\omega_c=omega_c/\omega_0$ {\rm vs} $\epsilon=B_{ac}/B_{dc}$ that separates regular from chaotic regimes. We also showed that the quantum spectrum statistics changed from Poisson to Gaussian orthogonal ensembles in the transition from classically integrable to chaotic dynamics. Here we find that, as a function of $N$ and $(\epsilon,\tilde\omega_c)$, there are clear quantum signatures in the magnetic response, when going from the single-particle classically regular to chaotic regimes. In the quasi-integrable regime the magnetization non-monotonically oscillates between diamagnetic and paramagnetic as a function of $N$. We quantitatively understand this behavior from a perturbation theory analysis. In the chaotic regime, however, we find that the magnetization oscillates as a function of $N$ but it is {\it always} diamagnetic. Equivalent results are also presented for the orbital currents. We also find that the time-averaged energy grows like $N^2$ in the quasi-integrable regime but changes to a linear $N$ dependence in the chaotic regime. In contrast, the results with Bose statistics are akin to the single-particle case and thus different from the fermionic case. We also give an estimate of possible experimental parameters were our results may be seen in semiconductor quantum dot billiards.Comment: 22 pages, 7 GIF figures, Phys. Rev. E. (1999

Biotechnique of rearing beluga (H.huso) using brackishwater of the Caspian Sea (different densities and water flow)

This study was conducted at the Applied Research Station for Sturgeon Culture (Chaboksar site) and was supported by the Iranian Fisheries Research Organization in order to obtain the bio technique for Huso huso culture in brackish water from the Caspian Sea. The effects of stocking density and water flow at the inlet of brackish water was studied for a period of 4 years using 4 weight classes and the results obtained were compared with those obtained from the culture of H. huso in freshwater. Huso huso in four weight classes of 3-20 g, 20-200 g, 325-1000 g and 1000-3000 g were stocked at stocking densities between 350 g to 15 kg m^-2. The effect of water flow in rearing tanks was studied in weight classes 30- 2700 g. In the weight class 3-20 g, highest growth was recorded in H. huso stocked at 1000 g m^-2 in brackish water which was significantly higher (P<0.5) than that recorded in freshwater suggesting the advantage of rearing H. huso in brackish water at improved density of 1000 g m^-2. Results obtained from total length in juvenile H. husoconform to these results. It may therefore be concluded that in the weight class 3-20 g, stocking density of 1000 g m^-2 is not a limiting factor on growth in juvenile H. huso. Low specific growth rate (SGR) was reported with a stocking density of 1500 g m^-2 in freshwater which was not significantly different from that in brackish water. Hence rearing juvenile H. huso in brackish water at high densities (1500 g m^-2) is preferred to rearing in freshwater as H. huso is more capable of adapting to stressful conditions of stocking density in brackish water. Similar trends were observed for percentage body weight increase (BWI%) showing the advantage of using a stocking density of 1000 g m^-2 in brackish water. Production in different groups showed variations depending on stocking density biomass. Condition factor was low when H. huso was reared in freshwater at a stocking density of 1500 g m^-2. Similarly CVw was low in the experimental group reared at a density of 500 g m-2 in brackish water, while CVtl in the group reared at 1500 g m^-2 in brackish water was low. The calculated value for CVw/tl was low with stocking density of 500 g m^-2 in brackish water and freshwater. Final body weight and growth indices in the 20-200 g weight class in the experimental group using 1000 g m^-2 in brackish water were higher than that in freshwater. Similarly growth indices and final body weight of juvenile H. huso at 2000 and 1500 g m^-2 stocking densities were higher than the values obtained with similar stocking densities in freshwater. SGR and growth rate (GR) of H. huso at stocking density of 1500 g m^-2 was significantly higher in brackish water than that in freshwater. Comparison of results obtained from weight and total length in weight classes 325-560 g showed that until they reach a weight of 560 g, stocking density of 1.3 kg m^-2 in brackish water is preferred to the densities 2.6, 3.9 and 5.2 kg m^-2. Comparison of results indicate that in the weight class 325-560 g, better results are obtained when juvenile H. huso are reared in brackish water at densities of 1.3, 2.6 and 3.9 kg m^-2 as compared to that obtained from the use similar densities in freshwater. Statistical analysis of SGR indicates that stocking densities up to 2.6 kg m^-2 do not limit growth. Also it was also evident from the analyses of SGR and FCR that stocking density of 5.2 kg m^-2 is not considered suitable for juvenile H. huso in the weight class 325-560 g. On the basis of results obtained for SGR, GR and FCR it maybe concluded that up to the 760 g weight class, stocking densities of 1.3 and 2.6 kg m^-2 were statistically better than other densities studied. Moreover rearing juvenile H. huso at these stocking densities in brackish water also proved better than that in freshwater. In the weight class 650-1000 g, stocking fish at densities of 2.6 -10 kg m^-2 in brackish water did not seem to affect final body weight, total length and SGR. At stocking densities 5.1 and 7 kg m^-2, GR for juvenile H. huso in brackish water were significantly higher than that obtained in freshwater using the same stocking densities. Similarly FCR and FE values obtained for juvenile H. huso in this weight class in brackish water were significantly better (P<0.05) than those obtained in freshwater. SGR values obtained at stocking densities 7 and 10 kg m^-2 support these findings. Based on body weight, total length and GR values it may be concluded that stocking density of 10 kg m^-2 does not restrict growth in juvenile H. huso until they reach a body weight of 1000 g. Similarly a stocking density of 7.5 kg m^-2 does not limit growth in juvenile H. huso until they reached a body weight of 1150 g and stocking densities of 5.1 kg m^-2 and 2.6 kg m^-2 do not limit growth in juvenile H. huso until they reach body weights of 1300 and 1500 g, respectively. Rearing H. huso in these weight classes at different stocking densities of 10, 7.5 and 5.1 kg m^-2 in brackish water was significantly better than rearing them in freshwater. Also based on feeding indices (FCR, FE, SGR and GR) in these weight classes, stocking densities of 2.6 and 5.1 kg m^-2 in brackish water were significantly more suitable than other stocking densities studied in the same culture medium. Results obtained from rearing juvenile H. huso at stocking densities of 2.6, 5.1 and 7.5 kg m^-2 in brackish water was significantly better than that obtained in freshwater at the same stocking densities. Based on growth (SGR, BWI) and feeding (FE) indices in the weight class 900-3000 g it is evident that experimental group 5 (with stocking density of 10 kg m^-2 , water flow of 3 L sec^-1) was significantly better (P<0.05) than all other groups studied. It may also be concluded from the results obtained by studying stocking densities and water flow that stocking density of 10 kg m^-2 used for rearing juvenile H. huso in the weight class 900 g until they reach a weight of 3000 g is not a limiting factor on their growth. It was also observed that juvenile H. huso are highly capable of adapting to their environment. The one-way water supply and daily water exchange with different water flow rates ranging from 1 to 6 L sec^-1 yielded similar results. It was clearly evident that a water flow rate of 0.5 L sec^-1 in brackish water and freshwater resulted in significantly lower growth in juvenile H. huso. Highest growth was reported in brackish water with a flow rate of 1.5 and 3 L sec-1. In freshwater, highest growth was recorded with flow rates of 3 L sec^-1. Higher water flow rates improved growth indices in H. huso. Improved condition factor and variable coefficients of weight and total length were observed in experimental groups in brackish water and freshwater, except in the experimental group with a flow rate of 0.5 L sec^-1 in freshwater. In the weight class 530-2000 g, water flow rate of 3 L sec-1 produced higher final weight in juvenile H. huso in freshwater as compared to that in brackish water. Similar results were obtained in freshwater and brackish water with water flow rate of 1.5 L sec^-1. Data on carcass composition of farmed H. huso indicated no significant effect of freshwater and brackish water on protein and lipid levels. In both rearing media, diets were formulated to meet the dietary requirements of H.huso and hence carcass composition conformed to the quality of diets

Life cycle assessment of bacterial cellulose production

Purpose Bacterial cellulose (BC), obtained by fermentation, is an innovative and promising material with a broad spectrum of potential applications. Despite the increasing efforts towards its industrialization, a deeper understanding of the environmental impact related to the BC production process is still required. This work aimed at quantifying the environmental, health, and resource depletion impacts related to a production of BC. Methods An attributional life cycle assessment (LCA) was applied to a process design of production of BC, by static culture, following a cradle-to-gate approach. The LCA was modeled with GaBi Pro Software using the ReCiPe 2016 (H) methodology with environmental impact indicators at midpoint level. The functional unit was defined as 1 kg of BC (dry mass), in 138.8 kg of water. Results From the total used resources (38.9 ton/kg of BC), water is the main one (36.1 ton/kg of BC), most of which (98%) is returned to fresh waters after treatment. The production of raw materials consumed 17.8 ton of water/kg of BC, 13.8 ton/kg of BC of which was for the production of carton packaging, culture medium raw materials, and sodium hydroxide (for the washing of BC). The remaining consumed water was mainly for the fermentation (3.9 ton/kg) and downstream process (7.7 ton/kg). From the identified potential environmental impacts, the production of raw materials had the highest impact, mainly on Climate change, Fossil depletion, Human toxicity, non-cancer, and Terrestrial toxicity. The sodium dihydrogen phosphate production, used in the culture medium, showed the highest environmental impacts in Human toxicity, non-cancer and Terrestrial ecotoxicity, followed by corn syrup and carton production. The static culture fermentation and downstream process showed impact in Climate change and Fossil depletion. Conclusions Per se, the BC production process had a small contribution to the consumption of resources and environmental impact of the BC global life cycle.This study was supported by the Portuguese Foundation for Science and Technology (FCT) within the scope of the strate gic funding of UIDB/04469/2020 and UIDB/00511/2020 units and MultiBiorefinery project (SAICTPAC/0040/2015-POCI-01-0145- FEDER-016403). This study was also supported by The Navigator Company through the I&D no. 21874, “Inpactus-–Produtos e Tecno logias Inovadores a partir do Eucalipto”, funded through the European Regional Development Fund (ERDF) and the Programa Operacional Competitividade e Internacionalização (POCI) is greatly acknowl edged. The work by Belmira Neto was fnancially supported by Base Funding—UIDB/00511/2020 of the Laboratory for Process Engineer ing, Environment, Biotechnology and Energy—LEPABE—funded by national funds through the FCT/MCTES (PIDDAC).info:eu-repo/semantics/publishedVersio

Effect of particle size, coupling agent and DDGS additions on Paulownia wood polypropylene composites

Studies aimed at improving the tensile, flexural, impact, thermal, and physical characteristics of wood–plastic composites composed of Paulownia wood flour derived from 36-month-old trees blended with polypropylene were conducted. Composites of 25% and 40% w/w of Paulownia wood were produced by twin-screw compounding and injection molding. Composites containing 0–10% by weight of maleated polypropylene were evaluated and an optimum maleated polypropylene concentration determined, i.e., 5%. The particle size distribution of Paulownia wood filler is shown to have an effect on the tensile and flexural properties of the composites. Novel combination composites of dried distiller’s grain with solubles mixed with Paulownia wood (up to 40% w/w) were produced and their properties evaluated. Depending on the composite tested, soaking composites for 872 h alters mechanical properties and causes weight gain

Biodegradable starch-based composites: effect of micro and nanoreinforcements on composite properties

Thermoplastic starch (TPS) matrix was reinforced with various kenaf bast cellulose nanofiber loadings (0–10 wt%). Thin films were prepared by casting and evaporating the mixture of aqueous suspension of nanofibers (NFs), starch, and glycerol which underwent gelatinization process at the same time. Moreover, raw fibers (RFs) reinforced TPS films were prepared with the same contents and conditions. The effects of filler type and loading on different characteristics of prepared materials were studied using transmission and scanning electron microscopies, X-ray diffractometry, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and moisture absorption analysis. Obtained results showed a homogeneous dispersion of NFs within the TPS matrix and strong association between the filler and matrix. Moreover, addition of nanoreinforcements decreased the moisture sensitivity of the TPS film significantly. About 20 % decrease in moisture content at equilibrium was observed with addition of 10 wt% NFs while this value was only 5.7 % for the respective RFs reinforced film

Enzymatic hydrophobic modification of jute fibers via grafting to reinforce composites

Horseradish peroxidase (HRP)/H2O2 system catalyzes the free-radical polymerization of aromatic compounds such as lignins and gallate esters. In this work, dodecyl gallate (DG) was grafted onto the surfaces of lignin-rich jute fabrics by HRP-mediated oxidative polymerization with an aim to enhance the hydrophobicity of the fibers. The DG-grafted jute fibers and reaction products of their model compounds were characterized by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The results clearly indicated the grafting of DG to the jute fiber by HRP. Furthermore, the hydrophobicity of jute fabrics was determined by measuring the wetting time and static contact angle. Compared to the control sample, the wetting time and static contact angle of the grated fabrics changed from ~1 s to 1 h and from ~0° to 123.68°, respectively. This clearly proved that the hydrophobicity of jute fabrics improved considerably. Conditions of the HRP-catalyzed DG-grafting reactions were optimized in terms of the DG content of modified jute fabrics. Moreover, the results of breaking strength and elongation of DG-grafted jute/ polypropylene (PP) composites demonstrated improved reinforcement of the composite due to enzymatic hydrophobic modification of jute fibers.This work was financially supported by the National Natural Science Foundation of China (51173071), the Program for New Century Excellent Talents in University (NCET-12-0883), Program for Changjiang Scholars and Innovative Research Team in University (No. IRT_15R26) the Fundamental Research Funds for the Central Universities (JUSRP51312B, JUSRP51505), and the Graduate Student Innovation Plan of Jiangsu Province of China (SJLX_0527)

Supply and protected different population of Litopenaeus vannamei subadult zero foster (F0) from difference provinces Iran

Nowadays, Litopenaeus vannamei are the most important species of farmed penaeidae shrimp in the world that is rapidly replacing native species in areas aquaculture. Due to demand increase for this species culture, shrimp displacement to different areas may be associated with some potential pathogens transferred to new areas farmed. Therefore, in this study were prepared bi-osecurity conditions for specific disease-free production of L. vannamei. Thereafter, three populations (Molokaei, High health and mix of Molokaei and High health) of the shrimp various reserves were detected base on origin and genetic indexes such as: observed heterozygosity, expected heterozygosity, allele frequency, coefficient inbreeding, genetic differentiation, genetic distance and genetic identity. On the other hand, epidemiological studies indicate non pathogens (viral, bacterial, fungal and parasitic) recognition of different populations selected in the quarantine salon. The bioassay results showed that the average weight and length of the populations of High health and Mix significantly greater than was a population of Molokaei. The shrimp populations were stocked in fiberglass tank (five ton) and were kept separated in the quarantine salon. During maintenance shrimp of populations in the quarantine salon were evaluated living and non-living pathogens with PCR, microbiology and biochemical methods. There is not any pathogens detection from shrimp populations stocking in the quarantine salon, so the shrimps were carried over to pond for broodstock culture of specific pathogenic free