Spin-Charge Separation and Kinetic Energy in the t-J Model

I show that spin-charge separation in 2-D t-J model leads to an increase of kinetic energy. Using a sum rule, I derive an exact expression for the lowest possible KE (E_{bound}) for any state without doubly occupied sites. KE of relevant slave-boson and Schwinger-boson mean-field states -- which exhibit complete spin-charge separation -- are found to be much larger than E_{bound}. Examination of n(k) shows that the large increse in KE is due to excessive depletion of electrons from the bottom of the band (Schwinger boson) and of holes from the top (slave boson). To see whether the excess KE is simply due to poor treatment of the constraints, I solve the constraint problem analytically for the Schwinger boson case in the J = 0 limit. This restores gauge invariance, incorrectly violated in MF theories. The result is a generalized Hartree-Fock state of the Hubbard model, but one that includes spin waves. Even after constraints are imposed correctly, the KE remains much larger than E_{bound}. These results support the notion, advanced earlier [PRB 61, 8663 (2000)] that spin-charge separation in the MF state costs excessive KE, and makes the state unstable toward recombination processes which lead to superconductivity in d = 2 and a Fermi liquid state in higher dimensions.Comment: 13 pages, LateX plus three figures. To appear in Phys Rev B Typos correcte

Liver virome of a Little Corella (Cacatua sanguinea) reveals coinfection with a novel parvovirus and two beak and feather disease viruses

Emerging diseases are acknowledged as a growing threat to wildlife, with the continued identification of pathogenic and potentially pathogenic viruses in avian species resulting from ongoing advances in molecular diagnostic techniques. Parvoviruses under the genus Chaphamaparvovirus (subfamily Hamaparvovirinae) are highly divergent. The detection and characterisation of parvoviruses in psittacine birds is limited. This study reports a novel parvovirus, tentatively named psittaciform chaphamaparvovirus 3 (PsChV-3) under the genus Chaphamaparvovirus, identified in an Australian free-ranging little corella (Cacatua sanguinea). The PsChV-3 genome is 4277 bp in length and encompasses four predicted open-reading frames, including two major genes, a nonstructural replicase gene (NS1), and a structural capsid gene (VP1). The NS1 and VP1 genes showed the closest amino acid identities of 78.8% and 69.7%, respectively, with a recently sequenced psittaciform chaphamaparvovirus 2 from Australian Neophema species grass parrots. In addition, the presence of two complete novel beak and feather disease (BFDV) genomes, 1993 and 1868 nt in length, respectively, were detected from the same bird. Both these BFDV genomes contained two bidirectional ORFs encoding the putative Rep and Cap proteins. Phylogenetic analysis showed that the sequenced novel BFDV genomes clustered in a distinct subclade with other BFDVs isolated from Australian cockatoos. This study contributes to the characterisation chaphamaparvoviruses and BFDV in Australian parrots and supports the need for ongoing monitoring and molecular studies into the avian virome in native Australian psittacine bird species

Study on Sedation with Local Analgesia in Calves

. The effect of sedatives and analgesics on heart rate, respiration rate and rectal temperature were observed. Heart rate and respiration rate significantly decreased during sedation with xylazine hydrochloride plus 2% lignocaine hydrochloride or 0.5% bupivacaine hydrochloride. A significantly decreased heart rate and respiration rate also found during sedation with diazepam plus 2% lignocaine hydrochloride or 0.5% bupivacaine hydrochloride. Two percent lignocaine hydrochloride showed short onset, rapid spreading and no side effect. Duration of analgesia was longer with 0.5 % bupivacaine hydrochloride (55.88±1.58 min in Group B and 48±11.25 min in Group D) compared to 2% lignocaine hydrochloride (39.60±5.77 min in Group A and 43.6±5.81 min in Group C). Xylazine hydrochloride showed short onset and long duration of sedation compared to diazepam. So for herniorraphy, xylazine hydrochloride can be used as a better sedative while 0.5 % bupivacaine hydrochloride can be used as a local analgesic for longer duration of action

Hydrogen absorption properties of amorphous (Ni0.6Nb0.4−yTay)100−xZrx membranes

Ni based amorphous materials have great potential as hydrogen purification membranes. In the present work the melt spun (Ni0.6Nb0.4−yTay)100−xZrx with y=0, 0.1 and x=20, 30 was studied. The result of X-ray diffraction spectra of the ribbons showed an amorphous nature of the alloys. Heating these ribbons below T < 400 °C, even in a hydrogen atmosphere (1−10 bar), the amorphous structure was retained. The crystallization process was characterized by differential thermal analysis and the activation energy of such process was obtained. The hydrogen absorption properties of the samples in their amorphous state were studied by the volumetric method, and the results showed that the addition of Ta did not significantly influence the absorption properties, a clear change of the hydrogen solubility was observed with the variation of the Zr content. The values of the hydrogenation enthalpy changed from ~37 kJ/mol for x=30 to ~9 kJ/mol for x=20. The analysis of the volumetric data provides the indications about the hydrogen occupation sites during hydrogenation, suggesting that at the beginning of the absorption process the deepest energy levels are occupied, while only shallower energy levels are available at higher hydrogen content, with the available interstitial sites forming a continuum of energy levels

Small-Scale Turkey Farming in Bangladesh: Farming Practices, Profitability and Supply Chain Mapping

The study was conducted to know the existing turkey production system, supply chain mapping, and identifying the prospects and problems of turkey rearing in some selected areas of Bangladesh during October 2019 to December 2019. A total of 100 turkey raisers were surveyed following convenience method of sampling technique. The primary data were collected, analyzed accordingly and tabular presentation method was applied with the help of simple descriptive statistical measures e.g. frequency distributions, percentage, sum and means to illustrating the results. Profitability analysis was done on the basis of variable cost, fixed cost, return by using arithmetic means and percentages. The study revealed that 87 male and 13 female respondents were surveyed, of them cent percent found educated. About 56% turkey keeper’s main occupation was business, 27% service and 12% in farming while 88.57% involved with farming as secondary sources of income. Average landholding for homestead, cultivable and non-cultivable was 24.40, 129.71 and 29.47 decimal, respectively. About 59% farms started for commercial purpose, 32% for non-commercial purpose and 9% for both. About 60% respondents kept less than 50 turkeys and only 2% kept 501-1000 turkeys. Among the surveyed farms55% stopped their operation and 45% farms found running their business. Among the running farms cent percent were small-scale group. The average feed intake was 192.13 grams per day per bird at 20 weeks of age. Turkey laid on an average 139 eggs a year irrespective of variety and for hatching poults, the fertility and hatchability rate found between 65 to 100% and 50 to 90%, respectively. About 28% farmers experienced the deaths of turkey because of Cold, Pox, Ranikhet, Bird flu and unknown cases and 69.47% farmers took veterinary advice from Upazila Livestock Hospital and rest from other sources. Farmers to consumers were the most common and widely used marketing channel for egg, chick and adult turkey. The market intermediaries of turkey farm carried out different marketing functions e.g. buying and selling, pricing, transportation, sorting, distribution and market information. The average net return and benefit-cost ratio was BDT 127838.04 and 1.38, respectively for 50 turkeys per year. In the study, turkey rearing found some comparative benefit over chicken and ducks e.g. higher weight gain, forage eater, lower diseases rate and suitability for the country. The main problem of turkey rearing identified as market instability, lack of quality turkey feed, higher feed price, lack of proper marketing facility and training on turkey farming. In conclusion, the small-scale turkey farming could be a viable source of income for the rural people of Bangladesh after taking some remedial steps by the Government of Bangladesh for the aforesaid hindrances faced by the turkey farmers

Surface magnetic phase transition of the double-exchange ferromagnet: Schwinger-boson mean-field study

The surface magnetic phase transition of a double-exchange model for metallic manganites is studied using a Schwinger-boson mean-field method. About three unit-cells wide surface layers are identified. The magnetic moment in these layers decreases more rapidly than that in the bulk when the temperature is increased. This behavior is consistent with experimental observations. We also discuss the implication of this behavior on the tunneling magnetoresistance effect using manganites and possible improvement of the magnetoresistance effect near the bulk Curie temperature.Comment: 7 pages, 9 figure

Temperature dependence of the resistivity in the double-exchange model

The resistivity around the ferromagnetic transition temperature in the double exchange model is studied by the Schwinger boson approach. The spatial spin correlation responsible for scattering of conduction electrons are taken into account by adopting the memory function formalism. Although the correlation shows a peak lower than the transition temperature, the resistivity in the ferromagnetic state monotonically increases with increasing temperature due to a variation of the electronic state of the conduction electron. In the paramagnetic state, the resistivity is dominated by the short range correlation of scattering and is almost independent of the temperature. It is attributed to a cancellation between the nearest-neighbor spin correlation, the fermion bandwidth, and the fermion kinetic energy. This result implies the importance of the temperature dependence of the electronic states of the conduction electron as well as the localized spin states in both ferromagnetic and paramagnetic phases.Comment: RevTex, 4 pages, 4 PostScript figures, To appear in Phys. Rev.

Effect of planting method on onion (Allium cepa L.) bulb production in Faridpur region of Bangladesh

The present study was undertaken to evaluate the effective planting method for onion production for motivating onion producing farmers in Faridpur region of Bangladesh during rabi season 2014-15 and 2015-16 at spices Research Sub-centre, Faridpur. The number of treatment was four viz., Raised bed + Spices Research Centre (SRC) recommended practice, Raised bed + Farmer’s practice, Flat method + Spices Research Centre (SRC) recommended practice and Flat method + Farmer’s practice. The onion variety BARI Piaz-1 used as planting material. The SRC recommended practice consist of seed sowing at 2nd week of November + seedlings transplanting at the end of December + Spacing (10cm × 10cm) + Irrigation (4times) + weeding (four at 15, 25, 45 and 60 DAT) + Fungi-cide application with Rovral and Ridomil gold (four spray when disease appears) + Insecticide application (2-3 spray when/before thrips / insect appears) + Fertilizer doses (cow dung 5 ton ha-1, N120, P54, k75 and S20 kg ha-1. On the other hand farmer’s practice consist of seed sowing at last week of November in flat seed bed + seedling transplanting at 3rd week of January + Spacing (10cm × 7cm) + Irrigation (2-3 times) + Weeding (2times) + Fungicide application with Rovral, Score and other type of ineffective fungicide at 5-7 days interval + insecticide application with Confidor after thrips / insect appears + Fertilizer doses (N46, P45, k30 and S16 kg ha-1. The results of the study revealed that planting method and management practices had significant impact on yield and yield attributes of onion and among the treatments the highest yield was found from Raised bed + SRC recommended practice. Significantly highest yield 14.42 t ha-1 in 2014-15 and 12.57 t ha-1 in 2015-16 was recorded from SRC recommended practice. The lowest yield 8.05 t ha-1 in 2014-15 and 7.66 t ha-1 in 2015-16 was recorded from Flat method + Farmer’s practice. Therefore, the farmers of Faridpur region of Bangladesh are advised to adopt SRC recommended practice with raised bed method for increasing their annual average onion productio

An Approach of Automated Electronic Voting Management System for Bangladesh Using Biometric Fingerprint

The existing system of election is running manually and the piloted electronic voting using electronic voting machine (EVM) has many limitations in its mechanism. In this paper we have proposed an automated biometric electronic voting system, where a four layered network system has been used for sending the votes from client to the main database, and there exist three application servers and a client. That means, the proposed systems starts with automated registration system that would provide the secured database of the votersrsquo; information, and voter details will be stored against their finger prints in the main database. Finally, at the end of the day, casted votes will be counted automatically which would take lesser time than the manual system and the result would be accurate, faster and reliable, and thus minimize the corruption

Bioactividad de los extractos y aislamiento de los lignanos de las semillas de Centaurea dealbata

Centaurea dealbata Willd. (Family: Asteraceae) belongs to the big genus Centaurea that comprises ca. 500 species. Then-hexane, dichloromethane (DCM) and methanol (MeOH) extracts of the seeds of C. dealbata have been assessed forantioxidant activity and general toxicity using, respectively, the DPPH assay, and the brine shrimp lethality assay. Boththe DCM and the MeOH extract showed signifi cant levels of antioxidant activities with an RC50 value 6.8 x 10-2 and4.7 x 10-2 mg/mL, respectively. None of the extracts exhibited any signifi cant general toxicity (LD50 = &gt;1000 mg/mL).Three major bioactive components of the MeOH extract were found to be the lignans, arctigenin, arctiin and matairesinoside.The structures of these lignans were elucidated by comprehensive spectroscopic analyses, and also by directcomparison with the respective published data. This is the fi rst report on the occurrence of arctiin and matairesionl inC. dealbata. The distribution of these lignans within the genus Centaurea has also been presented.La Centaurea dealbata Willd. (familia: Asteraceae) pertenece al género Centaurea, que comprende unas 500 especies.Para evaluar la actividad antioxidante y la toxicidad general de los extractos de n-hexano, diclorometano (DCM)y metanol (MeOH) de las semillas de C. dealbata se han utilizado, respectivamente, el ensayo DPPH y el ensayo deletalidad de gambas en salmuera. Tanto el extracto de DCM como el de MeOH presentaron niveles signifi cativosde actividad antioxidante, con valores de RC50 de 6,8 x 10-2 y 4,7 x 10-2 mg/mL, respectivamente. Ninguno de losextractos presentó una toxicidad general signifi cativa (LD50 = &gt;1000 mg/mL). Se observó que los tres principalescomponentes bioactivos del extracto de MeOH fueron los lignanos arctigenina, arctiina y matairesinosida. Lasestructuras de estos lignanos se dilucidaron mediante análisis espectroscópicos exhaustivos y comparación directacon los datos respectivos publicados. Éste es el primer informe sobre la ocurrencia de arctiina y matairesinol en C.dealbata. También se presenta la distribución de estos lignanos dentro del género Centaurea