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

Technology Adoption by Groups: A Valence Perspective

While past research has contributed to an understanding of how organizations or individuals adopt technologies, little is known about how such adoption occurs in groups. Given the widespread acknowledgment that organizations are moving to group-based structures and that groups often utilize technologies for performing their tasks, it is critical that we understand how such collective social entities adopt technologies. Such an understanding can better guide investment and implementation decisions. In this paper, we draw on existing literature about groups, technology characteristics, and valence to conceptualize a model of technology adoption by groups (referred to as the TAG model). We view the TAG phenomenon as a process of communication and negotiation in which analytically distinct factors-such as the individual members\u27 a priori attitudes toward the technology, the majority subgroup\u27s opinion, high-status members\u27 opinions, substantive conflict, and relevant characteristics of the technology play an important role. We develop several theoretical propositions regarding the nature of the contribution of these factors toward an adoption decision and discuss measurement tradeoffs and guidelines

An Exploration of Trust in Virtual Teams Using Three Perspectives

With the recent advancements in technology and the development of sophisticated tools for collaborative work, the use of computer-mediated groups in organizations has increased rapidly. Further, the need for globalization has forced members of such teams to be dispersed in both time and space, and has paved the way for the development and implementation of the concept of “virtual teams.” In this paper, we examine one of the primary factors leading to virtual team effectiveness, namely, the issue of trust. One of the objectives of this paper is to investigate the applicability of the research findings on trust in traditional face-to-face teams in a virtual context. Drawing on prior literature, the present study uses three perspectives to trust and proposes a model for trust development in virtual teams. Further, prior research has always treated trust as a static concept, and researchers appear to have assumed that it is always the same factors that influence trust at any point in a cooperative interaction. In this paper, a more dynamic model is proposed, which suggests that, different factors explain the level of trust in different points of team development. By uncovering some unique concepts leading to trust development in virtual teams, it is hoped that a contribution will be made to the existing literature on factors leading to virtual team effectiveness and success. Future research directions include an attempt to validate this dynamic model in a quasi-experimental setting of virtual teamwork

Rat floods and water floods: the ecological and sociological dynamics of rodent management in Bangladesh

Chakma, N., Belmain, S.R., Sarker, N.J., Sarker, S.U., Kamal, N.Q., Sarker, S.K

Influences of dietary lipid and phosphorus levels on retention and excretion of phosphorus and nitrogen in fingerlings red sea bream, Pagrus major

A laboratory based 2x3 factorial experiment was conducted for 12 weeks to investigate the influences of dietary lipid and phosphorus (P) levels on retention and excretion of phosphorus and nitrogen (N) in fingerling red sea bream. Two levels of lipid (210 and 260 g/kg) and three levels of phosphorus (17, 14 and 12 g/kgˉ¹) in the dry diets were tested. Duplicate groups of 25 red sea bream (average weight 3.74±0.07 g) per 60L glass tank were fed experimental diets three times a day near to satiation level at 22 to 28°C water temperature. A reduction in dietary fish meal from 500 to 300 g/kg dry diet, corresponding to a supplementation in both dietary lipid and P resulted in significant increase in both P and N retention which resulted in the reduction of their excretion by red sea bream. The overall results of the present study demonstrated that both lipid and phosphorus supplementation are necessary for developing less-polluting feed which in turn, reduce fish meal level in the diet of fingerling red sea bream. Further studies in this regard with different size and age groups of red sea bream are warranted

Effects of dietary phosphorus and zinc levels on growth artd bone mineralization in fingerlings of rainbow trout, Oncorhynchus mykiss

A laboratory based 2 x 2 factorial experiment was conducted to investigate the influences of dietary phosphorus and zinc levels on growth and bone mineralization in fingerlings of rainbow trout for 21 weeks. Two levels of phosphorus (19 and 30 mg/g) and two levels of zinc (55 and 103 Ag/g) in the dry diets were tested. Duplicate tanks of 30 rainbow trout (average weight 1.56 ± 0.24 g) per 60L glass tank were fed experimental diets three times a day to apparent satiation level at 15 to 24°C water temperature. The results of the present study demonstrated that dietary phosphorus supplementation influenced the growth and bone mineralization whereas zinc levels significantly (p<0.05) influenced bone mineralization in rainbow trout. Further investigations in this area with different size and age groups of this fish are broadly needed

Fire endurance of steel reinforced fly ash geopolymer concrete elements

As a new alternative to OPC, investigation into the fire endurance of geopolymer concrete is of utmost importance in order to ensure safety. Geopolymer and OPC concrete panels of 125–175 mm thickness containing a layer of steel mesh were exposed to fire for 2 h. Test results show higher heat transfer rate and less cracking and spalling in the geopolymer concrete specimens. The residual load capacity was between 61% and 71% for the geopolymer and between 50% and 53% for the OPC concrete panels. Thus, the reinforced geopolymer concrete elements demonstrated superior fire endurance than the OPC counterparts

Dynamical Casimir effect for magnons in a spinor Bose-Einstein condensate

Magnon excitation in a spinor Bose-Einstein condensate by a driven magnetic field is shown to have a close analogy with the dynamical Casimir effect. A time-dependent external magnetic field amplifies quantum fluctuations in the magnetic ground state of the condensate, leading to magnetization of the system. The magnetization occurs in a direction perpendicular to the magnetic field breaking the rotation symmetry. This phenomenon is numerically demonstrated and the excited quantum field is shown to be squeezed.Comment: 8 pages, 3 figure

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

Comment on 'Anti-tumour activity of abiraterone and diethylstilboestrol when administered sequentially to men with castration-resistant prostate cancer'

This work is licensed under the Creative Commons Attribution-NonCommercial-Share Alike 3.0 Unported License