Anderson-like impurity in the one-dimensional t-J model: formation of local states and magnetic behaviour

We consider an integrable model describing an Anderson-like impurity coupled to an open $t$--$J$ chain. Both the hybridization (i.e. its coupling to bulk chain) and the local spectrum can be controlled without breaking the integrability of the model. As the hybridization is varied, holon and spinon bound states appear in the many body ground state. Based on the exact solution we study the state of the impurity and its contribution to thermodynamic quantities as a function of an applied magnetic field. Kondo behaviour in the magnetic response of the impurity can be observed provided that its parameters have been adjusted properly to the energy scales of the holon and spinon excitations of the one-dimensional bulk.Comment: 32 pages, 11 figure

Quantum phase transitions and thermodynamics of the power-law Kondo model

We revisit the physics of a Kondo impurity coupled to a fermionic host with a diverging power-law density of states near the Fermi level, $\rho(\omega) \sim |\omega|^r$, with exponent $-1<r<0$. Using the analytical understanding of several fixed points, based partially on powerful mappings between models with bath exponents $r$ and $(-r)$, combined with accurate numerical renormalization group calculations, we determine thermodynamic quantities within the stable phases, and also near the various quantum phase transitions. Antiferromagnetic Kondo coupling leads to strong screening with a negative zero-temperature impurity entropy, while ferromagnetic Kondo coupling can induce a stable fractional spin moment. We formulate the quantum field theories for all critical fixed points of the problem, which are fermionic in nature and allow for a perturbative renormalization-group treatment.Comment: 13 pages, 11 figure

Improved algorithms for topic distillation in a hyperlinked environment

Abstract This paper addresses the problem of topic distillation on the World Wide Web, namely, given a typical user query to find quality documents related to the query topic. Connectivity analysis has been shown to be useful in identifying high quality pages within a topic specific graph of hyperlinked documents. The essence of our approach is to augment a previous connectivity analysis based algorithm with content analysis. We identify three problems with the existing approach and devise algorithms to tackle them. The results of a user evaluation are reported that show an improvement of precision at 10 documents by at least 45 % over pure connectivity analysis.

Value creation in brand alliances : a network approach.

Alliance; Brand; Governance; Network; Value;

Testing theory in practice: a simple experiment

In this paper we discuss the experiences gained in conducting a simple testing experiment. The goal of this experiment is to apply the abstract, formal testing framework [8] in a practical setting, and to indicate the critical aspects in its application to realistic testing situations. For that purpose a formal description of the system under test (SUT) is made from which tests are systematically derived. These tests are interpreted and executed by a tester against concrete implementations, thereby giving an indication about the correctness of these implementations

The influence of defined ante-mortem stressors on the early post-mortem biochemical processes in the abdominal muscle of the Norway lobster, Nephrops norvegicus (Linnaeus, 1758)

The effects of four different ante-mortem stressors (exercise, emersion, starvation and a patent infection with the parasite Hematodinium sp.) on post-mortem processes have been investigated in the abdominal muscle of Norway lobster Nephrops norvegicus by measuring changes in the pH, the levels of glycogen, l-lactate, arginine phosphate, ATP, ADP, AMP, IMP, HxR, Hx and the adenylate energy charge (AEC) over a time course of 24 h with samples being taken at 0, 3, 6, 12 and 24 h. The acute stresses of intense exercise and 2 h emersion resulted in a premature onset of anaerobic glycolysis, leading both to an enhanced glycogen depletion rate and an early accumulation of l-lactate. The chronic stressors, starvation and parasite infection, resulted in a complete ante-mortem depletion of muscle glycogen and consequently the failure of post-mortem glycolytic fermentation. Post-mortem pH and ATP inter-conversion were significantly altered in chronically stressed animals. Ante-mortem, a rapid, almost complete depletion of arginine phosphate was observed in all stress groups. The AEC was altered significantly by all stresses, indicating a strong energy demand. The findings suggest that ante-mortem stressors strongly influence the post-mortem biochemical processes. The laboratory-based results are compared to 'field' data and effects on post-harvest product quality are discussed

Metabolomic profiling of macrophages determines the discrete metabolomic signature and metabolomic interactome triggered by polarising immune stimuli

Priming and activating immune stimuli have profound effects on macrophages, however, studies generally evaluate stimuli in isolation rather than in combination. In this study we have investigated the effects of pro-inflammatory and anti-inflammatory stimuli either alone or in combination on macrophage metabolism. These stimuli include host factors such as IFNγ and ovalbumin-immunoglobulin immune complexes, or pathogen factors such as LPS. Untargeted LC-MS based metabolomics provided an in-depth profile of the macrophage metabolome, and revealed specific changes in metabolite abundance upon either individual stimuli or combined stimuli. Here, by factoring in an interaction term in the linear model, we define the metabolome interactome. This approach allowed us to determine whether stimuli interact in a synergistic or antagonistic manner. In conclusion this study demonstrates a robust approach to interrogate immune-metabolism, especially systems that model host-pathogen interactions