Doping a correlated band insulator: A new route to half metallic behaviour

We demonstrate in a simple model the surprising result that turning on an on-site Coulomb interaction U in a doped band insulator leads to the formation of a half-metallic state. In the undoped system, we show that increasing U leads to a first order transition between a paramagnetic, band insulator and an antiferomagnetic Mott insulator at a finite value U_{AF}. Upon doping, the system exhibits half metallic ferrimagnetism over a wide range of doping and interaction strengths on either side of U_{AF}. Our results, based on dynamical mean field theory, suggest a novel route to half-metallic behavior and provide motivation for experiments on new materials for spintronics.Comment: 5 pages, 7 figure

Phase Diagram of the Half-Filled Ionic Hubbard Model

We study the phase diagram of the ionic Hubbard model (IHM) at half-filling using dynamical mean field theory (DMFT), with two impurity solvers, namely, iterated perturbation theory (IPT) and continuous time quantum Monte Carlo (CTQMC). The physics of the IHM is governed by the competition between the staggered potential $\Delta$ and the on-site Hubbard U. In both the methods we find that for a finite $\Delta$ and at zero temperature, anti-ferromagnetic (AFM) order sets in beyond a threshold $U=U_{AF}$ via a first order phase transition below which the system is a paramagnetic band insulator. Both the methods show a clear evidence for a transition to a half-metal phase just after the AFM order is turned on, followed by the formation of an AFM insulator on further increasing U. We show that the results obtained within both the methods have good qualitative and quantitative consistency in the intermediate to strong coupling regime. On increasing the temperature, the AFM order is lost via a first order phase transition at a transition temperature $T_{AF}(U, \Delta)$ within both the methods, for weak to intermediate values of U/t. But in the strongly correlated regime, where the effective low energy Hamiltonian is the Heisenberg model, IPT is unable to capture the thermal (Neel) transition from the AFM phase to the paramagnetic phase, but the CTQMC does. As a result, at any finite temperature T, DMFT+CTQMC shows a second phase transition (not seen within DMFT+IPT) on increasing U beyond $U_{AF}$. At $U_N > U_{AF}$, when the Neel temperature $T_N$ for the effective Heisenberg model becomes lower than T, the AFM order is lost via a second order transition. In the 3-dimensonal parameter space of $(U/t,T/t,\Delta/t)$, there is a line of tricritical points that separates the surfaces of first and second order phase transitions.Comment: Revised versio

Can correlations drive a band insulator metallic?

We analyze the effects of the on-site Coulomb repulsion U on a band insulator using dynamical mean field theory (DMFT). We find the surprising result that the gap is suppressed to zero at a critical Uc1 and remains zero within a metallic phase. At a larger Uc2 there is a second transition from the metal to a Mott insulator, in which the gap increases with increasing U. These results are qualitatively different from Hartree-Fock theory which gives a monotonically decreasing but non-zero insulating gap for all finite U.Comment: 4 pages, 5 figure

Pathways Across the Valley of Death: Novel Intellectual Property Strategies for Accelerated Drug Discovery

Drug discovery is stagnating. Government agencies, industry analysts, and industry scientists have all noted that, despite significant increases in pharmaceutical R&D funding, the production of fundamentally new drugs - particularly drugs that work on new biological pathways and proteins - remains disappointingly low. To some extent, pharmaceutical firms are already embracing the prescription of new, more collaborative R&D organizational models suggested by industry analysts. In this Article, we build on collaborative strategies that firms are already employing by proposing a novel public-private collaboration that would help move upstream academic research across the valley of death that separates upstream research from downstream drug candidates. By exchanging trade secrecy for contract-based collaboration, our proposal would both protect intellectual property rights and enable many more researchers to search for potential drug candidates

PREFERENSI KONSUMEN TERHADAP ATRIBUT BUAH PEPAYA (Carica papaya L.) LOKAL DI PASAR TRADISIONAL KOTA BOGOR

This study aims to analyze consumer characteristics, determine the process of making purchasing decisions and determine consumer preferences for local papaya attributes in traditional markets in Bogor City. 30 respondents were determined by using accidental sampling. The method of analysis used are descriptive analysis, Multi-attribute Fishbein and Importance Performance Analysis (IPA). The results showed that the characteristics of local Papaya consumers were quite varied, namely gender, age, education, occupation, number of dependents and monthly income. Purchasing decisions are influenced by five factors, namely need recognition, information search, evaluation of alternatives, purchases and outcomes. Consumer preferences can be identified through the attributes found in local papaya fruit such as taste, skin color, size, shape, water content (juiciness), flesh color, flesh thickness, flesh texture and papaya skin texture. The result of Fishbein's Multi-attribute analysis shows that the most influencing attributes for consumer in making purchasing decisions are the color of the meat and the taste attribute of the local Papaya fruit. IPA Matrix Analysis shows that the attributes that must be maintained are taste and color of the meat, and the attributes that need to be developed are the thickness of the meat and the texture of the meat. Keywords: Local Papaya attribute, Fishbein Multi-attribute, IPA Matrix, Consumer Preference, traditional marke

Rheumatoid arthritis-associated interstitial lung disease seen in two generation of females in an Indian family

Interstitial lung diseases (ILDs) or diffuse parenchymal lung diseases (DPLDs) are a group of lung diseases that is distinguished by subacute or chronic inflammation and/or fibrosis. Family history is currently being considered one of the biggest risk factors for ILD. Rheumatoid arthritis (RA) a systemic autoimmune disease has lungs as its most common extraarticular organ involved. Interstitial lung disease associated with it is one of the major causes of mortality along with severe disability. Lung involvement in RA might appear as ILD, pleural effusion, or pulmonary vasculitis. In this case report a 42-year-old female presented with complain of progressive breathlessness, dry cough, chest pain, joint pain since past 10 years. HRCT Thorax of patient suggested it to be ILD of UIP pattern with raised RF, anti CCP and positivity in ANA profile. Patient had a family history with mother being diagnosed with ILD-NSIP pattern. She was suspicioned for RA as she had complained of small joint pains and swellings and was responding well to steroids and HCQ

Pathways Across the Valley of Death: Novel Intellectual Property Strategies for Accelerated Drug Discovery

Most therapeutic interventions produced by pharmaceutical firms take the form of small molecule drugs, which are mass produced at low marginal cost and ingested orally. Drug therapies typically work by affecting the activity of human proteins, known in the industry as targets, that have been implicated in disease pathways. Thus far, medical science has identified safe and effective therapies for only a few hundred of the estimated 3000 protein targets in the human genome that are potentially susceptible to a drug. Moreover, pharmaceutical firms have encountered major obstacles in producing fundamentally new small molecule drugs, especially those that work against new targets. According to one report, an average of only three drugs that act on novel targets have reached the market annually in recent years. This highly visible problem has attracted commentary in scholarly articles, government white papers, and the popular press. Government agencies, such as the National Institutes of Health, and industry insiders, have also recognized that one of the most serious pitfalls involves the difficulty of moving across the so-called valley of death that separates upstream research on promising genes, proteins, and biological pathways from downstream drug candidates. For example, an upstream finding that a given protein is differentially expressed in individuals with a particular disease may suggest that the protein merits further investigation. However, much more work (especially medicinal chemistry) is necessary to determine how good a target the protein really is and whether a marketable drug candidate that affects the activity of the protein is likely to be developed

BCS - BEC crossover at T=0: A Dynamical Mean Field Theory Approach

We study the T=0 crossover from the BCS superconductivity to Bose-Einstein condensation in the attractive Hubbard Model within dynamical mean field theory(DMFT) in order to examine the validity of Hartree-Fock-Bogoliubov (HFB) mean field theory, usually used to describe this crossover, and to explore physics beyond it. Quantum fluctuations are incorporated using iterated perturbation theory as the DMFT impurity solver. We find that these fluctuations lead to large quantitative effects in the intermediate coupling regime leading to a reduction of both the superconducting order parameter and the energy gap relative to the HFB results. A qualitative change is found in the single-electron spectral function, which now shows incoherent spectral weight for energies larger than three times the gap, in addition to the usual Bogoliubov quasiparticle peaks.Comment: 11 pages,12 figures, Published versio