Exploring the QCD phase diagram

Lattice simulations employing reweighting and Taylor expansion techniques have predicted a (m;T)-phase diagram according to general expectations, with an analytic quark-hadron crossover at m =0 turning into a first order transition at some critical chemical potential mE. By contrast, recent simulations using imgainary m followed by analytic continuation obtained a critical structure in the fmu;d;ms;T;mg parameter space favouring the absence of a critical point and first order line. I review the evidence for the latter scenario, arguing that the various raw data are not inconsistent with each other. Rather, the discrepancy appears when attempting to extract continuum results from the coarse (Nt =4) lattices simulated so far, and can be explained by cut-off effects. New (as yet unpublished) data are presented, which for Nf = 3 and on Nt = 4 confirm the scenario without a critical point. Moreover, simulations on finer Nt = 6 lattices show that even if there is a critical point, continuum extrapolation moves it to significantly larger values of mE than anticipated on coarse lattices

Correlations of chiral condensates and quark number densities with static quark sources

We investigate correlation functions of the Polyakov loop and static meson/diquark systems with the chiral condensate and the quark number density at finite temperature. In particular the latter observable can give insight in the mechanism of screening and string breaking at finite temperature. We use for our analysis gauge field configurations generated in 2+1 flavor QCD with an improved staggered fermion action with almost physical light quark masses and a physical value of the strange quark mass on lattices with temporal extent Nt=4 and 6.Comment: 7 pages, 6 figures, presented at the XXV International Symposium on Lattice Field Theory, July 30 - August 4 2007, Regensburg, German

QCD Thermodynamics with 2 and 3 Quark Flavors

We discuss the flavor dependence of the pressure and critical temperature calculated in QCD with 2, 2+1 and 3 flavors using improved gauge and staggered fermion actions on lattices with temporal extent Nt=4. For T > 2 Tc we find that bulk thermodynamics of QCD with 2 light and a heavier strange quark is well described by 3-flavor QCD while the transition temperature is closer to that of 2-flavor QCD. Furthermore, we present evidence that the chiral critical point of 3-flavor QCD, i.e. the second order endpoint of the line of first order chiral phase transitions, belongs to the universality class of the 3d Ising model.Comment: 6 pages, LaTeX2e File, 7 EPS-figures, presented at SEWM 2000, Marseille, June 13-17th, 200

Target-Selective Drug Delivery through Liposomes Labeled with Oligobranched Neurotensin Peptides.

The structure and the in vitro behavior of liposomes filled with the cytotoxic drug doxorubicin (Doxo) and functionalized on the external surface with a branched moiety containing four copies of the 8-13 neurotensin (NT) peptide is reported. The new functionalized liposomes, DOPC-NT(4) Lys(C(18) )(2) , are obtained by co-aggregation of the DOPC phospholipid with a new synthetic amphiphilic molecule, NT(4) Lys(C(18) )(2) , which contains a lysine scaffold derivatized with a lipophilic moiety and a tetrabranched hydrophilic peptide, NT8-13, a neurotensin peptide fragment well known for its ability to mimic the neurotensin peptide in receptor binding ability. Dynamic light scattering measurements indicate a value for the hydrodynamic radius (RH) of 88.3±4.4 nm. The selective internalization and cytotoxicity of DOPC-NT(4) Lys(C(18) )(2) liposomes containing Doxo, as compared to pure DOPC liposomes, were tested in HT29 human colon adenocarcinoma and TE671 human rhabdomyosarcoma cells, both of which express neurotensin receptors. Peptide-functionalized liposomes show a clear advantage in comparison to pure DOPC liposomes with regard to drug internalization in both HT29 and TE671 tumor cells: FACS analysis indicates an increase in fluorescence signal of the NT(4) -liposomes, compared to the DOPC pure analogues, in both cell lines; cytotoxicity of DOPC-NT(4) Lys(C(18) )(2) -Doxo liposomes is increased four-fold with respect to DOPC-Doxo liposomes in both HT29 and TE671 cell lines. These effects could to be ascribed to the higher rate of internalization for DOPC-NT(4) Lys(C(18) )(2) -Doxo liposomes, due to stronger binding driven by a lower dissociation constant of the NT(4) -liposomes that bind the membrane onto a specific protein, in contrast to DOPC liposomes, which approach the plasma membrane unselectively

Nature of the finite temperature transition in QCD with strange quark

The finite temperature transition in QCD is studied using Wilson quarks for the cases of $N_F=2$, 3 and 2+1. For $N_F=2$ the transition is smooth in the chiral limit on both \nt=4 and 6 lattices. For $N_F=3$, clear two state signals are observed for $\beta\leq4.7$ on $8^2\times10 \times4$ and $12^3\times4$ lattices, which implies the transition is first order for m_q \simm{<} 140 MeV. For $N_F=2+1$ we study two cases of $m_s \simeq 150$ and 400 MeV with $m_u=m_d \simeq 0$. In contrast to a previous result with staggered quarks, two state signals are clearly observed for both cases, suggesting a first order QCD phase transition in the real world.Comment: ps file, 3 pages with 4 figure

The Degrees of Freedom in Hot Quenched QCD

In quenched QCD, on lattices with \nt=4, the absence of a pole in the pseudoscalar meson channel for $T>T_c$ is demonstrated. A set of effective 4-fermi couplings is extracted. It is observed that this coupling is small in the vector channel for all $T>T_c$, but not in the pseudoscalar channel. The temperature dependence of hadronic parameters below \tc{} is found to be small. NOTE: Latex source, no figures, needs espcrc2.sty from hep-lat macros.Comment: 3 pages, HLRZ 92-7

High temperature QCD with three flavors of improved staggered quarks

We present an update of our study of high temperature QCD with three flavors of quarks, using a Symanzik improved gauge action and the Asqtad staggered quark action. Simulations are being carried out on lattices with Nt=4, 6 and 8 for the case of three degenerate quarks with masses less than or equal to the strange quark mass, $m_s$, and on lattices with Nt=6 and 8 for degenerate up and down quarks with masses in the range 0.2 m_s \leq m_{u,d} \leq 0.6 m_s, and the strange quark fixed near its physical value. We also report on first computations of quark number susceptibilities with the Asqtad action. These susceptibilities are of interest because they can be related to event-by-event fluctuations in heavy ion collision experiments. Use of the improved quark action leads to a substantial reduction in lattice artifacts. This can be seen already for free fermions and carries over into our results for QCD.Comment: Lattice2002(Non-zero temperature and density

Soil structure and earthworm activity under different tillage systems in organic farming

Organic farmers are encouraged to adopt conservation tillage to preserve soil quality and fertility and prevent erosion. However, many studies in different soil and climate conditions have demonstrated that the compaction of the untilled layer is higher in conservation tillage than in conventional tillage. As earthworm activity may help alleviate soil compaction in organic farming, the impact on the soil structure and earthworm population and activity was studied for 4 different tillage managements (1) mouldboard ploughing (MP), (2) shallow ploughing (SP), (3) reduced tillage (RT) and (4) no-tillage (NT), in 3 french areas. The first results are: (1) MP soil structure is better than SP, RT and NT, (2) water infiltration is higher at soil surface in SP, RT and NT, lower at 17 cm depth, (3) more earthworms, especially anecic species, are found in NT, (4) but more opening channels are found in MP. Then, during the first years of transition from MP to NT, soil structure is better in MP, and whereas earthworm numbers is reduced, it favours earthworm activity