Deformation of canonical morphisms and the moduli of surfaces of general type

In this article we study the deformation of finite maps and show how to use this deformation theory to construct varieties with given invariants in a projective space. Among other things, we prove a criterion that determines when a finite map can be deformed to a one--to--one map. We use this criterion to construct new simple canonical surfaces with different $c_1^2$ and $\chi$. Our general results enable us to describe some new components of the moduli of surfaces of general type. We also find infinitely many moduli spaces $\mathcal M_{(x',0,y)}$ having one component whose general point corresponds to a canonically embedded surface and another component whose general point corresponds to a surface whose canonical map is a degree 2 morphism.Comment: 32 pages. Final version with some simplifications and clarifications in the exposition. To appear in Invent. Math. (the final publication is available at springerlink.com

Finite Hilbert stability of (bi)canonical curves

We prove that a generic canonically or bicanonically embedded smooth curve has semistable m-th Hilbert points for all m. We also prove that a generic bicanonically embedded smooth curve has stable m-th Hilbert points for all m \geq 3. In the canonical case, this is accomplished by proving finite Hilbert semistability of special singular curves with G_m-action, namely the canonically embedded balanced ribbon and the canonically embedded balanced double A_{2k+1}-curve. In the bicanonical case, we prove finite Hilbert stability of special hyperelliptic curves, namely Wiman curves. Finally, we give examples of canonically embedded smooth curves whose m-th Hilbert points are non-semistable for low values of m, but become semistable past a definite threshold. (This paper subsumes the previous submission and arXiv:1110.5960).Comment: To appear in Inventiones Mathematicae, 2012. The final publication is available at http://www.springerlink.co

A search for neutral Higgs bosons in the MSSM and models with two scalar field doublets

A search is described for the neutral Higgs bosons h^0 and A^0 predicted by models with two scalar field doublets and, in particular, the Minimal Supersymmetric Standard Model (MSSM). The search in the Z^0 h^0 and h^0 A^0 production channels is based on data corresponding to an integrated luminosity of 25 pb^{-1} from e^+e^- collisions at centre-of-mass energies between 130 and 172GeV collected with the OPAL detector at LEP. The observation of a number of candidates consistent with Standard Model background expectations is used in combination with earlier results from data collected at the Z^0 resonance to set limits on m_h and m_A in general models with two scalar field doublets and in the MSSM. For example, in the MSSM, for tan(beta) > 1, minimal and maximal scalar top quark mixing and soft SUSY-breaking masses of 1 TeV, the 95% confidence level limits m_h > 59.0 GeV and m_A > 59.5 GeV are obtained. For the first time, the MSSM parameter space is explored in a detailed scan.A search is described for the neutral Higgs bosons h^0 and A^0 predicted by models with two scalar field doublets and, in particular, the Minimal Supersymmetric Standard Model (MSSM). The search in the Z^0 h^0 and h^0 A^0 production channels is based on data corresponding to an integrated luminosity of 25 pb^{-1} from e^+e^- collisions at centre-of-mass energies between 130 and 172 GeV collected with the OPAL detector at LEP. The observation of a number of candidates consistent with Standard Model background expectations is used in combination with earlier results from data collected at the Z^0 resonance to set limits on m_h and m_A in general models with two scalar field doublets and in the MSSM. For example, in the MSSM, for tan(beta) > 1, minimal and maximal scalar top quark mixing and soft SUSY-breaking masses of 1 TeV, the 95% confidence level limits m_h > 59.0 GeV and m_A > 59.5 GeV are obtained. For the first time, the MSSM parameter space is explored in a detailed scan

Spin alignment of leading K∗(892)0K^{*}(892)^{0} mesons in hadronic Z0Z^0 decays

Helicity density matrix elements for inclusive K*(892)^0 mesons from hadronic Z^0 decays have been measured over the full range of K^*0 momentum using data taken with the OPAL experiment at LEP. A preference for occupation of the helicity zero state is observed at all scaled momentum x_p values above 0.3, with the matrix element rho_00 rising to 0.66 +/- 0.11 for x_p > 0.7. The values of the real part of the off-diagonal element rho_1-1 are negative at large x_p, with a weighted average value of -0.09 +/- 0.03 for x_p > 0.3, in agreement with new theoretical predictions based on Standard Model parameters and coherent fragmentation of the qq(bar) system from the Z^0 decay. All other helicity density matrix elements measured are consistent with zero over the entire x_p range. The K^*0 fragmentation function has also been measured and the total rate determined to be 0.74 +/- 0.02 +/- 0.02 K*(892)^0 mesons per hadronic Z^0 decay.Helicity density matrix elements for inclusive K*(892)^0 mesons from hadronic Z^0 decays have been measured over the full range of K^*0 momentum using data taken with the OPAL experiment at LEP. A preference for occupation of the helicity zero state is observed at all scaled momentum x_p values above 0.3, with the matrix element rho_00 rising to 0.66 +/- 0.11 for x_p > 0.7. The values of the real part of the off-diagonal element rho_1-1 are negative at large x_p, with a weighted average value of -0.09 +/- 0.03 for x_p > 0.3, in agreement with new theoretical predictions based on Standard Model parameters and coherent fragmentation of the qq(bar) system from the Z^0 decay. All other helicity density matrix elements measured are consistent with zero over the entire x_p range. The K^*0 fragmentation function has also been measured and the total rate determined to be 0.74 +/- 0.02 +/- 0.02 K*(892)^0 mesons per hadronic Z^0 decay.Helicity density matrix elements for inclusive K*(892)^0 mesons from hadronic Z^0 decays have been measured over the full range of K^*0 momentum using data taken with the OPAL experiment at LEP. A preference for occupation of the helicity zero state is observed at all scaled momentum x_p values above 0.3, with the matrix element rho_00 rising to 0.66 +/- 0.11 for x_p > 0.7. The values of the real part of the off-diagonal element rho_1-1 are negative at large x_p, with a weighted average value of -0.09 +/- 0.03 for x_p > 0.3, in agreement with new theoretical predictions based on Standard Model parameters and coherent fragmentation of the qq(bar) system from the Z^0 decay. All other helicity density matrix elements measured are consistent with zero over the entire x_p range. The K^*0 fragmentation function has also been measured and the total rate determined to be 0.74 +/- 0.02 +/- 0.02 K*(892)^0 mesons per hadronic Z^0 decay.Helicity density matrix elements for inclusive K*(892)^0 mesons from hadronic Z^0 decays have been measured over the full range of K^*0 momentum using data taken with the OPAL experiment at LEP. A preference for occupation of the helicity zero state is observed at all scaled momentum x_p values above 0.3, with the matrix element rho_00 rising to 0.66 +/- 0.11 for x_p > 0.7. The values of the real part of the off-diagonal element rho_1-1 are negative at large x_p, with a weighted average value of -0.09 +/- 0.03 for x_p > 0.3, in agreement with new theoretical predictions based on Standard Model parameters and coherent fragmentation of the qq(bar) system from the Z^0 decay. All other helicity density matrix elements measured are consistent with zero over the entire x_p range. The K^*0 fragmentation function has also been measured and the total rate determined to be 0.74 +/- 0.02 +/- 0.02 K*(892)^0 mesons per hadronic Z^0 decay.Helicity density matrix elements for inclusive K ∗ (892) 0 mesons from hadronic Z 0 decays have been measured over the full range of K ∗ 0 momentum using data taken with the OPAL experiment at LEP. A preference for occupation of the helicity zero state is observed at all scaled momentum x p values above 0.3, with the matrix element ϱ 00 rising to 0.66 ± 0.11 for x p > 0.7. The values of the real part of the off-diagonal element ϱ 1 - 1 are negative at large x p , with a weighted average value of −0.09 ± 0.03 for x p > 0.3, in agreement with new theoretical predictions based on Standard Model parameters and coherent fragmentation of the q q system from the Z 0 decay. All other helicity density matrix elements measured are consistent with zero over the entire x p range. The K ∗ 0 fragmentation function has also been measured and the total rate determined to be 0.74 ± 0.02 ± 0.02 K ∗ (892) 0 mesons per hadronic Z 0 decay

Effects of purpurin on proton-pumping ATPase and morphological transition in Candida albicans

Opportunistic human fungal pathogen Candida albicans poses a serious threat to human health. The unicellular microbe exists as part of the normal microbiota on the skin and mucosal surfaces of oral cavity, digestive tract, and urogenital system, but can become invasive and cause local and/or disseminated diseases (candidiasis) in immunocompromised patients with high morbidity and mortality rates (40–60%). Clinical usefulness of the current limited arsenal of antifungal agents has been hampered by toxic side effects, poor pharmacokinetics, and emergence of drug-resistant isolates, indicating a dire need of new antifungal agents. In our earlier study, we have first reported the potent in vitro anti-Candidal activity of purpurin (an anthraquinone pigment found in madder root) against six pathogenic Candida species. One striking virulence trait of C. albicans is its ability to grow and switch between budded yeast and filamentous forms (hyphae), and this yeast-tohypha transition is closely linked with external pH. It is thus conceivable that perturbation of pH homeostasis can be attractive in the management of candidiasis through indirect modulation of morphogenesis. To this end, we extended the investigation and demonstrated the inhibitory actions of purpurin on pH homeostasis and hyphal growth in C. albicans SC5314. At sub-MIC levels (￡0.5 lg ml-1), purpurin suppressed glucosemediated proton pumping ATPase activity in a concentration-dependent manner, and partially inhibited yeast-to-hypha transition and biofilms. Physiological disturbance of cellular metabolism could be excluded as C. albicans growth was not affected. Safe concern and high selectivity of purpurin for C. albicans were justified by its non-toxic nature to primary human gingival fibroblasts (2•MIC; viability = 94%) and keratinocytes (1•MIC; viability = 95%). Therefore, purpurin may represent a potential candidate that deserves further investigations in the development of antifungal strategies against candidiasis - for example, combinational use of purpurin with antifungal agents possessing different modes of action may reduce the likelihood of acquired drug resistance

Investigation of the functional significance of phytase activity in human fungal pathogen Candida albicans

Introduction and Project Objectives: Candida albicans is one of the most prevalent human fungal pathogens. In healthy individuals, C. albicans cohabits as a harmless commensal on the skin and mucosal surfaces of oral cavity, digestive tract and urogenital system. In cases of impaired immunity, C. albicans can become invasive and cause an infection (candidiasis). Mild superficial infection is not fatal, but disseminated candidiasis can be life-threatening. The ability of pathogens to colonize and proliferate in host tissues contributes to pathogenicity. Phosphorus is a building block of nucleic acids, ATP and is involved in phosphorylation and glycolysis. Myo-inositol plays key role in membrane formation, signal transduction and osmoregulation. More importantly, it is a precursor of cell surface glycosylphosphatidylinositol-anchored glycolipids, a C. albicans virulence trait through interactions with human macrophages. Phytate degradation by phytase liberates myo-inositol and inorganic phosphate, both are essential molecules for fungal growth and pathobiology. Our previous study demonstrated the presence of phytase activity in Candida fungi and suggested its potential involvement in host-pathogen interactions. The objectives of this study were: (1) To create C. albicans phytase null mutants and examine their phenotypic determinants; (2) To examine the effects of pH and transcription factors on phytase activity; and (3) To evaluate the importance of phytase activity in C. albicans fitness and virulence. Methods: C. albicans phytase null mutants were created using a PCR-based gene targeting method. The phenotypic properties of the mutants were evaluated, including phytase activity, fungal growth, yeast-to-hyphal morphogenesis, adhesion to buccal epithelial cells (BECs), and virulence. The effect of pH on phytase activity was evaluated by incubating the fungal cells at different pH (from 4.0 to pH 8.5). The effect of transcription factors on phytase activity was investigated using quantitative PCR. Results: C. albicans phytase null mutants have been created and verified. Biochemical analyses indicated that PHO112 contributed to the C. albicans phytase activity. C. albicans pho112Δ/pho112Δ possessed decreased phytase activity, reduced ability to form hyphae in the presence of fetal calf serum at 37oC, and attenuated adhesion to BECs and virulence. pH and transcription factors had no effect on phytase activity. Conclusions: The collective data of the present study suggest that PHO112 is responsible for the C. albicans phytase activity, which is not affected by pH and transcription factors; and virulence

Deletion of Candida albicans PHO112 reduces phytase activity, hyphal development, and attenuates virulence

Objective: To investigate the functional roles of PHO112 in Candida albicans phytase activity, hyphal development, and virulence. Methods: C. albicans PHO112 null mutants were created by a PCR-based gene targeting method using gene-specific primers. C. albicans PHO112 reintegrants were created by transforming the full length PHO112 gene into the C. albicans PHO112 null mutants. Phytase activity in C. albicans PHO112 null mutants was determined by quantifying the amount of released inorganic phosphate from sodium phytate using ammonium molybdate. The ability to form hyphae was evaluated in YPD medium supplemented with 10% fetal bovine serum at 37oC (hyphal-inducing conditions). Adhesion to buccal epithelial cells (BECs) was evaluated by counting the number of attached fungal cells to Gram’s stained BECs under light microscope. Fungal pathogenicity was determined using reconstituted oral human epithelial (ROHE) tissues, and histological changes of the tissues were observed under light microscope after staining with hematoxylin and eosin. Results: C. albicans PHO112 null mutants were created and verified by PCR and genomic Southern hybridization. C. albicans PHO112 null mutants exhibited the following phenotypic properties (P \u3c 0.05) with respect to the wild type counterparts: (1) a reduction of ~25% of phytase activity; (2) a reduction of ~22% of hyphal growth under hyphal-inducing conditions; (3) a reduction of ~22% of adhesion to BECs; and (4) an inability to infect ROHE tissues. Conclusions: The collective data of the present study suggest that C. albicans PHO112 contributes to phytase activity, hyphal development, and fungal virulence. The ability to inhibit the novel virulence trait may provide another antifungal strategy in the fight against this common human fungal pathogen in clinical settings