Tailoring electronic and optical properties of TiO2: nanostructuring, doping and molecular-oxide interactions

Titanium dioxide is one of the most widely investigated oxides. This is due to its broad range of applications, from catalysis to photocatalysis to photovoltaics. Despite this large interest, many of its bulk properties have been sparsely investigated using either experimental techniques or ab initio theory. Further, some of TiO2's most important properties, such as its electronic band gap, the localized character of excitons, and the localized nature of states induced by oxygen vacancies, are still under debate. We present a unified description of the properties of rutile and anatase phases, obtained from ab initio state of the art methods, ranging from density functional theory (DFT) to many body perturbation theory (MBPT) derived techniques. In so doing, we show how advanced computational techniques can be used to quantitatively describe the structural, electronic, and optical properties of TiO2 nanostructures, an area of fundamental importance in applied research. Indeed, we address one of the main challenges to TiO2-photocatalysis, namely band gap narrowing, by showing how to combine nanostructural changes with doping. With this aim we compare TiO2's electronic properties for 0D clusters, 1D nanorods, 2D layers, and 3D bulks using different approximations within DFT and MBPT calculations. While quantum confinement effects lead to a widening of the energy gap, it has been shown that substitutional doping with boron or nitrogen gives rise to (meta-)stable structures and the introduction of dopant and mid-gap states which effectively reduce the band gap. Finally, we report how ab initio methods can be applied to understand the important role of TiO2 as electron-acceptor in dye-sensitized solar cells. This task is made more difficult by the hybrid organic-oxide structure of the involved systems.Comment: 32 pages, 8 figure

Syzygies of torsion bundles and the geometry of the level l modular variety over M_g

We formulate, and in some cases prove, three statements concerning the purity or, more generally the naturality of the resolution of various rings one can attach to a generic curve of genus g and a torsion point of order l in its Jacobian. These statements can be viewed an analogues of Green's Conjecture and we verify them computationally for bounded genus. We then compute the cohomology class of the corresponding non-vanishing locus in the moduli space R_{g,l} of twisted level l curves of genus g and use this to derive results about the birational geometry of R_{g, l}. For instance, we prove that R_{g,3} is a variety of general type when g>11 and the Kodaira dimension of R_{11,3} is greater than or equal to 19. In the last section we explain probabilistically the unexpected failure of the Prym-Green conjecture in genus 8 and level 2.Comment: 35 pages, appeared in Invent Math. We correct an inaccuracy in the statement of Prop 2.

Emerging giant resonant exciton induced by Ta-substitution in anatase TiO2_{2}: a tunable correlation effect

Titanium dioxide (TiO$_2$) has rich physical properties with potential implications in both fundamental physics and new applications. Up-to-date, the main focus of applied research is to tune its optical properties, which is usually done via doping and/or nano-engineering. However, understanding the role of $d$-electrons in materials and possible functionalization of $d$-electron properties are still major challenges. Herewith, within a combination of an innovative experimental technique, high energy optical conductivity, and of the state-of-the-art {\it ab initio} electronic structure calculations, we report an emerging, novel resonant exciton in the deep ultraviolet region of the optical response. The resonant exciton evolves upon low concentration Ta-substitution in anatase TiO$_{2}$ films. It is surprisingly robust and related to strong electron-electron and electron-hole interactions. The $d$- and $f$- orbitals localization, due to Ta-substitution, plays an unexpected role, activating strong electronic correlations and dominating the optical response under photoexcitation. Our results shed light on a new optical phenomenon in anatase TiO$_{2}$ films and on the possibility of tuning electronic properties by Ta substitution

Recombinant AAV-Mediated \u3cem\u3eBEST1\u3c/em\u3e Transfer to the Retinal Pigment Epithelium: Analysis of Serotype-Dependent Retinal Effects

Mutations in the BEST1 gene constitute an underlying cause of juvenile macular dystrophies, a group of retinal disorders commonly referred to as bestrophinopathies and usually diagnosed in early childhood or adolescence. The disease primarily affects macular and paramacular regions of the eye leading to major declines in central vision later in life. Currently, there is no cure or surgical management for BEST1-associated disorders. The recently characterized human disease counterpart, canine multifocal retinopathy (cmr), recapitulates a full spectrum of clinical and molecular features observed in human bestrophinopathies and offers a valuable model system for development and testing of therapeutic strategies. In this study, the specificity, efficiency and safety of rAAV-mediated transgene expression driven by the human VMD2 promoter were assessed in wild-type canine retinae. While the subretinal delivery of rAAV2/1 vector serotype was associated with cone damage in the retina when BEST1 and GFP were co-expressed, the rAAV2/2 vector serotype carrying either GFP reporter or BEST1 transgene under control of human VMD2 promoter was safe, and enabled specific transduction of the RPE cell monolayer that was stable for up to 6 months post injection. These encouraging studies with the rAAV2/2 vector lay the groundwork for development of gene augmentation therapy for human bestrophinopathies

Landau-Ginzburg/Calabi-Yau correspondence, global mirror symmetry and Orlov equivalence

We show that the Gromov-Witten theory of Calabi-Yau hypersurfaces matches, in genus zero and after an analytic continuation, the quantum singularity theory (FJRW theory) recently introduced by Fan, Jarvis and Ruan following ideas of Witten. Moreover, on both sides, we highlight two remarkable integral local systems arising from the common formalism of Gamma-integral structures applied to the derived category of the hypersurface {W=0} and to the category of graded matrix factorizations of W. In this setup, we prove that the analytic continuation matches Orlov equivalence between the two above categories.Comment: 72pages, v2: Appendix B and references added. Typos corrected, v3: several mistakes corrected, final versio

A clock network for geodesy and fundamental science

Leveraging the unrivaled performance of optical clocks in applications in fundamental physics beyond the standard model, in geo-sciences, and in astronomy requires comparing the frequency of distant optical clocks truthfully. Meeting this requirement, we report on the first comparison and agreement of fully independent optical clocks separated by 700 km being only limited by the uncertainties of the clocks themselves. This is achieved by a phase-coherent optical frequency transfer via a 1415 km long telecom fiber link that enables substantially better precision than classical means of frequency transfer. The fractional precision in comparing the optical clocks of three parts in $10^{17}$ was reached after only 1000 s averaging time, which is already 10 times better and more than four orders of magnitude faster than with any other existing frequency transfer method. The capability of performing high resolution international clock comparisons paves the way for a redefinition of the unit of time and an all-optical dissemination of the SI-second.Comment: 14 pages, 3 figures, 1 tabl

Global hybrids from the semiclassical atom theory satisfying the local density linear response

We propose global hybrid approximations of the exchange-correlation (XC) energy functional which reproduce well the modified fourth-order gradient expansion of the exchange energy in the semiclassical limit of many-electron neutral atoms and recover the full local density approximation (LDA) linear response. These XC functionals represent the hybrid versions of the APBE functional [Phys. Rev. Lett. 106, 186406, (2011)] yet employing an additional correlation functional which uses the localization concept of the correlation energy density to improve the compatibility with the Hartree-Fock exchange as well as the coupling-constant-resolved XC potential energy. Broad energetical and structural testings, including thermochemistry and geometry, transition metal complexes, non-covalent interactions, gold clusters and small gold-molecule interfaces, as well as an analysis of the hybrid parameters, show that our construction is quite robust. In particular, our testing shows that the resulting hybrid, including 20\% of Hartree-Fock exchange and named hAPBE, performs remarkably well for a broad palette of systems and properties, being generally better than popular hybrids (PBE0 and B3LYP). Semi-empirical dispersion corrections are also provided.Comment: 12 pages, 4 figure

Self-reported history of Pap-smear in HIV-positive women in Northern Italy: a cross-sectional study

BACKGROUND: The incidence of invasive cervical cancer in HIV-positive women is higher than in the general population. There is evidence that HIV-positive women do not participate sufficiently in cervical cancer screening in Italy, where cervical cancer is more than 10-fold higher in women with AIDS than in the general population. The aim of the present study was to evaluate the history of Pap-smear in HIV-positive women in Italy in recent years. We also examined the sociodemographic, clinical, and organizational factors associated with adherence to cervical cancer screening.METHODS: A cross-sectional study was conducted between July 2006 and June 2007 in Emilia-Romagna region (Northern Italy). All HIV-positive women who received a follow-up visit in one of the 10 regional infectivology units were invited to participate. History of Pap-smear, including abnormal smears and subsequent treatment, was investigated through a self-administered anonymous questionnaire. The association between lack of Pap-smear in the year preceding the interview and selected characteristics was assessed by means of odds ratios (OR) and 95% confidence intervals adjusted for study centre and age.RESULTS: A total of 1,002 HIV-positive women were interviewed. Nine percent reported no history of Pap-smear, and 39% had no Pap-smear in the year prior to the date of questionnaire (last year). The lack of Pap-smear in the last year was significantly associated with age <35 years (OR = 1.4, compared to age > or =45 years), lower education level (OR = 1.3), first HIV-positive test in the last 2 years (OR = 1.4), and CD4 count <200 cells/microl (OR = 1.6). Conversely, when women were advised by a gynecologist rather than other health workers to undergo screening, it significantly increased adherence. Non-significantly higher proportions of lack of Pap-smear in the last year were found in women born in Central-Eastern Europe (OR = 1.8) and Africa (OR = 1.3). No difference in history of Pap-smear emerged by mode of HIV-acquisition or AIDS status.Three hundred five (34%) women reported a previous abnormal Pap-smear, and of the 178 (58%) referred for treatment, 97% complied.CONCLUSIONS: In recent years the self-reported history of Pap-smear in HIV-positive women, in some public clinics in Italy, is higher than previously reported, but further efforts are required to make sure cervical cancer screening is accessible to all HIV-positive women

po 154 progesterone through progesterone receptor b inhibits invasion of human breast cancer cells by targeting cytoplasmic cyclin d1

Introduction Progesterone Receptor (PR) positivity is associated with a good prognosis and better response to breast cancer treatment. Conversely, cyclin D1 (CD1) is retained a marker of poor outcome since it has been associated with breast cancer metastasis in clinical studies. Material and methods 17-Hydroxyprogesterone (OHPg) was from Sigma-Aldrich. Antibodies and Protein A/GPLUS-Agarose were from Santa Cruz Biotechnology. T47-D, MCF-7 and MDA-MB-231 human breast cancer cells from the American Type Culture Collection; Total real-time RT-PCR assay; Western blotting and immunoprecipitation; Transfections and luciferase assays; Lipid-Mediated Transfection of siRNA Duplexes; Chromatin immunoprecipitation (ChIP) assays and realtime ChIP; Wound-healing assays; Transmigration assays; Cell invasion assay; Phalloidin staining. Results and discussions Herein we provide evidences that OHPg through PR-B isoform, reduces motility and invasion of T47-D and MCF-7 breast cancer cells, by targeting the cytoplasmic CD1. Specifically, OHPg reduces CD1 expression through a transcriptional mechanism due to the occupancy of CD1 promoter at a canonical half progesterone responsive element by PR-B. This allows the recruitment of HDAC1 influencing a less permissive chromatin conformation for gene transcription and the release of RNA Pol II. CD1 has an active role in the control of cell migration and metastasis through the interaction with key components of focal adhesion such as Paxillin (Pxn). In untreated T47-D and MCF-7 cells a specific co-immunoprecipitation of endogenous cytoplasmic CD1 with Pxn was detected. Interestingly, OHPg exposure reduced the interaction between these proteins although total Pxn expression was substantially unaffected. Moreover a concomitant reduction of p-Pxn levels was observed and these effects were required for OHPg/PR-B dependent delay in cell invasion, as evidenced by assays carried out with the phoshomimetic mutants of Pxn. Conclusion Collectively these findings support the importance of PR-B expression in breast cancer cells behaviour, suggesting potentiating of PR-B signalling as a prospective useful strategy to restrict breast tumour cells invasion and metastasis