Oxygen adsorption on clean and oxygen precovered Cu(100)

Kuparipinnan hapettumisen alkuvaiheet ovat vielä nykyisin tutkijoille epäselviä. Kuitenkin, jotta hapettumisprosessia voitaisiin säädellä, on sangen tärkeää ymmärtää mistä varsinainen hapettuminen lähtee liikkeelle ja mitkä ovat hapettumisen seuraavat vaiheet. Tähän kysymykseen haetaan vastauksia tässä työssä käyttäen puhtaasti teoreettisia menetelmiä pinnan käsittelyssä. Aikaisempien teoreettisten ja kokeellisten tutkimusten välillä on pieni ristiriita liittyen hapen tarttumistodennäköisyyteen. Teoreettisten tutkimusten mukaan happi ei puhtaalle pinnalle tullessaan näe potentiaalivallia, mutta kokeelliset tutkimukset osoittavat sellaisen kuitenkin olevan. Tuohon ristiriitaan pureudutaan käyttäen aikaisemmista laskuista poikkeavaa kvanttimekaaniseen molekyylidynamiikkaan perustuvaa lähestymistapaa. Työssä havaitaan, että aikaisemmin yleisesti käytetty menetelmä hukkaa huomattavan määrän tietoa ja siten tutkijat eivät voi ainoastaan tyytyä tarkastelemaan kyseisellä menetelmällä saatuja tuloksia. Kuparipinnalle havaittiin, että korkeilla molekyylin kineettisen energian arvolla aikaisemmin suoritetut laskut hajottavista trajektoreista pitävät paikkansa, mutta matalilla kineettisen energian arvoilla molekyyli kohtaa erittäin voimakkaan ``steering'' vaikutuksen ja trajektorit joiden piti olla hajottavia johtavatkin molekulaariseen adsorptioon. Kun hapen konsentraatio pinnalla on suurempi kuin 0.5 ML, pinta rekonstruoituu. Myös rekonstruktion jälkeistä pintaa on tutkittu samanlaisilla menetelmillä kuin puhdasta pintaa. Rekonstruoituneelle pinnalle ei löydetty hajottavia trajektoreita ja havaittiin, että hapelle annetun kineettisen energian matalilla arvoilla myös tässä tapauksessa on erittäin voimakas ``steering'' vaikutus.

Quantitative TCR:pMHC Dissociation Rate Assessment by NTAmers Reveals Antimelanoma T Cell Repertoires Enriched for High Functional Competence.

Experimental models demonstrated that therapeutic induction of CD8 T cell responses may offer protection against tumors or infectious diseases providing that T cells have sufficiently high TCR/CD8:pMHC avidity for efficient Ag recognition and consequently strong immune functions. However, comprehensive characterization of TCR/CD8:pMHC avidity in clinically relevant situations has remained elusive. In this study, using the novel NTA-His tag-containing multimer technology, we quantified the TCR:pMHC dissociation rates (koff) of tumor-specific vaccine-induced CD8 T cell clones (n = 139) derived from seven melanoma patients vaccinated with IFA, CpG, and the native/EAA or analog/ELA Melan-A(MART-1)(26-35) peptide, binding with low or high affinity to MHC, respectively. We observed substantial correlations between koff and Ca(2+) mobilization (p = 0.016) and target cell recognition (p < 0.0001), with the latter independently of the T cell differentiation state. Our strategy was successful in demonstrating that the type of peptide impacted on TCR/CD8:pMHC avidity, as tumor-reactive T cell clones derived from patients vaccinated with the low-affinity (native) peptide expressed slower koff rates than those derived from patients vaccinated with the high-affinity (analog) peptide (p < 0.0001). Furthermore, we observed that the low-affinity peptide promoted the selective differentiation of tumor-specific T cells bearing TCRs with high TCR/CD8:pMHC avidity (p < 0.0001). Altogether, TCR:pMHC interaction kinetics correlated strongly with T cell functions. Our study demonstrates the feasibility and usefulness of TCR/CD8:pMHC avidity assessment by NTA-His tag-containing multimers of naturally occurring polyclonal T cell responses, which represents a strong asset for the development of immunotherapy.

Combinative effects of β-Lapachone and APO866 on pancreatic cancer cell death through reactive oxygen species production and PARP-1 activation.

UNLABELLED: Pancreatic cancer (PC) is one of the most lethal human malignancies and a major health problem. Patients diagnosed with PC and treated with conventional approaches have an overall 5-year survival rate of less than 5%. Novel strategies are needed to treat this disease. Herein, we propose a combinatorial strategy that targets two unrelated metabolic enzymes overexpressed in PC cells: NAD(P)H: quinone oxidoreductase-1 (NQO1) and nicotinamide phosphoribosyl transferase (NAMPT) using β-lapachone (BL) and APO866, respectively. We show that BL tremendously enhances the antitumor activity of APO866 on various PC cell lines without affecting normal cells, in a PARP-1 dependent manner. The chemopotentiation of APO866 with BL was characterized by the following: (i) nicotinamide adenine dinucleotide (NAD) depletion; (ii) catalase (CAT) degradation; (iii) excessive H2O2 production; (iv) dramatic drop of mitochondrial membrane potential (MMP); and finally (v) autophagic-associated cell death. H2O2 production, loss of MMP and cell death (but not NAD depletion) were abrogated by exogenous supplementation with CAT or pharmacological or genetic inhibition of PARP-1. Our data demonstrates that the combination of a non-lethal dose of BL and low dose of APO866 optimizes significantly cell death on various PC lines over both compounds given separately and open new and promising combination in PC therapy.

Sierpinski curve Julia sets for quadratic rational maps

We investigate under which dynamical conditions the Julia set of a quadratic rational map is a Sierpiński curve.

First principles analysis of the stability and diffusion of oxygen vacancies in meetal oxides

Oxygen vacancies in metal oxides are known to determine their chemistry and physics. The properties of neutral oxygen vacancies in metal oxides of increasing complexity (MgO, CaO, alpha-Al2O3, and ZnO) have been studied using density functional theory. Vacancy formation energies, vacancy-vacancy interaction, and the barriers for vacancy migration are determined and rationalized in terms of the ionicity, the Madelung potential, and lattice relaxation. It is found that the Madelung potential controls the oxygen vacancy properties of highly ionic oxides whereas a more complex picture arises for covalent ZnO.

Bonding of gold nanoclusters to oxygen vacancies on rutile TiO2(110)

Through an interplay between scanning tunneling microscopy (STM) and density functional theory (DFT) calculations, we show that bridging oxygen vacancies are the active nucleation sites for Au clusters on the rutile TiO2(110) surface. We find that a direct correlation exists between a decrease in density of vacancies and the amount of Au deposited. From the DFT calculations we find that the oxygen vacancy is indeed the strongest Au binding site. We show both experimentally and theoretically that a single oxygen vacancy can bind 3 Au atoms on average. In view of the presented results, a new growth model for the TiO2(110) system involving vacancy-cluster complex diffusion is presented.

When Langmuir is too simple: H2 dissociation on Pd(111) at high coverage

Recent experiments of H2 adsorption on Pd(111) [T. Mitsui et al., Nature (London) 422, 705 (2003)] have questioned the classical Langmuir picture of second order adsorption kinetics at high surface coverage requiring pairs of empty sites for the dissociative chemisorption. Experiments find that at least three empty sites are needed. Through density functional theory, we find that H2 dissociation is favored on ensembles of sites that involve a Pd atom with no direct interaction with adsorbed hydrogen. Such active sites are formed by aggregation of at least 3 H-free sites revealing the complex structure of the "active sites."

The initial oxidation of transition metal surfaces

Due to their numerous novel technological applications ranging from the example of exhaust catalysts in the automotive industry to the catalytic production of hydro- gen, surface reactions on transition metal substrates have become to be one of the most essential subjects within the surface science community. Although numerous applications exist, there are many details in the different processes that, after many decades of research, remain unknown. There are perhaps as many applications for the corrosion resistant materials such as stainless steels. A thorough knowledge of the details of the simplest reactions occuring on the surfaces, such as oxidation, play a key role in the design of better catalysts, or corrosion resistant materials in the future. This thesis examines the oxidation of metal surfaces from a computational point of view mostly concentrating on copper as a model material. Oxidation is studied from the initial oxidation to the oxygen precovered surface. Important parameters for the initial sticking and dissociation are obtained. The saturation layer is thoroughly studied and the calculated results arecompared with available experimental results. On the saturated surface, some open questions still remain. The present calculations demonstrate, that the saturated part of the surface is excluded from being chemically reactive towards the oxygen molecules. The results suggest, that the reason for the chemical activity of the saturated surface is due to a strain effect occuring between the saturated areas of the surface.

Transition mutation in codon 248 of the p53 tumor suppressor gene induced by reactive oxygen species and a nitric oxide-releasing compound.

Exposing the human bronchial epithelial cell line BEAS-2B to the nitric oxide (NO) donor sodium 1-(N,N-diethylamino)diazen-1-ium-1, 2-diolate (DEA/NO) at an initial concentration of 0.6 mM while generating superoxide ion at the rate of 1 microM/min with the hypoxanthine/xanthine oxidase (HX/XO) system induced C:G-->T:A transition mutations in codon 248 of the p53 gene. This pattern of mutagenicity was not seen by 'fish-restriction fragment length polymorphism/polymerase chain reaction' (fish-RFLP/PCR) on exposure to DEA/NO alone, however, exposure to HX/XO led to various mutations, suggesting that co-generation of NO and superoxide was responsible for inducing the observed point mutation. DEA/NO potentiated the ability of HX/XO to induce lipid peroxidation as well as DNA single- and double-strand breaks under these conditions, while 0.6 mM DEA/NO in the absence of HX/XO had no significant effect on these parameters. The results show that a point mutation seen at high frequency in certain common human tumors can be induced by simultaneous exposure to reactive oxygen species and a NO source.

Pedaling rate is an important determinant of human oxygen uptake during exercise on the cycle ergometer.

Estimation of human oxygen uptake (V˙o2) during exercise is often used as an alternative when its direct measurement is not feasible. The American College of Sports Medicine (ACSM) suggests estimating human V˙o2 during exercise on a cycle ergometer through an equation that considers individual's body mass and external work rate, but not pedaling rate (PR). We hypothesized that including PR in the ACSM equation would improve its V˙o2 prediction accuracy. Ten healthy male participants' (age 19-48 years) were recruited and their steady-state V˙o2 was recorded on a cycle ergometer for 16 combinations of external work rates (0, 50, 100, and 150 W) and PR (50, 70, 90, and 110 revolutions per minute). V˙o2 was calculated by means of a new equation, and by the ACSM equation for comparison. Kinematic data were collected by means of an infrared 3-D motion analysis system in order to explore the mechanical determinants of V˙o2. Including PR in the ACSM equation improved the accuracy for prediction of sub-maximal V˙o2 during exercise (mean bias 1.9 vs. 3.3 mL O2 kg(-1) min(-1)) but it did not affect the accuracy for prediction of maximal V˙o2 (P > 0.05). Confirming the validity of this new equation, the results were replicated for data reported in the literature in 51 participants. We conclude that PR is an important determinant of human V˙o2 during cycling exercise, and it should be considered when predicting oxygen consumption.

Is the wage curve formal or informal? Evidence for Colombia

Using microdata from the 2002-2006 Colombian Continuous Household Survey, we find an elasticity of individual wages to local unemployment rates of -0.07. However, the elasticity for informal workers is significantly higher, a result which is consistent with efficiency wage theoretical models and relevant for regional labour markets analysis in developing countries.

Receiver operating characteristic (ROC) curve for classification of18F-NaF uptake on PET/CT

Abstract Objective: To assess the cutoff values established by ROC curves to classify18F-NaF uptake as normal or malignant. Materials and Methods: PET/CT images were acquired 1 hour after administration of 185 MBq of18F-NaF. Volumes of interest (VOIs) were drawn on three regions of the skeleton as follows: proximal right humerus diaphysis (HD), proximal right femoral diaphysis (FD) and first vertebral body (VB1), in a total of 254 patients, totalling 762 VOIs. The uptake in the VOIs was classified as normal or malignant on the basis of the radiopharmaceutical distribution pattern and of the CT images. A total of 675 volumes were classified as normal and 52 were classified as malignant. Thirty-five VOIs classified as indeterminate or nonmalignant lesions were excluded from analysis. The standardized uptake value (SUV) measured on the VOIs were plotted on an ROC curve for each one of the three regions. The area under the ROC (AUC) as well as the best cutoff SUVs to classify the VOIs were calculated. The best cutoff values were established as the ones with higher result of the sum of sensitivity and specificity. Results: The AUCs were 0.933, 0.889 and 0.975 for UD, FD and VB1, respectively. The best SUV cutoffs were 9.0 (sensitivity: 73%; specificity: 99%), 8.4 (sensitivity: 79%; specificity: 94%) and 21.0 (sensitivity: 93%; specificity: 95%) for UD, FD and VB1, respectively. Conclusion: The best cutoff value varies according to bone region of analysis and it is not possible to establish one value for the whole body.