Ordering in the dilute weakly-anisotropic antiferromagnet Mn(0.35)Zn(0.65)F2

The highly diluted antiferromagnet Mn(0.35)Zn(0.65)F2 has been investigated by neutron scattering in zero field. The Bragg peaks observed below the Neel temperature TN (approximately 10.9 K) indicate stable antiferromagnetic long-range ordering at low temperature. The critical behavior is governed by random-exchange Ising model critical exponents (nu approximately 0.69 and gamma approximately 1.31), as reported for Mn(x)Zn(1-x)F2 with higher x and for the isostructural compound Fe(x)Zn(1-x)F2. However, in addition to the Bragg peaks, unusual scattering behavior appears for |q|>0 below a glassy temperature Tg approximately 7.0 K. The glassy region T<Tg corresponds to that of noticeable frequency dependence in earlier zero-field ac susceptibility measurements on this sample. These results indicate that long-range order coexists with short-range nonequilibrium clusters in this highly diluted magnet.Comment: 7 pages, 5 figure

Influence of frustration on a d=3 diluted antiferromagnet: FexZn1−xF2Fe_{x}Zn_{1-x}F_{2}

The influence of a frustrated bond on the magnetic properties of a d=3 uniaxial (Ising) b.c.c. diluted antiferromagnet, with emphasis in the compound $Fe_{x}Zn_{1-x}F_{2}$, is investigated by a local mean-field numerical simulation. In particular we find that the initial drop of the saturation staggered magnetization ($M_{S}$) with concentration follows a percolation-like phenomenon characterized by an exponent $\beta_{p}$. For the frustrated samples, however, this regime is followed by a second one identified by a ``long tail" effect such that $M_{S}$ is zero only at the percolation threshold. Our numerical data also confirms a spin-glass phase near this threshold.Comment: 11 pages (Latex) with 3 uuencoded postscript figure

Percolation in three-dimensional random field Ising magnets

The structure of the three-dimensional random field Ising magnet is studied by ground state calculations. We investigate the percolation of the minority spin orientation in the paramagnetic phase above the bulk phase transition, located at [Delta/J]_c ~= 2.27, where Delta is the standard deviation of the Gaussian random fields (J=1). With an external field H there is a disorder strength dependent critical field +/- H_c(Delta) for the down (or up) spin spanning. The percolation transition is in the standard percolation universality class. H_c ~ (Delta - Delta_p)^{delta}, where Delta_p = 2.43 +/- 0.01 and delta = 1.31 +/- 0.03, implying a critical line for Delta_c < Delta <= Delta_p. When, with zero external field, Delta is decreased from a large value there is a transition from the simultaneous up and down spin spanning, with probability Pi_{uparrow downarrow} = 1.00 to Pi_{uparrow downarrow} = 0. This is located at Delta = 2.32 +/- 0.01, i.e., above Delta_c. The spanning cluster has the fractal dimension of standard percolation D_f = 2.53 at H = H_c(Delta). We provide evidence that this is asymptotically true even at H=0 for Delta_c < Delta <= Delta_p beyond a crossover scale that diverges as Delta_c is approached from above. Percolation implies extra finite size effects in the ground states of the 3D RFIM.Comment: replaced with version to appear in Physical Review

Growth inhibitory effects of 3′-nitro-3-phenylamino nor-beta-lapachone against HL-60: A redox-dependent mechanism

AbstractIn this study, the cytotoxicity, genotoxicity and early ROS generation of 2,2-dimethyl-(3H)-3-(N-3′-nitrophenylamino)naphtho[1,2-b]furan-4,5-dione (QPhNO2) were investigated and compared with those of its precursor, nor-beta-lapachone (nor-beta), with the main goal of proposing a mechanism of antitumor action. The results were correlated with those obtained from electrochemical experiments held in protic (acetate buffer pH 4.5) and aprotic (DMF/TBABF4) media in the presence and absence of oxygen and with those from dsDNA biosensors and ssDNA in solution, which provided evidence of a positive interaction with DNA in the case of QPhNO2. QPhNO2 caused DNA fragmentation and mitochondrial depolarization and induced apoptosis/necrosis in HL-60 cells. Pre-treatment with N-acetyl-l-cysteine partially abolished the observed effects related to the QPhNO2 treatment, including those involving apoptosis induction, indicating a partially redox-dependent mechanism. These findings point to the potential use of the combination of pharmacology and electrochemistry in medicinal chemistry

Mapping density, diversity and species-richness of the Amazon tree flora

Using 2.046 botanically-inventoried tree plots across the largest tropical forest on Earth, we mapped tree species-diversity and tree species-richness at 0.1-degree resolution, and investigated drivers for diversity and richness. Using only location, stratified by forest type, as predictor, our spatial model, to the best of our knowledge, provides the most accurate map of tree diversity in Amazonia to date, explaining approximately 70% of the tree diversity and species-richness. Large soil-forest combinations determine a significant percentage of the variation in tree species-richness and tree alpha-diversity in Amazonian forest-plots. We suggest that the size and fragmentation of these systems drive their large-scale diversity patterns and hence local diversity. A model not using location but cumulative water deficit, tree density, and temperature seasonality explains 47% of the tree species-richness in the terra-firme forest in Amazonia. Over large areas across Amazonia, residuals of this relationship are small and poorly spatially structured, suggesting that much of the residual variation may be local. The Guyana Shield area has consistently negative residuals, showing that this area has lower tree species-richness than expected by our models. We provide extensive plot meta-data, including tree density, tree alpha-diversity and tree species-richness results and gridded maps at 0.1-degree resolution

Levantamento soroepidemiológico para arbovírus em macaco-prego-galego (Cebus flavius) de vida livre no estado da Paraíba e em macaco-prego (Cebus libidinosus) de cativeiro do nordeste do Brasil

Este estudo descreve a primeira investigação de anticorpos para arbovírus em primatas não humanos do Novo Mundo no nordeste brasileiro. No período de março de 2008 a setembro de 2010 foram colhidos soros sanguíneos de 31 macacos-prego-galegos (Cebus flavius) de vida livre na Paraíba e de 100 macacos-prego (Cebus libidinosus) em cativeiro nos estados de Alagoas, Paraíba, Pernambuco, Piauí e Rio Grande do Norte. Para a pesquisa de anticorpos utilizou-se o teste de inibição da hemaglutinação (IH), usando antígenos de 19 diferentes tipos de arbovírus, pertencentes aos gêneros Flavivirus,Alphavirus e Bunyavirus. As amostras de soro foram testadas nas diluições de 1:20 a 1:1280. Dentre as amostras examinadas, todas as de C. flavius foram negativas e 46% das de C. libidinosus em cativeiro apresentaram anticorpos para arbovírus. Foram detectados anticorpos para nove (9/19) arbovírus. Foram observadas 17 reações heterotípicas, para dois ou mais vírus, do gênero Flavivirus, e 15 para o gênero Alphavirus, com títulos variando de 1:20 a 1:1280. Quinze amostras apresentaram reação monotípica para ILHV (n=4), MAYV (n=6), SLEV (n=1), ROCV (n=2), OROV (n=1) e MUCV (n=1). Estes resultados sugerem que houve intensa circulação de arbovírus na população estudada de macacos-prego em cativeiro

Growth Inhibitory Effects Of 3'-nitro-3-phenylamino Nor-beta-lapachone Against Hl-60: A Redox-dependent Mechanism

In this study, the cytotoxicity, genotoxicity and early ROS generation of 2,2-dimethyl-(3H)-3-(N-3'-nitrophenylamino)naphtho[1,2-b]furan-4,5-dione (QPhNO 2) were investigated and compared with those of its precursor, nor-beta-lapachone (nor-beta), with the main goal of proposing a mechanism of antitumor action. The results were correlated with those obtained from electrochemical experiments held in protic (acetate buffer pH 4.5) and aprotic (DMF/TBABF 4) media in the presence and absence of oxygen and with those from dsDNA biosensors and ssDNA in solution, which provided evidence of a positive interaction with DNA in the case of QPhNO 2. QPhNO 2 caused DNA fragmentation and mitochondrial depolarization and induced apoptosis/necrosis in HL-60 cells. Pre-treatment with N-acetyl-l-cysteine partially abolished the observed effects related to the QPhNO 2 treatment, including those involving apoptosis induction, indicating a partially redox-dependent mechanism. These findings point to the potential use of the combination of pharmacology and electrochemistry in medicinal chemistry. © 2012 Elsevier Ltd.264585594Asche, C., Antitumour quinones (2005) Mini-Rev. Med. Chem., 5, pp. 449-467Ausubel, F.M., Brent, R., Kingston, R.E., Moore, D.D., Seidmann, J.G., Struhl, K., (1990) Current Protocols in Molecular Biology, 2. , John Wiley & Sons, Inc., New YorkBova, M.P., Mattson, M.N., Vasile, S., Tam, D., Holsinge, L., Bremer, M., Hui, T., Fukuto, J.M., The oxidative mechanism of action of ortho-quinone inhibitors of protein-tyrosine phosphatase alpha is mediated by hydrogen peroxide (2004) Arch. Biochem. Biophys., 429, pp. 30-41Brett, A.M.O., Goulart, M.O.F., de Abreu, F.C., Reduction of lapachones and their reaction with L-cysteine and mercaptoethanol on glassy carbon electrodes (2002) Bioelectrochemistry, 56, pp. 53-55Cavalcanti, J.C.M., Oliveira, N.V., de Moura, M.A.B.F., Chaves, J.B., Alves, R.J., de Abreu, F.C., Goulart, M.O.F., Effect of the leaving group on the electrodic reduction mechanism of anti-Helicobacter pylori metronidazole derivatives, in aprotic and protic media (2004) Bioelectrochemistry, 63, pp. 353-357Cavalcanti, B.C., Barros, F.W.A., Cabral, I.O., Ferreira, J.R.O., Magalhães, H.I.F., Júnior, H.V.N., da Silva Júnior, E.N., Pessoa, C., Preclinical genotoxicology of nor-β-lapachone in human cultured lymphocytes and Chinese hamster lung fibroblasts (2011) Chem. Res. Toxicol., 24, pp. 1560-1574da Silva Júnior, E.N., de Souza, M.C.B.V., Pinto, A.V., Pinto, M.C.F.R., Goulart, M.O.F., Barros, F.W.A., Pessoa, C., Ferreira, V.F., Synthesis and potent antitumor activity of new arylamino derivatives of nor-β-lapachone and nor-α-lapachone (2007) Bioorg. Med. Chem., 15, pp. 7035-7041da Silva Júnior, E.N., Moura, M.A.B.F., Pinto, A.V., Pinto, M.C.F.R., de Souza, M.C.B.V., Araújo, A.J., Pessoa, C., Goulart, M.O.F., Cytotoxic, trypanocidal activities and physicochemical parameters of nor-β-lapachone-based 1,2,3-triazoles (2009) J. Braz. Chem. Soc., 20, pp. 635-643da Silva Júnior, E.N., de Deus, C.F., Martins, J.B.L., Lima, A.B., Cavalcanti, B.C., Pessoa, C., Costa-Lotufo, L.V., Pinto, A.V., 3-Arylamino and 3-alkoxy-nor-β-lapachone derivatives: synthesis and cytotoxicity against cancer cell lines (2010) J. Med. Chem., 53, pp. 504-508Darzynkiewicz, Z., Bruno, S., Del Bino, G., Gorczyca, M., Hotz, M.A., Lassota, P., Traganos, F., Features of apoptotic cells measured by flow cytometry (1992) Cytometry, 13, pp. 795-808de Abreu, F.C., Ferraz, P.A.M., Goulart, M.O.F., Some applications of electrochemistry in biomedical chemistry. Emphasis on the correlation of electrochemical and bioactive properties (2002) J. Braz. Chem. Soc., 13, pp. 19-35de Abreu, F.C., Goulart, M.O.F., Brett, A.M.O., Reduction of lapachones in aqueous media at a glassy carbon electrode (2002) Electroanalysis, 14, pp. 29-34de Abreu, F.C., Ferreira, D.C.M., Goulart, M.O.F., Buriez, O., Amatore, C., Electrochemical activation of beta-lapachone in beta-cyclodextrin inclusion complexes and reactivity of its reduced form towards oxygen in aqueous solutions (2007) J. Electroanal. Chem., 608, pp. 125-132de Abreu, F.C., de Paula, F.S., Ferreira, D.C.M., Nascimento, V.B., Santos, A.M.C., Santoro, M., Salas, C.E., Goulart, M.O.F., The application of DNA-biosensors and differential scanning calorimetry to the study of the DNA-binding agent berenil (2008) Sensors, 8, pp. 1519-1538de Souza, A.A., de Moura, M.A.B.F., de Abreu, F.C., Goulart, M.O.F., da Silva Júnior, E.N., Pinto, A.V., Ferreira, V.F., Squella, J.A., Electrochemical study, on mercury, of a meta-nitroarylamine derivative of nor-β-lapachone, an antitumor and trypanocidal compound (2010) Quim. Nova, 33, pp. 2075-2079Diculescu, V.C., Paquim, A.M.C., Brett, A.M.O., Electrochemical DNA sensors for detection of DNA damage (2005) Sensors, 5, pp. 377-393Enari, M., Sakahira, H., Yokoyama, H., Okawa, K., Iwamatsu, A., Nagata, S., A caspase-activated DNase that degrades DNA during apoptosis, and its inhibitor ICAD (1998) Nature, 391, pp. 43-50Eskes, R., Desagher, S., Antonsson, B., Martinou, J.C., Bid induces the oligomerization and insertion of Bax into the outer mitochondrial membrane (2000) Mol. Cell Biol., 20, pp. 929-935Ferreira, D.C.M., Tapsoba, I., Arbault, S., Bouret, Y., Alexandre Moreira, M.S., Pinto, A.V., Goulart, M.O.F., Amatore, C., Ex vivo activities of β-lapachone and α-lapachone on macrophages: a quantitative pharmacological analysis based on amperometric monitoring of oxidative bursts by single cells (2009) ChemBioChem, 10, pp. 528-538Foye, W.O., (1995) Cancer Chemotherapeutic Agents, , American Chemical Society, Washington, D.CGoulart, M.O.F., Ossowski, T., Pipka, P., Liwo, A., Electrochemical study of oxygen interaction with lapachol and its radical anions (2003) Bioelectrochemistry, 59, pp. 85-87Goulart, M.O.F., Lima, N.M.F., Santana, A.E.G., Ferraz, P.A.L., Cavalcanti, J.C.M., Liwo, A., Falkowsky, P., Ossowsky, T., Electrochemical studies of isolapachol with emphasis on oxygen interaction with its radical anions (2004) J. Electroanal. Chem., 566, pp. 25-29Goulart, M.O.F., de Souza, A.A., de Abreu, F.C., de Paula, F.S., Sales, E.M., Almeida, W.P., Buriez, O., Amatore, C., Electrochemical study of methyl 2-[p-nitrophenyl(hydroxy)methyl]acrylate (2007) J. Electrochem. Soc., 154, pp. 121-129Gupta, D., Podar, K., Tai, Y.T., Lin, B., Hideshima, T., Akiyama, M., LeBlanc, R., Anderson, K.C., Beta-lapachone, a novel plant product, overcomes drug resistance in human multiple myeloma cells (2002) Exp. Hematol., 30, pp. 711-720Hanahan, D., Weinberg, R.A., The hallmarks of cancer (2000) Cell, 100, pp. 57-70Hernández, D.M., de Moura, M.A.B.F., Valencia, D.P., González, F.J., González, I., de Abreu, F.C., da Silva Júnior, E.N., Frontana, C., Inner reorganization during the radical-biradical transition in a nor-beta-lapachone derivative possessing two redox centers (2008) Org. Biomol. Chem., 6, pp. 3414-3420Hileman, E.O., Liu, J., Albitar, M., Keateng, M.J., Huang, P., Intrinsic oxidative stress in cancer cells: a biochemical basis for therapeutic selectivity (2004) Cancer Chemother. Pharmacol., 53, pp. 209-219Hillard, E.A., de Abreu, F.C., Ferreira, D.C.M., Jaouen, G., Goulart, M.O.F., Amatore, C., Electrochemical parameters and techniques in drug development, with an emphasis on quinones and related compounds (2008) Chem. Commun., pp. 2612-2628Kerr, J.F.R., Wyllie, A.H., Currie, A.R., Apoptosis-Basic biological phenomenon with wide-ranging implications in tissue kinetics (1972) Brit. J. Cancer, 26, pp. 239-257Lebel, C.P., Ischiropoulos, H., Bondy, S.C., Evaluation of the probe 2',7'-dichlorofluorescin as an indicator of reactive oxygen species formation and oxidative stress (1992) Chem. Res. Toxicol., 5, pp. 227-231Li, P., Nijhawan, D., Budihardjo, I., Srinivasula, S.M., Ahmad, M., Alnemri, E.S., Wang, X., Cytochrome C and dATP-dependent formation of Apaf-1/caspase-9 complex initiates an apoptotic protease cascade (1997) Cell, 91, pp. 479-489Melino, G., The Sirens' song (2001) Nature, 412, p. 23Mizutani, H., Tada-Oikawa, S., Hiraku, Y., Oikawa, S., Kojima, M., Kawanishi, S., Mechanism of apoptosis induced by a new topoisomerase inhibitor through the generation of hydrogen peroxide (2002) J. Biol. Chem., 277, pp. 30684-30689Montenegro, R.C., Araújo, A.J., Molina, M.T., Marinho-Filho, J.D.B., Rocha, D.D., Lopez-Montero, E., Goulart, M.O.F., Costa-Lotufo, L.V., Cytotoxic activity of naphthoquinones with special emphasis on juglone and its 5-O-methyl derivative (2010) Chem. Biol. Interact., 184, pp. 439-448Mosmann, T., Rapid colorimetric assay for cellular growth and survival application to proliferation and cyto-toxicity assays (1983) J. Immunol. Methods, 65, pp. 55-63Okada, H., Mak, T.W., Pathways of apoptotic and non-apoptotic death in tumour cells (2004) Nat. Rev. Cancer, 4, pp. 592-603Oliveira-Brett, A.M., Vivan, M., Fernandes, I.R., Piedade, J.A.P., Electrochemical detection of in situ adriamycin oxidative damage to DNA (2002) Talanta, 56, pp. 959-970Ossowski, T., Pipka, P., Liwo, A., Jeziorek, D., Electrochemical and UV-spectrophotometric study of oxygen and superoxide anion radical interaction with anthraquinone derivatives and their radical anions (2000) Electrochim. Acta, 45, pp. 3581-3587Ozben, T., Oxidative stress and apoptosis: impact on cancer therapy (2007) J. Pharm. Sci., 96, pp. 2181-2196Piedade, J.A.P., Fernandez, I.R., Brett, A.M.O., Electrochemical sensing of DNA-adriamycin interactions (2002) Bioelectrochemistry, 56, pp. 81-83Planchon, S.M., Wuerzberger, S., Frydman, B., Witiak, D.T., Hutson, P., Church, D.R., Wilding, G., Boothman, D.A., β-Lapachone-mediated apoptosis in human promyelocytic leukemia (HL-60) and human prostate cancer cells: a p53-independent response (1995) Cancer Res., 55, pp. 3706-3711Planchon, S.M., Wuerzberger-Davis, S.M., Pink, J.J., Robertson, K.A., Bornmann, W.G., Boothman, D.A., Bcl-2 protects against beta-lapachone-mediated caspase 3 activation and apoptosis in human myeloid leukemia (HL-60) cells (1999) Oncol Rep., 6, pp. 485-492Rauf, S., Gooding, J.J., Akhtar, K., Ghauri, M.A., Rahman, M., Anwar, M.A., Khalid, A.M., Electrochemical approach of anticancer drugs - DNA interaction (2005) J. Pharm. Biomed. Anal., 37, pp. 205-217Singh, N.P., McCoy, M.T., Tice, R.R., Schneider, E.L., A simple technique for quantitation of low-levels of DNA damage in individual cells (1988) Exp. Cell Res., 175, pp. 184-191Wang, J., Ozsoz, M., Cai, X.H., Rivas, G., Shiraishi, H., Grant, D.H., Chicharro, M., Palecek, E., Interactions of antitumor drug daunomycin with DNA in solution and at the surface (1998) Bioelectrochem. Bioenerg., 45 (1998), pp. 33-40Zafarullaha, M., Lia, W.Q., Sylvestera, J., Ahmad, M., Molecular mechanisms of N-acetylcysteine actions (2003) Cell. Mol. Life Sci., 60, pp. 6-20Ziegler, U., Groscurth, P., Morphological features of cell death (2004) News Physiol. Sci., 19, pp. 124-12