Collective Almost Synchronization in Complex Networks

This work introduces the phenomenon of Collective Almost Synchronization (CAS), which describes a universal way of how patterns can appear in complex networks even for small coupling strengths. The CAS phenomenon appears due to the existence of an approximately constant local mean field and is characterized by having nodes with trajectories evolving around periodic stable orbits. Common notion based on statistical knowledge would lead one to interpret the appearance of a local constant mean field as a consequence of the fact that the behavior of each node is not correlated to the behaviors of the others. Contrary to this common notion, we show that various well known weaker forms of synchronization (almost, time-lag, phase synchronization, and generalized synchronization) appear as a result of the onset of an almost constant local mean field. If the memory is formed in a brain by minimising the coupling strength among neurons and maximising the number of possible patterns, then the CAS phenomenon is a plausible explanation for it.Comment: 3 figure

Chemisorption of Al and Ga on the GaAs (110) surface

We have studied the initial stages of the chemisorption of Al and Ga on the clean GaAs (110) surface by applying quantum chemical methods to small clusters representing Al or Ga on GaAs (110). These calculations suggest that at smallest coverages Al or Ga bind to a surface Ga atom; for higher coverages Al and the surface Ga interchange positions. We have obtained the binding energy, the chemical shifts of the Ga–3d, As–3d and Al–2p states, and the microscopic dipole associated with chemisorption of Al or Ga on GaAs (110). These results are compared to experimental values and further experiments are suggested

Awareness, perceived risk and practices related to cervical cancer and Pap smear screening: A crosssectional study among HIV-positive women attending an urban HIV clinic in Johannesburg, South Africa

Background. Cervical cancer is a major cause of cancer-related deaths, especially in the context of the HIV epidemic.Objective. To examine awareness, perceived risk and practices related to cervical cancer screening among HIV-positive women.Methods. Interviewer-administered structured questionnaires were administered to HIV-positive women (aged ≥18 years) enrolled in a cervical cancer screening study at the Themba Lethu Clinic, Johannesburg, South Africa, from November 2009 to December 2011. Modified Poisson regression with robust standard errors was used to identify factors at enrolment associated with awareness, perceived risk and adequate practice related to cervical screening. Adjusted relative risks (aRRs) with 95% confidence intervals (CIs) are presented.Results. Of the 1 202 women enrolled, 71.3% and 18.2% were aware of the Pap smear and HPV, respectively. Of the 1 192 participants with data evaluated, 76.5% were worried and 23.5% were not worried about cervical cancer; 28.6% of the women had adequate screening practice. Older age (40 - 49 years or ≥50 years v. 18 - 29 years) (aRR 1.63, 95% CI 1.12 - 2.37; aRR 2.22, 95% CI 1.44 - 3.41), higher education (tertiary v. less than grade 10) (aRR 1.39, 95% CI 1.00 - 1.93), initiation on combination antiretroviral therapy (aRR 1.36, 95% CI 1.00 - 1.85) and awareness of Pap smear screening (aRR 16.18, 95% CI 7.69 - 34.01) were associated with adequate screening practice.Conclusions. High levels of Pap smear awareness and low levels of Pap smear screening uptake were observed. However, Pap smear awareness was associated with adequate screening practice. More research into effective health education programmes to address these gaps is needed

Electrochemical and computational study of tungsten(0) ferrocene complexes: observation of the mono-oxidized tungsten(0) ferrocenium species and intramolecular electronic interactions

The series [(CO)5W=C(XR)Fc], 1 (XR = OEt) and 3 (XR = NHBu) as well as [(CO)5W=C(XR)-Fc'-(XR)C=W(CO)5], 2 (XR = OEt) and 4 (XR = NHBu) of mono- and biscarbene tungsten(0) complexes with Fc = FeII(C5H5)(C5H4) for monosubstituted derivatives and Fc¢ = FeII(C5H4)2 for disubstituted derivatives were synthesized and characterized spectroscopically. The oxidized ferrocenium complex [1+]•PF6 was also synthesized and characterized. Electrochemical and computational studies were mutually consistent in confirming the sequence of redox events for the carbene derivatives 1 - 4 as first a carbene double bond reduction to a radical anion, -W-C•, at peak cathodic potentials smaller than -2 V, then a ferrocenyl group oxidation in the range 0.206 < Eo' < 0.540 V and finally an electrochemically irreversible three-electron W(0) oxidation at Epa > 0.540 V vs. FcH/FcH+ in CH2Cl2 / [(nBu4)N][PF6]. This contrasts the sequence of oxidation events in ferrocenylcarbene complexes of chromium where Cr(0) is first oxidised in a one electron transfer process, then the ferrocenyl group, and finally formation of a Cr(II) species. The unpaired electron of the reductively formed radical anion is mainly located on the carbene carbon atom. Electronic interactions between two carbene double bonds (for biscarbenes 2 and 4) as well as between two W centers (for 4) were evident. Differences in redox potentials between the “a” and “b” components of the threeelectron W oxidation of 4 in CH2Cl2 or CH3CN / [(nBu4)N][PF6] are DEo' = Epa W(0) oxd 1b – Epa W(0) oxd 1a = ca. 51 and 337 mV respectively. Tungsten oxidation was restricted to a W0/II couple in CH2Cl2 / [(nBu4)N][B(C6F5)4]. From the computational results, the short-lived W(II) species were observed to be stabilized by agostic CH···W interactions.National Research Foundation, South Africa, (DIB, Grant number 76226; JCS, Grant number 81829), and by the Spanish MICINN and CAM (IF, Grants CTQ2010-20714-CO2-01/BQU, Consolider-Ingenio 2010, CSD2007-00006, S2009/PPQ-1634).http://pubs.acs.org/journal/orgnd7hb201

Synthesis and electrochemical investigation of chromium(0)ferrocenyl-substituted carbene complexes

Please read the abstract in the article.National Research Foundation, South Africa, (DIB, Grant number 76226; JCS, Grant number 81829), and by the Spanish MICINN and CAM (IF, Grants CTQ2010-20714-CO2-01/BQU, Consolider-Ingenio 2010, CSD2007-00006, S2009/PPQ-1634).http://www.elsevier.com/locate/icahb201

Electrochemical illumination of thienyl and ferrocenyl chromium(0) Fischer carbene complexes

A series of ferrocenyl and thienyl mono- and biscarbene chromium(0) complexes 1–6 were synthesised. The complexes were characterised both spectroscopically and electrochemically, and the single crystal X-ray structure of 3 was determined. Electrochemical measurements in CH2Cl2 revealed that the carbene double bond of 1–6 is reduced to an anion radical, −Cr–C˙ at formal reduction potentials <−1.7 V vs. FcH/FcH+. A computational study on 1, 3 and 4 (B3LYP/def2-SVP level) is consistent with electrochemical results in showing that electrochemically generated chromium(I) species may be further electrochemically irreversibly oxidised to chromium(II) at Epa > 0.95 V. The reactivity towards follow-up chemical reactions of the anodically produced Cr(II) species is much higher than the reactivity of the cathodically produced radical anions as the latter was still observably reoxidised to the parent CrvC species at fast scan rates. The ferrocenyl group is oxidised electrochemically reversibly to ferrocenium at larger potentials than the electrochemically reversible oxidation of the Cr(0) centre to Cr(I). That all redox centres in 1–6 are involved in one-electron transfer steps was confirmed by comparing the ferrocenyl voltammetric wave with those of the other redox centres in linear sweep voltammetric experiments. The ferrocenyl group was electrochemically shown to stabilise the CrvC centre almost as much as the NHBu, and much more than the ethoxy and thienyl groups.This work is supported by the National Research Foundation, (DIB, Grant number 76226; JCS, Grant number 81829). I. F. acknowledges the Spanish MICINN and CAM (Grants CTQ2010-20714-CO2-01/BQU, Consolider-Ingenio 2010, CSD2007-00006, S2009/PPQ-1634).http://pubs.rsc.orgam2013ai201

Redox behaviour of cymantrene Fischer carbene complexes in designing organometallic multi-tags

Please read abstract in the article.This work is supported by the National Research Foundation (NRF) of South Africa, (D.I.B., Grant number 76226;J.C.S., Grant number 81829). I. F. acknowledges the Spanish MICINN and CAM (Grants CTQ2010-20714-CO2-01/BQU, Consolider-Ingenio 2010, CSD2007-00006, S2009/PPQ-1634). O.Q.M. acknowledges financial support from the University of KwaZulu-Natal and the NRF.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1521-37652015-04-30hb201

Substituent effects on the electrochemical, spectroscopic, and structural properties of Fischer mono- and biscarbene complexes of Chromium(0)

A series of ten ferrocenyl, furyl, and thienyl mono- and biscarbene chromium(0) complexes were synthesized and characterized spectroscopically and electrochemically. The single crystal structure of the biscarbene complex [(CO)5Cr═C(OEt)-Fu′-(OEt)C═Cr(CO)5] (4a) was determined: C20H12Cr2O13; triclinic; P1̅; a = 6.2838(5), b = 12.6526(9), c = 29.1888(19) Å, α = 89.575(2), β = 88.030(2), γ = 87.423(2)°; Z = 4. Results from an electrochemical study in CH2Cl2 were mutually consistent with a computational study in showing that the carbene double bond of 1 – 6 is reduced to an anion radical, –Cr–C• at formal reduction potentials < −1.7 V vs FcH/FcH+. The Cr centers are oxidized in two successive one electron transfer steps to Cr(II) via the Cr(I) intermediate. Only Cr(I) oxidation is electrochemically irreversible. Dicationic Cr(II) species formed upon two consecutive one-electron oxidation processes are characterized by a peculiar bonding situation as they are stabilized by genuine CH···Cr agostic interactions. With respect to aryl substituents, carbene redox processes occurred at the lowest potentials for ferrocene derivatives followed by furan complexes. Redox process in the thiophene derivatives occurred at the highest potentials. This result is mutually consistent with a 13C NMR study that showed the Cr═C functionality of furyl complexes were more shielded than thienyl complexes. The NHBu carbene substituent resulted in carbene complexes showing redox processes at substantially lower redox potentials than carbenes having OEt substituents.The National Research Foundation, South Africa (D.I.B., Grant number 76226; J.C.S., Grant number 81829), and the Spanish MICINN and CAM (I.F., Grants CTQ2010-20714-CO2-01/BQU, Consolider-Ingenio 2010, CSD2007-00006, S2009/PPQ-1634).http://pubs.acs.org/journal/inocajhb2013ai201

Complete genome sequence of Syntrophobacter fumaroxidans strain (MPOB(T)).

Syntrophobacter fumaroxidans strain MPOB(T) is the best-studied species of the genus Syntrophobacter. The species is of interest because of its anaerobic syntrophic lifestyle, its involvement in the conversion of propionate to acetate, H2 and CO2 during the overall degradation of organic matter, and its release of products that serve as substrates for other microorganisms. The strain is able to ferment fumarate in pure culture to CO2 and succinate, and is also able to grow as a sulfate reducer with propionate as an electron donor. This is the first complete genome sequence of a member of the genus Syntrophobacter and a member genus in the family Syntrophobacteraceae. Here we describe the features of this organism, together with the complete genome sequence and annotation. The 4,990,251 bp long genome with its 4,098 protein-coding and 81 RNA genes is a part of the Microbial Genome Program (MGP) and the Genomes to Life (GTL) Program project