Syntheses and magnetic properties of substituted bis-indacenyl bi-metallic complexes & application / Síntesis y propiedades magnéticas de complejos bimetálicos de bis-indacenilo sustituido y su aplicación / Sínteses e propriedades magnéticas de complexos bimetálicos bis-indaceníli-cossubstituídos e aplicação

Abstract Organometallic compounds, Bis (2,4,6,8 teramethyl-indacenyl) di Iron (1), Bis (2,4,6,8 teramethyl s-indacenyl) mono iron, mono cobalt (2), and Bis (2,6 diethyl-4,8-dimethyl-s-indacenyl) di cobalt (3) were synthesised by means of salt elimination strategy, using Fe(II) and Co(II) salts. The compounds were characterised through spectroscopic and electrochemical methods. Magnetic measurements were carried out by Physical Property Measurement System (PPMS). Mossbauer spectroscopic data reveals that in all compounds, surprisingly, Iron is in +3 oxidation state. DFT calculations have been carried out to understand the change in the oxidation state of a metal. DFT study confirms the electron transfer nature of ligand to metal. Cyclic voltametric study on these compounds shows a large separation (ΔE>800mV) between two oxidation peaks confirming the strong interaction between the metal centres. Magnetic measurements on these organometallic compounds reveals that they exhibit a ferrimagnetic behaviour at temperatures below 40 K.

Resumen En este trabajo se sintetizaron los compuestos organometálicos Bis (2,4,6,8 terametil-indacenil) férrico (1), Bis (2,4,6,8 terametil s-indacenil) ferroso, cobaltoso (2) y Bis (2,6 dietil-4,8-dimetil-s-indacenil) di cobalto (3) mediante la estrategia de eliminación de sales, utilizando sales de Fe(II) y Co(II).Los compuestos se caracterizan por métodos espectroscópicos y electroquímicos. Las mediciones magnéticas se llevaron a cabo mediante el sistema de medición de propiedades físicas (PPMS). Los datos espectroscópicos Mossbauer revelan que, en todos los compuestos, sorprendentemente, el hierro se encuentra en el estado de oxidación +3. También se realizaron cálculos DFT para comprender el cambio en el estado de oxidación de los metales. El estudio DFT confirmó la naturaleza de transferencia de electrones del ligando al metal. El estudio voltamperométrico cíclico de estos compuestos muestra una gran separación (ΔE>800mV) entre los dos picos de oxidación que confirman la fuerte interacción entre los centros metálicos. Las mediciones magnéticas de estos compuestos organometálicos revelan que presentan un comportamiento ferrimagnético a temperaturas inferiores a 40 K.

Resumo Compostos organometálicos, Bis (2,4,6,8 terametil-indacenil) di ferro (1), Bis (2,4,6,8 terametil s-indacenil) mono ferro, mono cobalto (2) e Bis (2,6 dietil-4,8-dimetil-s-indacenil) di cobalto (3) foram sintetizados por estratégia de eliminação de sal, utilizando sais de Fe(II) e Co(II). Os compostossão caracterizados por métodos espectroscópicos e eletroquímicos. As medições magnéticas foram realizadas pelo Sistema de Medição de Propriedades Físicas (PPMS). Os dados espectroscópicos Mossbauerrevelam que em todos os compostos, surpreendentemente, o ferro está em +3 estado de oxidação.Os cálculos do DFT foram realizados para entender a mudança no estado de oxidação de um metal. O estudo DFT confirma a natureza da transferência de elétrons do ligante para o metal. O estudovoltamétrico cíclico dessescompostosmostrauma grande separação (ΔE>800mV) entre dois picos de oxidação confirmando a forteinteração entre os centros metálicos. As medições magnéticas nestescompostos organometálicos revelam que eles apresentam um comportamento ferrimagnético a uma temperatura abaixo de 40 K.

Role of interparticle interactions on the magnetic behavior of Mg(0.95)Mn(0.05)Fe(2)O(4) ferrite nanoparticles.

We present here a detailed investigation of the static and dynamic magnetic behavior of a Mg(0.95)Mn(0.05)Fe(2)O(4) spinel ferrite nanoparticle system synthesized by high-energy ball milling of almost identical particle size distributions ([Formula: see text], 5.1 and 6.0 ± 0.6 nm). The samples were characterized by using x-ray diffraction, Mössbauer spectroscopy, dc magnetization and frequency dependent real χ(')(T) and imaginary χ('')(T) parts of ac susceptibility measurements. The zero-field-cooled (ZFC) and field-cooled (FC) magnetization have been recorded in a low field and show a behavior typical of superparamagnetic particles above a temperature of 185 ± 5 K, which is further supported from the temperature dependent Mössbauer measurements. The fact that the blocking temperature calculated from the ZFC magnetization and Mössbauer data are almost similar gives a clear indication of the interparticle interactions among these nanoparticle systems. This is further supported from the FC magnetization curves, which are almost flat below a certain temperature (less than the blocking temperature), as compared with the monotonically increasing behavior characteristics of non-interacting superparamagnetic particles. A shift of the blocking temperature with increasing frequency was observed in the real χ(')(T) and imaginary χ('')(T) parts of the ac susceptibility measurements. The analysis of the results shows that the data fit well with the Vogel-Fulcher law, whereas trials using the Neel-Brown and power law are unproductive. The role of magnetic interparticle interactions on the magnetic behavior, namely superparamagnetic relaxation time and magnetic anisotropy, are discussed.

A multistate outbreak of Salmonella enterica Serotype Newport infection linked to mango consumption: impact of water-dip disinfestation technology.

Fresh produce increasingly is recognized as an important source of salmonellosis in the United States. In December 1999, the Centers for Disease Control and Prevention detected a nationwide increase in Salmonella serotype Newport (SN) infections that had occurred during the previous month. SN isolates recovered from patients in this cluster had indistinguishable pulsed-field gel electrophoresis (PFGE) patterns (which identified the outbreak strain), suggesting a common source. Seventy-eight patients from 13 states were infected with the outbreak strain. Fifteen patients were hospitalized; 2 died. Among 28 patients enrolled in the matched case-control study, 14 (50%) reported they ate mangoes in the 5 days before illness onset, compared with 4 (10%) of the control subjects during the same period (matched odds ratio, 21.6; 95% confidence interval, 3.53- infinity; P=.0001). Traceback of the implicated mangoes led to a single Brazilian farm, where we identified hot water treatment as a possible point of contamination; this is a relatively new process to prevent importation of an agricultural pest, the Mediterranean fruit fly. This is the first reported outbreak of salmonellosis implicating mangoes. PFGE was critical to the timely recognition of this nationwide outbreak. This outbreak highlights the potential global health impact of foodborne diseases and newly implemented food processes.

Virus maturation targets the protein capsid to concerted disassembly and unfolding.

Many animal viruses undergo post-assembly proteolytic cleavage that is required for infectivity. The role of maturation cleavage on Flock House virus was evaluated by comparing wild type (wt) and cleavage-defective mutant (D75N) Flock House virus virus-like particles. A concerted dissociation and unfolding of the mature wt particle was observed under treatment by urea, whereas the cleavage-defective mutant dissociated to folded subunits as determined by steady-state and dynamic fluorescence spectroscopy, circular dichroism, and nuclear magnetic resonance. The folded D75N alpha subunit could reassemble into capsids, whereas the yield of reassembly from unfolded cleaved wt subunits was very low. Overall, our results demonstrate that the maturation/cleavage process targets the particle for an "off pathway" disassembly, because dissociation is coupled to unfolding. The increased motions in the cleaved capsid, revealed by fluorescence and NMR, and the concerted nature of dissociation/unfolding may be crucial to make the mature particle infectious.