Effect of a fluctuating parameter mismatch and the associated time-scales on coupled Rossler oscillators

We study the effect of parameter fluctuations and the resultant multiplicative noise on the synchronization of coupled chaotic systems. We introduce a new quantity, the fluctuation rate ϕ as the number of perturbations occurring to the parameter in unit time. It is shown that ϕ is the most significant quantity that determines the quality of synchronization. It is found that parameter fluctuations with high fluctuation rates do not destroy synchronization, irrespective of the statistical features of the fluctuations. We also present a quasi-analytic explanation to the relation between ϕ and the error in synchrony.      

Mbaka lakes isotopic ((18)O and (2)H) and water balances: discussion on the used atmospheric moisture compositions

The water balances of small crater lakes Masoko, Katubwi, Kyambangunguru, Ilamba, Kingiri, located north of lake Malawi (Tanzania), are established with the Craig-Gordon model of evaporation. In this approach, it is difficult to evaluate the isotopic composition of evaporated vapour (deltaE), which is indirectly estimated from the atmospheric moisture signature (deltaA). Given that 'precipitation equilibrium' approach does not lead to realistic solutions in this tropical region, the lake balances are established and discussed from both the sampled deltaA and those derived from the terminal lake Rukwa. The mean local sampled signature (deltaAm : delta(18)O =-13.7per thousand and delta(2)H =-76per thousand) is inferior to that derived from lake Rukwa (deltaAtl : delta(18)O =-10.4per thousand and delta(2)H =-64per thousand), which may be due to altitudinal and latitudinal effects but both are influenced by recycling continental vapour. Water balances enable us to confirm and quantify high inflows and groundwater outflows that account for typologies of Mbaka lakes. The proposed sampling and measurement method allows us then to access reasonable moisture compositions in far-away regions.     

Improvement of hot-dip zinc coating by enriching the inner layers with iron oxide

The performance of hot-dip galvanic coating formed on steel not only depends on the alloy composition of the superficial layer but also significantly, on the composition of the inner alloy layers at the coating/substrate interface. Further, the presence of barrier oxide layers, if any can also improve the performance of galvanic coating. In the present work, the effect of inner iron oxide barrier layer formed prior to hot-dip galvanization was investigated. A continuous and adherent iron oxide layer was formed on steel by anodic oxidation of the steel substrate. Although the wettability of oxide surface by liquid zinc was initially poor, the increase in dipping time and the transition of the oxide layer to unstable form due to the presence of Cl⁻ ion in the flux facilitated localized growth of Fe-Zn alloy phases. The inhibitive nature of the oxide layer was temporary, since the presence of Cl⁻ induces micro cracks on the oxide surface thereby facilitating better zinc diffusion. The modification of the substrate structure during galvanization was found to influence the galvanizing process significantly. The present study predicts scope for application of this process for protection of rusted steel specimens too.     

Interaction between phospholipid vesicular structures with long chain zwitterionic surfactants

Solubilization of different zwitterionic phospholipid vesicles structures such as L--phosphatidylcholine (PC) and 1,2-didecanoyl-sn-glycero-3-phosphocholine (DPC) have been studied in aqueous bulk by using zwitterionic surfactant dimethylhexadecylammoniopropanesulfonate (HPS). This has been done by studying the aggregation of HPS in pure water and in the presence of 7–36 M of fixed concentrations of each lipid with the help of pyrene fluorescence intensity (I ₁/I ₃) measurements. The fluorescence measurements showed that HPS monomers undergo two kinds of aggregation process, which were identified by the three breaks in a plot of pyrene fluorescence versus HPS concentration. The first two breaks, C ₁ and C ₂, indicate the onset and completion of vesicle solubilization respectively, upon incorporation of HPS monomers into the vesicles and led to solubilization in the form of mixed micelles. This process was not clearly visible at low lipid concentration. We evaluated the partition coefficient (K), which defines the degree of partitioning of surfactant monomers into the vesicles with respect to the aqueous medium. A high K value of HPS-lipid aggregates indicates the stronger interactions between surfactant and lipid vesicles. The K values evaluated for PC and DPC are quite close to each other, which indicates that K values were independent of phospholipid chain length.     

Structural, thermoanalytical and molecular modeling studies on N-(3-hydroxypropyl) 3 alpha,12 alpha-dihydroxy-5 beta-cholan-24-amide and its monohydrates

The synthetic method for preparing N-(3-hydroxypropyl) 3 alpha,12 alpha-dihydroxy-5 beta-cholan-24-amide can lead to formation of at least three different crystal forms - an anhydrous compound and two monohydrates. The structural and thermal properties of these forms have been characterized by 13C-CP/MAS-NMR and IR spectroscopy, thermo- gravimetry, differential scanning calorimetry and by powder and single crystal x-ray crystallography. In addition, theoretical 13C-NMR chemical shift calculations were also performed for the anhydrous compound and for the first monohydrate, starting from single crystal structures and the structures of these species have now been verified. The first monohydrate, C27H47NO4 x H2O, crystallizes in orthorhombic space group P2(1)2(1)2(1) with cell parameters: a = 7.1148(2), b = 18.1775(5), c = 20.1813(6), Z = 4.     

Surface-tethered protein switches

Protein switches are engineered fusion proteins with an input domain that recognizes and responds to an input signal and an output domain whose function is regulated by the state of the input domain. Here we demonstrate a fully functional surface tethered protein switch that offers a potential route to a universal biosensing platform.     

Development and validation of reversed phase liquid chromatographic method utilizing ultraviolet detection for quantification of irinotecan (CPT-11) and its active metabolite, SN-38, in rat plasma and bile samples: application to pharmacokinetic studies

A new, simple, sensitive and specific reversed-phase high performance liquid chromatographic (HPLC) method using ultraviolet detection was developed and validated for the analysis of CPT-11 (lambda(max)=254 nm, 365 nm) and its major active metabolite, SN-38 (lambda(max)=380 nm) in rat plasma and bile. The sample pre-treatment from plasma involved a single protein precipitation step with cold acetonitrile. In case of bile, liquid-liquid extraction with dichloromethane: tert-butyl methyl ether (3:7) was carried out. Topotecan, a structurally related camptothecin, was used as an internal standard. An aliquot of 50 microL was injected onto a C-18 column. The chromatographic separation was achieved by gradient elution consisting of acetonitrile and water (pH 3.0 adjusted with 20% o-phosphoric acid) at a flow rate of 1.0 ml/min. Total run time for each sample was 30 min. All the analytes viz. topotecan, CPT-11, SN-38 were well separated with retention times of 11.4, 13.4 and 15.5 min, respectively. Method was found to be selective, linear (R(2) approximately 0.999), accurate (recovery+/-15%) and precise (<5% C.V.) in the selected concentration ranges for both the analytes. The quantification limit for CPT-11 was 40 ngml(-1) and for SN-38 was 25 ngml(-1). The percent extraction efficiency was approximately 97% for CPT-11 and SN-38 from plasma while extraction recovery of CPT-11 and SN-38 from bile was approximately 70% and approximately 60%, respectively. The method was successfully used to determine plasma and biliary excretion time profiles of CPT-11 and SN-38, following oral and intravenous CPT-11 administration in rats. In the present study, irinotecan showed an absolute bioavailability of 30% as calculated from the pharmacokinetic data.     

Interplay between size, composition, and phase transition of nanocrystalline Cr(3+)-doped BaTiO3 as a path to multiferroism in perovskite-type oxides

Multiferroics, materials that exhibit coupling between spontaneous magnetic and electric dipole ordering, have significant potential for high-density memory storage and the design of complex multistate memory elements. In this work, we have demonstrated the solvent-controlled synthesis of Cr(3+)-doped BaTiO(3) nanocrystals and investigated the effects of size and doping concentration on their structure and phase transformation using X-ray diffraction and Raman spectroscopy. The magnetic properties of these nanocrystals were studied by magnetic susceptibility, magnetic circular dichroism (MCD), and X-ray magnetic circular dichroism (XMCD) measurements. We observed that a decrease in nanocrystal size and an increase in doping concentration favor the stabilization of the paraelectric cubic phase, although the ferroelectric tetragonal phase is partly retained even in ca. 7 nm nanocrystals having the doping concentration of ca. 5%. The chromium(III) doping was determined to be a dominant factor for destabilization of the tetragonal phase. A combination of magnetic and magneto-optical measurements revealed that nanocrystalline films prepared from as-synthesized paramagnetic Cr(3+)-doped BaTiO(3) nanocrystals exhibit robust ferromagnetic ordering (up to ca. 2 μ(B)/Cr(3+)), similarly to magnetically doped transparent conducting oxides. The observed ferromagnetism increases with decreasing constituent nanocrystal size because of an enhancement in the interfacial defect concentration with increasing surface-to-volume ratio. Element-specific XMCD spectra measured by scanning transmission X-ray microscopy (STXM) confirmed with high spatial resolution that magnetic ordering arises from Cr(3+) dopant exchange interactions. The results of this work suggest an approach to the design and preparation of multiferroic perovskite materials that retain the ferroelectric phase and exhibit long-range magnetic ordering by using doped colloidal nanocrystals with optimized composition and size as functional building blocks.     

Structural studies on lithocholyl-N-(2-aminoethyl)amide in the solid state

The synthetic procedure of lithocholyl-N-(2-aminoethyl)amide yielded a mixture of several forms detected by solid state ¹³C CP/MAS NMR although the solution state NMR unambiguously ascertained that the compound was pure. By recrystallization from various solvents one pure polymorph alongside with four solvates were isolated. The structures of the pure polymorph and the solvates were characterized by ¹³C and ¹⁵N CP/MAS NMR and powder X-ray diffraction (PXRD) methods. Variable contact time and dipolar dephasing experiments were employed to obtain optimized CP parameters and to distinguish various CH _n (n = 0–3) resonances. CSA analyses of spinning side bands at different spinning rates showed small variations in the shielding tensor values of the carbonyl group between the pure polymorph (recrystallized from acetonitrile, tetrahydrofuran and 1,4-dioxane) and p-xylene solvate.