Fine-Tuning Dual Emission and Aggregation-Induced Emission Switching in NPI-BODIPY Dyads

Three new NPI-BODIPY dyads 1-3 (NPI = 1,8-naphthalimide, BODIPY = boron-dipyrromethene) were synthesized, characterized, and studied. The NPI and BODIPY moieties in these dyads are electronically separated by oxoaryl bridges, and the compounds only differ structurally with respect to methyl substituents on the BODIPY fluorophore. The NPI and BODIPY moieties retain their optical features in molecular dyads 1-3. Dyads 1-3 show dual emission in solution originating from the two separate fluorescent units. The variations of the dual emission in these compounds are controlled by the structural flexibilities of the systems. Dyads 13, depending on their molecular flexibilities, show considerably different spectral shapes and dissimilar intensity ratios of the two emission bands. The dyads also show significant aggregation-induced emission switching (AIES) on formation of nano-aggregates in THF/H2O with changes in emission color from green to red. Whereas the flexible and aggregation-prone compound 1 shows AIES, rigid systems with less favorable intermolecular interactions (i.e., 2 and 3) show aggregation-induced quenching of emission. Correlations of the emission intensity and structural flexibility were found to be reversed in solution and aggregated states. Photophysical and structural investigations suggested that intermolecular interactions (e. g., pi-pi stacking) play a major role in controlling the emission of these compounds in the aggregated state.

Traveling waves in trimer granular lattice I: Bifurcation structure of traveling waves in the unit-cell model

Present paper is the first one in the series devoted to the dynamics of traveling waves emerging in the uncompressed, tri-atomic granular crystals. This work is primarily concerned with the dynamics of one-dimensional periodic granular trimer (tri-atomic) chains in the state of acoustic vacuum. Each unit cell consists of three spherical particles of different masses subject to periodic boundary conditions. Hertzian interaction law governs the mutual interaction of these particles. Under the assumption of zero pre-compression, this interaction is modeled as purely nonlinear, which means the absence of linear force component. The dynamics of such chains is governed by the two system parameters that scale the mass ratios between the particles of the unit cell. Such a system supports two different classes of periodic solutions namely the traveling and standing waves. The primary objective of the present study is the numerical analysis of the bifurcation structure of these solutions with emphasis on the dynamics of traveling waves. In fact, understanding of the bifurcation structure of the traveling wave solutions emerging in the unit-cell granular trimer is rather important and can shed light on the more complex nonlinear wave phenomena emerging in semi-infinite trimer chains. (c) 2016 Elsevier B.V. All rights reserved.

Cell Dynamics of Model Proteins

We design rapidly folding sequences by assigning the strongest couplings to the contacts present in a target native state in a two dimensional model of heteropolymers. The pathways to folding and their dependence on the temperature are illustrated via a mapping of the dynamics into motion within the space of the maximally compact cells.

Unsteady free convection flow in the stagnation-point region of a three-dimensional body

The unsteady free convection flow in the stagnation-point region of a heated three-dimensional body placed in an ambient fluid is studied under boundary layer approximations. We have considered the case where there is an initial steady state that is perturbed by a step-change in the wall temperature. The non-linear coupled partial differential equations governing the free convection flow are solved numerically using a finite difference scheme. The presented results show the temporal development of the momentum and thermal boundary layer characteristics.

Immunization of male rabbits with sheep luteal receptor to LH results in production of antibodies exhibiting hormone-agonistic and -antagonistic activities

Antibodies to LH/chorionic gonadotrophin receptor (LH/CG-R; molecular weight 67 000), isolated in a homogenous state (established by SDS-PAGE and ligand blotting) from sheep luteal membrane using human CG (hCG)-Sepharose affinity chromatography, were raised in three adult male rabbits (R-I, R-II and R-III). Each of the rabbits received 20-30 mu g oi the purified receptor in Freund's complete adjuvant at a time. Primary immunization was followed by booster injection at intervals. Production of receptor antibodies was monitored by (1) determining the dilution of the serum (IgG fraction) that could specifically bind 50% of I-125-LH/CG-R added and (2) analysing sera for any chance in testosterone levels. Following primary immunization and the first booster, all three rabbits exhibited a 2.5- to 6.0-fold increase in serum testosterone over basal levels and this effect was spread over a period of time (similar to 40 days) coinciding with the rise and fall of receptor antibodies. The maximal antibody titre (ED(50)) produced at this time ranged from 1:350 to 1:100 to below detectable limits for R-I, R-II and R-III respectively. Subsequent immunizations followed by the second booster resulted in a substantial increase in antibody titre (ED(50) of 1:5000) in R-I, but this was not accompanied by any change in serum testosterone over preimmune levels, suggesting that with the progress of immunization the character of the antibody produced had also changed. Two pools of antisera from R-I collected 10 days following the booster (at day 70 (bleed I) and day 290 (bleed II)) were used in further experiments. IgG isolated from bleed I but not from bleed II antiserum showed a dose-dependent stimulation of testosterone production by mouse Leydig cells in vitro, thus confirming the in vivo hormone-mimicking activity antibodies generated during the early immunization phase. The IgG fractions from both bleeds were, however, capable of inhibiting (1) I-125-hCG binding to crude sheep luteal membrane (EC(50) of 1:70 and 1:350 for bleed I and II antisera respectively) and (2) ovine LH-stimulated testosterone production by mouse Leydig cells in vitro, indicating the presence oi antagonistic antibodies irrespective of the period of time during which the rabbits were immunized. The: fact that bleed I-stimulated testosterone production could be inhibited in a dose-dependent manner by the addition of IgG from bleed II to the mouse Leydig cell in vitro assay system showed that the agonistic activity is intrinsic to the bleed I antibody. The receptor antibody (bleed II) was also capable of blocking LH action in vivo, as rabbits passively (for 24 h with LH/CG-R antiserum) as well as actively (for 130 days) immunized against LH/CG-R failed to respond to a bolus injection of LH (50 mu g). At no time, however, was the serum testosterone reduced below the basal level. This study clearly shows that, unlike with LH antibody, attempts to achieve an LH deficiency effect in vivo by resorting to immunization with hole LH receptor is difficult, as receptor antibodies exhibit both hormone-mimicking (agonistic) as well as hormone-blocking (antagonistic) activities.

Analytical solution of unsteady three-dimensional MHD boundary layer flow and heat transfer due to impulsively stretched plane surface

The unsteady magnetohydrodynamic viscous flow and heat transfer of Newtonian fluids induced by an impulsively stretched plane surface in two lateral directions are studied by using an analytic technique, namely, the homotopy method. The analytic series solution presented here is highly accurate and uniformly valid for all time in the entire region. The effects of the stretching ratio and the magnetic field on the surface shear stresses and heat transfer are studied. The surface shear stresses in x- and y-directions and the surface heat transfer are enchanced by increasing stretching ratio for a fixed value of the magnetic parameter. For a fixed stretching ratio, the surface shear stresses increase with the magnetic parameter, but the heat transfer decreases. The Nusselt number takes longer time to reach the steady state than the skin friction coefficients. There is a smooth transition from the initial unsteady state to the steady state.

Steady state optimization of an ammonia reactor

A hybrid simulation technique for identification and steady state optimization of a tubular reactor used in ammonia synthesis is presented. The parameter identification program finds the catalyst activity factor and certain heat transfer coefficients that minimize the sum of squares of deviation from simulated and actual temperature measurements obtained from an operating plant. The optimization program finds the values of three flows to the reactor to maximize the ammonia yield using the estimated parameter values. Powell's direct method of optimization is used in both cases. The results obtained here are compared with the plant data.

State space formulation of ammonia reactor dynamics

The specific objective of this paper is to develop a state space model of a tubular ammonia reactor which is the heart of an ammonia plant in a fertiliser complex. A ninth order model with three control inputs and two disturbance inputs is generated from the nonlinear distributed model using linearization and lumping approximations. The lumped model is chosen such that the steady state temperature at the exit of the catalyst bed computed from the simplified state space model is close enough to the one computed from the nonlinear steady state model. The model developed in this paper is very useful for the design of continuous/discrete versions of single variable/multivariable control algorithms.

Spin-state equilibria in the LCoO3 system from 59Co NMR

Spin-state equilibria in the whole set of LCoO3 (where L stands for a rare-earth metal or Y) have been investigated with the use of 59Co NMR as a probe for the polycrystalline samples (except Ce) in the temperature interval 110-550 K and frequency range 3- 11.6 MHz. Besides confirming the coexistence of the high-spin—low-spin state in this temperature range, a quadrupolar interaction of ∼0.1 -0.5 MHz has been detected for the first time from 59Co NMR. The NMR line shape is found to depend strongly on the relative magnitude of the magnetic and quadrupolar interactions present. Analysis of the powder pattern reveals two basically different types of transferred hyperfine interaction between the lighter and heavier members of the rare-earth series. The first three members of the lighter rare-earth metals La, Pr (rhombohedral), and Nd (tetragonal), exhibit second-order quadrupolar interaction with a zero-asymmetry parameter at lower temperatures. Above a critical temperature TS (dependent on the size of the rare-earth ion), the quadrupolar interaction becomes temperature dependent and eventually gives rise to a first-order interaction thus indicating a possible second-order phase change. Sm and Eu (orthorhombic) exhibit also a second-order quadrupolar interaction with a nonzero asymmetry parameter ((η∼0.47)) at 300 K, while the orthorhombic second-half members (Dy,..., Lu and Y) exhibit first-order quadrupolar interaction at all temperatures. Normal paramagnetic behavior, i.e., a linear variation of Kiso with T-1, has been observed in the heavier rare-earth cobaltites (Er,..., Lu and Y), whereas an anomalous variation has been observed in (La,..., Nd)CoO3. Thus, Kiso increases with increasing temperature in PrCoO3 and NdCoO3. These observations corroborate the model of the spin-state equilibria in LCoO3 originally proposed by Raccah and Goodenough. A high-spin—low-spin ratio, r=1, can be stabilized in the perovskite structure by a cooperative displacement of the oxygen atoms from the high-spin towards the low-spin cation. Where this ordering into high- and low-spin sublattices occurs at r=1, one can anticipate equivalent displacement of all near-neighbor oxygen atoms towards a low-spin cobalt ion. Thus the heavier LCoO3 exhibits a small temperature-independent first-order quadrupolar interaction. Where r<1, the high- and low-spin states are disordered, giving rise to a temperature-dependent second-order quadrupolar interaction with an anomalous Kiso for the lighter LCoO3.

The carbon dioxide hydration activity of the sulfonamide-resistant carbonic anhydrase from the liver of male rat: pH independence of the steady-state kinetics

The steady-state kinetic constants for the catalysis of CO2 hydration by the sulfonamide-resistant and testosterone-induced carbonic anhydrase from the liver of the male rat has been determined by stopped-flow spectrophotometry. The turnover number was 2.6 ± 0.6 × 103 s− at 25 °C, and was invariant with pH ranging from 6.2 to 8.2 within experimental error. The Km at 25 °C was 5 ± 1 mImage , and was also pH independent. These data are in quantitative agreement with earlier findings of pH-independent CO2 hydration activity for the mammalian skeletal muscle carbonic anhydrase isozyme III. The turnover numbers for higher-activity isozymes I and II are strongly pH dependent in this pH range. Thus, the kinetic status of the male rat liver enzyme is that of carbonic anhydrase III. This finding is consistent with preliminary structural and immunologic data from other laboratories.

Use of α- and β-subunit specific antibodies in studying interaction of hCG with Leydig cell receptors

Antisera (a/s) raised to individual α- and β-subunits of human chorionic gonadotropin (hCG) have been characterized for specificity using immunoaffinity procedures and used to study the disposition of the two subunits when intact hCG is complexed with luteinizing hormone (LH) receptor of the Leydig cells. Three kinds of experiments were done. (a) The ability of the preformed hormone-antibody (H-Ab) complex to bind to receptor and stimulate a response; (b) the ability of the a/s to dissociate hCG from its complex with the receptor and thereby terminate response; and (c) the ability of the premixed antibody and receptor to compete for binding of labeled hCG. Although the subunit specific a/s used here were equipotent in binding hCG (capacity to bind and Ka being very similar), their behavior once the receptor preparation or Leydig cell is introduced into the system was drastically different. The β-subunit antibody relative to the α-subunit antibody, appeared to be poorly effective in preventing hCG from either binding to the receptor or inhibiting the continuation of response. The results suggest that hCG upon interaction with the receptor loses the determinants specific to the β-region more rapidly compared to those specific to the α-region suggesting thereby that the initial interaction of hCG with the receptor should be occurring through sites in the β-subunit. Although the α-subunit portion of the hCG molecule is available for binding to the antibody for a relatively longer time, the biological response of the cell seems very sensitive to such binding with the antibody as it invariably results in loss of response. In the Leydig cell system, the ability of the a/s to bind hCG that is already complexed to the receptor appears to be dependent upon the time of addition of the antibody to the incubation medium. The antisera were totally ineffective in inhibiting steroidogenic response to hCG if added 60 min after addition of hCG. This would suggest that the hormone-receptor complex once formed perhaps continues to change its orientation with the result that with time relatively less and less of antigenic determinants become available for antibody binding.

A Dual Seven-Level Inverter Supply for an Open-End Winding Induction Motor Drive

This paper develops a seven-level inverter structure for open-end winding induction motor drives. The inverter supply is realized by cascading four two-level and two three-level neutral-point-clamped inverters. The inverter control is designed in such a way that the common-mode voltage (CMV) is eliminated. DC-link capacitor voltage balancing is also achieved by using only the switching-state redundancies. The proposed power circuit structure is modular and therefore suitable for fault-tolerant applications. By appropriately isolating some of the inverters, the drive can be operated during fault conditions in a five-level or a three-level inverter mode, with preserved CMV elimination and DC-link capacitor voltage balancing, within a reduced modulation range.

Evolution of three-dimensional character across the Lan+1NinO3n+1 homologous series with increase in n1

Electrical and magnetic properties of La3Ni2O7 and La4Ni3O10 have been investigated in comparison with those of La2NiO4, LaNiO3, and LaSrNiO4. The results suggest an increasing 3-dimensional character across the homologous series Lan+1NinO3n+1 with increase in n. Accordingly, the electrical resistivity decreases in the order La3Ni2O7, La4Ni3O10, and LaNiO3 and this trend is suggested to be related to the percolation threshold. Magnetic properties of these oxides also show some interesting trends across the series.

Helical conformations of three crystalline pentapeptide fragments of suzukacillin, a membrane channel forming polypeptide

The crystal structures of three pentapeptide fragments of suzukacillin-A have been determined. Boc-Aib-Pro-Val-Aib-Val-OMe (peptide 1–5) adopts a distorted helical conformation, stabilized by three intramolecular hydrogen bonds (two 5→1, one 4→1). Boc-Ala-Aib-Ala-Aib-Aib-OMe (peptide 6–10) and Boc-Leu-Aib-Pro-Val-Aib-OMe (peptide 16–20) adopt 310 helical structures stabilized by three and two 4→1 intramolecular hydrogen bonds, respectively. These structures provide substantial support for a largely helical conformation for the suzukacillin membrane channel.

Two- and three-dimensional lead-1H-imidazole-4,5-dicarboxylates

Reaction of lead nitrate and 1H-imidazole-4,5-dicarboxylic acid under hydrothermal conditions carried out at different temperatures and pH yields a hybrid Compound Pb-2(1H-imidazole-4,5-dicarboxylate)2, 1, and a three-dimensional coordination polymer Pb(1H-imidazole-4,5-dicarboxylate), It. The two-dimensional double-layered compound, 1, with two-dimensional inorganic connectivities and one-dimensional organic connectivity is novel since hybrid compounds formed by 1H-imidazole-4,5-dicarboxylic acid are uncommon. The lead atoms in I have holodirectional geometry, while those in II show hemidirectionality. In both I and II, 1H-imidazole-4,5-dicarboxylic acid acts as a multi-dentate ligand with both the carboxylic groups and the amine group taking part in coordination. (C) 2009 Elsevier B.V. All rights reserved.