Droplet transport and coalescence kinetics in emulsions subjected to acoustic fields

A method to aid the separation of the oil phase from aqueous emulsions using a low-intensity, resonant ultrasonic field has recently been developed. The density and compressibility difference between the dispersed and continuous phases within the emulsion results in a net force on the oil drops that pushes them toward the pressure antinodes of the standing-wave field, where coalescence subsequently occurs. A trajectory model is developed to predict the relative motion of drops subjected to the acoustic field. Such trajectories are sensitive to the physical properties and relative size of interacting drops, the initial configuration of the drops, and acoustic field parameters. Model predictions are validated by comparing experimentally observed trajectories with those predicted by the model. The modeling approach is then extended to determine the temporal evolution of the size of the region surrounding a target drop cleared by coalescence as a function of physical and acoustic field parameters. These results form the basis of a population balance model that attempts to track the size-evolution of a drop population coalescing under the influence of an acoustic field.     

Radioactive ion beam post-acceleration at ISAC

ISAC at TRIUMF is a world-class facility for the production and post-acceleration of radioactive ion beams (RIB). Commissioned in 2002 the ISAC I linear accelerator serves three different beam lines delivering both stable and radioactive species. Two of them are permanent experiments (DRAGON and TUDA); the third one is a general purpose station (GPS). The maximum energy we can reach in ISAC I is 1.8 MeV/u. ISAC II is a phased upgrade of the ISAC facility. The beam coming from ISAC I is injected at 1.5 MeV/u into a new superconducting LINAC. In `Phase I' the LINAC adds 20 MV to the beam energy and 20 MV more will be added in `Phase II'. The paper will give an overview of both the ISAC I and ISAC II accelerators. Operational experience with accelerating RIBs in ISAC I is summarized. First ISAC II commissioning results are presented.     

Lysosome-damage-induced scattering changes coincide with release of cytochrome c

Light scattering measurements made at visible wavelengths have the ability to quantify subcellular morphology. Apoptosis, or programmed cell death, is associated with distinct morphological signatures such as mitochondrial swelling and nuclear condensation as well as characteristic biochemical signaling pathways, many of which are initiated by the release of cytochrome c from the mitochondria into the cytosol. In this Letter, we examine the time course of mitochondrial morphology changes as reported by light scattering and the subcellular location of cytochrome c measured by immunofluorescence microscopy in response to intracellular cell death signaling induced by photodynamic damage to lysosomes. We report that within this system, release of cytochrome c from the mitochondria into the cytosol occurs approximately simultaneously with mitochondrial-morphology-induced light scattering changes, providing further evidence that light scattering has the potential to play an important role in future studies of cell death biology.     

Experimental implementation of a three qubit quantum game with corrupt source using nuclear magnetic resonance quantum information processor

In a three player quantum 'Dilemma' game each player takes independent decisions to maximize his/her individual gain. The optimal strategy in the quantum version of this game has a higher payoff compared to its classical counterpart. However, this advantage is lost if the initial qubits provided to the players are from a noisy source. We have experimentally implemented the three player quantum version of the 'Dilemma' game as described by Johnson, [N.F. Johnson, Phys. Rev. A 63 (2001) 020302(R)] using nuclear magnetic resonance quantum information processor and have experimentally verified that the payoff of the quantum game for various levels of corruption matches the theoretical payoff.     

Proton-detected solid-state NMR spectroscopy of fully protonated proteins at 40 kHz magic-angle spinning

Remarkable progress in solid-state NMR has enabled complete structure determination of uniformly labeled proteins in the size range of 5-10 kDa. Expanding these applications to larger or mass-limited systems requires further improvements in spectral sensitivity, for which inverse detection of 13C and 15N signals with 1H is one promising approach. Proton detection has previously been demonstrated to offer sensitivity benefits in the limit of sparse protonation or with approximately 30 kHz magic-angle spinning (MAS). Here we focus on experimental schemes for proteins with approximately 100% protonation. Full protonation simplifies sample preparation and permits more complete chemical shift information to be obtained from a single sample. We demonstrate experimental schemes using the fully protonated, uniformly 13C,15N-labeled protein GB1 at 40 kHz MAS rate with 1.6-mm rotors. At 500 MHz proton frequency, 1-ppm proton line widths were observed (500 +/- 150 Hz), and the sensitivity was enhanced by 3 and 4 times, respectively, versus direct 13C and 15N detection. The enhanced sensitivity enabled a family of 3D experiments for spectral assignment to be performed in a time-efficient manner with less than a micromole of protein. CANH, CONH, and NCAH 3D spectra provided sufficient resolution and sensitivity to make full backbone and partial side-chain proton assignments. At 750 MHz proton frequency and 40 kHz MAS rate, proton line widths improve further in an absolute sense (360 +/- 115 Hz). Sensitivity and resolution increase in a better than linear manner with increasing magnetic field, resulting in 14 times greater sensitivity for 1H detection relative to that of 15N detection.     

Measurement of nitrophenols in air samples by impinger sampling and supported liquid membrane micro-extraction

A sensitive analytical technique for the detection of trace nitrophenols in air has been developed. The steps in this process are impinger sampling to capture the nitrophenols in an aqueous phase, which is then followed by supported liquid membrane micro-extraction (SLMME) and analytical detection. The nitrophenols were analyzed by reverse-phase high performance liquid chromatography (HPLC) and did not require any derivatization. Method detection limits (MDL) of 0.5-1.0 ng L⁻¹ from aqueous solutions and 3.1-46.7 ppbV from air extractions were observed. The high enrichment of nitrophenol in SLMME allowed low detection limits even with HPLC-UV detection. SLMME is an inexpensive, easy to use procedure that employs disposable membrane fibers.     

Microwave-assisted solution- and solid-phase synthesis of 2-amino-4-arylpyrimidine derivatives

An efficient and rapid microwave-assisted solution-phase method for the synthesis of 2-amino-4-arylpyrimidine-5-carboxylic acid derivatives has been developed. The five-step linear protocol involves an initial Biginelli multicomponent reaction leading to dihydropyrimidine-2-thiones which are subsequently S-alkylated with methyl iodide. The resulting 2-methylthiodihydropyrimidines are sequentially oxidized first with manganese dioxide and then with Oxone to provide 2-methylsulfonyl-pyrimidines which serve as excellent precursors for the generation of a variety of 2-substituted pyrimidines via displacement of the reactive sulfonyl group with nitrogen, oxygen, sulfur, and carbon nucleophiles. A modified protocol using a solid-phase method has also been developed.     

Temperature-dependent hydration at micellar surface: activation energy barrier crossing model revisited

In recent years, the validity of the activation energy barrier crossing model at the micellar surface brings notable controversy (Sen, P.; Mukherjee, S.; Halder, A.; Bhattacharyya, K. Chem. Phys. Lett. 2004, 385, 357-361. Kumbhakar, M.; Goel, T.; Mukherjee, T.; Pal, H. J. Phys. Chem. B 2004, 108, 19246-19254.) in the literature. In order to check the validity of the model by time-resolved solvation of a probe fluorophore, a wider range of temperature must be considered. At the same time, spatial heterogeneity (solubilization) of the probe and structural perturbation of the host micelle should carefully be avoided, which was not strictly maintained in the earlier studies. We report here the solvation dynamics of 4-(dicyanomethylene)-2-methyl-6(p-dimethylamino-styryl) 4H-pyran (DCM) in the SDS micelle at 298, 323, and 348 K. The probe DCM is completely insoluble in bulk water in this wide range of temperature. The size of the micelle at different temperatures using the dynamic light scattering (DLS) technique is found to have insignificant change. The hydration number of the micelle, determined by sound velocity measurements, decreases with increasing temperature. Time-resolved fluorescence anisotropy reveals the retention of the probe in the micellar interface within the temperature range. The average solvation time decreases with increasing temperature. The result of the solvation study has been analyzed in the light of energetics of bound to free water conversion at a constant size and decreasing hydration number at the micellar surface. The solvation process at the micellar surface has been found to be the activation energy barrier crossing type, in which interfacially bound type water molecules get converted into free type molecules. We have calculated Ea to be 3.5 kcal mol-1, which is in good agreement with that obtained by molecular dynamics simulation studies.     

Hexacyanometallate anions as precursors of two new trinuclear heterobimetallic assemblies: Syntheses,structures and cryomagnetic properties

Two new cyano bridged Cu–Co and Cu–Fe trinuclear bimetallic assemblies, [(CuL)[Co(CN)₆](CuL)]ClO₄ · 3.5H₂O (1) and [(CuL)[Fe(CN)₆](CuL)] · 13H₂O (2) where [L = (3E,5E)-N¹,N⁴-bis((pyridin-2-yl)methylene)butane-1,4-diamine] have been prepared using cyanometallates as anion precursors and characterised by elemental analyses, spectroscopic studies, single crystal X-ray diffraction and cryomagnetic susceptibility measurements. Magneto-structural correlations have been drawn from cryomagnetic susceptibility measurements over a wide temperature range (2–300 K) under 0.5 T magnetic fields. Weak antiferromagnetic interactions with J = −0.81 and −0.73 cm⁻¹ are found for 1 and 2, respectively, showing a very weak coupling, as expected from the diamagnetic long chain –NC–Co–CN–CN– and –NC–Fe–CN–CN– bridges revealed from the single crystal X-ray diffraction studies.     

Targeted particulate adhesion to cellulose surfaces mediated by bifunctional fusion proteins

The adhesion of particles to surfaces is an integral element in many commercial and biological applications. In this article, we report on the direct measurements of protein-mediated deposition and binding of particles to model cellulose surfaces. This system involves a family of heterobifunctional fusion proteins that bind specifically to both a red dye and cellulose. Amine-coated particles were labeled with a red dye, and a fusion protein was attached to these particles at various number densities. The strength of adhesion of a single particle to a cellulose fiber was measured using micropipette manipulation as a function of the specificity of the protein and its surface density and contact time. The frequency and force of adhesion were seen to increase with contact time in fiber experiments. The dynamics of adhesion of the functionalized particles to cellulose-coated glass slides under controlled hydrodynamic flow was explored using a flow chamber for two scenarios: detachment of bound particles and attachment of particles in suspension as a function of the shear rate and surface density of protein. Highly specific adhesion was observed. The critical shear rate for particle detachment was an increasing function of cellulose binding domain (CBD) density on particle surface. A rapid irreversible attachment of particles to cellulose was observed under flow. Using a family of proteins that were divalent for binding either the red dye or cellulose, we found that particle detachment occurred because of the failure of the cellulose-CBD bond. A comparison of fiber binding and particle detachment results suggests that forces of adhesion of particles to cellulose of up to 2 nN can be obtained with this molecular system through multiple interactions. This study, along with the adhesion simulations currently under development, forms the basis of particulate design for specific adhesion applications.