Imaging of Tautomerism in a Single Molecule

Fluorescence imaging is used to visualize directly the transfer of two inner hydrogen atoms in single porphycene molecules. This reaction leads to a chemically equivalent but differently oriented structure and hence results in a rotation of the transition dipole moments. By probing single immobilized molecules with an azimuthally polarized laser beam in the focal spot of a confocal microscope we observe ring-like emission patterns, possible only for a chromophore with two nearly orthogonal transition dipole moments. Numerical simulations of the observed emission patterns yield a value of 72° for the angle between the S0−S1 transition moments in the two tautomeric forms

Polarized Spectroscopy Studies of Single Molecules of Porphycenes

Using ambient atmosphere instead of pure nitrogen environment enabled efficient recording of room temperature fluorescence from single molecules of porphycenes, chromophores with a high triplet formation efficiency. Double hydrogen transfer between two chemically identical trans tautomers has been demonstrated for parent porphycene and three alkyl derivatives by the analysis of spatial patterns of the emission obtained after raster scanning the sample excited with an appropriately polarized laser beam. Because of tautomerization, fluorescence in porphycenes is due to two nearly orthogonal transition dipole moments. This property allows the spatial orientation of the single molecule chromophores to be determined using radially and azimuthally polarized laser beams as excitation sources

Structure and photophysics of 2-(2'-pyridyl)benzindoles: The role of intermolecular hydrogen bonds

The photophysical properties of two isomeric 2-(2′-pyridyl) benzindoles depend on the environment. Strong fluorescence is detected in nonpolar and polar aprotic solvents. In the presence of alcohols, the emission reveals an unusual behavior. Upon titration of n-hexane solutions with ethanol, the fluorescence intensity goes through a minimum and then increases with rising alcohol concentration. Transient absorption and time-resolved emission studies combined with ground- and excited-state geometry optimizations lead to the conclusion that two rotameric forms, syn and anti, coexist in alcohols, whereas in nonpolar and aprotic polar media, only the syn conformation is present. The latter can form cyclic complexes with alcohols, which are rapidly depopulated in the excited state. In the presence of excess alcohol, syn → anti rotamerization occurs in the ground state, promoted by the cooperative action of nonspecific and specific effects such as solvent polarity increase and the formation of hydrogen bonds to both donor and acceptor sites of the bifunctional compounds. © 2007 American Chemical Society

Effect of hydrogen bonding and complexation with metal ions on the fluorescence of luotonin A

Fluorescence characteristics of a biologically active natural alkaloid, luotonin A (LuA), were studied by steady-state and time-resolved spectroscopic methods. The rate constant of the radiationless deactivation from the singlet-excited state diminished by more than one order of magnitude when the solvent polarity was changed from toluene to water. Dual emission was found in polyfluorinated alcohols of large hydrogen bond donating ability due to photoinitiated proton displacement along the hydrogen bond. In CH 2Cl2, LuA produced both 1:1 and 1:2 hydrogen-bonded complexes with hexafluoro-2-propanol (HFIP) in the ground state. Photoexcitation of the 1:2 complex led to protonated LuA, whose fluorescence appeared at a long wavelength. LuA served as a bidentate ligand forming 1:1 complexes with metal ions in acetonitrile. The stability of the complexes diminished in the series of Cd2+ > Zn2+ > Ag+, and upon competitive binding of water to the metal cations. The effect of chelate formation on the fluorescent properties was revealed. © 2013 The Royal Society of Chemistry and Owner Societies

Infrared Laser Driven Double Proton Transfer. An Optimal Control Theory Study

Laser control of ultrafast double proton transfer is investigated for a two-dimensional model system describing stepwise and concerted transfer pathways. The pulse design has been done by employing optimal control theory in combination with the multiconfiguration time-dependent Hartree wave packet propagation. The obtained laser fields correspond to multiple pump-dump pulse sequences. Special emphasis is paid to the relative importance of stepwise and concerted transfer pathways for the driven wave packet and its dependence on the parameters of the model Hamiltonian as well as on the propagation time. While stepwise transfer is dominating in all cases considered, for high barrier systems concerted transfer proceeding via tunneling can make a contribution.Comment: 9 figure

Gauge invariant description of weak gravitational field on a spherically symmetric background with cosmological constant

We present a formalism for analysis of linear Cauchy data on a Kottler metric. Our method removes redundancy due to gauge transformations and constraints. A set of four gauge-invariant, scalar functions on the Cauchy surface is produced and shown to contain full physical information from the initial data. The symplectic form of the theory and equations of motion are reformulated in terms of these invariants and some simple solutions are explored.Comment: 34 page

Supply Chain Reduction for WellStar Kennestone Sterile Processing Department

The WellStar Healthcare System provides world-class healthcare across 11 hospitals. One of those hospitals is Kennestone located in Marietta, GA. They are continuously implementing new technology to attend to their patients in the operation rooms (ORs). However, the hospital’s Sterile Processing Department has seen an increase of unused supplies being returned after surgeries are completed. This results in certain supplies not being placed back in inventory immediately or accounted for. Upon discovering these process inadequacies, WellStar requested a project group to analyze and present a solution for decreasing its rate of returned supplies, quantify the cost of the current processes, reduce waste, and present findings to key stakeholders at Kennestone. Data analytics and research was performed focused on exploring opportunities for optimization within the Kennestone Hospital Sterilization Process Department’s internal processes. Our findings from the research conducted revealed that the source of the excess waste of supplies was a combination of a lack of workforce, inadequate supply tracking system, workflow design layout. Our team developed a preposition comprised of three solution considerations that could address the above stated inefficiencies: Proposed Solution 1 – Temporary Hire Outsource the task by hiring a worker dedicated specifically to the SPD’s inventory stocking through a Temp-Agency. Proposed Solution 2 – Retraining & SOP Implementation Retraining current staff by implementing a Standard Operating Procedure (SOP) for pulling supplies from inventory. Proposed Solution 3 – SKU Integration Utilizing software to develop an electronic binning system to allocate supplies according to need and type to digitalize inventory tracking of surgical supplies. Once our data findings were collated, we concluded that the facility has the capacity of improving the process of inventorying surgical instruments and supplies. Our team applied 5S methods to quantify the parameters of the problems and Lean management methods in our approach to determining the right recommendation from proposed solutions. With the goal of effective cost mitigation by eliminating excess waste, we determined each solution to be viable. However, once all implementation factors were considered, it was determined that solution 1 would have the highest ease of implementation with instant return on value and least disruption in other operations at the Kennestone Hospital. Our final recommendation to the WellStar Kennestone Hospital is to implement solution 1. We made this recommendation considering these factors: Solution 1 would did not have drastic requirements for implementation like the other two solutions would require. Solution 2 would require more supervisory oversight and tasks being added to current staffing duties in order to tackle the accumulation of returned supplies by increasing accountability of personnel by associating supplies list with persons who pull supplies from inventory within the SPD. Solution 3 would require the development and implementation of dynamic software for the inventory tracking system

The nature of the excited states of p-nitro-N,N-dimethylaniline.

Contrary to numerous derivatives of p-substituted N,N-dimethyl-aniline, p-nitro-N,N-dimethylaniline, does not form the TICT state. This behaviour is predicted by INDO/S calculations. The calculations also reveal an important role of the Coulomb interaction term in the evolution of intramolecular charge-transfer excited-state energy upon twisting of the dimethylamino group