Ordering of apolar and polar solutes in nematic solvents

The quadrupolar splittings of deuteriated para- and ortho-dichlorobenzene (1,4-DCB and 1,2-DCB, respectively) are measured by nuclear magnetic resonance(NMR) in the nematic solvents hexyl- and pentyloxy-substituted diphenyl diacetylene (DPDA-C6 and DPDA-OC5, respectively). Measurements are taken for all four combinations of the nominally apolar (1,4-DCB) and polar (1,2-DCB) solutes in the apolar (DPDA-C6) and polar (DPDA-OC5) solvents, and throughout the entire nematic temperature range of the solutions. The temperature dependence of the second-rank orientational order parameters of the solutes are obtained from these measurements and the respective order parameters of the mesogenic cores of solvent molecules are obtained independently from carbon-13 NMR measurements. The order parameter profiles of the two solutes are found to be very different but show little variation from one solvent to the other. The results are analyzed and interpreted in terms of the underlying molecular interactions using atomistic solvent–solute potentials. The influence of electrostaticinteractions on solute ordering is directly evaluated by computing the order parameters with and without the electrostatic component of the atomistic potential. It is observed to be small. It is also found that the important interactions in these solvent–solute systems are operative over short intermolecular distances for which the representation of the partial charge distributions in terms of overall molecular dipole and quadrupole moments is not valid

Nonideal parasitic resistance effects in bulk heterojunction organic solar cells

A common assumption in both experimental measurements and device modeling of bulk heterojunction (BHJ) organic solar cells is that parasitic resistances are ideal. In other words, series resistance (Rsr) is near zero while shunt resistance (Rsh) approaches infinity. Relaxation of this assumption affects device performance differently depending on the chosen BHJ material system. Specifically, the impact of nonideal Rsr is controlled by the electric field dependence of the probability of charge transfer (CT) state dissociation (PCT). This is demonstrated by evaluating the experimental current density versus voltage response within the framework of a drift/diffusion model for two BHJ systems that strongly differ in PCT. Second, light intensity measurements of devices with nonideal Rsr and Rsh are shown to convolute the scaling of short-circuit current and open-circuit voltage with light intensity, which is a common technique to study BHJ device physics. Finally, we show the connection between the drift/diffusion and equivalent circuit model with regard to each model's treatment of CT state dissociation. In particular, the equivalent circuit model utilizes a light intensity dependent Rsh to describe this dissociation process and predicts a photocurrent under reverse bias that exceeds the photocurrent permitted by light absorption

Electrophotonic enhancement of bulk heterojunction organic solar cells through photonic crystal photoactive layer

We present one- (1D) and two-dimensional (2D) periodic nanostructured designs for organic photovoltaics where a photonic crystal is formed between blended poly-3-hexylthiophene/[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) and nanocrystalline zinc oxide. Absorption enhancements over the full absorption range of P3HT:PCBM of 20% (one polarization) and 14% are shown for the 1D and 2D structures, respectively. These improvements result in part from band edge excitation of quasiguided modes. The geometries are also shown to create excitons 26% (1D) and 11% (2D) closer to P3HT:PCBM exit interfaces indicating further photovoltaic improvement

Absorption and quasiguided mode analysis of organic solar cells with photonic crystal photoactive layers

We analyze optical absorption enhancements and quasiguided mode properties of organic solar cells with highly ordered nanostructured photoactive layers comprised of the bulk heterojunction blend, poly-3- hexylthiophene/[6,6]-phenyl- C61-butyric acid methyl ester (P3HT:PCBM) and a low index of refraction conducting material (LICM). This photonic crystal geometry is capable of enhancing spectral absorption by ∼17% in part due to the excitation of quasiguided modes near the band edge of P3HT:PCBM. A nanostructure thickness between 200 nm and 300 nm is determined to be optimal, while the LICM must have an index of refraction ∼0.3 lower than P3HT:PCBM to produce absorption enhancements. Quasiguided modes that differ in lifetime by an order of magnitude are also identified and yield absorption that is concentrated in the P3HT:PCBM flash layer

Analyzing local exciton generation profiles as a means to extract transport lengths in organic solar cells

In this work, we determine the carrier-transport lengths of electrons and holes (Le,h) for bulk heterojunction (BHJ) organic solar cells using a method applicable to functional devices. By linking the local exciton generation profile [G (x)] in the photoactive layer to photocurrent losses, we are able to determine the onset of bimolecular recombination, which is the dominate loss process of free carrier transport. Even though many factors affect photocurrent generation, we single out bimolecular recombination by measuring the scaling of photocurrent with light intensity as a function of applied voltage. For the common BHJ system, annealed poly-3-hexylthiophene:[6,6]-phenyl- C61-butyric acid methyl ester (P3HT:PCBM), a minimum for Le in PCBM is found to be 340 nm while Lh is estimated to be 90 nm for P3HT. The relationship between G (x) and carrier transport is further exemplified by demonstrating a scaling exponent below that for traditional space-charge-limited photocurrent. Likewise, by incorporating a drift/diffusion model, an intuitive link between G (x) and charge transport is established where recombination is shown to occur in regions of the photoactive layer far from the electrode of the slowest carrier species. Finally, the consequences of Le,h on device design for operation under 1 Sun conditions are described

Identification and Characterization of an Adeno-Associated Virus Integration Site in CV-1 Cells from the African Green Monkey

Adeno-associated virus (AAV) is a classification given to a group of nonpathogenic, single-stranded DNA viruses known to reside latently in primates. During latency in humans, AAV type 2 (AAV2) preferentially integrates at a site on chromosome 19q13.3ter by targeting a sequence composed of an AAV Rep binding element (RBE), a spacer, and a nicking site. Here, we report the DNA sequence of an African green monkey AAV integration site isolated from CV-1 cells. Overall, it has 98% homology to the analogous human site, including identical spacer and nicking sequences. However, the simian RBE is expanded, having five perfect directly repeated GAGC tetramers. We carried out a number of in vitro and in vivo assays to determine the effect of this expanded RBE sequence on the Rep-RBE interaction and AAV targeted integration. Using electromobility shift assays it was demonstrated that AAV4 Rep68 bound the expanded RBE with a sixfold-greater affinity than the human RBE. To determine the basis for the affinity increase, DNase I protection and methylation interference (MI) assays were performed. Comparison of footprints on both the human and simian RBEs revealed nearly identical protection; however, MI analysis suggested greater interaction with the guanine nucleotides of the expanded RBE, thus providing a biochemical basis for the increased binding activity. In vivo, integration targeted to the simian RBE was demonstrated by PCR analysis of latently infected Cos-7 cells. Interestingly, the frequency of site-specific integration was twofold greater in Cos-7 cells than in HeLa cells. Overall, these experiments establish that the simian RBE, identified in CV-1 cells, functions analogously to the human RBE and provide further evidence for a developing model that proposes individual roles for the RBE and the spacer and nicking site elements

Benzene at 1GHz. Magnetic field-induced fine structure

The deuterium NMR spectrum of benzene-d6 in a high field spectrometer (1 GHz protons) exhibits a magnetic field-induced deuterium quadrupolar splitting ??. The magnitude of ?? observed for the central resonance is smaller than that observed for the 13C satellite doublets ???. This difference, ?(??) = ??? ? ??, is due to unresolved fine structure contributions to the respective resonances. We determine the origins of and simulate this difference, and report pulse sequences that exploit the connectivity of the peaks in the 13C and 2H spectra to determine the relative signs of the indirect coupling, JCD, and ??. The positive sign found for ?? is consonant with the magnetic field biasing of an isolated benzene molecule—the magnetic energy of the aromatic ring is lowest for configurations where the C6 axis is normal to the field. In the neat liquid the magnitude of ?? is decreased by the pair correlations in this prototypical molecular liquid

Adeno-Associated Viral Vectors Show Serotype Specific Transduction of Equine Joint Tissue Explants and Cultured Monolayers

Adeno-associated virus (AAV) receptors range from heparan sulfate proteoglycan to sialic acid moieties present on cell surfaces. Abundance of the glycan profiles is greatly influenced by animal species, cell type, and culture conditions. The objective of this study was to determine whether AAV serotypes' transduction efficiencies specifically in the equine monolayer culture model are an accurate representation of transduction efficiencies in tissue explants, a model more closely related to in vivo transduction. It was found that AAV 2 and 2.5 transduced cells more efficiently in explants than in monolayers. Through experiments involving assessing enzyme degradation of cell surface proteoglycans, this change could not be attributed to differences in the extra cellular matrix (ECM), but a similar change in AAV 5 transduction efficiency could be readily explained by differences in cell surface sialylated glycan. Unexpectedly it was found that in a small but diverse sample of horses evidence for serum neutralizing antibodies was only found to AAV 5. This suggests a unique relationship between this capsid and the equine host or an unresolved relationship between similar bovine AAV and the AAV 5 capsid immune response

Adeno-associated virus-mediated gene transfer of the heart/muscle adenine nucleotide translocator (ANT) in mouse

Mitochondrial myopathy, associated with muscle weakness and progressive external ophthalmoplegia, is caused by mutations in mitochondria oxidative phosphorylation genes including the heart–muscle isoform of the mitochondrial adenine nucleotide translocator (ANT1). To develop therapies for mitochondrial disease, we have prepared a recombinant adeno-associated viral vector (rAAV) carrying the mouse Ant1 cDNA. This vector has been used to transduce muscle cells and muscle from Ant1 mutant mice, which manifest mitochondrial myopathy. AAV-ANT1 transduction resulted in long-term, stable expression of the Ant1 transgene in muscle precursor cells as well as differentiated muscle fibers. The transgene ANT1 protein was targeted to the mitochondrion, was inserted into the mitochondrial inner membrane, formed a functional ADP/ATP carrier, increased the mitochondrial export of ATP and reversed the histopathological changes associated with the mitochondrial myopathy. Thus, AAV transduction has the potential of providing symptomatic relief for the ophthalmoplegia and ptosis resulting from paralysis of the extraocular eye muscles cause by mutations in the Ant1 gene

Large area nanofabrication of butterfly wings three dimensional ultrastructures

The authors report a simple method for the artificial fabrication of the complex three-dimensional (3D) ultrastructures of butterfly wing scales. This method uses chemical vapor deposition, UV lithography, and chemical etching to create the ultrastructures over a large area surpassing previously used focused ion beam techniques that are limited to microscopic areas. Furthermore, this method shows flexibility to modify nanostructure types and can precisely control shapes and dimensions and periodicity. Fabricated 3D ultrastructures are also replicated using a nanoimprint method into soft polymer materials. Reflectivity measurements and simulations of the master and polymer replicas show selective UV reflection consistent with the length scales used in such butterfly-like nanostructures