Robust spatially resolved pressure measurements using MRI with novel buoyant advection-free preparations of stable microbubbles in polysaccharide gels

MRI of fluids containing lipid coated microbubbles has been shown to be an effective tool for measuring the local fluid pressure. However, the intrinsically buoyant nature of these microbubbles precludes lengthy measurements due to their vertical migration under gravity and pressure-induced coalescence. A novel preparation is presented which is shown to minimize both these effects for at least 25 min. By using a 2% polysaccharide gel base with a small concentration of glycerol and 1,2-distearoyl-sn-glycero-3-phosphocholine coated gas microbubbles, MR measurements are made for pressures between 0.95 and 1.44 bar. The signal drifts due to migration and amalgamation are shown to be minimized for such an experiment whilst yielding very high NMR sensitivities up to 38% signal change per bar

Indirect Wafer Bonding and Epitaxial Transfer of GaSb-Based Materials

Results from a study of indirect wafer bonding and epitaxial transfer of GaSb-based materials are presented. Benzocyclobutene (BCB) was used as a bonding agent to bond GaSb and epitaxial structures lattice matched to GaSb onto Si, GaAs, and sapphire carrier substrates. To better understand sources of stress during the bonding process, which can result in cracking and subsurface damage of the GaSb-based materials, BCB’s hardness and reduced elastic modulus were measured at various stages during the curing process. Based on the results of curing experiments, a bonding and epitaxial transfer process for GaSb-based materials was then developed. Following bonding, using an experimentally determined low-stress cure cycle, GaSb substrates were removed from epitaxial layers of InAsSb using a combination of mechanical thinning and polishing followed by selective chemical etching using a hydrofluoric and chromic acid solution. Etch selectivity data are also presented where selectivity greater than 100:1 is achieved for GaSb:InAsSb

Funneling Light Through a Subwavelength Aperture with Epsilon-Near-Zero Materials

Integration of the next generation of photonic structures with electronic and optical on-chip components requires the development of effective methods for confining and controlling light in subwavelength volumes. Several techniques enabling light coupling to sub-wavelength objects have recently been proposed, including grating-, and composite-based solutions. However, experi-mental realization of these couplers involves complex fabrication with \sim 10nm resolution in three dimensions. One promising alternative to complex coupling structures involves materials with vanishingly small dielectric permittivity, also known as epsilon-near-zero (ENZ) materials. In contrast to the previously referenced approaches, a single at layer of ENZ-material is expected to provide effcient coupling between free-space radiation and sub-wavelength guiding structures. Here we report the first direct observation of bulk-ENZ-enhanced transmission through a subwavelength slit, accompanied by a theoretical study of this phenomenon. Our study opens the door to multiple practical applications of ENZ materials and ENZ-based photonic systems

Structural and reactivity analyses of nitrofurantoin 4 dimethylaminopyridine salt using spectroscopic and density functional theory calculations

YesPharmaceutical salt, nitrofurantoin–4-dimethylaminopyridine (NF-DMAP), along with its native components NF and DMAP are scrutinized by FT-IR and FT-Raman spectroscopy along with density functional theory so that an insight into the H-bond patterns in the respective crystalline lattices can be gained. Two different functionals, B3LYP and wB97X-D, have been used to compare the theoretical results. The FT-IR spectra obtained for NF-DMAP and NF clearly validate the presence of C33–H34⋅⋅⋅O4 and N23–H24⋅⋅⋅N9 hydrogen bonds by shifting in the stretching vibration of –NH and –CH group of DMAP+ towards the lower wavenumber side. To explore the significance of hydrogen bonding, quantum theory of atoms in molecules (QTAIM) has been employed, and the findings suggest that the N23–H24⋅⋅⋅N9 bond is a strong intermolecular hydrogen bond. The decrement in the HOMO-LUMO gap, which is calculated from NF → NF-DMAP, reveals that the active pharmaceutical ingredient is chemically less reactive compared to the salt. The electrophilicity index (ω) profiles for NF and DMAP confirms that NF is acting as electron acceptor while DMAP acts as electron donor. The reactive sites of the salt are plotted by molecular electrostatic potential (MEP) surface and calculated using local reactivity descriptors.SERB, DST, India, for providing the National Post-doctoral Fellowship (Project File Number: PDF/2016/003162); Central Facility for Computational Research (CFCR), University of Lucknow; Newton-Bhabha Ph.D. placement award (2017); Royal Society seed corn research grant (2018-19

High-optical-quality nanosphere lithographically formed InGaAs quantum dots using molecular beam epitaxy assisted GaAs mass transport and overgrowth

Optically active, highly uniform, cylindrical InGaAs quantum dot ͑QD͒ arrays have been fabricated using nanosphere lithography combined with Bromine ion-beam-assisted etching and molecular beam epitaxy ͑MBE͒-assisted GaAs mass transport. Previously fabricated QD nanopillar arrays showed significant degradation of optical properties due to the etch damage. Here, a novel mass transport process in a Riber 3200 was performed to encapsulate the lithographically defined InGaAs disk QDs in a GaAs matrix, resulting in the passivation of the etch-damaged QD sidewall layer. Photoluminescence emission intensity following the mass transport process increased by a magnitude of 4-10 as compared to that from unprocessed nanopillar sample. In addition, a PL peak energy redshift was observed after mass transport, presumably due to the decrease in the lateral barrier potential from vacuum to GaAs, as well as the elimination of the depletion layer. Furthermore, the mass transport process in the high vacuum MBE environment enables GaAs overgrowth with few defects and dislocations following mass transport for surface planarization. PL emission intensity increased by an additional factor of 4 following GaAs overgrowth, bringing the QD intensity to 1 2 of that of the original single quantum well. Thus, the potential of the MBE-assisted mass transport process has been demonstrated to fabricate high optical quality InGaAs quantum dots encapsulated in a GaAs matrix for device applications

Investigation of Plasmon Resonance Tunneling through Subwavelength Hole Arrays in Highly Doped Conductive ZnO Films

Experimental results pertaining to plasmon resonance tunneling through a highly conductive zinc oxide (ZnO) layer with subwavelength hole-arrays is investigated in the mid-infrared regime. Gallium-doped ZnO layers are pulsed-laser deposited on a silicon wafer. The ZnO has metallic optical properties with a bulk plasma frequency of 214 THz, which is equivalent to a free space wavelength of 1.4 μm. Hole arrays with different periods and hole shapes are fabricated via a standard photolithography process. Resonant mode tunneling characteristics are experimentally studied for different incident angles and compared with surface plasmontheoretical calculations and finite-difference time-domain simulations. Transmission peaks, higher than the baseline predicted by diffraction theory, are observed in each of the samples at wavelengths that correspond to the excitation of surface plasmon modes

Formulation and corneal permeation of ketorolac tromethamine-loaded chitosan nanoparticles

The aim of this work was to formulate chitosan (CS)-based nanoparticles (NPs) loaded with ketorolac tromethamine (KT) intended for topical ocular delivery. NPs were prepared using ionic gelation method incorporating tri-polyphosphate (TPP) as cross-linker. Following the preparation, the composition of the system was optimized in terms of their particle size, zeta potential, entrapment efficiency (EE) and morphology, as well as performing structural characterization studies using Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). The data suggested that the size of the NPs was affected by CS/TPP ratio where the diameter of the NPs ranged from 108.0 ± 2.4 nm to 257.2 ± 18.6 nm. A correlation between drug EE and the corresponding drug concentration added to the formulation was observed, where the EE of the NPs increased with increasing drug concentration, for up to 10 mg/mL. FT-IR and DSC revealed that KT was dispersed within the NPs where the phosphate groups of TPP were associated with the ammonium groups of CS. The in vitro release profile of KT from CS NPs showed significant differences (p < 0.05) compared to KT solution. Furthermore, mucoadhesion studies revealed adhesive properties of the formulated NPs. The KT-loaded NPs were found to be stable when stored at different storage conditions for a period of 3 months. The ex vivo corneal permeation studies performed on excised porcine eye balls confirmed the ability of NPs in retaining the drug on the eye surface for a relatively longer time. These results demonstrate the potential of CS-based NPs for the ocular delivery of KT

Proteomic and Transcriptional Profiles of Human Stem Cell-Derived beta Cells Following Enteroviral Challenge

Enteroviral infections are implicated in islet autoimmunity and type 1 diabetes (T1D) pathogenesis. Significant beta-cell stress and damage occur with viral infection, leading to cells that are dysfunctional and vulnerable to destruction. Human stem cell-derived beta (SC-beta) cells are insulin-producing cell clusters that closely resemble native beta cells. To better understand the events precipitated by enteroviral infection of beta cells, we investigated transcriptional and proteomic changes in SC-beta cells challenged with coxsackie B virus (CVB). We confirmed infection by demonstrating that viral protein colocalized with insulin-positive SC-beta cells by immunostaining. Transcriptome analysis showed a decrease in insulin gene expression following infection, and combined transcriptional and proteomic analysis revealed activation of innate immune pathways, including type I interferon (IFN), IFN-stimulated genes, nuclear factor-kappa B (NF-kappaB) and downstream inflammatory cytokines, and major histocompatibility complex (MHC) class I. Finally, insulin release by CVB4-infected SC-beta cells was impaired. These transcriptional, proteomic, and functional findings are in agreement with responses in primary human islets infected with CVB ex vivo. Human SC-beta cells may serve as a surrogate for primary human islets in virus-induced diabetes models. Because human SC-beta cells are more genetically tractable and accessible than primary islets, they may provide a preferred platform for investigating T1D pathogenesis and developing new treatments

A Novel Liposome-Based Adjuvant CAF01 for Induction of CD8+ Cytotoxic T-Lymphocytes (CTL) to HIV-1 Minimal CTL Peptides in HLA-A*0201 Transgenic Mice

Background: Specific cellular cytotoxic immune responses (CTL) are important in combating viral diseases and a highly desirable feature in the development of targeted HIV vaccines. Adjuvants are key components in vaccines and may assist the HIV immunogens in inducing the desired CTL responses. In search for appropriate adjuvants for CD8+ T cells it is important to measure the necessary immunological features e.g. functional cell killing/lysis in addition to immunological markers that can be monitored by simple immunological laboratory methods. Methodology/Principal Findings: We tested the ability of a novel two component adjuvant, CAF01, consisting of the immune stimulating synthetic glycolipid TDB (Trehalose-Dibehenate) incorporated into cationic DDA (Dimethyldioctade-cylammonium bromide) liposomes to induce CD8+ T-cell restricted cellular immune responses towards subdominant minimal HLA-A0201-restricted CTL epitopes from HIV-1 proteins in HLA-A*0201 transgenic HHD mice. CAF01 has an acceptable safety profile and is used in preclinical development of vaccines against HIV-1, malaria and tuberculosis. Conclusions/Significance: We found that CAF01 induced cellular immune responses against HIV-1 minimal CTL epitopes in HLA-A*0201 transgenic mice to levels comparable with that of incomplete Freund’s adjuvant