SELECTION OF TRAINING SAMPLES FOR MODEL UPDATING USING NEURAL NETWORKS

One unique feature of neural networks is that they have to be trained to function. In developing an iterative neural network technique for model updating of structures, it has been shown that the number of training samples required increases exponentially as the number of parameters to be updated increases. Training the neural network using these samples becomes a time-consuming task. In this study, we investigate the use of orthogonal arrays for the sample selection. A comparison between this orthogonal arrays method and four other methods is illustrated by two numerical examples. One is the update of the felxural rigidities of a simply supported beam and the other is the update of the material properties and the boundary conditions of a circular plate. The results indicate that the orthogonal arrays method can significantly reduce the number of training samples without affecting too much the accuracy of the neural network prediction.     

Application of mass spectrometry to copolymers of ethylene and propylene oxides. II. Kinetic analysis

Molecular-weight distributions derived from mass spectrometric studies of some alkylene oxide copolymers have been used to calculate rate constant ratios for the first eight steps in the polymerization process. Results suggest that there is a significant reduction in reactivity of the growing chains during this initial period.     

Coexisting aggregates in mixed aerosol OT and cholesterol microemulsions

Dynamic light scattering and NMR spectroscopic experimental evidence suggest the coexistence of two compositionally different self-assembled particles in solution. The self-assembled particles form in solutions containing water, Aerosol OT (AOT, sodium bis(2-ethylhexyl) sulfosuccinate) surfactant, and cholesterol in cyclohexane. In a similar series of studies carried out in 1-octanol only one aggregate type, that is, reverse micelles, is observed. Dynamic light scattering measurements reveal the presence of two different types of aggregates in the microemulsions formed in cyclohexane, demonstrating the coexistence of two compositionally distinct structures with very similar Gibbs energies. One particle type consists of standard AOT reverse micelles while the second type of particle consists of submicellar aggregates including cholesterol as well as small amounts of AOT and water. In microemulsions employing 1-octanol as the continuous medium, AOT reverse micelles form in a dispersed solution of cholesterol in 1-octanol. Although the size distribution of self-assembled particles is well-known for many different systems, evidence for simultaneous formation of two distinctly sized particles in solution that are chemically different is unprecedented. The ability to form microemulsion solutions that contain coexisting particles may have important applications in drug formulation and administration, particularly as applied to drug delivery using cholesterol as a targeting agent.     

Dispersion properties of high-contrast grating hollow-core waveguides

We present unique dispersion characteristics of high-contrast grating (HCG) hollow-core waveguides and show that slow light can be facilitated using internal resonances developing inside the waveguide walls. In addition, we show a fast and precise method of inferring the dispersion information from the waveguide angular reflectivity spectrum.     

Graphene nanoribbon-based supramolecular ensembles with dual-receptor targeting function for targeted photothermal tumor therapy

Triple negative breast cancer (TNBC) is one of the most malignant subtypes of breast cancer. Here, we report the construction of graphene nanoribbon (GNR)-based supramolecular ensembles with dual-receptor (mannose and α_vβ₃ integrin receptors) targeting function, denoted as GNR-Man/PRGD, for targeted photothermal treatment (PTT) of TNBC. The GNR-Man/PRGD ensembles were constructed through the solution-based self-assembly of mannose-grafted GNRs (GNR-Man) with a pyrene-tagged α_vβ₃ integrin ligand (PRGD). Enhanced PTT efficacies were achieved both in vitro and in vivo compared to that of the non-targeting equivalents. Tumor-bearing live mice were administered (tail vein) with GNR-Man/PRGD and then each mice group was subjected to PTT. Remarkably, GNR-Man/PRGD induced complete ablation of the solid tumors, and no tumor regrowth was observed over a period of 15 days. This study demonstrates a new and promising platform for the development of photothermal nanomaterials for targeted tumor therapy.

Dual receptor-targeting supramolecular glycomaterials are constructed based on graphene nanoribbons for the targeted photothermal therapy of triple-negative breast cancer in vivo.     

Fast atom bombardment mass spectrometry of butyloxycarbonyl protected (BOC) amino acids

The positive and negative ion mass spectra of a series of BOC-protected amino acids have been obtained using an FAB source. The spectra show characteristic features including a McLafferty type of rearrangement.     

Fast atom bombardment mass spectra of involatile naphthalene sulphonic acids and sulphonate salts

Fast Atom Bombardment mass spectra of a range of involatile naphthalene sulphonic acids and sulphonates are presented. Excellent spectra are obtained for the mono-, di- and the previously unexamined trisulphonated compounds. The relative value of positive and negative ion spectra for the study of these species is discussed. The results are shown to be superior to those obtained by other mass spectrometric methods.     

High-temperature reactions of hydroxyl and carboxyl PET chain end groups in the presence of aromatic phosphite

When melt-extruded in the presence of triphenylphosphite (TPP), the molecular weight of polyesters such as poly(ethylene terephthalate) (PET) increases with time. Analysis of the PET chain end groups and model studies of high-temperature reactions indicate that, most likely, the process leading to chain extension of PET in the presence of TPP takes place in two steps. In the first step, TPP rapidly reacts with the hydroxyl end groups by displacing one phenoxy group from the TPP. In the second step, a slow reaction takes place between the alkyldiphenyl phosphite and carboxylic chain end groups, forming an ester bond between the carboxyl and alkyl groups, and producing diphenylphosphite (DPP) as a reaction by-product. The DPP tautomerizes to its pentacovalently bonded stabler form of diphenylphosphate, the form in which the DPP was usually detected in our analyses. The ester formation results in the extension of the PET chains. Model studies are presented which support the proposed mechanism.     

Inelastic light scattering studies of silicon chemical vapor deposition (CVD) systems

Raman and resonance fluorescence spectra, determined by inelastic light scattering measurements, are used to identify molecular species and to measure their concentration gradients on a fine spatial scale throughout a CVD reactor. Raman spectra are also analyzed to give gas temperature and tempetature profiles. The temperature profiles near the leading edge of a horizontal rf heated susceptor in a laminar flow system are adequately described by using Lévêque's solution to an energy balance equation, assuming temperature-independent fluid properties. Raman spectra at room temperature of some of the compounds commonly used as source materials for Si epitaxial growth, SiCl₄, SiCl₃H, SiCl₂H₂ and Si₂Cl₆ indicate that these species are all detectable at the 10–100 ppm level and are distinguishable from each other. Measurements at 500–1300°C of these compounds reveal the presence of a common species, SiCl_x (probably SiCl₂), which exhibits a resonance flourescence spectrum at least 1000 times more intense than typical Raman spectra. SiCl_x density profile measurements above the susceptor indicate a concentration boundary layer thickness of 0.7-0.8 cm for one set of experimental conditions. SiCl_x density measurements as a function of suspector temperature are observed to vary over a range of 4 to 5 orders of magnitude, and are much higher for a SiCl₂H₂ input than for a SiCl₄ input.     

Protein encapsulation: a new approach for improving the capability of small-molecule fluorogenic probes

Herein, we report a protein-based hybridization strategy that exploits the host-guest chemistry of HSA (human serum albumin) to solubilize the otherwise cell impermeable ONOO⁻ fluorescent probe Pinkment-OAc. Formation of a HSA/Pinkment-OAc supramolecular hybrid was confirmed by SAXS and solution-state analyses. This HSA/Pinkment-OAc hybrid provided an enhanced fluorescence response towards ONOO⁻versusPinkment-OAc alone, as determined by in vitro experiments. The HSA/Pinkment-OAc hybrid was also evaluated in RAW 264.7 macrophages and HeLa cancer cell lines, which displayed an enhanced cell permeability enabling the detection of SIN-1 and LPS generated ONOO⁻ and the in vivo imaging of acute inflammation in LPS-treated mice. A remarkable 5.6 fold (RAW 264.7), 8.7-fold (HeLa) and 2.7-fold increased response was seen relative to Pinkment-OAc alone at the cellular level and in vivo, respectively. We anticipate that HSA/fluorescent probe hybrids will soon become ubiquitous and routinely applied to overcome solubility issues associated with hydrophobic fluorescent imaging agents designed to detect disease related biomarkers.

Herein, we report a protein-based hybridization strategy that exploits the host–guest chemistry of HSA (human serum albumin) to solubilize the otherwise cell impermeable ONOO⁻ fluorescent probe Pinkment-OAc.