Hyungchae Kim

Measurements of Silica Aggregate Particle Growth Using Light Scattering and Thermophoretic Sampling in a Coflow Diffusion Flame

The evolution of silica aggregate particles in a coflow diffusion flame has been studied experimentally using light scattering and thermophoretic sampling techniques. An attempt has been made to calculate the aggregate number density and volume fraction using the measurements of scattering cross section from 90° light scattering with combination of measuring the particle size and morphology from the localized sampling and a TEM image analysis. Aggregate or particle number densities and volume fractions were calculated using Rayleigh–Debye–Gans and Mie theory for fractal aggregates and spherical particles, respectively. Using this technique, the effects of H2 flow rates on the evolution of silica aggregate particles have been studied in a coflow diffusion flame burner. As the flow rate of H2 increases, the primary particle diameters of silica aggregates have been first decreased, but, further increase of H2 flow rate causes the diameter of primary particles to increase and for sufficiently larger flow rates, the fractal aggregates finally become spherical particles. For the cases of high flame temperatures, the particle sizes become larger and the number densities decrease by coagulation as the particles move up within the flame. For cases of low flame temperatures, the primary particle diameters of aggregates vary a little following the centerline of burner and for the case of the lowest flame temperature in the present experiments, the sizes of primary particles even decrease as particles move upward.

Triple-Junction Hybrid Tandem Solar Cells with Amorphous Silicon and Polymer-Fullerene Blends

Organic-inorganic hybrid tandem solar cells attract a considerable amount of attention due to their potential for realizing high efficiency photovoltaic devices at a low cost. Here, highly efficient triple-junction (TJ) hybrid tandem solar cells consisting of a double-junction (DJ) amorphous silicon (a-Si) cell and an organic photovoltaic (OPV) rear cell were developed. In order to design the TJ device in a logical manner, a simulation was carried out based on optical absorption and internal quantum efficiency. In the TJ architecture, the high-energy photons were utilized in a more efficient way than in the previously reported a-Si/OPV DJ devices, leading to a significant improvement in the overall efficiency by means of a voltage gain. The interface engineering such as tin-doped In2O3 deposition as an interlayer and its UV-ozone treatment resulted in the further improvement in the performance of the TJ solar cells. As a result, a power conversion efficiency of 7.81% was achieved with an open-circuit voltage of 2.35 V. The wavelength-resolved absorption profile provides deeper insight into the detailed optical response of the TJ hybrid solar cells.

Crystal structure of UbiX, an aromatic acid decarboxylase from the psychrophilic bacterium Colwellia psychrerythraea that undergoes FMN-induced conformational changes.

The ubiX gene of Colwellia psychrerythraea strain 34H encodes a 3-octaprenyl-4-hydroxybenzoate carboxylase (CpsUbiX, UniProtKB code: Q489U8) that is involved in the third step of the ubiquinone biosynthesis pathway and harbors a flavin mononucleotide (FMN) as a potential cofactor. Here, we report the crystal structures of two forms of CpsUbiX: an FMN-bound wild type form and an FMN-unbound V47S mutant form. CpsUbiX is a dodecameric enzyme, and each monomer possesses a typical Rossmann-fold structure. The FMN-binding domain of UbiX is composed of three neighboring subunits. The highly conserved Gly15, Ser41, Val47, and Tyr171 residues play important roles in FMN binding. Structural comparison of the FMN-bound wild type form with the FMN-free form reveals a significant conformational difference in the C-terminal loop region (comprising residues 170–176 and 195–206). Subsequent computational modeling and liposome binding assay both suggest that the conformational flexibility observed in the C-terminal loops plays an important role in substrate and lipid bindings. The crystal structures presented in this work provide structural framework and insights into the catalytic mechanism of CpsUbiX.

Efficient Planar-Heterojunction Perovskite Solar Cells Fabricated by High-Throughput Sheath-Gas-Assisted Electrospray

When a perovskite precursor solution is electrosprayed using the conventional method where the nebulization of the solution is primarily governed by electrostatics, its high electrical conductivity tends to cause electrospray instabilities and thus makes high-quality perovskite films very difficult to obtain. Here, we report high-throughput fabrication of efficient perovskite solar cells (PSCs) whose CH3NH3PbI3-xClx films are deposited using a sheath-gas-assisted electrospray system. Our system, based on strong pneumatic nebulization as well as high-voltage electrostatic charging of droplets, enables very stable high-flow electrospray of small charged droplets, even for the highly conductive perovskite precursor solution. Consequently, with the control of the drying rate of the droplets deposited on substrates by adjusting the substrate temperature during deposition, crystalline, void-free CH3NH3PbI3-xClx films with nearly 100% surface coverage and high thickness uniformity are obtained. Inverted planar-heterojunction PSCs employing these films have a maximum power conversion efficiency of 14.2% with a small standard deviation of 0.9%, comparable to that of the spin-coated device.

Multifunctional Bilayer Template for Near-Infrared Sensitive Organic Solar Cells

For organic solar cells (OSCs) based on nonplanar phthalocyanines, it has previously been reported that a thin film composed of triclinic crystals with face-on (or flat-lying)-oriented molecules, typically obtained with a CuI template layer, is desired for optical absorption in the near-infrared (NIR) spectral region. However, this work demonstrates that for a PbPc-C60 donor-acceptor pair, less face-on orientation with a broader orientation distribution obtained with a new template layer consisting of a ZnPc/CuI bilayer is more desirable in terms of solar cell efficiency than the face-on orientation. A NIR-sensitive PbPc-C60 OSC employing this bilayer-templated PbPc film is found to increase the internal quantum efficiency (IQE) by 36% on average in the NIR spectral region compared to a device using a CuI-templated PbPc film. Analyses of the change in IQE using the exciton diffusion model and the entropy- and disorder-driven charge-separation model suggest that the improved IQE is attributed to the facilitated dissociation of charge-transfer excitons as well as the reduction in exciton quenching near the indium tin oxide surface.

Scattering of surface plasmon polaritons at a planar interface by an embedded dielectric nanocube

We investigate scattering of surface plasmon polaritons (SPPs) at a planar metal-dielectric interface by a dielectric nanocube embedded in the metal layer using finite element method-based simulations. The scattering characteristics of the embedded nanocube, such as the scattering and absorption cross sections, far-field scattering patterns, reflectance, and transmittance, are calculated as functions of the wavelength of the incident SPP waves in the visible range. The main features of the characteristics are explained in connection with the excitation of plasmonic eigenmodes of the embedded nanocube. The most efficient scattering into waves propagating away from the metal surface, i.e., the radiating modes, occurs when a dipolar-like plasmonic mode is excited, whose eigenfrequency can be tuned by changing the edge length of the nanocube.

SAT0010 Common epitope structure of HLA-DPB1 in systemic sclerosis

Background Specific alleles of HLA-DPB1 (HLA-DPB1*0901, *1301, *0301) were found to be most strongly associated with anti-topoisomerase I (Topo-I)-positive systemic sclerosis (SSc) in multiethnic genome-wide association study and HLA-analysis (1, 2). However, structural basis on which HLA-DPB1 alleles can bind Topo-I peptides is unknown. Objectives To find common characteristics of amino acid sequences in the risk HLA-DPB1 alleles and to reveal the possible mode of binding with Topo-I. Methods We enrolled 127 Korean patients with SSc who were diagnosed as SSc according to the preliminary classification criteria of American College of Rheumatology and 548 healthy Korean controls. We compared amino acid sequences of the risk HLA-DPB1 alleles with non-risk alleles, focusing on known HLA-DP binding motifs. After revealing common peptides from risk alleles of HLA-DPB1, molecular dynamic simulation was conducted to show binding structures against hypothetically chosen sequences of amino acids in Topo-I. Results The triplet of negative charged amino acids in three critical sites were associated with SSc. At amino acid position 55-57, 67-69, and 82, 84-85 of HLA-DPB1, negatively charged amino acids were prevalent, which includes glutamine or lysine. The patients who have 3 negative charged triplets show OR of 5.99 (95% CI=2.17-16.6, p=1.8×10-4) for SSc and those who have 2 negative charged triplets show OR of 6.37 (95% CI=2.35-17.3, p=7.1×10-5) or 3.89 (95% CI=1.39-10.9, p=6.5×10-3), while those who do not have triplets have referent OR of 1.00. When peptides from Topo-I (peptide A (KDREHRHKEHKK) and peptide B (KLLKEYGFCIMD)) were selected to simulate interaction with “high risk” HLA-DP allele (HLA-DPB1*0901) and “low risk” allele (HLA-DPB1*040101), peptide A and B fit more closely into the binding cleft of HLA-DPB1*0901 than HLA-DPB1*040101. (Figure 1) Conclusions SSc-susceptible HLA-DPB1 alleles share negative charged amino acid triplets at critical positions in their peptide binding groove. References Zhou, X., et al., Arthritis Rheum, 2009. 60(12): p. 3807-14. Arnett, F.C., et al., Ann Rheum Dis, 2010. 69(5): p. 822-7. Disclosure of Interest None Declared

SAT0186 Abnormal Videofluoroscopy Swallow study Finding in Inflammatory Myopathy Patient with Dysphagia as Predictor of Prognosis

Background Previous reports of dysphagia in patients with inflammatory myopathy (IM) have been focused on detection, intervention and rehabilitation. However, whether dysphagia with abnormal videofluoroscopy swallow study (VFSS) findings is in relation to clinical manifestations and treatment response is not known. Objectives We hypothesized that clinical entities in IM patients with dysphagia would be distinct from non-dysphagia patients and abnormal VFSS finding could be a predictor of prognosis. Methods Total 236 patients with IM were reviewed in this study. Of them, the patients with dysphagia were evaluated with clinical functional scale, VFS scale, new VFSS scale, and American Speech-Language-Hearing Association National Outcome Measurement System swallowing scale. VFSS score was categorized into oral, pharyngeal and esophageal phase based on modified Logemann’s methods. Association between VFSS scale and serum creatinine kinase (CK), clinical findings, or treatment response were analyzed. Results Among 236 IM patients, 28 patients had IM related dysphagia (26 with dermatomyositis, 1 polymyositis and 1 inclusion body myositis). Ten male and 18 female with mean age of 42.7 were included. Dysphagia was a presenting symptom in 5 patients (17.9%) and rest of patients developed dysphagia in average 221 days later. The VFSS results showed more prevalent abnormalities in pharyngeal phase than oral phase (n=26 vs. n=9). Baseline CK level was higher in delayed laryngeal elevation and epiglottic closure (LEEC) patients than in normal LEEC patients (473.8 ± 415.6 mg/dl vs 3931.7 ± 5532.3 mg/dl, p=0.008) (Figure 1). There was no correlation in total VFSS score with baseline CK level. Intravenous immunoglobulin were significantly more prescribed in delayed LEEC patients than in normal LEEC patients (OR=10.7, p=0.047). Frequency of pulmonary involvement and malignancy were significantly different between patients with dysphagia and patients without dysphagia (7.1% vs 40.4%, p<0.001, 35.7% vs 9.6%, p=0001, respectively) (Table 1). Conclusions Abnormal VFSS findings in IM Patients with dysphagia were more prominent in pharyngeal phases than oral phases. Delayed LEEC was associated with higher baseline CK level and use of intravenous immunoglobulin. IM patients with dysphagia showed lower pulmonary involvement and higher malignancy. These results indicate that dysphagia in IM is not only a localized symptom or disabling condition, but also a predictor of prognosis. Acknowledgements None Disclosure of Interest None Declared