A Preliminary Research Study for Distribution Characteristics and Sources of Indoor Air Pollutants in the Valuable Archive of the National Library of Korea.

Important records can be damaged directly and indirectly. Their restoration, if possible, is difficult as it is very time-consuming and costly. Although measures have been taken to permanently preserve records, most studies focus on preventing short-term damage from physical or biological factors and not on preventive measures against chemical damage from long-term polluted air exposure. This study investigated the types, concentrations, and distribution characteristics of hazardous chemicals present in the valuable archive of the National Library of Korea (NLK) and identified the sources of these pollutants. Mean SO2, NOX, CO, CO2, and total volatile organic compound (TVOC) concentrations were 1.49 ± 0.44 ppb, 30.52 ± 19.70 ppb, 0.75 ± 0.21 ppm, 368.91 ± 32.23 ppm, and 320.03 ± 44.20 µg/m3, respectively, meeting the Ministry of the Interior and Safety (MOIS) of Korea standards. Toluene (66.43 ± 10.69 µg/m3) and acetaldehyde (157.23 ± 6.43 µg/m3) were present at the highest concentrations, respectively. Two principal components were extracted via a principal component analysis; the primary component (66%) was closely related to outdoor pollution sources and the secondary component (33%) to indoor sources. Results contribute to establishing air quality standards and management measures for preservation of this archive.

Large-scale synthesis of copper nanoparticles by chemically controlled reduction for applications of inkjet-printed electronics.

Copper nanoparticles are being given considerable attention as of late due to their interesting properties and potential applications in many areas of industry. One such exploitable use is as the major constituent of conductive inks and pastes used for printing various electronic components. In this study, copper nanoparticles were synthesized through a relatively large-scale (5 l), high-throughput (0.2 M) process. This facile method occurs through the chemical reduction of copper sulfate with sodium hypophosphite in ethylene glycol within the presence of a polymer surfactant (PVP), which was included to prevent aggregation and give dispersion stability to the resulting colloidal nanoparticles. Reaction yields were determined to be quantitative while particle dispersion yields were between 68 and 73%. The size of the copper nanoparticles could be controlled between 30 and 65 nm by varying the reaction time, reaction temperature, and relative ratio of copper sulfate to the surfactant. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) images of the particles revealed a spherical shape within the reported size regime, and x-ray analysis confirmed the formation of face-centered cubic (FCC) metallic copper. Furthermore, inkjet printing nanocopper inks prepared from the polymer-stabilized copper nanoparticles onto polyimide substrates resulted in metallic copper traces with low electrical resistivities (≥3.6 µΩ cm, or ≥2.2 times the resistivity of bulk copper) after a relatively low-temperature sintering process (200 °C for up to 60 min).

Direct synthesis and bonding origins of monolayer-protected silver nanocrystals from silver nitrate through in situ ligand exchange.

In this study, we attempt to present a direct synthesis of narrowly dispersed silver nanoparticles in a highly concentrated organic phase (>2 M) without the use of a size-selection process. The fully organic phase system contains silver nitrate as a silver precursor, n-butylamine as a medium dissolving the silver salt, dodecanoic acid as a capping molecule, toluene as a medium, and NaBH4 as a reducing reagent. Even using only generic chemicals, monodisperse silver nanocrystals with a size of 7 nm were easily synthesized on the 100-g scale in a 1-L reactor. In addition, systematic studies revealed that the silver nanocrystals synthesized through in situ ligand exchange were stabilized through bidentate bridging of carboxyl groups in dodecanoic acid.

Production of hydrogen by autothermal reforming of propane over Ni/delta-Al2O3.

The performance of Ni/delta-Al2O3 catalyst in propane autothermal reforming (ATR) for hydrogen production was investigated in the present study. The catalysts were characterized using XRD, TEM, and SEM. The activity of the Ni/delta-Al2O3 catalyst manufactured by the water-alcohol method was better than those of the catalysts manufactured by the impregnation and chemical reduction methods. The Ni/delta-Al2O3 catalysts were modified by the addition of promoters such as Mg, La, Ce, and Co, in order to improve their stability and yield. Hydrogen production was the largest for the Ni-Co-CeO2/Al2O3, catalyst.

Mechanistic differences in RNA-dependent DNA polymerization and fidelity between murine leukemia virus and HIV-1 reverse transcriptases.

We compared the mechanistic and kinetic properties of murine leukemia virus (MuLV) and human immunodeficiency virus type 1 (HIV-1) reverse transcriptases (RTs) during RNA-dependent DNA polymerization and mutation synthesis using pre-steady-state kinetic analysis. First, MuLV RT showed 6.5-121.6-fold lower binding affinity (K(d)) to deoxynucleotide triphosphate (dNTP) substrates than HIV-1 RT, although the two RTs have similar incorporation rates (k(pol)). Second, compared with HIV-1 RT, MuLV RT showed dramatic reduction during multiple dNTP incorporations at low dNTP concentrations. Presumably, due to its low dNTP binding affinity, the dNTP binding step becomes rate-limiting in the multiple rounds of the dNTP incorporation by MuLV RT, especially at low dNTP concentrations. Third, similar fold differences between MuLV and HIV-1 RTs in the K(d) and k(pol) values to correct and incorrect dNTPs were observed. This indicates that these two RT proteins have similar misinsertion fidelities. Fourth, these two RT proteins have different mechanistic capabilities regarding mismatch extension. MuLV RT has a 3.1-fold lower mismatch extension fidelity, compared with HIV-1 RT. Finally, MuLV RT has a 3.8-fold lower binding affinity to mismatched template/primer (T/P) substrate compared with HIV-1 RT. Our data suggest that the active site of MuLV RT has an intrinsically low dNTP binding affinity, compared with HIV-1 RT. In addition, instead of the misinsertion step, the mismatch extension step, which varies between MuLV and HIV-1 RTs, contributes to their fidelity differences. The implications of these kinetic differences between MuLV and HIV-1 RTs on viral cell type specificity and mutagenesis are discussed.

Macrophage tropism of HIV-1 depends on efficient cellular dNTP utilization by reverse transcriptase.

Retroviruses utilize cellular dNTPs to perform proviral DNA synthesis in infected host cells. Unlike oncoretroviruses, which replicate in dividing cells, lentiviruses, such as human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus, are capable of efficiently replicating in non-dividing cells (terminally differentiated macrophages) as well as dividing cells (i.e. activated CD4+ T cells). In general, non-dividing cells are likely to have low cellular dNTP content compared with dividing cells. Here, by employing a novel assay for cellular dNTP content, we determined the dNTP concentrations in two HIV-1 target cells, macrophages and activated CD4+ T cells. We found that human macrophages contained 130-250-fold lower dNTP concentrations than activated human CD4+ T cells. Biochemical analysis revealed that, unlike oncoretroviral reverse transcriptases (RTs), lentiviral RTs efficiently synthesize DNA even in the presence of the low dNTP concentrations equivalent to those found in macrophages. In keeping with this observation, HIV-1 vectors containing mutant HIV-1 RTs, which kinetically mimic oncoretroviral RTs, failed to transduce human macrophages despite retaining normal infectivity for activated CD4+ T cells and other dividing cells. These results suggest that the ability of HIV-1 to infect macrophages, which is essential to establishing the early pathogenesis of HIV-1 infection, depends, at least in part, on enzymatic adaptation of HIV-1 RT to efficiently catalyze DNA synthesis in limited cellular dNTP substrate environments.

A role for dNTP binding of human immunodeficiency virus type 1 reverse transcriptase in viral mutagenesis.

HIV-1 reverse transcriptase (RT) is a highly error prone DNA polymerase. We assessed whether the ability of RT to bind nucleotide substrates affects viral mutagenesis. Structural modeling predicts that the V148 and Q151 residues influence the interaction between RT and the incoming dNTP. When we introduce either a V148I or Q151N mutation, RT fidelity increases 8.7- or 13-fold, respectively, as measured by the M13 lacZalpha forward mutation assay. Interestingly, pre-steady state kinetic studies demonstrated that these mutations do not alter polymerase fidelity during the first step of mutation synthesis, misincorporation. Rather, the V148I and Q151N mutations alter RT fidelity by weakening the ability of the polymerase to complete mismatch extension, the second step of mutation synthesis. While both these mutations minimally affect the binding of RT (K(D)) to a mismatched template-primer complex (T/P), these mutant RTs are significantly impaired in their ability to bind (K(d)) and chemically incorporate (k(pol)) nucleotide substrate onto a mismatched T/P. These differences in binding and catalysis translate into 24- and 15.9-fold increase in mismatch extension fidelity for the V148I and Q151N RT mutants, respectively. Finally, we employed a cell-based pseudotyped HIV-1 mutation assay to determine whether changes in these dNTP binding residues alter RT fidelity in vivo. We found that the V148I and Q151N mutant viruses had 3.8- and 5.7-fold higher fidelities than wild-type viruses, respectively, indicating that the molecular interaction between HIV-1 RT and the dNTP substrate contributes to viral mutagenesis.

Mechanistic understanding of an altered fidelity simian immunodeficiency virus reverse transcriptase mutation, V148I, identified in a pig-tailed macaque.

We have recently reported that the reverse transcriptase (RT) of SIVMNE 170 (170), which is a representative viral clone of the late symptomatic phase of infection with the parental strain, SIVMNE CL8 (CL8), has a largely increased fidelity, compared with the CL8 RT. In the present study, we analyzed the mechanistic alterations of the high fidelity 170 RT variant. First, we found that among several 170 RT mutations, only one, V148I, is solely responsible for the fidelity increase over the CL8 RT. This V148I mutation lies near the Gln-151 residue that we recently found is important to the low fidelity of RT and the binding of incoming dNTPs. Second, we compared dNTP binding affinity (Kd) and catalysis (kpol) of the CL8 RT and the CL8-V148I RT using pre-steady state kinetic analysis. In this experiment, the high fidelity CL8-V148I RT has largely decreased binding to both correct and incorrect dNTP without altering kpol. The fidelity increase imparted by the V148I mutation is likely because of the major reduction seen in RT binding to dNTPs. This parallels our findings with the Q151N mutant. Third, site-directed mutagenesis targeting amino acid residue 148 has revealed that a valine amino acid at this position is essential to RT infidelity. Based on these findings, we discuss possible structural impacts of residue 148 (and mutations at this site) on the interaction of RT with incoming dNTPs and infer how alterations in these properties may relate to viral replication and fitness.

Helicopter-based lidar system for monitoring the upper ocean and terrain surface.

A compact helicopter-based lidar system is developed and tested under laboratory and field conditions. It is shown that the lidar can measure concentrations of chlorophyll a and dissolved organic matter at the surface of water bodies, detect fluorescence spectra of ground vegetation at a distance of up to 530 m, and determine the vertical profile of light-scattering particle concentration in the upper ocean. The possibilities of the lidar system are demonstrated by detection of polluted areas at the ocean surface, by online monitoring of three-dimensional distribution of light-scattering layers, and by recognition of plant types and physiological states.