Wavelength tunable optical time-domain reflectometry based on wavelength swept fiber laser employing two-dimensional digital micro-mirror array

We demonstrate a cost effective wavelength tunable optical time-domain reflectometry (OTDR) for wavelength division multiplexing passive optical networks (WDM-PON). In order to realize the unique wavelength tunable optical time-domain reflectometry (OTDR), the wavelength swept fiber laser was developed by a digital micro-mirror array device (DMD), and the correlation OTDR (COTDR) technique was used. We successfully detected the fault location at the remote node fibers with 20 m resolution and fast wavelength setting speed of ∼15 μs in conventional band (C-band).     

Electrodeposited ruthenium oxide thin films for supercapacitor: Effect of surface treatments

Amorphous and porous ruthenium oxide thin films have been deposited from aqueous Ru(III)Cl₃ solution on stainless steel substrates using electrodeposition method. Cyclic voltammetry study of a film showed a maximum specific capacitance of 650 F g⁻¹ in 0.5 M H₂SO₄ electrolyte. The surface treatments such as air annealing, anodization and ultrasonic weltering affected surface morphology. The supercapacitance of ruthenium oxide electrode is found to be dependent on the surface morphology.     

Investigation of sidewall roughness of the microgrooves manufactured with laser-induced etching technique

A novel laser etching technique utilizing an optical fiber as the laser beam guide is introduced. Depending upon whether a pulsed or a continuous wave (CW) laser is employed as the irradiation source, it was found that the etch depth and surface morphology of the grooves varied significantly. It was then demonstrated that deep microgrooves with smooth sidewalls can be obtained using a hybrid pulse and CW scanning process. The results of laser heating and chemical analyses revealed that sidewall roughness of the microgroove is mainly attributed to surface melting.     

cis‐Dinitrito(1,4,8,11‐tetra­aza­cyclo­tetra­decane‐κ4N)­chromium(III) nitrite

In the title compound, [Cr(ONO)₂(cyclam)]NO₂ (cyclam is 1,4,8,11‐tetra­aza­cyclo­tetra­decane, C₁₀H₂₄N₂), the complex cation is located on a twofold symmetry axis. The central Cr atom has a distorted octahedral coordination, involving two Cr—O bonds, with the monodentate nitrite O atoms adopting a cis configuration, and four Cr—N bonds. The mean Cr—N and Cr—O distances are 2.0895 (14) and 1.9698 (14) Å.     

Characteristics of the Molecular Weight of Polyhexamethylene Guanidine (PHMG) Used as a Household Humidifier Disinfectant

(1) Background: Household humidifier disinfectant (HD) brands containing polyhexamethylene guanidine (PHMG) have been found to cause the most HD-associated lung injuries (HDLIs) in the Republic of Korea. Nevertheless, no study has attempted to characterize the potential association of the health effects, including HDLI, with the physicochemical properties of PHMG dissolved in different HD brands. This study aimed to characterize the molecular weight (MW) distribution, the number-average molecular weight (M_n), the weight-average molecular weight (M_w), and the structural types of PHMG used in HD products. (2) Methods: Quantitative measurements were made using matrix-assisted laser desorption/ionization–time-of-flight mass spectrometry (MALDI-TOF MS). The M_n, M_w, and MW distributions were compared among various HD products. (3) Results: The mean M_n and M_w were 542.4 g/mol (range: 403.0–692.2 g/mol) and 560.7 g/mol (range: 424.0–714.70 g/mol), respectively. The degree of PHMG oligomerization ranged from 3 to 7. The MW distribution of PHMG indicated oligomeric compounds regardless of the HD brands. (4) Conclusions: Based on the molecular weight distribution, the average molecular weight of PHMG, and the degree of polymerization, the PHMG collected from HDLI victims could be regarded as an oligomer. PHMG, as used in household humidifiers, should not be exempted from toxic chemical registration as a polymer. Further study is necessary to examine the association of PHMG oligomeric compounds and respiratory health effects, including HDLI.     

NMR study of phase separation in D2O/ethanol solutions of poly(N-isopropylmethacrylamide) induced by solvent composition and temperature

¹H and ¹³C NMR spectroscopies were applied to investigate phase separation in solutions of poly(N-isopropylmethacrylamide) (PIPMAm) in D₂O/ethanol (EtOH) mixtures induced by solvent composition (cononsolvency) and temperature. Effects of EtOH content in D₂O/EtOH mixtures and temperature on the appearance and extent of the phase separation were characterized. Differences in mesoglobules formed during the phase separation induced by cononsolvency and temperature were found. For temperature-induced phase separation, ¹³C spin-spin relaxation times showed that besides the free EtOH expelled from the PIPMAm mesoglobules, there are also EtOH molecules bound in these mesoglobules. On the other hand, virtually no bound EtOH molecules were detected for mesoglobules formed as a consequence of the cononsolvency. For PIPMAm random copolymers containing negatively charged methacrylate units the phase separation induced by solvent composition was not observed.     

Inorganic Metal Hydroxide Nanoparticles for Targeted Cellular Uptake Through Clathrin‐Mediated Endocytosis

Layered double hydroxides (LDHs) are biocompatible materials which can be used as drug‐delivery nanovehicles. In order to define the optimum size of LDH nanoparticles for efficient cellular uptake and drug‐delivery pathway, we prepared different sized LDH nanoparticles with narrow size distribution by modulating the crystal growth rate, and labelled each LDH particle with a fluorophore using a silane coupling reaction. The cellular uptake rate of LDHs was found to be highly dependent on particle size (50>200≥100>350 nm), whose range of 50 to 200 nm was selectively internalized into cells through clathrin‐mediated endocytosis with enhanced permeability and retention. Our study clearly shows that not only the particle size plays an important role in the endocytic pathway and processing, but also the size control of LDH nanoparticles results in their targeted uptake to site‐specific clathrin‐mediated endocytosis. This result provides a new perspective for the design of LDH nanoparticles with maximum ability towards targeted drug delivery.     

Isothermal vapor–liquid equilibrium at 333.15 K and excess molar volumes and refractive indices at 298.15 K for the mixtures of di-methyl carbonate,ethanol and 2,2,4-trimethylpentane

Isothermal vapor–liquid equilibrium data at 333.15 K are measured for the binary system ethanol + 2,2,4-trimethylpentane and for ternary system di-methyl carbonate (DMC) + ethanol + 2,2,4-trimethylpentane by using headspace gas chromatography. The experimental binary and ternary vapor–liquid equilibrium data were correlated with different activity coefficient models. Excess volume and deviations in molar refractivity data are also reported for the binary systems DMC + ethanol and DMC + 2,2,4-trimethylpentane and the ternary system DMC + ethanol + 2,2,4-trimethylpentane at 298.15 K. These data were correlated with the Redlich-Kister equation for the binary systems and the Cibulka equation for the ternary system, respectively. The ternary excess volume and deviations in molar refractivity data were also compared with estimated values from the binary contribution models of Tsao–Smith, Kohler, Rastogi and Radojkovi?.     

Controlled preparation of poly(ethylene glycol) and poly(L‐lactide) block copolymers in the presence of a monomer activator

Polymerization of L ‐lactide (LA) was performed in the presence of trifluoromethanesulfonic acid (CF₃SO₃H) via an activated monomer mechanism to synthesize various block copolymers composed of polyethyleneglycol (PEG) and poly(L ‐lactide) (PLLA). The PLLAs obtained had molecular weights close to theoretical values calculated from LA/PEG molar ratios and exhibited monomodal GPC curves. A ¹H NMR spectroscopic study showed that the LA carbonyl carbon signal exhibited a change in chemical shift to lower field, caused by electron delocalization of the carbonyl carbon by CF₃SO₃H. We successfully prepared PEG and PLLA block copolymers using this activated monomer mechanism. We concluded that synthesis proceeded by LA ring‐opening polymerization caused by PEG in the presence of CF₃SO₃H to yield PEG and PLLA block copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5917–5922, 2009     

Molecular miscible blend of poly(2-cyano-1,4-phenyleneterephthalamide) and polyvinylpyrrolidone characterized by two-dimensional correlation FTIR and solid state C NMR spectroscopy

Miscibility of blends of poly(2-cyano-1,4-phenyleneterephthalamide/polyvinylpyrrolidone) (CN-PPTA/PVP) was investigated by dilute solution viscometry, two-dimensional (2D) correlation Fourier transformed infrared (FTIR) spectroscopy and solid state ¹³C NMR spectroscopy. It was shown that a large proportion of the PVP, the water-soluble component, could not be removed from CN-PPTA by extraction with water, and even with boiling water for blend films, suggesting that the flexible aliphatic PVP chain forms a blend with the rigid aromatic CN-PPTA chain through strong intermolecular interaction making it too difficult to dissolve even in boiling water. Viscometry on a polymer mixture of dilute solution showed that [η]_exp exhibited larger value than [η]_theo in all mixtures used in this experiment, suggesting occurrence of a strong attractive interaction between the two polymers. 2D correlation FTIR spectroscopy revealed that the carbonyl absorption band of PVP at 1675 cm⁻¹ shifted to a new low frequency absorption band at 1640 cm⁻¹ with a change of 35 cm⁻¹, suggesting strong hydrogen bonding with NH (amide II) proton of CN-PPTA. Another new absorption band at 1685 cm⁻¹ was due to the carbonyl absorption band of CN-PPTA shifting to a higher frequency than that at 1662 cm⁻¹, indicating that some of the carbonyl groups in the CN-PPTA components of the blends were in a free state or in a non-hydrogen bonded state as a consequence of the participation of NH proton of CN-PPTA in hydrogen bonding, resulting in the absorption bands of NH bend deformation of CN-PPTA at 1542 and 1313 cm⁻¹ being shifted to higher wavenumber of 1556 and 1324 cm⁻¹, respectively. Solid state ¹³C NMR spectroscopy revealed a chemical shift for CO of the PVP component in the blend fiber changing down-field (shift to left) at 177.346 ppm with a difference of 1.812 ppm; this was due to a lower electron density around the carbon atom of CO of lactam via hydrogen bonding with NH proton of amide in the CN-PPTA component, suggesting that a homogeneous blend of the CN-PPTA and PVP was produced on a molecular scale via hydrogen bonding.