Determination of stability constants of mercury(II) by garlic organosulfur ligands with differential pulse voltammetry

Journal of Applied Electrochemistry - In this work, interactions of mercury with di allyl disulfide (DADS), dimethyl disulfide (DMDS), and diallyl sulfide (DAS) were studied by differential pulse...     

The influence of the zone's indoor temperature settings on the cooling/heating loads for fixed and controlled ventilation

In this study, the thermal performance and the energy requirements of a building single-zone are investigated for both the cooling and heating seasons by employing a thermal-network model. The model has six primary heat-flow paths, in order to take into account the position of insulation in the building envelope, and two secondary paths for the ventilation and the cooling/heating unit. The desired indoor temperature of the zone is defined by a pair of preset points of a thermostat. The energy demands and the resulting indoor temperature variations are determined for fixed ventilation as well as for temperature-controlled ventilation. Computer results for both seasons show how the combined influence of slab structure formations, the desired indoor temperature and ventilation control affect the cooling and heating loads.     

Optical absorption spectrum of Co(NH4)2 (BeF4)2.6H2O complex

Optical absorption spectrum of ammonium cobalt orthofluoroberyllate hexahydrate has been investigated at the laboratory and liquid nitrogen temperatures. The gross features of the observed spectrum are characteristic of divalent cobalt ion in an octahedral field. Splittings of some of the bands at liquid nitrogen temperature are explained as due to an orthorhombic distortion.     

Effect of Co Addition on the Microstructure, Martensitic Transformation and Shape Memory Behavior of Fe-Mn-Si Alloys

The effect of Co addition has been studied in Fe-30Mn-6Si-xCo (x = 0 to 9 wt pct) shape memory alloys in terms of their microstructure, martensitic transformation and shape recovery. Microstructural investigations reveal that in Fe-Mn-Si-Co alloys, the microstructure remains single-phase austenite (??) up to 5 pct Co and beyond that becomes two-phase comprising ?? and off-stoichiometric (Fe,Co)₅Mn₃Si₂ intermetallic ??-phases. The forward ??-?? martensite transformation start temperature (M _S) decreases with the addition of Co up to 5 pct, and alloys containing more than 5 pct Co, show slightly higher M _S possibly on account of two-phase microstructure. Unlike M _S, the ??-?? reverse transformation start temperature (A _S) has been found to remain almost unaltered by Co addition. In general, addition of Co to Fe-Mn-Si alloys deteriorates shape recovery due to decreasing resistance to plastic yielding concomitant with the formation of stress induced ?? martensite. However, there is an improvement in shape recovery beyond 5 pct Co addition, possibly due to the strengthening effect arising from the presence of (Fe,Co)₅Mn₃Si₂ precipitates within the two-phase microstructure and due to higher amount of stress induced ?? martensite.     

Characteristics of an absolutely calibrated flat-field extreme ultraviolet spectrometer in the 10-130 A range for fusion plasma diagnostics

A flat-field extreme ultraviolet (EUV) spectrometer with a nominal 2400 grooves/mm aberration-corrected ruled grating has been developed to analyze the emission spectrum in the wavelength range of 10 to 130 A from large helical device (LHD) plasmas. Spectral properties such as resolution, sensitivity, contribution of higher-order light, and background stray light have been studied using emission spectra mainly from intrinsic impurities, e.g., C and Fe. It is found that the spectrometer well resolves closely existing spectral lines of highly ionized medium- and high-Z impurities even in a very short wavelength range such as 10 to 20 A. As a result, it allows one to study the charge state distribution of elements in high-temperature fusion plasma. The ruled grating was then replaced by a laminar type holographic grating for the comparative study. The spectral resolution for the ruled grating (Dlambda approximately 0.08 A at 33.73 A) is clearly better than the holographic grating (Dlambda approximately 0.13 A at 33.73 A). Both gratings well suppress the higher-order light, e.g., the second-order light is only less than 11% of the first-order light for C vi(33.73 A). Relative sensitivity calibration with the wavelength has been done using bremsstrahlung continuum from the LHD plasmas. Absolute intensity calibration has been done by comparing the spectral intensities directly with the absolutely calibrated 1200 grooves/mm EUV spectrometer in the overlapping range of 90-120 A due to the absence of a good branching pair in 10-130 A. As a typical result on the present spectrometer well-resolved n=2-3 full transition arrays from Ne- to Li-like ions are measured for Fe and Ti and wavelengths of the spectral array are tabulated for each charge state. Spectroscopic comparison is also made between the 1200 grooves/mm and 2400 grooves/mm gratings in a range of 50-130 A.     

α-Glucosidase and α-amylase inhibitory constituent of Carex baccans: Bio-assay guided isolation and quantification by validated RP-HPLC–DAD

Carex baccans is used extensively as food additive for its medicinal and nutritional properties. Its extract demonstrated significant inhibition of α-glucosidase and α-amylase with IC₅₀ 43.32 ± 1.22 and 562.18 ± 5.98 μg/mL, respectively. A bio-assay guided approach was employed to identify the active constituent(s). Fractionation and purification of the extract led to the isolation of a potent inhibitor, (+)-α-viniferin, and of weak inhibitors smiglasides A and B. (+)-α-Viniferin was quantified in the extract and fractions using HPLC and the method was validated for linearity, limit of detection, limit of quantification, precision, and accuracy. The calibration curve showed good linearity (r² > 0.999) in the range of 7.813–250 μg/mL. The identification of α-glucosidase and α-amylase inhibitory activity in C. baccans supports the possible use of the plant as functional food for the management of diabetes. The validated HPLC method for the study of plant extracts will be useful in future research.     

The corrosion behaviour of Fe-15Mn-7Si-9Cr-5Ni shape memory alloy

The corrosion behaviour of Fe-15Mn-7Si-9Cr-5Ni (mass%) shape memory alloy at 25 °C in 0.5 M H₂SO₄ and 3.5% NaCl solutions has been studied using potentiodynamic polarization and electrochemical impedance techniques. Three different microstructures viz., single-phase γ, γ-δ and γ-Fe₅Ni₃Si₂, were produced by heat-treating the alloy in different equilibrium phase fields. The corrosion behaviour in 0.5 M H₂SO₄ solution is almost same for all three microstructures, barring a slight difference in the passivation range. Although, the passivation current in 0.5 M H₂SO₄, is in the same range as that of SS 304, the critical current required for onset of passivation is almost three orders higher and the passivation range is much shorter. In 3.5% NaCl solution the corrosion behaviour of all three microstructures of the Fe-15Mn-7Si-9Cr-5Ni shape memory alloy was that of general dissolution without passivity or localized attack (pitting). The best corrosion resistance in both H₂SO₄ and NaCl solutions is shown by the single-phase γ microstructure.     

Measurement of probe displacement to the thermal resolution limit in photonic force microscopy using a miniature quadrant photodetector

A photonic force microscope comprises of an optically trapped micro-probe and a position detection system to track the motion of the probe. Signal collection for motion detection is often carried out using the backscattered light off the probe-however, this mode has problems of low S/N due to the small backscattering cross sections of the micro-probes typically used. The position sensors often used in these cases are quadrant photodetectors. To ensure maximum sensitivity of such detectors, it would help if the detector size matched with the detection beam radius after the condenser lens (which for backscattered detection would be the trapping objective itself). To suit this condition, we have used a miniature displacement sensor whose dimensions makes it ideal to work with 1:1 images of micrometer-sized trapped probes in the backscattering detection mode. The detector is based on the quadrant photo-integrated chip in the optical pick-up head of a compact disc player. Using this detector, we measured absolute displacements of an optically trapped 1.1 μm probe with a resolution of ～10 nm for a bandwidth of 10 Hz at 95% significance without any sample or laser stabilization. We characterized our optical trap for different sized probes by measuring the power spectrum for each probe to 1% accuracy, and found that for 1.1 μm diameter probes, the noise in our position measurement matched the thermal resolution limit for averaging times up to 10 ms. We also achieved a linear response range of around 385 nm with cross talk between axes ?4% for 1.1 μm diameter probes. The detector has extremely high bandwidth (few MHz) and low optical power threshold-other factors that can lead to its widespread use in photonic force microscopy.     

Spectroscopic comparison between 1200 grooves/mm ruled and holographic gratings of a flat-field spectrometer and its absolute sensitivity calibration using bremsstrahlung continuum

A flat-field extreme ultraviolet (EUV) spectrometer with a varied line spacing groove grating (1200 grooves/mm at grating center) has been developed to study the emission spectra from highly ionized medium Z impurities in large helical device (LHD). It covers a wavelength range of 50-500 A using a mechanically ruled grating, which was later replaced by a newly developed laminar-type holographic grating for comparative studies. Differences in spectral resolution, intensities of higher order spectra, and sensitivities of the spectrometer were studied between the two gratings by observing the emission spectra of LHD plasmas. Although the achieved resolution was alike between them, i.e., deltalambda approximately 0.24 A at 200 A, the holographic grating was much superior in suppressing the higher order light than the ruled grating. The relative sensitivity between the two gratings was evaluated using continuum radiation from LHD plasmas. As a result, it was found that the holographic grating has a flat response in the full wavelength range, but the sensitivity of the ruled grating drops sharply below 200 A. A new technique for the absolute calibration of the EUV holographic grating spectrometer was tried by combining the continuum radiation with a branching ratio of C IV lines (3p-3s: 5800 A/3p-2s: 312 A), and an accurate absolute sensitivity has been successfully obtained.     

Microarrays assembled in microfluidic chips fabricated from poly(methyl methacrylate) for the detection of low-abundant DNA mutations

Low-density arrays were assembled into microfluidic channels hot-embossed in poly(methyl methacrylate) (PMMA) to allow the detection of low-abundant mutations in gene fragments (K-ras) that carry point mutations with high diagnostic value for colorectal cancers. Following spotting, the chip was assembled with a cover plate and the array accessed using microfluidics in order to enhance the kinetics associated with hybridization. The array was configured with zip code sequences (24-mers) that were complementary to sequences present on the target. The hybridization targets were generated using an allele-specific ligase detection reaction (LDR), in which two primers (discriminating primer that carriers the complement base to the mutation being interrogated and a common primer) that flank the point mutation and were ligated joined together) only when the particular mutation was present in the genomic DNA. The discriminating primer contained on its 5'-end the zip code complement (directs the LDR product to the appropriate site of the array), and the common primer carried on its 3' end a fluorescent dye (near-IR dye IRD-800). The coupling chemistry (5'-amine-containing oligonucleotide tethered to PMMA surface) was optimized to maximize the loading level of the zip code oligonucleotide, improve hybridization sensitivity (detection of low-abundant mutant DNAs in high copy numbers of normal sequences), and increase the stability of the linkage chemistry to permit re-interrogation of the array. It was found that microfluidic addressing of the array reduced the hybridization time from 3 h for a conventional array to less than 1 min. In addition, the coupling chemistry allowed reuse of the array > 12 times before noticing significant loss of hybridization signal. The array was used to detect a point mutation in a K-ras oncogene at a level of 1 mutant DNA in 10,000 wild-type sequences.