Precise measurement of the line width of the photoassociation spectra of ultracold molecules by using a frequency shifter

We propose a technique to precisely measure the line width of the photoassociation spectra of the excited cesium molecule by using a frequency shifter to generate two laser beams with a precise frequency difference. A series of photoassociation (PA) spectra are recorded with two laser beam induced molecular lines, whose peak separation serves as an accurate frequency ruler to measure the line width of the PA spectra. The full width half maximum line width was studied as a function of PA laser intensity. The extrapolated value at zero laser intensity is (34.84 ± 0.22) MHz. By analyzing other broadening mechanisms, a value of (32.02 ± 0.70) MHz was deduced. It is shown that this scheme is inexpensive, simple, robust, and is promising for applications in a variety of other atomic species.     

Permeability of R6G across Cx43 hemichannels through a novel combination of patch clamp and surface enhanced Raman spectroscopy

We have measured the permeability of rhodamine-6G across Cx43 hemichannels reconstituted on a pipette tip. Cx43 hemichannels were overexpressed in Sf9 cells, and affinity-purified. The hemichannels were reconstituted in a lipid bilayer on a pipette tip by the tip-dip method. R6G in the pipette permeated across the channels into the bath. The permeability of R6G was quantified by measuring R6G concentration in the bath after several hours by surface enhanced Raman spectroscopy (SERS) with 100 nm silver colloid particles. The ratio of the permeability of dye to salt, as extracted by this combined electrical-SERS technique, is compatible with similar ratios for other dyes across whole gap junction channels. The results for the permeability ratio were further compared to fluorescence measurements. The novel combination of patch and SERS techniques can be extended to quantifying the transport of biologically significant non-fluorescent molecules, such as cAMP and IP3, across 1 nm sized pores, such as the gap junction channel.     

Effects of preheating on diaspore: Modifications in colour centres, structure and light emission

The thermal properties and thermal stability of diaspore-corundum (AlOOH-Al₂O₃), from Goian (Pontevedra, Spain) were studied by means of differential thermal analysis (DTA), thermogravimetry (TG), high temperature X-ray diffraction (HTXRD) and thermally stimulated luminescence (TL) techniques. The samples were annealed to link the combined effect of (i) dehydroxylation, (ii) oxidation-reduction of chromophores (Mn 0.5%, Fe₂O₃ 0.12%, TiO₂ 0.021% and Cr 80 ppm) determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and (iii) phase transitions whilst sample heating (i.e. α-AlOOH→α′-Al₂P₃→α-Al₂O₃). The blue colour of diaspore, attributed to the Ti⁴⁺-Fe²⁺ intervalence-charge-transfer mechanism, turns to white (circa 500 °C) in good agreement with the DTA endothermic peak (dehydroxylation). The coexistence of α-AlOOH and α′-Al₂P₃ phases has been detected by in situ HTXRD and could be correlated to the thermoluminescence tests performed on preheated aliquots (up to 500 °C).     

Enhancement of electrical properties due to Cr substitution in Co-ferrite nanoparticles synthesized by two chemical techniques

Nanocrystalline cobalt ferrites with nominal composition CoCr_xFe_2−xO₄ ranging from x=0.0 to 0.5 with step increment of 0.25 were prepared by sol–gel auto combustion and chemical co-precipitation techniques. A comparative study of structural, electrical and magnetic properties of these ferrites has been measured using different characterization techniques. Structural and micro-structural studies were measured using X-ray diffraction, Fourier transform infra-red spectroscopy (FTIR), scanning electron microscopy and atomic force microscopy. Crystallite sizes of the series are within the range of 12–29±2 nm. Lattice parameters decrease by increasing Cr³⁺ concentration. FTIR confirms the presence of two lattice absorption bands. DC electrical resistivity increases to a value of ∼10¹⁰ Ω-cm with increase in Cr³⁺ concentration, but the most significant increase is in samples prepared by sol–gel combustion. Dielectric properties have been measured as a function of frequency at room temperature. Dielectric loss decreases to 0.1037 and 0.0108 at 5 MHz for chemical co-precipitation and sol–gel combustion, respectively. Impedance measurements further helped in analyzing the electrical properties and to separate the grain and grain boundary resistance effects using a complex impedance analysis. Magnetic parameters were studied using a vibrating sample magnetometer in the applied field of 10 kOe. The saturation magnetization decreased from 63 to 10.8 emu/gm with increase in Cr³⁺ concentration.     

Use of hyperpolarized [1-C]pyruvate and [2-C]pyruvate to probe the effects of the anticancer agent dichloroacetate on mitochondrial metabolism in vivo in the normal rat

Development of hyperpolarized technology utilizing dynamic nuclear polarization has enabled the measurement of ¹³C metabolism in vivo at very high signal-to-noise ratio (SNR). In vivo mitochondrial metabolism can, in principle, be monitored with pyruvate, which is catalyzed to acetyl-CoA via pyruvate dehydrogenase (PDH). The purpose of this work was to determine whether the compound sodium dichloroacetate (DCA) could aid the study of mitochondrial metabolism with hyperpolarized pyruvate. DCA stimulates PDH by inhibiting its inhibitor, pyruvate dehydrogenase kinase. In this work, hyperpolarized [1-¹³C]pyruvate and [2-¹³C]pyruvate were used to probe mitochondrial metabolism in normal rats. Increased conversion to bicarbonate (+ 181±69%, P=.025) was measured when [1-¹³C]pyruvate was injected after DCA administration, and increased glutamate (+ 74±23%, P=.004), acetoacetate (+ 504±281%, P=.009) and acetylcarnitine (+ 377±157%, P=.003) were detected when [2-¹³C]pyruvate was used.     

Interaction of the docetaxel with human serum albumin using optical spectroscopy methods

Docetaxel is a semi-synthetic product derived from the needles of the European yew. It is an antineoplastic agent belonging to the taxoid family. The interaction between docetaxel and human serum albumin (HSA) has been investigated systematically by the fluorescence quenching technique, synchronous fluorescence spectroscopy, ultraviolet (UV)-vis absorption spectroscopy, circular dichroism (CD) spectroscopy and Fourier transform infrared (FT-IR) under physiological conditions. Our fluorescence data showed that HSA had only one docetaxel binding site and the binding process was a static quenching procedure. According to the Van’t Hoff equation, the thermodynamic parameters standard enthalpy (ΔH⁰) and standard entropy (ΔS⁰) were calculated to be −41.07 KJ mol⁻¹ and −49.72 J mol⁻¹ K⁻¹. These results suggested that hydrogen bond was the predominant intermolecular force stabling the docetaxel-HSA complex. The data from the CD, FT-IR and UV-vis spectroscopy supported the change in the secondary structure of protein caused by the interaction of docetaxel with HSA.     

Experimental low energy values of CH4 transitions near 1.33 μm by absorption spectroscopy at 81 K

The high resolution absorption spectrum of methane has been recorded at liquid nitrogen temperature by direct absorption spectroscopy between 1.36 and 1.30 μm (7351-7655 cm⁻¹) using a cryogenic cell and a series of distributed feed back (DFB) diode lasers. The investigated spectral range corresponds to the high energy part of the icosad dominated by the ν₂+2ν₃ band near 7510 cm⁻¹. The positions and strengths at 81 K of 3473 transitions were obtained from the spectrum analysis. The minimum value of the measured line intensities (at 81 K) is on the order of 10⁻²⁶ cm/molecule, i.e. significantly lower than the intensity cut off of the HITRAN database in the region (4×10⁻²⁵ cm/molecule at 296 K). From the variation of the line strength between 81 and 296 K, the low energy values of 1273 transitions could be determined. They represent 69% and 81% of the absorbance in the region at 296 and 81 K, respectively. The obtained results are discussed in relation with the few rovibrational assignments previously reported in the region.     

Microbial Reduction of Lepidocrocite γ-FeOOH by Shewanella putrefaciens; The Formation of Green Rust

Dissimilatory iron-reducing bacteria (DIRB) couple the oxidation of organic matter or H₂ to the reduction of iron oxides. The bacterial reduction of a most common well-crystallised ferric oxyhydroxide, -FeOOH was investigated using DIRB Shewanella putrefaciens, strain CIP 8040. Experiments were conducted in the presence of neither organic buffer nor phosphate, with formate as electron donor, bicarbonate, and anthraquinone-2,6-disulfonate (AQDS, a humic acid analogue) that influenced the extent of ferric oxide bioreduction. The production of Fe²⁺ was followed with time. The solid phases obtained after bacterial iron reduction were analysed by transmission Mössbauer spectroscopy (TMS) and X-ray diffraction (XRD). Biogenic formation of green rust 1 compound, which contains carbonate anions, [Fe^II ₂Fe^III ₂(OH)₈]²⁺[CO₃ ^2–]^2– was observed. TMS was used to follow the evolution of the green rust abundance during the bacterial culture.     

Effect of Precipitation Temperature and Number of Iron Atoms per Molecule on the Structure of Hydrated Iron(III) Oxyhydroxide Ferritin Cores Synthesised in vitro

Hyperfine Interactions - Horse spleen apoferritin was reconstituted with varying numbers of iron atoms per protein shell at 25 and 50°C. Samples with mean particle sizes ranging from...