Measurement of storage time, estimation of ion number and study of absorption line profile in a Paul trap

Europium (Eu⁺) ions were confined in a Paul trap and detected by non-destructive method. Storage time of Eu⁺ ions achieved in vacuum was improved by orders of magnitude employing buffer gas cooling. The experimentally detected signal was fitted to the ion response signal and the total number of ions trapped was estimated. It is found that the peak signal amplitude as well as the product of FWHM and the peak signal amplitude is proportional to the total number of trapped ions. The trapped ion secular frequency was swept at different rates and its effect on the absorption line profile was studied both experimentally and theoretically.     

Quadratic Integrals of Motion for the Systems of Identical Particles

The dynamical systems of identical particles admitting quadratic integrals of motion are classified. The relevant integrals are explicitly constructed and their relation to separation of variables in Hamilton-Jacobi equation is clarified.     

The aquation of hexachlorotechnetate(IV)

The photochemical decomposition of (NH₄)₂TcCl₆ in dilute HCl, HClO₄ and H₂SO₄ solutions has been studied. Electrophoresis and spectrophotometry were used to identify TcCl ₆ ^2? , TcCl₅ (H₂O)^?, cationic and uncharged species and TcO ₄ ^? . The yield of each species as a function of the time of uv irradiation was determined. The TcCl ₆ ^2? , yield decreases to zero after 50 h of irradiation. The TcCl₅(H₂O)^?, cationic and uncharged species and TcO ₄ ^? are formed in different proportions in the three acids. After 120 h of irradiation of the HCl solution the principal Tc species was the cationic one (≈70%) followed by the uncharged species (≈24%). In HClO₄ solution the cationic species (≈70%) was followed by TcO ₄ ^? , but in H₂SO₄ solution the uncharged species amounts to ≈90%.     

Soliton self-frequency shift in a short tapered air-silica microstructure fiber

We report a soliton self-frequency shift of more than 20% of the optical frequency in a tapered air-silica microstructure fiber that exhibits a widely flattened large anomalous dispersion in the near infrared. Remarkably, the large frequency shift was realized in a fiber of length as short as 15 cm, 2 orders of magnitude shorter than those reported previously with similar input pulse duration and pulse energies, owing to the small mode size and the large and uniform dispersion in the tapered fiber. By varying the power of the input pulses, we generated compressed sub-100-fs soliton pulses of ~1-nJ pulse energy tunable from 1.3 to 1.65 mum with greater than 60% conversion efficiency.     

Correction: Dermatan sulfate in tunicate phylogeny: Order-specific sulfation pattern and the effect of [→4IdoA(2-Sulfate)β-1→3GalNAc(4-Sulfate)β-1→] motifs in dermatan sulfate on heparin cofactor II activity

After the publication of the work entitled "Dermatan sulfate in tunicate phylogeny: Order-specific sulfation pattern and the effect of [→4IdoA(2-Sulfate)β-1→3GalNAc(4-Sulfate)β-1→] motifs in dermatan sulfate on heparin cofactor II activity", by Kozlowski et al., BMC Biochemistry 2011, 12:29, we found that the legends to Figures 2 to 5 contain serious mistakes that compromise the comprehension of the work. This correction article contains the correct text of the legends to Figures 2 to 5.     

Vibrational spectra and force constants calculations of the isotopic species of MgCaSiO4

FT-IR and Raman spectra in room and liquid N₂ temperature have been recorded for the isotopic species of the monticellite. The band assignments have been deduced from ²⁴Mg –²⁶Mg, ⁴⁰Ca –⁴⁴Ca and ²⁸Si –³⁰Si isotopic shifts. Based on these data isotopically adjusted GVFF force constants have been calculated with different models (unit cell, isolated SiO₄ anion with C point symmetry). Force constants for izomorphic Mg₂SiO₄ and α-C^sa₂SiO₄ structures have been also obtained.     

Rheological properties of poly(dimethylsiloxane) filled with fumed silica: II. Stress relaxation and stress growth

The steady-state viscosity, stress relaxation, and stress growth function were measured for a 3.0% by weight dispersion of fumed silica in poly(dimethylsiloxane); using a two-step shear rate history. For short rest times the stress growth function η⁺ increased monotonically towards steady-state, while at long rest times η⁺ exhibited large overshoot followed by a monotonic decrease to steady-state. For intermediate rest times η⁺ exhibited more complicated transient behaviour. The effect of both shear rates in the two-step shear-rate history on η⁺ have been studied, and the resulting rheological behaviour is discussed in terms of phenomenological microstructural models.     

A note on the asymptotic expansion of Feynman amplitudes

Employing the technique given by Bergere and Lam, we determine the asymptotic expansion of Feynman amplitude (in the Schwinger integral representation) when the masses of any subset of internal lines tend to zero.     

The effect of molecular weight on the rheological properties of poly(dimethylsiloxane) filled with fumed silica

The viscometric, stress relaxation, and stress growth rheological properties were measured for various molecular weight PDMS fluids filled with fumed silica. The stress growth function exhibited significant overshoot, when the continuous phase molecular weight was slightly greater than the entanglement molecular weight; however, significant overshoot peaks were not observed, when the continuous phase molecular weight was less than or much greater than the molecular weight between entanglements. The experimentally observed transient rheological properties are rationalized in terms of a molecular model, where interparticle interactions occur via entanglements of the polymer adsorbed on the silica surface. When the molecular weight of the adsorbed polymer is greater than the entanglement molecular weight, the strength of the interparticle interaction will increase substantially and the particle diffusivity will substantially decrease.