Spectroscopic tests of a 2.3 μm tunable diode laser

A 2.3 μm near-room temperature tunable diode laser was tested for applications in high-resolution laboratory spectroscopy. It was mounted using a simple adaptor in a spectrometer usually used with lead-salt diode lasers, and was found to be electrically and optically compatible with the system. Good output power (several milliwatts) was observed, and a tuning range of 4460–4150 cm⁻¹ was achieved for laser temperatures of 210–310 K. Some spectra of N₂O and NH₃ were recorded in the 4300–4430 cm⁻¹ region. However, the laser was not generally useful due to noisy and unstable output and high sensitivity to optical feedback.     

Guest-mediated phase transitions in a flexible pillared-layered metal–organic framework under high-pressure

The guest-dependent flexibility of the pillared-layered metal–organic framework (MOF), Zn₂bdc₂dabco·X(guest), where guest = EtOH, DMF or benzene, has been examined by high-pressure single crystal X-ray diffraction. A pressure-induced structural phase transition is found for the EtOH- and DMF-included frameworks during compression in a hydrostatic medium of the guest species, which is dependent upon the nature and quantity of the guest in the channels. The EtOH-included material undergoes a phase transition from P4/mmm to C2/m at 0.69 GPa, which is accompanied by a change in the pore shape from square to rhombus via super-filling of the pores. The DMF-included material undergoes a guest-mediated phase transition from I4/mcm to P4/mmm at 0.33 GPa via disordering of the DMF guest. In contrast, the benzene-included framework features a structure with rhombus-shaped channels at ambient pressure and shows direct compression under hydrostatic pressure. These results demonstrate the large influence of guest molecules on the high-pressure phase behavior of flexible MOFs. Guest-mediated framework flexibility is useful for engineering MOFs with bespoke pore shapes and compressibility.

The guest-dependent flexibility of the pillared-layered metal–organic framework (MOF), Zn₂bdc₂dabco·X(guest), where guest = EtOH, DMF or benzene, has been examined by high-pressure single crystal X-ray diffraction.     

KaonB parameter with static cavity QCD corrections

The kaonB parameter is computed in a framework in which static cavity QCD loop corrections to the weak interactions of hadrons are included by extending the Fock state wavefunction to includeO(g) bremsstrahlung and vacuum fluctuation states. Since the QCD corrections are inherent in the calculation of the matrix elements of the bare effective weak ΔS=2 Hamiltonian between hadronic states the scale matching problem of the standard short distance analysis is alleviated. The modified static cavity model used is characterised by four parameters; the effective quarkgluon coupling constant, the confinement pressure, the zero-point energy and a parameter governing the centre-of-mass corrections. These parameters are fitted to the π and ? masses and the charge radii of π andK. Results are given for the ultra-relativistic (m _u=m _d=0) sector and for a region (m _u=m _d≈140 MeV) where the ΔI=1/2 rule is uniquely reproduced. For the parameter set which describes the ΔI=1/2 rule we findB _K=0.58 at a basis size ofN _B=6.     

Efficient delivery of Cre-recombinase to neurons in vivo and stable transduction of neurons using adeno-associated and lentiviral vectors

Background

As development proceeds the human embryo attains an ever more complex three dimensional (3D) structure. Analyzing the gene expression patterns that underlie these changes and interpreting their significance depends on identifying the anatomical structures to which they map and following these patterns in developing 3D structures over time. The difficulty of this task greatly increases as more gene expression patterns are added, particularly in organs with complex 3D structures such as the brain. Optical Projection Tomography (OPT) is a new technology which has been developed for rapidly generating digital 3D models of intact specimens. We have assessed the resolution of unstained neuronal structures within a Carnegie Stage (CS)17 OPT model and tested its use as a framework onto which anatomical structures can be defined and gene expression data mapped.

Results

Resolution of the OPT models was assessed by comparison of digital sections with physical sections stained, either with haematoxylin and eosin (H&E) or by immunocytochemistry for GAP43 or PAX6, to identify specific anatomical features. Despite the 3D models being of unstained tissue, peripheral nervous system structures from the trigeminal ganglion (~300 μm by ~150 μm) to the rootlets of cranial nerve XII (~20 μm in diameter) were clearly identifiable, as were structures in the developing neural tube such as the zona limitans intrathalamica (core is ~30 μm thick). Fourteen anatomical domains have been identified and visualised within the CS17 model. Two 3D gene expression domains, known to be defined by Pax6 expression in the mouse, were clearly visible when PAX6 data from 2D sections were mapped to the CS17 model. The feasibility of applying the OPT technology to all stages from CS12 to CS23, which encompasses the major period of organogenesis for the human developing central nervous system, was successfully demonstrated.

Conclusion

In the CS17 model considerable detail is visible within the developing nervous system at a minimum resolution of ~20 μm and 3D anatomical and gene expression domains can be defined and visualised successfully. The OPT models and accompanying technologies for manipulating them provide a powerful approach to visualising and analysing gene expression and morphology during early human brain development.     

High resolution infrared spectra of H2-Kr and D2-Kr van der Waals complexes

Infrared spectra of weakly bound hydrogen-krypton complexes have been studied at high spectral resolution (0.04 cm(-1)) using a long-path (154 m) low temperature (100 K) absorption cell and a Fourier transform spectrometer. In addition to spectra from the regions of the H(2) and D(2) fundamental vibrational bands in the midinfrared, the results also include the region of the pure rotational S(0)(0) transition of H(2) in the far infrared. A total of 219 measured line positions from these spectra have been fully assigned to specific quantum transitions and form the basis for determining a greatly improved semiempirical three-dimensional intermolecular potential energy surface for hydrogen-krypton in an accompanying paper.     

The πNN vertex function and off-mass-shell πN scattering

We have extended the dispersion relation calculation of the πNN vertex function to include off-shell terms in the πN scattering matrix. These off-shell terms are constrained by the current algebra and PCAC results, and contribute to the $\text{N}\text{N}\text{→ ππ}$ s-wave. As such, they add to the kinematic off-shell effects which Durso, Jackson and VerWest found in the p-terms. The off-shell terms increase the calculated Goldberger-Treiman discrepancy from 0.02 to 0.03, bringing it into agreement with the field theory value of Jones and Scadron (0.035). The calculated discrepancy remains smaller than the experimental value of 0.06±0.01.     

Kinetics of chloroplast-mediated photoxidation of diketogluonate

Abstract— Illuminated chloroplasts can mediate a photoxidation of diketogulonic acid (DKGA) with rates of oxygen uptake equivalent to rates of Hill reactions with ferricyanide or quinone. The photoxidation of DKGA is sensitive to dichlorophenyl dimethylurea (DCMU) and exhibits the drop in quantum yield at long wavelengths characteristic of photosystem II. Still, the reaction is only partially inactivated by heating chloroplasts at 50° for 10 min (which destroys oxygen evolution). The photoxidation is inhibited by copper and detergents; and is stimulated by added flavin (or methyl viologen) and manganous ions. A model system containing Mn³⁺ (as manganipyrophosphate) and DKGA, mimics the chloroplast system. Pre-illuminated chloroplast suspensions can be substituted for Mn³⁺ in the model dark reaction. It seems that a light-dependent oxidation of Mn²⁺ to Mn³⁺ by photosystem II is the essential contribution of the chloroplasts. Electrons from Mn²⁺ move through the electron transport system to ferricyanide or to photosystem I where, via flavin (or methyl viologen), oxygen is reduced to H₂O₂.     

Positive integer solutions of the diophantine equation x 2 − L n xy + (−1) n y 2 = ±5 r

In this paper, we consider the equation x ²?L _n x y+(?1) ⁿ y ² = ±5 ^r and determine the values of n for which the equation has positive integer solutions x and y. Moreover, we give all positive integer solutions of the equation x ²?L _n x y+(?1) ⁿ y ² = ±5 ^r when the equation has positive integer solutions.