A determination of the Cabibbo-Kobayashi-Maskawa parameter |V us| using KL decays

We present a determination of the Cabibbo-Kobayashi-Maskawa parameter |V(us)| based on new measurements of the six largest K(L) branching fractions and semileptonic form factors by the KTeV (E832) experiment at Fermilab. We find |V(us)|=0.2252+/-0.0008(KTeV)+/-0.0021(ext), where the errors are from KTeV measurements and from external sources. We also use the measured branching fractions to determine the CP violation parameter |eta(+-)|=(2.228+/-0.005(KTeV)+/-0.009(ext))x10(-3).     

Measurements of the Decay KL-->e+ e- mu+ mu-

The KTeV experiment at Fermilab has isolated a total of 132 events from the rare decay K(L)-->e+ e- mu+ mu-, with an estimated background of 0.8 events. The branching ratio of this mode is determined to be [2.69+/-0.24(stat)+/-0.12(syst)]x10(-9), with a radiative cutoff of M(2)(ee mu mu)/M(2)(K)>0.95. The first measurement using this mode of the parameter alpha from the D'Ambrosio-Isidori-Portolès (DIP) model of the K(L)gamma*gamma* vertex yields a result of -1.59+/-0.37, consistent with values obtained from other decay modes. Because of the limited statistics, no sensitivity is found to the DIP parameter beta. We use this decay mode to set limits on CP and lepton violation.     

Stereoselective synthesis of beta-(chloro)vinylsilanes using a regio- and (E)-stereoselective bis-stannylation of unsymmetrically substituted butadiynes: application to the synthesis of a masked triyne

[reaction: see text] A highly regio- and stereoselective bis-stannylation of unsymmetrically substituted butadiyne 3 provides bis-stannane 4. Selective lithiation of the internal tin residue effects a 1,4-retro-Brook rearrangement to afford vinylsilane 5. This was elaborated into the novel diethynylethene 1, which also functions as a masked triyne.     

Difluoromethylene analogues of aspartyl phosphate: the first synthetic inhibitors of aspartate semi-aldehyde dehydrogenase

The difluoromethylene analogue of aspartyl phosphate 6 has been prepared by the fluoride catalysed coupling of diethyl trimethylsilyldifluoromethyl phosphonate with an appropriate aldehyde followed by Dess-Martin oxidation and deprotection; the deprotected compound inhibited (KI 95 microM) aspartate semi-aldehyde dehydrogenase, a key enzyme involved in bacterial amino acid and peptidoglycan biosynthesis.     

Local complete intersections in and Koszul syzygies

We study the syzygies of a codimension two ideal . Our main result is that the module of syzygies vanishing (scheme-theoretically) at the zero locus is generated by the Koszul syzygies iff is a local complete intersection. The proof uses a characterization of complete intersections due to Herzog. When is saturated, we relate our theorem to results of Weyman and Simis and Vasconcelos. We conclude with an example of how our theorem fails for four generated local complete intersections in and we discuss generalizations to higher dimensions.

     

Visualisation of mitochondria in living neurons with single- and two-photon fluorescence laser microscopy

In this work we investigated the relative merits of conventional single-photon confocal laser scanning fluorescence microscopy (CLSM) and two-photon laser scanning fluorescence microscopy (2p-LSM) for the study of mitochondria in living neurons. Dorsal root ganglion neurons were loaded with the mitochondrion-specific fluorescent dye JC-1, the ratio between red (J-aggregates) and green (monomer) fluorescence of which reflects mitochondrial membrane potential. Cells were illuminated at 488 nm for single-photon excitation or at 870 nm for two-photon excitation. In both modalities we found that mitochondria showed: (i) similar appearance; (ii) similar fluorescence ratio values over both whole cell bodies and individual mitochondria; and (iii) similar responses to mitochondrial uncoupler, which dropped the ratio values by 50%. However, 2p-LSM exhibited several advantages over CLSM: (i) better signal/noise ratio in the green emission channel; (ii) less phototoxicity upon repetitive scanning in the focal plane; and (iii) no significant loss of image quality upon repetitive scans in the z direction. We conclude that, while both techniques enable visualisation of individual mitochondria in living cells, 2p-LSM has significant advantages for physiological work requiring time-lapse experiments or four-dimensional reconstructions of mitochondria.     

Computer-generated, three-dimensional reconstruction of histological parallel serial sections displaying microvascular and glandular structures in human endometrium

This paper describes a technique to develop high-resolution three-dimensional (3D) images of microvasculature structures in curettage, hysterectomy or endometrial resection biopsies using parallel histological serial sections. Employing a labelled streptavidin-biotin-alkaline phosphatase (LSAB(+)) method and visualising by using DAB(+) with the primary antibody, mouse anti human Q-Bend-10, the images were directly digitised from a light microscope into the KS400 Universal Image Processing and Analysis software via a CCD colour camera; binary images of the structures were created and the binary images were exported into VoxBlast 3D rendering software to view still and rotating 3D images on a computer monitor. This in turn enabled hard copies of the full sequence to be printed.     

Origin of the high piezoelectric response in PbZr1-xTixO3

High resolution x-ray powder diffraction measurements on poled PbZr1-xTixO3 (PZT) ceramic samples close to the rhombohedral-tetragonal phase boundary (the so-called morphotropic phase boundary) have shown that for both rhombohedral and tetragonal compositions the piezoelectric elongation of the unit cell does not occur along the polar directions but along those directions associated with the monoclinic distortion. This work provides the first direct evidence for the origin of the very high piezoelectricity in PZT.