Critical petermann K factor for intensity noise squeezing

We investigate the impact of the Petermann-excess-noise factor K>/=1 on the possibility of intensity noise squeezing of laser light below the standard quantum limit. Using an N-mode model, we show that squeezing is limited to a floor level of 2(K-1) times the shot noise limit. Thus, even a modest Petermann factor significantly impedes squeezing, which becomes impossible when K>/=1.5. This appears as a serious limitation for obtaining sub-shot-noise light from practical semiconductor lasers. We present experimental evidence for our theory.     

Search for isovector giant monopole resonances via the Pb(3He,tp) reaction

The (nat)Pb(3He,tp) reaction at E(3He) = 177 MeV was studied to identify 2Planck's over 2piomega isovector monopole strength in Bi isotopes. Monopole strength was found in the region -45相似文献   

Creatine kinase B deficient neurons exhibit an increased fraction of motile mitochondria

Background  

Neurons require an elaborate system of intracellular transport to distribute cargo throughout axonal and dendritic projections. Active anterograde and retrograde transport of mitochondria serves in local energy distribution, but at the same time also requires input of ATP. Here we studied whether brain-type creatine kinase (CK-B), a key enzyme for high-energy phosphoryl transfer between ATP and CrP in brain, has an intermediary role in the reciprocal coordination between mitochondrial motility and energy distribution. Therefore, we analysed the impact of brain-type creatine kinase (CK-B) deficiency on transport activity and velocity of mitochondria in primary murine neurons and made a comparison to the fate of amyloid precursor protein (APP) cargo in these cells, using live cell imaging.     

Mass spectra of dimethylpyrimidines

The mass spectra of the four dimethylpyrimidines are compared with those of the isomeric dimethylpyrazines. It was necessary to synthesise three of the dimethylpyrimidines, and methods are described.     

An unexpected γ-hydrogen rearrangement in the mass spectra of di-ortho -substituted alkylbenzenes

In contradiction of long-accepted mass spectrometric dogma, the site-specific γ-hydrogen rearrangement is observed in alkylbenzenes in which both ortho positions are blocked with methyl substituents. Mass spectrometric studies of a series of five trimethyl- and three tetramethylisopentylbenzenes have shown that this rearrangement is only suppressed to a significant degree in those compounds in which all three positions ortho and para to the isopentyl group are blocked. Deuterium labelling has confirmed the γ-site-specific origin of the migrating H atom while metastable studies have been used to investigate the mechanism of the rearrangement process.     

On the stereospecificity of the structurally diagnostic m/z 84 ion in the mass spectra of gibberellins and kaurenes with a 15-hydroxy substituent

The presence of a 15-hydroxy substituent in naturally-occurring kaurenes and gibberellins gives rise to a structurally diagnostic ion at m/z84 (C₅H₈O) in their electron-impact mass spectra, which shifts to m/z156 for the TMS derivative, and is unaffected by differences in the A and B rings. Studies on a model tricyclic system have shown that this ion is more intense when the stereochemistry of the B/C ring junction is cis than when it is trans. In accordance with a previously proposed pathway for the formation of this ion, deuterium labelling confirms that there is a site-specific transfer of the β-hydrogen from the cis ring junction to the C₅ fragment ion, although a minor modification of the earlier mechanism is proposed.     

The toxic extractives from wedelia asperrima—II : The structure of wedeloside,a novel diterpenoid aminoglycoside

From chemical and spectroscopic evidence, the structure of the diterpenoid aglycone of wedeloside is proposed. The position of linkage of the previously described glycosidic moiety is established, allowing the structure of wedeloside to be formulated as (2β, 15α) - 2 - [[2 - deoxy - 2 - (3 - methyl -1 - oxobutyl)amino - 3 - 0- (1 - oxo - 3 - phenylpropyl) - β - D - glucopyranosyl]oxy] - 13, 15-dihydroxykaur -16 - ene - 18,19 - dioic acid.