33 research outputs found
A combined first and second order variational approach for image reconstruction
In this paper we study a variational problem in the space of functions of
bounded Hessian. Our model constitutes a straightforward higher-order extension
of the well known ROF functional (total variation minimisation) to which we add
a non-smooth second order regulariser. It combines convex functions of the
total variation and the total variation of the first derivatives. In what
follows, we prove existence and uniqueness of minimisers of the combined model
and present the numerical solution of the corresponding discretised problem by
employing the split Bregman method. The paper is furnished with applications of
our model to image denoising, deblurring as well as image inpainting. The
obtained numerical results are compared with results obtained from total
generalised variation (TGV), infimal convolution and Euler's elastica, three
other state of the art higher-order models. The numerical discussion confirms
that the proposed higher-order model competes with models of its kind in
avoiding the creation of undesirable artifacts and blocky-like structures in
the reconstructed images -- a known disadvantage of the ROF model -- while
being simple and efficiently numerically solvable.Comment: 34 pages, 89 figure
Evidence for phase formation in potassium intercalated 1,2;8,9-dibenzopentacene
We have prepared potassium intercalated 1,2;8,9-dibenzopentacene films under
vacuum conditions. The evolution of the electronic excitation spectra upon
potassium addition as measured using electron energy-loss spectroscopy clearly
indicate the formation of particular doped phases with compositions
Kdibenzopentacene ( = 1,2,3). Moreover, the stability of these phases as
a function of temperature has been explored. Finally, the electronic excitation
spectra also give insight into the electronic ground state of the potassium
doped 1,2;8,9-dibenzopentacene films.Comment: 6 pages, 5 figures. arXiv admin note: text overlap with
arXiv:1201.200
Sensitivity of the Mott Transition to Non-cubic Splitting of the Orbital Degeneracy: Application to NH3 K3C60
Within dynamical mean-field theory, we study the metal-insulator transition
of a twofold orbitally degenerate Hubbard model as a function of a splitting
\Delta of the degeneracy. The phase diagram in the U-\Delta plane exhibits
two-band and one-band metals, as well as the Mott insulator. The correlated
two-band metal is easily driven to the insulator state by a strikingly weak
splitting \Delta << W of the order of the Kondo-peak width zW, where z << 1 is
the metal quasiparticle weight. The possible relevance of this result to the
insulator-metal transition in the orthorhombic expanded fulleride NH3 K3C60 is
discussed.Comment: revtex, 15 pages including 6 ps figures. Submitted to Phys. Rev.
Characterisation of Mo and V interactions with ferrihydrite as an analogue for deep-sea hydrothermal plumes processes (abstract of paper presented at: 17th Annual V. M. Goldschmidt Conference Cologne, Germany August 2007)
Neuronal Number, Volume, and Apoptosis of the Left Dentate Gyrus of Chronically Stressed Pigs Correlate Negatively With Basal Saliva Cortisol Levels
Although the consequences of stress and hypercortisolemia for the rodent hippocampal dentate gyrus (DG) are well known, little is known about other species. For pigs, tethered housing represents a well-established chronic stressor that shares many similarities with restraint paradigms, as evidenced by profound changes in behavior and autonomic and endocrine dysfunction, including flattened cortisol rhythms and hypercortisolemia all conditions that may threaten hippocampal viability in rat. Here, we studied structural parameters of the porcine DG after 5 months of tethered housing in relation to basal saliva cortisol measured antemortem. We further investigated whether any neuropathology or alterations in apoptosis had occurred in the left hippocampal hemisphere. Stereological analysis revealed high correlations between DG volume and neuron number in individual animals in both hemispheres. Within individual animals, neuron numbers of the left and right lobes were not correlated. Notably, basal cortisol was negatively correlated with volume and neuron number of the left, but not the right DG. Although obvious neuropathology was absent, apoptosis was present in DG and alveus and less so in CA areas. Despite the short window of time during which apoptosis is detectable, their stereologically estimated numbers in the DG, but not in other regions, were negatively correlated with cortisol. In conclusion, our data indicate for the first time a profound lateralization in the relationship between DG structure, apoptosis, and basal cortisol after stress in pigs. Five months of chronic stress failed to induce lasting neuropathology. Although accumulating changes in apoptosis could have contributed to the structural DG alterations, further studies should reveal whether stress has been instrumental, or whether the differences between animals were present from birth onward. The present lateralization after stress is, however, consistent with lateralized hippocampal volume changes in stress-related human disorders and suggests that these effects are not limited to this species alone
Neuronal Number, Volume, and Apoptosis of the Left Dentate Gyrus of Chronically Stressed Pigs Correlate Negatively With Basal Saliva Cortisol Levels
Although the consequences of stress and hypercortisolemia for the rodent hippocampal dentate gyrus (DG) are well known, little is known about other species. For pigs, tethered housing represents a well-established chronic stressor that shares many similarities with restraint paradigms, as evidenced by profound changes in behavior and autonomic and endocrine dysfunction, including flattened cortisol rhythms and hypercortisolemia all conditions that may threaten hippocampal viability in rat. Here, we studied structural parameters of the porcine DG after 5 months of tethered housing in relation to basal saliva cortisol measured antemortem. We further investigated whether any neuropathology or alterations in apoptosis had occurred in the left hippocampal hemisphere. Stereological analysis revealed high correlations between DG volume and neuron number in individual animals in both hemispheres. Within individual animals, neuron numbers of the left and right lobes were not correlated. Notably, basal cortisol was negatively correlated with volume and neuron number of the left, but not the right DG. Although obvious neuropathology was absent, apoptosis was present in DG and alveus and less so in CA areas. Despite the short window of time during which apoptosis is detectable, their stereologically estimated numbers in the DG, but not in other regions, were negatively correlated with cortisol. In conclusion, our data indicate for the first time a profound lateralization in the relationship between DG structure, apoptosis, and basal cortisol after stress in pigs. Five months of chronic stress failed to induce lasting neuropathology. Although accumulating changes in apoptosis could have contributed to the structural DG alterations, further studies should reveal whether stress has been instrumental, or whether the differences between animals were present from birth onward. The present lateralization after stress is, however, consistent with lateralized hippocampal volume changes in stress-related human disorders and suggests that these effects are not limited to this species alone
Neuronal number, volume, and apoptosis of the left dentate gyrus of chronically stressed pigs correlate negatively with basal saliva cortisol levels
Prediction of sweet pepper (Capsicum annuum) flavour over different harvests
To better understand and predict the complex multifactorial trait flavor, volatile and non-volatile components were measured in fresh sweet pepper (Capsicum annuum) fruits throughout the growing season in a diverse panel of 24 breeding lines, hybrids, several cultivated genotypes and one gene bank accession. Biochemical profiles were linked to individual flavor attributes, that were objectively quantified by a trained descriptive expert panel. We used a Random Forest regression approach for prediction of the flavor attributes within and between harvests. Predictions of texture related attributes (juiciness, toughness, crunchiness and stickiness of the skin) and sweetness were good (around 60–65 %in the analyses with the three harvests combined). The predictions of the attributes aroma intensity, sourness and fruity/apple were somewhat lower and more variable between harvests. (E)-2-hexen-1-ol, neopentane, p-menth-1-en-9-al, 3-hepten-2-one, (Z)-b-ocimene, (Z)-2-penten-1-ol, 1-methyl-1,4-cyclohexadiene, glucose, fructose and three unknown volatile compounds were identified as key-metabolites involved in the flavor differences between both genotypes and harvests. The complex nature of flavor is exemplified by the observed masking effect of fructose and other sugars on sourness and sourness related metabolites, like citrate. The knowledge obtained from the overall biochemical, sensory and prediction analyses forms a basis for targeted flavor improvement by breeding
Prediction of sweet pepper (Capsicum annuum) flavour over different harvests
To better understand and predict the complex multifactorial trait flavor, volatile and non-volatile components were measured in fresh sweet pepper (Capsicum annuum) fruits throughout the growing season in a diverse panel of 24 breeding lines, hybrids, several cultivated genotypes and one gene bank accession. Biochemical profiles were linked to individual flavor attributes, that were objectively quantified by a trained descriptive expert panel. We used a Random Forest regression approach for prediction of the flavor attributes within and between harvests. Predictions of texture related attributes (juiciness, toughness, crunchiness and stickiness of the skin) and sweetness were good (around 60–65 %in the analyses with the three harvests combined). The predictions of the attributes aroma intensity, sourness and fruity/apple were somewhat lower and more variable between harvests. (E)-2-hexen-1-ol, neopentane, p-menth-1-en-9-al, 3-hepten-2-one, (Z)-b-ocimene, (Z)-2-penten-1-ol, 1-methyl-1,4-cyclohexadiene, glucose, fructose and three unknown volatile compounds were identified as key-metabolites involved in the flavor differences between both genotypes and harvests. The complex nature of flavor is exemplified by the observed masking effect of fructose and other sugars on sourness and sourness related metabolites, like citrate. The knowledge obtained from the overall biochemical, sensory and prediction analyses forms a basis for targeted flavor improvement by breeding