1,043 research outputs found
Evidence for breakdown of the DGLAP description in diffractive DIS at HERA
HERA data on diffractive DIS show deviations from twist 2 DGLAP predictions
below GeV at low pomeron , which may reach up to 100%.
These deviations are consistent with higher twists effects extracted from the
saturation model. It is a first direct evidence for the higher twists in DIS.
This finding affects determination of the diffractive parton densities that are
used for the predictions at the LHC.Comment: 5 pages, 2 figures, Based on the talk presented at the conference
Deep-Inelastic Scattering and Related Subjects (DIS2012), Bonn, 201
Evidence of strong higher twist effects in diffractive DIS at HERA at moderate Q2
We study a twist decomposition of diffractive structure functions in the
diffractive deep inelastic scattering (DDIS) at HERA. At low Q2 and at large
energy the data exhibit a strong excess, up to about 100%, above the twist 2
NLO DGLAP description. The excess in consistent with higher twist effects. It
is found, that complementing the DGLAP fit by twist 4 and 6 components of the
GBW saturation model leads to a good description of data at low Q2. We conclude
that the DDIS at HERA provides the first, strong evidence of higher twist
effects in DIS.Comment: 4 pages, 2 PDF figure
Inclusive diffraction in future electron-proton and electron-ion colliders
We analyse the possibilities for the study of inclusive diffraction offered
by future electron--proton/nucleus colliders in the TeV regime, the Large
Hadron-electron Collider as an upgrade of the HL-LHC and the Future Circular
Collider in electron-hadron mode. Compared to collisions at HERA, we find
an extension of the available kinematic range in by a factor of order
and of the maximum by a factor of order for LHeC, while the FCC
version would extend the coverage by a further order of magnitude both in
and . This translates into a range of available momentum fraction of the
diffractive exchange with respect to the hadron (), down to
for a wide range of the momentum fraction of the parton with
respect to the diffractive exchange (). Using the same framework and
methodology employed in previous studies at HERA, considering only the
experimental uncertainties and not those stemming from the functional form of
the initial conditions or other ones of theoretical origin, and under very
conservative assumptions for the luminosities and systematic errors, we find an
improvement in the extraction of diffractive parton densities from fits to
reduced cross sections for inclusive coherent diffraction in by about an
order of magnitude. For , we also perform the simulations for the Electron
Ion Collider. We find that an extraction of the currently unmeasured nuclear
diffractive parton densities is possible with similar accuracy to that in .Comment: 24 pages, 16 figure
Characterization of a new pathway that activates lumisterol <i>in vivo</i> to biologically active hydroxylumisterols
Abstract Using LC/qTOF-MS we detected lumisterol, 20-hydroxylumisterol, 22-hydroxylumisterol, 24-hydroxylumisterol, 20,22-dihydroxylumisterol, pregnalumisterol, 17-hydroxypregnalumisterol and 17,20-dihydroxypregnalumisterol in human serum and epidermis, and the porcine adrenal gland. The hydroxylumisterols inhibited proliferation of human skin cells in a cell type-dependent fashion with predominant effects on epidermal keratinocytes. They also inhibited melanoma proliferation in both monolayer and soft agar. 20-Hydroxylumisterol stimulated the expression of several genes, including those associated with keratinocyte differentiation and antioxidative responses, while inhibiting the expression of others including RORA and RORC. Molecular modeling and studies on VDRE-transcriptional activity excludes action through the genomic site of the VDR. However, their favorable interactions with the A-pocket in conjunction with VDR translocation studies suggest they may act on this non-genomic VDR site. Inhibition of RORα and RORγ transactivation activities in a Tet-on CHO cell reporter system, RORα co-activator assays and inhibition of (RORE)-LUC reporter activity in skin cells, in conjunction with molecular modeling, identified RORα and RORγ as excellent receptor candidates for the hydroxylumisterols. Thus, we have discovered a new biologically relevant, lumisterogenic pathway, the metabolites of which display biological activity. This opens a new area of endocrine research on the effects of the hydroxylumisterols on different pathways in different cells and the mechanisms involved
Melatonin: A Cutaneous Perspective on its Production, Metabolism, and Functions
Melatonin, an evolutionarily ancient derivative of serotonin with hormonal properties, is the main neuroendocrine secretory product of the pineal gland. Although melatonin is best known to regulate circadian rhythmicity and lower vertebrate skin pigmentation, the full spectrum of functional activities of this free radical-scavenging molecule, which also induces/promotes complex antioxidative and DNA repair systems, includes immunomodulatory, thermoregulatory, and antitumor properties. Because this plethora of functional melatonin properties still awaits to be fully appreciated by dermatologists, the current review synthesizes the main features that render melatonin a promising candidate for the management of several dermatoses associated with substantial oxidative damage. We also review why melatonin promises to be useful in skin cancer prevention, skin photo- and radioprotection, and as an inducer of repair mechanisms that facilitate the recovery of human skin from environmental damage. The fact that human skin and hair follicles not only express functional melatonin receptors but also engage in substantial, extrapineal melatonin synthesis further encourages one to systematically explore how the skin's melatonin system can be therapeutically targeted in future clinical dermatology and enrolled for preventive medicine strategies
Is alopecia areata an autoimmune-response against melanogenesis-related proteins, exposed by abnormal MHC class I expression in the anagen hair bulb?
The etiology of alopecia areata (AA), a putative autoimmune disease characterized by sudden hair loss, has remained obscure. It is not understood, how the characteristic inflammatory infiltrate that selectively attacks anagen hair follicles in AA is generated. We hypothesize that this reflects an unexplored form of autoimmunity, a cytotoxic T cell attack on rhythmically synthesized autoantigens normally sequestered by a lack or very low level of MHC class I (MHC I)-expression, and suggest the following mechanism of AA pathogenesis: Microtrauma, neurogenic inflammation, or microbial antigens cause a localized breakdown of MHC I-"negativity" in the proximal anagen hair bulb via proinflammatory cytokines. This exposes autoantigens derived from melanogenesis-related proteins (MRP-DP), which are only generated during anagen, and triggers two successive waves of autoimmune responses: CD8+ cytotoxic T cells initiate AA after recognizing MRP-DP abnormally presented by MHC I molecules on hair matrix melanocytes and/or keratinocytes; a secondary attack, carried by CD4+ T cells and antigen presenting cells, is then mounted against MHC class II--presented additional autoantigens exposed by damaged melanocytes and keratinocytes. The latter causes most of the follicular damage, and extrafollicular disease, and depends greatly on the immunogenetic background of affected individuals. This unifying hypothesis explains the clinical heterogeneity and all salient features of AA, and argues that only the unlikely coincidence of multiple predisposing events triggers AA. The suppression of MHC I--expression and synthesis of MRP in the hair bulb, and the "tolerization" of MRP-DP autoreactive CD8+ T cells may be promising strategies for treating AA
Diffractive longitudinal structure function at the Electron Ion Collider
Possibilities for the measurement of the longitudinal structure function in
diffraction at the future US Electron Ion Collider
are investigated. The sensitivity to arises from the
variation of the reduced diffractive cross section with centre-of-mass energy.
Simulations are performed with various sets of beam energy combinations and for
different assumptions on the precision of the diffractive cross section
measurements. Scenarios compatible with current EIC performance expectations
lead to an unprecedented precision on at the 5-10 %
level in the best measured regions. While scenarios with data at a larger
number of centre-of-mass energies allow the extraction of
in the widest kinematic domain and with the smallest
uncertainties, even the more conservative assumptions lead to precise
measurements. The ratio of photoabsorption cross sections for
longitudinally to transversely polarised photons can also be obtained with high
precision using a separate extraction method.Comment: LaTeX, 23 pages, 11 figures and 1 table; v2: some comments added,
results and conclusions unchanged, final versio
Dijet photoproduction of massless charm jets at next-to-leading order of QCD
We compute the charm dijet photoproduction cross section at next-to-leading
order of QCD in the zero-mass variable flavour number scheme, i.e. with active
charm quarks in the proton and photon. The results are compared to recent
measurements from the ZEUS experiment at HERA. The predictions for various
distributions agree well with the data, in particular for large momentum
fractions of the the partons in the photon, where direct photon processes
dominate. At low momentum fractions, the predictions are quite sensitive to the
charm content in the photon. The experimental data are shown to favour
parameterizations with a substantial charm quark density such as the one
proposed by Cornet et al.Comment: 18 pages, 11 figure
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