10 research outputs found
A Time-Varying Fine Structure Constant from Naturally Ultralight Dark Matter
We present a class of models in which the coupling of the photon to an
ultralight scalar field that has a time-dependent vacuum expectation value
causes the fine structure constant to oscillate in time. The scalar field is
assumed to constitute all or part of the observed dark matter. Its mass is
protected against radiative corrections by a discrete exchange
symmetry that relates the Standard Model to several copies to itself. The
abundance of dark matter is set by the misalignment mechanism. We show that the
oscillations in the fine structure constant are large enough to be observed in
current and near-future experiments.Comment: 15 pages, 5 figure
Constraining Vector Dark Matter with Neutrino experiments
Vector Dark Matter (VDM) that couples to lepton flavor (, ,
) acts similarly to a chemical potential for the neutrino flavor
eigenstates and modifies neutrino oscillations. VDM imparts unique signatures
such as time and directional dependence with longer baselines giving better
sensitivity. We use the non-observation of such a signal at Super-Kamiokande to
rule out the existence of VDM in a region of parameter space several orders of
magnitude beyond other constraints and show the projected reach of future
experiments such as DUNE.Comment: 23 pages, 5 figure
Precision Early Universe Cosmology from Stochastic Gravitational Waves
The causal tail of stochastic gravitational waves can be used to probe the
energy density in free streaming relativistic species as well as measure
and beta functions as a function of temperature. In the
event of the discovery of loud stochastic gravitational waves, we demonstrate
that LISA can measure the free streaming fraction of the universe down to the
the level, 100 times more sensitive than current constraints.
Additionally, it would be sensitive to deviations of
and the QCD function from their Standard Model value at temperatures
GeV. In this case, many motivated models such as split SUSY and
other solutions to the Electroweak Hierarchy problem would be tested. Future
detectors, such as DECIGO, would be 100 times more sensitive than LISA to these
effects and be capable of testing other motivated scenarios such as WIMPs and
axions. The amazing prospect of using precision gravitational wave measurements
to test such well motivated theories provides a benchmark to aim for when
developing a precise understanding of the gravitational wave spectrum both
experimentally and theoretically.Comment: 28 pages, 11 figure
Seco-B-Ring Steroidal Dienynes with Aromatic D Ring: Design, Synthesis and Biological Evaluation
Continuing our structure-activity studies on the vitamin D analogs with the altered intercyclic seco-B-ring fragment, we designed compounds possessing dienyne system conjugated with the benzene D ring. Analysis of the literature data and the docking experiments seemed to indicate that the target compounds could mimic the ligands with a good affinity to the vitamin D receptor (VDR). Multi-step synthesis of the C/D-ring building block of the tetralone structure was achieved and its enol triflate was coupled with the known A-ring fragments, possessing conjugated enyne moiety, using Sonogashira protocol. The structures of the final products were confirmed by NMR, UV and mass spectroscopy. Their binding affinities for the full-length human VDR were determined and it was established that compound substituted at C-2 with exomethylene group showed significant binding to the receptor. This analog was also able to induce monocytic differentiation of HL-60 cells
Detection of 7-Dehydrocholesterol and Vitamin D3 Derivatives in Honey
20(S)-Hydroxyvitamin D3 (20(OH)D3) is an endogenous metabolite produced by the action of CYP11A1 on the side chain of vitamin D3 (D3). 20(OH)D3 can be further hydroxylated by CYP11A1, CYP27A1, CYP24A1 and/or CYP27B1 to several hydroxyderivatives. CYP11A1 also hydroxylates D3 to 22-monohydroxyvitamin D3 (22(OH)D3), which is detectable in the epidermis. 20-Hydroxy-7-dehydrocholesterol (20(OH)-7DHC) has been detected in the human epidermis and can be phototransformed into 20(OH)D3 following the absorption of ultraviolet B (UVB) energy by the B-ring. 20(OH)D3 and its hydroxyderivatives have anti-inflammatory, pro-differentiation and anti-proliferative effects, comparable to 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). Since cytochromes P450 with 20- or 25-hydroxylase activity are found in insects participating in ecdysone synthesis from 7-dehydrocholesterol (7DHC), we tested whether D3-hydroxyderivatives are present in honey, implying their production in bees. Honey was collected during summer in the Birmingham area of Alabama or purchased commercially and extracted and analyzed using LC-MS. We detected a clear peak of m/z = 423.324 [M + Na]+ for 20(OH)D3 corresponding to a concentration in honey of 256 ng/g. We also detected peaks of m/z = 383.331 [M + H − H2O]+ for 20(OH)-7DHC and 25(OH)D3 with retention times corresponding to the standards. We further detected species with m/z = 407.329 [M + Na]+ corresponding to the RT of 7DHC, D3 and lumisterol3 (L3). Similarly, peaks with m/z = 399.326 [M + H − H2O]+ were detected at the RT of 1,25(OH)2D3 and 1,20-dihydroxyvitamin D3 (1,20(OH)2D3). Species corresponding to 20-monohydroxylumisterol3 (20(OH)L3), 22-monohydroxyvitamin D3 (22(OH)D3), 20,23-dihydroxyvitamin D3 (20,23(OH)2D3), 20,24/25/26-dihydroxyvitamin D3 (20,24/25/26(OH)2D3) and 1,20,23/24/25/26-trihydroxyvitamin D3 (1,20,23/24/25/26(OH)3D3) were not detectable above the background. In conclusion, the presence of 7DHC and D3 and of species corresponding to 20(OH)-7DHC, 20(OH)D3, 1,20(OH)2D3, 25(OH)D3 and 1,25(OH)2D3 in honey implies their production in bees, although the precise biochemistry and photochemistry of these processes remain to be defined