2,141 research outputs found
Exploring Vanadium Chemical Transferrin Mimetic Compounds for Insulin Enhancement
Diabetes Mellitus (DM) is caused by a lack of insulin production (Type 1) or the body’s cells’ inability to properly receive it, also known as insulin resistance (Type 2), resulting in greatly elevated levels of blood glucose. Vanadium(IV) and vanadium(V) ions are believed to enhance insulin activity by inhibition of protein tyrosine phosphatase 1B (PTP1B). PTP1B is normally responsible for downregulating the insulin signaling, but in DM type 2, PTP1B activity is overexpressed leading to the insulin signaling blocking. The most promising V(IV) compounds are designed for oral delivery: they are absorbed into the gut and delivered into the bloodstream where they are bound by the iron transporting protein serum transferrin (sTf). STf delivers the compound into cells via endocytosis, where vanadium can bind PTP1B. A limitation of these compounds is their poor stability at the stomach acidic conditions in which they undergo a significant amount of dissociation, resulting in a very inefficient gut absorption. This study explores the use of a chemical transferrin mimetic (cTfm) ligand to create V(IV) and V(V) compounds featuring excellent acidic pH stability for improved gut absorption. The cTfm-V(IV,V) compounds are expected to be labile in the pH of the bloodstream and thus the vanadium species can be quickly ligand exchanged with sTF. The cTfm ligand N,N\u27-di(o-hydroxybenzyl)ethylenediamine-N,N\u27-diacetic acid (HBED) was used to synthesize VO(IV)HBED and VO(V)HBED which demonstrated great aqueous stability in the 1-4 pH range. The role of citrate as a vehicle for delivering vanadium to sTf to regulate the transport of vanadium is also examined
A Primer for Designing a Small Spacecraft Mission Operations Architecture
A thesis presented to the faculty of the College of Science at Morehead State University in partial fulfillment of the requirements for the Degree of Master of Science by Joseph M. A. Feliciano on April 28, 2022
Coherent Neutrino Scattering in Dark Matter Detectors
Coherent elastic neutrino- and WIMP-nucleus interaction signatures are
expected to be quite similar. This paper discusses how a next generation
ton-scale dark matter detector could discover neutrino-nucleus coherent
scattering, a precisely-predicted Standard Model process. A high intensity
pion- and muon- decay-at-rest neutrino source recently proposed for oscillation
physics at underground laboratories would provide the neutrinos for these
measurements. In this paper, we calculate raw rates for various target
materials commonly used in dark matter detectors and show that discovery of
this interaction is possible with a 2 tonyear GEODM exposure in an
optimistic energy threshold and efficiency scenario. We also study the effects
of the neutrino source on WIMP sensitivity and discuss the modulated neutrino
signal as a sensitivity/consistency check between different dark matter
experiments at DUSEL. Furthermore, we consider the possibility of coherent
neutrino physics with a GEODM module placed within tens of meters of the
neutrino source.Comment: 8 pages, 4 figure
Plasma Processing of Large Curved Surfaces for SRF Cavity Modification
Plasma based surface modification of niobium is a promising alternative to
wet etching of superconducting radio frequency (SRF) cavities. The development
of the technology based on Cl2/Ar plasma etching has to address several crucial
parameters which influence the etching rate and surface roughness, and
eventually, determine cavity performance. This includes dependence of the
process on the frequency of the RF generator, gas pressure, power level, the
driven (inner) electrode configuration, and the chlorine concentration in the
gas mixture during plasma processing. To demonstrate surface layer removal in
the asymmetric non-planar geometry, we are using a simple cylindrical cavity
with 8 ports symmetrically distributed over the cylinder. The ports are used
for diagnosing the plasma parameters and as holders for the samples to be
etched. The etching rate is highly correlated with the shape of the inner
electrode, radio-frequency (RF) circuit elements, chlorine concentration in the
Cl2/Ar gas mixtures, residence time of reactive species and temperature of the
cavity. Using cylindrical electrodes with variable radius, large-surface
ring-shaped samples and d.c. bias implementation in the external circuit we
have demonstrated substantial average etching rates and outlined the
possibility to optimize plasma properties with respect to maximum surface
processing effect
Band Offsets at the Si/SiO Interface from Many-Body Perturbation Theory
We use many-body perturbation theory, the state-of-the-art method for band
gap calculations, to compute the band offsets at the Si/SiO interface. We
examine the adequacy of the usual approximations in this context. We show that
(i) the separate treatment of band-structure and potential lineup
contributions, the latter being evaluated within density-functional theory, is
justified, (ii) most plasmon-pole models lead to inaccuracies in the absolute
quasiparticle corrections, (iii) vertex corrections can be neglected, (iv)
eigenenergy self-consistency is adequate. Our theoretical offsets agree with
the experimental ones within 0.3 eV
Chandra Observations of ULIRGs: Extended Hot Gas Halos in Merging Galaxies
We study the properties of hot gaseous halos in 10 nearby ultraluminous IRAS
galaxies observed with the ACIS instrument on board Chandra. For all sample
galaxies, diffuse soft X-ray emissions are found within ~10 kpc of the central
region; their spectra are well fitted by a MEKAL model plus emission lines from
alpha-elements and other ions. The temperature of the hot gas is about 0.7 keV
and metallicity is about 1 solar. Outside the central region, extended hot
gaseous halos are found for nine out of the ten ULIRGs. Most spectra of these
extended halos can be fitted with a MEKAL model with a temperature of about 0.6
keV and a low metallicity (~ 0.1 solar). We discuss the implications of our
results on the origin of X-ray halos in elliptical galaxies and the feedback
processes associated with starbursts.Comment: 31 pages, 6 figuers, ApJ in press, accepted versio
A Chandra View Of Nonthermal Emission In The Northwestern Region Of Supernova Remnant RCW 86: Particle Acceleration And Magnetic Fields
The shocks of supernova remnants (SNRs) are believed to accelerate particles
to cosmic ray (CR) energies. The amplification of the magnetic field due to CRs
propagating in the shock region is expected to have an impact on both the
emission from the accelerated particle population, as well as the acceleration
process itself. Using a 95 ks observation with the Advanced CCD Imaging
Spectrometer (ACIS) onboard the Chandra X-ray Observatory, we map and
characterize the synchrotron emitting material in the northwestern region of
RCW 86. We model spectra from several different regions, filamentary and
diffuse alike, where emission appears dominated by synchrotron radiation. The
fine spatial resolution of Chandra allows us to obtain accurate emission
profiles across 3 different non-thermal rims in this region. The narrow width
(l = 10''-30'') of these filaments constrains the minimum magnetic field
strength at the post-shock region to be approximately 80 {\mu}G.Comment: 7 pages, 3 figures, submitted for publication at the Astrophysical
Journa
- …