10 research outputs found
Generation Gap and the Impact of the Web on Goods Quality Perceptions
This study explores how age and general online shopping experience affect consumer perceptions on product quality uncertainty. Using the survey data collected from 549 consumers, we investigated how they perceive the uncertainty of product quality on six search, experience and credence goods. The ANOVA results show that age and the Web shopping experience of consumers are significant factors. A generation gap is indeed seen for all but one experience good. Web shopping experience is not a significant factor for search goods but is for experience and credence goods. There is an interaction effect between age and Web shopping experience for one credence good. Implications of these results are discussed
Reactive oxygen species are involved in BMP-induced dendritic growth in cultured rat sympathetic neurons
Previous studies have shown that bone morphogenetic proteins (BMPs) promote dendritic growth in sympathetic neurons; however, the downstream signaling molecules that mediate the dendrite promoting activity of BMPs are not well characterized. Here we test the hypothesis that reactive oxygen species (ROS)-mediated signaling links BMP receptor activation to dendritic growth. In cultured rat sympathetic neurons, exposure to any of the three mechanistically distinct antioxidants, diphenylene iodinium (DPI), nordihydroguaiaretic acid (NGA) or desferroxamine (DFO), blocked de novo BMP-induced dendritic growth. Addition of DPI to cultures previously induced with BMP to extend dendrites caused dendritic retraction while DFO and NGA prevented further growth of dendrites. The inhibition of the dendrite promoting activity of BMPs by antioxidants was concentration-dependent and occurred without altering axonal growth or neuronal cell survival. Antioxidant treatment did not block BMP activation of SMAD 1,5 as determined by nuclear localization of these SMADs. While BMP treatment did not cause a detectable increase in intracellular ROS in cultured sympathetic neurons as assessed using fluorescent indicator dyes, BMP treatment increased the oxygen consumption rate in cultured sympathetic neurons as determined using the Seahorse XF24 Analyzer, suggesting increased mitochondrial activity. In addition, BMPs upregulated expression of NADPH oxidase 2 (NOX2) and either pharmacological inhibition or siRNA knockdown of NOX2 significantly decreased BMP-7 induced dendritic growth. Collectively, these data support the hypothesis that ROS are involved in the downstream signaling events that mediate BMP7-induced dendritic growth in sympathetic neurons, and suggest that ROS-mediated signaling positively modulates dendritic complexity in peripheral neurons
The Baryonic Tully-Fisher Relationship for SG Galaxies and the ``Condensed'' Baryon Fraction of Galaxies
We combine data from the Spitzer Survey for Stellar Structure in Galaxies
(SG), a recently calibrated empirical stellar mass estimator from Eskew et
al., and an extensive database of HI spectral line profiles to examine the
baryonic Tully-Fisher (BTF) relation. We find 1) that the BTF has lower scatter
than the classic Tully-Fisher (TF) relation and is better described as a linear
relationship, confirming similar previous results, 2) that the inclusion of a
radial scale in the BTF decreases the scatter but only modestly, as seen
previously for the TF relation, and 3) that the slope of the BTF, which we find
to be ( log log ), implies that
on average a nearly constant fraction () of all baryons expected to
be in a halo are "condensed" onto the central region of rotationally supported
galaxies. The condensed baryon fraction, , is, to our
measurement precision, nearly independent of galaxy circular velocity (our
sample spans circular velocities, , between 60 and 250 km s, but is
extended to km s using data from the literature). The
observed galaxy-to-galaxy scatter in this fraction is generally a factor
of 2 despite fairly liberal selection criteria. These results imply that
cooling and heating processes, such as cold vs. hot accretion, mass loss due to
stellar winds, and AGN driven feedback, to the degree that they affect the
global galactic properties involved in the BTF, are independent of halo mass
for galaxies with km/s and typically introduce no more than a
factor of two range in the resulting . Recent simulations
by Aumer et al. of a small sample of disk galaxies are in excellent agreement
with our data, suggesting that current simulations are capable of reproducing
the global properties of individual disk galaxies.Comment: accepted for publication in A