538 research outputs found
Opposing Effects of Oxygen Regulation on Kallistatin Expression: Kallistatin as a Novel Mediator of Oxygen-Induced HIF-1-eNOS-NO Pathway
Oxidative stress has both detrimental and beneficial effects. Kallistatin, a key component of circulation, protects against vascular and organ injury. Serum kallistatin levels are reduced in patients and animal models with hypertension, diabetes, obesity, and cancer. Reduction of kallistatin levels is inversely associated with elevated thiobarbituric acid-reactive substance. Kallistatin therapy attenuates oxidative stress and increases endothelial nitric oxide synthase (eNOS) and NO levels in animal models. However, kallistatin administration increases reactive oxygen species formation in immune cells and bacterial killing activity in septic mice. High oxygen inhibits kallistatin expression via activating the JNK-FOXO1 pathway in endothelial cells. Conversely, mild oxygen/hyperoxia stimulates kallistatin, eNOS, and hypoxia-inducible factor-1 (HIF-1) expression in endothelial cells and in the kidney of normal mice. Likewise, kallistatin stimulates eNOS and HIF-1, and kallistatin antisense RNA abolishes oxygen-induced eNOS and HIF-1 expression, indicating a role of kallistatin in mediating mild oxygen’s stimulation on antioxidant genes. Protein kinase C (PKC) activation mediates HIF-1-induced eNOS synthesis in response to hyperoxia/exercise; thus, mild oxygen through PKC activation stimulates kallistatin-mediated HIF-1 and eNOS synthesis. In summary, oxidative stress induces down- or upregulation of kallistatin expression, depending on oxygen concentration, and kallistatin plays a novel role in mediating oxygen/exercise-induced HIF-1-eNOS-NO pathway
DIP: Differentiable Interreflection-aware Physics-based Inverse Rendering
We present a physics-based inverse rendering method that learns the
illumination, geometry, and materials of a scene from posed multi-view RGB
images. To model the illumination of a scene, existing inverse rendering works
either completely ignore the indirect illumination or model it by coarse
approximations, leading to sub-optimal illumination, geometry, and material
prediction of the scene. In this work, we propose a physics-based illumination
model that explicitly traces the incoming indirect lights at each surface point
based on interreflection, followed by estimating each identified indirect light
through an efficient neural network. Furthermore, we utilize the Leibniz's
integral rule to resolve non-differentiability in the proposed illumination
model caused by one type of environment light -- the tangent lights. As a
result, the proposed interreflection-aware illumination model can be learned
end-to-end together with geometry and materials estimation. As a side product,
our physics-based inverse rendering model also facilitates flexible and
realistic material editing as well as relighting. Extensive experiments on both
synthetic and real-world datasets demonstrate that the proposed method performs
favorably against existing inverse rendering methods on novel view synthesis
and inverse rendering
On linear-algebraic notions of expansion
A fundamental fact about bounded-degree graph expanders is that three notions
of expansion -- vertex expansion, edge expansion, and spectral expansion -- are
all equivalent. In this paper, we study to what extent such a statement is true
for linear-algebraic notions of expansion.
There are two well-studied notions of linear-algebraic expansion, namely
dimension expansion (defined in analogy to graph vertex expansion) and quantum
expansion (defined in analogy to graph spectral expansion). Lubotzky and
Zelmanov proved that the latter implies the former. We prove that the converse
is false: there are dimension expanders which are not quantum expanders.
Moreover, this asymmetry is explained by the fact that there are two distinct
linear-algebraic analogues of graph edge expansion. The first of these is
quantum edge expansion, which was introduced by Hastings, and which he proved
to be equivalent to quantum expansion. We introduce a new notion, termed
dimension edge expansion, which we prove is equivalent to dimension expansion
and which is implied by quantum edge expansion. Thus, the separation above is
implied by a finer one: dimension edge expansion is strictly weaker than
quantum edge expansion. This new notion also leads to a new, more modular proof
of the Lubotzky--Zelmanov result that quantum expanders are dimension
expanders.Comment: 23 pages, 1 figur
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