A Numerical Approach to Coulomb Gauge QCD

We calculate the ghost two-point function in Coulomb gauge QCD with a simple model vacuum gluon wavefunction using Monte Carlo integration. This approach extends the previous analytic studies of the ghost propagator with this ansatz, where a ladder-rainbow expansion was unavoidable for calculating the path integral over gluon field configurations. The new approach allows us to study the possible critical behavior of the coupling constant, as well as the Coulomb potential derived from the ghost dressing function. We demonstrate that IR enhancement of the ghost correlator or Coulomb form factor fails to quantitatively reproduce confinement using Gaussian vacuum wavefunctional

Ascorbic acid and ascorbate-2-phosphate decrease HIF activity and malignant properties of human melanoma cells

Background: Hypoxia inducible factor-1 alpha (HIF-1α) is thought to play a role in melanoma carcinogenesis. Posttranslational regulation of HIF-1α is dependent on Prolyl hydroxylase (PHD 1–3) and Factor Inhibiting HIF (FIH) hydroxylase enzymes, which require ascorbic acid as a co-factor for optimal function. Depleted intra-tumoral ascorbic acid may thus play a role in the loss of HIF-1α regulation in melanoma. These studies assess the ability of ascorbic acid to reduce HIF-1α protein and transcriptional activity in metastatic melanoma and reduce its invasive potential. Methods: HIF-1α protein was evaluated by western blot, while transcriptional activity was measured by HIF-1 HRE-luciferase reporter gene activity. Melanoma cells were treated with ascorbic acid (AA) and ascorbate 2-phosphate (A2P) to assess their ability to reduce HIF-1α accumulation and activity. siRNA was used to deplete cellular PHD2 in order to evaluate this effect on AA’s ability to lower HIF-1α levels. A2P’s effect on invasive activity was measured by the Matrigel invasion assay. Data was analyzed by One-way ANOVA with Tukey’s multiple comparisons test, or Student-T test as appropriate, with p\u3c.05 considered significant. Results: Supplementation with both AA and A2P antagonized normoxic as well as cobalt chloride- and PHD inhibitor ethyl 3, 4-dihydroxybenzoate induced HIF-1α protein stabilization and transcriptional activity. Knockdown of the PHD2 isoform with siRNA did not impede the ability of AA to reduce normoxic HIF-1α protein. Additionally, reducing HIF-1α levels with A2P resulted in a significant reduction in the ability of the melanoma cells to invade through Matrigel. Conclusion: These studies suggest a positive role for AA in regulating HIF-1α in melanoma by demonstrating that supplementation with either AA, or its oxidation-resistant analog A2P, effectively reduces HIF-1α protein and transcriptional activity in metastatic melanoma cells. Our data, while supporting the function of AA as a necessary cofactor for PHD and likely FIH activity, also suggests a potential non-PHD/FIH role for AA in HIF-1α regulation by its continued ability to reduce HIF-1α in the presence of PHD inhibition. The use of the oxidation-resistant AA analog, A2P, to reduce the ability of HIF-1α to promote malignant progression in melanoma cells and enhance their response to therapy warrants further investigation

Acute ascending aortic dissection complicating open heart surgery: cerebral perfusion defines the outcome

Objective: This retrospective study was designed to assess the risks of acute ascending aorta dissection (AAD) as a rare but potentially fatal complication of open heart surgery. Method: Among 8624 cardiac surgical procedures under cardiopulmonary bypass (CPB) and cardioplegic myocardial protection from 1978 to 1997, 10 patients (0.12%) presented with a secondary or so called ‘iatrogenic' AAD. There were seven men and three women, mean age 64±9 years, ranging from 47 to 79. The original procedures involved five coronary artery bypass grafts (CABG), one repeat CABG, one aortic valve replacement (AVR), one AVR and CABG, one mitral valvuloplasty (MVP) and CABG and one ascending aorta replacement. We retrospectively analyzed their hospital records. Results: Group I consisted of seven patients with AAD intraoperatively and group II consisted of three patients who developed acute AAD 8-32 days after cardiac surgery. In group I, treatment consisted of the original procedure, plus grafting of the ascending aorta in six patients and closed plication and aortic wrapping in one. In group II, two patients received a dacron graft and one patient developed lethal tamponnade due to aortic rupture before surgery. Postoperatively, six patients responded well and three died (33%), two patients from group I on the 2nd postoperative day with severe post-anoxic encephalopathy, and one from group II with severe peroperative cardiogenic shock. Conclusion: Preventing AAD with the appropriate means remains standard practice in cardiac surgery. If AAD occurs, it requires prompt diagnosis and interposition graft to allow a better prognosis. Intraoperative AAD happens at the beginning of CPB jeopardizing perfusion of the supra-aortic arterie

Reconstruction of the 1941 GLOF process chain at Lake Palcacocha (Cordillera Blanca, Peru)

The Cordillera Blanca in Peru has been the scene of rapid deglaciation for many decades. One of numerous lakes formed in the front of the retreating glaciers is the moraine-dammed Lake Palcacocha, which drained suddenly due to an unknown cause in 1941. The resulting Glacial Lake Outburst Flood (GLOF) led to dam failure and complete drainage of Lake Jircacocha downstream, and to major destruction and thousands of fatalities in the city of Huaráz at a distance of 23 km. We chose an integrated approach to revisit the 1941 event in terms of topographic reconstruction and numerical back-calculation with the GIS-based open-source mass flow/process chain simulation framework r.avaflow, which builds on an enhanced version of the Pudasaini (2012) two-phase flow model. Thereby we consider four scenarios: (A) and (AX) breach of the moraine dam of Lake Palcacocha due to retrogressive erosion, assuming two different fluid characteristics; (B) failure of the moraine dam caused by the impact of a landslide on the lake; and (C) geomechanical failure and collapse of the moraine dam. The simulations largely yield empirically adequate results with physically plausible parameters, taking the documentation of the 1941 event and previous calculations of future scenarios as reference. Most simulation scenarios indicate travel times between 36 and 70 min to reach Huaráz, accompanied with peak discharges above 10 000 m3 s−1. The results of the scenarios indicate that the most likely initiation mechanism would be retrogressive erosion, possibly triggered by a minor impact wave and/or facilitated by a weak stability condition of the moraine dam. However, the involvement of Lake Jircacocha disguises part of the signal of process initiation farther downstream. Predictive simulations of possible future events have to be based on a larger set of back-calculated GLOF process chains, taking into account the expected parameter uncertainties and appropriate strategies to deal with critical threshold effects

New constraints on equatorial temperatures during a Late Neoproterozoic snowball Earth glaciation

Intense glaciation during the end of Cryogenian time (∼635 million years ago) marks the coldest climate state in Earth history – a time when glacial deposits accumulated at low, tropical paleolatitudes. The leading idea to explain these deposits, the snowball Earth hypothesis, predicts globally frozen surface conditions and subfreezing temperatures, with global climate models placing surface temperatures in the tropics between −20 °C and −60 °C. However, precise paleosurface temperatures based upon geologic constraints have remained elusive and the global severity of the glaciation undetermined. Here we make new geologic observations of tropical periglacial, aeolian and fluvial sedimentary structures formed during the end-Cryogenian, Marinoan glaciation in South Australia; these observations allow us to constrain ancient surface temperatures. We find periglacial sand wedges and associated deformation suggest that ground temperatures were sufficiently warm to allow for ductile deformation of a sandy regolith. The wide range of deformation structures likely indicate the presence of a paleoactive layer that penetrated 2–4 m below the ground surface. These observations, paired with a model of ground temperature forced by solar insolation, constrain the local mean annual surface temperature to within a few degrees of freezing. This temperature constraint matches well with our observations of fluvial deposits, which require temperatures sufficiently warm for surface runoff. Although this estimate coincides with one of the coldest near sea-level tropical temperatures in Earth history, if these structures represent peak Marinaon glacial conditions, they do not support the persistent deep freeze of the snowball Earth hypothesis. Rather, surface temperatures near 0 °C allow for regions of seasonal surface melting, atmosphere–ocean coupling and possible tropical refugia for early metazoans. If instead these structures formed during glacial onset or deglaciation, then they have implications for the timescale and character for the transition into or out of a snowball state

OGFOD1 catalyzes prolyl hydroxylation of RPS23 and is involved in translation control and stress granule formation

2-Oxoglutarate (2OG) and Fe(II)-dependent oxygenase domain-containing protein 1 (OGFOD1) is predicted to be a conserved 2OG oxygenase, the catalytic domain of which is related to hypoxia-inducible factor prolyl hydroxylases. OGFOD1 homologs in yeast are implicated in diverse cellular functions ranging from oxygen-dependent regulation of sterol response genes (Ofd1, Schizosaccharomyces pombe) to translation termination/mRNA polyadenylation (Tpa1p, Saccharomyces cerevisiae). However, neither the biochemical activity of OGFOD1 nor the identity of its substrate has been defined. Here we show that OGFOD1 is a prolyl hydroxylase that catalyzes the posttranslational hydroxylation of a highly conserved residue (Pro-62) in the small ribosomal protein S23 (RPS23). Unusually OGFOD1 retained a high affinity for, and forms a stable complex with, the hydroxylated RPS23 substrate. Knockdown or inactivation of OGFOD1 caused a cell type-dependent induction of stress granules, translational arrest, and growth impairment in a manner complemented by wild-type but not inactive OGFOD1. The work identifies a human prolyl hydroxylase with a role in translational regulation

Kinetic Heterogeneities in a Highly Supercooled Liquid

We study a highly supercooled two-dimensional fluid mixture via molecular dynamics simulation. We follow bond breakage events among particle pairs, which occur on the scale of the $\alpha$ relaxation time $\tau_{\alpha}$. Large scale heterogeneities analogous to the critical fluctuations in Ising systems are found in the spatial distribution of bonds which are broken in a time interval with a width of order $0.05\tau_{\alpha}$. The structure factor of the broken bond density is well approximated by the Ornstein-Zernike form. The correlation length is of order $100 \sigma_1$ at the lowest temperature studied, $\sigma_1$ being the particle size. The weakly bonded regions thus identified evolve in time with strong spatial correlations.Comment: 3 pages, 6 figure

Spontaneous chiral symmetry breaking in the linked cluster expansion

We investigate dynamical chiral symmetry breaking in the Coulomb gauge Hamiltonian QCD. Within the framework of the linked cluster expansion we extend the BCS ansatz for the vacuum and include correlation beyond the quark-antiquark paring. In particular we study the effects of the three-body correlations involving quark-antiquark and transverse gluons. The high momentum behavior of the resulting gap equation is discussed and numerical computation of the chiral symmetry breaking is presented.Comment: 13 pages, 9 figure

Corresponding States of Structural Glass Formers

The variation with respect to temperature T of transport properties of 58 fragile structural glass forming liquids (68 data sets in total) are analyzed and shown to exhibit a remarkable degree of universality. In particular, super-Arrhenius behaviors of all super-cooled liquids appear to collapse to one parabola for which there is no singular behavior at any finite temperature. This behavior is bounded by an onset temperature To above which liquid transport has a much weaker temperature dependence. A similar collapse is also demonstrated, over the smaller available range, for existing numerical simulation data.Comment: 6 pages, 2 figures. Updated References, Table Values, Submitted for Publicatio