Subverting sterols: rerouting an oxysterol-signaling pathway to promote tumor growth.

Oxysterols are oxidized derivatives of cholesterol that are generated enzymatically or through autoxidation. Initially identified as important lipid signaling molecules in the context of atherosclerosis and inflammation, accumulated evidence indicates that these lipid-signaling molecules can have pleiotropic effects on the fate and function of the immune system. These effects range from the regulation of immune cell survival and proliferation to chemotaxis and antiviral immunity. New studies now indicate that tumor-derived oxysterols can serve to subvert the immune system by recruiting protumorigenic neutrophils into the tumor microenvironment. The consequence of this recruitment is the generation of proangiogenic factors and matrix metalloproteinase proteins that provide a tumor a significant growth and survival advantage. In combination with other recent studies, these data highlight the ongoing cross talk between sterol metabolism and the immune system, and they raise the intriguing possibility that targeting oxysterol pathways could serve as a novel therapeutic approach in the war on cancer

Experimental validation of the mechanical coupling response for hygro-thermally curvature-stable laminated composite materials

Stacking sequence configurations for hygro-thermally curvature-stable (HTCS) laminates have recently been identified in 9 classes of coupled laminate with standard ply angle orientations +45, "1245, 0 and 9

High-Redshift Superclustering of QSO Absorption Line Systems on 100 Mpc Scales

We have analyzed the clustering of C IV absorption line systems in an extensive new catalog of heavy element QSO absorbers. The catalog permits exploration of clustering over a large range in both scale (from about 1 to over 300 Mpc) and redshift (z from 1.2 to 4.5). We find significant evidence (5.0 sigma) that C IV absorbers are clustered on comoving scales of 100 Mpc and less --- similar to the size of voids and walls found in galaxy redshift surveys of the local universe --- with a mean correlation function $\xi = 0.42 \pm 0.10$ over these scales. We find, on these scales, that the mean correlation function at low (z=1.7), medium (z=2.4), and high redshift (z=3.0) is $\xi=0.40 \pm 0.17$, $0.32 \pm 0.14$, and $0.72 \pm 0.25$, respectively. Thus, the superclustering is present even at high redshift; furthermore, it does not appear that the superclustering scale, in comoving coordinates, has changed significantly since then. We find 7 QSOs with rich groups of absorbers (potential superclusters) that account for a significant portion of the clustering signal, with 2 at redshift $z\sim 2.8$. We find that the superclustering is just as evident if we take $q_0=0.1$ instead of 0.5; however, the inferred scale of clustering is then 240 Mpc , which is larger than the largest scales of clustering known at present. This discrepancy may be indicative of a larger value of $q_0$, and hence $\Omega_0$. The evolution of the correlation function on 50 Mpc scales is consistent with that expected in cosmologies with density parameter ranging from $\Omega_0 =$ 0.1 to 1. Finally, we find no evidence for clustering on scales greater than 100 Mpc ($q_0=0.5$) or 240 Mpc ($q_0=0.1$).Comment: 16 LaTeX pages with 3 encapsulated Postscript figures included, uses AASTeX (v. 4.0) available at ftp://ftp.aas.org/pubs/ , to appear in The Astrophysical Journal Letter

Local and global properties of conformally flat initial data for black hole collisions

We study physical properties of conformal initial value data for single and binary black hole configurations obtained using conformal-imaging and conformal-puncture methods. We investigate how the total mass M_tot of a dataset with two black holes depends on the configuration of linear or angular momentum and separation of the holes. The asymptotic behavior of M_tot with increasing separation allows us to make conclusions about an unphysical ``junk'' gravitation field introduced in the solutions by the conformal approaches. We also calculate the spatial distribution of scalar invariants of the Riemann tensor which determine the gravitational tidal forces. For single black hole configurations, these are compared to known analytical solutions. Spatial distribution of the invariants allows us to make certain conclusions about the local distribution of the additional field in the numerical datasets

Slice Stretching Effects for Maximal Slicing of a Schwarzschild Black Hole

Slice stretching effects such as slice sucking and slice wrapping arise when foliating the extended Schwarzschild spacetime with maximal slices. For arbitrary spatial coordinates these effects can be quantified in the context of boundary conditions where the lapse arises as a linear combination of odd and even lapse. Favorable boundary conditions are then derived which make the overall slice stretching occur late in numerical simulations. Allowing the lapse to become negative, this requirement leads to lapse functions which approach at late times the odd lapse corresponding to the static Schwarzschild metric. Demanding in addition that a numerically favorable lapse remains non-negative, as result the average of odd and even lapse is obtained. At late times the lapse with zero gradient at the puncture arising for the puncture evolution is precisely of this form. Finally, analytic arguments are given on how slice stretching effects can be avoided. Here the excision technique and the working mechanism of the shift function are studied in detail.Comment: 16 pages, 4 figures, revised version including a study on how slice stretching can be avoided by using excision and/or shift

A Liquid Model Analogue for Black Hole Thermodynamics

We are able to characterize a 2--dimensional classical fluid sharing some of the same thermodynamic state functions as the Schwarzschild black hole. This phenomenological correspondence between black holes and fluids is established by means of the model liquid's pair-correlation function and the two-body atomic interaction potential. These latter two functions are calculated exactly in terms of the black hole internal (quasilocal) energy and the isothermal compressibility. We find the existence of a ``screening" like effect for the components of the liquid.Comment: 20 pages and 6 Encapsulated PostScript figure

Modelling Time-varying Dark Energy with Constraints from Latest Observations

We introduce a set of two-parameter models for the dark energy equation of state (EOS) $w(z)$ to investigate time-varying dark energy. The models are classified into two types according to their boundary behaviors at the redshift $z=(0,\infty)$ and their local extremum properties. A joint analysis based on four observations (SNe + BAO + CMB + $H_0$) is carried out to constrain all the models. It is shown that all models get almost the same $\chi^2_{min}\simeq 469$ and the cosmological parameters $(\Omega_M, h, \Omega_bh^2)$ with the best-fit results $(0.28, 0.70, 2.24)$, although the constraint results on two parameters $(w_0, w_1)$ and the allowed regions for the EOS $w(z)$ are sensitive to different models and a given extra model parameter. For three of Type I models which have similar functional behaviors with the so-called CPL model, the constrained two parameters $w_0$ and $w_1$ have negative correlation and are compatible with the ones in CPL model, and the allowed regions of $w(z)$ get a narrow node at $z\sim 0.2$. The best-fit results from the most stringent constraints in Model Ia give $(w_0,w_1) = (-0.96^{+0.26}_{-0.21}, -0.12^{+0.61}_{-0.89})$ which may compare with the best-fit results $(w_0,w_1) = (-0.97^{+0.22}_{-0.18}, -0.15^{+0.85}_{-1.33})$ in the CPL model. For four of Type II models which have logarithmic function forms and an extremum point, the allowed regions of $w(z)$ are found to be sensitive to different models and a given extra parameter. It is interesting to obtain two models in which two parameters $w_0$ and $w_1$ are strongly correlative and appropriately reduced to one parameter by a linear relation $w_1 \propto (1+w_0)$.Comment: 30 pages, 7 figure

Detecting cold gas at intermediate redshifts: GMRT survey using Mg II systems

Intervening HI 21-cm absorption systems at z > 1.0 are very rare and only 4 confirmed detections have been reported in the literature. Despite their scarcity, they provide interesting and unique insights into the physical conditions in the interstellar medium of high-z galaxies. Moreover, they can provide independent constraints on the variation of fundamental constants. We report 3 new detections based on our ongoing Giant Metrewave Radio Telescope (GMRT) survey for 21-cm absorbers at 1.10< z_abs< 1.45 from candidate damped Lyman_alpha systems. The 21-cm lines are narrow for the z_abs = 1.3710 system towards SDSS J0108-0037 and z_abs = 1.1726 system toward SDSS J2358-1020. Based on line full-width at half maximum, the kinetic temperatures are <= 5200 K and <=800 K, respectively. The 21-cm absorption profile of the third system, z_abs =1.1908 system towards SDSS J0804+3012, is shallow, broad and complex, extending up to 100 km/s. The centroids of the 21-cm lines are found to be shifted with respect to the corresponding centroids of the metal lines derived from SDSS spectra. This may mean that the 21-cm absorption is not associated with the strongest metal line component.Comment: 13 pages with 5 figures. Accepted for publication in ApJ