First-Principles Study on Structural Properties of GeO2_2 and SiO2_2 under Compression and Expansion Pressure

The detailed analysis of the structural variations of three GeO$_2$ and SiO$_2$ polymorphs ($\alpha$-quartz, $\alpha$-cristobalite, and rutile) under compression and expansion pressure is reported. First-principles total-energy calculations reveal that the rutile structure is the most stable phase among the phases of GeO$_2$, while SiO$_2$ preferentially forms quartz. GeO$_4$ tetrahedras of quartz and cristobalite GeO$_2$ phases at the equilibrium volume are more significantly distorted than those of SiO$_2$. Moreover, in the case of quartz GeO$_2$ and cristobalite GeO$_2$, all O-Ge-O bond angles vary when the volume of the GeO$_2$ bulk changes from the equilibrium point, which causes further deformation of tetrahedra. In contrast, the tilt angle formed by Si-O-Si in SiO$_2$ markedly changes. This flexibility of the O-Ge-O bonds reduces the stress at the Ge/GeO$_2$ interface due to the lattice-constant mismatch and results in the low defective interface observed in the experiments [Matsubara \textit{et al.}: Appl. Phys. Lett. \textbf{93} (2008) 032104; Hosoi \textit{et al.}: Appl. Phys. Lett. \textbf{94} (2009) 202112].Comment: 15 pages, 5 figures and 2 table

Biochemical Kinetics Model of DSB Repair and GammaH2AX FOCI by Non-homologous End Joining

We developed a biochemical kinetics approach to describe the repair of double strand breaks (DSB) produced by low LET radiation by modeling molecular events associated with the mechanisms of non-homologous end-joining (NHEJ). A system of coupled non-linear ordinary differential equations describes the induction of DSB and activation pathways for major NHEJ components including Ku(sub 70/80), DNA-PK(sub cs), and the Ligase IV-XRCC4 hetero-dimer. The autophosphorylation of DNA-PK(sub cs and subsequent induction of gamma-H2AX foci observed after ionizing radiation exposure were modeled. A two-step model of DNA-PK(sub cs) regulation of repair was developed with the initial step allowing access of other NHEJ components to breaks, and a second step limiting access to Ligase IV-XRCC4. Our model assumes that the transition from the first to second-step depends on DSB complexity, with a much slower-rate for complex DSB. The model faithfully reproduced several experimental data sets, including DSB rejoining as measured by pulsed-field electrophoresis (PFGE), quantification of the induction of gamma-H2AX foci, and live cell imaging of the induction of Ku(sub 70/80). Predictions are made for the behaviors of NHEJ components at low doses and dose-rates, where a steady-state is found at dose-rates of 0.1 Gy/hr or lower

Bis(aryl) Tetrasulfides as Cathode Materials for Rechargeable Lithium Batteries

An organotetrasulfide consists of a linear chain of four sulfur atoms that could accept up to 6 e− in reduction reactions, thus providing a promising high-capacity electrode material. Herein, we study three bis(aryl) tetrasulfides as cathode materials in lithium batteries. Each tetrasulfide exhibits two major voltage regions in the discharge. The high voltage slope region is governed by the formation of persulfides and thiolates, and the low voltage plateau region is due to the formation of Li2S2/Li2S. Based on theoretical calculations and spectroscopic analysis, three reduction reaction processes are revealed, and the discharge products are identified. Lithium half cells with tetrasulfide catholytes deliver high specific capacities over 200 cycles. The effects of the functional groups on the electrochemical characteristics of tetrasulfides are investigated, which provides guidance for developing optimum aryl polysulfides as cathode materials for high energy lithium batteries

High LET Radiation Can Enhance TGF(Beta) Induced EMT and Cross-Talk with ATM Pathways

The TGF(Beta) pathway has been shown to regulate or directly interact with the ATM pathway in the response to radiation in mammary epithelial cells. We investigated possible interactions between the TGF(Beta) and ATM pathways following simulated space radiation using hTERT immortalized human esophageal epithelial cells (EPC-hTERT), mink lung epithelial cells (Mv1lu), and several human fibroblast cell lines. TGF(Beta) is a key modulator of the Epithelial-Mesenchymal Transition (EMT), important in cancer progression and metastasis. The implication of EMT by radiation also has several lines of developing evidence, however is poorly understood. The identification of TGF(Beta) induced EMT can be shown in changes to morphology, related gene over expression or down regulation, which can be detected by RT-PCR, and immunostaining and western blotting. In this study, we have observed morphologic and molecular alternations consistent with EMT after Mv1lu cells were treated with TGF(Beta) High LET radiation enhanced TGF(Beta) mediated EMT with a dose as low as 0.1Gy. In order to consider the TGF(Beta) interaction with ATM we used a potent ATM inhibitor Ku55933 and investigated gene expression changes and Smad signaling kinetics. Ku559933 was observed to reverse TGF(Beta) induced EMT, while this was not observed in dual treated cells (radiation+TGF(Beta)). In EPC-hTERT cells, TGF(Beta) alone was not able to induce EMT after 3 days of application. A combined treatment with high LET, however, significantly caused the alteration of EMT markers. To study the function of p53 in the process of EMT, we knocked down P53 through RNA interference. Morphology changes associated with EMT were observed in epithelial cells with silenced p53. Our study indicates: high LET radiation can enhance TGF(Beta) induced EMT; while ATM is triggering the process of TGF(Beta)-induced EMT, p53 might be an essential repressor for EMT phenotypes

Bobmeyerite, a new mineral from Tiger, Arizona, USA, structurally related to cerchiaraite and ashburtonite

Bobmeyerite, Pb_4(Al_(3)Cu)(Si_(4)O_12)(S_(0.5)Si_(0.5)O_4)(OH)_(7)Cl(H_(2)O)_3, is a new mineral from the Mammoth - Saint Anthony mine, Tiger, Pinal County, Arizona, USA. It occurs in an oxidation zone assemblage attributed to progressive alteration and crystallization in a closed system. Other minerals in this assemblage include atacamite, caledonite, cerussite, connellite, diaboleite, fluorite, georgerobinsonite, hematite, leadhillite, matlockite, murdochite, phosgenite, pinalite, quartz, wulfenite and yedlinite. Bobmeyerite occurs as colourless to white or cream-coloured needles, up to 300 mm in length, that taper to sharp points. The streak is white and the lustre is adamantine, dull or silky. Bobmeyerite is not fluorescent. The hardness could not be determined, the tenacity is brittle and no cleavage was observed. The calculated density is 4.381 g cm^(-3). Bobmeyerite is biaxial (-) with a ≈ b = 1.759(2), γ = 1.756(2) (white light), it is not pleochroic; the orientation is X = c; Y or Z = a or b. Electron-microprobe analyses provided the empirical formula Pb_(3.80)Ca_(0.04)Al_(3.04) Cu^(2+)_(0.96)Cr^(3+)_(0.13)Si_(4.40)S_(0.58)O_(24.43) Cl_(1.05)F_(0.52)H_(11.83). Bobmeyerite is orthorhombic (pseudotetragonal), Pnnm with unit-cell parameters a = 13.969(9), b = 14.243(10), c = 5.893(4) Å, V = 1172.5(1.4) Å 3 and Z = 2. The nine strongest lines in the X-ray powder diffraction pattern, listed as [d_(obs)(Å )(I)(hkl)], are as follows: 10.051(35)(110); 5.474(54)(011,101); 5.011(35)(220); 4.333(43)(121,211); 3.545(34)(040,400); 3.278(77)(330,231,321); 2.9656(88)(141,002,411); 2.5485(93)(051,222,501); 1.873(39)(multiple). Bobmeyerite has the same structural framework as cerchiaraite and ashburtonite. In the structure, which refined to R_1 = 0.079 for 1057 reflections with F > 4σF, SiO_4 tetrahedra share corners to form four-membered Si_(4)O_12 rings centred on the c axis. The rings are linked by chains of edge-sharing AlO_6 octahedra running parallel to [001]. The framework thereby created contains large channels, running parallel to [001]. The Cl site is centred on the c axis alternating along [001] with the Si_(4)O_12 rings. Two non-equivalent Pb atoms are positioned around the periphery of the channels. Both are elevencoordinate, bonding to the Cl atom on the c axis, to eight O atoms in the framework and to two O (H_(2)O) sites in the channel. The Pb atoms are off-centre in these coordinations, as is typical of Pb^2+ with stereo-active lone-electron pairs. A (S, Si, Cr)O_4 group is presumed to be disordered in the channel. The name honours Robert (Bob) Owen Meyer, one of the discoverers of the new mineral

Biochemistry of mobile zinc and nitric oxide revealed by fluorescent sensors

Biological mobile zinc and nitric oxide (NO) are two prominent examples of inorganic compounds involved in numerous signaling pathways in living systems. In the past decade, a synergy of regulation, signaling, and translocation of these two species has emerged in several areas of human physiology, providing additional incentive for developing adequate detection systems for Zn(II) ions and NO in biological specimens. Fluorescent probes for both of these bioinorganic analytes provide excellent tools for their detection, with high spatial and temporal resolution. We review the most widely used fluorescent sensors for biological zinc and nitric oxide, together with promising new developments and unmet needs of contemporary Zn(II) and NO biological imaging. The interplay between zinc and nitric oxide in the nervous, cardiovascular, and immune systems is highlighted to illustrate the contributions of selective fluorescent probes to the study of these two important bioinorganic analytes.National Science Foundation (Grant Number CHE-0907905)National Institutes of Health (U.S.) (Grant Number GM065519)National Institutes of Health (U.S.) (Grant Number K99GM092970

On Transcendental Materialism and the Natural Real

This paper considers the status of both the natural real and thinking in transcendental or structural materialisms, and questions whether the relationship between thinking and being in such philosophies can really be considered dialectical or not. Looking at the recent work of Slavoj Žižek, but with an eye to work being done by thinkers such as Brassier, Johnston, and Meillassoux as well, I consider what is said about quantum physics in some of Žižek’s recent books, and argue that it is difficult to see how any version of the natural real – quantum or not – can have a status in a dialectical philosophy that does not end up at least implicitly giving ordinary human experience and thought a de-realized or ontologically degraded status, in a manner that is in fact very un-dialectical. The sciences basically require a reductionist perspective, such that it is hard to argue that there is any vigorous relationship between thinking and being in them. There is much about human experience and thinking that does need to be de-realized, of course. Hegelian philosophy and Freudo-Lacanian psychoanalysis have always done an excellent job of that

Alain Badiou, Kojève, and the Return of the Human Exception

The theory of life that Badiou proposes at the end of Logics of Worlds is considered in this paper as a retooling of the old idea that the human is an exception in the order of things. What distinguishes Badiou’s account of the human from others though is the fact that it posits the human not as an exception from other animals, nor as an exception to ordinary life, but an exception that is other to the individual as such. The way in which Alexandre Kojève framed the human in his reading of Hegel is used to establish the basic philosophical grammar for Badiou’s thinking about the human. What Badiou calls “democratic materialism” – his philosophical nemesis – is also considered from the perspective of that grammar

Genetic Correlation with the DNA Repair Assay in Mice Exposed to High-LET

We hypothesize that DNA damage induced by high local energy deposition, occurring when cells are traversed by high-LET (Linear Energy Transfer) particles, can be experimentally modeled by exposing cells to high doses of low-LET. In this work, we validate such hypothesis by characterizing and correlating the time dependence of 53BP1 radiation-induced foci (RIF) for various doses and LET across 72 primary skin fibroblast from mice. This genetically diverse population allows us to understand how genetic may modulate the dose and LET relationship. The cohort was made on average from 3 males and 3 females belonging to 15 different strains of mice with various genetic backgrounds, including the collaborative cross (CC) genetic model (10 strains) and 5 reference mice strains. Cells were exposed to two fluences of three HZE (High Atomic Energy) particles (Si 350 megaelectronvolts per nucleon, Ar 350 megaelectronvolts per nucleon and Fe 600 megaelectronvolts per nucleon) and to 0.1, 1 and 4 grays from a 160 kilovolt X-ray. Individual radiation sensitivity was investigated by high throughput measurements of DNA repair kinetics for different doses of each radiation type. The 53BP1 RIF dose response to high-LET particles showed a linear dependency that matched the expected number of tracks per cell, clearly illustrating the fact that close-by DNA double strand breaks along tracks cluster within one single RIF. By comparing the slope of the high-LET dose curve to the expected number of tracks per cell we computed the number of remaining unrepaired tracks as a function of time post-irradiation. Results show that the percentage of unrepaired track over a 48 hours follow-up is higher as the LET increases across all strains. We also observe a strong correlation between the high dose repair kinetics following exposure to 160 kilovolts X-ray and the repair kinetics of high-LET tracks, with higher correlation with higher LET. At the in-vivo level for the 10-CC strains, we observe that drops in the number of T-cells and B-cells found in the blood of mice 24 hours after exposure to 0.1 gray of 320 kilovolts X-ray correlate well with slower DNA repair kinetics in skin cells exposed to X-ray. Overall, our results suggest that repair kinetics found in skin is a surrogate marker for in-vivo radiation sensitivity in other tissue, such as blood cells, and that such response is modulated by genetic variability

Ho-Chunk Chiefs: Winnebago Leadership in An Era of Crisis

Review of: Ho-Chunk Chiefs: Winnebago Leadership in an Era of Crisis. Diedrich, Mark