First star signatures on high-z GRBs and DLAs

First stars were born after the dark age era of the Universe. They produced the first light and metal pollution in the Universe. This was predicted in theory a long time ago, but no direct observation is available. In this thesis I study the first star signatures in high-z Gamma-ray Bursts from Population II stars (GRBIIs) and in Damped Laymanα Absorbers (DLAs), using numerical N-body/hydrodynamic simulations that include atomic and molecular cooling, star formation and metal enrichment from stellar populations with different initial mass functions. I first use one simulation based on a very massive first star model (m∗ = [100, 500]M⊙) to study the GRBIIs hosted in a medium enriched by first stars (PopIII-dominated). I find that a high fraction of high-z GRBIIs are PopIII-dominated, e.g. ∼10% at z = 10, but this fraction decreases quickly with redshift, e.g. only ∼1% at z = 6. Then I study the possibility to distinguish different first star models using observations of high-z GRBs by running three simulations with different mass ranges and the corresponding lifetimes and metal yields for first stars. I find that the fraction of GRBs that are PopIII-dominated is independent from the first star models. Similarly, PopIII-dominated GRBIIs are mostly hosted in galaxies with low metallicity, star formation rate and stellar mass. Because of the special metal yields of metal-free stars, the first star signals could be identified with the metal abundance ratios derived from the absorption lines in the GRBII afterglow spectra, e.g. the [Si/O] vs [C/O] or [Fe/C] vs [Si/C] would distinguish an imprint from very massive and massive first stars. However, the currently observed high-z GRBs, e.g. GRB 130606A at z = 5.91 and GRB 111008A at z = 5.0, do not display obvious metal features from first stars, which is also consistent with the low fraction of PopIII-dominated GRBs in this redshift range. I also study the imprint of first stars on high-z DLAs, and explore how to use the observations of DLAs to constrain the first star models. Since DLAs are characterized by very high neutral hydrogen density, low gas temperature and ionization fraction, a high fraction of DLAs at z > 5.5 could contain first stars signatures. From my simulations, I find that ∼ 40% of DLAs contain such imprint if they are selected as galaxies with temperature 5 are more consistent with a model in which the first stars have a mass in the range m∗ = [0.1, 100]M⊙, rather than one with very massive first stars, although the comparison is not conclusive and still subject to some uncertainty

First star signatures on high-z GRBs and DLAs

First stars were born after the dark age era of the Universe. They produced the first light and metal pollution in the Universe. This was predicted in theory a long time ago, but no direct observation is available. In this thesis I study the first star signatures in high-z Gamma-ray Bursts from Population II stars (GRBIIs) and in Damped Laymanα Absorbers (DLAs), using numerical N-body/hydrodynamic simulations that include atomic and molecular cooling, star formation and metal enrichment from stellar populations with different initial mass functions. I first use one simulation based on a very massive first star model (m∗ = [100, 500]M⊙) to study the GRBIIs hosted in a medium enriched by first stars (PopIII-dominated). I find that a high fraction of high-z GRBIIs are PopIII-dominated, e.g. ∼10% at z = 10, but this fraction decreases quickly with redshift, e.g. only ∼1% at z = 6. Then I study the possibility to distinguish different first star models using observations of high-z GRBs by running three simulations with different mass ranges and the corresponding lifetimes and metal yields for first stars. I find that the fraction of GRBs that are PopIII-dominated is independent from the first star models. Similarly, PopIII-dominated GRBIIs are mostly hosted in galaxies with low metallicity, star formation rate and stellar mass. Because of the special metal yields of metal-free stars, the first star signals could be identified with the metal abundance ratios derived from the absorption lines in the GRBII afterglow spectra, e.g. the [Si/O] vs [C/O] or [Fe/C] vs [Si/C] would distinguish an imprint from very massive and massive first stars. However, the currently observed high-z GRBs, e.g. GRB 130606A at z = 5.91 and GRB 111008A at z = 5.0, do not display obvious metal features from first stars, which is also consistent with the low fraction of PopIII-dominated GRBs in this redshift range. I also study the imprint of first stars on high-z DLAs, and explore how to use the observations of DLAs to constrain the first star models. Since DLAs are characterized by very high neutral hydrogen density, low gas temperature and ionization fraction, a high fraction of DLAs at z > 5.5 could contain first stars signatures. From my simulations, I find that ∼ 40% of DLAs contain such imprint if they are selected as galaxies with temperature 5 are more consistent with a model in which the first stars have a mass in the range m∗ = [0.1, 100]M⊙, rather than one with very massive first stars, although the comparison is not conclusive and still subject to some uncertainty

Fiber-Optic Micro-Probes for Measuring Acidity Level, Temperature, and Antigens

A pH micro-probe, a temperature micro-probe, and an immuno-based micro-probe each include a shaft for transmuting an input light signal and a tip for inserting into a cell or other substance for measuring pH, temperature, and/or antigens. The pH micro-probe and the temperature micro-probe each include a luminescent material positioned on the tip of the micro-probe. The light signal excites the luminescent material so that the luminescent material emits a luminescent light signal. The luminescent light signal has a property value dependent on the pH or temperature being measured and reflects back through the shaft for being measured by a light signal measuring device. The immuno-based micro-probe includes a reflective material that has an effective refractive index dependent on the number of antigen-antibody bonds present on the reflective material

Effect of Freeze-Thaw Cycle on Shear Strength of Lime-Solidified Dispersion Soils

The freeze-thaw cycle of saline soil in the seasonal frozen area will produce diseases such as frost heave and thaw settlement, road frost boiling, collapse and uneven settlement. In order to reduce the occurrence of these undesirable phenomena, it is often necessary to improve the saline soil in engineering. In this paper, the typical carbonate saline soil in the west of Jilin Province, China is taken as the research object. By adding different content of lime (0%, 3%, 6%, 9%, 12%, 15%), the change of mechanical strength of lime solidified saline soil under different freeze-thaw cycles (0, 1, 3, 6, 10, 30, 60 times) is studied. The mechanical analysis is carried out by combining particle size analysis test and SEM image. The test results show that although repeated freeze-thaw cycles make the soil structure loose and the mechanical strength greatly reduced, the soil particles agglomerate obviously after adding lime, its dispersion is restrained by the flocculation of clay colloid, and the shear strength of soil is improved by the increase of the cohesive force between clay particles, and the optimal lime mixing ratio of the saline soil in this area is 9%

An Improved Method on Static Binary Analysis to Enhance the Context-Sensitive CFI

Control Flow Integrity (CFI) is one of the most promising technique to defend Code-Reuse Attacks (CRAs). Traditional CFI Systems and recent Context-Sensitive CFI use coarse control flow graphs (CFGs) to analyze whether the control flow hijack occurs, left vast space for attackers at indirect call-sites. Coarse CFGs make it difficult to decide which target to execute at indirect control-flow transfers, and weaken the existing CFI systems actually. It is an unsolved problem to extract CFGs precisely and perfectly from binaries now. In this paper, we present an algorithm to get a more precise CFG from binaries. Parameters are analyzed at indirect call-sites and functions firstly. By comparing counts of parameters prepared before call-sites and consumed by functions, targets of indirect calls are reduced. Then the control flow would be more constrained at indirect call-sites in runtime. Combined with CCFI, we implement our policy. Experimental results on some popular programs show that our approach is efficient. Further analysis show that it can mitigate COOP and other advanced attacks

Probing the high-z IGM with the hyperfine transition of 3^3He+^+

The hyperfine transition of $^3$He$^+$ at 3.5cm has been thought as a probe of the high-z IGM since it offers a unique insight into the evolution of the helium component of the gas, as well as potentially give an independent constraint on the 21cm signal from neutral hydrogen. In this paper, we use radiative transfer simulations of reionization driven by sources such as stars, X-ray binaries, accreting black holes and shock heated interstellar medium, and simulations of a high-z quasar to characterize the signal and analyze its prospects of detection. We find that the peak of the signal lies in the range 1-50 $\mu$K for both environments, but while around the quasar it is always in emission, in the case of cosmic reionization a brief period of absorption is expected. As the evolution of HeII is determined by stars, we find that it is not possible to distinguish reionization histories driven by more energetic sources. On the other hand, while a bright QSO produces a signal in 21cm that is very similar to the one from a large collection of galaxies, its signature in 3.5cm is very peculiar and could be a powerful probe to identify the presence of the QSO. We analyze the prospects of the signal's detectability using SKA1-mid as our reference telescope. We find that the noise power spectrum dominates over the power spectrum of the signal, although a modest S/N ratio can be obtained when the wavenumber bin width and the survey volume are sufficiently large.Comment: 10 pages, 13 figures, accepted for publication in MNRA

AcidoCEST-UTE MRI for the Assessment of Extracellular pH of Joint Tissues at 3 T.

ObjectivesThe goal of this study was to demonstrate feasibility of measuring extracellular pH in cartilage and meniscus using acidoCEST technique with a 3-dimensional ultrashort echo time readout (acidoCEST-UTE) magnetic resonance imaging (MRI).Materials and methodsMagnetization transfer ratio asymmetry, radiofrequency (RF) power mismatch, and relative saturation transfer were evaluated in liquid phantoms for iopromide, iopamidol, and iohexol over a pH range of 6.2 to 7.8, at various agent concentrations, temperatures, and buffer concentrations. Tissue phantoms containing cartilage and meniscus were evaluated with the same considerations for iopamidol and iohexol. Phantoms were imaged with the acidoCEST-UTE MRI sequence at 3 T. Correlation coefficients and coefficients of variations were calculated. Paired Wilcoxon rank-sum tests were used to evaluate for statistically significant differences.ResultsThe RF power mismatch and relative saturation transfer analyses of liquid phantoms showed iopamidol and iohexol to be the most promising agents for this study. Both these agents appeared to be concentration independent and feasible for use with or without buffer and at physiologic temperature over a pH range of 6.2 to 7.8. Ultimately, RF power mismatch fitting of iohexol showed the strongest correlation coefficients between cartilage, meniscus, and fluid. In addition, ratiometric values for iohexol are similar among liquid as well as different tissue types.ConclusionsMeasuring extracellular pH in cartilage and meniscus using acidoCEST-UTE MRI is feasible

Surgical Strategy for the Management of Renal Cell Carcinoma with Inferior Vena Cava Tumor Thrombus

The hallmark of renal cell carcinoma is its biological characteristic of invading the renal vein and/or inferior vena cava (IVC), which occurs in 4–10% of patients. Radical nephrectomy (RN) with tumor thrombectomy is the standard approach for treating such challenging cases. Except tumor thrombus height, several factors can determine the surgical strategy, including the effect of targeted molecular therapy (TMT), invasion of the IVC wall, venous occlusion, establishment of collateral circulation, IVC thromboembolism, and primary tumor location. The surgical strategy for patients with retrohepatic vena cava tumor thrombi depends on the upper extent of the tumor thrombus. In addition, the first porta hepatis and hepatic veins are important anatomical boundaries. Based on previous studies, the effect of pre-surgical TMT is limited. The safety of IVC venography, an imaging modality that can observe congestion of the tumor thrombus and show the collateral circulation, has considerably improved. IVC interruption plays an important role in tumor thrombectomy for patients with invasion of the venous walls, complete occlusion of the vena cava, and the presence of distal thrombus. A series of retrospective and prospective studies are needed to be conducted, which will provide our clinical work with more powerful reference and basis