Photolytic Hazes in the Atmosphere of 51 Eri b

We use a 1D model to address photochemistry and possible haze formation in the irradiated warm Jupiter, 51 Eridani b. The intended focus was to be carbon, but sulfur photochemistry turns out to be important. The case for organic photochemical hazes is intriguing but falls short of being compelling. If organic hazes form, they are likeliest to do so if vertical mixing in 51 Eri b is weaker than in Jupiter, and they would be found below the altitudes where methane and water are photolyzed. The more novel result is that photochemistry turns H$_2$S into elemental sulfur, here treated as S$_8$. In the cooler models, S$_8$ is predicted to condense in optically thick clouds of solid sulfur particles, whilst in the warmer models S$_8$ remains a vapor along with several other sulfur allotropes that are both visually striking and potentially observable. For 51 Eri b, the division between models with and without condensed sulfur is at an effective temperature of 700 K, which is within error its actual effective temperature; the local temperature where sulfur condenses is between 280 and 320 K. The sulfur photochemistry we have discussed is quite general and ought to be found in a wide variety of worlds over a broad temperature range, both colder and hotter than the 650-750 K range studied here, and we show that products of sulfur photochemistry will be nearly as abundant on planets where the UV irradiation is orders of magnitude weaker than it is on 51 Eri b.Comment: 24 pages including 11 figures and a tabl

Accounting Conservatism and its Benefits to Shareholders in Developing Capital Market: Evidence from Nigeria

This study investigated the relationship between accounting conservatism and shareholders value of selected quoted companies in Nigeria. The proxy for accounting conservatism was asymmetric accrual to cash-flow (AACF) and shareholders fund was the proxy for shareholders value. Exchange and inflation rates were included as control variables. This study adopted ex-post facto research design. The population of the study was all quoted companies on the Nigeria Stock Exchange from which a sample of 20 companies was chosen using judgmental sampling technique. Secondary data was obtained from annual report and accounts of the sampled companies for a period of ten years (2006 to 2015). Multiple regression analysis was used to analyze the data collected. The hypothesis was tested using F-Statistic. The result of the study revealed existence of a significant positive relationship between accounting conservatism and shareholders value with F-statistic p-value of 0.016 for all our explanatory variables. This result was validated with robustness checks and it was discovered that the relationship between conservatism and shareholders value was high for firms with higher information asymmetry. The finding implies that accounting conservatism is an efficient governance mechanism to mitigate information risk and control for agency problems. Hence, we concluded that shareholders derive benefits from accounting conservatism practice in Nigeria

Measurement of Gamma Radiation in an Automobile Mechanic Village in Abuja, North Central, Nigeria

Environmental radiation measurement was carried out in an automobile mechanic village, Apo, Abuja, Nigeria. An in-situ measurement approach was adopted using RDS-200 Universal Survey Meter and a handheld Global Positioning System (Garmin GPS 76S) equipment. It was observed that the dose equivalent varied from 0.04 μSv/h to 0.22 μSv/h with a mean of 0.10± 0.03 μSv/h which is below the standard background radiation of 0.133 μSv/h The study also revealed that the average annual effective dose rate is approximately 0.20±0.06 mSv/yr which is lower than the value of 1.0 mSv/yr averaged over five consecutive years according to the dose limit placed by the Basic Safety Standards (BSS) SCHEDULE II and the International Commission on Radiological Protection (ICRP) REPORT 60. This indicates that the automobile technicians, craftsmen and the people living and working within the area are safe and are not exposed to high doses of radiation as a result of activities in the Apo Automobile Mechanic Village.Keywords: Radiation Measurement; Apo Automobile Mechanic Village; Background Radiation; DoseEquivalent; Annual Effective Dose; Automobile Technician

Production and characterization of titanium carbide particulate reinforced AA6061 aluminum alloy composites using stir casting

Abstract: Stir casting is an economical method to produce aluminum matrix composites. In the present work, composites of aluminum alloy AA6061 reinforced with various amounts (0, 5, 10 and 15wt. %) of TiC particles were prepared by stir casting technique. X-ray diffraction patterns of the prepared composites clearly revealed the incorporation of TiC particles without the presence of any other compounds. The microstructures of the composites were studied using optical and scanning electron microscopy. It was observed that the TiC particles distributed all over the composite and properly bonded to the matrix alloy. Local clusters of TiC particle were also seen in a few places. The result shows that the reinforcement of TiC particles enhances the microhardness, ultimate tensile strength and wear resistance of the composite. The details of fracture morphology, worn surface and wear debris are also presented in this paper

Predicting the influence of process parameters on tensile strength of AA6061/TiC aluminum matrix composites produced using stir casting

Abstract: Stir casting is an economical method to produce aluminum matrix composites (AMCs). In this work, stir casting was used to produce AA6061/15wt. % TiC AMCs. An empirical relationship was developed to predict the effect of stir casting parameters on the ultimate tensile strength (UTS) of AA6061/TiC AMCs. A central composite rotatable design consisting of four factors and five levels was used to minimize the number of experiments i.e. castings. The factors considered were stirrer speed, stirring time, blade angle and casting temperature. The effect of those factors on the UTS of AA6061/TiC AMCs was derived using the developed empirical relationship and elucidated using microstructural characterization. Each factor significantly influenced the UTS. A higher or lower values of those factors resulted in poor tensile strength. The variation in the UTS was attributed to porosity content, cluster formation, segregation of TiC particles at the grain boundaries and 2 homogenous distribution in the aluminum matrix. The UTS was high when the porosity content was low and the distribution was homogenous. The present work concludes that a careful selection and control of stir casting parameters are necessary to reduce porosity content and obtain uniform distribution to improve the load bearing capacity of the AA6061/TiC AMCs

Influence of Homeotropic Anchoring Walls upon Nematic and Smectic Phases

McMillan liquid crystal model sandwiched between strong homeotropic anchoring walls is studied. Phase transitions between isotropic, nematic, and smectic A phases are investigated for wide ranges of an interaction parameter and of the system thickness. It is confirmed that the anchoring walls induce an increase in transition temperatures, dissappearance of phase transitions, and an appearance of non-spontaneous nematic phase. The similarity between influence of anchoring walls and that of external fields is discussed.Comment: 5 pages, 6 figure

Temperature dependence of the interlayer magnetoresistance of quasi-one-dimensional Fermi liquids at the magic angles

The interlayer magnetoresistance of a quasi-one-dimensional Fermi liquid is considered for the case of a magnetic field that is rotated within the plane perpendicular to the most-conducting direction. Within semi-classical transport theory dips in the magnetoresistance occur at integer amgic angles only when the electronic dispersion parallel to the chains is nonlinear. If the field direction is fixed at one of the magic angles and the temperature is varied the resulting variation of the scattering rate can lead to a non-monotonic variation of the interlayer magnetoresistance with temperature. Although the model considered here gives a good description of some of the properties of the Bechgaard salts, (TMTSF)2PF6 for pressures less than 8kbar and (TMTSF)2ClO4 it gives a poor description of their properties when the field is parallel to the layers and of the intralayer transport.Comment: 10pages, RevTeX + epsf, 3 figure