The K-band Hubble diagram of submillimetre galaxies and hyperluminous galaxies

We present the K -band Hubble diagrams ( K – z relations) of submillimetre-selected galaxies and hyperluminous galaxies (HLIRGs). We report the discovery of a remarkably tight K – z relation of HLIRGs, indistinguishable from that of the most luminous radio galaxies. Like radio galaxies, the HLIRG K – z relation at   z ≲ 3  is consistent with a passively evolving ∼3 L _* instantaneous starburst starting from a redshift of   z ∼ 10  . In contrast, many submillimetre-selected galaxies are ≳2 mag fainter, and the population has a much larger dispersion. We argue that dust obscuration and/or a larger mass range may be responsible for this scatter. The galaxies so far proved to be hyperluminous may have been biased towards higher AGN bolometric contributions than submillimetre-selected galaxies due to the 60-μm selection of some, so the location on the K – z relation may be related to the presence of the most massive active galactic nucleus. Alternatively, a particular host galaxy mass range may be responsible for both extreme star formation and the most massive active nuclei.     

Role of market agents in mitigating the climate change effects on food economy

Natural Hazards - Agriculture’s ability to adapt to the impacts of climate change is critical for agricultural households as well as the general public and policymakers. Economic agents can...     

An analysis of vegetation indices in relation to tree species diversity using by satellite data in the northern forests of Iran

Vegetation indices have been introduced for analyzing and assessing the status of quantitative and qualitative characteristics of vegetation using satellite images. However, choosing the best indices to be used in forest biodiversity and vegetation is one of the important problems faced by the users. The purpose of this research is to evaluate six vegetation indices in the analysis of tree species diversity in the northern forests of Iran. The present research uses LISS III sensor data from IRS-P6 satellite. Geometric rectification of images was performed using ground control points, and Chavez model was used for atmospheric correction of the data. The six spectral vegetation indices included NDVI, IPVI, Ashburn Vegetation Index (AVI), TVI, TTVI, and RVI. Shannon–Wiener species diversity index was used to analyze diversity, and the value of the index was calculated in each sample plot. Then, the spectral values of each sample plot were extracted from different bands. The best subset regression was used to analyze the relationship between species diversity and the related bands. The results obtained from the regression showed that polynomial equations under scrutiny as independent variables can assess tree and shrub species diversity better than other bands and compounds used (R ²?=?0.47). The obtained results also indicated a higher capacity in the case of the AVI index for estimating tree species diversity in the under study area.     

Toward an Ecological Explanation of Agricultural Unemployment in Bangladesh

Cultural ecology theoretical framework was found suitable to explain unemployment in agriculture in three villages in Bangladesh. Path analysis and multiple regression statistics were used to examine the direct, indirect, and total effects of eight independent human, social, environmental, and technology variables as well as their aggregate contribution on agricultural unemployment. The multiple regression model explains 86.2% of the total variation in unemployment in agriculture; they were followed by environmental constraints and labor saving technology variables.     

Prediction of riverine suspended sediment discharge using fuzzy logic algorithms, and some implications for estuarine settings

The ability of fuzzy logic algorithms to model relationships between stream flow and suspended sediment discharge was investigated using daily measurements of stream flow and suspended sediment discharge for the Escanaba River mouth station, situated on the shore of Lake Michigan and operated by the US Geological Survey. Three different configurations of inputs were applied, whereby the inputs were fuzzified into fuzzy subsets of variables by means of triangular membership functions. The relationships between inputs and suspended sediment discharge (output) were represented by a set of fuzzy rule expressed in IF–THEN format. The weighted average method served for defuzzification. The commonly used sediment rating curve was also applied to the data, and its performance compared with that of the three models by means of statistical analyses. For all three models, suspended sediment discharge predicted by the fuzzy logic algorithm was in satisfactory agreement with observations. Furthermore, the fuzzy logic algorithms performed better than the sediment rating curve, particularly at higher rates of suspended sediment discharge (in this study, more than 50  × 10⁶ g/day). Considered collectively, the use of fuzzy logic algorithms is suggested as a simple and effective approach for better prediction of suspended sediment discharge, also for estuaries.     

Aerosol characteristics during winter fog at Agra,North India

Simultaneous measurements on physical, chemical and optical properties of aerosols over a tropical semi-arid location, Agra in north India, were undertaken during December 2004. The average concentration of total suspended particulates (TSP) increased by about 1.4 times during intense foggy/hazy days. Concentrations of SO₄ ²⁻, NO₃ ⁻, NH₄ ⁺ and Black Carbon (BC) aerosols increased by 4, 2, 3.5 and 1.7 times, respectively during that period. Aerosols were acidic during intense foggy/hazy days but the fog water showed alkaline nature, mainly due to the neutralizing capacity of NH₄ aerosols. Trajectory analyses showed that air masses were predominantly from NW direction, which might be responsible for transport of BC from distant and surrounding local sources. Diurnal variation of BC on all days showed a morning and an evening peak that were related to domestic cooking and vehicular emissions, apart from boundary layer changes. OPAC (Optical properties of aerosols and clouds) model was used to compute the optical properties of aerosols. Both OPAC-derived and observed aerosol optical depth (AOD) values showed spectral variation with high loadings in the short wavelengths (<1 μm). AOD value at 0.5 μm wavelength was significantly high during intense foggy/hazy days (1.22) than during clear sky or less foggy/hazy days (0.63). OPAC-derived Single scattering albedo (SSA) was 0.84 during the observational period, indicating significant contribution of absorbing aerosols. However, the BC mass fraction to TSP increased by only 1% during intense foggy/hazy days and thereby did not show any impact on SSA during that period. A large increase was observed in the shortwave (SW) atmospheric (ATM) forcing during intense foggy/hazy days (+75.8 W/m²) than that during clear sky or less foggy/hazy days (+38 W/m²), mainly due to increase in absorbing aerosols. Whereas SW forcing at surface (SUF) increased from −40 W/m² during clear sky or less foggy/hazy days to −76 W/m² during intense foggy/hazy days, mainly due to the scattering aerosols like SO₄ ^2-.     

Modeling Seismic Attributes of Pn Waves using the Spectral-Element Method

To investigate the nature of Pn propagation, we have implemented the spectral-element method (SEM) for vertically and laterally varying media with and without attenuation. As a practical measure, essential features of the Pn waves are distilled into seismic attributes including arrival times, amplitudes and pulse frequencies. To validate the SEM simulations, we first compare the SEM results with reflectivity calculations of Braile and Smith (Geophys. J.R. Astr. Soc. 40, 145–176, 1975) and then to the asymptotic results of ?erveny and Ravindra (Theory of Seismic Headwaves, University of Toronto Press, pp. 235–250, 1971). Models with random, laterally varying Moho structures are then simulated, where the amplitude and pulse frequency characteristics are found to be stable to small Moho interface perturbations. SEM calculations for models with different upper-mantle velocity gradients are next performed where it is found that interference effects can strongly influence the Pn amplitudes and pulses frequencies. For larger-scale, laterally varying structures, SEM models similar to that found along the Hi-CLIMB array in Tibet are then performed. It is observed that large-scale structures, along with small-scale structures, upper-mantle velocity gradients and attenuation, can all significantly affect the Pn attributes. Ambiguities between upper-mantle velocity gradients and attenuation are also found when using Pn amplitudes and pulse frequency attributes. These ambiguities may be resolved, to some degree, by using the curvature of the travel times at longer regional distance, however, this would also be complicated by lateral variability.     

Present environmental status of Al-Kharrar Lagoon,central of the eastern Red Sea coast,Saudi Arabia

Al-Kharrar Lagoon is a fossil back-reef basin with hypersaline waters, situated 10 km northwest of Rabigh city, central of the eastern Red Sea coast, Saudi Arabia. About 130 stations were selected for measurements of the lagoon’s water temperature, salinity, pH, dissolved oxygen, and water depths during March 2014. The common macro-algae, flora, and fauna were also sampled and identified. The present study aims to investigate the prevailing environmental parameters and their impact on the macro-fauna/flora of the lagoon. The average water depth of the lagoon was around 5 m and reached maximum values of 8 and 16 at the lagoon centre and inlet, respectively. The results showed that the lagoon’s surface water temperature and salinity have mean values of 25 °C and 40‰, but with extreme values of 30 °C and 45‰ that occurred only at the enclosed intertidal areas, respectively. Their dissolved oxygen (DO) and pH were 6.5 mg/l and 8.3, respectively and the latter showing the highest values up to 8.5 in the intertidal areas dominated by the green cyanobacteria. These physicochemical conditions make the lagoon as a favorite place for the mangrove Avicennia marina, macro-algae, seagrasses (Halophila stipulacea and Cymodocea rotundata), and algal mats (Cyanobacteria) which dominate the intertidal and supratidal areas of the lagoon, tolerating extremely high-salinity and high-temperature conditions. On the other hand, corals were observed alive at the southern part of the lagoon, immediately south of the Al-Ultah Islet. Vertical profiles of temperature, salinity, and density in the lagoon’s water indicated that the water column consists of two layers throughout the year.