Regional climate simulation of present day temperature over India using RegCM3: Evaluation and analysis of model performance

The study has focused on the evaluation of model performance on simulated air temperature at surface and mid atmospheric level over the Indian subcontinent using a Regional Climate Model version 3 (RegCM3). The model is used at 40 km horizontal resolution over the domain approximately 58° E-102.5° E & 5° N-40° N for the period of 1982-2006. The temperatures at lower troposphere (850 hPa) and mid tropospheric level (500 hPa) have been simulated with reanalysis dataset of the National Centre for Environmental Prediction (NCEP). Various statistical measures namely Mean Bias Error (MBE), Root Mean Square Error (RMSE), Mean Percentage Error (MPE) and Correlation Coefficients (CCs) has been used to test the model results. It has been found that the RegCM3 is able to capture the main features of the observed mean surface climate and also patterns of surface and mid-level air temperatures over India. The model showed that cold biases were -4.29 °C (16.4%) at the lower troposphere, but insignificant at the mid atmospheric level in comparison to the NCEP dataset. The air temperature was well captured at mid tropospheric level. The CC between RegCM3 and NCEP is significantly high (0.82) over India in respect of annual surface air temperature (SAT). The trends of observed SAT were found to be significant increased by 0.32 °C with NCEP and 0.40 °C with RegCM3 over India. The annual SAT of cold biases ranging between -2 °C to -5 °C was found over major parts of India while cold biases of above -5 °C was found in the regions of low elevation or valley regions and below -2 °C in the mountainous regions. The analysis of annual and seasonal trends of maximum air temperature (Tmax), minimum air temperature (Tmin) and average air temperature (Tave) showed that the increasing trend was found over the Indo-Gangetic plain, Western Himalayas (WH) and North East India (NEI) in all seasons while decreasing trend over the North Central India (NCI) in the summer season and over the state of Gujarat in the monsoon season. The RegCM3 showed higher Water Vapour Mixing Ratio (WVMR) at the lower troposphere resulting more cooling at surface rather than at mid tropospheric level.

A prolonged, two-step oxygenation of Earth’s early atmosphere: Support from confidence intervals

The Great Oxidation Event (GOE), among Earth’s most transformative events, marked the sustained presence of oxygen above 10–5 times the present atmospheric level. Estimates of the onset of the GOE span 2501–2225 Ma and are based primarily on the loss of mass-independent fractionation of sulfur isotopes (MIF-S) in pyrite. To better constrain the timing of the GOE, we apply probabilistic techniques to estimate the confidence intervals of four proxies: MIF-S, redox-sensitive detrital minerals, "red beds," and I/(Ca + Mg). These GOE proxies are drawn from a highly fragmentary geologic record, and consequently, estimates of the 95% confidence intervals span tens to hundreds of millions of years—orders of magnitude larger than suggested by radiometric constraints on individual successions. Confidence interval results suggest that red beds and nonzero I/(Ca + Mg) values may have appeared earlier than 2480 Ma and 2460 Ma, respectively, whereas redox-sensitive detrital minerals and MIF-S may have disappeared after 2210 Ma and 2190 Ma, respectively. These data suggest a delay of potentially >300 m.y. between initial and permanent oxygenation of the atmosphere and a delay of tens of millions of years between onset of the Lomagundi-Jatuli carbon isotope excursion and permanent oxygenation of the atmosphere.

A case for low atmospheric oxygen levels during Earth's middle history

The oxygenation of the atmosphere — one of the most fundamental transformations in Earth's history — dramatically altered the chemical composition of the oceans and provides a compelling example of how life can reshape planetary surface environments. Furthermore, it is commonly proposed that surface oxygen levels played a key role in controlling the timing and tempo of the origin and early diversification of animals. Although oxygen levels were likely more dynamic than previously imagined, we make a case here that emerging records provide evidence for low atmospheric oxygen levels for the majority of Earth's history. Specifically, we review records and present a conceptual framework that suggest that background oxygen levels were below 1% of the present atmospheric level during the billon years leading up to the diversification of early animals. Evidence for low background oxygen levels through much of the Proterozoic bolsters the case that environmental conditions were a critical factor in controlling the structure of ecosystems through Earth's history.

Pathophysiology of pleural cavity disorders

The pleural cavity is normally a virtual space that is essential to guarantee the mechanical coupling between the lung and the chest wall. The volume of pleural liquid is determined by the equilibrium of fluid turnover. The determinants of this balance are the Starling forces, the lymphatic drainage, and the active trans-membrane transport. When fluid or air accumulate inside the pleural cavity, pleural pressure rises to atmospheric level causing the lung to collapse while the chest wall to expand. The displacement is not equally distributed between lung and chest wall, because it depends upon their own compliance. Pneumothorax and pleural effusion are common diseases in critically-ill patients. Pneumothorax is divided in two groups based upon the aetiological mechanism—spontaneous and traumatic. Pleural effusion is classified as transudates or exudates, mainly based on protein content; this classification comprises different pathological mechanisms beneath the two kind of pleural effusion.

Early metazoan life: divergence, environment and ecology

Recent molecular clock studies date the origin of Metazoa to 750–800 million years ago (Ma), roughly coinciding with evidence from geochemical proxies that oxygen levels rose from less than 0.1% present atmospheric level (PAL) to perhaps 1–3% PAL O 2 . A younger origin of Metazoa would require greatly increased substitution rates across many clades and many genes; while not impossible, this is less parsimonious. Yet the first fossil evidence for metazoans (the Doushantuo embryos) about 600 Ma is followed by the Ediacaran fossils after 580 Ma, the earliest undisputed bilaterians at 555 Ma, and an increase in the size and morphologic complexity of bilaterians around 542 Ma. This temporal framework suggests a missing 150–200 Myr of early metazoan history that encompasses many apparent novelties in the early evolution of the nervous system. This span includes two major glaciations, and complex marine geochemical changes including major changes in redox and other environmental changes. One possible resolution is that animals of these still unknown Cryogenian and early Ediacaran ecosystems were relatively simple, with highly conserved developmental genes involved in cell-type specification and simple patterning. In this model, complex nervous systems are a convergent phenomenon in bilaterian clades which occurred close to the time that larger metazoans appeared in the fossil record.

The use of solar energy can enhance the conversion of carbon dioxide into energy-rich products: stepping towards artificial photosynthesis

The need to cut CO 2 emission into the atmosphere is pushing scientists and technologists to discover and implement new strategies that may be effective for controlling the CO 2 atmospheric level (and its possible effects on climate change). One option is the capture of CO 2 from power plant flue gases or other industrial processes to avoid it entering the atmosphere. The captured CO 2 can be either disposed in natural fields (geological cavities, spent gas or oil wells, coal beads, aquifers; even oceans have been proposed) or used as a source of carbon in synthetic processes. In this paper, we present the options for CO 2 utilization and make an analysis of possible solutions for the conversion of large volumes of CO 2 by either combining it with H 2 , that must be generated from water, or by directly converting it into fuels by electrolysis in water using solar energy. A CO 2 –H 2 -based economy may address the issue of reducing the environmental burden of energy production, also saving fossil carbon for future generations. The integration of CO 2 capture and utilization with CO 2 capture and storage would result in a more economically and energetically viable practice of CO 2 capture.