Transition from Coherent to Stochastic electron heating in ultrashort relativistic laser interaction with structured targets.

Relativistic laser interaction with micro- and nano-scale surface structures enhances energy transfer to solid targets and yields matter in extreme conditions. We report on the comparative study of laser-target interaction mechanisms with wire-structures of different size, revealing a transition from a coherent particle heating to a stochastic plasma heating regime which occurs when migrating from micro-scale to nano-scale wires. Experiments and kinetic simulations show that large gaps between the wires favour the generation of high-energy electrons via laser acceleration into the channels while gaps smaller than the amplitude of electron quivering in the laser field lead to less energetic electrons and multi-keV plasma generation, in agreement with previously published experiments. Plasma filling of nano-sized gaps due to picosecond pedestal typical of ultrashort pulses strongly affects the interaction with this class of targets reducing the laser penetration depth to approximately one hundred nanometers. The two heating regimes appear potentially suitable for laser-driven ion/electron acceleration schemes and warm dense matter investigation respectively.

Spatio-temporal variation in chemical characteristics of PM10 over Indo Gangetic Plain of India.

The paper presents the spatio-temporal variation of chemical compositions (organic carbon (OC), elemental carbon (EC), and water-soluble inorganic ionic components (WSIC)) of particulate matter (PM10) over three locations (Delhi, Varanasi, and Kolkata) of Indo Gangetic Plain (IGP) of India for the year 2011. The observational sites are chosen to represent the characteristics of upper (Delhi), middle (Varanasi), and lower (Kolkata) IGP regions as converse to earlier single-station observation. Average mass concentration of PM10 was observed higher in the middle IGP (Varanasi 206.2 ± 77.4 µg m(-3)) as compared to upper IGP (Delhi 202.3 ± 74.3 µg m(-3)) and lower IGP (Kolkata 171.5 ± 38.5 µg m(-3)). Large variation in OC values from 23.57 µg m(-3) (Delhi) to 12.74 µg m(-3) (Kolkata) indicating role of formation of secondary aerosols, whereas EC have not shown much variation with maximum concentration over Delhi (10.07 µg m(-3)) and minimum over Varanasi (7.72 µg m(-3)). As expected, a strong seasonal variation was observed in the mass concentration of PM10 as well as in its chemical composition over the three locations. Principal component analysis (PCA) identifies the contribution of secondary aerosol, biomass burning, fossil fuel combustion, vehicular emission, and sea salt to PM10 mass concentration at the observational sites of IGP, India. Backward trajectory analysis indicated the influence of continental type aerosols being transported from the Bay of Bengal, Pakistan, Afghanistan, Rajasthan, Gujarat, and surrounding areas to IGP region.

Alteration of predominant gastrointestinal flora and oxidative damage of large intestine under simulated hypobaric hypoxia.

Hypobaric hypoxia is an immediate and crucial starting mechanism of acute mountain sickness included with some non-specific gastrointestinal (GI) complications. To study the effect of hypoxia on GI microflora and its upshot to this system, male albino rats were exposed to 55 kPa (air pressure ~ 4872.9 m altitude) consecutively 30 days for 8 hours/day. The different indicator group of large intestinal microbial populations were enumerated and correlated with the levels of antioxidant indicators like catalase (CAT), superoxide dismutase (SOD), malondialdehyde (MDA), reduced glutathione (GSH) and oxidized glutathione (GSSG) of large intestinal epithelial cells. In addition, the histological study was performed by haematoxylin eosin (HE), periodic acid schiff staining (PAS) and scanning electron microscopy (SEM). It was observed that the density of total aerobes (104 folds) significantly (p < 0.05) decreased but the population of total anaerobes (209 folds) and Escherichia coli (125 folds) elevated after 30 days of hypoxic stress. The strict anaerobes like Bifidobacterium spp. (3 folds), Bacteroides spp. (134 folds), Lactobacillus spp. (7 folds) and other selected obligate anaerobes like Clostridium perfringens (40 folds), Peptostreptococcus spp. (21 folds) increased in respect to their control population. The growth direction index (GDI) of anaerobic populations was positive and correlated with gas formation aptitude. The activities of CAT and SOD in the large intestinal epithelia decreased significantly (p < 0.05) and GSH/GSSG pool turned into oxidized state with higher MDA (p < 0.05) formation. Histological study revealed the necrotized epithelial layer with higher lymphocytes infiltration in lamina propia accompanied by reduction of acidic mucins secreting goblet cells. From this experiment, it can be hypothesized that high altitude induced hypoxia manipulated the bacterial imprint and damaged the epithelial barrier of the large intestine which may cause systemic infection.