Simulations of shock generation and propagation in laser-plasmas

AbstractWe analyze the results of a recent experiment performed at the PALS laboratory and concerning ablation pressure at 0.44 µm laser wavelength measured at irradiance up to 2 × 1014 W/cm2. Using the code "ATLANT," we have performed two-dimensional (2D) hydrodynamics simulations. Results show that 2D effects did not affect the experiment and also give evidence of the phenomenon of delocalized absorption of laser light

Surface morphology modifications of human teeth induced by a picosecond Nd:YAG laser operating at 532 nm

AbstractThe interaction of an Nd:YAG laser, operating at 532 nm with 40 ps pulse duration, with human teeth was studied. The results show that teeth were significantly modified at an energy fluence of about 11 J/cm2. Various surface morphologies of enamel and dentine were recorded. Features on enamel include crater (conical form) in the central part and cauliflower morphology at the periphery, whereas on dentine the crater looks like a stretched dome between sharp edges. The behavior of the enamel-dentine junction area showed different morphology with respect to both tooth enamel and dentine alone. Finally, the junction channel showed a removal of collagen fibers and the formation of a needle-like bottom structure. Generally, this investigation showed that the picosecond Nd:YAG laser can ablate a tooth surface practically instantaneously, implying that large tooth surfaces can be processed in short time

Effects of laser prepulses on laser-induced proton generation

Low-intensity laser prepulses (<10(13) W cm(-2), nanosecond duration) are a major issue in experiments on laser-induced generation of protons, often limiting the performances of proton sources produced by high-intensity lasers (approximate to 10(19) W cm(-2), picosecond or femtosecond duration). Depending on the intensity regime, several effects may be associated with the prepulse, some of which are discussed in this paper: (i) destruction of thin foil targets by the shock generated by the laser prepulse; (ii) creation of preplasma on the target front side affecting laser absorption; (iii) deformation of the target rear side; and (iv) whole displacement of thin foil targets affecting the focusing condition. In particular, we show that under oblique high-intensity irradiation and for low prepulse intensities, the proton beam is directed away from the target normal. Deviation is towards the laser forward direction, with an angle that increases with the level and duration of the ASE pedestal. Also, for a given laser pulse, the beam deviation increases with proton energy. The observations are discussed in terms of target normal sheath acceleration, in combination with a laser-controllable shock wave locally deforming the target surface

Stabilization of Soft Soil by a Sustainable Binder Comprises Ground Granulated Blast Slag (GGBS) and Cement Kiln Dust (CKD)

Due to its significant deficiencies such as low permeability, low bearing and shear strength, and excessive compressibility, soft soil is one of the most problematic types of soil in civil engineering and soil stabilization can be considered a suitable technique for pavements. This study investigates the use of ground granulated blast slag (GGBS) and cement kiln dust (CKD) as stabilizers for soft soil. Thus, this study involves two optimization stages; in the first stage, GGBS was incorporated into 0%, 3%, 6%, 9%, and 12% by the weight of cement to obtain the optimal percentage, which was 6%. Then, the optimal GGBS was blended with CKD in a binary system at 0%, 25%, 50%, 75%, and 100% by the dry weight of the soil. The testing program used in this paper was Atterberg limits with compaction parameters to investigate the physical properties and unconfined compressive strength (USC) at 7 and 28 days to examine the mechanical characteristics. In addition, the microstructures of the soil specimens were tested at 7 and 28 days using scanning electron microscopy (SEM). The findings reveal that the binary system enhanced the physical and mechanical properties of the soft soil. The optimum binder achieved in this study was 6% (25% GGBS and 75% CKD), which generates an increase in strength of about 3.3 times in 7 days, and of 5.5 times in 28 days in comparison to the untreated soil. The enhancement was attributed to the formation of the hydration products as approved by SEM. Consequently, in the case of soft subgrade soils, this technique can increase the pavement’s bearing capacity and performance

Physics Potential of the ICAL detector at the India-based Neutrino Observatory (INO)

The upcoming 50 kt magnetized iron calorimeter (ICAL) detector at the India-based Neutrino Observatory (INO) is designed to study the atmospheric neutrinos and antineutrinos separately over a wide range of energies and path lengths. The primary focus of this experiment is to explore the Earth matter effects by observing the energy and zenith angle dependence of the atmospheric neutrinos in the multi-GeV range. This study will be crucial to address some of the outstanding issues in neutrino oscillation physics, including the fundamental issue of neutrino mass hierarchy. In this document, we present the physics potential of the detector as obtained from realistic detector simulations. We describe the simulation framework, the neutrino interactions in the detector, and the expected response of the detector to particles traversing it. The ICAL detector can determine the energy and direction of the muons to a high precision, and in addition, its sensitivity to multi-GeV hadrons increases its physics reach substantially. Its charge identification capability, and hence its ability to distinguish neutrinos from antineutrinos, makes it an efficient detector for determining the neutrino mass hierarchy. In this report, we outline the analyses carried out for the determination of neutrino mass hierarchy and precision measurements of atmospheric neutrino mixing parameters at ICAL, and give the expected physics reach of the detector with 10 years of runtime. We also explore the potential of ICAL for probing new physics scenarios like CPT violation and the presence of magnetic monopoles.Comment: 139 pages, Physics White Paper of the ICAL (INO) Collaboration, Contents identical with the version published in Pramana - J. Physic

Effects of front surface plasma expansion on proton acceleration in ultraintense laser irradiation of foil targets

The properties of beams of high energy protons accelerated during ultraintense, picosecond laser-irradiation of thin foil targets are investigated as a function of preplasma expansion at the target front surface. Significant enhancement in the maximum proton energy and laser-to-proton energy conversion efficiency is observed at optimum preplasma density gradients, due to self-focusing of the incident laser pulse. For very long preplasma expansion, the propagating laser pulse is observed to filament, resulting in highly uniform proton beams, but with reduced flux and maximum energy

Glimpses of biodiversity in the Kadalundi-Vallikunnu Community Reserve, the first Community Reserve of Kerala

Biodiversity is the mainstay of ecosystem services and functions and supports the livelihood of millions of people. Sustainable utilization and conservation of our rich biological diversity is a prerequisite for human survival. India is a megadiverse country and with only 2.4% of the world’s geographical area, it accounts for 7 to 8% of all recorded species. Our country is a signatory to various international instruments focussing on matters of biodiversity, including the Convention on Biological Diversity (CBD). The country has an obligation to protect our rich biological diversity and is one of the leaders in having established a comprehensive legal and institutional system to achieve the objectives of the CBD. Expansion of India’s Protected Area (PA) network, including ‘Conservation and Community Reserves’ is one of the important action points of the National Biodiversity Action Plan of our country. The Kadalundi-Vallikunnu Community Reserve which lies in the Malabar region is the first Community Reserve of Kerala and is known for its rich biological diversity. Endowed with dense mangrove forests and mudflats, the Community Reserve is an abode to a large number of avian fauna, including many migratory species. Fishing and ecotourism have been the mainstay of income generation for many local inhabitants of the Community Reserve. Considering the ecological significance, diversity of wetland avian fauna and the burden of heavy anthropogenic pressures, the Kadalundi estuary was officially declared as the ‘Kadalundi-Vallikunnu Community Reserve’ in October, 2007. Bio-inventorying and documentation of biodiversity is invaluable for the wise use of our ecosystems and the sustainability of biological resources. This publication is an outcome of a detailed study conducted by the ICAR-Central Marine Fisheries Research Institute in collaboration with the Kerala State Biodiversity Board to document the rich biodiversity of the Kadalundi-Vallikunnu Community Reserve and to assess the economic value of the various ecosystem services rendered by the Community Reserve. The publication provides an insight in to the diversity of plankton, seagrass, mangroves, mangrove associates, avian fauna, molluscs, crustaceans and finfishes of the Community Reserve with an overview of the economic value of the ecosystem services. The various threats faced by the Community Reserve and meaningful options for the conservation and sustainable management of the Reserve is also highlighted in this document

The impact of agricultural activities on water quality: A case for collaborative catchment-scale management using integrated wireless sensor networks

The challenge of improving water quality is a growing global concern, typified by the European Commission Water Framework Directive and the United States Clean Water Act. The main drivers of poor water quality are economics, poor water management, agricultural practices and urban development. This paper reviews the extensive role of non-point sources, in particular the outdated agricultural practices, with respect to nutrient and contaminant contributions. Water quality monitoring (WQM) is currently undertaken through a number of data acquisition methods from grab sampling to satellite based remote sensing of water bodies. Based on the surveyed sampling methods and their numerous limitations, it is proposed that wireless sensor networks (WSNs), despite their own limitations, are still very attractive and effective for real-time spatio-temporal data collection for WQM applications. WSNs have been employed for WQM of surface and ground water and catchments, and have been fundamental in advancing the knowledge of contaminants trends through their high resolution observations. However, these applications have yet to explore the implementation and impact of this technology for management and control decisions, to minimize and prevent individual stakeholder’s contributions, in an autonomous and dynamic manner. Here, the potential of WSN-controlled agricultural activities and different environmental compartments for integrated water quality management is presented and limitations of WSN in agriculture and WQM are identified. Finally, a case for collaborative networks at catchment scale is proposed for enabling cooperation among individually networked activities/stakeholders (farming activities, water bodies) for integrated water quality monitoring, control and management

Using Intervention Mapping to Develop ISAC, a Comprehensive Intervention for Early Detection and Prevention of Oral Cancer in Saudi Arabia

Oral cancer forms a major public health issue. In Saudi Arabia, Jazan region has the highest rate of oral cancer; > 35% of total cases. Furthermore, dentists' engagement in oral cancer screening and patient education in Jazan region is limited. This paper aimed to describe the process used to develop a comprehensive oral cancer (OC) practice intervention to be implemented in dental clinics. The intervention was informed by the six steps of intervention mapping (IM). Steps 1-3 included mixed methods approach of reviewing relevant existing literature, focus group discussions, observations, one-on-one interviews, and questionnaires utilizing the community participatory approach. Step 4 used information form steps 1-3 to develop the intervention components and its associated tools to facilitate its delivery. Steps 5 and 6 specified the prospective plans for implementation and evaluation. ISAC is the developed intervention that comprises the following: Informing dental patients about performing routine OC screenings, Screenings for OC, Advising patients, and Connecting patients to the required services. ISAC practical applications were clustered into two components: (a) didactical session covering aspects related to OC practices and introducing ISAC and (b) practical session that included a step-by-step modeling of the intervention. Using IM facilitated the systematic planning of the ISAC intervention that covers the main issues revealed by the need's assessments. Working towards developing the ISAC required extensive work in assessing dental public health issues in a specific context with limited data - and this constituted a great challenge. The development of the ISAC was a lesson that casts light on the advantages of engaging multidisciplinary expertise to tackle serious public health issue like OC