Search

The friction and wear of worn surfaces is a principal cause of energy dissipation in automobile engines. The current study investigates graphene nanoplatelets (GNPs), based on a carbon allotrope, that have good thermal, physical and chemical properties, and cellulose nanocrystals (CNCs) as a universal nano-sized ecological biopolymer. In view of this, the objective of the present work is to enhance the tribological behavior and lubricant properties using hybrid GNPs and CNCs blended with SAE 40 engine oil with various concentrations in the range 0.01–0.10%. The characterization was carried out by using different techniques such as X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The XRD patterns confirmed the platelet structure of GNPs, and FESEM showed that the sizes of small and agglomerated particles were 20–50 and 200 nm for GNPs and CNCs, respectively. Scanning electron microscopy morphological evaluation was conducted for all volumetric concentrations of single and hybrid nanolubricants. Morphological investigation indicated that there is homogeneous dispersion and there is a smoother surface after using graphene:CNC nanolubricants compared with that using just SAE 40.

Fog holes were reported over cities of the Indo‐Gangetic plains of India, which were attributed to the urban heat island (UHI) effect. The present study reports the observational evidence of fog holes over rural area using satellite and ground observations. Delayed onset and early dissipation of fog is observed over the holes. Numerical simulations demonstrate that aerosol‐radiation interaction (ARI) leads to fog holes over both urban and rural regions. The anthropogenic aerosols and associated ARI dominate the UHI effect over the urban fog holes, while the aerosol absorption due to ARI mainly controls the rural fog holes. Turning off aerosol absorption causes ∼ 2 hours delay in the fog dissipation over urban area, whereas it yields persistent fog over rural area under saturated environment. An enhancement of soluble Aitken black carbon over the fog holes indicates the importance of aging process during fog dissipation. This study reports the occurrence of fog holes over rural and urban regions and investigates the mechanism behind the formation of fog holes using DM‐Chem. The main reason behind the fog hole formation over Indo‐Gangetic plains is the absorption of radiation by the total black carbon aerosols. The absence of the absorbing component of aerosol‐radiation interaction leads to the occurrence of fog over both the urban and rural hole areas. The fog hole areas are correlated with an enhanced formation of small sized soluble black carbon aerosols. These findings suggest the need for detailed aging processes of carbonaceous particles in atmospheric models. Fog holes over the rural regions reported for the first timeDelayed onset and early dissipation of fog over the hole regionsAerosol radiation effect (absorption) dominates over the urban heat island effect Fog holes over the rural regions reported for the first time Delayed onset and early dissipation of fog over the hole regions Aerosol radiation effect (absorption) dominates over the urban heat island effect

Telemedicine is a blooming field with inter-disciplinary research and wide area of application refinement. Various techniques are proposed since last decade with a primary focus of improving telemedicine. The algorithms are either data dependent or application centric. In this paper, a multi-objective optimal medical (MooM) data processing technique is proposed under multi-dimensional data types of medial samples such as text files, image files, log files, electronic health records (EHR), audio signal files and graphic files. The technique proposes a dedicated methodology for independent data-type processing to retrieve on a standard protocol platform for transmission of data via telemedicine channel. The technique uses unsupervised and hybrid clustering approaches of machine learning to predict data-types attributes for processing, thus resulting in higher-order accuracy and data scalability on transmission channel of telemedicine environment. The MooM technique processed on medical images retrieve the compressed stream of data frames with QoS recorded 9.23, for medical textural data the QoS is 9.87 and audio signal pattern data, the QoS is recorded 9.76 on a scale of 10.

Active RFID systems are utilised widely in extensive applications and have limited radio communication. Collisions subsist during the tag detection process of the reader which cause lassitude of tag's battery life. Surmounting these collisions and incrementing tag identification rate with remarkable high throughput remains as a key challenge in RFID based applications. Zigbee network provides multi hop data transmission and covers long distances. In this paper we propose a hybrid Zigbee RFID system model implemented with dynamic frame slotted grouping collision resolution protocol. During every iteration of tag estimation the frame size is adjusted predicated on the comparison of total number of singleton and idle slots against the number of collision slots without eliminating idle slots. Simulations were performed utilising Opnet simulator which showed decreased collision rate, execution time, system overhead and amended performance in the metrics of tag identification rate, energy efficiency with a maximum throughput of 0.63.

The monthly 1°×1° global snow cover (SC) data taken from version three of the twentieth-century reanalysis (20CR) project and the high-resolution gridded rainfall data provided by the India Meteorological Department (IMD) for the years 1957–2015 are used to study the relation between southwest monsoon rainfall (SWMR) over India and the SC over Eurasia (35°–65°N; 40°–80°E) and Himalayas (20°–50°N; 50°–110°E) for the four sesquidecades 1957–1970, 1971–1985, 1986–2000 and 2001–2015. It is observed that the SC over Eurasia in April–May shows generally the well-known negative correlation with the all India averaged SWMR. However, the correlation became positive in the recent sesquidecade 2001–2015. Though the correlation between Himalayan SC and SWMR is increasingly positive during the first three sesquidecades, it becomes negative during 2001–2015 over the majority of the grid points. This drastic change in the relationship is attributed to the decreasing trend in the area of SC and the increasing trend in the North Atlantic Sea surface temperature (SST) during the last decade.

The possible influence of potential vorticity (PV) intrusion events in the southern low-latitude upper troposphere over the longitude region 0–90°E during June–September on the southwest monsoon rainfall (SWMR) over India is investigated using ERA-interim potential vorticity data and high resolution gridded IMD (India Meteorological Department) rainfall data. It is found that unlike in the northern hemisphere, the PV intrusion events are more frequent in the southern low-latitudes in the longitude region 0–90°E during June–September and they are present irrespective of the phase of the El Nino Southern Oscillation (ENSO). More PV intrusion events into the southern hemispheric low-latitude upper troposphere are observed during the negative SWMR anomaly years. The cross-equatorial flow is observed to be weak during intrusion events. The deep penetration of PV into the lower troposphere in southern hemisphere reverses low-level wind direction from north to south during or the next day of the PV anomaly events. This reversal of low-level wind leads to a break in the SWMR, which can be inferred from the positive time mean removed OLR (>10 W/m2) during high PV event days. It is suggested that the reversal of low-level wind induced by PV intrusion event may have prevented moisture transport to India, resulting in break spell and hence reduced rainfall.

•Volumetric, acoustic and derived properties were reported for seven binary systems.•Influence of geometrical and hydrogen bonding on studied properties were reported.•FTIR analysis was carried out to confirm the hydrogen bond formation.•DFT calculations were performed, the resultant data is good agreement with experimental data.

ABSTRACTThe false data injected by the compromised sensor nodes in heterogeneous wireless sensor networks are not only a threat to data integrity but also consume bandwidth and power unnecessarily. The existing mechanisms for eliminating the injected false data are carried out with a fixed set of aggregator nodes. This causes battery drain at the aggregator nodes, leading to reduced network lifetime. Hence, it is necessary to reduce the battery drain by changing the aggregator nodes at regular intervals. The periodic change of aggregator nodes introduces the problem of pair-wise key establishment among the sensor nodes. This paper aims at eliminating the injected false data in heterogeneous wireless sensor networks. It also addresses the issue of battery drain at the aggregator nodes by periodically selecting the aggregator nodes based on location, exploiting the heterogeneity of the sensor nodes in the network. The problem of pair-wise key establishment is resolved by using a suitably modified cryptographic scheme based on Jacobian elliptic Chebyshev rational map. This modification is due to the fact that the original scheme is easily breakable.

We present r'- or i'-band WIYN images of the fields of 15 Sloan Digital Sky Survey quasars that have spectra exhibiting intervening Mg II absorption-line systems with rest equivalent widths 2.7 A [?] Wimg1.gif [?] 6.0 A and redshifts 0.42 < zabs < 0.84. Such systems are rare and exhibit projected absorption velocity spreads in excess of [?]300-650 km s-1. Approximately 60% are expected to be damped Lya systems. In each of our fields we detect at least one galaxy that, if at the absorption redshift, would have impact parameter b [?] 40 kpc and luminosity L [?] 0.3L*. We measure a significant excess of galaxies at low b to the sight lines over a large range of luminosity. Many of the sight lines are found to pass either through or close to the optically luminous extent of a galaxy. Considering the very large velocity spreads seen in absorption, this suggests that these absorbing regions are more kinematically complex than local spirals such as the Milky Way. Our data indicate that interactions and galaxy pairs may be a contributing factor to the production of such large velocity spreads. Finally, we also find evidence that a population of galaxies with luminosities in the range 4L* [?] L [?] 13L* may contribute to the presence of ultrastrong Mg II absorption. Thus, some of the absorbing galaxies may represent a population intermediate to the very luminous high-redshift Lyman break galaxies and the fainter local starburst population.

We present a statistical analysis of the photometric properties and spatial distribution of more than 2800 Mg II absorbers with 0.37 < z < 1 and rest equivalent width W0(l2796) > 0.8 A detected in SDSS quasar spectra. Using an improved image-stacking technique, we measure the cross-correlation between Mg II gas and light (in the g, r, i and z bands) from 10 to 200 kpc and infer the light-weighted impact parameter distribution of Mg II absorbers. This quantity is well described by a power law with an index that strongly depends on absorption rest equivalent width W0, ranging from ~-1 for W0 [?] 1 A to ~-2 for W0 [?] 1.5 A. At redshift 0.37 < zabs [?] 0.55, we find the average luminosity enclosed within 100 kpc around Mg II absorbers to be Mg = -20.65 +- 0.11 mag, which is ~0.5Limg1.gif. The global luminosity-weighted colors are typical of present-day intermediate-type galaxies. We then investigate these colors as a function of Mg II rest equivalent width and find that they follow the track between spiral and elliptical galaxies in color space; while the light of weaker absorbers originates mostly from red passive galaxies, stronger systems display the colors of blue star-forming galaxies. We argue that the origin of strong Mg II absorber systems might be better explained by models of metal-enriched gas outflows from star-forming/bursting galaxies. No significant redshift dependence for both impact parameter and rest-frame colors is observed up to z = 1. However, we do observe a brightening of the absorbers' related light at high redshift (~50% from zabs ~ 0.4 to 1). We argue that Mg II absorbers are a phenomenon typical of a given evolutionary phase that more massive galaxies experience earlier than less massive ones, in a "downsizing" fashion.

We present the results from a spectroscopic survey for intervening Mg II absorption in the spectra of 381 background QSOs conducted at the MMT telescope. This survey complements our earlier SDSS EDR Mg II survey, extending our results to lower redshift (z [?] 0.15) and weaker Mg II l2796 rest equivalent width (Wimg1.gif [?] 0.1 A). We confirm two major results from that survey: the transition in the Wimg1.gif distribution at Wimg1.gif [?] 0.3 A, and the Wimg1.gif-dependent evolution of the incidence of systems. The nature of [?]2N/[?]z[?]Wimg1.gif is consistent with the idea that multiple physically distinct components/processes contribute to the incidence of Mg II absorption systems in a W0-dependent manner and evolve at different rates. A significant decrease in the total proper absorption cross section is detected in our MMT data for systems as weak as 1.0 A [?] Wimg1.gif < 1.5 A at z [?] 0.4. We discuss this W0-dependent evolution in the context of the evolution of galaxy structures, processes including superwinds and interactions, and damped-Lya absorbers. We also consider the possibility that the observed redshift and Wimg1.gif dependence of the incidence of absorption in spectroscopic surveys for low-ionization/neutral gas results from the effects of dust-induced extinction.

We present results of our Hubble Space Telescope Cycle 11 survey for low-redshift (z < 1.65) damped Lya (DLA) systems in the UV spectra of quasars selected from the Sloan Digital Sky Survey (SDSS) Early Data Release. These quasars have strong intervening Mg II-Fe II systems that are known signatures of high column density neutral gas. In total, including our previous surveys, UV observations of Lya absorption in 197 Mg II systems with z < 1.65 and rest equivalent width (REW) Wimg1.gif [?] 0.3 A have now been obtained. The main results are as follows: (1) The success rate of identifying DLAs in a Mg II sample with Wimg1.gif [?] 0.5 A and Fe II Wimg2.gif [?] 0.5 A is 36% +- 6% and increases to 42% +- 7% for systems with Wimg1.gif/Wimg2.gif < 2 and Mg I Wimg3.gif > 0.1 A. (2) The mean H I column density of Mg II systems with 0.3 A [?] Wimg1.gif < 0.6 A is img4.gif = (9.7 +- 2.2) x 1018 cm-2. For the larger REW systems in our sample, img4.gif = (3.5 +- 0.7) x 1020 cm-2. (3) The DLA incidence per unit redshift for 0 < z < 5 is nDLA(z) = n0(1 + z)g, where n0 = 0.044 +- 0.005 and g = 1.27 +- 0.11. This parameterization is consistent with no evolution for z [?] 2 (OL = 0.7, OM = 0.3) but exhibits significant evolution for z [?] 2. (4) The cosmological neutral gas mass density due to DLAs is constant in the redshift interval 0.5 < z < 5.0 to within the uncertainties, ODLA [?] 1 x 10-3. This is larger than Ogas(z = 0) by a factor of [?]2. (5) The slope of the H I column density distribution does not change significantly with redshift. However, the low-redshift distribution is marginally flatter due to the higher fraction of high column density systems in our sample. (6) Finally, using the precision of Mg II survey statistics, we show that under the assumption of constant DLA fraction and H I column density suggested by our current sample, there may be evidence of a decreasing ODLA from z = 0.5 to 0.

Although cationic surfactants are of general interest for a variety of consumer and biomedical applications, only a limited number of partially fluorinated, single-tailed, cationic surfactants have been synthesized. To study the potential usefulness of fluorinated cationic surfactants for these applications we synthesized a series of partially fluorinated pyridinium bromide surfactants. Three 10-perfluoroalkyldecyl pyridinium surfactants were synthesized by coupling a perfluoroalkyl iodide with 9-decene-1-yl acetate using an AIBN mediated radical reaction. The resulting 9-iodo-10-perfluoroalkyldec-1-yl acetates were deiodinated using HI–Zn–EtOH and hydrolyzed using KOH–EtOH to yield the corresponding 10-perfluoroalkyldecanol. The partially fluorinated alcohol was converted into the bromide using Br2–PPh3. Alkylation of excess pyridine with the bromides gave the desired 10-perfluoroalkyldecyl pyridinium bromides in good yields. Three 10-perfluoroalkylundecyl surfactants were synthesized using a similar approach with 10-undecenoic acid methyl ester as starting material. Based on an initial in vitrotoxicity assessment, the toxicity of the partially fluorinated pyridinium surfactants was slightly lower or comparable to benzalkonium chloride, a typically cationic surfactant with IC50s of tested compounds ranging from 5 to 15 μM. An increase in the length andor the degree of fluorination of the hydrophobic tail correlated with a mild decrease of cytotoxicity and haemolytic activity. Partially fluorinated pyridinium surfactants may, therefore, be useful for biomedical applications such as components for novel gene and drug delivery systems.

We present the results of a Mg II ll2796, 2803 absorption-line survey using QSO spectra from the Sloan Digital Sky Survey (SDSS) Early Data Release. Over 1300 doublets with rest equivalent widths greater than 0.3 A and redshifts 0.366 [?] z [?] 2.269 were identified and measured. We find that the l2796 rest equivalent width (Wimg1.gif) distribution is described very well by an exponential function [?]N/[?]Wimg1.gif = img2.gif eimg3.gif, with N* = 1.187 +- 0.052 and W* = 0.702 +- 0.017 A. Previously reported power-law fits drastically overpredict the number of strong lines. Extrapolating our exponential fit underpredicts the number of Wimg1.gif [?] 0.3 A systems, indicating a transition in [?]N/[?]Wimg1.gif near Wimg1.gif [?] 0.3 A. A combination of two exponentials reproduces the observed distribution well, suggesting that Mg II absorbers are the superposition of at least two physically distinct populations of absorbing clouds. We also derive a new redshift parameterization for the number density of Wimg1.gif [?] 0.3 A lines: N* = 1.001 +- 0.132 (1 + z)0.226+-0.170 and W* = 0.443 +- 0.032 (1 + z)0.634+-0.097 A. We find that the distribution steepens with decreasing redshift, with W* decreasing from 0.80 +- 0.04 A at z = 1.6 to 0.59 +- 0.02 A at z = 0.7. The incidence of moderately strong (0.4 A [?] Wimg1.gif [?] 2 A) Mg II l2796 lines does not show evidence for evolution with redshift. However, lines stronger than [?]2 A show a decrease relative to the no-evolution prediction with decreasing redshift for z [?] 1. The evolution is stronger for increasingly stronger lines. Since W0 in saturated absorption lines is an indicator of the velocity spread of the absorbing clouds, we interpret this as an evolution in the kinematic properties of galaxies from moderate to low redshift. Monte Carlo simulations do not reveal any strong systematic effects or biases in our results. While more recent SDSS QSO spectra offer the opportunity to increase the Mg II absorber sample by another order of magnitude, systematic errors in line identification and measurement will begin to dominate in the determination of absorber property statistics.

We report new imaging and spectroscopic observations of the damped Lya absorber (DLA) galaxy SBS 1543+593, a nearby dwarf galaxy whose stellar disk is intersected by the sight line to the bright background QSO HS 1543+5921. Hubble Space Telescope imaging observations with WFPC2 in the F450W and F702W bands are used to measure the DLA galaxy's properties and compile a catalog of its (candidate) H II regions. Ground-based long-slit spectroscopy of the brightest H II region in the galaxy yields estimates of the star formation rate (SFR) and chemical abundances in the galaxy's interstellar medium. We find that SBS 1543+593 exhibits an SFR of [?]0.006 himg1.gif M yr-1, or an SFR per unit area of [?]1.4 x 10-4 himg1.gif M yr-1 kpc-2. We derive gas-phase abundances in the ionized gas of 12 + log (O/H) = 8.2 +- 0.2, which is about img3.gif of the solar value, and log (N/O) = -1.40img5.gif. These values are consistent with the morphological appearance of SBS 1543+593, an Sm dwarf of MB - 5 log h70 = -16.8 +- 0.2 and intermediate surface brightness. SBS 1543+593 is the first bona fide DLA for which abundances have been measured using emission-line diagnostics. When compared with future high-resolution ultraviolet spectroscopy, our results should prove key for interpreting abundance determinations in high-redshift DLAs.

We present optical and near-infrared ground-based imaging results on four low-redshift damped Lya (DLA) galaxies. The corresponding DLA systems were discovered in our Hubble Space Telescope spectroscopic surveys for DLA lines in known strong Mg II absorption-line systems toward the quasars B2 0827+243 (zDLA = 0.525), PKS 0952+179 (zDLA = 0.239), PKS 1127-145 (zDLA = 0.313), and PKS 1629+120 (zDLA = 0.532). Two of the four DLA galaxies have confirmed slit redshifts, one has a photometric redshift consistent with the absorption-line redshift, and the fourth identification is based on the galaxy's proximity to the quasar sight line. The DLA galaxies span a mixture of morphological types from patchy, irregular, and low surface brightness to spiral galaxies. The luminosities range from 0.02Limg1.gif to 1.2Limg1.gif. We also discovered several extremely red objects (EROs) in two of these fields and discuss the possibility that they are associated with the DLA galaxies. These observations add to the small but growing list of DLA galaxies at low redshift. At the present time, 14 DLA galaxies in the redshift range 0.05 [?] z [?] 1 have been studied. The distributions of DLA galaxy properties for these 14 cases are discussed, and some important trends emerge. Low-luminosity dwarf galaxies with small impact parameters dominate this small sample. Also, four of the five highest column density systems, which dominate in the determination of the cosmological neutral gas mass density, arise in low surface brightness dwarf galaxies. Zwaan et al. have shown that only 15% of the neutral gas at the present epoch is contained in low surface brightness galaxies. Thus, if the low-redshift DLA galaxy trends hold up with larger samples, it would indicate that a different population of objects is responsible for the bulk of the neutral hydrogen gas in the universe at z [?] 0.5.

Chandra X-Ray Observatory ACIS-S spectra of three quasars that lie behind three foreground damped Lya (DLA) absorbers are analyzed in order to attempt to determine the amount of photoelectric absorption due to metals present in their X-ray spectra. These absorbers are the three largest neutral hydrogen column density absorption-line systems known at low redshift (0.313 [?] zabs [?] 0.524). They have H I column densities that lie in the range 3 x 1021 [?] NH I [?] 5 x 1021 atoms cm-2. At these redshifts the amount of photoelectric absorption at X-ray energies is primarily an indicator of the oxygen abundance. Since the column densities of these systems are so high, one would expect accurate metallicity measurements of them to yield a robust estimate of the column density-weighted cosmic neutral gas-phase metallicity at z [?] 0.4. We consider cases in which the DLA gas has solar element abundance ratios and ones with the a group element abundance ratios enhanced. For the adopted assumptions, the column density-weighted cosmic neutral gas-phase metallicity of the nonenhanced elements (e.g., Zn) at z [?] 0.4 likely lies in the range [?]0.04-0.38 Z.

We report the results of Hubble Space Telescope Wide Field and Planetary Camera 2 broadband F555W and F702W photometric and F555W polarimetric observations of the "Cloverleaf" QSO H1413+1143. This is a four-component gravitationally-lensed broad absorption line (BAL) QSO. Observations were obtained at two epochs in 1999 March and 1999 June separated by [?]100 days. The observations were photometrically and polarimetrically calibrated using the standard "pipeline" calibration procedures implemented at the Space Telescope Science Institute. The goal of our program was to detect any relative changes among the components and between the two epochs. Over this time baseline we detected an [?]0.07 mag dimming in component D of the lensed image, which we interpret as evidence for microlensing. In 1999 March we find significant evidence for a difference in the relative linear polarization of component D in comparison to the other three components; in 1999 June the combined polarization of the Cloverleaf components was lower. In 1999 March the apparently microlensed component D has a rotated polarization position angle and a somewhat higher degree of polarization than the other three components. We suggest that this difference in polarization is due to microlensing magnification of part of a scatter-light (i.e., polarized) continuum-producing region. The results indicate that in the Cloverleaf the size scale of the polarized scattered-light region exceeds [?]1016 cm but lies interior to the region producing the broad emission lines (<1018 cm).

An analysis of Hubble Space Telescope (HST) Wide Field Planetary Camera (WFPC) and Wide Field Planetary Camera 2 (WFPC2) images of the gravitationally lensed Cloverleaf broad absorption line quasi-stellar object (QSO) H1413+1143 is presented. Astrometric and photometric measurements are derived for the four components of the lensed QSO for five different epochs over a baseline of 2.76 yr. Because of the replacement of WFPC with WFPC2 and the change in the purpose of the observation at the various epochs, the data were not always taken with the same filter. With the exception of the declination of component D, the relative positions of the four components are measured to within [?] 3 mas; these results are consistent with but considerably more accurate than earlier measurements. The relative photometric measurements at any one epoch are typically accurate to [?] 0.02-0.03 mag (1 s). The initial HST WFPC images cover a baseline of 1.26 yr (1992.21-1993.47 [1992 March 16-1993 June 22]), and over this time interval there is little evidence for brightness variations of any of the components relative to one another at levels >0.06 mag (>2 s). Photometric measurements of the more accurate WFPC2 data obtained with different filters extends this baseline an additional 1.50 yr (to 1994.97 [1994 December 22]). The WFPC2 data also fail to reveal significant brightness variations among the components. In addition, the WFPC2 data include both UV (F336W) and near-infrared (F814W) images. These color data indicate the presence of sight-line-dependent extinction, causing the F336W-F814W color index of component B (the most reddened component) to be 0.56 +- 0.04 mag redder than that of component C (the least reddened component). The lack of evidence for significant component brightness variations at all HST observation epochs suggests that the data could be reliably extinction-corrected to derive the relative amplifications of the four image components. This is done for several reasonable dust-extinction models. Thus, the derived astrometry along with the photometric analysis set clear constraints on models for the Cloverleaf. Since component D shows some evidence for microlensing, the results on its relative amplification should be used with caution. While existing models can successfully reproduce the relative positions, the relative amplifications have not yet been successfully modeled. The WFPC2 imaging data has also permitted a sensitive search for component structure and the gravitational lens itself. There is marginal evidence for elongated structure between components A and C that may be part of an Einstein ring. However, no significant evidence for the lensing object is found. The various measurements are quantified in ways useful for setting model constraints. Limits on the mass-to-light ratio and detectability of the lensing galaxy are also discussed.

For Abstract see ChemInform Abstract in Full Text.