Search

Accurately estimating wind from higher altitudes while using data from mesosphere stratosphere troposphere (MST) radar operating in the very high frequency (VHF) band is challenging. Several techniques implemented previously have their respective advantages and disadvantages. The present study implements an adaptive-Bayesian shrinkage technique with several advantages over its counterparts. The Bayesian mixture model employed implements parametric and nonparametric methods with predictability. It enhances the MST radar return signal and reduces noise optimally and efficiently. It elaborates on the constructed model comprising the likelihood, priors, Bayes rule, and hyperparameters used in the derivation. This technique can detect weak signals at higher altitudes and works better than the implemented denoising-based non-Bayesian techniques, which are contemporary. All cited techniques in this article use uniform signal enhancement, evaluated uniformly using five moments and six quality parameters. The accuracy of the derived wind is validated against the wind obtained from simultaneous GPS radiosonde observations and found to be consistent. The implemented C# code follows the detailed algorithm step-wise and does not use standard routines that make it fit to work in real time. It concludes that the implemented technique can effectively analyze VHF-MST radar signals and retrieve weak signals from higher altitudes ranging from 25.8 to 28.5 km. It enhances the standard 21-km MST radar reference range that is usually obtained using fast Fourier transform (FFT) and is essential for many scientific investigations.

Graphical Abstract:

Different meteor radars at low latitudes observed abnormally strong westward mesospheric winds around the March Equinox of 2023, that is, during the first phase of the Mesospheric Semiannual Oscillation. This event was the strongest of at least the last decade (2014–2023). The westward winds reached −80 m/s at 82 km of altitude in late March, and decreased with increasing altitude and latitude. A considerable increase in the diurnal tide amplitude was also observed. The Whole Atmosphere Community Climate Model with thermosphere‐ionosphere eXtension constrained to meteorological reanalysis up to ∼50 km does not capture the observed low‐latitude behavior. Additionally, these strong mesospheric winds developed during the westerly phase of the Quasi‐Biennial Oscillation, in accordance with the filtering mechanism of gravity waves in the stratosphere proposed in previous works. Finally, analysis of SABER temperatures strongly suggests that the breaking of the migrating diurnal tide may be the main driver of these strong winds. Around the March Equinox of 2023, abnormally strong westward winds were observed in the low latitude region at altitudes between 80 and 100 km. This event was the strongest in at least the last decade. The westward winds reached a maximum amplitude of 80 m/s at 82 km of altitude during late March, and decreased with increasing altitude and latitude. A considerable increase in the amplitude of the diurnal tide was also observed. Simulations based on a whole atmosphere global circulation model constrained to meteorological reanalysis up to ∼50 km do not capture the observed behavior. Results based on specular meteor radar and satellite measurements suggest that the strong westward winds were driven by two main factors: the filtering mechanism of eastward‐propagating gravity waves in the stratosphere and the breaking of the diurnal tide at about 85 km of altitude. Strong mesospheric westward winds during March equinox 2023 are observed globally at low latitudesThe westward winds reached a peak of −80 m/s at 82 km, the largest in the last ten years, accompanied by an enhancement of the diurnal tideThe breaking of the DW1 plays a role in generating these strong winds, in addition to the filtering of gravity waves in the stratosphere Strong mesospheric westward winds during March equinox 2023 are observed globally at low latitudes The westward winds reached a peak of −80 m/s at 82 km, the largest in the last ten years, accompanied by an enhancement of the diurnal tide The breaking of the DW1 plays a role in generating these strong winds, in addition to the filtering of gravity waves in the stratosphere

Meteor radars are widely used to study gravity wave (GW) variances and their momentum fluxes at the altitudes where meteor counts are sufficient to yield good statistical fits to the data. These radars provide hourly zonal and meridional wind observations round the clock in 80‐ to 100‐km height domain. However, the capability of meteor radars in estimating GW momentum fluxes should be evaluated before they can be used for any research applications. In this regard, the present study evaluates the meteor radar observations of GW momentum fluxes obtained from Thumba (8.5°N, 77°E; 2006–2015), Kototabang (0.2°S, 100.3°E; 2002–2017), and Tirupati (13.63°N, 79.4°E; 2013–2018) using three‐dimensional wind field simulations, which include specified tidal, planetary and GW fields. A modified composite day analysis is adopted to estimate the GW momentum fluxes, which also accounts for the tidal and planetary wave contributions. The results showed that the retrieved and specified GW momentum fluxes agree very well over Tirupati followed by Thumba and Kototabang. It is noted that the agreement between the retrieved and simulated fields depend on the number of meteor detections used in the analysis. After evaluating the meteor radar retrieved GW momentum fluxes by employing simulations, their interannual variability and climatologies over the three observational locations are constructed. The significance of the present study lies in evaluating the capability of three meteor radars located in equatorial and low‐latitudes in estimating GW momentum fluxes by employing three‐dimensional wind field simulations with specified mean winds, tidal, planetary, and GW fields. Evaluation of meteor wind radars operating at low and equatorial latitudes in estimating the MLT region gravity wave momentum fluxesThree‐dimensional wind simulations with specified mean, tidal, planetary, and gravity wave amplitudesClimatology of zonal and meridional gravity wave momentum fluxes in the MLT region over low and equatorial latitudes

In recent years, the middle atmosphere has evoked great scientific interest as long‐term changes can be clearly captured owing to the large perturbation amplitudes at these altitudes. In the present study, more than 25 years of the data are used to investigate the long‐term trends in the middle atmosphere by suitably combining the observations from different techniques (Rocketsonde, High‐Resolution Doppler Imager (HRDI)/Upper Atmosphere Research Satellite (UARS), Halogen Occultation Experiment (HALOE)/UARS, Sounding of the Atmosphere using Broadband Emission Radiometry (SABER)/Thermosphere Ionosphere Mesosphere Energetic Dynamics (TIMED), and Mesosphere‐stratosphere‐troposphere (MST) radar) from Indian region. As different instruments/techniques are used and the time periods are not the same, extreme care has been taken while merging various data sets to obtain meaningful long‐term trends. To understand the observed long‐term trends, Whole Atmosphere Community Climate Model–eXtended model simulations for the Indian low‐latitude regions are also used. A significant cooling trend of ~−1.7 ± 0.5 K/decade between 30 and 80 km is noticed. Large decreasing trend (~5 m/s/decade) in the eastward winds is noticed which is significant between 70 and 80 km only changing from strong eastward wind in 1970s to weak westward wind in recent decade. No significant trends are observed in the meridional wind. These observations are well captured by the Whole Atmosphere Community Climate Model–eXtended model simulations while considering changes in concentrations of greenhouse gases including carbon dioxide (CO2), methane (CH4), water vapor (H2O), and chlorofluorocarbon species that cause depletion of stratospheric ozone (O3). Thus, it is prudent to conclude that long‐term decreasing trends in the zonal winds and cooling trends in the temperature in the middle atmosphere are caused to a large extent by greenhouse gases suggesting the role of anthropogenic changes in the dynamics of the middle atmosphere. In the changing climate, several studies have shown long‐term trends in troposphere, stratosphere, and mesosphere. In general, long‐term trends in the middle atmosphere (10–100 km) can be clearly captured due to increasing amplitudes with the altitude. However, studies on long‐term trends in the temperature and winds over the low latitudes in the middle atmosphere are sparse. In the present study, long‐term trends observed in the temperature and winds obtained from the observations from multiinstrumental data covering more than 25 years is provided. To explain the observed trends we also used Whole Atmosphere Community Climate Model–eXtended model simulations. Long‐term decreasing trends in the zonal winds and cooling trends in the temperature in the middle atmosphere are observed. These observations are clearly captured in the Whole Atmosphere Community Climate Model–eXtended model simulations that examine the long‐term changes in the atmosphere due to the long‐term changes in concentrations of greenhouse gases, suggesting the role of anthropogenic changes in the dynamics of the middle atmosphere. Long‐term trends in the middle atmosphere temperature and winds over Indian region are presented using multiinstrumental dataTo explain the observed trends, WACCM‐X model simulations are used for the Indian region while considering major GHGsWACCM‐X model is able to simulate these observed trends suggesting the role of anthropogenic change on the middle atmosphere

To date, influence of aerosols on the atmospheric stability and hence on the convection/precipitation is not well understood. From the detailed analysis carried out using high‐accuracy radiosonde and Aethalometer measurements, a significant decrease in the convective available potential energy has been noticed in association with the increase in surface concentration of black carbon (BC) for a restricted range of precipitable water vapor and under similar environmental background (wind speed, direction, and cloud cover) over Gadanki (13.5°N, 79.2°E), a tropical rural site in southern peninsular India. A number of case studies along with statistical analysis indicate a notable perturbation in the temperature profile associated with high‐surface BC concentration conditions compared to the regional mean concentration of the same. A discernible fall in the temperature lapse rate within and above the local boundary layer in association with the higher BC concentration has been observed, which in turn reduces the available potential energy for convection decreasing the positive buoyancy required for a rising moist air parcel. This observation has been noticed over a nonurban location, but the phenomenon is not location dependent and is more applicable to the urban regions where BC concentration is likely to be much higher. Our daily needs of energy lead us to massive usage of fuel burning. These burnings release huge amount of tiny particles into the atmosphere, which significantly influence our environment. Black carbon (BC) is such a man‐made health hazardous pollutant aerosol particle which warms up our environment by absorbing solar radiation. Generally, the temperature of our surroundings decreases with height in a certain rate. Due to this nature of temperature in our atmosphere, the warm moist air from the ground can move upward and is cooled down. The upward movement of moist air eventually causes rainfall mostly during summer in tropical areas. But our present observation shows that higher amount of BC in our environment can disturb the normal upward movement of moist air by heating up the atmosphere. Thus, the increase in the amount of this man‐made pollutant particle affects not only human health but also the normality of our atmosphere disturbing its balance. Our study provides some important evidences on how BC particles can disturb the balance of our atmosphere. This observation has been done over a rural location, but the phenomenon should be more prominent over urban environment where BC is likely to be more in amount. Influence of black carbon on the atmospheric instability is investigated under similar background conditionsIt is found that increase in surface black carbon affects the lower tropospheric instability over a regionThere is significant decrease in temperature lapse rate and convective available potential energy during increase in black carbon concentration

We analyzed the structure and variability of observed winds and tides in the Antarctica mesosphere and lower thermosphere (MLT) during the 2002 major sudden stratospheric warming (SSW) and the 2010 minor SSWs. We noted the effect of SSW on the variability of MLT tides for the first time in the Southern Hemisphere, although it has been well recognized in the Northern Hemisphere. We utilized the winds measured by Rothera (68°S, 68°W) medium frequency radar and King Sejong Station (62.22°S, 58.78°W) meteor radar for estimating the tidal components (diurnal, semi‐diurnal, and ter‐diurnal) in the MLT region. The unusual behavior of diurnal tide (DT) and semidiurnal tide (SDT) was observed in 2002. Zonal SDT amplitudes were enhanced up to 27 m/s after 18 days from the associated SSW day. However, the meridional tidal amplitudes of both DT and SDT suddenly decreased during the peak SSW, and SDT amplitudes slightly increased to 18 m/s afterward. In the normal years, SDT amplitude stays below 15 m/s. During the 2010 SSW, SDT zonal amplitudes increased up to 40 m/s and 50 m/s at altitudes of 80 km and 90 km, respectively, ~30 days after the associated SSW. Similar but weaker effect is noticed in the meridional components. The ter‐diurnal tide does not show any significant variation during the SSW. The two SSWs offered a challenging issue to answer: why tidal amplitudes are enhanced with a delay after the SSW. The reasons for the delay are discussed in accordance with theoretical predictions. The 2002 major and 2010 minor SSWs over Southern Hemisphere showed a significant effect on the mesospheric tides after a few days of SSWThe ozone variability during SSWs reveals that the mesospheric tides were less predisposed by the ozone presence than other mechanismsThe secondary waves generated by planetary wave‐tidal interaction cause a major effect on the mesospheric tides after the SSW event

We have investigated the coupling between the stratosphere and mesosphere–lower thermosphere (MLT) in the Southern Hemisphere (SH) during 2010 minor sudden stratospheric warmings (SSWs). Three episodic SSWs were noticed in 2010. Mesospheric zonal winds between 82 and 92 km obtained from King Sejong Station (62.22°S, 58.78°W) meteor radar showed the significant difference from usual trend. The zonal wind reversal in the mesosphere is noticed a week before the associated SSW similar to 2002 major SSW. The mesosphere wind reversal is also noticed in “Specified Dynamics” version of Whole Atmosphere Community Climate Model (SD-WACCM) and Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy (GAIA) simulations. The similar zonal wind weakening/reversal in the lower thermosphere between 100 and 140 km is simulated by GAIA. Further, we observed the mesospheric cooling in consistency with SSWs using Microwave Limb Sounder data. However, the GAIA simulations showed warming between 130 and 140 km after few days of SSW. Thus, the observation and model simulation indicate for the first time that the 2010 minor SSW also affects dynamics of the MLT region over SH in a manner similar to 2002 major SSW.Graphical abstract.

The structure of tropical tropopause layer (TTL) is delineated based on static stability criteria. It is defined as the region extending from the level of minimum static stability to the level of maximum static stability. The static stability and dynamic instability steadily increase from the base to the top of the TTL. Radiosonde data from three tropical stations and Constellation Observing System for Meteorology, Ionosphere, and Climate GPS radio occultation (COSMIC) data over the tropics are used for this investigation. This study suggests that in terms of stability, the TTL can further be considered as a composite of three sublayers: a bottom layer (BL), a middle layer (ML), and an upper layer (UL) embedded between the potential temperatures ~350–360?K, ~360–380?K, and 380–420?K, respectively. While the BL is significantly influenced by frequent convective outflows, the influence of convection declines across the ML. Ozone and water vapor mixing ratios show a discernible change in their gradients across these sublayers. Occurrences of small-scale turbulence and cirrus are maximum in the BL and decrease in the ML and UL. Longitudinally, the BL is broad and the ML and UL are narrow over the deep convective cores. Strength of static stability in the UL (BL) is relatively strong (weak) centered about the equator, with pronounced features over the deep convective regions. These features of static stability centered about the equator in the BL could be attributed to the convective outflows in the troposphere and that in the UL to the dynamic and radiative processes in the upper troposphere and lower stratosphere. The TTL boundaries are defined based on static stability criteriaIn terms of stability, the TTL can be considered to be a composite of three distinct layersOccurrence of turbulence and cirrus maximizes in the bottom layer of TTL and decreases in the middle and upper layers

Analysis of one year measurements of in situradon (222Rn) and its progenies along with surface air temperature, relative humidity and pressure near to the Earth’s surface has been carried out for the first time at the National Atmospheric Research Laboratory (NARL, 13.5∘N and 79.2∘E) located in a rural site in Gadanki, south India. The dataset was analysed to understand the behaviour of radon in relation to the surface air temperature and relative humidity at a rural site. It was observed that over a period of the 24 hours in a day, the activity of radon and its progenies reaches a peak in the morning hours followed by a remarkable decrease in the afternoon hours. Relatively, a higher concentration of radon was observed at NARL during fair weather days, and this can be attributed to the presence of rocky hills and dense vegetation surrounding the site. The high negative correlation between surface air temperature and activity of radon (R= – 0.70, on an annual scale) suggests that dynamical removal of radon due to increased vertical mixing is one of the most important controlling processes of the radon accumulation in the atmospheric surface layer. The annual averaged activity of radon was found to be 12.01±0.66 Bq m−3and 4.25±0.18 Bq m−3for its progenies, in the study period.

The poor hardness of zirconia-toughened alumina (ZTA) with 5 wt-% CeO2(ZTA5CeO2) ceramic has limited its applications as a cutting insert. Therefore, in this work, the possibility of MgO nanoparticles (20 nm) as reinforcement to ZTA5CeO2ceramics was investigated. Mgo nanoparticles with different weight percentages (0-2 wt-%) were added to ZTA5CeO2ceramics. ZTA5CeO2with 0.5 wt-%MgO showed the highest fracture toughness of 9.14 MPa.vm. The addition of 0.5 wt-%MgO nanoparticles showed the excellent role of MgAl11CeO19grains as a crack deflector, which consequently produced a reasonable hardness value of 1591 HV and lowered the wear areas to 0.0528 mm2.

The poor hardness of zirconia-toughened alumina (ZTA) with 5 wt-% CeO2(ZTA5CeO2) ceramic has limited its applications as a cutting insert. Therefore, in this work, the possibility of MgO nanoparticles (20 nm) as reinforcement to ZTA5CeO2ceramics was investigated. Mgo nanoparticles with different weight percentages (0-2 wt-%) were added to ZTA5CeO2ceramics. ZTA5CeO2with 0.5 wt-%MgO showed the highest fracture toughness of 9.14 MPa.√m. The addition of 0.5 wt-%MgO nanoparticles showed the excellent role of MgAl11CeO19grains as a crack deflector, which consequently produced a reasonable hardness value of 1591 HV and lowered the wear areas to 0.0528 mm2.

A deep depression formed over the Bay of Bengal on 28 October 2012, and developed into a cyclonic storm. After landfall near the south coast of Chennai, cyclone Nilam moved north-northwestwards. Coordinated experiments were conducted from the Indian stations of Gadanki (13.5°N, 79.2°E) and Hyderabad (17.4°N, 78.5°E) to study the modification of gravity-wave activity and turbulence by cyclone Nilam, using GPS radiosonde and mesosphere–stratosphere–troposphere radar data. The horizontal velocities underwent large changes during the closest approach of the storm to the experimental sites. Hodograph analysis revealed that inertia gravity waves (IGWs) associated with the cyclone changed their directions from northeast (control time) to northwest following the path of the cyclone. The momentum flux of IGWs and short-period gravity waves (1–8 h) enhanced prior to, and during, the passage of the storm (±0.05 m2s−2and ±0.3 m2s−2, respectively), compared to the flux after its passage. The corresponding body forces underwent similar changes, with values ranging between ±2–4 m s−1d−1and ±12–15 m s−1d−1. The turbulence refractivity structure constant (Cn2) showed large values below 10 km before the passage of the cyclone when humidity in the region was very high. Turbulence and humidity reduced during the passage of the storm when a turbulent layer at ~17 km became more intense. Turbulence in the lower troposphere and near the tropopause became weak after the passage of the cyclone.

The present study deals with using long-term database for upper tropospheric water vapour (UTWV) variability studies over three tropical stations (Gadanki, Singapore and Truk), where different climatic conditions prevail. Over Gadanki (13.5°N, 79.2°E) strong seasonal variation in UTWV is revealed but not over Singapore (1.37°N, 103.98°E) and Truk (7.46°N, 151.85°E) except at 100 hPa. It is examined whether high resolution radiosonde measurements represent well the UTWV by comparing with different satellite based (Atmospheric Infrared Sounder (AIRS), Advanced Microwave Sounding Unit-B (AMSU-B) and Microwave Limb Sounder (MLS)) water vapour measurements. Very good comparison in the nature of variations of UTWV is observed between radiosonde data and satellite data, except over Singapore particularly with AIRS and MLS data, on long-term basis. An attempt is also made to examine the source for UTWV. A close relationship is found between UTWV and deep convection over Gadanki indicating that the source for UTWV is convection particularly during the summer monsoon season.

Several studies have been carried out on the tropopause, stratopause, and mesopause (collectively termed as ‘pauses’) independently; however, all the pauses have not been studied together. We present global distribution of altitudes and temperatures of these pauses observed with long-term space borne high-resolution measurements of Global Positioning System (GPS) Radio Occultation (RO) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) aboard Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite. Here we study the commonality and differences observed in the variability of all the pauses. We also examined how good other datasets will represent these features among (and in between) different satellite measurements, re-analysis, and model data. Hemispheric differences observed in all the pauses are also reported. In addition, we show that asymmetries between northern and southern hemispheres continue up to the mesopause. We analyze inter and intra-seasonal variations and long-term trends of these pauses at different latitudes. Finally, a new reference temperature profile is shown from the ground to 110 km for tropical, mid-latitudes, and polar latitudes for both northern and southern hemispheres.

This short communication reports on an attempt which has been made to study mesospheric echo occurrence duration for the first time, using a large data base (1998 to 2004) collected from MST radar located at Gadanki (13.5°N, 79.2°E), a tropical station in India. It is well known that VHF radar echoes in the mesosphere are due to both the presence of irregularities with scales of half the radar wavelengths, and also the production and loss rates of electrons in the lower D-region. The main aim of the present paper is to estimate the duration of mesospheric echoes at each altitude and to establish the preference of their occurrence, if any, in altitude and time. In general, mesospheric echoes show tilted layers, a sporadic nature above/below the main layer (70–80 km), and a seasonal shift in the height of occurrence. Based on the time and height of echo occurrence, we broadly divide the periods of mesospheric echo occurrence (duration) into 5–20 minutes (T1), 20–40 minutes (T2), and ≥40 minutes (T3), and the height of occurrence into 65–70 km (R1), 70–80 km (R2), and 80–85 km (R3). It is observed that long duration echoes (T2 and T3) occur mostly in the R2 region and are highly sporadic in the R1 and R3 regions. In addition, the solar zenith angle dependence on the duration of mesospheric echoes is also studied and no significant variation was found in any of the above-mentioned categories. This study will contribute to a better understanding of the dynamical aspects of the mesosphere using VHF radar observations.

In recent years, the mesosphere (50 to 85–100 km) has evoked great scientific interest as long‐term changes due to global warming can be clearly captured due to the large perturbation amplitudes at these altitudes. In the present study, zonal wind observations between 70 and 80 km over the Indian region provided by rocketsonde (1977–1991), HRDI/UARS (1991–1999), and MST radar (1995–2010) are used to construct a long‐term data set from 1977 to 2010. Using this unprecedented data set, a decreasing trend of 2 m/s/yr is found, changing from strong eastward winds during the 1970s to weak westward winds in recent years. On the other hand, between 80 and 98 km using medium frequency radar observations during 1993–2009, no perceptible trend is found. Simulations of NCAR TIME‐GCM also showed a similar change in the circulation when CO2in the atmosphere is doubled, suggesting role of anthropogenic changes in the dynamics of the mesosphere. Long‐term tends in the tropical lower mesosphereEvidence of Long‐term Change in Zonal Wind in the Tropical Lower MesosphereRole of anthropogenic changes in the dynamics of the mesosphere

Abstract: Relationship of outgoing long-wave radiation (OLR) with convective available potential energy (CAPE) and temperature at the 100-hPa pressure level is examined using daily radiosonde data for a period 1980–2006 over Delhi (28.3°N, 77.1°E) and Kolkata (22.3°N, 88.2°E), and during 1989–2005 over Cochin (10°N, 77°E) and Trivandrum (8.5°N, 77.0°E), India. Correlation coefficient (R xy) between monthly OLR and CAPE shows a significant (~ − 0.45) anti-correlation at Delhi and Kolkata suggesting low OLR associated with high convective activity during summer (seasonal variation). Though, no significant correlation was found between OLR and CAPE at Cochin and Trivandrum (low latitude region); analysis of OLR and temperature (at 100-hPa) association suggests that low OLR peaks appear corresponding to low temperature at Delhi (R xy~ 0.30) and Kolkata (R xy ~ 0.25) during summer. However, R xy between OLR and temperature becomes opposite as we move towards low latitudes (~8°–10°N) due to strong solar cycle influence. Large scale components mainly ENSO and quasi-biennial oscillaton (QBO) that contributed to the 100-hPa temperature variability were also analyzed, which showed that ENSO variance is larger by a factor of two in comparison to QBO over Indian region. ENSO warm conditions cause warming at 100-hPa over Delhi and Darwin. However, due to strong QBO and solar signals in the equatorial region, ENSO signal seems less effective. QBO, ENSO, and solar cycle contribution in temperature are found location-dependent (latitudinal variability) responding in consonance with shifting in convective activity regime during El Niño, seasonal variability in the tropical easterly jet, and the solar irradiance.

Characteristics of gravity waves are studied using radiosonde campaign conducted during November–December 2005 at Koto Tabang (KT, 0.2°S, 100.32°E). Intensive sounding with hourly launches was also conducted on seven days to study the characteristics of short period (2–6 hours) waves along with EAR data. Gravity waves with period (t) of 3 hours and vertical wavelength (?z) of 10 km seemed to be generated due to localized convection around KT, which is inferred from X-band Doppler radar. The energy of the gravity wave with period of 2–3 days and vertical wavelength of 3–5 km is largest between 15 and 20 km and 25 and 30 km. We also report the comparison of the wave activity and its interaction with background wind between the three campaigns (CPEA-I, CPEA-II and Nov. 2002). Most of the time waves are propagating towards east and the source of gravity waves is strongly related to the slowly eastward-advecting tropospheric convection, implying that the wave activity was generated at far distant sources located west of KT. A key finding of this study is neither short period nor long-period gravity waves are generated during stationary type of convection. The change in the propagation direction of the short period waves within the event is observed which is not expected.

Using stratospheric temperature profiles derived from GPS radio occultation (RO) measurements made by the German CHAMP satellite from June 2001 to May 2006, we studied the climatological behavior of atmospheric wave activity in the tropics. The wave potential energy, Ep, is calculated from temperature fluctuations with vertical scales shorter than 7 km in a longitude and latitude cell of 20° × 10° at 19–26 km. Epis then averaged every 3 months (June–July–August (JJA), September–October–November (SON), December–January–February (DJF), March–April–May (MAM)), and the averages are compared with the cloud top temperature from outgoing long-wave radiation (OLR) and the convective rain rate from the TRMM precipitation radar (PR). Epat 19–26 km in the western Pacific to Indian Ocean is found to show a clear seasonal variation, with a large Epduring DJF and MAM and a considerably enhanced Epin SON; it becomes minimum during JJA near the equator, when the center of the enhanced Epregion appears over north India and the Indochina peninsula. Localized enhancement of Epseems to be mainly due to atmospheric gravity waves. In addition, the longitudinally elongated portion of Epis partially affected by Kelvin wave-like disturbances with short horizontal scales. In DJF and MAM, the convective clouds are located over the western Pacific and around Indonesia, at which time the Kelvin wavelike disturbances are effectively generated. The spatial and seasonal variations of Epare closely related to the distribution of clouds, implying that convective wave generation is very important in the tropics. However, wave-mean flow interactions due to the wind shear of the QBO become important in the lower stratosphere, which considerably modifies our analysis of the Epdistribution at 19–26 km. Therefore, both wave generation and propagation characteristics must be taken into account in describing the climatological behavior of atmospheric wave activity in the equatorial stratosphere.

Horizontal winds from four low‐latitude (±15°) specular meteor radars (SMRs) and the Michelson Interferometer for Global High‐resolution Thermospheric Imaging (MIGHTI) instrument on the ICON satellite, are combined to investigate quasi‐2‐day waves (Q2DWs) in early 2020. SMRs cover 80–100 km altitude whereas MIGHTI covers 95–300 km. Q2DWs are the largest dynamical feature of the summertime middle atmosphere. At the overlapping altitudes, comparisons between the derived Q2DWs exhibit excellent agreement. The SMR sensor array analyses show that the dominant zonal wavenumbers are s= +2 and + 3, and help resolve ambiguities in MIGHTI results. We present the first Q2DW depiction for s= +2 and s= +3 between 95 and 200 km, and show that their amplitudes are almost invariant between 80 and 100 km. Above 106 km, Q2DW amplitudes and phases present structures that might result from the superposition of Q2DWs and their aliased secondary waves. In the mesosphere and lower‐thermosphere, quasi‐2‐day waves are spectacular planetary‐scale oscillations. Almost all relevant observational studies are based on ground‐based single‐station or single‐satellite methods and therefore cannot determine the zonal wavenumber unambiguously. In the current work, we employ a series of multi‐station methods on winds measured by four longitudinally separated low‐latitude ground‐based radars. These methods help us to determine two dominant zonal wavenumbers at 80–100 km altitude. These results are used to complement satellite measurements. The agreement between datasets is extraordinary, allowing us to extend the characteristics of the waves to higher altitudes using satellite measurements. The quasi‐2‐day waves (Q2DW) wind field at 80–200 km altitude is delineated from combining ground and space data in the low‐latitude region (+/−15°)Zonal wavenumber components s= +2 and s= +3 are the dominant ones in our observations, and their wave periods evolve differently with timeThe quasi‐2‐day waves s= +3 exhibits an excellent quantitative agreement between two datasets at 95–100 km, serving as a validation of the ICON‐MIGHTI winds The quasi‐2‐day waves (Q2DW) wind field at 80–200 km altitude is delineated from combining ground and space data in the low‐latitude region (+/−15°) Zonal wavenumber components s= +2 and s= +3 are the dominant ones in our observations, and their wave periods evolve differently with time The quasi‐2‐day waves s= +3 exhibits an excellent quantitative agreement between two datasets at 95–100 km, serving as a validation of the ICON‐MIGHTI winds

Horizontal wind measurements using meteor radars located at Thumba (8.5°N, 77°E; 2006–2015) Kototabang (0.2°S, 100.3°E; 2002–2017) and Tirupati (13.63°N, 79.4°E; 2013–2017) in the mesosphere‐lower thermosphere (MLT) and Specified Dynamics Whole Atmosphere Community Climate Model (SD‐WACCM) simulations are employed for investigating the diurnal tide variability at quasi‐biennial scales. The model simulations are evaluated using the meteor radar observations at three tropical locations. WACCM simulations could reproduce the seasonal evolution of diurnal tides very well over Thumba and Tirupati but there are small discrepancies over Kototabang. In order to investigate the modulation of the diurnal tide amplitudes in the MLT region by the stratospheric quasi‐biennial oscillation (SQBO), deseasonalized perturbations of diurnal tides and stratospheric winds are analyzed. A very good correspondence is found between meridional diurnal tide perturbation amplitudes and the SQBO with positive tidal perturbations during the eastward phase of SQBO and negative perturbations during the westward phase over Thumba and Tirupati. SQBO modulations of diurnal tides at global scales exhibits a positive correlation between the meridional diurnal tide perturbation with SQBO winds at 20 hPa and a negative correlation with SQBO winds at 70 hPa within ±40° latitude, except over the equator. It is also noted that the equatorial electrojet strength, is modulated by the SQBO over the Thumba, which is a dip equatorial location. The significance of present study lies in evaluating WACCM simulations at tropical locations using meteor radar measurements and in investigating the SQBO modulations of diurnal tides at global scales. Atmospheric tides are global scale oscillations having periods that are harmonics of solar day (24‐, 12‐, 8‐h, etc.) and play a significant role in coupling lower and middle/upper atmosphere. Tides are generated in the troposphere/stratosphere and propagate upwards. In order to conserve the momentum, the amplitude of tides increases with altitude in response to decreasing density with altitude. Among many atmospheric waves present in the mesosphere‐lower thermosphere (MLT), diurnal tides (24‐h period) have the largest amplitudes over the low‐latitudes and thus play a key role in shaping the structure and dynamics of this region. Even though tides are well represented in numerical models, time‐to‐time evaluation of these models against observations from several ground‐based measurements is needed to employ them in day‐to‐day research applications. In the present study, SD‐WACCM model simulations of mean winds and diurnal tides in the MLT region are evaluated using meteor radar observations over three tropical locations [Thumba (8.5°N, 77°) Kototabang (0.2°S, 100.3°E) and Tirupati (13.63°N, 79.4°E)]. There exists a long‐period oscillation in the stratosphere known as stratospheric quasi‐biennial oscillation (SQBO), which is believed to modulate the amplitude of diurnal tides at interannual scales. The present study also investigates the relationship between SQBO and the tidal variability in the MLT region. The results show significant correlation between the SQBO phase and the deseasonalized diurnal tide amplitudes in the MLT region. Diurnal tide amplitudes are relatively larger during the eastward phase as compared to the westward phase of the SQBO. It is also noted that the strength of the equatorial electrojet is also modulated by the SQBO. The WACCM simulations could reproduce this feature very well. The model simulations are further employed to study the response of diurnal tide amplitude to the phase of the SQBO at global scales. The results show that the SQBO phase influences the diurnal tide amplitude in the latitude belt of 40°N–40°S except at the equator. Thus, the present study evaluates WACCM simulations using meteor radar observations and discusses the role of SQBO in modulating the diurnal tide amplitudes over three tropical latitudes. Response of diurnal tide in the mesosphere‐lower thermosphere (MLT) to the stratospheric quasi‐biennial oscillation (SQBO) is investigated over three locations using meteor radar observation and Whole Atmosphere Community Climate Model (WACCM) simulationsThe monthly mean tidal variability in the MLT region is highly correlated with stratospheric winds at 20–40 hPa pressure levelStratospheric QBO modulation of tidal variability in the MLT imposes the QBO signature in the equatorial electrojet Response of diurnal tide in the mesosphere‐lower thermosphere (MLT) to the stratospheric quasi‐biennial oscillation (SQBO) is investigated over three locations using meteor radar observation and Whole Atmosphere Community Climate Model (WACCM) simulations The monthly mean tidal variability in the MLT region is highly correlated with stratospheric winds at 20–40 hPa pressure level Stratospheric QBO modulation of tidal variability in the MLT imposes the QBO signature in the equatorial electrojet

Meteor radar measurements of winds in the mesosphere and lower thermosphere (MLT) over Tirupati (13.63°N, 79.4°E; 2013–2020) and Microwave Limb Sounder (MLS) observations of ozone are used for investigating the effect of the disrupted stratospheric quasi‐biennial oscillation (SQBO) during the year 2016 on the diurnal tides. The positive tidal perturbations are observed during positive perturbations of ozone and eastward phase of the SQBO and vice versa. These observations are well captured by the Specified Dynamics Whole Atmosphere Community Climate Model (SD‐WACCM) simulations. The results suggest that the ozone and wind perturbations in the stratosphere induced by the sudden phase transition in the SQBO winds are the potential candidates for the observed abrupt changes in the diurnal tide amplitudes in the MLT region. The SQBO disruption thus provided an opportunity to seek further insights into the pathways through which the lower atmosphere influence the middle and upper atmosphere. Atmospheric tides are global scale oscillations with periods that are sub‐harmonics of a solar day (24, 12, 8 h etc.). Among these, diurnal tides (24 h) are very prominent over low latitudes and play a major role in shaping the structure and dynamics of the middle atmosphere. Stratospheric quasi‐biennial oscillation (SQBO) is a long period oscillation with a mean time period of ∼28 months in the stratosphere and is believed to modulate diurnal tides at interannual time scales. During the year 2016, for the first time the SQBO disruption took place. The present study investigates the effect of the SQBO disruption on the amplitudes of the diurnal tides in the MLT region using meteor radar observations over a low‐latitude station. Stratospheric ozone measurements obtained from Microwave Limb Sounder (MLS) as well as simulations from Specified Dynamics Whole Atmosphere Community Climate Model (SD‐WACCM) are also employed to shed light on the relation among diurnal tides, SQBO winds and ozone. The results suggest a positive correlation between diurnal tide perturbations and ozone perturbations as well as SQBO winds. During the SQBO disruption, there is a negative anomaly in the ozone perturbations and westward winds below 20 hPa, which are thought to be the prime candidates in reducing the observed diurnal tide amplitudes in the MLT. Response of diurnal tides in the low‐latitude mesosphere and lower thermosphere region to the stratospheric quasi‐biennial oscillation (SQBO) disruption during the year 2016 is investigatedObserved reduction in the diurnal tide amplitudes is associated with the stratospheric winds as well as ozone variability at SQBO scalesQuasi‐biennial oscillation disruption though lasted for a brief period, its effect is noted for a relatively longer period Response of diurnal tides in the low‐latitude mesosphere and lower thermosphere region to the stratospheric quasi‐biennial oscillation (SQBO) disruption during the year 2016 is investigated Observed reduction in the diurnal tide amplitudes is associated with the stratospheric winds as well as ozone variability at SQBO scales Quasi‐biennial oscillation disruption though lasted for a brief period, its effect is noted for a relatively longer period

The folate receptor (FR) type alpha may be distinguished from FR-beta by its higher affinity for the circulating folate coenzyme, (6S)-5-methyltetrahydrofolate (5-CH3H4folate), and its opposite stereospecificity for reduced folate coenzymes. Previous studies showed that a single leucine to alanine substitution at position 49 of the mature protein sequence is responsible for the functional divergence of FR-beta (Shen, F., Zheng, X., Wang, H., and Ratnam, M. (1997) Biochemistry 36, 6157-6163); however, the results also indicated that the minimum requirement for conversion of FR-beta to the functional equivalent of FR-alpha should include amino acid substitution(s) downstream of residue 92 in addition to mutation of L49A. To pinpoint those residues, chimeric FR-betaL49A/FR-alpha constructs including progressively shorter segments of FR-alpha downstream of position 92 as well as selected point mutants were studied. Simultaneous substitution of Leu-49, Phe-104, and Gly-166 in FR-beta with the corresponding FR-alpha residues Ala, Val, and Glu, respectively, reconstituted the ligand binding characteristics of FR-alpha. The results also exclude a role for other residues in FR-alpha in determining its functional divergence. A homology model of FR-alpha based on the three-dimensional structure of the chicken riboflavin-binding protein is used to show the position of residues 49, 104, and 166 in relation to the hydrophobic cleft corresponding to the riboflavin-binding pocket.

Abstract.: The distribution of the glycosyl-phosphatidylinositol (GPI)-anchored folate receptor (FR) in a diffuse pattern vs. functional clusters associated with caveolae has been debated. The equivocal nature of direct localization studies is due to possible experimental artifacts such as cross-linking of the protein by the antibody probes prior to fixation and alternatively the use of a disruptive fixation method. Such studies have also been complicated by the use of cells that vastly overexpress FR. In this study a monovalent probe, i.e., a biotinylated folate affinity analogue was used to covalently label FR. Cells expressing moderate levels of FR, i.e., JAR epithelial cells expressing FR-α and recombinant CHO fibroblasts expressing FR-β, were used. The affinity label and either caveolin or antigenic sites on FR were localized by electron microscopy using colloidal gold conjugated antibody probes post-embedding in the relatively permeable LR White resin. The method avoided both receptor cross-linking and early fixation steps and also enabled the use of transport permissive conditions while labeling FR at the cell surface. The results indicate that in steady-state FR is not significantly colocalized with caveolin. However, the receptor molecules occur predominantly in clusters, independent of cross-linking, providing a physical basis for the observed kinetics of receptor internalization and recycling during folate transport. Evidence is also presented to suggest that early mild fixation will disrupt the clustering of FR.

The human folate receptor (hFR) type gamma and gamma' are constitutively secreted proteins that are expressed primarily in hematopoietic tissues and are potential serum markers for certain hematopoietic malignancies. hFR-gamma' is a variant of hFR-gamma with a two base deletion in its cDNA resulting in a truncated polypeptide. The gene encoding hFR-gamma' was isolated from a placental genomic library. The gene has five exons, four introns and a 5' flanking sequence which contains multiple putative regulatory elements. From RNase protection assay and RACE analysis, the major site of transcriptional initiation was identified at -56 nt. Systematically deleted fragments in the 5' region of the genomic DNA of FR-gamma' were ligated into the PGL3Basic plasmid and the reporter luciferase activity was assayed in cell lysates from transiently transfected NIH3T3 cells. From those results, putative positive and negative regulatory regions in the 5' flanking sequences were noted, and a TATA-less proximal promoter was located between -206 and -22 nt. Gel mobility shift and supershift analyses as well as mutagenesis experiments revealed that Sp1 and ets binding elements in the proximal promoter region confer transcriptional activity. From partial sequencing of genomic DNA, genomic Southern blots, RACE analysis and RNase protection assays, it appears that hFR-gamma shares the gene organization of hFR-gamma'. The results of the analysis of genomic DNA in spleen tissues from several individuals, were consistent with the interpretation that hFR-gamma and hFR-gamma' are encoded by a polymorphic gene.

Abstract: The expansion-control characteristics of steel inserts in the open-sleeve type of diesel-engine pistons were investigated using holographic interferometry. The holographic measurements were compared with the predictions of a finite-elements model of the piston. Due to the complex internal geometry of the piston and the in-built stresses, certain assumptions were made in the model. The measurements made for a rise from 50°C to 60°C showed the effects of these assumptions. At the 130°C to 140°C range, the steel insert was found to have lost control of the expansion of the aluminum-alloy skirt. This was confirmed by releasing the skirt from the sleeve in the model and repeating the analysis. The study has shown that the holographic technique can provide the true deformation behavior of the piston at different temperatures. The measurements can also be used to improve the accuracy of the model.

Abstract: Holographic interferometry was used to measure the thermal expansion of a diesel-engine piston and the results are compared with those predicted by a finite-element model. Various assumptions were made in the generation of the model and the holographic results provided a means of assessing the effects of these assumptions on the deformed profile of the piston. A holographic rig has been developed that enables one to measure simultaneously the deformation on the front and rear surfaces of the piston using a single holographic plate and hence detect any body displacement. A simple lsquomirrorrsquo concept is introduced that can be used to measure in-plane and out-of-plane displacements simultaneously. The holographic results showed expansion values of ten-percent greater than the predictions of the model at midskirt level of the piston. A closer agreement of the results were observed at other levels of the skirt.

We compare coincident thermospheric neutral wind observations made by the Michelson Interferometer for Global High‐Resolution Thermospheric Imaging (MIGHTI) on the Ionospheric Connection Explorer (ICON) spacecraft, and four ground‐based specular meteor radars (SMRs). Using the green‐line MIGHTI channel, we analyze 1158 coincidences between Dec 2019 and May 2020 in the altitude range from 94 to 104 km where the observations overlap. We find that the two datasets are strongly correlated (r= 0.82) with a small mean difference (4.5 m/s). Although this agreement is good, an analysis of known error sources (e.g., shot noise, calibration errors, and analysis assumptions) can only account for about a quarter of the disagreement variance. The unexplained variance is 27.8% of the total signal variance and could be caused by unknown errors. However, based on an analysis of the spatial and temporal averaging of the two measurement modalities, we suggest that some of the disagreement is likely caused by temporal variability of the wind on scales ≲70 min. The observed magnitudes agree well during the night, but during the day, MIGHTI observes 16%–25% faster winds than the SMRs. This remains unresolved but is similar in certain ways to previous SMR‐satellite comparisons. Although Earth's atmosphere becomes less dense at high altitudes where it transitions to space, the wind speed grows faster, often exceeding 100 m/s (225 mph). One barrier to better predictions of conditions in the near‐Earth space environment is obtaining knowledge of the wind in the thermosphere, the uppermost layer of the atmosphere. Measurements of the thermospheric wind are difficult to make and historically sparse. ICON, a new NASA mission launched in October 2019, carries the MIGHTI instrument to measure the wind from 90 to 300 km altitude. In this study we compare the observations of MIGHTI to those of meteor radars, which measure the wind from the ground by analysis of radio waves reflected by meteor trails. The results indicate good agreement between the datasets when they measure the wind at the same time and place. Specifically, with 1158 coincidences over the first 6 months of the ICON mission, the correlation is 0.82 and the average difference is 4.5 m/s. This study is important because it validates the MIGHTI data, giving confidence for subsequent studies using its data. It also quantifies limits to the agreement between space‐based and ground‐based winds, which is useful information for future studies combining them. Coincident wind measurements by ICON‐MIGHTI and specular meteor radars are strongly correlated (r= 0.82)The mean discrepancy between the datasets is 4.5 m/s, validating the MIGHTI v03 zero referenceThe RMS discrepancy is 26 m/s, which is attributed to inherent data errors and variability on time scales ≲70 min Coincident wind measurements by ICON‐MIGHTI and specular meteor radars are strongly correlated (r= 0.82) The mean discrepancy between the datasets is 4.5 m/s, validating the MIGHTI v03 zero reference The RMS discrepancy is 26 m/s, which is attributed to inherent data errors and variability on time scales ≲70 min

Meteor radar observations of gravity wave momentum fluxes (GWMFs) in the 82–94 km altitude region, which is a part of mesosphere lower thermosphere (MLT), are employed to identify the best fit gravity wave source spectrum using Gravity wave Regional or Global Ray Tracer (GROGRAT) model simulations over a low‐latitude location, Tirupati (13.63°N, 79.4°E). GROGRAT model is used to propagate a spectrum of gravity waves from the troposphere to the lower thermosphere. A total number of five gravity wave source spectra with various permutations and combinations are considered for the model simulations and by comparing the model simulated and radar observed gravity wave fields in the 82–94 km region, a best fit source spectrum is identified. The significance of the present study lies in appropriating the gravity wave source spectrum using meteor radar observations for the first time, which will have implications in improving gravity parameterization schemes in global models. Gravity waves are ubiquitous in the Earth's atmosphere and play a pivotal role in coupling lower and upper atmosphere. Once generated in the lower atmosphere, these waves carry momentum and energy and deposit somewhere in the middle and upper atmosphere. One of the important areas of research in the realms of middle atmospheric dynamics is to identify the source spectra of these waves so that they can be represented reasonably well in the numerical models. In the present communication, five different forms of source spectra with several combinations of parameters are employed to estimate the gravity wave momentum fluxes using a ray tracing model. The simulated gravity wave momentum fluxes in the 82–94 km region are then compared with those estimated from meteor radar located at a low‐latitude station, Tirupati [13.63°N, 79.4°E]. The source spectrum, which simulates the meteor radar observed gravity wave momentum fluxes reasonably well, is identified to be the best fit spectrum. The present results are first of their kind and have implications in representing gravity wave source spectra in numerical models. GROGRAT model simulations and meteor radar observations are employed to identify the best fit gravity wave source spectrum for mesosphere lower thermosphere for the first timeThe gravity wave momentum fluxes measured by meteor radar and simulated by GROGRAT model agree reasonably well at seasonal scalesThe identified best fit source spectrum is employed to estimate momentum fluxes at the source level

During an extended volcanic unrest starting in 2017, two main moderate stratospheric eruptions occurred at the Ambae volcano (15°S and 167°E), Vanuatu, in April and July 2018. Observations from a geostationary orbit show that the April and July eruptions injected a volcanic plume into the lower stratosphere. While aerosol enhancements from the April eruption have only had an impact on the Southern Hemisphere, the plume from the July eruption was distributed within the lower branch of the Brewer–Dobson circulation to both hemispheres. Satellite, ground‐based and in situ observations show that the background aerosol is enhanced throughout the year after the July eruption on a global scale. A volcanic‐induced perturbation of the global stratospheric aerosol optical depth up to 0.011 is found, in the ultraviolet/visible spectral range. This perturbation is comparable to that of recent moderate stratospheric eruptions like from Kasatochi, Sarychev, and Nabro. Top of the atmosphere radiative forcing values are estimated between −0.45 and −0.6 W/m2for this event, showing that the Ambae eruption had the strongest climatic impact of the year 2018. Thus, the Ambae eruption in 2018 has to be taken into account when studying the decadal lower stratospheric aerosol budget and in climate studies. Two stratospheric eruptions occurred at the Ambae volcano in 2018, in April and JulyVarious satellite data reveal a significant impact on the global stratosphereA significant radiative forcing is found for the eruption of July 2018

This paper presents the climatology of stratospheric intrusion into the troposphere during the Indian Summer Monsoon (ISM) observed using the mesosphere‐stratosphere‐troposphere (MST) radar located at Gadanki (13.5°N, 79.2°E). The most significant and new observation is the presence of enhanced signal‐to‐noise ratio (SNR) of 3 dB and half‐power full spectral width of >0.2 m s−1in the vicinity of tropopause during the ISM. Downdrafts (updrafts) are dominated in the vicinity of tropopause from April to June (July to March). The result of stratospheric air intrusion is also supported with 10 years of ozone measurements obtained from Aura‐Microwave Limb Sounder (MLS) and 5 years of in situ ozonesonde observations. Detailed analysis shows that the horizontal advection along with turbulence in the vicinity of tropopause caused by the tropical easterly jet and tropopause altitude variability is the prime candidate for stratosphere to troposphere transport of ozone. In contrast, the tropical tropopause temperature plays a significant role in the troposphere to stratosphere transport of water vapor during the ISM. The significance of the present study is to qualitatively constitute the climatology of these exchange processes over Gadanki using Indian MST radar. MST radar used to study the climatology of stratosphere‐troposphere exchangeOzone intrusion during Indian summer monsoon using MLS and ozonesondeRole of tropopause altitude/temperature and convection in controlling the exchange of ozone and water vapor

In the past, most researchers have investigated the effect of tool flank wear on the average roughness parameter (Ra) during turning. The Ra parameter, however, is sensitive only to the height variations of the machined workiece profile and is insensitive to the spatial changes to the profile caused by gradual increase in tool wear. In this work, a non-contact vision-based method was used to investigate the effect of tool nose radius wear on the hybrid surface roughness parameters during finish turning. The roughness profile of the workpiece surface diametrically opposite the cutting tool was captured during turning of AISI 1035 steel using a digital camera. A high shutter speed (1/4000 s) was used to freeze the motion of the rotating spindle and obtain a blur-free image of the workpiece. The edge of the workpiece profile was extracted to sub-pixel accuracy using the grey level invariant moment method. The hybrid surface roughness parameters were determined from the workpiece profile. The effect on increased nose wear area on these parameters were investigated. Among these roughness parameters the mean wavelength (Rla) parameter showed the best correlation with tool nose radius wear with coefficients of determination of 0.9734.

Chipping in ceramic cutting inserts during machining can cause detrimental effects on the surface finish quality of the workpiece. Current methods of detecting chipping in ceramic inserts do not compare the minute changes in the workpiece profile in subsequent machining passes. In this work, an effective method of detecting chipping in ceramic inserts by analysing the workpiece surface profile using cross-correlation is proposed. In this method, the sub-pixel edge location method was used to extract the surface profile captured using a digital camera. Surface profiles corresponding to subsequent machining passes were cross-correlated at three different sections of the workpiece. An abrupt drop in the correlation coefficient was observed in the middle and end sections of the workpiece after the fifth machining pass, thus providing a reliable measure of tool chipping.

3D surface roughness of milled aluminium surface was evaluated using the laser speckle pattern. The milled surface was produced from aluminium alloy Al 6061 material at ten different feed rates using CNC milling machine. Laser beam was directed onto the aluminium surface and the scattered beam from the surface of the sample underwent interference to produce laser speckle pattern. Coefficient of Determination between various characteristic features and 3D surface roughness were determined and it was found that 3D surface roughness parameter Sv have coefficient determination above 0.5 with mean, Ga, roughness, entropy and normalized ACF.

Seasonal and diurnal variations in the thermal structure of the troposphere and lower stratosphere with special reference to the tropical tropopause layer (TTL) are studied using data from 3 h interval radiosonde launches carried out simultaneously from Trivandrum (8.5°N, 76.9°E) and Gadanki (13.5°N,79°E) during December 2010 to March 2014. TTL is defined as the region extending from the level of minimum stability (LMinS) to the level of maximum stability (LMaxS). Above the cold point tropopause (CPT), temperature showed warm anomaly (4–5 K) during summer monsoon (June–September) and cold anomaly (up to −4 K) during winter (December–February). The temperature in the troposphere showed a clear diurnal variation (±0.5 K) with a cold anomaly during early morning and warm anomaly during the day in all the seasons. At Gadanki, the diurnal temperature anomaly in the lower stratosphere showed its phase propagating downward with time, whereas at Trivandrum such variations are not clearly evident. At diurnal timescales, the TTL showed significant variations at LMinS (0.5–1.5 km/5–7 K) and smaller variations at CPT (0.2–0.5 km/2–3 K). In general, the amplitude of the diurnal component is greater than the semidiurnal component for all the TTL parameters, and these amplitudes are relatively larger at Trivandrum than at Gadanki. The observed diurnal variations could be the manifestation of tidal oscillations and/or due to the influence of local convection. Correlation analysis between different TTL parameters indicated a slow transition from a governing adiabatic process in the TTL base to a diabatic process at the TTL top. Diurnal variations are significant at the TTL‐base and are small at cold point tropopause (CPT)Amplitude of diurnal component is larger than the semidiurnal componentDiurnal variation of TTL could be the manifestation of tidal oscillations and local convection

In-process tool breakage monitoring can significantly save cost and prevent damages to machine tool. In this paper, a machine vision approach was employed to detect the tool fracture in commercial aluminium oxide ceramic cutting tool during turning of AISI 52100 hardened steel. The contour of the workpiece profile was captured with the aid of backlighting during turning using a high-resolution DSLR camera with a shutter speed of 1/4000 s. The surface profile of the workpiece was extracted to sub-pixel accuracy using the invariant moment method. The effect of fracture in ceramic cutting tools on the surface profile signature of the machined workpiece using autocorrelation was studied. Fracture in the aluminum oxide ceramic tool was found to cause the peaks of autocorrelation function of the workpiece profile to decrease rapidly as the lag distance increased. The envelope of the peaks of the autocorrelation function was observed to deviate significantly from one another at different workpiece angles when the tool has fractured due to the continuous fracture of ceramic cutting insert during machining.

Specific lipid self-associations in the fluid bilayer, particularly involving sphingolipids and cholesterol, are believed to result in the formation of membrane microdomains or “rafts” that mediate recycling of proteins between the cell surface and intracellular compartments or function as platforms for signal transduction events. Such membrane microdomains may be recovered in a low-density fraction that is insoluble in Triton X-100 at 4°C and referred to as detergent-insoluble, glycolipid-enriched complexes (DIGs). Membrane microdomains that constitute cell surface invaginations called caveolae can also be recovered in the form of DIGs. Caveolae are typically associated with a protein called caveolin, which coats their cytoplasmic surface.Various glycosyl-phosphatidylinositol (GPI)-anchored proteins such as the folate receptor (FR) are believed to be associated with membrane rafts and to constitutively internalize and recycle to the cell surface although FR is the only known GPI-anchored protein with a transport function, i.e.,

The combined effects of alkali treatment and compression molding temperature on the flexural strength and impact resistance of woven coir fibre composites are investigated. Ten pieces of composites plates made from single-layer woven coir fibre fabricated under different process parameters were used in the study. Five pieces of the coir woven fibre were treated with 6% sodium hydroxide (NaOH) solution while another five were left untreated. The compression molding temperature were varied between room temperature (25°C), 50°C, 75°C, 100°C and 125°C. The flexural properties of the composite were evaluated using the three-point flexural test, while the impact resistance was investigated by drop weight impact tests using a specially designed indenter. The indentation radius on each test specimen was measured using a 3-D metrology system and the depth of indentation was determined from the geometry of the indenter. The results show that the maximum flexural load to failure is improved by 38.9% when the fibres were treated and the compression molding temperature is increased to 125°C. The flexural modulus generally decreased with increase in the molding temperature. The depth of indentation in the treated coir woven composites is lower than that of untreated fibre composite at all molding temperatures. The impact resistance of both untreated and treated fibre composites decreased with the increase in the compression molding temperature. Composites fabricated by molding at room temperature, 50°C and 75°C using treated fibre produced the best impact properties.