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A novel scheme has been developed to show that the observed phase behaviour associated with subpulse drifting from two pulsars, J1034$-$3224 and J1720$-$2933, can be used to obtain the magnetic field configuration in the partially screened gap (PSG). The outflowing plasma along the open magnetic field line region of pulsars is generated due to spark discharges in an inner acceleration region (IAR) above the polar cap. The IAR has been modelled as a partially screened gap (PSG) with a steady supply of positively charged ions emitted from the heated polar cap surface dominated by strong non-dipolar magnetic fields. In a PSG the sparks are tightly packed and constrained to be present along the polar cap boundary. The sparks lag behind the rotation of the star during their lifetimes. As a result the sparking pattern evolves along two different directions in the clockwise and counter-clockwise manner around a stationary central spark, and can be associated with the observed phenomenon of subpulse drifting. PSR J1034$-$3224 has four prominent components and exhibit bi-drifting where alternate components show opposite sense of drifting, while PSR J1720$-$2933 has a single component profile and shows systematic coherent drift bands. We show that the differences in their drifting behaviour can be directly linked to different natures of the non-dipolar surface magnetic field configurations., Comment: 11 pages, 6 figures, accepted for publication in ApJ

The diverse polarization properties in pulsars are in conflict with applying a unique emission mechanism to the population. The polarization position angle (PPA) traverse in most pulsars shows a S-shaped curve that can be interpreted using the rotating vector model (RVM) as the radio emission being directed either parallel or perpendicular to the divergent magnetic field lines and argues for a coherent curvature radiation mechanism from charge bunches in a strongly magnetized pair plasma. However, in a subset of pulsars the radio emission is significantly depolarized and the PPA shows a complex pattern which cannot be explained using RVM. We propose that even in such cases the highly polarized time samples in the single pulses should follow the RVM with possibly two parallel tracks separated by 90\degr. We have investigated PSR J1645$-$0317, with complex PPA traverse, and demonstrated for the first time that considering only the highly polarized time samples in the single pulses, the PPA distribution clearly follows the RVM. We conclude that this strongly favour the coherent curvature radiation mechanism to be universally applicable in the pulsar population., Comment: 1 Figure, accepted for publication in MNRAS letters

Zika virus (ZIKV) is an arbovirus belonging to the family Flaviviridae. Since 2015, ZIKV infection has emerged as a leading cause of virus-induced placental insufficiency, microcephaly and other neuronal complications. Currently, no therapeutics have been approved to treat ZIKV infection. In this study, we examined how targeted inhibition of cellular organelles or trafficking processes affected ZIKV infection and replication in neural progenitor cells. We found that blocking endocytosis, Golgi function or structural filaments like actin or microtubules had moderate effects on virus replication. However, inducing endoplasmic reticulum (ER) stress by treatment with Thapsigargin substantially inhibited virus production, suggesting the ER might be a candidate cellular target. Further analysis showed that sarcoplasmic/endoplasmic reticulum Ca2+-ATPases (SERCA) was important for ZIKV inhibition. Collectively, these studies indicate that targeting the SERCA-dependent ER stress pathway may be useful to develop antivirals to inhibit ZIKV replication.

Many countries badly mismanage their natural resource endowments. We argue that a fundamental change in paradigm is needed. Specifically, we advocate treating non-renewable natural resources as a finite shared inheritance asset, and extraction as the sale of the inherited wealth. We identify several proposals that logically derive from treating mineral sale proceeds as intergenerational wealth rather than as revenues that can be spent. Wealth portfolio management suggests that mineral owners must strive for zero-loss when selling minerals, establish a passively invested future generations fund from the proceeds and distribute dividends from that fund to citizens as the rightful owners of the shared inheritance. The current dominant metaphor of proceeds from the exploitation of non-renewable mineral resources as being “windfall revenues” is underpinned by government accounting standards. The “windfall revenue” metaphor is not only inaccurate but also produces several pernicious effects that help explain the poor management of natural resource endowments in so many countries. We do not anticipate that our ideas will quickly overturn centuries of established practice. We do, however, believe that the case needs to be made.

The radio emission in many pulsars show sudden changes, usually within a period, that cannot be related to the steady state processes within the inner acceleration region (IAR) above the polar cap. These changes are often quasi-periodic in nature, where regular transitions between two or more stable emission states are seen. The durations of these states show a wide variety ranging from several seconds to hours at a time. There are strong, small scale magnetic field structures and huge temperature gradients present at the polar cap surface. We have considered several processes that can cause temporal modifications of the local magnetic field structure and strength at the surface of the polar cap. Using different magnetic field strengths and scales, and also assuming realistic scales of the temperature gradients, the evolutionary timescales of different phenomena affecting the surface magnetic field was estimated. We find that the Hall drift results in faster changes in comparison to both Ohmic decay and thermoelectric effects. A mechanism based on the Partially Screened Gap (PSG) model of the IAR has been proposed, where the Hall and thermoelectric oscillations perturb the polar cap magnetic field to alter the sparking process in the PSG. This is likely to affect the observed radio emission resulting in the observed state changes., Accepted for publication in MNRAS

A methodology is presented to decouple and isolate the separate solutions of a set of coupled partial differential equations describing the heat, mass, and surface energy transfer in nanomaterials and surface films. Calculation of the eigenvalues and eigenvectors give the solution in matrix form, whereby the stability and other characteristics of the solution are known. For illustration a binary set is chosen, however, the method is capable of extension to more than two coupled systems. Applications to radiation and radar-absorbing and attenuating surfaces for defence and consumer uses are envisaged.

Two-stage pretreatment conditions were optimized to convert corn fiber, separated from whole stillage in a corn dry grind ethanol plant, to fermentable sugars via hydrolysis. Liquid hot water pretreatment (25% solids) at 180 °C for 10 min, followed by three cycles of disk milling, provided maximum glucose, xylose, and arabinose yields of 88.5%, 41.0%, and 30.4% respectively after hydrolysis with Cellulase I. The glucose, xylose, and arabinose yields with Cellulase II at optimum conditions were 94.9%, 74.2%, and 66.3%, respectively. SSF of corn fiber using engineered yeast, with both Cellulase I and II, provided maximum ethanol concentrations of 2.13% and 2.73% (v/v). The protein content in the residual solid after fermentation was 47.95% and 52.05% for Cellulase I and II, respectively. This technology provides additional ethanol in a dry grind plant by converting corn fiber into ethanol and increases the protein content of DDGS, thereby improving the quality.

Smart self-healing materials may use embedded capsules and vascular channels containing a repair medium usually in liquid form. It is possible to connect the channels to an external reservoir or leave them sealed in the matrix. On damage, either mechanical or thermal, the repair substance diffuses to the damaged area and reacts with the matrix to perform self-healing. There exists an inbuilt control mechanism depending on the concentration and thermal gradients which decides where the repair medium should go. To approximate this situation for planar smart self-healing materials, the phase change problem in a semi-infinite slab with coupled temperature and concentration is solved for variable conductivity and mass diffusivity. As an approximation, the mass transfer equations are looked at, since temperature may not change significantly. The thermally coupled formulation is, however, also included. An integral technique is used to solve for concentration and temperature penetration lengths and phase change length. The temperature and concentration at the surface are held constant throughout. An analytic solution for variable properties under slowly varying conditions is obtained by dependent variable transformation using the Kirchhoff’s transformation. A comparison is made between numerical and exact solutions for constant and variable properties, by varying certain parameters. Agreement for Stefan numbers up to 1, high conductivity ratio, or high transformation temperatures was good. The exponent in the integral formulation did not display much significance.

Simultaneous observations of PSR B0823+26 with ESA's XMM-Newton, the Giant Metrewave Radio Telescope and international stations of the Low Frequency Array revealed synchronous X-ray/radio switching between a radio-bright (B) mode and a radio-quiet (Q) mode. During the B mode we detected PSR B0823+26 in 0.2$-$2 keV X-rays and discovered pulsed emission with a broad sinusoidal pulse, lagging the radio main pulse by 0.208 $\pm$ 0.012 in phase, with high pulsed fraction of 70$-$80%. During the Q mode PSR B0823+26 was not detected in X-rays (2 $\sigma$ upper limit a factor ~9 below the B-mode flux). The total X-ray spectrum, pulse profile and pulsed fraction can globally be reproduced with a magnetized partially ionized hydrogen atmosphere model with three emission components: a primary small hot spot ($T$$\sim$3.6$\times10^6$ K, $R$$\sim$17 m), a larger cooler concentric ring ($T$$\sim$1.1$\times10^6$ K, $R$$\sim$280 m) and an antipodal hot spot ($T$$\sim$1.1$\times10^6 $ K, $R$$\sim$100 m), for the angle between the rotation axis and line of sight direction $\sim66^\circ$. The latter is in conflict with the radio derived value of $(84\pm0.7)^\circ$. The average X-ray flux within hours-long B-mode intervals varied by a factor $\pm$20%, possibly correlated with variations in the frequency and lengths of short radio nulls or short durations of weak emission. The correlated X-ray/radio moding of PSR B0823+26 is compared with the anti-correlated moding of PSR B0943+10, and the lack of X-ray moding of PSR B1822-09. We speculate that the X-ray/radio switches of PSR B0823+26 are due to variations in the rate of accretion of material from the interstellar medium through which it is passing., Comment: 16 pages, 11 figures

We report a detailed study of subpulse drifting in four long period pulsars. These pulsars were observed in the Meterwavelength Single-pulse Polarimetric Emission Survey and the presence of phase modulated subpulse drifting was reported in each case. We have carried out longer duration and more sensitive observations lasting 7000-12000 periods, between frequency range of 306 and 339 MHz. The drifting features were characterised in great detail including the phase variations across the pulse window. In two pulsars J0820$-$1350 and J1720$-$2933 the phases changed steadily across the pulse window. The pulsar J1034$-$3224 has five components. The leading component was very weak and was barely detectable in our observations. The four trailing components showed the presence of subpulse drifting. The phase variations changed in alternate components with a reversal in the sign of the gradient. This phenomenon is known as bi-drifting. The pulsar J1555$-$3134 showed the presence of two distinct peak frequencies of comparable strengths in the fluctuation spectrum. The two peaks did not appear to be harmonically related and were most likely a result of different physical processes. Additionally, the long observations enabled us to explore the temporal variations of the drifting features. The subpulse drifting was largely constant with time but small fluctuations around a mean value was seen., 10 pages, 5 figures, Accepted for publication in MNRAS

We have estimated flux densities of several pulsars from radio interferometric observations mainly at 325 MHz using the Giant Metrewave Radio Telescope. The new observations allowed us to update the spectral nature of the observed pulsars, and in six sources we identified relatively high frequency turnovers, which can be classified as new GHz-peaked spectrum (GPS) pulsars. For such objects the turnover in the spectrum is most likely caused by absorption in the immediate vicinity of the pulsar (or in the interstellar medium). We modeled the turnover spectra using the thermal free–free absorption model and the physical parameters obtained from the fits enabled us to identify the environments that could potentially be responsible for the observed absorption, such as pulsar wind nebulae, supernova remnant nebulae or H ii regions. The discovery of 6 new GPS pulsars brings the total number of such objects to 33 and we discuss the properties of the entire sample.

Using the Giant Metrewave Radio Telescope, we report the detailed spectral measurements over a wide frequency range of three pulsars (J1741−3016, J1757−2223, and J1845−0743), which allow us to identify them as new gigahertz-peaked spectra pulsars. Our results indicate that their spectra show turnovers at the frequencies of 620 MHz, 640 MHz, and 650 MHz, respectively. Our analysis proves that wideband observations improve estimations of spectral nature using a free–free thermal absorption model, and thus allow for a more accurate approximation of the maximum energy in the spectrum. While there is no evidence as yet that these objects are associated with a supernova remnant or pulsar wind nebula, they will make good targets when looking for interesting environments in the future, or when conducting more sensitive sky surveys.

A model for coupled heat and mass transfer for self-freezing in a porous matrix is set up and solved. A stability criterion for the phase interface is linked with well-known parameters like under cooling and freezing rate. It is shown that heat and mass transfer balance at the interface can affect stability. The effect of parameters on freezing and sublimation rates is examined. Applications in food processing, freeze drying and temperature control of buildings are possible.

We present the flux density measurements of the pulsars observed in the Meterwavelength single-pulse polarimetric emission survey. The average flux densities were estimated in 113 pulsars at two frequencies of 325 and 610 MHz using interferometric imaging. The average profile and single pulse emission in each pulsar were calibrated using the estimated flux density. We have used the flux calibrated average profile to study the variation of the spectral index across the emission beam in 21 pulsars where the core, inner cone and the outer conal components could be clearly identified. The central core component showed a steeper increase in emission at the lower frequency compared with conal emission, with an average difference in spectral index $\delta\alpha_{core-cone}\sim-0.7$ between the core and the conal components in this frequency range. In contrast the inner conal components had positive difference in their spectral index compared to the outer cones with average difference $\delta\alpha_{in-out}\sim+0.3$. The variation in the spectral index across the pulse window should provide valuable inputs for constraining the radio emission processes. The single pulse emission showed the presence of emission mode changing in 12 pulsars with 3 cases where the phenomenon is being reported for the first time. In addition we have also detected enhanced emission for short durations or flaring, in parts or across the entire emission window in 14 pulsars. The sudden changes in the emission during mode changing as well as these bursting states are unrelated to the emission mechanism and suggest the presence of rapid and repetitive changes during the plasma generation process., Comment: 33 pages, 17 figures, Accepted for publication in ApJ

We have carried out a detailed study of the spectral nature of six pulsars surrounded by Pulsar wind nebulae (PWN). The pulsar flux density were estimated using the interferometric imaging technique of the Giant Metrewave Radio Telescope at three frequencies 325 MHz, 610 MHz and 1280 MHz. The spectra showed a turnover around gigahertz frequency in four out of six pulsars. It has been suggested that the gigahertz peaked spectra (GPS) in pulsars arises due to thermal absorption of the pulsar emission in surrounding medium like PWN, HII regions, Supernova remnants, etc. The relatively high incidence of GPS behaviour in pulsars surrounded by PWN impart further credence to this view. The pulsar J1747$-$2958 associated with the well known Mouse nebula was also observed in our sample and exhibited GPS behaviour. The pulsar was detected as a point source in the high resolution images. However, the pulsed emission was not seen in the phased array mode. It is possible that the pulsed emission was affected by extreme scattering causing considerable smearing of the emission at low radio frequencies. The GPS spectra were modeled using the thermal free-free absorption and the estimated absorber properties were largely consistent with PWN. The spatial resolution of the images made it unlikely that the point source associated with J1747$-$2958 was the compact head of the PWN, but the synchrotron self-absorption seen in such sources was a better fit to the estimated spectral shape., 8 pages, 4 figures, accepted for publication in MNRAS

In this short overview we summarize our knowledge of twenty five pulsars showing GPS characteristics. Especially, we will focus on two objects. The first is PSR B1800–21 - a Vela-like GPS pulsar with a variable spectrum. The second is PSR J1740+1000 - a pulsar that shows high frequency turnover based on our most recent observations using the Giant Meterwave Radio Telescope and the Green Bank Telescope.

Gap junctions (GJs) are important for maintenance of CNS homeostasis. GJ proteins, connexin 43 (Cx43) and connexin 47 (Cx47), play a crucial role in production and maintenance of CNS myelin. Cx43 is mainly expressed by astrocytes in the CNS and forms gap junction intercellular communications between astrocytes-astrocytes (Cx43–Cx43) and between astrocytes-oligodendrocytes (Cx43–Cx47). Mutations of these connexin (Cx) proteins cause dysmyelinating diseases in humans. Previously, it has been shown that Cx43 localization and expression is altered due to mouse hepatitis virus (MHV)-A59 infection both in vivo and in vitro; however, its mechanism and association with loss of myelin protein was not elaborated. Thus, we explored potential mechanisms by which MHV-A59 infection alters Cx43 localization and examined the effects of viral infection on Cx47 expression and its association with loss of the myelin marker proteolipid protein. Immunofluorescence and total internal reflection fluorescence microscopy confirmed that MHV-A59 used microtubules (MTs) as a conduit to reach the cell surface and restricted MT-mediated Cx43 delivery to the cell membrane. Co-immunoprecipitation experiments demonstrated that Cx43–β-tubulin molecular interaction was depleted due to protein–protein interaction between viral particles and MTs. During acute MHV-A59 infection, oligodendrocytic Cx47, which is mainly stabilized by Cx43 in vivo, was down-regulated, and its characteristic staining remained disrupted even at chronic phase. The loss of Cx47 was associated with loss of proteolipid protein at the chronic stage of MHV-A59 infection.

Coherent radio emission in pulsars is excited due to instabilities in a relativistically streaming non-stationary plasma flow, which is generated from sparking discharges in the inner acceleration region (IAR) near the stellar surface. A number of detailed works have shown the IAR to be a partially screened gap (PSG) dominated by non-dipolar magnetic fields with continuous outflow of ions from the surface. The phenomenon of subpulse drifting is expected to originate due to variable $\mathbf{E}\times\mathbf{B}$ drift of the sparks in PSG, where the sparks lag behind corotation velocity of the pulsar. Detailed observations show a wide variety of subpulse drifting behaviour where subpulses in different components of the profile have different phase trajectories. But the drifting periodicity is seen to be constant, within measurement errors, across all components of the profile. Using the concept of sparks lagging behind corotation speed in PSG as well as the different orientations of the surface non-dipolar magnetic fields we have simulated the expected single pulse behaviour in a representative sample of pulsars. Our results show that the different types of drifting phase behaviour can be reproduced using these simple assumptions of spark dynamics in a non-dipolar IAR., Comment: 22 pages, 19 figures, Accepted for publication in MNRAS

We have carried out a detailed study of single pulse emission from the pulsar B2000+40 (J2002+4050), observed at 1.6 GHz frequencies using the Effelsberg radio telescope. The pulsar has three components which are not well separated, with the central component resembling core emission. We have investigated modulations in single pulse behaviour using the fluctuation spectral analysis which showed presence of two prominent periodicities, around 2.5$P$ and 40$P$, respectively. The shorter periodicity was associated with the phenomenon of subpulse drifting and was seen to be absent in central core component. Drifting showed large phase variations in conal components. Additionally, the periodic modulations had significant evolution with time, varying between very sharp and highly diffuse features. In addition to drifting the pulsar also had presence of nulling in the single pulse sequence. The longer periodic feature in the fluctuation spectra was associated with nulling behaviour. The pulsar joins a select group which shows the presence of phase modulated drifting as well as periodic nulling in the presence of core emission. This provides further evidence for the two phenomena to be distinct from each other with different physical origin., 8 pages, 6 figures, accepted for publication in MNRAS

In this study, we report on a detailed single pulse polarimetric analysis of the radio emission from the pulsar J2321+6024 (B2319+60) observed with the Giant Metrewave Radio Telescope, over wide frequencies ranging between 300 to 500 MHz and widely separated observing sessions. The pulsar profile shows the presence of four distinct conal components and belongs to a small group of pulsars classified as a conal quadrupole profile type. The single pulse sequence reveals the presence of three distinct emission modes, A, B, and ABN showing subpulse drifting. Besides, there were sequences when the pulsar did not show any drifting behaviour suggesting the possibility of a new emission state, which we have termed as mode C. The evolution of the mode changing behavior was seen during the different observing sessions with different abundance as well as the average duration of the modes seen on each date. The drifting periodicities were 7.8$\pm$0.3 $P$, 4.3$\pm$0.4 $P$, and 3.1$\pm$0.2 $P$ in the modes A, B and ABN respectively, and showed large phase variations within the mode profile. The pulsar also showed the presence of orthogonal polarization modes, particularly in the leading and trailing components, which has different characteristics for the stronger and weaker pulses. However, no correlation was found between the emission modes and their polarization behavior, with the estimated emission heights remaining roughly constant throughout. We have used the Partially Screened Gap model to understand the connection between drifting, mode changing, and nulling., Comment: Accepted for publication in MNRAS

A low-cost Puma arm with wrist rotation and gripper is described. The Advent of IoT and 5g makes it feasible for remote medical applications. Surgical robots have inherent limitations due to tolerance and feedback errors. Procedures in ophthalmology, cardiology, neurology, and canulisation use robotics. Possibilities now exist to link up with a IoT network. Further enhancements are possible when AI is built into the controls, giving scope for a higher degree of autonomy. This topic remains a challenge given the exorbitant prices of equipment which are passed onto the patients. Developing countries require coordination between several disciplines to enhance the knowledge and support base.

We report on simultaneous X-ray and radio observations of the radio-mode-switching pulsar PSR B1822-09 with ESA's XMM-Newton and the WSRT, GMRT and Lovell radio telescopes. PSR B1822-09 switches between a radio-bright and radio-quiet mode, and we discovered a relationship between the durations of its modes and a known underlying radio-modulation timescale within the modes. We discovered X-ray (energies 0.2-1.4 keV) pulsations with a broad sinusoidal pulse, slightly lagging the radio main pulse in phase by 0.094 +/- 0.017, with an energy-dependent pulsed fraction varying from ~0.15 at 0.3 keV to ~0.6 at 1 keV. No evidence is found for simultaneous X-ray and radio mode switching. The total X-ray spectrum consists of a cool component (T ~ 0.96 x 10^6 K, hot-spot radius R ~ 2.0 km) and a hot component (T ~ 2.2 x 10^6 K, R ~ 100 m). The hot component can be ascribed to the pulsed emission and the cool component to the unpulsed emission. The high-energy characteristics of PSR B1822-09 resemble those of middle-aged pulsars such as PSR B0656+14, PSR B1055-52 and Geminga, including an indication for pulsed high-energy gamma-ray emission in Fermi LAT data. Explanations for the high pulsed fraction seem to require different temperatures at the two poles of this orthogonal rotator, or magnetic anisotropic beaming effects in its strong magnetic field. In the X-ray skymap we found a harder source at only (5.1+/- 0.5 )arcsec from PSR B1822-09, which might be a pulsar wind nebula., Comment: 22 pages, 16 figures, MNRAS accepted

Economy of motion in robots assembly lines, microelectronics, medical and space applications has not received much attention. It is however, as challenging and important as efficiency and ergonomics is to human beings in the factory workplace. Production lines with humans are prone to human fatigue. Hence robotic units are replacing human sorters for production line work. Mechanised operations are usually limited to batch processes with identical items taken from a conveyor belt and placed in a bin or stack. A further extension is to use AI programs to enable discrimination of objects and sorting into separate bins or stacks. In the present study a 5 d.o.f. arm kit was assembled by students and used to understand simple robotic concepts like degree of freedom, gripper action, pick and place, palletisation and other topics in a lab syllabus together with online simulators where factory robots are simulated. Basic algorithms are explored by testing with the 5 dof Puma arm. The addition of tactile and visual interfaces for pick and sort are discussed. Sample outputs are illustrated.

A sieving step was developed to recover corn fiber from whole stillage of a dry grind process as a cellulosic ethanol feedstock, and to reduce fiber contents in distillers dried grains with solubles (DDGS). Several processes have been developed to recover fiber in the dry grind process, such as wet fractionation, dry fractionation and elusieve process. Wet fractionation and dry fractionation recover fiber before liquefaction, but addition of these steps to existing plants requires considerable modifications with high capital costs. The elusieve process recovers fiber from DDGS, but it requires drying of DDGS. To simply integrate fiber recovery to current dry grind plants with less operating and capital costs, sieving was applied to whole stillage. Commercial whole stillage samples were ground, incubated with protease or with a surfactant, and sieved. Sieving was effective to recover neutral detergent fiber (NDF), and NDF contents in retentate samples were increased by 45–101%. In addition, permeate samples, called enhanced DDGS, exhibited decreased fiber contents and increased oil contents. Among treatments, grinding before sieving was more effective to recover fiber with high NDF contents and low protein and oil contents. Fiber recovered from whole stillage and ground whole stillage were hydrolyzed for cellulosic sugars. Whole stillage and ground whole stillage were sieved in a scaled-up (15×) vibrator shaker. The retentate samples were pretreated with dilute acid followed by hydrolysis. Ground whole stillage showed higher sugar yields than whole stillage. After hydrolysis, glucose, xylose and arabinose yields from ground whole stillage were 90.78, 92.93 and 76.99%, respectively. Grinding before sieving produces more eDDGS, and could potentially increase downstream ethanol yields.