Deep VLA Observations of the Cluster 1RXS J0603.3+4214 in the Frequency Range of 1-2 GHz

Rajpurohit, K.,Hoeft, M.,van Weeren, R. J.,Rudnick, L.,Rö,ttgering, H. J. A.,Forman, W. R.,Brü,ggen, M.,Croston, J. H.,Andrade-Santos, F.,Dawson, W. A.,Intema, H. T.,Kraft, R. P.,Jones, C.,Jee American Astronomical Society 2018 The Astrophysical Journal Vol.852 No.2

<P>We report L-band VLA observations of 1RXS J0603.3+4214, a cluster that hosts a bright radio relic, known as the Toothbrush, and an elongated giant radio halo. These new observations allow us to study the surface brightness distribution down to 1 arcsec resolution with very high sensitivity. Our images provide an unprecedented detailed view of the Toothbrush, revealing enigmatic filamentary structures. To study the spectral index distribution, we complement our analysis with published LOFAR and GMRT observations. The bright 'brush' of the Toothbrush shows a prominent narrow ridge to its north with a sharp outer edge. The spectral index at the ridge is in the range -0.70 <= alpha <= -0.80. We suggest that the ridge is caused by projection along the line of sight. With a simple toy model for the smallest region of the ridge, we conclude that the magnetic field is below 5 mu G and varies significantly across the shock front. Our model indicates that the actual Mach number is higher than that obtained from the injection index and agrees well with the one derived from the overall spectrum, namely M = 3.78(-0.2)(+0.3). The radio halo shows an average spectral index of alpha = -1.16 +/- 0.05 and a slight gradient from north to south. The southernmost part of the halo is steeper and possibly related to a shock front. Excluding the southernmost part, the halo morphology agrees very well with the X-ray morphology. A power-law correlation is found between the radio and X-ray surface brightness.</P>

Body melanization and its adaptive role in thermoregulation and tolerance against desiccating conditions in drosophilids

Subhash RAJPUROHIT,Ravi PARKASH,Seema RAMNIWAS 한국곤충학회 2008 Entomological Research Vol.38 No.1

Melanism seems to have evolved independently through diverse mechanisms in various taxa and different ecological factors could be responsible for selective responses. Increased body melanization at higher altitudes as well as latitudes is generally considered to be adaptive for thermoregulation. Physiological traits such as body melanization and desiccation resistance have been investigated independently in diverse insect taxa at three levels: within populations, between populations and among species. A substantial number of Drosophila studies have reported clinal variations in both these traits along latitude. A possible link between these traits had remained unexplored in wild and laboratory populations of ectothermic insect taxa, including drosophilids, to date. Simultaneous analysis of these traits in assorted darker and lighter phenotypes in each population in the present study showed parallel changes for body melanization and desiccation resistance. The mechanistic basis of evolving desiccation resistance was explained on the basis of differential rates of water loss per hour in darker versus lighter phenotypes in six populations of Drosophila melanogaster from adjacent localities differing substantially in altitude all along the Indian subcontinent. Data on cuticular impermeability suggest a possible role of melanization in desiccation tolerance. However, substantial gaps remain in extending these results to other insect taxa and further exploring the physiological and molecular changes involved in melanization for conferring desiccation resistance.

Climate change, boundary increase and elongation of a pre-existing cline: A case study in Drosophila ananassae

Subhash RAJPUROHIT,Ravi PARKASH,Shama SINGH,Seema RAMNIWAS 한국곤충학회 2008 Entomological Research Vol.38 No.4

During the past two to three decades, Drosophila ananassae, a warm adapted tropical species, has invaded low to mid altitude localities in the western Himalayas. Due to its cold sensitivity, this species had never been recorded from higher latitudes as well as altitudes in India to the 1960s. A latitudinal cline in this desiccation-sensitive species corresponds with southern humid tropical localities rather than northern drier subtropical localities. An extension of its cline into lowland to midland montane localities has resulted due to global climatic change as well as local thermal effects through anthropogenic impact. However, D. ananassae populations at species borders are characterized by lower genetic variability for body melanization as well as for desiccation resistance. There is a lack of thermal plastic effects for body melanization, and the observed extended cline might represent evolutionary (genetic) response due to selection pressure imposed by drier habitats. A comparison of fecundity, hatchability and viability at three growth temperatures (17, 20 and 25°C) showed significant reduction in trait values at 17 °C in D. ananassae. Thus, its recent range expansion into northern montane localities might involve genetic effects on stress-related traits and plastic effects on life history traits. We suggest that D. ananassae could serve as an indicator species for analyzing range expansion under changing climatic conditions.

Ratcheting Fatigue Behaviour of Zircaloy‑2 at 300 °C

R. S. Rajpurohit,Prerna Mishra,N. C. Santhi Srinivas,S. R. Singh,V. Singh 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.9

In laboratory, materials designed for engineering applications, specifically for fatigue, are generally tested under symmetricalcyclic loading (stress ratio, R = −1), but many structural components exhibit less fatigue life than predicted from symmetricloading due to asymmetric cyclic loading during service. This study deals with fatigue behaviour of Zircaloy-2 and presentsthe effect of mean stress (σm), stress amplitude (σa), stress rate ( ̇ ) on fatigue life, deformation and fracture behaviour at300 °C under asymmetric cyclic loading. A series of fatigue tests are performed at 300 °C under asymmetric stress-controlledloading with different combinations of σm (60–80 MPa), σa (115–135 MPa) and ̇ (30–750 MPa/s). Deformation behaviourand microstructural changes under the influence of above parameters (σm, σa and ̇ ) are examined by transmission electronmicroscope. It is observed that plastic strain increases with rise in σm as well as σa and cyclic life is reduced; on the otherhand, with increase in ̇ accumulation of plastic strain decreases and fatigue life is enhanced. The results are correlated withmicrostructural changes and fracture behaviour of the material under different test conditions.

Ratcheting Fatigue Behavior of Modified 9Cr–1Mo Steel at Room Temperature

Prerna Mishra,R. S. Rajpurohit,N. C. Santhi Srinivas,G. V. S. Sastry,Vakil Singh 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.12

Fusion reactor components undergo asymmetric cyclic loading,that leads to a progressive increase in plastic strain andcauses deterioration in life of engineering components. This investigation deals with fatigue behavior of modified 9Cr–1Mosteel at room temperature and presents the effect of mean stress (σm), stress amplitude (σa) and stress rate ( ̇ ) on fatigue life,deformation and fracture behavior under asymmetric cyclic loading. A series of fatigue tests were conducted under asymmetricstress-controlled loading with different combinations of σm (190–210 MPa), σa (400–420 MPa) and ̇ (50–450 MPa/s). The plastic strain increased with increase in σm and σa and the fatigue life was reduced, whereas increase in ̇ reduced theaccumulated plastic strain and the cyclic life was increased. The deformation behavior and microstructural changes under theinfluence of the three parameters (σm, σa and ̇ ) were examined by tranmission electron microscope (TEM). With increasein the three parameters (σm, σa, ̇ ), the lath martensitic structure changed to subgrain structure along with dislocation cellsand forest dislocations. Scanning electron microscopy revealed unique features of fractured specimens, with progressivereduction in diameter towards the fracture-end, fatigue striations on the tapered circumferential surface and dimples on thefracture surface.

Dynamic regulation of RNA editing in human brain development and disease

Hwang, Taeyoung,Park, Chul-Kee,Leung, Anthony K L,Gao, Yuan,Hyde, Thomas M,Kleinman, Joel E,Rajpurohit, Anandita,Tao, Ran,Shin, Joo Heon,Weinberger, Daniel R NATURE AMERICA 2016 NATURE NEUROSCIENCE Vol.19 No.8

<P>RNA editing is increasingly recognized as a molecular mechanism regulating RNA activity and recoding proteins. Here we surveyed the global landscape of RNA editing in human brain tissues and identified three unique patterns of A-to-I RNA editing rates during cortical development: stable high, stable low and increasing. RNA secondary structure and the temporal expression of adenosine deaminase acting on RNA (ADAR) contribute to cis- and trans-regulatory mechanisms of these RNA editing patterns, respectively. Interestingly, the increasing pattern was associated with neuronal maturation, correlated with mRNA abundance and potentially influenced miRNA binding energy. Gene ontology analyses implicated the increasing pattern in vesicle or organelle membrane-related genes and glutamate signaling pathways. We also found that the increasing pattern was selectively perturbed in spinal cord injury and glioblastoma. Our findings reveal global and dynamic aspects of RNA editing in brain, providing new insight into epitranscriptional regulation of sequence diversity.</P>