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Lahiri D.,Bhabha Atomic Research Center | Choi Y.,Argonne National Laboratory | Yusuf S.M.,Bhabha Atomic Research Center | Kumar A.,Bhabha Atomic Research Center | And 5 more authors.
Materials Research Express | Year: 2016

Wehave investigated the microscopic origin of temperature and magnetic-field actuated magnetization reversal in Cu0.73Mn0.77[Fe(CN)6].zH2O, using XMCD. Our results show a fair deviation from the mean-field-theory in the form of different ordering temperatures of Fe and Mnsublattices. A preferential sign reversal of Mn spin under magnetic field and different spin cant angles for the two sublattices have also been observed. An antiferromagnetic coupling between the Fe and Mnsublattices along with different ordering temperatures (sublattice decoupling) for these sublattices explain the temperature-dependent magnetization reversal. Whereas, Mnspin reversal alone (under external magnetic field) is responsible for the observed field-dependent magnetization reversal. The dissimilar magnetic behavior of Fe and Mnsublattices in this cubic 3d-orbital system has been understood by invoking disparity and competition among inter-sublattice magnetic control parameters, viz. magnetic Zeeman energy, exchange coupling constant and magnetic anisotropy constant. Our results have significant design implications for future magnetic switches, by optimizing the competition among these magnetic control parameters. © 2016 IOP Publishing Ltd.

Hutson J.D.,Northern Illinois University | Hutson J.D.,Elgin Community College
Acta Palaeontologica Polonica | Year: 2015

Therians (marsupials and placentals), archosaurs, and chameleons are remarkable in that they evolved postures and gaits with inturned forelimbs. However, recent studies have indirectly recognized that, unlike fully pronated therian and chameleon forearms, dinosaur forearms were mechanically constrained by semi-pronated (misaligned) joints. This has led to the hypothesis that quadrupedal dinosaurs mitigated this constraint via proximal migration of the radius, indirectly forming a more pronated, tubular manus distally. To test this hypothesis, a standardized pose was used to examine the forearm pronation of ornithischian dinosaurs that were obligatory quadrupeds and facultative bipeds. Results show that only restructuring of the distal, not the proximal radius, causes additional pronation of the pre-axial edge of the carpus, but also unexpectedly reveal that the ulna may help form a tubular manus by supinating the post-axial edge. Thus, relative to the plane of the elbow joint the wrist and finger joints remain wholly semi-pronated. These findings do not support the hypothesis that a tubular cross-section evolved in dinosaurs to pronate the manus further to allow the finger joints to participate in locomotion. Instead these results indicate that quadrupedal dinosaurs tended to abandon propulsive use of their wrist and finger joints by converting their carpus + metacarpus into a vertical stilt-like extension of the forearm. Prior studies have overlooked that this divergent path to parasagittal forelimb kinematics had its phylogenetic basis in the retention of the semi-pronated forearm joint alignment that is plesiomorphic to tetrapods. Thus, this test provides the first functional explanation for the convergent responses of quadrupedal archosaurs to their misaligned forearm joints, and provides a foundation for elucidating why the quadrupedal evolution of archosaur forelimbs diverged from those of therians and chameleons. © 2015 L. Xing et al.

Hutson J.D.,Northern Illinois University | Hutson J.D.,Elgin Community College
Journal of Experimental Biology | Year: 2013

Using the extant phylogenetic bracket of dinosaurs (crocodylians and birds), recent work has reported that elbow joint range of motion (ROM) studies of fossil dinosaur forearms may be providing conservative underestimates of fully fleshed in vivo ROM. As humeral ROM occupies a more central role in forelimb movements, the placement of quantitative constraints on shoulder joint ROM could improve fossil reconstructions. Here, we investigated whether soft tissues affect the more mobile shoulder joint in the same manner in which they affect elbow joint ROM in an extant archosaur. This test involved separately and repeatedly measuring humeral ROM in Alligator mississippiensis as soft tissues were dissected away in stages to bare bone. Our data show that the ROMs of humeral flexion and extension, as well as abduction and adduction, both show a statistically significant increase as flesh is removed, but then decrease when the bones must be physically articulated and moved until they separate from one another and/or visible joint surfaces. A similar ROM pattern is inferred for humeral pronation and supination. All final skeletonized ROMs were less than initial fully fleshed ROMs. These results are consistent with previously reported elbow joint ROM patterns from the extant phylogenetic bracket of dinosaurs. Thus, studies that avoid separation of complementary articular surfaces may be providing fossil shoulder joint ROMs that underestimate in vivo ROM in dinosaurs, as well as other fossil archosaurs. © 2013. Published by The Company of Biologists Ltd.

Saha A.,New Chemistry Unit | Shetty A.,Jawaharlal Nehru Centre for Advanced Scientific Research | Pavan A.R.,Jawaharlal Nehru Centre for Advanced Scientific Research | Chattopadhyay S.,CSRRI IIT | And 7 more authors.
Journal of Physical Chemistry Letters | Year: 2016

Effective manipulation of magnetic spin within a semiconductor leading to a search for ferromagnets with semiconducting properties has evolved into an important field of dilute magnetic semiconductors (DMS). Although a lot of research is focused on understanding the still controversial origin of magnetism, efforts are also underway to develop new materials with higher magnetic temperatures for spintronics applications. However, so far, efforts toward quantum-dots(QDs)-based DMS materials are plagued with problems of phase separation, leading to nonuniform distribution of dopant ions. In this work, we have developed a strategy to synthesize highly crystalline, single-domain DMS system starting from a small magnetic core and allowing it to diffuse uniformly inside a thick CdS semiconductor matrix and achieve DMS QDs. X-ray absorption fine structure (XAFS) spectroscopy and energy-dispersive X-ray spectroscopy-scanning transmission electron microscopy (STEM-EDX) indicates the homogeneous distribution of magnetic impurities inside the semiconductor QDs leading to superior magnetic property. Further, the versatility of this technique was demonstrated by obtaining ultra large particles (∼60 nm) with uniform doping concentration as well as demonstrating the high quality magnetic response. © 2016 American Chemical Society.

Hutson J.D.,Northern Illinois University | Hutson J.D.,Elgin Community College
Journal of Experimental Biology | Year: 2012

Recent studies have presented range of motion (ROM) data in degrees for dinosaur forelimb joints, usually via physical manipulation of one individual. Using these data, researchers have inferred limb orientations, postures, gaits, ecological functions and even phylogenetic trends within clades. However, important areas of concern remain unaddressed; for example, how does ROM at a forelimb joint change after soft tissues are lost in archosaurs? And are fossil ROM methodologies amenable to reproducibility and statistical analysis? Here, we investigated these questions using the extant phylogenetic bracket of dinosaurs. Repeated measures of elbow joint ROM from Struthio camelus and Alligator mississippiensis forelimbs were statistically analyzed as they were sequentially dissected through five levels of tissue removal treatment. Our data indicate that there are no statistically significant differences in repeated measures of ROM between observers who use the same techniques. Extrinsic soft tissues, such as integument, muscles and ligaments were found to impede ROM at the elbow joint. Intrinsic soft tissues, such as articular cartilage, may increase ROM. The hypothesis that the articular surfaces of the bones within the elbow joints of archosaurs provide a general approximation of mobility is supported. Final ROMs were less than the initial ROMs in both taxa, which suggests that prior reports of elbow joint ROMs in degrees for nonavian dinosaurs may represent conservative estimates. We conclude that if observer bias and other variables are controlled for, ROM studies of fossil archosaur limbs can obtain useful degree data for inferring joint mobility in vivo. © 2012 Published by The Company of Biologists Ltd.

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