1,033 research outputs found
Antimicrobial and antioxidative activities in the bark extracts of Sonneratia caseolaris, a mangrove plant
The present study deals with the phytochemical contents, antimicrobial and antioxidative activities of bark tissue of Sonneratia caseolaris, a mangrove plant from Sundarban estuary, India. Phytochemical analyses revealed the presence of high amounts of phenolics, flavonoids, tannins, alkaloids and saponins. Antimicrobial efficacies of various extracts of S. caseolaris were assessed by disc diffusion method against two Gram-positive (Bacillus subtilis and Bacillus coagulans), two Gram-negative (Escherichia coli and Proteus vulgaris) bacteria and one fungus (Saccharomyces cerevisiae). The methanolic extract among others showed significant minimum inhibitory concentration (MIC) values. The antioxidant activity as indicated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity of the bark tissue extract from the species was found to be quite appreciable. The extracts were found to retain their antimicrobial activities despite pH and thermal treatments, thus indicating the stability of their activity even at extreme conditions. The antioxidant activity was also found to be considerably stable after thermal treatments. The components of the tissue extracts were subjected to separation using thin layer chromatography (TLC). The constituents with antimicrobial and antioxidative properties were identified using TLC-bioautography by agar-overlay and DPPH spraying methods respectively. A number of bioactive constituents with antimicrobial and radical scavenging properties were observed on the developed bioautography plate. The fractions with antimicrobial properties were isolated from the reference TLC plates and subjected to gaschromatography-mass spectrometry (GC-MS) analysis for partial characterization and identification of the metabolites that might be responsible for the activities. The study suggests Sonneratia caseolaris bark as a potential source of bioactive compounds with stable antimicrobial and antioxidative properties and can be used as natural antimicrobial/antioxidative agents in clinical, pharmaceutical and food processing industries
Migration/mobility and vulnerability to HIV among male migrant workers: Maharashtra 2007-08
HIV prevalence in Maharashtra is one of the highest among Indian states. The specific objectives of this study were: to understand the patterns and drivers of migration/mobility of men who migrate for the purpose of work in the state of Maharashtra; to describe the characteristics of vulnerable subpopulations among migrant men; and to examine the determinants of high-risk sexual behavior among the subpopulations of migrant men with particular emphasis on the role of mobility in determining the sexual risk behavior. The present study clearly demonstrates that these male migrants, married or otherwise, retain strong connectivity to their native villages, but also show high levels of sexual activity—including significant levels of high-risk sexual activity—making it imperative to study the situation in the sending districts regarding HIV prevalence and spread. The indication from this study is clear: in the context of high-risk sexual behavior (among both married and unmarried migrants) and the low levels of knowledge, condom use, and risk perception, the chances of sending households and districts becoming areas of high HIV prevalence are great. Further exploration of the sexual behavior pattern in sending areas is necessary to obtain additional insights into the possible routes of HIV transmission
Tuning the multiferroic mechanisms of TbMnO3 by epitaxial strain
A current challenge in the field of magnetoelectric multiferroics is to
identify systems that allow a controlled tuning of states displaying distinct
magnetoelectric responses. Here we show that the multiferroic ground state of
the archetypal multiferroic TbMnO3 is dramatically modified by epitaxial
strain. Neutron diffraction reveals that in highly strained films the magnetic
order changes from the bulk-like incommensurate bc-cycloidal structure to
commensurate magnetic order. Concomitant with the modification of the magnetic
ground state, optical second-harmonic generation (SHG) and electric
measurements show an enormous increase of the ferroelectric polarization, and a
change in its direction from along the c- to the a-axis. Our results suggest
that the drastic change of multiferroic properties results from a switch of the
spin-current magnetoelectric coupling in bulk TbMnO3 to symmetric
magnetostriction in epitaxially-strained TbMnO3. These findings experimentally
demonstrate that epitaxial strain can be used to control single-phase
spin-driven multiferroic states
Spectral functions of CVD grown MoS monolayers after chemical transfer onto Au surface
The recent rise of van der Waals (vdW) crystals has opened new prospects for
studying versatile and exotic fundamental physics with future device
applications such as twistronics. Even though the recent development on
Angle-resolved photoemission spectroscopy (ARPES) with Nano-focusing optics,
making clean surfaces and interfaces of chemically transferred crystals have
been challenging to obtain high-resolution ARPES spectra. Here, we show that by
employing nano-ARPES with submicron sized beam and polystyrene-assisted
transfer followed by annealing process in ultra-high vacuum environment,
remarkably clear ARPES spectral features such as spin-orbit splitting and band
renormalization of CVD-grown, monolayered MoS2 can be measured. Our finding
paves a way to exploit chemically transferred crystals for measuring
high-resolution ARPES spectra to observe exotic quasi-particles in vdW
heterostructures
Coexistence of type-I and type-II superconductivity signatures in ZrB12 probed by muon spin rotation measurements
Superconductors usually display either type-I or type-II superconductivity and the coexistence of these two types in the same material, for example, at different temperatures, is rare in nature. We employed the muon spin rotation (ÎĽSR) technique to unveil the superconducting phase diagram of the dodecaboride ZrB12 and obtained clear evidence of both type-I and type-II characteristics. Most important, we found a region showing unusual behavior where the usually mutually exclusive ÎĽSR signatures of type-I and type-II superconductivity coexist. We reproduced that behavior in theoretical modeling that required taking into account multiple bands and multiple coherence lengths, which suggests that material has one coherence length larger and another smaller than the magnetic field penetration length (the type-1.5 regime). At stronger fields, a footprint of the type-II mixed state showing square flux-line lattice was also obtained using neutron diffraction
Coexisting multiple order parameters in single-layer LuMnO3 films
Magnetoelectric multiferroics hold great promise for electrical control of magnetism or magnetic control of ferroelectricity. However, single phase ferroelectric materials with a sizeable ferromagnetic magnetization are rare. Here, we demonstrate that a single- phase orthorhombic LuMnO3 thin film features coexisting magnetic and ferroelectric orders. The temperature dependence of the different order parameters are presented with ferromagnetic order appearing below 100 K and thus at much higher temperatures than ferroelectricity or antiferromagnetism (TN,TFE≤40K)
Fermi-crossing Type-II Dirac fermions and topological surface states in NiTe2
Transition-metal dichalcogenides (TMDs) offer an ideal platform to
experimentally realize Dirac fermions. However, typically these exotic
quasiparticles are located far away from the Fermi level, limiting the
contribution of Dirac-like carriers to the transport properties. Here we show
that NiTe2 hosts both bulk Type-II Dirac points and topological surface states.
The underlying mechanism is shared with other TMDs and based on the generic
topological character of the Te p-orbital manifold. However, unique to NiTe2, a
significant contribution of Ni d orbital states shifts the energy of the
Type-II Dirac point close to the Fermi level. In addition, one of the
topological surface states intersects the Fermi energy and exhibits a
remarkably large spin splitting of 120 meV. Our results establish NiTe2 as an
exciting candidate for next-generation spintronics devices
Uniaxial strain-induced phase transition in the 2D topological semimetal IrTe2
Strain is ubiquitous in solid-state materials, but despite its fundamental importance and technological relevance, leveraging externally applied strain to gain control over material properties is still in its infancy. In particular, strain control over the diverse phase transitions and topological states in two-dimensional transition metal dichalcogenides remains an open challenge. Here, we exploit uniaxial strain to stabilize the long-debated structural ground state of the 2D topological semimetal IrTe, which is hidden in unstrained samples. Combined angle-resolved photoemission spectroscopy and scanning tunneling microscopy data reveal the strain-stabilized phase has a 6 Ă— 1 periodicity and undergoes a Lifshitz transition, granting unprecedented spectroscopic access to previously inaccessible type-II topological Dirac states that dominate the modified inter-layer hopping. Supported by density functional theory calculations, we show that strain induces an Ir to Te charge transfer resulting in strongly weakened inter-layer Te bonds and a reshaped energetic landscape favoring the 6Ă—1 phase. Our results highlight the potential to exploit strain-engineered properties in layered materials, particularly in the context of tuning inter-layer behavior
Direct observation of the energy gain underpinning ferromagnetic superexchange in the electronic structure of CrGeTe3
Funding: The Leverhulme Trust (Grant No. RL-2016-006), The Royal Society, and the European Research Council (Grant No. ERC-714193-QUESTDO). Max Planck Research School for Chemistry and Physics of Quantum Materials (IMPRS-CPQM) (I.M. and E.A.M).We investigate the temperature-dependent electronic structure of the van der Waals ferromagnet, CrGeTe3. Using angle-resolved photoemission spectroscopy, we identify atomic- and orbital-specific band shifts upon cooling through TC. From these, together with x-ray absorption spectroscopy and x-ray magnetic circular dichroism measurements, we identify the states created by a covalent bond between the Te 5p and the Cr eg orbitals as the primary driver of the ferromagnetic ordering in this system, while it is the Cr t2g states that carry the majority of the spin moment. The t2g states furthermore exhibit a marked bandwidth increase and a remarkable lifetime enhancement upon entering the ordered phase, pointing to a delicate interplay between localized and itinerant states in this family of layered ferromagnets.PostprintPeer reviewe
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