| 1. |
- Bhatt, Isha M, et al.
(författare)
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Anatomical changes in the cell-wall structure of Leucaena leucocephala(Lam.) de Wit as caused by the decay fungi Trametes versicolorandTrametes hirsuta
- 2015
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Ingår i: Southern Forests, a journal of forest science. - : National Inquiry Services Center (NISC). - 2070-2620 .- 2070-2639. ; 77:4, s. 297-303
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Tidskriftsartikel (refereegranskat)abstract
- The structural changes in the cell wall and delignification pattern caused by Trametes versicolor and Trametes hirsuta in the sap wood of Leucaena leucocephala were examined by light and confocal laser scanning microscopy. The in vitro decay test was conducted for 12 weeks. Both species of Trametes used in this study caused anatomical characteristics specific to simultaneous white rot. Formation of boreholes, erosion troughs, erosion channels with U-shaped notches in tangential sections and thinning of cell walls were evident in the wood inoculated with each of the fungal species. Cell separation due to removal of middle lamellae occurred at the early stages of infection (30 d) with T. versicolor. In contrast, middle lamellae remained intact in wood inoculated with T. hirsuta and showed cell separation due to degradation of the outer layer of the secondary wall and degradation of the middle lamellae observed only in severely decayed wood at late stages. Confocal microscopy revealed the delignification pattern particularly from cell corners and vessel walls at an advanced stage of decay, indicating strong ligninolytic activity of both species in the sapwood of L. leucocephala.
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| 2. |
- Bhatt, I.M., et al.
(författare)
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Anatomical characterization of Eucalyptus globulus wood decay by two white rot species of Trametes
- 2016
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Ingår i: Journal of plant pathology. - : Springer. - 1125-4653 .- 2239-7264. ; 98:2, s. 227-234
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Tidskriftsartikel (refereegranskat)abstract
- Application of ligninolytic enzymes in paper and pulp industry has opened a new avenue to overcome the problems associated with mechanical and chemical pulping. The present study was therefore aimed to investigate the anatomical alterations in the cell wall of eucalyptus sap wood inoculated with Trametes hirsuta (Fr.) Pilat and T. versicolor (Fr.) Pilat. T. hirsuta caused cell separation, formation of oval shaped cavities rich in cellulosic polysaccharides and pit erosion during early stages of decay, suggesting selective delignification pattern. However, degradation of carbohydrate components resulting in large void areas was detected during advanced stages of decay. Thinning of cell wall was detected in the fibres of wood blocks colonized by T. versicolor, indicating simultaneous white rot decay. The degradation occurred preferentially to the middle layers of secondary wall, while compound middle lamellae and S₃ layer resisted degradation during early stages of decay. Confocal microscopy revealed strong delignification from vessel wall and separation of fibres following delignification of compound middle lamellae. The degradation of lignin rich vessel wall during advanced stages of decay by both species suggests their strong ligninolytic properties suitable for its use in paper and pulp industry.
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| 3. |
- Bhatt, Isha M., et al.
(författare)
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Histological changes in the cell wall structure during wood decay by Trametes hirsuta and Trametes versicolor in neem (Azadirachta Indica A. Juss)
- 2016
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Ingår i: Journal of Sustainable Forestry. - : Informa UK Limited. - 1054-9811 .- 1540-756X. ; 35:8, s. 578-590
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Tidskriftsartikel (refereegranskat)abstract
- Structural alterations in the wood cell walls of neem inoculated with by Trametes hirsuta and T. versicolor were studied by microscopic methods. In vitro decayed wood showed extensive weight loss of test blocks (26.7 and 41.38% by T. versicolor and T. hirsuta, respectively) at the end of 3 months. Selective delignification in the initial phase followed by simultaneous removal of lignin was evident in test blocks inoculated with both the species. The separation of middle lamellae and patches of cellulosic polysaccharides stained blue with Astra blue in the delignified region of the fiber wall during early stages indicates selective mode of decay. In contrast, the occurrence of erosion troughs with characteristic U-notch in tangential sections is a characteristic feature of simultaneous rot that was apparent after 3 months of incubation. The decay pattern occurred concomitantly in all the xylem elements irrespective of general resistance pattern shown by vessel and axial parenchyma cells. At an advance stage, both species of Trametes showed formation of erosion channels along the microfibrils angle of cellulose which is considered as characteristics of soft rot decay type. The sharing of white rot and soft rot decay pattern by both the fungi suggest a phylogenetic link between both groups of fungi.
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| 4. |
- Bhatt, Pramod, et al.
(författare)
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Correlation of structural, chemical and magnetic properties in annealed Ti/Ni multilayer structures
- 2005
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 97:4, s. 043509-
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Tidskriftsartikel (refereegranskat)abstract
- Ti/Ni multilayer samples have been synthesized on float glass substrates using an electron-beam evaporation technique under ultrahigh vacuum conditions at room temperature. Grazing incidence x-ray diffraction (GIXRD) and grazing incidence x-ray reflectivity (GIXRR) techniques were used, respectively, to study structural modifications and to determine corresponding changes in microstructural parameters, such as individual layer thickness, interface roughness, and electron density due to annealing treatment. In addition to this, the chemical nature of the surface and interfaces of these samples were also studied using a depth profile x-ray photoelectron spectroscopy (XPS) technique. The GIXRD measurement show clear amorphization of the as-deposited multilayer sample annealed in the temperature range of 300–400 °C. The corresponding GIXRR measurement indicates the formation of a sufficiently thick layer of Ti–Ni at interfaces converting the Ti/Ni bilayer into a Ti/Ti–Ni/Ni trilayer multilayer structure. The precipitation of the Ti–Ni alloy phase at the interface in the case of samples annealed at 400 °C has been confirmed by XPS measurements. The magnetization behavior investigated using the magneto-optical Kerr effect technique clearly shows well the saturation magnetization behavior for all samples annealed up to 300 °C, while the sample annealed at 400 °C does not show saturation magnetization. The corresponding coercivity value (Hc) is also found to be changed drastically from 15.5 to 0.6 Oe. This observed magnetization behavior is discussed and correlated with structural and chemical changes in the multilayer structure.
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| 5. |
- Bhatt, Pramod, et al.
(författare)
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Effect of phase formation on valence band photoemission and photoresonance study of Ti/Ni multilayers using synchrotron radiation
- 2006
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 15:1-2, s. 56-66
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents investigation of Ti–Ni alloy phase formation and its effect on valence band (VB) photoemission and photoresonance study of as-deposited as well as annealed Ti/Ni multilayers (MLs) up to 600 °C using synchrotron radiation. For this purpose [Ti (50 Å)/Ni (50 Å)]X10 ML structures were deposited by using electron-beam evaporation technique under ultra-high vacuum (UHV) conditions. Formation of different phases of Ti–Ni alloy due to annealing treatment has been confirmed by the X-ray diffraction (XRD) technique. The XRD pattern corresponding as-deposited ML sample shows crystalline nature of both Ti and Ni deposited layers, whereas 300 °C annealed ML sample show solid-state reaction (SSR) leading to amorphization and subsequent recrystallisation at higher temperatures of annealing (≥400 °C) with the formation of TiNi, TiNi3 and Ti2Ni alloy phases. The survey scans corresponding to 400, 500 and 600 °C annealed ML sample shows interdiffusion and intermixing of Ni atoms into Ti layers leading to chemical Ti–Ni alloys phase formation at interface. The corresponding recorded VB spectra using synchrotron radiation at 134 eV on as-deposited ML sample with successive sputtering shows alternately photoemission bands due to Ti 3d and Ni 3d, respectively, indicating there is no mixing of the consequent layers and any phase formation at the interface during deposition. However, ML samples annealed at higher temperatures of annealing, particularly at 400, 500 and 600 °C show a clear shift in Ni 3d band and its satellite peak position to higher BE side indicates Ti–Ni alloy phase formation. In addition to this, reduction of satellite peak intensity and Ni 3d density of states (DOS) near Fermi level is also observed due to Ti–Ni phase formation with higher annealing temperatures. The variable photon energy VB measurements on as-deposited and ML samples annealed at 400 °C confirms existence and BE position of observed Ni 3d satellite structure. The observed changes and modifications in the VB photoemission are discussed and interpreted in terms of structural changes at the interface due to annealing treatment.
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| 6. |
- Bhatt, Pramod, et al.
(författare)
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Electronic structure of thin film iron-tetracyanoethylene : Fe(TCNE)x
- 2009
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Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 95:1, s. 131-138
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Tidskriftsartikel (refereegranskat)abstract
- Thin film iron-tetracyanoethylene Fe(TCNE) x , x∼2, as determined by photoelectron spectroscopy, was grown in situ under ultra-high vacuum conditions using a recently developed physical vapor deposition-based technique for fabrication of oxygen- and precursor-free organic-based molecular magnets. Photoelectron spectroscopy results show no spurious trace elements in the films, and the iron is of Fe2+ valency. The highest occupied molecular orbital of Fe(TCNE) x is located at ∼1.7 eV vs. Fermi level and is derived mainly from the TCNE− singly occupied molecular orbital according to photoelectron spectroscopy and resonant photoelectron spectroscopy results. The Fe(3d)-derived states appear at higher binding energy, ∼4.5 eV, which is in contrast to V(TCNE)2 where the highest occupied molecular orbital is mainly derived from V(3d) states. Fitting ligand field multiplet and charge transfer multiplet calculations to the Fe L-edge near edge X-ray absorption fine structure spectrum yields a high-spin Fe2+ (3d6) configuration with a crystal field parameter 10Dq∼0.6 eV for the Fe(TCNE) x system. We propose that the significantly weaker Fe-TCNE ligand interaction as compared to the room temperature magnet V(TCNE)2 (10Dq∼2.3 eV) is a strongly contributing factor to the substantially lower magnetic ordering temperature (T C ) seen for Fe(TCNE) x -type magnets.
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| 7. |
- Bhatt, Pramod, 1979-
(författare)
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Fabrication and study of inorganic and organic thin film magnets
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Thin film magnets are very important for many kinds of electronic devices and play a crucial role to achieve optimum performance. Therefore an intense level of research is going on all around the world to fabricate advanced electronics devices using both new inorganic and organic thin-film magnets. Historically, most magnetic materials used for technological applications are based on inorganic materials and have been studied extensible up to now. Recently, however, organic or molecular magnets have opened a new prospective of thin film magnets which have begun to show promise, offering the possibility of light-weight flexible materials and devices that include magnetic functionality.The research presented in this thesis is hence divided into two parts, where inorganic and organic magnets in thin films form were studied. The Ti/Ni multilayer system is studied as an inorganic magnet in the first part, whereas M(TCNE)x thin films were studied in the second part with M= Fe, Ni and TCNE is tetracynoethelene, an organic compound, and x~2.The Ti/Ni multilayer is a potential candidate for industrial applications and also features solid-state amorphisation. Because of various interesting scientific and technological aspects of Ti/Ni multilayer structures, many structural properties and subsequent thermal stability studies have been extensively reported in the literature, but surprisingly few reports are available on the corresponding electronic and magnetic properties. The work in the present thesis is therefore focused on synthesis and systematic investigation of structural, electronic and magnetic properties of as prepared as well as annealed Ti/Ni multilayer structures and to establish correlation between them.The second part of the thesis deals with organic-based molecular magnets of the M(TCNE)x type, where x~2, M = Fe, Ni and TCNE = tetracynoethelene. Fe(TCNE)x and Ni(TCNE)x have for the first time been fabricated as thin films, free of oxygen- and precursor-induced defects. The films were fabricated in situ under ultra high vacuum conditions using our group’s recently developed fabrication techniques for organic-based molecular magnets. The previously unknown electronic structure of these thin film magnets are presented in the thesis. Room temperature magnetic ordering was observed for thin films of Ni(TCNE)2, in stark contrast to earlier versions of the material (fabricated with the old methods and hence containing various defects). Room temperature magnetic ordering for a similar system, Ni2(TCNE), previously has been reported by another group, but it is clear that more studies are necessary to completely resolve the underlying mechanisms for the magnetic properties seen in these materials.
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| 8. |
- Bhatt, Pramod, et al.
(författare)
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Ferromagnetism above room temperature in nickel-tetracyanoethylene thin films
- 2009
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 19:36, s. 6610-6615
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Tidskriftsartikel (refereegranskat)abstract
- Room temperature ferromagnetic ordering is reported in Ni-tetracyanoethylene (TCNE) thin films fabricated on Au substrates using physical vapor deposition (PVD) under ultra high vacuum conditions. This technique enables the preparation of very clean films without having any kind of contamination from oxygen-containing species, solvents or precursor molecules. Film stoichiometry was obtained from X-ray photoelectron spectroscopy (XPS) measurements. XPS derived stoichiometry points to a similar to 1 : 2 ratio between Ni and TCNE resulting in Ni(TCNE)(x), x approximate to 2. No evidence of pure Ni metal in the in situ grown films was present in the XPS or the ultraviolet photoelectron spectroscopy (UPS) measurements within the detection limits of the techniques.
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| 9. |
- Bhatt, Pramod, et al.
(författare)
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High temperature annealing effect on structural and magnetic properties of Ti/Ni multilayer
- 2006
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332. ; 253:5, s. 2572-2580
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Tidskriftsartikel (refereegranskat)abstract
- High temperature annealing effect on structural and magnetic properties of Ti/Ni multilayer (ML) up to 600 °C have been studied and reported in this paper. Ti/Ni multilayer samples having constant layer thicknesses of 50 Å each are deposited on float glass and Si(1 1 1) substrates using electron-beam evaporation technique under ultra-high vacuum (UHV) conditions at room temperatures. The micro-structural parameters and their evolution with temperature for as-deposited as well as annealed multilayer samples up to 600 °C in a step of 100 °C for 1 h are determined by using X-ray diffraction (XRD) and grazing incidence X-ray reflectivity techniques. The X-ray diffraction pattern recorded at 300 °C annealed multilayer sample shows interesting structural transformation (from crystalline to amorphous) because of the solid-state reaction (SSR) and subsequent re-crystallization at higher temperatures of annealing, particularly at ≥400 °C due to the formation of TiNi3 and Ti2Ni alloy phases. Sample quality and surface morphology are examined by using atomic force microscopy (AFM) technique for both as-deposited as well as annealed multilayer samples. In addition to this, a temperature dependent dc resistivity measurement is also used to study the structural transformation and subsequent alloy phase formation due to annealing treatment. The corresponding magnetization behavior of multilayer samples after each stage of annealing has been investigated by using Magneto-Optical Kerr Effect (MOKE) technique and results are interpreted in terms of observed micro-structural changes.
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| 10. |
- Bhatt, Pramod, et al.
(författare)
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Room temperature magnetism in thin film nickel-tetracynoethylene
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Room temperature magnetic ordering is reported in Ni-Tetracynoethelene (TCNE) thin films fabricated on gold substrates using physical vapor deposition (PVD) under ultra high vacuum conditions. This technique enables preparation of very clean films without having any kind of contamination from oxygen-containing species, solvents or precursor molecules. Film thickness and stoichiometry were obtained from x-ray photoelectron spectroscopy (XPS) measurements. XPS derived stoichiometry points to a 1:2 ratio between Ni and TCNE resulting in Ni(TCNE)x, x ~ 2. No evidence of pure Ni metal in the in situ grown films were present in the XPS and UPS measurements within the detection limits of the techniques.
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