| 82471. |
- Komitov, Lachezar, 1944
(författare)
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Polar Switching Mode in LCDs
- 2009
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Ingår i: Proceedings of the 29 International Display Research Conference, Eurodisplay 2009, Rome, Italy. ; , s. 89-90
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Konferensbidrag (refereegranskat)abstract
- Polar switching of the liquid crystal bulk arising from the coupling between an applied electric field and the polarized state of a nematic liquid crystal is studied.
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| 82472. |
- Komitov, Lachezar, 1944, et al.
(författare)
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Polymers for use as alignment layers in liquid crystal devices
- 2004
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Patent (övrigt vetenskapligt/konstnärligt)abstract
- The invention relates to a polymer for use as a surface-director alignment layer in a liq. crystal device, said polymer comprising a polymeric backbone and side-chains attached thereto, wherein the polymeric backbone lacks directly coupled ring structures, and each side-chain of at least some of the side-chains comprises >=2 unsubstituted and/or substituted phenyls coupled via a coupling selected from a carbon-carbon single bond, a carbon-carbon double bond contg. unit (CH:CH), a carbon-carbon triple bond contg. unit (C==C), a methylene eter unit (CH2O) , an ethylene eter unit (CH2CH2O), an ester unit (COO) and an azo unit (N:N), exhibits a permanent and/or induced dipole moment that in ordered phase provides dielec. anisotropy, and is attached to the polymeric backbone via at least two spacing atoms. Thus, 4'-(11,11-diethoxyundecyloxy)biphenyl-4-carbonitrile 0.70, octanal 0.081, and polyvinyl alc. 0.198 g were reacted in DMF at 55 Deg for 24 h to give a side-chain liq. crystal polymer, which was fabricated into a liq. crystal device as alignment layer.
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| 82473. |
- Komitov, Lachezar, 1944
(författare)
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Surface Driven Switching in Liquid Crystal Displays
- 2009
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Ingår i: Proceedings of the 9th International Meeting on Information Display (IMID 2009), KINTEX, Korea. ; , s. 14-16
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Konferensbidrag (refereegranskat)abstract
- Surface driven switching of the liquid crystal bulk arising from the coupling between an applied electric field and a polarized state of a nematic liquid crystal, both localized at the substrate surface, is reported. Fast switching is demonstrated in a hybrid aligned nematic cell with a fringe electric field generated by comb-like electrode structure.
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| 82474. |
- Komitov, Lachezar, 1944
(författare)
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Tuning the alignment of liquid crystals by means of nano-structured surfaces
- 2008
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Ingår i: Journal of the SID. - 1071-0922. ; 16:9, s. 919-925
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Forskningsöversikt (refereegranskat)abstract
- The solid-surface/liquid-crystal interactions, defining the field-free alignment of the liquid crystal in conventional liquid-crystal displays, are playing a vital role in their optical appearance and performance. Nano- scale changes in the solid-surface structure induced by light have been recently shown to affect the anchoring strength and the easy-axis direction. Fine tuning of the anchoring strength is also demonstrated by nano- structuring of the Langmuir–Blodgett monolayer employed as liquid-crystal alignment layers promoting homeotropic orientation. On the basis of nano-engineering of the surface alignment properties, two novel alignment concepts have been introduced: electrically commanded surfaces (ECS) and high-performance alignment layers (HiPAL). Nano-structured polymers related to these concepts have been designed, synthesized, and used as materials for alignment layers in LCDs. ECS materials belong to the category of active alignment materials designed to mediate switching of the liquid crystal, whereas the HiPALmaterials make possible the control of the molecular tilt angle in a broad range, from 0° to 90°, and they seem to enable the control of the anchoring strength as well. The nano-structured alignment materials are strong candidates for implementation in a new generation of advanced liquid-crystal displays and devices.
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| 82475. |
- Komitova, Mila, 1974, et al.
(författare)
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Enriched environment after focal cortical ischemia enhances the generation of astroglia and NG2 positive polydendrocytes in adult rat neocortex
- 2006
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Ingår i: EXPERIMENTAL NEUROLOGY. - : Elsevier BV. - 0014-4886. ; 199:1, s. 113-121
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Tidskriftsartikel (refereegranskat)abstract
- Environmental enrichment (EE) alleviates sensorimotor deficits after brain infarcts but the cellular correlates are not well-known. This study aimed to test the effects of postischemic EE on neocortical cell genesis. A neocortical infarct was caused by distal ligation of the middle cerebral artery in adult spontaneously hypertensive rats, subsequently housed in standard environment or EE. Bromodeoxyuridine (BrdU) was administered during the first postischemic week to label proliferating cells and BrdU incorporation was quantified 4 weeks later in the periinfarct, ipsilateral medial and contralateral cortex. Immunohistochemistry and confocal microscopy were used to analyze co-localization of BrdU with neuronal (calbindin D28k, calretinin, parvalbumin, glutamic acid decarboxylase, tyrosine hydroxylase), astrocytic (glial fibrillary acidic protein, glutamine synthetase, vimentin, nestin), microglia/macrophage (CD11b/Ox-42, CD68/ED-1), oligodendrocyte progenitor/polydendrocyte (NG2, platelet-derived growth factor alpha receptor) or mature oligodendrocyte (myelin basic protein) markers. BrdU positive cells were increased in all analyzed cortical regions in stroke EE rats compared with stroke standard environment rats. Newly born cells in the periinfarct cortex were mostly reactive astroglia. Occasionally, BrdU positive cells in the periinfarct cortex that were negative for glial or microglia/macrophage markers co-expressed markers typical for interneurons but did not express appropriate functional markers. The majority of BrdU positive cells in intact cortical regions, ipsi- and contralaterally, were identified as NG2 positive polydendrocytes. Perineuronally situated newly born cells and polydendrocytes were found to be brain-derived neurotrophic factor immunoreactive. In conclusion, EE enhanced newborn glial scar astroglia and NG2+ polydendrocytes in the postischemic neocortex which might be beneficial for brain repair and poststroke plasticity.
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| 82476. |
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| 82477. |
- Komitova, Mila, 1974
(författare)
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Neurogenesis and gliogenesis after focal brain ischemia. Modulation by enriched environment and exercise
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- New neurons are formed from dividing neural stem cells in restricted areas in the adult mammalian brain: the dentate gyrus of the hippocampal formation (DG) and the forebrain subventricular zone (SVZ). New glia also form constitutively and seem to be important for neuronal function. This thesis investigated the effects of experimental stroke, postischemic environmental enrichment (EE) and voluntary exercise (VE) on neurogenesis and gliogenesis in the adult rat brain. A neocortical infarct was induced by distal ligation of the middle cerebral artery and rats were subsequently housed in standard environment, EE (larger cages and animal groups, introduction of novel objects) or in cages with running wheels. Sensorimotor functions were tested on a rotating rod and with the limb placement test. Bromodeoxyuridine was administered during the first postischemic week and the animals were sacrificed 1 or 5 weeks postsurgery. Cell proliferation, differentiation and survival were studied with immunohistochemistry and confocal microscopy. Cortical ischemia was found to increase proliferation of neural stem cells, neural progenitors and neuronal precursors in the SVZ and the DG. Migrating neuroblasts were recruited to the infarct from the SVZ but did not survive into maturity. VE attenuated the lesion-induced activation of the SVZ. In contrast, EE had enhancing effects on the SVZ. DG cell proliferation was increased after cortical ischemia without further effects by EE or VE. The majority of newborn cells in the DG became mature neurons but new astroglia were not similarly increased in standard housed stroke rats. EE increased DG astrogliogenesis and thus normalized the astrogliogenesis-to-neurogenesis ratio. In the postischemic neocortex, EE increased newborn reactive astroglia and also newborn NG2 positive polydendrocytes, often found closely apposed to neurons and exhibiting brain-derived neurotrophic factor immunoreactivity. Stroke EE rats had the best scores in behavior tests among lesioned rats. In conclusion, neocortical stroke activated the adult neurogenic niches. Isolated exercise activity early poststroke attenuated the lesion-induced SVZ activation. EE enhanced cell genesis in diverse regions of the postischemic brain which might be of importance for function improvement. Future efforts need to be focussed on providing the necessary instructive cues to promote functional neuronal replacement after stroke.
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| 82478. |
- Komitova, Mila, 1974, et al.
(författare)
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On neural plasticity, new neurons and the postischemic milieu: An integrated view on experimental rehabilitation
- 2006
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Ingår i: EXPERIMENTAL NEUROLOGY. - : Elsevier BV. - 0014-4886. ; 199:1, s. 42-55
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Forskningsöversikt (refereegranskat)abstract
- This review discusses actual and potential contributors to functional improvement after stroke injuries. Topics that will be covered are neuronal re-organization and sprouting, neural stem/progenitor cell activation and neuronal replacement, as well as the neuronal milieu defined by glia, inflammatory cells and blood vessel supply. It is well established that different types of neuronal plasticity ultimately lead to post-stroke recovery. However, an untapped potential which only recently has started to be extensively explored is neuronal replacement through endogenous or exogenous resources. Major experimental efforts are needed to achieve progress in this burgeoning area. The review stresses the importance of applying neurodevelopmental principles as well as performing a characterization of the role of the postischemic milieu when studying adult brain neural stem/progenitor cells. Integrated and multifaceted experimentation, incorporating actual and possible poststroke function modulators, will be necessary in order to determine future strategies that will ultimately enable considerable progress in the field of neurorehabilitation.
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| 82479. |
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| 82480. |
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