Ordered nano-scale domains in lithium niobate single crystals via phase-mask assisted all-optical poling

We report the formation of directionally-ordered nanoscale surface domains on the +z face of undoped congruent lithium niobate single crystals by using UV illumination through a phase mask with an energy fluence between ~90mj/cm2 and 150 mJ/cm2 at lambda = 266 nm. We clearly show here that the UV-induced surface ferroelectric domains nucleate and then propagate along the maxima of laser intensity produced by the phase mask, thus enabling a degree of control over this all-optical poling process. Acid etching of the illuminated crystal faces was employed to reveal the induced domain nature and the spatial structure of the formed nanoscale domains

Physiologically regulated transgenic ABCA1 does not reduce amyloid burden or amyloid‐beta peptide levels in vivo

J Lipid Res. 2007 Apr;48(4):914-23. Epub 2007 Jan 18. Physiologically regulated transgenic ABCA1 does not reduce amyloid burden or amyloid-beta peptide levels in vivo. Hirsch-Reinshagen V, Chan JY, Wilkinson A, Tanaka T, Fan J, Ou G, Maia LF, Singaraja RR, Hayden MR, Wellington CL. Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, Canada. Abstract ABCA1-deficient mice have low levels of poorly lipidated apolipoprotein E (apoE) and exhibit increased amyloid load. To test whether excess ABCA1 protects from amyloid deposition, we crossed APP/PS1 mice to ABCA1 bacterial artificial chromosome (BAC) transgenic mice. Compared with wild-type animals, the ABCA1 BAC led to a 50% increase in cortical ABCA1 protein and a 15% increase in apoE abundance, demonstrating that this BAC supports modest ABCA1 overexpression in brain. However, this was observed only in animals that do not deposit amyloid. Comparison of ABCA1/APP/PS1 mice with APP/PS1 controls revealed no differences in levels of brain ABCA1 protein, amyloid, Abeta, or apoE, despite clear retention of ABCA1 overexpression in the livers of these animals. To further investigate ABCA1 expression in the amyloid-containing brain, we then compared ABCA1 mRNA and protein levels in young and aged cortex and cerebellum of APP/PS1 and ABCA1/APP/PS1 animals. Compared with APP/PS1 controls, aged ABCA1/APP/PS1 mice exhibited increased ABCA1 mRNA, but not protein, selectively in cortex. Additionally, ABCA1 mRNA levels were not increased before amyloid deposition but were induced only in the presence of extensive Abeta and amyloid levels. These data suggest that an induction of ABCA1 expression may be associated with late-stage Alzheimer's neuropathology. PMID: 17235115 [PubMed - indexed for MEDLINE

The absence of ABCA1 decreases soluble ApoE levels but does not diminish amyloid deposition in two murine models of Alzheimer disease.

J Biol Chem. 2005 Dec 30;280(52):43243-56. Epub 2005 Oct 5. The absence of ABCA1 decreases soluble ApoE levels but does not diminish amyloid deposition in two murine models of Alzheimer disease. Hirsch-Reinshagen V, Maia LF, Burgess BL, Blain JF, Naus KE, McIsaac SA, Parkinson PF, Chan JY, Tansley GH, Hayden MR, Poirier J, Van Nostrand W, Wellington CL. Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia V4Z 5H5, Canada. Abstract ABCA1, a cholesterol transporter expressed in the brain, has been shown recently to be required to maintain normal apoE levels and lipidation in the central nervous system. In addition, ABCA1 has been reported to modulate beta-amyloid (Abeta) production in vitro. These observations raise the possibility that ABCA1 may play a role in the pathogenesis of Alzheimer disease. Here we report that the deficiency of ABCA1 does not affect soluble or guanidine-extractable Abeta levels in Tg-SwDI/B or amyloid precursor protein/presenilin 1 (APP/PS1) mice, but rather is associated with a dramatic reduction in soluble apoE levels in brain. Although this reduction in apoE was expected to reduce the amyloid burden in vivo, we observed that the parenchymal and vascular amyloid load was increased in Tg-SwDI/B animals and was not diminished in APP/PS1 mice. Furthermore, we observed an increase in the proportion of apoE retained in the insoluble fraction, particularly in the APP/PS1 model. These data suggested that ABCA1-mediated effects on apoE levels and lipidation influenced amyloidogenesis in vivo. PMID: 16207707 [PubMed - indexed for MEDLINE

Liver biopsy may facilitate pancreatic graft evaluation: Positive association between liver steatosis and pancreatic graft adipose infiltration

OBJECTIVES: The number of pancreatic transplants has decreased in recent years. Pancreatic grafts have been underutilized compared to other solid grafts. One cause of discard is the macroscopic appearance of the pancreas, especially the presence of fatty infiltration. The current research is aimed at understanding any graft-related association between fatty tissue infiltration of the pancreas and liver steatosis. METHODS: From August 2013 to August 2014, a prospective cross-sectional clinical study using data from 54 multiple deceased donor organs was performed. RESULTS: Micro- and macroscopic liver steatosis were significantly correlated with the donor body mass index ([BMI]; p=0.029 and p=0.006, respectively). Positive gamma associations between pancreatic and liver macroscopic and microscopic findings (0.98; confidence interval [CI]: 0.95-1 and 0.52; CI 0.04-1, respectively) were observed. Furthermore, comparisons of liver microscopy findings showed significant differences between severe versus absent (

Surface domain inversion in LiNbO₃ by direct UV writing

Ferroelectric domain inversion has been achieved on the +z and the -z faces of congruent undoped lithium niobate (LiNbO3) single crystals by direct UV writing using a continuous wave (c.w.) frequency doubled argon ion laser (lambda = 244 nm). The width and the depth of the domains were observed to depend on the intensity and the spot size of the laser beam as well as the writing speed. The inverted domain structures were investigated by scanning electron microscopy (SEM), after HF acid differential etching, and piezoresponse force microscopy (PFM) [1]. UV laser inverted domains directly written on a multi domain crystal (PPLN) show that the PFM contrast of the UV written domains is lower as compared to the bulk domains (Fig. 1b). This indicates that the UV written domains are shallower than 1 micron because any domain depth exceeding ~ 1 micron in LiNbO3 would appear as bulk in PFM imaging. This is consistent with the extremely small absorption depth of << 1 micron at lambda = 244 nm [2].Although shallow these UV laser written domains can be also remarkably narrow and also they can be fabricated onto any surface independent of the crystal orientation. Driving these surface domains deeper in the crystal by optical or electric field post processing is currently under investigation

HDL and cholesterol handling in the brain

Cholesterol is an essential component of both the peripheral nervous system and central nervous system (CNS) of mammals. Brain cholesterol is synthesized in situ by astrocytes and oligodendrocytes and is almost completely isolated from other pools of cholesterol in the body, but a small fraction can be taken up from the circulation as 27-hydroxycholesterol, or via the scavenger receptor class B type I. Glial cells synthesize native high-density lipoprotein (HDL)-like particles, which are remodelled by enzymes and lipid transfer proteins, presumably as it occurs in plasma. The major apolipoprotein constituent of HDL in the CNS is apolipoprotein E, which is produced by astrocytes and microglia. Apolipoprotein A-I, the major protein component of plasma HDL, is not synthesized in the CNS, but can enter and become a component of CNS lipoproteins. Low HDL-C levels have been shown to be associated with cognitive impairment and various neurodegenerative diseases. On the contrary, no clear association with brain disorders has been shown in genetic HDL defects, with the exception of Tangier disease. Mutations in a wide variety of lipid handling genes can result in human diseases, often with a neuronal phenotype caused by dysfunctional intracellular lipid trafficking

Light-induced domain engineering in ferroelectrics: a route to sub-micron poling

While several techniques to achieve domain inversion in ferroelectric materials such as lithium niobate and lithium tantalate have been successfully demonstrated over the past years, even the 'best' established technique of electric field-induced domain inversion (E-field poling) fails when domain inversion at periodicities of a few microns and below are desired. In order to overcome the limitations associated with E-field poling, we have been investigating the feasibility of a relatively simple single-step technique, which exploits the interaction of intense laser light with ferroelectric materials to engineer their domains at micron and sub-micron scale-lengths. Some light-assisted poling experiments, which take advantage of the ultraviolet light induced transient change in the coercive field of the illuminated ferroelectric material to transfer a patterned light distribution into an equivalent domain structure in bulk crystals have already been reported for lithium niobate [1,2] and lithium tantalate [3,4] crystals.We have earlier reported a direct all optical poling (AOP) technique that employs pulsed ultraviolet (UV) laser light to induce surface domain inversion on the +[5] and -[6] z-faces of lithium niobate in a single step, We have been trying to understand the physical principles involved in light-matter interaction with an aim of controlling the shape, size and depth of the randomly orientated light-induced domains with an end goal of tailoring periodic structures in lithium niobate. This report presents the results of our attempts to achieve a degree of control over the nucleation and growth of the domains, via an imposed incident light pattern produced using a phase-mask. It is shown that it is possible to align the surface domains along the maxima of the spatially modulated UV laser light pattern

UV radiation-induced surface wetting changes in lithium niobate single crystals

Irradiation of lithium niobate crystal surfaces with UV radiation modifies the wetting properties of the surface which becomes super-hydrophilic. This effect is used for spatially selective attachment of chemical species on the laser exposed areas

Progress in ferroelectric domain engineering at the micro/nanoscale

Ferroelectric materials such as lithium niobate (LN) or lithium tantalate (LT) are examples of an extremely versatile class of optical crystals. In bulk single crystal, single domain format, these crystalline hosts find numerous applications in nonlinear optics, optical storage, photorefraction, surface acoustic wave devices, optical waveguides, piezoelectric and pyroelectric devices and electro-optic modulation. Single domain crystals can be subsequently engineered via spatially selective poling to yield domain structures whose size can lie in the region of a few tens of µm to sub-µm, for applications and device fabrication that are impossible to implement in single domain geometry. This paper discusses our progress to date in micro- and nanostructuring of such materials, for applications in nonlinear optics, switching and deflection, and 3-dimensional sculpting for possible MEMS use. The techniques and benefits are discussed of using both light-assisted and direct optical poling for achieving controllable domains that can be irregular or periodic, bulk or surface, at sizes that approach the 100 nm scale. For surface inversion, domain features can be produced that lack the otherwise characteristic crystal symmetry imposed hexagonal shapes observed in conventional electric field poling