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Sample records for al amyloid deposits

  1. 2A4 binds soluble and insoluble light chain aggregates from AL amyloidosis patients and promotes clearance of amyloid deposits by phagocytosis †

    PubMed Central

    Renz, Mark; Torres, Ronald; Dolan, Philip J.; Tam, Stephen J.; Tapia, Jose R.; Li, Lauri; Salmans, Joshua R.; Barbour, Robin M.; Shughrue, Paul J.; Nijjar, Tarlochan; Schenk, Dale; Kinney, Gene G.; Zago, Wagner

    2016-01-01

    Abstract Amyloid light chain (AL) amyloidosis is characterized by misfolded light chain (LC) (amyloid) deposition in various peripheral organs, leading to progressive dysfunction and death. There are no regulatory agency–approved treatments for AL amyloidosis, and none of the available standard of care approaches directly targets the LC protein that constitutes the amyloid. NEOD001, currently in late-stage clinical trials, is a conformation-specific, anti-LC antibody designed to specifically target misfolded LC aggregates and promote phagocytic clearance of AL amyloid deposits. The present study demonstrated that the monoclonal antibody 2A4, the murine form of NEOD001, binds to patient-derived soluble and insoluble LC aggregates and induces phagocytic clearance of AL amyloid in vitro. 2A4 specifically labeled all 21 fresh-frozen organ samples studied, which were derived from 10 patients representing both κ and λ LC amyloidosis subtypes. 2A4 immunoreactivity largely overlapped with thioflavin T–positive labeling, and 2A4 bound both soluble and insoluble LC aggregates extracted from patient tissue. Finally, 2A4 induced macrophage engagement and phagocytic clearance of AL amyloid deposits in vitro. These findings provide further evidence that 2A4/NEOD001 can effectively clear and remove human AL-amyloid from tissue and further support the rationale for the evaluation of NEOD001 in patients with AL amyloidosis. PMID:27494229

  2. Amyloid deposition in 2 feline thymomas.

    PubMed

    Burrough, E R; Myers, R K; Hostetter, S J; Fox, L E; Bayer, B J; Felz, C L; Waller, K R; Whitley, E M

    2012-07-01

    Two cases of feline thymoma with amyloid deposition were encountered between 1982 and 2010. Neoplastic cells were separated by abundant, pale eosinophilic, homogeneous material that was congophilic and birefringent. Ultrastructurally, the neoplastic cells were connected by desmosomes, and the extracellular deposits were composed of nonbranching, hollow-cored fibrils, 8-10 nm in diameter. In the case with sufficient archived tissue for additional sections, the amyloid remained congophilic following potassium permanganate incubation, and the neoplastic cells were immunoreactive for pancytokeratin. The histologic, histochemical, ultrastructural, and immunohistochemical features of both neoplasms are consistent with epithelial-predominant thymoma with the unusual feature of intratumoral amyloid deposition. The affinity of the amyloid for Congo red following potassium permanganate incubation is consistent with non-AA amyloid. The ultrastructural findings were consistent with amyloid production by the neoplastic epithelial cells.

  3. Peptide p5 binds both heparinase-sensitive glycosaminoglycans and fibrils in patient-derived AL amyloid extracts.

    PubMed

    Martin, Emily B; Williams, Angela; Heidel, Eric; Macy, Sallie; Kennel, Stephen J; Wall, Jonathan S

    2013-06-21

    In previously published work, we have described heparin-binding synthetic peptides that preferentially recognize amyloid deposits in a mouse model of reactive systemic (AA) amyloidosis and can be imaged by using positron and single photon emission tomographic imaging. We wanted to extend these findings to the most common form of visceral amyloidosis, namely light chain (AL); however, there are no robust experimental animal models of AL amyloidosis. To further define the binding of the lead peptide, p5, to AL amyloid, we characterized the reactivity in vitro of p5 with in situ and patient-derived AL amyloid extracts which contain both hypersulfated heparan sulfate proteoglycans as well as amyloid fibrils. Histochemical staining demonstrated that the peptide specifically localized with tissue-associated AL amyloid deposits. Although we anticipated that p5 would undergo electrostatic interactions with the amyloid-associated glycosaminoglycans expressing heparin-like side chains, no significant correlation between peptide binding and glycosaminoglycan content within amyloid extracts was observed. In contrast, following heparinase I treatment, although overall binding was reduced, a positive correlation between peptide binding and amyloid fibril content became evident. This interaction was further confirmed using synthetic light chain fibrils that contain no carbohydrates. These data suggest that p5 can bind to both the sulfated glycosaminoglycans and protein fibril components of AL amyloid. Understanding these complex electrostatic interactions will aid in the optimization of synthetic peptides for use as amyloid imaging agents and potentially as therapeutics for the treatment of amyloid diseases.

  4. Prevalence of amyloid deposition in mature healthy chickens in the flock that previously had outbreaks of vaccine-associated amyloidosis

    PubMed Central

    IBI, Kanata; MURAKAMI, Tomoaki; GODA, Wael Mohamed; KOBAYASHI, Naoki; ISHIGURO, Naotaka; YANAI, Tokuma

    2015-01-01

    Avian amyloid A (AA) amyloidosis is commonly observed in adult birds with chronic inflammation, such as that caused by bacterial infection. We previously described vaccine-associated AA amyloidosis in juvenile chickens. In this study, the prevalence of amyloid deposition was measured in mature healthy chickens that survived a previous outbreak of avian AA amyloidosis while they were juveniles. Herein, we analyzed the amyloid deposition in mature chickens and compared the prevalence of amyloid deposition with juvenile chickens obtained in our previous study (Murakami et al., 2013). We found that: 1) amyloid deposition in the liver was absent in mature chickens, while juvenile chickens had a rate of 24%; 2) amyloid deposition in the spleen was observed in 36% of juvenile chickens and in 40% of mature chickens; 3) amyloid deposition in the pectoral muscle of mature chickens (43.75%) was approximately half that of juvenile chickens (88%). These results suggest that additional amyloid deposition in chickens previously exposed to AA amyloidosis may not worsen with age. Further, amyloid deposition in chickens may tend to regress when causative factors, such as vaccinations and/or chronic inflammation, are absent. PMID:25985816

  5. Prevalence of amyloid deposition in mature healthy chickens in the flock that previously had outbreaks of vaccine-associated amyloidosis.

    PubMed

    Ibi, Kanata; Murakami, Tomoaki; Goda, Wael Mohamed; Kobayashi, Naoki; Ishiguro, Naotaka; Yanai, Tokuma

    2015-10-01

    Avian amyloid A (AA) amyloidosis is commonly observed in adult birds with chronic inflammation, such as that caused by bacterial infection. We previously described vaccine-associated AA amyloidosis in juvenile chickens. In this study, the prevalence of amyloid deposition was measured in mature healthy chickens that survived a previous outbreak of avian AA amyloidosis while they were juveniles. Herein, we analyzed the amyloid deposition in mature chickens and compared the prevalence of amyloid deposition with juvenile chickens obtained in our previous study (Murakami et al., 2013). We found that: 1) amyloid deposition in the liver was absent in mature chickens, while juvenile chickens had a rate of 24%; 2) amyloid deposition in the spleen was observed in 36% of juvenile chickens and in 40% of mature chickens; 3) amyloid deposition in the pectoral muscle of mature chickens (43.75%) was approximately half that of juvenile chickens (88%). These results suggest that additional amyloid deposition in chickens previously exposed to AA amyloidosis may not worsen with age. Further, amyloid deposition in chickens may tend to regress when causative factors, such as vaccinations and/or chronic inflammation, are absent.

  6. MR microscopy of human amyloiddeposits: characterization of parenchymal amyloid, diffuse plaques, and vascular amyloid.

    PubMed

    Nabuurs, Rob J A; Natté, Remco; de Ronde, Fenna M; Hegeman-Kleinn, Ingrid; Dijkstra, Jouke; van Duinen, Sjoerd G; Webb, Andrew G; Rozemuller, Annemieke J; van Buchem, Mark A; van der Weerd, Louise

    2013-01-01

    Cerebral deposits of amyloid-β peptides (Aβ) form the neuropathological hallmarks of Alzheimer's disease (AD) and cerebral amyloid angiopathy (CAA). In the brain, Aβ can aggregate as insoluble fibrils present in amyloid plaques and vascular amyloid, or as diffuse plaques consisting of mainly non-fibrillar Aβ. Previously, magnetic resonance imaging (MRI) has been shown to be capable of detecting individual amyloid plaques, not only via the associated iron, but also Aβ itself has been suggested to be responsible for a decrease in the image intensity. In this current study we aim to investigate the MRI properties of the different cerebral Aβ deposits including diffuse plaques and vascular amyloid. Postmortem 60-μm-thick brain sections of AD, CAA, and Down's syndrome patients, known to contain Aβ, were studied. High resolution T2*- and T2-weighted MRI scans and quantitative relaxation maps were acquired using a microcoil on a Bruker 9.4T MRI system. Specific MRI characteristics of each type of Aβ deposit were examined by co-registration of the MRI with Congo Red and Aβ-immunostainings of the same sections. Our results show that only fibrillar Aβ, present in both vascular and parenchymal amyloid, induced a significant change in T2* and T2 values. However, signal changes were not as consistent for all of the vessels affected by CAA, irrespective of possible dyshoric changes. In contrast, the non-fibrillar diffuse plaques did not create any detectable MRI signal changes. These findings are relevant for the interpretation and further development of (quantitative) MRI methods for the detection and follow-up of AD and CAA.

  7. Pharmacological removal of serum amyloid P component from intracerebral plaques and cerebrovascular Aβ amyloid deposits in vivo

    PubMed Central

    Millar, David J.; Richard-Londt, Angela

    2016-01-01

    Human amyloid deposits always contain the normal plasma protein serum amyloid P component (SAP), owing to its avid but reversible binding to all amyloid fibrils, including the amyloid β (Aβ) fibrils in the cerebral parenchyma plaques and cerebrovascular amyloid deposits of Alzheimer's disease (AD) and cerebral amyloid angiopathy (CAA). SAP promotes amyloid fibril formation in vitro, contributes to persistence of amyloid in vivo and is also itself directly toxic to cerebral neurons. We therefore developed (R)-1-[6-[(R)-2-carboxy-pyrrolidin-1-yl]-6-oxo-hexanoyl]pyrrolidine-2-carboxylic acid (CPHPC), a drug that removes SAP from the blood, and thereby also from the cerebrospinal fluid (CSF), in patients with AD. Here we report that, after introduction of transgenic human SAP expression in the TASTPM double transgenic mouse model of AD, all the amyloid deposits contained human SAP. Depletion of circulating human SAP by CPHPC administration in these mice removed all detectable human SAP from both the intracerebral and cerebrovascular amyloid. The demonstration that removal of SAP from the blood and CSF also removes it from these amyloid deposits crucially validates the strategy of the forthcoming ‘Depletion of serum amyloid P component in Alzheimer's disease (DESPIAD)’ clinical trial of CPHPC. The results also strongly support clinical testing of CPHPC in patients with CAA. PMID:26842068

  8. Proflavine derivatives as fluorescent imaging agents of amyloid deposits.

    PubMed

    Garin, Dominique; Oukhatar, Fatima; Mahon, Andrew B; Try, Andrew C; Dubois-Dauphin, Michel; Laferla, Frank M; Demeunynck, Martine; Sallanon, Marcelle Moulin; Chierici, Sabine

    2011-04-15

    A series of proflavine derivatives for use to further image Aβ amyloid deposits were synthesized and characterized. Aged 3xTg-AD (23 months old) mice hippocampus sections incubated with these derivatives revealed preferential labeling of amyloid plaques. Furthermore an in vitro binding study showed an inhibitory effect, although moderate, of these compounds on Aβ(40) fibril formation. This study highlights the potential of proflavine as a molecular scaffold for designing new Aβ imaging agents, its native fluorescence allowing in vitro neuropathological staining in AD damaged brain sections.

  9. [Salmon-pink colored conjunctival tumor with amyloid deposits].

    PubMed

    Müller, P L; Loeffler, K U; Holz, F G; Fischer, H-P; Herwig, M C

    2016-07-01

    An 82-year-old male patient presented with a salmon-pink colored conjunctival tumor of the left eye. A circumscribed, dense and whitish portion was detected by clinical examination. The histophological and immunhistochemical examination of the biopsy tissue revealed a CD20+ marginal zone lymphoma of the conjunctiva with amyloid deposits. Extranodal marginal zone lymphoma at this site is the most common lymphoma of the ocular adnexa and accounts for 5-10% of malignant diseases. An association with amyloid production is very rare and according to the current state of knowledge has no known impact on the outcome.

  10. Engineering theranostic nanovehicles capable of targeting cerebrovascular amyloid deposits.

    PubMed

    Agyare, Edward K; Jaruszewski, Kristen M; Curran, Geoffry L; Rosenberg, Jens T; Grant, Samuel C; Lowe, Val J; Ramakrishnan, Subramanian; Paravastu, Anant K; Poduslo, Joseph F; Kandimalla, Karunya K

    2014-07-10

    Cerebral amyloid angiopathy (CAA) is characterized by the deposition of amyloid beta (Aβ) proteins within the walls of the cerebral vasculature with subsequent aggressive vascular inflammation leading to recurrent hemorrhagic strokes. The objective of the study was to develop theranostic nanovehicles (TNVs) capable of a) targeting cerebrovascular amyloid; b) providing magnetic resonance imaging (MRI) contrast for the early detection of CAA; and c) treating cerebrovascular inflammation resulting from CAA. The TNVs comprised of a polymeric nanocore made from Magnevist (MRI contrast agent) conjugated chitosan. The nanocore was also loaded with cyclophosphamide (CYC), an immunosuppressant shown to reduce the cerebrovascular inflammation in CAA. Putrescine modified F(ab')2 fragment of anti-amyloid antibody, IgG4.1 (pF(ab')24.1) was conjugated to the surface of the nanocore to target cerebrovascular amyloid. The average size of the control chitosan nanoparticles (conjugated with albumin and are devoid of Magnevist, CYC, and pF(ab')24.1) was 164±1.2 nm and that of the TNVs was 239±4.1 nm. The zeta potential values of the CCNs and TNVs were 21.6±1.7 mV and 11.9±0.5 mV, respectively. The leakage of Magnevist from the TNVs was a modest 0.2% over 4 days, and the CYC release from the TNVs followed Higuchi's model that describes sustained drug release from polymeric matrices. The studies conducted in polarized human microvascular endothelial cell monolayers (hCMEC/D3) in vitro as well as in mice in vivo have demonstrated the ability of TNVs to target cerebrovascular amyloid. In addition, the TNVs provided contrast for imaging cerebrovascular amyloid using MRI and single photon emission computed tomography. Moreover, the TNVs were shown to reduce pro-inflammatory cytokine production by the Aβ challenged blood brain barrier (BBB) endothelium more effectively than the cyclophosphamide alone.

  11. Characterization of AmyloidDeposits in Bovine Brains.

    PubMed

    Vallino Costassa, Elena; Fiorini, Michele; Zanusso, Gianluigi; Peletto, Simone; Acutis, Pierluigi; Baioni, Elisa; Maurella, Cristiana; Tagliavini, Fabrizio; Catania, Marcella; Gallo, Marina; Faro, Monica Lo; Chieppa, Maria Novella; Meloni, Daniela; D'Angelo, Antonio; Paciello, Orlando; Ghidoni, Roberta; Tonoli, Elisa; Casalone, Cristina; Corona, Cristiano

    2016-01-01

    Amyloid-β (Aβ) deposits are seen in aged individuals of many mammalian species that possess the same aminoacid sequence as humans. This study describes Aβ deposition in 102 clinically characterized cattle brains from animals aged 0 to 20 years. Extracellular and intracellular Aβ deposition was detected with 4G8 antibody in the cortex, hippocampus, and cerebellum. X-34 staining failed to stain Aβ deposits, indicating the non β-pleated nature of these deposits. Western blot analysis and surface-enhanced laser desorption/ionization time-of-flight (SELDI-TOF) mass spectrometry revealed in Tris, Triton, and formic acid fractions the presence of different Aβ peptides, characterized mainly by C-terminally truncated forms. Exploration of the genetic variability of APOE, PSEN1, and PSEN2 genes involved in Alzheimer's disease pathogenesis revealed several previously unreported polymorphisms. This study demonstrates certain similarities between Aβ deposition patterns exhibited in cattle brains and those in the human brain in early stages of aging. Furthermore, the identification of the same Aβ peptides reported in humans, but unable to form aggregates, supports the hypothesis that cattle may be protected against amyloid plaque formation.

  12. In vitro binding of [³H]PIB to human amyloid deposits of different types.

    PubMed

    Hellström-Lindahl, Ewa; Westermark, Per; Antoni, Gunnar; Estrada, Sergio

    2014-03-01

    Systemic amyloidosis is caused by extracellular deposition of insoluble fibrillar proteins arranged in β-pleated sheets. [(11)C]PIB has been used in PET studies to assess Aβ deposition in brain of patients with Alzheimer's disease (AD). The possibility to visualize other types of amyloid deposits with [(11)C]PIB would be of potential clinical importance in early diagnosis and for following therapeutic effects. In the present study, we evaluated in vitro binding of [(3)H]PIB to tissues containing transthyretin (ATTR), immunoglobulin light-chain (AL), amyloid protein A (AA) and Aβ amyloid. We found significantly higher binding of [(3)H]PIB in tissue from systemic amyloidoses than in control tissue, i.e. 4.7 times higher (p < 0.05). [(3)H]PIB showed the highest affinity to cortex of AD brain (IC50 = 3.84 nM), while IC50 values were much higher for ATTR, AA and AL type of amyloidosis and large variations in affinity were observed even within tissues having the same type of amyloidosis. Extraction with guanidine-HCl, which disrupts the β-sheet structure, decreased the protein levels and, concomitantly, the binding of [(3)H]PIB in all four types of amyloidoses.

  13. Generalized AA-amyloidosis in Siberian tigers (Panthera tigris altaica) with predominant renal medullary amyloid deposition.

    PubMed

    Schulze, C; Brügmann, M; Böer, M; Brandt, H P; Pohlenz, J; Linke, R P

    1998-01-01

    Generalized amyloidosis with predominant renal medullary amyloid deposition was found in four closely related Siberian tigers (Panthera tigris altaica) suffering from end stage kidney diseases. Only minimal to mild amounts of amyloid were deposited in various organs outside the kidneys with individually variable organ involvement. The Congo red staining affinity of amyloid deposits was sensitive to potassium permanganate oxidation. The deposits were further characterized as being of the amyloid-A (AA) type by immunohistochemistry using the mouse monoclonal antibody mc4 directed against a conserved region of the human AA-protein. A combination of immunohistochemistry and Congo red staining was much more sensitive for the diagnosis of amyloid deposits than Congo red staining alone. With this combination, even minimal amyloid deposits were detected that had been missed in the first reading using Congo-red-stained slides alone. Since no common primary cause was identified, the amyloidosis was classified as idiopathic generalized AA-amyloidosis with a potential familial predisposition.

  14. Long-term kinetics of AA amyloidosis and effects of inflammatory restimulation after disappearance of amyloid depositions in mice.

    PubMed

    Muhammad, N; Murakami, T; Inoshima, Y; Ishiguro, N

    2015-07-01

    Amyloid A (AA) amyloidosis is characterized by extracellular pathogenic deposition of insoluble fibril protein in various body organs. Deposited amyloid generally remains in a variety of organs for long periods, but its disappearance has been reported after the precursor protein is diminished. The kinetics of AA deposition are not completely understood and, in particular, the roles of cells and cytokines in the deposition and clearance of amyloid remain unclear. In this study, we investigated the disappearance of amyloid depositions in mice over a 1-year period. AA amyloidosis was induced experimentally in mice by injecting amyloid-enhancing factor (AEF) and silver nitrate. Mice were killed at different time-points to examine the occurrence and disappearance of amyloid depositions. Maximum levels of amyloid depositions were observed at 20 days after inoculation. Clearance of amyloid depositions was observed from the 40th day onwards, with only minute traces of amyloid present by 240 days. A second inflammatory stimulus consisting of AEF and silver nitrate was given at 330 or 430 days, after amyloid depositions had disappeared almost completely. After that, serum amyloid A was overproduced and redeposition of amyloid was observed, indicating that all mice were primed for aggressive amyloid depositions. After administration of the inflammatory stimuli, the proinflammatory environment was found to have increased levels of interleukin (IL)-6, while anti-inflammatory conditions were established by IL-10 as regression of amyloid deposition occurred. These results suggest that the proinflammatory and anti-inflammatory status have key roles in both amyloid deposition and clearance.

  15. 18F-Florbetapir Binds Specifically to Myocardial Light Chain and Transthyretin Amyloid Deposits: An Autoradiography Study

    PubMed Central

    Park, Mi-Ae; Padera, Robert F.; Belanger, Anthony; Dubey, Shipra; Hwang, David H.; Veeranna, Vikas; Falk, Rodney H.; Di Carli, Marcelo F.; Dorbala, Sharmila

    2015-01-01

    Background 18F-florbetapir is a promising imaging biomarker for light chain (AL) and transthyretin (ATTR) cardiac amyloidosis. Our aim, using human autopsy myocardial specimens, was to test the hypothesis that 18F-florbetapir binds specifically to myocardial AL and ATTR amyloid deposits. Methods and Results We studied myocardial sections from 30 subjects with autopsy documented AL (N = 10), ATTR (N = 10) and non-amyloid controls (N = 10), using 18F-florbetapir and cold florbetapir compound and digital autoradiography. Total and non-specific binding of 18F-florbetapir was determined using the maximum signal intensity values. Specific binding of 18F-florbetapir was calculated by subtracting non-specific from total binding measurements (in decays per minute/mm2, DPM mm2), and was compared to cardiac structure and function on echocardiography and the histological extent of amyloid deposits. Diffuse or focally increased 18F-florbetapir uptake was noted in all AL and ATTR samples and in none of the control samples. Compared to control samples, mean 18F-florbetapir specific uptake was significantly higher in the amyloid samples (0.94 ± 0.43 vs. 2.00 ± 0.58 DPM/mm2, p < 0.001), and in the AL compared to the ATTR samples (2.48 ± 0.40 vs. 1.52 ± 0.22 DPM/mm2, p < 0.001). The samples from subjects with atypical echocardiographic features of amyloidosis showed quantitatively more intense 18F-florbetapir specific uptake compared to control samples (1.50 ± 0.17 vs. 0.94 ± 0.43 DPM/mm2, p = 0.004), despite smaller amyloid extent than in subjects with typical echocardiograms. Conclusions 18F-florbetapir specifically binds to myocardial AL and ATTR deposits in humans and offers the potential to screen for the two most common types of myocardial amyloid. PMID:26259579

  16. Accelerated amyloid deposition, neurofibrillary degeneration and neuronal loss in double mutant APP/tau transgenic mice.

    PubMed

    Ribé, Elena M; Pérez, Mar; Puig, Berta; Gich, Ignasi; Lim, Filip; Cuadrado, Mar; Sesma, Teresa; Catena, Silvia; Sánchez, Belén; Nieto, María; Gómez-Ramos, Pilar; Morán, M Asunción; Cabodevilla, Felipe; Samaranch, Lluis; Ortiz, Lourdes; Pérez, Alberto; Ferrer, Isidro; Avila, Jesús; Gómez-Isla, Teresa

    2005-12-01

    Even though the idea that amyloid beta peptide accumulation is the primary event in the pathogenesis of Alzheimer's disease has become the leading hypothesis, the causal link between aberrant amyloid precursor protein processing and tau alterations in this type of dementia remains controversial. We further investigated the role of beta-amyloid production/deposition in tau pathology and neuronal cell death in the mouse brain by crossing Tg2576 and VLW lines expressing human mutant amyloid precursor protein and human mutant tau, respectively. The resulting double transgenic mice showed enhanced amyloid deposition accompanied by neurofibrillary degeneration and overt neuronal loss in selectively vulnerable brain limbic areas. These findings challenge the idea that tau pathology in Alzheimer's disease is merely a downstream effect of amyloid production/deposition and suggest that reciprocal interactions between beta-amyloid and tau alterations may take place in vivo.

  17. Dietary exposure to an environmental toxin triggers neurofibrillary tangles and amyloid deposits in the brain

    PubMed Central

    Cox, Paul Alan; Davis, David A.; Mash, Deborah C.; Metcalf, James S.; Banack, Sandra Anne

    2016-01-01

    Neurofibrillary tangles (NFT) and β-amyloid plaques are the neurological hallmarks of both Alzheimer's disease and an unusual paralytic illness suffered by Chamorro villagers on the Pacific island of Guam. Many Chamorros with the disease suffer dementia, and in some villages one-quarter of the adults perished from the disease. Like Alzheimer's, the causal factors of Guamanian amyotrophic lateral sclerosis/parkinsonism dementia complex (ALS/PDC) are poorly understood. In replicated experiments, we found that chronic dietary exposure to a cyanobacterial toxin present in the traditional Chamorro diet, β-N-methylamino-l-alanine (BMAA), triggers the formation of both NFT and β-amyloid deposits similar in structure and density to those found in brain tissues of Chamorros who died with ALS/PDC. Vervets (Chlorocebus sabaeus) fed for 140 days with BMAA-dosed fruit developed NFT and sparse β-amyloid deposits in the brain. Co-administration of the dietary amino acid l-serine with l-BMAA significantly reduced the density of NFT. These findings indicate that while chronic exposure to the environmental toxin BMAA can trigger neurodegeneration in vulnerable individuals, increasing the amount of l-serine in the diet can reduce the risk. PMID:26791617

  18. The risk of renal disease is increased in lambda myeloma with bone marrow amyloid deposits

    PubMed Central

    Kozlowski, Piotr; Montgomery, Scott; Befekadu, Rahel; Hahn-Strömberg, Victoria

    2017-01-01

    Background Light chain amyloidosis (AL) is a rare deposition disease and is present in 10–15% of patients with myeloma (MM). In contrast to symptomatic AL in MM, presence of bone marrow (BM) amyloid deposits (AD) in MM is not connected to kidney damage. Renal AD but not BM-AD occur mostly in MM with lambda paraprotein (lambda MM). Methods We investigated amyloid presence in BM clots taken at diagnosis in 84 patients with symptomatic MM and compared disease characteristics in MM with kappa paraprotein (kappa MM)/lambda MM with and without BM-AD. Results Lambda MM with BM-AD was compared with kappa MM without BM-AD, kappa MM with BM-AD, and lambda MM without BM-AD: lambda MM with BM-AD patients had a significantly higher mean creatinine level (4.23 mg/dL vs 1.69, 1.14, and 1.28 mg/dL, respectively) and a higher proportion presented with severe kidney failure (6/11 [55%] vs 6/32 [19%], 1/22 [5%], and 3/19 [16%], respectively). Proteinuria was more common in lambda MM with BM-AD patients compared with kappa MM without BM-AD patients (8/11 [73%] vs 5/32 [16%], respectively). Conclusion Kidney damage was more common in lambda MM with BM-AD indicating presence of renal AD. PMID:28293126

  19. De novo induction of amyloiddeposition in vivo.

    PubMed

    Morales, R; Duran-Aniotz, C; Castilla, J; Estrada, L D; Soto, C

    2012-12-01

    Alzheimer's disease (AD), the most common type of senile dementia, is associated to the build-up of misfolded amyloid-β (Aβ) in the brain. Although compelling evidences indicate that the misfolding and oligomerization of Aβ is the triggering event in AD, the mechanisms responsible for the initiation of Aβ accumulation are unknown. In this study, we show that Aβ deposition can be induced by injection of AD brain extracts into animals, which, without exposure to this material, will never develop these alterations. The accumulation of Aβ deposits increased progressively with the time after inoculation, and the Aβ lesions were observed in brain areas far from the injection site. Our results suggest that some of the typical brain abnormalities associated with AD can be induced by a prion-like mechanism of disease transmission through propagation of protein misfolding. These findings may have broad implications for understanding the molecular mechanisms responsible for the initiation of AD, and may contribute to the development of new strategies for disease prevention and intervention.

  20. Beta-amyloid deposition in chronic traumatic encephalopathy.

    PubMed

    Stein, Thor D; Montenigro, Philip H; Alvarez, Victor E; Xia, Weiming; Crary, John F; Tripodis, Yorghos; Daneshvar, Daniel H; Mez, Jesse; Solomon, Todd; Meng, Gaoyuan; Kubilus, Caroline A; Cormier, Kerry A; Meng, Steven; Babcock, Katharine; Kiernan, Patrick; Murphy, Lauren; Nowinski, Christopher J; Martin, Brett; Dixon, Diane; Stern, Robert A; Cantu, Robert C; Kowall, Neil W; McKee, Ann C

    2015-07-01

    Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease associated with repetitive mild traumatic brain injury. It is defined pathologically by the abnormal accumulation of tau in a unique pattern that is distinct from other tauopathies, including Alzheimer's disease (AD). Although trauma has been suggested to increase amyloid β peptide (Aβ) levels, the extent of Aβ deposition in CTE has not been thoroughly characterized. We studied a heterogeneous cohort of deceased athletes and military veterans with neuropathologically diagnosed CTE (n = 114, mean age at death = 60) to test the hypothesis that Aβ deposition is altered in CTE and associated with more severe pathology and worse clinical outcomes. We found that Aβ deposition, either as diffuse or neuritic plaques, was present in 52 % of CTE subjects. Moreover, Aβ deposition in CTE occurred at an accelerated rate and with altered dynamics in CTE compared to a normal aging population (OR = 3.8, p < 0.001). We also found a clear pathological and clinical dichotomy between those CTE cases with Aβ plaques and those without. Aβ deposition was significantly associated with the presence of the APOE ε4 allele (p = 0.035), older age at symptom onset (p < 0.001), and older age at death (p < 0.001). In addition, when controlling for age, neuritic plaques were significantly associated with increased CTE tauopathy stage (β = 2.43, p = 0.018), co-morbid Lewy body disease (OR = 5.01, p = 0.009), and dementia (OR = 4.45, p = 0.012). A subset of subjects met the diagnostic criteria for both CTE and AD, and in these subjects both Aβ plaques and total levels of Aβ1-40 were increased at the depths of the cortical sulcus compared to the gyral crests. Overall, these findings suggest that Aβ deposition is altered and accelerated in a cohort of CTE subjects compared to normal aging and that Aβ is associated with both pathological and clinical progression of CTE independent of age.

  1. Electron tomography reveals the fibril structure and lipid interactions in amyloid deposits

    PubMed Central

    Kollmer, Marius; Meinhardt, Katrin; Haupt, Christian; Liberta, Falk; Wulff, Melanie; Linder, Julia; Handl, Lisa; Heinrich, Liesa; Loos, Cornelia; Schmidt, Matthias; Syrovets, Tatiana; Simmet, Thomas; Westermark, Per; Westermark, Gunilla T.; Horn, Uwe; Schmidt, Volker; Walther, Paul; Fändrich, Marcus

    2016-01-01

    Electron tomography is an increasingly powerful method to study the detailed architecture of macromolecular complexes or cellular structures. Applied to amyloid deposits formed in a cell culture model of systemic amyloid A amyloidosis, we could determine the structural morphology of the fibrils directly in the deposit. The deposited fibrils are arranged in different networks, and depending on the relative fibril orientation, we can distinguish between fibril meshworks, fibril bundles, and amyloid stars. These networks are frequently infiltrated by vesicular lipid inclusions that may originate from the death of the amyloid-forming cells. Our data support the role of nonfibril components for constructing fibril deposits and provide structural views of different types of lipid–fibril interactions. PMID:27140609

  2. The effects of white matter hyperintensities and amyloid deposition on Alzheimer dementia

    PubMed Central

    Gordon, Brian A.; Najmi, Safa; Hsu, Phillip; Roe, Catherine M.; Morris, John C.; Benzinger, Tammie L.S.

    2015-01-01

    Background and purpose Elevated levels of amyloid deposition as well as white matter damage are thought to be risk factors for Alzheimer Disease (AD). Here we examined whether qualitative ratings of white matter damage predicted cognitive impairment beyond measures of amyloid. Materials and methods The study examined 397 cognitively normal, 51 very mildly demented, and 11 mildly demented individuals aged 42–90 (mean 68.5). Participants obtained a T2-weighted scan as well as a positron emission tomography scan using 11[C] Pittsburgh Compound B. Periventricular white matter hyperintensities (PVWMHs) and deep white matter hyperintensities (DWMHs) were measured on each T2 scan using the Fazekas rating scale. The effects of amyloid deposition and white matter damage were assessed using logistic regressions. Results Levels of amyloid deposition (ps < 0.01), as well as ratings of PVWMH (p < 0.01) and DWMH (p < 0.05) discriminated between cognitively normal and demented individuals. Conclusions The amount of amyloid deposition and white matter damage independently predicts cognitive impairment. This suggests a diagnostic utility of qualitative white matter scales in addition to measuring amyloid levels. PMID:26106548

  3. Phosphorylation modifies the molecular stability of β-amyloid deposits

    PubMed Central

    Rezaei-Ghaleh, Nasrollah; Amininasab, Mehriar; Kumar, Sathish; Walter, Jochen; Zweckstetter, Markus

    2016-01-01

    Protein aggregation plays a crucial role in neurodegenerative diseases. A key feature of protein aggregates is their ubiquitous modification by phosphorylation. Little is known, however, about the molecular consequences of phosphorylation of protein aggregates. Here we show that phosphorylation of β-amyloid at serine 8 increases the stability of its pathogenic aggregates against high-pressure and SDS-induced dissociation. We further demonstrate that phosphorylation results in an elevated number of hydrogen bonds at the N terminus of β-amyloid, the region that is critically regulated by a variety of post-translational modifications. Because of the increased lifetime of phosphorylated β-amyloid aggregates, phosphorylation can promote the spreading of β-amyloid in Alzheimer pathogenesis. Our study suggests that regulation of the molecular stability of protein aggregates by post-translational modifications is a crucial factor for disease progression in the brain. PMID:27072999

  4. Phosphorylation modifies the molecular stability of β-amyloid deposits

    NASA Astrophysics Data System (ADS)

    Rezaei-Ghaleh, Nasrollah; Amininasab, Mehriar; Kumar, Sathish; Walter, Jochen; Zweckstetter, Markus

    2016-04-01

    Protein aggregation plays a crucial role in neurodegenerative diseases. A key feature of protein aggregates is their ubiquitous modification by phosphorylation. Little is known, however, about the molecular consequences of phosphorylation of protein aggregates. Here we show that phosphorylation of β-amyloid at serine 8 increases the stability of its pathogenic aggregates against high-pressure and SDS-induced dissociation. We further demonstrate that phosphorylation results in an elevated number of hydrogen bonds at the N terminus of β-amyloid, the region that is critically regulated by a variety of post-translational modifications. Because of the increased lifetime of phosphorylated β-amyloid aggregates, phosphorylation can promote the spreading of β-amyloid in Alzheimer pathogenesis. Our study suggests that regulation of the molecular stability of protein aggregates by post-translational modifications is a crucial factor for disease progression in the brain.

  5. Attenuation of β-Amyloid Deposition and Neurotoxicity by Chemogenetic Modulation of Neural Activity

    PubMed Central

    Yuan, Peng

    2016-01-01

    Aberrant neural hyperactivity has been observed in early stages of Alzheimer's disease (AD) and may be a driving force in the progression of amyloid pathology. Evidence for this includes the findings that neural activity may modulate β-amyloid (Aβ) peptide secretion and experimental stimulation of neural activity can increase amyloid deposition. However, whether long-term attenuation of neural activity prevents the buildup of amyloid plaques and associated neural pathologies remains unknown. Using viral-mediated delivery of designer receptors exclusively activated by designer drugs (DREADDs), we show in two AD-like mouse models that chronic intermittent increases or reductions of activity have opposite effects on Aβ deposition. Neural activity reduction markedly decreases Aβ aggregation in regions containing axons or dendrites of DREADD-expressing neurons, suggesting the involvement of synaptic and nonsynaptic Aβ release mechanisms. Importantly, activity attenuation is associated with a reduction in axonal dystrophy and synaptic loss around amyloid plaques. Thus, modulation of neural activity could constitute a potential therapeutic strategy for ameliorating amyloid-induced pathology in AD. SIGNIFICANCE STATEMENT A novel chemogenetic approach to upregulate and downregulate neuronal activity in Alzheimer's disease (AD) mice was implemented. This led to the first demonstration that chronic intermittent attenuation of neuronal activity in vivo significantly reduces amyloid deposition. The study also demonstrates that modulation of β-amyloid (Aβ) release can occur at both axonal and dendritic fields, suggesting the involvement of synaptic and nonsynaptic Aβ release mechanisms. Activity reductions also led to attenuation of the synaptic pathology associated with amyloid plaques. Therefore, chronic attenuation of neuronal activity could constitute a novel therapeutic approach for AD. PMID:26758850

  6. Association between Cerebral Amyloid Deposition and Clinical Factors Including Cognitive Function in Geriatric Depression: Pilot Study Using Amyloid Positron Emission Tomography

    PubMed Central

    Kim, Hye-Geum; Kong, Eun-Jung; Cheon, Eun-Jin; Kim, Hae-Won; Koo, Bon-Hoon

    2016-01-01

    The purpose of this study was to explore the relationship between cerebral amyloid deposition and overall clinical factors including cognitive functions in geriatric depression by using 18F-florbetaben positron emission tomography. Thirteen subjects aged over 60 years who had a history of major depressive disorder and also had subjective memory complaint were included. Of all subjects, 3 subjects judged as amyloid positive, and the others judged as amyloid negative. Their memory, visuospatial functions and attention abilities were negatively correlated with amyloid deposition in specific brain regions, but their language and recognition abilities were not correlated with any region. The amyloid deposition of the whole brain region was significantly negatively correlated with immediate memory. PMID:27776391

  7. Heart failure with silent coronary artery spasm exhibiting microscopic focal myocardial necrosis and amyloid-deposition.

    PubMed

    Suzuki, Satoru; Sugiyama, Seigo; Usuku, Hiroki; Hirai, Nobutaka; Kaikita, Koichi; Sakashita, Naomi; Sakamoto, Tomohiro; Yoshimura, Michihiro; Ogawa, Hisao

    2004-03-01

    We report a 67-year-old Japanese man who presented with worsening heart failure with asymptomatically transient ischemic ST-segment depression. Left ventriculography showed diffuse hypokinesis; asymptomatic coronary artery spasm was evoked by the acetylcholine provocation test. Endomyocardial biopsy exhibited hypertrophic cardiomyocytes and scattered microscopic focal myocardial necrosis with amyloid-deposition. Transient ST-segment depression improved after treatment with a calcium antagonist, but cardiac contraction was still impaired. We hypothesize that asymptomatic coronary spasm may cause irreversible cardiac damage and heart failure with amyloid-deposition; the presence or absence of coronary spasm in heart failure patients should be clarified in order to determine therapeutic strategy.

  8. Amyloid Deposition Begins in the Striatum of Presenilin-1 Mutation Carriers from Two Unrelated Pedigrees

    PubMed Central

    Klunk, William E.; Price, Julie C.; Mathis, Chester A.; Tsopelas, Nicholas D.; Lopresti, Brian J.; Ziolko, Scott K.; Bi, Wenzhu; Hoge, Jessica A.; Cohen, Ann D.; Ikonomovic, Milos D.; Saxton, Judith A.; Snitz, Beth E.; Pollen, Daniel A.; Moonis, Majaz; Lippa, Carol F.; Swearer, Joan M.; Johnson, Keith A.; Rentz, Dorene M.; Fischman, Alan J.; Aizenstein, Howard J.; DeKosky, Steven T.

    2012-01-01

    The amyloid cascade hypothesis suggests that the aggregation and deposition of amyloid-β protein is an initiating event in Alzheimer's disease (AD). Using amyloid imaging technology, such as the positron emission tomography (PET) agent Pittsburgh compound-B (PiB), it is possible to explore the natural history of preclinical amyloid deposition in people at high risk for AD. With this goal in mind, asymptomatic (n = 5) and symptomatic (n = 5) carriers of presenilin-1 (PS1) mutations (C410Y or A426P) that lead to early-onset AD and noncarrier controls from both kindreds (n = 2) were studied with PiB–PET imaging and compared with sporadic AD subjects (n = 12) and controls from the general population (n = 18). We found intense and focal PiB retention in the striatum of all 10 PS1 mutation carriers studied (ages 35–49 years). In most PS1 mutation carriers, there also were increases in PiB retention compared with controls in cortical brain areas, but these increases were not as great as those observed in sporadic AD subjects. The two PS1 mutation carriers with a clinical diagnosis of early-onset AD did not show the typical regional pattern of PiB retention observed in sporadic AD. Postmortem evaluation of tissue from two parents of PS1C410Y subjects in this study confirmed extensive striatal amyloid deposition, along with typical cortical deposition. The early, focal striatal amyloid deposition observed in these PS1 mutation carriers is often is not associated with clinical symptoms. PMID:17553989

  9. Deposition of kappa and lambda light chains in amyloid filaments of dialysis-related amyloidosis.

    PubMed

    Brancaccio, D; Ghiggeri, G M; Braidotti, P; Garberi, A; Gallieni, M; Bellotti, V; Zoni, U; Gusmano, R; Coggi, G

    1995-10-01

    beta 2-Microglobulin (beta 2m) is considered to be the amyloidogenic precursor in dialysis-related amyloidosis, although the implication of other relevant cofactors in the pathogenesis of this disease has also been hypothesized. It is conceivable that substances found in amyloid deposits might represent something more than simple codeposition, possibly playing a pathogenic role in amyloidogenesis. Along these lines, a detailed analysis of the protein composition of amyloid fibrils purified from synovial material surgically obtained from nine patients on long-term dialysis was carried out. By the use of sodium dodecyl sulfate-polyacrylamide gel electrophoresis, several other protein components, in addition to beta 2m, were found. These were characterized by NH2 amino-terminal sequencing and immunoblotting. In fibrils obtained by water extraction, which fulfill the electron microscopy criteria of highly pure amyloid material, polyclonal kappa and lambda light chains were detected with a concentration of 15 micrograms/mL in the water extraction material; the beta 2m concentration was 200 micrograms/mL. Light microscopy immunohistochemistry was performed on samples from five patients. Amyloid deposits reacted with anti-beta 2m, and anti-light (kappa, lambda), chain antibodies. The immunoreaction of amyloid filaments to anti-beta 2m, anti-lambda, and anti-kappa light chain antibodies was also tested by electron microscopy by use of the immunogold staining procedure. Amyloid filaments were labeled by the three antibodies and showed a different intensity of immunostaining apparently related to their different aggregation pattern. These observations demonstrate that polyclonal immunoglobulin light chains (kappa and lambda) are not contaminants but, together with beta 2m, represent a major constituent of amyloid deposits in dialysis-related osteoarticular amyloidosis, thus indicating their possible role in amyloidogenesis.

  10. Visual Hallucinations and Amyloid Deposition in Parkinson's Disease Dementia: A Case Report.

    PubMed

    Um, Yoo Hyun; Kim, Tae-Won; Jeong, Jong-Hyun; Seo, Ho-Jun; Han, Jin-Hee; Hong, Seung-Chul; Jung, Won-Sang; Choi, Woo Hee; Lee, Chang-Uk; Lim, Hyun Kook

    2016-05-01

    Parkinson's disease dementia (PDD) is notorious for its debilitating clinical course and high mortality rates. Consequently, various attempts to investigate predictors of cognitive decline in Parkinson's disease (PD) have been made. Here we report a case of a 75-year-old female patient with PD who visited the clinic with complaints of recurrent visual hallucinations and cognitive decline, whose symptoms were ameliorated by the titration of rivastigmine. Imaging results showed pronounced diffuse cortical amyloid deposition evidenced by 18F-florbetaben amyloid positron emission tomography (PET) imaging. This observation suggests that pronounced amyloid deposition and visual hallucinations in PD patients could be clinically significant predictors of cognitive decline in PD patients. Future research should concentrate on accumulating more evidence for possible predictors of cognitive decline and their association with PD pathology that can enable an early intervention and standardized treatment in PDD patients.

  11. Hitchhiking vesicular transport routes to the vacuole: Amyloid recruitment to the Insoluble Protein Deposit (IPOD).

    PubMed

    Kumar, Rajesh; Neuser, Nicole; Tyedmers, Jens

    2017-03-09

    Sequestration of aggregates into specialized deposition sites occurs in many species across all kingdoms of life ranging from bacteria to mammals and is commonly believed to have a cytoprotective function. Yeast cells possess at least 3 different spatially separated deposition sites, one of which is termed "Insoluble Protein Deposit (IPOD)" and harbors amyloid aggregates. We have recently discovered that recruitment of amyloid aggregates to the IPOD uses an actin cable based recruitment machinery that also involves vesicular transport. (1) Here we discuss how different proteins known to be involved in vesicular transport processes to the vacuole might act to guide amyloid aggregates to the IPOD. These factors include the Myosin V motor protein Myo2 involved in transporting vacuolar vesicles along actin cables, the transmembrane protein Atg9 involved in the recruitment of large precursor hydrolase complexes to the vacuole, the phosphatidylinositol/ phosphatidylcholine (PI/PC) transfer protein Sec 14 and the SNARE chaperone Sec 18. Furthermore, we present new data suggesting that the yeast dynamin homolog Vps1 is also crucial for faithful delivery of the amyloid model protein PrD-GFP to the IPOD. This is in agreement with a previously identified role for Vps1 in recruitment of heat-denatured aggregates to a perivacuolar deposition site. (2).

  12. Endogenous murine Aβ increases amyloid deposition in APP23 but not in APPPS1 transgenic mice.

    PubMed

    Mahler, Jasmin; Morales-Corraliza, Jose; Stolz, Julia; Skodras, Angelos; Radde, Rebecca; Duma, Carmen C; Eisele, Yvonne S; Mazzella, Matthew J; Wong, Harrison; Klunk, William E; Nilsson, K Peter R; Staufenbiel, Matthias; Mathews, Paul M; Jucker, Mathias; Wegenast-Braun, Bettina M

    2015-07-01

    Endogenous murine amyloid-β peptide (Aβ) is expressed in most Aβ precursor protein (APP) transgenic mouse models of Alzheimer's disease but its contribution to β-amyloidosis remains unclear. We demonstrate ∼ 35% increased cerebral Aβ load in APP23 transgenic mice compared with age-matched APP23 mice on an App-null background. No such difference was found for the much faster Aβ-depositing APPPS1 transgenic mouse model between animals with or without the murine App gene. Nevertheless, both APP23 and APPPS1 mice codeposited murine Aβ, and immunoelectron microscopy revealed a tight association of murine Aβ with human Aβ fibrils. Deposition of murine Aβ was considerably less efficient compared with the deposition of human Aβ indicating a lower amyloidogenic potential of murine Aβ in vivo. The amyloid dyes Pittsburgh Compound-B and pentamer formyl thiophene acetic acid did not differentiate between amyloid deposits consisting of human Aβ and deposits of mixed human-murine Aβ. Our data demonstrate a differential effect of murine Aβ on human Aβ deposition in different APP transgenic mice. The mechanistically complex interaction of human and mouse Aβ may affect pathogenesis of the models and should be considered when models are used for translational preclinical studies.

  13. Effects of stress and stress hormones on amyloid-beta protein and plaque deposition.

    PubMed

    Dong, Hongxin; Csernansky, John G

    2009-01-01

    Growing evidence indicates that physical and psychosocial stressors, in part acting through the hypothalamic-pituitary-adrenal (HPA) axis, may accelerate the process of Alzheimer's disease (AD). In this review, we summarize recent research related to the effects of stress and stress hormones on the various disease process elements associated with AD. Specifically, we focus on the relationships among chronic stressors, HPA axis activity, amyloid-beta protein, and amyloid-beta plaque deposition in mouse models of AD. The potential mechanisms by which stress and stress-related components, especially corticotrophin-releasing factor and its receptors, influence the pathogenesis of AD are discussed.

  14. Beta-Amyloid Deposition and Alzheimer's Type Changes Induced by Borrelia Spirochetes

    SciTech Connect

    Miklossy,J.; Kis, A.; Radenovic, A.; Miller, L.; Forro, L.; Martins, R.; Reiss, K.; Darbinian, N.; Darekar, P.; et al.

    2006-01-01

    The pathological hallmarks of Alzheimer's disease (AD) consist of {beta}-amyloid plaques and neurofibrillary tangles in affected brain areas. The processes, which drive this host reaction are unknown. To determine whether an analogous host reaction to that occurring in AD could be induced by infectious agents, we exposed mammalian glial and neuronal cells in vitro to Borrelia burgdorferi spirochetes and to the inflammatory bacterial lipopolysaccharide (LPS). Morphological changes analogous to the amyloid deposits of AD brain were observed following 2-8 weeks of exposure to the spirochetes. Increased levels of {beta}-amyloid presursor protein (A{beta}PP) and hyperphosphorylated tau were also detected by Western blots of extracts of cultured cells that had been treated with spirochetes or LPS. These observations indicate that, by exposure to bacteria or to their toxic products, host responses similar in nature to those observed in AD may be induced.

  15. Amyloid Deposition and Cognition in Older Adults: The Effects of Premorbid Intellect

    PubMed Central

    Duff, Kevin; Foster, Norman L.; Dennett, Kathryn; Hammers, Dustin B.; Zollinger, Lauren V.; Christian, Paul E.; Butterfield, Regan I.; Beardmore, Britney E.; Wang, Angela Y.; Morton, Kathryn A.; Hoffman, John M.

    2013-01-01

    Although amyloid deposition remains a marker of the development of Alzheimer's disease, results linking amyloid and cognition have been equivocal. Twenty-five community-dwelling non-demented older adults were examined with 18F-flutemetamol, an amyloid imaging agent, and a cognitive battery, including an estimate of premorbid intellect and the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). In the first model, 18F-flutemetamol uptake significantly correlated with the Delayed Memory Index of the RBANS (r = −.51, p = .02) and premorbid intellect (r = .43, p = .03). In the second model, the relationship between 18F-flutemetamol and cognition was notably stronger when controlling for premorbid intellect (e.g., three of the five RBANS Indexes and its Total score significantly correlated with 18F-flutemetamol, r's = −.41 to −.58). Associations were found between amyloid-binding 18F-flutemetamol and cognitive functioning in non-demented older adults. These associations were greatest with delayed memory and stronger when premorbid intellect was considered, suggesting that cognitive reserve partly compensates for the symptomatic expression of amyloid pathology in community-dwelling elderly. PMID:23817438

  16. Amyloid deposition and cognition in older adults: the effects of premorbid intellect.

    PubMed

    Duff, Kevin; Foster, Norman L; Dennett, Kathryn; Hammers, Dustin B; Zollinger, Lauren V; Christian, Paul E; Butterfield, Regan I; Beardmore, Britney E; Wang, Angela Y; Morton, Kathryn A; Hoffman, John M

    2013-11-01

    Although amyloid deposition remains a marker of the development of Alzheimer's disease, results linking amyloid and cognition have been equivocal. Twenty-five community-dwelling non-demented older adults were examined with (18)F-flutemetamol, an amyloid imaging agent, and a cognitive battery, including an estimate of premorbid intellect and the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). In the first model, (18)F-flutemetamol uptake significantly correlated with the Delayed Memory Index of the RBANS (r = -.51, p = .02) and premorbid intellect (r = .43, p = .03). In the second model, the relationship between (18)F-flutemetamol and cognition was notably stronger when controlling for premorbid intellect (e.g., three of the five RBANS Indexes and its Total score significantly correlated with (18)F-flutemetamol, r's = -.41 to -.58). Associations were found between amyloid-binding (18)F-flutemetamol and cognitive functioning in non-demented older adults. These associations were greatest with delayed memory and stronger when premorbid intellect was considered, suggesting that cognitive reserve partly compensates for the symptomatic expression of amyloid pathology in community-dwelling elderly.

  17. Neuronal and microglial involvement in beta-amyloid protein deposition in Alzheimer's disease.

    PubMed Central

    Cras, P.; Kawai, M.; Siedlak, S.; Mulvihill, P.; Gambetti, P.; Lowery, D.; Gonzalez-DeWhitt, P.; Greenberg, B.; Perry, G.

    1990-01-01

    This study was undertaken to localize amyloid precursor protein (APP) and to determine how APP might be released and proteolyzed to yield the beta-amyloid protein deposits found in senile plaques in the brains of Alzheimer's disease patients. We found that antibodies to recombinantly expressed APP labeled many normal neurons and neurites. In addition, dystrophic neurites in different types of senile plaques and degenerating neurons in the temporal cortex and hippocampus of Alzheimer's disease patients were immunostained. We also detected small clusters of dystrophic APP immunoreactive neurites that were not associated with beta-amyloid protein deposits. Microglia was involved in different types of senile plaques and often were associated closely with APP immunoreactive neurites and neurons. The greatest concurrence of APP immunoreactivity and reactive microglia was seen in the subiculum and area CA1, regions with a high density of congophilic plaques and subject to intense Alzheimer's pathology. Our findings suggest that neuronally derived APP is the source for senile plaque beta-amyloid protein, while microglia may act as processing cells. Images Figure 1 Figure 2 PMID:2117395

  18. Beta amyloid and hyperphosphorylated tau deposits in the pancreas in type 2 diabetes

    SciTech Connect

    Miklossy, J.; Miller, L.; Qing, H.; Radenovic, A.; Kis, A.; Vileno, B.; Laszlo, F.; Martins, R.N.; Waeber, G.; Mooser, V.; Bosman, F.; Khalili, K.; Darbinian, N.; McGeer, P.L.

    2008-08-25

    Strong epidemiologic evidence suggests an association between Alzheimer disease (AD) and type 2 diabetes. To determine if amyloid beta (A{beta}) and hyperphosphorylated tau occurs in type 2 diabetes, pancreas tissues from 21 autopsy cases (10 type 2 diabetes and 11 controls) were analyzed. APP and tau mRNAs were identified in human pancreas and in cultured insulinoma beta cells (INS-1) by RT-PCR. Prominent APP and tau bands were detected by Western blotting in pancreatic extracts. Aggregated A{beta}, hyperphosphorylated tau, ubiquitin, apolipoprotein E, apolipoprotein(a), IB1/JIP-1 and JNK1 were detected in Langerhans islets in type 2 diabetic patients. A{beta} was co-localized with amylin in islet amyloid deposits. In situ beta sheet formation of islet amyloid deposits was shown by infrared microspectroscopy (SIRMS). LPS increased APP in non-neuronal cells as well. We conclude that A{beta} deposits and hyperphosphorylated tau are also associated with type 2 diabetes, highlighting common pathogenetic features in neurodegenerative disorders, including AD and type 2 diabetes and suggesting that A{beta} deposits and hyperphosphorylated tau may also occur in other organs than the brain.

  19. Amyloiddeposition and regional grey matter atrophy rates in dementia with Lewy bodies.

    PubMed

    Sarro, Lidia; Senjem, Matthew L; Lundt, Emily S; Przybelski, Scott A; Lesnick, Timothy G; Graff-Radford, Jonathan; Boeve, Bradley F; Lowe, Val J; Ferman, Tanis J; Knopman, David S; Comi, Giancarlo; Filippi, Massimo; Petersen, Ronald C; Jack, Clifford R; Kantarci, Kejal

    2016-10-01

    Alzheimer's disease pathology frequently coexists with Lewy body disease at autopsy in patients with probable dementia with Lewy bodies. More than half of patients with probable dementia with Lewy bodies have high amyloiddeposition as measured with (11)C-Pittsburgh compound B binding on positron emission tomography. Biomarkers of amyloiddeposition precede neurodegeneration on magnetic resonance imaging during the progression of Alzheimer's disease, but little is known about how amyloiddeposition relates to longitudinal progression of atrophy in patients with probable dementia with Lewy bodies. We investigated the associations between baseline (11)C-Pittsburgh compound B binding on positron emission tomography and the longitudinal rates of grey matter atrophy in a cohort of clinically diagnosed patients with dementia with Lewy bodies (n = 20), who were consecutively recruited to the Mayo Clinic Alzheimer's Disease Research Centre. All patients underwent (11)C-Pittsburgh compound B positron emission tomography and magnetic resonance imaging examinations at baseline. Follow-up magnetic resonance imaging was performed after a mean (standard deviation) interval of 2.5 (1.1) years. Regional grey matter loss was determined on three-dimensional T1-weighted magnetic resonance imaging with the tensor-based morphometry-symmetric normalization technique. Linear regression was performed between baseline (11)C-Pittsburgh compound B standard unit value ratio and longitudinal change in regional grey matter volumes from an in-house modified atlas. We identified significant associations between greater baseline (11)C-Pittsburgh compound B standard unit value ratio and greater grey matter loss over time in the posterior cingulate gyrus, lateral and medial temporal lobe, and occipital lobe as well as caudate and putamen nuclei, after adjusting for age (P < 0.05). Greater baseline (11)C-Pittsburgh compound B standard unit value ratio was also associated with greater

  20. Amyloid Angiopathy and Variability in Amyloid β Deposition Is Determined by Mutation Position in Presenilin-1-Linked Alzheimer’s Disease

    PubMed Central

    Mann, David M. A.; Pickering-Brown, Stuart M.; Takeuchi, Ayano; Iwatsubo, Takeshi

    2001-01-01

    The presenilins (PSs) are components of large molecular complexes that contain β-catenin and function as γ-secretase. We report here a striking correlation between amyloid angiopathy and the location of mutation in PS-1 linked Alzheimer’s disease. The amount of amyloid β protein, Aβ42(43), but not Aβ40, deposited in the frontal cortex of the brain is increased in 54 cases of early-onset familial Alzheimer’s disease, encompassing 25 mutations in the presenilin-1 (PS-1) gene, compared to sporadic Alzheimer’s disease. The amount of Aβ40 in PS-1 Alzheimer’s disease varied according to the copy number of ε4 alleles of the Apolipoprotein E gene. Although the amounts of Aβ40 and Aβ42(43) deposited did not correlate with the genetic location of the mutation in a strict linear sense, the histological profile did so vary. Cases with mutations between codon 1 and 200 showed, in frontal cortex, many diffuse plaques, few cored plaques, and mild or moderate amyloid angiopathy. Cases with mutations occurring after codon 200 also showed many diffuse plaques, but the number and size of cored plaques were increased (even when ε4 allele was not present) and these were often clustered around blood vessels severely affected by amyloid angiopathy. Similarly, diverging histological profiles, mainly according to the degree of amyloid angiopathy, were seen in the cerebellum. Mutations in the PS-1 gene may therefore alter the topology of the PS-1 protein so as to favor Aβ formation and deposition, generally, but also to facilitate amyloid angiopathy particularly in cases in which the mutation lies beyond codon 200. Finally we report that the amount of Aβ42(43) deposited in the brain correlated with the amount of this produced in culture by cells bearing the equivalent mutations. PMID:11395394

  1. Neural compensation in older people with brain β-amyloid deposition

    PubMed Central

    Elman, Jeremy A.; Oh, Hwamee; Madison, Cindee M.; Baker, Suzanne L.; Vogel, Jacob W.; Marks, Shawn M.; Crowley, Sam; O'Neil, James P.; Jagust, William J.

    2014-01-01

    The recruitment of additional neural resources may allow elderly adults to maintain normal cognition despite β-amyloid (Aβ) plaques. Previous fMRI studies have reported such hyperactivation, but it is currently unclear if these increases represent compensation or aberrant over-excitation. We found that older adults with Aβ deposition had reduced deactivations in task negative regions, but increased activation in task positive regions related to more detailed memory encoding. The association between higher activity levels and more detailed memories suggests that Aβ-related hyperactivation is a compensatory mechanism, potentially reflecting brain plasticity in response to Aβ deposition. PMID:25217827

  2. Independent contribution of temporal beta-amyloid deposition to memory decline in the pre-dementia phase of Alzheimer's disease.

    PubMed

    Chételat, Gaël; Villemagne, Victor L; Pike, Kerryn E; Ellis, Kathryn A; Bourgeat, Pierrick; Jones, Gareth; O'Keefe, Graeme J; Salvado, Olivier; Szoeke, Cassandra; Martins, Ralph N; Ames, David; Masters, Colin L; Rowe, Christopher C

    2011-03-01

    The relationship between β-amyloid deposition and memory deficits in early Alzheimer's disease is unresolved, as past studies show conflicting findings. The present study aims to determine the relative contribution of regional β-amyloid deposition, hippocampal atrophy and white matter integrity to episodic memory deficits in non-demented older individuals harbouring one of the characteristic hallmarks of Alzheimer's disease, i.e. with β-amyloid pathology. Understanding these relationships is critical for effective therapeutic development. Brain magnetic resonance imaging and [(11)C]Pittsburgh Compound B-positron emission tomography scans were obtained in 136 non-demented individuals aged over 60 years, including 93 healthy elderly and 43 patients with mild cognitive impairment. Voxel-based correlations were computed between a memory composite score and grey matter volume, white matter volume and β-amyloid deposition imaging datasets. Hierarchical linear regression analyses were then performed using values extracted in regions of most significant correlations to determine the relative contribution of each modality to memory deficits. All analyses were conducted pooling all groups together as well as within separate subgroups of cognitively normal elderly, patients with mild cognitive impairment and individuals with high versus low neocortical β-amyloid. Brain areas of highest correlation with episodic memory deficits were the hippocampi for grey matter volume, the perforant path for white matter volume and the temporal neocortex for β-amyloid deposition. When considering these three variables together, only hippocampal volume and temporal β-amyloid deposition provided independent contributions to memory deficits. In contrast to global β-amyloid deposition, temporal β-amyloid deposition was still related to memory independently from hippocampal atrophy within subgroups of cognitively normal elderly, patients with mild cognitive impairment or cases with high

  3. Myocardial infarction with "clean coronaries" caused by amyloid light-chain AL amyloidosis: a case report and literature review.

    PubMed

    Tsai, Stephanie B; Seldin, David C; Wu, Hao; O'Hara, Carl; Ruberg, Frederick L; Sanchorawala, Vaishali

    2011-09-01

    In AL (amyloid light-chain) amyloidosis, the greatest risk of death occurs in patients with cardiac involvement, who typically develop diastolic dysfunction and then systolic heart failure, with predisposition to arrhythmias and sudden death. Here, we present an alternate variation of cardiac amyloidosis. This patient had recent non-obstructive coronary angiography, yet suffered a fatal myocardial infarction shortly after stem cell collection and mobilization in preparation for treatment with high-dose melphalan and autologous stem cell transplantation (HDM/SCT). On autopsy, widespread deposition of amyloid was found in the small vessels of the heart with evidence of associated acute infarction. While the typical presentation of cardiac amyloidosis is an infiltrating restrictive cardiomyopathy, this case report and literature review illustrate that ischemic small vessel amyloidosis may also occur. Small vessel coronary disease and associated myocardial ischemia should be considered in patients with AL amyloidosis with angina, as its presence may increase treatment-related complications. Contemporary testing should aim to detect both forms of cardiac amyloidosis, which may impact management and prognosis.

  4. Parenchymal cystatin C focal deposits and glial scar formation around brain arteries in Hereditary Cystatin C Amyloid Angiopathy.

    PubMed

    Osk Snorradottir, Asbjorg; Isaksson, Helgi J; Kaeser, Stephan A; Skodras, Angelos A; Olafsson, Elias; Palsdottir, Astridur; Thor Bragason, Birkir

    2015-10-05

    Hereditary Cystatin C Amyloid Angiopathy (HCCAA) is an amyloid disorder in Icelandic families caused by an autosomal dominant mutation in the cystatin C gene. Mutant cystatin C forms amyloid deposits in brain arteries and arterioles which are associated with changes in the arterial wall structure, notably deposition of extracellular matrix proteins. In this post-mortem study we examined the neuroinflammatory response relative to the topographical distribution of cystatin C deposition, and associated haemorrhages, in the leptomeninges, cerebrum, cerebellum, thalamus, and midbrain of HCCAA patients. Cystatin C was deposited in all brain areas, grey and white matter alike, most prominently in arteries and arterioles; capillaries and veins were not, or minimally, affected. We also observed perivascular deposits and parenchymal focal deposits proximal to affected arteries. This study shows for the first time, that cystatin C does not exclusively form CAA and perivascular amyloid but also focal deposits in the brain parenchyma. Haemorrhages were observed in all patients and occurred in all brain areas, variable between patients. Microinfarcts were observed in 34.6% of patients. The neuroinflammatory response was limited to the close vicinity of affected arteries and perivascular as well as parenchymal focal deposits. Taken together with previously reported arterial accumulation of extracellular matrix proteins in HCCAA, our results indicate that the central nervous system pathology of HCCAA is characterised by the formation of a glial scar within and around affected arteries.

  5. [Hippocampal and cognitive alterations precede amyloid deposition in a mouse model for Alzheimer's disease].

    PubMed

    Beauquis, Juan; Vinuesa, Angeles; Pomilio, Carlos; Pavía, Patricio; Saravia, Flavia

    2014-01-01

    Although there is strong evidence about neuronal and glial disturbances at advanced stages of Alzheimer's disease, less attention has been directed to early, preamyloid changes that could contribute to the progression of the disease. We evaluated neuronal and glial morphological changes and behavioral disturbances in PDAPP-J20 transgenic (Tg) mice, carrying mutated human APP gene (amyloid precursor protein), at 5 months of age, before brain amyloid deposition occurs. Using NeuN immunohistochemistry we found decreased numbers of pyramidal and granular neurons in the hippocampus associated with a reduction of hippocampal volume in Tg mice compared with controls. Neurogenesis was impaired, evidenced by means of DCX immunohistochemistry in the dentate gyrus. In the CA3 region we found a decreased density of synaptophysin, suggesting synaptic disturbance, but no changes were found in CA1 synaptic spine density. Using confocal microscopy we observed decreased number and cell complexity of GFAP+ astrocytes, indicating potential glial atrophy. Cognitive impairment (novel location recognition test) and increased anxiety (open field) were detected in Tg mice, associated with more c-Fos+ nuclei in the amygdala, possibly indicating a role for emotionality in early stages of the disease. The study of early alterations in the course of amyloid pathology could contribute to the development of diagnostic and preventive strategies.

  6. Early-onset amyloid deposition and cognitive deficits in transgenic mice expressing a double mutant form of amyloid precursor protein 695.

    PubMed

    Chishti, M A; Yang, D S; Janus, C; Phinney, A L; Horne, P; Pearson, J; Strome, R; Zuker, N; Loukides, J; French, J; Turner, S; Lozza, G; Grilli, M; Kunicki, S; Morissette, C; Paquette, J; Gervais, F; Bergeron, C; Fraser, P E; Carlson, G A; George-Hyslop, P S; Westaway, D

    2001-06-15

    We have created early-onset transgenic (Tg) models by exploiting the synergistic effects of familial Alzheimer's disease mutations on amyloid beta-peptide (Abeta) biogenesis. TgCRND8 mice encode a double mutant form of amyloid precursor protein 695 (KM670/671NL+V717F) under the control of the PrP gene promoter. Thioflavine S-positive Abeta amyloid deposits are present at 3 months, with dense-cored plaques and neuritic pathology evident from 5 months of age. TgCRND8 mice exhibit 3,200-4,600 pmol of Abeta42 per g brain at age 6 months, with an excess of Abeta42 over Abeta40. High level production of the pathogenic Abeta42 form of Abeta peptide was associated with an early impairment in TgCRND8 mice in acquisition and learning reversal in the reference memory version of the Morris water maze, present by 3 months of age. Notably, learning impairment in young mice was offset by immunization against Abeta42 (Janus, C., Pearson, J., McLaurin, J., Mathews, P. M., Jiang, Y., Schmidt, S. D., Chishti, M. A., Horne, P., Heslin, D., French, J., Mount, H. T. J., Nixon, R. A., Mercken, M., Bergeron, C., Fraser, P. E., St. George-Hyslop, P., and Westaway, D. (2000) Nature 408, 979-982). Amyloid deposition in TgCRND8 mice was enhanced by the expression of presenilin 1 transgenes including familial Alzheimer's disease mutations; for mice also expressing a M146L+L286V presenilin 1 transgene, amyloid deposits were apparent by 1 month of age. The Tg mice described here suggest a potential to investigate aspects of Alzheimer's disease pathogenesis, prophylaxis, and therapy within short time frames.

  7. Exercise is more effective than diet control in preventing high fat diet-induced β-amyloid deposition and memory deficit in amyloid precursor protein transgenic mice.

    PubMed

    Maesako, Masato; Uemura, Kengo; Kubota, Masakazu; Kuzuya, Akira; Sasaki, Kazuki; Hayashida, Naoko; Asada-Utsugi, Megumi; Watanabe, Kiwamu; Uemura, Maiko; Kihara, Takeshi; Takahashi, Ryosuke; Shimohama, Shun; Kinoshita, Ayae

    2012-06-29

    Accumulating evidence suggests that some dietary patterns, specifically high fat diet (HFD), increase the risk of developing sporadic Alzheimer disease (AD). Thus, interventions targeting HFD-induced metabolic dysfunctions may be effective in preventing the development of AD. We previously demonstrated that amyloid precursor protein (APP)-overexpressing transgenic mice fed HFD showed worsening of cognitive function when compared with control APP mice on normal diet. Moreover, we reported that voluntary exercise ameliorates HFD-induced memory impairment and β-amyloid (Aβ) deposition. In the present study, we conducted diet control to ameliorate the metabolic abnormality caused by HFD on APP transgenic mice and compared the effect of diet control on cognitive function with that of voluntary exercise as well as that of combined (diet control plus exercise) treatment. Surprisingly, we found that exercise was more effective than diet control, although both exercise and diet control ameliorated HFD-induced memory deficit and Aβ deposition. The production of Aβ was not different between the exercise- and the diet control-treated mice. On the other hand, exercise specifically strengthened the activity of neprilysin, the Aβ-degrading enzyme, the level of which was significantly correlated with that of deposited Aβ in our mice. Notably, the effect of the combination treatment (exercise and diet control) on memory and amyloid pathology was not significantly different from that of exercise alone. These studies provide solid evidence that exercise is a useful intervention to rescue HFD-induced aggravation of cognitive decline in transgenic model mice of AD.

  8. Tau and Beta-Amyloid Deposition, Microhemorrhage and Brain Function after Traumatic Brain Injury in War Veterans

    DTIC Science & Technology

    2015-10-01

    AWARD NUMBER: W81XWH-14-1-0418 TITLE: Tau and Beta-Amyloid Deposition, Microhemorrhage and Brain Function after Traumatic Brain Injury in War...COVERED 25 Sep 2014 - 24 Sep 2015 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Tau and Beta-Amyloid Deposition, Microhemorrhage and Brain Function after...Traumatic Brain Injury in War Veterans 5b. GRANT NUMBER W81XWH-14-1-0418 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Christopher Rowe 5d. PROJECT

  9. Cerebral β-amyloid deposition predicts HIV-associated neurocognitive disorders in APOE ε4 carriers

    PubMed Central

    Soontornniyomkij, Virawudh; Moore, David J.; Gouaux, Ben; Soontornniyomkij, Benchawanna; Tatro, Erick T.; Umlauf, Anya; Masliah, Eliezer; Levine, Andrew J.; Singer, Elyse J.; Vinters, Harry V.; Gelman, Benjamin B.; Morgello, Susan; Cherner, Mariana; Grant, Igor; Achim, Cristian L.

    2013-01-01

    Objective The apolipoprotein E (APOE) ε4 allele enhances cerebral accumulation of β-amyloid (Aβ) and is a major risk factor for sporadic Alzheimer’s disease (AD). We hypothesized that HIV-associated neurocognitive disorders (HAND) would be associated with the APOE ε4 genotype and cerebral Aβ deposition. Design Clinico-pathological study of HIV-infected adults from four prospective cohorts in the U.S. National NeuroAIDS Tissue Consortium. Methods We used multivariable logistic regressions to model outcomes (Aβ plaques [immunohistochemistry] and HAND [standard criteria]) on predictors (APOE ε4 [allelic discrimination assay], older age [≥ 50 years], Aβ plaques, and their two-way interactions) and co-morbid factors. Results Isocortical Aβ deposits generally occurred as diffuse plaques and mild to moderate amyloid angiopathy. Isocortical phospho-Tau-immunoreactive neurofibrillary lesions were sparse. The APOE ε4 and older age were independently associated with the presence of Aβ plaques (adjusted odds ratio [OR] 10.16 and 5.77 [95% confidence interval (CI) 2.89–35.76 and 1.91–17.48], P=0.0003 and 0.0019, respectively, n=96). The probability of HAND was increased in the presence of Aβ plaques among APOE ε4 carriers (adjusted OR 30.00 [95% CI 1.41–638.63], P=0.029, n=15), but not in non-ε4 carriers (n=57). Conclusion The APOE ε4 and older age increased the likelihood of cerebral Aβ plaque deposition in HIV-infected adults. Generally Aβ plaques in HIV brains were immunohistologically different from those in symptomatic AD brains. Nonetheless, Aβ plaques were associated with HAND among APOE ε4 carriers. The detection of APOE ε4 genotype and cerebral Aβ deposition biomarkers may be useful in identifying living HAND subjects who could benefit from Aβ-targeted therapies. PMID:23018443

  10. Astrocytic LRP1 Mediates Brain Aβ Clearance and Impacts Amyloid Deposition.

    PubMed

    Liu, Chia-Chen; Hu, Jin; Zhao, Na; Wang, Jian; Na, Wang; Cirrito, John R; Kanekiyo, Takahisa; Holtzman, David M; Bu, Guojun

    2017-03-08

    Accumulation and deposition of amyloid-β (Aβ) in the brain represents an early and perhaps necessary step in the pathogenesis of Alzheimer's disease (AD). Aβ accumulation leads to the formation of Aβ aggregates which may directly and indirectly lead to eventual neurodegeneration. While Aβ production is accelerated in many familial forms of early-onset AD, increasing evidence indicates that impaired clearance of Aβ is more evident in late-onset AD. To uncover the mechanisms underlying impaired Aβ clearance in AD, we examined the role of low-density lipoprotein receptor-related protein 1 (LRP1) in astrocytes. Although LRP1 has been shown to play critical roles in brain Aβ metabolism in neurons and vascular mural cells, its role in astrocytes, the most abundant cell type in the brain responsible for maintaining neuronal homeostasis, remains unclear. Here, we show that astrocytic LRP1 plays a critical role in brain Aβ clearance. LRP1 knockdown in primary astrocytes resulted in decreased cellular Aβ uptake and degradation. In addition, silencing of LRP1 in astrocytes led to down-regulation of several major Aβ-degrading enzymes, including matrix metalloproteases MMP2, MMP9 and insulin-degrading enzyme (IDE). More important, conditional knockout of the Lrp1 gene in astrocytes in the background of APP/PS1 mice impaired brain Aβ clearance, exacerbated Aβ accumulation and accelerated amyloid plaque deposition without affecting its production. Together, our results demonstrate that astrocytic LRP1 plays an important role in Aβ metabolism and that restoring LRP1 expression and function in the brain could be an effective strategy to facilitate Aβ clearance and counter amyloid pathology in AD.SIGNIFICANCE STATEMENTAstrocytes represent a major cell type regulating brain homeostasis; however, their roles in brain clearance of amyloid-β (Aβ) and underlying mechanism are not clear. In this study, we used both cellular models and conditional knockout mouse models to

  11. Markers of cholesterol transport are associated with amyloid deposition in the brain.

    PubMed

    Hughes, Timothy M; Lopez, Oscar L; Evans, Rhobert W; Kamboh, M Ilyas; Williamson, Jeff D; Klunk, William E; Mathis, Chester A; Price, Julie C; Cohen, Ann D; Snitz, Beth E; Dekosky, Steven T; Kuller, Lewis H

    2014-04-01

    Cholesterol is implicated in the development of late-onset Alzheimer's disease (AD). We sought to determine the associations between beta amyloid (Aβ) plaque deposition in vivo using Pittsburgh compound B (PiB) and several indices of cholesterol homeostasis (i.e., total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, apolipoprotein E (ApoE), clusterin, oxysterol metabolites of cholesterol, and previously reported genes associated with late-onset AD) in 175 nondemented elderly subjects. High Aβ deposition was associated significantly with a lower Mini-Mental State Examination score (<27 points, p = 0.04), high systolic blood pressure (p = 0.04), carrying the apolipoprotein E epsilon 4 allele (p < 0.01), and lower plasma ApoE levels (p = 0.02), and variation in the ABCA7 (p = 0.02) and EPHA1 genes (p = 0.02). Cholesterol measures were not related to Aβ deposition in this cohort of nondemented elderly adults. However, plasma and genetic factors relating to cholesterol transport were associated with Aβ deposition in the brain. A better understanding of cholesterol transport mechanisms may lead to the design of potential targets for the prevention of Aβ deposition in the brain.

  12. Clinically different stages of Alzheimer's disease associated by amyloid deposition with [11C]-PIB PET imaging.

    PubMed

    Hatashita, Shizuo; Yamasaki, Hidetomo

    2010-01-01

    We investigated whether [11C]-PIB PET detects underlying amyloid deposition at clinically different stages of Alzheimer's disease (AD) and preclinical dementia. The Japanese cohort of 214 subjects underwent cognitive testing and 60-min dynamic [11C]-PIB PET. [11C]-PIB data were acquired from 35-60 min after injection. Regions of interest were defined on co-registered MRI. Distribution volume ratios (DVR) of PIB retention were determined using Logan graphical analysis. All 56 patients with AD showed a robust increase in PIB retention in cortical areas (typical PIB AD-pattern). A mean DVR value in 11 patients with moderate AD (CDR: 2.1 ± 0.4) showed significantly higher PIB retention (2.38 ± 0.42, p < 0.01) than amyloid-negative healthy control (HC) subjects. The DVR values in 23 patients with very mild AD (CDR: 0.5) and 22 patients with mild AD (CDR: 1.0) were 2.32 ± 0.45 and 2.34 ± 0.42, respectively, similar to moderate AD. In contrast, 28 (48%) of the 58 mild cognitive impairment (MCI) patients (MMSE: 27.3 ± 1.7) showed a typical AD-like pattern with a DVR value of 2.07 ± 0.34. Further, 17 (18%) of 91 HC subjects had a typical AD-like pattern with a DVR value of 2.06 ± 0.28. They did not significantly differ from very mild AD. The prevalence of AD among the 53 amyloid positive patients aged 75 years or older increased greatly to 74% whereas that of amyloid positive HC decreased by only 9% and amyloid positive MCI by 17%. Prodromal AD and AD dementia is identified, based on cognitive function and amyloid deposition by PIB PET imaging. Further, the cortical amyloid deposition could be detected at preclinical stage of AD.

  13. Dynamic relationships between age, amyloiddeposition, and glucose metabolism link to the regional vulnerability to Alzheimer's disease.

    PubMed

    Oh, Hwamee; Madison, Cindee; Baker, Suzanne; Rabinovici, Gil; Jagust, William

    2016-08-01

    SEE HANSSON AND GOURAS DOI101093/AWW146 FOR A SCIENTIFIC COMMENTARY ON THIS ARTICLE: Although some brain regions such as precuneus and lateral temporo-parietal cortex have been shown to be more vulnerable to Alzheimer's disease than other areas, a mechanism underlying the differential regional vulnerability to Alzheimer's disease remains to be elucidated. Using fluorodeoxyglucose and Pittsburgh compound B positron emission tomography imaging glucose metabolism and amyloiddeposition, we tested whether and how life-long changes in glucose metabolism relate to amyloiddeposition and Alzheimer's disease-related hypometabolism. Nine healthy young adults (age range: 20-30), 96 cognitively normal older adults (age range: 61-96), and 20 patients with Alzheimer's disease (age range: 50-90) were scanned using fluorodeoxyglucose and Pittsburgh compound B positron emission tomography. Among cognitively normal older subjects, 32 were further classified as amyloid-positive, with 64 as amyloid-negative. To assess the contribution of glucose metabolism to the regional vulnerability to amyloiddeposition, we defined the highest and lowest metabolic regions in young adults and examined differences in amyloid deposition between these regions across groups. Two-way analyses of variance were conducted to assess regional differences in age and amyloid-β-related changes in glucose metabolism. Multiple regressions were applied to examine the association between amyloiddeposition and regional glucose metabolism. Both region of interest and whole-brain voxelwise analyses were conducted to complement and confirm the results derived from the other approach. Regional differences in glucose metabolism between the highest and lowest metabolism regions defined in young adults (T = 12.85, P < 0.001) were maintained both in Pittsburgh compound B-negative cognitively normal older subjects (T = 6.66, P < 0.001) and Pittsburgh compound B-positive cognitively normal older subjects (T

  14. Cryptotanshinone, a compound from Salvia miltiorrhiza modulates amyloid precursor protein metabolism and attenuates beta-amyloid deposition through upregulating alpha-secretase in vivo and in vitro.

    PubMed

    Mei, Zhengrong; Zhang, Fangyan; Tao, Liang; Zheng, Wenhua; Cao, Yingnan; Wang, Zhaohe; Tang, Shu; Le, Kang; Chen, Shaorui; Pi, Rongbiao; Liu, Peiqing

    2009-03-13

    The amyloid precursor protein (APP) is cleaved enzymatically by non-amyloidogenic and amyloidogenic pathways. alpha-Secretase cleaves APP within beta-amyloid protein (Abeta) sequence, resulting in the release of a secreted fragment of APP (sAPPalpha) and precluding Abeta generation. Cryptotanshinone (CTS), an active component of the medicinal herb Salvia miltiorrhiza, has been shown to improve learning and memory in several pharmacological models of Alzheimer's disease (AD). However, the effects of CTS on the Abeta plaque pathology and the APP processing in AD are unclear. Here we reported that CTS strongly attenuated amyloid plaque deposition in the brain of APP/PS1 transgenic mice. In addition, CTS significantly improved spatial learning and memory in APP/PS1 mice assessed by the Morris water maze testing. To define the exact molecular mechanisms involved in the beneficial effects of CTS, we investigated the effects of the CTS on APP processing in rat cortical neuronal cells overexpressing Swedish mutant human APP695. CTS was found to decrease Abeta generation in concentration-dependent (0-10muM) manner. Interestingly, the N-terminal APP cleavage product, sAPPalpha was markedly increased by CTS. Further study showed that alpha-secretase activity was increased by CTS. Taken together, our results suggested CTS improved the cognitive ability in AD transgenic mice and promoted APP metabolism toward the non-amyloidogenic products pathway in rat cortical neuronal cells. CTS shows a promising novel way for the therapy of AD.

  15. Patients that have Undergone Hemodialysis Exhibit Lower Amyloid Deposition in the Brain: Evidence Supporting a Therapeutic Strategy for Alzheimer's Disease by Removal of Blood Amyloid.

    PubMed

    Sakai, Kazuyoshi; Senda, Takao; Hata, Ryuji; Kuroda, Makoto; Hasegawa, Midori; Kato, Masao; Abe, Masato; Kawaguchi, Kazunori; Nakai, Shigeru; Hiki, Yoshiyuki; Yuzawa, Yukio; Kitaguchi, Nobuya

    2016-01-01

    As a proof of concept that removal of blood amyloid-β (Aβ) can reduce Aβ deposition in the brains of patients with Alzheimer's disease, cortices of patients who had undergone hemodialysis (HD), which removes Aβ from the blood, were histochemically analyzed; postmortem brain sections were stained with anti-Aβ antibodies. Brains from patients who had undergone HD had significantly fewer senile plaques than those of patient who had not undergone HD. This significant difference was also confirmed by silver staining. Our findings suggest that removal of blood Aβ by hemodialysis results in lower accumulation of Aβ in the brain.

  16. Episodic memory loss is related to hippocampal-mediated beta-amyloid deposition in elderly subjects.

    PubMed

    Mormino, E C; Kluth, J T; Madison, C M; Rabinovici, G D; Baker, S L; Miller, B L; Koeppe, R A; Mathis, C A; Weiner, M W; Jagust, W J

    2009-05-01

    Although beta-amyloid (Abeta) plaques are a primary diagnostic criterion for Alzheimer's disease, this pathology is commonly observed in the brains of non-demented older individuals. To explore the importance of this pathology in the absence of dementia, we compared levels of amyloid deposition (via 'Pittsburgh Compound-B' (PIB) positron emission tomography (PET) imaging) to hippocampus volume (HV) and episodic memory (EM) in three groups: (i) normal controls (NC) from the Berkeley Aging Cohort (BAC NC, n = 20); (ii) normal controls (NC) from the Alzheimer's disease neuroimaging initiative (ADNI NC, n = 17); and (iii) PIB+ mild cognitive impairment subjects from the ADNI (ADNI PIB+ MCI, n = 39). Age, gender and education were controlled for in each statistical model, and HV was adjusted for intracranial volume (aHV). In BAC NC, elevated PIB uptake was significantly associated with smaller aHV (P = 0.0016) and worse EM (P = 0.0086). Within ADNI NC, elevated PIB uptake was significantly associated with smaller aHV (P = 0.047) but not EM (P = 0.60); within ADNI PIB+ MCI, elevated PIB uptake was significantly associated with both smaller aHV (P = 0.00070) and worse EM (P = 0.046). To further understand these relationships, a recursive regression procedure was conducted within all ADNI NC and PIB+ MCI subjects (n = 56) to test the hypothesis that HV mediates the relationship between Abeta and EM. Significant correlations were found between PIB index and EM (P = 0.0044), PIB index and aHV (P < 0.0001), as well as between aHV and EM (P < 0.0001). When both aHV and PIB were included in the same model to predict EM, aHV remained significant (P = 0.0015) whereas PIB index was no longer significantly associated with EM (P = 0.50). These results are consistent with a model in which Abeta deposition, hippocampal atrophy, and EM occur sequentially in elderly subjects, with Abeta deposition as the primary event in this cascade. This pattern suggests that declining EM in older

  17. Deposition of amyloid β in the walls of human leptomeningeal arteries in relation to perivascular drainage pathways in cerebral amyloid angiopathy☆

    PubMed Central

    Keable, Abby; Fenna, Kate; Yuen, Ho Ming; Johnston, David A.; Smyth, Neil R.; Smith, Colin; Salman, Rustam Al-Shahi; Samarasekera, Neshika; Nicoll, James A.R.; Attems, Johannes; Kalaria, Rajesh N.; Weller, Roy O.; Carare, Roxana O.

    2016-01-01

    Deposition of amyloid β (Aβ) in the walls of cerebral arteries as cerebral amyloid angiopathy (CAA) suggests an age-related failure of perivascular drainage of soluble Aβ from the brain. As CAA is associated with Alzheimer's disease and with intracerebral haemorrhage, the present study determines the unique sequence of changes that occur as Aβ accumulates in artery walls. Paraffin sections of post-mortem human occipital cortex were immunostained for collagen IV, fibronectin, nidogen 2, Aβ and smooth muscle actin and the immunostaining was analysed using Image J and confocal microscopy. Results showed that nidogen 2 (entactin) increases with age and decreases in CAA. Confocal microscopy revealed stages in the progression of CAA: Aβ initially deposits in basement membranes in the tunica media, replaces first the smooth muscle cells and then the connective tissue elements to leave artery walls completely or focally replaced by Aβ. The pattern of development of CAA in the human brain suggests expansion of Aβ from the basement membranes to progressively replace all tissue elements in the artery wall. Establishing this full picture of the development of CAA is pivotal in understanding the clinical presentation of CAA and for developing therapies to prevent accumulation of Aβ in artery walls. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock. PMID:26327684

  18. Clinical and MRI models predicting amyloid deposition in progressive aphasia and apraxia of speech.

    PubMed

    Whitwell, Jennifer L; Weigand, Stephen D; Duffy, Joseph R; Strand, Edythe A; Machulda, Mary M; Senjem, Matthew L; Gunter, Jeffrey L; Lowe, Val J; Jack, Clifford R; Josephs, Keith A

    2016-01-01

    Beta-amyloid (Aβ) deposition can be observed in primary progressive aphasia (PPA) and progressive apraxia of speech (PAOS). While it is typically associated with logopenic PPA, there are exceptions that make predicting Aβ status challenging based on clinical diagnosis alone. We aimed to determine whether MRI regional volumes or clinical data could help predict Aβ deposition. One hundred and thirty-nine PPA (n = 97; 15 agrammatic, 53 logopenic, 13 semantic and 16 unclassified) and PAOS (n = 42) subjects were prospectively recruited into a cross-sectional study and underwent speech/language assessments, 3.0 T MRI and C11-Pittsburgh Compound B PET. The presence of Aβ was determined using a 1.5 SUVR cut-point. Atlas-based parcellation was used to calculate gray matter volumes of 42 regions-of-interest across the brain. Penalized binary logistic regression was utilized to determine what combination of MRI regions, and what combination of speech and language tests, best predicts Aβ (+) status. The optimal MRI model and optimal clinical model both performed comparably in their ability to accurately classify subjects according to Aβ status. MRI accurately classified 81% of subjects using 14 regions. Small left superior temporal and inferior parietal volumes and large left Broca's area volumes were particularly predictive of Aβ (+) status. Clinical scores accurately classified 83% of subjects using 12 tests. Phonological errors and repetition deficits, and absence of agrammatism and motor speech deficits were particularly predictive of Aβ (+) status. In comparison, clinical diagnosis was able to accurately classify 89% of subjects. However, the MRI model performed well in predicting Aβ deposition in unclassified PPA. Clinical diagnosis provides optimum prediction of Aβ status at the group level, although regional MRI measurements and speech and language testing also performed well and could have advantages in predicting Aβ status in unclassified PPA subjects.

  19. Viscoelastic response of neural cells governed by the deposition of amyloid-β peptides (Aβ)

    NASA Astrophysics Data System (ADS)

    Gong, Ze; You, Ran; Chang, Raymond Chuen-Chung; Lin, Yuan

    2016-06-01

    Because of its intimate relation with Alzheimer's disease (AD), the question of how amyloid-β peptide (Aβ) deposition alters the membrane and cytoskeltal structure of neural cells and eventually their mechanical response has received great attention. In this study, the viscoelastic properties of primary neurons subjected to various Aβ treatments were systematically characterized using atomic force microrheology. It was found that both the storage ( G ') and loss ( G ″) moduli of neural cells are rate-dependent and grow by orders of magnitude as the driving frequency ω varies from 1 to 100 Hz. However, a much stronger frequency dependence was observed in the loss moduli (with a scaling exponent of ˜0.96) than that in G ' ( ˜ ω 0.2 ). Furthermore, both cell moduli increase gradually within the first 6 h of Aβ treatment before steady-state values are reached, with a higher dosage of Aβ leading to larger changes in cell properties. Interestingly, we showed that the measured neuron response can be well-explained by a power law structural damping model. Findings here establish a quantitative link between Aβ accumulation and the physical characteristics of neural cells and hence could provide new insights into how disorders like AD affect the progression of different neurological processes from a mechanics point of view.

  20. Optical-resolution photoacoustic microscopy of amyloiddeposits in vivo

    NASA Astrophysics Data System (ADS)

    Hu, Song; Yan, Ping; Maslov, Konstantin; Lee, Jin-Moo; Wang, Lihong V.

    2010-02-01

    Advances in high-resolution imaging have permitted microscopic observations within the brains of living animals. Applied to Alzheimer's disease (AD) mouse models, multiphoton microscopy has opened a new window to study the real-time appearance and growth of amyloid plaques. Here, we report an alternative technology-optical-resolution photoacoustic microscopy (OR-PAM)-for in vivo imaging of amyloid plaques in a transgenic AD mouse model. In vivo validation using multiphoton microscopy shows that OR-PAM has sufficient sensitivity and spatial resolution to identify amyloid plaques in living brains. In addition, with dual-wavelength OR-PAM, the three-dimensional morphology of amyloid plaques and the surrounding microvasculature are imaged simultaneously through a cranial window. In vivo transcranial OR-PAM imaging of amyloid plaques is highly likely once the imaging parameters are optimized.

  1. CCR5 deficiency accelerates lipopolysaccharide-induced astrogliosis, amyloid-beta deposit and impaired memory function

    PubMed Central

    Hwang, Jae Yeon; Kim, Ju Hwan; Yun, Na Young; Oh, Sang Yeon; Song, Ju Kyung; Seo, Hyun Ok; Kim, Yun-Bae; Hwang, Dae Yeon; Oh, Ki-Wan; Han, Sang-Bae; Hong, Jin Tae

    2016-01-01

    Chemokine receptors are implicated in inflammation and immune responses. Neuro-inflammation is associated with activation of astrocyte and amyloid-beta (Aβ) generations that lead to pathogenesis of Alzheimer disease (AD). Previous our study showed that deficiency of CC chemokine receptor 5 (CCR5) results in activation of astrocytes and Aβ deposit, and thus memory dysfunction through increase of CC chemokine receptor 2 (CCR2) expression. CCR5 knockout mice were used as an animal model with memory dysfunction. For the purpose LPS was injected i.p. daily (0.25 mg/kg/day). The memory dysfunctions were much higher in LPS-injected CCR5 knockout mice compared to CCR5 wild type mice as well as non-injected CCR5 knockout mice. Associated with severe memory dysfuction in LPS injected CCR5 knockout mice, LPS injection significant increase expression of inflammatory proteins, astrocyte activation, expressions of β-secretase as well as Aβ deposition in the brain of CCR5 knockout mice as compared with that of CCR5 wild type mice. In CCR5 knockout mice, CCR2 expressions were high and co-localized with GFAP which was significantly elevated by LPS. Expression of monocyte chemoattractant protein-1 (MCP-1) which ligands of CCR2 also increased by LPS injection, and increment of MCP-1 expression is much higher in CCR5 knockout mice. BV-2 cells treated with CCR5 antagonist, D-ala-peptide T-amide (DAPTA) and cultured astrocytes isolated from CCR5 knockout mice treated with LPS (1 μg/ml) and CCR2 antagonist, decreased the NF-ĸB activation and Aβ level. These findings suggest that the deficiency of CCR5 enhances response of LPS, which accelerates to neuro-inflammation and memory impairment. PMID:26910914

  2. CCR5 deficiency accelerates lipopolysaccharide-induced astrogliosis, amyloid-beta deposit and impaired memory function.

    PubMed

    Hwang, Chul Ju; Park, Mi Hee; Hwang, Jae Yeon; Kim, Ju Hwan; Yun, Na Young; Oh, Sang Yeon; Song, Ju Kyung; Seo, Hyun Ok; Kim, Yun-Bae; Hwang, Dae Yeon; Oh, Ki-Wan; Han, Sang-Bae; Hong, Jin Tae

    2016-03-15

    Chemokine receptors are implicated in inflammation and immune responses. Neuro-inflammation is associated with activation of astrocyte and amyloid-beta (Aβ) generations that lead to pathogenesis of Alzheimer disease (AD). Previous our study showed that deficiency of CC chemokine receptor 5 (CCR5) results in activation of astrocytes and Aβ deposit, and thus memory dysfunction through increase of CC chemokine receptor 2 (CCR2) expression. CCR5 knockout mice were used as an animal model with memory dysfunction. For the purpose LPS was injected i.p. daily (0.25 mg/kg/day). The memory dysfunctions were much higher in LPS-injected CCR5 knockout mice compared to CCR5 wild type mice as well as non-injected CCR5 knockout mice. Associated with severe memory dysfuction in LPS injected CCR5 knockout mice, LPS injection significant increase expression of inflammatory proteins, astrocyte activation, expressions of β-secretase as well as Aβ deposition in the brain of CCR5 knockout mice as compared with that of CCR5 wild type mice. In CCR5 knockout mice, CCR2 expressions were high and co-localized with GFAP which was significantly elevated by LPS. Expression of monocyte chemoattractant protein-1 (MCP-1) which ligands of CCR2 also increased by LPS injection, and increment of MCP-1 expression is much higher in CCR5 knockout mice. BV-2 cells treated with CCR5 antagonist, D-ala-peptide T-amide (DAPTA) and cultured astrocytes isolated from CCR5 knockout mice treated with LPS (1 μg/ml) and CCR2 antagonist, decreased the NF-ĸB activation and Aβ level. These findings suggest that the deficiency of CCR5 enhances response of LPS, which accelerates to neuro-inflammation and memory impairment.

  3. Cortical Amyloid β Deposition and Current Depressive Symptoms in Alzheimer Disease and Mild Cognitive Impairment.

    PubMed

    Chung, Jun Ku; Plitman, Eric; Nakajima, Shinichiro; Chakravarty, M Mallar; Caravaggio, Fernando; Gerretsen, Philip; Iwata, Yusuke; Graff-Guerrero, Ariel

    2016-05-01

    Depressive symptoms are frequently seen in patients with dementia and mild cognitive impairment (MCI). Evidence suggests that there may be a link between current depressive symptoms and Alzheimer disease (AD)-associated pathological changes, such as an increase in cortical amyloid-β (Aβ). However, limited in vivo studies have explored the relationship between current depressive symptoms and cortical Aβ in patients with MCI and AD. Our study, using a large sample of 455 patients with MCI and 153 patients with AD from the Alzheimer's disease Neuroimaging Initiatives, investigated whether current depressive symptoms are related to cortical Aβ deposition. Depressive symptoms were assessed using the Geriatric Depression Scale and Neuropsychiatric Inventory-depression/dysphoria. Cortical Aβ was quantified using positron emission tomography with the Aβ probe(18)F-florbetapir (AV-45).(18)F-florbetapir standardized uptake value ratio (AV-45 SUVR) from the frontal, cingulate, parietal, and temporal regions was estimated. A global AV-45 SUVR, defined as the average of frontal, cingulate, precuneus, and parietal cortex, was also used. We observed that current depressive symptoms were not related to cortical Aβ, after controlling for potential confounds, including history of major depression. We also observed that there was no difference in cortical Aβ between matched participants with high and low depressive symptoms, as well as no difference between matched participants with the presence and absence of depressive symptoms. The association between depression and cortical Aβ deposition does not exist, but the relationship is highly influenced by stressful events in the past, such as previous depressive episodes, and complex interactions of different pathways underlying both depression and dementia.

  4. Mesangial proliferative glomerulonephritis associated with progressive amyloid deposition in hamsters experimentally infected with Leishmania donovani.

    PubMed Central

    Oliveira, A. V.; Roque-Barreira, M. C.; Sartori, A.; Campos-Neto, A.; Rossi, M. A.

    1985-01-01

    In the present work, 42 golden hamsters (Mesocricetus auratus) were infected by intracardiac injection of 5 X 10(6) amastigote forms of Leishmania donovani. Another group of 28 animals served as uninfected controls. Six hamsters of the infected group and four hamsters of the control group were selected randomly and sacrificed at Days 7, 14, 21, 28, 35, 42, and 49 after inoculation. The kidneys were studied by light microscopy, immunofluorescence and electron microscopy. The levels of serum and urinary immunoglobulins were determined. None of the control hamsters had kidney lesions. Light-microscopically the kidneys of infected hamsters showed a marked mesangial proliferation from Day 7 after infection. These changes were more pronounced at Day 21, when a discrete infiltration of mononuclear cells was frequent. These glomerular changes diminished after Day 28 and were replaced by deposits of amyloid. In the beginning these deposits were in the mesangium and progressively became more extensive, involving capillary loops, Bowman's capsule, and interstitium. The immunofluorescence study showed L donovani antigens and hamster immunoglobulins, primarily in the mesangial areas, by Days 7-14 after infection. These deposits extended into contiguous loops from Day 21 to Day 28. In the last 2 weeks the fluorescent staining for L donovani antigens remained intensely positive, whereas the staining for hamster immunoglobulins became moderate to slightly positive. The ultrastructural study revealed mesangial proliferation, mesangial and paramesangial electron-dense deposits, and amyloidosis in the glomeruli of infected animals. The serum immunoglobulins increased from Day 7 after infection, reaching a peak at Day 21 and falling thereafter until Day 49 to near control values. Immunoglobulins were detected in the urine of infected hamsters at day 21, increasing in amount thereafter. Since L donovani antigens and immunoglobulins were identified in the glomerular lesions, it is

  5. Cerebrolysin reduces amyloiddeposits, apoptosis and autophagy in the thalamus and improves functional recovery after cortical infarction.

    PubMed

    Xing, Shihui; Zhang, Jian; Dang, Chao; Liu, Gang; Zhang, Yusheng; Li, Jingjing; Fan, Yuhua; Pei, Zhong; Zeng, Jinsheng

    2014-02-15

    Focal cerebral infarction causes amyloid-β (Aβ) deposits and secondary thalamic neuronal degeneration. The present study aimed to determine the protective effects of Cerebrolysin on Aβ deposits and secondary neuronal damage in thalamus after cerebral infarction. At 24h after distal middle cerebral artery occlusion (MCAO), Cerebrolysin (5 ml/kg) or saline as control was once daily administered for consecutive 13 days by intraperitoneal injection. Sensory function and secondary thalamic damage were assessed with adhesive-removal test, Nissl staining and immunofluorescence at 14 days after MCAO. Aβ deposits, activity of β-site amyloid precursor protein-cleaving enzyme 1 (BACE1), apoptosis and autophagy were determined by TUNEL staining, immunofluorescence and immunoblot. The results showed that Cerebrolysin significantly improved sensory deficit compared to controls (p<0.05). Aβ deposits and BACE1 were obviously reduced by Cerebrolysin, which was accompanied by decreases in neuronal loss and astroglial activation compared to controls (all p < 0.05). Coincidently, Cerebrolysin markedly inhibited cleaved caspase-3, conversion of LC3-II, downregulation of Bcl-2 and upregulation of Bax in the ipsilateral thalamus compared to controls (all p<0.05). These findings suggest that Cerebrolysin reduces Aβ deposits, apoptosis and autophagy in the ipsilateral thalamus, which may be associated with amelioration of secondary thalamic damage and functional recovery after cerebral infarction.

  6. Laminar distribution of β-amyloid (Aβ) peptide deposits in the frontal lobe in familial and sporadic Alzheimer's disease.

    PubMed

    Armstrong, R A

    2015-01-01

    To determine whether genetic factors influence frontal lobe degeneration in Alzheimer's disease (AD), the laminar distributions of diffuse, primitive, and classic β-amyloid (Aβ) peptide deposits were compared in early-onset familial AD (EO-FAD) linked to mutations of the amyloid precursor protein (APP) or presenilin 1 (PSEN1) gene, late-onset familial AD (LO-FAD), and sporadic AD (SAD). The influence of apolipoprotein E (Apo E) genotype on laminar distribution was also studied. In the majority of FAD and SAD cases, maximum density of the diffuse and primitive Aβdeposits occurred in the upper cortical layers, whereas the distribution of the classic Aβ deposits was more variable, either occurring in the lower layers, or a double-peaked (bimodal) distribution was present, density peaks occurring in upper and lower layers. The cortical layer at which maximum density of Aβ deposits occurred and maximum density were similar in EO-FAD, LO-FAD and SAD. In addition, there were no significant differences in distributions in cases expressing Apo E ε4 alleles compared with cases expressing the ε2 or ε3 alleles. These results suggest that gene expression had relatively little effect on the laminar distribution of Aβ deposits in the frontal lobe of the AD cases studied. Hence, the pattern of frontal lobe degeneration in AD is similar regardless of whether it is associated with APP and PSEN1, mutation, allelic variation in Apo E, or with SAD.

  7. Oxidative stress accelerates amyloid deposition and memory impairment in a double-transgenic mouse model of Alzheimer's disease.

    PubMed

    Kanamaru, Takuya; Kamimura, Naomi; Yokota, Takashi; Iuchi, Katsuya; Nishimaki, Kiyomi; Takami, Shinya; Akashiba, Hiroki; Shitaka, Yoshitsugu; Katsura, Ken-Ichiro; Kimura, Kazumi; Ohta, Shigeo

    2015-02-05

    Oxidative stress is known to play a prominent role in the onset and early stage progression of Alzheimer's disease (AD). For example, protein oxidation and lipid peroxidation levels are increased in patients with mild cognitive impairment. Here, we created a double-transgenic mouse model of AD to explore the pathological and behavioral effects of oxidative stress. Double transgenic (APP/DAL) mice were constructed by crossing Tg2576 (APP) mice, which express a mutant form of human amyloid precursor protein (APP), with DAL mice expressing a dominant-negative mutant of mitochondrial aldehyde dehydrogenase 2 (ALDH2), in which oxidative stress is enhanced. Y-maze and object recognition tests were performed at 3 and 6 months of age to evaluate learning and memory. The accumulation of amyloid plaques, deposition of phosphorylated-tau protein, and number of astrocytes in the brain were assessed histopathologically at 3, 6, 9, and 12-15 months of age. The life span of APP/DAL mice was significantly shorter than that of APP or DAL mice. In addition, they showed accelerated amyloid deposition, tau phosphorylation, and gliosis. Furthermore, these mice showed impaired performance on Y-maze and object recognition tests at 3 months of age. These data suggest that oxidative stress accelerates cognitive dysfunction and pathological insults in the brain. APP/DAL mice could be a useful model for exploring new approaches to AD treatment.

  8. PGC-1α overexpression exacerbates β-amyloid and tau deposition in a transgenic mouse model of Alzheimer's disease

    PubMed Central

    Dumont, Magali; Stack, Cliona; Elipenahli, Ceyhan; Jainuddin, Shari; Launay, Nathalie; Gerges, Meri; Starkova, Natalia; Starkov, Anatoly A.; Calingasan, Noel Y.; Tampellini, Davide; Pujol, Aurora; Beal, M. Flint

    2014-01-01

    The peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α) interacts with various transcription factors involved in energy metabolism and in the regulation of mitochondrial biogenesis. PGC-1α mRNA levels are reduced in a number of neurodegenerative diseases and contribute to disease pathogenesis, since increased levels ameliorate behavioral defects and neuropathology of Huntington's disease, Parkinson's disease, and amyotrophic lateral sclerosis. PGC-1α and its downstream targets are reduced both in postmortem brain tissue of patients with Alzheimer's disease (AD) and in transgenic mouse models of AD. Therefore, we investigated whether increased expression of PGC-1α would exert beneficial effects in the Tg19959 transgenic mouse model of AD; Tg19959 mice express the human amyloid precursor gene (APP) with 2 familial AD mutations and develop increased β-amyloid levels, plaque deposition, and memory deficits by 2–3 mo of age. Rather than an improvement, the cross of the Tg19959 mice with mice overexpressing human PGC-1α exacerbated amyloid and tau accumulation. This was accompanied by an impairment of proteasome activity. PGC-1α overexpression induced mitochondrial abnormalities, neuronal cell death, and an exacerbation of behavioral hyperactivity in the Tg19959 mice. These findings show that PGC-1α overexpression exacerbates the neuropathological and behavioral deficits that occur in transgenic mice with mutations in APP that are associated with human AD.—Dumont, M., Stack, C., Elipenahli, C., Jainuddin, S., Launay, N., Gerges, M., Starkova, N., Starkov, A. A., Calingasan, N. Y., Tampellini, D., Pujol, A., Beal, M. F. PGC-1α overexpression exacerbates β-amyloid and tau deposition in a transgenic mouse model of Alzheimer's disease. PMID:24398293

  9. Microstructural Characterization of Laser-Deposited Al 4047 Alloy

    NASA Astrophysics Data System (ADS)

    Dinda, G. P.; Dasgupta, A. K.; Bhattacharya, S.; Natu, H.; Dutta, B.; Mazumder, J.

    2013-05-01

    Direct metal deposition (DMD) technology is a laser-aided rapid prototyping method that can be used to fabricate near net shape components from their CAD files. In the present study, a series of Al-Si samples have been deposited by DMD in order to optimize the laser deposition parameters to produce high quality deposit with minimum porosity and maximum deposition rate. This paper presents the microstructural evolution of the as-deposited Al 4047 sample produced with optimized process parameters. Optical, scanning, and transmission electron microscopes have been employed to characterize the microstructure of the deposit. The electron backscattered diffraction method was used to investigate the grain size distribution, grain boundary misorientation, and texture of the deposits. Metallographic investigation revealed that the microstructural morphology strongly varies with the location of the deposit. The layer boundaries consist of equiaxed Si particles distributed in the Al matrix. However, a systematic transition from columnar Al dendrites to equiaxed dendrites has been observed in each layer. The observed variation of the microstructure was correlated with the thermal history and local cooling rate of the melt pool.

  10. Bioenergetic Mechanisms in Astrocytes May Contribute to Amyloid Plaque Deposition and Toxicity*

    PubMed Central

    Fu, Wen; Shi, Diya; Westaway, David; Jhamandas, Jack H.

    2015-01-01

    Alzheimer disease (AD) is characterized neuropathologically by synaptic disruption, neuronal loss, and deposition of amyloid β (Aβ) protein in brain structures that are critical for memory and cognition. There is increasing appreciation, however, that astrocytes, which are the major non-neuronal glial cells, may play an important role in AD pathogenesis. Unlike neurons, astrocytes are resistant to Aβ cytotoxicity, which may, in part, be related to their greater reliance on glycolytic metabolism. Here we show that, in cultures of human fetal astrocytes, pharmacological inhibition or molecular down-regulation of a main enzymatic regulator of glycolysis, 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase (PFKFB3), results in increased accumulation of Aβ within and around astrocytes and greater vulnerability of these cells to Aβ toxicity. We further investigated age-dependent changes in PFKFB3 and astrocytes in AD transgenic mice (TgCRND8) that overexpress human Aβ. Using a combination of Western blotting and immunohistochemistry, we identified an increase in glial fibrillary acidic protein expression in astrocytes that paralleled the escalation of the Aβ plaque burden in TgCRND8 mice in an age-dependent manner. Furthermore, PFKFB3 expression also demonstrated an increase in these mice, although at a later age (9 months) than GFAP and Aβ. Immunohistochemical staining showed significant reactive astrogliosis surrounding Aβ plaques with increased PFKFB3 activity in 12-month-old TgCRND8 mice, an age when AD pathology and behavioral deficits are fully manifested. These studies shed light on the unique bioenergetic mechanisms within astrocytes that may contribute to the development of AD pathology. PMID:25814669

  11. Evidence that a synthetic amyloid-ß oligomer-binding peptide (ABP) targets amyloiddeposits in transgenic mouse brain and human Alzheimer's disease brain.

    PubMed

    Chakravarthy, Balu; Ito, Shingo; Atkinson, Trevor; Gaudet, Chantal; Ménard, Michel; Brown, Leslie; Whitfield, James

    2014-03-14

    The synthetic ~5 kDa ABP (amyloid-ß binding peptide) consists of a region of the 228 kDa human pericentrioloar material-1 (PCM-1) protein that selectively and avidly binds in vitro Aβ1-42 oligomers, believed to be key co-drivers of Alzheimer's disease (AD), but not monomers (Chakravarthy et al., (2013) [3]). ABP also prevents Aß1-42 from triggering the apoptotic death of cultured human SHSY5Y neuroblasts, likely by sequestering Aß oligomers, suggesting that it might be a potential AD therapeutic. Here we support this possibility by showing that ABP also recognizes and binds Aβ1-42 aggregates in sections of cortices and hippocampi from brains of AD transgenic mice and human AD patients. More importantly, ABP targets Aβ1-42 aggregates when microinjected into the hippocampi of the brains of live AD transgenic mice.

  12. Arresting Amyloid with Coulomb’s Law: Acetylation of ALS-Linked SOD1 by Aspirin Impedes Aggregation

    PubMed Central

    Abdolvahabi, Alireza; Shi, Yunhua; Rhodes, Nicholas R.; Cook, Nathan P.; Martí, Angel A.; Shaw, Bryan F.

    2015-01-01

    Although the magnitude of a protein’s net charge (Z) can control its rate of self-assembly into amyloid, and its interactions with cellular membranes, the net charge of a protein is not viewed as a druggable parameter. This article demonstrates that aspirin (the quintessential acylating pharmacon) can inhibit the amyloidogenesis of superoxide dismutase (SOD1) by increasing the intrinsic net negative charge of the polypeptide, i.e., by acetylation (neutralization) of multiple lysines. The protective effects of acetylation were diminished (but not abolished) in 100 mM NaCl and were statistically significant: a total of 432 thioflavin-T amyloid assays were performed for all studied proteins. The acetylation of as few as three lysines by aspirin in A4V apo-SOD1—a variant that causes familial amyotrophic lateral sclerosis (ALS)—delayed amyloid nucleation by 38% and slowed amyloid propagation by twofold. Lysines in wild-type- and ALS-variant apo-SOD1 could also be peracetylated with aspirin after fibrillization, resulting in supercharged fibrils, with increases in formal net charge of ∼2 million units. Peracetylated SOD1 amyloid defibrillized at temperatures below unacetylated fibrils, and below the melting temperature of native Cu2,Zn2-SOD1 (e.g., fibril Tm = 84.49°C for acetylated D90A apo-SOD1 fibrils). Targeting the net charge of native or misfolded proteins with small molecules—analogous to how an enzyme’s Km or Vmax are medicinally targeted—holds promise as a strategy in the design of therapies for diseases linked to protein self-assembly. PMID:25762331

  13. Continuation of exercise is necessary to inhibit high fat diet-induced β-amyloid deposition and memory deficit in amyloid precursor protein transgenic mice.

    PubMed

    Maesako, Masato; Uemura, Kengo; Iwata, Ayana; Kubota, Masakazu; Watanabe, Kiwamu; Uemura, Maiko; Noda, Yasuha; Asada-Utsugi, Megumi; Kihara, Takeshi; Takahashi, Ryosuke; Shimohama, Shun; Kinoshita, Ayae

    2013-01-01

    High fat diet (HFD) is prevalent in many modern societies and HFD-induced metabolic condition is a growing concern worldwide. It has been previously reported that HFD clearly worsens cognitive function in amyloid precursor protein (APP) transgenic mice. On the other hand, we have demonstrated that voluntary exercise in an enriched environment is an effective intervention to rescue HFD-induced β-amyloid (Aβ) deposition and memory deficit. However, it had been unclear whether consumption of HFD after exercising abolished the beneficial effect of exercise on the inhibition of Alzheimer's disease (AD) pathology. To examine this question, we exposed wild type (WT) and APP mice fed with HFD to exercise conditions at different time periods. In our previous experiment, we gave HFD to mice for 20 weeks and subjected them to exercise during weeks 10-20. In the present study, mice were subjected to exercise conditions during weeks 0-10 or weeks 5-15 while being on HFD. Interestingly, we found that the effect of exercise during weeks 0-10 or weeks 5-15 on memory function was not abolished in WT mice even if they kept having HFD after finishing exercise. However, in APP transgenic mice, HFD clearly disrupted the effect of exercise during weeks 0-10 or weeks 5-15 on memory function. Importantly, we observed that the level of Aβ oligomer was significantly elevated in the APP mice that exercised during weeks 0-10: this might have been caused by the up-regulation of Aβ production. These results provide solid evidence that continuation of exercise is necessary to rescue HFD-induced aggravation of cognitive decline in the pathological setting of AD.

  14. Proliferation in the Alzheimer Hippocampus Is due to Microglia, Not Astroglia, and Occurs at Sites of Amyloid Deposition

    PubMed Central

    Marlatt, Michael W.; Bauer, Jan; Aronica, Eleonora; van Haastert, Elise S.; Hoozemans, Jeroen J. M.; Joels, Marian; Lucassen, Paul J.

    2014-01-01

    Microglia and astrocytes contribute to Alzheimer's disease (AD) etiology and may mediate early neuroinflammatory responses. Despite their possible role in disease progression and despite the fact that they can respond to amyloid deposition in model systems, little is known about whether astro- or microglia can undergo proliferation in AD and whether this is related to the clinical symptoms or to local neuropathological changes. Previously, proliferation was found to be increased in glia-rich regions of the presenile hippocampus. Since their phenotype was unknown, we here used two novel triple-immunohistochemical protocols to study proliferation in astro- or microglia in relation to amyloid pathology. We selected different age-matched cohorts to study whether proliferative changes relate to clinical severity or to neuropathological changes. Proliferating cells were found across the hippocampus but never in mature neurons or astrocytes. Almost all proliferating cells were colabeled with Iba1+, indicating that particularly microglia contribute to proliferation in AD. Proliferating Iba1+ cells was specifically seen within the borders of amyloid plaques, indicative of an active involvement in, or response to, plaque accumulation. Thus, consistent with animal studies, proliferation in the AD hippocampus is due to microglia, occurs in close proximity of plaque pathology, and may contribute to the neuroinflammation common in AD. PMID:25215243

  15. Trafficking CD11b-positive blood cells deliver therapeutic genes to the brain of amyloid depositing transgenic mice

    PubMed Central

    Lebson, Lori; Nash, Kevin; Kamath, Siddharth; Herber, Donna; Carty, Nikisha; Lee, Daniel; Li, Qingyou; Szekeres, Karoly; Jinwal, Umesh; Koren, John; Dickey, Chad A.; Gottschall, Paul; Morgan, Dave; Gordon, Marcia N

    2010-01-01

    A major question for gene therapy in brain concerns methods to administer therapeutic genes in a uniform manner over major portions of the brain. A second question in neuroimmunology concerns the extent to which monocytes migrate to the CNS in degenerative disorders. Here we show that CD11b+ cells (largely monocytes) isolated from the bone marrow of green fluorescent protein (GFP) expressing donors spontaneously home to compacted amyloid plaques in the brain. Injections of these cells as a single pulse show a rapid clearance from circulation (90 minute half-life) and tissue residence half-lives of roughly 3 days. The uptake into brain was minimal in nontransgenic mice. In transgenic mice containing amyloid deposits, uptake was dramatically increased and associated with a corresponding decrease in monocyte uptake into peripheral organs compared to nontransgenic littermates. Twice weekly infusions of the CD11b+ bone marrow cells transfected with a genetically engineered form of the protease neprilysin completely arrest amyloid deposition in an aggressively depositing transgenic model. Exploiting the natural homing properties of peripherally derived blood cells to deliver therapeutic genes has the advantages of access to the entire CNS, expression largely restricted to sites of injury, low risk of immune reactivity, and fading of expression if adverse reactions are encountered. These observations support the feasibility of testing autologous monocytes for application of therapeutic genes in human CNS disease. Moreover, these data support the results from bone marrow grafts that circulating CD11b+ cells can enter the CNS without requiring the use of lethal irradiation. PMID:20660248

  16. Dendritic spine density, morphology, and fibrillar actin content surrounding amyloid-β plaques in a mouse model of amyloiddeposition.

    PubMed

    Kirkwood, Caitlin M; Ciuchta, Jennifer; Ikonomovic, Milos D; Fish, Kenneth N; Abrahamson, Eric E; Murray, Patrick S; Klunk, William E; Sweet, Robert A

    2013-08-01

    Dendritic spines are the site of most excitatory synapses, the loss of which correlates with cognitive impairment in patients with Alzheimer disease. Substantial evidence indicates that amyloid-β (Aβ) peptide, either insoluble fibrillar Aβ deposited into plaques or soluble nonfibrillar Aβ species, can cause spine loss but the concurrent contributions of fibrillar Aβ and nonfibrillar Aβ to spine loss has not been previously assessed. We used multiple-label immunohistochemistry to measure spine density, size, and F-actin content surrounding plaques in the cerebral cortex in the PSAPP mouse model of Aβ deposition. Our approach allowed us to measure fibrillar Aβ plaque content and an index of nonfibrillar Aβ species concurrently. We found that spine density was reduced within 6 μm of the plaque perimeter, remaining spines were more compact, and F-actin content per spine was increased. Measures of fibrillar Aβ plaque content were associated with reduced spine density near plaques, whereas measures of nonfibrillar Aβ species were associated with reduced spine density and size but not altered F-actin content. These findings suggest that strategies to preserve dendritic spines in AD patients may need to address both nonfibrillar and fibrillar forms of Aβ and that nonfibrillar Aβ may exert spine toxicity through pathways not mediated by depolymerization of F-actin.

  17. Amyloid misfolding, aggregation, and the early onset of protein deposition diseases: insights from AFM experiments and computational analyses

    PubMed Central

    Lyubchenko, Yuri L.

    2016-01-01

    The development of Alzheimer’s disease is believed to be caused by the assembly of amyloid β proteins into aggregates and the formation of extracellular senile plaques. Similar models suggest that structural misfolding and aggregation of proteins are associated with the early onset of diseases such as Parkinson’s, Huntington’s, and other protein deposition diseases. Initially, the aggregates were structurally characterized by traditional techniques such as x-ray crystallography, NMR, electron microscopy, and AFM. However, data regarding the structures formed during the early stages of the aggregation process were unknown. Experimental models of protein deposition diseases have demonstrated that the small oligomeric species have significant neurotoxicity. This highlights the urgent need to discover the properties of these species, to enable the development of efficient diagnostic and therapeutic strategies. The oligomers exist transiently, making it impossible to use traditional structural techniques to study their characteristics. The recent implementation of single-molecule imaging and probing techniques that are capable of probing transient states have enabled the properties of these oligomers to be characterized. Additionally, powerful computational techniques capable of structurally analyzing oligomers at the atomic level advanced our understanding of the amyloid aggregation problem. This review outlines the progress in AFM experimental studies and computational analyses with a primary focus on understanding the very first stage of the aggregation process. Experimental approaches can aid in the development of novel sensitive diagnostic and preventive strategies for protein deposition diseases, and several examples of these approaches will be discussed. PMID:27830177

  18. Nigral Tau pathology and striatal amyloiddeposition does not correlate with striatal dopamine deficit in Alzheimer's disease.

    PubMed

    Schauer, Tabea H; Lochner, Maximilian; Kovacs, Gabor G

    2012-12-01

    Extrapyramidal symptoms may appear in Alzheimer's disease (AD). In the present study, using morphometric immunohistochemistry in 34 cases with AD-related pathology, we evaluated whether nigral burden of tau pathology or striatal burden of amyloiddeposition correlates with dopamine transporter (DAT) expression in the striatum. Our observations show a lack of correlation between these variables and support the notion that lower striatal DAT expression in AD patients suggests concomitant nigral α-synuclein pathology. Extrapyramidal symptoms may have a complex background in AD.

  19. Immunolocalization of Kisspeptin Associated with AmyloidDeposits in the Pons of an Alzheimer's Disease Patient

    PubMed Central

    Ashioti, Maria; Nercessian, Amanda N.; Milton, Nathaniel G. N.

    2013-01-01

    The pons region of the Alzheimer's disease (AD) brain is one of the last to show amyloid-β (Aβ) deposits and has been suggested to contain neuroprotective compounds. Kisspeptin (KP) is a hormone that activates the hypothalamic-pituitary-gonadal axis and has been suggested to be neuroprotective against Aβ toxicity. The localization of KP, plus the established endogenous neuroprotective compounds corticotropin releasing hormone (CRH) and catalase, in tissue sections from the pons region of a male AD subject has been determined in relation to Aβ deposits. Results showed Aβ deposits also stained with KP, CRH, and catalase antibodies. At high magnification the staining of deposits was either KP or catalase positive, and there was only a limited area of the deposits with KP-catalase colocalization. The CRH does not bind Aβ, whilst both KP and catalase can bind Aβ, suggesting that colocalization in Aβ deposits is not restricted to compounds that directly bind Aβ. The neuroprotective actions of KP, CRH, and catalase were confirmed in vitro, and fibrillar Aβ preparations were shown to stimulate the release of KP in vitro. In conclusion, neuroprotective KP, CRH, and catalase all colocalize with Aβ plaque-like deposits in the pons region from a male AD subject. PMID:26317001

  20. Elevated amyloid β production in senescent retinal pigment epithelium, a possible mechanism of subretinal deposition of amyloid β in age-related macular degeneration.

    PubMed

    Wang, Jiying; Ohno-Matsui, Kyoko; Morita, Ikuo

    2012-06-22

    Age-related macular degeneration (AMD) is the most common cause of legal blindness in the elderly individuals in developed countries. Subretinally-deposited amyloid β (Aβ) is a main contributor of developing AMD. However, the mechanism causing Aβ deposition in AMD eyes is unknown. Aging is the most significant risk of AMD, thus, we examined the effect of aging on subretinal Aβ deposition. mRNAs and cell lysates were isolated from retinal pigment epithelial (RPE) cells derived from 24-month-old (24M RPE) and 2-month-old (2M RPE) C57BL/6 mice. Aβ concentration in culture supernatants was measured by ELISA. Activity and expression of proteins that regulate Aβ level were examined by activity assay and real time PCR. Effect of β-secretase (BACE) on Aβ production was examined by siRNA silencing. Aβ amounts in supernatants of 24M RPE were significantly higher than 2M RPE. Activity and mRNA levels of neprilysin, an Aβ degrading enzyme, were significantly decreased in 24M RPE compared to 2M RPE. PCR analysis found that BACE2 was significantly more abundantly expressed than BACE1 in RPE cells, however, inactivation of BACE2 gene did not affect Aβ production. BACE1 protein amounts did not differ between 24M and 2M RPE, however, BACE1 activity was significantly higher in 24M RPE compared to 2M RPE. There were no significant changes in the activities of α- or γ-secretase between 2M and 24M RPE. In conclusion, RPE cells produce more amounts of Aβ when they are senescent, and this is probably caused by a decrease in Aβ degradation due to a reduction in the expression and activity of neprilysin and an increase in Aβ synthesis due to increased activity of BACE1.

  1. Rapid β-Amyloid Deposition and Cognitive Impairment after Cholinergic Denervation in APP/PS1 Mice

    PubMed Central

    Ramos-Rodriguez, Juan Jose; Pacheco-Herrero, Mar; Thyssen, Diana; Murillo-Carretero, Maria Isabel; Berrocoso, Esther; Spires-Jones, Tara L.; Bacskai, Brian J.; Garcia-Alloza, Monica

    2013-01-01

    Although extensive evidence supports the role of amyloid-β (Aβ) in Alzheimer disease (AD), the neurotoxic mechanisms underlying AD pathogenesis are not understood. On the other hand, neuronal loss is the pathological feature that best correlates with cognitive impairment. We hypothesized that cholinergic neurodegeneration may lead to Aβ deposition and tested this by inducing selective cholinergic lesions in APPswe/PS1dE9 mice with murine p75NTR saporin (mu p75-SAP). Intracerebroventricular lesions that removed ~50% of cholinergic innervation to the cortex and hippocampus were induced in animals with incipient (~3 months) and marked (~7 months of age) Aβ deposition. Cranial windows were implanted and Aβ deposition was monitored in vivo using multiphoton microscopy. Aβ deposition was increased as soon as 7 days after the lesion and this effect was maintained up to 3 months later. Postmortem studies using immunohistochemistry with an anti-Aβ antibody corroborated these findings in both cerebral cortex and hippocampus. Tau phosphorylation was also significantly increased after the lesions. Cholinergic denervation resulted in early memory impairment at 3 months of age that worsened with age (~7 months); there was a synergistic effect between cholinergic denervation and the presence of APP/PS1 transgenes. Altogether, our data suggest that cholinergic denervation may trigger Aβ deposition and synergistically contribute to cognitive impairment in AD patients. PMID:23481704

  2. Age-dependent cognitive decline in the APP23 model precedes amyloid deposition.

    PubMed

    Van Dam, Debby; D'Hooge, Rudi; Staufenbiel, Matthias; Van Ginneken, Chris; Van Meir, Frans; De Deyn, Peter P

    2003-01-01

    Heterozygous APP23 mice, expressing human amyloid-precursor protein with the Swedish double mutation and control littermates, were subjected to behavioral and neuromotor tasks at the age of 6-8 weeks, 3 and 6 months. A hidden-platform Morris-type water maze showed an age-dependent decline of spatial memory capacities in the APP23 model. From the age of 3 months onwards, the APP23 mice displayed major learning and memory deficits as demonstrated by severely impaired learning curves during acquisition and impaired probe trial performance. In addition to the cognitive deficit, APP23 mice displayed disturbed activity patterns. Overnight cage-activity recording showed hyperactivity in the transgenics for the three age groups tested. However, a short 2-h recording during dusk phase demonstrated lower activity levels in 6-month-old APP23 mice as compared to controls. Moreover, at this age, APP23 mice differed from control littermates in exploration and activity levels in the open-field paradigm. These findings are reminiscent of disturbances in circadian rhythms and activity observed in Alzheimer patients. Determination of plaque-associated human amyloid-beta 1-42 peptides in brain revealed a fivefold increase in heterozygous APP23 mice at 6 months as compared to younger transgenics. This increase coincided with the first appearance of plaques in hippocampus and neocortex. Spatial memory deficits preceded plaque formation and increase in plaque-associated amyloid-beta 1-42 peptides, but probe trial performance did correlate negatively with soluble amyloid-beta brain concentration in 3-month-old APP23 mutants. Detectable plaque formation is not the (only) causal factor contributing to memory defects in the APP23 model.

  3. Amyloid deposition after cerebral hypoperfusion: evidenced on [(18)F]AV-45 positron emission tomography.

    PubMed

    Huang, Kuo-Lun; Lin, Kun-Ju; Ho, Meng-Yang; Chang, Yeu-Jhy; Chang, Chien-Hung; Wey, Shiaw-Pyng; Hsieh, Chia-Ju; Yen, Tzu-Chen; Hsiao, Ing-Tsung; Lee, Tsong-Hai

    2012-08-15

    Animal studies have shown that cerebral hypoperfusion may be associated with amyloid plaque accumulation. Amyloid plaque is known to be associated with dementia and [(18)F]AV-45 is a positron emission tomography (PET) ligand that binds to extracelluar plaques. We hypothesized that demented patients with cerebral hypoperfusion may have increased [(18)F]AV-45 uptake. Five demented patients with cerebral hypoperfusion due to unilateral carotid artery stenosis (CAS) were examined with [(18)F]AV-45 PET, and the results were compared with six elderly controls. The standard uptake value ratio (SUVR) of each region of interest (ROI) was created using whole cerebellum as the reference region. All subjects underwent magnetic resonance imaging (MRI) for obtaining structural information. Patients with dementia and unilateral CAS had a higher global [(18)F]AV-45 SUVR (1.34 ± 0.06) as compared with controls (1.10 ± 0.04, p=0.0043), especially over the frontal, temporal, precuneus, anterior cingulate and occipital regions. The statistical distribution maps revealed a significantly increased [(18)F]AV-45 SUVR in the medial frontal, caudate, thalamus, posterior cingulate, occipital and middle and superior temporal regions ipsilateral to the side of CAS (p<0.01). The present study found that cerebral [(18)F]AV-45 binding is increased in demented patients with CAS, and its distribution is lateralized to the CAS side, suggesting that amyloid-related dementia may occur under cerebral hypoperfusion.

  4. Focal glial activation coincides with increased BACE1 activation and precedes amyloid plaque deposition in APP[V717I] transgenic mice

    PubMed Central

    Heneka, Michael T; Sastre, Magdalena; Dumitrescu-Ozimek, Lucia; Dewachter, Ilse; Walter, Jochen; Klockgether, Thomas; Van Leuven, Fred

    2005-01-01

    Background Inflammation is suspected to contribute to the progression and severity of neurodegeneration in Alzheimer's disease (AD). Transgenic mice overexpressing the london mutant of amyloid precursor protein, APP [V717I], robustly recapitulate the amyloid pathology of AD. Methods Early and late, temporal and spatial characteristics of inflammation were studied in APP [V717I] mice at 3 and 16 month of age. Glial activation and expression of inflammatory markers were determined by immunohistochemistry and RT-PCR. Amyloid deposition was assessed by immunohistochemistry, thioflavine S staining and western blot experiments. BACE1 activity was detected in brain lysates and in situ using the BACE1 activity kit from R&D Systems, Wiesbaden, Germany. Results Foci of activated micro- and astroglia were already detected at age 3 months, before any amyloid deposition. Inflammation parameters comprised increased mRNA levels coding for interleukin-1β, interleukin-6, major histocompatibility complex II and macrophage-colony-stimulating-factor-receptor. Foci of CD11b-positive microglia expressed these cytokines and were neighbored by activated astrocytes. Remarkably, β-secretase (BACE1) mRNA, neuronal BACE1 protein at sites of focal inflammation and total BACE1 enzyme activity were increased in 3 month old APP transgenic mice, relative to age-matched non-transgenic mice. In aged APP transgenic mice, the mRNA of all inflammatory markers analysed was increased, accompanied by astroglial iNOS expression and NO-dependent peroxynitrite release, and with glial activation near almost all diffuse and senile Aβ deposits. Conclusion The early and focal glial activation, in conjunction with upregulated BACE1 mRNA, protein and activity in the presence of its substrate APP, is proposed to represent the earliest sites of amyloid deposition, likely evolving into amyloid plaques. PMID:16212664

  5. Consumption of grape seed extract prevents amyloid-beta deposition and attenuates inflammation in brain of an Alzheimer's disease mouse.

    PubMed

    Wang, Yan-Jiang; Thomas, Philip; Zhong, Jin-Hua; Bi, Fang-Fang; Kosaraju, Shantha; Pollard, Anthony; Fenech, Michael; Zhou, Xin-Fu

    2009-01-01

    Polyphenols extracted from grape seeds are able to inhibit amyloid-beta (Abeta) aggregation, reduce Abeta production and protect against Abeta neurotoxicity in vitro. We aimed to investigate the therapeutic effects of a polyphenol-rich grape seed extract (GSE) in Alzheimer's disease (AD) mice. APP(Swe)/PS1dE9 transgenic mice were fed with normal AIN-93G diet (control diet), AIN-93G diet with 0.07% curcumin or diet with 2% GSE beginning at 3 months of age for 9 months. Total phenolic content of GSE was 592.5 mg/g dry weight, including gallic acid (49 mg/g), catechin (41 mg/g), epicatechin (66 mg/g) and proanthocyanidins (436.6 mg catechin equivalents/g). Long-term feeding of GSE diet was well tolerated without fatality, behavioural abnormality, changes in food consumption, body weight or liver function. The Abeta levels in the brain and serum of the mice fed with GSE were reduced by 33% and 44%, respectively, compared with the Alzheimer's mice fed with the control diet. Amyloid plaques and microgliosis in the brain of Alzheimer's mice fed with GSE were also reduced by 49% and 70%, respectively. Curcumin also significantly reduced brain Abeta burden and microglia activation. Conclusively, polyphenol-rich GSE prevents the Abeta deposition and attenuates the inflammation in the brain of a transgenic mouse model, and this thus is promising in delaying development of AD.

  6. Distinct synthetic Aβ prion strains producing different amyloid deposits in bigenic mice

    PubMed Central

    Stöhr, Jan; Condello, Carlo; Watts, Joel C.; Bloch, Lillian; Oehler, Abby; Nick, Mimi; DeArmond, Stephen J.; Giles, Kurt; DeGrado, William F.; Prusiner, Stanley B.

    2014-01-01

    An increasing number of studies continue to show that the amyloid β (Aβ) peptide adopts an alternative conformation and acquires transmissibility; hence, it becomes a prion. Here, we report on the attributes of two strains of Aβ prions formed from synthetic Aβ peptides composed of either 40 or 42 residues. Modifying the conditions for Aβ polymerization increased both the protease resistance and prion infectivity compared with an earlier study. Approximately 150 d after intracerebral inoculation, both synthetic Aβ40 and Aβ42 prions produced a sustained rise in the bioluminescence imaging signal in the brains of bigenic Tg(APP23:Gfap-luc) mice, indicative of astrocytic gliosis. Pathological investigations showed that synthetic Aβ40 prions produced amyloid plaques containing both Aβ40 and Aβ42 in the brains of inoculated bigenic mice, whereas synthetic Aβ42 prions stimulated the formation of smaller, more numerous plaques composed predominantly of Aβ42. Synthetic Aβ40 preparations consisted of long straight fibrils; in contrast, the Aβ42 fibrils were much shorter. Addition of 3.47 mM (0.1%) SDS to the polymerization reaction produced Aβ42 fibrils that were indistinguishable from Aβ40 fibrils produced in the absence or presence of SDS. Moreover, the Aβ amyloid plaques in the brains of bigenic mice inoculated with Aβ42 prions prepared in the presence of SDS were similar to those found in mice that received Aβ40 prions. From these results, we conclude that the composition of Aβ plaques depends on the conformation of the inoculated Aβ polymers, and thus, these inocula represent distinct synthetic Aβ prion strains. PMID:24982137

  7. Environmental impact of multi-wall carbon nanotubes in a novel model of exposure: systemic distribution, macrophage accumulation, and amyloid deposition.

    PubMed

    Albini, Adriana; Pagani, Arianna; Pulze, Laura; Bruno, Antonino; Principi, Elisa; Congiu, Terenzio; Gini, Elisabetta; Grimaldi, Annalisa; Bassani, Barbara; De Flora, Silvio; de Eguileor, Magda; Noonan, Douglas M

    2015-01-01

    Carbon nanotubes (CNTs) have been extensively investigated and employed for industrial use because of their peculiar physical properties, which make them ideal for many industrial applications. However, rapid growth of CNT employment raises concerns about the potential risks and toxicities for public health, environment, and workers associated with the manufacture and use of these new materials. Here we investigate the main routes of entry following environmental exposure to multi-wall CNTs (MWCNTs; currently the most widely used in industry). We developed a novel murine model that could represent a surrogate of a workplace exposure to MWCNTs. We traced the localization of MWCNTs and their possible role in inducing an innate immune response, inflammation, macrophage recruitment, and inflammatory conditions. Following environmental exposure of CD1 mice, we observed that MWCNTs rapidly enter and disseminate in the organism, initially accumulating in lungs and brain and later reaching the liver and kidney via the bloodstream. Since recent experimental studies show that CNTs are associated with the aggregation process of proteins associated with neurodegenerative diseases, we investigated whether MWCNTs are able to induce amyloid fibril production and accumulation. Amyloid deposits in spatial association with macrophages and MWCNT aggregates were found in the brain, liver, lungs, and kidneys of exposed animals. Our data suggest that accumulation of MWCNTs in different organs is associated with inflammation and amyloid accumulation. In the brain, where we observed rapid accumulation and amyloid fibril deposition, exposure to MWCNTs might enhance progression of neurodegenerative and other amyloid-related diseases. Our data highlight the conclusion that, in a novel rodent model of exposure, MWCNTs may induce macrophage recruitment, activation, and amyloid deposition, causing potential damage to several organs.

  8. Environmental impact of multi-wall carbon nanotubes in a novel model of exposure: systemic distribution, macrophage accumulation, and amyloid deposition

    PubMed Central

    Albini, Adriana; Pagani, Arianna; Pulze, Laura; Bruno, Antonino; Principi, Elisa; Congiu, Terenzio; Gini, Elisabetta; Grimaldi, Annalisa; Bassani, Barbara; De Flora, Silvio; de Eguileor, Magda; Noonan, Douglas M

    2015-01-01

    Carbon nanotubes (CNTs) have been extensively investigated and employed for industrial use because of their peculiar physical properties, which make them ideal for many industrial applications. However, rapid growth of CNT employment raises concerns about the potential risks and toxicities for public health, environment, and workers associated with the manufacture and use of these new materials. Here we investigate the main routes of entry following environmental exposure to multi-wall CNTs (MWCNTs; currently the most widely used in industry). We developed a novel murine model that could represent a surrogate of a workplace exposure to MWCNTs. We traced the localization of MWCNTs and their possible role in inducing an innate immune response, inflammation, macrophage recruitment, and inflammatory conditions. Following environmental exposure of CD1 mice, we observed that MWCNTs rapidly enter and disseminate in the organism, initially accumulating in lungs and brain and later reaching the liver and kidney via the bloodstream. Since recent experimental studies show that CNTs are associated with the aggregation process of proteins associated with neurodegenerative diseases, we investigated whether MWCNTs are able to induce amyloid fibril production and accumulation. Amyloid deposits in spatial association with macrophages and MWCNT aggregates were found in the brain, liver, lungs, and kidneys of exposed animals. Our data suggest that accumulation of MWCNTs in different organs is associated with inflammation and amyloid accumulation. In the brain, where we observed rapid accumulation and amyloid fibril deposition, exposure to MWCNTs might enhance progression of neurodegenerative and other amyloid-related diseases. Our data highlight the conclusion that, in a novel rodent model of exposure, MWCNTs may induce macrophage recruitment, activation, and amyloid deposition, causing potential damage to several organs. PMID:26457053

  9. Automated PET-only quantification of amyloid deposition with adaptive template and empirically pre-defined ROI

    NASA Astrophysics Data System (ADS)

    Akamatsu, G.; Ikari, Y.; Ohnishi, A.; Nishida, H.; Aita, K.; Sasaki, M.; Yamamoto, Y.; Sasaki, M.; Senda, M.

    2016-08-01

    Amyloid PET is useful for early and/or differential diagnosis of Alzheimer’s disease (AD). Quantification of amyloid deposition using PET has been employed to improve diagnosis and to monitor AD therapy, particularly in research. Although MRI is often used for segmentation of gray matter and for spatial normalization into standard Montreal Neurological Institute (MNI) space where region-of-interest (ROI) template is defined, 3D MRI is not always available in clinical practice. The purpose of this study was to examine the feasibility of PET-only amyloid quantification with an adaptive template and a pre-defined standard ROI template that has been empirically generated from typical cases. A total of 68 subjects who underwent brain 11C-PiB PET were examined. The 11C-PiB images were non-linearly spatially normalized to the standard MNI T1 atlas using the same transformation parameters of MRI-based normalization. The automatic-anatomical-labeling-ROI (AAL-ROI) template was applied to the PET images. All voxel values were normalized by the mean value of cerebellar cortex to generate the SUVR-scaled images. Eleven typical positive images and eight typical negative images were normalized and averaged, respectively, and were used as the positive and negative template. Positive and negative masks which consist of voxels with SUVR  ⩾1.7 were extracted from both templates. Empirical PiB-prone ROI (EPP-ROI) was generated by subtracting the negative mask from the positive mask. The 11C-PiB image of each subject was non-rigidly normalized to the positive and negative template, respectively, and the one with higher cross-correlation was adopted. The EPP-ROI was then inversely transformed to individual PET images. We evaluated differences of SUVR between standard MRI-based method and PET-only method. We additionally evaluated whether the PET-only method would correctly categorize 11C-PiB scans as positive or negative. Significant correlation was observed between the SUVRs

  10. Characterization of amyloid in equine recurrent uveitis as AA amyloid.

    PubMed

    Ostevik, L; de Souza, G A; Wien, T N; Gunnes, G; Sørby, R

    2014-01-01

    Two horses with chronic uveitis and histological lesions consistent with equine recurrent uveitis (ERU) were examined. Microscopical findings in the ciliary body included deposits of amyloid lining the non-pigmented epithelium, intracytoplasmic, rod-shaped, eosinophilic inclusions and intraepithelial infiltration of T lymphocytes. Ultrastructural examination of the ciliary body of one horse confirmed the presence of abundant extracellular deposits of non-branching fibrils (9-11 nm in diameter) consistent with amyloid. Immunohistochemistry revealed strong positive labelling for AA amyloid and mass spectrometry showed the amyloid to consist primarily of serum amyloid A1 in both cases. The findings suggest that localized, intraocular AA amyloidosis may occur in horses with ERU.

  11. Amyloid-β plaque deposition measured using propagation-based X-ray phase contrast CT imaging

    PubMed Central

    Astolfo, Alberto; Lathuilière, Aurélien; Laversenne, Vanessa; Schneider, Bernard; Stampanoni, Marco

    2016-01-01

    Amyloid beta accumulation into insoluble plaques (Aβp) is known to play a significant role in the pathological process in Alzheimer’s disease (AD). The presence of Aβp is also one of the neuropathological hallmarks for the disease. AD final diagnosis is generally acknowledged after the evaluation of Aβp deposition in the brain. Insoluble Aβp accumulation may also concur to cause AD as postulated in the so-called amyloid hypothesis. Therefore, the visualization, evaluation and quantification of Aβp are nowadays the keys for a better understanding of the disease, which may point to a possible cure for AD in the near future. Synchrotron-based X-ray phase contrast (XPC) has been demonstrated as the only imaging method that can retrieve the Aβp signal with high spatial resolution (up to 10 µm), high sensitivity and three-dimensional information at the same time. Although at the moment XPC is suitable for ex vivo samples only, it may develop into an alternative to positron emission tomography and magnetic resonance imaging in Aβp imaging. In this contribution the possibility of using synchrotron-based X-ray phase propagation computed tomography to visualize and measure Aβp on mouse brains is presented. A careful setup optimization for this application leads to a significant improvement of spatial resolution (∼1 µm), data acquisition speed (five times faster), X-ray dose (five times lower) and setup complexity, without a substantial loss in sensitivity when compared with the classic implementation of grating-based X-ray interferometry. PMID:27140162

  12. Sequence variants of IDE are associated with the extent of beta-amyloid deposition in the Alzheimer's disease brain.

    PubMed

    Blomqvist, Mia E-L; Chalmers, Katy; Andreasen, Niels; Bogdanovic, Nenad; Wilcock, Gordon K; Cairns, Nigel J; Feuk, Lars; Brookes, Anthony J; Love, Seth; Blennow, Kaj; Kehoe, Patrick G; Prince, Jonathan A

    2005-06-01

    Insulin degrading enzyme, encoded by IDE, plays a primary role in the degradation of amyloid beta-protein (A beta), the deposition of which in senile plaques is one of the defining hallmarks of Alzheimer's disease (AD). We recently identified haplotypes in a broad linkage disequilibrium (LD) block encompassing IDE that associate with several AD-related quantitative traits. Here, by examining 32 polymorphic markers extending across IDE and testing quantitative measures of plaque density and cognitive function in three independent Swedish AD samples, we have refined the probable position of pathogenic sequences to a 3' region of IDE, with local maximum effects in the proximity of marker rs1887922. To replicate these findings, a subset of variants were examined against measures of brain A beta load in an independent English AD sample, whereby maximum effects were again observed for rs1887922. For both Swedish and English autopsy materials, variation at rs1887922 explained approximately 10% of the total variance in the respective histopathology traits. However, across all clinical materials studied to date, this variant site does not appear to associate directly with disease, suggesting that IDE may affect AD severity rather than risk. Results indicate that alleles of IDE contribute to variability in A beta deposition in the AD brain and suggest that this relationship may have relevance for the degree of cognitive dysfunction in AD patients.

  13. CX3CR1 Deficiency Alters Microglial Activation and Reduces Beta-Amyloid Deposition in Two Alzheimer’s Disease Mouse Models

    PubMed Central

    Lee, Sungho; Varvel, Nicholas H.; Konerth, Megan E.; Xu, Guixiang; Cardona, Astrid E.; Ransohoff, Richard M.; Lamb, Bruce T.

    2010-01-01

    Microglia, the primary immune effector cells in the brain, continually monitor the tissue parenchyma for pathological alterations and become activated in Alzheimer’s disease. Loss of signaling between neurons and microglia via deletion of the microglial receptor, CX3CR1, worsens phenotypes in various models of neurodegenerative diseases. In contrast, CX3CR1 deficiency ameliorates pathology in murine stroke models. To examine the role of CX3CR1 in Alzheimer’s disease–related β-amyloid pathology, we generated APPPS1 and R1.40 transgenic mouse models of Alzheimer’s disease deficient for CX3CR1. Surprisingly, CX3CR1 deficiency resulted in a gene dose-dependent reduction in β-amyloid deposition in both the APPPS1 and R1.40 mouse models of AD. Immunohistochemical analysis revealed reduced staining for CD68, a marker of microglial activation. Furthermore, quantitative immunohistochemical analysis revealed reduced numbers of microglia surrounding β-amyloid deposits in the CX3CR1-deficient APPPS1 animals. The reduced β-amyloid pathology correlated with reduced levels of TNFα and CCL2 mRNAs, but elevated IL1β mRNA levels, suggesting an altered neuroinflammatory milieu. Finally, to account for these seemingly disparate results, both in vitro and in vivo studies provided evidence that CX3CL1/CX3CR1 signaling alters the phagocytic capacity of microglia, including the uptake of Aβ fibrils. Taken together, these results demonstrate that loss of neuron-microglial fractalkine signaling leads to reduced β-amyloid deposition in mouse models of AD that is potentially mediated by altered activation and phagocytic capability of CX3CR1-deficient microglia. PMID:20864679

  14. Beta amyloid deposition and neurofibrillary tangles spontaneously occur in the brains of captive cheetahs (Acinonyx jubatus).

    PubMed

    Serizawa, S; Chambers, J K; Une, Y

    2012-03-01

    Alzheimer disease is a dementing disorder characterized pathologically by Aβ deposition, neurofibrillary tangles, and neuronal loss. Although aged animals of many species spontaneously develop Aβ deposits, only 2 species (chimpanzee and wolverine) have been reported to develop Aβ deposits and neurofibrillary tangles in the same individual. Here, the authors demonstrate the spontaneous occurrence of Aβ deposits and neurofibrillary tangles in captive cheetahs (Acinonyx jubatus). Among 22 cheetahs examined in this study, Aβ deposits were observed in 13. Immunostaining (AT8) revealed abnormal intracellular tau immunoreactivity in 10 of the cheetahs with Aβ deposits, and they were mainly distributed in the parahippocampal cortex and CA1 in a fashion similar to that in human patients with Alzheimer disease. Ultrastructurally, bundles of straight filaments filled the neuronal somata and axons, consistent with tangles. Interestingly, 2 of the cheetahs with the most severe abnormal tau immunoreactivity showed clinical cognitive dysfunction. The authors conclude that cheetahs spontaneously develop age-related neurodegenerative disease with pathologic changes similar to Alzheimer disease.

  15. Discovery of a Novel Fluorescent Probe for the Sensitive Detection of β-Amyloid Deposits

    PubMed Central

    Ren, Wenming; Xu, Mingming; Liang, Steven H.; Xiang, Huaijiang; Tang, Li; Zhang, Minkui; Ding, Dejun; Li, Xin; Zhang, Haiyan; Hu, Youhong

    2016-01-01

    Here we reported the development of the first photoinduced electron transfer (PeT) probe (1) to directly locate β-amyloid aggregates (Aβ plaques) in the brain without the need of post-washing procedures. The probe showed a high affinity for Aβ aggregates with a Kd value of 3.5 nM. It is weakly emissive by itself with its fluorescence quenched by electron transfer from PeT donor to the excited fluorophore. But selective binding to Aβ plaques would attenuate the PeT process and restore the fluorescence, therefore facilitating the tracking of Aβ plaques. The probe is advantageous in that its fluorescence is environment-less-sensitive and no washing procedure is required to provide high contrast fluorescent signal when applied to stain brain tissues. As a proof of concept, its application has been exemplified by staining Aβ plaques in slices of brain tissue from double transgenic (APP/PS1) mice of Alzheimer’s disease. PMID:26313423

  16. Detection of Alzheimer’s disease amyloid-beta plaque deposition by deep brain impedance profiling

    NASA Astrophysics Data System (ADS)

    Béduer, Amélie; Joris, Pierre; Mosser, Sébastien; Fraering, Patrick C.; Renaud, Philippe

    2015-04-01

    Objective. Alzheimer disease (AD) is the most common form of neurodegenerative disease in elderly people. Toxic brain amyloid-beta (Aß) aggregates and ensuing cell death are believed to play a central role in the pathogenesis of the disease. In this study, we investigated if we could monitor the presence of these aggregates by performing in situ electrical impedance spectroscopy measurements in AD model mice brains. Approach. In this study, electrical impedance spectroscopy measurements were performed post-mortem in APPPS1 transgenic mice brains. This transgenic model is commonly used to study amyloidogenesis, a pathological hallmark of AD. We used flexible probes with embedded micrometric electrodes array to demonstrate the feasibility of detecting senile plaques composed of Aß peptides by localized impedance measurements. Main results. We particularly focused on deep brain structures, such as the hippocampus. Ex vivo experiments using brains from young and old APPPS1 mice lead us to show that impedance measurements clearly correlate with the percentage of Aβ plaque load in the brain tissues. We could monitor the effects of aging in the AD APPPS1 mice model. Significance. We demonstrated that a localized electrical impedance measurement constitutes a valuable technique to monitor the presence of Aβ-plaques, which is complementary with existing imaging techniques. This method does not require prior Aβ staining, precluding the risk of variations in tissue uptake of dyes or tracers, and consequently ensuring reproducible data collection.

  17. Relationships between sleep quality and brain volume, metabolism, and amyloid deposition in late adulthood.

    PubMed

    Branger, Pierre; Arenaza-Urquijo, Eider M; Tomadesso, Clémence; Mézenge, Florence; André, Claire; de Flores, Robin; Mutlu, Justine; de La Sayette, Vincent; Eustache, Francis; Chételat, Gaël; Rauchs, Géraldine

    2016-05-01

    Recent studies in mouse models of Alzheimer's disease (AD) and in humans suggest that sleep disruption and amyloid-beta (Aβ) accumulation are interrelated, and may, thus, exacerbate each other. We investigated the association between self-reported sleep variables and neuroimaging data in 51 healthy older adults. Participants completed a questionnaire assessing sleep quality and quantity and underwent positron emission tomography scans using [18F]florbetapir and [18F]fluorodeoxyglucose and an magnetic resonance imaging scan to measure Aβ burden, hypometabolism, and atrophy, respectively. Longer sleep latency was associated with greater Aβ burden in prefrontal areas. Moreover, the number of nocturnal awakenings was negatively correlated with gray matter volume in the insular region. In asymptomatic middle-aged and older adults, lower self-reported sleep quality was associated with greater Aβ burden and lower volume in brain areas relevant in aging and AD, but not with glucose metabolism. These results highlight the potential relevance of preserving sleep quality in older adults and suggest that sleep may be a factor to screen for in individuals at risk for AD.

  18. Thermal Stability Threshold for Amyloid Formation in Light Chain Amyloidosis

    PubMed Central

    Poshusta, Tanya L.; Katoh, Nagaaki; Gertz, Morie A.; Dispenzieri, Angela; Ramirez-Alvarado, Marina

    2013-01-01

    Light chain (AL) amyloidosis is a devastating disease characterized by amyloid deposits formed by immunoglobulin light chains. Current available treatments involve conventional chemotherapy and autologous stem cell transplant. We have recently concluded a phase III trial comparing these two treatments. AL amyloidosis patients who achieve hematological complete response (CR) do not necessarily achieve organ response regardless of the treatment they received. In order to investigate the possible correlation between amyloid formation kinetics and organ response, we selected AL amyloidosis patients from the trial with kidney involvement and CR after treatment. Six patients were selected and their monoclonal immunoglobulin light chains were characterized. The proteins showed differences in their stability and their kinetics of amyloid formation. A correlation was detected at pH 7.4, showing that less stable proteins are more likely to form amyloid fibrils. AL-T03 is too unstable to form amyloid fibrils at pH 7.4. This protein was found in the only patient in the study that had organ response, suggesting that partially folded species are required for amyloid formation to occur in AL amyloidosis. PMID:24248061

  19. An amyloid-like cascade hypothesis for C9orf72 ALS/FTD.

    PubMed

    Edbauer, Dieter; Haass, Christian

    2016-02-01

    Expansion of a GGGGCC repeat in C9orf72 causes amyotrophic lateral sclerosis, frontotemporal dementia, or a combination of both. Bidirectional repeat transcripts sequester RNA-binding proteins into nuclear RNA foci. The repeat is translated into dipeptide repeat (DPR) proteins that are crucial for repeat-induced toxicity. DPRs inhibit the proteasome and sequester other proteins. These changes are accompanied by widespread brain atrophy and subclinical cognitive impairment before disease onset. Both repeat RNA and DPRs impair nucleocytoplasmic transport and promote TDP-43 mislocalization and aggregation. Thus, repeat RNA and DPRs may gradually trigger TDP-43 pathology and subsequent region-specific neurodegeneration in a cascade similar to amyloid-β peptide in Alzheimer's disease. The key components of the C9orf72 cascade are promising therapeutic targets in different disease stages.

  20. Laser Metal Deposition of the Intermetallic TiAl Alloy

    NASA Astrophysics Data System (ADS)

    Thomas, Marc; Malot, Thierry; Aubry, Pascal

    2017-03-01

    Laser metal deposition of the commercial intermetallic Ti-47Al-2Cr-2Nb alloy was investigated. A large number of experiments were conducted under controlled atmosphere by changing the processing parameters to manufacture a series of beads, thin walls, and massive blocks. Optimal process parameters were successfully found to prevent cracking which is generally observed in this brittle material due to built-up residual stresses during fast cooling. These non-equilibrium cooling conditions tend to generate ultra-fine and metastable structures exhibiting high microhardness values, thus requiring post-heat treatments. The latter were successfully used to restore homogeneous lamellar or duplex microstructures and to relieve residual stresses. Subsequent tensile tests enabled us to validate the soundness and homogeneity of the Intermetallic TiAl alloy. Finally, a higher mechanical performance was achieved for the LMD material with respect to cast+HIP and EBM counterparts.

  1. Extrusion of amyloid fibrils to the extracellular space in experimental mesangial AL-amyloidosis: transmission and scanning electron microscopy studies and correlation with renal biopsy observations.

    PubMed

    Teng, Jiamin; Turbat-Herrera, Elba A; Herrera, Guillermo A

    2014-04-01

    In vitro studies have provided much information regarding the process of glomerular AL-amyloidogenesis. Research efforts have been successful in deciphering how glomerulopathic light chains interact with mesangial cells. The sequential steps involved in the genesis of amyloid fibrils include interactions with surface caveolae in mesangial cells and internalization of the monoclonal light chains through a clathrin-mediated process followed by trafficking in the mesangial cells to the mature lysosomal compartment where fibrils are formed. This manuscript focuses on how mesangial cells, once amyloid has been formed, deliver the fibrils to the extracellular matrix. The delivery of amyloid fibrils to the outside of the cells is carried out by lysosomes, which abut the mesangial cell membranes and extrude their contents into the extracellular space. This final step responsible for the fibrils to be present predominantly in the extracellular space is well demonstrated with scanning electron microscopy.

  2. Interferon-gamma and tumor necrosis factor-alpha regulate amyloid-beta plaque deposition and beta-secretase expression in Swedish mutant APP transgenic mice.

    PubMed

    Yamamoto, Masaru; Kiyota, Tomomi; Horiba, Masahide; Buescher, James L; Walsh, Shannon M; Gendelman, Howard E; Ikezu, Tsuneya

    2007-02-01

    Reactive astrocytes and microglia in Alzheimer's disease surround amyloid plaques and secrete proinflammatory cytokines that affect neuronal function. Relationship between cytokine signaling and amyloid-beta peptide (Abeta) accumulation is poorly understood. Thus, we generated a novel Swedish beta-amyloid precursor protein mutant (APP) transgenic mouse in which the interferon (IFN)-gamma receptor type I was knocked out (APP/GRKO). IFN-gamma signaling loss in the APP/GRKO mice reduced gliosis and amyloid plaques at 14 months of age. Aggregated Abeta induced IFN-gamma production from co-culture of astrocytes and microglia, and IFN-gamma elicited tumor necrosis factor (TNF)-alpha secretion in wild type (WT) but not GRKO microglia co-cultured with astrocytes. Both IFN-gamma and TNF-alpha enhanced Abeta production from APP-expressing astrocytes and cortical neurons. TNF-alpha directly stimulated beta-site APP-cleaving enzyme (BACE1) expression and enhanced beta-processing of APP in astrocytes. The numbers of reactive astrocytes expressing BACE1 were increased in APP compared with APP/GRKO mice in both cortex and hippocampus. IFN-gamma and TNF-alpha activation of WT microglia suppressed Abeta degradation, whereas GRKO microglia had no changes. These results support the idea that glial IFN-gamma and TNF-alpha enhance Abeta deposition through BACE1 expression and suppression of Abeta clearance. Taken together, these observations suggest that proinflammatory cytokines are directly linked to Alzheimer's disease pathogenesis.

  3. Electromagnetic treatment to old Alzheimer's mice reverses β-amyloid deposition, modifies cerebral blood flow, and provides selected cognitive benefit.

    PubMed

    Arendash, Gary W; Mori, Takashi; Dorsey, Maggie; Gonzalez, Rich; Tajiri, Naoki; Borlongan, Cesar

    2012-01-01

    Few studies have investigated physiologic and cognitive effects of "long-term" electromagnetic field (EMF) exposure in humans or animals. Our recent studies have provided initial insight into the long-term impact of adulthood EMF exposure (GSM, pulsed/modulated, 918 MHz, 0.25-1.05 W/kg) by showing 6+ months of daily EMF treatment protects against or reverses cognitive impairment in Alzheimer's transgenic (Tg) mice, while even having cognitive benefit to normal mice. Mechanistically, EMF-induced cognitive benefits involve suppression of brain β-amyloid (Aβ) aggregation/deposition in Tg mice and brain mitochondrial enhancement in both Tg and normal mice. The present study extends this work by showing that daily EMF treatment given to very old (21-27 month) Tg mice over a 2-month period reverses their very advanced brain Aβ aggregation/deposition. These very old Tg mice and their normal littermates together showed an increase in general memory function in the Y-maze task, although not in more complex tasks. Measurement of both body and brain temperature at intervals during the 2-month EMF treatment, as well as in a separate group of Tg mice during a 12-day treatment period, revealed no appreciable increases in brain temperature (and no/slight increases in body temperature) during EMF "ON" periods. Thus, the neuropathologic/cognitive benefits of EMF treatment occur without brain hyperthermia. Finally, regional cerebral blood flow in cerebral cortex was determined to be reduced in both Tg and normal mice after 2 months of EMF treatment, most probably through cerebrovascular constriction induced by freed/disaggregated Aβ (Tg mice) and slight body hyperthermia during "ON" periods. These results demonstrate that long-term EMF treatment can provide general cognitive benefit to very old Alzheimer's Tg mice and normal mice, as well as reversal of advanced Aβ neuropathology in Tg mice without brain heating. Results further underscore the potential for EMF treatment

  4. PiB Fails to Map Amyloid Deposits in Cerebral Cortex of Aged Dogs with Canine Cognitive Dysfunction.

    PubMed

    Fast, Rikke; Rodell, Anders; Gjedde, Albert; Mouridsen, Kim; Alstrup, Aage K; Bjarkam, Carsten R; West, Mark J; Berendt, Mette; Møller, Arne

    2013-01-01

    Dogs with Canine Cognitive Dysfunction (CCD) accumulate amyloid beta (Aβ) in the brain. As the cognitive decline and neuropathology of these old dogs share features with Alzheimer's disease (AD), the relation between Aβ and cognitive decline in animal models of cognitive decline is of interest to the understanding of AD. However, the sensitivity of the biomarker Pittsburgh Compound B (PiB) to the presence of Aβ in humans and in other mammalian species is in doubt. To test the sensitivity and assess the distribution of Aβ in dog brain, we mapped the brains of dogs with signs of CCD (n = 16) and a control group (n = 4) of healthy dogs with radioactively labeled PiB ([(11)C]PiB). Structural magnetic resonance imaging brain scans were obtained from each dog. Tracer washout analysis yielded parametric maps of PiB retention in brain. In the CCD group, dogs had significant retention of [(11)C]PiB in the cerebellum, compared to the cerebral cortex. Retention in the cerebellum is at variance with evidence from brains of humans with AD. To confirm the lack of sensitivity, we stained two dog brains with the immunohistochemical marker 6E10, which is sensitive to the presence of both Aβ and Aβ precursor protein (AβPP). The 6E10 stain revealed intracellular material positive for Aβ or AβPP, or both, in Purkinje cells. The brains of the two groups of dogs did not have significantly different patterns of [(11)C]PiB binding, suggesting that the material detected with 6E10 is AβPP rather than Aβ. As the comparison with the histological images revealed no correlation between the [(11)C]PiB and Aβ and AβPP deposits in post-mortem brain, the marked intracellular staining implies intracellular involvement of amyloid processing in the dog brain. We conclude that PET maps of [(11)C]PiB retention in brain of dogs with CCD fundamentally differ from the images obtained in most humans with AD.

  5. Treadmill exercise enhances synaptic plasticity, but does not alter β-amyloid deposition in hippocampi of aged APP/PS1 transgenic mice.

    PubMed

    Zhao, G; Liu, H L; Zhang, H; Tong, X J

    2015-07-09

    Several studies reveal that the beneficial effects of exercise interventions are dependent on the progression of Alzheimer's disease (AD). We have previously shown that long-term treadmill exercise begun before the onset of β-amyloid (Aβ) pathology prevents the deficits of cognition and long-term potentiation (LTP) in amyloid precursor protein (APP)/presenilin 1 (PS1) transgenic mice (8 months of age) paralleled by the reduction of soluble Aβ levels and Aβ deposition in the hippocampus. In the present study, treadmill exercise was initiated at a developed Aβ deposition stage in order to further investigate whether or not treadmill exercise in this phase can delay the progression of AD in aged APP/PS1 mice (17 months of age). Our results show that 5-month treadmill exercise ameliorates the impairment of spatial learning and memory with age paralleled by synaptic plasticity enhancement in aged APP/PS1 mice. In addition, exercise-induced enhancement of synaptic plasticity was accompanied by a significant reduction of soluble Aβ levels rather than Aβ plaque deposition. Therefore, the investigation demonstrates that long-term treadmill exercise has beneficial effects on cognition and synaptic plasticity even when the brain has developed Aβ deposition, and changes in soluble Aβ levels rather than Aβ plaque deposition may contribute to exercise-induced benefits.

  6. Light Chain Amyloid Fibrils Cause Metabolic Dysfunction in Human Cardiomyocytes

    PubMed Central

    McWilliams-Koeppen, Helen P.; Foster, James S.; Hackenbrack, Nicole; Ramirez-Alvarado, Marina; Donohoe, Dallas; Williams, Angela; Macy, Sallie; Wooliver, Craig; Wortham, Dale; Morrell-Falvey, Jennifer; Foster, Carmen M.; Kennel, Stephen J.; Wall, Jonathan S.

    2015-01-01

    Light chain (AL) amyloidosis is the most common form of systemic amyloid disease, and cardiomyopathy is a dire consequence, resulting in an extremely poor prognosis. AL is characterized by the production of monoclonal free light chains that deposit as amyloid fibrils principally in the heart, liver, and kidneys causing organ dysfunction. We have studied the effects of amyloid fibrils, produced from recombinant λ6 light chain variable domains, on metabolic activity of human cardiomyocytes. The data indicate that fibrils at 0.1 μM, but not monomer, significantly decrease the enzymatic activity of cellular NAD(P)H-dependent oxidoreductase, without causing significant cell death. The presence of amyloid fibrils did not affect ATP levels; however, oxygen consumption was increased and reactive oxygen species were detected. Confocal fluorescence microscopy showed that fibrils bound to and remained at the cell surface with little fibril internalization. These data indicate that AL amyloid fibrils severely impair cardiomyocyte metabolism in a dose dependent manner. These data suggest that effective therapeutic intervention for these patients should include methods for removing potentially toxic amyloid fibrils. PMID:26393799

  7. Light Chain Amyloid Fibrils Cause Metabolic Dysfunction in Human Cardiomyocytes

    SciTech Connect

    McWilliams-Koeppen, Helen P.; Foster, James S.; Hackenbrack, Nicole; Ramirez-Alvarado, Marina; Donohoe, Dallas; Williams, Angela; Macy, Sallie; Wooliver, Craig; Wortham, Dale; Morrell-Falvey, Jennifer; Foster, Carmen M.; Kennel, Stephen J.; Wall, Jonathan S.

    2015-09-22

    Light chain (AL) amyloidosis is the most common form of systemic amyloid disease, and cardiomyopathy is a dire consequence, resulting in an extremely poor prognosis. AL is characterized by the production of monoclonal free light chains that deposit as amyloid fibrils principally in the heart, liver, and kidneys causing organ dysfunction. We have studied the effects of amyloid fibrils, produced from recombinant λ6 light chain variable domains, on metabolic activity of human cardiomyocytes. The data indicate that fibrils at 0.1 μM, but not monomer, significantly decrease the enzymatic activity of cellular NAD(P)H-dependent oxidoreductase, without causing significant cell death. The presence of amyloid fibrils did not affect ATP levels; however, oxygen consumption was increased and reactive oxygen species were detected. Confocal fluorescence microscopy showed that fibrils bound to and remained at the cell surface with little fibril internalization. Ultimately, these data indicate that AL amyloid fibrils severely impair cardiomyocyte metabolism in a dose dependent manner. These data suggest that effective therapeutic intervention for these patients should include methods for removing potentially toxic amyloid fibrils.

  8. Light Chain Amyloid Fibrils Cause Metabolic Dysfunction in Human Cardiomyocytes

    DOE PAGES

    McWilliams-Koeppen, Helen P.; Foster, James S.; Hackenbrack, Nicole; ...

    2015-09-22

    Light chain (AL) amyloidosis is the most common form of systemic amyloid disease, and cardiomyopathy is a dire consequence, resulting in an extremely poor prognosis. AL is characterized by the production of monoclonal free light chains that deposit as amyloid fibrils principally in the heart, liver, and kidneys causing organ dysfunction. We have studied the effects of amyloid fibrils, produced from recombinant λ6 light chain variable domains, on metabolic activity of human cardiomyocytes. The data indicate that fibrils at 0.1 μM, but not monomer, significantly decrease the enzymatic activity of cellular NAD(P)H-dependent oxidoreductase, without causing significant cell death. The presencemore » of amyloid fibrils did not affect ATP levels; however, oxygen consumption was increased and reactive oxygen species were detected. Confocal fluorescence microscopy showed that fibrils bound to and remained at the cell surface with little fibril internalization. Ultimately, these data indicate that AL amyloid fibrils severely impair cardiomyocyte metabolism in a dose dependent manner. These data suggest that effective therapeutic intervention for these patients should include methods for removing potentially toxic amyloid fibrils.« less

  9. Replacement of brain-resident myeloid cells does not alter cerebral amyloiddeposition in mouse models of Alzheimer’s disease

    PubMed Central

    Varvel, Nicholas H.; Grathwohl, Stefan A.; Degenhardt, Karoline; Resch, Claudia; Bosch, Andrea; Jucker, Mathias

    2015-01-01

    Immune cells of myeloid lineage are encountered in the Alzheimer’s disease (AD) brain, where they cluster around amyloid-β plaques. However, assigning functional roles to myeloid cell subtypes has been problematic, and the potential for peripheral myeloid cells to alleviate AD pathology remains unclear. Therefore, we asked whether replacement of brain-resident myeloid cells with peripheral monocytes alters amyloid deposition in two mouse models of cerebral β-amyloidosis (APP23 and APPPS1). Interestingly, early after repopulation, infiltrating monocytes neither clustered around plaques nor showed Trem2 expression. However, with increasing time in the brain, infiltrating monocytes became plaque associated and also Trem2 positive. Strikingly, however, monocyte repopulation for up to 6 mo did not modify amyloid load in either model, independent of the stage of pathology at the time of repopulation. Our results argue against a long-term role of peripheral monocytes that is sufficiently distinct from microglial function to modify cerebral β-amyloidosis. Therefore, myeloid replacement by itself is not likely to be effective as a therapeutic approach for AD. PMID:26458770

  10. N-terminal region of myelin basic protein reduces fibrillar amyloiddeposition in Tg-5xFAD mice.

    PubMed

    Ou-Yang, Ming-Hsuan; Xu, Feng; Liao, Mei-Chen; Davis, Judianne; Robinson, John K; Van Nostrand, William E

    2015-02-01

    Alzheimer's disease is a progressive neurodegenerative disorder that is characterized by extensive deposition of fibrillar amyloid-β (Aβ) in the brain. Previously, myelin basic protein (MBP) was identified to be a potent inhibitor to Aβ fibril formation, and this inhibitory activity was localized to the N-terminal residues 1-64, a fragment designated MBP1. Here, we show that the modest neuronal expression of a fusion protein of the biologically active MBP1 fragment and the enhanced green fluorescent protein (MBP1-EGFP) significantly improved the performance of spatial learning memory in Tg-5xFAD mice, a model of pathologic Aβ accumulation in brain. The levels of insoluble Aβ and fibrillar amyloid were significantly reduced in bigenic Tg-5xFAD/Tg-MBP1-EGFP mice. Quantitative stereological analysis revealed that the reduction in amyloid was because of a reduction in the size of fibrillar plaques rather than a decrease in plaque numbers. The current findings support previous studies showing that MBP1 inhibits Aβ fibril formation in vitro and demonstrate the ability of MBP1 to reduce Aβ pathology and improve behavioral performance.

  11. Pathway-specific polygenic risk scores as predictors of β-amyloid deposition and cognitive function in a sample at increased risk for Alzheimer’s disease

    PubMed Central

    Darst, Burcu F.; Koscik, Rebecca L.; Racine, Annie M.; Oh, Jennifer M.; Krause, Rachel A.; Carlsson, Cynthia M.; Zetterberg, Henrik; Blennow, Kaj; Christian, Bradley T.; Bendlin, Barbara B.; Okonkwo, Ozioma C.; Hogan, Kirk J.; Hermann, Bruce P.; Sager, Mark A.; Asthana, Sanjay; Johnson, Sterling C.; Engelman, Corinne D.

    2016-01-01

    Polygenic risk scores (PRSs) have been used to combine the effects of variants with small effects identified by genome-wide association studies. We explore the potential for using pathway-specific PRSs as predictors of early changes in Alzheimer’s disease (AD)-related biomarkers and cognitive function. Participants were from the Wisconsin Registry for Alzheimer’s Prevention, a longitudinal study of adults who were cognitively asymptomatic at enrollment and enriched for a parental history of AD. Using genes associated with AD in the International Genomics of Alzheimer’s Project’s meta-analysis, we identified clusters of genes that grouped into pathways involved in β-amyloid (Aβ) deposition and neurodegeneration: Aβ clearance, cholesterol metabolism, and immune response. Weighted pathway-specific and overall PRSs were developed and compared to APOE alone. Mixed models were used to assess whether each PRS was associated with cognition in 1,200 individuals, cerebral Aβ deposition measured using amyloid ligand (Pittsburgh compound B) positron emission imaging (PET) in 168 individuals, and cerebrospinal fluid (CSF) Aβ deposition, neurodegeneration, and tau pathology in 111 individuals, with replication performed in an independent sample. We found that PRSs including APOE appeared to be driven by the inclusion of APOE, suggesting that the pathway-specific PRSs used here were not more predictive than an overall PRS or APOE alone. However, pathway-specific PRSs could prove to be useful as more knowledge is gained on the genetic variants involved in specific biological pathways of AD. PMID:27662287

  12. Surface preparation and homoepitaxial deposition of AlN on (0001)-oriented AlN substrates by metalorganic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Rice, A.; Collazo, R.; Tweedie, J.; Dalmau, R.; Mita, S.; Xie, J.; Sitar, Z.

    2010-08-01

    Chemical surface treatments were conducted on mechanically polished (MP) and chemomechanically polished (CMP) (0001)-oriented single crystalline aluminum nitride (AlN) substrates to determine a surface preparation procedure for the homoepitaxial deposition of AlN epitaxial layers by metalorganic chemical vapor deposition. MP AlN substrates characterized by atomic force microscopy exhibited 0.5 nm rms roughness and polishing scratches, while CMP AlN substrates exhibited 0.1 nm rms roughness and were scratch-free. X-ray photoelectron spectroscopy analysis of MP and CMP AlN substrates indicated the presence of a surface hydroxide layer composed of mixed aluminum oxide hydroxide and aluminum trihydroxide. Wet etching with sulfuric and phosphoric acid mixtures reduced the amount of surface hydroxide. Ammonia annealing at 1250 °C converted the substrate hydroxide layer to AlN and increased the rms roughness of MP and CMP AlN substrates to 2.2 nm and 0.2 nm, respectively. AlN epitaxial layers were deposited at 1100-1250 °C under 20 Torr total pressure with a V/III ratio of 180-300 in either N2 or H2 diluent. High-resolution x-ray diffraction measurements revealed that AlN epitaxial layers deposited on MP substrates were strained due to nucleation and coalescence of AlN grains on the mechanically damaged surfaces. AlN deposited on CMP substrates was epitaxial and strain-free. Thermodynamic models for nitridation and AlN deposition were also proposed and evaluated.

  13. AMYLOID NEUROPATHIES

    PubMed Central

    Shin, Susan C.; Robinson-Papp, Jessica

    2012-01-01

    Peripheral neuropathy is a common complication of many of the systemic amyloidoses. Although the cause of neuropathy is not entirely clear, it is likely related to amyloid deposition within the nerve. This may lead to focal, multifocal, or diffuse neuropathies involving sensory, motor and/or autonomic fibers. The presenting symptoms depend on the distribution of nerves affected. One of the most common phenotypes is sensorimotor polyneuropathy, which is characterized by symptoms of neuropathic pain, numbness, and in advanced cases weakness. Symptoms begin in the feet and ultimately progress to the proximal legs and hands. The most common focal neuropathy is a median neuropathy at the wrist, or clinically known as carpal tunnel syndrome. Carpal tunnel symptoms may include pain and sensory disturbances in the lateral palm and fingers; hand weakness may ensue if the focal neuropathy is severe. Autonomic neuropathy may affect a variety of organ systems such as the cardiovascular, gastrointestinal, and genitourinary systems. Symptoms may be non-specific making the diagnosis of autonomic neuropathy more difficult to identify. However, it is important to recognize and distinguish autonomic neuropathy from diseases of the end-organs themselves. This chapter reviews the inherited and acquired amyloidoses that affect the peripheral nervous system including familial amyloid polyneuropathy, and primary, secondary and senile amyloidosis. We emphasize the clinical presentation of the neurologic aspects of these diseases, physical examination findings, appropriate diagnostic evaluation, treatment and prognosis. PMID:23239211

  14. Kinetics and Properties of Micro Arc Oxidation Coatings Deposited on Commercial Al Alloys

    NASA Astrophysics Data System (ADS)

    Krishna, L. Rama; Purnima, A. Sudha; Wasekar, Nitin P.; Sundararajan, G.

    2007-02-01

    The micro arc oxidation (MAO) technique is being increasingly recognized as a novel and ecofriendly means of depositing dense ceramic oxide coatings on Al and its alloys. In the present study, the deposition kinetics, surface roughness, morphology, phase distribution and the microhardness of the MAO coatings deposited on ten different commercially available Al substrates having widely differing chemical composition has been investigated. Further, the tribological properties of the coatings obtained on different Al alloys in comparison with the bare substrates have also been evaluated using dry sand abrasion, solid-particle erosion and pin-on-disc dry sliding wear tests. The results clearly demonstrate that the alloying elements added to the Al substrate substantially influence the MAO coating deposition kinetics and coating properties. In the case of Al-Si alloys, the coating deposition kinetics is non-linear and the Al6Si2O13 (mullite) is observed to form. With increasing Si content, the corresponding mullite phase also increases. Increasing mullite content in the coating adversely affects the tribological performance. Excepting Al-Si alloys, all other alloys investigated including commercial purity Al exhibit linear coating deposition kinetics. Of all the alloys investigated, Al-Li alloy exhibits the highest coating deposition rate and the 6061 T6 Al alloy exhibits the best coating properties.

  15. Origins of amyloid

    PubMed Central

    2013-01-01

    Background Amyloid-β plaques are a defining characteristic of Alzheimer Disease. However, Amyloiddeposition is also found in other forms of dementia and in non-pathological contexts. Amyloiddeposition is variable among vertebrate species and the evolutionary emergence of the amyloidogenic property is currently unknown. Evolutionary persistence of a pathological peptide sequence may depend on the functions of the precursor gene, conservation or mutation of nucleotides or peptide domains within the precursor gene, or a species-specific physiological environment. Results In this study, we asked when amyloidogenic Amyloid-β first arose using phylogenetic trees constructed for the Amyloid-β Precursor Protein gene family and by modeling the potential for Amyloid-β aggregation across species in silico. We collected the most comprehensive set of sequences for the Amyloid-β Precursor Protein family using an automated, iterative meta-database search and constructed a highly resolved phylogeny. The analysis revealed that the ancestral gene for invertebrate and vertebrate Amyloid-β Precursor Protein gene families arose around metazoic speciation during the Ediacaran period. Synapomorphic frequencies found domain-specific conservation of sequence. Analyses of aggregation potential showed that potentially amyloidogenic sequences are a ubiquitous feature of vertebrate Amyloid-β Precursor Protein but are also found in echinoderm, nematode, and cephalochordate, and hymenoptera species homologues. Conclusions The Amyloid-β Precursor Protein gene is ancient and highly conserved. The amyloid forming Amyloid-β domains may have been present in early deuterostomes, but more recent mutations appear to have resulted in potentially unrelated amyoid forming sequences. Our results further highlight that the species-specific physiological environment is as critical to Amyloid-β formation as the peptide sequence. PMID:23627794

  16. X-ray photoelectron spectroscopic study of the chemical vapor deposited W/Al interface

    NASA Astrophysics Data System (ADS)

    Ohshima, H.; Katayama, M.; Onoda, K.; Hattori, T.; Suzuki, H.; Tokuda, Y.

    1993-07-01

    The dependence of the amount of aluminum trifluoride (AlF3) piled up at the interface of chemical vapor deposited tungsten and the aluminum under layer on the deposition time and subsequent annealing in ultrahigh vacuum (UHV) or in monosilane (SiH4) gas has been studied. AlF3 is formed by the reaction of the aluminum under layer with tungsten hexafluoride (WF6) during the initial state of tungsten chemical vapor deposition. Tungsten was deposited on an Al layer under selective deposition conditions by SiH4 reduction at 250 °C. X-ray photoelectron spectroscopy measurement reveals that the amount of AlF3 decreases with an increase in the tungsten deposition time and that the reduction of AlF3 by volatilization of aluminum fluorides, which occurs at higher temperatures (≳400 °C) is not observed at low temperature (270 °C). Annealing in SiH4 gas after the tungsten deposition was effective to reduce the amount of AlF3 compared with annealing in UHV. This result and thermochemical data would suggest that the dependence of the amount of AlF3 on the tungsten deposition time is explained by the reduction of AlF3 with hydrogen atoms supplied from the dissociation of SiH4.

  17. Genesis and evolution of the Baid al Jimalah tungsten deposit, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Kamilli, Robert J.

    1986-01-01

    Baid al Jimalah is similar in character and origin to other tungsten-tin greisen deposits in the world, especially the Hemerdon deposit in Devon, England. It is also analogous to Climax-type molybdenum deposits, which contain virtually identical mineral assemblages, but with the relative intensities of the molybdenum and tungsten mineralization reversed.

  18. HIV Associated Neurocognitive Disorder (HAND) is Not Associated with Increased Fibrillar Amyloid Deposits Using 11C-PiB in Middle-Aged HIV+ Participants

    PubMed Central

    Ances, Beau M.; Benzinger, Tammie L.; Christensen, Jon J.; Thomas, Jewell; Venkat, Rohit; Teshome, Mengesha; Aldea, Patricia; Fagan, Anne M.; Holtzman, David M.; Morris, John C.; Clifford, David B.

    2011-01-01

    Objectives Diagnostic challenges exist for differentiating HIV associated neurocognitive disorders (HAND) from symptomatic Alzheimer’s disease (AD) in HIV+ participants. Both disorders have cerebral amyloid containing plaques associated with abnormalities in amyloid beta protein 1–42 (Aβ42) metabolism. We evaluated if the amyloid-binding agent 11C-Pittsburgh compound B (11C-PiB) could discriminate AD from HAND in middle-aged HIV+ participants. Design 11C-PiB scanning, clinical assessment, and cerebrospinal fluid (CSF) analysis were performed. χ2 and t-tests assessed differences in clinical and demographic variables between HIV+ participants and community-living individuals followed by Alzheimer Disease Research Center (ADRC). An analysis of variance (ANOVA) assessed for regional differences in Aβ42 using 11C-PiB. Setting ADRC and HIV clinic Participants 16 HIV+ participants (11 cognitively normal, 5 with HAND) and 19 ADRC participants (8 cognitively normal, 11 with symptomatic AD). Main Outcome Measure(s) Mean and regional 11C-PiB binding potentials Results Symptomatic AD were older (p < 0.001), had lower CSF Aβ42 (p < 0.001), and had higher CSF tau levels (p < 0.001) than other groups. Regardless of degree of impairment, HIV+ participants did not have increased 11C-PiB. Mean and regional binding potentials were elevated for symptomatic AD participants (p <0.0001). Conclusions Middle-aged HIV+ participants, even with HAND, do not exhibit increased 11C-PiB while symptomatic AD individuals have increased fibrillar Aβ42 deposition in cortical and subcortical regions. Observed dissimilarities between HAND and AD may reflect differences in Aβ42 metabolism. 11C-PiB may provide a diagnostic biomarker for distinguishing symptomatic AD from HAND in middle-aged HIV+ participants. Future cross sectional and longitudinal studies are required to assess utility of 11C-PiB in older HAND individuals. PMID:22232345

  19. Brain Accumulation of Amyloid-beta in Non-Alzheimer Neurodegeneration.

    PubMed

    Primavera, James; Lu, Bing-Xun; Riskind, Peter J.; Iulian, Maria; De La Monte, Suzanne M.

    1999-10-01

    We report an unusual case of amyotrophic lateral sclerosis (ALS) marked by extensive cerebral amyloid-beta deposition in small and medium-size vessels, capillaries, and perivascular plaques in the cerebral cortex, and in most leptomeningeal vessels. Despite considerable cerebral amyloidosis, the patient remained cognitively intact until death. For comparison with other neuro-degenerative diseases and normal aging, we assessed the densities of amyloid-beta-immunoreactive cortical vessels and plaques in matched frontal and temporal lobe sections from archival uncomplicated cases of Alzheimer's disease (N=10), Pick's disease (PkD; N=4), Parkinson's disease (PD; N=6), Diffuse Lewy body disease (DLBD; N=7), progressive supranuclear palsy (PSP; N=5), multiple systems atrophy (MSA; N=4), ALS (N=7), or normal aging (N=10) by semi-quantitative grading (0 to 3+). Moderate (2+) or abundant (3+) cerebrovascular amyloid-beta immunoreactivity was detected in 8/10 AD, 3/7 DLBD, 3/6 PD, 1 each with PSP or PkD, and 2/10 controls. Moderate or abundant densities of amyloid-beta-immunoreactive diffuse plaques were detected in all cases of AD or DLBD, 4/6 with PD, 3/5 with PSP, and 2/10 controls. Moderate or abundant amyloid-beta-immunoreactive mature (dense core) plaques were present in all cases of AD or DLBD, and 3 each with PD or PSP. Importantly, amyloid-beta-immunoreactivity was not observed in the 4 MSA or 7 archival ALS cases. This study demonstrates that prominent amyloid-beta accumulation in cerebral vessels and plaques occurs frequently in AD, DLBD, PSP, and PD, but not in ALS or MSA, indicating that the case described is unique. The lack of cognitive impairment in the case presented argues against the idea that extensive amyloid-beta deposition in the brain causes dementia.

  20. Effects of Al Doping on the Properties of ZnO Thin Films Deposited by Atomic Layer Deposition

    NASA Astrophysics Data System (ADS)

    Zhai, Chen-Hui; Zhang, Rong-Jun; Chen, Xin; Zheng, Yu-Xiang; Wang, Song-You; Liu, Juan; Dai, Ning; Chen, Liang-Yao

    2016-09-01

    The tuning of structural, optical, and electrical properties of Al-doped ZnO films deposited by atomic layer deposition technique is reported in this work. With the increasing Al doping level, the evolution from (002) to (100) diffraction peaks indicates the change in growth mode of ZnO films. Spectroscopic ellipsometry has been applied to study the thickness, optical constants, and band gap of AZO films. Due to the increasing carrier concentration after Al doping, a blue shift of band gap and absorption edge can be observed, which can be interpreted by Burstein-Moss effect. The carrier concentration and resistivity are found to vary significantly among different doping concentration, and the optimum value is also discussed. The modulations and improvements of properties are important for Al-doped ZnO films to apply as transparent conductor in various applications.

  1. Effects of Al Doping on the Properties of ZnO Thin Films Deposited by Atomic Layer Deposition.

    PubMed

    Zhai, Chen-Hui; Zhang, Rong-Jun; Chen, Xin; Zheng, Yu-Xiang; Wang, Song-You; Liu, Juan; Dai, Ning; Chen, Liang-Yao

    2016-12-01

    The tuning of structural, optical, and electrical properties of Al-doped ZnO films deposited by atomic layer deposition technique is reported in this work. With the increasing Al doping level, the evolution from (002) to (100) diffraction peaks indicates the change in growth mode of ZnO films. Spectroscopic ellipsometry has been applied to study the thickness, optical constants, and band gap of AZO films. Due to the increasing carrier concentration after Al doping, a blue shift of band gap and absorption edge can be observed, which can be interpreted by Burstein-Moss effect. The carrier concentration and resistivity are found to vary significantly among different doping concentration, and the optimum value is also discussed. The modulations and improvements of properties are important for Al-doped ZnO films to apply as transparent conductor in various applications.

  2. Al2O3 on Black Phosphorus by Atomic Layer Deposition: An in Situ Interface Study.

    PubMed

    Zhu, Hui; McDonnell, Stephen; Qin, Xiaoye; Azcatl, Angelica; Cheng, Lanxia; Addou, Rafik; Kim, Jiyoung; Ye, Peide D; Wallace, Robert M

    2015-06-17

    In situ "half cycle" atomic layer deposition (ALD) of Al2O3 was carried out on black phosphorus ("black-P") surfaces with modified phosphorus oxide concentrations. X-ray photoelectron spectroscopy is employed to investigate the interfacial chemistry and the nucleation of the Al2O3 on black-P surfaces. This work suggests that exposing a sample that is initially free of phosphorus oxide to the ALD precursors does not result in detectable oxidation. However, when the phosphorus oxide is formed on the surface prior to deposition, the black-P can react with both the surface adventitious oxygen contamination and the H2O precursor at a deposition temperature of 200 °C. As a result, the concentration of the phosphorus oxide increases after both annealing and the atomic layer deposition process. The nucleation rate of Al2O3 on black-P is correlated with the amount of oxygen on samples prior to the deposition. The growth of Al2O3 follows a "substrate inhibited growth" behavior where an incubation period is required. Ex situ atomic force microscopy is also used to investigate the deposited Al2O3 morphologies on black-P where the Al2O3 tends to form islands on the exfoliated black-P samples. Therefore, surface functionalization may be needed to get a conformal coverage of Al2O3 on the phosphorus oxide free samples.

  3. Optogenetic Restoration of Disrupted Slow Oscillations Halts Amyloid Deposition and Restores Calcium Homeostasis in an Animal Model of Alzheimer’s Disease

    PubMed Central

    Kastanenka, Ksenia V.; Hou, Steven S.; Shakerdge, Naomi; Logan, Robert; Feng, Danielle; Wegmann, Susanne; Chopra, Vanita; Hawkes, Jonathan M.; Chen, Xiqun; Bacskai, Brian J.

    2017-01-01

    Slow oscillations are important for consolidation of memory during sleep, and Alzheimer’s disease (AD) patients experience memory disturbances. Thus, we examined slow oscillation activity in an animal model of AD. APP mice exhibit aberrant slow oscillation activity. Aberrant inhibitory activity within the cortical circuit was responsible for slow oscillation dysfunction, since topical application of GABA restored slow oscillations in APP mice. In addition, light activation of channelrhodopsin-2 (ChR2) expressed in excitatory cortical neurons restored slow oscillations by synchronizing neuronal activity. Driving slow oscillation activity with ChR2 halted amyloid plaque deposition and prevented calcium overload associated with this pathology. Thus, targeting slow oscillatory activity in AD patients might prevent neurodegenerative phenotypes and slow disease progression. PMID:28114405

  4. Evaluation of systemic amyloidosis by scintigraphy with sup 123 I-labeled serum amyloid P component

    SciTech Connect

    Hawkins, P.N.; Lavender, J.P.; Pepys, M.B. )

    1990-08-23

    In systemic amyloidosis the distribution and progression of disease have been difficult to monitor, because they can be demonstrated only by biopsy. Serum amyloid P component (SAP) is a normal circulating plasma protein that is deposited on amyloid fibrils because of its specific binding affinity for them. We investigated whether labeled SAP could be used to locate amyloid deposits. Purified human SAP labeled with iodine-123 was given intravenously to 50 patients with biopsy-proved systemic amyloidosis--25 with the AL (primary) type and 25 with the AA (secondary) type--and to 26 control patients with disease and 10 healthy subjects. Whole-body images and regional views were obtained after 24 hours and read in a blinded fashion. In the patients with amyloidosis the 123I-SAP was localized rapidly and specifically in amyloid deposits. The scintigraphic images obtained were characteristic and appeared to identify the extent of amyloid deposition in all 50 patients. There was no uptake of the 123I-SAP by the control patients and the healthy subjects. In all patients with AA amyloidosis the spleen was affected, whereas the scans showed uptake in the heart, skin, carpal region, and bone marrow only in patients with the AL type. Positive images were seen in six patients in whom biopsies had been negative or unsuccessful; in all six, amyloid was subsequently found on biopsy or at autopsy. Progressive amyloid deposition was observed in 9 of 11 patients studied serially. Scintigraphy after the injection of 123I-SAP can be used for diagnosing, locating, and monitoring the extent of systemic amyloidosis.

  5. Magnetron deposited TiN coatings for protection of Al-Cu-Ag-Mg-Mn alloy

    NASA Astrophysics Data System (ADS)

    Stepanova, Tatiana V.; Kaziev, Andrey V.; Atamanov, Mikhail V.; Tumarkin, Alexander V.; Dolzhikova, Svetlana A.; Izmailova, Nelly Ph; Kharkov, Maxim M.; Berdnikova, Maria M.; Mozgrin, Dmitry V.; Pisarev, Alexander A.

    2016-09-01

    TiN coatings were deposited on a new Al super-alloy by magnetron sputtering in argon/nitrogen environment. The deposited layer structure, microhardness, adhesion, corrosion resistance, and fatigue life were investigated and tests demonstrated improved performance of the alloy.

  6. Characteristics of nanocomposite ZrO2/Al2O3 films deposited by plasma-enhanced atomic layer deposition.

    PubMed

    Yun, Sun Jin; Lim, Jung Wook; Kim, Hyun-Tak

    2007-11-01

    Nanocomposite ZrO2/Al2O3 (ZAO) films were deposited on Si by plasma-enhanced atomic layer deposition and the film characteristics including interfacial oxide formation, dielectric constant (k), and electrical breakdown strength were investigated without post-annealing process. In both the mixed and nano-laminated ZAO films, the thickness of the interfacial oxide layer (T(IL)) was considerably reduced compared to ZrO2 and Al2O3 films. The T(IL) was 0.8 nm in nano-composite films prepared at a mixing ratio (ZrO2:Al2O3) of 1:1. The breakdown strength and the leakage current level were greatly improved by adding Al2O3 as little as 7.9% compared to that of ZrO2 and were enhanced more with increasing content of Al2O3. The k of ZrO2 and mixed ZAO (Al2O3 7.9%) films were 20.0 and 16.5, respectively. These results indicate that the addition of Al2O3 to ZrO2 greatly improves the electrical properties with less cost of k compared to the addition of SiO2.

  7. Strain and Cohesive Energy of TiN Deposit on Al(001) Surface: Density Functional Calculation

    NASA Astrophysics Data System (ADS)

    Ren, Yuan; Liu, Xuejie

    2016-07-01

    To apply the high hardness of TiN film to soft and hard multilayer composite sheets, we constructed a new type of composite structural material with ultra-high strength. The strain of crystal and cohesive energy between the atoms in the eight structures of N atom, Ti atom, 2N2Ti island and TiN rock salt deposited on the Al(001) surface were calculated with the first-principle ultra-soft pseudopotential approach of the plane wave based on the density functional theory. The calculations of the cohesive energy showed that N atoms could be deposited in the face-centered-cubic vacancy position of the Al(001) surface and results in a cubic structure AlN surface. The TiN film could be deposited on the interface of β-AlN. The calculations of the strains showed that the strain in the TiN film deposited on the Al(001) surface was less than that in the 2N2Ti island deposited on the Al(001) surface. The diffusion behavior of interface atom N was investigated by a nudged elastic band method. Diffusion energy calculation showed that the N atom hardly diffused to the substrate Al layer.

  8. Atomic layer deposition of Al-doped ZnO thin films

    SciTech Connect

    Tynell, Tommi; Yamauchi, Hisao; Karppinen, Maarit; Okazaki, Ryuji; Terasaki, Ichiro

    2013-01-15

    Atomic layer deposition has been used to fabricate thin films of aluminum-doped ZnO by depositing interspersed layers of ZnO and Al{sub 2}O{sub 3} on borosilicate glass substrates. The growth characteristics of the films have been investigated through x-ray diffraction, x-ray reflection, and x-ray fluorescence measurements, and the efficacy of the Al doping has been evaluated through optical reflectivity and Seebeck coefficient measurements. The Al doping is found to affect the carrier density of ZnO up to a nominal Al dopant content of 5 at. %. At nominal Al doping levels of 10 at. % and higher, the structure of the films is found to be strongly affected by the Al{sub 2}O{sub 3} phase and no further carrier doping of ZnO is observed.

  9. Preparation of γ-Al2O3 films by laser chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Gao, Ming; Ito, Akihiko; Goto, Takashi

    2015-06-01

    γ- and α-Al2O3 films were prepared by chemical vapor deposition using CO2, Nd:YAG, and InGaAs lasers to investigate the effects of varying the laser wavelength and deposition conditions on the phase composition and microstructure. The CO2 laser was found to mostly produce α-Al2O3 films, whereas the Nd:YAG and InGaAs lasers produced γ-Al2O3 films when used at a high total pressure. γ-Al2O3 films had a cauliflower-like structure, while the α-Al2O3 films had a dense and columnar structure. Of the three lasers, it was the Nd:YAG laser that interacted most with intermediate gas species. This promoted γ-Al2O3 nucleation in the gas phase at high total pressure, which explains the cauliflower-like structure of nanoparticles observed.

  10. Deposition and characterization of highly energetic Al/MoOx multilayer nano-films

    NASA Astrophysics Data System (ADS)

    Fu, Shuai; Zhu, Ying; Li, Dongle; Zhu, Peng; Hu, Bo; Ye, Yinghua; Shen, Ruiqi

    2013-12-01

    Al/MoOx nanoenergetic multilayer films (nEMFs) were deposited by magnetron deposition method. The samples with bilayer thicknesses of 75 nm and 225 nm were prepared, respectively, and the total thickness is 3 μm. The as-deposited Al/MoOx nEMFs were characterized with varied analytical techniques, including SEM, XRD, XPS and DSC. Results show that the MoOx films are amorphous, and are composed of MoO3, Mo2O5 and MoO2. The values of heat release in samples are 3524 J/g and 2508 J/g, respectively, and the final products are Mo, MoO2, and Al2O3. Finally, the reaction paths and reaction kinetics of Al/MoOx exothermic reactions were discussed.

  11. Vitamin C deficiency in the brain impairs cognition, increases amyloid accumulation and deposition, and oxidative stress in APP/PSEN1 and normally aging mice.

    PubMed

    Dixit, Shilpy; Bernardo, Alexandra; Walker, Jennifer Michelle; Kennard, John Andrew; Kim, Grace Youngeun; Kessler, Eric Sean; Harrison, Fiona Edith

    2015-04-15

    Subclinical vitamin C deficiency is widespread in many populations, but its role in both Alzheimer's disease and normal aging is understudied. In the present study, we decreased brain vitamin C in the APPSWE/PSEN1deltaE9 mouse model of Alzheimer's disease by crossing APP/PSEN1(+) bigenic mice with SVCT2(+/-) heterozygous knockout mice, which have lower numbers of the sodium-dependent vitamin C transporter required for neuronal vitamin C transport. SVCT2(+/-) mice performed less well on the rotarod task at both 5 and 12 months of age compared to littermates. SVCT2(+/-) and APP/PSEN1(+) mice and the combination genotype SVCT2(+/-)APP/PSEN1(+) were also impaired on multiple tests of cognitive ability (olfactory memory task, Y-maze alternation, conditioned fear, Morris water maze). In younger mice, both low vitamin C (SVCT2(+/-)) and APP/PSEN1 mutations increased brain cortex oxidative stress (malondialdehyde, protein carbonyls, F2-isoprostanes) and decreased total glutathione compared to wild-type controls. SVCT2(+/-) mice also had increased amounts of both soluble and insoluble Aβ1-42 and a higher Aβ1-42/1-40 ratio. By 14 months of age, oxidative stress levels were similar among groups, but there were more amyloid-β plaque deposits in both hippocampus and cortex of SVCT2(+/-)APP/PSEN1(+) mice compared to APP/PSEN1(+) mice with normal brain vitamin C. These data suggest that even moderate intracellular vitamin C deficiency plays an important role in accelerating amyloid pathogenesis, particularly during early stages of disease development, and that these effects are likely modulated by oxidative stress pathways.

  12. Al2O3 thin films by plasma-enhanced chemical vapour deposition using trimethyl-amine alane (TMAA) as the Al precursor

    NASA Astrophysics Data System (ADS)

    Chryssou, C. E.; Pitt, C. W.

    We report the low temperature (200-300 °C) deposition of uniform, amorphous Al2O3 thin films by plasma-enhanced chemical vapour deposition (PECVD) using trimethyl-amine alane (TMAA) as the Al precursor. The thin films were deposited on both Si and quartz silica (SiO2) substrates. Deposition rates were typically 60 Åmin-1 keeping the TMAA temperature constant at 45 °C. The deposited Al2O3 thin films were stoichiometric alumina with low carbon contamination (0.7-1.3 At%). The refractive index ranged from 1.54 to 1.62 depending on the deposition conditions. The deposition rate was studied as a function of both the RF power and the substrate temperature. The structure and the surface of the deposited Al2O3 thin films were studied using X-ray diffraction, atomic force microscopy (AFM) and scanning electron microscopy (SEM).

  13. Evaluation of ARCAM Deposited Ti-6Al-4V

    NASA Technical Reports Server (NTRS)

    Slattery, Kevin; Slaughter, Blake; Speorl, Emily; Good, James; Gilley, Scott; McLemore, Carole

    2008-01-01

    A wide range of Metal Additive Manufacturing (MAM) technologies are becoming available. One of the challenges in using new technologies for aerospace systems is demonstrating that the process and system has the ability to manufacture components that meet the high quality requirements on a statistically significant basis. The widest-used system for small to medium sized components is the ARCAM system manufactured in Gothenburg, Sweden. This system features a 4kW electron-beam gun, and has a chamber volume of 250mm long x 250mm wide x 250mm to 400mm tall. This paper will describe the basis for the quality and consistency requirements, the experimental and evaluation procedures used for the evaluation, and an analysis of the results for Ti-6Al-4V.

  14. Method of making AlInSb by metal-organic chemical vapor deposition

    DOEpatents

    Biefeld, Robert M.; Allerman, Andrew A.; Baucom, Kevin C.

    2000-01-01

    A method for producing aluminum-indium-antimony materials by metal-organic chemical vapor deposition (MOCVD). This invention provides a method of producing Al.sub.X In.sub.1-x Sb crystalline materials by MOCVD wherein an Al source material, an In source material and an Sb source material are supplied as a gas to a heated substrate in a chamber, said Al source material, In source material, and Sb source material decomposing at least partially below 525.degree. C. to produce Al.sub.x In.sub.1-x Sb crystalline materials wherein x is greater than 0.002 and less than one.

  15. Deposition of dual-layer coating on Ti6Al4V

    NASA Astrophysics Data System (ADS)

    Hussain Din, Sajad; Shah, M. A.; Sheikh, N. A.

    2017-03-01

    Dual-layer diamond coatings were deposited on titanium alloy (Ti6Al4V) using a hot filament chemical vapour deposition technique with the anticipation of studying the structural and morphology properties of the alloy. The coated diamond films were characterized using scanning electron microscope, x-ray diffraction (XRD), and Raman spectroscopy. The XRD studies reveal that the deposited films are highly crystalline in nature, whereas morphological studies show that the films have a cauliflower structure. XRD analysis was used to calculate the structural parameters of the Ti6Al4V and CVD-coated Ti6Al4V. Raman spectroscopy was used to determine the nature and magnitude of the residual stress of the coatings.

  16. Current transport mechanisms in plasma-enhanced atomic layer deposited AlN thin films

    SciTech Connect

    Altuntas, Halit E-mail: biyikli@unam.bilkent.edu.tr; Ozgit-Akgun, Cagla; Donmez, Inci; Biyikli, Necmi E-mail: biyikli@unam.bilkent.edu.tr

    2015-04-21

    Here, we report on the current transport mechanisms in AlN thin films deposited at a low temperature (i.e., 200 °C) on p-type Si substrates by plasma-enhanced atomic layer deposition. Structural characterization of the deposited AlN was carried out using grazing-incidence X-ray diffraction, revealing polycrystalline films with a wurtzite (hexagonal) structure. Al/AlN/ p-Si metal-insulator-semiconductor (MIS) capacitor structures were fabricated and investigated under negative bias by performing current-voltage measurements. As a function of the applied electric field, different types of current transport mechanisms were observed; i.e., ohmic conduction (15.2–21.5 MV/m), Schottky emission (23.6–39.5 MV/m), Frenkel-Poole emission (63.8–211.8 MV/m), trap-assisted tunneling (226–280 MV/m), and Fowler-Nordheim tunneling (290–447 MV/m). Electrical properties of the insulating AlN layer and the fabricated Al/AlN/p-Si MIS capacitor structure such as dielectric constant, flat-band voltage, effective charge density, and threshold voltage were also determined from the capacitance-voltage measurements.

  17. In vivo detection of amyloid β deposition using ¹⁹F magnetic resonance imaging with a ¹⁹F-containing curcumin derivative in a mouse model of Alzheimer's disease.

    PubMed

    Yanagisawa, D; Amatsubo, T; Morikawa, S; Taguchi, H; Urushitani, M; Shirai, N; Hirao, K; Shiino, A; Inubushi, T; Tooyama, I

    2011-06-16

    Amyloid β (Aβ) deposition in the brain is considered the initiating event in the progression of Alzheimer's disease (AD). Amyloid imaging is widely studied in diagnosing AD and evaluating the disease stage, with considerable advances achieved in recent years. We have developed a novel ¹⁹F-containing curcumin derivative (named FMeC1) as a potential imaging agent. This compound can exist in equilibrium between keto and enol tautomers, with the enol form able to bind Aβ aggregates while the keto form cannot. This study investigated whether FMeC1 is suitable as a ¹⁹F magnetic resonance imaging (MRI) probe to detect Aβ deposition in the Tg2576 mouse, a model of AD. In ¹⁹F nuclear magnetic resonance (NMR) spectra obtained from the whole head, a delayed decreased rate of F ¹⁹F signal was observed in Tg2576 mice that were peripherally injected with FMeC1 in comparison to wild-type mice. Furthermore, ¹⁹F MRI displayed remarkable levels of ¹⁹F signal in the brain of Tg2576 mice after the injection of FMeC1. Histological analysis of FMeC1-injected mouse brain showed penetration of the compound across the blood-brain barrier and binding to Aβ plaques in peripherally injected Tg2576 mice. Moreover, the distribution of Aβ deposits in Tg2576 mice was in accordance with the region of the brain in which the ¹⁹F signal was imaged. FMeC1 also exhibited an affinity for senile plaques in human brain sections. These findings suggest the usefulness of FMeC1 as a ¹⁹F MRI probe for the detection of amyloid deposition in the brain. Furthermore, the properties of FMeC1 could form the basis for further novel amyloid imaging probes.

  18. Cholesterol enhances amyloid {beta} deposition in mouse retina by modulating the activities of A{beta}-regulating enzymes in retinal pigment epithelial cells

    SciTech Connect

    Wang, Jiying; Ohno-Matsui, Kyoko; Morita, Ikuo

    2012-08-10

    Highlights: Black-Right-Pointing-Pointer Cholesterol-treated RPE produces more A{beta} than non-treated RPE. Black-Right-Pointing-Pointer Neprilysin expression and activity decreased in cholesterol-treated RPE. Black-Right-Pointing-Pointer {alpha}-Secretase expression and activity decreased in cholesterol-treated RPE. Black-Right-Pointing-Pointer Cholesterol-enriched diet induced subRPE deposits in aged mice. Black-Right-Pointing-Pointer A{beta} were present in cholesterol-enriched-diet-induced subRPE deposits in aged mice. -- Abstract: Subretinally-deposited amyloid {beta} (A{beta}) is a main contributor of developing age-related macular degeneration (AMD). However, the mechanism causing A{beta} deposition in AMD eyes is unknown. Hypercholesterolemia is a significant risk for developing AMD. Thus, we investigated the effects of cholesterol on A{beta} production in retinal pigment epithelial (RPE) cells in vitro and in the mouse retina in vivo. RPE cells isolated from senescent (12-month-old) C57BL/6 mice were treated with 10 {mu}g/ml cholesterol for 48 h. A{beta} amounts in culture supernatants were measured by ELISA. Activity and expression of enzymes and proteins that regulate A{beta} production were examined by activity assay and real time PCR. The retina of mice fed cholesterol-enriched diet was examined by transmission electron microscopy. Cholesterol significantly increased A{beta} production in cultured RPE cells. Activities of A{beta} degradation enzyme; neprilysin (NEP) and anti-amyloidogenic secretase; {alpha}-secretase were significantly decreased in cell lysates of cholesterol-treated RPE cells compared to non-treated cells, but there was no change in the activities of {beta}- or {gamma}-secretase. mRNA levels of NEP and {alpha}-secretase (ADAM10 and ADAM17) were significantly lower in cholesterol-treated RPE cells than non-treated cells. Senescent (12-month-old) mice fed cholesterol-enriched chow developed subRPE deposits containing A{beta}, whereas

  19. Geology and genesis of the Baid al Jimalah tungsten deposit, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Kamilli, R.J.; Cole, J.C.; Elliott, J.E.; Criss, R.E.

    1993-01-01

    The Baid ad Jimalah tungsten deposit in Saudi Arabia consists predominantly of swarms of steeply dipping, subparallel, tungsten-bearing quartz veins and of less abundant, smaller stockwork veins. It is spatially, temporally, and genetically associated with a 569 Ma, highly differentiated, porphyritic, two-feldspar granite that intrudes Late Proterozoic immature sandstones. Baid al Jimalah is similar in character and origin to Phanerozoic tungsten-tin greisen deposits throughout the world, especially the Hemerdon deposit in Devon, England. It is also analogous to Climax-type molybdenum deposits, which contain virtually identical mineral assemblages, but with the relative proportions of molybdenum and tungsten mineralization reversed, primarily owing to differences in oxygen fugacity. This similarity in mineralization styles and fluid histories indicates that metallogenic processes in granite-related deposits in the late Precambrian were similar to those seen in the Phanerozoic. -from Authors

  20. Cerebral Amyloid Angiopathy: Emerging Concepts

    PubMed Central

    2015-01-01

    Cerebral amyloid angiopathy (CAA) involves cerebrovascular amyloid deposition and is classified into several types according to the amyloid protein involved. Of these, sporadic amyloid β-protein (Aβ)-type CAA is most commonly found in older individuals and in patients with Alzheimer's disease (AD). Cerebrovascular Aβ deposits accompany functional and pathological changes in cerebral blood vessels (CAA-associated vasculopathies). CAA-associated vasculopathies lead to development of hemorrhagic lesions [lobar intracerebral macrohemorrhage, cortical microhemorrhage, and cortical superficial siderosis (cSS)/focal convexity subarachnoid hemorrhage (SAH)], ischemic lesions (cortical infarction and ischemic changes of the white matter), and encephalopathies that include subacute leukoencephalopathy caused by CAA-associated inflammation/angiitis. Thus, CAA is related to dementia, stroke, and encephalopathies. Recent advances in diagnostic procedures, particularly neuroimaging, have enabled us to establish a clinical diagnosis of CAA without brain biopsies. Sensitive magnetic resonance imaging (MRI) methods, such as gradient-echo T2* imaging and susceptibility-weighted imaging, are useful for detecting cortical microhemorrhages and cSS. Amyloid imaging with amyloid-binding positron emission tomography (PET) ligands, such as Pittsburgh Compound B, can detect CAA, although they cannot discriminate vascular from parenchymal amyloid deposits. In addition, cerebrospinal fluid markers may be useful, including levels of Aβ40 for CAA and anti-Aβ antibody for CAA-related inflammation. Moreover, cSS is closely associated with transient focal neurological episodes (TFNE). CAA-related inflammation/angiitis shares pathophysiology with amyloid-related imaging abnormalities (ARIA) induced by Aβ immunotherapies in AD patients. This article reviews CAA and CAA-related disorders with respect to their epidemiology, pathology, pathophysiology, clinical features, biomarkers, diagnosis

  1. Electron transport in Al-doped ZnO nanolayers obtained by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Blagoev, B. S.; Dimitrov, D. Z.; Mehandzhiev, V. B.; Kovacheva, D.; Terziyska, P.; Pavlic, J.; Lovchinov, K.; Mateev, E.; Leclercq, J.; Sveshtarov, P.

    2016-03-01

    Al-doped ZnO thin films with different Al content were prepared by atomic layer deposition (ALD). To carry out thermal ALD, diethyl zinc (DEZ) and tri-methyl aluminium (TMA) were used as Zn and Al precursors, respectively, and water vapor as oxidant. Various numbers n of DEZ and m TMA cycles was used to obtain different [ZnO] n [Al2O3] m films, where n = 100 - 95, m = 1 - 5. The X-ray diffraction analysis showed a predominantly (100) oriented polycrystalline phase for the ZnO:Al films with a low Al content (m = 1 - 3) and an amorphous structure for pure Al2O3. In ZnO:Al with a higher Al content (m = 4 - 6) the (100) reflection disappeared and the (002) peak increased. The resistivity of the films decreased with the increase in the Al content, reaching a minimum of 3.3×10-3 Ω cm at about 1.1 % Al2O3 for the [ZnO]99[Al2O3]2 sample; for higher dopant concentrations, the resistivity increased because of the increased crystal inhomogeneity due to axis reorientation.

  2. Interfacial development of electrophoretically deposited graphene oxide films on Al alloys

    DOE PAGES

    Jin, Sumin; Dickerson, James H.; Pham, Viet Hung; ...

    2015-07-28

    Adhesion between film and substrate is critical for electronic device and coating applications. Interfacial development between electrophoretically deposited graphene oxide films on Al 1100 and Al 5052 alloys were investigated using FT-IR and XPS depth profiling techniques. Obtained results suggest metal ion permeation from the substrates into deposited graphene oxide films. The interface between the films and the substrates were primarily composed of Al-O-C bonds from oxygenated defects on graphene oxide plane rather than expected Al-C formation. Films heat treated at 150 °C had change in microstructure and peak shifts in XPS spectra suggesting change in chemical structure of bondsmore » between the films and the substrates.« less

  3. Interfacial development of electrophoretically deposited graphene oxide films on Al alloys

    SciTech Connect

    Jin, Sumin; Dickerson, James H.; Pham, Viet Hung; Brochu, Mathieu

    2015-07-28

    Adhesion between film and substrate is critical for electronic device and coating applications. Interfacial development between electrophoretically deposited graphene oxide films on Al 1100 and Al 5052 alloys were investigated using FT-IR and XPS depth profiling techniques. Obtained results suggest metal ion permeation from the substrates into deposited graphene oxide films. The interface between the films and the substrates were primarily composed of Al-O-C bonds from oxygenated defects on graphene oxide plane rather than expected Al-C formation. Films heat treated at 150 °C had change in microstructure and peak shifts in XPS spectra suggesting change in chemical structure of bonds between the films and the substrates.

  4. The Human Disease-Associated Aβ Amyloid Core Sequence Forms Functional Amyloids in a Fungal Adhesin

    PubMed Central

    Rameau, Rachele D.; Jackson, Desmond N.; Beaussart, Audrey; Dufrêne, Yves F.

    2016-01-01

    ABSTRACT There is increasing evidence that many amyloids in living cells have physiological functions. On the surfaces of fungal cells, amyloid core sequences in adhesins can aggregate into 100- to 1,000-nm-wide patches to form high-avidity adhesion nanodomains on the cell surface. The nanodomains form through interactions that have amyloid-like properties: binding of amyloid dyes, perturbation by antiamyloid agents, and interaction with homologous sequences. To test whether these functional interactions are mediated by typical amyloid interactions, we substituted an amyloid core sequence, LVFFA, from human Aβ protein for the native sequence IVIVA in the 1,419-residue Candida albicans adhesin Als5p. The chimeric protein formed cell surface nanodomains and mediated cellular aggregation. The native sequence and chimeric adhesins responded similarly to the amyloid dye thioflavin T and to amyloid perturbants. However, unlike the native protein, the nanodomains formed by the chimeric protein were not force activated and formed less-robust aggregates under flow. These results showed the similarity of amyloid interactions in the amyloid core sequences of native Als5p and Aβ, but they also highlighted emergent properties of the native sequence. Also, a peptide composed of the Aβ amyloid sequence flanked by amino acids from the adhesin formed two-dimensional sheets with sizes similar to the cell surface patches of the adhesins. These results inform an initial model for the structure of fungal cell surface amyloid nanodomains. PMID:26758179

  5. Thermal conductivity of amorphous Al2O3/TiO2 nanolaminates deposited by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Ali, Saima; Juntunen, Taneli; Sintonen, Sakari; Ylivaara, Oili M. E.; Puurunen, Riikka L.; Lipsanen, Harri; Tittonen, Ilkka; Hannula, Simo-Pekka

    2016-11-01

    The thermophysical properties of Al2O3/TiO2 nanolaminates deposited by atomic layer deposition (ALD) are studied as a function of bilayer thickness and relative TiO2 content (0%-100%) while the total nominal thickness of the nanolaminates was kept at 100 nm. Cross-plane thermal conductivity of the nanolaminates is measured at room temperature using the nanosecond transient thermoreflectance method. Based on the measurements, the nanolaminates have reduced thermal conductivity as compared to the pure amorphous thin films, suggesting that interfaces have a non-negligible effect on thermal transport in amorphous nanolaminates. For a fixed number of interfaces, we find that approximately equal material content of Al2O3 and TiO2 produces the lowest value of thermal conductivity. The thermal conductivity reduces with increasing interface density up to 0.4 nm-1, above which the thermal conductivity is found to be constant. The value of thermal interface resistance approximated by the use of diffuse mismatch model was found to be 0.45 m2 K GW-1, and a comparative study employing this value supports the interpretation of non-negligible interface resistance affecting the overall thermal conductivity also in the amorphous limit. Finally, no clear trend in thermal conductivity values was found for nanolaminates grown at different deposition temperatures, suggesting that the temperature in the ALD process has a non-trivial while modest effect on the overall thermal conductivity in amorphous nanolaminates.

  6. Thermal conductivity of amorphous Al2O3/TiO2 nanolaminates deposited by atomic layer deposition.

    PubMed

    Ali, Saima; Juntunen, Taneli; Sintonen, Sakari; Ylivaara, Oili M E; Puurunen, Riikka L; Lipsanen, Harri; Tittonen, Ilkka; Hannula, Simo-Pekka

    2016-11-04

    The thermophysical properties of Al2O3/TiO2 nanolaminates deposited by atomic layer deposition (ALD) are studied as a function of bilayer thickness and relative TiO2 content (0%-100%) while the total nominal thickness of the nanolaminates was kept at 100 nm. Cross-plane thermal conductivity of the nanolaminates is measured at room temperature using the nanosecond transient thermoreflectance method. Based on the measurements, the nanolaminates have reduced thermal conductivity as compared to the pure amorphous thin films, suggesting that interfaces have a non-negligible effect on thermal transport in amorphous nanolaminates. For a fixed number of interfaces, we find that approximately equal material content of Al2O3 and TiO2 produces the lowest value of thermal conductivity. The thermal conductivity reduces with increasing interface density up to 0.4 nm(-1), above which the thermal conductivity is found to be constant. The value of thermal interface resistance approximated by the use of diffuse mismatch model was found to be 0.45 m(2) K GW(-1), and a comparative study employing this value supports the interpretation of non-negligible interface resistance affecting the overall thermal conductivity also in the amorphous limit. Finally, no clear trend in thermal conductivity values was found for nanolaminates grown at different deposition temperatures, suggesting that the temperature in the ALD process has a non-trivial while modest effect on the overall thermal conductivity in amorphous nanolaminates.

  7. EBV-positive low-grade marginal zone lymphoma in the breast with massive amyloid deposition arising in a heart transplant patient: A report of an unusual case.

    PubMed

    Nassif, Samer; Ozdemirli, Metin

    2013-09-01

    According to the 2008 World Health Organization classification, low-grade lymphomas arising in transplant recipients are not considered as specific types of PTLD. Most such cases are not associated with EBV infections, although rare reports of post-transplant marginal zone lymphoma have been described. We describe the case of an 18-yr-old female with history of heart transplant who developed a breast mass, but was otherwise completely asymptomatic. Surgical excision of the mass and histopathologic examination showed a low-grade B-cell lymphoma most consistent with marginal zone lymphoma with massive amyloid deposition; furthermore, numerous tumor cells were positive for EBV by in situ hybridization for EBV-encoded RNA. The patient was treated with reduction in immunosuppression, and no additional lesions developed. This case describes an atypical presentation of post-transplant low-grade B-cell lymphoma, unusual in its location, histopathologic features, and association with EBV, thereby adding to the rare previous accounts of such an entity, suggesting the need to include post-transplant marginal zone lymphomas in the current classification of PTLD, and helping in determining the optimal treatment modalities for such tumors.

  8. High quality AlN epilayers grown on nitrided sapphire by metal organic chemical vapor deposition.

    PubMed

    Wang, Jiaming; Xu, Fujun; He, Chenguang; Zhang, Lisheng; Lu, Lin; Wang, Xinqiang; Qin, Zhixin; Shen, Bo

    2017-02-21

    Influence of sapphire pretreatment conditions on crystalline quality of AlN epilayers has been investigated by metal organic chemical vapor deposition (MOCVD). Compared to alumination treatment, it is found that appropriate sapphire nitridation significantly straightens the surface atomic terraces and decreases the X-ray diffraction (0002) full width at half maximum (FWHM) to a minimum of 55 arcsec, indicating a great improvement of the tilting feature of the grain structures in the AlN epilayer. More importantly, there is no inversion domains (IDs) found in the AlN epilayers, which clarifies that optimal sapphire nitridation is promising in the growth of high quality AlN. It is deduced that the different interfacial atomic structures caused by various pretreatment conditions influence the orientation of the AlN nucleation layer grains, which eventually determines the tilting features of the AlN epilayers.

  9. High quality AlN epilayers grown on nitrided sapphire by metal organic chemical vapor deposition

    PubMed Central

    Wang, Jiaming; Xu, Fujun; He, Chenguang; Zhang, Lisheng; Lu, Lin; Wang, Xinqiang; Qin, Zhixin; Shen, Bo

    2017-01-01

    Influence of sapphire pretreatment conditions on crystalline quality of AlN epilayers has been investigated by metal organic chemical vapor deposition (MOCVD). Compared to alumination treatment, it is found that appropriate sapphire nitridation significantly straightens the surface atomic terraces and decreases the X-ray diffraction (0002) full width at half maximum (FWHM) to a minimum of 55 arcsec, indicating a great improvement of the tilting feature of the grain structures in the AlN epilayer. More importantly, there is no inversion domains (IDs) found in the AlN epilayers, which clarifies that optimal sapphire nitridation is promising in the growth of high quality AlN. It is deduced that the different interfacial atomic structures caused by various pretreatment conditions influence the orientation of the AlN nucleation layer grains, which eventually determines the tilting features of the AlN epilayers. PMID:28220829

  10. High quality AlN epilayers grown on nitrided sapphire by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Wang, Jiaming; Xu, Fujun; He, Chenguang; Zhang, Lisheng; Lu, Lin; Wang, Xinqiang; Qin, Zhixin; Shen, Bo

    2017-02-01

    Influence of sapphire pretreatment conditions on crystalline quality of AlN epilayers has been investigated by metal organic chemical vapor deposition (MOCVD). Compared to alumination treatment, it is found that appropriate sapphire nitridation significantly straightens the surface atomic terraces and decreases the X-ray diffraction (0002) full width at half maximum (FWHM) to a minimum of 55 arcsec, indicating a great improvement of the tilting feature of the grain structures in the AlN epilayer. More importantly, there is no inversion domains (IDs) found in the AlN epilayers, which clarifies that optimal sapphire nitridation is promising in the growth of high quality AlN. It is deduced that the different interfacial atomic structures caused by various pretreatment conditions influence the orientation of the AlN nucleation layer grains, which eventually determines the tilting features of the AlN epilayers.

  11. Characterization and prevention of humidity related degradation of atomic layer deposited Al2O3

    NASA Astrophysics Data System (ADS)

    Rückerl, Andreas; Zeisel, Roland; Mandl, Martin; Costina, Ioan; Schroeder, Thomas; Zoellner, Marvin H.

    2017-01-01

    Atomic layer deposited aluminum oxide (ALD-Al2O3) is a dielectric material, which is widely used in organic light emitting diodes in order to prevent their organic layers from humidity related degradation. Unfortunately, there are strong hints that in some cases, ALD-Al2O3 itself is suffering from humidity related degradation. Especially, high temperature and high humidity seem to enhance ALD-Al2O3 degradation strongly. For this reason, the degradation behavior of ALD-Al2O3 films at high temperature and high humidity was investigated in detail and a way to prevent it from degradation was searched. The degradation behavior is analyzed in the first part of this paper. Using infrared absorbance measurements and X-ray diffraction, boehmite (γ-AlOOH) was identified as a degradation product. In the second part of the paper, it is shown that ALD-Al2O3 films can be effectively protected from degradation using a silicon oxide capping. The deposition of very small amounts of silicon in a molecular beam epitaxy system and an X-ray photoelectron spectroscopy investigation of the chemical bonding between the silicon and the ALD-Al2O3 surface led to the conclusion that a silicon termination of the ALD-Al2O3 surface (Al*-O-SiOx) is able to stop humidity related degradation of the underlying ALD-Al2O3 films. The third part of the paper shows that the protection mechanism of the silicon termination is probably due to the strong tendency of silicic acid to resilificate exposed ALD-Al2O3 surfaces. The protective effect of a simple silicon source on an ALD-Al2O3 surface is shown exemplary and the related chemical reactions are presented.

  12. The investigation of Ni-Al and Co-Al based layered double hydroxides and their derived mixed oxides thin films deposited by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Birjega, R.; Matei, A.; Filipescu, M.; Stokker-Cheregi, F.; Luculescu, C.; Colceag, D.; Zavoianu, R.; Pavel, O. D.; Dinescu, M.

    2013-08-01

    Layered Double Hydroxides (LDHs) are host-guest materials consisting of positively charged metal/hydroxides sheets with intercalated anions and water molecules. LDHs can be described by the generic formula [[ṡmHO and their structure is formed by layers containing divalent cations (M2+: Mg, Zn, Ni, Co,…) and trivalent cations (M3+: Al, Ga, Cr,…) with an octahedral coordination. LDH films with well-oriented structure and controlled thickness are needed for numerous applications like sensors, protective coatings, catalysts, components for optoelectronics etc. In this work, we report on the deposition of Ni-Al and Co-Al based LDHs and their derived mixed oxides by pulsed laser deposition as a new approach to fabricate oriented LDHs or highly dispersed metallic mixed oxides. The influence of the laser characteristics, such as wavelength and fluence, on the films properties was studied. The films investigation techniques were X-Ray Diffraction, Atomic Force Microscopy, Scanning Electron Microscopy combined with energy dispersive X-ray analysis, and Secondary Ions Mass Spectrometry.

  13. Endocytic pathway abnormalities precede amyloid beta deposition in sporadic Alzheimer's disease and Down syndrome: differential effects of APOE genotype and presenilin mutations.

    PubMed

    Cataldo, A M; Peterhoff, C M; Troncoso, J C; Gomez-Isla, T; Hyman, B T; Nixon, R A

    2000-07-01

    Endocytosis is critical to the function and fate of molecules important to Alzheimer's disease (AD) etiology, including the beta protein precursor (betaPP), amyloid beta (Abeta) peptide, and apolipoprotein E (ApoE). Early endosomes, a major site of Abeta peptide generation, are markedly enlarged within neurons in the Alzheimer brain, suggesting altered endocytic pathway (EP) activity. Here, we show that neuronal EP activation is a specific and very early response in AD. To evaluate endocytic activation, we used markers of internalization (rab5, rabaptin 5) and recycling (rab4), and found that enlargement of rab5-positive early endosomes in the AD brain was associated with elevated levels of rab4 immunoreactive protein and translocation of rabaptin 5 to endosomes, implying that both endocytic uptake and recycling are activated. These abnormalities were evident in pyramidal neurons of the neocortex at preclinical stages of disease when Alzheimer-like neuropathology, such as Abeta deposition, was restricted to the entorhinal region. In Down syndrome, early endosomes were significantly enlarged in some pyramidal neurons as early as 28 weeks of gestation, decades before classical AD neuropathology develops. Markers of EP activity were only minimally influenced by normal aging and other neurodegenerative diseases studied. Inheritance of the epsilon4 allele of APOE, however, accentuated early endosome enlargement at preclinical stages of AD. By contrast, endosomes were normal in size at advanced stages of familial AD caused by mutations of presenilin 1 or 2, indicating that altered endocytosis is not a consequence of Abeta deposition. These results identify EP activation as the earliest known intraneuronal change to occur in sporadic AD, the most common form of AD. Given the important role of the EP in Abeta peptide generation and ApoE function, early endosomal abnormalities provide a mechanistic link between EP alterations, genetic susceptibility factors, and Abeta

  14. Age and Amyloid Effects on Human CNS Amyloid-Beta Kinetics

    PubMed Central

    Patterson, Bruce W.; Elbert, Donald L.; Mawuenyega, Kwasi G.; Kasten, Tom; Ovod, Vitaliy; Ma, Shengmei; Xiong, Chengjie; Chott, Robert; Yarasheski, Kevin; Sigurdson, Wendy; Zhang, Lily; Goate, Alison; Phil, D.; Benzinger, Tammie; Morris, John C.; Holtzman, David; Bateman, Randall J.

    2015-01-01

    Objective Age is the single greatest risk factor for Alzheimer’s disease with the incidence doubling every 5 years after age 65. However, our understanding of the mechanistic relationship between increasing age and the risk for Alzheimer’s disease is currently limited. We therefore sought to determine the relationship between age, amyloidosis, and amyloid-beta kinetics in the central nervous system (CNS) of humans Methods Amyloid-beta kinetics were analyzed in 112 participants and compared to the ages of participants and the amount of amyloid deposition. Results We found a highly significant correlation between increasing age and slowed amyloid-beta turnover rates (2.5-fold longer half-life over five decades of age). In addition, we found independent effects on amyloid-beta42 kinetics specifically in participants with amyloid deposition. Amyloidosis was associated with a higher (>50%) irreversible loss of soluble amyloid-beta42 and a 10-fold higher amyloid-beta42 reversible exchange rate. Interpretation These findings reveal a mechanistic link between human aging and the risk of amyloidosis which may be due to a dramatic slowing of amyloid-beta turnover, increasing the likelihood of protein misfolding that leads to deposition. Alterations in amyloid-beta kinetics associated with aging and amyloidosis suggest opportunities for diagnostic and therapeutic strategies. More generally, this study provides an example of how changes in protein turnover kinetics can be used to detect physiologic and pathophysiologic changes and may be applicable to other proteinopathies. PMID:26040676

  15. Kinetic Spraying Deposition of Reactive-Enhanced Al-Ni Composite for Shaped Charge Liner Applications

    NASA Astrophysics Data System (ADS)

    Byun, Gyeongjun; Kim, Jaeick; Lee, Changhee; Kim, See Jo; Lee, Seong

    2016-02-01

    Liners used in shaped charges (SC) must possess good penetration ability and explosive power. Producing the reactive layer (i.e., the Al-Ni composite) on a well-penetrating liner (i.e., Cu) via spray coating is a novel method; the exothermic reaction of this reactive layer can be enhanced by controlling the structure of the feedstock material. However, preceding studies have been unable to completely succeed in achieving this goal. There is still an opportunity to improve the performance of reactive layers in SC liner applications. In order to address this problem, a reactive Al-Ni composite powder was produced via arrested reactive milling (ARM) and deposited by a kinetic spray process. Afterward, the deposition state and self-propagating high-temperature synthesis (SHS) reaction behavior of the ARMed Al-Ni deposit were investigated. The deposition state was degraded by the ARM process due to the remaining solid lubricant and the strain-hardening effect, but the practically estimated bond strength was not poor (~40 MPa). No SHS reactions were induced by the ARM and kinetic spray process, which resulted in the quantitative maximization of the exothermic reaction. It is noteworthy that the initiation temperature of the SHS reaction was highly advanced (~300 °C) relative to preceding studies (~500 °C); this change is due to the additional mechanical activation initiated by the kinetic spray deposition.

  16. Epitaxial Graphene Surface Preparation for Atomic Layer Deposition of Al2O3

    DTIC Science & Technology

    2011-06-01

    j dielectrics such as Al2O3 , HfO2, Ta2O5, and TiO2 , are important for the realization of graphene-based top-gated electronic devices including field... ALD pulse sequencing of NO2-trimethylaluminum (TMA); 16 oxidation of electron beam evaporated metallic Al, Hf, Ti, Ta;17,18 and spin- coating of a... ALD of Al2O3 films in promoting uni- form, high quality oxide deposition. Initial treatments resulted in partial coverage, while the optimized treatment

  17. Growth evolution of AlN films on silicon (111) substrates by pulsed laser deposition

    SciTech Connect

    Wang, Haiyan; Wang, Wenliang; Yang, Weijia; Zhou, Shizhong; Lin, Zhiting; Li, Guoqiang

    2015-05-14

    AlN films with various thicknesses have been grown on Si(111) substrates by pulsed laser deposition (PLD). The surface morphology and structural property of the as-grown AlN films have been investigated carefully to comprehensively explore the epitaxial behavior. The ∼2 nm-thick AlN film initially grown on Si substrate exhibits an atomically flat surface with a root-mean-square surface roughness of 0.23 nm. As the thickness increases, AlN grains gradually grow larger, causing a relatively rough surface. The surface morphology of ∼120 nm-thick AlN film indicates that AlN islands coalesce together and eventually form AlN layers. The decreasing growth rate from 240 to 180 nm/h is a direct evidence that the growth mode of AlN films grown on Si substrates by PLD changes from the islands growth to the layer growth. The evolution of AlN films throughout the growth is studied deeply, and its corresponding growth mechanism is hence proposed. These results are instructional for the growth of high-quality nitride films on Si substrates by PLD, and of great interest for the fabrication of AlN-based devices.

  18. Low-temperature (< 100 C) growth of AlN by ion beam assisted deposition

    SciTech Connect

    Karimy, H.; Tobin, E.; Bricault, R.; Cremins-Costa, A.; Colter, P.; Namavar, F.; Perry, D.

    1996-12-31

    During the past few years, there has been growing interest in aluminum nitride (AlN) thin films because of their excellent optical, electrical, chemical, mechanical and high-temperature properties. Ion beam assisted deposition (IBAD) was used to deposit AlN films on flat and curved substrates, including Si, SIMOX, sapphire, quartz, aluminum, stainless steel, and carbon, at temperatures substantially below 100 C. The objective as to enhance the physical and mechanical properties of AlN film by controlling the crystal size and structures. Experimental results, as obtained by Rutherford backscattering spectroscopy (RBS) show the formation of stoichiometric AlN. Plan-view/cross-sectional transmission electron microscopy (TEM), clearly demonstrated the formation of a smooth, uniform AlN film. Electron diffraction and dark field TEM studies clearly show the growth of AlN crystallites with cubic and/or hexagonal structures and dimensions of 30 to 100 {angstrom}. The films are transparent and have good adhesion to all substrates. In addition to excellent high temperature (up to 1,050 C measured) and chemical stability (shown through a variety of acid tests), these films have demonstrated extreme hardness, greater than two times that of bulk AlN.

  19. Properties of Al-doped ZnS Films Grown by Chemical Bath Deposition

    NASA Astrophysics Data System (ADS)

    Nagamani, K.; Prathap, P.; Lingappa, Y.; Miles, R. W.; Reddy, K. T. R.

    Zinc sulphide (ZnS) buffer layers are a cadmium free, wider energy band gap, alternative to the cadmium sulphide (CdS) buffer layers commonly used in copper indium gallium diselenide (CuInGaSe2)-based solar cells. However extrinsic doping of the ZnS is important to lower the resistivity of the layers and to improve flexibility of device design. In this work, Al-doped ZnS nanocrystalline films have been produced on glass substrates using a chemical bath deposition (CBD) method. The Al- concentration was varied from 0 at. % to 10 at. %, keeping other deposition parameters constant. The elemental composition of a typical sample with 6 at. % 'Al' in ZnS was Zn=44.9 at. %, S=49.8 at. % and Al=5.3 at.%. The X-ray diffraction data taken on these samples showed a broad peak corresponding to the (111) plane of ZnS while the crystallite size varied in the range, 8 - 15 nm, depending on the concentration of Al in the layers. The films with a Al-doping content of 6 at. % had an optical transmittance of 75% in the visible range and the energy band gap evaluated from the data was 3.66 eV. The films n-type electrical conductivities and the electrical resistivity varied in the range, 107-103 Ωcm, it decreasing with an increase of the Al-concentration in the solution.

  20. Florbetapir PET analysis of amyloiddeposition in the presenilin 1 E280A autosomal dominant Alzheimer’s disease kindred: a cross-sectional study

    PubMed Central

    Fleisher, Adam S; Chen, Kewei; Quiroz, Yakeel T; Jakimovich, Laura J; Gomez, Madelyn Gutierrez; Langois, Carolyn M; Langbaum, Jessica B S; Ayutyanont, Napatkamon; Roontiva, Auttawut; Thiyyagura, Pradeep; Lee, Wendy; Mo, Hua; Lopez, Liliana; Moreno, Sonia; Acosta-Baena, Natalia; Giraldo, Margarita; Garcia, Gloria; Reiman, Rebecca A; Huentelman, Matthew J; Kosik, Kenneth S; Tariot, Pierre N; Lopera, Francisco; Reiman, Eric M

    2012-01-01

    Summary Background Fibrillar amyloid-β (Aβ) is thought to begin accumulating in the brain many years before the onset of clinical impairment in patients with Alzheimer’s disease. By assessing the accumulation of Aβ in people at risk of genetic forms of Alzheimer’s disease, we can identify how early preclinical changes start in individuals certain to develop dementia later in life. We sought to characterise the age-related accumulation of Aβ deposition in presenilin 1 (PSEN1) E280A mutation carriers across the spectrum of preclinical disease. Methods Between Aug 1 and Dec 6, 2011, members of the familial Alzheimer’s disease Colombian kindred aged 18–60 years were recruited from the Alzheimer’s Prevention Initiative’s registry at the University of Antioquia, Medellín, Colombia. Cross-sectional assessment using florbetapir PET was done in symptomatic mutation carriers with mild cognitive impairment or mild dementia, asymptomatic carriers, and asymptomatic non-carriers. These assessments were done at the Banner Alzheimer’s Institute in Phoenix, AZ, USA. A cortical grey matter mask consisting of six predefined regions. was used to measure mean cortical florbetapir PET binding. Cortical-to-pontine standard-uptake value ratios were used to characterise the cross-sectional accumulation of fibrillar Aβ deposition in carriers and non-carriers with regression analysis and to estimate the trajectories of fibrillar Aβ deposition. Findings We enrolled a cohort of 11 symptomatic individuals, 19 presymptomatic mutation carriers, and 20 asymptomatic non-carriers, ranging in age from 20 to 56 years. There was greater florbetapir binding in asymptomatic PSEN1 E280A mutation carriers than in age matched non-carriers. Fibrillar Aβ began to accumulate in PSEN 1E280A mutation carriers at a mean age of 28·2 years (95% CI 27·3–33·4), about 16 years and 21 years before the predicted median ages at mild cognitive impairment and dementia onset, respectively. 18F

  1. Fabrication of Ti-6Al-4V Scaffolds by Direct Metal Deposition

    NASA Astrophysics Data System (ADS)

    Dinda, G. P.; Song, L.; Mazumder, J.

    2008-12-01

    Direct metal deposition (DMD) is a rapid laser-aided deposition method that can be used to manufacture near-net-shape components from their computer aided design (CAD) files. The method can be used to produce fully dense or porous metallic parts. The Ti-6Al-4V alloy is widely used as an implantable material mainly in the application of orthopedic prostheses because of its high strength, low elastic modulus, excellent corrosion resistance, and good biocompatibility. In the present study, Ti-6Al-4V scaffold has been fabricated by DMD technology for patient specific bone tissue engineering. Good geometry control and surface finish have been achieved. The structure and properties of the scaffolds were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and tension test. The microstructures of laser-deposited Ti-6Al-4V scaffolds are fine Widmanstätten in nature. The tensile and yield strengths of the as-deposited Ti-6Al-4V were 1163 ± 22 and 1105 ± 19 MPa, respectively, which are quite higher than the ASTM limits (896 and 827 MPa) for Ti-6Al-4V implants. However, the ductility of the as-deposited sample was very low (˜4 pct), which is well below the ASTM limit (10 pct). After an additional heat treatment (sample annealed at 950 °C followed by furnace cooling), both strength (UTS ˜ 1045 ± 16, and YS ˜ 959 ± 12 MPa) and ductility (˜10.5 ± 1 pct) become higher than ASTM limits for medical implants.

  2. Interface of atomic layer deposited Al2O3 on H-terminated silicon

    NASA Astrophysics Data System (ADS)

    Gao, K. Y.; Speck, F.; Emtsev, K.; Seyller, Th.; Ley, L.; Oswald, M.; Hansch, W.

    2006-07-01

    Al2O3 films 1 to 20 nm thick were deposited as alternative high- gate dielectric on hydrogen-terminated silicon by Atomic Layer Deposition (ALD) and characterized by Synchrotron X-ray Photoelectron Spec-troscopy (SXPS), Fourier Transform Infrared (FTIR) absorption spectroscopy and admittance measure-ments. The SXPS results indicate that about 60% of the original Si-H surface bonds are preserved at the Al2O3/Si interface and this is confirmed by monitoring the Si-H stretching modes by FTIR spectroscopy in the Attenuated Total Reflection (ATR) mode both before and after ALD of Al2O3. The remaining 40% of Si-H bonds are replaced by Si-O bonds as verified by SXPS. In addition, a fraction of a monolayer of SiO2 forms on top of the Al2O3 dielectric during deposition. The presence of OH-groups at a level of 3% of the total oxygen content was detected throughout the Al2O3 layer through a chemically shifted O 1s component in SXPS. Admittance measurements give a dielectric constant of 9.12, but a relatively high density of interface traps between 1011 and 1012 cm-2 eV-1.

  3. Structural and mechanical properties of Al-C-N films deposited at room temperature by plasma focus device

    NASA Astrophysics Data System (ADS)

    Z, A. Umar; R, Ahmad; R, S. Rawat; M, A. Baig; J, Siddiqui; T, Hussain

    2016-07-01

    The Al-C-N films are deposited on Si substrates by using a dense plasma focus (DPF) device with aluminum fitted central electrode (anode) and by operating the device with CH4/N2 gas admixture ratio of 1:1. XRD results verify the crystalline AlN (111) and Al3CON (110) phase formation of the films deposited using multiple shots. The elemental compositions as well as chemical states of the deposited Al-C-N films are studied using XPS analysis, which affirm Al-N, C-C, and C-N bonding. The FESEM analysis reveals that the deposited films are composed of nanoparticles and nanoparticle agglomerates. The size of the agglomerates increases at a higher number of focus deposition shots for multiple shot depositions. Nanoindentation results reveal the variation in mechanical properties (nanohardness and elastic modulus) of Al-C-N films deposited with multiple shots. The highest values of nanohardness and elastic modulus are found to be about 11 and 185 GPa, respectively, for the film deposited with 30 focus deposition shots. The mechanical properties of the films deposited using multiple shots are related to the Al content and C-N bonding.

  4. Industrial Application of Thin Films (TiAl)N Deposited on Thermo-Wells

    SciTech Connect

    Velez, G.; Jaramillo, S.; Arango, Y. C.; Devia, D.; Quintero, J.; Devia, A.

    2006-12-04

    The thermo-well is formed by two layers, one layer is a ceramic and the other layer is anviloy (comprised tungsten). They are used to coat the thermocouple in the control temperature system during the Aluminum-Silicon alloy melting process. After two weeks of continuous work at 750 deg. C of temperature (the alloy temperature), a high wear in this material is observed, affecting the ceramic. (TiAl)N thin films are deposited directly on the anviloy substrates by the PAPVD (Plasma Assisted Physics Vapor Deposition) in arc pulsed technique, using a TiAl target in a mono-vaporizer system, composed by a reactor and a power controlled system. Two opposite electrodes are placed into the reactor and discharge is produced by a controlled power system. The XRD (X-ray diffraction) patterns show the presence of the (TiAl)N thin film peaks. The morphological characteristics are studied by the scanning probe microscopy (SPM)

  5. Electrowetting properties of atomic layer deposited Al2O3 decorated silicon nanowires

    NASA Astrophysics Data System (ADS)

    Rajkumar, K.; Rajavel, K.; Cameron, D. C.; Mangalaraj, D.; Rajendrakumar, R. T.

    2015-06-01

    This paper reports the electrowetting properties of liquid droplet on superhydrophobic silicon nanowires with Atomic layer deposited (ALD) Al2O3 as dielectric layer. Silicon wafer were etched by metal assisted wet chemical etching with silver as catalyst. ALD Al2O3 films of 10nm thickness were conformally deposited over silicon nanowires. Al2O3 dielectric film coated silicon nanowires was chemically modified with Trichloro (1H, 1H, 2H, 2H-perfluorooctyl) silane to make it superhydrophobic(SHP). The contact angle was measured and all the samples exhibited superhydrophobic nature with maximum contact angles of 163° and a minimum contact angle hysteresis of 6°. Electrowetting induced a maximum reversible decrease of the contact angle of 20°at 150V in air.

  6. Growing oriented AlN films on sapphire substrates by plasma-enhanced atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Tarala, V. A.; Altakhov, A. S.; Ambartsumov, M. G.; Martens, V. Ya.

    2017-01-01

    The possibility of growing oriented AlN films on Al2O3 substrates at temperatures below 300°C by plasma-enhanced atomic layer deposition was examined. The samples were subjected to X-ray phase analysis and ellipsometry. It was demonstrated that the refraction index of films deposited with plasma exposures longer than 20 s was 2.03 ± 0.03. The (0002) and (0004) reflections at 2Θ angles of 35.7° and 75.9° were present in the X-ray diffraction patterns of these samples. These reflections are typical of the hexagonal AlN polytype. The full width at half maximum of the rocking curve of reflection (0002) in the best sample was 162 ± 11 arcsec.

  7. Pulsed laser deposition of AlMgB14 thin films

    SciTech Connect

    Britson, Jason Curtis

    2008-11-18

    Hard, wear-resistant coatings of thin film borides based on AlMgB14 have the potential to be applied industrially to improve the tool life of cutting tools and pump vanes and may account for several million dollars in savings as a result of reduced wear on these parts. Past work with this material has shown that it can have a hardness of up to 45GPa and be fabricated into thin films with a similar hardness using pulsed laser deposition. These films have already been shown to be promising for industrial applications. Cutting tools coated with AlMgB14 used to mill titanium alloys have been shown to substantially reduce the wear on the cutting tool and extend its cutting life. However, little research into the thin film fabrication process using pulsed laser deposition to make AlMgB14 has been conducted. In this work, research was conducted into methods to optimize the deposition parameters for the AlMgB14 films. Processing methods to eliminate large particles on the surface of the AlMgB14 films, produce films that were at least 1m thick, reduce the surface roughness of the films, and improve the adhesion of the thin films were investigated. Use of a femtosecond laser source rather than a nanosecond laser source was found to be effective in eliminating large particles considered detrimental to wear reduction properties from the films. Films produced with the femtosecond laser were also found to be deposited at a rate 100 times faster than those produced with the nanosecond laser. However, films produced with the femtosecond laser developed a relatively high RMS surface roughness around 55nm. Attempts to decrease the surface roughness were largely unsuccessful. Neither increasing the surface temperature of the substrate during deposition nor using a double pulse to ablate the material was found to be extremely successful to reduce the surface roughness. Finally, the adhesion of the thin films to M2 tool steel

  8. Insight into Amyloid Structure Using Chemical Probes

    PubMed Central

    Reinke, Ashley A.; Gestwicki, Jason E.

    2011-01-01

    Alzheimer’s disease (AD) is a common neurodegenerative disorder characterized by the deposition of amyloids in the brain. One prominent form of amyloid is composed of repeating units of the amyloid-β (Aβ) peptide. Over the past decade, it has become clear that these Aβ amyloids are not homogeneous; rather, they are composed of a series of structures varying in their overall size and shape and the number of Aβ peptides they contain. Recent theories suggest that these different amyloid conformations may play distinct roles in disease, although their relative contributions are still being discovered. Here, we review how chemical probes, such as congo red, thioflavin T and their derivatives, have been powerful tools for better understanding amyloid structure and function. Moreover, we discuss how design and deployment of conformationally selective probes might be used to test emerging models of AD. PMID:21457473

  9. Alternative Dielectric Films for rf MEMS Capacitive Switches Deposited using Atomic Layer Deposited Al2O3/ZnO Alloys

    DTIC Science & Technology

    2006-07-02

    switches deposited using atomic layer deposited Al2O3/ZnO alloys Cari F. Herrmann a,b, Frank W. DelRio a, David C. Miller a, Steven M. George b,c, Victor...The layer is an alloy mixture of Al2O3 and ZnO and is proposed for use as charge dissipative layers in which the dielectric onstant is significant...investigates Al2O3/ZnO ALD alloys deposited at 100 and 177 ◦C and compares their material properties. Auger electron pectroscopy was used to determine the

  10. [The disease of beta 2-amyloid deposition in the differential diagnosis of juxta-articular subchondral geode lesions].

    PubMed

    Marri, C; Romagnoli, C; Solano, G; Caldeo, A; Emiliani, G

    1993-01-01

    Beta-2 amyloidosis deposition is a new type of amyloidosis recently observed in long-term hemodialysis patients. One of the major osteoarticular complications of this disease is the appearance of subchondral bone cysts. In this paper the radiologic features of such radiolucencies are described and the criteria are outlined of the differential diagnosis from the geodes found in other arthropathies or para-physiologic conditions. The importance of the status of the joint space is stressed: on the basis of its patterns, arthropathies may be grouped as follows: inhomogeneous space narrowing in degenerative arthritis; homogeneous space narrowing in inflammatory arthritis; normal or nearly normal joint space if there is no/not-prevalent involvement of articular cartilage.

  11. Crystalline gamma-Al2O3 physical vapour deposition-coating for steel thixoforging tools.

    PubMed

    Bobzin, K; Hirt, G; Bagcivan, N; Khizhnyakova, L; Ewering, M

    2011-10-01

    The process of thixoforming, which has been part of many researches during the last decades, combines the advantages of forging and casting for the shaping of metallic components. But due to the high temperatures of semi-solid steel alloys high demands on the tools are requested. To resists the thermal and mechanical loads (wear, friction, thermal and thermomechanical fatigue) protecting thin films are necessary. In this regard crystalline gamma-Al2O3 deposited via Physical Vapour Deposition (PVD) is a promising candidate: It exhibits high thermal stability, high oxidation resistance and high hot hardness. In the present work the application of a (Ti, Al)N/gamma-Al2O3 coating deposited by means of Magnetron Sputter Ion Plating in an industrial coating unit is presented. The coating was analysed by means of Rockwell test, nanoindentation, and Scanning Electron Microscopy (SEM). The coated tool was tested in thixoforging experiments with steel grade X210CrW12 (AlSI D6). The surface of the coated dies was examined with Scanning Electron Microscope (SEM) after 22, 42, 90 and 170 forging cycles.

  12. Episodic-like memory deficits in the APPswe/PS1dE9 mouse model of Alzheimer's disease: relationships to beta-amyloid deposition and neurotransmitter abnormalities.

    PubMed

    Savonenko, Alena; Xu, Guilian M; Melnikova, Tatiana; Morton, Johanna L; Gonzales, Victoria; Wong, Molly P F; Price, Donald L; Tang, Fai; Markowska, Alicja L; Borchelt, David R

    2005-04-01

    Transgenic mice made by crossing animals expressing mutant amyloid precursor protein (APPswe) to mutant presenilin 1 (PS1dE9) allow for incremental increases in Abeta42 production and provide a model of Alzheimer-type amyloidosis. Here, we examine cognition in 6- and 18-month old transgenic mice expressing APPswe and PS1dE9, alone and in combination. Spatial reference memory was assessed in a standard Morris Water Maze task followed by assessment of episodic-like memory in Repeated Reversal and Radial Water maze tasks. We then used factor analysis to relate changes in performance in these tasks with cholinergic markers, somatostatin levels, and amyloid burden. At 6 months of age, APPswe/PS1dE9 double-transgenic mice showed visible plaque deposition; however, all genotypes, including double-transgenic mice, were indistinguishable from nontransgenic animals in all cognitive measures. In the 18-month-old cohorts, amyloid burdens were much higher in APPswe/PS1dE9 mice with statistically significant but mild decreases in cholinergic markers (cortex and hippocampus) and somatostatin levels (cortex). APPswe/PS1dE9 mice performed all cognitive tasks less well than mice from all other genotypes. Factor and correlation analyses defined the strongest correlation as between deficits in episodic-like memory tasks and total Abeta loads in the brain. Collectively, we find that, in the APPswe/PS1dE9 mouse model, some form of Abeta associated with amyloid deposition can disrupt cognitive circuits when the cholinergic and somatostatinergic systems remain relatively intact; and that episodic-like memory seems to be more sensitive to the toxic effects of Abeta.

  13. In vivo PET imaging of beta-amyloid deposition in mouse models of Alzheimer's disease with a high specific activity PET imaging agent [18F]flutemetamol

    PubMed Central

    2014-01-01

    Background The purpose of the study was to evaluate the applicability of 18F-labelled amyloid imaging positron emission tomography (PET) agent [18F]flutemetamol to detect changes in brain beta-amyloid (Aβ) deposition in vivo in APP23, Tg2576 and APPswe-PS1dE9 mouse models of Alzheimer's disease. We expected that the high specific activity of [18F]flutemetamol would make it an attractive small animal Aβ imaging agent. Methods [18F]flutemetamol uptake in the mouse brain was evaluated in vivo at 9 to 22 months of age with an Inveon Multimodality PET/CT camera (Siemens Medical Solutions USA, Knoxville, TN, USA). Retention in the frontal cortex (FC) was evaluated by Logan distribution volume ratios (DVR) and FC/cerebellum (CB) ratios during the late washout phase (50 to 60 min). [18F]flutemetamol binding to Aβ was also evaluated in brain slices by in vitro and ex vivo autoradiography. The amount of Aβ in the brain slices was determined with Thioflavin S and anti-Aβ1−40 immunohistochemistry. Results In APP23 mice, [18F]flutemetamol retention in the FC increased from 9 to 18 months. In younger mice, DVR and FC/CB50-60 were 0.88 (0.81) and 0.88 (0.89) at 9 months (N = 2), and 0.98 (0.93) at 12 months (N = 1), respectively. In older mice, DVR and FC/CB50-60 were 1.16 (1.15) at 15 months (N = 1), 1.13 (1.16) and 1.35 (1.35) at 18 months (N = 2), and 1.05 (1.31) at 21 months (N = 1). In Tg2576 mice, DVR and FC/CB50-60 showed modest increasing trends but also high variability. In APPswe-PS1dE9 mice, DVR and FC/CB50-60 did not increase with age. Thioflavin S and anti-Aβ1−40 positive Aβ deposits were present in all transgenic mice at 19 to 22 months, and they co-localized with [18F]flutemetamol binding in the brain slices examined with in vitro and ex vivo autoradiography. Conclusions Increased [18F]flutemetamol retention in the brain was detected in old APP23 mice in vivo. However, the high specific activity of [18F]flutemetamol did not

  14. Correlation between orphan nuclear receptor Nurr1 expression and amyloid deposition in 5XFAD mice, an animal model of Alzheimer's disease.

    PubMed

    Moon, Minho; Jeong, Inhye; Kim, Chun-Hyung; Kim, Jihong; Lee, Paula K J; Mook-Jung, Inhee; Leblanc, Pierre; Kim, Kwang-Soo

    2015-01-01

    The functional roles of the orphan nuclear receptor, Nurr1, have been extensively studied and well established in the development and survival of midbrain dopamine neurons. As Nurr1 and other NR4A members are widely expressed in the brain in overlapping and distinct manners, it has been an open question whether Nurr1 has important function(s) in other brain areas. Recent studies suggest that up-regulation of Nurr1 expression is critical for cognitive functions and/or long-term memory in forebrain areas including hippocampal formation. Questions remain about the association between Nurr1 expression and Alzheimer's disease (AD) brain pathology. Here, using our newly developed Nurr1-selective antibody, we report that Nurr1 protein is prominently expressed in brain areas with Aβ accumulation, that is, the subiculum and the frontal cortex, in the 5XFAD mouse and that Nurr1 is highly co-expressed with Aβ at early stages. Furthermore, the number of Nurr1-expressing cells significantly declines in the 5XFAD mouse in an age-dependent manner, accompanied by increased plaque deposition. Thus, our findings suggest that altered expression of Nurr1 is associated with AD progression. Using our newly developed Nurr1-selective antibody, we show that Nurr1 protein is prominently expressed in brain areas accumulating amyloid-beta (Aβ) in the transgenic mouse model of Alzheimer's disease (AD) and that Nurr1 is highly co-expressed with Aβ at early stages (upper panel). Furthermore, in the AD brain the number of Nurr1-expressing cells significantly declines in an age-dependent manner concomitant with increased Aβ accumulation (lower diagram) highlighting a possible Nurr1 involvement in AD pathology.

  15. AL Amyloidosis

    PubMed Central

    2012-01-01

    Definition of the disease AL amyloidosis results from extra-cellular deposition of fibril-forming monoclonal immunoglobulin (Ig) light chains (LC) (most commonly of lambda isotype) usually secreted by a small plasma cell clone. Most patients have evidence of isolated monoclonal gammopathy or smoldering myeloma, and the occurrence of AL amyloidosis in patients with symptomatic multiple myeloma or other B-cell lymphoproliferative disorders is unusual. The key event in the development of AL amyloidosis is the change in the secondary or tertiary structure of an abnormal monoclonal LC, which results in instable conformation. This conformational change is responsible for abnormal folding of the LC, rich in β leaves, which assemble into monomers that stack together to form amyloid fibrils. Epidemiology AL amyloidosis is the most common type of systemic amyloidois in developed countries with an estimated incidence of 9 cases/million inhabitant/year. The average age of diagnosed patients is 65 years and less than 10% of patients are under 50. Clinical description The clinical presentation is protean, because of the wide number of tissues or organs that may be affected. The most common presenting symptoms are asthenia and dyspnoea, which are poorly specific and may account for delayed diagnosis. Renal manifestations are the most frequent, affecting two thirds of patients at presentation. They are characterized by heavy proteinuria, with nephrotic syndrome and impaired renal function in half of the patients. Heart involvement, which is present at diagnosis in more than 50% of patients, leading to restrictive cardiopathy, is the most serious complication and engages prognosis. Diagnostic methods The diagnosis relies on pathological examination of an involved site showing Congo red-positive amyloid deposits, with typical apple-green birefringence under polarized light, that stain positive with an anti-LC antibody by immunohistochemistry and/or immunofluorescence. Due to the

  16. Influence of argon plasma on the deposition of Al2O3 film onto the PET surfaces by atomic layer deposition.

    PubMed

    Edy, Riyanto; Huang, Xiaojiang; Guo, Ying; Zhang, Jing; Shi, Jianjun

    2013-02-15

    In this paper, polyethyleneterephthalate (PET) films with and without plasma pretreatment were modified by atomic layer deposition (ALD) and plasma-assisted atomic layer deposition (PA-ALD). It demonstrates that the Al2O3 films are successfully deposited onto the surface of PET films. The cracks formed on the deposited Al2O3 films in the ALD, plasma pretreated ALD, and PA-ALD were attributed to the energetic ion bombardment in plasmas. The surface wettability in terms of water contact angle shows that the deposited Al2O3 layer can enhance the wetting property of modified PET surface. Further characterizations of the Al2O3 films suggest that the elevated density of hydroxyl -OH group improve the initial growth of ALD deposition. Chemical composition of the Al2O3-coated PET film was characterized by X-ray photoelectron spectroscopy, which shows that the content of C 1s reduces with the growing of O 1s in the Al2O3-coated PET films, and the introduction of plasma in the ALD process helps the normal growth of Al2O3 on PET in PA-ALD.

  17. Globular hepatic amyloid is highly sensitive and specific for LECT2 amyloidosis.

    PubMed

    Chandan, Vishal S; Shah, Sejal S; Lam-Himlin, Dora M; Petris, Giovanni De; Mereuta, Oana M; Dogan, Ahmet; Torbenson, Michael S; Wu, Tsung-Teh

    2015-04-01

    Globular hepatic amyloid (GHA) is rare, and its clinical significance remains unclear. Recently, leukocyte chemotactic factor-associated amyloidosis (ALECT2) has been reported to involve the liver, showing a globular pattern. We reviewed 70 consecutive cases of hepatic amyloidosis to determine the prevalence and morphology of hepatic amyloid subtypes, especially ALECT2 and its association with GHA. Each case was reviewed for amyloid subtype (immunohistochemistry and/or mass spectrometry), its pattern (linear or globular), and distribution (vascular, perisinusoidal, or stromal). In addition, 24 cases of confirmed hepatic ALECT2 on mass spectrometry from our consultation files were also reviewed. LECT2 immunostaining was performed in 49 cases. Of the 70 cases, immunoglobulin light chain (AL) type was most common with 41 cases (59%), followed by transthyretin (ATTR) 15 cases (22%), 3 cases each of fibrinogen A (AFib) (4%), serum amyloid A (AA) (4%), and ALECT2 (4%), 2 cases of apolipoproteins (AApoA1) (3%), and 3 cases (4%) were unclassified. Three of our 70 cases (4%), with ALECT2, and all 24 cases (100%) of mass spectrometry-confirmed hepatic ALECT2 showed only GHA deposits in the hepatic sinusoids and portal tracts. Three (4%) other cases of AL type showed a focal globular pattern admixed with prominent linear amyloid. None of the other amyloid subtypes showed GHA. LECT2 immunostain was positive in all 27 cases (100%) of ALECT2 and negative in the other 22 non-ALECT2 cases (100%) (14 AL, 5 ATTR, 1 AA, 1 AFib, 1 AApoA1). Pure GHA is uncommon (4%) but is highly specific for ALECT2, and LECT2 immunostain is helpful in confirming this amyloid type.

  18. On the feasibility of silicene encapsulation by AlN deposited using an atomic layer deposition process

    SciTech Connect

    Van Bui, H. E-mail: M.P.deJong@utwente.nl; Wiggers, F. B.; Kovalgin, A. Y.; Jong, M. P. de E-mail: M.P.deJong@utwente.nl; Friedlein, R.; Yamada-Takamura, Y.

    2015-02-14

    Since epitaxial silicene is not chemically inert under ambient conditions, its application in devices and the ex-situ characterization outside of ultrahigh vacuum environments require the use of an insulating capping layer. Here, we report on a study of the feasibility of encapsulating epitaxial silicene on ZrB{sub 2}(0001) thin films grown on Si(111) substrates by aluminum nitride (AlN) deposited using trimethylaluminum (TMA) and ammonia (NH{sub 3}) precursors. By in-situ high-resolution core-level photoelectron spectroscopy, the chemical modifications of the surface due to subsequent exposure to TMA and NH{sub 3} molecules, at temperatures of 300 °C and 400 °C, respectively, have been investigated. While an AlN-related layer can indeed be grown, silicene reacts strongly with both precursor molecules resulting in the formation of Si–C and Si–N bonds such that the use of these precursors does not allow for the protective AlN encapsulation that leaves the electronic properties of silicene intact.

  19. Atomic layer deposition of TiO2 / Al2O3 films for optical applications

    NASA Astrophysics Data System (ADS)

    Triani, Gerry; Evans, Peter J.; Mitchell, David R. G.; Attard, Darren J.; Finnie, Kim S.; James, Michael; Hanley, Tracey; Latella, Bruno; Prince, Kathryn E.; Bartlett, John

    2005-09-01

    Atomic layer deposition (ALD) is an important technology for depositing functional coatings on accessible, reactive surfaces with precise control of thickness and nanostructure. Unlike conventional chemical vapour deposition, where growth rate is dependent on reactant flux, ALD employs sequential surface chemical reactions to saturate a surface with a (sub-) monolayer of reactive compounds such as metal alkoxides or covalent halides, followed by reaction with a second compound such as water to deposit coatings layer-by-layer. A judicious choice of reactants and processing conditions ensures that the reactions are self-limiting, resulting in controlled film growth with excellent conformality to the substrate. This paper investigates the deposition and characterisation of multi-layer TiO2 /Al2O3 films on a range of substrates, including silicon <100>, soda glass and polycarbonate, using titanium tetrachloride/water and trimethylaluminium/water as precursor couples. Structure-property correlations were established using a suite of analytical tools, including transmission electron microscopy (TEM), secondary ion mass spectrometry (SIMS), X-ray reflectometry (XRR) and spectroscopic ellipsometry (SE). The evolution of nanostructure and composition of multi-layer high/low refractive index stacks are discussed as a function of deposition parameters.

  20. Coating Layer Characterization of Laser Deposited AlSi Coating over Laser Weld Bead

    NASA Astrophysics Data System (ADS)

    Gu, Hongping; Van Gelder, Aldo

    Corrosion protection of steel components is an important topic in automotive industry. Laser beam welding makes a narrow weld bead, thus minimizing the damage to the original coating on the steel material. However, the weld bead loses its original coating and is vulnerable to corrosive attack. It was demonstrated in this study that laser beam generated AlSi coating is an effective way to apply a protective coating on the weld bead. Coatings with different thickness and topography have been deposited under different laser power and processing speed. The microstructure of the as-deposited coating and its evolution after heat treatment has been studied. EDS was employed to analyze the distribution of chemical compositions of the laser generated coatings. Several metallic compounds of Al and iron have been identified. It was found that the type of metallic compounds can be influenced by the laser processing parameters.

  1. Al Kushaymiyah as a target for a Colorado-type molybdenite deposit

    USGS Publications Warehouse

    Theobald, P.K.

    1971-01-01

    The granitic complex in the vicinity of Al Kushaymiyah was singled out by Whitlow (19,69, 1969a, 1971), as one of the most promising areas for exploration in the Southern Wajd quadrangle (Jackson and others, 1962). He noted in particular the intensity of shattering and silicification of these potassium-rich granites, and the presence of unusual concentrations of tungsten , molybdenum, and tin in samples from the area. In the light of shield-wide compilations, this area again stands out as the principal geochemical anomaly for the three metals. The similarity of these unusual geologic and geochemical features to those of Colorado-type molybdenite deposits is striking and suggests that the Al Kushaymiyah provides a favorableenvironment to explore for a stockwork molybdenum deposit.

  2. The effect of focal brain injury on beta-amyloid plaque deposition, inflammation and synapses in the APP/PS1 mouse model of Alzheimer's disease.

    PubMed

    Collins, Jessica M; King, Anna E; Woodhouse, Adele; Kirkcaldie, Matthew T K; Vickers, James C

    2015-05-01

    Traumatic brain injury is a risk factor for Alzheimer's disease (AD), however the effect of such neural damage on the onset and progression of beta-amyloid (Aβ) plaque pathology is not well understood. This study utilized an in vivo model of focal brain injury to examine how localized damage may acutely affect the onset and progression of Aβ plaque deposition as well as inflammatory and synaptic changes, in the APP/PS1 (APPSWE, PSEN1dE9) transgenic model of AD relative to wild-type (Wt) mice. Acute focal brain injury in 3- and 9-month-old APP/PS1 and Wt mice was induced by insertion of a needle into the somatosensory neocortex, as compared to sham surgery, and examined at 24h and 7d post-injury (PI). Focal brain injury did not induce thioflavine-S stained or (pan-Aβ antibody) MOAB-2-labeled plaques at either 24h or 7d PI in 3-month-old APP/PS1 mice or Wt mice. Nine-month-old APP/PS1 mice demonstrate cortical Aβ plaques but focal injury had no statistically significant (p>0.05) effect on thioflavine-S or MOAB-2 plaque load surrounding the injury site at 24h PI or 7d PI. There was a significant (p<0.001) increase in cross-sectional cortical area occupied by Iba-1 positive microglia in injured mice compared to sham animals, however this response did not differ between APP/PS1 and Wt mice (p>0.05). For both Wt and APP/PS1 mice alike, synaptophysin puncta near the injury site were significantly reduced 24h PI (compared to sites distant to the injury and the corresponding area in sham mice; p<0.01), but not after 7d PI (p>0.05). There was no significant effect of genotype on this response (p>0.05). These results indicate that focal brain injury and the associated microglial response do not acutely alter Aβ plaque deposition in the APP/PS1 mouse model. Furthermore the current study demonstrated that the brains of both Wt and APP/PS1 mice are capable of recovering lost synaptophysin immunoreactivity post-injury, the latter in the presence of Aβ plaque pathology that

  3. Atomic layer deposition of Al2O3 on NF3-pre-treated graphene

    NASA Astrophysics Data System (ADS)

    Junige, Marcel; Oddoy, Tim; Yakimova, Rositsa; Darakchieva, Vanya; Wenger, Christian; Lupina, Grzegorz; Kitzmann, Julia; Albert, Matthias; Bartha, Johann W.

    2015-06-01

    Graphene has been considered for a variety of applications including novel nanoelectronic device concepts. However, the deposition of ultra-thin high-k dielectrics on top of graphene has still been challenging due to graphene's lack of dangling bonds. The formation of large islands and leaky films has been observed resulting from a much delayed growth initiation. In order to address this issue, we tested a pre-treatment with NF3 instead of XeF2 on CVD graphene as well as epitaxial graphene monolayers prior to the Atomic Layer Deposition (ALD) of Al2O3. All experiments were conducted in vacuo; i. e. the pristine graphene samples were exposed to NF3 in the same reactor immediately before applying 30 (TMA-H2O) ALD cycles and the samples were transferred between the ALD reactor and a surface analysis unit under high vacuum conditions. The ALD growth initiation was observed by in-situ real-time Spectroscopic Ellipsometry (irtSE) with a sampling rate above 1 Hz. The total amount of Al2O3 material deposited by the applied 30 ALD cycles was cross-checked by in-vacuo X-ray Photoelectron Spectroscopy (XPS). The Al2O3 morphology was determined by Atomic Force Microscopy (AFM). The presence of graphene and its defect status was examined by in-vacuo XPS and Raman Spectroscopy before and after the coating procedure, respectively.

  4. Fabrication of AlN/BN bishell hollow nanofibers by electrospinning and atomic layer deposition

    SciTech Connect

    Haider, Ali; Kayaci, Fatma; Uyar, Tamer; Biyikli, Necmi; Ozgit-Akgun, Cagla; Okyay, Ali Kemal

    2014-09-01

    Aluminum nitride (AlN)/boron nitride (BN) bishell hollow nanofibers (HNFs) have been fabricated by successive atomic layer deposition (ALD) of AlN and sequential chemical vapor deposition (CVD) of BN on electrospun polymeric nanofibrous template. A four-step fabrication process was utilized: (i) fabrication of polymeric (nylon 6,6) nanofibers via electrospinning, (ii) hollow cathode plasma-assisted ALD of AlN at 100 °C onto electrospun polymeric nanofibers, (iii) calcination at 500 °C for 2 h in order to remove the polymeric template, and (iv) sequential CVD growth of BN at 450 °C. AlN/BN HNFs have been characterized for their chemical composition, surface morphology, crystal structure, and internal nanostructure using X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and selected area electron diffraction. Measurements confirmed the presence of crystalline hexagonal BN and AlN within the three dimensional (3D) network of bishell HNFs with relatively low impurity content. In contrast to the smooth surface of the inner AlN layer, outer BN coating showed a highly rough 3D morphology in the form of BN nano-needle crystallites. It is shown that the combination of electrospinning and plasma-assisted low-temperature ALD/CVD can produce highly controlled multi-layered bishell nitride ceramic hollow nanostructures. While electrospinning enables easy fabrication of nanofibrous template, self-limiting reactions of plasma-assisted ALD and sequential CVD provide control over the wall thicknesses of AlN and BN layers with sub-nanometer accuracy.

  5. Effects of plasma-enhanced chemical vapor deposition (PECVD) on the carrier lifetime of Al2O3 passivation stack

    NASA Astrophysics Data System (ADS)

    Cho, Kuk-Hyun; Cho, Young Joon; Chang, Hyo Sik; Kim, Kyung-Joong; Song, Hee Eun

    2015-09-01

    We investigated the effect on the minority carrier lifetime of atomic layer deposition (ALD) Al2O3 passivation by a plasma-enhanced chemical vapor deposition (PECVD) SiON layer in Si/Al2O3/SiON-passivated structure. The lifetime variation of the Al2O3/SiON stack layer was found to depend on both the plasma power and the deposition temperature during the PECVD SiON process and to show better thermal stability than the Al2O3/SiNx:H stack under the same deposition conditions. The lifetime after a high-temperature firing process was improved dramatically at the PECVD deposition temperature of 200 °C. Our results provide a significant clue to reason for the improvement of the passivation performance for passivated emitter and rear contact (PERC) silicon solar cells.

  6. Exploring metalorganic chemical vapor deposition of Si-alloyed Al2O3 dielectrics using disilane

    NASA Astrophysics Data System (ADS)

    Chan, Silvia H.; Keller, Stacia; Koksaldi, Onur S.; Gupta, Chirag; DenBaars, Steven P.; Mishra, Umesh K.

    2017-04-01

    The alloying of Al2O3 films with Si is a promising route to improve gate dielectric properties in Si- and wide-bandgap- based MOS devices. Here we present a comprehensive investigation of alloyed film growth by metalorganic chemical vapor deposition (MOCVD) using trimethylaluminum, disilane, and oxygen precursors over a variety of temperature and flow conditions. Binary growth rates of Al2O3 and SiO2 were evaluated to explain the aggregate growth kinetics of Si-alloyed Al2O3 films, and refractive indices were used to monitor Si incorporation efficiencies. The temperature dependence of the reaction rate of disilane with oxygen was found to be similar to that of trimethylaluminum and oxygen, leading to well-behaved deposition behavior in the kinetic and mass-transport controlled growth regimes. Compositional predictability and stability was achieved over a wider growth space with disilane-based growths as compared to previous work, which used silane as the Si precursor instead. In situ (Al,Si)O/n-GaN MOS gate stacks were grown and showed increasing reduction of net positive fixed charges with higher Si composition.

  7. C-axis orientated AlN films deposited using deep oscillation magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Lin, Jianliang; Chistyakov, Roman

    2017-02-01

    Highly <0001> c-axis orientated aluminum nitride (AlN) films were deposited on silicon (100) substrates by reactive deep oscillation magnetron sputtering (DOMS). No epitaxial favored bond layer and substrate heating were applied for assisting texture growth. The effects of the peak target current density (varied from 0.39 to 0.8 Acm-2) and film thickness (varied from 0.25 to 3.3 μm) on the c-axis orientation, microstructure, residual stress and mechanical properties of the AlN films were investigated by means of X-ray diffraction rocking curve methodology, transmission electron microscopy, optical profilometry, and nanoindentation. All AlN films exhibited a <0001> preferred orientation and compressive residual stresses. At similar film thicknesses, an increase in the peak target current density to 0.53 Acm-2 improved the <0001> orientation. Further increasing the peak target current density to above 0.53 Acm-2 showed limited contribution to the texture development. The study also showed that an increase in the thickness of the AlN films deposited by DOMS improved the c-axis alignment accompanied with a reduction in the residual stress.

  8. Structure and function of amyloid in Alzheimer's disease.

    PubMed

    Morgan, Carlos; Colombres, Marcela; Nuñez, Marco Tulio; Inestrosa, Nibaldo C

    2004-12-01

    This review is focused on the structure and function of Alzheimer's amyloid deposits. Amyloid formation is a process in which normal well-folded cellular proteins undergo a self-assembly process that leads to the formation of large and ordered protein structures. Amyloid deposition, oligomerization, and higher order polymerization, and the structure adopted by these assemblies, as well as their functional relationship with cell biology are underscored. Numerous efforts have been directed to elucidate these issues and their relation with senile dementia. Significant advances made in the last decade in amyloid structure, dynamics and cell biology are summarized and discussed. The mechanism of amyloid neurotoxicity is discussed with emphasis on the Wnt signaling pathway. This review is focused on Alzheimer's amyloid fibrils in general and has been divided into two parts dealing with the structure and function of amyloid.

  9. Characteristics of Al-doped ZnO films grown by atomic layer deposition for silicon nanowire photovoltaic device.

    PubMed

    Oh, Byeong-Yun; Han, Jin-Woo; Seo, Dae-Shik; Kim, Kwang-Young; Baek, Seong-Ho; Jang, Hwan Soo; Kim, Jae Hyun

    2012-07-01

    We report the structural, electrical, and optical characteristics of Al-doped ZnO (ZnO:Al) films deposited on glass by atomic layer deposition (ALD) with various Al2O3 film contents for use as transparent electrodes. Unlike films fabricated by a sputtering method, the diffraction peak position of the films deposited by ALD progressively moved to a higher angle with increasing Al2O3 film content. This indicates that Zn sites were effectively replaced by Al, due to layer-by-layer growth mechanism of ALD process which is based on alternate self-limiting surface chemical reactions. By adjusting the Al2O3 film content, a ZnO:Al film with low electrical resistivity (9.84 x 10(-4) Omega cm) was obtained at an Al2O3 film content of 3.17%, where the Al concentration, carrier mobility, optical transmittance, and bandgap energy were 2.8 wt%, 11.20 cm2 V(-1) s(-1), 94.23%, and 3.6 eV, respectively. Moreover, the estimated figure of merit value of our best sample was 8.2 m7Omega(-1). These results suggest that ZnO:Al films deposited by ALD could be useful for electronic devices in which especially require 3-dimensional conformal deposition of the transparent electrode and surface passivation.

  10. Pulsed Nd-YAG laser deposition of TiN and TiAlN coating

    NASA Astrophysics Data System (ADS)

    Kathuria, Y. P.; Uchida, Yoshiyuki

    This paper demonstrates the feasibility of generating a thin clad coating of TiN and TiAlN on SS304 base material by using the pulsed Nd-YAG laser. In the experiment TiN based coating was created with and without the addition of Al-powder. In the post processing, a precision grinder was employed to smoothen the top surface. SEM, XRD and EDS analysis were employed to study the surface topography etc. Microhardness mapping was performed at various points across the surface. The results show the average microhardness of the coating deposited with TiN is lower (1035 HV) than that of using Al-mixed powder (1264 HV).

  11. Nano-Al{sub 2}O{sub 3} multilayer film deposition on cotton fabrics by layer-by-layer deposition method

    SciTech Connect

    Ugur, Sule S.; Sariisik, Merih; Aktas, A. Hakan

    2011-08-15

    Highlights: {yields} Cationic charges were created on the cotton fibre surfaces with 2,3-epoxypropyltrimethylammonium chloride. {yields} Al{sub 2}O{sub 3} nanoparticles were deposited on the cotton fabrics by layer-by-layer deposition. {yields} The fabrics deposited with the Al{sub 2}O{sub 3} nanoparticles exhibit better UV-protection and significant flame retardancy properties. {yields} The mechanical properties were improved after surface film deposition. -- Abstract: Al{sub 2}O{sub 3} nanoparticles were used for fabrication of multilayer nanocomposite film deposition on cationic cotton fabrics by electrostatic self-assembly to improve the mechanical, UV-protection and flame retardancy properties of cotton fabrics. Cotton fabric surface was modified with a chemical reaction to build-up cationic charge known as cationization. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy, X-ray Photoelectron Spectroscopy and Scanning Electron Microscopy were used to verify the presence of deposited nanolayers. Air permeability, whiteness value, tensile strength, UV-transmittance and Limited Oxygen Index properties of cotton fabrics were analyzed before and after the treatment of Al{sub 2}O{sub 3} nanoparticles by electrostatic self-assemblies. It was proved that the flame retardancy, tensile strength and UV-transmittance of cotton fabrics can be improved by Al{sub 2}O{sub 3} nanoparticle additive through electrostatic self-assembly process.

  12. Comparison of core control and geophysical investigations, silica sand deposits, Dawmat Al Jandal, Al Jawf at Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Alsulaimani, Ghassan Salem

    This thesis is a summary of a comprehensive geophysical investigation in southern Dawmat Al Jandal, Al Jawf in Saudi Arabia. This research demonstrates that the acquisition of both core control and geophysical data is superior to the acquisition of core control alone. Coring is expensive and is limited in subsurface coverage. Geophysical surveying, however, is a relatively rapid and cost-effective means of deriving information about the subsurface between core holes. Ground penetrating radar (GPR), Multichannel Analysis of Surface Waves (MASW), and Seismic Refraction methods were used as exploration techniques to locate surficial mineral deposits within the study area. During the course of these investigations, the author tries to review the acquired 1620 meters of ground penetrating radar (GPR) data to image internal reflections (if any) within the sand and the top of the underlying sandstone; 27 MASW field records were acquired at each core hole location, which generated 1-D and 2-D shear wave velocity profiles, and 27 seismic refraction profiles were acquired, which did not image the top of the sandstone. The purpose was to estimate the thickness of the sand and to map bedding planes within the sand to better understand depositional environments under the same conditions, based on the high-resolution 2-D surveys, mostly performed in mining areas. The Geophysical investigations were successful and proved to be useful methods for the exploration of shallow subsurface areas where the results are equal to, or slightly different from, the corresponding with of the core holes' values. Therefore, geophysical surveying does not remove the need for core control, but when it is properly applied it can optimize exploration rating programs by maximizing the rate of ground coverage and minimizing the amount of core drilling that is required.

  13. Peptide Detection of Fungal Functional Amyloids in Infected Tissue

    PubMed Central

    Garcia-Sherman, Melissa C.; Lysak, Nataliya; Filonenko, Alexandra; Richards, Hazel; Sobonya, Richard E.; Klotz, Stephen A.; Lipke, Peter N.

    2014-01-01

    Many fungal cell adhesion proteins form functional amyloid patches on the surface of adhering cells. The Candida albicans Agglutinin-like sequence (Als) adhesins are exemplars for this phenomenon, and have amyloid forming sequences that are conserved between family members. The Als5p amyloid sequence mediates amyloid fibril formation and is critical for cell adhesion and biofilm formation, and is also present in the related adhesins Als1p and Als3p. We have developed a fluorescent peptide probe containing the conserved Als amyloid-forming sequence. This peptide bound specifically to yeast expressing Als5p, but not to cells lacking the adhesin. The probe bound to both yeast and hyphal forms of C. albicans. Δals1/Δals3 single and double deletion strains exhibited reduced fluorescence, indicating that probe binding required expression of these proteins. Additionally, the Als peptide specifically stained fungal cells in abscesses in autopsy sections. Counterstaining with calcofluor white showed colocalization with the amyloid peptide. In addition, fungi in autopsy sections derived from the gastrointestinal tract showed colocalization of the amyloid-specific dye thioflavin T and the fluorescent peptide. Collectively, our data demonstrate that we can exploit amyloid sequence specificity for detection of functional amyloids in situ. PMID:24465872

  14. Natural polyphenols binding to amyloid: a broad class of compounds to treat different human amyloid diseases.

    PubMed

    Ngoungoure, Viviane L Ndam; Schluesener, Jan; Moundipa, Paul F; Schluesener, Hermann

    2015-01-01

    Polyphenols are a large group of phytonutrients found in herbal beverages and foods. They have manifold biological activities, including antioxidative, antimicrobial, and anti-inflammatory properties. Interestingly, some polyphenols bind to amyloid and substantially ameliorate amyloid diseases. Misfolding, aggregation, and accumulation of amyloid fibrils in tissues or organs leads to a group of disorders, called amyloidoses. Prominent diseases are Alzheimer's, Parkinson's, and Huntington's disease, but there are other, less well-known diseases wherein accumulation of misfolded protein is a prominent feature. Amyloidoses are a major burden to public health. In particular, Alzheimer's disease shows a strong increase in patient numbers. Accelerated development of effective therapies for amyloidoses is a necessity. A viable strategy can be the prevention or reduction of protein misfolding, thus reducing amyloid build-up by restoring the cellular aggretome. Amyloid-binding polyphenols affect amyloid formation on various levels, e.g. by inhibiting fibril formation or steering oligomer formation into unstructured, nontoxic pathways. Consequently, preclinical studies demonstrate reduction of amyloid-formation by polyphenols. Amyloid-binding polyphenols might be suitable lead structures for development of imaging agents for early detection of disease and monitoring amyloid deposition. Intake of dietary polyphenols might be relevant to the prevention of amyloidoses. Nutraceutical strategies might be a way to reduce amyloid diseases.

  15. Hot Corrosion Performance of AlO-CrO/NiCoCrAlYTa and AlO/NiCoCrAlYTa Coatings Deposited by Atmospheric Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Tao, Chong; Wang, Lei; Cheng, Nailiang; Hu, Hengfa; Liu, Yang; Song, Xiu

    2016-04-01

    AlO-CrO/NiCoCrAlYTa and AlO/NiCoCrAlYTa coatings were deposited on 316L stainless steel substrate using atmospheric plasma spraying, respectively, in order to improve the oxidation and corrosion resistance. The hot corrosion performance of the coatings at 700 and 900 °C were studied, and the detailed microstructures and phase composition of the coatings were analyzed using x-ray diffraction, scanning electron microscope with energy dispersive spectrometer, and transmission electron microscope. The results show that both coatings are structurally featured by slatted layers, consisting of amorphous phase, Cr2O3, Ni3Al, and Al2O3. The hot corrosion resistance of AlO-CrO/NiCoCrAlYTa coating is better than that of AlO/NiCoCrAlYTa coating. This improvement is attributed to lower porosity and more compact Cr2O3 in AlO-CrO/NiCoCrAlYTa coating which performs better than Al2O3 in blocking further inward progress of corrosion and oxidization.

  16. Al-Cd Alloy Formation by Aluminum Underpotential Deposition from AlCl3+NaCl Melts on Cadmium Substrate

    NASA Astrophysics Data System (ADS)

    Jovićević, Niko; Cvetković, Vesna S.; Kamberović, Željko J.; Jovićević, Jovan N.

    2013-02-01

    Aluminum was incorporated into a polycrystalline cadmium electrode surface by underpotential deposition from equimolar AlCl3+ NaCl melt at 473 K, 523 K, and 573 K (200 °C, 250 °C, and 300 °C). The process was studied by linear sweep voltammetry and potentiostatic deposition/galvanostatic striping. The deposits were characterized X-ray diffraction (XRD), Auger electron spectroscopy (AES), and electron probe microanalyzer (EPMA). The electrochemical measurements showed evidence of Cd-Al alloys being formed but they could not be identified. The growth kinetics of the Cd-Al layers of various proportion and depths that depended on temperature and deposition time were described.

  17. Deposition pressure effect on chemical, morphological and optical properties of binary Al-nitrides

    NASA Astrophysics Data System (ADS)

    Pérez Taborda, Jaime Andrés; Caicedo, J. C.; Grisales, M.; Saldarriaga, W.; Riascos, H.

    2015-06-01

    Aluminum nitride films (AlN) were produced by Nd:YAG pulsed laser (PLD), with repetition rate of 10 Hz. The laser interaction on Al target under nitrogen gas atmosphere generates plasma which is produced at room temperature with variation in the pressure work from 0.39 Pa to 1.5 Pa thus producing different AlN films. In this sense the dependency of optical properties with the pressure of deposition was studied. The plasma generated at different pressures was characterized by optical emission spectroscopy (OES). Additionally ionic and atomic species from the emission spectra obtained were observed. The plume electronic temperature has been determined by assuming a local thermodynamic equilibrium of the emitting species. Finally the electronic temperature was calculated with Boltzmann plot from relative intensities of spectral lines. The morphology and composition of the films were studied using atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy analysis (XPS) and Raman Spectroscopy. The optical reflectance spectra and color coordinates of the films were obtained by optical spectral reflectometry technique in the range from 400 nm to 900 nm. A clear dependence in morphological properties and optical properties, as a function of the applied deposition pressure, was found in this work which offers a novel application in optoelectronic industry.

  18. Impact of Al2O3 on the aggregation and deposition of graphene oxide.

    PubMed

    Ren, Xuemei; Li, Jiaxing; Tan, Xiaoli; Shi, Weiqun; Chen, Changlun; Shao, Dadong; Wen, Tao; Wang, Longfei; Zhao, Guixia; Sheng, Guoping; Wang, Xiangke

    2014-05-20

    To assess the environmental behavior and impact of graphene oxide (GO) on living organisms more accurately, the aggregation of GO and its deposition on Al2O3 particles were systematically investigated using batch experiments across a wide range of solution chemistries. The results indicated that the aggregation of GO and its deposition on Al2O3 depended on the solution pH and the types and concentrations of electrolytes. MgCl2 and CaCl2 destabilized GO because of their effective charge screening and neutralization, and the presence of NaH2PO4 and poly(acrylic acid) (PAA) improved the stability of GO with the increase in pH values as a result of electrostatic interactions and steric repulsion. Specifically, the dissolution of Al2O3 contributed to GO aggregation at relatively low pH or high pH values. Results from this study provide critical information for predicting the fate of GO in aquatic-terrestrial transition zones, where aluminum (hydro)oxides are present.

  19. In situ stress evolution during and after sputter deposition of Al thin films.

    PubMed

    Pletea, M; Koch, R; Wendrock, H; Kaltofen, R; Schmidt, O G

    2009-06-03

    The stress, growth, and morphology evolution of Al thin films up to 300 nm thick, sputter deposited at a constant rate of 0.04 nm s(-1) onto thermally oxidized Si(100) substrates have been investigated for various sputter pressures in the range from 0.05 to 6 Pa. The stress evolution has been studied during and after the film deposition by means of in situ substrate curvature measurements using an optical two-beam deflection method. In order to obtain insight into the mechanisms of stress generation and relaxation, the microstructure of the films was investigated by scanning electron microscopy, focused-ion-beam microscopy, and atomic force microscopy. The stress evolution during the early stage of deposition of films is consistent with the Volmer-Weber growth mode known for metals with high adatom mobility. For thicker films, the compressive stress increases in the sputter pressure range of 0.05-0.5 Pa, whereas at even higher sputter pressures a transition from compressive to tensile stress takes place. This transition is correlated with a change from a relatively dense to a more porous microstructure characterized by decreasing mass density and increasing electrical resistivity with increasing sputter pressure. The dependence of the stress and microstructure on the sputter pressure can be consistently understood through a combination of the stress mechanisms for vapor and sputter deposited films proposed in the literature.

  20. Cold spray deposition of Ti2AlC coatings for improved nuclear fuel cladding

    NASA Astrophysics Data System (ADS)

    Maier, Benjamin R.; Garcia-Diaz, Brenda L.; Hauch, Benjamin; Olson, Luke C.; Sindelar, Robert L.; Sridharan, Kumar

    2015-11-01

    Coatings of Ti2AlC MAX phase compound have been successfully deposited on Zircaloy-4 (Zry-4) test flats, with the goal of enhancing the accident tolerance of LWR fuel cladding. Low temperature powder spray process, also known as cold spray, has been used to deposit coatings ∼90 μm in thickness using powder particles of <20 μm. X-ray diffraction analysis showed the phase-content of the deposited coatings to be identical to the powders indicating that no phase transformation or oxidation had occurred during the coating deposition process. The coating exhibited a high hardness of about 800 HK and pin-on-disk wear tests using abrasive ruby ball counter-surface showed the wear resistance of the coating to be significantly superior to the Zry-4 substrate. Scratch tests revealed the coatings to be well-adhered to the Zry-4 substrate. Such mechanical integrity is required for claddings from the standpoint of fretting wear resistance and resisting wear handling and insertion. Air oxidation tests at 700 °C and simulated LOCA tests at 1005 °C in steam environment showed the coatings to be significantly more oxidation resistant compared to Zry-4 suggesting that such coatings can potentially provide accident tolerance to nuclear fuel cladding.

  1. Microstructure and chemical wet etching characteristics of AlN films deposited by ac reactive magnetron sputtering

    SciTech Connect

    Tanner, S. M.; Felmetsger, V. V.

    2010-01-15

    The influence of the surface morphology of a molybdenum underlayer on the crystallinity and etchability of reactively sputtered c-axis oriented aluminum nitride thin films was investigated. Atomic force microscopy, scanning electron microscopy, transmission electron microscopy, high resolution x-ray diffraction, and defect selective chemical etching were used to characterize the microstructure of the Mo and AlN films. 1000 nm thick films of AlN with a full width at half maximum (FWHM) of the x-ray rocking curve ranging from 1.1 deg. to 1.9 deg. were deposited on 300 nm thick Mo underlayers with a FWHM of around 1.5 deg. The Ar pressure during the Mo deposition had a critical effect on the Mo film surface morphology, affecting the structure of the subsequently deposited AlN films and, hence, their wet etching characteristics. AlN films deposited on Mo sputtered at a relatively high pressure could not be etched completely, while AlN films deposited on low pressure Mo etched more easily. Postdeposition etching of the Mo surface in Ar rf discharge prior to deposition of the AlN film was found to influence the formation of AlN residuals that were difficult to etch. Optimal rf plasma etching conditions were found, which minimized the formation of these residuals.

  2. Electrophoretic deposition of double-layer HA/Al composite coating on NiTi.

    PubMed

    Karimi, Esmaeil; Khalil-Allafi, Jafar; Khalili, Vida

    2016-01-01

    In order to improve the bioactivity of NiTi alloys, which are being known as the suitable materials for biomedical applications, numerous NiTi disks were electrophoretically coated by hetero-coagulated hydroxyapatite/aluminum composite coatings in three main voltages from suspensions with different Al concentrations. In this paper, the amount of Ni ions release and bioactivity of prepared samples as well as bonding strength of the coating to substrate were investigated. The surface characterization of the coating by XRD, EDX, SEM, and FTIR showed that HA particles bonded by Al particles. It caused the formation of a free crack coating on NiTi disks. Moreover, the bonding strength of HA/Al coatings to NiTi substrate were improved by two times as compared to that of the pure HA coatings. Immersing of coated samples in SBF for 1 week showed that apatite formation ability was improved on HA/Al composite coating and Ni ions release from the surface of composite coating decreased. These results induce the appropriate bioactivity and biocompatibility of the deposited HA/Al composite coatings on NiTi disks.

  3. Deposition of ultrathin AlN films for high frequency electroacoustic devices

    SciTech Connect

    Felmetsger, Valery V.; Laptev, Pavel N.; Graham, Roger J.

    2011-03-15

    The authors investigate the microstructure, crystal orientation, and residual stress of reactively sputtered aluminum nitride (AlN) films having thicknesses as low as 200 down to 25 nm. A two-step deposition process by the dual cathode ac (40 kHz) powered S-gun magnetron enabling better conditions for AlN nucleation on the surface of the molybdenum (Mo) bottom electrode was developed to enhance crystallinity of ultrathin AlN films. Using the two-step process, the residual in-plane stress as well as the stress gradient through the film thickness can be effectively controlled. X-ray rocking curve measurements have shown that ultrathin films grown on Mo using this technology are highly c-axis oriented with full widths at half maximum of 1.8 deg. and 3.1 deg. for 200- and 25-nm-thick films, respectively, which are equal to or even better than the results previously reported for relatively thick AlN films. High-resolution transmission electron microscopy and fast Fourier transform analyses have confirmed strong grain orientation in 25-100-nm-thick films. A fine columnar texture and a continuous lattice microstructure within a single grain from the interface with the Mo substrate through to the AlN surface have been elicited even in the 25-nm-thick film.

  4. Silicon surface passivation by atomic layer deposited Al{sub 2}O{sub 3}

    SciTech Connect

    Hoex, B.; Sanden, M. C. M. van de; Kessels, W. M. M.; Schmidt, J.; Pohl, P.

    2008-08-15

    Thin Al{sub 2}O{sub 3} films with a thickness of 7-30 nm synthesized by plasma-assisted atomic layer deposition (ALD) were used for surface passivation of crystalline silicon (c-Si) of different doping concentrations. The level of surface passivation in this study was determined by techniques based on photoconductance, photoluminescence, and infrared emission. Effective surface recombination velocities of 2 and 6 cm/s were obtained on 1.9 {omega} cm n-type and 2.0 {omega} cm p-type c-Si, respectively. An effective surface recombination velocity below 1 cm/s was unambiguously obtained for nearly intrinsic c-Si passivated by Al{sub 2}O{sub 3}. A high density of negative fixed charges was detected in the Al{sub 2}O{sub 3} films and its impact on the level of surface passivation was demonstrated experimentally. The negative fixed charge density results in a flat injection level dependence of the effective lifetime on p-type c-Si and explains the excellent passivation of highly B-doped c-Si by Al{sub 2}O{sub 3}. Furthermore, a brief comparison is presented between the surface passivations achieved for thermal and plasma-assisted ALD Al{sub 2}O{sub 3} films prepared in the same ALD reactor.

  5. Structural, electrical, and optical properties of atomic layer deposition Al-doped ZnO films

    SciTech Connect

    Banerjee, P; Lee, W. J.; Bae, K. R.; Lee, Sang Bok; Rubloff, Gary W

    2010-01-01

    Al-doped ZnO (AZO) films of ~100nm thickness with various Aldoping were prepared at 150°C by atomic layer deposition on quartz substrates. At low Aldoping, the films were strongly textured along the [100] direction, while at higher Aldoping the films remained amorphous. Atomic force microscopy results showed that Al–O cycles when inserted in a ZnOfilm, corresponding to a few atomic percent Al, could remarkably reduce the surface roughness of the films. Hall measurements revealed a maximum mobility of 17.7cm{sup 2} /Vs . Film resistivity reached a minima of 4.4×10{sup -3} Ωcm whereas the carrier concentration reached a maxima of 1.7×10{sup 20} cm{sup -3} , at 3 at.% Al. The band gap of AZO films varied from 3.23 eV for undoped ZnOfilms to 3.73 eV for AZO films with 24.6 at.% Al. Optical transmittance over 80% was obtained in the visible region. The detrimental impact of increased Al resulting in decreased conductivity due to doping past 3.0 at.% is evident in the x-ray diffraction data, as an abrupt increase in the optical band gap and as a deviation from the Burstein–Moss effect.

  6. CoFe2/Al2O3/PMNPT multiferroic heterostructures by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Zhou, Ziyao; Grocke, Garrett; Yanguas-Gil, Angel; Wang, Xinjun; Gao, Yuan; Sun, Nianxiang; Howe, Brandon; Chen, Xing

    2016-05-01

    Multiferroic materials and applications allow electric bias control of magnetism or magnetic bias control of polarization, enabling fast, compact, energy-efficient devices in RF/microwave communication systems such as filters, shifters, and antennas; electronics devices such as inductors and capacitors; and other magnetic material related applications including sensors and memories. In this manuscript, we utilize atomic layer deposition technology to grow magnetic CoFe metallic thin films onto PMNPT, with a ˜110 Oe electric field induced ferromagnetic resonance field shift in the CoFe/Al2O3/PMNPT multiferroic heterostructure. Our work demonstrates an atomic layer deposition fabricated multiferroic heterostructure with significant tunability and shows that the unique thin film growth mechanism will benefit integrated multiferroic application in near future.

  7. Reactivity of deposited carbon on Co-Al/sub 2/O/sub 3/ catalyst

    SciTech Connect

    Nakamura, J.; Tanaka, K.; Toyoshima, I.

    1987-11-01

    Reactivity and characteristics of the carbon deposited on Co-Al/sub 2/O/sub 3/ by disproportionation of CO (the Boudouard reaction) were studied by pulse experiments using /sup 13/C or D isotopes. Three types of deposited carbon were identified by the reaction with hydrogen: highly reactive CH and/or CH/sub 2/ species, reactive carbidic carbon, and less reactive graphitic carbon. The existence of CH and CH/sub 2/ species was proved by the reaction with D/sub 2/ pulse at 80/sup 0/C, but the predominant species was carbidic carbon when the disproportionation of CO was performed on cobalt catalyst at 230/sup 0/C. Carbidic carbon was decomposed to graphitic carbon by raising the temperature. However, a certain amount of carbidic carbon was found to remain on the surface even at 430/sup 0/C. This phenomenon may suggest reversible formation of carbidic carbon from graphitic carbon on the catalyst.

  8. Sputtering deposition of Al-doped zinc oxide thin films using mixed powder targets

    NASA Astrophysics Data System (ADS)

    Ohshima, Tamiko; Maeda, Takashi; Tanaka, Yuki; Kawasaki, Hiroharu; Yagyu, Yoshihito; Ihara, Takeshi; Suda, Yoshiaki

    2016-01-01

    Sputtering deposition generally uses high-density bulk targets. Such a fabrication process has various problems including deterioration of the material during heating and difficulty in mixing a large number of materials in precise proportions. However, these problems can be solved by using a powder target. In this study, we prepared Al-doped ZnO (AZO) as transparent conductive thin films by radio-frequency magnetron sputtering with powder and bulk targets. Both the powder and bulk targets formed crystalline structures. The ZnO (002) peak was observed in the X-ray diffraction measurements. The mean transparency and resistivity of the films prepared with the powder target were 82% and 0.548 Ω · cm, respectively. The deposition rate with the powder target was lower than that with the bulk target.

  9. A comparative study on electrical characteristics of crystalline AlN thin films deposited by ICP and HCPA-sourced atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Altuntas, Halit; Bayrak, Turkan

    2017-03-01

    In this work, we aimed to investigate the effects of two different plasma sources on the electrical properties of low-temperature plasma-assisted atomic layer deposited (PA-ALD) AlN thin films. To compare the electrical properties, 50 nm thick AlN films were grown on p-type Si substrates at 200 °C by using an inductively coupled RF-plasma (ICP) and a stainless steel hollow cathode plasma-assisted (HCPA) ALD systems. Al/AlN/ p-Si metal-insulator-semiconductor (MIS) capacitor devices were fabricated and capacitance versus voltage ( C- V) and current-voltage ( I- V) measurements performed to assess the basic important electrical parameters such as dielectric constant, effective charge density, flat-band voltage, breakdown field, and threshold voltage. In addition, structural properties of the films were presented and compared. The results show that although HCPA-ALD deposited AlN thin films has structurally better and has a lower effective charge density ( N eff ) value than ICP-ALD deposited AlN films, those films have large leakage current, low dielectric constant, and low breakdown field. This situation was attributed to the involvement of Si atoms into the AlN layers during the HCPA-ALD processing leads to additional current path at AlN/Si interface and might impair the electrical properties.

  10. A comparative study on electrical characteristics of crystalline AlN thin films deposited by ICP and HCPA-sourced atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Altuntas, Halit; Bayrak, Turkan

    2016-12-01

    In this work, we aimed to investigate the effects of two different plasma sources on the electrical properties of low-temperature plasma-assisted atomic layer deposited (PA-ALD) AlN thin films. To compare the electrical properties, 50 nm thick AlN films were grown on p-type Si substrates at 200 °C by using an inductively coupled RF-plasma (ICP) and a stainless steel hollow cathode plasma-assisted (HCPA) ALD systems. Al/AlN/p-Si metal-insulator-semiconductor (MIS) capacitor devices were fabricated and capacitance versus voltage (C-V) and current-voltage (I-V) measurements performed to assess the basic important electrical parameters such as dielectric constant, effective charge density, flat-band voltage, breakdown field, and threshold voltage. In addition, structural properties of the films were presented and compared. The results show that although HCPA-ALD deposited AlN thin films has structurally better and has a lower effective charge density (N eff ) value than ICP-ALD deposited AlN films, those films have large leakage current, low dielectric constant, and low breakdown field. This situation was attributed to the involvement of Si atoms into the AlN layers during the HCPA-ALD processing leads to additional current path at AlN/Si interface and might impair the electrical properties.

  11. Synchrotron-based Infrared and X-ray Imaging Shows Focalized Accumulation of Cu and Zn Co-localized With Beta-amyloid Deposits in Alzheimer's Disease

    SciTech Connect

    Miller,L.; Wang, Q.; Telivala, T.; Smith, R.; Lanzirotti, A.; Miklossy, J.

    2006-01-01

    Alzheimer's disease (AD) is characterized by the misfolding and plaque-like accumulation of a naturally occurring peptide in the brain called amyloid beta (Abeta). Recently, this process has been associated with the binding of metal ions such as iron (Fe), copper (Cu), and zinc (Zn). It is thought that metal dyshomeostasis is involved in protein misfolding and may lead to oxidative stress and neuronal damage. However, the exact role of the misfolded proteins and metal ions in the degenerative process of AD is not yet clear. In this study, we used synchrotron Fourier transform infrared micro-spectroscopy (FTIRM) to image the in situ secondary structure of the amyloid plaques in brain tissue of AD patients. These results were spatially correlated with metal ion accumulation in the same tissue sample using synchrotron X-ray fluorescence (SXRF) microprobe. For both techniques, a spatial resolution of 5-10 microm was achieved. FTIRM results showed that the amyloid plaques have elevated beta-sheet content, as demonstrated by a strong amide I absorbance at 1625cm(-1). Using SXRF microprobe, we find that AD tissue also contains 'hot spots' of accumulated metal ions, specifically Cu and Zn, with a strong spatial correlation between these two ions. The 'hot spots' of accumulated Zn and Cu were co-localized with beta-amyloid plaques. Thus for the first time, a strong spatial correlation has been observed between elevated beta-sheet content in Abeta plaques and accumulated Cu and Zn ions, emphasizing an association of metal ions with amyloid formation in AD.

  12. Impact of post-deposition annealing on interfacial chemical bonding states between AlGaN and ZrO{sub 2} grown by atomic layer deposition

    SciTech Connect

    Ye, Gang; Arulkumaran, Subramaniam; Ng, Geok Ing; Li, Yang; Ang, Kian Siong; Wang, Hong; Liu, Zhi Hong

    2015-03-02

    The effect of post-deposition annealing on chemical bonding states at interface between Al{sub 0.5}Ga{sub 0.5}N and ZrO{sub 2} grown by atomic layer deposition (ALD) is studied by angle-resolved x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. It has been found that both of Al-O/Al 2p and Ga-O/Ga 3d area ratio decrease at annealing temperatures lower than 500 °C, which could be attributed to “clean up” effect of ALD-ZrO{sub 2} on AlGaN. Compared to Ga spectra, a much larger decrease in Al-O/Al 2p ratio at a smaller take-off angle θ is observed, which indicates higher effectiveness of the passivation of Al-O bond than Ga-O bond through “clean up” effect near the interface. However, degradation of ZrO{sub 2}/AlGaN interface quality due to re-oxidation at higher annealing temperature (>500 °C) is also found. The XPS spectra clearly reveal that Al atoms at ZrO{sub 2}/AlGaN interface are easier to get oxidized as compared with Ga atoms.

  13. Familial amyloid polyneuropathy.

    PubMed

    Planté-Bordeneuve, Violaine; Said, Gerard

    2011-12-01

    Familial amyloid polyneuropathies (FAPs) are a group of life-threatening multisystem disorders transmitted as an autosomal dominant trait. Nerve lesions are induced by deposits of amyloid fibrils, most commonly due to mutated transthyretin (TTR). Less often the precursor of amyloidosis is mutant apolipoprotein A-1 or gelsolin. The first identified cause of FAP-the TTR Val30Met mutation-is still the most common of more than 100 amyloidogenic point mutations identified worldwide. The penetrance and age at onset of FAP among people carrying the same mutation vary between countries. The symptomatology and clinical course of FAP can be highly variable. TTR FAP typically causes a nerve length-dependent polyneuropathy that starts in the feet with loss of temperature and pain sensations, along with life-threatening autonomic dysfunction leading to cachexia and death within 10 years on average. TTR is synthesised mainly in the liver, and liver transplantation seems to have a favourable effect on the course of neuropathy, but not on cardiac or eye lesions. Oral administration of tafamidis meglumine, which prevents misfolding and deposition of mutated TTR, is under evaluation in patients with TTR FAP. In future, patients with FAP might benefit from gene therapy; however, genetic counselling is recommended for the prevention of all types of FAP.

  14. Direct Metal Deposition of Functional Graded Structures in Ti- Al System

    NASA Astrophysics Data System (ADS)

    Shishkovsky, I.; Missemer, F.; Smurov, I.

    A direct laser metal deposition (DLMD) technology with co-axial powder injection is used to fabricate a complex functional graded structure (FGS) fabrication. The aim of the study is to demonstrate the possibility to produce intermetallic phases in the Ti-Al powder systems in the course of a single-step DMD process. Besides, relationships between the main laser cladding parameters and the intermetallic phase structures of the built-up objects have been studied. In our research we applied the optical microscopy, X-ray analysis, microhardness measurement and SEM with EDX analysis of the laser-fabricated intermetallics. The discussion of the mechanisms of Ti x Al y (x,y = 1.3) intermetallic transformations in exothermal reactions is also offered in the report.

  15. Properties of AlN films deposited by reactive ion-plasma sputtering

    SciTech Connect

    Bert, N. A.; Bondarev, A. D.; Zolotarev, V. V.; Kirilenko, D. A.; Lubyanskiy, Ya. V.; Lyutetskiy, A. V.; Slipchenko, S. O.; Petrunov, A. N.; Pikhtin, N. A. Ayusheva, K. R.; Arsentyev, I. N.; Tarasov, I. S.

    2015-10-15

    The properties of SiO{sub 2}, Al{sub 2}O{sub 3}, and AlN dielectric coatings deposited by reactive ion-plasma sputtering are studied. The refractive indices of the dielectric coatings are determined by optical ellipsometry. It is shown that aluminum nitride is the optimal material for achieving maximum illumination of the output mirror of a semiconductor laser. A crystalline phase with a hexagonal atomic lattice and oxygen content of up to 10 at % is found by transmission electron microscopy in the aluminum-nitride films. It is found that a decrease in the concentration of residual oxygen in the chamber of the reactive ion-plasma sputtering installation makes it possible to eliminate the appearance of vertical pores in the bulk of the aluminum-nitride film.

  16. Review: history of the amyloid fibril.

    PubMed

    Sipe, J D; Cohen, A S

    2000-06-01

    Rudolph Virchow, in 1854, introduced and popularized the term amyloid to denote a macroscopic tissue abnormality that exhibited a positive iodine staining reaction. Subsequent light microscopic studies with polarizing optics demonstrated the inherent birefringence of amyloid deposits, a property that increased intensely after staining with Congo red dye. In 1959, electron microscopic examination of ultrathin sections of amyloidotic tissues revealed the presence of fibrils, indeterminate in length and, invariably, 80 to 100 A in width. Using the criteria of Congophilia and fibrillar morphology, 20 or more biochemically distinct forms of amyloid have been identified throughout the animal kingdom; each is specifically associated with a unique clinical syndrome. Fibrils, also 80 to 100 A in width, have been isolated from tissue homogenates using differential sedimentation or solubility. X-ray diffraction analysis revealed the fibrils to be ordered in the beta pleated sheet conformation, with the direction of the polypeptide backbone perpendicular to the fibril axis (cross beta structure). Because of the similar dimensions and tinctorial properties of the fibrils extracted from amyloid-laden tissues and amyloid fibrils in tissue sections, they have been assumed to be identical. However, the spatial relationship of proteoglycans and amyloid P component (AP), common to all forms of amyloid, to the putative protein only fibrils in tissues, has been unclear. Recently, it has been suggested that, in situ, amyloid fibrils are composed of proteoglycans and AP as well as amyloid proteins and thus resemble connective tissue microfibrils. Chemical and physical definition of the fibrils in tissues will be needed to relate the in vitro properties of amyloid protein fibrils to the pathogenesis of amyloid fibril formation in vivo.

  17. Uniform Atomic Layer Deposition of Al2O3 on Graphene by Reversible Hydrogen Plasma Functionalization

    PubMed Central

    2017-01-01

    A novel method to form ultrathin, uniform Al2O3 layers on graphene using reversible hydrogen plasma functionalization followed by atomic layer deposition (ALD) is presented. ALD on pristine graphene is known to be a challenge due to the absence of dangling bonds, leading to nonuniform film coverage. We show that hydrogen plasma functionalization of graphene leads to uniform ALD of closed Al2O3 films down to 8 nm in thickness. Hall measurements and Raman spectroscopy reveal that the hydrogen plasma functionalization is reversible upon Al2O3 ALD and subsequent annealing at 400 °C and in this way does not deteriorate the graphene’s charge carrier mobility. This is in contrast with oxygen plasma functionalization, which can lead to a uniform 5 nm thick closed film, but which is not reversible and leads to a reduction of the charge carrier mobility. Density functional theory (DFT) calculations attribute the uniform growth on both H2 and O2 plasma functionalized graphene to the enhanced adsorption of trimethylaluminum (TMA) on these surfaces. A DFT analysis of the possible reaction pathways for TMA precursor adsorption on hydrogenated graphene predicts a binding mechanism that cleans off the hydrogen functionalities from the surface, which explains the observed reversibility of the hydrogen plasma functionalization upon Al2O3 ALD.

  18. Texture Evolution During Laser Direct Metal Deposition of Ti-6Al-4V

    SciTech Connect

    Sridharan, Niyanth; Chaudhary, Anil; Nandwana, Peeyush; Babu, Sudarsanam Suresh

    2016-01-20

    Titanium alloys are used in a wide variety of high performance applications and hence the processing of the titanium and the resulting microstructures after additive manufacturing has received significant attention. During additive manufacturing the processing route involves the transition from a liquid to solid state. The addition of successive layers results in a complex microstructure due to solid-state transformations. The current study focuses on understanding the phase transformations and relate it to the transformation texture in Ti-6Al-4V to identify conditions leading to a strong alpha transformation texture. The as deposited builds were characterized using optical microscopy and electron backscattered diffraction. The results showed columnar prior β grains with a martensitic structure after the deposition of a single layer. On subsequent depositions the martensitic microstructure decomposes to a colony and basketweave microstructure with a stronger transformation texture. The alpha texture with a colony and basketweave microstructure shows a stronger transformation texture as a result of variant selection. Thus by controlling the cooling rate of the build from the β transus it is possible to control the alpha transformation texture.

  19. Texture Evolution During Laser Direct Metal Deposition of Ti-6Al-4V

    DOE PAGES

    Sridharan, Niyanth; Chaudhary, Anil; Nandwana, Peeyush; ...

    2016-01-20

    Titanium alloys are used in a wide variety of high performance applications and hence the processing of the titanium and the resulting microstructures after additive manufacturing has received significant attention. During additive manufacturing the processing route involves the transition from a liquid to solid state. The addition of successive layers results in a complex microstructure due to solid-state transformations. The current study focuses on understanding the phase transformations and relate it to the transformation texture in Ti-6Al-4V to identify conditions leading to a strong alpha transformation texture. The as deposited builds were characterized using optical microscopy and electron backscattered diffraction.more » The results showed columnar prior β grains with a martensitic structure after the deposition of a single layer. On subsequent depositions the martensitic microstructure decomposes to a colony and basketweave microstructure with a stronger transformation texture. The alpha texture with a colony and basketweave microstructure shows a stronger transformation texture as a result of variant selection. Thus by controlling the cooling rate of the build from the β transus it is possible to control the alpha transformation texture.« less

  20. Enhancement of photoluminescence properties in ZnO/AlN bilayer heterostructures grown by atomic layer deposition

    SciTech Connect

    Zhu, Shang-Bin; Lu, Hong-Liang Zhang, Yuan; Sun, Qing-Qing; Zhou, Peng; Ding, Shi-Jin; Zhang, David Wei; Zhang, Qiu-Xiang

    2015-01-15

    The AlN/ZnO bilayer heterostructures were deposited on Si (100) substrate by thermal atomic layer deposition. X-ray diffraction results show that the crystallinity of polycrystalline ZnO layer is enhanced by amorphous AlN capping layer. Compared with ZnO thin film, ZnO/AlN bilayer with 10.7 nm AlN capping layer exhibits three times enhanced near band edge (NBE) emission from the photoluminescence measurements. In addition, the near band edge emission from the ZnO can be further increased by ∼10 times through rapid thermal annealing at 600 °C. The underlying mechanisms for the enhancement of the NBE emission after coating AlN capping layer and thermal treatment are discussed. These results suggest that coating of a thin AlN layer and sequential thermal treatments can effectively tailor the luminescence properties of ZnO film.

  1. Electrochemistry in ultrahigh vacuum: underpotential deposition of Al on polycrystalline W and Au from room temperature AlCl(3)/1-ethyl-3-methylimidazolium chloride melts.

    PubMed

    Johnston, Matthew; Lee, Jae-Joon; Chottiner, Gary S; Miller, Barry; Tsuda, Tetsuya; Hussey, Charles L; Scherson, Daniel A

    2005-06-09

    The voltammetric characteristics of polycrystalline Au and W electrodes cleaned (thermal annealing at 1100 K) and characterized (Auger electron spectroscopy) in ultrahigh vacuum (UHV) have been examined in ultrapure AlCl(3)/1-ethyl-3-methylimidazolium chloride (EtMeImCl) melts in UHV. These experiments were performed using a custom-designed transfer system that allows for the all-Al electrochemical cell to be filled with EtMeImCl in an auxiliary UHV chamber and later transferred under UHV to the main UHV chamber that houses the Auger electron spectrometer. The results obtained for the underpotential (UPD) and bulk deposition of Al on Au were found to be very similar to those reported in the literature for measurements carried out under 1 atm of an inert gas in a glovebox. For the far more reactive W surfaces, voltammetric features ascribed to the stripping of underpotential-deposited Al could be observed following a single scan from 1.0 V vs Al(3+)/Al to a potential negative enough for bulk deposition of Al to ensue. This behavior is unlike that reported in the literature for experiments performed in a glovebox, which required either extensive potential cycling in the Al bulk deposition and stripping region or excursions to potentials positive enough for chlorine evolution to ensue for Al UPD features to be clearly discerned. These observations open new prospects for fundamental electrochemical studies of well-characterized, highly reactive metals, including single crystals, in a variety of low vapor pressure ionic liquids.

  2. A novel approach to the identification and quantitative elemental analysis of amyloid deposits-Insights into the pathology of Alzheimer's disease

    SciTech Connect

    Rajendran, Reshmi; Minqin, Ren; Ynsa, Maria Dolores; Casadesus, Gemma; Smith, Mark A.; Perry, George; Halliwell, Barry; Watt, Frank

    2009-04-24

    There is considerable interest in the role of metals such as iron, copper, and zinc in amyloid plaque formation in Alzheimer's disease. However to convincingly establish their presence in plaques in vivo, a sensitive technique is required that is both quantitatively accurate and avoids isolation of plaques or staining/fixing brain tissue, since these processes introduce contaminants and redistribute elements within the tissue. Combining the three ion beam techniques of scanning transmission ion microscopy, Rutherford back scattering spectrometry and particle induced X-ray emission in conjunction with a high energy (MeV) proton microprobe we have imaged plaques in freeze-dried unstained brain sections from CRND-8 mice, and simultaneously quantified iron, copper, and zinc. Our results show increased metal concentrations within the amyloid plaques compared with the surrounding tissue: iron (85 ppm compared with 42 ppm), copper (16 ppm compared to 6 ppm), and zinc (87 ppm compared to 34 ppm).

  3. High rate reactive magnetron sputter deposition of Al-doped ZnO with unipolar pulsing and impedance control system

    SciTech Connect

    Nishi, Yasutaka; Hirohata, Kento; Tsukamoto, Naoki; Sato, Yasushi; Oka, Nobuto; Shigesato, Yuzo

    2010-07-15

    Al-doped ZnO (AZO) films were deposited on quartz glass substrates, unheated and heated to 200 deg. C, using reactive sputtering with a special feedback system of discharge impedance combined with midfrequency pulsing. A planar Zn-Al alloy target was connected to the switching unit, which was operated in a unipolar pulse mode. The oxidation of the target surface was precisely controlled by a feedback system for the entire O{sub 2} flow ratio including ''the transition region''. The deposition rate was about 10-20 times higher than that for films deposited by conventional sputtering using an oxide target. A deposition rate of AZO films of 390 nm/min with a resistivity of 3.8x10{sup -4} {Omega} cm and a transmittance in the visible region of 85% was obtained when the films were deposited on glass substrates heated to 200 deg. C with a discharge power of 4 kW.

  4. In situ study of e-beam Al and Hf metal deposition on native oxide InP (100)

    SciTech Connect

    Dong, H.; KC, Santosh; Azcatl, A.; Cabrera, W.; Qin, X.; Brennan, B.; Cho, K.; Wallace, R. M.; Zhernokletov, D.

    2013-11-28

    The interfacial chemistry of thin Al (∼3 nm) and Hf (∼2 nm) metal films deposited by electron beam (e-beam) evaporation on native oxide InP (100) samples at room temperature and after annealing has been studied by in situ angle resolved X-ray photoelectron spectroscopy and low energy ion scattering spectroscopy. The In-oxides are completely scavenged forming In-In/In-(Al/Hf) bonding after Al and Hf metal deposition. The P-oxide concentration is significantly decreased, and the P-oxide chemical states have been changed to more P-rich oxides upon metal deposition. Indium diffusion through these metals before and after annealing at 250 °C has also been characterized. First principles calculation shows that In has lower surface formation energy compared with Al and Hf metals, which is consistent with the observed indium diffusion behavior.

  5. Liu et al. suspect that Zhu et al. (2015) may have underestimated dissolved organic nitrogen (N) but overestimated total particulate N in wet deposition in China.

    PubMed

    Liu, Xuejun; Xu, Wen; Pan, Yuepeng; Du, Enzai

    2015-07-01

    In a recent publication in the journal Science of the Total Environment, Zhu et al. (2015) reported the composition, spatial patterns, and factors influencing atmospheric wet nitrogen (N) deposition based on one year's data from 41-monitoring sites in China. We suspect their results may largely underestimate dissolved organic N (DON) but overestimate total particulate N (TPN) in wet deposition due to the uncertainty resulting from the sampling, storage and analysis methods in their study. Our suspicions are based mainly on our experience from earlier measurements and the literature. We therefore suggest that enhanced data quality control on atmospheric N deposition measurements should be taken into account in future studies.

  6. Using Pb-Al ratios to discriminate between internal and external deposition of Pb in feathers.

    PubMed

    Cardiel, Iris E; Taggart, Mark A; Mateo, Rafael

    2011-05-01

    Feathers provide a potentially useful biomonitoring option in studies regarding pollution exposure in avian species. However, they must be used with care because the complex, fine structure is highly prone to accumulating surface contamination. This may therefore give a misleading indication of pollutant intake in the animal. Here, data are presented for 4 large scavenging raptor species collected in Spain, and analyses are undertaken on feather barbs and rachis for both Pb and Al concentrations. Aluminium levels are used as a marker of surface contamination by inorganic particulate material. Despite using a thorough washing technique, feather barbs showed significantly higher levels of Pb than did the rachis for all 4 species studied. We also observed a significant correlation (r=0.782, p<0.001) between Al and Pb levels in the barbs, whilst rachis Al levels were below our detection limit in all samples analysed. Results indicate that the rachis would provide more representative data as regards Pb (or other heavy metal) uptake and tissue deposition within bird tissues during the period of feather growth. As such, data would be more toxicologically relevant.

  7. Additive Manufacturing of AlSi10Mg Alloy Using Direct Energy Deposition: Microstructure and Hardness Characterization

    NASA Astrophysics Data System (ADS)

    Javidani, M.; Arreguin-Zavala, J.; Danovitch, J.; Tian, Y.; Brochu, M.

    2016-12-01

    This paper aims to study the manufacturing of the AlSi10Mg alloy with direct energy deposition (DED) process. Following fabrication, the macro- and microstructural evolution of the as-processed specimens was initially investigated using optical microscopy and scanning electron microscopy. Columnar dendritic structure was the dominant solidification feature of the deposit; nevertheless, detailed microstructural analysis revealed cellular morphology near the substrate and equiaxed dendrites at the top end of the deposit. Moreover, the microstructural morphology in the melt pool boundary of the deposit differed from the one in the core of the layers. The remaining porosity of the deposit was evaluated by Archimedes' principle and by image analysis of the polished surface. Crystallographic texture in the deposit was also assessed using electron backscatter diffraction and x-ray diffraction analysis. The dendrites were unidirectionally oriented at an angle of 80° to the substrate. EPMA line scans were performed to evaluate the compositional variation and elemental segregation in different locations. Eventually, microhardness (HV) tests were conducted in order to study the hardness gradient in the as-DED-processed specimen along the deposition direction. The presented results, which exhibited a deposit with an almost defect free structure, indicate that the DED process can suitable for the deposition of Al-Si-based alloys with a highly consolidated structure.

  8. Surgical considerations about amyloid goiter.

    PubMed

    García Villanueva, Augusto; García Villanueva, María Jesús; García Villanueva, Mercedes; Rojo Blanco, Roberto; Collado Guirao, María Vicenta; Cabañas Montero, Jacobo; Beni Pérez, Rafael; Moreno Montes, Irene

    2013-05-01

    Amyloidosis is an uncommon syndrome consisting of a number of disorders having in common an extracellular deposit of fibrillary proteins. This results in functional and structural changes in the affected organs, depending on deposit location and severity. Amyloid infiltration of the thyroid gland may occur in 50% and up to 80% of patients with primary and secondary amyloidosis respectively. Amyloid goiter (AG) is a true rarity, usually found associated to secondary amyloidosis. AG may require surgical excision, usually because of compressive symptoms. We report the case of a patient with a big AG occurring in the course of a secondary amyloidosis associated to polyarticular onset juvenile idiopathic arthritis who underwent total thyroidectomy. Current literature is reviewed, an attempt is made to provide action guidelines, and some surgical considerations on this rare condition are given.

  9. Electrical properties of GaAs metal-oxide-semiconductor structure comprising Al2O3 gate oxide and AlN passivation layer fabricated in situ using a metal-organic vapor deposition/atomic layer deposition hybrid system

    NASA Astrophysics Data System (ADS)

    Aoki, Takeshi; Fukuhara, Noboru; Osada, Takenori; Sazawa, Hiroyuki; Hata, Masahiko; Inoue, Takayuki

    2015-08-01

    This paper presents a compressive study on the fabrication and optimization of GaAs metal-oxide-semiconductor (MOS) structures comprising a Al2O3 gate oxide, deposited via atomic layer deposition (ALD), with an AlN interfacial passivation layer prepared in situ via metal-organic chemical vapor deposition (MOCVD). The established protocol afforded self-limiting growth of Al2O3 in the atmospheric MOCVD reactor. Consequently, this enabled successive growth of MOCVD-formed AlN and ALD-formed Al2O3 layers on the GaAs substrate. The effects of AlN thickness, post-deposition anneal (PDA) conditions, and crystal orientation of the GaAs substrate on the electrical properties of the resulting MOS capacitors were investigated. Thin AlN passivation layers afforded incorporation of optimum amounts of nitrogen, leading to good capacitance-voltage (C-V) characteristics with reduced frequency dispersion. In contrast, excessively thick AlN passivation layers degraded the interface, thereby increasing the interfacial density of states (Dit) near the midgap and reducing the conduction band offset. To further improve the interface with the thin AlN passivation layers, the PDA conditions were optimized. Using wet nitrogen at 600 °C was effective to reduce Dit to below 2 × 1012 cm-2 eV-1. Using a (111)A substrate was also effective in reducing the frequency dispersion of accumulation capacitance, thus suggesting the suppression of traps in GaAs located near the dielectric/GaAs interface. The current findings suggest that using an atmosphere ALD process with in situ AlN passivation using the current MOCVD system could be an efficient solution to improving GaAs MOS interfaces.

  10. Differential recruitment efficacy of patient-derived amyloidogenic and myeloma light chain proteins by synthetic fibrils—A metric for predicting amyloid propensity

    PubMed Central

    Wooliver, Craig; Heidel, R. Eric; Adams, Sarah; Dunlap, John; Lands, Ronald H.

    2017-01-01

    Background Monoclonal free light chain (LC) proteins are present in the circulation of patients with immunoproliferative disorders such as light chain (AL) amyloidosis and multiple myeloma (MM). Light chain-associated amyloid is a complex pathology composed of proteinaceous fibrils and extracellular matrix proteins found in all patients with AL and in ~10–30% of patients who presented with MM. Amyloid deposits systemically in multiple organs and tissues leading to dysfunction and ultimately death. The overall survival of patients with amyloidosis is worse than for those with early stage MM. Methods and findings We have developed a sensitive binding assay quantifying the recruitment of full length, patient-derived LC proteins by synthetic amyloid fibrils, as a method for studying their amyloidogenic potential. In a survey of eight urinary LC, both AL and MM-associated proteins were recruited by synthetic amyloid fibrils; however, AL-associated LC bound significantly more efficiently (p < 0.05) than did MM LCs. The LC proteins used in this study were isolated from urine and presumed to represent a surrogate of serum free light chains. Conclusion The binding of LC to synthetic fibrils in this assay accurately differentiated LC with amyloidogenic propensity from MM LC that were not associated with clinical amyloid disease. Notably, the LC from a MM patient who subsequently developed amyloid behaved as an AL-associated protein in the assay, indicating the possibility for identifying MM patients at risk for developing amyloidosis based on the light chain recruitment efficacy. With this information, at risk patients can be monitored more closely for the development of amyloidosis, allowing timely administration of novel, amyloid-directed immunotherapies—this approach may improve the prognosis for these patients. PMID:28350808

  11. Effect of bias voltage on TiAlSiN nanocomposite coatings deposited by HiPIMS

    NASA Astrophysics Data System (ADS)

    Ma, Quansheng; Li, Liuhe; Xu, Ye; Gu, Jiabin; Wang, Lei; Xu, Yi

    2017-01-01

    TiAlSiN nanocomposite coatings were deposited onto cemented carbide (WC-10 wt.%, Co) substrates by high power impulse magnetron sputtering (HiPIMS). The effect of substrate bias voltage on plasma discharge characterization of HiPIMS, element concentration, deposition rate, microstructure, surface/cross-sectional morphology, hardness and adhesion strength of coatings were studied. Compared with those deposited with direct current magnetic sputtering (DCMS), HiPIMS-deposited TiAlSiN coatings show improvements in some properties, including the surface roughness, the grain size, the hardness and adhesion strength, but a decrease in the deposition rate. When the bias voltage increases, the discharge current rose up from 118A to 165A. HiPIMS-deposited TiAlSiN coatings show a shift of the preferred crystallographic orientation from (220) to (200) and decreases in surface roughness from 14.1 nm down to 7.4 nm and grain size from 10.5 nm to 7.4 nm. Meanwhile, a change in crystal morphology from columnar to equiaxial and a grain refinement, as well as an increase of hardness from 30 GPa up to 42 GPa of those TiAlSiN coatings were observed with the increasing bias voltage and a decrease in adhesion strength from HF2 to HF5 of those coatings were revealed by indentation adhesion test.

  12. Electrical and optical properties of Al-doped ZnO and ZnAl2O4 films prepared by atomic layer deposition

    PubMed Central

    2013-01-01

    ZnO/Al2O3 multilayers were prepared by alternating atomic layer deposition (ALD) at 150°C using diethylzinc, trimethylaluminum, and water. The growth process, crystallinity, and electrical and optical properties of the multilayers were studied with a variety of the cycle ratios of ZnO and Al2O3 sublayers. Transparent conductive Al-doped ZnO films were prepared with the minimum resistivity of 2.4 × 10−3 Ω·cm at a low Al doping concentration of 2.26%. Photoluminescence spectroscopy in conjunction with X-ray diffraction analysis revealed that the thickness of ZnO sublayers plays an important role on the priority for selective crystallization of ZnAl2O4 and ZnO phases during high-temperature annealing ZnO/Al2O3 multilayers. It was found that pure ZnAl2O4 film was synthesized by annealing the specific composite film containing alternative monocycle of ZnO and Al2O3 sublayers, which could only be deposited precisely by utilizing ALD technology. PMID:23537274

  13. Pt-Al2O3 dual layer atomic layer deposition coating in high aspect ratio nanopores.

    PubMed

    Pardon, Gaspard; Gatty, Hithesh K; Stemme, Göran; van der Wijngaart, Wouter; Roxhed, Niclas

    2013-01-11

    Functional nanoporous materials are promising for a number of applications ranging from selective biofiltration to fuel cell electrodes. This work reports the functionalization of nanoporous membranes using atomic layer deposition (ALD). ALD is used to conformally deposit platinum (Pt) and aluminum oxide (Al(2)O(3)) on Pt in nanopores to form a metal-insulator stack inside the nanopore. Deposition of these materials inside nanopores allows the addition of extra functionalities to nanoporous materials such as anodic aluminum oxide (AAO) membranes. Conformal deposition of Pt on such materials enables increased performances for electrochemical sensing applications or fuel cell electrodes. An additional conformal Al(2)O(3) layer on such a Pt film forms a metal-insulator-electrolyte system, enabling field effect control of the nanofluidic properties of the membrane. This opens novel possibilities in electrically controlled biofiltration. In this work, the deposition of these two materials on AAO membranes is investigated theoretically and experimentally. Successful process parameters are proposed for a reliable and cost-effective conformal deposition on high aspect ratio three-dimensional nanostructures. A device consisting of a silicon chip supporting an AAO membrane of 6 mm diameter and 1.3 μm thickness with 80 nm diameter pores is fabricated. The pore diameter is reduced to 40 nm by a conformal deposition of 11 nm Pt and 9 nm Al(2)O(3) using ALD.

  14. Sputter deposition of Al-doped ZnO films with various incident angles

    SciTech Connect

    Sato, Yasushi; Yanagisawa, Kei; Oka, Nobuto; Nakamura, Shin-ichi; Shigesato, Yuzo

    2009-09-15

    Al-doped ZnO (AZO) films were sputter deposited on glass substrates heated at 200 degree sign C under incident angles of sputtered particles at 0 degree sign (incidence normal to substrate), 20 deg., 40 deg., 60 deg., and 80 deg. In the case of normal incidence, x-ray diffraction pole figures show a strong [001] preferred orientation normal to the film surface. In contrast, in the case wherein the incident angles were higher than 60 degree sign , the [001] orientation inclined by 25 deg. - 35 deg. toward the direction of sputtered particles. Transmission electron microscopy revealed that the tilt angle of the [001] orientation increased with increasing angle of the incident sputtered particles, whereas the columnar structure did not show any sign of inclination with respect to the substrate plane.

  15. Competition between Al2O3 atomic layer etching and AlF3 atomic layer deposition using sequential exposures of trimethylaluminum and hydrogen fluoride.

    PubMed

    DuMont, Jaime W; George, Steven M

    2017-02-07

    The thermal atomic layer etching (ALE) of Al2O3 can be performed using sequential and self-limiting reactions with trimethylaluminum (TMA) and hydrogen fluoride (HF) as the reactants. The atomic layer deposition (ALD) of AlF3 can also be accomplished using the same reactants. This paper examined the competition between Al2O3 ALE and AlF3 ALD using in situ Fourier transform infrared (FTIR) vibrational spectroscopy measurements on Al2O3 ALD-coated SiO2 nanoparticles. The FTIR spectra could observe an absorbance loss of the Al-O stretching vibrations during Al2O3 ALE or an absorbance gain of the Al-F stretching vibrations during AlF3 ALD. The transition from AlF3 ALD to Al2O3 ALE occurred versus reaction temperature and was also influenced by the N2 or He background gas pressure. Higher temperatures and lower background gas pressures led to Al2O3 ALE. Lower temperatures and higher background gas pressures led to AlF3 ALD. The FTIR measurements also monitored AlCH3* and HF(*) species on the surface after the TMA and HF reactant exposures. The loss of AlCH3* and HF(*) species at higher temperatures is believed to play a vital role in the transition between AlF3 ALD at lower temperatures and Al2O3 ALE at higher temperatures. The change between AlF3 ALD and Al2O3 ALE was defined by the transition temperature. Higher transition temperatures were observed using larger N2 or He background gas pressures. This correlation was associated with variations in the N2 or He gas thermal conductivity versus pressure. The fluorination reaction during Al2O3 ALE is very exothermic and leads to temperature rises in the SiO2 nanoparticles. These temperature transients influence the Al2O3 etching. The higher N2 and He gas thermal conductivities are able to cool the SiO2 nanoparticles more efficiently and minimize the size of the temperature rises. The competition between Al2O3 ALE and AlF3 ALD using TMA and HF illustrates the interplay between etching and growth and the importance of

  16. Conduction mechanisms in thin atomic layer deposited Al2O3 layers

    NASA Astrophysics Data System (ADS)

    Spahr, Holger; Montzka, Sebastian; Reinker, Johannes; Hirschberg, Felix; Kowalsky, Wolfgang; Johannes, Hans-Hermann

    2013-11-01

    Thin Al2O3 layers of 2-135 nm thickness deposited by thermal atomic layer deposition at 80 °C were characterized regarding the current limiting mechanisms by increasing voltage ramp stress. By analyzing the j(U)-characteristics regarding ohmic injection, space charge limited current (SCLC), Schottky-emission, Fowler-Nordheim-tunneling, and Poole-Frenkel-emission, the limiting mechanisms were identified. This was performed by rearranging and plotting the data in a linear scale, such as Schottky-plot, Poole-Frenkel-plot, and Fowler-Nordheim-plot. Linear regression then was applied to the data to extract the values of relative permittivity from Schottky-plot slope and Poole-Frenkel-plot slope. From Fowler-Nordheim-plot slope, the Fowler-Nordheim-energy-barrier was extracted. Example measurements in addition to a statistical overview of the results of all investigated samples are provided. Linear regression was applied to the region of the data that matches the realistic values most. It is concluded that ohmic injection and therefore SCLC only occurs at thicknesses below 12 nm and that the Poole-Frenkel-effect is no significant current limiting process. The extracted Fowler-Nordheim-barriers vary in the range of up to approximately 4 eV but do not show a specific trend. It is discussed whether the negative slope in the Fowler-Nordheim-plot could in some cases be a misinterpreted trap filled limit in the case of space charge limited current.

  17. Texture and Crystal Orientation in Ti-6Al-4V Builds Fabricated by Shaped Metal Deposition

    NASA Astrophysics Data System (ADS)

    Baufeld, Bernd; van der Biest, Omer; Dillien, Steven

    2010-08-01

    The texture and crystal orientation of Ti-6Al-4V components, manufactured by shaped metal deposition (SMD), is investigated. SMD is a novel rapid prototyping tungsten inert gas (TIG) welding technique leading to near-net-shape components. This involves sequential layer by layer deposition with repeated partial melting and heat treatment, which results in epitaxial growth of large elongated prior β grains. This leads to a directionally solidified texture, where the prior β grains exhibit only a small misorientation with each other. The β grains grow in left< { 100} rightrangle direction with a second left< { 100} rightrangle direction perpendicular to the wall surface. During cooling, the α phase transformation follows the Burgers orientation relationship leading to a Widmanstätten structure, with orientation relations between most of the α lamellae and also of the residual β phase. The directionally solidification and the transformation into the α phase following the Burgers relationship results in a texture, where the hcp pole figures look similar to bcc pole figures.

  18. The Effect of Deposition Conditions on Adhesion Strength of Ti and Ti6Al4V Cold Spray Splats

    NASA Astrophysics Data System (ADS)

    Goldbaum, Dina; Shockley, J. Michael; Chromik, Richard R.; Rezaeian, Ahmad; Yue, Stephen; Legoux, Jean-Gabriel; Irissou, Eric

    2012-03-01

    Cold spray is a complex process where many parameters have to be considered in order to achieve optimized material deposition and properties. In the cold spray process, deposition velocity influences the degree of material deformation and material adhesion. While most materials can be easily deposited at relatively low deposition velocity (<700 m/s), this is not the case for high yield strength materials like Ti and its alloys. In the present study, we evaluate the effects of deposition velocity, powder size, particle position in the gas jet, gas temperature, and substrate temperature on the adhesion strength of cold spayed Ti and Ti6Al4V splats. A micromechanical test technique was used to shear individual splats of Ti or Ti6Al4V and measure their adhesion strength. The splats were deposited onto Ti or Ti6Al4V substrates over a range of deposition conditions with either nitrogen or helium as the propelling gas. The splat adhesion testing coupled with microstructural characterization was used to define the strength, the type and the continuity of the bonded interface between splat and substrate material. The results demonstrated that optimization of spray conditions makes it possible to obtain splats with continuous bonding along the splat/substrate interface and measured adhesion strengths approaching the shear strength of bulk material. The parameters shown to improve the splat adhesion included the increase of the splat deposition velocity well above the critical deposition velocity of the tested material, increase in the temperature of both powder and the substrate material, decrease in the powder size, and optimization of the flow dynamics for the cold spray gun nozzle. Through comparisons to the literature, the adhesion strength of Ti splats measured with the splat adhesion technique correlated well with the cohesion strength of Ti coatings deposited under similar conditions and measured with tubular coating tensile (TCT) test.

  19. Mechanism of interfacial layer suppression after performing surface Al(CH3)3 pretreatment during atomic layer deposition of Al2O3

    NASA Astrophysics Data System (ADS)

    Xu, Min; Zhang, Chi; Ding, Shi-Jin; Lu, Hong-Liang; Chen, Wei; Sun, Qing-Qing; Zhang, David Wei; Wang, Li-Kang

    2006-11-01

    During atomic layer deposition of high permittivity (high-k) metal oxide gate dielectrics, an interfacial layer (IL) containing SiOx between high-k dielectric and Si substrate is almost unavoidable. However, an Al(CH3)3 (TMA) pretreatment for 3600s on H-terminated silicon surface can effectively reduce the interfacial layer from 1.7to0.5nm during atomic layer deposition of aluminum oxide. Interestingly, the surface TMA pretreatment increases the thickness of the initial IL during atomic layer deposition, but it greatly suppresses the final IL after 35 growth cycles. A reasonable mechanism is proposed based on the steric hindrance effect cofunctioning with the interfacial Al catalyzing effect.

  20. Experimental Study of Direct Laser Deposition of Ti-6Al-4V and Inconel 718 by Using Pulsed Parameters

    PubMed Central

    Shah, Kamran; Haq, Izhar Ul; Shah, Shaukat Ali; Khan, Farid Ullah; Khan, Sikander

    2014-01-01

    Laser direct metal deposition (LDMD) has developed from a prototyping to a single metal manufacturing tool. Its potential for creating multimaterial and functionally graded structures is now beginning to be explored. This work is a first part of a study in which a single layer of Inconel 718 is deposited on Ti-6Al-4V substrate. Single layer tracks were built at a range of powder mass flow rates using a coaxial nozzle and 1.5 kW diode laser operating in both continuous and pulsed beam modes. This part of the study focused on the experimental findings during the deposition of Inconel 718 powder on Ti-6Al-4V substrate. Scanning electron microscopy (SEM) and X-ray diffraction analysis were performed for characterization and phase identification. Residual stress measurement had been carried out to ascertain the effects of laser pulse parameters on the crack development during the deposition process. PMID:24592190

  1. Experimental study of direct laser deposition of Ti-6Al-4V and Inconel 718 by using pulsed parameters.

    PubMed

    Shah, Kamran; Izhar Ul Haq; Shah, Shaukat Ali; Khan, Farid Ullah; Khan, Muhammad Tahir; Khan, Sikander

    2014-01-01

    Laser direct metal deposition (LDMD) has developed from a prototyping to a single metal manufacturing tool. Its potential for creating multimaterial and functionally graded structures is now beginning to be explored. This work is a first part of a study in which a single layer of Inconel 718 is deposited on Ti-6Al-4V substrate. Single layer tracks were built at a range of powder mass flow rates using a coaxial nozzle and 1.5 kW diode laser operating in both continuous and pulsed beam modes. This part of the study focused on the experimental findings during the deposition of Inconel 718 powder on Ti-6Al-4V substrate. Scanning electron microscopy (SEM) and X-ray diffraction analysis were performed for characterization and phase identification. Residual stress measurement had been carried out to ascertain the effects of laser pulse parameters on the crack development during the deposition process.

  2. Uniaxial magnetic anisotropy in Pd/Fe bilayers on Al2O3 (0001) induced by oblique deposition

    NASA Astrophysics Data System (ADS)

    Chi, Chiao-Sung; Wang, Bo-Yao; Pong, Way-Faung; Ho, Tsung-Ying; Tsai, Cheng-Jui; Lo, Fang-Yuh; Chern, Ming-Yau; Lin, Wen-Chin

    2012-06-01

    This study reports the preparation of self-organized 1-dimensional magnetic structures of Fe on Al2O3 (0001) by oblique deposition. The x-ray diffraction (XRD) results in this study show the preferred (110) texture of the Fe films. XRD and extended x-ray adsorption fine structure measurements indicate larger oblique deposition angle (65°) leads to more disorder in the Fe crystalline structure. After capping with a Pd overlayer, the Pd/Fe/Al2O3 (0001) still exhibits uniaxial magnetic anisotropy induced by the underlying 1-dimensional Fe nanostructure. This uniaxial magnetic anisotropy changes with the variation in Fe thickness and oblique deposition angle. These results clearly indicate the feasibility of manipulating uniaxial magnetic anisotropy and crystalline order through the oblique deposition of magnetic materials.

  3. Growth dynamics of reactive-sputtering-deposited AlN films

    SciTech Connect

    Auger, M.A.; Vazquez, L.; Sanchez, O.; Jergel, M.; Cuerno, R.; Castro, M.

    2005-06-15

    We have studied the surface kinetic roughening of AlN films grown on Si(100) substrates by dc reactive sputtering within the framework of the dynamic scaling theory. Films deposited under the same experimental conditions for different growth times were analyzed by atomic force microscopy and x-ray diffraction. The AlN films display a (002) preferred orientation. We have found two growth regimes with a crossover time of 36 min. In the first regime, the growth dynamics is unstable and the films present two types of textured domains, well textured and randomly oriented, respectively. In contrast, in the second regime the films are homogeneous and well textured, leading to a relative stabilization of the surface roughness characterized by a growth exponent {beta}=0.37{+-}0.03. In this regime a superrough scaling behavior is found with the following exponents: (i) Global exponents: roughness exponent {alpha}=1.2{+-}0.2 and {beta}=0.37{+-}0.03 and coarsening exponent 1/z=0.32{+-}0.05; (ii) local exponents: {alpha}{sub loc}=1, {beta}{sub loc}=0.32{+-}0.01. The differences between the growth modes are found to be related to the different main growth mechanisms dominating their growth dynamics: sticking anisotropy and shadowing, respectively.

  4. Amyloid imaging in prodromal Alzheimer's disease

    PubMed Central

    2011-01-01

    Patients with mild cognitive impairment are at an increased risk of progression to Alzheimer's disease. However, not all patients with mild cognitive impairment progress, and it is difficult to accurately identify those patients who are in the prodromal stage of Alzheimer's disease. In a recent paper, Koivunen and colleagues report that Pittsburgh compound-B, an amyloid-beta positron emission tomography ligand, predicts the progression of patients with mild cognitive impairment to Alzheimer's disease. Of 29 subjects with mild cognitive impairment, 21 (72%) had a positive Pittsburgh compound-B positron emission tomography baseline scan. In their study, 15 of these 21 (71%) patients progressed to Alzheimer's disease, whilst only 1 out of 8 (12.5%) Pittsburgh compound-B-negative patients with mild cognitive impairment did so. Moreover, in these mild cognitive impairment patients, the overall amyloid burden increased approximately 2.5% during the follow-up period. This is consistent with other longitudinal amyloid imaging studies that found a similar increase in amyloid deposition over time in patients with mild cognitive impairment. These studies together challenge current theories that propose a flattening of the increase of brain amyloid deposition already in the preclinical stage of Alzheimer's disease. These findings may have important implications for the design of future clinical trials aimed at preventing progression to Alzheimer's disease by lowering the brain amyloid-beta burden in patients with mild cognitive impairment. PMID:21936965

  5. Presence of glycosaminoglycans in purified AA type amyloid fibrils associated with juvenile rheumatoid arthritis.

    PubMed Central

    Magnus, J H; Husby, G; Kolset, S O

    1989-01-01

    Previous studies have strongly suggested an association between glycosaminoglycans and tissue deposits of amyloid. The present study was aimed at studying this association in purified preparations of hepatic amyloid fibrils obtained from human AA type secondary amyloidosis. Glycosaminoglycans were isolated by gradient ion exchange chromatography of purified amyloid fibrils treated with pronase. Degradation with specific enzymes identified the glycosaminoglycans as chondroitin sulphate, dermatan sulphate, and heparin/heparan sulphate. The total amount of glycosaminoglycans specifically coisolated with the amyloid fibrils was 15 micrograms/mg fibril weight. The presence of glycosaminoglycans in amyloid may play a part in the incorporation of structurally diverse protein precursors into amyloid fibrils of identical ultrastructure. PMID:2930277

  6. Al{sub 2}O{sub 3} multi-density layer structure as a moisture permeation barrier deposited by radio frequency remote plasma atomic layer deposition

    SciTech Connect

    Jung, Hyunsoo; Jeon, Heeyoung; Choi, Hagyoung; Ham, Giyul; Shin, Seokyoon; Jeon, Hyeongtag

    2014-02-21

    Al{sub 2}O{sub 3} films deposited by remote plasma atomic layer deposition have been used for thin film encapsulation of organic light emitting diode. In this study, a multi-density layer structure consisting of two Al{sub 2}O{sub 3} layers with different densities are deposited with different deposition conditions of O{sub 2} plasma reactant time. This structure improves moisture permeation barrier characteristics, as confirmed by a water vapor transmission rate (WVTR) test. The lowest WVTR of the multi-density layer structure was 4.7 × 10{sup −5} gm{sup −2} day{sup −1}, which is one order of magnitude less than WVTR for the reference single-density Al{sub 2}O{sub 3} layer. This improvement is attributed to the location mismatch of paths for atmospheric gases, such as O{sub 2} and H{sub 2}O, in the film due to different densities in the layers. This mechanism is analyzed by high resolution transmission electron microscopy, elastic recoil detection, and angle resolved X-ray photoelectron spectroscopy. These results confirmed that the multi-density layer structure exhibits very good characteristics as an encapsulation layer via location mismatch of paths for H{sub 2}O and O{sub 2} between the two layers.

  7. Cardiac resynchronization therapy in a patient with amyloid cardiomyopathy.

    PubMed

    Zizek, David; Cvijić, Marta; Zupan, Igor

    2013-06-01

    Cardiac involvement in systemic light chain amyloidosis carries poor prognosis. Amyloid deposition in the myocardium can alter regional left ventricular contraction and cause dyssynchrony. Cardiac resynchronization therapy (CRT) is an effective treatment strategy for patients with advanced heart failure and echocardiographic dyssynchrony. We report a clinical and echocardiographic response of a patient with amyloid cardiomyopathy, treated with a combination of chemotherapy and CRT.

  8. Sputter deposition of stress-controlled piezoelectric AlN and AlScN films for ultrasonic and energy harvesting applications.

    PubMed

    Barth, Stephan; Bartzsch, Hagen; Gloess, Daniel; Frach, Peter; Herzog, Thomas; Walter, Susan; Heuer, Henning

    2014-08-01

    This paper reports on the deposition and characterization of piezoelectric AlN and AlXSc1-XN layers. Characterization methods include XRD, SEM, active thermo probe, pulse echo, and piezometer measurements. A special focus is on the characterization of AlN regarding the mechanical stress in the films. The stress in the films changed between -2.2 GPa (compressive) and 0.2 GPa (tensile) and showed a significant dependence on film thickness. The cause of this behavior is presumed to be the different mean grain sizes at different film thicknesses, with bigger mean grain sizes at higher thicknesses. Other influences on film stress such as the sputter pressure or the pulse mode are presented. The deposition of gradient layers using those influences allowed the adjustment of film stress while retaining the piezoelectric properties.

  9. Hydrophobicity enhancement of Al2O3 thin films deposited on polymeric substrates by atomic layer deposition with perfluoropropane plasma treatment

    NASA Astrophysics Data System (ADS)

    Ali, Kamran; Choi, Kyung-Hyun; Kim, Chang Young; Doh, Yang Hoi; Jo, Jeongdai

    2014-06-01

    The optoelectronics devices such as organic light emitting diodes are greatly vulnerable to moisture, which reduces their functionality and life cycle. The Al2O3 thin films are mostly used as barrier coatings in such electronic devices to protect them from water vapors. The performance of the Al2O3 barrier films can be improved by enhancing their hydrophobicity. Greater the hydrophobicity of the barrier films, greater will be their protection against water vapors. This paper reports on the enhancement of hydrophobicity of Al2O3 thin films through perfluoropropane (C3F8) plasma treatment. Firstly, good quality Al2O3 films have been fabricated through atomic layer deposition (ALD) on polyethylene naphthalate (PEN) substrates at different temperatures. The fabricated films are then plasma treated with C3F8 to enhance their hydrophobicity. Hydrophobic Al2O3 thin films have shown good morphological and optical properties. Low average arithmetic roughness (Ra) of 1.90 nm, 0.93 nm and 0.88 nm have been recorded for the C3F8 plasma treated films deposited at room temperature (RT), 50 °C and 150 °C, respectively. Optical transmittance of more than 90% has been achieved for the C3F8 plasma treated films grown at 50 °C and 150 °C. The contact angle has been increased from 48° ± 3 to 158° ± 3 for the films deposited at RT and increased from 41° ± 3 to 148° ± 3 for the films deposited at 150 °C.

  10. Reduction of β-amyloid deposits by γ-secretase inhibitor is associated with the attenuation of secondary damage in the ipsilateral thalamus and sensory functional improvement after focal cortical infarction in hypertensive rats.

    PubMed

    Zhang, Yusheng; Xing, Shihui; Zhang, Jian; Li, Jingjing; Li, Chuo; Pei, Zhong; Zeng, Jinsheng

    2011-02-01

    Abnormal β-amyloid (Aβ) deposits in the thalamus have been reported after cerebral cortical infarction. In this study, we investigated the association of Aβ deposits, with the secondary thalamic damage after focal cortical infarction in rats. Thirty-six stroke-prone renovascular hypertensive rats were subjected to distal middle cerebral artery occlusion (MCAO) and then randomly divided into MCAO, vehicle, and N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT) groups and 12 sham-operated rats as control. The DAPT was administered orally at 72 hours after MCAO. Seven days after MCAO, sensory function, neuron loss, and glial activation and proliferation were evaluated using adhesive removal test, Nissl staining, and immunostaining, respectively. Thalamic Aβ accumulation was evaluated using immunostaining and enzyme-linked immunosorbent assay (ELISA). Compared with vehicle group, the ipsilateral thalamic Aβ, neuronal loss, glial activation and proliferation, and the mean time to remove the stimulus from right forepaw significantly decreased in DAPT group. The mean time to remove the stimulus from the right forepaw and thalamic Aβ burden were both negatively correlated with the number of thalamic neurons. These findings suggest that Aβ deposits are associated with the secondary thalamic damage. Reduction of thalamic Aβ by γ-secretase inhibitor may attenuate the secondary damage and improve sensory function after cerebral cortical infarction.

  11. Critical Deposition Condition of CoNiCrAlY Cold Spray Based on Particle Deformation Behavior

    NASA Astrophysics Data System (ADS)

    Ichikawa, Yuji; Ogawa, Kazuhiro

    2017-02-01

    Previous research has demonstrated deposition of MCrAlY coating via the cold spray process; however, the deposition mechanism of cold spraying has not been clearly explained—only empirically described by impact velocity. The purpose of this study was to elucidate the critical deposit condition. Microscale experimental measurements of individual particle deposit dimensions were incorporated with numerical simulation to investigate particle deformation behavior. Dimensional parameters were determined from scanning electron microscopy analysis of focused ion beam-fabricated cross sections of deposited particles to describe the deposition threshold. From Johnson-Cook finite element method simulation results, there is a direct correlation between the dimensional parameters and the impact velocity. Therefore, the critical velocity can describe the deposition threshold. Moreover, the maximum equivalent plastic strain is also strongly dependent on the impact velocity. Thus, the threshold condition required for particle deposition can instead be represented by the equivalent plastic strain of the particle and substrate. For particle-substrate combinations of similar materials, the substrate is more difficult to deform. Thus, this study establishes that the dominant factor of particle deposition in the cold spray process is the maximum equivalent plastic strain of the substrate, which occurs during impact and deformation.

  12. Critical Deposition Condition of CoNiCrAlY Cold Spray Based on Particle Deformation Behavior

    NASA Astrophysics Data System (ADS)

    Ichikawa, Yuji; Ogawa, Kazuhiro

    2016-12-01

    Previous research has demonstrated deposition of MCrAlY coating via the cold spray process; however, the deposition mechanism of cold spraying has not been clearly explained—only empirically described by impact velocity. The purpose of this study was to elucidate the critical deposit condition. Microscale experimental measurements of individual particle deposit dimensions were incorporated with numerical simulation to investigate particle deformation behavior. Dimensional parameters were determined from scanning electron microscopy analysis of focused ion beam-fabricated cross sections of deposited particles to describe the deposition threshold. From Johnson-Cook finite element method simulation results, there is a direct correlation between the dimensional parameters and the impact velocity. Therefore, the critical velocity can describe the deposition threshold. Moreover, the maximum equivalent plastic strain is also strongly dependent on the impact velocity. Thus, the threshold condition required for particle deposition can instead be represented by the equivalent plastic strain of the particle and substrate. For particle-substrate combinations of similar materials, the substrate is more difficult to deform. Thus, this study establishes that the dominant factor of particle deposition in the cold spray process is the maximum equivalent plastic strain of the substrate, which occurs during impact and deformation.

  13. Laser damage properties of TiO2/Al2O3 thin films grown by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Wei, Yaowei; Liu, Hao; Sheng, Ouyang; Liu, Zhichao; Chen, Songlin; Yang, Liming

    2011-08-01

    Research on thin film deposited by atomic layer deposition (ALD) for laser damage resistance is rare. In this paper, it has been used to deposit TiO2/Al2O3 films at 110° C and 280° C on fused silica and BK7 substrates. Microstructure of the thin films was investigated by x-ray diffraction. The laser-induced damage threshold (LIDT) of samples was measured by a damage test system. Damage morphology was studied under a Nomarski differential interference contrast microscope and further checked under an atomic force microscope. Multilayers deposited at different temperatures were compared. The results show that the films deposited by ALD had better uniformity and transmission; in this paper, the uniformity is better than 99% over 100mm Φ samples, and the transmission is more than 99.8% at 1064nm. Deposition temperature affects the deposition rate and the thin film microstructure and further influences the LIDT of the thin films. As to the TiO2/Al2O3 films, the LIDTs were 6.73±0.47J/cm2 and 6.5±0.46J/cm2 at 110° C on fused silica and BK7 substrates, respectively. The LIDTs at 110° C are notably better than 280° C.

  14. Aggregation of Full-length Immunoglobulin Light Chains from Systemic Light Chain Amyloidosis (AL) Patients Is Remodeled by Epigallocatechin-3-gallate.

    PubMed

    Andrich, Kathrin; Hegenbart, Ute; Kimmich, Christoph; Kedia, Niraja; Bergen, H Robert; Schönland, Stefan; Wanker, Erich; Bieschke, Jan

    2017-02-10

    Intervention into amyloid deposition with anti-amyloid agents like the polyphenol epigallocatechin-3-gallate (EGCG) is emerging as an experimental secondary treatment strategy in systemic light chain amyloidosis (AL). In both AL and multiple myeloma (MM), soluble immunoglobulin light chains (LC) are produced by clonal plasma cells, but only in AL do they form amyloid deposits in vivo We investigated the amyloid formation of patient-derived LC and their susceptibility to EGCG in vitro to probe commonalities and systematic differences in their assembly mechanisms. We isolated nine LC from the urine of AL and MM patients. We quantified their thermodynamic stabilities and monitored their aggregation under physiological conditions by thioflavin T fluorescence, light scattering, SDS stability, and atomic force microscopy. LC from all patients formed amyloid-like aggregates, albeit with individually different kinetics. LC existed as dimers, ∼50% of which were linked by disulfide bridges. Our results suggest that cleavage into LC monomers is required for efficient amyloid formation. The kinetics of AL LC displayed a transition point in concentration dependence, which MM LC lacked. The lack of concentration dependence of MM LC aggregation kinetics suggests that conformational change of the light chain is rate-limiting for these proteins. Aggregation kinetics displayed two distinct phases, which corresponded to the formation of oligomers and amyloid fibrils, respectively. EGCG specifically inhibited the second aggregation phase and induced the formation of SDS-stable, non-amyloid LC aggregates. Our data suggest that EGCG intervention does not depend on the individual LC sequence and is similar to the mechanism observed for amyloid-β and α-synuclein.

  15. Demonstration of InAlN/AlGaN high electron mobility transistors with an enhanced breakdown voltage by pulsed metal organic chemical vapor deposition

    SciTech Connect

    Xue, JunShuai Zhang, JinCheng; Hao, Yue

    2016-01-04

    In this work, InAlN/AlGaN heterostructures employing wider bandgap AlGaN instead of conventional GaN channel were grown on sapphire substrate by pulsed metal organic chemical vapor deposition, where the nominal Al composition in InAlN barrier and AlGaN channel were chosen to be 83% and 5%, respectively, to achieve close lattice-matched condition. An electron mobility of 511 cm{sup 2}/V s along with a sheet carrier density of 1.88 × 10{sup 13 }cm{sup −2} were revealed in the prepared heterostructures, both of which were lower compared with lattice-matched InAlN/GaN due to increased intrinsic alloy disorder scattering resulting from AlGaN channel and compressively piezoelectric polarization in barrier, respectively. While the high electron mobility transistor (HEMT) processed on these structures not only exhibited a sufficiently high drain output current density of 854 mA/mm but also demonstrated a significantly enhanced breakdown voltage of 87 V, which is twice higher than that of reported InAlN/GaN HEMT with the same device dimension, potential characteristics for high-voltage operation of GaN-based electronic devices.

  16. Effect of substrate temperature on structural, morphological and optical properties of deposited Al/ZnO films

    NASA Astrophysics Data System (ADS)

    Ghorannevis, Z.; Hosseinnejad, M. T.; Habibi, M.; Golmahdi, P.

    2015-12-01

    Al-doped ZnO (Al/ZnO) thin film is a promising alternative to an ITO electrode in solar cell applications due to its low price, non-toxicity and other promising properties. In this paper, Al/ZnO thin films at different substrate temperatures were deposited on glass substrates as transparent conducting (TCO) films by DC magnetron sputtering. The effect of substrate temperature on the structural, morphological and optical properties of Al/ZnO films was investigated. X-ray diffraction (XRD) analysis suggests that crystal structure characteristics of synthesized thin films depend on the substrate temperature. The structure growth and variation in surface roughness with increasing substrate temperature are revealed by scanning electron microscope (SEM) micrographs and atomic force microscopy (AFM) analyses. Thicknesses of the deposited films were also examined by surface profiler. Moreover, obtained results from optical transmission patterns revealed that with the increasing substrate temperature, optical transmittance decreases.

  17. Characteristics of LaAlO3 gate dielectrics on Si grown by metalorganic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Li, Ai-Dong; Shao, Qi-Yue; Ling, Hui-Qin; Cheng, Jin-Bo; Wu, Di; Liu, Zhi-Guo; Ming, Nai-Ben; Wang, Cathy; Zhou, Hong-Wei; Nguyen, Bich-Yen

    2003-10-01

    Amorphous LaAlO3 (LAO) gate dielectric thin films have been deposited on Si substrates using La(dpm)3 and Al(acac)3 sources by low-pressure metalorganic chemical vapor deposition. The growth mechanism, interfacial structure, and electrical properties have been investigated by various techniques. The ultrathin films show smaller roughness of ˜0.3 nm, larger band gap of 6.47 eV, and good thermal stability. The growth follows a chemical dynamic control mechanism. High-resolution transmission electron microscopy confirms there exists no interfacial layer, or only thinner ones, between LAO and Si. X-ray photoelectron spectroscopy analyses reveal that the thinner interfacial layer is compositionally graded La-Al-Si-O silicate and Al element is deficient in the interfacial layer. The reliable value of equivalent oxide thickness around 1.2 nm of LAO/Si has been achieved.

  18. Structural, optical and electrical properties of AlSb thin films deposited by pulsed laser deposition using aluminum-antimony alloying target

    NASA Astrophysics Data System (ADS)

    Yang, Ke; Li, Bing; Zhang, Jingquan; Li, Wei; Wu, Lili; Zeng, Guanggen; Wang, Wenwu; Liu, Cai; Feng, Lianghuan

    2017-02-01

    AlSb films which are a promising absorber layer for thin film solar cells were grown on glass substrate at different substrate temperature ranging from room temperature to 400 °C on glass substrates using aluminum-antimony alloying target by pulsed laser deposition (PLD) technique. Structural, optical and electrical properties of AlSb thin films were studied by X-ray diffraction (XRD), ultraviolet-visible spectrophotometer and a home-made four-probe-contact high temperature system respectively. XRD pattern shows that AlSb film is amorphous at room temperature, but when substrate temperature is higher than 100 °C, AlSb films present cubic phase structure with the preferential orientation of (111) plane. And intensity of diffraction peaks of AlSb film prepared at substrate temperature of 200 °C are stronger than that of other substrate temperature. The electrical measurement results show that conductivity activation energy of AlSb film is 0.25 eV and 0.28 eV. The indirect optical band gap is about 1.63 eV, which is very close to its theoretical value of 1.62 eV. The results of energy dispersive spectrometer (EDS) indicated the ratio of Al to Sb of AlSb films is about 1:1.

  19. Electrochemical deposition and microstructural characterization of AlCrFeMnNi and AlCrCuFeMnNi high entropy alloy thin films

    NASA Astrophysics Data System (ADS)

    Soare, V.; Burada, M.; Constantin, I.; Mitrică, D.; Bădiliţă, V.; Caragea, A.; Târcolea, M.

    2015-12-01

    Al-Cr-Fe-Mn-Ni and Al-Cr-Cu-Fe-Mn-Ni high entropy alloy thin films were prepared by potentiostatic electrodeposition and the microstructure of the deposits was investigated. The thin films were co-deposited in an electrolyte based on a DMF (N,N-dimethylformamide)-CH3CN (acetonitrile) organic compound. The energy dispersive spectrometry investigation (EDS) indicated that all the five respectively six elements were successfully co-deposited. The scanning electron microscopy (SEM) analysis revealed that the film consists of compact and uniform particles with particle sizes of 500 nm to 4 μm. The X-ray diffractometry (XRD) patterns indicated that the as-deposited thin films were amorphous. Body-centered-cubic (BCC) structures were identified by XRD after the films were annealed at various temperatures under inert Ar atmosphere. The alloys adhesion on the substrate was determined by the scratch-testing method, with higher values obtained for the Al-Cr-Cu-Fe-Mn-Ni alloy.

  20. Conduction mechanisms in thin atomic layer deposited Al{sub 2}O{sub 3} layers

    SciTech Connect

    Spahr, Holger; Montzka, Sebastian; Reinker, Johannes; Hirschberg, Felix; Kowalsky, Wolfgang; Johannes, Hans-Hermann

    2013-11-14

    Thin Al{sub 2}O{sub 3} layers of 2–135 nm thickness deposited by thermal atomic layer deposition at 80 °C were characterized regarding the current limiting mechanisms by increasing voltage ramp stress. By analyzing the j(U)-characteristics regarding ohmic injection, space charge limited current (SCLC), Schottky-emission, Fowler-Nordheim-tunneling, and Poole-Frenkel-emission, the limiting mechanisms were identified. This was performed by rearranging and plotting the data in a linear scale, such as Schottky-plot, Poole-Frenkel-plot, and Fowler-Nordheim-plot. Linear regression then was applied to the data to extract the values of relative permittivity from Schottky-plot slope and Poole-Frenkel-plot slope. From Fowler-Nordheim-plot slope, the Fowler-Nordheim-energy-barrier was extracted. Example measurements in addition to a statistical overview of the results of all investigated samples are provided. Linear regression was applied to the region of the data that matches the realistic values most. It is concluded that ohmic injection and therefore SCLC only occurs at thicknesses below 12 nm and that the Poole-Frenkel-effect is no significant current limiting process. The extracted Fowler-Nordheim-barriers vary in the range of up to approximately 4 eV but do not show a specific trend. It is discussed whether the negative slope in the Fowler-Nordheim-plot could in some cases be a misinterpreted trap filled limit in the case of space charge limited current.

  1. Atomic-layer-deposited Al2O3 and HfO2 on InAlAs: A comparative study of interfacial and electrical characteristics

    NASA Astrophysics Data System (ADS)

    Wu, Li-Fan; Zhang, Yu-Ming; Lv, Hong-Liang; Zhang, Yi-Men

    2016-10-01

    Al2O3 and HfO2 thin films are separately deposited on n-type InAlAs epitaxial layers by using atomic layer deposition (ALD). The interfacial properties are revealed by angle-resolved x-ray photoelectron spectroscopy (AR-XPS). It is demonstrated that the Al2O3 layer can reduce interfacial oxidation and trap charge formation. The gate leakage current densities are 1.37 × 10-6 A/cm2 and 3.22 × 10-6 A/cm2 at +1 V for the Al2O3/InAlAs and HfO2/InAlAs MOS capacitors respectively. Compared with the HfO2/InAlAs metal-oxide-semiconductor (MOS) capacitor, the Al2O3/InAlAs MOS capacitor exhibits good electrical properties in reducing gate leakage current, narrowing down the hysteresis loop, shrinking stretch-out of the C-V characteristics, and significantly reducing the oxide trapped charge (Q ot) value and the interface state density (D it). Project supported by the National Basic Research Program of China (Grant No. 2010CB327505), the Advanced Research Foundation of China (Grant No. 914xxx803-051xxx111), the National Defense Advance Research Project, China (Grant No. 513xxxxx306), the National Natural Science Foundation of China (Grant No. 51302215), the Scientific Research Program Funded by Shaanxi Provincial Education Department, China (Grant No. 14JK1656), and the Science and Technology Project of Shaanxi Province, China (Grant No. 2016KRM029).

  2. Cerebral Amyloid Angiopathy: A Systematic Review

    PubMed Central

    Greenberg, Steven M.

    2011-01-01

    Cerebral amyloid angiopathy (CAA) is a disorder characterized by amyloid deposition in the walls of leptomeningeal and cortical arteries, arterioles, and less often capillaries and veins of the central nervous system. CAA occurs mostly as a sporadic condition in the elderly, its incidence associating with advancing age. All sporadic CAA cases are due to deposition of amyloid-β, originating from proteolytic cleavage of the Amyloid Precursor Protein. Hereditary forms of CAA are generally familial (and therefore rare in the general population), more severe and earlier in onset. CAA-related lobar intracerebral hemorrhage is the most well-studied clinical condition associated with brain amyloid deposition. Despite ever increasing understanding of CAA pathogenesis and availability of reliable clinical and diagnostic tools, preventive and therapeutic options remain very limited. Further research efforts are required in order to identify biological targets for novel CAA treatment strategies. We present a systematic review of existing evidence regarding the epidemiology, genetics, pathogenesis, diagnosis and clinical management of CAA. PMID:21519520

  3. Au-free ohmic Ti/Al/TiN contacts to UID n-GaN fabricated by sputter deposition

    NASA Astrophysics Data System (ADS)

    Garbe, V.; Weise, J.; Motylenko, M.; Münchgesang, W.; Schmid, A.; Rafaja, D.; Abendroth, B.; Meyer, D. C.

    2017-02-01

    The fabrication and characterization of an Au-free Ti/Al/TiN (20/100/100 nm) contact stack to unintentionally doped n-GaN with TiN serving as the diffusion barrier is presented. Sputter deposition and lift-off in combination with post deposition annealing at 850 °C are used for contact formation. After annealing, contact shows ohmic behavior to n-GaN and a specific contact resistivity of 1.60 × 10-3 Ω cm2. To understand the contact formation on the microscopic scale, the contact was characterized by current-voltage measurements, linear transmission line method, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results show the formation of Ti-N bonds at the GaN/Ti interface in the as-deposited stack. Annealing leads to diffusion of Ti, Al, Ga, and N, and the remaining metallic Ti is fully consumed by the formation of the intermetallic tetragonal Al3Ti phase. Native oxide from the GaN surface is trapped during annealing and accumulated in the Al interlayer. The TiN capping layer, however, was chemically stable during annealing. It prevented oxidation of the Ti/Al contact bilayer successfully and thus proved to be a well suitable diffusion barrier with ideal compatibility to the Ti/Al contact metallization.

  4. The deposition of aluminide and silicide coatings on {gamma}-TiAl using the halide-activated pack cementation method

    SciTech Connect

    Munro, T.C; Gleeson, B.

    1996-12-01

    The halide-activated pack cementation method (HAPC) was utilized to deposit aluminide and silicide coatings on nominally stoichiometric {gamma}-TiAl. The deposition temperature was 1,000 C and deposition times ranged from 2 to 12 hours. The growth rates of the coatings were diffusion controlled, with the rate of aluminide growth being about a factor of 2 greater than that of silicide growth. The aluminide coating was inward growing and consisted of a thick, uniform outer layer of TiAl{sub 3} and a thin inner layer of TiAl{sub 2}, with the rate-controlling step being the diffusion of aluminum from the pack into the substrate. Annealing experiments at 1,100 C showed that the interdiffusion between the aluminide coating and the {gamma}-TiAl substrate was rapid. In contrast to the aluminide coating, the silicide coating was nonuniform and porous, consisting primarily of TiSi{sub 2}, TiSi, and Ti{sub 5}Si{sub 4}, with the rate-controlling step for the coating growth believed to be the diffusion of aluminum into the {gamma}-TiAl ahead of the silicide/{gamma}-TiAl interface. The microstructural evolution of the aluminide and silicide coating structures is discussed qualitatively.

  5. Vanadium dioxide film protected with an atomic-layer-deposited Al{sub 2}O{sub 3} thin film

    SciTech Connect

    Wang, Xiao; Cao, Yunzhen Yang, Chao; Yan, Lu; Li, Ying

    2016-01-15

    A VO{sub 2} film exposed to ambient air is prone to oxidation, which will degrade its thermochromic properties. In this work, the authors deposited an ultrathin Al{sub 2}O{sub 3} film with atomic layer deposition (ALD) to protect the underlying VO{sub 2} film from degradation, and then studied the morphology and crystalline structure of the films. To assess the protectiveness of the Al{sub 2}O{sub 3} capping layer, the authors performed a heating test and a damp heating test. An ultrathin 5-nm-thick ALD Al{sub 2}O{sub 3} film was sufficient to protect the underlying VO{sub 2} film heated at 350 °C. However, in a humid environment at prolonged durations, a thicker ALD Al{sub 2}O{sub 3} film (15 nm) was required to protect the VO{sub 2}. The authors also deposited and studied a TiO{sub 2}/Al{sub 2}O{sub 3} bilayer, which significantly improved the protectiveness of the Al{sub 2}O{sub 3} film in a humid environment.

  6. Characterization of DC magnetron plasma in Ar/Kr/N2 mixture during deposition of (Cr,Al)N coating

    NASA Astrophysics Data System (ADS)

    Bobzin, K.; Bagcivan, N.; Theiß, S.; Brugnara, R.; Bibinov, N.; Awakowicz, P.

    2017-02-01

    Reactive sputter deposition of (Cr,Al)N coatings in DC magnetron plasmas containing Ar/Kr/N2 mixtures is characterized by applying a combination of voltage–current measurement, optical emission spectroscopy (OES) and numerical simulation. Theoretical and experimental methods supplement each other and their combination permits us to obtain the most reliable information about the processes by physical vapor deposition. Gas temperature (T g) and plasma parameters, namely electron density n e and electron temperature T e are determined by spatial resolved measurements of molecular nitrogen photoemission. Steady-state densities of Cr and Al atoms are measured using OES. The sputtering of Cr and Al atoms is simulated using the TRIDYN code, measured electric current and applied voltage. Transport of sputtered atoms through the plasma volume is simulated by adopting a Monte-Carlo code. In order to quantify the ‘poisoning’ of the target surface with nitrogen, simulated steady state densities of Al and Cr atoms at different states of poisoning and at different distances from the target are compared with the measured densities. In addition, simulated fluxes of Cr and Al atoms to the substrate are compared with the measured deposition rates of the (Cr,Al)N coating.

  7. Reliability study of Zr and Al incorporated Hf based high-k dielectric deposited by advanced processing

    NASA Astrophysics Data System (ADS)

    Bhuyian, Md Nasir Uddin

    Hafnium-based high-kappa dielectric materials have been successfully used in the industry as a key replacement for SiO2 based gate dielectrics in order to continue CMOS device scaling to the 22-nm technology node. Further scaling according to the device roadmap requires the development of oxides with higher kappa values in order to scale the equivalent oxide thickness (EOT) to 0.7 nm or below while achieving low defect densities. In addition, next generation devices need to meet challenges like improved channel mobility, reduced gate leakage current, good control on threshold voltage, lower interface state density, and good reliability. In order to overcome these challenges, improvements of the high-kappa film properties and deposition methods are highly desirable. In this dissertation, a detail study of Zr and Al incorporated HfO 2 based high-kappa dielectrics is conducted to investigate improvement in electrical characteristics and reliability. To meet scaling requirements of the gate dielectric to sub 0.7 nm, Zr is added to HfO2 to form Hf1-xZrxO2 with x=0, 0.31 and 0.8 where the dielectric film is deposited by using various intermediate processing conditions, like (i) DADA: intermediate thermal annealing in a cyclical deposition process; (ii) DSDS: similar cyclical process with exposure to SPA Ar plasma; and (iii) As-Dep: the dielectric deposited without any intermediate step. MOSCAPs are formed with TiN metal gate and the reliability of these devices is investigated by subjecting them to a constant voltage stress in the gate injection mode. Stress induced flat-band voltage shift (DeltaVFB), stress induced leakage current (SILC) and stress induced interface state degradation are observed. DSDS samples demonstrate the superior characteristics whereas the worst degradation is observed for DADA samples. Time dependent dielectric breakdown (TDDB) shows that DSDS Hf1-xZrxO2 (x=0.8) has the superior characteristics with reduced oxygen vacancy, which is affiliated to

  8. Optical characteristics of nanocrystalline Al{sub x}Ga{sub 1−x}N thin films deposited by hollow cathode plasma-assisted atomic layer deposition

    SciTech Connect

    Goldenberg, Eda; Ozgit-Akgun, Cagla; Biyikli, Necmi; Kemal Okyay, Ali

    2014-05-15

    Gallium nitride (GaN), aluminum nitride (AlN), and Al{sub x}Ga{sub 1−x}N films have been deposited by hollow cathode plasma-assisted atomic layer deposition at 200 °C on c-plane sapphire and Si substrates. The dependence of film structure, absorption edge, and refractive index on postdeposition annealing were examined by x-ray diffraction, spectrophotometry, and spectroscopic ellipsometry measurements, respectively. Well-adhered, uniform, and polycrystalline wurtzite (hexagonal) GaN, AlN, and Al{sub x}Ga{sub 1−x}N films were prepared at low deposition temperature. As revealed by the x-ray diffraction analyses, crystallite sizes of the films were between 11.7 and 25.2 nm. The crystallite size of as-deposited GaN film increased from 11.7 to 12.1 and 14.4 nm when the annealing duration increased from 30 min to 2 h (800 °C). For all films, the average optical transmission was ∼85% in the visible (VIS) and near infrared spectrum. The refractive indices of AlN and Al{sub x}Ga{sub 1−x}N were lower compared to GaN thin films. The refractive index of as-deposited films decreased from 2.33 to 2.02 (λ = 550 nm) with the increased Al content x (0 ≤ x ≤ 1), while the extinction coefficients (k) were approximately zero in the VIS spectrum (>400 nm). Postdeposition annealing at 900 °C for 2 h considerably lowered the refractive index value of GaN films (2.33–1.92), indicating a significant phase change. The optical bandgap of as-deposited GaN film was found to be 3.95 eV, and it decreased to 3.90 eV for films annealed at 800 °C for 30 min and 2 h. On the other hand, this value increased to 4.1 eV for GaN films annealed at 900 °C for 2 h. This might be caused by Ga{sub 2}O{sub 3} formation and following phase change. The optical bandgap value of as-deposited Al{sub x}Ga{sub 1−x}N films decreased from 5.75 to 5.25 eV when the x values decreased from 1 to 0.68. Furthermore, postdeposition annealing did not

  9. Effects of Al concentration on microstructural characteristics and electrical properties of Al-doped ZnO thin films on Si substrates by atomic layer deposition.

    PubMed

    Lee, Ju Ho; Lee, Jae-Won; Hwang, Sooyeon; Kim, Sang Yun; Cho, Hyung Koun; Lee, Jeong Yong; Park, Jin-Seong

    2012-07-01

    Al-doped ZnO (AZO) thin films with various Al concentrations were synthesized on Si(001) substrates with native oxide layers by atomic layer deposition process. The effects of the Al concentration on the microstructural characteristics of the AZO thin films grown at 250 degrees C and the correlation between their microstructural characteristics and electrical properties of the AZO thin films were investigated by AFM, XRD, HRTEM and Hall measurements. The XRD and HRTEM results revealed that the crystallinity and electrical properties of the undoped ZnO thin films were enhanced by 2.48 at% Al doping. However, 12.62 at% Al doping induced the deterioration of their crystallinity and electrical properties due to the formation of nano-sized metallic Al clusters and randomly oriented ZnO-based nano-crystals. To enhance the electrical properties of the AZO thin films while maintaining their crystallinity and electrical properties, a moderate Al concentration has to be chosen under the solubility limit of Al in ZnO.

  10. Study of ZrO2/Al2O3/ZrO2 and Al2O3/ZrO2/Al2O3 stack structures deposited by sol-gel method on Si

    NASA Astrophysics Data System (ADS)

    Vitanov, P.; Harizanova, A.; Ivanova, T.; Dimitrova, T.

    2010-02-01

    Based on our previous experience with pseudobinary alloys of (Al2O3)x(ZrO2)1-x as high-k materials and passivating coatings for solar cells, stack systems of ZrO2/Al2O3/ZrO2and Al2O3/ZrO2/Al2O3, deposited by simple and low cost sol-gel technology have been studied. The thin films of ZrO2 and Al2O3 were sequentially obtained on Si substrates including spin coating deposition from stable solutions. High resolution scanning electron microscopy (HRSEM) was used to compare the morphology of the nanolaminates. The layers were optically characterized by UV-VIS spectrophotometry. The electrical measurements were carried out on metal-insulator-semiconductor (MIS) structures. Their leakage current and relative permittivity were determined.

  11. The effect of glycosaminoglycans (GAGs) on amyloid aggregation and toxicity.

    PubMed

    Iannuzzi, Clara; Irace, Gaetano; Sirangelo, Ivana

    2015-02-02

    Amyloidosis is a protein folding disorder in which normally soluble proteins are deposited extracellularly as insoluble fibrils, impairing tissue structure and function. Charged polyelectrolytes such as glycosaminoglycans (GAGs) are frequently found associated with the proteinaceous deposits in tissues of patients affected by amyloid diseases. Experimental evidence indicate that they can play an active role in favoring amyloid fibril formation and stabilization. Binding of GAGs to amyloid fibrils occurs mainly through electrostatic interactions involving the negative polyelectrolyte charges and positively charged side chains residues of aggregating protein. Similarly to catalyst for reactions, GAGs favor aggregation, nucleation and amyloid fibril formation functioning as a structural templates for the self-assembly of highly cytotoxic oligomeric precursors, rich in β-sheets, into harmless amyloid fibrils. Moreover, the GAGs amyloid promoting activity can be facilitated through specific interactions via consensus binding sites between amyloid polypeptide and GAGs molecules. We review the effect of GAGs on amyloid deposition as well as proteins not strictly related to diseases. In addition, we consider the potential of the GAGs therapy in amyloidosis.

  12. Tribological and mechanical properties of Ti/TiAlN/TiAlCN nanoscale multilayer PVD coatings deposited on AISI H11 hot work tool steel

    NASA Astrophysics Data System (ADS)

    AL-Bukhaiti, M. A.; Al-hatab, K. A.; Tillmann, W.; Hoffmann, F.; Sprute, T.

    2014-11-01

    A new [Ti/TiAlN/TiAlCN]5 multilayer coatings were deposited onto polished substrate AISI H11 (DIN 1.2343) steel by an industrial magnetron sputtering device. The tribological performance of the coated system was investigated by a ball-on-disk tribometer against 100Cr6 steel and Al2O3 balls. The friction coefficients and specific wear rates were measured at various normal loads (2, 5, 8, and 10 N) and sliding velocities (0.2, 0.4, and 0.8 m/s) in ambient air and dry conditions. The phase structure, composition, wear tracks morphologies, hardness, and film/substrate adhesion of the coatings were characterized by light-microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), 3D-surface analyzer, nanoindentation, and scratch tests. Results showed that the deposited coatings showed low wear rates in the scale of 10-15 m3/N m, low friction coefficients against 100Cr6 and Al2O3 balls in the range of 0.25-0.37, and good hardness in the range of 17-20 GPa. Results also revealed that the friction coefficients and disc wear rates decrease and increase, respectively with the increase in normal load and sliding velocity for both coating/Al2O3 and coating/100Cr6 sliding system. Compared with the uncoated-H11 substrate, the deposited coating exhibited superior tribological and mechanical properties. The dominant wear mechanism was abrasive wear for coating/Al2O3 pair, while for coating/100Cr6 pair, a combination of mild adhesive wear, severe adhesive wear, and abrasive wear (extensive plowing) were the dominant wear mechanisms at different applied normal loads.

  13. Transparent oxygen impermeable AlO x thin films on polycarbonate deposited by reactive ion beam sputtering

    NASA Astrophysics Data System (ADS)

    Seong, Jin-Wook; Kim, Sang-Mun; Choi, Daiwon; Yoon, K. H.

    2005-08-01

    The AlO x thin films were deposited on the polycarbonate by reactive ion beam sputtering (RIBS) at different oxygen partial pressures where the AlO x thin film with O/Al ratio of 1.5 was formed when oxygen partial pressure increased from 4 × 10 -5 to 2 × 10 -4 Torr. As a result, oxygen transmission rate (OTR) of the barrier significantly decreased from 24 cm 3/m 2 day to around 2 cm 3/m 2 day with increase in oxygen partial pressure. Optical transmittances of the films were in the 86-88% range at 550 nm versus 89% for the pure polycarbonate film.

  14. Effect of Al Enrichment by Pack Cementation of FeCr Coatings Deposited by HVOF

    NASA Astrophysics Data System (ADS)

    Bellucci, A.; Bellini, S.; Pileggi, R.; Stocchi, D.; Tuurna, S.

    2015-01-01

    A great contribution to CO2 emissions comes from coal fired power generation. Combination of carbon capture sequestering technologies with sustainable biomass conversion constitutes a decisive boost in limiting rise in global temperature. Co-firing alternative materials with pulverized coal and using oxy-fuel combustion conditions (oxy-fuel co-combustion) is a very attractive process for power industry. Materials with both high mechanical properties and high environmental resistance are required by such advanced combustion systems. One approach to improve high-temperature oxidation/corrosion resistance is to apply protective coatings. In the present work, low and high Cr content Fe-based alloys have been deposited in order to investigate the influence of Cr content on coating protective performance in oxy-fuel co-combustion conditions. Grade 91 steel has been assumed as reference substrate. Effect of Al enrichment on coating environmental resistance has also been analyzed. Activities have been performed within the framework of Macplus Project (Integrated Project co-founded by the European Commission under the 7th Framework Program in the Energy area).

  15. High Rate Deposition of High Quality ZnO:Al by Filtered Cathodic Arc

    SciTech Connect

    Mendelsberg, Rueben J.; Lim, S.H.N.; Milliron, D.J.; Anders, Andre

    2010-11-18

    High quality ZnO:Al (AZO) thin films were prepared on glass substrates by direct current filtered cathodic arc deposition. Substrate temperature was varied from room temperature to 425oC, and samples were grown with and without the assistance of low power oxygen plasma (75W). For each growth condition, at least 3 samples were grown to give a statistical look at the effect of the growth environment on the film properties and to explore the reproducibility of the technique. Growth rate was in the 100-400 nm/min range but was apparently random and could not be easily traced to the growth conditions explored. For optimized growth conditions, 300-600 nm AZO films had resistivities of 3-6 x 10-4 ?Omega cm, carrier concentrations in the range of 2-4 x 1020 cm3, Hall mobility as high as 55 cm2/Vs, and optical transmittance greater than 90percent. These films are also highly oriented with the c-axis perpendicular to the substrate and a surface roughness of 2-4 nm.

  16. Laser-induced propagation and destruction of amyloid beta fibrils.

    PubMed

    Yagi, Hisashi; Ozawa, Daisaku; Sakurai, Kazumasa; Kawakami, Toru; Kuyama, Hiroki; Nishimura, Osamu; Shimanouchi, Toshinori; Kuboi, Ryoichi; Naiki, Hironobu; Goto, Yuji

    2010-06-18

    The amyloid deposition of amyloid beta (Abeta) peptides is a critical pathological event in Alzheimer disease (AD). Preventing the formation of amyloid deposits and removing preformed fibrils in tissues are important therapeutic strategies against AD. Previously, we reported the destruction of amyloid fibrils of beta(2)-microglobulin K3 fragments by laser irradiation coupled with the binding of amyloid-specific thioflavin T. Here, we studied the effects of a laser beam on Abeta fibrils. As was the case for K3 fibrils, extensive irradiation destroyed the preformed Abeta fibrils. However, irradiation during spontaneous fibril formation resulted in only the partial destruction of growing fibrils and a subsequent explosive propagation of fibrils. The explosive propagation was caused by an increase in the number of active ends due to breakage. The results not only reveal a case of fragmentation-induced propagation of fibrils but also provide insights into therapeutic strategies for AD.

  17. Regional brain hypometabolism is unrelated to regional amyloid plaque burden

    PubMed Central

    Altmann, Andre; Ng, Bernard; Landau, Susan M.; Jagust, William J.

    2015-01-01

    See Sorg and Grothe (doi:10.1093/brain/awv302) for a scientific commentary on this article. In its original form, the amyloid cascade hypothesis of Alzheimer’s disease holds that fibrillar deposits of amyloid are an early, driving force in pathological events leading ultimately to neuronal death. Early clinicopathological investigations highlighted a number of inconsistencies leading to an updated hypothesis in which amyloid plaques give way to amyloid oligomers as the driving force in pathogenesis. Rather than focusing on the inconsistencies, amyloid imaging studies have tended to highlight the overlap between regions that show early amyloid plaque signal on positron emission tomography and that also happen to be affected early in Alzheimer’s disease. Recent imaging studies investigating the regional dependency between metabolism and amyloid plaque deposition have arrived at conflicting results, with some showing regional associations and other not. We extracted multimodal neuroimaging data from the Alzheimer’s disease neuroimaging database for 227 healthy controls and 434 subjects with mild cognitive impairment. We analysed regional patterns of amyloid deposition, regional glucose metabolism and regional atrophy using florbetapir (18F) positron emission tomography, 18F-fluordeoxyglucose positron emission tomography and T1-weighted magnetic resonance imaging, respectively. Specifically, we derived grey matter density and standardized uptake value ratios for both positron emission tomography tracers in 404 functionally defined regions of interest. We examined the relation between regional glucose metabolism and amyloid plaques using linear models. For each region of interest, correcting for regional grey matter density, age, education and disease status, we tested the association of regional glucose metabolism with (i) cortex-wide florbetapir uptake; (ii) regional (i.e. in the same region of interest) florbetapir uptake; and (iii) regional florbetapir uptake

  18. Nucleation and growth mechanisms of Al2O3 atomic layer deposition on synthetic polycrystalline MoS2

    NASA Astrophysics Data System (ADS)

    Zhang, H.; Chiappe, D.; Meersschaut, J.; Conard, T.; Franquet, A.; Nuytten, T.; Mannarino, M.; Radu, I.; Vandervorst, W.; Delabie, A.

    2017-02-01

    Two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) are of great interest for applications in nano-electronic devices. Their incorporation requires the deposition of nm-thin and continuous high-k dielectric layers on the 2D TMDs. Atomic layer deposition (ALD) of high-k dielectric layers is well established on Si surfaces: the importance of a high nucleation density for rapid layer closure is well known and the nucleation mechanisms have been thoroughly investigated. In contrast, the nucleation of ALD on 2D TMD surfaces is less well understood and a quantitative analysis of the deposition process is lacking. Therefore, in this work, we investigate the growth of Al2O3 (using Al(CH3)3/H2O ALD) on MoS2 whereby we attempt to provide a complete insight into the use of several complementary characterization techniques, including X-ray photo-electron spectroscopy, elastic recoil detection analysis, scanning electron microscopy, and time-of-flight secondary ion mass spectrometry. To reveal the inherent reactivity of MoS2, we exclude the impact of surface contamination from a transfer process by direct Al2O3 deposition on synthetic MoS2 layers obtained by a high temperature sulfurization process. It is shown that Al2O3 ALD on the MoS2 surface is strongly inhibited at temperatures between 125°C and 300°C, with no growth occurring on MoS2 crystal basal planes and selective nucleation only at line defects or grain boundaries at MoS2 top surface. During further deposition, the as-formed Al2O3 nano-ribbons grow in both vertical and lateral directions. Eventually, a continuous Al2O3 film is obtained by lateral growth over the MoS2 crystal basal plane, with the point of layer closure determined by the grain size at the MoS2 top surface and the lateral growth rate. The created Al2O3/MoS2 interface consists mainly of van der Waals interactions. The nucleation is improved by contributions of reversible adsorption on the MoS2 basal planes by using low

  19. Enhancement of the photoluminescence in Er-doped Al2O3 fabricated by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Rönn, John; Karvonen, Lasse; Pyymäki-Perros, Alexander; Peyghambarian, Nasser; Lipsanen, Harri; Säynätjoki, Antti; Sun, Zhipei

    2016-02-01

    We show the enhancement of the photoluminescence at λ = 1:5 μm in highly-doped (> 1021 cm-3) Er-Al2O3 samples by controlling the vertical distance between the Er-ions using atomic layer deposition (ALD) technique. Er2O3 and Al2O3 were deposited on top of silicon in an alternating fashion with ALD. Five Er2O3-Al2O3 samples were fabricated by keeping the amount of Er2O3 constant but changing the thickness of the Al2O3-layers between the Er2O3-layers. The PL spectra of the samples reveal that the PL signal enhances up to 90% when the vertical distance (the number of Al2O3-layers) between the Er-ions increases. The PL enhancement can be related to the reduction of up-conversion signal at 532 and 650 nm in the Er-ions. Our results demonstrate that ALD is an excellent technique to fabricate and to optimize Er-doped materials due to its unique depositions properties.

  20. Band offsets of Al{sub 2}O{sub 3} and HfO{sub 2} oxides deposited by atomic layer deposition technique on hydrogenated diamond

    SciTech Connect

    Liu, J. W.; Liao, M. Y.; Imura, M.; Koide, Y.

    2012-12-17

    High-k oxide insulators (Al{sub 2}O{sub 3} and HfO{sub 2}) have been deposited on a single crystalline hydrogenated diamond (H-diamond) epilayer by an atomic layer deposition technique at temperature as low as 120 Degree-Sign C. Interfacial electronic band structures are characterized by X-ray photoelectron spectroscopy. Based on core-level binding energies and valence band maximum values, valence band offsets are found to be 2.9 {+-} 0.2 and 2.6 {+-} 0.2 eV for Al{sub 2}O{sub 3}/H-diamond and HfO{sub 2}/H-diamond heterojunctions, respectively. Band gaps of the Al{sub 2}O{sub 3} and HfO{sub 2} have been determined to be 7.2 {+-} 0.2 and 5.4 {+-} 0.2 eV by measuring O 1s energy loss spectra, respectively. Both the Al{sub 2}O{sub 3}/H-diamond and HfO{sub 2}/H-diamond heterojunctions are concluded to be type-II staggered band configurations with conduction band offsets of 1.2 {+-} 0.2 and 2.7 {+-} 0.2 eV, respectively.

  1. Electrowetting properties of atomic layer deposited Al{sub 2}O{sub 3} decorated silicon nanowires

    SciTech Connect

    Rajkumar, K.; Rajavel, K.; Cameron, D. C.; Mangalaraj, D.; Rajendrakumar, R. T.

    2015-06-24

    This paper reports the electrowetting properties of liquid droplet on superhydrophobic silicon nanowires with Atomic layer deposited (ALD) Al{sub 2}O{sub 3} as dielectric layer. Silicon wafer were etched by metal assisted wet chemical etching with silver as catalyst. ALD Al{sub 2}O{sub 3} films of 10nm thickness were conformally deposited over silicon nanowires. Al{sub 2}O{sub 3} dielectric film coated silicon nanowires was chemically modified with Trichloro (1H, 1H, 2H, 2H-perfluorooctyl) silane to make it superhydrophobic(SHP). The contact angle was measured and all the samples exhibited superhydrophobic nature with maximum contact angles of 163° and a minimum contact angle hysteresis of 6°. Electrowetting induced a maximum reversible decrease of the contact angle of 20°at 150V in air.

  2. Tunable optoelectronic properties of pulsed dc sputter-deposited ZnO:Al thin films: Role of growth angle

    NASA Astrophysics Data System (ADS)

    Kumar, Mohit; Singh, Ranveer; Nandy, Suman; Ghosh, Arnab; Rath, Satchidananda; Som, Tapobrata

    2016-07-01

    In this paper, we investigate the role of deposition angle on the physical properties and work function of pulsed dc sputter-deposited Al-doped zinc oxide (AZO) thin films. It is observed that average grain size and crystal quality increase with higher angle of deposition, yielding improved optical properties. A systematic blue shift as well as a decrease in the resistivity takes place with the increasing growth angle up to 70°, while an opposite trend is observed beyond that. In addition, the work function of AZO films is also measured using Kelvin probe force microscopy, which corroborates well with the optical and structural properties. The observed results are explained in the framework of growth angle induced diffusion and shadowing effects. The films deposited at higher angles will be important for rapid incorporation into new technological applications that require a transparent conductive oxide.

  3. Au/n-InP Schottky diodes using an Al2O3 interfacial layer grown by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Kim, Hogyoung; Kim, Min Soo; Yoon, Seung Yu; Choi, Byung Joon

    2017-02-01

    We investigated the effect of an Al2O3 interfacial layer grown by atomic layer deposition on the electrical properties of Au Schottky contacts to n-type InP. Considering barrier inhomogeneity, modified Richardson plots yielded a Richardson constant of 8.4 and 7.5 Acm-2K-2, respectively, for the sample with and without the Al2O3 interlayer (theoretical value of 9.4 Acm-2K-2 for n-type InP). The dominant reverse current flow for the sample with an Al2O3 interlayer was found to be Poole-Frenkel emission. From capacitance-voltage measurements, it was observed that the capacitance for the sample without the Al2O3 interlayer was frequency dependent. Sputter-induced defects as well as structural defects were passivated effectively with an Al2O3 interlayer.

  4. AlN nanorod and nanoneedle arrays prepared by chloride assisted chemical vapor deposition for field emission applications.

    PubMed

    Song, Xubo; Guo, Zhigang; Zheng, Jie; Li, Xingguo; Pu, Yikang

    2008-03-19

    Hexagonal AlN nanorod and nanoneedle arrays were synthesized through the direct reaction of AlCl(3) and NH(3) by chemical vapor deposition at about 750 °C. Both the AlN nanoneedle and nanorod samples were of wurtzite structure and grew preferentially along the c-axis. With an increase in the ratio of NH(3) to Ar, an evolution from nanorods to nanoneedles was observed. A growth model was proposed to explain the possible growth mechanism. Measurements in field emission show that AlN nanoneedle arrays have a much lower turn-on field (3.1 V µm(-1)) compared to nanorod arrays (15.3 V µm(-1)), due to their large curvature geometry. The AlN nanoneedle arrays have potential applications in many fields, such as electron-emitting nanodevices and field-emission-based flat-panel displays.

  5. Characterization of plasma-enhanced atomic layer deposition of Al{sub 2}O{sub 3} using dimethylaluminum isopropoxide

    SciTech Connect

    Yang, Jialing; Eller, Brianna S.; Nemanich, Robert J.; Kaur, Manpuneet

    2014-03-15

    In this research, Al{sub 2}O{sub 3} films were grown by remote plasma-enhanced atomic layer deposition using a nonpyrophoric precursor, dimethylaluminum isopropoxide (DMAI), and oxygen plasma. After optimization, the growth rate was determined to be ∼1.5 Å/cycle within a growth window of 25–220 °C; the higher growth rate than reported for thermal atomic layer deposition was ascribed to the higher reactivity of the plasma species compared with H{sub 2}O and the adsorption of active oxygen at the surface, which was residual from the oxygen plasma exposure. Both effects enhance DMAI chemisorption and increase the saturation density. In addition, a longer oxygen plasma time was required at room temperature to complete the reaction and decrease the carbon contamination below the detection limit of x-ray photoemission spectroscopy. The properties of the subsequent Al{sub 2}O{sub 3} films were measured for different temperatures. When deposited at 25 °C and 200 °C, the Al{sub 2}O{sub 3} films demonstrated a single Al-O bonding state as measured by x-ray photoemission spectroscopy, a similar band gap of 6.8±0.2 eV as determined by energy loss spectroscopy, a similar index of refraction of 1.62±0.02 as determined by spectroscopic ellipsometry, and uniform growth with a similar surface roughness before and after growth as confirmed by atomic force microscopy. However, the room temperature deposited Al{sub 2}O{sub 3} films had a lower mass density (2.7 g/cm{sup 3} compared with 3.0 g/cm{sup 3}) and a higher atomic ratio of O to Al (2.1 compared with 1.6) as indicated by x-ray reflectivity and Rutherford backscattering spectroscopy, respectively.

  6. Functional amyloids in bacteria.

    PubMed

    Romero, Diego; Kolter, Roberto

    2014-06-01

    The term amyloidosis is used to refer to a family of pathologies altering the homeostasis of human organs. Despite having a name that alludes to starch content, the amyloid accumulations are made up of proteins that polymerize as long and rigid fibers. Amyloid proteins vary widely with respect to their amino acid sequences but they share similarities in their quaternary structure; the amyloid fibers are enriched in β-sheets arranged perpendicular to the axis of the fiber. This structural feature provides great robustness, remarkable stability, and insolubility. In addition, amyloid proteins specifically stain with certain dyes such as Congo red and thioflavin-T. The aggregation into amyloid fibers, however, it is not restricted to pathogenic processes, rather it seems to be widely distributed among proteins and polypeptides. Amyloid fibers are present in insects, fungi and bacteria, and they are important in maintaining the homeostasis of the organism. Such findings have motivated the use of the term "functional amyloid" to differentiate these amyloid proteins from their toxic siblings. This review focuses on systems that have evolved in bacteria that control the expression and assembly of amyloid proteins on cell surfaces, such that the robustness of amyloid proteins are used towards a beneficial end.

  7. Adeno-associated Virus Gene Therapy With Cholesterol 24-Hydroxylase Reduces the Amyloid Pathology Before or After the Onset of Amyloid Plaques in Mouse Models of Alzheimer's Disease

    PubMed Central

    Hudry, Eloise; Van Dam, Debby; Kulik, Wim; De Deyn, Peter P; Stet, Femke S; Ahouansou, Ornella; Benraiss, Abdellatif; Delacourte, André; Bougnères, Pierre; Aubourg, Patrick; Cartier, Nathalie

    2009-01-01

    The development of Alzheimer's disease (AD) is closely connected with cholesterol metabolism. Cholesterol increases the production and deposition of amyloid-β (Aβ) peptides that result in the formation of amyloid plaques, a hallmark of the pathology. In the brain, cholesterol is synthesized in situ but cannot be degraded nor cross the blood–brain barrier. The major exportable form of brain cholesterol is 24S-hydroxycholesterol, an oxysterol generated by the neuronal cholesterol 24-hydroxylase encoded by the CYP46A1 gene. We report that the injection of adeno-associated vector (AAV) encoding CYP46A1 in the cortex and hippocampus of APP23 mice before the onset of amyloid deposits markedly reduces Aβ peptides, amyloid deposits and trimeric oligomers at 12 months of age. The Morris water maze (MWM) procedure also demonstrated improvement of spatial memory at 6 months, before the onset of amyloid deposits. AAV5-wtCYP46A1 vector injection in the cortex and hippocampus of amyloid precursor protein/presenilin 1 (APP/PS) mice after the onset of amyloid deposits also reduced markedly the number of amyloid plaques in the hippocampus, and to a less extent in the cortex, 3 months after the injection. Our data demonstrate that neuronal overexpression of CYP46A1 before or after the onset of amyloid plaques significantly reduces Aβ pathology in mouse models of AD. PMID:19654569

  8. Electrical characteristics of multilayered HfO2-Al2O3 charge trapping stacks deposited by ALD

    NASA Astrophysics Data System (ADS)

    Spassov, D.; Paskaleva, A.; Guziewicz, E.; Luka, G.; AKrajewski, T.; Kopalko, K.; Wierzbicka, A.; Blagoev, B.

    2016-10-01

    Electrical and charge trapping properties of atomic layer deposited HfO2-Al2O3 multilayer stacks with two different Al2O3 sublayer thicknesses were investigated regarding their implementation in charge trapping non-volatile memories. The effect of post deposition annealing in oxygen at 600°C is also studied. The decreasing Al2O3 thickness increases the stack's dielectric constant and the density of the initial positive oxide charge. The initial oxide charge increases after annealing to ∼6×1012 cm-2 and changes its sign to negative for the stacks with thicker Al2O3. The annealing enhances the dielectric constant of the stacks and reduces their thickness preserving the amorphous status. Nevertheless the annealing is not beneficial for the stacks with thicker Al2O3 as it considerably increases leakage currents. Conduction mechanisms in stacks were considered in terms of hopping conduction at low electric fields, and Fowler- Nordheim tunnelling, Schottky emission and Poole-Frenkel effect at higher ones. Maximum memory windows of about 12 and 16V were obtained for the as-grown structures with higher and lower Al2O3 content, respectively. In latter case additional improvement (the memory window increase up to 23V) is achieved by the annealing.

  9. Copper(II) ions and the Alzheimer's amyloid-β peptide: Affinity and stoichiometry of binding

    NASA Astrophysics Data System (ADS)

    Tõugu, Vello; Friedemann, Merlin; Tiiman, Ann; Palumaa, Peep

    2014-10-01

    Deposition of amyloid beta (Aβ) peptides into amyloid plaques is the hallmark of Alzheimer's disease. According to the amyloid cascade hypothesis this deposition is an early event and primary cause of the disease, however, the mechanisms that cause this deposition remain elusive. An increasing amount of evidence shows that the interactions of biometals can contribute to the fibrillization and amyloid formation by amyloidogenic peptides. From different anions the copper ions deserve the most attention since it can contribute not only toamyloid formation but also to its toxicity due to the generation of ROS. In this thesis we focus on the affinity and stoichiometry of copper(II) binding to the Aβ molecule.

  10. Tribological characterization of zirconia coatings deposited on Ti6Al4V components for orthopedic applications.

    PubMed

    Berni, M; Lopomo, N; Marchiori, G; Gambardella, A; Boi, M; Bianchi, M; Visani, A; Pavan, P; Russo, A; Marcacci, M

    2016-05-01

    One of the most important issues leading to the failure of total joint arthroplasty is related to the wear of the plastic components, which are generally made of ultra high molecular weight polyethylene (UHMWPE). Therefore, the reduction of joint wear represents one of the main challenges the research in orthopedics is called to address nowadays. Surface treatments and coatings have been recognized as innovative methods to improve tribological properties, also in the orthopedic field. This work investigated the possibility to realize hard ceramic coatings on the metal component of a prosthesis, by means of Pulsed Plasma Deposition, in order to reduce friction and wear in the standard coupling against UHMWPE. Ti6Al4V substrates were coated with a 2 μm thick yttria-stabilized zirconia (YSZ) layer. The mechanical properties of the YSZ coatings were assessed by nanoindentation tests performed on flat Ti6Al4V substrates. Tribological performance was evaluated using a ball-on-disk tribometer in dry and lubricated (i.e. with fetal bovine serum) highly-stressing conditions, up to an overall distance of 10 km. Tribology was characterized in terms of coefficient of friction (CoF) and wear rate of the UHMWPE disk. After testing, specimens were analyzed through optical microscopy and SEM images, in order to check the wear degradation mechanisms. Progressive loading scratch tests were also performed in dry and wet conditions to determine the effects of the environment on the adhesion of the coating. Our results supported the beneficial effect of YSZ coating on metal components. In particular, the proposed solution significantly reduced UHMWPE wear rate and friction. At 10 km of sliding distance, a wear rate reduction of about 18% in dry configuration and of 4% in presence of serum, was obtained by the coated group compared to the uncoated group. As far as friction in dry condition is concerned, the coating allowed to maintain low CoF values until the end of the tests, with an

  11. Thermal stability of surface and interface structure of atomic layer deposited Al2O3 on H-terminated silicon

    NASA Astrophysics Data System (ADS)

    Gao, K. Y.; Speck, F.; Emtsev, K.; Seyller, Th.; Ley, L.

    2007-11-01

    Using the atomic layer deposition technique, 1.2nm Al2O3 films were deposited as high-k gate dielectric layer on hydrogen-terminated silicon and annealed in vacuum and pure hydrogen in order to elucidate the effects of growth and annealing on the structure of film, interface, and surface. As analytical tools, high resolution core level spectroscopy using synchrotron radiation as variable photon source and Fourier Transform Infrared absorption spectroscopy in the attenuated total refraction mode were employed. For Al2O3 on H-terminated Si(111) and (100) surfaces the Si-H bonds are preserved at the interface, while Si-O-Al bonds provide the atomically abrupt interface between Al2O3 and Si. The chemical and structural integrity of the interface is maintained upon annealing except for a gradual loss of Si-H bonds. Growth of a SiO2 layer is observed after annealing, that is unambiguously located at the Al2O3 surface and not at the interface. Stress-induced emission of Si atoms from the interface is identified as the source of SiO2 based on a substantial broadening of the Si 2p core lines. A thermally induced reaction between Si and Al2O3 to form volatile SiO and Al2O is suggested to be responsible for the significant thickness reduction of Al2O3 that accompanies annealing at temperatures of 750°C. Conclusions for the likely effects of forming gas anneals on Al2O3/Si are drawn from this work.

  12. Atomic layer deposition of AlN for thin membranes using trimethylaluminum and H2/N2 plasma

    NASA Astrophysics Data System (ADS)

    Goerke, Sebastian; Ziegler, Mario; Ihring, Andreas; Dellith, Jan; Undisz, Andreas; Diegel, Marco; Anders, Solveig; Huebner, Uwe; Rettenmayr, Markus; Meyer, Hans-Georg

    2015-05-01

    Aluminum nitride (AlN) thin films with thicknesses from 20 to 100 nm were deposited on silicon, amorphous silica, silicon nitride, and vitreous carbon by plasma enhanced atomic layer deposition (PE-ALD). Trimethylaluminum (TMA) and a H2/N2 plasma mixture were used as precursors. We investigated the influence of deposition temperature and plasma parameters on the growth characteristics and the film properties of AlN. Stable PE-ALD growth conditions were obtained from 150 °C to the highest tested temperature of 300 °C. The growth rate, refractive index, and thickness homogeneity on 4″ wafers were determined by spectroscopic ellipsometry. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and Rutherford backscattering spectrometry (RBS) were carried out to analyze crystallinity and composition of the films. Furthermore, the thermal conductivity and the film stress were determined. The stress was sufficiently low to fabricate mechanically stable free-standing AlN membranes with lateral dimensions of up to 2.2 × 2.2 mm2. The membranes were patterned with focused ion beam etching. Thus, these AlN membranes qualify as dielectric support material for a variety of potential applications.

  13. Stoichiometry of LaAlO3 films grown on SrTiO3 by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Golalikhani, M.; Lei, Q. Y.; Chen, G.; Spanier, J. E.; Ghassemi, H.; Johnson, C. L.; Taheri, M. L.; Xi, X. X.

    2013-07-01

    We have studied the stoichiometry of epitaxial LaAlO3 thin films on SrTiO3 substrate grown by pulsed laser deposition as a function of laser energy density and oxygen pressure during the film growth. Both x-ray diffraction (θ-2θ scan and reciprocal space mapping) and transmission electron microscopy (geometric phase analysis) revealed a change of lattice constant in the film with the distance from the substrate. Combined with composition analysis using x-ray fluorescence we found that the nominal unit-cell volume expanded when the LaAlO3 film was La-rich, but remained near the bulk value when the film was La-poor or stoichiometric. La excess was found in all the films deposited in oxygen pressures lower than 10-2 Torr. We conclude that the discussion of LaAlO3/SrTiO3 interfacial properties should include the effects of cation off-stoichiometry in the LaAlO3 films when the deposition is conducted under low oxygen pressures.

  14. Comparative study of atomic-layer-deposited HfO2/Al2O3, Hf0.8Al0.2Ox and Hf0.5Al0.5Ox on N-GaAs

    NASA Astrophysics Data System (ADS)

    Yu, Xinjiang; Lv, Hongliang; Zhang, Yuming; Zhang, Yimen; Qin, Zaiyang

    2016-11-01

    Interfacial properties of n-GaAs metal-oxide-semiconductor (MOSCAPs) with the gate dielectrics of HfO2/Al2O3, Hf0.8Al0.2Ox and Hf0.5Al0.5Ox are investigated. The results reveal that Hf0.5Al0.5Ox has larger permittivity and lower interface trap density than that of HfO2/Al2O3. In order to explain the result from the physical perspective, the XPS tests of all three samples are performed. It is found that the main reason to form interface trap of three samples treated with 500 °C post-deposition annealing, is attributed to the interfacial component of Ga2O3 and The Hf0.5Al0.5Ox dielectric is beneficial to reducing the formation of Ga2O3.

  15. Radio frequency plasma power dependence of the moisture permeation barrier characteristics of Al{sub 2}O{sub 3} films deposited by remote plasma atomic layer deposition

    SciTech Connect

    Jung, Hyunsoo; Choi, Hagyoung; Lee, Sanghun; Jeon, Heeyoung; Jeon, Hyeongtag

    2013-11-07

    In the present study, we investigated the gas and moisture permeation barrier properties of Al{sub 2}O{sub 3} films deposited on polyethersulfone films (PES) by capacitively coupled plasma (CCP) type Remote Plasma Atomic Layer Deposition (RPALD) at Radio Frequency (RF) plasma powers ranging from 100 W to 400 W in 100 W increments using Trimethylaluminum [TMA, Al(CH{sub 3}){sub 3}] as the Al source and O{sub 2} plasma as the reactant. To study the gas and moisture permeation barrier properties of 100-nm-thick Al{sub 2}O{sub 3} at various plasma powers, the Water Vapor Transmission Rate (WVTR) was measured using an electrical Ca degradation test. WVTR decreased as plasma power increased with WVTR values for 400 W and 100 W of 2.6 × 10{sup −4} gm{sup −2}day{sup −1} and 1.2 × 10{sup −3} gm{sup −2}day{sup −1}, respectively. The trends for life time, Al-O and O-H bond, density, and stoichiometry were similar to that of WVTR with improvement associated with increasing plasma power. Further, among plasma power ranging from 100 W to 400 W, the highest power of 400 W resulted in the best moisture permeation barrier properties. This result was attributed to differences in volume and amount of ion and radical fluxes, to join the ALD process, generated by O{sub 2} plasma as the plasma power changed during ALD process, which was determined using a plasma diagnosis technique called the Floating Harmonic Method (FHM). Plasma diagnosis by FHM revealed an increase in ion flux with increasing plasma power. With respect to the ALD process, our results indicated that higher plasma power generated increased ion and radical flux compared with lower plasma power. Thus, a higher plasma power provides the best gas and moisture permeation barrier properties.

  16. Bone marrow-derived mesenchymal stem cells contribute to the reduction of amyloiddeposits and the improvement of synaptic transmission in a mouse model of pre-dementia Alzheimer's disease.

    PubMed

    Bae, Jae-sung; Jin, Hee Kyung; Lee, Jong Kil; Richardson, Jill C; Carter, Janet E

    2013-06-01

    The remarkable potentiality of bone marrow-derived mesenchymal stem cells (BM-MSCs) after transplantation to models of neurological disease and injury has been described. We have previously published data confirming the influence of BM-MSCs on β-amyloid (Aβ) deposition in an Alzheimer's disease (AD) mouse model. However, therapeutic approaches in neurological diseases such as AD, including those for BM-MSCs, are increasingly centered on the potential for prophylactic therapy in pro-dromal states where the underlying cause of the disease is apparent but functional deficits are not. In order to investigate whether BM-MSCs could have a beneficial effect in high-risk pre-dementia AD individuals, we treated young AD mice, at an age at which they display neuropathological, but not cognitive features of AD. Following a single intra-cerebral injection of BM-MSCs, interestingly, we found a significant decrease in the cerebral Aβ deposition compared with controls treated with PBS that was sustained up to 2 months post-injection. Expression of dynamin 1 and Synapsin 1, key pre-synaptic proteins associated with synaptic transmission, which are typically decreased in brains of AD patients, were considerably enhanced in the brains of AD mice treated with BM-MSCs and this response was sustained beyond 2 months. These data demonstrate that BM-MSCs produce an acute reduction in Aβ deposits and facilitate changes in key proteins required for synaptic transmission. These findings suggest that BM-MSC transplantation warrants further investigation as a potential therapy for early intervention in pro-dromal AD.

  17. Spectroscopic characterization of the plasmas formed during the deposition of ZnO and Al-doped ZnO films by plasma-assisted pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Liang, Peipei; Cai, Hua; Yang, Xu; Li, Hui; Zhang, Wu; Xu, Ning; Sun, Jian; Wu, Jiada

    2016-11-01

    An oxygen-zinc plasma and an oxygen-zinc-aluminum plasma are formed by pulsed laser ablation of a Zn target or pulsed laser co-ablation of a Zn target and an Al target in an electron cyclotron resonance (ECR) discharge-generated oxygen plasma for the deposition of ZnO and Al-doped ZnO (AZO) films. The plasmas are characterized spectroscopically by time-integrated and time-resolved optical emission spectroscopy. Both the oxygen-zinc plasma and the oxygen-zinc-aluminum plasma contain excited species originally present in the working O2 gas and energetic species ablated from the targets. The optical emission of the oxygen-zinc-aluminum plasma is abundant in the emission bands of oxygen molecular ions and the emission lines of mono-atomic oxygen, zinc and aluminum atoms and atomic ions. The time-integrated spectra as well as the time-resolved spectra of the plasma emission indicate that the oxygen species in the ECR oxygen plasma experience additional excitation by the expanding ablation plumes, and the ablated species are excited frequently when traveling accompanying the plume expansion in the oxygen plasma, making the formed plasma highly excited and very reactive, which plays an important role in the reactive growth of ZnO matrix and the in-situ doping of Al into the growing ZnO matrix. The deposited ZnO and AZO films were evaluated for composition analysis by energy dispersive X-ray spectroscopy, structure characterization by X-ray diffraction and optical transmission measurement. The deposited ZnO is slightly rich in O. The Al concentration of the AZO films can be controlled and varied simply by changing the repetition rate of the laser used for Al target ablation. Both the ZnO and the AZO films are featured with hexagonal wurtzite crystal structure and exhibit high optical transparency in a wide spectral region. Al doping results in an improvement in the ultraviolet transparency, a blue shift in the absorption edge and a widening of the band gap.

  18. Characterization and oxidation behavior of NiCoCrAlY coating fabricated by electrophoretic deposition and vacuum heat treatment

    NASA Astrophysics Data System (ADS)

    Li, Zhiming; Qian, Shiqiang; Wang, Wei

    2011-03-01

    Electrophoretic deposition (EPD) was showed to be a feasible and convenient method to fabricate NiCoCrAlY coatings on nickel based supperalloys. The microstructure and composition of the NiCoCrAlY coatings after vacuum heat treatment were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDAX). Isothermal-oxidation test was performed at 1100 °C in static air for 100 h. The results show that the major phases in electrophoretic deposited and vacuum heat treated NiCoCrAlY coating are γ-Ni and γ‧-Ni3Al phases, also there is an extremely small quantity of Al2O3 in the coating. Composition fluctuations occur in the coating and a certain amount of titanium diffuse from the superalloy substrate to the top of the coating during vacuum heat treatment. The oxidation test results exhibit that the oxidation kinetics of this coating has two typical stages. The protective oxide layer is mainly formed in the initial linear growth stage and then the oxide layer hinders further oxidation of the coating in the subsequent parabolic growth stage. The coating can effectively protect the superalloy substrate from oxidation. A certain amount of rutile TiO2 is formed in the coating during oxidation and it is adverse to the oxidation resistance of the coating.

  19. AlN thin films deposited by DC reactive magnetron sputtering: effect of oxygen on film growth

    NASA Astrophysics Data System (ADS)

    García Molleja, Javier; José Gómez, Bernardo; Ferrón, Julio; Gautron, Eric; Bürgi, Juan; Abdallah, Bassam; Abdou Djouadi, Mohamed; Feugeas, Jorge; Jouan, Pierre-Yves

    2013-11-01

    Aluminum nitride is a ceramic compound with many technological applications in many fields, for example optics, electronics and resonators. Contaminants play a crucial role in the AlN performance. This paper focuses mainly in the effect of oxygen when AlN, with O impurities in its structure, is grown on oxidized layers. In this study, AlN thin films have been deposited at room temperature and low residual vacuum on SiO2/Si (1 0 0) substrates. AlN films were grown by DC reactive magnetron sputtering (aluminum target) and atmosphere composed by an argon/nitrogen mixture. Working pressure was 3 mTorr. Film characterization was performed by AES, XRD, SEM, EDS, FTIR, HRTEM, SAED and band-bending method. Our results show that oxidized interlayer imposes compressive stresses to AlN layer, developing a polycrystalline deposition. Indeed, when film thickness is over 900 nm, influence of oxidized interlayer diminishes and crystallographic orientation changes to the (0 0 0 2) one, i.e., columnar structure, and stress relief is induced (there is a transition from compressive to tensile stress). Also, we propose a growth scenario to explain this behaviour.

  20. AlOx prepared by atomic layer deposition for high efficiency-type crystalline silicon solar cell

    NASA Astrophysics Data System (ADS)

    Qiu, Hong-Bo; Li, Hui-Qi; Liu, Bang-Wu; Zhang, Xiang; Shen, Ze-Nan

    2014-02-01

    The influence of atomic layer deposition parameters on the negative charge density in AlOx film is investigated by the corona-charge measurement. Results show that the charge density can reach up to -1.56 × 1012 cm-2 when the thickness of the film is 2.4 nm. The influence of charge density on cell conversion efficiency is further simulated using solar cell analyzing software (PC1D). With AlOx passivating the rear surface of the silicon, the cell efficiency of 20.66% can be obtained.

  1. Amyloid plaque structure and cell surface interactions of β-amyloid fibrils revealed by electron tomography.

    PubMed

    Han, Shen; Kollmer, Marius; Markx, Daniel; Claus, Stephanie; Walther, Paul; Fändrich, Marcus

    2017-02-27

    The deposition of amyloid fibrils as plaques is a key feature of several neurodegenerative diseases including in particular Alzheimer's. This disease is characterized, if not provoked, by amyloid aggregates formed from Aβ peptide that deposit inside the brain or are toxic to neuronal cells. We here used scanning transmission electron microscopy (STEM) to determine the fibril network structure and interactions of Aβ fibrils within a cell culture model of Alzheimer's disease. STEM images taken from the formed Aβ amyloid deposits revealed three main types of fibril network structures, termed amorphous meshwork, fibril bundle and amyloid star. All three were infiltrated by different types of lipid inclusions from small-sized exosome-like structures (50-100 nm diameter) to large-sized extracellular vesicles (up to 300 nm). The fibrils also presented strong interactions with the surrounding cells such that fibril bundles extended into tubular invaginations of the plasma membrane. Amyloid formation in the cell model was previously found to have an intracellular origin and we show here that it functionally destroys the integrity of the intracellular membranes as it leads to lysosomal leakage. These data provide a mechanistic link to explain why intracellular fibril formation is toxic to the cell.

  2. Amyloid plaque structure and cell surface interactions of β-amyloid fibrils revealed by electron tomography

    PubMed Central

    Han, Shen; Kollmer, Marius; Markx, Daniel; Claus, Stephanie; Walther, Paul; Fändrich, Marcus

    2017-01-01

    The deposition of amyloid fibrils as plaques is a key feature of several neurodegenerative diseases including in particular Alzheimer’s. This disease is characterized, if not provoked, by amyloid aggregates formed from Aβ peptide that deposit inside the brain or are toxic to neuronal cells. We here used scanning transmission electron microscopy (STEM) to determine the fibril network structure and interactions of Aβ fibrils within a cell culture model of Alzheimer’s disease. STEM images taken from the formed Aβ amyloid deposits revealed three main types of fibril network structures, termed amorphous meshwork, fibril bundle and amyloid star. All three were infiltrated by different types of lipid inclusions from small-sized exosome-like structures (50–100 nm diameter) to large-sized extracellular vesicles (up to 300 nm). The fibrils also presented strong interactions with the surrounding cells such that fibril bundles extended into tubular invaginations of the plasma membrane. Amyloid formation in the cell model was previously found to have an intracellular origin and we show here that it functionally destroys the integrity of the intracellular membranes as it leads to lysosomal leakage. These data provide a mechanistic link to explain why intracellular fibril formation is toxic to the cell. PMID:28240273

  3. Investigation of the HA film deposited on the porous Ti6Al4V alloy prepared via additive manufacturing

    NASA Astrophysics Data System (ADS)

    Surmeneva, M.; Chudinova, E.; Syrtanov, M.; Koptioug, A.; Surmenev, R.

    2015-11-01

    This study is focused on the use of radio frequency magnetron sputtering to modify the surface of porous Ti6Al4V alloy fabricated via additive manufacturing technology. The hydroxyapatite (HA) coated porous Ti6Al4V alloy was studied in respect with its chemical and phase composition, surface morphology, water contact angle and hysteresis, and surface free energy. Thin nanocrystalline HA film was deposited while its structure with diamond-shaped cells remained unchanged. Hysteresis and water contact angle measurements revealed an effect of the deposited HA films, namely an increased water contact angle and contact angle hysteresis. The increase of the contact angle of the coating-substrate system compared to the uncoated substrate was attributed to the multiscale structure of the resulted surfaces.

  4. Plasma damage-free deposition of Al cathode on organic light-emitting devices by using mirror shape target sputtering

    SciTech Connect

    Kim, Han-Ki; Kim, D.-G.; Lee, K.-S.; Huh, M.-S.; Jeong, S.H.; Kim, K.I.; Kim, H.; Han, D.W.; Kwon, J.H.

    2004-11-08

    We report on the fabrication of plasma damage-free organic light-emitting devices (OLEDs) by using a mirror shape target sputtering (MSTS) technique. It is shown that OLEDs with Al cathode deposited by the MSTS show much lower leakage current (1x10{sup -5} mA/cm{sup 2}) at reverse bias of -6 V, compared to that (1x10{sup -1}-{approx}10{sup -2} mA/cm{sup 2} at -6 V) of OLEDs with Al cathodes grown by conventional dc magnetron sputtering. This indicates that there is no plasma damage, which is caused by the bombardment of energetic particles. This suggests that MSTS could be a useful plasma damage-free and low-temperature deposition technique for both top- and bottom-emitting OLEDs and flexible displays.

  5. Effect of substrate pretreatments on the atomic layer deposited Al{sub 2}O{sub 3} passivation quality

    SciTech Connect

    Bao, Yameng; Li, Shuo Gastrow, Guillaume von; Repo, Päivikki; Savin, Hele; Putkonen, Matti

    2015-01-15

    The authors show here that the passivation quality of Al{sub 2}O{sub 3} is highly sensitive to the surface condition prior to the atomic layer deposition, affecting especially the thermal stability of the film. Pretreatments like diluted HCl bath or preheating at 200 °C both improved significantly the passivation quality and thermal stability of the films. In addition, the authors observed that a thin chemical SiO{sub 2} layer resulting from diluted HCl solves the blistering problem often encountered in H{sub 2}O based atomic layer deposited process. Finally, the authors show that the chemical oxide protects the surface from contaminants, enabling long storage times in a dirty ambient between the cleaning and the film deposition.

  6. Simulation of Cooling Rate Effects on Ti-48Al-2Cr-2Nb Crack Formation in Direct Laser Deposition

    NASA Astrophysics Data System (ADS)

    Yan, Lei; Li, Wei; Chen, Xueyang; Zhang, Yunlu; Newkirk, Joe; Liou, Frank; Dietrich, David

    2017-03-01

    Transient temperature history is vital in direct laser deposition (DLD) as it reveals the cooling rate at specific temperatures. Cooling rate directly relates to phase transformation and types of microstructure formed in deposits. In this paper, finite element analysis simulation was employed to study the transient temperature history and cooling rate at different experimental setups in the Ti-48Al-2Cr-2Nb DLD process. An innovative prediction strategy was developed to model with a moving Gaussian distribution heat source and element birth and death technology in ANSYS®, and fabricate crack-free deposits. This approach helps to understand and analyze the impact of cooling rate and also explain phase information gathered from x-ray diffraction.

  7. High quality ZnO:Al transparent conducting oxide films synthesized by pulsed filtered cathodic arc deposition

    SciTech Connect

    Anders, Andre; Lim, Sunnie H.N.; Yu, Kin Man; Andersson, Joakim; Rosen, Johanna; McFarland, Mike; Brown, Jeff

    2009-04-24

    Aluminum-doped zinc oxide, ZnO:Al or AZO, is a well-known n-type transparent conducting oxide with great potential in a number of applications currently dominated by indium tin oxide (ITO). In this study, the optical and electrical properties of AZO thin films deposited on glass and silicon by pulsed filtered cathodic arc deposition are systematically studied. In contrast to magnetron sputtering, this technique does not produce energetic negative ions, and therefore ion damage can be minimized. The quality of the AZO films strongly depends on the growth temperature while only marginal improvements are obtained with post-deposition annealing. The best films, grown at a temperature of about 200?C, have resistivities in the low to mid 10-4 Omega cm range with a transmittance better than 85percent in the visible part of the spectrum. It is remarkable that relatively good films of small thickness (60 nm) can be fabricated using this method.

  8. Principal component analysis with pre-normalization improves the signal-to-noise ratio and image quality in positron emission tomography studies of amyloid deposits in Alzheimer's disease

    NASA Astrophysics Data System (ADS)

    Razifar, Pasha; Engler, Henry; Blomquist, Gunnar; Ringheim, Anna; Estrada, Sergio; Långström, Bengt; Bergström, Mats

    2009-06-01

    This study introduces a new approach for the application of principal component analysis (PCA) with pre-normalization on dynamic positron emission tomography (PET) images. These images are generated using the amyloid imaging agent N-methyl [11C]2-(4'-methylaminophenyl)-6-hydroxy-benzothiazole ([11C]PIB) in patients with Alzheimer's disease (AD) and healthy volunteers (HVs). The aim was to introduce a method which, by using the whole dataset and without assuming a specific kinetic model, could generate images with improved signal-to-noise and detect, extract and illustrate changes in kinetic behavior between different regions in the brain. Eight AD patients and eight HVs from a previously published study with [11C]PIB were used. The approach includes enhancement of brain regions where the kinetics of the radiotracer are different from what is seen in the reference region, pre-normalization for differences in noise levels and removal of negative values. This is followed by slice-wise application of PCA (SW-PCA) on the dynamic PET images. Results obtained using the new approach were compared with results obtained using reference Patlak and summed images. The new approach generated images with good quality in which cortical brain regions in AD patients showed high uptake, compared to cerebellum and white matter. Cortical structures in HVs showed low uptake as expected and in good agreement with data generated using kinetic modeling. The introduced approach generated images with enhanced contrast and improved signal-to-noise ratio (SNR) and discrimination power (DP) compared to summed images and parametric images. This method is expected to be an important clinical tool in the diagnosis and differential diagnosis of dementia.

  9. Electrochemical promotion of propane oxidation on Pt deposited on a dense β"-Al2O3 ceramic Ag+ conductor

    NASA Astrophysics Data System (ADS)

    Tsampas, Michail; Kambolis, Anastasios; Obeid, Emil; Lizarraga, Leonardo; Sapountzi, Foteini; Vernoux, Philippe

    2013-08-01

    A new kind of electrochemical catalyst based on a Pt porous catalyst film deposited on a β"-Al2O3 ceramic Ag+ conductor was developed and evaluated during propane oxidation. It was observed that upon anodic polarization, the rate of propane combustion was significantly electropromoted up to 400%. Moreover, for the first time, exponential increase of the catalytic rate was evidenced during galvanostatic transient experiment in excellent agreement with EPOC equation.

  10. White matter hyperintensities predict amyloid increase in Alzheimer's disease.

    PubMed

    Grimmer, Timo; Faust, Maximilian; Auer, Florian; Alexopoulos, Panagiotis; Förstl, Hans; Henriksen, Gjermund; Perneczky, Robert; Sorg, Christian; Yousefi, Behrooz H; Drzezga, Alexander; Kurz, Alexander

    2012-12-01

    Impaired amyloid clearance probably contributes to increased amyloid deposition in sporadic Alzheimer's disease (AD). Diminished perivascular drainage due to cerebral small-vessel disease (CSVD) has been proposed as a cause of reduced amyloid clearance. White matter hyperintensities (WMHs) are considered to reflect CSVD and can be measured using fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI). Amyloid deposition can be determined in vivo using Pittsburgh compound B ([11C]PiB) positron emission tomography (PET). We aimed to elucidate the association between WMH and the progression of amyloid deposition in patients with AD. Twenty-two patients with probable AD underwent FLAIR-MRI and [11C]PiB-PET examinations at baseline (BL) and after a mean follow-up (FU) interval of 28 months. The relationship between BL-WMH and the progression of cerebral amyloid between BL and FU was examined using a regions-of-interest (ROI) approach. The region-specific variability of this relationship was analyzed using a voxel-based method. The longitudinal analysis revealed a statistically significant association between the amount of BL-WMH and the progression of amyloid load between BL and FU (p = 0.006, adjusted R2 = 0.375, standardized coefficient β = 0.384). The association was particularly observed in parieto-occipital regions and tended to be closer in regions adjacent to the brain surface. According to our knowledge, this is the first in vivo study in human being supporting the hypothesis that impaired amyloid clearance along perivascular drainage pathways may contribute to β-amyloid deposition in sporadic AD. The extent of WMH might be a relevant factor to be assessed in antiamyloid drug trials.

  11. Characterization of Al-As codoped p-type ZnO films by magnetron cosputtering deposition

    SciTech Connect

    Yun, Eui-Jung; Park, Hyeong-Sik; Lee, Kyu H.; Nam, Hyoung G.; Jung, Myunghee

    2008-04-01

    We report the preparation of Al-As codoped p-type ZnO films by rf magnetron cosputtering deposition. The p-type conductivity of the films was revealed by Hall measurements, x-ray photoelectron spectroscopy (XPS), and photoluminescence measurements after being annealed in O{sub 2}. It was observed by XPS that Al content increased with increasing AlAs target power from 80 to 160 W and reached a maximum value at an AlAs target power of 160 W. Hole concentration decreased with increasing Al content. With increasing AlAs target power greater than 160 W, the samples exhibit increases in As and O contents and decreases in Al and Zn contents, which contribute to the increase in hole concentration. A high hole concentration of 2.354x10{sup 20} cm{sup -3}, a low resistivity of 2.122x10{sup -2} {omega} cm, and a Hall mobility of 0.13 cm{sup 2}/V s for the films with high As content of 16.59% were obtained. XPS has also been used to address the unresolved issues related to the p-type formation mechanism of As-doped ZnO, supporting that the acceptor is As{sub Zn}-2V{sub Zn}.

  12. Formation of graphene/SiC/AlN multilayers synthesized by pulsed laser deposition on Si(110) substrates

    NASA Astrophysics Data System (ADS)

    Narita, S.; Meguro, K.; Takami, T.; Enta, Y.; Nakazawa, H.

    2017-02-01

    We have grown aluminum nitride (AlN) films on Si(110) substrates by pulsed laser deposition (PLD), and investigated the effects of laser power on the crystallinity and surface morphology of the AlN films. First, we epitaxially grew a fairly flat, high-quality AlN film, which contained no rotation domains, onto the Si(110) substrate in a well-lattice-matched relationship. Secondly, we formed a SiC interfacial buffer layer on the AlN film to grow a high-quality 3C-SiC film on the SiC buffer layer by PLD, which gave rise to a 3C-SiC(111)3×3 surface. The root-mean-square-roughness value of the SiC film was smaller than the previously reported values of SiC/AlN multilayers on Si(100) and Si(111) substrates. Thirdly, we grew graphene by annealing the SiC film at a high temperature in an ultra-high vacuum. It was demonstrated that the qualified graphene layer without rotation domains was grown on the SiC film. The formation of voids and the outdiffusion of Al and N atoms from the AlN film were successfully suppressed during the high-temperature annealing.

  13. Commentary to Krishna et al. (2014): brain deposition and neurotoxicity of manganese in adult mice exposed via the drinking water.

    PubMed

    Kumasaka, Mayuko Y; Yajima, Ichiro; Ohgami, Nobutaka; Naito, Hisao; Omata, Yasuhiro; Kato, Masashi

    2014-05-01

    Krishna et al. (Arch Toxicol 88(1):47-64, 2014) recently published the results of a study in which adult C57BL/6 mice were subchronically exposed to 400,000 μg/L manganese (Mn) using manganese chloride via drinking water for 8 weeks and examined the neurotoxic effects. After 5 weeks of Mn exposure, significant deposition of Mn in all of the brain regions examined by magnetic resonance imaging was detected. After 6 weeks of Mn exposure, neurobehavioral deficits in an open field test, a grip strength test, and a forced swim test were observed. Eight weeks of Mn exposure increased striatal 5-hydroxyindoleacetic acid (a serotonin metabolite) levels, but did not alter the levels of striatal dopamine, its metabolites and serotonin. Krishna et al. also reported significant increases in mRNA levels of GFAP (an astrocyte activation marker), HO-1 (an oxidative stress marker) and NOS2 (a nitrosative stress marker), and in protein expression level of GFAP in the substantia nigra pars reticulata after 8 weeks of Mn exposure. These results suggest that 400,000 μg/L Mn exposure via drinking water in mice induces neurobehavioral deficits, serotonergic imbalance, and glial activation accompanied by an increase in brain Mn deposition. The report by Krishna et al. is interesting because the studies on the neurobehavioral effect of Mn exposure by drinking water in mice are very limited. However, Mn concentrations previously reported in well drinking water (Agusa et al. in Vietnam Environ Pollut 139(1):95-106, 2006; Buschmann et al. in Environ Int 34(6):756-764, 2008; Hafeman et al. in Environ Health Perspect 115(7):1107-1112, 2007; Wasserman et al. in Bangladesh Environ Health Perspect 114(1):124-129, 2006) were lower than 400,000 μg/L.

  14. Different configurational states of beta-amyloid and their distributions relative to plaques and tangles in Alzheimer disease.

    PubMed Central

    Spillantini, M G; Goedert, M; Jakes, R; Klug, A

    1990-01-01

    Antibodies have been raised against synthetic peptides corresponding to different parts of the beta-amyloid sequence. These antibodies stain different kinds of amyloid distributions in the hippocampal formation in Alzheimer disease, suggesting the existence of different states of aggregation and/or folding of beta-amyloid molecules. An antibody directed against the middle region of beta-amyloid stained mostly amyloid plaques without cores, whereas an antibody directed against the carboxyl-terminal region of beta-amyloid stained only amyloid plaques with cores. An antiserum directed against the amino terminus of beta-amyloid stained numerous tangle-bearing cells and bodies, as well as the neuritic component of plaques and neuropil threads. These antibodies, in conjunction with anti-tau antibodies, were used to demonstrate a close spatial relationship between amyloid deposits and neurofibrillary tangles. Images PMID:2111023

  15. Fibrillar dimer formation of islet amyloid polypeptides

    NASA Astrophysics Data System (ADS)

    Chiu, Chi-cheng; de Pablo, Juan J.

    2015-09-01

    Amyloid deposits of human islet amyloid polypeptide (hIAPP), a 37-residue hormone co-produced with insulin, have been implicated in the development of type 2 diabetes. Residues 20 - 29 of hIAPP have been proposed to constitute the amyloidogenic core for the aggregation process, yet the segment is mostly unstructured in the mature fibril, according to solid-state NMR data. Here we use molecular simulations combined with bias-exchange metadynamics to characterize the conformational free energies of hIAPP fibrillar dimer and its derivative, pramlintide. We show that residues 20 - 29 are involved in an intermediate that exhibits transient β-sheets, consistent with recent experimental and simulation results. By comparing the aggregation of hIAPP and pramlintide, we illustrate the effects of proline residues on inhibition of the dimerization of IAPP. The mechanistic insights presented here could be useful for development of therapeutic inhibitors of hIAPP amyloid formation.

  16. Fibrillar dimer formation of islet amyloid polypeptides

    SciTech Connect

    Chiu, Chi -cheng; de Pablo, Juan J.

    2015-05-08

    Amyloid deposits of human islet amyloid polypeptide (hIAPP), a 37-residue hormone co-produced with insulin, have been implicated in the development of type 2 diabetes. Residues 20 – 29 of hIAPP have been proposed to constitute the amyloidogenic core for the aggregation process, yet the segment is mostly unstructured in the mature fibril, according to solid-state NMR data. Here we use molecular simulations combined with bias-exchange metadynamics to characterize the conformational free energies of hIAPP fibrillar dimer and its derivative, pramlintide. We show that residues 20 – 29 are involved in an intermediate that exhibits transient β-sheets, consistent with recent experimental and simulation results. By comparing the aggregation of hIAPP and pramlintide, we illustrate the effects of proline residues on inhibition of the dimerization of IAPP. The mechanistic insights presented here could be useful for development of therapeutic inhibitors of hIAPP amyloid formation.

  17. Exploring amyloid formation by a de novo design.

    PubMed

    Kammerer, Richard A; Kostrewa, Dirk; Zurdo, Jesús; Detken, Andreas; García-Echeverría, Carlos; Green, Janelle D; Müller, Shirley A; Meier, Beat H; Winkler, Fritz K; Dobson, Christopher M; Steinmetz, Michel O

    2004-03-30

    Protein deposition as amyloid fibrils underlies many debilitating human disorders. The complexity and size of disease-related polypeptides, however, often hinders a detailed rational approach to study effects that contribute to the process of amyloid formation. We report here a simplified peptide sequence successfully designed de novo to fold into a coiled-coil conformation under ambient conditions but to transform into amyloid fibrils at elevated temperatures. We have determined the crystal structure of the coiled-coil form and propose a detailed molecular model for the peptide in its fibrillar state. The relative stabilities of the two structural forms and the kinetics of their interconversion were found to be highly sensitive to small sequence changes. The results reveal the importance of specific packing interactions on the kinetics of amyloid formation and show the potential of this exceptionally favorable system for probing details of the molecular origins of amyloid disease.

  18. Deposition and parametric analysis of RF sputtered ZnO:Al thin films with very low resistivity

    NASA Astrophysics Data System (ADS)

    Jahed, N. M. S.; Mahmoudysepehr, M.; Sivoththaman, S.

    2016-11-01

    RF sputtered, aluminum-doped zinc oxide (ZnO:Al or AZO) is an attractive candidate material as transparent conductive oxides in the fabrication of opto-electronic devices. High electrical conductivity and optical transparency are two key requirements in such applications. This paper reports on the formation of AZO films on glass substrates in an RF-sputtering chamber modified to facilitate in situ heating during deposition. The influence of chamber pressure, RF power, and deposition temperature has been systematically studied and the electrical parameters such as film resistivity, carrier concentration, carrier mobility as well as optical transmission have been analyzed. Film deposition at 250 °C and a low chamber pressure of 0.5 mT resulted in a very low resistivity of 2.94 × 10-4 ohm cm. The structural properties of the films with the lowest resistivity have been further analyzed by x-ray diffraction (XRD) and PL measurements and are compared with the film deposited at room temperature. The XRD results show dominant peaks along (103) orientation for the AZO films with slightly improved crystal quality at higher temperature. Evolution of near band edge and deep level emission photoluminescence peaks also indicate improvement in crystal structure with increased deposition temperature.

  19. An amyloid lung

    PubMed Central

    Zundel, W. E.; Prior, A. P.

    1971-01-01

    A 55-year-old housewife died from an illness characterized by progressive respiratory incapacity. Changes were confined to the lungs and consisted of a diffuse infiltration by amyloid. No adequate cause was found for this amyloid, and we suggest that this is a case of primary alveolar septal amyloidosis. Images PMID:5559913

  20. Investigations of AlGaN/GaN MOS-HEMT with Al2O3 deposition by ultrasonic spray pyrolysis method

    NASA Astrophysics Data System (ADS)

    Chou, Bo-Yi; Hsu, Wei-Chou; Liu, Han-Yin; Lee, Ching-Sung; Wu, Yu-Sheng; Sun, Wen-Ching; Wei, Sung-Yen; Yu, Sheng-Min; Chiang, Meng-Hsueh

    2015-01-01

    This work investigates Al2O3/AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs) grown on SiC substrate by using the non-vacuum ultrasonic spray pyrolysis deposition (USPD) method. The Al2O3 was deposited as gate dielectric and surface passivation simultaneously to effectively suppress gate leakage current, enhance output current density, reduce RF drain current collapse, and improve temperature-dependent stabilities performance. The present MOS-HEMT design has shown improved device performances with respect to a Schottky-gate HEMT, including drain-source saturation current density at zero gate bias (IDSS: 337.6 mA mm-1 → 462.9 mA mm-1), gate-voltage swing (GVS: 1.55 V → 2.92 V), two-terminal gate-drain breakdown voltage (BVGD: -103.8 V → -183.5 V), unity-gain cut-off frequency (fT: 11.3 GHz → 17.7 GHz), maximum oscillation frequency (fmax: 14.2 GHz → 19.1 GHz), and power added effective (P.A.E.: 25.1% → 43.6%). The bias conditions for measuring fT and fmax of the studied MOS-HEMT (Schottky-gate HEMT) are VGS = -2.5 (-2) V and VDS = 7 V. The corresponding VGS and VDS biases are -2.5 (-2) V and 15 V for measuring the P.A.E. characteristic. Moreover, small capacitance-voltage (C-V) hysteresis is obtained in the Al2O3-MOS structure by using USPD. Temperature-dependent characteristics of the present designs at 300-480 K are also studied.

  1. Phase-coherent electron transport in (Zn, Al)O{sub x} thin films grown by atomic layer deposition

    SciTech Connect

    Saha, D. E-mail: pmisra@rrcat.gov.in; Misra, P. E-mail: pmisra@rrcat.gov.in; Ajimsha, R. S.; Joshi, M. P.; Kukreja, L. M.

    2014-11-24

    A clear signature of disorder induced quantum-interference phenomena leading to phase-coherent electron transport was observed in (Zn, Al)O{sub x} thin films grown by atomic layer deposition. The degree of static-disorder was tuned by varying the Al concentration through periodic incorporation of Al{sub 2}O{sub 3} sub-monolayer in ZnO. All the films showed small negative magnetoresistance due to magnetic field suppressed weak-localization effect. The temperature dependence of phase-coherence length (l{sub φ}∝T{sup −3/4}), as extracted from the magnetoresistance measurements, indicated electron-electron scattering as the dominant dephasing mechanism. The persistence of quantum-interference at relatively higher temperatures up to 200 K is promising for the realization of ZnO based phase-coherent electron transport devices.

  2. Microstructure and wear properties of Al-20Si alloy prepared by spray deposition with following continuous extrusion forming technique

    NASA Astrophysics Data System (ADS)

    Liu, Yingli; Yin, Jiancheng; Zhong, Yi

    2016-10-01

    Spray deposition with following continuous extrusion forming technique (SD-CE) is an innovative manufacturing technique to produce high alloy net-shape products. Al-20Si alloy rods have been fabricated by SD-CE at different extrusion ratio. Microstructure, hardness and wear resistance of the alloy have been investigated in details. The results show that Al-20Si alloy can be refined effectively by SD-CE, and the size and shape of Si particles become fine and spherical with the increasing extrusion ratio. When the extrusion ratio reaches 20:1, fully dense material with uniform distribution of Si particles can be obtained. The Al-20Si alloys fabricated by SD-CE exhibit excellent wear resistance, which can be further improved by large extrusion ratio, due to increasing hardness and density. A mechanically mixed layer containing a considerable amount of oxygen and iron was formed on the worn surface.

  3. Porous α-Al2O3 thermal barrier coatings with dispersed Pt particles prepared by cathode plasma electrolytic deposition

    NASA Astrophysics Data System (ADS)

    Wang, Peng; He, Ye-dong; Deng, Shun-jie; Zhang, Jin

    2016-01-01

    Porous α-Al2O3 thermal barrier coatings (TBCs) containing dispersed Pt particles were prepared by cathode plasma electrolytic deposition (CPED). The influence of the Pt particles on the microstructure of the coatings and the CPED process were studied. The prepared coatings were mainly composed of α-Al2O3. The average thickness of the coatings was approximately 100 μm. Such single-layer TBCs exhibited not only excellent high-temperature cyclic oxidation and spallation resistance, but also good thermal insulation properties. Porous α-Al2O3 TBCs inhibit further oxidation of alloy substrates because of their extremely low oxygen diffusion rate, provide good thermal insulation because of their porous structure, and exhibit excellent mechanical properties because of the toughening effect of the Pt particles and because of stress relaxation induced by deformation of the porous structure.

  4. Passivation of type II InAs/GaSb superlattice photodetectors with atomic layer deposited Al2O3

    NASA Astrophysics Data System (ADS)

    Salihoglu, Omer; Muti, Abdullah; Kutluer, Kutlu; Tansel, Tunay; Turan, Rasit; Kocabas, Coskun; Aydinli, Atilla

    2012-06-01

    We have achieved significant improvement in the electrical performance of the InAs/GaSb midwave infrared photodetector (MWIR) by using atomic layer deposited (ALD) aluminium oxide (Al2O3) as a passivation layer. Plasma free and low operation temperature with uniform coating of ALD technique leads to a conformal and defect free coverage on the side walls. This conformal coverage of rough surfaces also satisfies dangling bonds more efficiently while eliminating metal oxides in a self cleaning process of the Al2O3 layer. Al2O3 passivated and unpassivated diodes were compared for their electrical and optical performances. For passivated diodes the dark current density was improved by an order of magnitude at 77 K. The zero bias responsivity and detectivity was 1.33 A/W and 1.9 x 1013 Jones, respectively at 4 μm and 77 K. Quantum efficiency (QE) was determined as %41 for these detectors.

  5. Quartz crystal microbalance studies of Al2O3 atomic layer deposition using trimethylaluminum and water at 125 degrees C.

    PubMed

    Wind, R A; George, S M

    2010-01-28

    Al(2)O(3) atomic layer deposition (ALD) growth with Al(CH(3))(3) (trimethylaluminum (TMA)) and H(2)O as the reactants was examined at the relatively low temperature of 125 degrees C using quartz crystal microbalance (QCM) measurements. The total Al(2)O(3) ALD mass gain per cycle (MGPC) and MGPCs during the individual TMA and H(2)O reactions were measured versus TMA and H(2)O exposures. The Al(2)O(3) MGPC increased with increasing H(2)O and TMA exposures at fixed TMA and H(2)O exposures, respectively. However, the TMA and H(2)O reactions were not completely self-limiting. The slower surface reaction kinetics at lower temperature may require very long exposures for the reactions to reach completion. The Al(2)O(3) MGPCs increased quickly versus H(2)O exposure and slowly reached limiting values that were only weakly dependent on the TMA doses. Small TMA exposures were also sufficient for the Al(2)O(3) MGPCs to reach different limiting values for different H(2)O doses. The TMA MGPCs increased for higher TMA exposures at all H(2)O exposures. In contrast, the H(2)O MGPCs decreased for higher TMA exposures at all H(2)O exposures. This decrease may occur from more dehydroxylation at larger hydroxyl coverages after the H(2)O exposures. The hydroxyl coverage after the H(2)O exposure was dependent only on the H(2)O exposure. The Al(2)O(3) MGPC was also linearly dependent on the hydroxyl coverage after the H(2)O dose. Both the observed hydroxyl coverage versus H(2)O exposure and the Al(2)O(3) ALD growth versus H(2)O and TMA exposures were fit using modified Langmuir adsorption isotherm expressions where the pressures are replaced with exposures. These results should be useful for understanding low-temperature Al(2)O(3) ALD, which is important for coating organic, polymeric, and biological substrates.

  6. Islet amyloid polypeptide forms rigid lipid-protein amyloid fibrils on supported phospholipid bilayers.

    PubMed

    Domanov, Yegor A; Kinnunen, Paavo K J

    2008-02-08

    Islet amyloid polypeptide (IAPP) forms fibrillar amyloid deposits in the pancreatic islets of Langerhans of patients with type 2 diabetes mellitus, and its misfolding and aggregation are thought to contribute to beta-cell death. Increasing evidence suggests that IAPP fibrillization is strongly influenced by lipid membranes and, vice versa, that the membrane architecture and integrity are severely affected by amyloid growth. Here, we report direct fluorescence microscopic observations of the morphological transformations accompanying IAPP fibrillization on the surface of supported lipid membranes. Within minutes of application in submicromolar concentrations, IAPP caused extensive remodeling of the membrane including formation of defects, vesiculation, and tubulation. The effects of IAPP concentration, ionic strength, and the presence of amyloid seeds on the bilayer perturbation and peptide aggregation were examined. Growth of amyloid fibrils was visualized using fluorescently labeled IAPP or thioflavin T staining. Two-color imaging of the peptide and membranes revealed that the fibrils were initially composed of the peptide only, and vesiculation occurred in the points where growing fibers touched the lipid membrane. Interestingly, after 2-5 h of incubation, IAPP fibers became "wrapped" by lipid membranes derived from the supported membrane. Progressive increase in molecular-level association between amyloid and membranes in the maturing fibers was confirmed by Förster resonance energy transfer spectroscopy.

  7. Thermoelectric properties of lattice-matched AlInN alloy grown by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Tong, Hua; Zhang, Jing; Liu, Guangyu; Herbsommer, Juan A.; Huang, G. S.; Tansu, Nelson

    2010-09-01

    Thermoelectric properties of lattice-matched AlInN grown by metal organic chemical vapor deposition were measured and analyzed. The n-type Al0.83In0.17N alloy exhibited thermal conductivity of 4.87 W/(m K) measured by 3ω differential method. The Seebeck coefficient of n-Al0.83In0.17N was measured as -6.012×10-4 V/K by thermal gradient method. The sheet resistivity of n-Al0.83In0.17N was measured by using Van der Pauw method, and the electrical conductivity was measured as 2.38×104/(Ω m). The thermoelectric figure of merit (Z∗T) of n-type Al0.83In0.17N was measured as 0.532 at room temperature (T =300 K). The finding indicates lattice-matched AlInN alloy on GaN as excellent material candidate for thermoelectric application.

  8. Diffusion behavior of 3.2% Si-grain-oriented steel coated with Al by plasma vapor deposition

    NASA Astrophysics Data System (ADS)

    Park, Se Min; Lee, Jae Sang; Kim, Jae Su; Han, Kyu Seak; Koo, Yang Mo

    2015-05-01

    Diffusion annealing has been performed to investigate the influence of diffusion parameters on the diffusion behavior of 3.2% Si-grain-oriented steel coated with Al using plasma vapor deposition (PVD). When Fe-Si steel sheets coated with Al-PVD were annealed at 1373 K, a single-phase solution of Al with uniform concentration was formed in α-Fe without intermetallic phases. It was confirmed that Kirkendall voids nucleate during interdiffusion between solid Al and Fe in the annealing process and volume fraction of Kirkendall voids decreased as the heating rate increased. Rapid heating (55 K/s) can prevent the formation of Kirkendall voids, possibly by reducing the time available for interdiffusion between solid Al and Fe. The results show that the alloying of 2 wt% Al was achieved without the formation of interme-tallic phases and Kirkendall voids, and that this alloy can increase resistivity and reduce eddy current loss. This was found to results in reduced core loss by 10%.

  9. Characteristics of CrAlSiN + DLC coating deposited by lateral rotating cathode arc PVD and PACVD process

    NASA Astrophysics Data System (ADS)

    Lukaszkowicz, Krzysztof; Sondor, Jozef; Balin, Katarzyna; Kubacki, Jerzy

    2014-09-01

    Coating system composed of CrAlSiN film covered by diamond-like carbon (DLC)-based lubricant, deposited on hot work tool steel substrate was the subject of the research. The CrAlSiN and DLC layers were deposited by PVD lateral rotating ARC-cathodes (LARC) and PACVD technology on the X40CrMoV5-1 respectively. HRTEM investigation shows an amorphous character of DLC layer. It was found that the tested CrAlSiN layer has a nanostructural character with fine crystallites while their average size is less than 10 nm. Based on the XRD pattern of the CrAlSiN, the occurrence of fcc phase was only observed in the coating, the texture direction <3 1 1> is perpendicular to the sample surface. Combined SEM, AES and ToF-SIMS studies confirmed assumed chemical composition and layered structure of the coating. The chemical distribution of the elements inside the layers and at the interfaces was analyzed by SEM and AES methods. It was shown that additional CrN layer is present between substrate and CrAlSiN coating. The atomic concentration of the particular elements of DLC and CrAlSiN layer was calculated from the XPS measurements. In sliding dry friction conditions the friction coefficient for the investigated elements is set in the range between 0.05 and 0.07. The investigated coating reveals high wear resistance. The coating demonstrated a dense cross-sectional morphology as well as good adhesion to the substrate.

  10. Amyloid burden in cognitively normal elderly is associated with preferential hippocampal subfield volume loss

    PubMed Central

    Hsu, Phillip J.; Shou, Haochang; Benzinger, Tammie; Marcus, Daniel; Durbin, Tony; Morris, John C.; Sheline, Yvette I.

    2015-01-01

    The earliest sites of brain atrophy in Alzheimer’s disease are in the medial temporal lobe, following widespread cerebral cortical amyloid deposition. We assessed 74 cognitively normal participants with clinical measurements, Aβ-PET imaging, MRI, and a newly developed technique for MRI-based hippocampal subfield segmentation to determine the differential association of amyloid deposition and hippocampal subfield volume. Compared to amyloid-negative participants, amyloid-positive participants had significantly smaller hippocampal tail, presubiculum, subiculum, and total hippocampal gray matter volumes. We conclude that, prior to the development of cognitive impairment, atrophy in particular hippocampal subfields (HS) occurs preferentially with Aβ accumulation. PMID:25428255

  11. Atomic layer deposition of highly-doped Er:Al2O3 and Tm:Al2O3 for silicon-based waveguide amplifiers (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Roenn, John; Karvonen, Lasse; Pyymäki-Perros, Alexander; Peyghambarian, Nasser; Lipsanen, Harri; Säynätjoki, Antti; Sun, Zhipei

    2016-05-01

    Recently, rare-earth doped waveguide amplifiers (REDWAs) have drawn significant attention as a promising solution to on-chip amplification of light in silicon photonics and integrated optics by virtue of their high excited state lifetime (up to 10 ms) and broad emission spectrum (up to 200 nm) at infrared wavelengths. In the family of rare-earths, at least erbium, holmium, thulium, neodymium and ytterbium have been demonstrated to be good candidates for amplifier operation at moderate concentrations (< 0.1 %). However, efficient amplifier operation in REDWAs is a very challenging task because high concentration of ions (<0.1%) is required in order to produce reasonable amplification over short device length. Inevitably, high concentration of ions leads to energy-transfer between neighboring ions, which results as decreased gain and increased noise in the amplifier system. It has been shown that these energy-transfer mechanisms in highly-doped gain media are inversely proportional to the sixth power of the distance between the ions. Therefore, novel fabrication techniques with the ability to control the distribution of the rare-earth ions within the gain medium are urgently needed in order to fabricate REDWAs with high efficiency and low noise. Here, we show that atomic layer deposition (ALD) is an excellent technique to fabricate highly-doped (<1%) RE:Al2O3 gain materials by using its nanoscale engineering ability to delicately control the incorporation of RE ions during the deposition. In our experiment, we fabricated Er:Al2O3 and Tm:Al2O3 thin films with ALD by varying the concentration of RE ions from 1% to 7%. By measuring the photoluminescence response of the fabricated samples, we demonstrate that it is possible to incorporate up to 5% of either Er- or Tm-ions in Al2O3 host before severe quenching occurs. We believe that this technique can be extended to other RE ions as well. Therefore, our results show the exceptionality of ALD as a deposition technique for

  12. Characterization of Ti-C-N coatings deposited on Ti6Al4V for biomedical applications.

    PubMed

    de Viteri, V Sáenz; Barandika, M G; de Gopegui, U Ruiz; Bayón, R; Zubizarreta, C; Fernández, X; Igartua, A; Agullo-Rueda, F

    2012-12-01

    Ti6Al4V alloy is the most commonly employed implant material for orthopedic replacements due to its good mechanical properties close to those of bones, biocompatibility and its good corrosion resistance in biological media. Nevertheless, it does not exhibit good wear resistance, showing friction and wear even with soft tissues. This latter feature can lead to a premature failure of the implant with the subsequent component replacement. Therefore, a system with good tribological resistance is required for several medical applications. One possible alternative to solve tribological problems consists of protecting the alloy surface by means of biocompatible Ti-C-N coatings. In this work, five types of metallic Ti-C-N coatings deposited by physical vapor deposition (PVD) cathodic arc method on Ti6Al4V substrate have been studied. Different deposition conditions have been analyzed, and the superficial properties of films have been characterized. Additionally, tribological response of these films have been determined and compared with the substrate one under fretting conditions in simulated body fluid. The results indicate that Ti-C-N coatings improve the general response of the biomaterial.

  13. Surface Thiolation of Al Microspheres to Deposite Thin and Compact Ag Shells for High Conductivity.

    PubMed

    Wang, Yilong; Wen, Jianghong; Zhao, Suling; Chen, Zhihong; Ren, Ke; Sun, Jie; Guan, Jianguo

    2015-12-15

    In this work, we have demonstrated a method for controllable thiolated functionalization coupled with electroless silver plating to achieve aluminum@silver (Al@Ag) core-shell composite particles with thin and compact layers. First, Al microspheres were functionalized by a well-known polymerizable silane coupling agent, i.e., 3-mercaptopropyltrimethoxysilane (MPTMS). Decreasing the ethanol-to-water volume ratio (F) in silane solution produces modification films with high content of thiol groups on Al microspheres, owing to the dehydration of silane molecules with hydroxyl groups on Al microspheres and self-polymerization of silane molecules. Then, ethanol was used as one of the solvents to play a major role in the uniform dispersion of silane coupling agent in the solution, resulting in uniformly distributing and covalently attaching thiol groups on Al microspheres. In electroless silver plating, thiol groups being densely grafted on the surface of Al microspheres favor the heterogeneous nucleation of Ag, since the thiol group can firmly bind with Ag(+) and enable the in situ reduction by the reducing reagent. In this manner, dense Ag nuclei tend to produce thin and compact silver shells on the Al microspheres surfaces. The as-obtained Al@Ag core-shell composite particles show a resistivity as low as (8.58 ± 0.07) × 10(-5) Ω·cm even when the Ag content is as low as 15.46 wt %. Therefore, the as-obtained Al@Ag core-shell composite particles have advantages of low weight, low silver content and high conductivity, which could make it a promising candidate for application in conductive and electromagnetic shielding composite materials.

  14. Cell adhesion to cathodic arc plasma deposited CrAlSiN thin films

    NASA Astrophysics Data System (ADS)

    Kim, Sun Kyu; Pham, Vuong-Hung; Kim, Chong-Hyun

    2012-07-01

    Osteoblast cell response (cell adhesion, actin cytoskeleton and focal contact adhesion as well as cell proliferation) to CrN, CrAlSiN and Ti thin films was evaluated in vitro. Cell adhesion and actin stress fibers organization depended on the film composition significantly. Immunofluorescent staining of vinculin in osteoblast cells showed good focal contact adhesion on the CrAlSiN and Ti thin films but not on the CrN thin films. Cell proliferation was significantly greater on the CrAlSiN thin films as well as on Ti thin films than on the CrN thin films.

  15. Direct Metal Deposition by Laser in TiNi-Al System for Graded Structure Fabrication

    NASA Astrophysics Data System (ADS)

    Shishkovsky, I.; Kakovkina, N.; Missemer, F.

    2016-07-01

    Intermetallic phase formation was studied in powdered TiNi-Al system under layerwise laser cladding with the aim of forming a gradient of properties due to a change in the concentration relation of Al in the NiTi powder mixture from one layer to another. The relationship between the laser cladding parameters and the intermetallic phase structures in consecutively cladded layers were determined. The structure of intermetallic compounds formed by laser synthesis was studied by optical microscopy, measurement of microhardness, SEM with EDX analysis. Microhardness doubling from 500 HV to 1000 HV was achieved due to nitinol matrix enrichment by Al, which is promising for aerospace applications.

  16. Epitaxial growth of aligned AlGalnN nanowires by metal-organic chemical vapor deposition

    DOEpatents

    Han, Jung; Su, Jie

    2008-08-05

    Highly ordered and aligned epitaxy of III-Nitride nanowires is demonstrated in this work. <1010> M-axis is identified as a preferential nanowire growth direction through a detailed study of GaN/AlN trunk/branch nanostructures by transmission electron microscopy. Crystallographic selectivity can be used to achieve spatial and orientational control of nanowire growth. Vertically aligned (Al)GaN nanowires are prepared on M-plane AlN substrates. Horizontally ordered nanowires, extending from the M-plane sidewalls of GaN hexagonal mesas or islands demonstrate new opportunities for self-aligned nanowire devices, interconnects, and networks.

  17. Atomic layer deposition of Al-doped ZnO/Al2O3 double layers on vertically aligned carbon nanofiber arrays.

    PubMed

    Malek, Gary A; Brown, Emery; Klankowski, Steven A; Liu, Jianwei; Elliot, Alan J; Lu, Rongtao; Li, Jun; Wu, Judy

    2014-05-14

    High-aspect-ratio, vertically aligned carbon nanofibers (VACNFs) were conformally coated with aluminum oxide (Al2O3) and aluminum-doped zinc oxide (AZO) using atomic layer deposition (ALD) in order to produce a three-dimensional array of metal-insulator-metal core-shell nanostructures. Prefunctionalization before ALD, as required for initiating covalent bonding on a carbon nanotube surface, was eliminated on VACNFs due to the graphitic edges along the surface of each CNF. The graphitic edges provided ideal nucleation sites under sequential exposures of H2O and trimethylaluminum to form an Al2O3 coating up to 20 nm in thickness. High-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy images confirmed the conformal core-shell AZO/Al2O3/CNF structures while energy-dispersive X-ray spectroscopy verified the elemental composition of the different layers. HRTEM selected area electron diffraction revealed that the as-made Al2O3 by ALD at 200 °C was amorphous, and then, after annealing in air at 450 °C for 30 min, was converted to polycrystalline form. Nevertheless, comparable dielectric constants of 9.3 were obtained in both cases by cyclic voltammetry at a scan rate of 1000 V/s. The conformal core-shell AZO/Al2O3/VACNF array structure demonstrated in this work provides a promising three-dimensional architecture toward applications of solid-state capacitors with large surface area having a thin, leak-free dielectric.

  18. Optical and electrical properties of ZnO nanocrystal thin films passivated by atomic layer deposited Al2O3

    NASA Astrophysics Data System (ADS)

    Choi, Ji-Hyuk; Kim, Jungwoo; Oh, Soong Ju; Kim, Daekyoung; Kim, Yong-Hoon; Chae, Heeyeop; Kim, Hyoungsub

    2016-07-01

    While colloidal semiconductor nanocrystal (NC) is preferred for use in solution-based optoelectronic devices, the large number of surface defects associated with its high surface-to-volume ratio degrades the optimal performance of NC-based devices due to the extensive trapping of free carriers available for charge transport. Here, we studied a simple and effective strategy to control the degree of passivation and doping level of solution-deposited ZnO NC films by infilling with ultra-thin Al2O3 using an atomic layer deposition (ALD) technique. According to various spectroscopic, microstructural, and electrical analyses, the ALD-Al2O3 treatment dramatically reduced the number of surface trap states with high ambient stability while simultaneously supplied excess carriers probably via a remote doping mechanism. As a consequence, the field-effect transistors built using the ZnO NC films with ALD-Al2O3 treatment for an optimal number of cycles exhibited significantly enhanced charge transport.

  19. Reduced defect density at the CZTSSe/CdS interface by atomic layer deposition of Al2O3

    NASA Astrophysics Data System (ADS)

    Erkan, Mehmet Eray; Chawla, Vardaan; Scarpulla, Michael A.

    2016-05-01

    The greatest challenge for improving the power conversion efficiency of Cu2ZnSn(S,Se)4 (CZTSSe)/CdS/ZnO thin film solar cells is increasing the open circuit voltage (VOC). Probable leading causes of the VOC deficit in state-of-the-art CZTSSe devices have been identified as bulk recombination, band tails, and the intertwined effects of CZTSSe/CdS band offset, interface defects, and interface recombination. In this work, we demonstrate the modification of the CZTSSe absorber/CdS buffer interface following the deposition of 1 nm-thick Al2O3 layers by atomic layer deposition (ALD) near room temperature. Capacitance-voltage profiling and quantum efficiency measurements reveal that ALD-Al2O3 interface modification reduces the density of acceptor-like states at the heterojunction resulting in reduced interface recombination and wider depletion width. Indications of increased VOC resulting from the modification of the heterojunction interface as a result of ALD-Al2O3 treatment are presented. These results, while not conclusive for application to state-of-the-art high efficiency CZTSSe devices, suggest the need for further studies as it is probable that interface recombination contributes to reduced VOC even in such devices.

  20. Post-deposition annealing influenced structural and electrical properties of Al/TiO2/Si gate capacitors

    NASA Astrophysics Data System (ADS)

    Chandra Sekhar, M.; Kondaiah, P.; Mohan Rao, G.; Jagadeesh Chandra, S. V.; Uthanna, S.

    2013-10-01

    Titanium dioxide (TiO2) thin films are deposited on unheated p-Si (100) and quartz substrates by employing DC reactive magnetron sputtering technique. The effect of post-deposition annealing in air at temperatures in the range 673-973 K on the structural, electrical, and dielectric properties of the films was investigated. The chemical composition of the TiO2 films was analyzed with X-ray photoelectron spectroscopy. The surface morphology of the films was studied by atomic force microscope. The optical band gap of the as-deposited film was 3.50 eV, and it increased to 3.55 eV with the increase in annealing temperature to 773 K. The films annealed at higher temperature of 973 K showed the optical band gap of 3.43 eV. Thin film capacitors were fabricated with the MOS configuration of Al/TiO2/p-Si. The leakage current density of the as-deposited films was 1.2 × 10-6 A/cm2, and it decreased to 5.9 × 10-9 A/cm2 with the increase in annealing temperature to 973 K. These films showed high dielectric constant value of 36.

  1. Wear and Friction Behavior of the Spray-Deposited SiCp/Al-20Si-3Cu Functionally Graded Material

    NASA Astrophysics Data System (ADS)

    Su, B.; Yan, H. G.; Chen, J. H.; Zeng, P. L.; Chen, G.; Chen, C. C.

    2013-05-01

    The spray-deposited SiCp/Al-20Si-3Cu functionally graded material (FGM) can meet the structure design requirements of brake disk. The effects of rotational speed and load on the wear and friction behaviors of the SiCp/Al-20Si-3Cu FGM sliding against the resin matrix friction material were investigated. For comparison, the wear and friction behaviors of a commercially used cast iron (HT250) brake rotor were also studied. The results indicate that the friction coefficient of the SiCp/Al-20Si-3Cu FGM decreases constantly with the increase of load or rotational speed and is affected by the gradient distribution of SiC particles. The wear rate of the SiCp/Al-20Si-3Cu FGM firstly increases, then decreases and finally increases again with increasing load or speed, and is about 1/10 of that of HT250. Based on observations and analyses on the morphology and substructure of the worn surface, the mechanical mixing layer acts as a protective coating and lubricant, and its thickness reduces with the SiC content increasing. Furthermore, it is proposed that the dominant wear mechanism of SiCp/Al-20Si-3Cu FGM changes from the abrasive wear to the oxidative wear and further to the delamination wear with increasing load or speed.

  2. Investigation on dielectric properties of atomic layer deposited Al{sub 2}O{sub 3} dielectric films

    SciTech Connect

    Yıldız, Dilber Esra; Yıldırım, Mert; Gökçen, Muharrem

    2014-05-15

    Al/Al{sub 2}O{sub 3}/p-Si Schottky barrier diodes (SBDs) were fabricated using atomic layer deposition technique in order to investigate dielectric properties of SBDs. For this purpose, admittance measurements were conducted at room temperature between −1 V and 3 V in the frequency range of 10 kHz and 1 MHz. In addition to the investigation of Al{sub 2}O{sub 3} morphology using atomic force microscope, dielectric parameters; such as dielectric constant (ε′), dielectric loss (ε″), dielectric loss tangent (tan δ), and real and imaginary parts of dielectric modulus (M′ and M″, respectively), were calculated and effect of frequency on these parameters of Al/Al{sub 2}O{sub 3}/p-Si SBDs was discussed. Variations in these parameters at low frequencies were associated with the effect of interface states in low frequency region. Besides dielectric parameters, ac electrical conductivity of these SBDs was also investigated.

  3. W:Al2O3 nanocomposite thin films with tunable optical properties prepared by atomic layer deposition

    DOE PAGES

    Babar, Shaista; Mane, Anil U.; Yanguas-Gil, Angel; ...

    2016-06-17

    Here, a systematic alteration in the optical properties of W:Al2O3 nanocomposite films is demonstrated by precisely varying the W cycle percentage (W%) from 0 to 100% in Al2O3 during atomic layer deposition. The direct and indirect band energies of the nanocomposite materials decrease from 5.2 to 4.2 eV and from 3.3 to 1.8 eV, respectively, by increasing the W% from 10 to 40. X-ray absorption spectroscopy reveals that, for W% < 50, W is present in both metallic and suboxide states, whereas, for W% ≥ 50, only metallic W is seen. This transition from dielectric to metallic character at W%more » ~ 50 is accompanied by an increase in the electrical and thermal conductivity and the disappearance of a clear band gap in the absorption spectrum. The density of the films increases monotonically from 3.1 g/cm3 for pure Al2O3 to 17.1 g/cm3 for pure W, whereas the surface roughness is greatest for the W% = 50 films. The W:Al2O3 nanocomposite films are thermally stable and show little change in optical properties upon annealing in air at 500 °C. These W:Al2O3 nanocomposite films show promise as selective solar absorption coatings for concentrated solar power applications.« less

  4. Passivation Effect of Atomic Layer Deposition of Al2O3 Film on HgCdTe Infrared Detectors

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Ye, Zhen-Hua; Sun, Chang-Hong; Chen, Yi-Yu; Zhang, Tian-Ning; Chen, Xin; Lin, Chun; Ding, Ring-Jun; He, Li

    2016-09-01

    The passivation effect of atomic layer deposition of (ALD) Al2O3 film on a HgCdTe infrared detector was investigated in this work. The passivation effect of Al2O3 film was evaluated by measuring the minority carrier lifetime, capacitance versus voltage ( C- V) characteristics of metal-insulator-semiconductor devices, and resistance versus voltage ( R- V) characteristics of variable-area photodiodes. The minority carrier lifetime, C- V characteristics, and R- V characteristics of HgCdTe devices passivated by ALD Al2O3 film was comparable to those of HgCdTe devices passivated by e-beam evaporation of ZnS/CdTe film. However, the baking stability of devices passivated by Al2O3 film is inferior to that of devices passivated by ZnS/CdTe film. In future work, by optimizing the ALD Al2O3 film growing process and annealing conditions, it may be feasible to achieve both excellent electrical properties and good baking stability.

  5. Cerebral vascular amyloid seeds drive amyloid β-protein fibril assembly with a distinct anti-parallel structure

    PubMed Central

    Xu, Feng; Fu, Ziao; Dass, Sharmila; Kotarba, AnnMarie E.; Davis, Judianne; Smith, Steven O.; Van Nostrand, William E.

    2016-01-01

    Cerebrovascular accumulation of amyloid β-protein (Aβ), a condition known as cerebral amyloid angiopathy (CAA), is a common pathological feature of patients with Alzheimer's disease. Familial Aβ mutations, such as Dutch-E22Q and Iowa-D23N, can cause severe cerebrovascular accumulation of amyloid that serves as a potent driver of vascular cognitive impairment and dementia. The distinctive features of vascular amyloid that underlie its unique pathological properties remain unknown. Here, we use transgenic mouse models producing CAA mutants (Tg-SwDI) or overproducing human wild-type Aβ (Tg2576) to demonstrate that CAA-mutant vascular amyloid influences wild-type Aβ deposition in brain. We also show isolated microvascular amyloid seeds from Tg-SwDI mice drive assembly of human wild-type Aβ into distinct anti-parallel β-sheet fibrils. These findings indicate that cerebrovascular amyloid can serve as an effective scaffold to promote rapid assembly and strong deposition of Aβ into a unique structure that likely contributes to its distinctive pathology. PMID:27869115

  6. Microwave assisted apatite coating deposition on Ti6Al4V implants.

    PubMed

    Zhou, Huan; Nabiyouni, Maryam; Bhaduri, Sarit B

    2013-10-01

    In this work we report a novel microwave assisted technology to deposit a uniform, ultra-thin apatite coating without any cracks on titanium implants in minutes. This method comprises of conventional biomimetic coating in synergism with microwave irradiation to result in alkaline earth phosphate nucleation. The microwave assisted coating process mainly follows the initial stages of biomimetic coating until the step of the Ca-P nuclei formation. After that, due to microwave irradiation more Ca-P nuclei are formed to cover the whole surface of the implant instead of the growth of deposited Ca-P nuclei to Ca-P globules and coatings. It is interesting to note the doping of Mg(2+) to Ca-P apatite coating can significantly change the properties and performances of as-deposited coatings. The hydrophilicity, physical properties, bioactivity, cell adhesion, and growth capability of as-deposited microwave assisted coatings were investigated. The study shows that this coating technology has great potential in biomedical applications. Additionally, since biomimetic coating can be applied to series of implant materials such as polymer, metals and glass, it is expected this microwave assisted coating technology can also be applied to these materials if they can remains stable at 100 °C, the boiling point of water.

  7. Growing LaAlO{sub 3}/SrTiO{sub 3} interfaces by sputter deposition

    SciTech Connect

    Dildar, I. M.; Neklyudova, M.; Xu, Q.; Zandbergen, H. W.; Harkema, S.; Boltje, D.; Aarts, J.

    2015-06-15

    Sputter deposition of oxide materials in a high-pressure oxygen atmosphere is a well-known technique to produce thin films of perovskite oxides in particular. Also interfaces can be fabricated, which we demonstrated recently by growing LaAlO{sub 3} on SrTiO{sub 3} substrates and showing that the interface showed the same high degree of epitaxy and atomic order as is made by pulsed laser deposition. However, the high pressure sputtering of oxides is not trivial and number of parameters are needed to be optimized for epitaxial growth. Here we elaborate on the earlier work to show that only a relatively small parameter window exists with respect to oxygen pressure, growth temperature, radiofrequency power supply and target to substrate distance. In particular the sensitivity to oxygen pressure makes it more difficult to vary the oxygen stoichiometry at the interface, yielding it insulating rather than conducting.

  8. Analysis of the co-deposition of Al2O3 particles with nickel by an electrolytic route: The influence of organic additives presence and Al2O3 concentration

    NASA Astrophysics Data System (ADS)

    Temam, H. B.; Temam, E. G.

    2016-04-01

    Alloy coatings were prepared by co-deposition of Al2O3 particles in Ni matrix on carbon steel substrate from nickel chloride bath in which metallic powders were held in suspension. The influence of metal powder amount in the bath on chemical composition, morphology, thickness, microhardness and corrosion behavior of obtained coatings, has been investigated. It was shown that the presence of Al2O3 particles in deposit greatly improves the hardness and the wear resistance of alloy coatings. Characterization by microanalysis (EDX) of the various deposits elaborated confirms that the rate of particles incorporated increases as the concentration of solid particles increasing. The results showed that the presence of organic additives in Ni-Al2O3 electrolyte deposition led to an increase in the hardness and corrosion resistance of the deposits.

  9. Peptide Amyloid Surface Display

    PubMed Central

    2015-01-01

    Homomeric self-assembly of peptides into amyloid fibers is a feature of many diseases. A central role has been suggested for the lateral fiber surface affecting gains of toxic function. To investigate this, a protein scaffold that presents a discrete, parallel β-sheet surface for amyloid subdomains up to eight residues in length has been designed. Scaffolds that present the fiber surface of islet amyloid polypeptide (IAPP) were prepared. The designs show sequence-specific surface effects apparent in that they gain the capacity to attenuate rates of IAPP self-assembly in solution and affect IAPP-induced toxicity in insulin-secreting cells. PMID:25541905

  10. Enhancement mode AlGaN/GaN MOS high-electron-mobility transistors with ZrO2 gate dielectric deposited by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Anderson, Travis J.; Wheeler, Virginia D.; Shahin, David I.; Tadjer, Marko J.; Koehler, Andrew D.; Hobart, Karl D.; Christou, Aris; Kub, Francis J.; Eddy, Charles R., Jr.

    2016-07-01

    Advanced applications of AlGaN/GaN high-electron-mobility transistors (HEMTs) in high-power RF and power switching are driving the need for insulated gate technology. We present a metal-oxide-semiconductor (MOS) gate structure using atomic-layer-deposited ZrO2 as a high-k, high-breakdown gate dielectric for reduced gate leakage and a recessed barrier structure for enhancement mode operation. Compared to a Schottky metal-gate HEMT, the recessed MOS-HEMT structure demonstrated a reduction in the gate leakage current by 4 orders of magnitude and a threshold voltage shift of +6 V to a record +3.99 V, enabled by a combination of a recessed barrier structure and negative oxide charge.

  11. Critical tensile and compressive strains for cracking of Al2O3 films grown by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Jen, Shih-Hui; Bertrand, Jacob A.; George, Steven M.

    2011-04-01

    Al2O3 atomic layer deposition (ALD) is a model ALD system and Al2O3 ALD films are excellent gas diffusion barrier on polymers. However, little is known about the response of Al2O3 ALD films to strain and the potential film cracking that would restrict the utility of gas diffusion barrier films. To understand the mechanical limitations of Al2O3 ALD films, the critical strains at which the Al2O3 ALD films will crack were determined for both tensile and compressive strains. The tensile strain measurements were obtained using a fluorescent tagging technique to image the cracks. The results showed that the critical tensile strain is higher for thinner thicknesses of the Al2O3 ALD film on heat-stabilized polyethylene naphthalate (HSPEN) substrates. A low critical tensile strain of 0.52% was measured for a film thickness of 80 nm. The critical tensile strain increased to 2.4% at a film thickness of 5 nm. In accordance with fracture mechanics modeling, the critical tensile strains and the saturation crack densities scaled as (1/h)1/2 where h is the Al2O3 ALD film thickness. The fracture toughness for cracking, KIC, of the Al2O3 ALD film was also determined to be KIC = 2.30 MPa m1/2. Thinner Al2O3 ALD film thicknesses also had higher critical strains for cracking from compressive strains. Field-emission scanning electron microscopy (FE-SEM) images revealed that Al2O3 ALD films with thicknesses of 30-50 nm on Teflon fluorinated ethylene propylene (FEP) substrates cracked at a critical compressive strain of ˜1.0%. The critical compressive strain increased to ˜2.0% at a film thickness of ˜20 nm. A comparison of the critical tensile strains on HSPEN substrates and critical compressive strains on Teflon FEP substrates revealed some similarities. The critical strain was ˜1.0% for film thicknesses of 30-50 nm for both tensile and compressive strains. The critical compressive strain then increased more rapidly than the critical tensile strain for thinner films with thicknesses

  12. Electrical characteristics and conduction mechanisms of amorphous subnanometric Al2O3-TiO2 laminate dielectrics deposited by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Kahouli, Abdelkader; Lebedev, Oleg; Dao, Vu Hung; Elbahri, Marwa Ben; Prellier, Wilfrid; Lüders, Ulrike

    2016-11-01

    Electric conduction mechanisms of amorphous Al2O3/TiO2 (ATO)-laminates deposited by atomic layer deposition with sub-nanometer individual layer thicknesses were studied in a large temperature range. Two characteristic field regions are identified. In the low field region (E ≤ 0.31 MV/cm), the leakage current is dominated by the trap-assisted tunneling through oxygen vacancies occurring in the TiO2, while in the high electric field region (E > 0.31 MV/cm) the Poole Frenkel (PF) hopping is the appropriate conduction process with energy levels depending on the temperature and the electric field. It is shown that the PF potential levels decrease with the applied ATO field due to the overlapping of the Coulomb potential. Amorphous ATO-laminates show the presence of two intrinsic potential energy levels ϕi, which are 0.18 eV for low temperature region and 0.4 eV at high temperature region. Oxygen vacancies are the main origin of traps, which is consistent with the principal mechanisms for leakage in ATO-laminates.

  13. In situ spectroscopic ellipsometry growth studies on the Al-doped ZnO films deposited by remote plasma-enhanced metalorganic chemical vapor deposition

    SciTech Connect

    Volintiru, I.; Creatore, M.; Sanden, M. C. M. van de

    2008-02-01

    In situ spectroscopic ellipsometry (SE) was applied to study the pyramidlike and pillarlike growth of Al doped ZnO (AZO) films deposited by means of remote plasma-enhanced metalorganic chemical vapor deposition for transparent conductive oxide applications. Real time SE studies in the visible region allowed discerning between the two growth modes by addressing the time evolution of the bulk and surface roughness layer thickness. While the pillarlike mode is characterized by a constant growth rate, a slower rate in the initial stage (up to 150-200 nm film thickness), compared to the bulk, is observed for the growth of pyramidlike AZO films. The two modes differ also in terms of surface roughness development: a saturation behavior is observed for film thickness above 150-200 nm in the case of the pyramidlike films, while a slow linear increase with film thickness characterizes the pillarlike mode. By extending the SE analysis of the AZO films to the near infrared region, valuable information about the in grain properties could be extracted: excellent in grain mobility values, i.e., larger than 100 and 50 cm{sup 2}/V s, are determined for the pyramidlike and pillarlike AZO layers, respectively. The comparison between the outcome of the in situ real time SE studies and the ex situ electrical and chemical characterization highlights the limitations in the electron transport occurring in both types of films and allows one to address routes toward further improvement in AZO conductivity.

  14. Amyloid Goiter Associated with Amyloidosis Secondary to Rheumatoid Arthritis

    PubMed Central

    Uzum, Gungor; Kaya, Fatih Oner; Uzum, Ayse Kubat; Kucukyilmaz, Meltem; Duzkoylu, Yigit; Leblebici, Cem; Koc, Oguz

    2013-01-01

    Amyloidosis refers to a variety of conditions in which amyloid proteins are abnormally deposited in organs and/or tissues. The most common forms of systemic amyloidosis are primary amyloidosis (PA) of light chains and secondary amyloidosis (SA) caused by chronic inflammatory diseases such as rheumatoid arthritis (RA). Although involvement of the thyroid gland by amyloid is a relatively common phenomenon, clinically significant enlargement of the thyroid owing to amyloid deposition is a rare occurrence. In SA, the deposition of amyloid associated (AA) protein is associated with atrophy of thyroid follicles. The clinical picture of these patients is characterized by rapid, painless thyroid gland enlargement which may be associated with dysphagia, dyspnea, or hoarseness. Thyroid function is not impaired in most cases. Although amyloid goitre secondary to systemic amyloidosis due to chronic inflammatory diseases is relatively common, specifically related to RA is much more uncommon one and it is reported less in the literature. In this report, A 52-old-year female patient with amyloid goiter associated with amyloidosis secondary to rheumatoid arthritis is presented. PMID:24368922

  15. Fabrication and Electrical Characterization of the Si/ZnO/ZnO:Al Structure Deposited by RF-Magnetron Sputtering

    NASA Astrophysics Data System (ADS)

    Alaya, A.; Djessas, K.; El Mir, L.; Khirouni, K.

    2016-10-01

    The electrical transport properties of the structures of Si(p)/ZnO(i)/ZnO: Al(3%) and Si(p)/PS/ZnO(i)/ZnO: Al(3%) deposited by radio-frequency-magnetron sputtering were investigated and compared by using current-voltage and impedance spectroscopy measurements in a wide temperature range of 80-300 K. Aluminum-doped ZnO is considered to be one of the most important transparent conducting oxide materials due to its high conductivity, good transparency and low cost. From the current-voltage-temperature ( I- V- T) characteristics, it was found that both structures had a good rectifying behavior. This behavior decreases according to the porous silicon layer. The variation of the conductance with frequency indicates the semiconducting behavior and superposition of different conduction mechanisms. The insertion of the porous silicon layer results in a decrease of conductivity, which is attributed to reduced conductivity of defect-rich porous silicon.

  16. Top gate ZnO-Al2O3 thin film transistors fabricated using a chemical bath deposition technique

    NASA Astrophysics Data System (ADS)

    Gogoi, Paragjyoti; Saikia, Rajib; Changmai, Sanjib

    2015-04-01

    ZnO thin films were prepared by a simple chemical bath deposition technique using an inorganic solution mixture of ZnCl2 and NH3 on glass substrates and then were used as the active material in thin film transistors (TFTs). The TFTs were fabricated in a top gate coplanar electrode structure with high-k Al2O3 as the gate insulator and Al as the source, drain and gate electrodes. The TFTs were annealed in air at 500 °C for 1 h. The TFTs with a 50 μm channel length exhibited a high field-effect mobility of 0.45 cm2/(V·s) and a low threshold voltage of 1.8 V. The sub-threshold swing and drain current ON-OFF ratio were found to be 0.6 V/dec and 106, respectively.

  17. Atomic layer deposited Al2O3 passivation of type II InAs/GaSb superlattice photodetectors

    NASA Astrophysics Data System (ADS)

    Salihoglu, Omer; Muti, Abdullah; Kutluer, Kutlu; Tansel, Tunay; Turan, Rasit; Kocabas, Coskun; Aydinli, Atilla

    2012-04-01

    Taking advantage of the favorable Gibbs free energies, atomic layer deposited (ALD) aluminum oxide (Al2O3) was used as a novel approach for passivation of type II InAs/GaSb superlattice (SL) midwave infrared (MWIR) single pixel photodetectors in a self cleaning process (λcut-off ˜ 5.1 μm). Al2O3 passivated and unpassivated diodes were compared for their electrical and optical performances. For passivated diodes, the dark current density was improved by an order of magnitude at 77 K. The zero bias responsivity and detectivity was 1.33 A/W and 1.9 × 1013 Jones, respectively at 4 μm and 77 K. Quantum efficiency (QE) was determined as %41 for these detectors. This conformal passivation technique is promising for focal plane array (FPA) applications.

  18. Atomic layer deposition (ALD) of TiO2 and Al2O3 thin films on silicon

    NASA Astrophysics Data System (ADS)

    Mitchell, David R. G.; Triani, Gerry; Attard, Darren J.; Finnie, Kim S.; Evans, Peter J.; Barbe, Christophe J.; Bartlett, John R.

    2004-04-01

    The essential features of the ALD process involve sequentially saturating a surface with a (sub)monolayer of reactive species, such as a metal halide, then reacting it with a second species to form the required phase in-situ. Repetition of the reaction sequence allows the desired thickness to be deposited. The self-limiting nature of the reactions ensures excellent conformality, and sequential processing results in exquisite control over film thickness, albeit at rather slow deposition rates, typically <200nm/hr. We have been developing our capability with ALD deposition, to understand the influence of deposition parameters on the nature of TiO2 and Al2O3 films (high and low refractive index respectively), and multilayer stacks thereof. These stacks have potential applications as anti-reflection coatings and optical filters. This paper will explore the evolution of structure in our films as a function of deposition parameters including temperature and substrate surface chemistry. A broad range of techniques have been applied to the study of these films, including cross sectional transmission electron microscopy, spectroscopic ellipsometry, secondary ion mass spectrometry etc. These have enabled a wealth of microstructural and compositional information on the films to be acquired, such as accurate film thickness, composition, crystallization sequence and orientation with respect to the substrate. The ALD method is shown to produce single layer films and multilayer stacks with exceptional uniformity and flatness, and in the case of stacks, chemically abrupt interfaces. We are currently extending this technology to the coating of polymeric substrates.

  19. Hard α-Al2O3 Film Coating on Industrial Roller Using Aerosol Deposition Method

    NASA Astrophysics Data System (ADS)

    Seto, Naoki; Endo, Kazuteru; Sakamoto, Nobuo; Hirose, Shingo; Akedo, Jun

    2014-12-01

    It is well known that α-Al2O3 forms very hard, highly insulating, smooth films. There is demand for the use of such films instead of conventional hard, smooth films; For example, industrial rollers such as calendering rollers etc. are always required to have a harder and smoother surface than conventional rollers. Therefore, this work investigated the specification of α-Al2O3 films, e.g., their wear resistance and chemical stability, using various tests. This paper also discusses whether α-Al2O3 film can take the place of Cr plating film as a hard, smooth film by comparing their wear resistance and chemical stability.

  20. Identification and spatial distribution of light-toned deposits enriched in Al-phyllosilicates on the plateaus around Valles Marineris, Mars

    NASA Astrophysics Data System (ADS)

    Le Deit, L.; Flahaut, J.; Quantin, C.; Allemand, P.

    2009-12-01

    The plateaus around Valles Marineris consist in series of mafic rocks suggested to be flood basalts (McEwen et al., 1998), lavas interbedded with sediments (Malin and Edgett, 2000), layered intrusive rocks (Williams et al., 2003), or lava flows dated from the Noachian to the late Hesperian epochs (Scott and Carr, 1978). Recent studies show the occurrence of light layered deposits of hundred meters thick cropping out on plateaus near Ius Chasma, Melas Chasma, Candor Chasma, Juventae Chasma and Ganges Chasma deposited during the Hesperian epoch by fluvio-lacustrine processes (Weitz et al., 2009), or by air-fall processes (Le Deit et al., 2009). These layered deposits are enriched in hydrated minerals including opaline silica (Milliken et al., 2008), hydroxylated ferric sulfates (Bishop et al., 2009), and possibly Al-rich phyllosilicates (Le Deit et al., 2009). We identified another type of formation corresponding to light-toned massive deposits cropping out around Valles Marineris. It appears that these light-toned deposits are associated to bright, rough, and highly cratered terrains, located beneath a dark and thin capping unit. Previous studies report the occurrence of phyllosilicates on few locations around Valles Marineris based on OMEGA data analyses (Gondet et al., 2007; Carter et al., 2009). The analysis of CRISM data show that the light-toned deposits are associated with spectra displaying absorption bands at 1.4 μm, 1.9 μm, and a narrow band at 2.2 μm. These spectral characteristics are consistent with the presence of Al-rich phyllosilicates such as montmorillonite, or illite in the light-toned deposits. They constitute dozens of outcrops located on the plateaus south and east of Coprates Chasma and Capri Chasma, and west of Ganges Chasma. All outcrops investigated so far are present over Noachian terrains mapped as the unit Npl2 by Scott and Tanaka (1986), and Witbeck et al. (1991). These light-toned deposits could result from in situ aqueous alteration

  1. Bioactivity of fluorapatite/alumina composite coatings deposited on Ti6Al4V substrates by laser cladding

    NASA Astrophysics Data System (ADS)

    Chien, C. S.; Liu, C. W.; Kuo, T. Y.; Wu, C. C.; Hong, T. F.

    2016-04-01

    Hydroxyapatite (HA) is one of the most commonly used coating materials for metal implants. However, following high-temperature deposition, HA easily decomposes into an unstable phase or forms an amorphous phase, and hence, the long-term stability of the implant is reduced. Accordingly, the present study investigates the use of fluorapatite (FA) fortified with 20 wt% alumina (α-Al2O3) as an alternative biomedical coating material. The coatings are deposited on Ti6Al4V substrates using a Nd:YAG laser cladding process performed with laser powers and travel speeds of 400 W/200 mm/min, 800 W/400 mm/min and 1200 W/600 mm/min, respectively. The results show that for all of the specimens, a strong metallurgical bond is formed at the interface between the coating layer and the transition layer due to melting and diffusion. The XRD analysis results reveal that the cladding layers in all of the specimens consist mainly of FA, β-TCP, CaF2, Ti and θ-Al2O3 phases. In addition, the cladding layers of the specimens prepared using laser powers of 400 and 800 W also contain CaTiO3 and CaAl2O4, while that of the specimen clad using a power of 1200 W contains TTCP and CaO. Following immersion in simulated body fluid for 14 days, all of the specimens precipitate dense bone-like apatite and exhibit excellent bioactivity. However, among all of the specimens, the specimen that is prepared with a laser power of 800 W shows the best biological activity due to the presence of residual FA, apatite-generating CaTiO3 and a rough cladding layer surface.

  2. When amyloids become prions.

    PubMed

    Sabate, Raimon

    2014-01-01

    The conformational diseases, linked to protein aggregation into amyloid conformations, range from non-infectious neurodegenerative disorders, such as Alzheimer disease (AD), to highly infectious ones, such as human transmissible spongiform encephalopathies (TSEs). They are commonly known as prion diseases. However, since all amyloids could be considered prions (from those involved in cell-to-cell transmission to those responsible for real neuronal invasion), it is necessary to find an underlying cause of the different capacity to infect that each of the proteins prone to form amyloids has. As proposed here, both the intrinsic cytotoxicity and the number of nuclei of aggregation per cell could be key factors in this transmission capacity of each amyloid.

  3. When amyloids become prions

    PubMed Central

    Sabate, Raimon

    2014-01-01

    The conformational diseases, linked to protein aggregation into amyloid conformations, range from non-infectious neurodegenerative disorders, such as Alzheimer's disease (AD), to highly infectious ones, such as human transmissible spongiform encephalopathies (TSEs). They are commonly known as prion diseases. However, since all amyloids could be considered prions (from those involved in cell-to-cell transmission to those responsible for real neuronal invasion), it is necessary to find an underlying cause of the different capacity to infect that each of the proteins prone to form amyloids has. As proposed here, both the intrinsic cytotoxicity and the number of nuclei of aggregation per cell could be key factors in this transmission capacity of each amyloid. PMID:24831240

  4. Growth and characterisation of NiAl and N-doped NiAl films deposited by closed field unbalanced magnetron sputtering ion plating using elemental ni and Al targets.

    PubMed

    Said, R; Ahmed, W; Abuain, T; Abuazza, A; Gracio, J

    2010-04-01

    Closed Field Unbalanced Magnetron Sputtering Ion Plating (CFUBMSIP) has been used to deposit undoped and nitrogen doped NiAI thin films onto glass and stainless steel 316 substrates. These films have potential applications in tribological, electronic media and thermal barrier coatings. The surface characteristics, composition, mechanical and structural properties have been investigated using stylus profilometry, X-ray diffraction (XRD), Energy dispersive spectroscopy (EDAX), Atomic force microscopy (AFM) and nanoindentation. The average thickness of the films was approximately 1 microm. The X-ray diffraction spectra revealed the presence of the beta NiAl phase. The EDAX results revealed that all of the undoped and nitrogen doped NiAl thin films exhibited the near equiatomic NiAl composition with the best results being achieved using 300 Watts DC power for Ni and 400 Watts DC power for Al targets respectively. AFM results of both types of films deposited on glass samples exhibited a surface roughness of less than 100 nm. The nanoindenter results for coatings on glass substrates displayed hardness and elastic modulus of 7.7 GPa and 100 GPa respectively. The hardest coatings obtained were obtained at 10% of nitrogen.

  5. Adjustment of threshold voltage in AlN/AlGaN/GaN high-electron mobility transistors by plasma oxidation and Al{sub 2}O{sub 3} atomic layer deposition overgrowth

    SciTech Connect

    Gregušová, D. Jurkovič, M.; Haščík, Š.; Blaho, M.; Seifertová, A.; Fedor, J.; Ťapajna, M.; Fröhlich, K.; Kuzmik, J.; Vogrinčič, P.; Liday, J.; Derluyn, J.; Germain, M.

    2014-01-06

    We discuss possibilities of adjustment of a threshold voltage V{sub T} in normally off GaN high-electron mobility transistors (HEMTs) without compromising a maximal drain current I{sub DSmax}. Techniques of a low power plasma or thermal oxidation of 2-nm thick AlN cap over 3-nm thick AlGaN barrier are developed and calibrated for a thorough oxidation of the cap with a minimal density of surface donors at the inherent oxide-semiconductor interface. It has been shown that while a thermal oxidation technique leads to the channel and/or interface degradation, low density of surface donors and scalability of V{sub T} with additionally overgrown Al{sub 2}O{sub 3} may be obtained for plasma oxidized HEMTs. With 10-nm thick Al{sub 2}O{sub 3} deposited at 100 °C by atomic-layer deposition, we obtained V{sub T} of 1.6 V and I{sub DSmax} of 0.48 A/mm at a gate voltage of V{sub GS} = 8 V. Density of surface donors was estimated to be about 1.2 × 10{sup 13} cm{sup −2}, leaving most of the negative polarization charge at the semiconductor surface uncompensated. Further reduction of surface donors may be needed for even higher V{sub T}.

  6. Impact of spillover from white matter by partial volume effect on quantification of amyloid deposition with [(11)C]PiB PET.

    PubMed

    Matsubara, Keisuke; Ibaraki, Masanobu; Shimada, Hitoshi; Ikoma, Yoko; Suhara, Tetsuya; Kinoshita, Toshibumi; Itco, Hiroshi

    2016-12-01

    High non-specific uptake of [(11)C]Pittsburgh compound B ([(11)C]PiB) in white matter and signal spillover from white matter, due to partial volume effects, confound radioactivity measured in positron emission tomography (PET) with [(11)C]PiB. We aimed to reveal the partial volume effect in absolute values of kinetic parameters for [(11)C]PiB, in terms of spillover from white matter. Dynamic data acquired in [(11)C]PiB PET scans with five healthy volunteers and eight patients with Alzheimer's disease were corrected with region-based and voxel-based partial volume corrections. Binding potential (BPND) was estimated using the two-tissue compartment model analysis with a plasma input function. Partial volume corrections significantly decreased cortical BPND values. The degree of decrease in healthy volunteers (-52.7±5.8%) was larger than that in Alzheimer's disease patients (-11.9±4.2%). The simulation demonstrated that white matter spillover signals due to the partial volume effect resulted in an overestimation of cortical BPND, with a greater degree of overestimation for lower BPND values. Thus, an overestimation due to partial volume effects is more severe in healthy volunteers than in Alzheimer's disease patients. Partial volume corrections may be useful for accurately quantifying Aβ deposition in cortical regions.

  7. Effects of Annealing Ambient on the Characteristics of LaAlO3 Films Grown by Atomic Layer Deposition.

    PubMed

    Zhao, Lu; Liu, Hong-Xia; Wang, Xing; Fei, Chen-Xi; Feng, Xing-Yao; Wang, Yong-Te

    2017-12-01

    We investigated the effects of different annealing ambients on the physical and electrical properties of LaAlO3 films grown by atomic layer deposition. Post-grown rapid thermal annealing (RTA) was carried out at 600 °C for 1 min in vacuum, N2, and O2, respectively. It was found that the chemical bonding states at the interfacial layers (ILs) between LaAlO3 films and Si substrate were affected by the different annealing ambients. The formation of IL was enhanced during the RTA process, resulting in the decrease of accumulation capacitance, especially in O2 ambient. Furthermore, based on the capacitance-voltage characteristics of LaAlO3/Si MIS capacitors, positive V FB shifting tendency could be observed, indicating the decrease of positive oxide charges. Meanwhile, both trapped charge density and interface trap density showed decreased trends after annealing treatments. In addition, RTA process in various gaseous ambients can reduce the gate leakage current due to the enhancement of valence band offset and the reduction of defects in the LaAlO3/Si structure in varying degrees.

  8. Determination of fracture toughness of calcium phosphate coatings deposited onto Ti6Al4V substrate by using indentation technique

    NASA Astrophysics Data System (ADS)

    Aydin, Ibrahim; Cetinel, Hakan; Pasinli, Ahmet

    2012-09-01

    In this study, fracture toughness values of calcium phosphate (CaP) coatings deposited onto Ti6Al4V substrate were determined by using Vickers indentation method. In this new patent holding method, the activation processes were performed with NaOH and NaOH+H2O2 on the Ti6Al4V material surface. Thicknesses of CaP coatings were measured from cross-sections of the samples by using optical microscopy. Vickers indentation tests were performed by using microhardness tester. Young's modulus values of the coatings were determined by using ultra microhardness tester. As a result, fracture toughness (K1C) values of the CaP coatings produced by using two different activation processes, were calculated by using experimental study results. These were found to be 0.43 MPa m1/2 and 0.39 MPa m1/2, respectively. It was determined that the CaP coating on Ti6Al4V activated by NaOH+H2O2 had higher fracture toughness than the CaP coating on Ti6Al4V activated by NaOH.

  9. Effects of Annealing Ambient on the Characteristics of LaAlO3 Films Grown by Atomic Layer Deposition

    NASA Astrophysics Data System (ADS)

    Zhao, Lu; Liu, Hong-xia; Wang, Xing; Fei, Chen-xi; Feng, Xing-yao; Wang, Yong-te

    2017-02-01

    We investigated the effects of different annealing ambients on the physical and electrical properties of LaAlO3 films grown by atomic layer deposition. Post-grown rapid thermal annealing (RTA) was carried out at 600 °C for 1 min in vacuum, N2, and O2, respectively. It was found that the chemical bonding states at the interfacial layers (ILs) between LaAlO3 films and Si substrate were affected by the different annealing ambients. The formation of IL was enhanced during the RTA process, resulting in the decrease of accumulation capacitance, especially in O2 ambient. Furthermore, based on the capacitance-voltage characteristics of LaAlO3/Si MIS capacitors, positive V FB shifting tendency could be observed, indicating the decrease of positive oxide charges. Meanwhile, both trapped charge density and interface trap density showed decreased trends after annealing treatments. In addition, RTA process in various gaseous ambients can reduce the gate leakage current due to the enhancement of valence band offset and the reduction of defects in the LaAlO3/Si structure in varying degrees.

  10. Tumoral Presentation of Homonymous Hemianopia and Prosopagnosia in Cerebral Amyloid Angiopathy-Related Inflammation.

    PubMed

    Hainline, Clotilde; Rucker, Janet C; Zagzag, David; Golfinos, John G; Lui, Yvonne W; Liechty, Benjamin; Warren, Floyd A; Balcer, Laura J; Galetta, Steven L

    2017-03-01

    While cerebral amyloid angiopathy is a common cause of lobar hemorrhage, rarely it may be associated with an inflammatory response, thought to be incited by amyloid deposits. We report a 73-year-old woman with an extensive cancer history who presented with tumor-like lesions and symptoms of homonymous hemianopia and prosopagnosia. Found to have cerebral amyloid angiopathy-related inflammation proven by brain biopsy, she was treated successfully with immunosuppression.

  11. Temperature dependence of the crystalline quality of AlN layer grown on sapphire substrates by metalorganic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Li, Xiao-Hang; Wei, Yong O.; Wang, Shuo; Xie, Hongen; Kao, Tsung-Ting; Satter, Md. Mahbub; Shen, Shyh-Chiang; Douglas Yoder, P.; Detchprohm, Theeradetch; Dupuis, Russell D.; Fischer, Alec M.; Ponce, Fernando A.

    2015-03-01

    We studied temperature dependence of crystalline quality of AlN layers at 1050-1250 °C with a fine increment step of around 18 °C. The AlN layers were grown on c-plane sapphire substrates by metalorganic chemical vapor deposition (MOCVD) and characterized by X-ray diffraction (XRD) ω-scans and atomic force microscopy (AFM). At 1050-1068 °C, the templates exhibited poor quality with surface pits and higher XRD (002) and (102) full-width at half-maximum (FWHM) because of insufficient Al atom mobility. At 1086 °C, the surface became smooth suggesting sufficient Al atom mobility. Above 1086 °C, the (102) FWHM and thus edge dislocation density increased with temperatures which may be attributed to the shorter growth mode transition from three-dimension (3D) to two-dimension (2D). Above 1212 °C, surface macro-steps were formed due to the longer diffusion length of Al atoms than the expected step terrace width. The edge dislocation density increased rapidly above 1212 °C, indicating this temperature may be a threshold above which the impact of the transition from 3D to 2D is more significant. The (002) FWHM and thus screw dislocation density were insensitive to the temperature change. This study suggests that high-quality AlN/sapphire templates may be potentially achieved at temperatures as low as 1086 °C which is accessible by most of the III-nitride MOCVD systems.

  12. Deposition and Characterization of Al:ZnO Thin Films for Optoelectronic Applications

    NASA Astrophysics Data System (ADS)

    Pandey, R. K.; Mishra, Swati; Bajpai, P. K.

    2016-11-01

    Transparent aluminum-doped zinc oxide (Al:ZnO) thin films have been successfully synthesized on silicon substrates at room temperature using a sol-gel spin-coating method. The structural and optical properties and surface morphology of the synthesized films were characterized using x-ray diffraction (XRD) analysis, ultraviolet-visible (UV-Vis) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, micro-Raman spectroscopy, and atomic force microscopy (AFM). The prepared Al:ZnO retained the hexagonal wurtzite structure of ZnO. FTIR and Raman spectra clearly revealed a major peak at 437 cm-1, associated with the ZnO bond. UV-Vis spectra showed that the Al:ZnO films were transparent from the near-ultraviolet to near-infrared region. The effect of film thickness on the physical and optical properties of the Al:ZnO thin films for 2.0 at.% aluminum concentration was investigated. Measurements revealed that the film transparency, optical energy bandgap, Urbach energy, extinction coefficient, and porosity varied with the film thickness. The energy bandgap values for the prepared thin films increased in the range of 3.18 eV to 3.2 eV with increasing film thickness.

  13. Formation and Yield of Multi-Walled Carbon Nanotubes Synthesized via Chemical Vapour Deposition Routes Using Different Metal-Based Catalysts of FeCoNiAl, CoNiAl and FeNiAl-LDH

    PubMed Central

    Hussein, Mohd Zobir; Mohamad Jaafar, Adila; Hj. Yahaya, Asmah; Masarudin, Mas Jaffri; Zainal, Zulkarnain

    2014-01-01

    Multi-walled carbon nanotubes (MWCNTs) were prepared via chemical vapor deposition (CVD) using a series of different catalysts, derived from FeCoNiAl, CoNiAl and FeNiAl layered double hydroxides (LDHs). Catalyst-active particles were obtained by calcination of LDHs at 800 °C for 5 h. Nitrogen and hexane were used as the carrier gas and carbon source respectively, for preparation of MWCNTs using CVD methods at 800 °C. MWCNTs were allowed to grow for 30 min on the catalyst spread on an alumina boat in a quartz tube. The materials were subsequently characterized through X-ray diffraction, Fourier transform infrared spectroscopy, surface area analysis, field emission scanning electron microscopy and transmission electron microscopy. It was determined that size and yield of MWCNTs varied depending on the type of LDH catalyst precursor that is used during synthesis. MWCNTs obtained using CoNiAl-LDH as the catalyst precursor showed smaller diameter and higher yield compared to FeCoNiAl and FeNiAl LDHs. PMID:25380526

  14. Potential petroleum source rock deposition in the middle Cretaceous Wasia Formation, Rub'Al Khali, Saudi Arabia

    SciTech Connect

    Newell, K.D.; Hennington, R.D.

    1983-03-01

    Stratigraphic correlation and regional geochemical sampling in the Rub'Al Khali (The Empty Quarter) of Saudi Arabia indicate at least two potential petroleum source rock units occur in the middle Cretaceous Wasia Formation. These two sequences, informally named the Safaniya ''source rock'' and the lower Mishrif, are dominated by oil-prone amorphous (Type II) organic matter, in places in excess of 10 weight percent organic carbon. Both units are fine-grained pelagic lime mudstones which were probably deposited in relatively quiet anoxic waters of large intraplatform embayments or basins. The Safaniya ''source rock'' and the lower Mishrif reflect strong marine transgressions on the Arabian craton in Albian to Cenomanian and Cenomanian to Turonian time, respectively. Regressive-phase sedimentary rocks overlying these two transgressive organic-rock phases are generally poor in organic carbon despite being deposited, in part, in similar forereef open-marine depositional settings. The sealevel high-stands associated with the Safaniya ''source rock'' and the lower Mishrif are partly synchronous with two recently described ''oceanic anoxic events'' respectively occurring in late Barremian to late Albian time and late Cenomanian to early Turonian time. Although there is a credible time correlation of these organic-rock units with oceanic anoxic events, their connection to oceanic anoxic events could be strengthened if they could be traced out to the vicinity of the middle Cretaceous continental margin.

  15. Electrophoretic deposition and characterization of HA/chitosan nanocomposite coatings on Ti6Al7Nb alloy

    NASA Astrophysics Data System (ADS)

    Moskalewicz, Tomasz; Kot, Marcin; Seuss, Sigrid; Kędzierska, Aleksandra; Czyrska-Filemonowicz, Aleksandra; Boccaccini, Aldo R.

    2015-01-01

    Nano-hydroxyapatite/chitosan (nc-HA/chitosan) composite coatings were produced on two phase (α+β) Ti6Al7Nb titanium alloy substrates by electrophoretic deposition (EPD). The microstructure of the coatings was examined by scanning- and transmission electron microscopy methods as well as by X-ray diffractometry. The coatings, 770 nm-800 nm thick, were uniform, without any cracks or presence of large voids and they exhibited good adhesion to the titanium alloy substrate. The microstructure of the coatings consisted of nc-HA needle-like particles homogeneously embedded in a chitosan matrix. The deposited coatings exhibited good adhesion to the substrate. The best adhesion to the titanium alloy was determined for the coating deposited from suspensions containing 4 g/L of HA at 10 V during 240 s. The results confirm EPD as a convenient method to develop uniform and crack-free nanoscale organic-inorganic composite coatings on two phase titanium alloy substrates with potential application in orthopedic and dental implants.

  16. Field-effect transistors with LaAlO3 and LaAlOxNy gate dielectrics deposited by laser molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Lu, X. B.; Lu, H. B.; Chen, Z. H.; Zhang, X.; Huang, R.; Zhou, H. W.; Wang, X. P.; Nguyen, B. Y.; Wang, C. Z.; Xiang, W. F.; He, M.; Cheng, B. L.

    2004-10-01

    High permittivity LaAlO3 (LAO) and LaAlOxNy (LAON) thin films have been deposited directly on a Si(100) substrate using a laser molecular-beam epitaxy technique. Metal-oxide-silicon field-effect transistors (MOSFETs) are fabricated using such LAO and LAON thin films as gate dielectrics and well-behaved transistor characteristics have been observed. High-resolution transmission electron microscopy observations indicate that LAO thin films can remain amorphous structure even after annealing at 1000°C. The small equivalent oxide thickness (EOT) of 17Å is achieved for 75Å LAO film with an effective dielectric constant of 17.2±1 for the whole gate stack. Furthermore, a smaller EOT, larger drive current, and lower subthreshold slope have been observed for devices with the LAON thin film. For all the devices, the gate leakage currents are at least two orders of magnitude lower than that of the same electrical thickness SiO2. Reasonable subthreshold slopes of 248 and 181mV /dec were obtained for MOSFETs with LAO and LAON films, respectively.

  17. Structural model of quasiperiodic Pb monolayer deposited on fivefold i-Al-Pd-Mn surface

    NASA Astrophysics Data System (ADS)

    Krajčí, M.; Hafner, J.; Ledieu, J.; Fournée, V.

    2010-04-01

    On the basis of analysis of experimental STM images and ab-initio calculations we propose a structural model of the quasiperiodic Pb monolayer grown on the fivefold i-Al-Pd-Mn surface at a coverage close to the saturation. The skeleton of the Pb monolayer can be seen as a network of the "star-fish" (SF) clusters. The atomic structure of the monolayer is based on a decorated P1 tiling. The model can reproduce also the experimentally observed quasiperiodic τ-scaled P1 ordering (τ is the golden mean). The bright spots seen in STM images appear at Pb atoms in the centers of those SF clusters where the substrate has Al atoms at these positions.

  18. Targeting the proper amyloid-beta neuronal toxins: a path forward for Alzheimer’s disease immunotherapeutics

    PubMed Central

    2014-01-01

    Levels of amyloid-beta monomer and deposited amyloid-beta in the Alzheimer’s disease brain are orders of magnitude greater than soluble amyloid-beta oligomer levels. Monomeric amyloid-beta has no known direct toxicity. Insoluble fibrillar amyloid-beta has been proposed to be an in vivo mechanism for removal of soluble amyloid-beta and exhibits relatively low toxicity. In contrast, soluble amyloid-beta oligomers are widely reported to be the most toxic amyloid-beta form, both causing acute synaptotoxicity and inducing neurodegenerative processes. None of the amyloid-beta immunotherapies currently in clinical development selectively target soluble amyloid-beta oligomers, and their lack of efficacy is not unexpected considering their selectivity for monomeric or fibrillar amyloid-beta (or both) rather than soluble amyloid-beta oligomers. Because they exhibit acute, memory-compromising synaptic toxicity and induce chronic neurodegenerative toxicity and because they exist at very low in vivo levels in the Alzheimer’s disease brain, soluble amyloid-beta oligomers constitute an optimal immunotherapeutic target that should be pursued more aggressively. PMID:25045405

  19. Electric and pyroelectric properties of AlN thin films deposited by reactive magnetron sputtering on Si substrate

    NASA Astrophysics Data System (ADS)

    Stan, G. E.; Botea, M.; Boni, G. A.; Pintilie, I.; Pintilie, L.

    2015-10-01

    Electric and pyroelectric properties of AlN layers deposited on Si substrates with different resistivities were investigated. The dielectric constant was found to be around 12, while the conductance determined from dc current measurements was found to be in the 10-9 to 10-10 S range. The pyroelectric measurements were performed in voltage mode using two types of IR sources: a laser diode with 800 nm wavelength and a black body at 700 °C. A peculiar behavior was observed for the signal recorded when the laser diode was used as IR source. It was found that the Si substrate is introducing a signal component, due to the photogenerated carriers, which is adding to the pyroelectric signal generated by the AlN layer. This component is strongly dependent on the resistivity of the Si substrate. For strongly doped Si (Si++) the signal generated into the substrate represents only 10% of the recorded pyroelectric voltage. For electronic grade Si the signal generated into the substrate is about 100 times larger than the pyroelectric signal generated in the AlN layer. This effect can be used as an optical amplification of the pyroelectric signal. The frequency dependence observed for the pyroelectric signal recorded when the black body is used as IR source is typical for a pyroelectric detector. A value as large as 12.4 μC m-2 K-1 was obtained for the pyroelectric coefficient using for estimation the constant signal at low modulation frequencies of the IR beam. However, the value of the pyroelectric coefficient is strongly affected by the electrical conductance of the AlN layer. As the conductance is frequency dependent it results that the value of the pyroelectric coefficient is frequency dependent, the value from above being valid only for very small frequencies of the temperature variation. It was also found that the electric and pyroelectric properties are dependent on the crystalline quality of the AlN layer.

  20. Using bacterial inclusion bodies to screen for amyloid aggregation inhibitors

    PubMed Central

    2012-01-01

    Background The amyloid-β peptide (Aβ42) is the main component of the inter-neuronal amyloid plaques characteristic of Alzheimer's disease (AD). The mechanism by which Aβ42 and other amyloid peptides assemble into insoluble neurotoxic deposits is still not completely understood and multiple factors have been reported to trigger their formation. In particular, the presence of endogenous metal ions has been linked to the pathogenesis of AD and other neurodegenerative disorders. Results Here we describe a rapid and high-throughput screening method to identify molecules able to modulate amyloid aggregation. The approach exploits the inclusion bodies (IBs) formed by Aβ42 when expressed in bacteria. We have shown previously that these aggregates retain amyloid structural and functional properties. In the present work, we demonstrate that their in vitro refolding is selectively sensitive to the presence of aggregation-promoting metal ions, allowing the detection of inhibitors of metal-promoted amyloid aggregation with potential therapeutic interest. Conclusions Because IBs can be produced at high levels and easily purified, the method overcomes one of the main limitations in screens to detect amyloid modulators: the use of expensive and usually highly insoluble synthetic peptides. PMID:22553999

  1. Immunoglobulin light chains, glycosaminoglycans and amyloid.

    SciTech Connect

    Stevens, F. J.; Kisilevsky, R.; Biosciences Division; Queen's Univ.

    2000-03-01

    Immunoglobulin light chains are the precursor proteins for fibrils that are formed during primary amyloidosis and in amyloidosis associated with multiple myeloma. As found for the approximately 20 currently described forms of focal, localized, or systemic amyloidoses, light chain-related fibrils extracted from physiological deposits are invariably associated with glycosaminoglycans, predominantly heparan sulfate. Other amyloid-related proteins are either structurally normal, such as g2-microglobulin and islet amyloid polypeptide, fragments of normal proteins such as serum amyloid A protein or the precursor protein of the g peptide involved in Alzheimer's disease, or are inherited forms of single amino acid variants of a normal protein such as found in the familial forms of amyloid associated with transthyretin. In contrast, the primary structures of light chains involved in fibril formation exhibit extensive mutational diversity rendering some proteins highly amyloidogenic and others non-pathological. The interactions between light chains and glycosaminoglycans are also affected by amino acid variation and may influence the clinical course of disease by enhancing fibril stability and contributing to resistance to protease degradation. Relatively little is currently known about the mechanisms by which glycosaminoglycans interact with light chains and light-chain fibrils. It is probable that future studies of this uniquely diverse family of proteins will continue o shed light on the processes of amyloidosis, and contribute as well to a greater understanding of the normal physiological roles of glycosaminoglycans.

  2. Brain amyloid and cognition in Lewy body diseases.

    PubMed

    Gomperts, Stephen N; Locascio, Joseph J; Marquie, Marta; Santarlasci, Andrea L; Rentz, Dorene M; Maye, Jacqueline; Johnson, Keith A; Growdon, John H

    2012-07-01

    Many patients with PD develop PD with dementia (PDD), a syndrome that overlaps clinically and pathologically with dementia with Lewy bodies (DLB); PDD and DLB differ chiefly in the relative timing of dementia and parkinsonism. Brain amyloid deposition is an early feature of DLB and may account, in part, for its early dementia. We sought to confirm this hypothesis and also to determine whether amyloid accumulation contributes to cognitive impairment and dementia in the broad range of parkinsonian diseases. Twenty-nine cognitively healthy PD, 14 PD subjects with mild cognitive impairment (PD-MCI), 18 with DLB, 12 with PDD, and 85 healthy control subjects (HCS) underwent standardized neurologic and neuropsychological examinations and Pittsburgh compound B (PiB) imaging with PET. Apolipoprotein E (ApoE) genotypes were obtained in many patients. PiB retention was expressed as the distribution volume ratio using a cerebellar tissue reference. PiB retention was significantly higher in DLB than in any of the other diagnostic groups. PiB retention did not differ across PDD, PD-MCI, PD, and HCS. Amyloid burden increased with age and with the presence of the ApoE ε4 allele in all patient groups. Only in the DLB group was amyloid deposition associated with impaired cognition. DLB subjects have higher amyloid burden than subjects with PDD, PD-MCI, PD, or HCS; amyloid deposits are linked to cognitive impairment only in DLB. Early amyloid deposits in DLB relative to PDD may account for their difference in the timing of dementia and parkinsonism.

  3. Doxycycline reduces fibril formation in a transgenic mouse model of AL amyloidosis

    PubMed Central

    Ward, Jennifer Ellis; Ren, Ruiyi; Toraldo, Gianluca; SooHoo, Pam; Guan, Jian; O'Hara, Carl; Jasuja, Ravi; Trinkaus-Randall, Vickery; Liao, Ronglih; Connors, Lawreen H.

    2011-01-01

    Systemic AL amyloidosis results from the aggregation of an amyloidogenic immunoglobulin (Ig) light chain (LC) usually produced by a plasma cell clone in the bone marrow. AL is the most rapidly fatal of the systemic amyloidoses, as amyloid fibrils can rapidly accumulate in tissues including the heart, kidneys, autonomic or peripheral nervous systems, gastrointestinal tract, and liver. Chemotherapy is used to eradicate the cellular source of the amyloidogenic precursor. Currently, there are no therapies that target the process of LC aggregation, fibril formation, or organ damage. We developed transgenic mice expressing an amyloidogenic λ6 LC using the cytomegalovirus (CMV) promoter to circumvent the disruption of B cell development by premature expression of recombined LC. The CMV-λ6 transgenic mice develop neurologic dysfunction and Congophilic amyloid deposits in the stomach. Amyloid deposition was inhibited in vivo by the antibiotic doxycycline. In vitro studies demonstrated that doxycycline directly disrupted the formation of recombinant LC fibrils. Furthermore, treatment of ex vivo LC amyloid fibrils with doxycycline reduced the number of intact fibrils and led to the formation of large disordered aggregates. The CMV-λ6 transgenic model replicates the process of AL amyloidosis and is useful for testing the antifibril potential of orally available agents. PMID:21998211

  4. Deposition of LaMO3 (M=Ni,Co,Cr,Al)-Oriented Films by Spray Combustion Flame Technique

    NASA Astrophysics Data System (ADS)

    Ichinose, Hiromichi; Shiwa, Yuzo; Nagano, Masamitsu

    1994-10-01

    LaMO3 (M=Ni,Co,Cr,Al) films were prepared on sintered alumina, sapphire (001) and MgO(100) at 500 900°C by spraying ultrasonically atomized aqueous solutions of nitrates into a combustion flame (spray combustion flame technique). LaNiO3 and LaCoO3 on MgO(100) crystallized in high-temperature phases (cubic) while LaCrO3 and LaAlO3 crystallized in room-temperature phases. LaMO3 (M=Ni,Co,Cr,Al) films on MgO(100) were highly oriented to (100), (100), (001) and (100), respectively, while the films on sintered alumina and sapphire were not. The electric resistivities of the dense LaMO3 (M=Ni,Co,Cr) films were as low as those of bulk ceramics. LaNiO3 film deposited on MgO above 700°C showed the lowest resistivity of about 6×10-6 Ω m. It was suggested that the reactivities of the constituent metal atoms with OH in the flame are associated with the preferred phase and the morphology of the films.

  5. Low substrate temperature deposition of transparent and conducting ZnO:Al thin films by RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Waykar, Ravindra; Amit, Pawbake; Kulkarni, Rupali; Jadhavar, Ashok; Funde, Adinath; Waman, Vaishali; Dewan, Rupesh; Pathan, Habib; Jadkar, Sandesh

    2016-04-01

    Transparent and conducting Al-doped ZnO (ZnO:Al) films were prepared on glass substrate using the RF sputtering method at different substrate temperatures from room temperature (RT) to 200 °C. The structural, morphological, electrical and optical properties of these films were investigated using a variety of characterization techniques such as low angle XRD, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), Hall measurement and UV-visible spectroscopy. The electrical properties showed that films deposited at RT have the lowest resistivity and it increases with an increase in the substrate temperature whereas carrier mobility and concentration decrease with an increase in substrate temperature. Low angle XRD and Raman spectroscopy analysis reavealed that films are highly crystalline with a hexagonal wurtzite structure and a preferred orientation along the c-axis. The FE-SEM analysis showed that the surface morphology of films is strongly dependent on the substrate temperature. The band gap decreases from 3.36 to 3.29 eV as the substrate temperature is increased from RT to 200 °C. The fundamental absorption edge in the UV region shifts towards a longer wavelength with an increase in substrate temperature and be attributed to the Burstein-Moss shift. The synthesized films showed an average transmission (> 85%) in the visible region, which signifies that synthesized ZnO:Al films can be suitable for display devices and solar cells as transparent electrodes.

  6. Amyloid fibril protein nomenclature: 2012 recommendations from the Nomenclature Committee of the International Society of Amyloidosis.

    PubMed

    Sipe, Jean D; Benson, Merrill D; Buxbaum, Joel N; Ikeda, Shu-ichi; Merlini, Giampaolo; Saraiva, Maria J M; Westermark, Per

    2012-12-01

    The Nomenclature Committee of the International Society of Amyloidosis (ISA) met during the XIIIth International Symposium, May 6-10, 2012, Groningen, The Netherlands, to formulate recommendations on amyloid fibril protein nomenclature and to consider newly identified candidate amyloid fibril proteins for inclusion in the ISA Amyloid Fibril Protein Nomenclature List. The need to promote utilization of consistent and up to date terminology for both fibril chemistry and clinical classification of the resultant disease syndrome was emphasized. Amyloid fibril nomenclature is based on the chemical identity of the amyloid fibril forming protein; clinical classification of the amyloidosis should be as well. Although the importance of fibril chemistry to the disease process has been recognized for more than 40 years, to this day the literature contains clinical and histochemical designations that were used when the chemical diversity of amyloid diseases was poorly understood. Thus, the continued use of disease classifications such as familial amyloid neuropathy and familial amyloid cardiomyopathy generates confusion. An amyloid fibril protein is defined as follows: the protein must occur in body tissue deposits and exhibit both affinity for Congo red and green birefringence when Congo red stained deposits are viewed by polarization microscopy. Furthermore, the chemical identity of the protein must have been unambiguously characterized by protein sequence analysis when so is practically possible. Thus, in nearly all cases, it is insufficient to demonstrate mutation in the gene of a candidate amyloid protein; the protein itself must be identified as an amyloid fibril protein. Current ISA Amyloid Fibril Protein Nomenclature Lists of 30 human and 10 animal fibril proteins are provided together with a list of inclusion bodies that, although intracellular, exhibit some or all of the properties of the mainly extracellular amyloid fibrils.

  7. Hydrogen and Carbon Effects on Al2O3 Surface Phases and Metal Deposition

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Gang; Smith, John

    2005-03-01

    Effects of H and C impurities on α-Al2O3 (0001) surface stability and metal wetting behavior are determined from first principles[1]. The ab initio surface phase diagram for H and C on the alumina surface reveals six distinct surface phases. These different surface phases exhibit a variety of adhesion strengths with Cu and Co, and correspondingly different wetting behaviors. These results are consistent with the varied wetting characteristics observed experimentally. [1] Xiao-Gang Wang and John R. Smith, Phys. Rev. B70, Rapid communications, 081401 (2004).

  8. Control of texture during vapor deposition of Al on (111) Si

    SciTech Connect

    Thangaraj, N.; Westmacott, K.H.; Dahmen, U.; Reyes-Gasga, J.

    1991-04-01

    The growth of Al on (111) Si single crystal substrates by various techniques usually leads to films with (111) texture, sometimes with a small (100) component. Using X-ray diffraction and electron microscopy, the present study shows that the (100) texture component can be enhanced to the point of forming an oriented (100) continuous tricrystal structure. The formation of this texture is shown to be related the presence of Cu. It is concluded that an understanding of heteroepitaxy must take into account the effect of chemistry in addition to the crystallographic criteria of lattice matching.

  9. Application of spectral ellipsometry to in situ diagnostics of atomic layer deposition of dielectrics on silicon and AlGaN

    NASA Astrophysics Data System (ADS)

    Clemente, Iosif E.; Miakonkikh, Andrey V.

    2016-12-01

    Atomic layer deposition (ALD) of Al2O3 on Si and AlGaN substrates was studied in situ by means of spectral ellipsometry. Method was used for optimization of process of atomic layer deposition. Optical model takes into account all layers of transparent structure typical for gallium nitride devices Al2O3/AlGaN/AlN/GaN. Developed model is able to measure in situ temperature of wafer before the process and its change during the deposition which is critical for development of new process and understanding of chemical reactions. Difference in temperature between chuck and sample were calculated. Spectral ellipsometry was used to determine initial nucleation lag of film growth which is different on silicon and AlGaN surface and chemical transient during the first steps of deposition. Removal of native oxide in AlGaN structures could play key role in observed effects of passivation GaN transistor structures by alumina.

  10. Alzheimer's Disease and the Amyloid Cascade Hypothesis: A Critical Review

    PubMed Central

    Reitz, Christiane

    2012-01-01

    Since 1992, the amyloid cascade hypothesis has played the prominent role in explaining the etiology and pathogenesis of Alzheimer's disease (AD). It proposes that the deposition of β-amyloid (Aβ) is the initial pathological event in AD leading to the formation of senile plaques (SPs) and then to neurofibrillary tangles (NFTs), neuronal cell death, and ultimately dementia. While there is substantial evidence supporting the hypothesis, there are also limitations: (1) SP and NFT may develop independently, and (2) SPs and NFTs may be the products rather than the causes of neurodegeneration in AD. In addition, randomized clinical trials that tested drugs or antibodies targeting components of the amyloid pathway have been inconclusive. This paper provides a critical overview of the evidence for and against the amyloid cascade hypothesis in AD and provides suggestions for future directions. PMID:22506132

  11. Amyloid A amyloidosis secondary to rheumatoid arthritis: pathophysiology and treatments.

    PubMed

    Nakamura, Tadashi

    2011-01-01

    The introduction of biological therapies targeting specific inflammatory mediators revolutionised the treatment of rheumatoid arthritis (RA). Targeting key components of the immune system allows efficient suppression of the pathological inflammatory cascade that leads to RA symptoms and subsequent joint destruction. Reactive amyloid A (AA) amyloidosis, one of the most severe complications of RA, is a serious, potentially life-threatening disorder caused by deposition of AA amyloid fibrils in multiple organs. These AA amyloid fibrils derive from the circulatory acute-phase reactant serum amyloid A protein (SAA), and may be controlled by treatment. New biologics may permit AA amyloidosis secondary to RA to become a treatable, manageable disease. Rheumatologists, when diagnosing and treating patients with AA amyloidosis secondary to RA, must understand the pathophysiology and clinical factors related to development and progression of the disease, including genetic predisposition and biological versatility of SAA.

  12. Characteristics of AZO thin films prepared at various Al target input current deposited on PET substrate

    NASA Astrophysics Data System (ADS)

    Kim, Yun-Hae; Park, Chang-Wook; Lee, Jin-Woo; Lee, Dong Myung

    2015-03-01

    Transparent conductive oxide is a thin film to be used in numerous applications throughout the industry in general. Transparent electrode materials used in these industries are in need of light transmittance with excellent high and low electrical characteristics, substances showing the most excellent physical properties while satisfying all the characteristics such as indium tin oxide film. However, reserves of indium are very small, there is an environmental pollution problem. So the study of zinc oxide (ZnO) is actively carried out in an alternative material. This study analyzed the characteristics by using a direct current (DC) magnetron sputtering system. The electric and optical properties of these films were studied by Hall measurement and optical spectroscopy, respectively. When the Al target input current is 2 mA and 4 mA, it demonstrates about 80% transmittance in the range of the visible spectrum. Also, when Al target input current was 6 mA, sheet resistance was the smallest on PET substrate. The minimum resistivity is 3.96×10-3 ohm/sq.

  13. Growth of nanostructured Cu-Al-O film deposited on porous aluminium oxide

    NASA Astrophysics Data System (ADS)

    Park, Y.; Ko, H.; Shim, I.-B.; Kim, C. S.; Kouh, T.

    2010-03-01

    Anodic aluminium oxide has been gaining much attention due to the formation of a highly ordered porous structure, and this self-ordered structure is very appealing as an alternate method for fabricating various nanostructures and devices. On top of this porous aluminium oxide substrate prepared by two-step anodization technique, we have RF-sputtered Cu-Al-O thin films from a single-phase CuAlO 2 target at room temperature. These films show the formation of a highly ordered array of clusters on the nucleation sites provided by the porous substrate with their sizes increasing with film thickness, following the hexagonal pattern underneath. The corresponding surface coverage of the film on the substrate is proportional to the square of film thickness, which can be understood with a simple two-dimensional disk model. Our study suggests that the underlying structure of the anodic aluminium oxide substrate plays a crucial role on the growth of nanostructured thin films and affects the detailed growth mechanism.

  14. Amyloid Beta Mediates Memory Formation

    ERIC Educational Resources Information Center

    Garcia-Osta, Ana; Alberini, Cristina M.

    2009-01-01

    The amyloid precursor protein (APP) undergoes sequential cleavages to generate various polypeptides, including the amyloid [beta] (1-42) peptide (A[beta][1-42]), which is believed to play a major role in amyloid plaque formation in Alzheimer's disease (AD). Here we provide evidence that, in contrast with its pathological role when accumulated,…

  15. Low-Temperature Process for Atomic Layer Chemical Vapor Deposition of an Al2O3 Passivation Layer for Organic Photovoltaic Cells.

    PubMed

    Kim, Hoonbae; Lee, Jihye; Sohn, Sunyoung; Jung, Donggeun

    2016-05-01

    Flexible organic photovoltaic (OPV) cells have drawn extensive attention due to their light weight, cost efficiency, portability, and so on. However, OPV cells degrade quickly due to organic damage by water vapor or oxygen penetration when the devices are driven in the atmosphere without a passivation layer. In order to prevent damage due to water vapor or oxygen permeation into the devices, passivation layers have been introduced through methods such as sputtering, plasma enhanced chemical vapor deposition, and atomic layer chemical vapor deposition (ALCVD). In this work, the structural and chemical properties of Al2O3 films, deposited via ALCVD at relatively low temperatures of 109 degrees C, 200 degrees C, and 300 degrees C, are analyzed. In our experiment, trimethylaluminum (TMA) and H2O were used as precursors for Al2O3 film deposition via ALCVD. All of the Al2O3 films showed very smooth, featureless surfaces without notable defects. However, we found that the plastic flexible substrate of an OPV device passivated with 300 degrees C deposition temperature was partially bended and melted, indicating that passivation layers for OPV cells on plastic flexible substrates need to be formed at temperatures lower than 300 degrees C. The OPV cells on plastic flexible substrates were passivated by the Al2O3 film deposited at the temperature of 109 degrees C. Thereafter, the photovoltaic properties of passivated OPV cells were investigated as a function of exposure time under the atmosphere.

  16. Bimodal substrate biasing to control γ-Al{sub 2}O{sub 3} deposition during reactive magnetron sputtering

    SciTech Connect

    Prenzel, Marina; Kortmann, Annika; Stein, Adrian; Keudell, Achim von; Nahif, Farwah; Schneider, Jochen M.

    2013-09-21

    Al{sub 2}O{sub 3} thin films have been deposited at substrate temperatures between 500 °C and 600 °C by reactive magnetron sputtering using an additional arbitrary substrate bias to tailor the energy distribution of the incident ions. The films were characterized by X-ray diffraction and Fourier transform infrared spectroscopy. The film structure being amorphous, nanocrystalline, or crystalline was correlated with characteristic ion energy distributions. The evolving crystalline structure is connected with different levels of displacements per atom (dpa) in the growing film as being derived from TRIM simulations. The boundary between the formation of crystalline films and amorphous or nanocrystalline films was at 0.8 dpa for a substrate temperature of 500 °C. This threshold shifts to 0.6 dpa for films grown at 550 °C.

  17. Effect of concurrent joule heat and charge trapping on RESET for NbAlO fabricated by atomic layer deposition

    PubMed Central

    2013-01-01

    The RESET process of NbAlO-based resistive switching memory devices fabricated by atomic layer deposition is investigated at low temperatures from 80 to 200 K. We observed that the conduction mechanism of high resistance state changed from hopping conduction to Frenkel-Poole conduction with elevated temperature. It is found that the conductive filament rupture in RRAM RESET process can be attributed not only to the Joule heat generated by internal current flow through a filament but also to the charge trap/detrapping effect. The RESET current decreases upon heating. Meanwhile, the energy consumption also decreases exponentially. This phenomenon indicates the temperature-related charge trap/detrapping process which contributes to the RESET besides direct Joule heat. PMID:23421401

  18. Effect of concurrent joule heat and charge trapping on RESET for NbAlO fabricated by atomic layer deposition.

    PubMed

    Zhou, Peng; Ye, Li; Sun, Qing Qing; Wang, Peng Fei; Jiang, An Quan; Ding, Shi Jin; Zhang, David Wei

    2013-02-19

    The RESET process of NbAlO-based resistive switching memory devices fabricated by atomic layer deposition is investigated at low temperatures from 80 to 200 K. We observed that the conduction mechanism of high resistance state changed from hopping conduction to Frenkel-Poole conduction with elevated temperature. It is found that the conductive filament rupture in RRAM RESET process can be attributed not only to the Joule heat generated by internal current flow through a filament but also to the charge trap/detrapping effect. The RESET current decreases upon heating. Meanwhile, the energy consumption also decreases exponentially. This phenomenon indicates the temperature-related charge trap/detrapping process which contributes to the RESET besides direct Joule heat.

  19. Effect of pH on mechanical, physical and tribological properties of electroless Ni-P-Al2O3 composite deposits for marine applications

    NASA Astrophysics Data System (ADS)

    Julka, Sahil; Ansari, Mohd Imran; Thakur, Dineshsingh G.

    2016-12-01

    Successful co-deposition of fine particulate matter within an Electroless Nickel-Phosphorous (ENi-P) matrix is dependent on various factors like bath composition, particle compatibility with metallic matrix, bath reactivity (pH), particle size and their distribution. ENi-P deposits incorporating Al2O3/Alumina in a disperse phase have varied effects on properties and attributes like surface roughness ( Ra), microhardness, wear resistance, corrosion resistance and surface morphology of the deposits obtained. This paper experimentally investigates the effect of alumina (1.55 g/L) on Ra, microhardness, surface morphology, deposition rate, wettability, wear resistance and corrosion resistance of ENi-P-Al2O3 composite deposits on mild steel substrates at bath pH 5, 7 and 9. Study reveals that optimum deposit parameters and deposition rates are achieved with bath pH. However, not much study has been undertaken concerning composite deposits obtained from higher bath pH or basic bath. This is attributable to the fact that at higher bath pH or alkaline baths, the bath gets unstable and eventually degrades or decomposes, thereby resulting in sub optimal or poor deposition. Hence, experimental investigations carried out by preparing suitable baths, operating under optimum conditions, and enabling successful composite deposition in acidic and alkaline baths have revealed that there is a significant improvement in the above mentioned properties of the as-deposited composite deposits, as the pH is increased from pH 5 to pH 9. This aspect can therefore be advantageously utilized for preparing various marine components like fasteners, nuts, bolts, washers, pipes, cables, components having relative motion etc.

  20. Surface modification of Ca-α-SiAlON: Eu2+ phosphor particles by SiO2 coating and fabrication of its deposit by electrophoretic deposition (EPD) process

    NASA Astrophysics Data System (ADS)

    Zhang, Chenning; Uchikoshi, Tetsuo; Kitabatake, Takuya; Sakka, Yoshio; Hirosaki, Naoto

    2013-09-01

    Ca-α-SiAlON: Eu2+ phosphor powder was modified with a SiO2 coating by the adsorption, hydrolysis, and polymerization of the TEOS precursor. Through the modification for the surface defects of the particles by the SiO2 coating, the photoluminescence (PL) emission could be significantly strengthened in the SiO2-coated Ca-α-SiAlON: Eu2+ powder. The electrophoretic deposition (EPD) technique was employed to fabricate the deposit layer on ITO glass using the SiO2 coated phosphor powder. The prepared deposit exhibited a uniform surface morphology with strong adhesion to the substrate. The SiO2-coated Ca-α-SiAlON: Eu2+ powder indicates a potential application when used in pseudo white light-emitting diodes (LEDs) devices.

  1. Amyloid Fibril Solubility.

    PubMed

    Rizzi, L G; Auer, S

    2015-11-19

    It is well established that amyloid fibril solubility is protein specific, but how solubility depends on the interactions between the fibril building blocks is not clear. Here we use a simple protein model and perform Monte Carlo simulations to directly measure the solubility of amyloid fibrils as a function of the interaction between the fibril building blocks. Our simulations confirms that the fibril solubility depends on the fibril thickness and that the relationship between the interactions and the solubility can be described by a simple analytical formula. The results presented in this study reveal general rules how side-chain-side-chain interactions, backbone hydrogen bonding, and temperature affect amyloid fibril solubility, which might prove to be a powerful tool to design protein fibrils with desired solubility and aggregation properties in general.

  2. Effects of Post Annealing Treatments on the Interfacial Chemical Properties and Band Alignment of AlN/Si Structure Prepared by Atomic Layer Deposition.

    PubMed

    Sun, Long; Lu, Hong-Liang; Chen, Hong-Yan; Wang, Tao; Ji, Xin-Ming; Liu, Wen-Jun; Zhao, Dongxu; Devi, Anjana; Ding, Shi-Jin; Zhang, David Wei

    2017-12-01

    The influences of annealing temperature in N2 atmosphere on interfacial chemical properties and band alignment of AlN/Si structure deposited by atomic layer deposition have been investigated based on x-ray photoelectron spectroscopy and spectroscopic ellipsometry. It is found that more oxygen incorporated into AlN film with the increasing annealing temperature, resulting from a little residual H2O in N2 atmosphere reacting with AlN film during the annealing treatment. Accordingly, the Si-N bonding at the interface gradually transforms to Si-O bonding with the increasing temperature due to the diffusion of oxygen from AlN film to the Si substrate. Specially, the Si-O-Al bonding state can be detected in the 900 °C-annealed sample. Furthermore, it is determined that the band gap and valence band offset increase with increasing annealing temperature.

  3. Effects of Post Annealing Treatments on the Interfacial Chemical Properties and Band Alignment of AlN/Si Structure Prepared by Atomic Layer Deposition

    NASA Astrophysics Data System (ADS)

    Sun, Long; Lu, Hong-Liang; Chen, Hong-Yan; Wang, Tao; Ji, Xin-Ming; Liu, Wen-Jun; Zhao, Dongxu; Devi, Anjana; Ding, Shi-Jin; Zhang, David Wei

    2017-02-01

    The influences of annealing temperature in N2 atmosphere on interfacial chemical properties and band alignment of AlN/Si structure deposited by atomic layer deposition have been investigated based on x-ray photoelectron spectroscopy and spectroscopic ellipsometry. It is found that more oxygen incorporated into AlN film with the increasing annealing temperature, resulting from a little residual H2O in N2 atmosphere reacting with AlN film during the annealing treatment. Accordingly, the Si-N bonding at the interface gradually transforms to Si-O bonding with the increasing temperature due to the diffusion of oxygen from AlN film to the Si substrate. Specially, the Si-O-Al bonding state can be detected in the 900 °C-annealed sample. Furthermore, it is determined that the band gap and valence band offset increase with increasing annealing temperature.

  4. Substrate Heating Effect on c-Axis Texture and Piezoelectric Properties of AlN Thin Films Deposited by Unbalanced Magnetron Sputtering

    NASA Astrophysics Data System (ADS)

    Hasheminiasari, Masood; Lin, Jianliang

    2016-06-01

    Aluminum nitride (AlN) thin films with highly preferred (002) orientations have been reactively deposited by a pulsed-closed field unbalanced magnetron sputtering system using TiN/Ti as the seed/adhesion layer with various substrate temperatures. The texture, orientation and piezoelectric properties of AlN films were characterized by means of x-ray diffraction, rocking curves and laser interferometry. A Michelson laser interferometer was designed and built to obtain the converse piezoelectric response of the deposited AlN thin films. It was found that a slight substrate temperature increase would significantly affect the (002) orientation and the piezoelectric coefficient of AlN thin films compared to the coating obtained with no intentional substrate heating, while higher temperature applications on substrate deteriorated the c-axis texture of the coatings without significant improvement in the piezoelectric response of AlN films.

  5. An Alternative Low-Cost Process for Deposition of MCrAlY Bond Coats for Advanced Syngas/Hydrogen Turbine Applications

    SciTech Connect

    Zhang, Ying

    2015-09-11

    The objective of this project was to develop and optimize MCrAlY bond coats for syngas/hydrogen turbine applications using a low-cost electrolytic codeposition process. Prealloyed CrAlY-based powders were codeposited into a metal matrix of Ni, Co or Ni-Co during the electroplating process, and a subsequent post-deposition heat treatment converted it to the MCrAlY coating. Our research efforts focused on: (1) investigation of the effects of electro-codeposition configuration and parameters on the CrAlY particle incorporation in the NiCo-CrAlY composite coatings; (2) development of the post-deposition heat treating procedure; (3) characterization of coating properties and evaluation of coating oxidation performance; (4) exploration of a sulfurfree electroplating solution; (5) cost analysis of the present electrolytic codeposition process. Different electro-codeposition configurations were investigated, and the rotating barrel system demonstrated the capability of depositing NiCo-CrAlY composite coatings uniformly on the entire specimen surface, with the CrAlY particle incorporation in the range 37-42 vol.%. Post-deposition heat treatment at 1000-1200 °C promoted interdiffusion between the CrAlY particles and the Ni-Co metal matrix, resulting in β/γ’/γ or β/γ’ phases in the heat-treated coatings. The results also indicate that the post-deposition heat treatment should be conducted at temperatures ≤1100 °C to minimize Cr evaporation and outward diffusion of Ti. The electro-codeposited NiCrAlY coatings in general showed lower hardness and surface roughness than thermal spray MCrAlY coatings. Coating oxidation performance was evaluated at 1000-1100 °C in dry and wet air environments. The initial electro-codeposited NiCoCrAlY coatings containing relatively high sulfur did not show good oxidation resistance. After modifications of the coating process, the cleaner NiCoCrAlY coating exhibited good oxidation performance at 1000 °C during the 2,000 1-h cyclic

  6. Understanding the Microstructure Formation of Ti-6Al-4V During Direct Laser Deposition via In-Situ Thermal Monitoring

    NASA Astrophysics Data System (ADS)

    Marshall, Garrett J.; Young, W. Joseph; Thompson, Scott M.; Shamsaei, Nima; Daniewicz, Steve R.; Shao, Shuai

    2016-03-01

    Understanding the thermal phenomena associated with direct laser deposition (DLD) is an important step toward obtaining `process-property-performance' relationships for various designed parts and materials, as well as achieving increased process control for meeting application constraints. In this study, a thermally monitored laser engineered net shaping (LENS™) system was used with time-invariant (uncontrolled) build parameters to construct Ti-6Al-4V cylinders. During fabrication, the part's thermal history and melt pool temperature were recorded via an in-chamber infrared camera and a dual-wavelength pyrometer, respectively. These tools demonstrate the use of non-destructive thermographic inspection for ensuring target part quality and/or microstructure. For the chosen part geometry, the melt pool was found to be approximately 40%-50% superheated during DLD, reaching temperatures as high as 2500°C. Temperature gradients varied and peaked around 1000°C/mm along the diameter of the relatively small cylinders. Cooling rates within the melt pool were found to increase as maximum melt pool temperature increased, for instance, from 12,000°C/s to 25,000°C/s. The post-DLD Ti-6Al-4V microstructure was found to vary from columnar near the substrate, or substrate-affected zone, to equiaxed approximately 2-3 mm from the substrate. Bulk heating of the part due to successive layer deposits was shown to promote α″ to an α + β decomposition, while prior- β grains were observed near and far from the substrate.

  7. Effective passivation of defects in Ge-rich SiGe-on-insulator substrates by Al 2O 3 deposition and subsequent post-annealing

    NASA Astrophysics Data System (ADS)

    Yang, Haigui; Iyota, Masatoshi; Ikeura, Shogo; Wang, Dong; Nakashima, Hiroshi

    2011-06-01

    A method of Al 2O 3 deposition and subsequent post-deposition annealing (Al 2O 3-PDA) was proposed to passivate electrically active defects in Ge-rich SiGe-on-insulator (SGOI) substrates, which were fabricated using Ge condensation by dry oxidation. The effect of Al 2O 3-PDA on defect passivation was clarified by surface analysis and electrical evaluation. It was found that Al 2O 3-PDA could not only suppress the surface reaction during Al-PDA in our previous work [Yang H, Wang D, Nakashima H, Hirayama K, Kojima S, Ikeura S. Defect control by Al-deposition and the subsequent post-annealing for SiGe-on-insulator substrates with different Ge fractions. Thin Solid Films 2010; 518: 2342-5.], but could also effectively passivate p-type defects generated during Ge condensation. The concentration in the range of 10 16-10 18 cm -3 for defect-induced acceptors and holes in Ge-rich SGOI drastically decreased after Al 2O 3-PDA. As a result of defect passivation, the electrical characteristics of both back-gate p-channel and n-channel metal-oxide-semiconductor field-effect transistors fabricated on Ge-rich SGOI were greatly improved after Al 2O 3-PDA.

  8. Pseudosinhalite: discovery of the hydrous MgAl-borate as a new mineral in the Tayozhnoye, Siberia, skarn deposit

    NASA Astrophysics Data System (ADS)

    Schreyer, W.; Pertsev, N. N.; Medenbach, O.; Burchard, M.; Dettmar, D.

    After its initial synthesis as the new compound Mg2Al3B2O9(OH) (Daniels et al. 1997) pseudosinhalite has now been discovered as a new mineral. It occurs, together with hydrotalcite, as a replacement product of sinhalite, MgAlBO4, in an impure marble of the contact metasomatic iron boron deposit of Tayozhnoye in the Aldan Shield of Siberia. Its chemical composition determined by electron microprobe is (wt%): Al2O3 46.88; MgO 25.12; FeO 1.99; B2O3 (calculated) 21.75; H2O (calculated) 2.81 giving a total of 98.55 and leading to the empirical formula (Mg2.00 Fe2+0.09)Σ=2.09 Al2.94 B2O9(OH). The small deviation from the ideal stoichiometry with (Mg+Fe2+):Al≠2:3 may be caused by either solid solution towards, or submicroscopic interlayering with lamellae of, the structurally similar mineral sinhalite. The underlying substitution involving also B and H would be (Mg+Fe)+B=Al+2H. Pseudosinhalite is monoclinic, space group P21/c, with a=7.49(1), b=4.33(1), c=9.85(2) Å β=110.7(1)° V=299(1) Å3 Z=2. Calculated density is 3.508g/cm3. Pseudosinhalite is colourless with white streak and has a vitreous lustre. It is transparent; no fluorescence was detected. There is no cleavage and parting; fractures are concoidal. Optical constants could not be measured properly due to polysynthetic microtwinning, but α<1.72<γ. For synthetic pseudosinhalite α=1.691(1) β=1.713(1) γ=1.730(1) Δ=0.039 2V=80°. The temperature of pseudosinhalite formation was below about 400°C at low pressures and with a hydrous, CO2-bearing fluid participating in the reaction.

  9. Systemic AL amyloidosis in a Beech Marten (Martes foina).

    PubMed

    Scaglione, F E; Mignone, W; Ferrero, E; Poggi, M; Biolatti, B; Bollo, E

    2013-10-01

    A wild Beech Marten (Martes foina), was referred for necropsy to the Department of Animal Pathology of the University of Turin (Italy). At gross examination, whitish and firm masses, 10-mm in diameter, were found on the heart and in the kidney. Spleen showed lighter color and greater consistency, and the cut surface of the liver appeared scattered with whitish-yellow coalescing foci homogeneously distributed. Amyloid deposits were present in the perivascular and intercellular spaces of the visceral organs, such as the heart, liver, and kidneys. Amyloid stained positively with Congo red with and without 5% potassium permanganate pretreatment and showed green birefringence observable under polarized light. A diagnosis of systemic AL amyloidosis was made. This is the first description of systemic AL amyloidosis in a wild Stone Marten.

  10. Oxidation and particle deposition modeling in plasma spraying of Ti-6Al-4V/SiC fiber composites

    NASA Astrophysics Data System (ADS)

    Cochelin, E.; Borit, F.; Frot, G.; Jeandin, M.; Decker, L.; Jeulin, D.; Taweel, B. Al; Michaud, V.; Noël, P.

    1999-03-01

    Plasma spraying is known to be a promising process for the manufacturing of Ti/SiC long-fiber composites. However, some improvements remain for this process to be applied in an industrial route. These include: oxygen contamination of the sprayed material through that of titanium particles before and during spraying, damage to fibers due to a high level of thermal stresses induced at the spraying stage, adequate deposition of titanium-base powder to achieve a low-porosity matrix and good impregnation of the fiber array. This article deals with work that resulted in a threefold study of the process. Oxidation was studied using electron microprobe analysis of elementary particles quenched and trapped into a closed box at various given flight distances. Oxygen diffusion phenomena within the particles are discussed from a preliminary theoretical approach coupled with experimental data. Isothermal and thermomechanical calculations were made using the ABAQUS code to determine stresses arising from contact of a liquid Ti-6Al-4V particle onto a SiC fiber. On the scale of the sprayed powder flow, a two-dimensional new type of model simulating the deposition of droplets onto a substrate was developed. This new type of model is based on a lattice-gas automaton that reproduces the hydrodynamical behavior of fluids.

  11. Imaging of oxide charges and contact potential difference fluctuations in atomic layer deposited Al2O3 on Si

    NASA Astrophysics Data System (ADS)

    Sturm, J. M.; Zinine, A. I.; Wormeester, H.; Poelsema, Bene; Bankras, R. G.; Holleman, J.; Schmitz, J.

    2005-03-01

    Ultrathin 2.5nm high-k aluminum oxide (Al2O3) films on p-type silicon (001) deposited by atomic layer deposition (ALD) were investigated with noncontact atomic force microscopy (NC-AFM) in ultrahigh vacuum, using a conductive tip. Constant force gradient images revealed the presence of oxide charges and experimental observations at different tip-sample potentials were compared with calculations of the electric force gradient based on a spherical tip model. This model could be substantially improved by the incorporation of the image of the tip in the semiconductor substrate. Based on the signals of different oxide charges observed, a homogenous depth distribution of those charges was derived. Application of a potential difference between sample and tip was found to result in a net electric force depending on the contact potential difference (CPD) and effective tip-sample capacitance, which depends on the depletion or accumulation layer that is induced by the bias voltage. CPD images could be constructed from height-voltage spectra with active feedback. Apart from oxide charges large-scale (150-300nm lateral size) and small-scale (50-100nm) CPD fluctuations were observed, the latter showing a high degree of correlation with topography features. This correlation might be a result from the surface-inhibited growth mode of the investigated layers.

  12. In situ analyses on negative ions in the sputtering process to deposit Al-doped ZnO films

    SciTech Connect

    Tsukamoto, Naoki; Watanabe, Daisuke; Saito, Motoaki; Sato, Yasushi; Oka, Nobuto; Shigesato, Yuzo

    2010-07-15

    The origin of high energy negative ions during deposition of aluminum doped zinc oxide (AZO) films by dc magnetron sputtering of an AZO (Al{sub 2}O{sub 3}: 2.0 wt %) target was investigated by in situ analyses using the quadrupole mass spectrometer combined with the electrostatic energy analyzer. High energy negative oxygen (O{sup -}) ions which possessed the kinetic energy corresponding to the cathode sheath voltage were detected. The maximum flux of the O{sup -} ions was clearly observed at the location opposite to the erosion track area on the target. The flux of the O{sup -} ions changed hardly with increasing O{sub 2} flow ratio [O{sub 2}/(Ar+O{sub 2})] from 0% to 5%. The kinetic energy of the O{sup -} ions decreased with decreasing cathode sheath voltage from 403 to 337 V due to the enhancement of the vertical maximum magnetic field strength at the cathode surface from 0.025 to 0.100 T. The AZO films deposited with the lower O{sup -} bombardment energy showed the higher crystallinity and improved the electrical conductivity.

  13. Highly potent soluble amyloid-β seeds in human Alzheimer brain but not cerebrospinal fluid

    PubMed Central

    Kaeser, Stephan A.; Maia, Luis F.; Portelius, Erik; Pinotsi, Dorothea; Kaminski, Clemens F.; Winkler, David T.; Maetzler, Walter; Keyvani, Kathy; Spitzer, Philipp; Wiltfang, Jens; Kaminski Schierle, Gabriele S.; Zetterberg, Henrik; Staufenbiel, Matthias; Jucker, Mathias

    2017-01-01

    The soluble fraction of brain samples from patients with Alzheimer’s disease contains highly biologically active amyloid-β seeds. In this study, we sought to assess the potency of soluble amyloid-β seeds derived from the brain and cerebrospinal fluid. Soluble Alzheimer’s disease brain extracts were serially diluted and then injected into the hippocampus of young, APP transgenic mice. Eight months later, seeded amyloiddeposition was evident even when the hippocampus received subattomole amounts of brain-derived amyloid-β. In contrast, cerebrospinal fluid from patients with Alzheimer’s disease, which contained more than 10-fold higher levels of amyloid-β peptide than the most concentrated soluble brain extracts, did not induce detectable seeding activity in vivo. Similarly, cerebrospinal fluid from aged APP-transgenic donor mice failed to induce cerebral amyloiddeposition. In comparison to the soluble brain fraction, cerebrospinal fluid largely lacked N-terminally truncated amyloid-β species and exhibited smaller amyloid-β-positive particles, features that may contribute to the lack of in vivo seeding by cerebrospinal fluid. Interestingly, the same cerebrospinal fluid showed at least some seeding activity in an in vitro assay. The present results indicate that the biological seeding activity of soluble amyloid-β species is orders of magnitude greater in brain extracts than in the cerebrospinal fluid. PMID:25212850

  14. Unwinding fibril formation of medin, the peptide of the most common form of human amyloid.

    PubMed

    Larsson, Annika; Söderberg, Linda; Westermark, Gunilla T; Sletten, Knut; Engström, Ulla; Tjernberg, Lars O; Näslund, Jan; Westermark, Per

    2007-10-05

    Medin amyloid affects the medial layer of the thoracic aorta of most people above 50 years of age. The consequences of this amyloid are not completely known but the deposits may contribute to diseases such as thoracic aortic aneurysm and dissection or to the general diminished elasticity of blood vessels seen in elderly people. We show that the 50-amino acid residue peptide medin forms amyloid-like fibrils in vitro. With the use of Congo red staining, Thioflavin T fluorescence, electron microscopy, and a solid-phase binding assay on different synthetic peptides, we identified the last 18-19 amino acid residues to constitute the amyloid-promoting region of medin. We also demonstrate that the two C-terminal phenylalanines, previously suggested to be of importance for amyloid formation, are not required for medin amyloid formation.

  15. Unwinding fibril formation of medin, the peptide of the most common form of human amyloid

    SciTech Connect

    Larsson, Annika; Soederberg, Linda; Westermark, Gunilla T.; Sletten, Knut; Engstroem, Ulla; Tjernberg, Lars O.; Naeslund, Jan; Westermark, Per

    2007-10-05

    Medin amyloid affects the medial layer of the thoracic aorta of most people above 50 years of age. The consequences of this amyloid are not completely known but the deposits may contribute to diseases such as thoracic aortic aneurysm and dissection or to the general diminished elasticity of blood vessels seen in elderly people. We show that the 50-amino acid residue peptide medin forms amyloid-like fibrils in vitro. With the use of Congo red staining, Thioflavin T fluorescence, electron microscopy, and a solid-phase binding assay on different synthetic peptides, we identified the last 18-19 amino acid residues to constitute the amyloid-promoting region of medin. We also demonstrate that the two C-terminal phenylalanines, previously suggested to be of importance for amyloid formation, are not required for medin amyloid formation.

  16. Mutation of the Alzheimer's Disease Amyloid Gene in Hereditary Cerebral Hemorrhage, Dutch Type

    NASA Astrophysics Data System (ADS)

    Levy, Efrat; Carman, Mark D.; Fernandez-Madrid, Ivan J.; Power, Michael D.; Lieberburg, Ivan; van Duinen, Sjoerd G.; Bots, Gerard Th. A. M.; Luyendijk, Willem; Frangione, Blas

    1990-06-01

    An amyloid protein that precipitates in the cerebral vessel walls of Dutch patients with hereditary cerebral hemorrhage with amyloidosis is similar to the amyloid protein in vessel walls and senile plaques in brains of patients with Alzheimer's disease, Down syndrome, and sporadic cerebral amyloid angiopathy. Cloning and sequencing of the two exons that encode the amyloid protein from two patients with this amyloidosis revealed a cytosine-to-guanine transversion, a mutation that caused a single amino acid substitution (glutamine instead of glutamic acid) at position 22 of the amyloid protein. The mutation may account for the deposition of this amyloid protein in the cerebral vessel walls of these patients, leading to cerebral hemorrhages and premature death.

  17. Nanomaterials for reducing amyloid cytotoxicity.

    PubMed

    Zhang, Min; Mao, Xiaobo; Yu, Yue; Wang, Chen-Xuan; Yang, Yan-Lian; Wang, Chen

    2013-07-26

    This review is intended to reflect the recent progress on therapeutic applications of nanomaterials in amyloid diseases. The progress on anti-amyloid functions of various nanomaterials including inorganic nanoparticles, polymeric nanoparticles, carbon nanomaterials and biomolecular aggregates, is reviewed and discussed. The main functionalization strategies for general nanoparticle modifications are reviewed for potential applications of targeted therapeutics. The interaction mechanisms between amyloid peptides and nanomaterials are discussed from the perspectives of dominant interactions and kinetics. The encapsulation of anti-amyloid drugs, targeted drug delivery, controlled drug release and drug delivery crossing blood brain barrier by application of nanomaterials would also improve the therapeutics of amyloid diseases.

  18. Residual Strain and Fracture Response of Al2O3 Coatings Deposited via APS and HVOF Techniques

    NASA Astrophysics Data System (ADS)

    Ahmed, R.; Faisal, N. H.; Paradowska, A. M.; Fitzpatrick, M. E.

    2012-01-01

    The aim of this investigation was to nondestructively evaluate the residual stress profile in two commercially available alumina/substrate coating systems and relate residual stress changes with the fracture response. Neutron diffraction, due to its high penetration depth, was used to measure residual strain in conventional air plasma-sprayed (APS) and finer powder high velocity oxy-fuel (HVOF (θ-gun))-sprayed Al2O3 coating/substrate systems. The purpose of this comparison was to ascertain if finer powder Al2O3 coatings deposited via θ-gun can provide improved residual stress and fracture response in comparison to conventional APS coatings. To obtain a through thickness residual strain profile with high resolution, a partially submerged beam was used for measurements near the coating surface, and a beam submerged in the coating and substrate materials near the coating-substrate interface. By using the fast vertical scanning method, with careful leveling of the specimen using theodolites, the coating surface and the coating/substrate interface were located with an accuracy of about 50 μm. The results show that the through thickness residual strain in the APS coating was mainly tensile, whereas the HVOF coating had both compressive and tensile residual strains. Further analysis interlinking Vickers indentation fracture behavior using acoustic emission (AE) was conducted. The microstructural differences along with the nature and magnitude of the residual strain fields had a direct effect on the fracture response of the two coatings during the indentation process.

  19. Deposition of LaMO 3 (M=Co, Cr, Al) films by spray pyrolysis in inductively coupled plasma

    NASA Astrophysics Data System (ADS)

    Ichinose, Hiromichi; Katsuki, Hiroaki; Nagano, Masamitsu

    1994-11-01

    LaMO 3 (M=Co, Cr, Al) films were prepared on substrates by introducing ultrasonically atomized metal nitrate solutions into an inductively coupled plasma under atmospheric pressure (spray-ICP technique). Dense perovskite-type oxide films of LaCoO 3 and LaCrO 3 were obtained at 600-900°C, while the LaAiO 3 films consisted of loosely packed aggregates. Deposition rates of the films were 6-35 nm/min at 600-900°C. The high temperature phases (cubic) of LaCoO 3 and LaAlO 3 crystallized due to effect of grain size. LaCrO 3 film crystallized in the room temperature phase (orthorhombic). LaCoO 3 was highly oriented to (100) on MgO(100), and LaCrO 3 to (011) and (101) on sapphire(001). Lowest electric resistivities of LaCoO 3 and LaCrO 3 film on MgO were 9.8X10 -3 and 2.7X10 -1 Ω m, respectively, at room temperature.

  20. Preparation of AlGaN/GaN Heterostructures on Sapphire Using Light Radiation Heating Metal-Organic Chemical Vapor Deposition at Low Pressure

    NASA Astrophysics Data System (ADS)

    Zhou, Yu-Gang; Shen, Bo; Zhang, Rong; Li, Wei-Ping; Chen, Peng; Chen, Zhi-Zhong; Gu, Shu-Lin; Shi, Yi; Z, Huang C.; Zheng, You-Dou

    2000-08-01

    AlGaN/GaN heterostructures on sapphire substrate were fabricated by using light radiation heating metalorganic chemical vapor deposition. Photoluminescence excitation spectra show that there are two abrupt slopes corresponding to the absorption edges of AlGaN and GaN, respectively. X-ray diffraction spectra clearly exhibit the GaN (0002), (0004), and AlGaN (0002), (0004) diffraction peaks, and no diffraction peak other than those from the GaN {0001} and AlGaN {0001} planes is found. Reciprocal space mapping indicates that there is no tilt between the AlGaN layer and the GaN layer. All results also indicate that the sample is of sound quality and the Al composition in the AlGaN layer is of high uniformity.

  1. Blue-Emitting Eu2+-Doped CaAl2O4 Phosphor Thin Films Prepared Using Pulsed Laser Deposition Technique with Post Annealing

    NASA Astrophysics Data System (ADS)

    Kunimoto, Takashi; Kakehi, Ken-nosuke; Yoshimatsu, Ryo; Ohmi, Koutoku; Tanaka, Shosaku; Kobayashi, Hiroshi

    2001-10-01

    Blue-emitting Eu2+-doped calcium aluminate phosphor thin films were obtained using the pulsed laser deposition technique with post annealing. As-deposited films were amorphous and showed weak red Eu3+ photoluminescence (PL). By annealing in reducing atmosphere (N2/H2:2% mixed gas) at 950°C for 3 h, the film was crystallized and showed a PL emission band peaking at about 447 nm, which originated from the 4f65d to 4f7 transition of Eu2+ ion. It is considered that the deposited film consists mainly of CaAl2O4 and partly of other binary compounds of the CaO-Al2O3 system. It was determined that the PL intensity of Eu2+ in CaAl2O4 can be controlled by the laser fluence, target-substrate distance and injection gas.

  2. ACAT inhibition and amyloid beta reduction.

    PubMed

    Bhattacharyya, Raja; Kovacs, Dora M

    2010-08-01

    Alzheimer's disease (AD) is a devastating neurodegenerative disorder. Accumulation and deposition of the beta-amyloid (Abeta) peptide generated from its larger amyloid precursor protein (APP) is one of the pathophysiological hallmarks of AD. Intracellular cholesterol was shown to regulate Abeta production. Recent genetic and biochemical studies indicate that not only the amount, but also the distribution of intracellular cholesterol is critical to regulate Abeta generation. Acyl-coenzyme A: cholesterol acyl-transferase (ACAT) is a family of enzymes that regulates the cellular distribution of cholesterol by converting membrane cholesterol into hydrophobic cholesteryl esters for cholesterol storage and transport. Using pharmacological inhibitors and transgenic animal models, we and others have identified ACAT1 as a potential therapeutic target to lower Abeta generation and accumulation. Here we discuss data focusing on ACAT inhibition as an effective strategy for the prevention and treatment of AD.

  3. Chronic imaging of amyloid plaques in the live mouse brain using multiphoton microscopy

    NASA Astrophysics Data System (ADS)

    Bacskai, Brian J.; Kajdasz, Stephen T.; Christie, R. H.; Zipfel, Warren R.; Williams, Rebecca M.; Kasischke, Karl A.; Webb, Watt W.; Hyman, B. T.

    2001-04-01

    Transgenic mice expressing the human Amyloid Precursor Protein (APP) develop amyloid plaques as they age. These plaques resemble those found in the human disease. Multiphoton laser scanning microscopy combined with a novel surgical approach was used to measure amyloid plaque dynamics chronically in the cortex of living transgenic mice. Thioflavine S (thioS) was used as a fluorescent marker of amyloid deposits. Multiphoton excitation allowed visualization of amyloid plaques up to 200 micrometers deep into the brain. The surgical site could be imaged repeatedly without overt damage to the tissue, and individual plaques within this volume could be reliably identified over periods of several days to several months. On average, plaque sizes remained constant over time, supporting a model of rapid deposition, followed by relative stability. Alternative reporters for in vivo histology include thiazine red, and FITC-labeled amyloid-(Beta) peptide. We also present examples of multi-color imaging using Hoechst dyes and FITC-labeled tomato lectin. These approaches allow us to observe cell nuclei or microglia simultaneously with amyloid-(Beta) deposits in vivo. Chronic imaging of a variety of reporters in these transgenic mice should provide insight into the dynamics of amyloid-(Beta) activity in the brain.

  4. Effects of injected Alzheimer beta-amyloid cores in rat brain.

    PubMed Central

    Frautschy, S A; Baird, A; Cole, G M

    1991-01-01

    Although amyloid deposits have long been known to accumulate in Alzheimer disease (AD) brain, their origin and significance remain speculative. Because of the lack of an in vivo model where amyloid deposits can be induced, the relationship of the extracellular beta-amyloid deposits to other AD pathology has never been directly investigated. Therefore, we injected SDS-isolated amyloid cores into rat cortex and hippocampus. Similarly isolated lipofuscin fractions from control human brains were injected on the contralateral side. Rats were perfused and brains were examined immunohistochemically at 2 days, 7 days, and 1 month after injection. Alz-50, a monoclonal antibody against abnormally phosphorylated tau proteins, stained neurons along the cortical needle track at 2 but not 7 days after injection of either amyloid or lipofuscin. At 1 month, however, ubiquitin, Alz-50 antigen, and silver-positive structures were observed only in response to amyloid. In 7 of 10 animals, there was considerable neuronal loss in the hippocampal layers. In each instance, these effects were in the immediate vicinity of beta-protein immunoreactive material. Marked neuronal loss was never observed at any time after lipofuscin injection. These results indicate a neuronal response to amyloid. When preparations of mature plaque amyloid isolated from the AD brain are injected into the rat brain, they exert neurotoxic effects and induce antigens found in the AD brain. Images PMID:1924295

  5. A Human Monoclonal IgG That Binds Aβ Assemblies and Diverse Amyloids Exhibits Anti-Amyloid Activities In Vitro and In Vivo

    PubMed Central

    O'Nuallain, Brian; Puligedda, Rama Devudu; Ondrejcak, Tomas; Adekar, Sharad P.; Chen, Cindy; Cruz, Pedro E.; Rosario, Awilda M.; Macy, Sallie; Mably, Alexandra J.; Walsh, Dominic M.; Vidal, Ruben; Solomon, Alan; Brown, Daniel; Rowan, Michael J.; Golde, Todd E.

    2015-01-01

    Alzheimer's disease (AD) and familial Danish dementia (FDD) are degenerative neurological diseases characterized by amyloid pathology. Normal human sera contain IgG antibodies that specifically bind diverse preamyloid and amyloid proteins and have shown therapeutic potential in vitro and in vivo. We cloned one of these antibodies, 3H3, from memory B cells of a healthy individual using a hybridoma method. 3H3 is an affinity-matured IgG that binds a pan-amyloid epitope, recognizing both Aβ and λ Ig light chain (LC) amyloids, which are associated with AD and primary amyloidosis, respectively. The pan-amyloid-binding properties of 3H3 were demonstrated using ELISA, immunohistochemical studies, and competition binding assays. Functional studies showed that 3H3 inhibits both Aβ and LC amyloid formation in vitro and abrogates disruption of hippocampal synaptic plasticity by AD-patient-derived soluble Aβ in vivo. A 3H3 single-chain variable fragment (scFv) retained the binding specificity of the 3H3 IgG and, when expressed in the brains of transgenic mice using an adeno-associated virus (AAV) vector, decreased parenchymal Aβ amyloid deposition in TgCRND8 mice and ADan (Danish Amyloid) cerebral amyloid angiopathy in the mouse model of FDD. These data indicate that naturally occurring human IgGs can recognize a conformational, amyloid-specific epitope and have potent anti-amyloid activities, providing a rationale to test their potential as antibody therapeutics for diverse neurological and other amyloid diseases. PMID:25904780

  6. Preparation of ZnO/Al2O3 catalysts by using atomic layer deposition for plasma-assisted non-oxidative methane coupling

    NASA Astrophysics Data System (ADS)

    Jeong, Myung-Geun; Kim, Young Dok; Park, Sunyoung; Kasinathan, Palraj; Hwang, Young Kyu; Chang, Jong-San; Park, Yong-Ki

    2016-05-01

    We prepared a ZnO/mesoporous Al2O3-shell/core structure by using atomic layer deposition (ALD) of ZnO on commercially-available mesoporous Al2O3. We used various analysis techniques such as scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, inductively coupled plasma-atomic emission spectroscopy, and surface area and pore size analyses based on nitrogen isotherm data. A 200 nm-thick slab of mesoporous Al2O3 particles was decorated by ZnO upon ALD deposition, whereas the inner part of the Al2O3 particle was free of ZnO. We evaluated the catalytic activity of the bare and the ZnO-covered Al2O3 for plasma-assisted nonoxidative coupling of methane. The catalytic behavior was shown to be sensitive to the amount of ZnO deposited. Particularly, 40-cycled ZnO/Al2O3 showed an enhanced selectivity to the olefin product with almost the same CH4 conversion as that of bare Al2O3. Preparation of the shell/core structure by using ALD can be an interesting strategy for finding highly-efficient catalysts in a plasma-assisted catalytic reaction.

  7. Influence of plasma density on the chemical composition and structural properties of pulsed laser deposited TiAlN thin films

    SciTech Connect

    Quiñones-Galván, J. G.; Camps, Enrique; Muhl, S.; Flores, M.; Campos-González, E.

    2014-05-15

    Incorporation of substitutional Al into the TiN lattice of the ternary alloy TiAlN results in a material with improved properties compared to TiN. In this work, TiAlN thin films were grown by the simultaneous ablation of Ti and Al targets in a nitrogen containing reactive atmosphere. The deposit was formed on silicon substrates at low deposition temperature (200 °C). The dependence of the Al content of the films was studied as a function of the ion density of the plasma produced by the laser ablation of the Al target. The plasma parameters were measured by means of a planar Langmuir probe and optical emission spectroscopy. The chemical composition of the films was measured by energy dispersive X-ray spectroscopy. The results showed a strong dependence of the amount of aluminum incorporated in the films with the plasma density. The structural characterization of the deposits was carried out by Raman spectroscopy, X-ray diffraction, and transmission electron microscopy, where the substitutional incorporation of the Al into the TiN was demonstrated.

  8. Enhanced density of negative fixed charges in Al2O3 layers on Si through a subsequent deposition of TiO2

    NASA Astrophysics Data System (ADS)

    Schneider, Thomas; Ziegler, Johannes; Kaufmann, Kai; Ilse, Klemens; Sprafke, Alexander; Wehrspohn, Ralf B.

    2016-04-01

    The passivation of silicon surfaces play an important role for achieving high-efficiency crystalline silicon solar cells. In this work, a stack system comprising of 20nm Al2O3 with a 22nm TiO2 topping layer was deposited on p-type Si using thermal atomic layer deposition (ALD) and was investigated regarding its passivation quality. Quasi-steady-state photo conductance (QSSPC) measurements reveal that the minority carrier lifetime at an injection density of 1015cm-3 increased from 1.10ms to 1.96ms after the deposition of TiO2, which shows that the deposition of TiO2 onto Al2O3 is capable of enhancing its passivation quality. Capacity voltage (CV) measurements show that the amount of negative charges in the dielectric layer has increased from -2.4·1012cm-2 to -6.3·1012cm-2 due to the deposition of TiO2. The location of the additional charges was analyzed in this work by etching the dielectric layer stack in several steps. After each step CV measurements were performed. It is found that the additional negative charges are created within the Al2O3 layer. Additionally, ToF-SIMS measurements were performed to check for diffusion processes within the Al2O3 layer.

  9. First effects of rising amyloid-β in transgenic mouse brain: synaptic transmission and gene expression

    PubMed Central

    Cummings, Damian M.; Liu, Wenfei; Portelius, Erik; Bayram, Sevinç; Yasvoina, Marina; Ho, Sui-Hin; Smits, Hélène; Ali, Shabinah S.; Steinberg, Rivka; Pegasiou, Chrysia-Maria; James, Owain T.; Matarin, Mar; Richardson, Jill C.; Zetterberg, Henrik; Blennow, Kaj; Hardy, John A.; Salih, Dervis A.

    2015-01-01

    Detecting and treating Alzheimer’s disease, before cognitive deficits occur, has become the health challenge of our time. The earliest known event in Alzheimer’s disease is rising amyloid-β. Previous studies have suggested that effects on synaptic transmission may precede plaque deposition. Here we report how relative levels of different soluble amyloid-β peptides in hippocampus, preceding plaque deposition, relate to synaptic and genomic changes. Immunoprecipitation-mass spectrometry was used to measure the early rise of different amyloid-β peptides in a mouse model of increasing amyloid-β (‘TASTPM’, transgenic for familial Alzheimer’s disease genes APP/PSEN1). In the third postnatal week, several amyloid-β peptides were above the limit of detection, including amyloid-β40, amyloid-β38 and amyloid-β42 with an intensity ratio of 6:3:2, respectively. By 2 months amyloid-β levels had only increased by 50% and although the ratio of the different peptides remained constant, the first changes in synaptic currents, compared to wild-type mice could be detected with patch-clamp recordings. Between 2 and 4 months old, levels of amyloid-β40 rose by ∼7-fold, but amyloid-β42 rose by 25-fold, increasing the amyloid-β42:amyloid-β40 ratio to 1:1. Only at 4 months did plaque deposition become detectable and only in some mice; however, synaptic changes were evident in all hippocampal fields. These changes included increased glutamate release probability (P < 0.001, n = 7–9; consistent with the proposed physiological effect of amyloid-β) and loss of spontaneous action potential-mediated activity in the cornu ammonis 1 (CA1) and dentate gyrus regions of the hippocampus (P < 0.001, n = 7). Hence synaptic changes occur when the amyloid-β levels and amyloid-β42:amyloid-β40 ratio are still low compared to those necessary for plaque deposition. Genome-wide microarray analysis revealed changes in gene expression at 2–4 months including synaptic genes being

  10. First effects of rising amyloid-β in transgenic mouse brain: synaptic transmission and gene expression.

    PubMed

    Cummings, Damian M; Liu, Wenfei; Portelius, Erik; Bayram, Sevinç; Yasvoina, Marina; Ho, Sui-Hin; Smits, Hélène; Ali, Shabinah S; Steinberg, Rivka; Pegasiou, Chrysia-Maria; James, Owain T; Matarin, Mar; Richardson, Jill C; Zetterberg, Henrik; Blennow, Kaj; Hardy, John A; Salih, Dervis A; Edwards, Frances A

    2015-07-01

    Detecting and treating Alzheimer's disease, before cognitive deficits occur, has become the health challenge of our time. The earliest known event in Alzheimer's disease is rising amyloid-β. Previous studies have suggested that effects on synaptic transmission may precede plaque deposition. Here we report how relative levels of different soluble amyloid-β peptides in hippocampus, preceding plaque deposition, relate to synaptic and genomic changes. Immunoprecipitation-mass spectrometry was used to measure the early rise of different amyloid-β peptides in a mouse model of increasing amyloid-β ('TASTPM', transgenic for familial Alzheimer's disease genes APP/PSEN1). In the third postnatal week, several amyloid-β peptides were above the limit of detection, including amyloid-β40, amyloid-β38 and amyloid-β42 with an intensity ratio of 6:3:2, respectively. By 2 months amyloid-β levels had only increased by 50% and although the ratio of the different peptides remained constant, the first changes in synaptic currents, compared to wild-type mice could be detected with patch-clamp recordings. Between 2 and 4 months old, levels of amyloid-β40 rose by ∼7-fold, but amyloid-β42 rose by 25-fold, increasing the amyloid-β42:amyloid-β40 ratio to 1:1. Only at 4 months did plaque deposition become detectable and only in some mice; however, synaptic changes were evident in all hippocampal fields. These changes included increased glutamate release probability (P < 0.001, n = 7-9; consistent with the proposed physiological effect of amyloid-β) and loss of spontaneous action potential-mediated activity in the cornu ammonis 1 (CA1) and dentate gyrus regions of the hippocampus (P < 0.001, n = 7). Hence synaptic changes occur when the amyloid-β levels and amyloid-β42:amyloid-β40 ratio are still low compared to those necessary for plaque deposition. Genome-wide microarray analysis revealed changes in gene expression at 2-4 months including synaptic genes being strongly

  11. Laser damage properties of TiO{sub 2}/Al{sub 2}O{sub 3} thin films grown by atomic layer deposition

    SciTech Connect

    Wei Yaowei; Liu Hao; Sheng Ouyang; Liu Zhichao; Chen Songlin; Yang Liming

    2011-08-20

    Research on thin film deposited by atomic layer deposition (ALD) for laser damage resistance is rare. In this paper, it has been used to deposit TiO{sub 2}/Al{sub 2}O{sub 3} films at 110 deg. C and 280 deg. C on fused silica and BK7 substrates. Microstructure of the thin films was investigated by x-ray diffraction. The laser-induced damage threshold (LIDT) of samples was measured by a damage test system. Damage morphology was studied under a Nomarski differential interference contrast microscope and further checked under an atomic force microscope. Multilayers deposited at different temperatures were compared. The results show that the films deposited by ALD had better uniformity and transmission; in this paper, the uniformity is better than 99% over 100 mm {Phi} samples, and the transmission is more than 99.8% at 1064 nm. Deposition temperature affects the deposition rate and the thin film microstructure and further influences the LIDT of the thin films. As to the TiO{sub 2}/Al{sub 2}O{sub 3} films, the LIDTs were 6.73{+-}0.47 J/cm{sup 2} and 6.5{+-}0.46 J/cm{sup 2} at 110 deg. C on fused silica and BK7 substrates, respectively. The LIDTs at 110 deg. C are notably better than 280 deg. C.

  12. Discussion of "Atmospheric deposition as an important nitrogen load to a typical agro-ecosystem in the Huang-Huai-Hai Plain" by Huang et al. (2016)

    NASA Astrophysics Data System (ADS)

    Pan, Yuepeng; Xu, Wen; Wentworth, Gregory R.; Tian, Shili

    2017-03-01

    In a recent publication of Atmospheric Environment, Huang et al. (2016) reported nitrogen (N) deposition estimates using the water surrogate surface method. This method may be suitable to evaluate the atmospheric N input to a body of water, wetland or paddy fields rather than dry crop land without sustained waterlogged conditions. Such a method may also result in the potential underestimation of both dry and wet N deposition due to the release of ammonia (NH3) from water evaporation and/or N loss from biological activities, and hence bias the relative contribution of dry deposition to total deposition. Besides the uncertainties regarding the magnitude and pathways of N deposition, the statement by Huang et al. (2016) that "nitrate was the dominant species in N deposition even in cropland" is also questionable. We suggest that reduced species dominate the N deposition in Huang-Huai-Hai Plain (i.e., North China Plain) even in urban and industrial regions due to the abundance of NH3.

  13. Atomic layer deposition of Sc2O3 for passivating AlGaN/GaN high electron mobility transistor devices

    NASA Astrophysics Data System (ADS)

    Wang, Xinwei; Saadat, Omair I.; Xi, Bin; Lou, Xiabing; Molnar, Richard J.; Palacios, Tomás; Gordon, Roy G.

    2012-12-01

    Polycrystalline, partially epitaxial Sc2O3 films were grown on AlGaN/GaN substrates by atomic layer deposition (ALD). With this ALD Sc2O3 film as the insulator layer, the Sc2O3/AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors showed excellent electrical performance with a high Ion/Ioff ratio of over 108 and a low subthreshold slope of 75 mV/dec. The UV/NH4OH surface treatment on AlGaN/GaN prior to ALD was found to be critical for achieving these excellent figures. In addition, the Sc2O3 dielectric is found to be negatively charged, which facilitates the enhancement-mode operation. While bare Sc2O3 suffers from moisture degradation, depositing a moisture blocking layer of ALD Al2O3 can effectively eliminate this effect.

  14. Room temperature photoluminescence from In{sub x}Al{sub (1−x)}N films deposited by plasma-assisted molecular beam epitaxy

    SciTech Connect

    Kong, W. Jiao, W. Y.; Kim, T. H.; Brown, A. S.; Mohanta, A.; Roberts, A. T.; Fournelle, J.; Losurdo, M.; Everitt, H. O.

    2014-09-29

    InAlN films deposited by plasma-assisted molecular beam epitaxy exhibited a lateral composition modulation characterized by 10–12 nm diameter, honeycomb-shaped, columnar domains with Al-rich cores and In-rich boundaries. To ascertain the effect of this microstructure on its optical properties, room temperature absorption and photoluminescence characteristics of In{sub x}Al{sub (1−x)}N were comparatively investigated for indium compositions ranging from x = 0.092 to 0.235, including x = 0.166 lattice matched to GaN. The Stokes shift of the emission was significantly greater than reported for films grown by metalorganic chemical vapor deposition, possibly due to the phase separation in these nanocolumnar domains. The room temperature photoluminescence also provided evidence of carrier transfer from the InAlN film to the GaN template.

  15. Interface Properties of Atomic-Layer-Deposited Al2O3 Thin Films on Ultraviolet/Ozone-Treated Multilayer MoS2 Crystals.

    PubMed

    Park, Seonyoung; Kim, Seong Yeoul; Choi, Yura; Kim, Myungjun; Shin, Hyunjung; Kim, Jiyoung; Choi, Woong

    2016-05-11

    We report the interface properties of atomic-layer-deposited Al2O3 thin films on ultraviolet/ozone (UV/O3)-treated multilayer MoS2 crystals. The formation of S-O bonds on MoS2 after low-power UV/O3 treatment increased the surface energy, allowing the subsequent deposition of uniform Al2O3 thin films. The capacitance-voltage measurement of Au-Al2O3-MoS2 metal oxide semiconductor capacitors indicated n-type MoS2 with an electron density of ∼10(17) cm(-3) and a minimum interface trap density of ∼10(11) cm(-2) eV(-1). These results demonstrate the possibility of forming a high-quality Al2O3-MoS2 interface by proper UV/O3 treatment, providing important implications for their integration into field-effect transistors.

  16. Insulin amyloid at injection sites of patients with diabetes.

    PubMed

    Nilsson, Melanie R

    2016-09-01

    The formation of insulin amyloid can dramatically impact glycemic control in patients with diabetes, making it an important therapeutic consideration. In addition, the cost associated with the excess insulin required by patients with amyloid is estimated to be $3K per patient per year, which adds to the growing financial burden of this disease. Insulin amyloid has been observed with every mode of therapeutic insulin administration (infusion, injection and inhalation), and the number of reported cases has increased significantly since 2002. The new cases represent a much broader demographic, and include many patients who have used exclusively human insulin and human insulin analogs. The reason for the increase in case reports is unknown, but this review explores the possibility that changes in patient care, improved differential diagnosis and/or changes in insulin type and insulin delivery systems may be important factors. The goal of this review is to raise key questions that will inspire proactive measures to prevent, identify and treat insulin amyloid. Furthermore, this comprehensive examination of insulin amyloid can provide insight into important considerations for other injectable drugs that are prone to form amyloid deposits.

  17. Atomic layer deposition of Al2O3 on H-passivated Si: Al(CH3)2OH surface reactions with H/Si(100)-2×1

    NASA Astrophysics Data System (ADS)

    Halls, Mathew D.; Raghavachari, Krishnan; Frank, Martin M.; Chabal, Yves J.

    2003-10-01

    Infrared absorption studies of Al(CH3)3 interacting with H-terminated Si reveal that O incorporation from gas-phase impurities may be a crucial factor in interface formation in atomic layer deposition. Hybrid density-functional calculations have therefore been carried out on silicon cluster models to investigate the possible pathways for reaction between the important atomic layer deposition side-reaction product Al(CH3)2OH (DMAOH) and the H/Si(100)-2×1 surface. Comparisons with the analogous surface reactions for Al(CH3)3 and H2O are made. In general, the DMAOH surface reaction pathways are characterized by an activation of reactions involving the OH groups and suppression of CH3 group reactions, compared to Al(CH3)3 and H2O. A unique reaction pathway for DMAOH and the H/Si(100)-2×1 surface is identified resulting in the deposition of -O-Al(CH3)2 on the surface, which is significant since it represents an atomic-layer interface between Si and Al2O3. This reaction has an energy barrier of 1.3 eV and is the most thermodynamically favored pathway with an exothermicity of 0.9 eV.

  18. Optical properties of double layer thin films zinc oxide doping aluminum (ZnO/Al) were deposited on glass substrates by sol gel method spray coating technique

    NASA Astrophysics Data System (ADS)

    Permatasari, Anes; Sutanto, Heri; Marito Siagian, Sinta

    2017-01-01

    Thin films of double layer of ZnO/Al has succeeded in deposition on a glass substrate using sol-gel method and spray coating techniques. Variations of doping Al as much as 2%, 4%, 6% and 8%. ZnO precursor synthesized using zinc acetate dehydrate (Zn(COOCH3)2.2H2O), isopropanol ((CH3)2CHOH) and monoethanolamine (MEA) were stirred using a magnetic stirrer for 45 minutes. ZnO precursor get homogeneous and then added of aluminum nitrate nonahydrate predetermined doping concentration and stirred again for 15 minutes. Deposition solution is done by the spray on a glass substrate and then heated at a temperature of 450°C. A layer of ZnO/Al deposited over the ZnO to produce a thin layer of a double layer. Optical properties layer of ZnO/Al characterized using UV-Vis spectrophotometer. Based on data from UV-Vis absorbance was determined the value of the energy band gap. Pure and dopped layers has different energy due the Al dopping. For pure ZnO layer has energy band gap of 3.347 eV and decreased to 3.09 eV for ZnO layer with Al dopant.

  19. Characterization and corrosion behavior of hydroxyapatite coatings on Ti6Al4V fabricated by electrophoretic deposition

    NASA Astrophysics Data System (ADS)

    Kwok, C. T.; Wong, P. K.; Cheng, F. T.; Man, H. C.

    2009-04-01

    In order to increase the bone bioactivity of the metallic implants, hydroxyapatite (HA) is often coated on their surface so that a real bond with the surrounding bone tissue can be formed. Plasma spraying of HA coatings is currently the only commercial process in use but long-term stability of plasma sprayed coatings could be a problem because of their high degree of porosities, poor bond strength, presence of a small amount of amorphous phase with non-stoichiometric composition, and non-uniformity. In the present study, cathodic electrophoretic deposition (EPD) has been attempted for depositing HA coatings on Ti6Al4V followed by vacuum sintering at 800 °C. Submicron HA powders with different morphologies including spherical, needle-shaped and flake-shaped were used in the EDP process to produce dense coatings. Moreover, carbon nanotubes (CNTs) were also used to reinforce the HA coating for enhancing its hardness. The surface morphology, compositions and microstructure of the HA coated Ti6Al4V were investigated by electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffractometry, respectively. Electrochemical corrosion behavior of the HA coatings in Hanks' solution at 37 °C was investigated by means of open-circuit potential measurement and cyclic potentiodynamic polarization tests. Surface hardness, adhesion strength and bone bioactivity of the coatings were also studied. All HA coated specimens had a thickness of about 10 μm and free of cracks, with corrosion resistance higher than that of the substrate and adhesion strength higher than that of plasma sprayed coating. The enhanced properties could be attributed to the use of submicron-sized HA particles in the low-temperature EDP process. Among the three types of HA powder, spherical powder yielded the densest coating whereas the flake-shaped powder yielded the most porous coatings. Compared with monolithic HA coating, the CNT-reinforced HA coating markedly increased the coating hardness

  20. Low-frequency dielectric properties of intrinsic and Al-doped rutile TiO2 thin films grown by the atomic layer deposition technique

    NASA Astrophysics Data System (ADS)

    Kassmi, M.; Pointet, J.; Gonon, P.; Bsiesy, A.; Vallée, C.; Jomni, F.

    2016-06-01

    Dielectric spectroscopy is carried out for intrinsic and aluminum-doped TiO2 rutile films which are deposited on RuO2 by the atomic layer deposition technique. Capacitance and conductance are measured in the 0.1 Hz-100 kHz range, for ac electric fields up to 1 MVrms/cm. Intrinsic films have a much lower dielectric constant than rutile crystals. This is ascribed to the presence of oxygen vacancies which depress polarizability. When Al is substituted for Ti, the dielectric constant further decreases. By considering Al-induced modification of polarizability, a theoretical relationship between the dielectric constant and the Al concentration is proposed. Al doping drastically decreases the loss in the very low frequency part of the spectrum. However, Al doping has almost no effect on the loss at high frequencies. The effect of Al doping on loss is discussed through models of hopping transport implying intrinsic oxygen vacancies and Al related centers. When increasing the ac electric field in the MVrms/cm range, strong voltage non-linearities are evidenced in undoped films. The conductance increases exponentially with the ac field and the capacitance displays negative values (inductive behavior). Hopping barrier lowering is proposed to explain high-field effects. Finally, it is shown that Al doping strongly improves the high-field dielectric behavior.

  1. Amyloid Aggregation and Membrane Disruption by Amyloid Proteins

    NASA Astrophysics Data System (ADS)

    Ramamoorthy, Ayyalusamy

    2013-03-01

    Amyloidogenesis has been the focus of intense basic and clinical research, as an increasing number of amyloidogenic proteins have been linked to common and incurable degenerative diseases including Alzheimer's, type II diabetes, and Parkinson's. Recent studies suggest that the cell toxicity is mainly due to intermediates generated during the assembly process of amyloid fibers, which have been proposed to attack cells in a variety of ways. Disruption of cell membranes is believed to be one of the key components of amyloid toxicity. However, the mechanism by which this occurs is not fully understood. Our research in this area is focused on the investigation of the early events in the aggregation and membrane disruption of amyloid proteins, Islet amyloid polypeptide protein (IAPP, also known as amylin) and amyloid-beta peptide, on the molecular level. Structural insights into the mechanisms of membrane disruption by these amyloid proteins and the role of membrane components on the membrane disruption will be presented.

  2. Interfacial reaction control and its mechanism of AlN epitaxial films grown on Si(111) substrates by pulsed laser deposition

    PubMed Central

    Wang, Wenliang; Yang, Weijia; Liu, Zuolian; Wang, Haiyan; Wen, Lei; Li, Guoqiang

    2015-01-01

    High-quality AlN epitaxial films have been grown on Si substrates by pulsed laser deposition (PLD) by effective control of the interfacial reactions between AlN films and Si substrates. The surface morphology, crystalline quality and interfacial property of as-grown AlN/Si hetero-interfaces obtained by PLD have been systemically studied. It is found that the amorphous SiAlN interfacial layer is formed during high temperature growth, which is ascribed to the serious interfacial reactions between Si atoms diffused from the substrates and the AlN plasmas produced by the pulsed laser when ablating the AlN target during the high temperature growth. On the contrary, abrupt and sharp AlN/Si hetero-interfaces can be achieved by effectively controlling the interfacial reactions at suitable growth temperature. The mechanisms for the evolution of interfacial layer from the amorphous SiAlN layer to the abrupt and sharp AlN/Si hetero-interfaces by PLD are hence proposed. This work of obtaining the abrupt interfaces and the flat surfaces for AlN films grown by PLD is of paramount importance for the application of high-quality AlN-based devices on Si substrates. PMID:26089026

  3. Annealing study of H2O and O3 grown Al2O3 deposited by atomic layer chemical vapour deposition on n-type 4H-SiC

    NASA Astrophysics Data System (ADS)

    Avice, Marc; Grossner, Ulrike; Nilsen, Ola; Christensen, Jens S.; Fjellvåg, Helmer; Svensson, Bengt G.

    2006-09-01

    Al2O3 has been grown by atomic layer chemical vapour deposition on HF cleaned n-type 4H-SiC using either H2O or O3 as an oxidant. After post-deposition annealing at high temperature (1000°C) in argon atmosphere for different durations (1, 2 and 3 h), bulk and interface properties of the films were studied by capacitance-voltage (CV), current-voltage (IV) and secondary ion mass spectrometry (SIMS) measurements. Electrical measurements show a decreasing shift of the flatband voltage indicating a diminution of the negative oxide charges with increasing annealing time. The SIMS measurements reveal accumulation of boron, sodium and potassium at the Al2O3/SiC interface but the accumulation decreases with annealing at 1000°C where also out diffusion of silicon into the Al2O3 film takes place.

  4. Role of oxygen pressure on the structural, morphological and optical properties of c-Al2O3 films deposited by thermal evaporator

    NASA Astrophysics Data System (ADS)

    Khan, Ijaz Ahmad; Amna, Noureen; Kanwal, Nosheen; Razzaq, Maleeha; Farid, Amjad; Amin, Nasir; Ikhlaq, Uzma; Saleem, Murtaza; Ahmad, Riaz

    2017-03-01

    Aluminum oxide (c-Al2O3) films are deposited for various (0.5, 1, 1.5 and 2 mbar) oxygen pressures on glass substrates by thermal evaporator. The x-ray diffraction patterns exhibit the development of single diffraction peak related to c-Al2O3 phase which grows along (2 2 0) orientation up to 1.5 mbar pressure. For 2 mbar pressure, the deposited film becomes amorphous because no diffraction peak is observed. A minimum FWHM and maximum crystallite size of c-Al2O3 (2 2 0) plane is observed for 1 mbar pressure. The enhanced crystallite size of c-Al2O3 (2 2 0) plane is responsible to decrease the dislocation density and residual stresses developed during the deposition process. The field emission scanning electron microscopic analysis reveals the formation of smooth, uniform and compact films showing uniform distribution of nano-particles of different shapes and sizes. The energy dispersive x-ray spectroscopic analysis confirms the presence of Al whose content is decreased with the increase of oxygen pressures. The ellipsometric analysis confirms that the refractive index and the thickness of c-Al2O3 film deposited for 0.5 mbar pressure are found to 1.685 and 124.43 nm respectively. In short, the crystal structure, surface morphology, film thickness and refractive index of c-Al2O3 films are associated with the increase of oxygen pressures.

  5. Bottom-gate coplanar graphene transistors with enhanced graphene adhesion on atomic layer deposition Al{sub 2}O{sub 3}

    SciTech Connect

    Park, Dong-Wook; Mikael, Solomon; Chang, Tzu-Hsuan; Ma, Zhenqiang; Gong, Shaoqin

    2015-03-09

    A graphene transistor with a bottom-gate coplanar structure and an atomic layer deposition (ALD) aluminum oxide (Al{sub 2}O{sub 3}) gate dielectric is demonstrated. Wetting properties of ALD Al{sub 2}O{sub 3} under different deposition conditions are investigated by measuring the surface contact angle. It is observed that the relatively hydrophobic surface is suitable for adhesion between graphene and ALD Al{sub 2}O{sub 3}. To achieve hydrophobic surface of ALD Al{sub 2}O{sub 3}, a methyl group (CH{sub 3})-terminated deposition method has been developed and compared with a hydroxyl group (OH)-terminated deposition. Based on this approach, bottom-gate coplanar graphene field-effect transistors are fabricated and characterized. A post-thermal annealing process improves the performance of the transistors by enhancing the contacts between the source/drain metal and graphene. The fabricated transistor shows an I{sub on}/I{sub off} ratio, maximum transconductance, and field-effect mobility of 4.04, 20.1 μS at V{sub D} = 0.1 V, and 249.5 cm{sup 2}/V·s, respectively.

  6. Effect of film thickness on structural and mechanical properties of AlCrN nanocompoite thin films deposited by reactive DC magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Prakash, Ravi; Kaur, Davinder

    2016-05-01

    In this study, the influence of film thickness on the structural, surface morphology and mechanical properties of Aluminum chromium nitride (AlCrN) thin films has been successfully investigated. The AlCrN thin films were deposited on silicon (100) substrate using dc magnetron reactive co-sputtering at substrate temperature 400° C. The structural, surface morphology and mechanical properties were studied using X-ray diffraction, field-emission scanning electron microscopy and nanoindentation techniques respectively. The thickness of these thin films was controlled by varying the deposition time therefore increase in deposition time led to increase in film thickness. X-ray diffraction pattern of AlCrN thin films with different deposition time shows the presence of (100) and (200) orientations. The crystallite size varies in the range from 12.5 nm to 36.3 nm with the film thickness due to surface energy minimization with the higher film thickness. The hardness pattern of these AlCrN thin films follows Hall-Petch relation. The highest hardness 23.08 Gpa and young modulus 215.31 Gpa were achieved at lowest grain size of 12.5 nm.

  7. Targeting vascular amyloid in arterioles of Alzheimer disease transgenic mice with amyloid β protein antibody-coated nanoparticles.

    PubMed

    Poduslo, Joseph F; Hultman, Kristi L; Curran, Geoffry L; Preboske, Gregory M; Chamberlain, Ryan; Marjańska, Małgorzata; Garwood, Michael; Jack, Clifford R; Wengenack, Thomas M

    2011-08-01

    The relevance of cerebral amyloid angiopathy (CAA) to the pathogenesis of Alzheimer disease (AD) and dementia in general emphasizes the importance of developing novel targeting approaches for detecting and treating cerebrovascular amyloid (CVA) deposits. We developed a nanoparticle-based technology that uses a monoclonal antibody against fibrillar human amyloid-β42 that is surface coated onto a functionalized phospholipid monolayer. We demonstrate that this conjugated nanoparticle binds to CVA deposits in arterioles of AD transgenic mice (Tg2576) after infusion into the external carotid artery using 3 different approaches. The first 2 approaches use a blood vessel enrichment of homogenized brain and a leptomeningeal vessel preparation from thin tangential brain slices from the surface of the cerebral cortex. Targeting of CVA by the antibody-coated nanoparticle was visualized using fluorescent lissamine rhodamine-labeled phospholipids in the nanoparticles, which were compared with fluorescent staining of the endothelial cells and amyloid deposits using confocal laser scanning microscopy. The third approach used high-field strength magnetic resonance imaging of antibody-coated iron oxide nanoparticles after infusion into the external carotid artery. Dark foci of contrast enhancement in cortical arterioles were observed in T2*-weighted images of ex vivo AD mouse brains that correlated histologically with CVA deposits. The targeting ability of these nanoparticles to CVA provides opportunities for the prevention and treatment of CAA.

  8. Impact of the surface-near silicon substrate properties on the microstructure of sputter-deposited AlN thin films

    SciTech Connect

    Schneider, M.; Bittner, A.; Patocka, F.; Schmid, U.; Stoeger-Pollach, M.

    2012-11-26

    In micro-/nanomachined devices and systems, aluminum nitride (AlN) thin films are widely used due to their piezoelectric properties. This work evaluates the potential of modifying the interface between the AlN thin film and the silicon (Si) wafer serving as bottom electrode for optimized crystallographic orientation and, hence, improved electrical and piezoelectric properties. The films were analyzed using temperature-dependant leakage current measurements, transmission electron microscopy, and x-ray diffraction. By preconditioning of the Si substrate surface applying sputter etching prior to film deposition, leakage current levels are substantially decreased and an increased (002) orientation of the AlN grains is observed.

  9. Impact of the surface-near silicon substrate properties on the microstructure of sputter-deposited AlN thin films

    NASA Astrophysics Data System (ADS)

    Schneider, M.; Bittner, A.; Patocka, F.; Stöger-Pollach, M.; Halwax, E.; Schmid, U.

    2012-11-01

    In micro-/nanomachined devices and systems, aluminum nitride (AlN) thin films are widely used due to their piezoelectric properties. This work evaluates the potential of modifying the interface between the AlN thin film and the silicon (Si) wafer serving as bottom electrode for optimized crystallographic orientation and, hence, improved electrical and piezoelectric properties. The films were analyzed using temperature-dependant leakage current measurements, transmission electron microscopy, and x-ray diffraction. By preconditioning of the Si substrate surface applying sputter etching prior to film deposition, leakage current levels are substantially decreased and an increased (002) orientation of the AlN grains is observed.

  10. Nonlinear absorption properties of AlGaAs/GaAs multiple quantum wells grown by metalorganic chemical vapor deposition

    NASA Technical Reports Server (NTRS)

    Lee, Hsing-Chung; Kost, A.; Kawase, M.; Hariz, A.; Dapkus, P. Daniel

    1988-01-01

    The nonlinear absorption properties of the excitonic resonances associated with multiple quantum wells (MQWs) in AlGaAs/GaAs grown by metalorganic chemical vapor deposition are reported. The dependence of the saturation properties on growth parameters, especially growth temperature, and the well width are described. The minimum measured saturation intensity for these materials is 250 W/sq cm, the lowest reported value to date. The low saturation intensities are the result of excellent minority carrier properties. A systematic study of minority carrier lifetimes in quantum wells are reported. Lifetimes range from 50-350 ns depending on growth temperature and well width. When corrected for lateral diffusion effects and the measured minority carrier lifetime, the saturation data suggest that saturation intensities as low as 2.3 W/sq cm can be achieved in this system. The first measurements of the dependence of the exciton area and the magnitude of the excitonic absorption on well width are prsented. The growth of MQW structures on transparent GaP substrates is demonstrated and the electroabsorption properties of these structures are reviewed.

  11. ALS-based hummock size-distance relationship assessment of Mt Shasta debris avalanche deposit, Northern California, USA

    NASA Astrophysics Data System (ADS)

    Tortini, Riccardo; Carn, Simon; van Wyk de Vries, Benjamin

    2015-04-01

    The failure of destabilized volcano flanks is a likely occurrence during the lifetime of a stratovolcano, generating large debris avalanches and drastically changing landforms around volcanoes. The significant hazards associated with these events in the Cascade range were demonstrated, for example, by the collapse of Mt St Helens (WA), which triggered its devastating explosive eruption in 1980. The rapid modification of the landforms due to these events makes it difficult to estimate the magnitude of prehistoric avalanches. However, the widespread preservation of hummocks along the course of rockslide-debris avalanches is highly significant for understanding the physical characteristics of these landslides. Mt Shasta is a 4,317 m high, snow-capped, steep-sloped stratovolcano located in Northern California. The current edifice began forming on the remnants of an ancestral Mt Shasta that collapsed ~300-380k years ago producing one of the largest debris avalanches known on Earth. The debris avalanche deposit (DAD) covers a surface of ~450 km2 across the Shasta valley, with an estimated volume of ~26 km3. We analyze ALS data on hummocks from the prehistoric Shasta valley DAD in northern California (USA) to derive the relationship between hummock size and distance from landslide source, and interpret the geomorphic significance of the intercept and slope coefficients of the observed functional relationships. Given the limited extent of the ALS survey (i.e. 40 km2), the high-resolution dataset is used for validation of the morphological parameters extracted from freely available, broader coverage DTMs such as the National Elevation Dataset (NED). The ALS dataset also permits the identification of subtle topographic features not apparent in the field or in coarser resolution datasets, including a previously unmapped fault, of crucial importance for both seismic and volcanic hazard assessment in volcanic areas. We present evidence from the Shasta DAD of neotectonic

  12. Improved thermal stability and electrical properties of atomic layer deposited HfO{sub 2}/AlN high-k gate dielectric stacks on GaAs

    SciTech Connect

    Cao, Yan-Qiang; Li, Xin; Zhu, Lin; Cao, Zheng-Yi; Wu, Di; Li, Ai-Dong

    2015-01-15

    The thermal stability and electrical properties of atomic layer deposited HfO{sub 2}/AlN high-k gate dielectric stacks on GaAs were investigated. Compared to HfO{sub 2}/Al{sub 2}O{sub 3} gate dielectric, significant improvements in interfacial quality as well as electrical characteristics after postdeposition annealing are confirmed by constructing HfO{sub 2}/AlN dielectric stacks. The chemical states were carefully explored by the x-ray photoelectron spectroscopy, which indicates the AlN layers effectively prevent from the formation of defective native oxides at elevated temperatures. In addition, it is found that NH{sub 3} plasma during AlN plasma-enhanced atomic layer deposition also has the self-cleaning effect as Al(CH{sub 3}){sub 3} in removing native oxides. The passivating AlN layers suppress the formation of interfacial oxide and trap charge, leading to the decrease of capacitance equivalent thickness after annealing. Moreover, HfO{sub 2}/AlN/GaAs sample has a much lower leakage current density of 2.23 × 10{sup −4} A/cm{sup 2} than HfO{sub 2}/Al{sub 2}O{sub 3}/GaAs sample of 2.58 × 10{sup −2} A/cm{sup 2}. For the HfO{sub 2}/AlN/GaAs sample annealed at 500 °C, it has a lowest interface trap density value of 2.11 × 10{sup 11} eV{sup −1} cm{sup −2}. These results indicate that adopting HfO{sub 2}/AlN dielectric stacks may be a promising approach for the realization of high quality GaAs-based transistor devices.

  13. Partial Volume Correction in Quantitative Amyloid Imaging

    PubMed Central

    Su, Yi; Blazey, Tyler M.; Snyder, Abraham Z.; Raichle, Marcus E.; Marcus, Daniel S.; Ances, Beau M.; Bateman, Randall J.; Cairns, Nigel J.; Aldea, Patricia; Cash, Lisa; Christensen, Jon J.; Friedrichsen, Karl; Hornbeck, Russ C.; Farrar, Angela M.; Owen, Christopher J.; Mayeux, Richard; Brickman, Adam M.; Klunk, William; Price, Julie C.; Thompson, Paul M.; Ghetti, Bernardino; Saykin, Andrew J.; Sperling, Reisa A.; Johnson, Keith A.; Schofield, Peter R.; Buckles, Virginia; Morris, John C.; Benzinger, Tammie. LS.

    2014-01-01

    Amyloid imaging is a valuable tool for research and diagnosis in dementing disorders. As positron emission tomography (PET) scanners have limited spatial resolution, measured signals are distorted by partial volume effects. Various techniques have been proposed for correcting partial volume effects, but there is no consensus as to whether these techniques are necessary in amyloid imaging, and, if so, how they should be implemented. We evaluated a two-component partial volume correction technique and a regional spread function technique using both simulated and human Pittsburgh compound B (PiB) PET imaging data. Both correction techniques compensated for partial volume effects and yielded improved detection of subtle changes in PiB retention. However, the regional spread function technique was more accurate in application to simulated data. Because PiB retention estimates depend on the correction technique, standardization is necessary to compare results across groups. Partial volume correction has sometimes been avoided because it increases the sensitivity to inaccuracy in image registration and segmentation. However, our results indicate that appropriate PVC may enhance our ability to detect changes in amyloid deposition. PMID:25485714

  14. Iatrogenic amyloid polyneuropathy after domino liver transplantation

    PubMed Central

    Mnatsakanova, Diana; Živković, Saša A

    2017-01-01

    Liver transplantation has been used in treatment of transthyretin amyloidosis, and some patients undergo domino liver transplantation (DLT) with explanted liver being transplanted to another patient with liver failure as the liver is otherwise usually functionally normal. Until end of 2015, there were 1154 DLT performed worldwide. DLT for transthyretin amyloidosis is associated with the risk of developing de novo systemic amyloidosis and amyloid neuropathy, and the risk may be greater with some non-Val30Met mutations. De novo amyloid neuropathy has been described in up to 23% of transplant recipients. Neuropathy may be preceded by asymptomatic amyloid deposition in various tissues and symptoms of neuropathy started after a median of 7 years following DLT (5.7 ± 3.2 years; range 2 mo to 10 years). Typical initial symptoms include neuropathic pain and sensory loss, while dysautonomia usually starts later. Progression of neuropathy may necessitate liver re-transplantation, and subsequent improvement of neuropathy has been reported in some patients. Explant allograft recipients need close monitoring for signs of systemic amyloidosis, neuropathy and dysautonomia as progressive symptoms may require re-transplantation. PMID:28217248

  15. Cooperative Hydrogen Bonding in Amyloid Formation.

    SciTech Connect

    Tsemekhman, Kiril L.; Goldschmidt, Lukasz; Eisenberg, Dvaid; Baker, David

    2007-04-01

    The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. Amyloid diseases, including Alzheimer's and prion diseases, are each associated with unbranched protein fibrils. Each fibril is made of a particular protein, yet they share common properties. One such property is nucleation-dependent fibril growth. Monomers of amyloid-forming proteins can remain in dissolved form for long periods, before rapidly assembly into fibrils. The lag before growth has been attributed to slow kinetics of formation of a nucleus, on which other molecules can deposit to form the fibril. We have explored the energetics of fibril formation, based on the known molecular structure of a fibril-forming peptide from the yeast prion, Sup35, using both classical and quantum (density functional theory) methods. We find that the energetics of fibril formation for the first three layers are cooperative using both methods. This cooperativity is consistent with the observation that formation of amyloid fibrils involves slow nucleation and faster growth.

  16. Fibrillar dimer formation of islet amyloid polypeptides

    DOE PAGES

    Chiu, Chi -cheng; de Pablo, Juan J.

    2015-05-08

    Amyloid deposits of human islet amyloid polypeptide (hIAPP), a 37-residue hormone co-produced with insulin, have been implicated in the development of type 2 diabetes. Residues 20 – 29 of hIAPP have been proposed to constitute the amyloidogenic core for the aggregation process, yet the segment is mostly unstructured in the mature fibril, according to solid-state NMR data. Here we use molecular simulations combined with bias-exchange metadynamics to characterize the conformational free energies of hIAPP fibrillar dimer and its derivative, pramlintide. We show that residues 20 – 29 are involved in an intermediate that exhibits transient β-sheets, consistent with recent experimentalmore » and simulation results. By comparing the aggregation of hIAPP and pramlintide, we illustrate the effects of proline residues on inhibition of the dimerization of IAPP. The mechanistic insights presented here could be useful for development of therapeutic inhibitors of hIAPP amyloid formation.« less

  17. Electrical conduction and dielectric relaxation properties of AlN thin films grown by hollow-cathode plasma-assisted atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Altuntas, Halit; Bayrak, Turkan; Kizir, Seda; Haider, Ali; Biyikli, Necmi

    2016-07-01

    In this study, aluminum nitride (AlN) thin films were deposited at 200 °C, on p-type silicon substrates utilizing a capacitively coupled hollow-cathode plasma source integrated atomic layer deposition (ALD) reactor. The structural properties of AlN were characterized by grazing incidence x-ray diffraction, by which we confirmed the hexagonal wurtzite single-phase crystalline structure. The films exhibited an optical band edge around ˜5.7 eV. The refractive index and extinction coefficient of the AlN films were measured via a spectroscopic ellipsometer. In addition, to investigate the electrical conduction mechanisms and dielectric properties, Al/AlN/p-Si metal-insulator-semiconductor capacitor structures were fabricated, and current density-voltage and frequency dependent (7 kHz-5 MHz) dielectric constant measurements (within the strong accumulation region) were performed. A peak of dielectric loss was observed at a frequency of 3 MHz and the Cole-Davidson empirical formula was used to determine the relaxation time. It was concluded that the native point defects such as nitrogen vacancies and DX centers formed with the involvement of Si atoms into the AlN layers might have influenced the electrical conduction and dielectric relaxation properties of the plasma-assisted ALD grown AlN films.

  18. Enhanced Performance of GaN-Based Light-Emitting Diodes by Using Al Mirror and Atomic Layer Deposition-TiO2/Al2O3 Distributed Bragg Reflector Backside Reflector with Patterned Sapphire Substrate

    NASA Astrophysics Data System (ADS)

    Chen, Hongjun; Guo, Hao; Zhang, Peiyuan; Zhang, Xiong; Liu, Honggang; Wang, Shengkai; Cui, Yiping

    2013-02-01

    GaN-based light-emitting diodes (LEDs) coated with an Al mirror and a three-pair TiO2/Al2O3 distributed Bragg reflector (DBR) by atomic layer deposition (ALD) grown on a patterned sapphire substrate (PSS) were proposed and realized for the first time. A 43.1% enhancement in light output power (LOP) was realized at 60 mA with the LED coated with an Al mirror and a three-pair ALD-grown TiO2/Al2O3 DBR compared with the LED without a backside reflector, as well as a 10.7% enhancement compared with the LED with a conventional Al mirror and a three-pair TiO2/SiO2 DBR reflector.

  19. Amyloids: from Pathogenesis to Function.

    PubMed

    Nizhnikov, A A; Antonets, K S; Inge-Vechtomov, S G

    2015-09-01

    The term "amyloids" refers to fibrillar protein aggregates with cross-β structure. They have been a subject of intense scrutiny since the middle of the previous century. First, this interest is due to association of amyloids with dozens of incurable human diseases called amyloidoses, which affect hundreds of millions of people. However, during the last decade the paradigm of amyloids as pathogens has changed due to an increase in understanding of their role as a specific variant of quaternary protein structure essential for the living cell. Thus, functional amyloids are found in all domains of the living world, and they fulfill a variety of roles ranging from biofilm formation in bacteria to long-term memory regulation in higher eukaryotes. Prions, which are proteins capable of existing under the same conditions in two or more conformations at least one of which having infective properties, also typically have amyloid features. There are weighty reasons to believe that the currently known amyloids are only a minority of their real number. This review provides a retrospective analysis of stages in the development of amyloid biology that during the last decade resulted, on one hand, in reinterpretation of the biological role of amyloids, and on the other hand, in the development of systems biology of amyloids, or amyloidomics.

  20. Fabrication and laser performance of Yb3+/Al3+ co-doped photonic crystal fiber synthesized by plasma nonchemical vapor deposition method

    NASA Astrophysics Data System (ADS)

    Xia, Changming; Zhou, Guiyao; Liu, Jiantao; Wang, Chao; Han, Ying; Zhang, Wei; Yuan, Jinhui

    2015-10-01

    In this paper, the bulk Yb3+/Al3+ co-doped silica glass with 1.3 Yb2O3-2.5Al2O3-96.2SiO2 (wt%) are synthesized by plasma nonchemical vapor deposition method combining solution doping technology, where the inductively coupled plasma is used as the heat source. The influence of different O2/N2 ratios on the fluorescence properties of Yb3+/Al3+ co-doped silica glass are investigated. The large mode area photonic crystal fiber (PCF) is fabricated by using the bulk Yb3+/Al3+ co-doped silica glass as fiber core. The laser performance of Yb3+/Al3+ co-doped photonic crystal fiber is studied.

  1. Defects reduction in a-plane AlGaN epi-layers grown on r-plane sapphire substrates by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhao, Jianguo; Zhang, Xiong; Dai, Qian; Wang, Nan; Wu, Zili; Wang, Shuchang; Cui, Yiping

    2017-01-01

    Nonpolar a-plane AlGaN epi-layers were grown on a semi-polar r-plane sapphire substrate with an innovative two-way pulsed-flows metal organic chemical vapor deposition growth technology. A root-mean-square value of 1.79 nm was achieved, and the relative light transmittance of the a-plane AlGaN epi-layer was enhanced by 36.9%. These results reveal that the innovative growth method is able to improve the surface morphology and reduce the defect density in nonpolar a-plane Al x Ga1- x N epi-layers, particularly those with an Al composition greater than 0.5, which are key materials for the fabrication of nonpolar AlGaN-based high light emission efficiency deep-ultraviolet light-emitting diodes.

  2. Formation and stability of crystalline and amorphous Al2O3 layers deposited on Ga2O3 nanowires by atomic layer epitaxy

    NASA Astrophysics Data System (ADS)

    Katz, M. B.; Twigg, M. E.; Prokes, S. M.

    2016-09-01

    Although the crystalline α and γ phases are the most stable forms of alumina, small-diameter (<6 nm) nanoparticles are known to be completely amorphous, due to the surface energy being correspondingly lower for the less stable non-crystalline phase. Al2O3 films with a thickness of 5 nm grown by low temperature (200 °C) atomic layer deposition (ALD) on small-diameter (<20 nm) Ga2O3 nanowires (NWs), however, are identified by transmission electron microscopy as belonging to the α, γ, and possibly θ crystalline phases of Al2O3, while films deposited on larger diameter (>20 nm) NWs are found to be amorphous. Indeed, until recently, all Al2O3, films deposited by low-temperature ALD using trimethylaluminum and water have been reported to be amorphous, regardless of film thickness or substrate. The formation of a crystalline ALD film can be understood in terms of the energetics of misfit dislocations that maintain the registry between the ALD film and the NW substrate, as well as the influence of strain and surface energy. The decreasing energy of co-axial misfit dislocations with NW diameter results in a corresponding decrease in the contribution of the Al2O3/Ga2O3 interface to the free energy, while the interfacial energy for an amorphous film is independent of the NW diameter. Therefore, for NW cores of sufficiently small diameter, the free energy contribution of the Al2O3/Ga2O3 interface is smaller for crystalline films than for amorphous films, thereby favoring the formation of crystalline films for small-diameter NWs. For ALD Al2O3 films of 10 nm thickness