24 results on '"Himali D"'
Search Results
2. Temporal effects on spectroscopic line shapes, resolution, and sensitivity of the broad-band sum frequency generation.
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Stiopkin, Igor V., Jayathilake, Himali D., Weeraman, Champika, and Benderskii, Alexander V.
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SPECTRUM analysis , *OPTICAL resolution , *SPECTRAL sensitivity , *FEMTOSECOND lasers , *ULTRASHORT laser pulses - Abstract
Sum frequency generation (SFG) is a surface-selective spectroscopy that provides a wealth of molecular-level information on the structure and dynamics at surfaces and interfaces. This paper addresses the general issue of spectral resolution and sensitivity of the broad-band (BB) SFG that involves a spectrally narrow nonresonant (usually visible) and a BB resonant (usually infrared) laser pulses. We examine how the spectral width and temporal shape of the two pulses, and the time delay between them, relate to the spectroscopic line shape and signal level in the BB-SFG measurement. By combining experimental and model calculations, we show that the best spectral resolution and highest signal level are simultaneously achieved when the nonresonant narrow-band upconversion pulse arrives with a nonzero time delay after the resonant BB pulse. The nonzero time delay partially avoids the linear trade-off of improving spectral resolution at the expense of decreasing signal intensity, which is common in BB-SFG schemes utilizing spectral filtering to produce narrow-band visible pulses. [ABSTRACT FROM AUTHOR]
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- 2010
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3. Rubbing-induced anisotropy of long alkyl side chains at polyimide surfaces.
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Jayathilake, Himali D., Zhu, Min Hua, Rosenblatt, Charles, Bordenyuk, Andrey N., Weeraman, Champika, and Benderskii, Alexander V.
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ANISOTROPY , *POLYIMIDES , *POLYMER liquid crystals , *VIBRATIONAL spectra , *MOLECULAR structure , *INFRARED imaging , *LIQUID crystal displays - Abstract
Molecular organization at polyimide surfaces used as alignment layers in liquid crystal displays was investigated using vibrational sum frequency generation (SFG) spectroscopy. We focus on the orientation of the long alkyl side groups at the polymer surface using polarization-selected SFG spectra of the CH3- and CH2-stretch modes of the side chain. Mechanical rubbing and baking, an accepted industrial procedure used to produce pretilt of the liquid crystal, was found to induce pronounced azimuthal anisotropy in the orientational distribution of the alkyl side chains. Orientational analysis of the SFG vibrational spectra in terms of the azimuthal and tilt angles (in and out of plane, respectively) of the alkyl side chains shows their preferential tilt along the rubbing direction, with the azimuthal distribution narrower for stronger rubbed polymer samples. [ABSTRACT FROM AUTHOR]
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- 2006
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4. Heterodyne-detected vibrational sum frequency generation spectroscopy
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Stiopkin, Igor V., Jayathilake, Himali D., Bordenyuk, Andrey N., and Benderskii, Alexander V.
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Monomolecular films -- Chemical properties ,Monomolecular films -- Optical properties ,Spectrum analysis -- Technology application ,Technology application ,Chemistry - Abstract
A new method of broad-band heterodyne-detected sum frequency generation (HD-SFG) spectroscopy is developed and its high sensitivity is demonstrated, allowing measurements of vibrational spectra of submonolayers. The HD-SFG spectroscopy has provided the phase as well the amplitude of the signal and has allowed accurate subtraction of the non-resonant background.
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- 2008
5. Heterodyne-Detected Vibrational Sum Frequency Generation Spectroscopy
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Igor V. Stiopkin, Alexander V. Benderskii, and Andrey N. Bordenyuk, and Himali D. Jayathilake
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Models, Molecular ,Heterodyne ,Sum-frequency generation ,Spectrophotometry, Infrared ,Surface Properties ,Chemistry ,Analytical chemistry ,Phase (waves) ,General Chemistry ,1-Octanol ,Interference (wave propagation) ,Sensitivity and Specificity ,Biochemistry ,Signal ,Molecular physics ,Catalysis ,Colloid and Surface Chemistry ,Reference beam ,Adsorption ,Spectroscopy ,Sum frequency generation spectroscopy - Abstract
We present a new technique of broad-band heterodyne-detected sum frequency generation (HD-SFG) spectroscopy and demonstrate its high sensitivity allowing surface-selective measurements of vibrational spectra at submonolayer surface coverage, as low as a few percent of a monolayer. This was achieved without the help of surface enhancement phenomena, on a transparent dielectric substrate (water), and without introducing fluorescent labels, in fact, without utilizing any electronic resonances. Only the intrinsic vibrational transitions were employed for the detection of the analyte molecules (1-octanol). Unlike conventional (homodyne-detected) SFG spectroscopy, where the signal intensity decreases quadratically with decreasing surface coverage, in HD-SFG, the scaling is linear, and the signal is amplified by interference with a reference beam, significantly improving sensitivity and detection limits. At the same time, HD-SFG provides the phase as well as the amplitude of the signal and thus allows accurate subtraction of the non-resonant background--a common problem for surfaces with low concentrations of analyte molecules (i.e., weak resonant signals).
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- 2008
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6. Vibrational Sum Frequency Generation Spectroscopy of Dodecanethiol on Metal Nanoparticles
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Achani K. Yatawara, Alexander V. Benderskii, Andrey N. Bordenyuk, Igor V. Stiopkin, Yi Liu, Himali D. Jayathilake, and Champika Weeraman
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Range (particle radiation) ,Materials science ,Sum-frequency generation ,Dodecane ,Analytical chemistry ,Nanoparticle ,Substrate (electronics) ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,General Energy ,chemistry ,Monolayer ,Physical and Theoretical Chemistry ,Spectroscopy ,Sum frequency generation spectroscopy - Abstract
We report studies of metal nanoparticle surfaces using vibrational sum frequency generation (SFG) spectroscopy. SFG is demonstrated as a sensitive and information-rich probe of nanostructured surfaces. Detection of SFG spectra from a few percent of a monolayer of nanoparticles on a transparent substrate was achieved, corresponding to as few as 105 isolated particles within the laser beam spot. A new effect arises when the nanoparticle size approaches the molecular scale: the dependence of the molecular conformation on the geometry of the substrate. Conformation of the dodecane chain of the ligand shows systematic variation with the particle diameter in the 1.8−25 nm range. More gauche defects are observed on smaller particles, judged from the relative intensities of the CH2 and CH3 stretch transitions in SFG spectra. Similar behavior observed for both gold and silver particles suggests a nanoscale geometric packing effect, whence more volume is available to the chain on a curved surface than a flat surfa...
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- 2007
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7. Promotion of early and exclusive breastfeeding in neonatal care units in rural Rwanda: a pre- and post-intervention study
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Saidath Gato, Francois Biziyaremye, Catherine M. Kirk, Chiquita Palha De Sousa, Alain Mukuralinda, Hamissy Habineza, Maya Asir, Himali de Silva, Marie Louise Manirakiza, Egide Karangwa, Alphonse Nshimyiryo, Alex Tugume, and Kathryn Beck
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Neonatal nutrition ,Small and sick newborns ,Rwanda ,Exclusive breastfeeding ,Nurturing care ,Baby-friendly ,Pediatrics ,RJ1-570 ,Public aspects of medicine ,RA1-1270 - Abstract
Abstract Background Early initiation of breastfeeding after birth and exclusive breastfeeding for the first six months improves child survival, nutrition and health outcomes. However, only 42% of newborns worldwide are breastfed within the first hour of life. Small and sick newborns are at greater risk of not receiving breastmilk and often require additional support for feeding. This study compares breastfeeding practices in Rwandan neonatal care units (NCUs) before and after the implementation of a package of interventions aimed to improve breastfeeding. Methods This pre-post intervention study was conducted at two district hospital NCUs in rural Rwanda from October–December 2017 (pre-intervention) and September 2018–March 2019 (post-intervention). Only newborns admitted before their second day of life (DOL) were included. Data were extracted from patient charts for clinical and demographic characteristics, feeding, and patient outcomes. Exclusive breastfeeding at discharge was based on last recorded infant feeding on the day of discharge. Logistic regression analysis was used to evaluate factors associated with exclusive breastfeeding at discharge. Results Pre-intervention, 255 newborns were admitted in the NCUs and 793 were admitted in post-intervention. Exclusive breastfeeding on the day of birth (DOL0) increased from 5.4% (12/255) to 35.9% (249/793). At discharge, exclusive breastfeeding increased from 69.6% (149/214) to 87.0% (618/710). The mortality rate decreased from 16.1% (41/255) to 10.5% (83/793). Factors associated with greater odds of exclusive breastfeeding at discharge included admission during the post-intervention period (aOR 4.91; 95% CI 1.99, 12.11), and admission for infection (aOR 2.99; 95% CI 1.13, 7.93). Home deliveries (aOR 0.15; 95% CI 0.05, 0.47), preterm delivery (aOR 0.36; 95% CI 0.15, 0.87) and delayed first breastmilk feed (aOR 0.04 for DOL3 vs. DOL0; 95% CI 0.01, 0.35) reduced odds of exclusive breastfeeding at discharge. Conclusions Expansion and adoption of evidenced-based guidelines, using innovative approaches, aimed at the unique needs of small and sick newborns may help to improve earlier initiation of breastfeeding, decrease mortality, and improve exclusive breastfeeding on discharge from hospital among small and sick newborns. These interventions should be replicated in similar settings to determine their effectiveness.
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- 2022
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8. Identifying underweight in infants and children using growth charts, lookup tables and a novel 'MAMI' slide chart: A cross-over diagnostic and acceptability study
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Meenakshi Monga, Catherine Sikorski, Himali de silva, Marie McGrath, and Marko Kerac
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Public aspects of medicine ,RA1-1270 - Abstract
Malnutrition is a leading cause of preventable deaths in infants and children. To benefit from treatment and prevention programmes, malnourished children must first be identified. Low weight-for-age is an anthropometric indicator of malnutrition which is gaining much recent attention because it is particularly effective at identifying children at highest risk of death. However, assessing weight-for-age can be challenging. We aimed to evaluate a novel, low-cost weight-for-age slide chart and compare its performance against two traditional methods. We conducted a cross-over diagnostic study comparing a new “MAMI” slide-chart against traditional growth charts and look-up tables. Participants were health and public health professionals working or studying in the UK. Each acted as their own control, using all three methods but in random order. Under timed conditions, they evaluated hypothetical scenarios, arranged in a random sequence. Each tool’s diagnostic accuracy and response rate were compared. User preferences were also recorded. Sixty-two participants took part. Diagnostic accuracy was highest for the MAMI chart: 79%(351/445) correct assessments. Accuracy using look-up tables was 70%(308/438). Growth charts performed worst: 61%(217/353) correct (p-value
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- 2023
9. Molecular order in Langmuir-Blodgett monolayers of metal-ligand surfactants probed by sum frequency generation
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Libo Wu, Cláudio N. Verani, Jeffery A. Driscoll, Andrey N. Bordenyuk, Alexander V. Benderskii, Himali D. Jayathilake, and Sandro R. P. da Rocha
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chemistry.chemical_classification ,Stereochemistry ,Ligand ,chemistry.chemical_element ,Surfaces and Interfaces ,Condensed Matter Physics ,Langmuir–Blodgett film ,Copper ,Crystallography ,chemistry ,Monolayer ,Amphiphile ,Electrochemistry ,Molecule ,General Materials Science ,Spectroscopy ,Alkyl - Abstract
Molecular organization of Langmuir-Blodgett (LB) monolayers of novel copper-containing metal-ligand surfactants was characterized by the surface-selective vibrational sum frequency generation (SFG) spectroscopy. The orientational and conformational order inferred from the SFG peak amplitudes and line shapes were correlated with the two-dimensional phases of the monolayers observed in the compression isotherms. The octadecyl-pyridin-2-ylmethyl-amine (L(PyC18)) ligand by itself shows good amphiphilic properties, as indicated by the high monolayer collapse pressure at the air/water interface, but its LB films transferred onto fused silica exhibit a high degree of trans-gauche conformational disorder in the alkyl tails. Coordination of copper(II) ions to the chelating head group enhances the molecular alignment and reduces the fraction of gauche defects of the alkyl chains. Monolayers of single-tail (L(PyC18)Cu(II)Cl(2)) and double-tail [(L(PyC18))(2)Cu(II)]Cl(2) metallosurfactants show distinctly different behavior of their molecular organization as a function of the area per molecule. Our observations suggest metal-ligand interactions as a pathway to induce molecular order in LB monolayer films.
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- 2009
10. Coherent vibrational quantum beats as a probe of Langmuir-Blodgett monolayers
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Alexander V. Benderskii, Andrey N. Bordenyuk, and Himali D. Jayathilake
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Condensed Matter::Materials Science ,Quantum beats ,Chemistry ,Monolayer ,Femtosecond ,Physics::Atomic and Molecular Clusters ,Materials Chemistry ,Analytical chemistry ,Physical and Theoretical Chemistry ,Langmuir–Blodgett film ,Molecular physics ,Surfaces, Coatings and Films - Abstract
We combine frequency- and femtosecond time-domain measurements of vibrational coherences for spectroscopic characterization of surface monolayer films, utilizing 3-wave mixing as the surface-selective technique. Frequency-domain spectra in the CH-stretch region are obtained by infrared + visible sum frequency generation (SFG). Time-domain coherences are measured using SFG free induction decay (SFG-FID), where a 75 fs IR pulse excites several vibrational modes and a delayed 40 fs visible pulse probes the oscillating surface polarization. A unified framework based on optical Bloch equations is used to simultaneously analyze the time- and frequency-domain data. We compare molecular organization of monolayers in different two-dimensional phases. Highly ordered films transferred at high surface pressure are dominated by two transitions in the frequency domain, CH3 symmetric stretch (2875 cm(-1)) and CH3-Fermi resonance with bend overtone (2935 cm(-1)), and a coherent quantum beat in the time-domain at the difference frequency (approximately 540 fs period). At lower surface pressure, relative amplitudes change and additional transitions emerge (CH3 asymmetric stretch and CH2 modes), indicating changes in molecular orientation and onset of disorder. Information redundancy in the combined frequency- and time-domain data allows more accurate determination of the spectral parameters than purely frequency- or time-domain techniques.
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- 2006
11. OSQR: A framework for ontology-based semantic query routing in unstructured P2P networks
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Himali, D M Rasanjalee, primary, Navathe, Shamkant B., additional, and Prasad, Sushil K, additional
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- 2012
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12. Molecular Order in Langmuir−Blodgett Monolayers of Metal−Ligand Surfactants Probed by Sum Frequency Generation
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Jayathilake, Himali D., primary, Driscoll, Jeffery A., additional, Bordenyuk, Andrey N., additional, Wu, Libo, additional, da Rocha, Sandro R. P., additional, Verani, Claudio N., additional, and Benderskii, Alexander V., additional
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- 2009
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13. Vibrational Sum Frequency Generation Spectroscopy of Dodecanethiol on Metal Nanoparticles
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Bordenyuk, Andrey N., primary, Weeraman, Champika, additional, Yatawara, Achani, additional, Jayathilake, Himali D., additional, Stiopkin, Igor, additional, Liu, Yi, additional, and Benderskii, Alexander V., additional
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- 2007
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14. Molecular Order in Langmuir−Blodgett Monolayers of Metal−Ligand Surfactants Probed by Sum Frequency Generation.
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Himali D. Jayathilake, Jeffery A. Driscoll, Andrey N. Bordenyuk, Libo Wu, Sandro R. P. da Rocha, Claudio N. Verani, and Alexander V. Benderskii
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MOLECULAR probes , *MULTILAYERED thin films , *MONOMOLECULAR films , *SURFACE active agents , *LIGANDS (Chemistry) , *METALS , *SURFACE analysis , *COPPER - Abstract
Molecular organization of Langmuir−Blodgett (LB) monolayers of novel copper-containing metal−ligand surfactants was characterized by the surface-selective vibrational sum frequency generation (SFG) spectroscopy. The orientational and conformational order inferred from the SFG peak amplitudes and line shapes were correlated with the two-dimensional phases of the monolayers observed in the compression isotherms. The octadecyl-pyridin-2-ylmethyl-amine (LPyC18) ligand by itself shows good amphiphilic properties, as indicated by the high monolayer collapse pressure at the air/water interface, but its LB films transferred onto fused silica exhibit a high degree of trans−gaucheconformational disorder in the alkyl tails. Coordination of copper(II) ions to the chelating head group enhances the molecular alignment and reduces the fraction of gauchedefects of the alkyl chains. Monolayers of single-tail (LPyC18CuIICl2) and double-tail [(LPyC18)2CuII]Cl2metallosurfactants show distinctly different behavior of their molecular organization as a function of the area per molecule. Our observations suggest metal−ligand interactions as a pathway to induce molecular order in LB monolayer films. [ABSTRACT FROM AUTHOR]
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- 2009
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15. Short Sleep Duration and Hypertension: A Double Hit for the Brain.
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Yiallourou S, Baril AA, Wiedner C, Song X, Bernal R, Himali D, Cavuoto MG, DeCarli C, Beiser A, Seshadri S, Himali JJ, and Pase MP
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- Humans, Female, Middle Aged, Male, Aged, Time Factors, Executive Function, Blood Pressure physiology, Risk Factors, Cognitive Dysfunction physiopathology, Cognitive Dysfunction etiology, Sleep Duration, Hypertension physiopathology, Hypertension complications, Magnetic Resonance Imaging, Brain physiopathology, Brain diagnostic imaging, Sleep, Cognition, Polysomnography
- Abstract
Background: Short sleep duration has been associated with an increased risk of cognitive impairment and dementia. Short sleep is associated with elevated blood pressure, yet the combined insult of short sleep and hypertension on brain health remains unclear. We assessed whether the association of sleep duration with cognition and vascular brain injury was moderated by hypertensive status., Methods and Results: A total of 682 dementia-free participants (mean age, 62±9 years; 53% women) from the Framingham Heart Study completed assessments of cognition, office blood pressure, and self-reported habitual and polysomnography-derived sleep duration; 637 underwent brain magnetic resonance imaging. Linear regressions were performed to assess effect modification by hypertensive status on total sleep time (coded in hours) and cognitive and magnetic resonance imaging outcomes. There was a significant interaction between sleep duration and hypertensive status when predicting executive function/processing speed (Trail Making B-A) and white matter hyperintensities. When results were stratified by hypertensive status, longer sleep duration was associated with better executive functioning/processing speed scores in the hypertensive group (meaning that shorter sleep duration was associated with poorer executive function/processing speed scores) (self-report sleep: β=0.041 [95% CI, 0.012-0.069], P =0.005; polysomnography sleep: β=0.045 [95% CI, 0.002-0.087], P =0.038), but no association was observed for the normotensive group. Similarly, shorter subjective sleep duration was associated with higher white matter hyperintensity burden in the hypertensive group (β=-0.115 [95% CI, -0.227 to -0.004], P =0.042), but not in the normotensive group., Conclusions: In individuals with hypertension, shorter sleep duration was associated with worse cognitive performance and greater brain injury.
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- 2024
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16. Sleep macro-architecture and dementia risk in adults: Meta-analysis of 5 cohorts from the Sleep and Dementia Consortium.
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Yiallourou S, Baril AA, Wiedner C, Misialek JR, Kline CE, Harrison S, Cannon E, Yang Q, Bernal R, Bisson A, Himali D, Cavuoto M, Weihs A, Beiser A, Gottesman RF, Leng Y, Lopez O, Lutsey PL, Purcell SM, Redline S, Seshadri S, Stone KL, Yaffe K, Ancoli-Israel S, Xiao Q, Vaou EO, Himali JJ, and Pase MP
- Abstract
Study Objectives: Poor sleep may play a role in the risk of dementia. However, few studies have investigated the association between polysomnography (PSG)-derived sleep architecture and dementia incidence. We examined the relationship between sleep macro-architecture and dementia incidence across five US-based cohort studies from the Sleep and Dementia Consortium (SDC)., Methods: Percent of time spent in stages of sleep (N1, N2, N3, REM sleep), wake after sleep onset and sleep maintenance efficiency were derived from a single night home-based PSG. Dementia was ascertained in each cohort using its cohort-specific criteria. Each cohort performed Cox proportional hazard regressions for each sleep exposure and incident dementia, adjusting for age, sex, body mass index, anti-depressant use, sedative use, and APOE e4 status. Results were then pooled in random effects meta-analyses., Results: The pooled sample comprised 4,657 participants (30% women) aged ≥60 years (mean age was 74 years at sleep assessment). There were 998 (21.4%) dementia cases (median follow-up time of 5 to 19 years). Pooled effects of the five cohorts showed no association between sleep architecture and incident dementia. When meta-analyses were restricted to the three cohorts which had dementia case ascertainment based on DSM-IV/V criteria (n=2,374), higher N3% was marginally associated with an increased risk of dementia (HR: 1.06; 95%CI: 1.00-1.12, per percent increase N3, p=0.050)., Conclusions: There were no consistent associations between sleep macro-architecture measured and the risk of incident dementia. Implementing more nuanced sleep metrics remains an important next step for uncovering more about sleep-dementia associations.
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- 2024
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17. Association of Sleep Duration and Change Over Time With Imaging Biomarkers of Cerebrovascular, Amyloid, Tau, and Neurodegenerative Pathology.
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Baril AA, Kojis DJ, Himali JJ, Decarli CS, Sanchez E, Johnson KA, El Fakhri G, Thibault E, Yiallourou SR, Himali D, Cavuoto MG, Pase MP, Beiser AS, and Seshadri S
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- Male, Humans, Middle Aged, Aged, Female, Cross-Sectional Studies, Neuroimaging, Biomarkers, Sleep Duration, Amyloidogenic Proteins
- Abstract
Background and Objectives: Both short and long sleep duration were previously associated with incident dementia, but underlying mechanisms remain unclear. We evaluated how self-reported sleep duration and its change over time associate with (A)myloid, (T)au, (N)eurodegeneration, and (V)ascular neuroimaging markers of Alzheimer disease., Methods: Two Framingham Heart Study overlapping samples were studied: participants who underwent
11 C-Pittsburg Compound B amyloid and18 F-flortaucipir tau PET imaging and participants who underwent an MRI. MRI metrics estimated neurodegeneration (total brain volume) and cerebrovascular injuries (white matter hyperintensities [WMHs] volume, covert brain infarcts, free-water [FW] fraction). Self-reported sleep duration was assessed and split into categories both at the time of neuroimaging testing and approximately 13 years before: short ≤6 hours. average 7-8 hours, and long ≥9 hours. Logistic and linear regression models were used to examine sleep duration and neuroimaging metrics., Results: The tested cohort was composed of 271 participants (age 53.6 ± 8.0 years; 51% male) in the PET imaging sample and 2,165 participants (age 61.3 ± 11.1 years; 45% male) in the MRI sample. No fully adjusted association was observed between cross-sectional sleep duration and neuroimaging metrics. In fully adjusted models compared with consistently sleeping 7-8 hours, groups transitioning to a longer sleep duration category over time had higher FW fraction (short to average β [SE] 0.0062 [0.0024], p = 0.009; short to long β [SE] 0.0164 [0.0076], p = 0.031; average to long β [SE] 0.0083 [0.0022], p = 0.002), and those specifically going from average to long sleep duration also had higher WMH burden (β [SE] 0.29 [0.11], p = 0.007). The opposite associations (lower WMH and FW) were observed in participants consistently sleeping ≥9 hours as compared with people consistently sleeping 7-8 hours in fully adjusted models (β [SE] -0.43 [0.20], p = 0.028; β [SE] -0.019 [0.004], p = 0.020). Each hour of increasing sleep (continuous, β [SE] 0.12 [0.04], p = 0.003; β [SE] 0.002 [0.001], p = 0.021) and extensive increase in sleep duration (≥2 hours vs 0 ± 1 hour change; β [SE] 0.24 [0.10], p = 0.019; β [SE] 0.0081 [0.0025], p = 0.001) over time was associated with higher WMH burden and FW fraction in fully adjusted models. Sleep duration change was not associated with PET amyloid or tau outcomes., Discussion: Longer self-reported sleep duration over time was associated with neuroimaging biomarkers of cerebrovascular pathology as evidenced by higher WMH burden and FW fraction. A longer sleep duration extending over time may be an early change in the neurodegenerative trajectory.- Published
- 2024
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18. Association Between Slow-Wave Sleep Loss and Incident Dementia.
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Himali JJ, Baril AA, Cavuoto MG, Yiallourou S, Wiedner CD, Himali D, DeCarli C, Redline S, Beiser AS, Seshadri S, and Pase MP
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- Humans, Female, Aged, Middle Aged, Male, Cohort Studies, Prospective Studies, Apolipoprotein E4 genetics, Sleep, Alzheimer Disease genetics, Sleep, Slow-Wave
- Abstract
Importance: Slow-wave sleep (SWS) supports the aging brain in many ways, including facilitating the glymphatic clearance of proteins that aggregate in Alzheimer disease. However, the role of SWS in the development of dementia remains equivocal., Objective: To determine whether SWS loss with aging is associated with the risk of incident dementia and examine whether Alzheimer disease genetic risk or hippocampal volumes suggestive of early neurodegeneration were associated with SWS loss., Design, Setting, and Participants: This prospective cohort study included participants in the Framingham Heart Study who completed 2 overnight polysomnography (PSG) studies in the time periods 1995 to 1998 and 2001 to 2003. Additional criteria for individuals in this study sample were an age of 60 years or older and no dementia at the time of the second overnight PSG. Data analysis was performed from January 2020 to August 2023., Exposure: Changes in SWS percentage measured across repeated overnight sleep studies over a mean of 5.2 years apart (range, 4.8-7.1 years)., Main Outcome: Risk of incident all-cause dementia adjudicated over 17 years of follow-up from the second PSG., Results: From the 868 Framingham Heart Study participants who returned for a second PSG, this cohort included 346 participants with a mean age of 69 years (range, 60-87 years); 179 (52%) were female. Aging was associated with SWS loss across repeated overnight sleep studies (mean [SD] change, -0.6 [1.5%] per year; P < .001). Over the next 17 years of follow-up, there were 52 cases of incident dementia. In Cox regression models adjusted for age, sex, cohort, positivity for at least 1 APOE ε4 allele, smoking status, sleeping medication use, antidepressant use, and anxiolytic use, each percentage decrease in SWS per year was associated with a 27% increase in the risk of dementia (hazard ratio, 1.27; 95% CI, 1.06-1.54; P = .01). SWS loss with aging was accelerated in the presence of Alzheimer disease genetic risk (ie, APOE ε4 allele) but not hippocampal volumes measured proximal to the first PSG., Conclusions and Relevance: This cohort study found that slow-wave sleep percentage declined with aging and Alzheimer disease genetic risk, with greater reductions associated with the risk of incident dementia. These findings suggest that SWS loss may be a modifiable dementia risk factor.
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- 2023
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19. Sleep Architecture, Obstructive Sleep Apnea, and Cognitive Function in Adults.
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Pase MP, Harrison S, Misialek JR, Kline CE, Cavuoto M, Baril AA, Yiallourou S, Bisson A, Himali D, Leng Y, Yang Q, Seshadri S, Beiser A, Gottesman RF, Redline S, Lopez O, Lutsey PL, Yaffe K, Stone KL, Purcell SM, and Himali JJ
- Subjects
- Male, Female, Humans, Adult, Middle Aged, Aged, Aged, 80 and over, Cognition, Sleep, Osteoporotic Fractures, Sleep Apnea, Obstructive complications, Sleep Apnea, Obstructive epidemiology, Dementia epidemiology, Dementia complications
- Abstract
Importance: Good sleep is essential for health, yet associations between sleep and dementia risk remain incompletely understood. The Sleep and Dementia Consortium was established to study associations between polysomnography (PSG)-derived sleep and the risk of dementia and related cognitive and brain magnetic resonance imaging endophenotypes., Objective: To investigate association of sleep architecture and obstructive sleep apnea (OSA) with cognitive function in the Sleep and Dementia Consortium., Design, Setting, and Participants: The Sleep and Dementia Consortium curated data from 5 population-based cohorts across the US with methodologically consistent, overnight, home-based type II PSG and neuropsychological assessments over 5 years of follow-up: the Atherosclerosis Risk in Communities study, Cardiovascular Health Study, Framingham Heart Study (FHS), Osteoporotic Fractures in Men Study, and Study of Osteoporotic Fractures. Sleep metrics were harmonized centrally and then distributed to participating cohorts for cohort-specific analysis using linear regression; study-level estimates were pooled in random effects meta-analyses. Results were adjusted for demographic variables, the time between PSG and neuropsychological assessment (0-5 years), body mass index, antidepressant use, and sedative use. There were 5946 participants included in the pooled analyses without stroke or dementia. Data were analyzed from March 2020 to June 2023., Exposures: Measures of sleep architecture and OSA derived from in-home PSG., Main Outcomes and Measures: The main outcomes were global cognitive composite z scores derived from principal component analysis, with cognitive domains investigated as secondary outcomes. Higher scores indicated better performance., Results: Across cohorts, 5946 adults (1875 females [31.5%]; mean age range, 58-89 years) were included. The median (IQR) wake after sleep onset time ranged from 44 (27-73) to 101 (66-147) minutes, and the prevalence of moderate to severe OSA ranged from 16.9% to 28.9%. Across cohorts, higher sleep maintenance efficiency (pooled β per 1% increase, 0.08; 95% CI, 0.03 to 0.14; P < .01) and lower wake after sleep onset (pooled β per 1-min increase, -0.07; 95% CI, -0.13 to -0.01 per 1-min increase; P = .02) were associated with better global cognition. Mild to severe OSA (apnea-hypopnea index [AHI] ≥5) was associated with poorer global cognition (pooled β, -0.06; 95% CI, -0.11 to -0.01; P = .01) vs AHI less than 5; comparable results were found for moderate to severe OSA (pooled β, -0.06; 95% CI, -0.11 to -0.01; P = .02) vs AHI less than 5. Differences in sleep stages were not associated with cognition., Conclusions and Relevance: This study found that better sleep consolidation and the absence of OSA were associated with better global cognition over 5 years of follow-up. These findings suggest that the role of interventions to improve sleep for maintaining cognitive function requires investigation.
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- 2023
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20. The prevalence, correlation, and co-occurrence of neuropathology in old age: harmonisation of 12 measures across six community-based autopsy studies of dementia.
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Nichols E, Merrick R, Hay SI, Himali D, Himali JJ, Hunter S, Keage HAD, Latimer CS, Scott MR, Steinmetz JD, Walker JM, Wharton SB, Wiedner CD, Crane PK, Keene CD, Launer LJ, Matthews FE, Schneider J, Seshadri S, White L, Brayne C, and Vos T
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- Prevalence, Male, Cross-Sectional Studies, Aged, 80 and over, Dementia, Female, TDP-43 Proteinopathies, Humans, Autopsy, Aged, Alzheimer Disease, Limbic Encephalitis, Cerebral Amyloid Angiopathy, Atherosclerosis
- Abstract
Background: Population-based autopsy studies provide valuable insights into the causes of dementia but are limited by sample size and restriction to specific populations. Harmonisation across studies increases statistical power and allows meaningful comparisons between studies. We aimed to harmonise neuropathology measures across studies and assess the prevalence, correlation, and co-occurrence of neuropathologies in the ageing population., Methods: We combined data from six community-based autopsy cohorts in the US and the UK in a coordinated cross-sectional analysis. Among all decedents aged 80 years or older, we assessed 12 neuropathologies known to be associated with dementia: arteriolosclerosis, atherosclerosis, macroinfarcts, microinfarcts, lacunes, cerebral amyloid angiopathy, Braak neurofibrillary tangle stage, Consortium to Establish a Registry for Alzheimer's disease (CERAD) diffuse plaque score, CERAD neuritic plaque score, hippocampal sclerosis, limbic-predominant age-related TDP-43 encephalopathy neuropathologic change (LATE-NC), and Lewy body pathology. We divided measures into three groups describing level of confidence (low, moderate, and high) in harmonisation. We described the prevalence, correlations, and co-occurrence of neuropathologies., Findings: The cohorts included 4354 decedents aged 80 years or older with autopsy data. All cohorts included more women than men, with the exception of one study that only included men, and all cohorts included decedents at older ages (range of mean age at death across cohorts 88·0-91·6 years). Measures of Alzheimer's disease neuropathological change, Braak stage and CERAD scores, were in the high confidence category, whereas measures of vascular neuropathologies were in the low (arterioloscerosis, atherosclerosis, cerebral amyloid angiopathy, and lacunes) or moderate (macroinfarcts and microinfarcts) categories. Neuropathology prevalence and co-occurrence was high (2443 [91%] of 2695 participants had more than one of six key neuropathologies and 1106 [41%] of 2695 had three or more). Co-occurrence was strongly but not deterministically associated with dementia status. Vascular and Alzheimer's disease features clustered separately in correlation analyses, and LATE-NC had moderate associations with Alzheimer's disease measures (eg, Braak stage ρ=0·31 [95% CI 0·20-0·42])., Interpretation: Higher variability and more inconsistency in the measurement of vascular neuropathologies compared with the measurement of Alzheimer's disease neuropathological change suggests the development of new frameworks for the measurement of vascular neuropathologies might be helpful. Results highlight the complexity and multi-morbidity of the brain pathologies that underlie dementia in older adults and suggest that prevention efforts and treatments should be multifaceted., Funding: Gates Ventures., Competing Interests: Declaration of interests SS reports consulting fees from Biogen and Eisai. JS reports consulting fees from AVID, Alnylam Pharmaceuticals, and Cerveau Technologies. All other authors declare no competing interests., (Copyright © 2023 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license. Published by Elsevier Ltd.. All rights reserved.)
- Published
- 2023
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21. Association of Red Blood Cell Omega-3 Fatty Acids With MRI Markers and Cognitive Function in Midlife: The Framingham Heart Study.
- Author
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Satizabal CL, Himali JJ, Beiser AS, Ramachandran V, Melo van Lent D, Himali D, Aparicio HJ, Maillard P, DeCarli CS, Harris WS, and Seshadri S
- Subjects
- Middle Aged, Humans, Female, Aged, Male, Cross-Sectional Studies, Docosahexaenoic Acids metabolism, Eicosapentaenoic Acid metabolism, Cognition, Longitudinal Studies, Apolipoproteins E genetics, Erythrocytes metabolism, Magnetic Resonance Imaging, Fatty Acids, Omega-3
- Abstract
Background and Objectives: Diet may be a key contributor to brain health in midlife. In particular, omega-3 fatty acids have been related to better neurologic outcomes in older adults. However, studies focusing on midlife are lacking. We investigated the cross-sectional association of red blood cell (RBC) omega-3 fatty acid concentrations with MRI and cognitive markers of brain aging in a community-based sample of predominantly middle-aged adults and further explore effect modification by APOE genotype., Methods: We included participants from the Third-Generation and Omni 2 cohorts of the Framingham Heart Study attending their second examination. Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) concentrations were measured from RBC using gas chromatography, and the Omega-3 index was calculated as EPA + DHA. We used linear regression models to relate omega-3 fatty acid concentrations to brain MRI measures (i.e., total brain, total gray matter, hippocampal, and white matter hyperintensity volumes) and cognitive function (i.e., episodic memory, processing speed, executive function, and abstract reasoning) adjusting for potential confounders. We further tested for interactions between omega-3 fatty acid levels and APOE genotype (e4 carrier vs noncarrier) on MRI and cognitive outcomes., Results: We included 2,183 dementia-free and stroke-free participants (mean age of 46 years, 53% women, 22% APOE -e4 carriers). In multivariable models, higher Omega-3 index was associated with larger hippocampal volumes (standard deviation unit beta ±standard error; 0.003 ± 0.001, p = 0.013) and better abstract reasoning (0.17 ± 0.07, p = 0.013). Similar results were obtained for DHA or EPA concentrations individually. Stratification by APOE -e4 status showed associations between higher DHA concentrations or Omega-3 index and larger hippocampal volumes in APOE -e4 noncarriers, whereas higher EPA concentrations were related to better abstract reasoning in APOE -e4 carriers. Finally, higher levels of all omega-3 predictors were related to lower white matter hyperintensity burden but only in APOE -e4 carriers., Discussion: Our results, albeit exploratory, suggest that higher omega-3 fatty acid concentrations are related to better brain structure and cognitive function in a predominantly middle-aged cohort free of clinical dementia. These associations differed by APOE genotype, suggesting potentially different metabolic patterns by APOE status. Additional studies in middle-aged populations are warranted to confirm these findings., (© 2022 American Academy of Neurology.)
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- 2022
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22. Self-reported sleepiness associates with greater brain and cortical volume and lower prevalence of ischemic covert brain infarcts in a community sample.
- Author
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Baril AA, Beiser AS, DeCarli C, Himali D, Sanchez E, Cavuoto M, Redline S, Gottlieb DJ, Seshadri S, Pase MP, and Himali JJ
- Subjects
- Aged, Brain diagnostic imaging, Brain pathology, Brain Infarction pathology, Female, Humans, Magnetic Resonance Imaging, Male, Middle Aged, Prevalence, Self Report, Apolipoprotein E4, Sleepiness
- Abstract
Study Objectives: We evaluated if self-reported sleepiness was associated with neuroimaging markers of brain aging and ischemic damage in a large community-based sample., Methods: Participants from the Framingham Heart Study Offspring cohort (n = 468, 62.5 ± 8.7 years old, 49.6%M) free of dementia, stroke, and neurological diseases, completed sleep questionnaires and polysomnography followed by magnetic resonance imaging (MRI), 3 years later on average. We used linear and logistic regression models to evaluate the associations between Epworth Sleepiness Scale (ESS) scores and total brain, cortical and subcortical gray matter, and white matter hyperintensities volumes, and the presence of covert brain infarcts., Results: Higher sleepiness scores were associated with larger total brain volume, greater cortical gray matter volume, and a lower prevalence of covert brain infarcts, even when adjusting for a large array of potential confounders, including demographics, sleep profiles and disorders, organic health diseases, and proxies for daytime cognitive and physical activities. Interactions indicated that more sleepiness was associated with larger cortical gray matter volume in men only and in APOE ε4 noncarriers, whereas a trend for smaller cortical gray matter volume was observed in carriers. In longitudinal analyses, those with stable excessive daytime sleepiness over time had greater total brain and cortical gray matter volumes, whereas baseline sleepiness scores were not associated with subsequent atrophy or cognitive decline., Conclusion: Our findings suggest that sleepiness is not necessarily a marker of poor brain health when not explained by diseases or sleep debt and sleep disorders. Rather, sleepiness could be a marker of preserved sleep-regulatory processes and brain health in some cases., (© The Author(s) 2022. Published by Oxford University Press on behalf of Sleep Research Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.comm.)
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- 2022
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23. Insomnia symptom severity and cognitive performance: Moderating role of APOE genotype.
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Baril AA, Beiser AS, Sanchez E, Mysliwiec V, Redline S, Gottlieb DJ, O'Connor GT, Gonzales MM, Himali D, Seshadri S, Himali JJ, and Pase MP
- Subjects
- Aged, Alzheimer Disease diagnosis, Apolipoprotein E4 genetics, Female, Genotype, Humans, Male, Middle Aged, Neuropsychological Tests, Apolipoproteins E genetics, Cognition, Sleep Initiation and Maintenance Disorders genetics
- Abstract
Introduction: We evaluated whether insomnia symptom severity was associated with cognitive function, and whether this relationship was modified by biomarkers associated with Alzheimer's disease risk., Methods: We examined insomnia symptoms and neuropsychological performance 3.4 years later in 511 dementia-free Framingham Heart Study participants (62.65 ± 8.7 years, 50.9% male). Additionally, we explored insomnia symptoms combined with self-reported short habitual sleep duration and effect modification by apolipoprotein E (APOE) ε4 allele status., Results: More severe insomnia symptoms were associated with lower performance on global cognition, and immediate and delayed Logical Memory recall, especially when insomnia symptoms were combined with short sleep duration. The association between insomnia symptoms and poorer memory recall was more pronounced in APOE ε4 allele carriers., Discussion: Insomnia symptom severity was associated with worse subsequent global cognitive and memory performance, which was especially apparent in APOE ε4 allele carriers, suggesting that poor sleep might be particularly detrimental when the brain is already vulnerable to neurodegeneration., (© 2021 the Alzheimer's Association.)
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- 2022
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24. Microwave flash pyrolysis.
- Author
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Cho HY, Ajaz A, Himali D, Waske PA, and Johnson RP
- Subjects
- Graphite, Hot Temperature, Methods, Nanotubes, Carbon, Organic Chemicals chemistry, Vacuum, Heating methods, Microwaves, Organic Chemistry Phenomena
- Abstract
In a microwave reactor, graphite heats rapidly to high surface temperatures; applications of graphite thermal "sensitization" have been described previously. We report here that microwave thermal sensitization with graphite, carbon nanotubes, or silicon carbide can be used to carry out reactions more typically accomplished by flash vacuum pyrolysis (FVP) and which usually require temperatures much higher than the nominal limit of a microwave reactor. The graphite-sensitized microwave reaction of azulene in the solid phase at temperatures of 100 to 300 degrees C affords rapid rearrangement to naphthalene, a reaction typically observed by FVP at 700-900 degrees C. Multiwall carbon nanotubes give similar results when used as a thermal sensitizer. Other graphite-sensitized reactions that we have observed include the following: conversion of 2-ethynylbiphenyl to phenanthrene, fragmentation of phthalic anhydride to benzyne, cleavage of iodobenzene to phenyl radical, aryl-aryl bond cleavage, and a variety of cycloaromatizations. An advantage is seen for less volatile substrates. Rearrangement of azulene and generation of benzyne from phthalic anhydride have also been observed on powdered silicon carbide. Because of the high temperature, rapid heating, and frequent ejection of material from the irradiation zone, we refer to this general method as microwave flash pyrolysis (MFP).
- Published
- 2009
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