Slot waveguide ring resonators coated by an atomic layer deposited organic/inorganic nanolaminate.

In this study, slot waveguide ring resonators patterned on a silicon-on-insulator (SOI) wafer and coated with an atomic layer deposited nanolaminate consisting of alternating layers of tantalum pentoxide and polyimide were fabricated and characterized. To the best of our knowledge, this is the first demonstration of atomic layer deposition (ALD) of organic materials in waveguiding applications. In our nanolaminate ring resonators, the optical power is not only confined in the narrow central air slot but also in several parallel sub-10 nm wide vertical polyimide slots. This indicates that the mode profiles in the silicon slot waveguide can be accurately tuned by the ALD method. Our results show that ALD of organic and inorganic materials can be combined with conventional silicon waveguide fabrication techniques to create slot waveguide ring resonators with varying mode profiles. This can potentially open new possibilities for various photonic applications, such as optical sensing and all-optical signal processing.

Enhanced stability of rubbery amylose-rich maize starch films plasticized with a combination of sorbitol and glycerol.

Well known aging problems with rubbery starch films are the migration of plasticizer and increased crystallinity leading to embrittlement. The effects of a combination of sorbitol and glycerol used as plasticizers on mechanical, moisture permeability and solid-state properties of rubbery amylose maize starch (Hylon VII) films were studied. The films were prepared by casting and were exposed to conditions of 25 degrees C/60% relative humidity (RH) and 40 degrees C/75% RH for 9 months. The starch films plasticized with a combination of sorbitol and glycerol (1:1) at equal amount to the polymer weight, were shown to be the most stable alternative of the studied films during the 9 months storage period. The water vapor transmission (WVTR) of the films did not change during the period of storage and neither did the elongation at break, but the tensile strength increased. X-ray diffraction (XRD) results showed that during storage no crystallization had occurred. The combination of sorbitol and glycerol prevented the migration of the plasticizer molecules out of the film.

A bio-originated porous template for the fabrication of very long, inorganic nanotubes and nanowires.

A biopolymer-based template assembly constructed around the spines of the bristle worm Aphrodita aculeata (sea mouse) was used to fabricate very high aspect ratio nanowires and nanotubes using established methods adopted from nanofabrication in porous membranes. The easily available bio-originated template contains more than 100 000 highly ordered, very high aspect ratio nanochannels, each about 150 to 200 nm in diameter but up to a centimetre in length. Their parallel, hexagonal arrangement in the spine constitutes a photonic crystal, which gives the animal its colourful, iridescent appearance. Around the nanochannels, the spines consist of a chitin/protein composite material, which has been shown to withstand the chemical and thermal conditions needed for established template-assisted nanofabrication strategies. A template preparation procedure was developed and the template was used to fabricate copper and nickel nanowires by electrodeposition and aluminium oxide nanotubes by atomic layer deposition. Due to their high thermal and chemical stability, decomposition of the filled templates proved to be difficult, and different approaches to obtain separated nanostructures are described and discussed. Alongside this, the presented system of parallel nanowires or nanotubes in a biopolymer matrix might be utilized in applications, where such separated structures are not needed. Comparing to porous membranes, the presented template allows us to increase the maximum length of nanotubes and nanowires produced using nanochannel-based templates by at least one order of magnitude.

Ancillary ligand effect on the properties of "Mg(thd)2" and crystal structures of [Mg(thd)2(ethylenediamine)]2, [Mg(thd)2(tmeda)], and [Mg(thd)2(trien)].

Complexes [Mg(thd)2(A)] (Hthd = 2,2,6,6-tetramethyl-3,5-heptanedione; A = ethylenediamine, en (2); N,N'-dimethylethylenediamine, dmeda (3); N,N'-diethylethylenediamine, deeda (4); N,N,N',N'-tetramethylethylenediamine, tmeda (5); diethylenetriamine, dien (6); triethylenetetra-amine, trien (7); 1,2-ethanediol (8)) and [Mg(thd)2(EtOH)]2(1,3-propanediol) (9) were prepared and characterized by NMR spectroscopy, mass spectrometry, and thermal analysis. Crystal structures of compounds 2, 5, and 7 are presented. In all structures, Mg exhibits distorted six-coordination, with four shorter distances between Mg and keto-oxygens and two longer distances between Mg and nitrogen atoms (2, 5, 7). The structure of 2 consists of two monomeric complexes which form an asymmetric unit. The structure of 7 is similar to 2, but the trien molecule has coordinated through one terminal and one vicinal N atom to Mg. All complexes containing amines evaporated almost completely, but the complex 8, which contained 1,2-ethanediol, was thermally unstable and decomposed when heated. At temperatures below the dissociation temperature, all adducts of diamines appeared to evaporate intact.

Evaluation of various methods of assessing symptoms of cognitive impairment and dementia.

BACKGROUND AND PURPOSE: The effect of different diagnostic criteria for detecting dementia in both epidemiological and stroke cohort studies has been shown, but comparison between different assessment methods has only seldom been done. We compared both assessment methods and diagnostic criteria for dementia in a large well-defined stroke cohort. SUBJECT AND METHODS: A group of 227 of 486 patients aged 55 to 85 years who 3 months after ischemic stroke completed a comprehensive neuropsychological test battery, structured clinical mental status examination of defined cognitive domains with expanded Mini-Mental State Examination. The criteria for dementia were those of the Diagnostic and Statistical Manual of Mental Disorders (DSM-III, DSM-III-R) and the National Institute of Neurological Disorders and Stroke-Associated Internationale pour la Recherche et l'Enseignement en Neurosciences (NINDS-AIREN). RESULTS: The main differences between clinical and neuropsychological examinations were seen in memory functions: clinically 24.7% and neuropsychologically 54.2% had impairment in short-term memory and 10.4% versus 5.3% in long-term memory. Accordingly, the prevalence of dementia varied greatly: It was clinically 14.1% by DSM-III, 9.7% by DSM-III-R and 8.4% by NINDS-AIREN criteria. The corresponding frequencies based on neuropsychological evaluation were 27.3%, 4.0% and 25.6%. Between these 3 diagnostic criteria the concordance varied in clinical testing between 59.4%-68.8% (kappa 0.72-0.79) and in neuropsychological testing between 14.5%-81.1% (kappa 0.20-0.86). The concordance between clinical and neuropsychological testing was 56.8% (kappa 0.42) by DSM-III, 31.6% (kappa 0.35) by DSM-III-R and 25.5% (kappa 0.24) by NINDS-AIREN. CONCLUSIONS: The frequency of poststroke dementia and cognitive decline varied sharply when different systems of diagnostic classification and methods were used. This may have serious influences on investigation and treatment of patients. We underline the importance of further debate and studies to refine the categories of cognitive impairment used in the setting of CVD.

Executive functions and speed of mental processing in elderly patients with frontal or nonfrontal ischemic stroke.

Impairments in executive functions have been related to aging and frontal lobe lesions. Aging also causes slowing of mental processing. We examined whether ischemic stroke in the frontal brain area results in dysexecutive syndrome, or whether the frontal stroke causes increased slowing of mental processing. Neurological, radiological and neuropsychological examinations were carried out 3 months post-stroke on 250 ischemic stroke patients (55-85 years) and on 39 healthy control subjects. Of the patients, 62 had frontal and 188 had nonfrontal lesions. The neuropsychological examination comprised several cognitive domains, including tests considered to measure executive functions. The frontal group was slower than the nonfrontal group in tasks measuring speed of mental processing which were time-limited (Trail Making A, Stroop dots and fluency). They were also inferior in the Digit Span backwards task. There were no differences between the groups in other cognitive domains, nor in some tests which are considered to be measures of executive functions (e.g. WCST). Impairments in executive functions were evident in both the frontal and the nonfrontal groups compared with the controls, but no dysexecutive syndrome specifically related to frontal lesions was found. Frontal stroke related mainly to the slowing of mental processing.

Hippocampal and temporal lobe atrophy and age-related decline in memory.

OBJECTIVES: To evaluate the relationship of memory decline that accompanies aging with structural changes in the medial temporal lobe, in healthy middle-aged and older subjects. MATERIAL AND METHODS: A sample of 35 neurologically non-diseased subjects, between 55 and 70 years of age, were examined in a 5-year follow-up study. Neuropsychological investigation included tests of learning, verbal memory, and visual memory. MRI was performed with a superconducting MRI system operating at 1.0 T, using coronal slices of T1-weighted images. Medial temporal lobe atrophy was rated separately in the neocortical, entorhinal and hippocampal regions. RESULTS: We did not find any statistically significant relationship between mild hippocampal or temporal atrophy and memory test performance. Nor did the longitudinal decline in memory show a relationship with temporal lobe atrophy. CONCLUSIONS: The main outcome of our study was that age-related memory decline was not related to mild temporal lobe atrophy in healthy subjects without mild cognitive impairment. There could be other factors influencing memory functions besides age-related structural changes in temporal lobes.

Post-stroke depression, executive dysfunction and functional outcome.

The early diagnosis of vascular cognitive impairment has been challenged and executive control function has been suggested to be a rational basis for the diagnosis of vascular dementia. We sought to examine the correlates of executive dysfunction in a well-defined stroke cohort. A group of 256 patients from a consecutive cohort of 486 patients with ischaemic stroke, aged 55-85 years, was subjected to a comprehensive neuropsychological examination 3-4 months after ischaemic stroke and 188 of them in addition to detailed psychiatric examination. Basic and complex activities of daily living (ADLs) (bADLs and cADLs) post-stroke were assessed. The DSM-III-R criteria were used for the diagnosis of the depressive disorders. Altogether 40.6% (n=104) of the patients had executive dysfunction. The patients with executive dysfunction were older, had lower level of education, were more often dependent, did worse in bADLs and cADLs, had more often DSM-III dementia, had worse cognition as measured by Mini Mental State Examination (MMSE) and were more depressed as measured by the BECK depression scale, but not with the more detailed psychiatric evaluation. They had more often stroke in the anterior circulation and less often in the posterior circulation. The independent correlates of executive dysfunction were cADLs (OR 1.1, 95% CI 1.03-1.16), each point of worsening in cognition by MMSE (OR 1.7, 95% CI 1.42-1.97) and stroke in the posterior circulation area (OR 0.4, 95% CI 0.18-0.84). Clinically significant executive dysfunction is frequent after ischaemic stroke and is closely connected with cADLs and to overall cognitive status but could be distinguished from depression by detailed neuropsychological examination. Executive measures may detect patients at risk of dementia and disability post-stroke.

Clinical and radiological determinants of prestroke cognitive decline in a stroke cohort.

OBJECTIVES: Stroke seems to be related to dementia more often than previously assumed and vascular factors are also related to Alzheimer's disease. The pathophysiology of poststroke dementia includes ischaemic changes in the brain, a combination of degenerative and vascular changes, and changes only related to Alzheimer's disease. Some cognitive decline recognised after a stroke may be due to pre-existing cognitive decline. The aim of this study was to determine the clinical and radiological determinants of prestroke cognitive decline. METHODS: The study group comprised 337 of 486 consecutive patients aged 55 to 85 years who 3 months after ischaemic stroke completed a comprehensive neuropsychological test battery; structured medical, neurological, and mental status examination; interview of a knowledgeable informant containing structured questions on abnormality in the cognitive functions; assessment of social functions before the index stroke; and MRI. RESULTS: Frequency of prestroke cognitive decline including that of dementia was 9.2% (31/337). The patients with prestroke cognitive decline were older, more often had less than 6 years of education, and had history of previous stroke. Vascular risk factors did not differ significantly between these two groups. White matter changes (p=0.004), cortical entorhinal, hippocampal, and medial temporal atrophy (p<0.001), cortical frontal atrophy (p=0.008); and any central atrophy (p<0.01), but not the frequencies or volumes of old, silent, or all infarcts on MRI differentiated those with and without prestroke cognitive decline. The correlates of prestroke cognitive decline in logistic regression analysis were medial temporal cortical atrophy (odds ratio (OR) 7.5, 95% confidence interval (95%CI) 3.2-18.2), history of previous ischaemic stroke (OR 4.4, 95% CI 1.8-10.6), and education (OR 0.9, 95% CI 0.8-0.9). CONCLUSIONS: History of previous stroke, but not volumes or frequencies was found to correlate with prestroke cognitive decline. Other associating factors were rather those usually associated with degenerative dementia: white matter changes and cerebral atrophy; and in multiple models medial temporal cortical atrophy and education. The possible overlap between two or more underlying diseases must be remembered in diagnosis and treatment of patients with vascular cognitive impairment.

MRI correlates of executive dysfunction in patients with ischaemic stroke.

Executive dysfunction (ED) may lead to problem behaviour and impaired activities of daily living in many neuropsychiatric disorders, but the neuroanatomical correlates of ED are still not well known. Different aspects of executive functions were studied by widely used neuropsychological tests in 214 elderly patients 3 months after ischaemic stroke, and a sum score of eight different measures was counted in each patient. The number and site of brain infarcts as well as severity and location of white matter lesions (WMLs) and brain atrophy on magnetic resonance imaging were recorded and compared between patients with and without ED. ED was present in 73 (34.1%) of the 214 patients. The mean frequency of brain infarcts in the brain and in the left hemisphere was higher in the patients with ED. Lesions affecting the frontal-subcortical circuits (e.g. pallidum, corona radiata or centrum semiovale) were more frequent in patients with ED than in those without. Also, patients with pontine brain infarcts frequently had ED, but this may have been due to more extensive ischaemic changes in these patients in general. Mean number of brain infarcts affecting the pons and posterior centrum semiovale on the left side, moderate to severe medial temporal atrophy, the Fazekas white matter score, the Mini-Mental State Examination score and low education were independent correlates of ED. Brain infarcts and WML affecting the frontal-subcortical circuits or the pons may increase risk for ED in stroke patients.

Atomic layer deposition of oxide thin films with metal alkoxides as oxygen sources

A chemical approach to atomic layer deposition (ALD) of oxide thin films is reported here. Instead of using water or other compounds for an oxygen source, oxygen is obtained from a metal alkoxide, which serves as both an oxygen and a metal source when it reacts with another metal compound such as a metal chloride or a metal alkyl. These reactions generally enable deposition of oxides of many metals. With this approach, an alumina film has been deposited on silicon without creating an interfacial silicon oxide layer that otherwise forms easily. This finding adds to the other benefits of the ALD method, especially the atomic-level thickness control and excellent uniformity, and takes a major step toward the scientifically challenging and technologically important task of replacing silica as the gate dielectric in the future generations of metal oxide semiconductor field effect transistors.