| 1. |
|
|
| 2. |
- Bryllert, Tomas, et al.
(författare)
-
Designed emitter states in resonant tunneling through quantum dots
- 2002
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 80:15, s. 2681-2683
-
Tidskriftsartikel (refereegranskat)abstract
- Resonant tunneling through a single layer of self-assembled quantum dots (QDs) is compared to tunneling through two layers of vertically aligned (stacked) dots. The difference can be viewed as going from a two-dimensional emitter to a zero-dimensional emitter. The temperature dependence of current peaks originating in tunneling through individual QDs and individual stacks is used to clarify this point. In addition, we show that the statistical size distribution of self-assembled quantum dots causing the inhomogeneous broadening in luminescence experiments can be analyzed in a resonant tunneling experiment. (C) 2002 American Institute of Physics.
|
|
| 3. |
- Bryllert, Tomas, et al.
(författare)
-
Resonant tunneling through coupled self-assembled quantum dots and the influence of inhomogeneous broadening
- 2002
-
Ingår i: 7th International Conference on Nanometer-Scale Science and Technology and 21st European Conference on Surface Science.
-
Konferensbidrag (refereegranskat)abstract
- Resonant tunneling through a single layer of self-assembled quantum dots (QDs) as well as tunneling through two layers of vertically aligned (stacked) dots is investigated. The difference between single and double layers of QDs can be viewed as going from a two-dimensional emitter to a zero-dimensional emitter. By fabricating small-area devices we are able to probe single stacks of quantum dots, revealing details of the coupling between the stacked dots. Very sharp resonances, with peak-to-valley ratios of several hundred, have been measured in the current-voltage characteristics. We also show that the statistical size distribution of self-assembled quantum dots causing the inhomogeneous broadening in luminescence experiments can be analysed in a resonant tunneling experiment
|
|
| 4. |
- Edvinsson, Lars, et al.
(författare)
-
Neuropeptides in cerebrospinal fluid of patients with Alzheimer's disease and dementia with frontotemporal lobe degeneration
- 1993
-
Ingår i: Dementia (Switzerland). - 1013-7424. ; 4:3-4, s. 71-167
-
Tidskriftsartikel (refereegranskat)abstract
- The two major primary degenerative dementias, dementia of Alzheimer type (DAT) and frontal lobe degeneration of non-Alzheimer type (FLD) have several clinical features in common but also many symptoms that differ. In a clinical material of 80 patients with either of the two forms of dementia (DAT = 39, FLD = 41) we have studied the levels of neuropeptides in the cerebrospinal fluid (CSF) in order to find biochemical markers for CNS affection. The dementia forms were evaluated by careful clinical analysis, psychometric testing and measurement of regional cerebral blood flow. Approximately one third of the subjects died during the completion of the study and neuropathology was performed, confirming the diagnoses. We observed reductions in the CSF levels of antidiuretic hormone and somatostatin in both DAT and FLD. A strong tendency to reduction was noted for neuropeptide Y (NPY). There was a correlation with the duration of disease demonstrating a significant reduction in NPY levels in subjects with DAT. Most notably there was a strong reduction in the levels of delta sleep inducing peptide (DSIP) in DAT cases only. The levels of DSIP in FLD were the same as in controls. The reverse was found for corticotropin releasing factor (CRF) which had a significant reduction in FLD patients but not in those with DAT. The present study indicates a difference in the CSF levels of neuropeptides, observations that these may serve as biochemical markers which differentiate DAT and FLD.
|
|
| 5. |
- Gustafson, Boel, et al.
(författare)
-
Coupling between lateral modes in a vertical resonant tunneling structure
- 2002
-
Ingår i: Physica E: Low-Dimensional Systems and Nanostructures. - 1386-9477. ; 13:2-4, s. 950-953
-
Tidskriftsartikel (refereegranskat)abstract
- We present experimental results and theoretical calculations of the vertical electron transport through a laterally constricted resonant tunneling transistor. Current-voltage measurements at 4.2 K show numerous current peaks that exhibit a complex dependence on the applied gate voltage. A scattering-matrix approach combined with the Landauer formalism was used to perform quantum mechanical calculations of the electron transport through a quantum dot structure with laterally confined emitter and collector regions. The simulations qualitatively reproduce the measured data, suggesting a strong coupling between the lateral modes in the quantum dot and the collector
|
|
| 6. |
- Minthon, Lennart, et al.
(författare)
-
Correlation between clinical characteristics and cerebrospinal fluid neuropeptide Y levels in dementia of the Alzheimer type and frontotemporal dementia
- 1996
-
Ingår i: Alzheimer Disease and Associated Disorders. - 1546-4156. ; 10:4, s. 197-203
-
Tidskriftsartikel (refereegranskat)abstract
- Neuropeptide Y (NPY) has been shown to be involved in the control of several neuroendocrine functions. Moreover, in animal models, NPY produces behavioral effects that are similar to those induced by anxiolytics. We studied NPY-like immunoreactivity (NPY-LI) in cerebrospinal fluid (CSF) in two primary degenerative dementias, Alzheimer disease (AD, n = 34) and frontotemporal dementia (FTD, n = 22) and correlated the CSF NPY-LI levels with clinical characteristics, as rated with the Organic Brain Syndrome scale. There were significant correlations between NPY-LI and such clinical items as suspiciousness, anxiousness, restlessness-agitation, and irritability in both AD and FTD. AD patients, but not FTD patients, showed a significant negative correlation between NPY-LI and duration of the disease. Thus, the study found significant correlations between CSF NPY-LI and emotional symptoms and behavior in organic dementia.
|
|
| 7. |
- Minthon, Lennart, et al.
(författare)
-
Long-term effects of tacrine on regional cerebral blood flow changes in Alzheimer's disease
- 1995
-
Ingår i: Dementia and Geriatric Cognitive Disorders. - 1420-8008. ; 6:5, s. 245-251
-
Tidskriftsartikel (refereegranskat)abstract
- Regional cerebral blood flow (rCBF) was studied in patients with Alzheimer's disease (AD) before and after 14 months of tacrine treatment. The treated group was compared with an identical reference group of untreated AD patients. At baseline the two groups showed an identical rCBF and mean hemispheric blood flow. After 14 months the tacrine-treated patients showed a stable rCBF level and a significant increase in rCBF in the central-parietal regions, compared to the untreated reference group, who showed typical AD reductions in rCBF in these regions. Clinical outcome: 7 of 9 patients in the tacrine group were clinically unchanged or slightly improved during the study time. In the untreated group 8 of 11 patients had deteriorated in clinical assessments and none had improved. Long-term tacrine treatment in Alzheimer's disease may delay the progression of symptoms.
|
|
| 8. |
- Minthon, Lennart, et al.
(författare)
-
Neuropeptide levels in Alzheimer's disease and dementia with frontotemporal degeneration
- 1990
-
Ingår i: Journal of neural transmission. Supplementum. ; 30, s. 57-67
-
Tidskriftsartikel (refereegranskat)abstract
- The CSF levels of somatostatin-LI (SLI), neuropeptide Y (NPY-LI) and Delta Sleep Inducing Peptide (DSIP-LI) have been measured in patients with dementia of Alzheimer type (DAT) and dementia with frontotemporal degeneration of non-Alzheimer type (FTD). The distribution pattern of cortical degeneration differs between these two types of dementia. DAT shows degeneration of mainly temporo-parietal and temporo-limbic structures, whereas FTD discloses its main degeneration in the frontotemporal regions (Brun, 1987). The somatostatin-LI was significantly reduced both in DAT and FTD. NPY-LI showed a significant reduction in DAT but not in FTD. A tendency to a reduction with duration of the disease was observed in DAT whereas the contrary was noted in FTD. The DSIP-LI levels were reduced in DAT and slightly increased in FTD. The study provides an evidence of neurochemical differences between the two primary degenerative dementias.
|
|
| 9. |
- Minthon, Lennart, et al.
(författare)
-
Somatostatin and neuropeptide Y in cerebrospinal fluid: correlations with severity of disease and clinical signs in Alzheimer's disease and frontotemporal dementia
- 1997
-
Ingår i: Dementia and Geriatric Cognitive Disorders. - : S. Karger AG. - 1421-9824 .- 1420-8008. ; 8:4, s. 232-239
-
Tidskriftsartikel (refereegranskat)abstract
- Alzheimer's disease (AD) and frontotemporal dementia (FTD) are the most common types of progressive neurodegenerative disorder in our catchment area. The distribution of cortical degeneration in FTD is mainly the reverse of that in AD, while there are both differences and similarities in the clinical characteristics. Somatostatin and neuropeptide Y (NPY) are neuropeptides with a widespread distribution in the human cerebral cortex. Somatostatin is involved in the regulation of hormone release from the anterior pituitary and may act as a neurotransmitter-modulator. NPY is a potent anxiolytic neuropeptide. Somatostatin and NPY coexist in the cerebral cortex, basal ganglia and in amygdaloid complexes. The present study of AD (n = 34) and FTD (n = 22) analyses the cerebrospinal-fluid (CSF) levels of somatostatin-like immunoreactivity and NPY-like immunoreactivity and correlates their levels to 54 different clinical items, such as restlessness, anxiety, irritability and depression. The CSF levels of the two neuropeptides somatostatin and NPY were significantly correlated in FTD (p < 0.02), but not in AD. Several significant correlations to the clinical signs were found: in AD disorientation and dyspraxia, and in FTD agitation, irritability and restlessness. Somatostatin showed a significant negative correlation with severity of dementia in AD (p < 0.013).
|
|
| 10. |
- Minthon, Lennart, et al.
(författare)
-
Tacrine treatment modifies cerebrospinal fluid neuropeptide levels in Alzheimer's disease
- 1994
-
Ingår i: Dementia (Switzerland). - : S. Karger AG. - 1013-7424. ; 5:6, s. 295-301
-
Tidskriftsartikel (refereegranskat)abstract
- Biochemical and histochemical studies have demonstrated a widespread deficit in the activity of acetylcholinesterase (AChE) in the brains of patients with Alzheimer's disease (DAT). Multiple disturbances in several transmitter systems have been found. The most consistent neurochemical changes in DAT are reductions in the cholinergic system. The major pharmacological approach today in DAT is based on the cholinergic theory assuming that acetylcholine has a major cortical impact on cognitive processes. Tetrahydroaminoacridine (THA, tacrine) is a centrally active reversible acetylcholinesterase inhibitor. A large number of trials have been performed in patients with DAT. This article was to evaluate whether THA treatment induced neuropeptide alteration in DAT before and after 1 year on oral THA treatment.
|
|
