| 1. |
- Palma, Carlos-Andres, et al.
(författare)
-
Photo-induced C-C reactions on insulators towards photolithography of graphene nanoarchitectures
- 2014
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 136, s. 4651-4658
-
Tidskriftsartikel (refereegranskat)abstract
- On-surface chemistry for atomically precise sp2 macromolecules requires top-down lithographic methods on insulating surfaces in order to pattern the long-range complex architectures needed by the semiconductor industry. Here, we fabricate sp2-carbon nm-thin films on insulators and under ultra-high vacuum (UHV) conditions from photo-coupled brominated precursors. We reveal that covalent coupling is initiated by C-Br bond cleavage through photon energies exceeding 4.4 eV, as monitored by laser desorption ionization (LDI) mass spectrometry (MS) and X-ray photoelectron spectroscopy (XPS). Density functional theory (DFT) gives insight into the mechanisms of C-Br scission and C-C coupling processes. Further, unreacted material can be sublimed and the coupled sp2-carbon precursors can be graphitized by e-beam treatment at 500°C, demonstrating promising applications in photolithography of graphene nanoarchitectures. Our results present UV-induced reactions on insulators for the formation of all sp2-carbon architectures, thereby converging top-down lithography and bottom-up on-surface chemistry into technology.
|
|
| 2. |
- Pham, Tuan D., et al.
(författare)
-
Automated detection of white matter changes in elderly people using fuzzy, geostatistical, and information combining models
- 2011
-
Ingår i: IEEE transactions on information technology in biomedicine. - : Institute of Electrical and Electronics Engineers (IEEE). - 1089-7771 .- 1558-0032. ; 15:2, s. 242-250
-
Tidskriftsartikel (refereegranskat)abstract
- Detection of white matter changes of the brain using magnetic resonance imaging (MRI) has increasingly been an active and challenging research area in computational neuroscience. There have rarely been any single image analysis methods that can effectively address the issue of automated quantification of neuroimages, which are subject to different interests of various medical hypotheses. This paper presents new image segmentation models for automated detection of white matter changes of the brain in an elderly population. The methods are based on the computational models of fuzzy clustering, possibilistic clustering, geostatistics, and knowledge combination. Experimental results on MRI data have shown that the proposed image analysis methodology can be applied as a very useful computerized tool for the validation of our particular medical question, where white matter changes of the brain are thought to be the most important social medical evidence.
|
|
| 3. |
- Pham, Tuan D, et al.
(författare)
-
Structural simplexity of the brain
- 2010
-
Ingår i: Journal of neuroscience methods. - : Elsevier BV. - 0165-0270. ; 188:1, s. 113-126
-
Tidskriftsartikel (refereegranskat)abstract
- Simplexity is an emerging concept that expresses a possible complementary relationship between complexity and simplicity. The brain has been known as the most complex structure, and tremendous effort has been spent to study how it works. By understanding complex function of the brain, one can hope to unravel the mystery of its diseases and its biological systems. We propose herein an entropy-based framework for analysis of complexity with a particular application to the study of white matter changes of the human brain. In this analysis, the proposed approach takes into account both morphological structure and image intensity values of MRI scans to construct the complexity profiles of the brain. It has been realized that the quantity and spatial distribution of white matter changes play an important role in cognitive decline (i.e. dementia) and other neuropsychiatric disorders (i.e. multiple sclerosis, depression) as well as in other dementia disorders such as Alzheimers disease. Thus, the results can be utilized as a tool for automated quantification and comparison of various spatial distributions and orientations of age-related white matter changes where manual analysis is difficult and leads to different sensitivities for the respective MRI-based information of the brain.
|
|
| 4. |
- Pham, Tuan D., et al.
(författare)
-
The hidden-Markov brain comparison and inference of white matter hyperintensities on magnetic resonance imaging (MRI)
- 2011
-
Ingår i: Journal of Neural Engineering. - : IOP Publishing. - 1741-2560 .- 1741-2552. ; 8:1, s. 1-10
-
Tidskriftsartikel (refereegranskat)abstract
- Rating and quantification of cerebral white matter hyperintensities on magnetic resonance imaging (MRI) are important tasks in various clinical and scientific settings. As manual evaluation is time consuming and imprecise, much effort has been made to automate the quantification of white matter hyperintensities. There is rarely any report that attempts to study the similarity/dissimilarity of white matter hyperintensity patterns that have different sizes, shapes and spatial localizations on the MRI. This paper proposes an original computational neuroscience framework for such a conceptual study with a standpoint that the prior knowledge about white matter hyperintensities can be accumulated and utilized to enable a reliable inference of the rating of a new white matter hyperintensity observation. This computational approach for rating inference of white matter hyperintensities, which appears to be the first study, can be utilized as a computerized rating-assisting tool and can be very economical for diagnostic evaluation of brain tissue lesions.
|
|
| 5. |
- Wang, Xiao-Ye, et al.
(författare)
-
Exploration of pyrazine-embedded antiaromatic polycyclic hydrocarbons generated by solution and on-surface azomethine ylide homocoupling
- 2017
-
Ingår i: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- Nanographenes, namely polycyclic aromatic hydrocarbons (PAHs) with nanoscale dimensions (amp;gt;1 nm), are atomically precise cutouts from graphene. They represent prime models to enhance the scope of chemical and physical properties of graphene through structural modulation and functionalization. Defined nitrogen doping in nanographenes is particularly attractive due to its potential for increasing the number of p-electrons, with the possibility of introducing localized antiaromatic ring elements. Herein we present azomethine ylide homocoupling as a strategy to afford internally nitrogen-doped, non-planar PAH in solution and planar nanographene on surfaces, with central pyrazine rings. Localized antiaromaticity of the central ring is indicated by optical absorption spectroscopy in conjunction with theoretical calculations. Our strategy opens up methods for chemically tailoring graphene and nanographenes, modified by antiaromatic dopants.
|
|
