| 1. |
- Foerster, Bradley R., et al.
(författare)
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Reduced insular gamma-aminobutyric acid in fibromyalgia
- 2012
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Ingår i: Arthritis and Rheumatism. - : Wiley. - 1529-0131 .- 0004-3591. ; 64:2, s. 579-583
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Tidskriftsartikel (refereegranskat)abstract
- Objective Recent scientific findings have reinvigorated interest in examining the role of gamma-aminobutyric acid (GABA), the major inhibitory central nervous system neurotransmitter, in chronic pain conditions. Decreased inhibitory neurotransmission is a proposed mechanism in the pathophysiology of chronic pain syndromes such as fibromyalgia (FM). The purpose of this study was to test the hypothesis that decreased levels of insular and anterior cingulate GABA would be present in FM patients, and that the concentration of this neurotransmitter would be correlated with pressurepain thresholds. Methods. Sixteen FM patients and 17 age-and sex-matched healthy controls underwent pressure-pain testing and a 3T proton magnetic resonance spectroscopy session in which the right anterior insula, right posterior insula, anterior cingulate, and occipital cortex were examined in subjects at rest. Results. GABA levels in the right anterior insula were significantly lower in FM patients compared with healthy controls (mean +/- SD 1.17 +/- 0.24 arbitrary institutional units versus 1.42 +/- 0.32 arbitrary institutional units; P = 0.016). There was a trend toward increased GABA levels in the anterior cingulate of FM patients compared with healthy controls (P = 0.06). No significant differences between groups were detected in the posterior insula or occipital cortex (P > 0.05 for all comparisons). Within the right posterior insula, higher levels of GABA were positively correlated with pressurepain thresholds in the FM patients (Spearman's rho = 0.63; P = 0.02). Conclusion. Diminished inhibitory neurotransmission resulting from lower concentrations of GABA within the right anterior insula may play a role in the pathophysiology of FM and other central pain syndromes.
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| 2. |
- Ni, W.-X., et al.
(författare)
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δ-function-shaped Sb-doping profiles in Si(001) obtained using a low-energy accelerated-ion source during molecular-beam epitaxy
- 1992
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Ingår i: Physical Review B. - 0163-1829. ; 46:12, s. 7551-7558
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional (2D) buried delta-function-shaped Sb-doping profiles have been obtained in Si using a low-energy accelerated Sb-ion source during molecular-beam epitaxy. A combination of secondary-ion mass spectrometry (SIMS), capacitance-voltage (C-V) measurements, and cross-sectional transmission electron microscopy (XTEM) was used to investigate dopant distributions and to determine profile widths. The 2D-sheet Sb-doping concentration N(Sb), obtained by integrating SIMS delta-doping profiles in samples grown with substrate temperature T(s) = 620-degrees-C and Sb-ion acceleration potentials V(Sb) = 200 and 300 V, was found to vary linearly with the product of the Sb-ion flux and the exposure time (i.e., the ion dose) over the N(Sb) range from 5 X 10(12) to 2 X 10(14) cm-2. The full width at half maximum (FWHM) concentration of 8-doping profiles in Si(001) films was less than the depth resolution of both SIMS and C-V measurements (approximately 10 and 3 nm, respectively). High-resolution XTEM lattice images show that the FWHM was less-than-or-equal-to 2 nm. This is consistent with dopant incorporation simulations, based upon a multisite transition-state dopant incorporation model, which show that accelerated-beam dopant species are trapped in near-surface substitutional sites with atomic mobilities between those of surface and bulk atoms. Dopant surface segregation during growth is strongly suppressed, and the dopant distribution is determined primarily by the straggle in ion trapping distributions. The present results are compared with profile broadening observed in 8-doped layers obtained by solid-phase epitaxy of amorphous Si containing a buried Sb layer.
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| 3. |
- Chirita, Valeriu, et al.
(författare)
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Cluster diffusion and surface morphological transitions on Pt (111) via reptation and concerted motion
- 2000
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 370:1, s. 179-185
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Tidskriftsartikel (refereegranskat)abstract
- Embedded-atom molecular dynamics simulations were used to follow the diffusion dynamics of compact Pt clusters with up to 19 atoms on Pt (111) surfaces. The results reveal a novel cluster diffusion mechanism, involving successive shear translations of adjacent subcluster regions, which give rise to reptation, a snake-like gliding motion. We show that for compact clusters with 4 to 6 atoms, this mechanism competes energetically with that of island diffusion through concerted motion. However, as the cluster size increases from > 7 to ? 20 atoms, reptation becomes the energetically favored diffusion mechanism. The concerted shear motion of subcluster regions, leading to reptation, is also shown to play a significant role in dendritic-to-compact morphological transitions of Pt island.
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| 4. |
- Hellgren, N., et al.
(författare)
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Nitrogen bonding structure in carbon nitride thin films studied by soft x-ray spectroscopy
- 2001
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 79:26, s. 4348-4350
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Tidskriftsartikel (refereegranskat)abstract
- Soft x-ray absorption (SXAS) and emission (SXES) spectroscopies were applied to study the nitrogen bonding structure in magnetron sputtered CNx thin films. By comparing with calculated spectra of N in different model systems, N in three main bonding environments can be identified: (i) C equivalent toN bonds, with a sharp SXAS peak at 399.5 eV, (ii) pyridine-like N (i.e., N bonded to two C atoms), with an x-ray absorption resonance at similar to 398.5 eV, and (iii) N substituted in graphite, possibly with one sp(3) carbon as a neighbor (SXAS energy similar to 401 eV). These bondings are present in all CNx films analyzed; however, as shown earlier, the relative intensities between the peaks may vary with the growth conditions. Differences in the coordination of the nearest or second nearest C neighbors only cause slight changes in the peak positions and spectrum shape.
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| 5. |
- Zheng, W.T., et al.
(författare)
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Chemical bonding in carbon nitride films studied by X-ray spectroscopies
- 2001
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Ingår i: Diamond and related materials. - 0925-9635 .- 1879-0062. ; 10:9-10, s. 1897-1900
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Tidskriftsartikel (refereegranskat)abstract
- Carbon nitride films are deposited using dc magnetron sputtering in a N2 discharge. The nature of chemical bonding of the films is investigated using X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure, and X-ray emission spectroscopy. X-Ray photoelectron spectroscopy spectra show that N1s binding states depend on substrate temperature, in which two pronounced peaks can be observed. The near edge X-ray absorption fine structure at C1s and N1s exhibits a similar absorption profile in the p* resonance region, but the s* resonance is sharper in the N1s spectra. Resonant N K-emission spectra show a strong dependence on excitation photo energies. Compared XPS N1s spectra with recent theoretical calculations by Johansson and Stafstrom, two main nitrogen sites are assigned in which N bound to sp3 hybridized C and sp2 hybridized C, respectively. The correlation of X-ray photoelectron, X-ray absorption, and X-ray emission spectra for N in carbon nitride films is also discussed. © 2001 Elsevier Science B.V. All rights reserved.
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| 6. |
- Zheng, W.T., et al.
(författare)
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Chemical bonding, structure, and hardness of carbon nitride thin films
- 2000
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Ingår i: Diamond and related materials. - 0925-9635 .- 1879-0062. ; 9:9-10, s. 1790-1794
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Carbon nitride films are deposited on Si(001) substrates by reactive d.c. magnetron sputtering graphite in a pure N2 discharge. The chemical bonding and structure of carbon nitride films were probed using Fourier transformation infrared (FTIR) and near edge X-ray absorption fine structure (NEXAFS), and the hardness was evaluated using nanoindentation experiments. The structure and hardness for the films are dependent on the substrate temperature (T(s)). FTIR and NEXAFS spectra show that N atoms are bound to sp1, sp2 and sp3 hybridized C atoms, and the intensity of p(*) resonance for C1s NEXAFS spectra is the lowest for the film grown at T(s) = 350°C, having a turbostratic-like structure, high hardness and stress. The correlation between the structure and hardness of carbon nitride films is discussed. (C) 2000 Elsevier Science S.A. All rights reserved.Carbon nitride films are deposited on Si(001) substrates by reactive d.c. magnetron sputtering graphite in a pure N2 discharge. The chemical bonding and structure of carbon nitride films were probed using Fourier transformation infrared (FTIR) and near edge X-ray absorption fine structure (NEXAFS), and the hardness was evaluated using nanoindentation experiments. The structure and hardness for the films are dependent on the substrate temperature (Ts). FTIR and NEXAFS spectra show that N atoms are bound to sp1, sp2 and sp3 hybridized C atoms, and the intensity of p* resonance for C1s NEXAFS spectra is the lowest for the film grown at Ts = 350°C, having a turbostratic-like structure, high hardness and stress. The correlation between the structure and hardness of carbon nitride films is discussed.
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| 7. |
- Birch, J., et al.
(författare)
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Structural characterization of precious-mean quasiperiodic Mo/V single-crystal superlattices grown by dual-target magnetron sputtering
- 1990
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Ingår i: Physical Review B. - 1098-0121. ; 41:15, s. 10398-10407
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Tidskriftsartikel (refereegranskat)abstract
- A class of quasiperiodic superlattice structures, which can be generated by the concurrent inflation rule A→AmB and B→A (where m=positive integer), has been studied both theoretically and experimentally. Given that the ratios between the thicknesses of the two superlattice building blocks, A and B, are chosen to be γ(m)=[m+(m2+4)1/2]/2 (known as the ‘‘precious means’’), then the x-ray- and electron-diffraction peak positions are analytically found to be located at the wave vectors q=2πΛ−1r[γ(m)]k, where r and k are integers and Λ is an average superlattice wavelength. The analytically obtained results have been compared to experimental results from single-crystalline Mo/V superlattice structures, generated with m=1, 2, and 3. The superlattices were grown by dual-target dc-magnetron sputtering on MgO(001) substrates kept at 700 °C. X-ray diffraction (XRD) and selected-area electron diffraction (SAED) showed that the analytical model mentioned above predicts the peak positions of the experimental XRD and SAED spectra with a very high accuracy. Furthermore, numerical calculations of the diffraction intensities based on a kinematical model of diffraction showed good agreement with the experimental data for all three cases. In addition to a direct verification of the quasiperiodic modulation, both conventional and high-resolution cross-sectional transmission electron microscopy (XTEM) showed that the superlattices are of high crystalline quality with sharp interfaces. Based on lattice resolution images, the width of the interfaces was determined to be less than two (002) lattice-plane spacings (≊0.31 nm).
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| 8. |
- Broitman, E., et al.
(författare)
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Electrical and optical properties of CNx(0=x=0.25) films deposited by reactive magnetron sputtering
- 2001
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 89:2, s. 1184-1190
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Tidskriftsartikel (refereegranskat)abstract
- The electrical and optical properties of carbon-nitride CNx films (O=x=0.25) deposited by unbalanced reactive magnetron sputtering from a graphite target in mixed Ar/N2 discharges at a substrate temperature of 350°C have been investigated. Pure C films exhibit a dark conductivity at room temperature of 250 O-1 cm-1, which grows up to 250 O-1 cm-1 for CNx films with N content of 20%. For CNx films, temperature-dependent conductivity measurements suggest that two electron conduction processes exist in the investigated temperature range 130
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| 9. |
- Broitman, E., et al.
(författare)
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Mechanical and tribological properties of CNx films deposited by reactive magnetron sputtering
- 2001
-
Ingår i: Wear. - 0043-1648 .- 1873-2577. ; 248:1-2, s. 55-64
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Tidskriftsartikel (refereegranskat)abstract
- The hardness, elasticity, wear rate and friction coefficient of carbon nitride (CNx) films of defined microstructure and composition are presented. CNx films were deposited by dc reactive magnetron sputtering from a C target in N2/Ar plasma. Films were grown on Si (001), Ni, and HSS substrates to thickness of ~0.5 µm at a total pressure of 3 mTorr with the N2 fraction varied from 0 to 1, and the substrate temperature Ts, varied from ambient to 350°C. The mechanical and tribological properties of the coatings were evaluated by nanoindentation and dry ball-on-disk test. For CNx (0 = x = 0.35) films deposited below 200°C (amorphous structure), the elastic recovery and hardness do not change significantly with increasing N concentration, however, the friction coefficient increases from 0.19 to 0.45, while the coating wear rate is low. For CNx (0 = x = 0.15) films grown at Ts = 350°C, where a transition from a graphite-like to a "fullerene-like" phase occurs, a dramatic increase in hardness and elasticity is observed. Furthermore, the rms surface roughness decreases from 15.0 to 0.4 nm. For 0.15 = x = 0.20, CNx films deposited at Ts = 350°C (fullerene-like phase) exhibit a smooth surface, high hardness and elasticity (~90% recovery), and a coefficient of friction against hard steel of ~0.25. For all substrates, film friction coefficient tends to increase as the nitrogen content in the film is increased. Results also indicate the formation of a transfer layer which improves the tribological properties of the films. © 2001 Elsevier Science B.V. All rights reserved.
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| 10. |
- Cagnoli, Patricia, et al.
(författare)
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Reduced Insular Glutamine and N-Acetylaspartate in Systemic Lupus Erythematosus: A Single-Voxel H-1-MR Spectroscopy Study
- 2013
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Ingår i: Academic Radiology. - : Elsevier BV. - 1878-4046 .- 1076-6332. ; 20:10, s. 1286-1296
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Tidskriftsartikel (refereegranskat)abstract
- Rationale and Objectives: To investigate for differences in metabolic concentrations and ratios between patients with systemic lupus erythematosus (SLE) without (group SLE) and those with neurological symptoms (group NPSLE) compared to a healthy control (group HC) in three normal-appearing brain regions: the frontal white matter, right insula (RI), and occipital gray matter and whether changes in any of the metabolites or metabolic ratios are correlated to disease activity and other clinical parameters. Materials and Methods: Twenty patients with SLE (18 women and 2 men, age range 23.4-64.6 years, mean age 43.9 years), 23 NPSLE patients (23 women, age range 23.7-69.8 years, mean age 42.4 years), and 21 HC (19 women and 2 men, age range 21.0-65.7 years, mean age 43.4 years) were included. All subjects had conventional brain magnetic resonance imaging and H-1 single-voxel spectroscopy, clinical assessment, and laboratory testing. Results: NPSLE patients had significantly reduced N-acetylaspartate (NAA)/creatine compared to HC (P = .02) and SLE patients (P = .01) in the RI. Lower glutamine/creatine levels were also detected in RI in both patient groups and in frontal white matter in NPSLE patients compared to HC (P = .01, P = .02). NAA/Cr ratio in the RI was significantly negatively correlated with the Systemic Lupus Erythematosus Disease Activity Index (r = -0.41; P = .008), and patients with active SLE symptoms also had a trend toward lower NAA/creatine ratios (1.02 vs 1.12; P = .07). Conclusions: The present data support previous findings of abnormal metabolic changes in normal-appearing regions in the brain of both SLE and NPSLE patients and raise the possibility that especially NAA, glutamine, and glutamate may be additional biomarkers for cerebral disease activity in SLE patients as these early metabolic changes occur in the brain of SLE patients before neurologic and imaging manifestations become apparent.
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| 11. |
- Chirita, Valeriu, et al.
(författare)
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Reptation : a mechanism for cluster migration on (111) face-centered-cubic metal surfaces
- 1999
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Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 436:1-3, s. L641-L647
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Tidskriftsartikel (refereegranskat)abstract
- Embedded-atom molecular-dynamics simulations were used to follow the diffusion dynamics of compact platinum clusters with up to 19 atoms on Pt(lll). The results reveal a cluster diffusion mechanism on (111) face-centered-cubic (fcc) surfaces involving successive shear translations of adjacent subcluster regions giving rise to reptation, a snake-like gliding motion. We show that for compact clusters with <7 atoms, this mechanism competes energetically with that of island diffusion through concerted motion. However, for cluster sizes of between 8 and similar or equal to 20 atoms, reptation becomes energetically favorable, especially for elongated clusters. Reptation is also shown to be an important migration mechanism for fractal (randomly ramified) and dendritic (symmetrically branched) islands. (C) 1999 Elsevier Science B.V. All rights reserved.
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| 12. |
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| 13. |
- F., Durmo, et al.
(författare)
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Multivoxel 1H MR spectroscopy biometrics for preoprerative differentiation between brain tumors
- 2018
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Ingår i: Neuroradiology. - : Springer Science and Business Media LLC. - 1432-1920 .- 0028-3940. ; 60:S2, s. 444-444
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Konferensbidrag (refereegranskat)abstract
- Purpose To investigate multivoxel proton Magnetic Resonance Spectroscopy (1HMRS) biometrics for preoperative differentiation and prognosis of patients with brain metastases (MET), low-(LGG) and high grade glioma (HGG). Methods Thirty-five patients (15 HGG, 9 LGG and 11 MET) were included. Proton Magnetic Resonance Spectroscopy Imaging(1H-MRSI) data was assessed and neurochemical profiles for metabolites (NAA+NAAG, Cr+PCr, Glu+Gln (Glx), Lac, Ins, GPC+PCho) and total Lipids (tLip) and macromolecule (tMM) signals were estimated. Concentrations were reported as either absolute or ratios to total choline (tCho=GPC+PCho) and creatine (tCr=Cr+PCr) levels. Voxels of interest (VOIs) in a MRSI matrix were labelled accordingly to contrast-enhancing/nonenhancing lesional, edema, ipsi- or contralateral healthy appearing tissue and the metabolite averages were reported for each tissue type. Multi-biometric analysis with logistic regression, ROC- and Kaplan-Meier survival analysis was performed in SPSS v.24 and postprocessing with LC Model. Results Across HGG/LGG/MET; the average Ins/tCho was shown to be prognostic for overall survival (OS): with low values (≤1.29) in affected hemisphere predicting worse OS than high values (>1.29), (Log Rank
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| 14. |
- Foerster, B R, et al.
(författare)
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Cerebral Blood Flow Alterations in Pain-Processing Regions of Patients with Fibromyalgia Using Perfusion MR Imaging.
- 2011
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Ingår i: AJNR. American journal of neuroradiology. - 1936-959X. ; 32, s. 1873-1878
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND PURPOSE: Widespread pain sensitivity in patients with FM suggests a CNS processing problem. The purpose of this study was to assess alterations in perfusion as measured by DSC in a number of brain regions implicated in pain processing between patients with FM and healthy controls. MATERIALS AND METHODS: Twenty-one patients with FM and 27 healthy controls underwent conventional MR imaging and DSC. For DSC, 12 regions of interest were placed in brain regions previously implicated in pain processing. rCBF values were calculated for each region of interest. Subjects answered mood/pain coping questionnaires and underwent clinical/experimental pain assessment. RESULTS: There were significant correlations between the thalamic rCBF values and the pain-control beliefs of FM subjects. The strength of the relationship between clinical pain measures and thalamic rCBF values increased after adjusting for pain-control beliefs. There was a significantly different distribution pattern of rCBF values across various brain regions between the FM group and the healthy controls. There was a lower degree of correlation in the FM group between the thalamic rCBF values and the other brain regions relative to the healthy controls. CONCLUSIONS: Significant correlations were found between thalamic rCBF values and pain belief values. These data suggest that there are baseline alterations of brain perfusion in patients with FM. rCBF values of the thalami exhibited lower correlations with respect to other brain regions thought to be involved in pain processing compared with those in healthy controls.
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| 15. |
- Gerstner, G. E., et al.
(författare)
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Posterior Insular Molecular Changes in Myofascial Pain
- 2012
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Ingår i: Journal of Dental Research. - : SAGE Publications. - 0022-0345 .- 1544-0591. ; 91:5, s. 485-490
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Tidskriftsartikel (refereegranskat)abstract
- Temporomandibular disorders (TMD) include craniocervical pain conditions with unclear etiologies. Central changes are suspected; however, few neuroimaging studies of TMD exist. Single-voxel proton magnetic resonance spectroscopy (H-1-MRS) was used before and after pressure-pain testing to assess glutamate (Glu), glutamine (Gln), N-acetylaspartate (NAA), and choline (Cho) levels in the right and left posterior insulae of 11 individuals with myofascial TMD and 11 matched control individuals. Glu levels were significantly lower in all individuals after pain testing. Among those with TMD, left-insular Gln levels were related to reported pain, left posterior insular NAA and Cho levels were significantly higher at baseline than in control individuals, and NAA levels were significantly correlated with pain-symptom duration, suggesting adaptive changes. The results suggest that significant central cellular and molecular changes can occur in individuals with TMD.
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| 16. |
- Hellgren, N., et al.
(författare)
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Anisotropies in magnetron sputtered carbon nitride thin films
- 2001
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 78:18, s. 2703-2705
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Tidskriftsartikel (refereegranskat)abstract
- Carbon nitride CNx (O=x=0.35) thin films, deposited by reactive dc magnetron sputtering in Ar/N2 discharges have been studied with respect to microstructure using electron microscopy, and elastic modulus using nanoindentation and surface acoustic wave analyses. For growth temperature of 100°C, the films were amorphous, and with an isotropic Young's modulus of ~170-200 GPa essentially unaffected by the nitrogen fraction. The films grown at elevated temperatures (350-550°C) show anisotropic mechanical properties due to a textured microstructure with standing basal planes, as observed from measuring the Young's modulus in different directions. The modulus measured in the plane of the film was ~60-80 GPa, while in the vertical direction the modulus increased considerably from ~25 to ~200 GPa as the nitrogen content was increased above ~15 at. %. © 2001 American Institute of Physics.
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| 17. |
- Hellgren, N., et al.
(författare)
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Effect of chemical sputtering on the growth and structural evolution of magnetron sputtered CNx thin films
- 2001
-
Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 382:1-2, s. 146-152
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Tidskriftsartikel (refereegranskat)abstract
- The growth and microstructure evolution of carbon nitride CNx (0=x=0.35) films, deposited by reactive d.c. magnetron sputtering in Ar/N2 discharges has been studied. The substrate temperature TS varied between 100 and 550 °C, and the N2 fraction in the discharge gas varied from 0 to 100%. It is found that the deposition rate and film morphology show strong dependence on TS and nitrogen fraction. For growth temperature of 100 °C, the films are amorphous, and essentially unaffected by the nitrogen fraction. For TS>200 °C, however, the nitrogen fraction has more significant effect on the growth and structural evolution of the films. The pure carbon films appear porous and have a high surface roughness. For increasing nitrogen fraction the films become denser and the roughness decreases by one order of magnitude. It is suggested that a chemical sputtering process, during which desorption of volatile N2 and CN-species, predominantly C2N2, is important not only for the deposition rate and the nitrogen incorporation, but also for the resulting film structure. The chemical sputtering process becomes more pronounced at elevated temperatures with higher nitrogen fractions.
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| 18. |
- Hellgren, N., et al.
(författare)
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Growth, structure, and mechanical properties of CNxHy films deposited by dc magnetron sputtering in N2/Ar/H2 discharges
- 2000
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Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 18:5, s. 2349-2358
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Tidskriftsartikel (refereegranskat)abstract
- Reactive direct current magnetron sputtering was used to deposit the hydrogenated carbon nitride films in mixed nitrogen (N2)/argon (Ar)/ hydrogen (H2) discharges. Growth and structure evolution of films was found to be affected by chemical sputtering effects. The hydrogen were found to be bonded to nitrogen and hydrogen incorporation decreases the elasticity and hardness.
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| 19. |
- Håkansson, G., et al.
(författare)
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Ion irradiation effects during growth of Mo/V(001) superlattices by dual-target magnetron sputtering
- 1992
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Ingår i: Journal of Crystal Growth. - 0022-0248. ; 121:3, s. 399-412
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Tidskriftsartikel (refereegranskat)abstract
- Epitaxial (001)-oriented Mo/V superlattice films with wavelengths of ≈ 5 nm have been grown on MgO(001) substrates, kept at 700°C, by dual-target unbalanced magnetron sputter deposition in Ar discharges. Low-energy (15-250 eV) Ar ion irradiation with incident ion-to-metal flux ratio of ≈ 1 during film growth was obtained through the application of a negative potential Vs to the substrate. The effects of ion bombardment on interface roughness and mixing, resputtering rates, and defect structure were investigated using a combination of cross-sectional transmission electron microscopy (XTEM), X-ray diffraction (XRD), and simulation of XRD patterns. High-resolution XTEM images showed that the interfaces were relatively sharp for Vs ≤ 100 V while higher Vs values resulted in more diffuse interfaces indicating ion-induced intermixing. By using a kinematical model of diffraction, and comparing with experimental XRD results, it could be concluded that the intermixing increased from ≈ 0.3 nm (2 monolayers) at Vs = 15 V to & 0.9 nm (6 monolayers) at Vs = 250 V. The inhomogeneous strain showed a large increase for Vs & 50 V. This is explained by an incorporation of point defects. Coherency strain relaxation between layers is suggested to take place through the formation of edge dislocations with Burgers vector 〈110〉 by climb processes. Finally, increasing Vs also resulted in resputtering, preferentially from the V layers.
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| 20. |
- Johansson, M P, et al.
(författare)
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Growth of CNx/BN : C multilayer films by magnetron sputtering
- 2000
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 360:1-2, s. 17-23
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Tidskriftsartikel (refereegranskat)abstract
- Symmetric CNx/BN:C multilayer thin films, with nominal compositional modulation periods of ? = 2.5, 5, and 9 nm were deposited by unbalanced dual cathode magnetron sputtering from C (graphite) and B4C targets in an Ar/N2 (60/40) discharge. The multilayers and single-layer of the constituent CNx and BN:C compounds were grown to a total thickness of 0.5 µm onto Si(001) substrates held at 225°C and a negative floating potential of approx. 30 V (Ei = 24 eV). Layer characterizations were performed by TEM, X-ray reflectivity, RBS, and nanoindentation measurements. Results show that CN0.33 and BN:C (35, 50, and 15 at.% of B, N, and C, respectively) layers were prepared at the above conditions. It is suggested that all films exhibit a three-dimensional interlocked structure with a cylindrical texture in the film growth direction. The structure was continuous over relatively well defined and smooth CNx/BN:C interfaces. All coatings exhibit extreme elasticity with elastic recoveries as high as 85-90% (10 mN maximum load) attributed to the observed structure. However, the multilayers were stiffer and more elastic compared to that of the single-layers and thus shows promise for improved protective properties.
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| 21. |
- Münger, Peter, et al.
(författare)
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Adatom-induced diffusion of two-dimensional close-packed Pt-7 clusters on Pt(111)
- 1996
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 355:1-3, s. L325-L330
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Tidskriftsartikel (refereegranskat)abstract
- Molecular dynamics simulations were used to follow the dynamics of the motion of hexagonal Pt heptamers on Pt(111). Close packed Pt-7 clusters on fee sites were found to be very stable structures with reconfiguration or translation events occurring only rarely over simulation times >30 ns at 1000 K. The adsorption of a single adatom on the cluster surface, however, induced rapid intracluster bond breaking, reconfiguration, the introduction of stacking faults, and greatly enhanced cluster diffusion rates. Cluster migration occurred primarily through sequences of individual atom and concerted dimer jumps, but concerted cluster motion was also observed. The adatoms eventually descended to the terrace, predominantly through push-out/exchange reactions with cluster atoms at B edges.
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| 22. |
- Münger, Peter, et al.
(författare)
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Destabilization and diffusion of two-dimensional close-packed Pt clusters on Pt(111) during film growth from the vapor phase
- 1998
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 318:1-2, s. 57-60
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Tidskriftsartikel (refereegranskat)abstract
- Cluster migration is known to be an important process during film growth at elevated temperatures, but relatively little quantitative data is available. We have used molecular dynamics simulations to follow the dynamics of small two-dimensional Pt clusters on Pt(lll) at 1000 K. While close-packed Pt-7 heptamers are extremely stable structures, the addition of a single-cluster vacancy or an on-top adatom immediately results in intracluster bond breaking, reconfigurations, rotations, the introduction of stacking faults, and greatly enhanced cluster-diffusion rates. Mapping center-of-mass motion for total simulation times > 145 ns revealed increases in cluster velocities by more than an order of magnitude with cluster migration occurring primarily by concerted motion and a novel diffusion mechanism involving double shearing of dimers/trimers. Contrary to some previous reports, edge-atom diffusion plays only a minor role. (C) 1998 Elsevier Science S.A.
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| 23. |
- Pougeoise, E., et al.
(författare)
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Experimental characteristics and analysis of transverse modes in 1.3 μm strained InGaAs quantum well VCSELs
- 2006
-
Ingår i: Proc SPIE Int Soc Opt Eng. - : SPIE. - 0819462411 - 9780819462411
-
Konferensbidrag (refereegranskat)abstract
- In the context of optical interconnection applications, we report on results obtained on strained InGaAs quantum well Vertical Cavity Surface Emitting Lasers (VCSELs). Our devices are top p-type DBR oxide-confined VCSEL, grown by metalorganic vapour-phase epitaxy (MOVPE). These lasers exhibit low threshold currents and deliver up to 1.77 mW in continuous wave operation at room temperature. Fundamental mode continuous-wave lasing at wavelengths beyond 1300 nm at room temperature is reached for a 4 μm oxide diameter VCSEL. The particular design of the active layer based on a large detuning between the gain maximum and the cavity resonance gives our devices a very specific thermal and modal behaviour. Therefore, we study the spectral and spatial distributions of the transverse modes by near field scanning optical microscopy using a micropolymer tip at the end of an optical fibre.
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| 24. |
- Pougeoise, E., et al.
(författare)
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Experimental study of the lasing modes of 1.3-ÎŒm highly strained InGaAs-GaAs quantum-well oxide-confined VCSELs
- 2009
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Ingår i: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 21:6, s. 377-379
-
Tidskriftsartikel (refereegranskat)abstract
- We present an experimental study of the main modes involved in the emission properties of InGaAs-GaAs quantum-well oxide-confined long wavelength vertical-cavity surface-emitting lasers. Lasing properties are dominated by the so-called "oxide modes" and by aperture modes, respectively, for small and large driving currents. We present complementary investigations of the laser emission including far-field angular distribution and spectroscopic near-field optical microscopy to a better understanding of the nature of the "oxide modes."
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| 25. |
- Pougeoise, E., et al.
(författare)
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Strained InGaAs quantum well vertical cavity surface emitting lasers emitting at 1.3 mu m
- 2006
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 0013-5194 .- 1350-911X. ; 42:10, s. 584-586
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Tidskriftsartikel (refereegranskat)abstract
- Results on strained InGaAs quantum well vertical cavity surface emitting lasers for optical interconnection applications are reported. Fundamental mode continuous-wave lasing at wavelengths beyond 1300 nm is demonstrated at room temperature. The metal-organic vapour-phase epitaxy grown structure was processed as top p-type distribute Bragg reflector oxide-confined devices.
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| 26. |
- Rydelius, A., et al.
(författare)
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Predictive value of diffusion MRI-based parametric response mapping for prognosis and treatment response in glioblastoma
- 2023
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Ingår i: Magnetic Resonance Imaging. - 0730-725X. ; 104, s. 88-96
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Tidskriftsartikel (refereegranskat)abstract
- Background: Early detection of treatment response is important for the management of patients with malignant brain tumors such as glioblastoma to assure good quality of life in relation to therapeutic efficacy. Aim: To investigate whether parametric response mapping (PRM) with diffusion MRI may provide prognostic information at an early stage of standard therapy for glioblastoma. Materials and methods: This prospective study included 31 patients newly diagnosed with glioblastoma WHO grade IV, planned for primary standard postoperative treatment with radiotherapy 60Gy/30 fractions with concomitant and adjuvant Temozolomide. MRI follow-up including diffusion and perfusion weighting was performed at 3 T at start of postoperative chemoradiotherapy, three weeks into treatment, and then regularly until twelve months postoperatively. Regional mean diffusivity (MD) changes were analyzed voxel-wise using the PRM method (MD-PRM). At eight and twelve months postoperatively, after completion of standard treatment, patients were classified using conventional MRI and clinical evaluation as either having stable disease (SD, including partial response) or progressive disease (PD). It was assessed whether MD-PRM differed between patients having SD versus PD and whether it predicted the risk of disease progression (progression-free survival, PFS) or death (overall survival, OS). A subgroup analysis was performed that compared MD-PRM between SD and PD in patients only undergoing diagnostic biopsy. MGMT-promotor methylation status (O6-methylguanine-DNA methyltransferase) was registered and analyzed with respect to PFS, OS and MD-PRM. Results: Of the 31 patients analyzed: 21 were operated by resection and ten by diagnostic biopsy. At eight months, 19 patients had SD and twelve had PD. At twelve months, ten patients had SD and 20 had PD, out of which ten were deceased within twelve months and one was deceased without known tumor progression. Median PFS was nine months, and median OS was 17 months. Eleven patients had methylated MGMT-promotor, 16 were MGMT unmethylated, and four had unknown MGMT-status. MD-PRM did not significantly predict patients having SD versus PD neither at eight nor at twelve months. Patients with an above median MD-PRM reduction had a slightly longer PFS (P = 0.015) in Kaplan-Maier analysis, as well as a non-significantly longer OS (P = 0.099). In the subgroup of patients only undergoing biopsy, total MD-PRM change at three weeks was generally higher for patients with SD than for patients with PD at eight months, although no tests were performed. MGMT status strongly predicted both PFS and OS but not MD-PRM change. Conclusion: MD-PRM at three weeks was not demonstrated to be predictive of treatment response, disease progression, or survival. Preliminary results suggested a higher predictive value in non-resected patients, although this needs to be evaluated in future studies.
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| 27. |
- Suenaga, K, et al.
(författare)
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Carbon nitride nanotubulite - densely-packed and well-aligned tubular nanostructures
- 1999
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Ingår i: Chemical Physics Letters. - 0009-2614. ; 300:5-6, s. 695-700
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Tidskriftsartikel (refereegranskat)abstract
- Tubular carbon nitride (CNx, x=0.01–0.32) nanoparticles were successfully synthesized by d.c. magnetron sputtering. These tubes were grown in a highly packed form perpendicularly on a sodium chloride substrate. Their number density is estimated to be ∼1×104 per μm2 and is constant over macroscopic regions. Sub-nanometer scale chemical mapping shows that the nitrogen to carbon atomic ratio is rather constant across these tubes. This successful synthesis of a nanotubulite – made of a rather compact aggregation of tubular nanoparticles – could facilitate experimental approaches to measure mechanical or electrical transport properties of such nanotubes and to open the way to variable nanotube applications.
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| 28. |
- Asplund, Carl, et al.
(författare)
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1260 nm InGaAs vertical-cavity lasers
- 2002
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 0013-5194 .- 1350-911X. ; 38:13, s. 635-636
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Tidskriftsartikel (refereegranskat)abstract
- The fabrication and performance of highly strained double-quantum well InGaAs/GaAs vertical-cavity lasers with record-long emission wavelength of 1260 nm at room temperature is reported. Depending on device diameter, the minimum threshold current is in the low mA-regime while the maximum output power exceeds 1 mW. The devices work continuous-wave over a wide temperature range of at least 10-120degrees C.
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| 29. |
- Bauer, A. D., et al.
(författare)
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Corrosion behaviour of monocrystalline titanium nitride
- 1997
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Ingår i: Surface and Coatings Technology. ; 91:3, s. 208-214
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Tidskriftsartikel (refereegranskat)abstract
- The corrosion behaviour of monocrystalline and highly textured TiN films deposited onto single crystalline MgO has been investigated. It was found that films with high defect concentrations and elements of polycrystallinity had a reduced corrosion resistance. These films had low corrosion potentials and high critical and passive current densities. For high quality films the [110]- and [111]-orientations generally displayed better corrosion properties than films with [100]-orientation. Corrosion had different effects on films of different orientations: On [100]-oriented films loose rectangularly shaped flakes were observed. [110]-oriented films cracked because of compressive stresses, which in many cases caused the films to peel off during corrosion. On [111]-oriented films, finally, triangular pits were detected after corrosion. Films with high corrosion potentials had low values of critical and passive current densities. Non-destructive electrochemical analysis in combination with defect analysis can thus be used to predict the behaviour of these films on anodic polarisation.
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| 30. |
- Fjalldal, S., et al.
(författare)
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Detailed assessment of hypothalamic damage in craniopharyngioma patients with obesity
- 2019
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Ingår i: International Journal of Obesity. - : Springer Science and Business Media LLC. - 0307-0565 .- 1476-5497. ; 43:3, s. 533-544
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Tidskriftsartikel (refereegranskat)abstract
- Background/objectives: Hypothalamic obesity (HO) occurs in 50% of patients with the pituitary tumor craniopharyngioma (CP). Attempts have been made to predict the risk of HO based on hypothalamic (HT) damage on magnetic resonance imaging (MRI), but none have included volumetry. We performed qualitative and quantitative volumetric analyses of HT damage. The results were explored in relation to feeding related peptides and body fat. Subjects/methods: A cross-sectional study of childhood onset CPs involving 3 Tesla MRI, was performed at median 22 years after first operation; 41 CPs, median age 35 (range: 17–56), of whom 23 had HT damage, were compared to 32 controls. After exclusions, 35 patients and 31 controls remained in the MRI study. Main outcome measures were the relation of metabolic parameters to HT volume and qualitative analyses of HT damage. Results: Metabolic parameters scored persistently very high in vascular risk particularly among HT damaged patients. Patients had smaller HT volumes compared to controls 769 (35–1168) mm3 vs. 879 (775–1086) mm3; P < 0.001. HT volume correlated negatively with fat mass and leptin among CP patients (rs = −0.67; P <.001; rs = −0.53; P = 0.001), and explained 39% of the variation in fat mass. For every 100 mm3 increase in HT volume fat mass decreased by 2.7 kg (95% CI: 1.5–3.9; P < 0.001). Qualitative assessments revealed HT damage in three out of six patients with normal volumetry, but HT damage according to operation records. Conclusions: A decrease in HT volume was associated with an increase in fat mass and leptin. We present a method with a high inter-rater reliability (0.94) that can be applied by nonradiologists for the assessment of HT damage. The method may be valuable in the risk assessment of diseases involving the HT.
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| 31. |
- Fjalldal, S., et al.
(författare)
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Microstructural white matter alterations and hippocampal volumes are associated with cognitive deficits in craniopharyngioma
- 2018
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Ingår i: European Journal of Endocrinology. - : BIOSCIENTIFICA LTD. - 0804-4643 .- 1479-683X. ; 178:6, s. 577-587
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Tidskriftsartikel (refereegranskat)abstract
- Context: Patients with craniopharyngioma (CP) and hypothalamic lesions (HL) have cognitive deficits. Which neural pathways are affected is unknown. Objective: To determine whether there is a relationship between microstructural white matter (WM) alterations detected with diffusion tensor imaging (DTI) and cognition in adults with childhood-onset CP. Design: A cross-sectional study with a median follow-up time of 22 (6-49) years after operation. Setting: The South Medical Region of Sweden (2.5 million inhabitants). Participants: Included were 41 patients (24 women, amp;gt;= 17 years) surgically treated for childhood-onset CP between 1958-2010 and 32 controls with similar age and gender distributions. HI was found in 23 patients. Main outcome measures: Subjects performed cognitive tests and magnetic resonance imaging, and images were analyzed using DTI of uncinate fasciculus, fornix, cingulum, hippocampus and hypothalamus as well as hippocampal volumetry. Results: Right uncinate fasciculus was significantly altered (P amp;lt;= 0.01) Microstructural WM alterations in left ventral cingulum were significantly associated with worse performance in visual episodic memory, explaining approximately 50% of the variation. Alterations in dorsal cingulum were associated with worse performance in immediate, delayed recall and recognition, explaining 26-38% of the variation, and with visuospatial ability and executive function, explaining 19-29%. Patients who had smaller hippocampal volume had worse general knowledge (P = 0.028), and microstructural WM alterations in hippocampus were associated with a decline in general knowledge and episodic visual memory. Conclusions: A structure to function relationship is suggested between microstructural WM alterations in cingulum and in hippocampus with cognitive deficits in CP.
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| 32. |
- Gilet, Ph., et al.
(författare)
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1.3 μm VCSELs : InGaAs/GaAs, GaInNAs/GaAs multiple quantum wells and InAs/GaAs quantum dots- Three candidates as active material
- 2007
-
Ingår i: Vertical - Cavity Surface - Emitting Lasers XI. - San Jose, CA : SPIE. ; , s. F4840-F4840
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Konferensbidrag (refereegranskat)abstract
- In this article, we report our results on 1.3ÎŒm VCSELs for optical interconnection applications. Room temperature continuous-wave lasing operation is demonstrated for top emitting oxide-confined devices with three different active materials, highly strained InGaAs/GaAs(A) and GalnNAs/GaAs (B) multiple quantum wells (MQW) or InAs/GaAs (C) quantum dots (QD). Conventional epitaxial structures grown respectively by Metal Organic Vapour Phase Epitaxy (MOVPE), Molecular Beam Epitaxy (MBE) and MBE, contain rully doped GaAs/AlGaAs DBRs. All three epilayers are processed in the same way. Current and optical confinement are realized by selective wet oxidation. Circular apertures from 2 ÎŒm to 16 ÎŒm diameters are defined. At room temperature and in continuous wave operation, all three systems exhibit lasing operation at wavelengths above 1 275nm and reached 1 300nm for material (A). Typical threshold currents are in the range [1-10]mA and are strongly dependent firstly on oxide diameter and secondly on temperature. Room temperature cw maximum output power corresponds respectively to 1.77mW, 0.5mW and 0.6mW. By increasing driving current, multimode operation occurs at different level depending on the oxide diameter. In case (A), non conventional modal behaviors will be presented and explained by the presence of specific oxide modes. Thermal behaviors of the different devices have been compared. In case (A) and (C) we obtain a negative T0. We will conclude on the different active materials in terms of performances with respect to 1300nm VCSEL applications.
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| 33. |
- Hammar, Mattias, et al.
(författare)
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1.3-mu m InGaAs vertical-cavity surface-emitting lasers
- 2005
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Ingår i: 2005 IEEE LEOS Annual Meeting Conference Proceedings (LEOS). - 0780392175 ; , s. 396-397
-
Konferensbidrag (refereegranskat)abstract
- We report on the fabrication and performance of N-free InGaAs/GaAs 1.3-mu m range vertical-cavity surface-emitting lasers (VCSELs). Using optimized quantum-well (QW) growth conditions in combination with negative gain-cavity tuning, high-performance VCSELs with emission wavelength up to 1300 nm are realized. The performance figures include mA-range threshold currents, mW-range singlemode output power, continuous-wave operation up to 140 degrees C and 10 Gbit/s data transmission.
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| 34. |
- Hammar, M., et al.
(författare)
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1300-nm GaAs-based vertical-cavity lasers
- 2002
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - Brugge : SPIE. ; , s. 137-149
-
Konferensbidrag (refereegranskat)abstract
- We compare GaInNAs and highly strained InGaAs quantum-wells (QWs) for applications in metal-organic vapor-phase epitaxy (MOVPE)-grown GaAs-based 1300-nm vertical-cavity lasers (VCLs). While the peak wavelength of InGaAs QWs can be extended by a small fraction of N, the luminescence efficiency degrades strongly with wavelength. On the other hand, using highly strained InGaAs QWs in combination with a large VCL detuning it is also possible to push the emission wavelength towards 1.3 ÎŒm. The optimized MOVPE growth conditions for such QW and VCL structures are discussed in some detail. It is noted that GaInNAs and InGaAs QWs preferably are grown at low temperature, but with quite different V/III ratios and growth rates. We also point out the importance of reduced doping concentration and growth temperature of the n-doped bottom distributed Bragg reflector to minimize optical loss and for compatibility with GaInNAs QWs. InGaAs VCLs with emission wavelengths beyond 1260 nm are demonstrated. This includes mW-range output power, mA-range threshold current and 10 Gb/s data transmission.
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| 35. |
- Harris, Richard E, et al.
(författare)
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Pregabalin rectifies aberrant brain chemistry, connectivity, and functional response in chronic pain patients.
- 2013
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Ingår i: Anesthesiology. - 1528-1175. ; 119:6, s. 1453-1464
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Tidskriftsartikel (refereegranskat)abstract
- Chronic pain remains a significant challenge for modern health care as its pathologic mechanisms are largely unknown and preclinical animal models suffer from limitations in assessing this complex subjective experience. However, human brain neuroimaging techniques enable the assessment of functional and neurochemical alterations in patients experiencing chronic pain and how these factors may dynamically change with pharmacologic treatment.
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| 36. |
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| 37. |
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| 38. |
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| 39. |
- Hoppe, Magnus, 1963-, et al.
(författare)
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Intended Involvement – How Public Organizations Struggle to Become Co-producers of New Public Values
- 2024
-
Ingår i: Scandinavian Journal of Public Administration. - : University of Gothenburg School of Public Administration. - 2001-7405 .- 2001-7413. ; 28:1, s. 78-98
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Tidskriftsartikel (refereegranskat)abstract
- The paper is guided by the question of how public organizations can adapt to include citizens as co-producers of public values. To answer it, eleven researchers and civil servants, all involved in the transformation of a collaborative platform encompassing a university and four different public organizations, formed a collaborative and boundary-spanning author. Building on personal expertise and situated organizational experiences we conclude that public organizations do not adapt except for specific confined areas where they can still control and command outcomes important to them. Hence, public organizations struggle to become co-producers of new public values. From the process, we also conclude that academics and civil servants together writing an academic article cannot be viewed as a fertile common ground for equal collaboration and co-production. Nevertheless, it might still work as an interesting boundary-spanning activity for arriving at shared understandings and important insights on for instance why organizational moves from intended to actual involvement appear difficult.
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| 40. |
- Ichesco, Eric, et al.
(författare)
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Altered Functional Connectivity Between the Insula and the Cingulate Cortex in Patients With Temporomandibular Disorder: A Pilot Study.
- 2012
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Ingår i: Headache. - : Wiley. - 1526-4610. ; 52, s. 441-454
-
Tidskriftsartikel (refereegranskat)abstract
- Background.- Among the most common chronic pain conditions, yet poorly understood, are temporomandibular disorders (TMDs), with a prevalence estimate of 3-15% for Western populations. Although it is increasingly acknowledged that central nervous system mechanisms contribute to pain amplification and chronicity in TMDs, further research is needed to unravel neural correlates that might abet the development of chronic pain. Objective.- The insular cortex (IC) and cingulate cortex (CC) are both critically involved in the experience of pain. The current study sought specifically to investigate IC-CC functional connectivity in TMD patients and healthy controls (HCs), both during resting state and during the application of a painful stimulus. Methods.- Eight patients with TMD, and 8 age- and sex-matched HCs were enrolled in the present study. Functional magnetic resonance imaging data during resting state and during the performance of a pressure pain stimulus to the temple were acquired. Predefined seed regions were placed in the IC (anterior and posterior insular cortices) and the extracted signal was correlated with brain activity throughout the whole brain. Specifically, we were interested whether TMD patients and HCs would show differences in IC-CC connectivity, both during resting state and during the application of a painful stimulus to the face. Results.- As a main finding, functional connectivity analyses revealed an increased functional connectivity between the left anterior IC and pregenual anterior cingulate cortex (ACC) in TMD patients, during both resting state and applied pressure pain. Within the patient group, there was a negative correlation between the anterior IC-ACC connectivity and clinical pain intensity as measured by a visual analog scale. Conclusions.- Since the pregenual region of the ACC is critically involved in antinociception, we hypothesize that an increase in anterior IC-ACC connectivity is indicative of an adaptation of the pain modulatory system early in the chronification process.
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| 41. |
- Karlsson, L., et al.
(författare)
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Influence of residual stresses on the mechanical properties of TiCxN1-x (x = 0, 0.15, 0.45) thin films deposited by arc evaporation
- 2000
-
Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 371:1, s. 167-177
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of residual stress state and composition on the mechanical properties of arc evaporated TiCxN1-x thin films been investigated. By controlling the flow ratios of the reactive gases, N2 and CH4, films with compositions x = 0 (TIN), x to approximately 0.15, and x to approximately 0.45 have been grown on cemented carbide substrates. The residual stress state was altered through variations in the negative substrate bias over the range 20 V=Vs=820 V. The intrinsic stress, sint, measured by the X-ray diffraction (XRD) sin2? method was compressive and increased with decreasing Vs and increasing x. The latter behavior is suggested to be due to increased effective stability of defect complexes when the carbon content increases. Maximum stress level was between -6 and -7 GPa and limited by interior cracking of the films. The increase in intrinsic stress was accompanied by an increase in XRD peak broadening due to inhomogeneous strains. The hardness, H, and Young's modulus, E, of as-deposited films were measured using the nanoindentation technique. Apparently linear correlations between sint and H were found for each film composition where H increased with x. The maximum H, 44 GPa, was thus obtained for the x to approximately 0.45 film with sint = -5.5 GPa. The lowest hardness for this composition was 35 GPa for a film with sint = -2.7 GPa. For the TiN films, a similar variation in hardness of 33 GPa at sint = -5.8 to 26 GPa at sint = -1.2 GPa was obtained. E was constant at approximately 610 GPa for most of the films, with a slight decrease in the films with the lowest sint values.
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| 42. |
- Mogg, S., et al.
(författare)
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1.3-ÎŒm InGaAs(N)/GaAs vertical-cavity lasers
- 2003
-
Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - San Jose, CA : SPIE. ; , s. 139-151
-
Konferensbidrag (refereegranskat)abstract
- In this work we present performance characteristics of metalorganic vapor-phase epitaxy grown GaInNAs and InGaAs quantum-well (QW) vertical-cavity lasers (VCLs) for 1.3-Όm applications. The InGaAs VCLs emit in a wavelength range from 1200 to somewhat above 1260 nm, while the GaInNAs VCLs operate from 1265 to 1303 nm. The InGaAs VCLs are based on highly strained InGaAs double QWs, with photoluminescence (PL) maximum at around 1190 nm, and extensive negative gain-cavity detuning. As a consequence, these devices are strongly temperature sensitive and the minimum threshold current is found at very high temperature (∌90-100°C). Both kind of VCLs work continuous-wave well above 100°C, and while the InGaAs VCLs reach slightly higher light output power, they show significantly larger threshold currents. In addition, the large device detuning also has profound effects on the high-frequency response. Nevertheless, for a 1260-nm device, 10 Gb/s transmission is demonstrated in a back-to-back configuration. We also show that by further optimization of the InGaAs QWs the PL peak wavelength can be extended to at least 1240 nm. The incorporation of such QWs in the present VCL structure should considerably improve the device performance, resulting in higher light output power, lower threshold current, and reduced temperature sensitivity with a shift of the minimum threshold current towards room temperature, thus approaching standard VCL tuning.
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| 43. |
- Pougeoise, E., et al.
(författare)
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1.3 ÎŒm strained InGaAs quantum well VCSELs : Operation characteristics and transverse modes analysis
- 2006
-
Ingår i: Vertical-Cavity Surface-Emitting Lasers X. - San Jose, CA : SPIE. ; , s. 13207-13207
-
Konferensbidrag (refereegranskat)abstract
- We report results on strained InGaAs quantum well Vertical Cavity Surface Emitting Lasers (VCSELs) for optical interconnection applications. The structure was grown by metalorganic vapour-phase epitaxy (MOVPE) and processed as top p-type DBR oxide-confined device. Our VCSELs exhibit low threshold currents and deliver up to 1.77 mW in continuous wave operation at room temperature. Fundamental mode continuous-wave lasing at wavelengths beyond 1300 nm is demonstrated at room temperature. The thermal behaviour of our devices is explained through the threshold current-temperature characteristics. Furthermore, the effective index model is used to understand the modal behaviour.
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| 44. |
- Selinder, T.I., et al.
(författare)
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Yttrium oxide inclusions in YBa2Cu3Ox thin films : Enhanced flux pinning and relation to copper oxide surface particles
- 1992
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Ingår i: Physica C: Superconductivity and its Applications. - 0921-4534. ; 202:1-2, s. 69-74
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Tidskriftsartikel (refereegranskat)abstract
- Semi-coherent Y2O3 (yttria) inclusions are identified in high quality epitaxial YBa2Cu3Ox (YBCO) thin films by using transmission electron microscopy and energy dispersive X-ray analyses. Magnetization measurements show enhanced flux pinning in films containing an increasing number density of inclusions. The inclusions are incorporated into the films without disturbing the YBCO structure appreciably. The number density is ≈ 1017 cm-3 in films having transport critical currents of 4x106 A cm-2 at 77 K. Nucleation of the yttria inclusions is suggested to occur spontaneously during film growth. The abundance of yttria inclusions is connected to the occurrence of large Cu-rich surface particles in films that have optimum superconducting properties.
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| 45. |
- Sjostrom, H., et al.
(författare)
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Characterization of interfaces between hydrogenated amorphous carbon films and steel substrates using high resolution cross-sectional transmission electron microscopy
- 1993
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Ingår i: Diamond and Related Materials. - 0925-9635. ; 2:2-4, s. 562-566
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Tidskriftsartikel (refereegranskat)abstract
- Cross-sectional transmission electron microscopy, including high resolution microscopy, was employed to characterize the interfaces between hydrogenated amorphous carbon (a-C:H) films and steel substrates. Films were deposited both by ion beam decomposition of large hydrocarbon molecules and by magnetron plasma decomposition of C2H2. The latter method was also used to deposit Mo- and W-containing a-C:H films onto steel substrates with interlayers of the pure metals between the steel substrate and the a-C:H films. The films were found to be amorphous except for the metal-containing films where 1–4 nm crystalline clusters were present in an a-C:H matrix. The metal interlayers had a columnar microstructure with column widths of ∼30 nm. The interfaces between the a-C:H films and the Mo or W interlayers were found to extend over 20–40 nm with a gradual crystalline-to-amorphous transition. In most of the a-C:H film-substrate interface regions a thin (less than 10 nm) layer was observed which was predominantly amorphous, but contained a small fraction of crystalline grains. Additional analyses carried out using Auger electron spectroscopy showed an increase in both O and N close to the interface. However, for the cases with Mo and W interlayers, the substrate surface contaminants were less localized and on some parts of the substrate surface the lattice fringes were continuous across the atomically sharp interface.
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| 46. |
- Sundgren, Pia C., et al.
(författare)
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Acute spinal trauma
- 2012
-
Ingår i: Diseases of the Brain, Head and Neck, Spine 2012-2015 : Diagnostic Imaging and Interventional Techniques - Diagnostic Imaging and Interventional Techniques. - Milano : Springer Milan. - 9788847026278 - 9788847026285 ; , s. 167-172
-
Bokkapitel (refereegranskat)abstract
- Injuries to the spinal column and spinal cord are a major cause of disability, affecting predominately young, healthy individuals. The majority of the spinal injuries (60%) affect young healthy males between 15 and 35 years of age, with important socioeconomic consequences, and the costs of lifetime care and rehabilitation are extremely high. As the longevity of the general population increases, there has been a concordant increase in the mean age of the typical spinal cord injury patient. The main cause for spinal injuries is blunt trauma, most commonly due to motor vehicle accidents (48%), followed by falls (21%) and sport injuries (14.6%). Assault and penetrating trauma account for approximately 10–20% of cases.
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| 47. |
- Wang, Page I., et al.
(författare)
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Perfusion-weighted MR Imaging in Cerebral Lupus Erythematosus
- 2012
-
Ingår i: Academic Radiology. - : Elsevier BV. - 1878-4046 .- 1076-6332. ; 19:8, s. 965-970
-
Tidskriftsartikel (refereegranskat)abstract
- Rationale and Objective: Neuropsychiatric systemic lupus erythematosus (NPSLE) is a diagnostically challenging, severe, and life-threatening condition, which is currently lacking a "gold standard." Our aim with this study is to look for magnetic resonance (MR) perfusion differences in NPSLE, SLE, and healthy control (HC) patients and correlate our findings with clinical parameters. Materials and Methods: Twenty-four NPSLE patients, 21 SLE patients, and 21 HC underwent dynamic susceptibility contrast enhanced MR perfusion using a 3-T scanner. Nine prospectively selected intracranial regions of interest were placed in white and gray matter and the cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MU) values were calculated. Subjects underwent clinical evaluation with SLEDAI and serum antibodies. Results: The SLE patients had higher CBF and CBV compared to the HC overall (P =.01) and in specific areas (P =.03-.048). SLE patients with signs of active disease (elevated SLEDAI and anti-double-stranded DNA) had significantly elevated CBV, CBF, and MU in the posterior cingulate gyrus (P =.01-.02). No significant difference was seen in the magnetic resonance perfusion measurements of NPSLE patients compared to SLE and HC, although the NPSLE patients also showed higher CBV variability compared to the SLE (P =.0004) and HC cohort (P <.0001). Conclusion: SLE patients have increased CBV and CBF compared to healthy controls. The SLE patients with clinical markers for active disease have elevated CBV, CBF, and MU in the posterior cingulate gyrus. NPSLE patients show increased variability in perfusion measurements, which may explain why susceptibility contrast enhanced MRI has not yet provided a specific target for NPSLE.
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