| 51. |
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| 52. |
- Johansson, Stefan, et al.
(author)
-
Implementation of an OFDM Synchronization Algorithm
- 1999
-
In: 42nd Midwest Symposium on Circuits and Systems, 1999.. - 0780354915 ; 1, s. 228-231
-
Conference paper (peer-reviewed)abstract
- In this paper, a implementation of an OFDM synchronization algorithm is presented. Both time and frequency offsets are estimated simultaneously, using the cyclic prefix. The algorithm is implemented on a commercial DSP, an FPGA and as an ASIC. It is shown that although the algorithm is too complex to be implemented on a standard DSP, a hardware architecture that is optimized for the algorithm can be implemented with moderate complexity
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| 53. |
- Johansson, Stefan, et al.
(author)
-
Silicon realization of an OFDM synchronization algorithm
- 1999
-
In: The 6th IEEE International Conference on Electronics, Circuits and Systems, Proceedings of ICECS '99.. - 0780356829 ; 1, s. 319-322
-
Conference paper (peer-reviewed)abstract
- n this paper a hardware architecture for an OFDM synchronizer is presented. The proposed synchronization unit can be used in any OFDM system that uses a cyclic prefix. The algorithm is based on the correlation introduced by the cyclic prefix, which is exploited in the time domain where both time and frequency offset are estimated simultaneously. The synchronization unit also performs frequency correction, which means that no feedback to the analog parts is necessary. Although the algorithm is too complex to be implemented on today's most powerful standard DSP, a hardware architecture that is optimized for the algorithm can be implemented with moderate complexity. The unit contains 32 kbit RAM and 5000 gates and the sample rate is 25 Msamples/s
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| 54. |
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| 55. |
- Johansson, Stefan, et al.
(author)
-
Wordlength Optimization of a Pipelined FFT Processor
- 1999
-
In: 42nd Midwest Symposium on Circuits and Systems, 1999.. - 0780354915 ; 1, s. 501-503
-
Conference paper (peer-reviewed)abstract
- This paper describes the optimization of the word lengths in an 8 k-points pipelined FFT processor. The word lengths can be freely chosen since the FFT is implemented as a full custom ASIC. According to the specification, input and output word lengths are 12 bits but improved performance on be achieved by using a longer wordlength internally. Increased wordlength means increased size, both for memory and arithmetic operations. Since the FFT processor uses large memories, especially in the early stages, it is especially important to keep wordlength short in the beginning of the pipeline. Finding a good trade-off between precision and size is a difficult problem and it is not reasonable to solve analytically. Simulations using a C-model are therefore used to find an acceptable solution. The simulations show that a good solution is obtained by starting with 12 bits and gradually increasing the wordlength up to 16 bits. The final result is rounded back to 12 bits. This is a good trade-off between precision and complexity
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| 56. |
- Kalén, Peter, et al.
(author)
-
Host Brain Regulation of Fetal Locus Coeruleus Neurons Grafted to the Hippocampus in 6-Hydroxydopamine-Treated Rats. An Intracerebral Microdialysis Study
- 1991
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In: European Journal of Neuroscience. - : Wiley. - 1460-9568 .- 0953-816X. ; 3:9, s. 905-918
-
Journal article (peer-reviewed)abstract
- Release properties of intrahippocampal transplants of noradrenergic neurons were monitored by microdialysis in awake and halothane-anaesthetized rats. Fetal locus coeruleus neurons were implanted as a cell suspension into hippocampi deprived of their innate noradrenalin (NA) innervation by intraventricular 6-hydroxydopamine treatment. Dialysis probes of the loop type were implanted into the dorsal hippocampus 1 - 2 days before each experiment, i.e. 7 - 11 months after grafting. Age-matched intact and lesion-only animals served as controls. Microscopic analysis showed a graft-derived tyrosine hydroxylase immunoreactive, presumably noradrenergic, fibre network throughout the dorsal hippocampal formation, surrounding the probe site. The innervation density varied from sub- to supranormal. The grafts restored baseline NA release in the graft-reinnervated hippocampus to near-normal levels both in awake and halothane-anaesthetized animals. Potassium chloride (100 mM) in the perfusion fluid induced a dramatic increase in NA release that was similar in magnitude in the grafted and intact hippocampi. A NA uptake blocker (desipramine) added to the perfusion fluid at 5 microM induced a similar increase in NA output in the grafted and intact hippocampi, and the output was substantially reduced by tetrodotoxin, added at 1 microM in the presence of uptake blockade. Electrical stimulation of the lateral habenular nucleus (15 Hz, 0.5 mA) in halothane-anaesthetized rats induced a significant increase in NA output both in the intact and grafted hippocampi. This effect was abolished by transection of the fasciculus retroflexus, which carries the efferent projections of the habenular complex. Behavioural activation through handling induced a consistent increase in NA release only in the intact animals, but in a few grafted rats (which also responded to habenular stimulation) the NA output was clearly elevated by handling. Forced immobilization induced a significant increase in NA output both in the intact and grafted hippocampi, but in the grafted ones the response was somewhat smaller and more transient. In the same set of animals, swimming in warm water (25 - 30 degrees C) induced a sharp increase in NA output in the intact animals, whereas only one of the grafted rats responded by increased NA output. The results indicate that the locus coeruleus grafts, despite their ectopic location, can become functionally integrated with the host brain, and that the activity of the transplanted noradrenergic neurons can, under some circumstances, be modulated from the host brain in response to environmental challenges.
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| 57. |
- Kimme, Peter, et al.
(author)
-
Cerebral blood flow of the exposed brain surface measured by laser Doppler perfusion imaging
- 1997
-
In: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 159:1, s. 15-22
-
Journal article (peer-reviewed)abstract
- A novel application of laser Doppler flowmetry (LDF), laser Doppler perfusion imaging (LDPI), was used to study cerebral cortical blood flow (CBFcortex). In contrast to the conventional laser Doppler perfusion monitor, LDPI creates two-dimensional maps of the tissue perfusion in a well defined area of up to 120×120 mm comprising 4096 measurement points. Measurements of CBFcortex were made through an optically transparent polyester film applied to a cranial window preparation in ventilated anaesthetized pigs. Temporal and spatial heterogeneity in CBFcortex were visualized by LDPI during provocations which are known to alter CBF (varying arterial PCO2 or MABP, or infusion of adenosine at constant MABP (concomitant angiotensin administration) or by hyperoxemia). During hypercapnia the recorded CBFcortex increased homogeneously. The adenosine-mediated increase in recorded CBFcortex was concentrated on the lower flow interval, as was the hyperoxemia-caused decline. At decreasing MABP the autoregulatory threshold was found to vary locally within the cortex. The results suggest that LDPI, apart from detecting localized changes in CBFcortex, also visualizes flow changes within different vascular segments. Together with the practical advantages of the system, i.e. not necessitating direct contact with the tissues, this feature makes the technique suitable for studies of CBFcortex distributions.
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| 58. |
- Kyhse-Andersen, Jan, et al.
(author)
-
Serum cystatin C, determined by a rapid, automated particle-enhanced turbidimetric method, is a better marker than serum creatinine for glomerular filtration rate
- 1994
-
In: Clinical Chemistry. - 0009-9147. ; 40:10, s. 1921-1926
-
Journal article (peer-reviewed)abstract
- We describe a fully automated particle-enhanced turbidimetric assay for cystatin C in undiluted serum and EDTA-plasma. The throughput is 90 samples per hour and urgent samples can be analyzed in 7 min. The assay range (0.4-14.1 mg/L) covers the concentration range in health and disease. The within- and between-run imprecision is 0.9% and 2.2%, respectively. Analytical recovery of additions of recombinant cystatin C averaged 98%. Rheumatoid factors (< or = 323,000 IU/L), bilirubin (< or = 150 mumol/L), hemoglobin (< or = 1.2 g/L), and triglycerides (< or = 8.5 mmol/L) do not interfere in the assay. In view of the superior (by ROC analysis) diagnostic accuracy of serum concentrations of cystatin C for reduced glomerular filtration rate (GFR) in comparison with creatinine, cystatin C seems an attractive alternative to creatinine for estimation of GFR.
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| 59. |
- Larsson, Peter, 1966, et al.
(author)
-
Manufacturing of nanometer structures in YBa2Cu3O7 thin films using a carbon based multilayer mask
- 1995
-
In: Applied Superconductivity 1995. Proceedings of EUCAS 1995, the Second European Conference on Applied Superconductivity. - 0750303484 ; 2, s. 935-938
-
Conference paper (peer-reviewed)abstract
- A process method that will produce ion milled bridges and trenches of ultra small dimensions in YBa2Cu3O7(YBCO) thin films is presented. The method is based on electron beam lithography, reactive ion etching (RIE), ion milling and a multilayer mask, which consists of an electron resist and an amorphous carbon layer with intermediate niobium. Carbon has two unique properties that are used in the process. First, carbon can easily be reactive ion etched in an oxygen atmosphere, since the oxides of carbon are gases. Furthermore, carbon has an extremely low ion milling etching rate. The electron resist pattern is transferred to the niobium and the carbon layers by a reactive ion etching process with CF4 and O2 In such a way a durable carbon mask for ion milling is formed. When the ion milling is completed, the result of the process is 50-60 nm wide bridges and 30-60 nm wide trenches in 100 nm thick YBCO films.
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| 60. |
- Lemne, Carola, et al.
(author)
-
Dyslipoproteinemic changes in borderline hypertension
- 1994
-
In: Hypertension. - 1524-4563. ; 24:5, s. 605-610
-
Journal article (peer-reviewed)abstract
- The present study examined plasma lipoprotein, lipoprotein lipase, hepatic lipase, and insulin levels in men with borderline hypertension (diastolic blood pressure 85 to 94 mm Hg) compared with age-matched normotensive control subjects (diastolic blood pressure less than or equal to 80 mm Hg, n = 75 + 75). High-density lipoprotein (HDL) subclasses were determined in a subset (n = 45 + 45). While total and low-density lipoprotein cholesterol levels were similar, levels of very-low-density lipoprotein (VLDL) cholesterol and triglycerides (0.46 versus 0.41 mmol/L, P = .027, and 1.0 versus 0.85 mmol/L, P = .031) and total triglycerides (1.53 versus 1.33 mmol/L, P = .009) were elevated and HDL cholesterol was reduced in the borderline group compared with the normotensive group (1.17 versus 1.26 mmol/L, P = .043). The HDL subclass HDL2b concentration was lower (0.16 versus 0.24 mmol/L, P = .006), while HDL3b and HDL3c concentrations were higher in the borderline group (0.38 versus 0.32 mmol/L, P = .016, and 0.19 versus 0.16 mmol/L, P = .042). Significantly higher activities of hepatic lipase in the borderline group (282 versus 232 mU/mL, P = .024) and significant correlations between lipoprotein lipase activity and VLDL and HDL concentrations suggest an involvement of these enzymes in the development of these differences. When adjusted for body mass index or insulin level, all differences disappeared, except for HDL3b and HDL3c concentrations, which remained significantly elevated. These results indicate that dyslipoproteinemic changes are present in early hypertension. Although most of these changes are related to obesity, alterations in HDL profile were not explained by influences of body mass index and insulin.
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