| 21. |
- Chen, Xiaowen, et al.
(författare)
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A Variable-Size FFT Hardware Accelerator Based on Matrix Transposition
- 2018
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Ingår i: IEEE Transactions on Very Large Scale Integration (vlsi) Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 1063-8210 .- 1557-9999. ; 26:10, s. 1953-1966
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Tidskriftsartikel (refereegranskat)abstract
- Fast Fourier transform (FFT) is the kernel and the most time-consuming algorithm in the domain of digital signal processing, and the FFT sizes of different applications are very different. Therefore, this paper proposes a variable-size FFT hardware accelerator, which fully supports the IEEE-754 single-precision floating-point standard and the FFT calculation with a wide size range from 2 to 220 points. First, a parallel Cooley-Tukey FFT algorithm based on matrix transposition (MT) is proposed, which can efficiently divide a large size FFT into several small size FFTs that can be executed in parallel. Second, guided by this algorithm, the FFT hardware accelerator is designed, and several FFT performance optimization techniques such as hybrid twiddle factor generation, multibank data memory, block MT, and token-based task scheduling are proposed. Third, its VLSI implementation is detailed, showing that it can work at 1 GHz with the area of 2.4 mm(2) and the power consumption of 91.3 mW at 25 degrees C, 0.9 V. Finally, several experiments are carried out to evaluate the proposal's performance in terms of FFT execution time, resource utilization, and power consumption. Comparative experiments show that our FFT hardware accelerator achieves at most 18.89x speedups in comparison to two software-only solutions and two hardware-dedicated solutions.
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| 22. |
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| 23. |
- Chen, Xiaohong, et al.
(författare)
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Hydrological Design of Nonstationary Flood Extremes and Durations in Wujiang River, South China : Changing Properties, Causes, and Impacts
- 2013
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Ingår i: Mathematical problems in engineering (Print). - : Hindawi Limited. - 1024-123X .- 1563-5147. ; , s. 527461-
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Tidskriftsartikel (refereegranskat)abstract
- The flood-duration-frequency (QDF) analysis is performed using annual maximum streamflow series of 1-10 day durations observed at Pingshi and Lishi stations in southern China. The trends and change point of annual maximum flood flow and flood duration are also investigated by statistical tests. The results indicate that (1) the annual maximum flood flow only has a marginally increasing trend, whereas the flood duration exhibits a significant decreasing trend at the 0.10 significant level. The change point for the annual maximum flood flow series was found in 1991 and after which the mean maximum flood flow increased by 45.26%. (2) The period after 1991 is characterized by frequent and shorter duration floods due to increased rainstorm. However, land use change in the basin was found intensifying the increased tendency of annual maximum flow after 1991. And (3) under nonstationary environmental conditions, alternative definitions of return period should be adapted. The impacts on curve fitting of flood series showed an overall change of upper tail from "gentle" to "steep," and the design flood magnitude became larger. Therefore, a nonstationary frequency analysis taking account of change point in the data series is highly recommended for future studies.
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| 24. |
- Chen, Xiaomei, et al.
(författare)
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Influence of peptide transporter 2 (PEPT2) on the distribution of cefadroxil in mouse brain : A microdialysis study
- 2017
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Ingår i: Biochemical Pharmacology. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0006-2952 .- 1356-1839. ; 131, s. 89-97
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Tidskriftsartikel (refereegranskat)abstract
- Peptide transporter 2 (PEPT2) is a high-affinity low-capacity transporter belonging to the proton-coupled oligopeptide transporter family. Although many aspects of PEPT2 structure-function are known, including its localization in choroid plexus and neurons, its regional activity in brain, especially extracellular fluid (ECF), is uncertain. In this study, the pharmacokinetics and regional brain distribution of cefadroxil, a beta-lactam antibiotic and PEN 2 substrate, were investigated in wildtype and Pept2 null mice using in vivo intracerebral microdialysis. Cefadroxil was infused intravenously over 4 h at 0.15 mg/min/kg, and samples obtained from plasma, brain ECF, cerebrospinal fluid (CSF) and brain tissue. A permeability surface area experiment was also performed in which 0.15 mg/min/kg cefadroxil was infused intravenously for 10 min, and samples obtained from plasma and brain tissues. Our results showed that PEPT2 ablation significantly increased the brain ECF and CSF levels of cefadroxil (2- to 2.5-fold). In contrast, there were no significant differences between wildtype and Pept2 null mice in the amount of cefadroxil in brain cells. The unbound volume of distribution of cefadroxil in brain was 60% lower in Pept2 null mice indicating an uptake function for PEPT2 in brain cells. Finally, PEPT2 did not affect the influx clearance of cefadroxil, thereby, ruling out differences between the two genotypes in drug entry across the blood-brain barriers. These findings demonstrate, for the first time, the impact of PEPT2 on brain ECF as well as the known role of PEPT2 in removing peptide-like drugs, such as cefadroxil, from the CSF to blood.
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| 25. |
- Chen, Xiao-Jia, et al.
(författare)
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Effect of ion adsorption on CEC separation of small molecules using hypercrosslinked porous polymer monolithic capillary columns
- 2012
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Ingår i: Journal of Separation Science. - : Wiley-VCH Verlagsgesellschaft. - 1615-9306 .- 1615-9314. ; 35:12, s. 1502-1505
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Tidskriftsartikel (refereegranskat)abstract
- Both poly(styrene-co-vinylbenzyl chloride-co-divinylbenzene) and poly(4-methylstyrene-co-vinylbenzyl chloride-co-divinylbenzene) monolithic columns have been hypercrosslinked and for the first time used to achieve capillary electrochromatographic separations. Although these columns do not contain ionizable functionalities, electroosmotic flow was observed due to adsorption of ions from a buffer solution contained in the mobile phase on the surface of the hydrophobic polymer. An increase of more than one order of magnitude was observed with the use of both monolithic polymers. The hypercrosslinking reaction creates a large surface area thus enabling adsorption of a much larger number of ions. Alkylbenzenes were successfully separated using the hypercrosslinked monolithic columns.
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| 26. |
- Chen, X. M., et al.
(författare)
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Verification of the Rician K-factor-based uncertainty model for measurements in reverberation chambers
- 2015
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Ingår i: IET Science, Measurement and Technology. - : Institution of Engineering and Technology (IET). - 1751-8822 .- 1751-8830. ; 9:5, s. 534-539
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Tidskriftsartikel (refereegranskat)abstract
- Measurements in reverberation chamber (RC) produce data that are random, and therefore they need to be processed from the statistical point-of-view for obtaining the desired characteristics and the accuracy. The complex channel transfer function in the RC follows complex Gaussian distribution provided that the RC is well stirred. The authors have recently presented a new uncertainty model based on the presence of an unstirred component of the transfer function, which was modelled by introducing an average Rician K-factor. The model was validated in two RCs with translating mode-stirring plates, being able to correctly describe the improvement in accuracy by rotating the antenna under test, and by blocking the line-of-sight between this and the fixed RC antenna(s). In the present study, they apply this uncertainty model to four RCs with different settings (e.g. RC volumes, number of plates or fixed RC antennas, translating and rotating mode-stirrers etc.). For each RC, they examine the measurement uncertainty under different loading conditions. To repeat (during the different measurements) the actual mode-stirrer positions at which the transfer function is sampled, they conduct all the measurements with stepwise (instead of continuous) mode-stirring. The model is shown to work well for all the cases.
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| 27. |
- Chen, Xin, et al.
(författare)
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Maintenance and Reformulation of Filial Piety and Filial Practice in Sweden : Perspectives of Digitally Empowered Midlife and Older Chinese Immigrants
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Filial piety is a core cultural norm in East Asian countries that shapes eldercare obligations and responsibilities. Research on migration and science technology studies (STS) demonstrates the potential of digital technologies to influence the acculturation experiences of immigrants, but the primary focus has been on younger generations. This paper explores how the combination of digital technologies and acculturation influences expectations of filial piety and filial practices of midlife and older Chinese immigrants in Sweden. In-depth interviews of eight midlife and older Chinese immigrants provided qualitative data for thematic analysis, revealing that the in-formants expected to be more independent in later life but to maintain a close and reciprocally supportive relationship with their adult children. They considered their acculturation experiences to be both satisfying and challenging. The uptake of digital technology ensured frequent contact with Chinese communities and enhanced their experience of life in Sweden. The findings suggest a potential need for intervention through formal care supports for older Chinese immigrants, despite the stereotype of interdependence and family-based care. This study also provides insight into the need for social inclusion in Sweden by incorporating cultural preferences into digital communication and the design of care provision.
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| 28. |
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| 29. |
- Deacon, CF, et al.
(författare)
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Inhibitors of dipeptidyl peptidase IV: a novel approach for the prevention and treatment of Type 2 diabetes?
- 2004
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Ingår i: Expert Opinion on Investigational Drugs. - : Informa Healthcare. - 1744-7658 .- 1354-3784. ; 13:9, s. 1091-1102
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Forskningsöversikt (refereegranskat)abstract
- Inhibitors of the enzyme dipeptidyl peptidase IV (DPP IV) are of increasing interest to both diabetologists and the pharmaceutical industry alike, as they may become established as the next member of the oral antidiabetic class of therapeutic agents, designed to lower blood glucose and, possibly, prevent the progressive impairment of glucose metabolism in patients with impaired glucose tolerance and Type 2 diabetes. DPP IV has become a focus of attention for drug design, as it has a pivotal role in the rapid degradation of at least two of the hormones released during food ingestion, a property that has warranted the design of inhibitor-based drugs. At the molecular level, DPP IV cleaves two amino acids from the N-terminus of the intact, biologically active forms of both so-called incretin hormones, glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide (formerly known as gastric inhibitory polypeptide), resulting in truncated metabolites, which are largely inactive. Inhibition of the enzyme, therefore, is thought to increase levels of the active forms of both incretin hormones, culminating in an increase in insulin release after a meal, in a fully glucosedependant manner. DPP IV inhibitors combine several features of interest to the drug design process. They can be readily optimised for their target and be designed as low molecular weight, orally active entities compatible with once-daily administration.
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| 30. |
- Deadman, Mary E., et al.
(författare)
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Specific amino acids of the glycosyltransferase LpsA direct the addition of glucose or galactose to the terminal inner core heptose of Haemophilus influenzae lipopolysaccharide via alternative linkages
- 2006
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 281:40, s. 29455-29467
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Tidskriftsartikel (refereegranskat)abstract
- Lipopolysaccharide is the major glycolipid of the cell wall of the bacterium Haemophilus influenzae, a Gram-negative commensal and pathogen of humans. Lipopolysaccharide is both a virulence determinant and a target for host immune responses. Glycosyltransferases have high donor and acceptor substrate specificities that are generally limited to catalysis of one unique glycosidic linkage. The H. influenzae glycosyltransferase LpsA is responsible for the addition of a hexose to the distal heptose of the inner core of the lipopolysaccharide molecule and belongs to the glycosyltransferase family 25. The hexose added can be either glucose or galactose and linkage to the heptose can be either beta 1-2 or beta 1-3. Each H. influenzae strain uniquely produces only one of the four possible combinations of linked sugar in its lipopolysaccharide. We show that, in any given strain, a specific allelic variant of LpsA directs the anomeric linkage and the added hexose, glucose, or galactose. Site-directed mutagenesis of a single key amino acid at position 151 changed the hexose added in vivo from glucose to galactose or vice versa. By constructing chimeric lpsA gene sequences, it was shown that the 3' end of the gene directs the anomeric linkage (beta 1-2 or beta 1-3) of the added hexose. The lpsA gene is the first known example where interstrain variation in lipopolysaccharide core structure is directed by the specific sequence of a genetic locus encoding enzymes directing one of four alternative possible sugar additions from the inner core.
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