| 1. |
|
|
| 2. |
- Kashif, Ahsan-Ullah, et al.
(författare)
-
Influence of interface state charges on RF performance of LDMOS transistor
- 2008
-
Ingår i: Solid-State Electronics. - : Elsevier. - 0038-1101 .- 1879-2405. ; 52:7, s. 1099-1105
-
Tidskriftsartikel (refereegranskat)abstract
- Si-LDMOS transistor is studied by TCAD simulation for improved RF performance. In LDMOS structure, a low-doped reduced surface field (RESURF) region is used to obtain high breakdown voltage, but it reduces the transistor RF performance due to high on-resistance. The interface charges between oxide and the RESURF region are studied and found to have a strong impact on the transistor performance both in DC and RF. The presence of excess interface state charges at the RESURF region results not only higher DC drain current but also improved RF performance in terms of power, gain and efficiency. The most important achievement is the enhancement of operating frequency and RF output power is obtained well above 1 W/mm up to 4 GHz.
|
|
| 3. |
- Willerslev, E, et al.
(författare)
-
Fifty thousand years of arctic vegetation change and megafauna diet
- 2014
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 506:7486, s. 47-47
-
Tidskriftsartikel (refereegranskat)abstract
- Although it is generally agreed that the Arctic flora is among the youngest and least diverse on Earth, the processes that shaped it are poorly understood. Here we present 50 thousand years (kyr) of Arctic vegetation history, derived from the first large-scale ancient DNA metabarcoding study of circumpolar plant diversity. For this interval we also explore nematode diversity as a proxy for modelling vegetation cover and soil quality, and diets of herbivorous megafaunal mammals, many of which became extinct around 10 kyr bp (before present). For much of the period investigated, Arctic vegetation consisted of dry steppe-tundra dominated by forbs (non-graminoid herbaceous vascular plants). During the Last Glacial Maximum (25–15 kyr bp), diversity declined markedly, although forbs remained dominant. Much changed after 10 kyr bp, with the appearance of moist tundra dominated by woody plants and graminoids. Our analyses indicate that both graminoids and forbs would have featured in megafaunal diets. As such, our findings question the predominance of a Late Quaternary graminoid-dominated Arctic mammoth steppe.
|
|
| 4. |
- Chen, F., et al.
(författare)
-
Reply to "comment on 'Ultrafast terahertz-field-driven ionic response in ferroelectric BaTiO3 ' "
- 2018
-
Ingår i: Physical Review B. - 2469-9950. ; 97:22
-
Tidskriftsartikel (refereegranskat)abstract
- In this reply to S. Durbin's comment on our original paper "Ultrafast terahertz-field-driven ionic response in ferroelectric BaTiO3," we concur that his final equations 8 and 9 more accurately describe the change in diffracted intensity as a function of Ti displacement. We also provide an alternative derivation based on an ensemble average over unit cells. The conclusions of the paper are unaffected by this correction.
|
|
| 5. |
- Chen, F., et al.
(författare)
-
Ultrafast terahertz-field-driven ionic response in ferroelectric BaTiO3
- 2016
-
Ingår i: Physical Review B. - 1098-0121. ; 94:18
-
Tidskriftsartikel (refereegranskat)abstract
- The dynamical processes associated with electric field manipulation of the polarization in a ferroelectric remain largely unknown but fundamentally determine the speed and functionality of ferroelectric materials and devices. Here we apply subpicosecond duration, single-cycle terahertz pulses as an ultrafast electric field bias to prototypical BaTiO3 ferroelectric thin films with the atomic-scale response probed by femtosecond x-ray-scattering techniques. We show that electric fields applied perpendicular to the ferroelectric polarization drive large-amplitude displacements of the titanium atoms along the ferroelectric polarization axis, comparable to that of the built-in displacements associated with the intrinsic polarization and incoherent across unit cells. This effect is associated with a dynamic rotation of the ferroelectric polarization switching on and then off on picosecond time scales. These transient polarization modulations are followed by long-lived vibrational heating effects driven by resonant excitation of the ferroelectric soft mode, as reflected in changes in the c-axis tetragonality. The ultrafast structural characterization described here enables a direct comparison with first-principles-based molecular-dynamics simulations, with good agreement obtained.
|
|
| 6. |
|
|
| 7. |
- Gilbert, M. Thomas P., et al.
(författare)
-
Intraspecific phylogenetic analysis of Siberian woolly mammoths using complete mitochondrial genomes
- 2008
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 105:24, s. 8327-8332
-
Tidskriftsartikel (refereegranskat)abstract
- We report five new complete mitochondrial DNA (mtDNA) genomes of Siberian woolly mammoth (Mammuthus primigenius), sequenced with up to 73-fold coverage from DNA extracted from hair shaft material. Three of the sequences present the first complete mtDNA genomes of mammoth clade II. Analysis of these and 13 recently published mtDNA genomes demonstrates the existence of two apparently sympatric mtDNA clades that exhibit high interclade divergence. The analytical power afforded by the analysis of the complete mtDNA genomes reveals a surprisingly ancient coalescence age of the two clades, approximate to 1-2 million years, depending on the calibration technique. Furthermore, statistical analysis of the temporal distribution of the C-14 ages of these and previously identified members of the two mammoth clades suggests that clade II went extinct before clade I. Modeling of protein structures failed to indicate any important functional difference between genomes belonging to the two clades, suggesting that the loss of clade II more likely is due to genetic drift than a selective sweep.
|
|
| 8. |
- Gilbert, M. Thomas P., et al.
(författare)
-
Whole-genome shotgun sequencing of mitochondria from ancient hair shafts
- 2007
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 317:5846, s. 1927-1930
-
Tidskriftsartikel (refereegranskat)abstract
- Although the application of sequencing-by-synthesis techniques to DNA extracted from bones has revolutionized the study of ancient DNA, it has been plagued by large fractions of contaminating environmental DNA. The genetic analyses of hair shafts could be a solution: We present 10 previously unexamined Siberian mammoth (Mammuthus primigenius) mitochondrial genomes, sequenced with up to 48-fold coverage. The observed levels of damage-derived sequencing errors were lower than those observed in previously published frozen bone samples, even though one of the specimens was >50,000 14C years old and another had been stored for 200 years at room temperature. The method therefore sets the stage for molecular-genetic analysis of museum collections.
|
|
| 9. |
|
|
| 10. |
- Kubler, Andre, et al.
(författare)
-
Cathepsin K Contributes to Cavitation and Collagen Turnover in Pulmonary Tuberculosis
- 2016
-
Ingår i: Journal of Infectious Diseases. - : Oxford University Press. - 0022-1899 .- 1537-6613. ; 213:4, s. 618-627
-
Tidskriftsartikel (refereegranskat)abstract
- Cavitation in tuberculosis enables highly efficient person-to-person aerosol transmission. We performed transcriptomics in the rabbit cavitary tuberculosis model. Among 17 318 transcripts, we identified 22 upregulated proteases. Five type I collagenases were overrepresented: cathepsin K (CTSK), mast cell chymase-1 (CMA1), matrix metalloproteinase 1 (MMP-1), MMP-13, and MMP-14. Studies of collagen turnover markers, specifically, collagen type I C-terminal propeptide (CICP), urinary deoxypyridinoline (DPD), and urinary helical peptide, revealed that cavitation in tuberculosis leads to both type I collagen destruction and synthesis and that proteases other than MMP-1, MMP-13, and MMP-14 are involved, suggesting a key role for CTSK. We confirmed the importance of CTSK upregulation in human lung specimens, using immunohistochemical analysis, which revealed perigranulomatous staining for CTSK, and we showed that CTSK levels were increased in the serum of patients with tuberculosis, compared with those in controls (3.3 vs 0.3 ng/mL; P = .005).
|
|
