| 51. |
- Biemont, E, et al.
(författare)
-
Radiative lifetime measurements and transition probabilities of astrophysical interest in ErIII
- 2001
-
Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 321:3, s. 481-486
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Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes of seven excited states of Er iii have been measured using time-resolved laser-induced fluorescence following two-photon excitation. Relativistic Hartree-Fock calculations taking core-polarization effects into account are found to be in excellent agreement with the experimental results. A large set of new calculated transition probabilities is presented for many transitions of astrophysical interest. These results will be useful for investigating the composition of chemically peculiar stars.
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| 52. |
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| 53. |
- Chen, C. C., et al.
(författare)
-
Different strain relaxation mechanisms in strained Si/Si1-xGex/Si heterostructures by high dose B+ and BF2+ doping
- 2002
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 198:02-jan, s. 57-63
-
Tidskriftsartikel (refereegranskat)abstract
- Strained Si/Si0.8Ge0.2/Si heterostructures are implanted at room temperature with 7.5 keV B+ and 33 keV BF2+ ions to a high dose of 2 x 10(15) ions/cm(2), respectively. The samples are subsequently subjected to three-step anneals (spacer anneal, oxidation anneal and rapid thermal anneal), which are used to simulate a real fabrication process of SiGe-based MOSFET devices. The damage induced by implantation and its recovery are characterized by 2 MeV He-4(+) RBS/ channeling spectrometry. A damage layer on the surface is induced by B+ implantation, but BF2+ ion implantation amorphizes the surface of Si/Si0.8Ge0.2/Si heterostructure. Channeling angular scans along the (110) axial direction demonstrate that the strain stored in the SiGe layer could be nearly completely retained for the B+ implantated and subsequently annealed sample. However, the strain in the BF2+ implanted/annealed SiGe layer has decreased drastically.
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| 54. |
- d'Heurle, F. M., et al.
(författare)
-
Formation of C54TiSi(2) : Effects of niobium additions on the apparent activation energy
- 2001
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 90:12, s. 6409-6415
-
Tidskriftsartikel (refereegranskat)abstract
- The formation of C54 TiSi2 using Ti-Nb alloys deposited on polycrystalline Si substrates was studied by means of in situ x-ray diffraction and resistance measurements during temperature ramping. Alloys with Nb contents ranging from 0 to 13.6 at. % were used. The formation temperature of C54 TiSi2 was reduced in the presence of Nb. However, the addition of Nb in Ti did not cause fundamental changes in the evolution of resistance versus temperature. This latter observation suggests that the mechanism for the formation of C54 TiSi2 remained the same in spite of the enhancement effect. For alloys with up to 8 at. % of Nb, the C49 TiSi2 phase formed first, as with pure Ti. When annealing the alloy with 13.6 at. % Nb, neither C49 TiSi2 nor C54 were found in the usual temperature ranges, instead, C40 (Nb,Ti)Si-2 was observed. This phase transformed to C54 (Nb,Ti)Si-2 above 950 degreesC. The apparent activation energy associated with the formation of C54 TiSi2 was obtained by annealing the samples at four different ramp rates from 3 to 27 K/s; it decreased continuously from 3.8 to 2.5 eV with increasing Nb content from 0 to 8 at. %. The apparent activation energy for the formation of C40 (Nb,Ti)Si-2 was found to be 2.6 eV. The possible physical meaning, or lack thereof, of the high activation energies derived from experimental measurements is extensively discussed. A qualitative model is proposed whereby nucleation would be rate controlling in pure TiSi2, and interface motion in samples with 8 at. % Nb.
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| 55. |
- Du, J, et al.
(författare)
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Estimation of Performance Loss Due to Delay in Channel Feedback in MIMO Systems
- 2004
-
Ingår i: 2004 IEEE 60th Vehicular Technology Conference, 2004. VTC2004-Fall.. - 0780385217 ; 3, s. 1619-1622
-
Konferensbidrag (refereegranskat)abstract
- Latency of available channel state information (CSI) at the transmitter in time-varying channels greatly affects the performance of multiple-input multiple-output (MIMO) systems. We have derived a simple algorithm to calculate an approximation of the expected performance loss based on the most recent channel feedback. The proposed algorithm can be used to determine the maximum tolerable channel feedback delay for each particular channel realization.
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| 56. |
- Du, Jianxuan, et al.
(författare)
-
Space-Time LDPC with Layered Structure for MIMO Systems
- 2004
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we incorporate the layered structure with low-density parity-check codes (LDPC) to develop a quasi-block diagonal LDPC space-time structure. The lower triangular structure of the parity check matrix introduces correlation between layers. In addition, each layer, as a part of the whole codeword, can be decoded while taking information from other undetected layers to improve the decoding performance. Belief propagation of the current layer is stopped as soon as those parity checks involving only the current layer and detected layers are satisfied. Simulation shows that the proposed system outperforms the conventional V-BLAST by 0.5 dB at WER=1%. Wireless Personal Multimedia Communications (WPMC)
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| 57. |
- Hellberg, Per-Erik, et al.
(författare)
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Threshold voltage control for PMOSFETs using an undoped epitaxial Si channel and a p(+)-SixGe1-x gate
- 2000
-
Ingår i: Solid-State Electronics. - 0038-1101 .- 1879-2405. ; 44:11, s. 2085-2088
-
Tidskriftsartikel (refereegranskat)abstract
- This paper examines experimentally the performance of PMOSFETs with an undoped epitaxial Si channel in combination with a p(+)-SixGe1-x gate electrode. The channel doping profiles were made using shallow As-implantation followed by selective epitaxy of undoped Si to different thicknesses of 40, 80 and 120 nm. The p(+)-SixGe1-x gate with different values of x was used to tailor the threshold voltage. The transconductance and saturation current were found to increase and the threshold voltage to decrease with increasing thickness of the undoped Si channel for the same gate material. Increasing Ge content in the p(+)-SixGe1-x gate resulted in an increased threshold voltage. Compared to the p(+)-Si gate, the threshold voltage was increased by 0.15 and 0.35 V with a p(+)-Si0.79Ge0.21 and p(+)-Si0.53Ge0.47 gate, respectively, independently of the Si channel thickness. Therefore, the use of a p(+)-SixGe1-x gate introduces an extra degree of freedom when designing the channel for high performance PMOSFETs.
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| 58. |
- Henriksson, Gunnar, et al.
(författare)
-
Is cellobiose dehydrogenase from Phanerochaete chrysosporium a lignin degrading enzyme?
- 2000
-
Ingår i: Biochimica et Biophysica Acta - Protein Structure and Molecular Enzymology. - 0167-4838 .- 1879-2588. ; 1480:02-jan, s. 83-91
-
Tidskriftsartikel (refereegranskat)abstract
- Cellobiose dehydrogenase (CDH) is an extracellular redox enzyme of ping-pong type, i.e. it has separate oxidative and reductive half reactions. Several wood degrading fungi produce CDH, but the biological function of the enzyme is not known with certainty. It can, however, indirectly generate hydroxyl radicals by reducing Fe3+ to Fe2+ and O-2 to H2O2. Hydroxyl radicals are then generated by a Fenton type reaction and they can react with various wood compounds, including lignin. In this work we study the effect of CDH on a non-phenolic lignin model compound (3,4-dimethoxyphenyl glycol). The results indicate that CDH can affect lignins in three important ways. (1) It breaks beta-ethers; (2) it demethoxylates aromatic structures in lignins; (3) it introduces hydroxyl groups in non-phenolic lignins. The gamma-irradiated model compound gave a similar pattern of products as the CDH treated model compound? when the samples were analyzed by HPLC, suggesting that hydroxyl radicals are the active component of the CDH system.
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| 59. |
- Henriksson, G, et al.
(författare)
-
Is cellobiose dehydrogenase from Phanerochaete chrysosporium a lignin degrading enzyme?
- 2000
-
Ingår i: BIOCHIMICA ET BIOPHYSICA ACTA-PROTEIN STRUCTURE AND MOLECULAR ENZYMOLOGY. - 0167-4838. ; 1480:1-2, s. 83-91
-
Tidskriftsartikel (refereegranskat)abstract
- Cellobiose dehydrogenase (CDH) is an extracellular redox enzyme of ping-pong type, i.e. it has separate oxidative and reductive half reactions. Several wood degrading fungi produce CDH, but the biological function of the enzyme is not known with certainty
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| 60. |
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