| 1. |
- Sodergren, Erica, et al.
(författare)
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The genome of the sea urchin Strongylocentrotus purpuratus.
- 2006
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 314:5801, s. 941-52
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Tidskriftsartikel (refereegranskat)abstract
- We report the sequence and analysis of the 814-megabase genome of the sea urchin Strongylocentrotus purpuratus, a model for developmental and systems biology. The sequencing strategy combined whole-genome shotgun and bacterial artificial chromosome (BAC) sequences. This use of BAC clones, aided by a pooling strategy, overcame difficulties associated with high heterozygosity of the genome. The genome encodes about 23,300 genes, including many previously thought to be vertebrate innovations or known only outside the deuterostomes. This echinoderm genome provides an evolutionary outgroup for the chordates and yields insights into the evolution of deuterostomes.
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| 2. |
- Bassoo, Vandana, et al.
(författare)
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A potential transmitter architecture for future generation green wireless base station
- 2009
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Ingår i: Eurasip Journal on Wireless Communications and Networking. - : Springer Science and Business Media LLC. - 1687-1472 .- 1687-1499. ; :doi:10.1155/2009/821846
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Tidskriftsartikel (refereegranskat)abstract
- Current radio frequency power amplifiers in 3G base stations have very high power consumption leading to a hefty cost and negative environmental impact. In this paper, we propose a potential architecture design for future wireless base station. Issues associated with components of the architecture are investigated. The all-digital transmitter architecture uses a combination of envelope elimination and restoration (EER) and pulse width modulation(PWM)/ pulse position modulation (PPM). The performance of this architecture is predicted from the measured output power and efficiency curves of a GaN amplifier. 57% efficiency is obtained for an OFDM signal limited to 8dB peak to average power ratio. The PWM/PPM drive signal is generated using the improved Cartesian sigma delta techniques. It is shown that an RF oversampling by a factor of four meets the WLAN spectral mask and WCDMA specification is met by an RF oversampling of sixteen.
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| 3. |
- Bassoo, Vandana, et al.
(författare)
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Potential Architecture for Future Generation "Green" Wireless Base Station
- 2009
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Ingår i: 4th International Symposium on Wireless and Pervasive Computing (ISWPC) 2009. - : IEEE. - 9781424429653 - 9781424429660
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Konferensbidrag (refereegranskat)abstract
- Current radio frequency power amplifiers (PAs) in 3G base stations have very high power consumption leading to a hefty cost and negative environmental impact. In this paper, we propose a potential architecture design for future wireless base station. Issues associated with components of the architecture are investigated. A comparison of PA with pulse width modulation drive and PA with envelope elimination and restoration (EER) drive is offered. EER-driven PA promises high efficiency over a wide dynamic range but has bandwidth expansion problems. A novel approach which reduces bandwidth expansion on the envelope by 54% is proposed. A modulator is used to convert amplitude and phase information into the edges of a pulse train. The modulator also eradicates some analog components present in traditional base station design.
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| 4. |
- Cijvat, Pieternella, et al.
(författare)
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A comparison of polar transmitter architectures using a GaN HEMT power amplifier
- 2008
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Konferensbidrag (refereegranskat)abstract
- In this paper three transmitter architectures are compared, that each use the low-frequency envelope and high-frequency phase component of an RF signal. A power amplifier (PA) with Pulse Width Modulation by Variable Gate Bias (PWMVGB) is compared to an Envelope Elimination and Restoration (EER) and Envelope Tracking (ET) configuration. The test circuit is implemented using a discrete GaN HEMT power amplifier and discrete surface-mount passive components assembled on a PCB. Measurements show that the EER architecture maintains a drain efficiency of 56 to 69% for a wide output power range, while the PA with variable gate bias shows a significant drop in efficiency for lower output powers (from 59 to 6%). Other comparison issues are modulation of the supply voltage and transmitter complexity.
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| 5. |
- Cijvat, Pieternella, et al.
(författare)
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A GaN HEMT power amplifier with variable gate bias for envelope and phase signals
- 2007
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Ingår i: [Host publication title missing]. - Aalborg, Denmark : Institute of Electrical and Electronics Engineers (IEEE). - 9781424415168 ; , s. 108-111
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Konferensbidrag (refereegranskat)abstract
- This paper describes the design, simulation and measurement of a GaN power amplifier suitable for envelope and phase signal combination. The low-frequency envelope signal is used to vary the gate (bias) voltage of the device, resulting in a pulse width modulated drain voltage, while modulation of supply voltage or current is avoided. The test circuit is implemented using a discrete GaN HEMT power amplifier and discrete surface-mount passive components assembled on a PCB. Measurements showed a maximum drain efficiency of 59% at 360 MHz, at an output power of 29 dBm. The output power as a function of the gate bias voltage varied between 3 and 29 dBm, with the drain efficiency varying between 6 and 59%.
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| 6. |
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| 7. |
- Erlandsson, Martin, et al.
(författare)
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A comparison of MAGIC and paleolimnological predictions of preindustrial pH for 55 Swedish lakes.
- 2008
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Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 42:1, s. 43-8
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Tidskriftsartikel (refereegranskat)abstract
- Two fundamentally different approaches to define reference conditions for acidification assessments are hydrogeochemical modeling and paleolimnological reconstructions. Both methods have been applied to calculate the preindustrial chemistry for 55 Swedish lakes in two independent studies. This paper investigates whether these methods give similar reconstructions of the preindustrial pH for these lakes. Special focus has been attached to the importance of total organic carbon concentrations and CO2 partial pressure (pCO(2)) in the conversion from ANC to pH in the hydrogeochemical modeling. With a uniform pCO(2) value for all the lakes of 0.63 matm, the mean absolute difference between pH from the hydrogeochernical model and the paleolimnological pH was +0.23 units (mean absolute difference 0.36 units). If instead a lake specific preindustrial pCO(2) is assumed, equal to contemporary pCO(2), the mean difference in the predicted preindustrial pH between the two methods was reduced to +0.03 units (mean absolute difference 0.22 units). Statistical analyses indicated that with a lake specific pCO(2), the difference between the reconstructions is smaller than 0.13 pH-units at a 95% level of significance. The results of this study build confidence in the reliability of both methods, providing that lake-specific estimates of pCO(2) are used.
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| 8. |
- Mehlig, Bernhard, 1964, et al.
(författare)
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Aggregation of inertial particles in random flows.
- 2005
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Ingår i: Physical review. E, Statistical, nonlinear, and soft matter physics. - 1539-3755. ; 72:5 Pt 1
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Tidskriftsartikel (refereegranskat)abstract
- We consider the trajectories of particles suspended in a randomly moving fluid. If the Lyapunov exponent of these trajectories is negative, the paths of these particles coalesce, so that particles aggregate. Here we give a detailed account of a method [B. Mehlig and M. Wilkinson, Phys. Rev. Lett. 92, 250602 (2004)] for calculating this exponent: it is expressed as the expectation value of a random variable evolving under a stochastic differential equation. We analyze this equation in detail in the limit where the correlation time of the velocity field of the fluid is very short, such that the stochastic differential equation is a Langevin equation. We derive an asymptotic perturbation expansion of the Lyapunov exponent for particles suspended in three-dimensional flows in terms of a dimensionless measure of the inertia of the particles, epsilon, and a measure of the relative intensities of potential and solenoidal components of the velocity field, Gamma. We determine the phase diagram in the epsilon-Gamma plane.
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