1,200 research outputs found
81 fJ/bit energy-to-data ratio of 850 nm vertical-cavity surface-emitting lasers for optical interconnects
No full textThis article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 98, 231106 (2011) and may be found at https://doi.org/10.1063/1.3597799.Extremely energy-efficient oxide-confined high-speed 850 nm vertical-cavity surface-emitting lasers for optical interconnects are presented. Error-free performance at 17 and 25 Gb/s via a 100 m multimode fiber link is demonstrated at record high dissipation-power-efficiencies of up to 69 fJ/bit (<0.1mW/Gbps) and 99 fJ/bit, respectively. These are the most power efficient high-speed directly modulated light sources reported to date. The total energy-to-data ratio is 83 fJ/bit at 25°C and reduces to 81 fJ/bit at 55°C. These results were obtained without adjustment of driving conditions. A high -factor of 12.0GHz/(mA)0.5 and a -factor of 0.41 ns are measured.EC/FP7/224211/EU/VISIT - Vertically Integrated Systems for Information Transfer/VISITDFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, Bauelement
Single-drive high-speed lumped depletion-type modulators toward 10 fJ/bit energy consumption
No full textReduction of modulator energy consumption to 10 fJ/bit is essential for the sustainable development of communication systems. Lumped modulators might be a viable solution if instructed by a complete theory system. Here, we present a complete analytical electro-optic response theory, energy consumption analysis, and eye diagrams on absolute scales for lumped modulators. Consequently the speed limitation is understood and alleviated by single-drive configuration, and comprehensive knowledge into the energy dependence on structural parameters significantly reduces energy consumption. The results show that silicon modulation energy as low as 80.8 and 21.5 fJ/bit can be achieved at 28 Gbd under 50 and 10 Omega impedance drivers, respectively. A 50 Gbd modulation is also shown to be possible. The analytical models can be extended to lumped modulators on other material platforms and offer a promising solution to the current challenges of modulation energy reduction. (C) 2017 Chinese Laser PressNational Natural Science Foundation of China (NSFC) [61120106012]SCI(E)ARTICLE2134-142
Social norms, morals and self-interest as determinants of pro-environment behaviours : the case of household recycling
No full textThe first author gratefully acknowledges the support of the Polish Ministry of Science and Higher Education and the Foundation for Polish Science.This paper considers the role which selfish, moral and social incentives and pressures play in explaining the extent to which stated choices over pro-environment behaviours vary across individuals. The empirical context is choices over household waste contracts and recycling actions in Poland. A theoretical model is used to show how cost-based motives and the desire for a positive self and social image combine to determine the utility from alternative choices of recycling behaviour. We then describe a discrete choice experiment designed to empirically investigate the effects such drivers have on stated choices. A hybrid logit model is used to link statements over attitudes to recycling to choices, dealing with a potential endogeneity problem caused by the joint effects of un-observables on attitudes and choices. We find that a substantial share of our respondents prefer to sort their waste at home rather than in a central sorting facility. This preference is associated with a moral/intrinsic motivation, involving a belief that sorting at home is more thorough than central sorting.Peer reviewe
Author Arna Bontemps reads to children at the East Winston Branch Library, 1956.
No full textAuthor Arna Bontemps reads to children at the East Winston Branch Library, 1956
SPIN AND CHARGE FLUCTUATIONS IN ITINERANT-ELECTRON MAGNETISM - A VARIATIONAL FUNCTIONAL-INTEGRAL APPROXIMATION
No full textThe single-site spin-fluctuation theory of metallic magnetism developed by Hubbard and Hasegawa is modified and extended to investigate the effects of spin and charge fluctuations on the magnetic properties at finite temperature. The key point of our scheme is to adopt a continuous decomposition of the interacting part of the Hubbard Hamiltonian in the Stratonovich-Hubbard transformation, resulting in the separation of the charge fluctuations from the spin fluctuations. This separation makes a better description for the contrary nature between the two types of fluctuations. In order to remove the ambiguity, a variational principle is introduced to determine the appropriate form of the decomposition of the Hubbard model. The ground-state properties, the Curie temperature, the magnetization, and the paramagnetic susceptibility, etc., at finite temperature are calculated and compared with the Hasegawa theory. The improvement of the Curie temperature is significant, and better behavior of the temperature dependence of the magnetization is obtained.Physics, Condensed MatterSCI(E)6ARTICLE1712795-128044
Plasticity of salamander skeletal muscle cells
No full textRegeneration is unevenly spread throughout the animal kingdom. Some of the invertebrates have a very high regenerative capacity but the capacity to replace lost or damaged tissues in mammals is limited. Among the vertebrates, the aquatic salamanders are the champions of regeneration, being able to regenerate body parts such as their limbs, tail, and jaw. Understanding the cell- and molecular machinery underlying these events can in the end lead to improvements in the field of regenerative medicine.When a salamander limb is amputated, a so called blastema is formed at the tip of the stump. This is a mesenchymal growth zone, from where the cells for the new limb originate. The skeletal muscle is believed to contribute to the blastema and the newly formed limb during regeneration in salamanders. There are two possible mechanisms by which this could occur. First, the muscle reserve cells, satellite cells, become activated, and after subsequent expansion they incorporate in to the blastema. Second, the multinucleated muscle cell dedifferentiates in a cellularization process, forming several new progenitor cells that contribute to the regenerate. These two mechanisms are the subjects of study in this thesis.In the first paper, satellite cells were monitored during the regeneration of the salamander limb. The satellite cell population was found to be restored after several rounds of amputation/regeneration, demonstrating a robust mechanism to replenish this cell population. By genetically labeling satellite cell progeny with GFP, cells were traced during limb regeneration. The labeled cells were found to contribute to cartilage tissue as well as to muscle, suggesting that they have lineage switching potential. The satellite cell marker Pax7 was rapidly down regulated in the blastema, indicating that the blastema has a reprogramming activity.In the second paper, the link between injury and dedifferentiation of muscle was explored. Previously it was shown that the skeletal muscle fiber must suffer a direct cellular injury in order to dedifferentiate in vivo. This led us to hypothesize that a programmed cell death response initiated by the injury, is linked to the dedifferentiation of this cell type. In order to investigate this, cellular events were examined after treating the cells with a known cellularization inducer called myoseverin, and pro-apoptotic drugs. The responses after these treatments were found to be similar, they both evoked cellularization of the muscle cells, and this was preceded by features of an activated apoptotic machinery. By inhibiting the intrinsic pathway of the apoptotic machinery, cellularization was inhibited. Finally, dedifferentiated progeny generated by pro-apoptotic stimuli was found to be capable of reentering the cell cycle and proliferate. Together these results indicate that the injury is directly linked to dedifferentiation through the apoptotic machinery.List of scientific papersI. Jamie I Morrison, Paula Borg, and András Simon. Plasticity and recovery of skeletal muscle satellite cells during limb regeneration. FASEB J. 2010 Mar;24(3):750-6. https://doi.org/10.1096/fj.09-134825 II. Sara Lööf, Paula Borg, Jamie I Morrison, Bertrand Joseph, and András Simon. Cellular dedifferentiation by a programmed cell death response. [Manuscript]</p
Two-Photon AMPK and ATP Imaging Reveals Metabolic Recovery in Mouse Rod Photoreceptor Cells
No full textThe title of publisher's version: Two-photon AMPK and ATP imaging reveals the bias between rods and cones in glycolysis utility.In vertebrates, retinal rod and cone photoreceptor cells rely significantly on glycolysis. Lactate released from photoreceptor cells fuels neighboring retinal pigment epithelium cells and Müller glial cells through oxidative phosphorylation. To understand this highly heterogeneous metabolic environment around photoreceptor cells, single-cell analysis is needed. Here, we visualized cellular AMP-activated protein kinase (AMPK) activity and ATP levels in the retina by two-photon microscopy. Transgenic mice expressing a hyBRET-AMPK biosensor were used for measuring the AMPK activity. GO-ATeam2 transgenic mice were used for measuring the ATP level. Temporal metabolic responses were successfully detected in the live retinal explants upon drug perfusion. A glycolysis inhibitor, 2-deoxy-d-glucose (2-DG), activated AMPK and reduced ATP. These effects were clearly stronger in rods than in cones. Notably, rod AMPK and ATP started to recover at 30 min from the onset of 2-DG perfusion. Consistent with these findings, ex vivo electroretinogram recordings showed a transient slowdown in rod dim flash responses during a 60-min 2-DG perfusion, whereas cone responses were not affected. Based on these results, we propose that cones surrounded by highly glycolytic rods become less dependent on glycolysis, and rods also become less dependent on glycolysis within 60 min upon the glycolysis inhibition
A low noise, low power dynamic amplifier with common mode detect and a low power, low noise comparator for pipelined SAR-ADC
No full textThis thesis presents a high gain, low noise and low power dynamic residue amplifier and a low power, low noise dynamic comparator designed in TSMC 28nm process for a two step Pipelined SAR-ADC. The cascoded integrator dynamic residue amplifier (CIDRA) achieves a gain of 30dB with THD of 47dB (11 mV pp input). The input referred noise across tem- perature and process corner is 55 µV and it operates at a frequency of 500MHz while the energy consumption is 390 fJ. The low power and low noise pseudo-latch preamp dynamic comparator (PLPDC) shows a delay of 250pSec for a differential input of 16 pV and consumes 91 fJ (current is 91 µA for 100 MHz clock) of energy. The input referred offset is 4 mV (?).Microelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
Cryogenic Comparator Characterization and Modeling for a Cryo-CMOS 7b 1-GSa/s SAR ADC
No full textThis paper reports the experimental characterization and modelling of a stand-Alone StrongARM comparator at both room temperature (RT) and cryogenic temperature (4.2 K). The observed 6-dB improvement in the comparator input noise at 4.2 K is attributed to the reduction of the thermal noise and to the suppressed shot noise in the MOS transistors becoming dominant at cryogenic temperature. The proposed model is employed in the design of a loop-unrolled 2\times time-interleaved 1-GSa/s 7b SAR ADC for spin-qubit readout. As predicted by the comparator model, the ADC is noise-limited at RT to a SNDR of 38.2 dB at Nyquist input, while this improves to 41.1 dB at 4.2 K, now limited by distortion, thus resulting in the state-of-The-Art FoMw for cryo-CMOS ADC of 20.9 fJ/conv-step. Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.QCD/Sebastiano LabElectrical Engineering, Mathematics and Computer ScienceElectronicsQuantum Circuit Architectures and Technolog
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