Alcatel-Lucent

About: Alcatel-Lucent is a based out in Stuttgart, Germany. It is known for research contribution in the topics: Signal & Network packet. The organization has 37003 authors who have published 53332 publications receiving 1430547 citations. The organization is also known as: Alcatel-Lucent S.A. & Alcatel.

Zero-point entropy in ‘spin ice’

Abstract: Common water ice (ice I-h) is an unusual solid-the oxygen atoms form a periodic structure but the hydrogen atoms are highly disordered due to there being two inequivalent O-H bond lengths'. Pauling showed that the presence of these two bond lengths leads to a macroscopic degeneracy of possible ground states(2,3), such that the system has finite entropy as the temperature tends towards zero. The dynamics associated with this degeneracy are experimentally inaccessible, however, as ice melts and the hydrogen dynamics cannot be studied independently of oxygen motion(4). An analogous system(5) in which this degeneracy can be studied is a magnet with the pyrochlore structure-termed 'spin ice'-where spin orientation plays a similar role to that of the hydrogen position in ice I-h. Here we present specific-heat data for one such system, Dy2Ti2O7, from which we infer a total spin entropy of 0.67Rln2. This is similar to the value, 0.71Rln2, determined for ice I-h, SO confirming the validity of the correspondence. We also find, through application of a magnetic field, behaviour not accessible in water ice-restoration of much of the ground-state entropy and new transitions involving transverse spin degrees of freedom.

Distributed redundant database

Abstract: A distributed redundant database architecture (10) primarily for storing a plurality of wireless service subscriber files (84, 86) is provided. The database architecture (10) include a first set of processors (44 46, 48) each having a shared memory (72, 74, 76), where the processors (44, 46, 48) are divided into processor groups (38, 40, 42). A memory storage device (80, 82) is coupled to each processor group (38, 40, 42) in a multi-initiator mode so that each memory storage device (80, 82) is accessible by the processors (44, 46, 48) in its respective processor group (38, 40, 42). The plurality of subscriber files (84, 86) are assigned to the processor groups (38, 40, 42) and further assigned to the processors (44, 46, 48) in each processor group (38, 40, 42) to achieve a substantially even distribution. The plurality of subscriber files are stored in the memory storage devices (80, 82) of respective assigned processor groups (38, 40, 42), and are mapped into the respective shared memories (72, 74, 76) of the processors. A database manager (52, 54, 66) associated with the processors and processor groups is provided for managing the distribution and redistribution of the subscriber files to the processors. A second set of similarly configured processors residing at a remote site (14) maintains a second copy of the subscriber files (84, 86) to provide database backup.

Temporal structure in neuronal activity during working memory in macaque parietal cortex

Abstract: Many cortical structures have elevated firing rates during working memory, but it is not known how the activity is maintained. To investigate whether reverberating activity is important, we studied the temporal structure of local field potential (LFP) activity and spiking from area LIP in two awake macaques during a memory-saccade task. Using spectral analysis, we found spatially tuned elevated power in the gamma band (25-90 Hz) in LFP and spiking activity during the memory period. Spiking and LFP activity were also coherent in the gamma band but not at lower frequencies. Finally, we decoded LFP activity on a single-trial basis and found that LFP activity in parietal cortex discriminated between preferred and anti-preferred direction with approximately the same accuracy as the spike rate and predicted the time of a planned movement with better accuracy than the spike rate. This finding could accelerate the development of a cortical neural prosthesis.

Digital predistortion of wideband signals based on power amplifier model with memory

Abstract: Memory effects in the power amplifier limit the performance of digital predistortion for wideband signals. Novel algorithms that take into account such effects are proposed. Measured results are presented for single and multicarrier UMTS signals to demonstrate the effectiveness of the new approach.

The bell laboratories H I survey

Abstract: We present a galactic survey which to date consists of 73,000 positions covering −5° < l < 122°, −1° < b < 1° , observed in the J=1 → 0 line of 13CO to an rms noise level of 0.15 K in 0.68 km s−1 channels, using the 7 m antenna at Crawford Hill. It is shown that the internal velocity dispersions of molecular clouds tend to vary inversely with galactocentric radius.