Dome building activity is common at many volcanoes and due to the gravitational instability, a dome represents one of the most hazardous volcanic phenomena. Shallow volcanic processes as well as ...rheological and structural changes of the dome affecting the fluid transport have been linked to transitions in eruptive activity. Also, hydrothermal alteration may affect the structural integrity of the dome, increasing the potential for collapse. However, mapping the deformation and details of fluid escape at the summit of steep sloped volcanoes and integrating these with other types of data is challenging due to difficult access and poor coverage. Here we present for the first time the near-vertical and near-horizontal surface deformation field of a quiescent summit dome and the relationships with degassing and topographic patterns. Our results are derived from high resolution satellite radar interferometry (InSAR) time series based on a year of TerraSAR-X SpotLight acquisitions and Structure from Motion (SfM) processing of overflight infrared data at Volcán de Colima, Mexico. The identified deformation is dominated by localized heterogeneous subsidence of the summit dome exceeding rates of 15 cm/yr, and strongly decreasing over the year 2012, up to the renewal of explosive and extrusive activity in early 2013. We tentatively attribute the deformation to the degassing, cooling and contraction of the dome and shallow conduit material. We also find that the results strongly differ depending on the chosen InSAR time series method, which potentially overprints the true physical complexities of small scale, shallow deformation processes. The combined interpretation of the deformation and infrared data reveals a complex spatial relationship between the degassing pathways and the deformation. While we observe no deformation across the crater rim fumaroles, discontinuities in the deformation field are more commonly observed around the dome rim fumaroles and occasionally on the dome upper surface. We propose that the deformation pattern is also linked to processes controlling the fumarole formation and distribution (topography, permeability and volcanic activity), and the lack of direct relationships may be explained by how the influence of these processes varies across the volcanic summit. The presented work provides a new approach for safely monitoring the activity and stability of internal dome structures, as well as for constraining and validating models of dome degassing pathways and densification processes.
•First high resolution deformation maps of a degassing summit dome.•Integration of multiple PS-InSAR results by point cloud processing.•Highly localized and heterogeneous deformation, decreasing in rate.•Comparison with spatial distribution of fumaroles derived from SfM.•Multiple controls of degassing pathways and deformation during quiescence.
The paper deals with transmit pre-filtering using antenna arrays in the downlink of wireless cellular systems based on multi-carrier code division multiple access (MC-CDMA). In addition to the signal ...separation in frequency obtained by spreading codes, the base station exploits the spatial separation of users to improve interference mitigation, which enables the use of low-complexity mobile receivers. We propose transmit filtering techniques optimizing the signal separation in space only, or jointly in space and frequency, according to single- and multi-user criteria. These techniques assume channel knowledge at transmission, and are particularly destined for time division duplex systems, where we may benefit from channel reciprocity between up- and downlink. We compare the performance of the proposed techniques in terms of interference reduction and robustness to time variant channels. Simulation results emphasize the benefit of transmit filtering optimized jointly in space and frequency, which allows a striking increase on the user capacity thanks to space division multiple access.
Today link-to-system (L2S) interfaces are more and more used in order to speed up complete system-level simulations. In this paper a simple extension to generic incremental redundancy (IR) hybrid ...automatic repeat request (HARQ) strategies is presented for two well-known L2S interfaces: the exponential effective SNR metric (EESM) and the mutual information effective SNR metric (MIESM). Then we focus on the problem of the L2S interface tuning, which is necessary to achieve the highest accuracy of the prediction models. The standard calibration procedure is compared with a new method, based on the average (over channel and noise) physical (PHY) layer performance. The latter, called average calibration procedure, is less time consuming than the standard procedure. Moreover, we show by simulation that the optimal calibration factors, calculated with the two methods, converge to close values thus obtaining equivalent prediction accuracy for the same L2S interface.
Ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine synthesis, is important in cochlear development. Whereas tissue specific differences in cochlear ODC activity have been ...demonstrated, cellular localization of ODC protein in the inner ear of the immature rat has not. ODC was localized in inner ear structures using an ODC polyclonal antibody and the effects of cycloheximide on ODC immunoreactivity and enzymatic activity were determined. Tissues demonstrating elevated enzymatic activity contained cells with the strong immunoreactivity. ODC activity was highest in the organ of Corti and lateral wall followed by the cochlear nerve. Immunoreactivity was demonstrated throughout the cochlea with intense staining of the hair cells, pillar cells, Deiter's cells, inner sulcus cells, basilar membrane, stria vascularis, spiral ganglion cell bodies and cochlear nerve fibers. Cycloheximide rapidly diminished cochlear ODC activity and expression of ODC protein. The half-life of cochlear ODC was 30 min. Localization of cellular sites of ODC is important in understanding the role of the ODC-polyamine pathway in cochlear development and will be a valuable marker for tissue damage from ototoxic agents.
To compare the transcutaneous and transconjunctival approaches for repair of orbital rim and floor fractures.
We conducted a retrospective study of the occurrence of eyelid retraction following the ...repair of 63 orbital fracture, 27 with the subciliary skin-muscle flap approach and 36 with the transconjunctival preseptal approach.
Academic tertiary referral medical center.
Fifty-nine patients underwent 63 orbital explorations.
Of the 27 transcutaneous explorations, 24 were done early within the first 2 weeks of injury and three were performed for correction of late posttraumatic enophthalmos. Of the 36 transconjunctival explorations, 25 were done early and 11 were performed for correction of late posttraumatic enophthalmos.
Clinically noted complications.
We found a 12% rate of transient ectropion and a 28% rate of permanent scleral show with the subciliary skin-muscle flap approach compared with no transient ectropion and a 3% rate of permanent scleral show with the transconjunctival approach.
We believe that the transconjunctival approach provides excellent exposure with less risk of postoperative eyelid retraction and ectropion.
In the evaluation of facial paralysis, electroneurography provides a quantitative assessment of the degree of degeneration. Near the endpoint of degeneration, the facial musculature compound action ...potential may be contaminated by masseter artifact resulting from supramaximal stimulation. We propose the use of both masseter electromyography and electroneurography in the evaluation of advanced degeneration to better define the current level for supramaximal stimulation, to eliminate masseter artifact, and to more accurately assess the degree of facial nerve degeneration.
Vestibular compensation is a process of behavioral recovery from ocular, motor and postural disorders following unilateral damage to the vestibular end-organ. Although restoration of the normal ...resting discharge rate in the ipsilateral vestibular nuclei is important in compensation, the biochemical and molecular mechanisms mediating recovery are largely unknown. The ornithine decarboxylase polyamine pathway is activated in the nervous system following axotomy or denervation. The authors postulate that changes in polyamines mediate vestibular compensation. Within 150-micron brain stem coronal section micropunches analyzed by high performance liquid chromatography techniques, the polyamine spermidine was significantly increased in the ipsilateral lateral vestibular nucleus 8 hours following labyrinthectomy in the guinea pig model. Because naturally occurring polyamines modulate excitatory amino acid receptors (N-methyl-D-aspartate NMDA) which in turn mediate neurotransmission between primary afferents and second order vestibular neurons, stimulation of polyamine pathways following neural injury may play a critical role in compensation.
Transmit beamforming (BF) for space division multiple access (SDMA) is studied in the downlink of wireless cellular systems based on multi-carrier code division multiple access (MC-CDMA). This ...combination allows a separation of users' signals in space, thanks to BF, and frequency, thanks to CDMA, and thus improves mitigation of multiple access interference. We propose to perform BF on each subcarrier independently to allow any kind of detection algorithms at the mobile terminal. Single user criteria based on maximum ratio transmission and a multiuser criterion maximizing the signal over interference-plus-noise ratio are studied. We show that beamforming impairs the orthogonality of the user's signals in frequency. However, the advantage of separation in space clearly prevails, especially when low complexity detection techniques are used at the mobile terminal. Furthermore, we propose a simple and efficient combination of CDMA and SDMA that significantly increases the system capacity by reallocation of spreading codes.
We consider joint scheduling and beamforming in a broadcast channel with multiple antennas at the transmitter and a single antenna at the mobile receiver. Perfect channel knowledge is assumed to be ...available at the receiver while the transmitter is provided with partial channel state information (CSIT) through a limited rate feedback channel. Each user feeds back quantized information regarding the channel vector direction (from a codebook) and a quantized (scalar) channel quality indicator. We identify the tradeoff between multiuser diversity and spatial multiplexing gain given a limited amount of feedback bits. Scaling laws of the above parameters are derived in order to achieve a target rate performance. Our results reveal useful design guidelines for the split of feedback bits for channel quantization and channel quality.
We consider a downlink channel where a base station equipped with M transmit antennas communicates with K ≥ M single-antenna receivers and has partial channel knowledge obtained via a limited rate ...feedback channel. We propose scalar feedback metrics that provide an estimate of the received signal-to-noise plus interference ratio (SINR), which are combined with efficient user selection algorithms and zero-forcing beamforming. The asymptotic system sum rate for large K is analyzed and numerical results are provided, showing the performance of each metric in different scenarios.
PDF
