Fast Decompression Research Articles

Heat can cool near-critical fluids

We report experiments with very compressible fluids near the liquid-gas critical point. These experiments are performed (i) under microgravity in low Earth orbit by using SF(6) at liquidlike density and (ii) under Earth's gravity with CO(2) at gaslike density. The sample fluid is filled in an interferometer cell with its walls maintained at constant temperature. In situ thermistors measure the local fluid temperature. One of the thermistors is also used as a heat source to generate heat pulses. With no gravity-induced fluid convection, the evolution of fluid temperature is governed by the balance of heat flux between the thermal boundary layer of the heat source, which compresses the bulk fluid, and the thermal boundary layer at the wall, which expands it. When heat pulses are applied to the fluid under weak or Earth's gravity, a long thermal transient is observed at the end of the heat pulse where the bulk fluid temperature reaches significantly below the initial temperature. This unconventional cooling originates from the fast decompression of the fluid, which is induced by the rapid convectively disappearing hot boundary layer at the heat source, and the persistence of an anomalously thin cold boundary layer convectively induced at the cell wall. This striking phenomenon is observed in a large range of temperature, density, and various thermodynamic conditions. This anomalous cooling effect persists for an appreciable period of time corresponding to the diffusive destruction of the cold boundary layer. We found that the effect is also more pronounced when the free fall acceleration is large. We have analyzed the result by using a simple one-dimensional model with ad hoc convective heat losses.

Shortcuts to adiabaticity for trapped ultracold gases

We study experimentally and theoretically the controlled transfer of harmonically trapped ultracold gases between different quantum states. In particular, we experimentally demonstrate a fast decompression and displacement of both a non-interacting gas and an interacting Bose–Einstein condensate, which are initially at equilibrium. The decompression parameters are engineered such that the final state is identical to that obtained after a perfectly adiabatic transformation despite the fact that the fast decompression is performed in the strongly non-adiabatic regime. During the transfer the atomic sample goes through strongly out-of-equilibrium states, while the external confinement is modified until the system reaches the desired stationary state. The scheme is theoretically based on the invariants of motion and scaling equation techniques and can be generalized to decompression trajectories including an arbitrary deformation of the trap. It is also directly applicable to arbitrary initial non-equilibrium states.

Molecular Dynamics Trajectory Compression with a Coarse-Grained Model

Molecular dynamics trajectories are very data-intensive thereby limiting sharing and archival of such data. One possible solution is compression of trajectory data. Here, trajectory compression based on conversion to the coarse-grained model PRIMO is proposed. The compressed data is about one third of the original data and fast decompression is possible with an analytical reconstruction procedure from PRIMO to all-atom representations. This protocol largely preserves structural features and to a more limited extent also energetic features of the original trajectory.

An analog investigation of magma fragmentation and degassing: Effects of pressure, volatile content, and decompression rate

We conducted analog experiments using gum rosin–acetone (GRA) mixtures to approximate behavior of magmas containing dissolved and exsolved volatiles. The main objective was to investigate the role of pressure upon fragmentation behavior for GRA mixtures undergoing slow and fast decompressions. We found that under conditions of slow decompression (22–80 Pa s − 1 ), the GRA mixture never fragmented, exhibiting characteristic styles of surface degassing at different pressures. Under fast decompression (620–2400 kPa s − 1 ), fragmentation behavior was controlled principally by the initial volatile content of the GRA mixture, as well as by the extent and rate of decompression. Low-viscosity GRA mixtures with high levels of acetone fragmented efficiently at high final pressures, while viscous mixtures containing less acetone did not fragment except when subjected to small final pressures, high pressure differentials, and rapid decompression. Based on our observations, we propose that GRA mixtures near the fragmentation threshold are disrupted in a ductile fashion by intense vesiculation and bubble movements, while mixtures subject to elevated pressure differentials which are significantly higher than this threshold fragment in a brittle manner due to foam disruption. In non-fragmenting GRA mixtures, a form of stick–slip behavior was observed, the dynamics of which varied with the rheology of the mixture and the pressure differential applied during the decompression. In low-viscosity GRA mixtures, gas transfer occurred mainly in the form of gas bubbles and slugs which moved vertically upward through the material, creating permeable pathways to promote degassing and disruption of the mixture by bubble bursts. In viscous GRA mixtures dominated by foam development, vertical permeability gradients were observed, with a strongly degassed brittle foam at the top and a less degassed ductile foam beneath. Our observations have implications for submarine volcanism, volcanoes on Venus, and lava dome eruptions. For submarine volcanism, our experiments show that explosive fragmentation of magma may not be limited by water depth if the volatile content of the magma is sufficiently high (i.e., 4–6 wt.% H 2O). Our experimental results also suggest that the high-pressure atmospheric conditions of Venus (9300 kPa) are not an impediment to the explosive eruption of high volatile content magmas, which casts doubt on the interpretation of large-volume pancake lava domes on Venus as the high-pressure equivalent of terrestrial ignimbrite eruptions. Together with our experimental results, observations of actively growing lava domes demonstrate that explosive fragmentation is promoted by rapid, large-volume collapses of a dome, and by unroofed magma which is comparatively volatile-rich and vesicular.

IMPROVED FRACTAL IMAGE COMPRESSION BASED ON ROBUST FEATURE DESCRIPTORS

Fractal image compression is one of the most promising techniques for image compression due to advantages such as resolution independence and fast decompression. It exploits the fact that natural scenes present self-similarity to remove redundancy and obtain high compression rates with smaller quality degradation compared to traditional compression methods. The main drawback of fractal compression is its computationally intensive encoding process, due to the need for searching regions with high similarity in the image. Several approaches have been developed to reduce the computational cost to locate similar regions. In this work, we propose a method based on robust feature descriptors to speed up the encoding time. The use of robust features provides more discriminative and representative information for regions of the image. When the regions are better represented, the search for similar parts of the image can be reduced to focus only on the most likely matching candidates, which leads to reduction on the computational time. Our experimental results show that the use of robust feature descriptors reduces the encoding time while keeping high compression rates and reconstruction quality.

Decoding-Aware Compression of FPGA Bitstreams

Bitstream compression is important in reconfigurable system design since it reduces the bitstream size and the memory requirement. It also improves the communication bandwidth and thereby decreases the reconfiguration time. Existing research in this field has explored two directions: efficient compression with slow decompression or fast decompression at the cost of compression efficiency. This paper proposes a novel decode-aware compression technique to improve both compression and de compression efficiencies. The three major contributions of this paper are: 1) smart placement of compressed bitstreams that can significantly decrease the overhead of decompression engine; 2) selection of profitable parameters for bitstream compression; and 3) efficient combination of bitmask-based compression and run length encoding of repetitive patterns. Our proposed technique outperforms the existing compression approaches by 15%, while our decompression hardware for variable-length coding is capable of operating at the speed closest to the best known field-programmable gate array-based decoder for fixed-length coding.

Compression of DNA sequence reads in FASTQ format

Modern sequencing instruments are able to generate at least hundreds of millions short reads of genomic data. Those huge volumes of data require effective means to store them, provide quick access to any record and enable fast decompression. We present a specialized compression algorithm for genomic data in FASTQ format which dominates its competitor, G-SQZ, as is shown on a number of datasets from the 1000 Genomes Project (www.1000genomes.org). DSRC is freely available at http:/sun.aei.polsl.pl/dsrc.

Oxygen pretreatment as protection against decompression sickness in rats: pressure and time necessary for hypothesized denucleation and renucleation

Pretreatment with HBO at 300-500 kPa for 20 min reduced the incidence of decompression sickness (DCS) in a rat model. We investigated whether this procedure would be effective with lower oxygen pressures and shorter exposure, and tried to determine how long the pretreatment would remain effective. Rats were pretreated with oxygen at 101 or 203 kPa for 20 min and 304 kPa for 5 or 10 min. After pretreatment, the animals were exposed to air at 1,013 kPa for 33 min followed by fast decompression. Pretreatment at 101 or 203 kPa for 20 min and 304 kPa for 10 min significantly reduced the number of rats with DCS to 45%, compared with 65% in the control group. However, after pretreatment at 304 kPa for 5 min, 65% of rats suffered DCS. When pretreatment at 304 kPa for 20 min was followed by 2 h in normobaric air before compression and decompression, the outcome was worse, with 70-90% of the animals suffering DCS. This is probably due to the activation of "dormant" micronuclei. The risk of DCS remained lower (43%) when pretreatment with 100% O(2) at normobaric pressure for 20 min was followed by a 2 h interval in normobaric air (but not 6 or 24 h) before the hyperbaric exposure. The loss of effectiveness after a 6 or 24 h interval in normobaric air is related to micronuclei rejuvenation. Although pretreatment with hyperbaric O(2) may have an advantage over normobaric hyperoxia, decompression should not intervene between pretreatment and the dive.

The crystalline basement of the Adria microplate in the eastern Alps: a review of the palaeostructural evolution from the Neoproterozoic to the Cenozoic

The frontal northern part of the continental Adriatic microplate is formed by a stack of Austroalpine nappes and by the Southalpine basement and cover units. Both basement portions are now side by side, separated by the Periadriatic (Insubric) fault system, but they became juxtaposed only during the Alpine orogeny. Permian HT-LP metamorphism is now recognised also within the Austroalpine basement of the eastern Alps, whilst it was known since long in the Southalpine basement. High thermal heat flow responsible for HT-LP metamorphism is related to the extensional tectonics and lithospheric thinning during the Permian and by concurrent magmatic underplating. During the Variscan orogeny, eclogite facies metamorphism is documented within the Ötztal and the Silvretta basements (350 Ma), as well as within the Nonsberg-Ulten unit (336 Ma). The HP events in the Ötztal and the Silvretta basements correlate temporarily with the closure of the Rheic Ocean between the Hanseatic and the Galatian terranes. Docking of the Galatian-Hanseatic composite terrane with Laurussia resulted in large-scale strike-slip tectonics and potentially in the formation of mega-folds (“Schlingen”) within the Austroalpine basement during the Visean. Palaeo-Tethys ridge subduction may be responsible for fast decompression and isobaric heating documented within the Ötztal basement. The Palaeozoic sedimentary sequences of the Austroalpine and the Southalpine phyllitic complexes testify that from Silurian to Devonian, both basement portions were in a passive margin position. During the Cambrian–Ordovician, the Austroalpine basement occupied a position along the leading edge of Gondwana facing the Proto-Tethys Ocean. The compositional variation of the intruded granitic suites confirm an evolution from a magmatic arc towards a collisional-type geodynamic setting related to the closure of the previously opened back-arc basins.

Fast optimal transition between two equilibrium states

We demonstrate a technique based on invariants of motion for a time-dependent Hamiltonian, allowing a fast transition to a final state identical in theory to that obtained through a perfectly adiabatic transformation. This method is experimentally applied to the fast decompression of an ultracold cloud of Rubidium 87 atoms held in a harmonic magnetic trap, in the presence of gravity. We are able to decompress the trap by a factor of 15 within 35 ms with a strong suppression of the sloshing and breathing modes induced by the large vertical displacement and curvature reduction of the trap. When compared to a standard linear decompression, we achieve a gain of a factor of 37 on the transition time.

Testing the validity of organic and inorganic thermal indicators in different tectonic settings from continental subduction to collision: the case history of the Calabria–Lucania border (southern Apennines, Italy)

Abstract: This paper investigates the applicability of organic and inorganic thermal parameters in a range of thermal conditions, from diagenesis to epizone, and in HP–LT settings within the framework of continental subduction and exhumation in the southern Apennines, where independent thermobarometric constraints are available. Two juxtaposed tectonic units, the HP–LT Lungro–Verbicaro Unit (in the hanging wall) and the non-metamorphic Pollino–Ciagola Unit (in the footwall) have been analysed. For the Lungro–Verbicaro Unit, clay mineral thermal parameters and vitrinite reflectance underestimate metamorphic conditions (constrained by petrology), suggesting that, in relatively HP units, these indicators are ‘retarded' and strongly depend on P – T evolution through time. On the other hand, the K-white mica b cell dimension provides a robust estimate of peak pressure. Fluid inclusion textures indicate a fast isothermal decompression during exhumation. Two-phase inclusions from early stage syntectonic veins were trapped after isothermal exhumation at a pressure of 0.3 GPa. For the Pollino–Ciagola Unit, the correlation of analysed parameters effectively unravels the thermal evolution, with maximum palaeotemperatures of c . 150 °C. Apatite fission tracks provide details of the final stages of exhumation, indicating that both units were coherently exhumed in the Late Miocene, following the tectonic emplacement of the Lungro–Verbicaro Unit on top of the Pollino–Ciagola Unit. Supplementary material: X-ray diffraction data (whole-rock composition, quantitative analysis of the <2 μm grain-size fraction, mica polytypes, illite content in mixed layer illite–smectite (I–S), Kübler and Árkai data, and b cell dimension) are available at http://www.geolsoc.org.uk/SUP18416 .

Simulating bubble number density of rhyolitic pumices from Plinian eruptions: constraints from fast decompression experiments

Decompression experiments of a crystal-free rhyolitic liquid with ≈ 6.6 wt. % H2O were carried out at a pressure range from 250 MPa to 30–75 MPa in order to characterize effects of magma ascent rate and temperature on bubble nucleation kinetics, especially on the bubble number density (BND, the number of bubbles produced per unit volume of liquid). A first series of experiments at 800°C and fast decompression rates (10–90 MPa/s) produced huge BNDs (≈ 2 × 1014 m−3 at 10 MPa/s ; ≈ 2 × 1015 m−3 at 90 MPa/s), comparable to those in natural silicic pumices from Plinian eruptions (1015–1016 m−3). A second series of experiments at 700°C and 1 MPa/s produced BNDs (≈ 9×1012 m−3) close to those observed at 800°C and 1 MPa/s (≈ 6 × 1012 m−3), showing that temperature has an insignificant effect on BNDs at a given decompression rate. Our study strengthens the theory that the BNDs are good markers of the decompression rate of magmas in volcanic conduits, irrespective of temperature. Huge number densities of small bubbles in natural silicic pumices from Plinian eruptions imply that a major nucleation event occurs just below the fragmentation level, at which the decompression rate of ascending magmas is a maximum (≥ 1 MPa/s).

RACBVHs: Random-Accessible Compressed Bounding Volume Hierarchies

We present a novel compressed bounding volume hierarchy (BVH) representation, random-accessible compressed bounding volume hierarchies (RACBVHs), for various applications requiring random access on BVHs of massive models. Our RACBVH representation is compact and transparently supports random access on the compressed BVHs without decompressing the whole BVH. To support random access on our compressed BVHs, we decompose a BVH into a set of clusters. Each cluster contains consecutive bounding volume (BV) nodes in the original layout of the BVH. Also, each cluster is compressed separately from other clusters and serves as an access point to the RACBVH representation. We provide the general BVH access API to transparently access our RACBVH representation. At runtime, our decompression framework is guaranteed to provide correct BV nodes without decompressing the whole BVH. Also, our method is extended to support parallel random access that can utilize the multicore CPU architecture. Our method can achieve up to a 12:1 compression ratio, and more importantly, can decompress 4.2 M BV nodes ({=}135 {\rm MB}) per second by using a single CPU-core. To highlight the benefits of our approach, we apply our method to two different applications: ray tracing and collision detection. We can improve the runtime performance by more than a factor of 4 as compared to using the uncompressed original data. This improvement is a result of the fast decompression performance and reduced data access time by selectively fetching and decompressing small regions of the compressed BVHs requested by applications.

Dynamics of magma supply at Mt. Etna volcano (Southern Italy) as revealed by textural and compositional features of plagioclase phenocrysts

A systematic study of textural and compositional zoning (An% and FeO variation) in plagioclase phenocrysts of historic (pre-1971) and recent (post-1971) lavas at Mount Etna was made through back-scattered electron (BSE) images and electron microprobe analyses (EMP). The textures considered include oscillatory zoning and several types of dissolution, resorption and growth textures at the phenocryst cores and/or rims. Two patterns of oscillation were recognized from the combined An–FeO variation: 1) Low Amplitude–High Frequency (LAHF) and 2) High Amplitude–Low Frequency (HALF). The first pattern is interpreted here as due to kinetic effects at the plagioclase/melt interface which developed during crystallization in closed reservoirs. The second, which sometimes involves thin dissolution surfaces marked by irregular edges, angular unconformities and complex dissolution–regrowth patterns, might imply crystallization in a more dynamic regime, probably driven by chemical and physical gradients of the system (e.g., convection in a steadily degassing open-conduit). Dissolution and resorption textures at the core vary from patchy (exclusive to plagioclases within pre-1971 lavas) to strongly sieved, and can be related to increasing rates of decompression under H 2O-undersaturated conditions. Thick sieve-textured envelopes at the phenocryst rims, generally coupled with marked An–FeO increase, result from mixing with more primitive and volatile-rich magmas. In the same crystals from recent activity, An and, to a lesser extent, FeO increase, consistent with the mixing of H 2O-rich magmas similar in their mafic character to the resident magma (cryptic mixing). Two types of growth textures were also recognized at the crystal rims: 1) stripes of regularly-shaped melt inclusions and 2) swallow-tailed, skeletal crystals. In the first instance, the concordant An–FeO decrease suggests crystallization caused by fast ascent-related decompression accompanied by volatile loss. In the second, An decrease at effectively constant FeO contents may indicate crystallization at a high level of undercooling from already degassed magma, followed by rapid quenching; such a feature might be acquired during syn- or post-eruptive conditions. Although textures found in historic lavas are rather similar to those in the recent ones, some differences occur, such as lack of crystals with patchy cores in recent products and lower An contents in crystals of historic ones. The available data allowed us to obtain information on the dynamics of the feeding system, highlighting their possible modifications over time. In particular, historically erupted magmas, generally acknowledged to be volatile-poor, may have ascended through the deep portions of the plumbing system under H 2O-undersaturated conditions at lower rates than the recent ones, recognized as more volatile-rich. Eruption triggering mechanisms from closed reservoirs in the shallow portions of the feeding system are similar for both historic and recent events, and may be generally favoured by a recharging phase of more primitive, undegassed magma or by a few episodes of important fracture opening (e.g., in response to an earthquake swarm).

Improved Dictionary-Based Code-Compression Schemes with XOR Reference for RISC/VLIW Architecture

Embedded systems are constrained by the available memory, and code-compression techniques address this issue by reducing the code size of application programs. The main challenge for the development of an effective code-compression technique is to reduce code size without affecting the overall system performance. Dictionary-based code-compression schemes are the most commonly used code-compression methods, because they can provide both good compression ratio and fast decompression. We propose an XOR-based reference scheme that can enhance the compression ratio on all the existing dictionary-based algorithms by changing the distribution of the symbols. Our approach works on all kinds of computer architecture with fixed length instructions, such as RISC or VLIW. Experiments show that our approach can further improve the compression ratio with nearly no hardware, performance, and power overheads.

A Universal Placement Technique of Compressed Instructions for Efficient Parallel Decompression

Instruction compression is important in embedded system design since it reduces the code size (memory requirement) and thereby improves the overall area, power, and performance. Existing research in this field has explored two directions: efficient compression with slow decompression, or fast decompression at the cost of compression efficiency. This paper combines the advantages of both approaches by introducing a novel bitstream placement method. Our contribution in this paper is a novel compressed bitstream placement technique to support parallel decompression without sacrificing the compression efficiency. The proposed technique enables splitting a single bitstream (instruction binary) fetched from memory into multiple bitstreams, which are then fed into different decoders. As a result, multiple slow decoders can simultaneously work to produce the effect of high decode bandwidth. We prove that our approach is a close approximation of the optimal placement scheme. Our experimental results demonstrate that our approach can improve the decode bandwidth up to four times with minor impact (less than 3%) on the compression efficiency.

Changing eruptive styles in basaltic explosive volcanism: Examples from Croscat complex scoria cone, Garrotxa Volcanic Field (NE Iberian Peninsula)

The Croscat pyroclastic succession has been analysed to investigate the transition between different eruptive styles in basaltic monogenetic volcanoes, with particular emphasis on the role of phreatomagmatism in triggering Violent Strombolian eruptions. Croscat volcano, an 11 ka basaltic complex scoria cone in the Quaternary Garrotxa Volcanic Field (GVF) shows pyroclastic deposits related both to magmatic and phreatomagmatic explosions. Lithofacies analysis, grain size distribution, chemical composition, glass shard morphologies, vesicularity, bubble-number density and crystallinity of the Croscat pyroclastic succession have been used to characterize the different eruptive styles. Eruptions at Croscat began with fissural Hawaiian-type fountaining that rapidly changed to eruption types transitional between Hawaiian and Strombolian from a central vent. A first phreatomagmatic phase occurred by the interaction between magma and water from a shallow aquifer system at the waning of the Hawaiian- and Strombolian-types stage. A Violent Strombolian explosion then occurred, producing a widespread (8 km 2), voluminous tephra blanket. The related deposits are characterized by the presence of wood-shaped, highly vesicular scoriae. Glass-bearing xenoliths (buchites) are also present within the deposit. At the waning of the Violent Strombolian phase a second phreatomagmatic phase occurred, producing a second voluminous deposit dispersed over 8.4 km 2. The eruption ended with a lava flow emission and consequent breaching of the western-side of the volcano. Our data suggest that the Croscat Violent Strombolian phase was related to the ascent of deeper, crystal-poor, highly vesicular magma under fast decompression rate. Particles and vesicles elongation and brittle failure observed in the wood-shaped clasts indicate that fragmentation during Violent Strombolian phase was enhanced by high strain-rate of the magma within the conduit.

Optimizing the degree of distension and reducing discomfort in CT colonography by means of a microprocessor interface system for air insufflation

Abstract The patients’ discomfort during CT colonography determines which method is used and its frequency of use. The discomfort is largely associated with the colon’s insufflation with gas. A system for an automatic room-air insufflation has been developed that ensures a continuous and steady air insufflation and an increase in colonic pressure and enables a relatively fast decompression. This system provides constant pressure monitoring and can alert the operator, if necessary. The degree of discomfort was evaluated for 36 patients, who were subjected to manual and automated air insufflation. The degree of the colonic distension achieved by the two methods was compared. The data analysis showed a significantly lower level of discomfort in patients with automated air insufflation. The degree of colonic distension was evaluated by comparing the diameters of similar segments of the colon, as well as by the subjective opinion of the operator. The distension with automated air insufflation was higher than that with manual air insufflation. In some cases there was a significant difference (P<0,05). In conclusion, the results show that the automatic insufflation of air at room temperature can be used to optimize CT colonography.

A decompression pipeline for accelerating out-of-core volume rendering of time-varying data

This paper presents a decompression pipeline capable of accelerating out-of-core volume rendering of time-varying scalar data. Our pipeline is based on a two-stage compression method that cooperatively uses the CPU and the graphics processing unit (GPU) to transfer compressed data entirely from the storage device to the video memory. This method combines two different compression algorithms, namely packed volume texture compression (PVTC) and Lempel-Ziv-Oberhumer (LZO) compression, allowing us to exploit both temporal and spatial coherence in time-varying data. Furthermore, it achieves fast decompression by taking architectural advantages of each processing unit: a hardware component on the GPU and a large cache on the CPU, each suited to decompress PVTC and LZO encoded data, respectively. We also integrate the method with a thread-based pipeline mechanism to increase the data throughput by overlapping data loading, data decompression, and rendering stages. Our pipelined renderer runs on a quad-core PC and achieves a video rate of 41 frames per second (fps) in average for 258x258x208 voxel data with 150 time steps. It also demonstrates an almost interactive rate of 8fps for 512x512x295 voxel data with 411 time steps.

112 Neuropathies optiques traumatiques extra-canalaires sévères : efficacité de la stratégie chirurgicale première

Despite numerous studies addressing intra-orbital traumatic optic neuropathy (TON) after facial trauma, therapeutic strategy is still unclear regarding use of corticosteroids, surgical treatment, or clinical observation alone in literature: recent studies recommend an observation period with corticoid therapy before surgical management, which is completely different from our primary urgent surgical management. Our work was designed to assess visual outcomes using this strategy. A 5-year retrospective review of surgically treated patients with TON following orbital fracture in maxillo-facial surgery and ophthalmology services in hospital. Visual acuities, visual outcomes, surgical technique and delay were recorded. Among 1053 patients undergoing surgery for orbital fracture, 20 patients experienced TON with dramatic visual loss and were surgically treated. Several intra-orbital mechanisms for visual loss were recorded. Complete visual recovery was reached in 80% when surgery occurred within 12 hours after amaurotic TON. Optic nerve decompression used mid-palpebral approach in all cases. After literature review, reported percentage of complete recovery after severe TON (i.e. with visual loss < counting fingers) vary from 10% to 55%. Our results (visual improvement > 80%) suggest that fast intra-orbital optic nerve decompression provides a better visual outcome as compared to clinical observation, primary 24- or 48-hours corticoid therapy, or delayed surgery. Primary urgent orbital decompression is an efficient strategy for severe, even amaurotic, extracanalar traumatic optic neuropathy, as compared to literature review.