Tilt Field Research Articles

Robust estimation of structural orientation parameters and 2D/3D local anisotropic Tikhonov regularization

Understanding the orientation of geologic structures is crucial for analyzing the complexity of the earths’ subsurface. For instance, information about geologic structure orientation can be incorporated into local anisotropic regularization methods as a valuable tool to stabilize the solution of inverse problems and produce geologically plausible solutions. We introduce a new variational method that uses the alternating direction method of multipliers within an alternating minimization scheme to jointly estimate orientation and model parameters in 2D and 3D inverse problems. Specifically, our approach adaptively integrates recovered information about structural orientation, enhancing the effectiveness of anisotropic Tikhonov regularization in recovering geophysical parameters. The paper also discusses the automatic tuning of algorithmic parameters to maximize the new method’s performance. Our algorithm is tested across diverse 2D and 3D examples, including structure-oriented denoising and trace interpolation. The results indicate that the algorithm is robust in solving the considered large and challenging problems, alongside efficiently estimating the associated tilt field in 2D cases and the dip, strike, and tilt fields in 3D cases. Synthetic and field examples show that our anisotropic regularization method produces a model with enhanced resolution and provides a more accurate representation of the true structures.

Changes to mixed layer acoustic energy from spice and isopycnal tilt

Mixed layer acoustic propagation is predicted for fields that approximate two dynamically separate sources of sound speed variation: the tilting of isopycnals and “spice,” density compensated temperature and salinity changes. These fields are decomposed from a transect measurement over approximately 1000 km of the northeast Pacific Ocean. At a frequency with only one mixed layer mode, both fields contain blocking features, defined as sound speed structures less than 5 km wide that create significant acoustic energy loss. The transect shows two distinct regions where blocking features are caused by tilt or spice, indicating the acoustic importance of these dynamic processes depends on location. Statistics of mixed layer acoustic energy are investigated at two frequencies, averaging one or three mixed layer modes, both with and without blocking features. The spice field was found to produce higher loss than the tilt field. Both fields create more loss at lower frequencies when locations with blocking features were included, and more loss at higher frequencies without blocking features. Mixed layer mode amplitudes demonstrate more mixed layer modes at the higher frequency increases mode coupling, both preventing large scale acoustic energy loss and creating a more consistent loss mechanism.

Phreatic volcanic eruption preceded by observable shallow groundwater flow at Iwo-Yama, Kirishima Volcanic Complex, Japan

It is difficult to forecast phreatic eruptions because they are often characterised by an abrupt onset at shallow depths beneath volcanoes. Here we show that temporal changes in the tilt, tremor, and horizontal electric field have occurred repeatedly near the vent of a small phreatic eruption at Iwo-Yama, Kirishima Volcanic Complex, Japan. Such geophysical changes were observed 13 times, with one of these events occurring immediately before the onset of the 2018 phreatic eruption. These observations suggest that shallow hydrothermal intrusions, which are observed as tilt changes with tremors, commonly induce near-surface cold groundwater flow, which is observed as electric-field changes. Near-surface groundwater flows towards the active vent, potentially inhibiting a phreatic eruption. However, explosive phreatic eruptions occur when the intrusion is shallow and cold groundwater flow is depleted. The near-surface groundwater is key in controlling the occurrence of phreatic eruptions and can be monitored using electric-field measurements.

Viability of the mixed layer duct with observed dynamics

While the upper ocean of the north Pacific is largely mixed due to air-sea interaction, a 1000 km sea-soar transect shows the existence of stratification in the mixed layer that persists over many tens of kilometers. The effects of this stratification on mixed layer acoustic propagation depends on the sound speed differences across the different density layers, and observations show the sound speed varies rapidly both between and along the isopycnals. Acoustic models are used to separately quantify the importance of the mixed layer stratification and the density compensated sound speed variability on propagation in the mixed layer duct. The observed sound speed field is modeled as the superposition of three fields: a smooth background, the stratification field with slow isopycnal sound speed variability, and the remnant unstratified sound speed variation. The sound speed variation in the stratified mixed layer is attributed to internal waves and eddy filaments and in the unstratified field to ocean spice. Both types of observed sound speed variation significantly change, or completely block, mixed layer propagation. Examples are presented of blocking features in the tilt or spice fields separately, and where they exist only in the superposition of the two fields.

D-band strain underestimates fibril strain for twisted collagen fibrils at low strains

Collagen fibrils are the main structural component of load-bearing tissues such as tendons, ligaments, skin, the cornea of the eye, and the heart. The D-band of collagen fibrils is an axial periodic density modulation that can be easily characterized by tissue-level X-ray scattering. During mechanical testing, D-band strain is often used as a proxy for fibril strain. However, this approach ignores the coupling between strain and molecular tilt. We examine the validity of this approximation using an elastomeric collagen fibril model that includes both the D-band and a molecular tilt field. In the low strain regime, we show that the D-band strain substantially underestimates fibril strain for strongly twisted collagen fibrils — such as fibrils from skin or corneal tissue.

Light and heavy particles on a fluctuating surface: Bunchwise balance, irreducible sequences, and local density-height correlations

We study the early time and coarsening dynamics in the Light-Heavy model, a system consisting of two species of particles ($light$ and $heavy$) coupled to a fluctuating surface (described by tilt fields). The dynamics of particles and tilts are coupled through local update rules, and are known to lead to different ordered and disordered steady state phases depending on the microscopic rates. We introduce a generalized balance mechanism in non-equilibrium systems, namely $bunchwise~balance$, in which incoming and outgoing transition currents are balanced between groups of configurations. This allows us to exactly determine the steady state in a subspace of the phase diagram of this model. We introduce the concept of $irreducible~sequences$ of interfaces and bends in this model. These sequences are non-local, and we show that they provide a coarsening length scale in the ordered phases at late times. Finally, we propose a $local$ correlation function ($\mathcal{S}$) that has a direct relation to the number of irreducible sequences, and is able to distinguish between several phases of this system through its coarsening properties. Starting from a totally disordered initial configuration, $\mathcal{S}$ displays an initial linear rise and a broad maximum. As the system evolves towards the ordered steady states, $\mathcal{S}$ further exhibits power law decays at late times that encode coarsening properties of the approach to the ordered phases. Focusing on early time dynamics, we posit coupled mean-field evolution equations governing the particles and tilts, which at short times are well approximated by a set of linearized equations, which we solve analytically. Beyond a timescale set by a lattice cutoff and preceding the onset of coarsening, our linearized theory predicts the existence of an intermediate power-law stretch, which we also find in simulations of the ordered regime of the system.

Effect of peripapillary tilt direction and magnitude on central visual field defects in primary open-angle glaucoma with high myopia.

To evaluate the relationship between peripapillary tilt and visual field (VF) defects in glaucomatous eyes with axial myopia. Retrospective cross-sectional study. One hundred four eyes of 104 patients with primary open-angle glaucoma (POAG) with myopia were included (52 eyes with high myopia [HM], 26.5mm ≤ axial length [AL] < 30.0mm; and 52 eyes without HM, 24.0mm < AL < 26.5mm). The direction and magnitude of the peripapillary tilt were evaluated using optical coherence tomography. The eyes were divided into 12 groups according to the tilt directions defined by clock-hour sectors in a clockwise direction in the right eyes and in a counterclockwise direction in the left eyes. The mean deviation (MD) and central VF (CVF) values, ie, the mean threshold values of 4 paracentral points within 5 degrees of the Swedish Interactive Threshold Algorithm 30-2 test, were evaluated. The direction of the tilt was toward sector 9 (47.1%) and sector 8 (34.6%). The MD and CVF values were significantly worse (P = 0.013 and P = 0.019, respectively) in the sector 9 group than in the sector 8 group. Furthermore, the smaller peripapillary tilt magnitude in the sector 9 group was negatively correlated (P = 0.0019) with the CVF but not with the MD (P = 0.1) among the POAG eyes with HM. In contrast, the ovality index in the sector 9 group was not significantly correlated with the MD (P = 0.4) or the CVF (P = 0.36). A smaller temporal peripapillary tilt correlated with CVF defects in POAG eyes with HM. The peripapillary tilt direction and magnitude affect the CVF defect in POAG eyes with HM.

The 2010 seismovolcanic crisis at Taal Volcano (Philippines)

Typical eruptions of Taal Volcano in the Philippines are frequent and violently explosive. The last devastating phreatomagmatic eruption from 1965 to 1977 resulted in the death of about 200 persons. For this and other earlier events, no warnings of impending eruptions were issued. Since this time, volcanic crises involving episodes of seismicity, deformation, gas release, temperature change, etc., have occurred frequently. Each of these did not, but possibly could have, evolved into an explosive eruption. One such event occurred between April 2010 and March 2011. This paper reports various types of geophysical data (electric/magnetic field, ground temperature, seismicity and ground deformation) taken during this period of activity together with the current state of geophysical knowledge about the volcano in order to throw light on activity evolution. While the 2010 seismovolcanic crisis was preceded by unusual changes in electric field, ground tilting and uplift, the major signals from all data were concomitant with the evolution of the crisis. On April 20, 2010, felt earthquakes first started to occur. The numbers increased sharply after April 29 with repeated pulses of seismicity that ended finally in March 2011. Overall, we can identify three periods of seismic activity, from April 20 to August 4–8, from August 4–8 to November 18, and from November 18 to March 28, 2011. Although only a single tiltmeter was in operation, it recorded three phases of deformation that correspond generally with the pulses in seismic activity. Phase 1 appears to correspond to inflation at a depth of about 5 km just to the NW of Main Crater Lake from April 20 to June 11, 2010. This resulted in an eastward tilting of the northern flank of the volcano. This apparently triggered rapid but shallower inflation (Phase 2) in the hydrothermal region of the volcano under the northern edge of Main Crater Lake from June 11 to July 13 just to the SE of the initial deeper source as indicated by northward tilting of the volcano’s northern flank. Progressive deflation began after July 13. By March 28, 2011, the deformation state recovered to the pre-crisis level and felt seismic activity ceased. Apparent related changes in seismicity, tilt, magnetic and electric fields occur during smaller NS inflations in the Phase 3 deflation—Phase 3a (July 13 to August 4–8), Phase 3b (August 4–8 to November 18) and Phase 3c (November 18 to March 28, 2011). These likely result from interrelated stress change, fluid/gas migration and thermal activity at depth and in the hydrothermal system. The rapidity of changes in the state of the volcano over a matter of hours during this entire process indicates rapid communication occurs between processes at depth and in the hydrothermal system and this could easily result in the dramatic evolution to violent phreatic explosions with little warning.

Optical design of double-grating and double wave band spectrometers using a common CCD

A new type of optical system comprising double-grating and double wave band spectrometers is designed for atmospheric detection. The optical system can bring oxygen A band (758-778nm) and water vapor absorption band (758-880nm) on a charge-coupled device (CCD) at the same time for ultrahigh resolution spectrum measurement. Each absorbed band with three observation directions of atmospheric radiation is imaged in different positions of a common CCD. The spectral resolution is less than 0.07nm in oxygen A band (758-778nm), and the spectral resolution is less than 0.28nm in water vapor absorption band (758-880nm). Three end faces of the optical fiber are on the slit plane for each wave band, and each end face corresponds to an observation angle. The optical fiber core diameter is 600μm, the slit width is 25μm, and the slit length is 18.4mm. The principle of smile correction is analyzed. The smile of the Czerny-Turner double-grating spectrometer can be compensated by using the tilt field lens in front of the focal plane. The design results corroborate that the maximum smile of the double-grating spectrometer is 5μm and that the approach of correcting smile is effective. The stray light is analyzed, and the approaches of suppressing the stray light are proposed.

Nature inspired capacitive sensor with unique and unclonable characteristic

Background of this paper is the development of sensors showing a nature like characteristic. The sensor is able to detect excitations on inertia bases and operates capacitive. It consists of a miniaturized interdigitated electrode structure on a printed circuit board, a flexible and conductive membrane of PDMS located in a certain distance above and a certain number of steel balls fixed on top of the membrane. The steel ball distribution is random and the conductivity of the membrane is not homogeneous across the membrane. Due to this double random distribution, no sensor equals the other, although the external geometry is equal. The overall size of the sensor is 4.7mm x 4.7mm x 1.7mm. Tilt, acceleration or magnetic fields are capable of causing forces on the steel balls and therefore relative movements between the membrane and the electrode structures. Due to this movement, capacity changes of the arrangement are measurable. This paper describes besides the fabrication of conductive membranes the preparation of regarding sensors. Process technology makes cloning of the sensors impossible. Although all process steps are suited for mass production, no sensor equals the other. Measurements with these sensors prove that each sensor reacts differently to the same excitation. Calculations of the Intra-Concordance-Coefficient show the similarity of the sensors for equal excitations. On the other hand, the maximum Inter-Concordance-Coefficient reveals the differences of such sensors very clearly. Such a characteristic, i.e. equal reaction to equal excitation and an output of significantly different signals allows considering each sensor as a unique device. The sensors obviously behave like receptors in natural organisms. These unusual properties of uniqueness and impossibility to clone make the sensors very interesting for highly secure identification demands. In combination with a very simple measurement procedure, the sensors are an attractive hardware base for technical security solutions.

Observation of an Even–Odd Asymmetric Transport in High Landau Levels**Supported by the National Basic Research Program of China under Grant Nos 2014CB920904 and 2013CB921702, the National Natural Science Foundation of China under Grant Nos 11174340, 11174357, 91221203 and 91421303, the Strategic Priority Research Program B of the Chinese Academy of Sciences under Grant No XDB07010100, the Gordon and Betty Moore

Magnetotransport experiments including tilt fields are performed on ultrahigh mobility L-shaped Hall-bar samples of GaAs/AlGaAs quantum wells. The low-temperature longitudinal resistivity (ρxx) data demonstrate that a striking even–odd asymmetric transport exists along the [] direction at half filling in N ≥ 2 high Landau levels. Although the origin for the peculiar even–odd asymmetry remains unclear, we propose that the coupling strength between electrons within the same Landau level and between the neighboring two Landau levels should be considered in future studies. The tilt field data show that the in-plane field can suppress the formation of both bubble and stripe phases.

Postural stabilization in cerebral palsy adults in response to combined support surface tilt and visual field motion

Introduction The relationship between visual field motion and intersegmental behavior during postural destabilization was explored. Individuals with cerebral palsy (CP) were separated through a rod and frame test into those with visual dependence (VD) or independence (VI) to determine whether reliance upon an allocentric reference frame alters the postural organization. We hypothesized that VD reduces intersegmental motion so that whole body responses reflect visual flow direction and velocity; VI would reflect visual flow parameters only at the head. Material and methods Eleven individuals (31 ± 10.5 years) with spastic CP who were VD and 11 with VI, and 18 VI individuals (32 ± 11.5 years) with typical development (TD), stood on either a stationary or 3° dorsiflexion tilted force platform within an immersive, 3-wall virtual environment. Subjects stood quietly for 30 s with eyes closed while the visual scene remained stationary or rotated 15°/s and 30°/s in the pitch-up or pitch-down directions. Motion analysis data were collected and strategies of segmental stabilization were identified with an anchoring index. Group differences and visual and platform conditions were examined with a mixed model, repeated measures ANOVA and simple contrasts (corrected α = 0.01) to determine the effect of condition against stationary visual field motion. Results Either platform or visual motion produced a head locked to upper trunk stabilizing strategy across all subjects (P = 0.015). When the supporting surface was tilted, VI individuals stabilized the thorax to the hip (P = 0.02) whereas VD individuals stabilized the thorax to global space (P = 0.0125). Discussion Both biomechanical and sensory environment motion evoked head to trunk stabilization. CP individuals with visual dependence stabilized the upper trunk to an allocentric rather than egocentric reference frame, thus increasing their potential for instability. Possible causes of an increased reliance on an allocentric frame of reference could be a perceptual inability to suppress external feedback, or diminished signals from internal feedback.

Determining the Lipid Tilt Modulus by Simulating Membrane Buckles.

Lipid tilt affects the energy of membrane deformations on scales comparable to the membrane's thickness. The surface divergence of the tilt field creates a local spontaneous curvature, while tilt itself is quadratically penalized with a strength given by the tilt modulus. Traditionally, this modulus is determined by measuring the power spectrum of lipid orientation fluctuations. Here we present a novel approach which does not rely on fluctuations but instead exploits the fact that curvature gradients induce a tilt field. Its implementation extends a technique previously developed by us for localizing the position of the pivotal plane in buckling simulations, which quantifies the lipid imbalance across segments cut out from a complete buckle. Lipid tilt affects this count in a predictable way, and the signal can be quantified well enough to back out the tilt modulus-at no additional cost and with about 5% precision for not too coarse models. We apply our technique to three lipid models of very different resolution: the highly coarse grained Cooke model, and two versions of DMPC, using both the (less highly coarse grained) MARTINI and the (united atom) Berger force field. For Cooke, we find an effective bilayer tilt modulus of 29 ± 9 pN/nm, and for the less generic DMPC lipid, we find 115 ± 6 pN/nm for MARTINI and 39 ± 2 pN/nm for Berger, both in reasonable agreement with existing studies for these models. We also show that the position of the pivotal plane for Berger DMPC lies just below the glycerol backbone-unlike for MARTINI DMPC, where this plane lies closer to the middle of the lipid.

基于倾斜场镜的C-T成像光谱仪优化设计

Residual smile limits the application of Czerny;Turner plane grating spectrometer in the imaging spectrometer. In this paper, different from the traditional method of smile correction based on prism, a method is proposed, which is based on the tilt field mirror. The field curve is corrected, at the same time, the different wavelength slit images in different regions of the field lens are corrected, and the other optical properties of the system are not changed. The Czerny Turner imaging spectrometer slit is 7.8 millimeter length and 0.016 millimeter wide, spectral range from 0.31 to 0.5 microns, spectral resolution 0.4 nanometers, the object focal length 70 millimeters, 1:1 magnification. Optimization design results, MTF over 0.8, RMS spot radius less than 9 microns, the relative smile less than 0.2%, meet the design requirements. It shows that the method can be used in the systems with weak signal and low transmittance optical glass. © 2016, Chinese Optical Society. All right reserved.

A strategy to explore the topography-driven distortions in the tilt field induced by a spherical pressure source: the case of Mt Etna

A strategy to explore the topography-driven distortions in the tilt field induced by a spherical pressure source: the case of Mt Etna

Electroclinic effect in nematic liquid crystals: The role of molecular and environmental chirality

The electroclinic (EC) effect is the tilt of the optical axis of a liquid crystal in the plane perpendicular to an applied electric field. Chirality plays a key role for its emergence. Based on the molecular and phase symmetry we derive a molecular expression for the EC coefficient, the material property that quantifies the linear coupling between tilt and electric field, in nematic liquid crystals. Modeling the relevant molecular properties (shape, electric dipole moment, and polarizability) with atomic resolution, we calculate the EC coefficient for prototype molecular structures. We demonstrate that molecular chirality, needed for the occurrence of the EC effect in nematics with a uniform director, is not a necessary requirement in the presence of a twisted director. Our results show that in the latter case conformational deracemization, invoked to explain recent experiments, is not the only mechanism.

Poroelastic model for induced stresses and deformations in hydrocarbon and geothermal reservoirs

Fluid migration and heat transport result in changes in pore pressure and temperature within a reservoir, which can induce stresses and deformations in the reservoir and the bounding rock system through poroelastic and thermoelastic couplings. Analytical and semi-analytical solutions for investigating the induced stresses and deformations are therefore extremely useful when applied to both predicting and monitoring the reservoir volume changes and associated subsurface and surface deformation. The poroelastic and thermoelastic eigenstrains are used here to characterize the pore pressure change and temperature variation, respectively, in the reservoir. The induced stresses and deformations are then obtained by using the single- and double-inclusion models, and are expressed in terms of the Galerkin vector stress function, which is related to the corresponding eigenstrains in a straightforward way. The difference in mechanical properties between the reservoir and the bounding rocks is accounted for using the theory of inhomogeneous inclusions. The effect of the reservoir shape, elastic properties, and the distribution of pore pressure change within the reservoir on the surface deformation has been investigated. The magnitude and pattern of the induced surface tilt have been compared with those produced by a hydraulic fracture. The analytical expressions obtained here for the displacement and tilt fields can serve as a useful forward model for monitoring and mapping hydraulic fractures, subsurface fluid migration and heat transport associated with injection or production of fluid into or from a reservoir by surface deformation-based monitoring techniques, such as tiltmeter monitoring.

ν=5/2Fractional Quantum Hall Effect at 10 T: Implications for the Pfaffian State

We report on the magnetotransport (including tilt fields) around Landau level filling factor nu=5/2 in a high-purity modulation-doped GaAs/AlGaAs quantum well with twice the electron density of standard samples. A quantized 5/2 Hall plateau is observed at B approximately = 10 T, with an activation gap approximately 125 mK; the plateau can persist up to approximately 25 degree tilt field. This finding is discussed in the context of a proposed Moore-Read Pfaffian (or anti-Pfaffian) wave function being a possible ground state at 5/2. The tilt fields induce a background resistance at 5/2 that could be either isotropic or anisotropic, depending simply on the in-plane magnetic field direction with respect to the GaAs crystalline axis. Such data indicate a substantial coupling between the 5/2 collective phases and the GaAs crystal.

Crustal Tilt Fields and Propagation Velocities Associated with Earthquakes†

Summary Tilt steps similar to strain steps have been observed for earthquakes with magnitudes ranging from 2 to 8 and distances ranging from 10 to 12 000 km. Tilt-step propagation velocities from the hypocentre to the station of 1.2–3.8 km s-1 have been observed in addition to those corresponding to the arrival time of teleseismic S waves. Tilt directions, amplitudes, and velocities observed at several stations simultaneously for the same earthquake are internally consistent and are likely to depend on the tectonic environment of the station in addition to the focal mechanism. The low velocity of 1.2 km s-1 is consistent with plastic-wave propagation. Other velocities are close to the Rayleigh wave short-period group velocity over continental paths. Theoretical tilt amplitudes for fixed epicentral distance, focal depth, and stress system depend logarithmically on the magnitude, with a possible cut-off. However, observed tilt amplitudes are too large when compared to existing theoretical dislocation models for a single-layered homogeneous isotropic elastic crust. Alternative solutions in terms of more realistic crustal layering and including plastic deformation under pre-existing tectonic stress probably could account for a number of observations.

Cover Picture: On the Origin of the “Giant” Electroclinic Effect in a “De Vries”‐Type Ferroelectric Liquid Crystal Material for Chirality Sensing Applications (ChemPhysChem 6/2009)

AbstractThe cover picture shows characteristics of a new ‘de Vries’‐type ferroelectric liquid crystal in which the ferroelectric transition is an order–disorder transition where the directions of molecular tilt inside a smectic layer order into a certain direction. Since the rod‐like molecules (drawn as cylinders) are tilted in the paraelectric SmA* (with random tilt directions) as well as in the ferroelectric SmC* phase, the ferroelectric transition is connected with a rather weak contraction of the smectic layer thickness (even though the optical tilt θ reaches values of about 25°). On page 890, F. Giesselmann et al. show that this new ferroelectric material exhibits a remarkably weak temperature dependence of its giant electroclinic effect (the coupling between tilt and elelctric field) in the SmA* phase. The origin of this striking electroclinic effect is the co‐occurrence of a ‘de Vries’‐type ordering with a weak first‐order tilting transition.magnified image