Plateau Shape Research Articles

Radiocarbon chronology of Iron Age Jerusalem reveals calibration offsets and architectural developments

Reconstructing the absolute chronology of Jerusalem during the time it served as the Judahite Kingdom's capital is challenging due to its dense, still inhabited urban nature and the plateau shape of the radiocarbon calibration curve during part of this period. We present 103 radiocarbon dates from reliable archaeological contexts in five excavation areas of Iron Age Jerusalem, which tie between archaeology and biblical history. We exploit Jerusalem's rich past, including textual evidence and vast archaeological remains, to overcome difficult problems in radiocarbon dating, including establishing a detailed chronology within the long-calibrated ranges of the Hallstatt Plateau and recognizing short-lived regional offsets in atmospheric 14C concentrations. The key to resolving these problems is to apply stringent field methodologies using microarchaeological methods, leading to densely radiocarbon-dated stratigraphic sequences. Using these sequences, we identify regional offsets in atmospheric 14C concentrations c. 720 BC, and in the historically secure stratigraphic horizon of the Babylonian destruction in 586 BC. The latter is verified by 100 single-ring measurements between 624 to 572 BC. This application of intense 14C dating sheds light on the reconstruction of Jerusalem in the Iron Age. It provides evidence for settlement in the 12th to 10th centuries BC and that westward expansion had already begun by the 9th century BC, with extensive architectural projects undertaken throughout the city in this period. This was followed by significant damage and rejuvenation of the city subsequent to the mid-eight century BC earthquake, after which the city was heavily fortified and continued to flourish until the Babylonian destruction.

Thermonuclear explosions as Type II supernovae

We consider a binary stellar system in which a low-mass (0.6M⊙) carbon-oxygen white dwarf (WD) merges with the degenerate helium core (0.4M⊙) of a red giant. We analyse the outcome of a merger within a common envelope (CE). We predict the observational properties of the resulting transient. We find that the double detonation of the WD, being a pure thermonuclear explosion and embedded into the hydrogen-rich CE, has a light curve with the distinct plateau shape of a supernova (SN) Type IIP, with a duration of about 40 days. We find five observed SNe IIP (SN 2004dy, SN 2005af, SN 2005hd, SN 2007aa, and SN 2008bu) that match theV-band light curve of our models. Hence, we show that a thermonuclear explosion within a CE might be mistakenly identified as a SN IIP, believed to be an outcome of a core-collapse neutrino-driven explosion of a massive star. We discuss a number of diagnostics that may help to distinguish this kind of thermonuclear explosion from a core-collapse SN.

Simulation of a sessile nanofluid droplet freezing with an immersed boundary-lattice Boltzmann model

The freezing process of a sessile nanofluid droplet has been reported to behave differently from a pure sessile water droplet in terms of freezing dynamics and the final shape of the ice droplet. When nanoparticles are added to the water droplet, instead of forming a pointed tip on the top, the completely frozen droplet exhibits a flat plateau shape. To investigate this unique scenario, we developed a lattice Boltzmann (LB) model that combines the multiphase solidification model (MSM) with the immersed boundary method (IBM). The MSM is based on our previous work of simulating the freezing of a pure droplet, while the IBM is used to handle the interaction forces between the suspended particles and the different phases in the freezing droplet. Using this LB model, we succeeded in simulating the formation process of the frozen plateau shape. The simulation takes into account the dynamics of the dispersed particles, including their expulsion from the propagation freezing front and their segregation, which brings the liquid water to the edge. We compared the simulated freezing shape profiles with the experimental images and found that the shape forms in a similar manner. We then used the developed model to explore more cases, considering the effects of droplet contact angles and particle volume concentration. Results show that the distribution of particles and final droplet height depend on the surface wettability, as the freezing front exhibits a concave/convex shape on hydrophilic/hydrophobic surfaces, resulting in different particle separation distributions on the freezing front interface. Furthermore, our simulation results confirm the experimental conclusion that the plateau size on the frozen top increases with particle concentration and appears to be independent of the initial droplet contact angle.

Energy-absorption analyses of grooved Al-sheet stacks using modified split Hopkinson pressure bar

This study suggests that stacks of thin aluminum (Al) sheets with fine rectangular or triangular grooves are effective materials for energy absorption. The energy-absorbing performance of these materials was evaluated using a modified split Hopkinson pressure bar (SHPB). Two important energy-absorbing parameters, impact momentum (I) and maximum impact acceleration (amax), were measured from stress-time (σ-t) curves. These parameters were found to vary with groove shape, groove cavity fraction, and specimen thickness. Both I and amax showed a continuous decrease as the specimen thickness increased from 6 to 18 mm or as the groove cavity fraction increased from 29–30% to 38–39%. Analyzing the σ-t curve shapes revealed that the triangular grooved specimens exhibited broad-peak shaped curves, resulting in a greater reduction in I compared to the broadened plateau shape observed in the rectangular grooved specimens. Taking into account both I and amax, the overall energy-absorbing performance of the triangular grooved specimens was better than that of the rectangular grooved specimens. Notably, in the triangular grooved specimens with a high cavity fraction, the triangular embossing intruded into the groove cavities, resembling a 'zipper' mechanism, further enhancing the effectiveness of energy absorption. This study presents a promising approach for developing various grooved Al sheet stacks that exhibit reduced amax and I by strategically exploring suitable groove shapes, cavity fractions, and stack thicknesses, especially in dynamically compressed artillery environments.

Shape variation and flat plateau formation of a frozen nanofluid droplet

Droplet freezing is a phenomenon of great interest, not only from a fundamental perspective, but also due to its significant contributions to various industrial and ecological processes. Despite the extensive research on pure water droplet freezing, the freezing dynamics of nanofluid droplets have not been investigated to the same extent. It has been observed that frozen nanofluid droplets exhibit a distinctive flat plateau shape at their apex, in contrast to the pointed tip observed in pure water droplets. Our experimental investigation has revealed that when the vertical velocity of nanofluid droplet's freezing front is lower than a critical value, nanoparticles are expelled from the freezing liquid and aggregate at the freezing front to form a particle layer. This layer causes a deviation between the motion direction of the tri-junction line and the interface curve of the unfrozen liquid, resulting in an increased angle growth and the formation of a plateau at the top of the frozen droplet. The critical freezing velocity was found to be independent of the contact angle but showed a slight increase with subfreezing temperature. As the subfreezing temperature rises, the flat plateau of the frozen droplet transitions to a pointed tip. To further explore the freezing dynamics of nanofluid droplets, we conducted a statistical analysis of the cone angle at the apex of the frozen droplets. Our results indicates that in most cases, the cone angle is greater than the universal value observed for pure water droplets. And the cone angle is effected by the droplet volume size and subfreezing temperature.

Correlation between Local Structure and Reaction Mechanism in Disordered Rock-Salt-Type Lithium–Manganese Oxides

First-principles (FP) calculations of disordered rock-salt-type lithium–manganese oxides were performed by assuming a quasi-random structure model with the composition of Li16Mn16O32. The effects of randomness in the crystal structure and the changes in local atomic configurations during the Li extraction process on electronic structures, phase stability, and electrochemical properties were investigated by the FP calculations. The calculations indicate that the randomness of local atomic configurations, which originates from the disordered structure, makes it possible for Mn and O sites to take on a variety of electronic states. Analyses of densities of states, magnetic moments of Mn atoms, and Bader charges indicate the possibility that not only Mn but also oxygen atoms contribute to the redox reaction. The migration of Li and Mn is found to appear from octahedral to tetrahedral sites at a high state of charge. The FP calculations suggest that the change in local atomic configurations and electronic structures causes the transition in voltage profiles from sloping to 3 V plateau shape as the cycle progresses, which is characteristic of spinel-related positive electrode materials.

Morphological Study of the Mandibular Lingula and Antilingula by Cone-Beam Computed Tomography.

The patterns of the lingula and antilingula are crucial surgical reference points for ramus osteotomy. Cone-beam computed tomography (CBCT) provides three-dimensional images, and patient radiation dose is significantly lower for CBCT than for medical CT. The morphology of the mandibular lingula and antilingula of ninety patients (180 sides) were investigated using CBCT. The lingula were classified as having triangular, truncated, nodular, and assimilated shapes. The antilingula were classified as having hill, ridge, plateau, and plain shapes. The patients' sex, skeletal patterns (Classes I, II, and III), and right and left sides were recorded. The most to least common lingula shapes were nodular (37.8%), followed by truncated (32.8%), triangular (24.4%), and assimilated (5%). The most to least common antilingulae were hill (62.8%), plain (18.9%), plateau (13.9%), and ridge (4.4%) patterns, respectively. The lingula and antilingula had identical patterns on both sides in 47 (52.2%) and 46 patients (51.1%), respectively. Sex and skeletal pattern were not significantly correlated to lingula and antilingula shapes. No significant correlation was observed between lingula and antilingula shapes.

Association of Inflammation, Ectopic Bone Formation, and Sacroiliac Joint Variation in Ossification of the Posterior Longitudinal Ligament

Ossification of the posterior longitudinal ligament (OPLL) is considered a multifactorial condition characterized by ectopic new bone formation in the spinal ligament. Recently, its connections with inflammation as well as sacroiliac (SI) joint ankylosis have been discussed. Nevertheless, whether inflammation, spinal ligament ossification, and SI joint changes are linked in OPLL has never been investigated. In this study, whole-spinal computed tomography and serum high-sensitive C-reactive protein (hs-CRP) levels were obtained in 162 patients with cervical OPLL. Ossification lesions were categorized as plateau and hill shapes. Accordingly, patients were divided into plateau-shaped (51 males and 33 females; mean age: 67.7 years) and hill-shaped (50 males and 28 females; mean age: 67.2 years) groups. SI joint changes were classified into four types and three subtypes, as previously described. Interactions among ossification shapes, hs-CRP levels, and morphological changes in the SI joint were investigated. The plateau shape was more common in the vertebral segments (59.5%), compared to the hill shape, which was predominant in the intervertebral regions (65.4%). Serum hs-CRP levels in the plateau-shaped group (0.11 ± 0.10 mg/dL) were significantly higher than those in the hill-shaped group (0.07 ± 0.08 mg/dL). SI joint intra-articular fusion was the main finding in the plateau-shaped group and showed significantly higher hs-CRP levels compared to the anterior para-articular bridging, which more frequently occurred in the hill-shaped group. Our findings suggested a possible inflammation mechanism that might contribute to the new bone formation in OPLL, particularly the plateau shape.

Topological piezoelectric response in moiré graphene systems

We theoretically study the piezoelectric effects in moir\`e graphene systems. Since the strain couples to the electrons in the system as a pseudo vector potential, which has opposite signs for the $K$ and $K'$ valleys of graphene, its effects on the two valleys with opposite Chern numbers do not cancel out, but adds up. As a result, some components of the piezoelectric tensor in these systems, which typically have non-trivial topology in their flat bands, are nearly quantized in terms of the valley Chern numbers. Such a conclusion is verified by numerical calculations of the in-plane piezoelectric response of hBN-aligned twisted bilayer graphene, twisted bilayer-monolayer graphene, and twisted double bilayer graphene systems using both continuum model and atomistic tight-binding model. We find that by tuning the vertical displacement field and/or twist angle, which may induce gap closures between the flat bands and remote bands in these systems, plateau shapes of the piezoelectric response are obtained, with abrupt jumps across the topological phase transitions. We propose that such nearly quantized piezoelectric response may serve as a direct experimental probe for the valley Chern numbers of the flat bands in moir\'e graphene systems.

Effect of bone morphology of the tibia plateau on joint line convergence angle in medial open wedge high tibial osteotomy

BackgroundChange in the joint line convergence angle (JLCA) of the knee after high tibial osteotomy (HTO) is difficult to predict accurately. Given that any change in JLCA is intra-articular, the shape of the articular surface, including the bone morphology of the proximal tibia, may affect the alignment of the knee joint postoperatively. The purpose of this study was to investigate the relationship between the shape of the tibial plateau and postoperative alignment of the knee joint by focusing on changes in JLCA.MethodsOne hundred and nine knees that underwent HTO were retrospectively reviewed. The shape of the tibial plateau was classified based on the slope of the medial and lateral articular surfaces as depressed, flat (within 3 degrees), or convex (pagoda-like). The relationship between the shape of the tibial plateau and radiological parameters was investigated.ResultsThe shape of the tibial plateau was depressed in 38 knees, flat in 52 knees, and pagoda-like in 19 knees. There was a moderate correlation between the postoperative change in JLCA and the preoperative hip-knee-ankle angle for knees with a pagoda-shaped tibial plateau (r = 0.56) but not for the other two shapes.ConclusionsThese findings suggest that knees with marked varus deformity before HTO are likely to show more change in JLCA postoperatively if the tibial plateau is pagoda-shaped than if it has a depressed or flat shape. The advantage of focusing on the bone morphology of the proximal tibia is that surgeons can easily perform visual assessment using preoperative radiograph.

FTIR in situ measurement of swelling and CO2 sorption in acrylic polymers at high CO2 pressures

A FTIR (Fourier Transform Infrared) microscope combined to a CO2 high-pressure cell has been used to determine simultaneously the CO2 uptake and the swelling of acrylic polymer systems, precursors of CO2-foamed polymers (PMMA), a triblock copolymer (MAM) and a PMMA/10 wt% MAM blend. Samples were saturated with supercritical CO2 (scCO2) up to high pressures (5, 10, 30 MPa) at 40 °C and 130 °C. The behavior upon pressure increase is indeed different at the two temperatures in the three systems, showing either a linear or a plateau shape. These two regimes are analyzed in view of literature. Addition of 10 wt% MAM copolymer led to a significant increase of CO2 uptake (23% for neat PMMA to 42% for the blend, 40 °C, 30 MPa). Such data are useful to find out, before foaming, the best routes to produce low-density and nanoporous polymer foams, using scCO2 as foaming agent.

Structure and Stress Field of the Lithosphere Between Pamir and Tarim

AbstractThe Pamir plateau protrudes ∼300 km between the Tajik‐ and Tarim‐basin lithosphere of Central Asia. Whether its salient location and shape are caused by forceful indentation of a promontory of Indian mantle lithosphere is debated. We present a new local‐seismicity and focal‐mechanism catalog, and a P‐wave velocity model of the eastern part of the collision system. The data suggest a south‐dipping Asian slab that overturns in its easternmost segment. The largest principal stress at depth acts normal on the slab and is orientated parallel to the plate convergence direction. In front (south) of the Asian slab, a volume of mantle with elevated velocities and lined by weak seismicity constitutes the postulated Indian mantle indenter. We propose that the indenter delaminates and overturns the Asian slab, underthrusts the Tarim lithosphere along a compressive transform boundary, and controls the location and shape of the Pamir plateau.

On the micro-PIV accuracy and reliability utilizing non-Gaussian particle images

Optical investigations of the dynamics of concentrated suspensions, such as in blood flows (Fitzgibbon et al. in Biophys J 108(10):2601–2608, 2015. http://doi/org/10.1016/j.bpj.2015.04.013) or slurry flows (Li et al. in Ocean Eng 163(October 2017):691–705, 2018. http://doi/org/10.1016/j.oceaneng.2018.06.046), are challenging due to reduced optical accessibility. Furthermore, the suspension particle image size can strongly deviate from the optimal particle image size for PIV measurements. Optical accessibility can be achieved by refractive index matching of surface labelled suspension particles. This results in particle images that are transparent in the particle image centre, but fluoresce at the particle image rim, resulting in ring-shaped particle images. In the present study, the influence of the particle image size on the cross-correlation result of such ring-shaped particle images is compared with Gaussian and plateau-shaped particle images. Particles of Gaussian image shape result from fully labelled particles with small image diameters and are commonly used in PIV measurements. Such particles are also utilized for the determination of the continuous phase velocities in the experimental part of the present study. With increasing image diameter, fully labelled particles are observed to assume plateau-shaped particle images. Monte Carlo simulations of synthetically generated images show that ring-shaped particle images have a superior behaviour, i.e. they assume a reduced displacement estimation error for noisy as well as for noise-free image data, compared to Gaussian and plateau-shaped particle images. This is also true for large particle image diameters when particle images are intersected at interrogation window borders or when different values of nonzero particle image displacements are considered. The detectability is similar for all three particle image shapes as long as particles do not intersect with the interrogation window border. Interestingly, for intersected particles of large image diameter, ring-shaped particle images show a slightly improved detectability compared to particle images of Gaussian and plateau shape. Furthermore, the detectability is insensitive against a nonzero particle image displacement. The usage of refractive index matched, ring-shaped particle images results in a good optical accessibility of the suspension. This allows to perform simultaneous cross-correlation evaluations on large ring-shaped particle images and fluid tracers with Gaussian particle images that are two orders of magnitude smaller compared to suspension particle images. Velocity measurements are taken on a suspension containing 5 vol% surface labelled, refractive index matched 60 upmu hbox {m} polymethylmethacrylate (PMMA) particles. Simultaneously, upmuPIV measurements of the carrier liquid flow are performed utilizing 1.19 upmu text {m} fluorescent polystyrene (PS) particles. Measurement results reveal a parabolic shape of the velocity profiles of both phases with a mean slip velocity of 7.4% at the position of maximum streamwise velocity in a 580 upmu text {m} high trapezoidal channel. An error analysis confirms the presence of these slip velocities within a 68.5% confidence interval. A measurement uncertainty in the order of magnitude of {mathcal {O}}(10^{-1} mathrm{px}) is reached for both fluid tracers and suspension particles. Overall, the present study demonstrates theoretically and experimentally that the usage of suspension particles with ring-shaped images is superior compared to Gaussian and plateau-shaped particle images of the same size. Additionally, the present study demonstrates that the usage of ring-shaped particle images allows to investigate suspension bulk dynamics by measuring velocity fields of both the suspended and the continuous phase simultaneously and with an overall uncertainty that is in the same order of magnitude as for standard upmuPIV measurements.Graphic abstract

Repair of a Complete Radial Tear of the Lateral Meniscus

Background: Recognizing and repairing a lateral meniscus complete radial tear is critical, as this tear pattern makes the meniscus nonfunctional for load sharing of axial forces, and the convex shape of the lateral tibial plateau increases contact pressure. Indications: The diagnosis of a lateral meniscus complete radial tear was supported by joint effusion, lateral joint line tenderness, positive McMurray test, and magnetic resonance imaging findings. Arthroscopy confirmed the complete radial tear. Technique Description: During the procedure, a self-capturing suture passer was used to pass a size 0 high-strength suture through the meniscus. To start the repair, the free ends of the suture were passed from top to bottom on both sides of the tear. These free ends were then crossed on the bottom of the meniscus to create an X configuration and passed from the bottom to top slightly further back from the first suture passes. A spinal needle and a chia were used from outside-in to create a side-to-side suture across the tear to reinforce the repair, and a knot was then tied on the outer capsule. The chia was used once again to shuttle the size 0 sutures to the exterior portion of the knee and the knots were tied on top of the capsule. Results: Postoperatively, patients are 25% weightbearing with a 0° to 90° range of motion restriction for 6 weeks, with no deep squatting for 3 months. With an isolated radial tear repair, the patient can expect to return to sport by 5 months. Radial tear repair outcomes demonstrate reduced lateral meniscus extrusion, complete meniscus healing in 86.4% of patients, and significantly improved International Knee Documentation Committee, Lysholm, and Tegner scores. Discussion/Conclusion: Repairing a complete radial tear of the lateral meniscus restores the function of the meniscus. This surgical technique provides a high rate of complete meniscus healing and excellent patient satisfaction.

Freezing of a nanofluid droplet: From a pointy tip to flat plateau

Understanding the dynamics during freezing of nanofluid droplets is of importance from both fundamental and practical viewpoints. It is known that a universal pointy tip is formed on the top of a frozen water droplet [Marín et al., Phys. Rev. Lett. 113(5), 054301 (2014)]. Here, we report that the formation of a pointy tip is broken down due to the presence of nanoparticles; instead, the top of a frozen nanofluid droplet exhibits a flat plateau shape and such a plateau becomes larger at higher particle concentrations. We show that the phenomenon of such shape changes in freezing nanofluid droplets is universal, independent of contact angle, droplet volume, particle size, and particle material. We propose an analytical model to attribute the plateau formation to a capillary driven compensating flow due to segregated particles moving along the freezing interface.

An X-Ray- and SZ-bright Diffuse Source toward M31: A Local Hot Bridge

Abstract We report a large-scale ( ) X-ray-bright and Sunyaev–Zeldovich (SZ)-bright diffuse enhancement toward M31, which might be a Local Hot Bridge connecting the Milky Way (MW) with M31. We subtract the Galactic emission from the all-sky O vii and O viii emission-line measurement survey, and find that the emission of these two ions is enhanced within projected around M31. The mean emission enhancements are 5.6 ± 1.3 L.U., and 2.8 ± 0.6 L.U. for O vii and O viii, respectively ( for both ions). We also extract the SZ signal around M31, which suggests a surface brightness y of , an enhancement (and a best fit of ). These three measurements trace the hot gas with a temperature , showing similar plateau shapes (flat within , and zero beyond ≈30°). A single-phase assumption leads to a temperature of , which is determined by the O vii/O viii line ratio. Combining X-ray and SZ measurements, we suggest that this feature is unlikely to be the hot halo around M31 (too massive) or in the MW (too high pressure and X-ray bright). The plateau shape may be explained by a cylinder connecting the MW and M31 (the Local Hot Bridge). We constrain its length to be about 400 kpc, with a radius of 120 kpc, a density of , and a metallicity of . The baryon mass is , and the oxygen mass is about , which contribute to the baryon or metal budget of the Local Group.

Modulation induced transport signatures in correlated electron waveguides

Recent transport experiments in spatially modulated quasi-1D structures created on top of LaAlO_33/SrTiO_33 interfaces have revealed some interesting features, including phenomena conspicuously absent without the modulation. In this work, we focus on two of these remarkable features and provide theoretical analysis allowing their interpretation. The first one is the appearance of two-terminal conductance plateaus at rational fractions of e^2/he2/h. We explain how this phenomenon, previously believed to be possible only in systems with strong repulsive interactions, can be stabilized in a system with attraction in the presence of the modulation. Using our theoretical framework we find the plateau amplitude and shape, and characterize the correlated phase which develops in the system due to the partial gap, namely a Luttinger liquid of electronic trions. The second observation is a sharp conductance dip below a conductance of 1\times e^2/h1×e2/h, which changes its value over a wide range when tuning the system. We theorize that it is due to resonant backscattering caused by a periodic spin-orbit field. The behavior of this dip can be reliably accounted for by considering the finite length of the electronic waveguides, as well as the interactions therein. The phenomena discussed in this work exemplify the intricate interplay of strong interactions and spatial modulations, and reveal the potential for novel strongly correlated phases of matter in systems which prominently feature both.

Experimental Study on Overburden Deformation Evolution under Mining Effect Based on Fiber Bragg Grating Sensing Technology

In order to study the regularity of overburden deformation and mining pressure changes in the stope. Take the geological conditions of Hanglaiwan coal mine in Yushen mining area as the background, a 3000 mm×1340 mm×200 mm physical similar material model was established in laboratory. Eight fiber Bragg grating sensors were embedded in the model, used to monitor the movement and deformation of the overburden key stratum and the change of mining abutment pressure in real time and then to determine the influencing factors and strain transfer coefficients of the fiber grating through theoretical analysis and calibration experiments. The results show the following. (1) The changes in value, position, and shape of the strain can reflect the dynamic evolution process of bending deformation, breaking, and rotation of the key strata. When the key layer breaks for the first time, the strain curve shows a peak shape; when the key layer breaks periodically, the strain curve of the fiber grating sensor showed a plateau shape for a period of time. (2) The strain curve has a good corresponding relationship with the change in supporting pressure. When the strain curve of the fiber Bragg grating sensor was at the trough stage, the abutment pressure was at the peak stage, with the increase of sensor buried height, and the supporting pressure and the strain value had a linear relationship within the range of the advanced abutment pressure. The conclusion shows that the fiber Bragg grating sensor monitoring technology has good effect on the internal strain and key supporting pressure monitoring of the overburden in the model test; it provides new monitoring methods and means for the model tests.

Strong-field ionization of homonuclear diatomic molecules using orthogonally polarized two-color laser fields

Using the improved molecular strong-field approximation we investigate high-order above-threshold ionization (HATI) of homonuclear diatomic molecules by an orthogonally polarized two-color (OTC) laser field. The OTC field components are linearly polarized, having the relative phase $\ensuremath{\varphi}$ and frequencies $r\ensuremath{\omega}$ and $s\ensuremath{\omega}$ ($r$ and $s$ are integers and $\ensuremath{\omega}$ is the fundamental frequency). The molecule is aligned in the laser-field polarization plane. We have found that for even values of $r+s$ the HATI spectra obey the ${C}_{2}$ rotational symmetry regardless of the relative phase, component intensities, and molecular orientation, while the spectra calculated for odd values of $r+s$ and for certain molecular orientations exhibit the reflection symmetry. We have also explored the symmetry transformations of the HATI spectra for a shift of the relative phase by ${180}^{\ensuremath{\circ}}$ and for various values of $r$ and $s$. These symmetries are illustrated by numerical examples of the HATI spectra of the ${\mathrm{N}}_{2}$ molecule. For particular values of the laser-field parameters, internuclear distance, and the electron emission angle we observed minima in the ionization yield as a function of the molecular orientation angle and the photoelectron energy. These minima are well fitted with the curve obtained using a condition for the destructive interference minima which we derived for an arbitrary laser field and applied to the OTC field. The relative phase between the OTC field components can be used to control the length and shape of the HATI plateau, as well as the appearance of these destructive interference minima.

Fermi surface electron–hole instability of the (TMTSF)2PF6 Bechgaard salt revealed by the first-principles Lindhard response function

We report the first-principles DFT calculation of the electron–hole Lindhard response function of the (TMTSF)2PF6 Bechgaard salt using the real triclinic low-temperature structure. The Lindhard response is found to change considerably with temperature. Near the 2kF spin density wave (SDW) instability it has the shape of a broad triangular plateau as a result of the multiple nesting associated with the warped quasi-one-dimensional Fermi surface. The evolution of the 2kF broad maximum as well as the effect of pressure and deuteration is calculated and analyzed. The thermal dependence of the electron–hole coherence length deduced from these calculations compares very well with the experimental thermal evolution of the 2kF bond order wave correlation length. The existence of a triangular plateau of maxima in the low-temperature electron–hole Lindhard response of (TMTSF)2PF6 should favor a substantial mixing of q-dependent fluctuations which can have important consequences in understanding the phase diagram of the 2kF SDW ground state, the mechanism of superconductivity and the magneto-transport of this paradigmatic quasi-one-dimensional material. The first-principles DFT Lindhard response provides a very accurate and unbiased approach to the low-temperature instabilities of (TMTSF)2PF6 which can take into account in a simple way 3D effects and subtle structural variations, thus providing a very valuable tool in understanding the remarkable physics of molecular conductors.