Right-handed Region Research Articles

Comprehensive Evaluation of Rock Mechanical Properties and in-situ Stress in Tight Sandstone Oil Reservoirs

Comprehensive research on reservoir rock mechanics and in-situ stress properties combined with petrophysical experiments, logging models and numerical simulation is an important means to achieve efficient development of tight sandstone oil reservoirs. In this study, a large number of rock mechanics and acoustic experiments, full-wave train array acoustic wave tests, hydraulic fracturing data and three-dimensional finite element simulations were used to study the rock mechanical properties and in-situ stress characteristics of continental tight oil reservoirs in the Yanchang Formation. The results show that under uniaxial conditions, the tight sandstone samples mainly suffer from tensional ruptures. With the increase of confining pressure, the tight sandstone samples undergo obvious shear ruptures. When the confining pressure is loaded to 35 MPa, a typical vertical shear fracture will be formed. The hydraulic fracturing calculation results show that the in-situ stress state of the target layer satisfies σv (vertical principal stress)>σH (maximum horizontal principal stress)>σh (minimum horizontal principal stress). Based on the results of rock mechanics and acoustic tests, we have constructed the dynamic and static mechanical parameter conversion models of tight oil reservoirs and the logging interpretation model of current in-situ stress. Furthermore, the finite element method is used to simulate the three-dimensional structural stress field of the target layer. The simulations show that the horizontal principal stress distribution in the work area is consistent with the applied environmental stress. The σH of the target layer is mainly distributed in 32–50 MPa, and the σh is mainly distributed in 20–34 MPa. Both σH and σh are relatively high in the southern uplift of the work area; among them, σH is usually greater than 44 MPa, and σh is usually greater than 24 MPa. The northern part of the study area developed several grooved areas with relatively low stress values. The regions with high stress values are often distributed in bands, which may be related to the compression caused by the deformation of the strata. For shear stress, left-handed and right-handed regions usually alternate with each other. However, the extent of the left-handed area in the southern uplift area is larger than that of the right-handed area, indicating that the tight oil reservoirs in the study area are mainly affected by left-handed activities.

The first non-helical Aib-containing hexapeptide: The crystal structure of Z-Gly-Aib-Gly-Aib-Gly-Aib-OtBu.

The synthetic peptide Z-Gly-Aib-Gly-Aib-Gly-Aib-OtBu was crystallized from a mixture of ethyl acetate and n-hexane. The crystals belong to the centrosymmetric space group Pbca. There are three molecules in the asymmetric unit. The three molecules differ mainly in the Z-group conformation. The first Gly residue adopts a fully extended conformation, residues 2 and 3 lie in the left-handed helical region, residues 4 and 5 in the right-handed helical region, and residue 6 again in the left-handed helical region of the Ramachandran plot. There are only two of four possible intramolecular hydrogen bonds formed, namely, between Aib4 and Gly1 forming a β-turn of type III' and between Aib6 and Gly3 forming a β-turn of type I. The inverted molecules (by space group symmetry) lie in the regions with opposite handedness and form β-turns of type III and I'. In contrast to all known long synthetic and naturally occurring Aib-containing peptides that fold as 310 - or α-helix, Z-(Gly-Aib)3 -OtBu folds in a quite flat structure from which only the protecting groups bulge out.

Terahertz Quasi-TEM Mode Tunable Composite Right/Left-Handed Leaky-Wave Antennas Using Graphene-Based Coplanar Waveguides

A novel and simple scheme for the realization of the terahertz (THz) fundamental-mode composite right/left-handed leaky-wave antennas (CRLH LWAs) is proposed. The CRLH LWAs are reconstructed by graphene-based coplanar waveguide transmission line (CPW TL) unit cells. Their signal lines are grounded by narrow graphene strips to achieve the shunt inductances, and parallel-plates are periodically added along the signal line to obtain the series capacitances. The propagation properties of the LWAs are detailed. The LWAs have both left-handed (LH) and right-handed (RH) regions by varying frequency. By numerical simulations, the LWAs are verified. Their backfire-to-endfire beam-steering capabilities through frequency scanning are confirmed. Compared with the CRLH LWAs at THz proposed in previous literature, the graphene-based CRLH LWAs operate in the Quasi-TEM mode. They possess low fabrication, excitation, and impedance matching difficulty. They also show the possibility of integration with other micro-devices. With the application of graphene, the LWAs exhibit strong tunable characteristics that conventional CRLH LWAs are absent. Therefore, the proposed CRLH LWAs have great potential applications for the development of beam-steering antennas at THz.

Classical and quantal aspects of Minkowski's four-momentum in analog gravity

The electrodynamic theory of continuous media is probably the most convenient platform when trying to construct analog gravity theories. Quite naturally, this topic has gained considerable interest. One peculiar but not so very known feature in this context is the unconventional behavior of radiation energy and momentum in cases where superluminal fluid velocities are encountered, what, as known, is a major ingredient in analog gravity theories. These peculiar features are intimately connected with the spacelike character of Minkowski's four-momentum in electrodynamics. Here, we first consider an artificial model in which a Kerr-induced superluminal region is created in the right-hand region ($z>0$) in a left-moving, originally subluminal, fluid. We analyze the behavior of energy density, Poynting vector, and momentum density, and calculate the force on the artificial black hole horizon. Also, we delve into quantal aspects, looking for eventual production of particles associated with the sudden creation of the horizon, finding, however, that no particles are predicted to occur. The present paper continues a previous investigation by the author on the same topic, in Phys. Rev. A {\bf 100}, 032109 (2019). The subject as such is closely related to the famous Abraham-Minkowski problem.

Double‐layer metasurface‐based low profile broadband X‐band microstrip antenna

In this paper, a novel technology based on double-layer metasurfaces is proposed in order to broaden the bandwidth of microstrip antennas, which has been verified in X-band linearly polarised and circularly polarised antennas. Referring to the conventional metasurface antenna that employs slot-coupled feeding, these designs add an extra metasurface between the radiation patch and the ground plane so as to establish dual resonance modes, TM10 and TM20. Following the adoption of the composite right/left-handed transmission lines principle, this technique aims to adjust the propagation constant in the right-hand region by introducing parallel inductors and capacitors to widen the dual resonant frequencies' interval, thereby realising a broadband antenna. In addition, the interlayer metasurface may also be utilised as a director to balance the E-field of the radiation patch. A linearly polarised double-layer metasurface antenna with a size of 0.8 0.8 0.058 (wavelength in free space at the centre frequency) is filled with F4B substrate with a dielectric constant of 2.2. It finally realises an impedance matching bandwidth (VSWR 2) from 8.41 to 11.67 GHz, occupying about 32.47 of the centre frequency. This circularly polarised antenna attains both an impedance matching bandwidth of 32.44 (i.e. 8.29–11.5 GHz) and an axial-ratio bandwidth of 19.72 (i.e. 9.6–11.7 GHz).

Alternate backward and forward waves in a coupled nonlinear transmission line

In this work, we investigate backward and forward waves in a coupled nonlinear discrete electrical lattice. It is made of several of the well-known Noguchi electrical transmission line that are transversely coupled to one another by an inductor $$L_{2}$$. Based on the linear dispersion law, we show that the behavior of this model depends on the wave frequency that it propagates. It can adopt purely right-handed, purely left-handed or composite right-/left-handed behaviors without changing its structure. It appears that for fixed line’s parameters, the network is right-handed for low frequencies and becomes left-handed for high frequencies. It also appears that the increase of the coupling linear inductor induces a decrease of the width of the bandpass filter in the left-handed region while it increases its width in the right-handed region. By means of a method based on the semi-discrete limit and in suitably scaled coordinates, we derive a two-dimensional NLS equation governing the propagation of slowly modulated waves in the network. The exact transverse bright solitary solution is found. Using this solution, we investigate numerically both right-handed and left-handed behaviours of the system and show how to manipulate the coupling inductor to modify the width and the motion of the bright solitary voltage signals in the network.

Deletion of Subtelomeric Regions in the Linear Chromosome of Variants Isolated from Streptomyces avermitilis NBRC 14893T

Background: Streptomyces avermitilis is an actinomytcete producing avermectins and the complete genome sequence of S. avermitilis K139 was determined in 2003. In our previous study, we have revealed that S. avermitilis NBRC 14893T harbors two extra secondary metabolite-biosynthetic gene clusters (smBGCs), com and ptx, which are not present in strain K139. Methods: To determine the genomic loci encoding com and ptx gene clusters, we carried out whole genome sequencing for S. avermitilis NBRC 14893T and ATCC 31267T by the SMRT DNA sequencing technology. Results: Genome sizes of strains NBRC 14893T and ATCC 31267T were 10.5 Mb, which were 1.4 Mb-larger than that of strain K139. Chromosomes of these type strains included extra 1.1 Mb-long right-hand region that is not present in the K139 genome and encodes com and ptx gene clusters. Variants without ptx and/or com were spontaneously obtained by isolating single colonies from strain NBRC 14893T. Genome analysis of the variants indicated that the chromosome was step-by-step deleted from subtelomeric region(s) in strains NBRC 14893T. Conclusions: These results suggest instability of the linear chromosome of S. avermitilis. This study provides useful experimental materials and their genome information to clue the mechanism for genomic instability in the genus Streptomyces.

Chameleon’s behavior of modulable nonlinear electrical transmission line

We show that modulable discrete nonlinear transmission line can adopt Chameleon’s behavior due to the fact that, without changing its appearance structure, it can become alternatively purely right or left handed line which is different to the composite one. Using a quasidiscrete approximation, we derive a nonlinear Schrödinger equation, that predicts accurately the carrier frequency threshold from the linear analysis. It appears that the increasing of the linear capacitor in parallel in the series branch induced the selectivity of the filter in the right-handed region while it increases band pass filter in the left-handed region. Numerical simulations of the nonlinear model confirm the forward wave in the right handed line and the backward wave in the left handed one.

The first N-terminal unprotected (Gly-Aib)n peptide: H-Gly-Aib-Gly-Aib-OtBu.

Glycine (Gly) is incorporated in roughly half of all known peptaibiotic (nonribosomally biosynthesized antibiotic peptides of fungal origin) sequences and is the residue with the greatest conformational flexibility. The conformational space of Aib (α-aminoisobutyric acid) is severely restricted by the second methyl group attached to the Cα atom. Most of the crystal structures containing Aib are N-terminal protected. Deprotection of the N- or C-terminus of peptides may alter the hydrogen-bonding scheme and/or the structure and may facilitate crystallization. The structure reported here for glycyl-α-aminoisobutyrylglycyl-α-aminoisobutyric acid tert-butyl ester, C16H30N4O5, describes the first N-terminal-unprotected (Gly-Aib)n peptide. The achiral peptide could form an intramolecular hydrogen bond between the C=O group of Gly1 and the N-H group of Aib4. This hydrogen bond is found in all tetrapeptides and N-terminal-protected tripeptides containing Aib, apart from one exception. In the present work, this hydrogen bond is not observed (N...O = 5.88 Å). Instead, every molecule is hydrogen bonded to six other symmetry-related molecules with a total of eight hydrogen bonds per molecule. The backbone conformation starts in the right-handed helical region (and the left-handed helical region for the inverted molecule) and reverses the screw sense in the last two residues.

Leaky-Wave Antennas Using Negative-Refractive-Index Transmission-Line Metamaterial Supercells

Leaky-wave antennas (LWAs) are designed based on supercells which are expanded versions of conventional negative-refractive-index transmission line (NRI-TL) unit cells. In the proposed LWAs with NRI-TL supercells, the number and values of inductors are reduced by half, decreasing the complexity of their design and reducing the Ohmic loss, which increases the antenna gain and efficiency. Compared with conventional NRI-TL unit cells, NRI-TL supercells operate over narrower bandwidth while showing proper Bloch impedance behavior over both left-hand (LH) and right-hand (RH) regions, leading to broadband impedance matching. Using coplanar waveguide (CPW) technology, closed-stopband LWAs based on NRI-TL supercells are designed, and their performance compared with that of the conventional unit cell LWAs. Finally, by using CPW supercells with a backing ground and vias, high-gain LWAs with sharp beams and suppressed backlobes are designed and realized.

Dual-Band Circularly Polarized Patch Antenna With First Positive and Negative Modes

A dual-band circularly polarized (CP) patch antenna having a first positive ( +1) mode and negative ( -1) mode is proposed in this letter. The +1 mode is a half-wavelength mode in the right-handed (RH) region, and the -1 mode is induced by a composite right/left-handed (CRLH) transmission line (TL) in the left-handed (LH) region. In order to realize CP properties, a trimmed square patch antenna and a 2 × 2 triangle mushroom antenna are employed, respectively, and the two antennas are combined to obtain small size. The proposed antenna has a single feed and a single-layered substrate even though it contains two antennas. Measurements show that the antenna has CP bandwidths of 2.879-2.901 GHz at the low band and 3.822-3.829 GHz at the high band. Finally, peak gains of 6.26 and 6.97 dBic are obtained and radiation efficiencies of 82% and 65% are measured at each band, respectively.

Handedness Inversions in a Simple Model of Fibrillar Superstructure Formation

Aggregation of misfolded proteins into amyloid fibrils has been linked to several disorders such as Alzheimer's disease, or diabetes mellitus type II. Factors such as low pH, high temperature, and agitation have been recognized to accelerate this process in vitro. Amyloid fibrils from unrelated proteins share similar features on different levels of structural hierarchy: e.g. cross-beta structure, and tendency of individual fibrils to form intertwined chiral superstructures with defined morphological handedness and optical activity.In this work we investigate this phenomenon numerically with the use of coarse-grained numerical model of chiral fibrils. The aggregate morphologies, chirality and stability are then analyzed as a function of temperature and initial pitch of the fibrils. The simulations show the existence of a critical pitch below which the handedness of the aggregates is opposite to that of the constituting fibrils. We also observe and analyze the process of spontaneous chirality inversion of individual fibrils in the aggregate. This inversion is accompanied by a helical wave propagation along the fibril axis, with a kink separating left-haded and right-handed regions moving along the chain. The frequency of this process is strongly dependent on the initial pitch of the fibrils with a local maximum near the critical pitch.

Chirality inversions in self-assembly of fibrillar superstructures: a computational study

The formation of aggregates of helical fibrils is analyzed numerically. The aggregate morphology, chirality and stability are studied as a function of temperature and helical pitch of individual fibrils. The simulations show the existence of a critical pitch above which the handedness of the aggregates is opposite to that of the constituting fibrils. We also observe and analyze the process of spontaneous chirality inversion of individual fibrils within the aggregates. This inversion is accompanied by a helical wave propagating along the fibril axis, with a kink separating left-handed and right-handed regions moving along the fibril. The frequency of this process is strongly dependent on the initial pitch of the fibrils with a local maximum near the critical pitch.

Leaky-Wave Radiation Behavior From a Double Periodic Composite Right/Left-Handed Substrate Integrated Waveguide

A double periodic composite right/left-handed ( DP-CRLH ) substrate integrated waveguide (SIW) is proposed based on the transmission line theory. A new leaky-wave radiation is observed at low frequency below the left-handed passband in addition to the composite right/left-handed property. First, the equivalent circuit of the proposed structure is analyzed, and dispersion characteristics are obtained including the expression for the cutoff frequencies. It is noted that transmission lines double periodically loaded with either alternate capacitances, or alternate inductances will contribute the new leaky-wave behavior. Next, SIW implementation of a DP-CRLH transmission line is designed and illustrated with simulated and experimentally demonstrated results. The electric field distribution plots are extracted from a full-wave simulation tool and exhibit the forward and backward wave propagation in the new leaky-wave region and the typical left-handed region, respectively. Finally, a compact leaky-wave antenna based on the DP-CRLH SIW is designed, and the radiation characteristics are tested and demonstrated to exhibit forward radiation at the new leaky-wave region from 5.2 to 5.8 GHz (covering IEEE 802.11a band) and frequency scanning from backward to forward directions in the left-handed and conventional right-handed region from 12.6 to 17.8 GHz.

DESIGN OF LEAKY WAVE ANTENNA WITH COMPOSITE RIGHT-/LEFT-HANDED TRANSMISSION LINE STRUCTURE FOR CIRCULAR POLARIZATION RADIATION

This paper presents a design procedure for the generation of circular polarization (CP) from the composite right/left handed (CRLH) transmission line (TL) with a coupled inter-digit structure and an inductive stub. The Ex and Ey components are generated from the parallel stubs and the flngers, respectively. The 90 - -phase difierence can be obtained by optimizing the dimension of the unit cell. In addition, the suitable amplitude ratio of jExj and jEyj for CP generation is obtained by selecting a suitable position of the CRLH-TL between both edges of the ground. As a result, a CP with a measured bandwidth of 30.5% for an axial ratio (AR) of < 3dB in the boresight direction is obtained. Using the behavior in both the left-handed (LH) and right-handed (RH) frequency regions, a scanning angle of the main beam of approximately 30 - can be obtained by varying the frequency between 2.58GHz and 2.99GHz. Furthermore, the principle of CP generation is discussed.

A New Insight into the Radiation Mechanism of Fast and Slow Traveling Waves

In this paper, a new explanation on the radiation mechanisms of slow and fast traveling waves is presented. The effective radiation sections that give rise to the far-field radiation of the traveling-wave structure are found and studied for the cases of slow and fast waves, respectively. A composite right/left-handed transmission line that can support both of the slow and fast waves in left- and right-handed regions is employed as an example. Based on the uniform line-source assumption, an ideal model of traveling-wave current with the same dispersion behavior as that of the CRLH structure is proposed and used to demonstrate the radiations of slow and fast waves in physical sense. This new understanding of the radiation mechanism of traveling-wave structures is useful to the applications of traveling-wave antennas.

A Simple CRLH LWA Circuit Condition for Constant Radiation Rate

A simple analytical condition for the radiation resistance and conductance (R, G) of an equivalent composite right/ left-handed (CRLH) leaky-wave antenna unit-cell is pro- posed to achieve a constant radiation rate. Similar to the CRLH balanced condition, which allows a smooth phase transition from the left-handed to the right-handed frequency regions, the pro- posed R-G condition provides a continuous and smooth transition of the radiation losses from the left-handed to the right-handed frequency region. Moreover, this condition also solves the phase fluctuations that traditionally occur around the CRLH transition frequency due to real radiation losses. Several numerical results are included to confirm the uniform radiation rate obtained when the new derived condition is used.

A Left-Handed Transmission Line Composed of Two Waveguides with Stubs

A new structure of a waveguide-type left-handed transmission line is proposed. It is composed of two rectangular waveguides with many stubs. One waveguide is put on another waveguide symmetrically. When one mode with odd electric field distribution is excited, the stubs work as open stubs and the mode propagates with very small loss. Guided regions of the left-handed mode and a right-handed mode are discussed using an approximate equivalent circuit. Tuning the structure parameters, the band gap between the two regions can be removed, and the wave propagates continuously from the left-handed frequency regions to the right-handed frequency region. The transmission line is applied to a leaky waveguide. It is confirmed experimentally that the beam angle of the radiation wave changes from the backward to the forward directions.

Chondroid Syringoma of the Hand: A Rare Localization

Chondroid syringoma is a rare benign neoplasm of the sweat glands that usually occurs in the head and neck region. We describe a 18-year-old male patient with a benign chondroid syringoma that occurred at an unusual site, leading to compression symptoms of the ulnar nerve causing symptoms at the hypothenar region of the right hand. Although it is a rare tumor at an unusual site, it should be included in the differential diagnosis of the hand tumors.

Conformational Manifold of α-Aminoisobutyric Acid (Aib) Containing Alanine-Based Tripeptides in Aqueous Solution Explored by Vibrational Spectroscopy, Electronic Circular Dichroism Spectroscopy, and Molecular Dynamics Simulations

Replacement of the alpha-proton of an alanine residue to generate alpha-aminoisobutyric acid (Aib) in alanine-based oligopeptides favors the formation of a 3(10) helix when the length of the oligopeptide is about four to six residues. This research was aimed at experimentally identifying the structural impact of an individual Aib residue in an alanine context of short peptides in water and Aib's influence on the conformation of nearest-neighbor residues. The amide I band profile of the IR, isotropic and anisotropic Raman, and vibrational circular dichroism (VCD) spectra of Ac-Ala-Ala-Aib-OMe, Ac-Ala-Aib-Ala-OMe, and Ac-Aib-Ala-Ala-OMe were measured and analyzed in terms of different structural models by utilizing an algorithm that exploits the excitonic coupling between amide I' modes. The conformational search was guided by the respective 1H NMR and electronic circular dichroism spectra of the respective peptides, which were also recorded. From these analyses, all peptides adopted multiple conformations. Aib predominantly sampled the right-handed and left-handed 3(10)-helix region and to a minor extent the bridge region between the polyproline (PPII) and the helical regions of the Ramachandran plot. Generally, alanine showed the anticipated PPII propensity, but its conformational equilibrium was shifted towards helical conformations in Ac-Aib-Ala-Ala-OMe, indicating that Aib can induce helical conformations of neighboring residues positioned towards the C-terminal direction of the peptide. An energy landscape exploration by molecular dynamics simulations corroborated the results of the spectroscopic studies. They also revealed the dynamics and pathways of potential conformational transitions of the corresponding Aib residues.