Soft modes of the dielectric response in the twist–bend nematic phase and identification of the transition to a nematic splay bend phase in the CBC7CB dimer

Two collective processes resulting from distortion of the heliconical structure of the twist–bend nematic phase of an achiral dimer: one tilt mode due to distortions of the conical angle and second related to long range fluctuation of the cone phase.

Identification of Manganese Distribution Using Very Low Frequency (VLF) Method at Karangsari Village, Pengasih Sub-District, Kulonprogo Regency, DIY

Research of manganese distribution was conducted in the village of Karangsari, Pengasih sub-district, Kulonprogo Regency, DIY which is the former area exploration and exploitation of manganese. The purpose of the research is known the value of relative conductivity and the distribution of manganese. The method used very low frequency tilt mode. The tools used 2 set of T-VLF BRGM (sensor and monitor) and the data processing software are Ms. Excel and KHFILT. T-VLF operated with 2 frequencies that are 19800 Hz from Australia and 22.200 Hz from Elbino Japan. The total lines are 6 lines with 75 m space. Distance between measured points is 15 m, whereas line length is 300 m. The parameters measured from VLF method are tilt (%) and ellipticity (%). The raw data VLF is processed by Ms Excel to obtain a tilt, ellipse, fraser graph vs distance and the RAE from Karous Hjelt filter. While the results of processed by KHFILT software is the equivalent current density contour map. Relative conductivity of area research are line 1 (-10 to 10) mho/m, line 2 (-40 to 30) mho/m, line 3 (-20 to 20) mho/m, line 4 (-30 to 10) mho/m, line 5 (-40 to 30) mho/m and line 6 (-30 to 40) mho/m. The spread of manganese were in the high conductivity, toward west and east of research area with depth up to 45 m.

Studies on Local Structural Inhomogeneity and Origin of Ferroelectricity in Yttrium chromite Ceramics

ABSTRACTYCrO3 (YCO) is known to be a multiferroic with orthorhombic, Pnma, structure with center of inversion. However, the local structural inhomogeneity in this compound is believed to give rise to ferroelectric behavior. In this study we explore high temperature Raman investigations of YCO and observed that one of its Raman mode B3g (3) (CrO6 Octahedral tilt mode) softens around the structural phase transition which could be the origin of ferroelectric nature in YCO. In addition, we substitute bismuth (Bi) in YCO to understand the structural distortions that lead to local structural inhomogeneity. Besides B3g (3) mode softening with composition and high temperature studies in Y1-xBixCrO3 the study reveals the structural distortions and the structural tunability Bi offers in such systems.

Response of a Simulated Hurricane to Misalignment Forcing Compared to the Predictions of a Simple Theory

This paper compares the tilt dynamics of a mature tropical cyclone simulated with a conventional cloud model to reduced modeling results and theoretical predictions. The primary experiment involves a tropical cyclone of hurricane strength on the f plane exposed to a finite period of idealized misalignment forcing. A complementary experiment shows how the vortex responds to the same forcing when moisture and symmetric secondary circulation (SSC) are removed from the initial condition. It is found that the applied forcing excites a much stronger tilt mode in the dry nonconvective vortex than in the moist convective hurricane. The evolution of tilt in both experiments agrees reasonably well with a simple linear response theory that neglects the SSC and assumes moisture merely reduces static stability in the vortex core. An additional experiment with suspended cloud water but no substantial SSC supports the theoretical notion that reduction of static stability is sufficient to inhibit the excitation of a tilt mode. However, there is some discrepancy between theory and details of asymmetric convection in the eyewall region of the simulated hurricane. Moreover, a final experiment without moisture but with an artificially maintained secondary circulation suggests that the SSC has a nonnegligible role in reducing tilt. Diagnosis of the primary hurricane simulation further illustrates how the SSC has discernible influence over misalignment at least in the eyewall. Sensitivity of tilt dynamics to the azimuthally averaged vortex structure is briefly addressed.

On the Warm Water Volume and Its Changing Relationship with ENSO

The interannual, equatorial Pacific, 20°C isotherm depth variability since 1980 is dominated by two empirical orthogonal function (EOF) modes: the “tilt” mode, having opposite signs in the eastern and western equatorial Pacific and in phase with zonal wind forcing and El Niño–Southern Oscillation (ENSO) indices, and a second EOF mode of one sign across the Pacific. Because the tilt mode is of opposite sign in the eastern and western equatorial Pacific while the second EOF mode is of one sign, the second mode has been associated with the warm water volume (WWV), defined as the volume of water above the 20°C isotherm from 5°S to 5°N, 120°E to 80°W. Past work suggested that the WWV led the tilt mode by about 2–3 seasons, making it an ENSO predictor. But after 1998 the lead has decreased and WWV-based predictions of ENSO have failed. The authors constructed a sea level–based WWV proxy back to 1955, and before 1973 it also exhibited a smaller lead. Analysis of data since 1980 showed that the decreased WWV lead is related to a marked increase in the tilt mode contribution to the WWV and a marked decrease in second-mode EOF amplitude and its contribution. Both pre-1973 and post-1998 periods of reduced lead were characterized by “mean” La Niña–like conditions, including a westward displacement of the anomalous wind forcing. According to recent theory, and consistent with observations, such westward displacement increases the tilt mode contribution to the WWV and decreases the second-mode amplitude and its WWV contribution.