Asymmetric Polarization Research Articles

After the “Master Theory”: Downs, Schattschneider, and the Rebirth of Policy-Focused Analysis

Drawing on the pioneering work of Anthony Downs, political scientists have tended to characterize American politics as a game among undifferentiated competitors, played out largely through elections, with outcomes reflecting how formal rules translate election results into legislative votes. In this perspective, voters, campaigns, elections, and the ideological distribution of legislators merit extensive scrutiny. Other features of the political environment—most notably, the policies these legislators help create and the interest groups that struggle over these policies—are deemed largely peripheral. However, contemporary politics often looks very different than the world described by Downs. Instead, it more closely resembles the world depicted by E. E. Schattschneider—a world in which policy and groups loom large, the influence of voters is highly conditional, and the key struggle is not over gaining office but over reshaping governance. Over the last twenty years, a growing body of scholarship has emerged that advances this corrective vision—an approach we call “policy-focused political science.” In this framework, politics is centrally about the exercise of government authority for particular substantive purposes. Such exercises of authority create the “terrain” for political struggle, profoundly shaping both individual and group political behavior. More important, because policies can be so consequential, they also serve as the “prize” for many of the most enduring political players, especially organized interest groups. The payoffs of a policy-focused perspective include a more accurate portrayal of the institutional environment of modern politics, an appreciation for the fundamental importance of organized groups, a better understanding of the dynamics of policy change, and a more accurate mapping of interests, strategies, and influence. These benefits are illustrated through brief examinations of two of the biggest changes in American politics over the last generation: asymmetric partisan polarization and the growing concentration of income at the top.

Co-evolution between an endosymbiont and its nematode host: Wolbachia asymmetric posterior localization and AP polarity establishment.

While bacterial symbionts influence a variety of host cellular responses throughout development, there are no documented instances in which symbionts influence early embryogenesis. Here we demonstrate that Wolbachia, an obligate endosymbiont of the parasitic filarial nematodes, is required for proper anterior-posterior polarity establishment in the filarial nematode B. malayi. Characterization of pre- and post-fertilization events in B. malayi reveals that, unlike C. elegans, the centrosomes are maternally derived and produce a cortical-based microtubule organizing center prior to fertilization. We establish that Wolbachia rely on these cortical microtubules and dynein to concentrate at the posterior cortex. Wolbachia also rely on PAR-1 and PAR-3 polarity cues for normal concentration at the posterior cortex. Finally, we demonstrate that Wolbachia depletion results in distinct anterior-posterior polarity defects. These results provide a striking example of endosymbiont-host co-evolution operating on the core initial developmental event of axis determination.

High-performance ionic diode membrane for salinity gradient power generation.

Salinity difference between seawater and river water is a sustainable energy resource that catches eyes of the public and the investors in the background of energy crisis. To capture this energy, interdisciplinary efforts from chemistry, materials science, environmental science, and nanotechnology have been made to create efficient and economically viable energy conversion methods and materials. Beyond conventional membrane-based processes, technological breakthroughs in harvesting salinity gradient power from natural waters are expected to emerge from the novel fluidic transport phenomena on the nanoscale. A major challenge toward real-world applications is to extrapolate existing single-channel devices to macroscopic materials. Here, we report a membrane-scale nanofluidic device with asymmetric structure, chemical composition, and surface charge polarity, termed ionic diode membrane (IDM), for harvesting electric power from salinity gradient. The IDM comprises heterojunctions between mesoporous carbon (pore size ∼7 nm, negatively charged) and macroporous alumina (pore size ∼80 nm, positively charged). The meso-/macroporous membrane rectifies the ionic current with distinctly high ratio of ca. 450 and keeps on rectifying in high-concentration electrolytes, even in saturated solution. The selective and rectified ion transport furthermore sheds light on salinity-gradient power generation. By mixing artificial seawater and river water through the IDM, substantially high power density of up to 3.46 W/m(2) is discovered, which largely outperforms some commercial ion-exchange membranes. A theoretical model based on coupled Poisson and Nernst-Planck equations is established to quantitatively explain the experimental observations and get insights into the underlying mechanism. The macroscopic and asymmetric nanofluidic structure anticipates wide potentials for sustainable power generation, water purification, and desalination.

Theoretical characterization of highly efficient porphyrazin dye sensitized solar cells

Density functional theory (DFT) and time-dependent DFT (TD-DFT) methodologies have been applied in an attempt to improve the performance of the dye YD2-o-C8 which is characterized by 11.9–12.7 % efficiencies. We aimed at narrowing the band gap of YD2-o-C8 to extend the light harvesting region to near IR. This was done through replacing the porphyrin macrocycle by the tetraazaporphyrin (porphyrazin) macrocycle, so that the performances of the suggested cells could be improved with Ti38O76, (TiO2)60, SiC, ZrO2, and GaP semiconductor electrodes. The effects of modifying the central macrocycle on cell performance are confirmed in terms of FMOs, energy gaps, electrode (VB and CB) edges, density of states (DOS), MEPs, dipole moments, IP, EA, reorganization energies, UV–Vis absorption, ΦLHE, Φinjection, and life times of the excited states. Replacing porphyrin macrocycle by porphyrazin macrocycle resulted in charge separated states, unidirectional charge transfer, narrower band gaps, increase of DOS nearby Fermi levels, asymmetric polarization, delocalization of the negative charges near the anchoring groups, efficient electron injection, suppressing macrocycle aggregation, active dye regeneration, longer life times of the excited states, and inhibited dye recombination. Co-sensitizers are suggested for near IR sensitization to improve the photo-to-current conversion efficiency. Size ranges: for dyes (0.1–1 nm), and for pore diameters of a dye sensitized mesoporous film of TiO2 (2–50 nm).

Ideological Moderates Won’t Run: How Party Fit Matters for Partisan Polarization in Congress

Scholars have focused on elite-level and mass-level changes to explain partisan polarization in Congress. This article offers a candidate entry explanation for the persistence of polarization and the rise in asymmetric polarization. The central claim is that ideological conformity with the party—what I call party fit—influences the decision to run for office, and I suggest that partisan polarization in Congress has discouraged ideological moderates in the pipeline from pursuing a congressional career. I test this hypothesis with a survey of state legislators and with ideology estimates of state legislators who did and did not run for Congress from 2000 to 2010. I find that liberal Republican and conservative Democratic state legislators are less likely to run for Congress than those at the ideological poles, though this disparity is especially pronounced among Republicans. The findings provide an additional explanation for recent patterns of polarization in Congress.

Electronic simulation of the supported liquid membrane in electromembrane extraction systems: Improvement of the extraction by precise periodical reversing of the field polarity

In order to understand the limitations of electromebrane extraction procedure better, a simple equivalent circuit has been proposed for a supported liquid membrane consisting of a resistor and a low leakage capacitor in series. To verify the equivalent circuit, it was subjected to a simulated periodical polarity changing potential and the resulting time variation of the current was compared with that of a real electromembrane extraction system. The results showed a good agreement between the simulated current patterns and those of the real ones. In order to investigate the impact of various limiting factors, the corresponding values of the equivalent circuit were estimated for a real electromembrane extraction system and were attributed to the physical parameters of the extraction system. A dual charge transfer mechanism was proposed for electromembrane extraction by combining general migration equation and fundamental aspects derived from the simulation. Dual mechanism comprises a current dependent contribution of analyte in total current and could support the possibility of an improvement in performance of an electromembrane extraction by application of an asymmetric polarity changing potential. The optimization of frequency and duty cycle of the asymmetric polarity exchanging potential resulted in a higher recovery (2.17 times greater) in comparison with the conventional electromebrane extraction. The simulation also provided more quantitative approaches toward the investigation of the mechanism of extraction and contribution of different limiting factors in electromembrane extraction. Results showed that the buildup of the double layer is the main limiting factor and the Joule heating has lesser impact on the performance of an electromebrane extraction system.

Asymmetric simultaneous phase-inversion cross-polarization in solid-state MAS NMR: Relaxing selective polarization transfer condition between two dilute spins

Double cross polarization (DCP) has been widely used for heteronuclear polarization transfer between 13C and 15N in solid-state magic-angle spinning (MAS) NMR. However, DCP is such sensitive to experimental settings that small variations or deviations in RF fields would deteriorate its efficiency. Here, we report on asymmetric simultaneous phase-inversion cross polarization (referred as aSPICP) for selective polarization transfer between low-γ 13C and 15N spins. We have demonstrated through simulations and experiments using biological solids that the asymmetric duration in the simultaneous phase-inversion cross polarization scheme leads to efficient polarization transfer between 13C and 15N even with large chemical shift anisotropies in the presence of B1 field variations or mismatch of the Hartmann–Hahn conditions. This could be very useful in the aspect of long-duration experiments for membrane protein studies at high fields.

Cycle Slip Compensation with Polarization Block Coding for Coherent Optical Transmission: Two-dimensional phases constellation corresponds to a slip state

Cycle slip (CS) compensation is a critical technique for nondifferential coded coherent optical transmission. By monitoring the sparse, asymmetric polarization block-coded symbol mapped signal phases of two orthogonal polarizations, the CS can be estimated from a relatively short stretch of symbols (unit). Simulation shows that the polarization block coding-based method compensates CS and improves the Q-factor by 1 dB or more compared to differential coding.

Asymmetric bistable reflection and polarization switching in a magnetic nonlinear multilayer structure

Optical properties of one-dimensional photonic structures consisting of Kerr-type nonlinear and magnetic layers under the action of an external static magnetic field in the Faraday geometry are investigated. The structure is a periodic arrangement of alternating nonlinear and magnetic layers (a one-dimensional photonic crystal) with one of the layers doubled to create a defect where periodicity is violated. Strong enhancement of nonreciprocity is observed at the frequencies of the defect modes, where linearly polarized light incident from one side of the structure undergoes polarization rotation upon reflection, while light reflected from the other side has its polarization unchanged. Using the nonlinear transfer matrix calculations in the frequency domain, it is demonstrated that defect resonances in the nonlinear reflection spectra undergo bending, resulting in polarization bistability of reflected light. This bistability is shown to result in abrupt switching between linear polarization of the output reflected light when the input intensity is varied. This switching is confirmed in finite-difference time-domain simulations, and its hysteresis character is established.

Compact asymmetric metamaterial circular polarization transformer based on twisted double split-ring resonator structure

In this paper, a compact asymmetric metamaterial circular polarization transformer using twisted double square split-ring resonator was proposed and investigated experimentally and numerically. This compact structure can convert an incident linearly y-polarized (x-polarized) wave propagation along the −z (+z) direction to the transmitted right-hand circular polarization (RCP) and left-hand circular polarization (LCP) at 7.3 and 8.3 GHz, respectively. The difference in level between the transmitted waves with LCP and RCP can reach more than 35 dB at the resonant frequencies. The experiment results are in good agreement with the numerical results. The surface current distributions on the structure are analyzed to illustrate this linear to circular transformation phenomenon.

Alumina Membrane with Hour‐Glass Shaped Nanochannels: Tunable Ionic Current Rectification Device Modulated by Ions Gradient

A new alumina membrane with hour‐glass shaped nanochannels is reported using the double‐side anodization method and the subsequently in situ pore opening procedure, which is applied to develop the tunable ionic current rectification devices that were modulated by ions gradient. By regulating the pH gradient, tunable ionic current rectification properties which are mainly dependent on the asymmetric surface charge density or polarity distribution on the inner walls of the nanochannels can be obtained. The enhanced ionic current rectification properties were presented due to the synergistic effect of the voltage driven ion flow and diffusion driven ion flow with the application of pH and electrolyte concentration gradients. Therefore, such specific alumina nanochannels would be considered as a promising candidate for building bioinspired artificial ion channel systems.

Carbon-coated LiCrTiO4 electrode material promoting phase transition to reduce asymmetric polarization for lithium-ion batteries

In this work, carbon-free and carbon-coated spinel LiCrTiO4 oxides were synthesized by a conventional solid state reaction. The lithium-ion diffusion coefficient and electronic conductivity of prepared electrode materials were systematically investigated using the galvanostatic intermittent titration technique (GITT), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The rate performances of the prepared materials were evaluated by galvanostatic charge-discharge. Carefully comparing the charge-discharge polarization potential of both materials, we unexpectedly discovered that the pristine LiCrTiO4 electrode demonstrated asymmetric polarization during the charging-discharging process, which is possibly attributed to the nonuniform electron conductivity between the endmember of a two-phase reaction, whereas carbon coating could level this phenomenon. Additionally, using an asymmetric core-shell model from the microscopic point of view can easily explain this common phenomenon. Meanwhile, this new research perspective can be extended to other active materials in lithium ion batteries.

Applying sampling theories to attitude learning in a virtual school class environment

According to sampling theories of attitude formation, evaluative learning depends on the sampling in the environment. We investigated teachers’ student evaluations in a simulated school class. Two experiments were designed to test distinct implications of experience-sampling models. While the model advanced by Fazio, Eiser, and Shook (2004) and Denrell (2005) led to the prediction of a negativity effect through asymmetric depolarization, another model (Fiedler, 1996) suggested a positivity effect through asymmetric polarization. Findings supported the latter contention. The selective tendency to oversample good students while neglecting weaker students was not radical enough to prevent the correction of negative impressions, precluding a negativity effect. Instead, extended selective sampling led to gradually increasing polarization of positive impressions, and facilitated detection of positive performance changes. While these findings can be reconciled with the Fazio–Denrell model, they highlight the crucial role of auxiliary psychological assumptions about attitude learning, as distinguished from the formal model itself.

Optical near-field–mediated polarization asymmetry induced by two-layer nanostructures

We demonstrate that a two-layer shape-engineered nanostructure exhibits asymmetric polarization conversion efficiency thanks to near-field interactions. We present a rigorous theoretical foundation based on an angular-spectrum representation of optical near-fields that takes account of the geometrical features of the proposed device architecture and gives results that agree well with electromagnetic numerical simulations. The principle used here exploits the unique intrinsic optical near-field processes associated with nanostructured matter, while eliminating the need for conventional scanning optical fiber probing tips, paving the way to novel nanophotonic devices and systems.

Regulation of asymmetric cell division and polarity by Scribble is not required for humoral immunity

The production of protective antibody requires effective signalling of naive B cells following encounter with antigen, and the divergence of responding B lymphocytes into distinct lineages. Polarity proteins have recently been proposed as important mediators of both the initial B cell response, and potentially of asymmetric cell division. Here we show that, although polarity proteins of the Scribble complex, Scribble, Dlg1 and Lgl1, are expressed and polarized during early B cell activation, their deficiency has no effect on the in vivo outcome of immunization or challenge with influenza infection. Furthermore, we find a striking correlation in the differentiation outcome of daughters of single founder B cells in vitro. Taken together, our results indicate that B cell differentiation does not require polarity proteins of the Scribble complex, and the findings do not support a role for asymmetric cell division in B cell activation and differentiation.

EB1, p150Glued, and Clasp1 control endothelial tubulogenesis through microtubule assembly, acetylation, and apical polarization

AbstractVascular tube morphogenesis requires the establishment of endothelial cell (EC) apical–basal polarity in three-dimensional (3D) extracellular matrices. To date, there is little understanding of how EC polarity is controlled during these highly dynamic and rapid morphogenic events. We show that the microtubule tip complex proteins, end binding 1 (EB1), p150Glued, and Clasp1, control human EC tube formation by (1) inducing microtubule assembly and asymmetric cytoskeletal polarization, whereby acetylated and detyrosinated tubulins distribute in a subapical membrane location and filamentous actin distributes basally; (2) increasing tubulin posttranslational modifications, including required acetylation events; and (3) regulating an EC lumen signaling cascade that involves membrane type 1 matrix metallopatrinase (MT1-MMP)–dependent proteolysis as well as Pak, Raf, and Erk kinases. Another regulator of this process is the microtubule stabilizing protein, tau, which binds p150Glued and similarly affects EC lumen formation by controlling the levels of acetylated and detyrosinated tubulins. Increased expression of the tubulin deacetylases, sirtuin 2, and histone deacetylase 6 (HDAC6), blocks EC tube formation and cytoskeletal polarization, while siRNA suppression of these deacetylases stimulates these events. Overall, this work reveals a fundamental role for microtubule tip complex proteins in coordinating microtubule assembly, posttranslational modifications including acetylation, and apical–basal cytoskeletal polarization to control the developing apical membrane surface during blood vessel tubulogenesis in 3D matrix environments.

Asymmetric wave propagation in planar chiral fibers

We demonstrate the realization of a two-dimensional chiral optical waveguide with an infinite translational symmetry that exhibits asymmetric wave propagation. The low-symmetry geometry of the cross-section that lacks any rotational and mirror symmetries shows in-principal directional asymmetric polarization rotation. We use general symmetry arguments to provide qualitative analysis of the waveguide's eigenstates and numerically corroborate this using finite element simulation. We show that despite the only perturbative break of time-reversal symmetry via small modal losses, the structure supports a non-degenerate pair of co-rotating elliptical modes. We fabricated meters long fiber with a spiral structure and studied its optical properties.

Structural Adaptation of Proteins to Different Biological Membranes

Transmembrane polarity profiles and distributions of different protein groups that interact directly with lipids were calculated for 3D structuresof 187 α-helical and 73 β-barrel proteins from eight types of biological membranes. The polarity profiles were represented by H-bonding donor and acceptor capacities (α and β) and polarizability parameter (π∗) calculated for protein surface. The proteins from the set have different hydrophobic thicknesses, with average values of 23.1, 27.3 and 32.5 Å for outer bacterial, inner mitochondrial and eukaryotic plasma membranes, respectively, and 29.5 to 30.6Å for endoplasmic reticulum, thylakoid and different bacterial membranes. The proteins have three distinct polarity regions: lipid head group area with peaks for positively charged groups and crystallized water (15 to 25Å from the bilayer center); interfacial “mid-polar” region with peaks for Tyr and Trp (8 to 15Å); and aliphatic hydrocarbon core (±8Å). Polarity of the core region was nearly identical for different membranes (α∼0.01, β∼0.04, π∗=0.09-0.14). Main changes in polarity occur at the level of lipid carbonyl groups (∼15±5Å), but the changes are more gradual than in DOPC bilayer. The locations and amplitudes of peaks for Trp, Tyr, and Phe are frequently asymmetric and dependent on the type of membrane. The distributions of crystallized water have two peaks at ±20Å. Head groups of crystallized lipids are shitted closer to the hydrocarbon boundary, especially in mitochondrial membrane and on the inner side of eukaryotic plasma membrane. All proteins have a peak of positive net charge at ∼20 Å on the inner side, consistent with the “positive inside” rule, except single-chain β-barrels that follow “negative inside” rule. All curves are shifted inwards in β-barrels, consistent with their smaller thickness. Computational modeling of membrane proteins can be improved using hydrophobic thicknesses and asymmetric polarity profiles for different membranes.

Size dependent polarization reversal at nanoscale metal-ferroelectric interfaces

Ferroelectric oxides possess a unique set of physical properties that have not been maximally exploited due to a lack of understanding of the origins of the switching behavior. Currently, controversy exists over whether switching in ferroelectric oxides is due to polarization or defect mediated switching. Here, we use ultra-high vacuum scanning tunneling microscopy and atomic force microscopy to investigate the process of polarization reversal and to assess the effect of the electronic structure and conductance on the switching behavior of single crystal BaTiO3 (001). Measurements of the local density of states revealed the surface switching behavior was initially due to polarization and that a transition occurred to defected mediated switching after repeated switching cycles. Atomic force microscopy investigations of the size effects at nanoscale Au-BaTiO3 (001) interfaces revealed asymmetric polarization reversal at large interfaces with a convergence to symmetric behavior as the size scale decreased, in agreement with the tunneling-based scanning tunneling microscopy technique.

A dedicated multilayer technique for the fabrication of three-dimensional metallic nanoparticles

► Metallic nanoparticles are investigated for their fascinating properties in nanooptics. ► Most metallic nanoparticles are structured as a single functional layer only. ► This limits their degrees of freedom and the potential to explore their symmetry properties. ► We show a dedicated nanoscale technique to fabricate 3D nanoparticles. ► Extraordinary properties, e.g. asymmetric transmission and giant polarization rotation, emerge. High resolution electron-beam lithography has been applied to the fabrication of three-dimensional metallic nanostructures. The herein developed fabrication process, which is demonstrated at the example of two ensembles of complex nanoscale particles, comprises a dedicated combination of multilayer electron-beam exposure, vacuum evaporation, lift-off and dry etching. The designs of the two nanostructures rely on the principles of a low degree of spatial symmetry and a high degree of chirality, respectively. Their optical properties are evaluated by means of far-field transmittance spectroscopy. Our fabrication technique delivers an excellent quality of miniaturized three-dimensional nanostructures and yields great potential to be extended towards the fabrication of large-area optical metamaterials composed of truly three-dimensional metallic nanoparticles.