Polar Ring Research Articles

Ferroelectric and Spin Crossover Behavior in a Cobalt(II) Compound Induced by Polar‐Ligand‐Substituent Motion

AbstractFerroelectric spin crossover (SCO) behavior is demonstrated to occur in the cobalt(II) complex, [Co(FPh‐terpy)2](BPh4)2⋅3ac (1⋅3 ac; FPh‐terpy=4′‐((3‐fluorophenyl)ethynyl)‐2,2′:6′,2′′‐terpyridine) and is dependent on the degree of 180° flip–flop motion of the ligand's polar fluorophenyl ring. Single crystal X‐ray structures at several temperatures confirmed the flip–flop motion of fluorobenzene ring and also gave evidence for the SCO behavior with the latter behavior also confirmed by magnetic susceptibility measurements. The molecular motion of the fluorobenzene ring was also revealed using solid‐state 19F NMR spectroscopy. Thus the SCO behavior is accompanied by the flip–flop motion of the fluorobenzene ring, leading to destabilization of the low spin cobalt(II) state; with the magnitude of rotation able to be controlled by an electric field. This first example of spin‐state conversion being dependent on the molecular motion of a ligand‐appended fluorobenzene ring in a SCO cobalt(II) compound provides new insight for the design of a new category of molecule‐based magnetoelectric materials.

Pulsed high-repetition rate diode-pumped Nd:YAG laser source with advanced ring Q-switch modulator

It has been experimentally shown that incorporation of the λ/4 phase plate into a cavity of the solid-state laser with the ring Q-switch modulator leads to an enhancement of the maximum achievable energy Emax of the output lasing pulses over a wide interval of the pulse repetition rate f. This is achieved by an improvement of the spatial phase distribution for two orthogonal polarization components formed in the laser cavity by the ring Q-switch modulator. These components transform into each other during every round trip of the laser cavity, thus forming the polarization ring cavity without appreciable hole burning effects. For the transversally diode pumped Nd:YAG laser source with the ring Q-switch modulator and λ/4 phase plate the output pulses with Emax ≈ 584–600 mJ were obtained in the range of f ~ 30–100 Hz at the excitation energy of 2.0–2.2 J.

Adsorption/Coagulation/Ceramic Microfiltration for Treating Challenging Waters for Drinking Water Production

Pressurized powdered activated carbon/coagulation/ceramic microfiltration (PAC/Alum/MF) was investigated at pilot scale for treating low turbidity and low natural organic matter (NOM) surface waters spiked with organic microcontaminants. A total of 11 trials with clarified or non-clarified waters spiked with pesticides, pharmaceutical compounds, or microcystins were conducted to assess the removal of microcontaminants, NOM (as 254 nm absorbance, A254, and dissolved organic carbon, DOC), trihalomethane formation potential (THMFP), aerobic endospores as protozoan (oo)cysts indicators, bacteriophages as viruses indicators, and regular drinking water quality parameters. PAC/(Alum)/MF achieved 75% to complete removal of total microcontaminants with 4–18 mg/L of a mesoporous PAC and 2 h contact time, with a reliable particle separation (turbidity < 0.03 NTU) and low aluminium residuals. Microcontaminants showed different amenabilities to PAC adsorption, depending on their charge, hydrophobicity (Log Kow), polar surface area and aromatic rings count. Compounds less amenable to adsorption showed higher vulnerability to NOM competition (higher A254 waters), greatly benefiting from DOC-normalized PAC dose increase. PAC/Alum/MF also attained 29–47% NOM median removal, decreasing THMFP by 26%. PAC complemented NOM removal by coagulation (+15–19%), though with no substantial improvement towards THMFP and membrane fouling. Furthermore, PAC/Alum/MF was a full barrier against aerobic endospores, and PAC dosing was crucial for ≥1.1-log reduction in bacteriophages.

Using Polar Cap (Pc) Indices to Predict Magnetic Storm Developments

Abstract . The present work examines the relations between Polar Cap (PC) indices and the 1-min SYM-H and hourly Dst indices characterizing total (symmetrical) magnetospheric ring current intensities with particular emphasis on possible space weather applications. Using real-time PC indices in a source function may provide gradient values for the ring current intensities characterized by the Dst or SYM-H indices. Upon integration during magnetic storm events the PC-based gradients may provide estimate of ring current index values up to one hour ahead. In a study of the strongest storm events in 2009-2018, the average correlation between real and corresponding equivalent SYM-H index values based on simulated real-time PC indices was 0.836. It is demonstrated that amplitude relations and timing differences for peak polar cap and ring current indices suggested in publications over the years and in a recent report from the International Standards Organisation (ISO) are not valid particularly for the stronger magnetic storms (Dst(peak)<-90 nT) and could be misleading.

Design, synthesis, and biological evaluation of new raloxifene analogues of improved antagonist activity and endometrial safety

Raloxifene agonism of estrogen receptor (ER) in post-menopausal endometrium is not negligible. Based on a rational drug design workflow, we synthesized 14 analogues of raloxifene bearing a polar group in the aromatic ring of the basic side chain (BSC) and/or changes in the bulkiness of the BSC amino group. Analogues with a polar BSC aromatic ring and amino group substituents of increasing volume displayed increasing ER antagonism in Ishikawa cells. Analogues with cyclohexylaminoethoxy (13a) or adamantylaminoethoxy BSC (13b) lacking a polar aromatic ring displayed high ER-binding affinity and ER antagonism in Ishikawa cells higher than raloxifene and similar to fulvestrant (ICI182,780). The endometrial surface epithelium of immature female CD1 mice injected with 13b was comparable to that of vehicle-treated mice, while that of mice treated with estradiol, raloxifene or 13b in combination with estradiol was hyperplastic. These findings indicate that raloxifene analogues with a bulky BSC amino group could provide for higher endometrial safety treatment of the menopausal syndrome.

C. elegans CLASP/CLS-2 negatively regulates membrane ingression throughout the oocyte cortex and is required for polar body extrusion.

The requirements for oocyte meiotic cytokinesis during polar body extrusion are not well understood. In particular, the relationship between the oocyte meiotic spindle and polar body contractile ring dynamics remains largely unknown. We have used live cell imaging and spindle assembly defective mutants lacking the function of CLASP/CLS-2, kinesin-12/KLP-18, or katanin/MEI-1 to investigate the relationship between meiotic spindle structure and polar body extrusion in C. elegans oocytes. We show that spindle bipolarity and chromosome segregation are not required for polar body contractile ring formation and chromosome extrusion in klp-18 mutants. In contrast, oocytes with similarly severe spindle assembly defects due to loss of CLS-2 or MEI-1 have penetrant and distinct polar body extrusion defects: CLS-2 is required early for contractile ring assembly or stability, while MEI-1 is required later for contractile ring constriction. We also show that CLS-2 both negatively regulates membrane ingression throughout the oocyte cortex during meiosis I, and influences the dynamics of the central spindle-associated proteins Aurora B/AIR-2 and MgcRacGAP/CYK-4. We suggest that proper regulation by CLS-2 of both oocyte cortical stiffness and central spindle protein dynamics may influence contractile ring assembly during polar body extrusion in C. elegans oocytes.

Interstellar detection of the highly polar five-membered ring cyanocyclopentadiene

Much like six-membered rings, five-membered rings are ubiquitous in organic chemistry, frequently serving as the building blocks for larger molecules, including many of biochemical importance. From a combination of laboratory rotational spectroscopy and a sensitive spectral line survey in the radio band toward the starless cloud core TMC-1, we report the astronomical detection of 1-cyano-1,3-cyclopentadiene (1-cyano-CPD, c-C5H5CN), a highly polar, cyano derivative of cyclopentadiene. The derived abundance of 1-cyano-CPD is far greater than predicted from astrochemical models that well reproduce the abundance of many carbon chains. This finding implies that either an important production mechanism or a large reservoir of aromatic material may need to be considered. The apparent absence of its closely related isomer, 2-cyano-1,3-cyclopentadiene, may arise from that isomer’s lower stability or may be indicative of a more selective pathway for formation of the 1-cyano isomer, perhaps one starting from acyclic precursors. The absence of N-heterocycles such as pyrrole and pyridine is discussed in light of the astronomical finding of 1-cyano-CPD.

Epoxy resin and TiO2 composite as anticorrosive material for carbon steel in 3% NaCl medium: Experimental and computational studies

The anticorrosive effect of an epoxy resin (DGEDDS-MDA) based on diglycidyl ether 4, 4′-dihydroxydiphenylsulfone (DGEDDS) and 4,4′-Methylene dianiline (MDA) with and without titanium dioxide (TiO2) for carbon steel (CS) corrosion in 3% NaCl solution is reported. The composite of DGEDDS-MDA with TiO2 is designated as DGEDDS-MDA-TiO2. Electrochemical and computational techniques were used to demonstrate the anticorrosive effectiveness of the DGEDDS-MDA and its TiO2 composite. The effect of UV irradiation (for 2000 h) on effectiveness of DGEDDS-MDA and its TiO2 composite showed that the presence of the TiO2 appreciably enhanced the corrosion inhibition effect of DGEDDS-MDA. In order to reinforce the experimental findings, reactivity of DGEDDS-MDA with metallic surface was also studied using computational techniques. DFT study revealed that DGEDDS-MDA interacts strongly with metal surface using donor-acceptor mechanism. Polar functional groups (–OH & –N–) and aromatic rings act as adsorption centers. MD simulations study showed that DGEDDS-MDA adsorbs using flat orientation and its orientation is greatly affected by TiO2.

THE LIGHT MICROSCOPY AND ULTRASTRUCTURAL CHARACTERISTICS OF SARCOCYSTIS FUSIFORMIS INFECTING BUFFALOES IN IRAQ

Samples from fresh muscles of 2-12 years old buffalo (Bubalus bubalis) from Al-Shuala,Baghdad were examined for Sarcocystis infection. Macroscopic ovoid Sarcocystisembedded in the muscle tissues of the examined buffalo were detected, they measured 150-223 (209+7) μm length and 35-130 (85+3) μm width. Esophagus was the highly infectedorgan followed by diaphragm, tongue while the heart muscles were the lowest infected part.The cyst cavity was compartmentalized by septa derived from the ground substance locatedunder the primary cyst wall. By TEM, the primary cyst wall bordered sarcocysts, 0.08-0.22μm in thickness, raised from the parasitophorous vacuolar membrane and surrounded by asecondary cyst wall of host origin. The primary cyst wall had irregular wall folds withnumerous cauliflower projections of variable size and shape accompanied with a knob-likeelectron dense elevation. The interior of the cyst contained merozoites consisted of thestructural elements of the Apicomplexa, polar rings, micronemes, conoid and rhoptries.

THE LIGHT MICROSCOPY AND ULTRASTRUCTURAL CHARACTERISTICS OF SARCOCYSTIS FUSIFORMIS INFECTING BUFFALOES IN IRAQ

Samples from fresh muscles of 2-12 years old buffalo (Bubalus bubalis) from Al-Shuala,Baghdad were examined for Sarcocystis infection. Macroscopic ovoid Sarcocystisembedded in the muscle tissues of the examined buffalo were detected, they measured 150-223 (209+7) μm length and 35-130 (85+3) μm width. Esophagus was the highly infectedorgan followed by diaphragm, tongue while the heart muscles were the lowest infected part.The cyst cavity was compartmentalized by septa derived from the ground substance locatedunder the primary cyst wall. By TEM, the primary cyst wall bordered sarcocysts, 0.08-0.22μm in thickness, raised from the parasitophorous vacuolar membrane and surrounded by asecondary cyst wall of host origin. The primary cyst wall had irregular wall folds withnumerous cauliflower projections of variable size and shape accompanied with a knob-likeelectron dense elevation. The interior of the cyst contained merozoites consisted of thestructural elements of the Apicomplexa, polar rings, micronemes, conoid and rhoptries.

Cdc42 regulates cell polarization and contractile actomyosin rings during terminal differentiation of human erythroblasts

The molecular mechanisms involved in the terminal differentiation of erythroblasts have been elucidated by comparing enucleation and cell division. Although various similarities and differences between erythroblast enucleation and cytokinesis have been reported, the mechanisms that control enucleation remain unclear. We previously reported that dynein and microtubule-organizing centers mediated the polarization of nuclei in human erythroblasts. Moreover, the accumulation of F-actin was noted during the enucleation of erythroblasts. Therefore, during enucleation, upstream effectors in the signal transduction pathway regulating dynein or actin, such as cell division control protein 42 homolog (Cdc42), may be crucial. We herein investigated the effects of the Cdc42 inhibitor, CASIN, on cytokinesis and enucleation in colony-forming units-erythroid (CFU-Es) and mature erythroblasts (day 10). CASIN blocked the proliferation of CFU-Es and their enucleation in a dose-dependent manner. Dynein adopted an island-like distribution in the cytoplasm of non-treated CFU-Es, but was concentrated near the nucleus as a dot and co-localized with γ-tubulin in CASIN-treated cells. CASIN blocked the accumulation of F-actin in CFU-Es and day 10 cells. These results demonstrated that Cdc42 plays an important role in cytokinesis, nuclear polarization and nuclear extrusion through a relationship with dynein and actin filament organization during the terminal differentiation of erythroblasts.

Design and analysis of decoupled tetra‐polar ring‐coils for wireless power transfer in rotary mechanism applications

Decoupling of same-sided coils is a critical issue for multi-input and/or multi-output inductive power transfer (IPT) systems. The mutual inductance between the same-sided coils may lead to the system detuning and the decrease of power transfer capacity and efficiency. In this study, a tetra polar ring coils (TPR-coils) and its decoupling method are proposed for IPT systems applied to rotary mechanism. Firstly, an analytical expression, which illustrates the relationship between the mutual inductance and geometric parameters of coaxial cylindrical helical coils, is given. Then the equivalent circuit model of TPR-coils is established, and the mutual inductance constraints for the decoupling of TPR-coils are proposed. Combined with the expression of mutual inductance, a geometric parameter solution of decoupled TPR-coils is derived. The correctness of theoretical analysis is verified by finite element method simulations and experiments. The experimental results show that the mutual inductance between the same-sided coils can be reduced to 0.6 μH, and the effectiveness of TPR-coils is also verified on an IPT prototype with 231 W power and over 86% efficiency.

Polar Organofluorine Substituents: Multivicinal Fluorines on Alkyl Chains and Alicyclic Rings.

This Review outlines the progression, primarily of our own work, but with important contributions from other labs, on the synthesis and properties of multiple vicinally fluorinated alkyl chains and rings. Chain conformations of individual diastereoisomers with -CHF- at adjacent carbons are influenced by stereoelectronic factors associated with the polar C-F bond and the polarised geminal hydrogens. Generally, the chain will prefer a conformation which acts to minimise overall molecular polarity, and where the C-F bonds orient away from each other. However, when vicinal fluorine atoms are positioned on a ring then conformations are more constrained. The ring will adopt optimal conformations such as a chair in cyclohexane and then C-F bonds can be introduced with a stereochemistry that forces parallel (axial) orientations. In the case of cyclohexane, 1,3-diaxial arrangements of C-F bonds impart considerable polarity to the ring, resulting in an electronegative 'fluorine face' and an electropositive 'hydrogen face'. For all-syn 1,2,3,4,5,6-hexafluorocyclohexane, this arrangement generates an unusually polar aliphatic ring system. Most recently the concept has been extended to the preparation of all-syn 1,2,3-trifluorocyclopropanes, a rigid ring system with fluorine atoms on one face and hydrogens on the other. Lipophilicity Log P values of such compounds indicate that they are significantly more polar than their parent alicyclic hydrocarbons and give some positive indication for a future role of such substituents in medicinal chemistry. Expanding to such a role will require access to improved synthesis methods to these motifs and consequently access to a broader a range of building blocks, however some exciting new methods have emerged recently and these are briefly reviewed.

Essential function of the alveolin network in the subpellicular microtubules and conoid assembly in Toxoplasma gondii.

The coccidian subgroup of Apicomplexa possesses an apical complex harboring a conoid, made of unique tubulin polymer fibers. This enigmatic organelle extrudes in extracellular invasive parasites and is associated to the apical polar ring (APR). The APR serves as microtubule-organizing center for the 22 subpellicular microtubules (SPMTs) that are linked to a patchwork of flattened vesicles, via an intricate network composed of alveolins. Here, we capitalize on ultrastructure expansion microscopy (U-ExM) to localize the Toxoplasma gondii Apical Cap protein 9 (AC9) and its partner AC10, identified by BioID, to the alveolin network and intercalated between the SPMTs. Parasites conditionally depleted in AC9 or AC10 replicate normally but are defective in microneme secretion and fail to invade and egress from infected cells. Electron microscopy revealed that the mature parasite mutants are conoidless, while U-ExM highlighted the disorganization of the SPMTs which likely results in the catastrophic loss of APR and conoid.

Synthesis of bio-based plasticizer with improved migration resistance for poly(vinyl chloride)

Bio-based plasticizers have attracted more attention due to their sustainability. In order to replace dioctyl phthalate (DEHP) in poly(vinyl chloride) (PVC) products, the authors designed and synthesized a kind of bio-based plasticizer based on dehydroabietic acid and castor oil (BPDC). Its chemical structure was characterized. The performance of PVC films plasticized with BPDC was investigated and compared with that of DEHP. The obtained bio-based plasticizer with flexible long alkane chains and polar benzene ring groups showed improved volatility resistance and solvent extraction resistance. The introduction of BPDC improved the thermal stability of PVC films due to the thermal stability of the ester groups and benzene groups of BPDC. The reduction in the glass transition temperature and increase in the elongation at break of PVC films indicated an effective plasticizing efficiency.

Magnetization Analysis for Outer Rotor Brushless DC Motors Using Polar Anisotropic Ferrite Ring Magnets

Ferrite-bonded magnets have been extensively used in small brushless DC (BLDC) motors for low torque applications such as fans and pumps. In particular, some motors of them with ferrite-bonded magnets, frequently called as plastic magnets, do not have a rotor core in order to reduce manufacturing costs and inertia of the rotating part. Accordingly, the magnetization distribution of the bonded magnets has a polar anisotropic direction to secure more magnetic flux. As a result, the magnetization orientation of the magnets is highly significant to accurately predict the performances of the BLDC motors. This paper deals with the magnetization analysis of the polar anisotropic ferrite ring magnet applied to an outer rotor type BLDC motor. The motor is employed for an electric water pump, and its rotor including the impeller consists of only the ferrite-bonded magnet material and made by injection molding. Consequently, a magnetizing fixture and an impulse magnetizer are not used for the magnetization of the outer rotor type motor. Instead, samarium–cobalt (SmCo) magnets having a relatively high curie temperature are applied for generating magnetic field. Finally, this paper presents a process to determine the anisotropic orientations of a ferrite ring magnet by finite element method. In addition, the validity of the analysis method is verified by test results.

Tunable Liquid Chromatographic Separation of H/D Isotopologues Enabled by Aromatic π Interactions.

We report hydrogen/deuterium (H/D) isotope effects based on weak intermolecular interactions with polar functional groups and aromatic rings in liquid chromatography (LC). Various LC experiments with different aromatic analytes, separation media, and nonpolar mobile phases were conducted under normal phase LC conditions, where the hydrophobic interaction was completely suppressed. The separation media that had polar functional groups, such as silanol groups, allowed for higher separation efficiencies for the pairs of aromatic H/D isotopologues. In comparing the 13C NMR spectra of protiated and deuterated aromatic analytes, the electron density of the deuterated analyte was found to be slightly higher than that of the protiated analytes. In the case of silanol functional groups, aromatic rings of the analyte acted as donors through the OH-π interaction to hydrogen atoms in the silanol groups. Thus, the deuterated analytes were able to be greatly retained by the stronger OH-π interactions. Furthermore, a C70-fullerene bonded monolithic column (C70 column), which effectively provides CH-π interactions, allowed the opposite isotope effect. Briefly, an electrostatic attraction based on the dipole-(induced) dipole interaction dominated in the CH-π interactions, according to a van't Hoff analysis. Hence, the bonding lengths of the C-H or D bonds were sensitively affected, such that we were able to conclude that the CH-π interaction depended on the geometric effect. Applying these opposing H/D isotope effects, we were able to finally demonstrate effective H/D isotopologue separations by utilizing the complementary action of the OH-π and CH-π interactions.

Arbitrary-Oriented Object Detection in Remote Sensing Images Based on Polar Coordinates

Arbitrary-oriented object detection is an important task in the field of remote sensing object detection. Existing studies have shown that the polar coordinate system has obvious advantages in dealing with the problem of rotating object modeling, that is, using fewer parameters to achieve more accurate rotating object detection. However, present state-of-the-art detectors based on deep learning are all modeled in Cartesian coordinates. In this article, we introduce the polar coordinate system to the deep learning detector for the first time, and propose an anchor free Polar Remote Sensing Object Detector (P-RSDet), which can achieve competitive detection accuracy via using simpler object representation model and less regression parameters. In P-RSDet method, arbitrary-oriented object detection can be achieved by predicting the center point and regressing one polar radius and two polar angles. Besides, in order to express the geometric constraint relationship between the polar radius and the polar angle, a Polar Ring Area Loss function is proposed to improve the prediction accuracy of the corner position. Experiments on DOTA, UCAS-AOD and NWPU VHR-10 datasets show that our P-RSDet achieves state-of-the-art performances with simpler model and less regression parameters.

Malaria Transmission Assisted by Interaction between &lt;i&gt;Plasmodium α-Tubulin-I and Anopheles FREP1 Protein&lt;/i&gt;

Invasion of the mosquito midgut by Plasmodium parasites is essential for malaria transmission. FREP1, a mosquito midgut peritrophic matrix protein, binds to the parasite ookinete stage and mediates Plasmodium infection of Anopheles mosquitoes. The FREP1-mediated Plasmodium invasion pathway is highly conserved across multiple species of Plasmodium and Anopheles. During mosquito infection, ookinetes must orient their apical invasion apparatus toward the midgut epithelium. Here, we conducted biochemical and cell biological studies to identify Plasmodium ookinete proteins that bind mosquito FREP1. Among these newly identified FREP1-binding partners (FBP), we demonstrate that Plasmodium α-tubulin-I at the ookinete apical complex is critical for invasion. Cell biological studies revealed that anti-α-tubulin antibodies bound to the apical polar ring of the living P. falciparum ookinetes. Functional analyses showed that polyclonal serum directed against P. falciparum α-tubulin-I, but not other FBPs, significantly reduced the number of P. falciparum oocysts in An. gambiae midguts. Our data support that interactions between Anopheles FREP1 protein and Plasmodium α-tubulin-I anchors and directs the ookinete invasive apparatus towards midgut peritrophic matrix, which is critical for the efficient invasion and transmission of Plasmodium to mosquitoes. Thus, Anopheles FREP1 and Plasmodium α-tubulin-I are potential targets for blocking malaria transmission.

Self-Assembled Monolayers with Distributed Dipole Moments Originating from Bipyrimidine Units

The concept of distributed dipoles in molecular self-assembly on solid substrates was tested for the example of thiolate self-assembled monolayers (SAMs) on Au(111) containing dipolar 2,5′-bipyrimidine units. These were attached to a thiol anchoring group either directly or via a phenylene–methylene spacer, with the spacer decoupling the dipolar moiety from the substrate and promoting layer formation. As expected, the SAMs containing the spacer groups exhibited a higher quality, including a higher packing density and nearly upright molecular orientation. The electrostatic effects of the dipolar bipyrimidine moieties were tested through C 1s and N 1s photoemission spectra, where electrostatic core-level shifts impact the shapes of the spectra. Additionally, changing the orientation of the dipoles allows a variation of the work function over a range of ∼1.35 eV. The experiments were complemented by density-functional theory calculations. The work function tuning range was reasonably high, but smaller than expected considering that for SAMs with a single embedded pyrimidine group per molecule work function changes already amounted to ∼1.0 eV. This behavior is rooted in an asymmetry of the studied SAMs: For dipoles pointing away from the substrate, the expected doubling of the work function change between monopyrimidine and bipyrimidine SAMs essentially occurs. Conversely, for the downward-oriented pyrimidine dipoles, the second polar ring has hardly any effect. Consistent observations were made for the core-level shifts. We discuss several factors, which are potentially responsible for this asymmetry, like disorder, depolarization, or Fermi-level pinning. Of these, the most likely explanation is the adsorption of airborne contaminants interacting with the nitrogen atoms in the immediate vicinity of the outer surface. These are present only in films with downward oriented dipoles. In spite of these complications, some of the introduced distributed dipole SAMs serve as important model systems for understanding electrostatic effects at interfaces. They are also of interest for controlling carrier-injection barriers in organic (opto) electronic devices.