Parameterization of Debye Model for Dielectrics Using Voltage Response Measurements and a Benchmark Problem

The Voltage Response measurement since its introduction in the 1960s has been used successfully for the diagnostics of electrical insulation. The method is based on two quantities of decay and return voltage slopes and can be used to study the conduction and polarization processes inside the insulation. Extended Voltage Response method, being an advanced version of the Voltage Response measurement helps in further studying the polarization process by using a large polarization spectrum and hence dielectric relaxation processes. These dielectric relaxation processes can be modeled by the Debye model. Since as most of the techniques used for diagnostic purpose does not give the information about the conduction and polarization processes separately, it is difficult to determine the R-C parameters of the Debye model. The Voltage Response technique is very useful in this regard because of the two voltage slopes. The paper shows a novel experimental benchmark for testing the function fitting methodologies of the Voltage Response methodologies, which helps in determining the R-C parameters. Moreover, the problem can be used for testing the novel genetic, evolutionary algorithms, where benchmarking is an actual challenge. The proposed nonlinear function fitting method uses the genetic algorithms via the Ārtap framework, which lets it possible to select the most accurate optimization algorithm from the provided list of the algorithms and achieve better fitting precision, faster calculation time or more powerful processing ability.

Proteoglycan-4 is an Essential Regulator of Synovial Macrophage Polarization and Inflammatory Macrophage Joint Infiltration

Background: Synovial macrophages (SMs) perform a multitude of functions that include clearance of cell debris and foreign bodies, tissue immune surveillance, and resolution of inflammation. At one end of the macrophage polarization spectrum is the inflammatory phenotype (M1), which secretes IL-1β, IL-6 and expresses iNOS. On the opposite end of the spectrum is the anti-inflammatory phenotype (M2) which is characterized by the secretion of IL-10 and TGF-β. PRG4 is an important regulator of synovial hyperplasia and fibrotic remodeling and the involvement of SM activation in PRG4’s homeostatic role is yet to be defined. Our objectives were to study PRG4’s importance to SM homeostasis, M1 and M2 polarization and joint infiltration of bone marrow-derived macrophages (BMDMs) and investigate the role of SMs in mediating synovial fibrosis in Prg4 gene-trap (Prg4GT/GT) murine knee joints.Methods: SM phenotyping in Prg4GT/GT and Prg4+/+ joints was performed using flow cytometry and the balance between CD86+/CD206- (M1) and CD86-/CD206+ (M2) SMs was studied as animals aged. Expression of iNOS and IL-6 in CD86+ SMs, arginase-1 in CD206+ SMs and the impact of Prg4 recombination on SM polarization and BMDM infiltration following a TLR2 agonist challenge were determined. Inflammatory SMs were depleted using liposomal clodronate and synovial membrane thickness and expression of fibrotic markers: α-SMA, PLOD2 and collagen type I (COL-I) were assessed using immunohistochemistry.Results: Total macrophages in Prg4GT/GT joints were higher than corresponding age-matched Prg4+/+ joints (p<0.0001) and the percentages of CD86+/CD206- and CD86+/CD206+ SMs increased in Prg4GT/GT joints as animals aged (p<0.0001), whereas the percentage of CD86-/CD206+ SMs decreased (p<0.001). CD86+ SMs expressed iNOS and IL-6 compared to CD86- SMs (p<0.0001) while CD206+ SMs also expressed arginase-1. Prg4 re-expression limited the accumulation of CD86+ SMs, increased CD86-/CD206+ SMs and attenuated BMDM recruitment (p<0.001). Liposomal clodronate reduced inflammatory SMs and in turn reduced synovial hyperplasia, α-SMA, PLOD2 and COL-I expression in the synovium (p<0.0001).Conclusions: SM accumulation in the joint and the balance between inflammatory and anti-inflammatory SM subsets are regulated by PRG4. In the absence of PRG4’s role, the synovium is populated with inflammatory macrophages that drive synovial fibrosis.

Perfect and Defective 13C-Furan-Derived Nanothreads from Modest-Pressure Synthesis Analyzed by 13C NMR

<p>¹³C-enrichment of furan by custom synthesis followed by modest-pressure synthesis of ¹³C-enriched nanothreads enabled a detailed characterization of the reaction products by a full complement of advanced solid-state NMR techniques, with validation by <i>ab initio</i> calculation of chemical shifts. The ¹³C NMR spectrum was complex, with more than a dozen distinct features, but almost all (> 95%) represented CH moieties are as expected in nanothreads, with only 2–4% CH₂, 0.3% C=O, and 0.3% COO groups, according to spectral editing. Different components were quantified by integration of the fully equilibrated direct-polarization spectrum. Symmetric and asymmetric alkene-containing rings as well as trapped furan were identified by ¹³C-¹³C and ¹H-¹³C NMR. The most intriguing component observed was fully saturated perfect <i>anti</i> furan-derived nanothread segments, with two distinct, sharp peaks, accounting for ca. 10% of the material. The bonding patterns in these periodic structures deduced from DQ/SQ NMR was that of a [4+2] cycloaddition product. While the small number of chemically inequivalent carbon sites eliminated low-symmetry <i>syn/anti</i> threads, the large number of magnetically inequivalent ones (<i>i.e.,</i> distinct C-H orientations) in CODEX NMR was incompatible with the high-symmetry <i>syn</i> threads. <i>Anti</i> threads with two chemically and eight magnetically inequivalent sites provide the only consistent fit of the experimental data. These conclusions were convincingly corroborated by quantum-chemical simulations, which showed good agreement of isotropic chemical shifts only for the <i>anti</i> threads. This represents the first molecular-level identification of a specific type of nanothread. The typical length of the perfect, fully saturated thread segments was around 14 bonds and they accordingly constitute small clusters (according to ¹³C and ¹H spin diffusion analyses) which likely reside within an overall hexagonal thread packing along with other, less-perfect or less-saturated brethren. The relatively slow <i>T</i>_1C relaxation confirms the nanometer-scale length of the periodic perfect structure, indicates that the perfect threads are particularly rigid, and enables their selective observation in ¹³C NMR. </p>

Perfect and Defective 13C-Furan-Derived Nanothreads from Modest-Pressure Synthesis Analyzed by 13C NMR

<p>¹³C-enrichment of furan by custom synthesis followed by modest-pressure synthesis of ¹³C-enriched nanothreads enabled a detailed characterization of the reaction products by a full complement of advanced solid-state NMR techniques, with validation by <i>ab initio</i> calculation of chemical shifts. The ¹³C NMR spectrum was complex, with more than a dozen distinct features, but almost all (> 95%) represented CH moieties are as expected in nanothreads, with only 2–4% CH₂, 0.3% C=O, and 0.3% COO groups, according to spectral editing. Different components were quantified by integration of the fully equilibrated direct-polarization spectrum. Symmetric and asymmetric alkene-containing rings as well as trapped furan were identified by ¹³C-¹³C and ¹H-¹³C NMR. The most intriguing component observed was fully saturated perfect <i>anti</i> furan-derived nanothread segments, with two distinct, sharp peaks, accounting for ca. 10% of the material. The bonding patterns in these periodic structures deduced from DQ/SQ NMR was that of a [4+2] cycloaddition product. While the small number of chemically inequivalent carbon sites eliminated low-symmetry <i>syn/anti</i> threads, the large number of magnetically inequivalent ones (<i>i.e.,</i> distinct C-H orientations) in CODEX NMR was incompatible with the high-symmetry <i>syn</i> threads. <i>Anti</i> threads with two chemically and eight magnetically inequivalent sites provide the only consistent fit of the experimental data. These conclusions were convincingly corroborated by quantum-chemical simulations, which showed good agreement of isotropic chemical shifts only for the <i>anti</i> threads. This represents the first molecular-level identification of a specific type of nanothread. The typical length of the perfect, fully saturated thread segments was around 14 bonds and they accordingly constitute small clusters (according to ¹³C and ¹H spin diffusion analyses) which likely reside within an overall hexagonal thread packing along with other, less-perfect or less-saturated brethren. The relatively slow <i>T</i>_1C relaxation confirms the nanometer-scale length of the periodic perfect structure, indicates that the perfect threads are particularly rigid, and enables their selective observation in ¹³C NMR. </p>

Perfect and Defective 13C-Furan-Derived Nanothreads from Modest-Pressure Synthesis Analyzed by 13C NMR

<p>¹³C-enrichment of furan by custom synthesis followed by modest-pressure synthesis of ¹³C-enriched nanothreads enabled a detailed characterization of the reaction products by a full complement of advanced solid-state NMR techniques, with validation by <i>ab initio</i> calculation of chemical shifts. The ¹³C NMR spectrum was complex, with more than a dozen distinct features, but almost all (> 95%) represented CH moieties are as expected in nanothreads, with only 2–4% CH₂, 0.3% C=O, and 0.3% COO groups, according to spectral editing. Different components were quantified by integration of the fully equilibrated direct-polarization spectrum. Symmetric and asymmetric alkene-containing rings as well as trapped furan were identified by ¹³C-¹³C and ¹H-¹³C NMR. The most intriguing component observed was fully saturated perfect <i>anti</i> furan-derived nanothread segments, with two distinct, sharp peaks, accounting for ca. 10% of the material. The bonding patterns in these periodic structures deduced from DQ/SQ NMR was that of a [4+2] cycloaddition product. While the small number of chemically inequivalent carbon sites eliminated low-symmetry <i>syn/anti</i> threads, the large number of magnetically inequivalent ones (<i>i.e.,</i> distinct C-H orientations) in CODEX NMR was incompatible with the high-symmetry <i>syn</i> threads. <i>Anti</i> threads with two chemically and eight magnetically inequivalent sites provide the only consistent fit of the experimental data. These conclusions were convincingly corroborated by quantum-chemical simulations, which showed good agreement of isotropic chemical shifts only for the <i>anti</i> threads. This represents the first molecular-level identification of a specific type of nanothread. The typical length of the perfect, fully saturated thread segments was around 14 bonds and they accordingly constitute small clusters (according to ¹³C and ¹H spin diffusion analyses) which likely reside within an overall hexagonal thread packing along with other, less-perfect or less-saturated brethren. The relatively slow <i>T</i>_1C relaxation confirms the nanometer-scale length of the periodic perfect structure, indicates that the perfect threads are particularly rigid, and enables their selective observation in ¹³C NMR. </p>

TRPV4 Plays a Role in Matrix Stiffness-Induced Macrophage Polarization

Phenotypic polarization of macrophages is deemed essential in innate immunity and various pathophysiological conditions. We have now determined key aspects of the molecular mechanism by which mechanical cues regulate macrophage polarization. We show that Transient Receptor Potential Vanilloid 4 (TRPV4), a mechanosensitive ion channel, mediates substrate stiffness-induced macrophage polarization. Using atomic force microscopy, we showed that genetic ablation of TRPV4 function abrogated fibrosis-induced matrix stiffness generation in skin tissues. We have determined that stiffer skin tissue promotes the M1 macrophage subtype in a TRPV4-dependent manner; soft tissue does not. These findings were further validated by our in vitro results which showed that stiff matrix (50 kPa) alone increased expression of macrophage M1 markers in a TRPV4-dependent manner, and this response was further augmented by the addition of soluble factors; neither of which occurred with soft matrix (1 kPa). A direct requirement for TRPV4 in M1 macrophage polarization spectrum in response to increased stiffness was evident from results of gain-of-function assays, where reintroduction of TRPV4 significantly upregulated the expression of M1 markers in TRPV4 KO macrophages. Together, these data provide new insights regarding the role of TRPV4 in matrix stiffness-induced macrophage polarization spectrum that may be explored in tissue engineering and regenerative medicine and targeted therapeutics.

Polarized kilonovae from black hole–neutron star mergers

ABSTRACT We predict linear polarization for a radioactively powered kilonova following the merger of a black hole and a neutron star. Specifically, we perform 3D Monte Carlo radiative transfer simulations for two different models, both featuring a lanthanide-rich dynamical ejecta component from numerical-relativity simulations while only one including an additional lanthanide-free disc-wind component. We calculate polarization spectra for nine different orientations at 1.5, 2.5, and 3.5 d after the merger and in the $0.1\!-\!2\, \mu$m wavelength range. We find that both models are polarized at a detectable level 1.5 d after the merger while show negligible levels thereafter. The polarization spectra of the two models are significantly different. The model lacking a disc wind shows no polarization in the optical, while a signal increasing at longer wavelengths and reaching $\sim 1\!-\!6{{\ \rm per\ cent}}$ at $2\, \mu$m depending on the orientation. The model with a disc-wind component, instead, features a characteristic ‘double-peak’ polarization spectrum with one peak in the optical and the other in the infrared. Polarimetric observations of future events will shed light on the debated neutron richness of the disc-wind component. The detection of optical polarization would unambiguously reveal the presence of a lanthanide-free disc-wind component, while polarization increasing from zero in the optical to a peak in the infrared would suggest a lanthanide-rich composition for the whole ejecta. Future polarimetric campaigns should prioritize observations in the first ∼48 h and in the $0.5\!-\!2\, \mu$m range, where polarization is strongest, but also explore shorter wavelengths/later times where no signal is expected from the kilonova and the interstellar polarization can be safely estimated.

An iterative reconstruction algorithm for Faraday tomography

ABSTRACT Faraday tomography offers crucial information on the magnetized astronomical objects, such as quasars, galaxies, or galaxy clusters, by observing its magnetoionic media. The observed linear polarization spectrum is inverse Fourier transformed to obtain the Faraday dispersion function (FDF), providing us a tomographic distribution of the magnetoionic media along the line of sight. However, this transform gives a poor reconstruction of the FDF because of the instrument’s limited wavelength coverage. The current Faraday tomography techniques’ inability to reliably solve the above inverse problem has noticeably plagued cosmic magnetism studies. We propose a new algorithm inspired by the well-studied area of signal restoration, called the Constraining and Restoring iterative Algorithm for Faraday Tomography (craft). This iterative model-independent algorithm is computationally inexpensive and only requires weak physically motivated assumptions to produce high fidelity FDF reconstructions. We demonstrate an application for a realistic synthetic model FDF of the Milky Way, where craft shows greater potential over other popular model-independent techniques. The dependence of observational frequency coverage on the various techniques’ reconstruction performance is also demonstrated for a simpler FDF. craft exhibits improvements even over model-dependent techniques (i.e. QU-fitting) by capturing complex multiscale features of the FDF amplitude and polarization angle variations within a source. The proposed approach will be of utmost importance for future cosmic magnetism studies, especially with broad-band polarization data from the Square Kilometre Array and its precursors. We make the craft code publicly available†.