Unknown Charge Research Articles

Natural and synthetic plagioclases: Surface charge characterization and sorption of trivalent lanthanides (Eu) and actinides (Am, Cm)

The environmental fate of radiotoxic actinides may be controlled by their interactions with feldspars. Here, the sorption of trivalent minor actinides (Am, Cm) and their rare earth analog Eu onto synthetic pure Ca-feldspar (anorthite) and natural plagioclases of different Ca contents is investigated, covering ranges of [M3+] (52 nM–10 μM), solid-liquid ratios (1–3 g/L), pH (3–9), and ionic strengths (0.01–0.1 M NaCl) under both ambient and CO2-free conditions. As a first step to understand the uptake behavior of the heavy metals, the hitherto unknown surface charge and (de-)protonation reaction of Ca-feldspars is characterized. The zeta potential shows an unusual increase and charge reversal between pH 4 and 7 , which becomes more pronounced with increasing amounts of Ca in the crystal lattice and is likely connected to adsorption and/or surface precipitation of dissolved Al3+. Streaming potential measurements yield (de)protonation constants for anorthite surface sites of log K- = −6.94 ± 0.38 and log K+ = +6.84 ± 0.38. Batch sorption data shows strong immobilization of M3+ by plagioclases at mildly acidic and basic pH. Time-resolved laser fluorescence spectroscopy using Cm indicates the formation of an inner-sphere complex and its two hydrolyzed forms. The complex reactivity of dissolved Al3+ at the plagioclase-water interface severely complicated the development of a surface complexation model, emphasizing the need for additional research in this area. Our study highlights the importance of molecular-level studies to understand surface reactions and uncover unknown processes, which may have significant impact on the transport of (radiotoxic) contaminants in the geosphere.

Analysis of Magnetotherapy Device-Induced Fields Using Cylindrical Human Body Model

This paper deals with the analysis of induced current density and the induced electric field in the body of a human exposed to the magnetic field of a magnetotherapy device. As the displacement currents at extremely low frequencies can be neglected, the biological tissues can thus be considered a weakly conducting medium, facilitating the use of a quasi-static eddy current approximation. The formulation is based on the surface integral equation for the unknown surface charges, whose numerical solution is obtained using the method of moments technique. A simplified model of the human body is utilized to examine various scenarios during the magnetotherapy procedure. The numerical results for the induced current density and the induced electric field are obtained using the proposed model. The analyses of various stimulating coil parameters, human body model parameters, and a displacement of the magnetotherapy coil were carried out to assess their effects on the induced current density. The results suggest that selection of the stimulating coil should be matched based on the size of the human body, but also that the position and orientation of the coil with respect to the body surface will result in different distributions of the induced fields. The results of this study could be useful for medical professionals by showing the importance of various magnetotherapy coil parameters for preparation of various treatment scenarios.

Predictions of nuclear charge radii* *Supported by National Natural Science Foundation of China (11905130)

In this study, we improve the relations of the charge-radius difference of two isotopes by considering a term that relates to the proton number and the parity of the neutron number. The correction reduces the root-mean-squared deviation to 0.0041 fm for 651 nuclei with a neutron number larger than 20, in comparison with experimental data compiled in the CR2013 database. The improved relations are combined with local relations consisting of the charge radii of four neighboring nuclei. These combinations also prove to be efficient in describing and predicting nuclear charge radii and can reflect the structure evolutions of nuclei. Our predictions of 2467 unknown nuclear charge radii at competitive accuracy, which are calculated using these two types of relations, are tabulated in the Supplemental Material.

Timing of Immune Reconstitution in Patients With Congenital Athymia After Treatment With Allogeneic Processed Thymus Tissue-agdc

Congenital athymia is a rare pediatric condition characterized by the absence of a functioning thymus resulting in extremely low naïve T-cell numbers and severe immune deficiency. Allogeneic processed thymus tissue-agdc is approved for immune reconstitution in these patients. In clinical studies, naïve T-cell numbers increased from baseline through year 2 after allogeneic processed thymus tissue-agdc implantation. Based on these studies, immune reconstitution sufficient to overcome infection (>100 naïve CD4+ T cells/mm3) is unlikely to develop before 6–12 months after implantation and may take 2 years in some patients (Figure 1). This analysis aims to identify clinical features associated with delayed naïve T-cell development and impacts on clinical outcomes. In this post hoc analysis of data at year 1 (Y1) after allogeneic processed thymus tissue-agdc implantation, we evaluated clinical features of patients with < 100 naïve CD4+/mm3. Of 95 patients implanted in clinical trials, all 65 patients with baseline measurements had < 50 naïve CD4+/mm3. Of patients with Y1 measurements, 30/45 (66.7%) achieved >100 naïve CD4+/mm3 and 15/45 (33.3%) had < 100 naïve CD4+/mm3 (Tables 1, 2). Among patients with < 100 naïve CD4+/mm3 at Y1, 11/15 (73.3%) had atypical complete DiGeorge Syndrome (cDGS); all 11 atypical patients received glucocorticoids pre-implantation and calcineurin inhibitors pre- and post-implantation, and 6/11 received glucocorticoids post-implantation. Four of 15 patients (26.7%) with < 100 naïve CD4+/mm3 at Y1 had typical cDGS; 1 received calcineurin inhibitors pre- and post-implantation and 2 received glucocorticoids (pre-implantation only). Of 15 patients with < 100 naïve CD4+/mm3 at Y1, 10 (66.7%) experienced infection-related adverse events starting >1 year post-implantation. These events were reported for 8 atypical patients (all on pre-or post-implantation immunosuppressive therapy) and 2 typical patients (with no immunosuppressive therapy); most events resolved. At the time of last follow-up, 93.3% of patients (14/15) were alive; 1 patient died 7.6 years post-treatment (respiratory failure). In summary, most patients (66.7%) with available data achieved >100 naïve CD4+/mm3 by Y1 after allogeneic processed thymus tissue-agdc implantation. Amongst patients who did not, many had atypical cDGS and received immunosuppressive medications. No infection-related deaths were reported in patients with delayed naïve CD4+ T-cell reconstitution. [Display omitted] Table 1(abstract: 100) Characteristics of Patients With < 100 Naïve CD4+ T Cells/mm3 at Year 1 and Year 2 After ImplantationPatientAge at implantation, yearscDGS phenotypeGenetic backgroundaAlive at last follow-upInfection-related AE>1 year post-implantationImmunosuppression useCIPatients with <100 cells/mm3 at the year 1 visit10.8AtypicalHemizygous 22q11.2 deletion✓✓✓✓21.1AtypicalHemizygous 22q11.2 deletion✓No✓✓32.2AtypicalNo known mutation✓No✓✓40.7AtypicalCHARGE✓✓✓✓50.8AtypicalNo known mutation✓✓✓✓60.7AtypicalCHARGE✓✓✓✓71.3AtypicalCHARGE✓✓✓✓80.7TypicalHemizygous 22q11.2 deletion✓No✓✓92.3TypicalHemizygous 22q11.2 deletion✓NoNo✓10c0.2TypicalCHARGE✓✓NoNo110.4TypicalNo known mutationNod✓NoNoPatients with <100 cells/mm3 at the year 1 and year 2 visits121.4AtypicalHemizygous 22q11.2 deletion✓✓✓✓131.2AtypicalCHARGE✓No✓✓140.7AtypicalNo known mutation✓✓✓✓151.8AtypicalCHARGE✓✓✓✓Patients with <100 cells/mm3 at the year 2 visite160.3TypicalHemizygous 22q11.2 deletion✓✓NoNo170.9TypicalHemizygous 22q11.2 deletion✓✓NoNoAE, adverse event; cDGS, complete DiGeorge syndrome; CHARGE, coloboma, heart defect, choanal atresia, growth and developmental delay, genital hypoplasia, and ear anomalies or deafness syndrome; CHD7, chromodomain-helicase DNA-binding protein 7; CI, calcineurin inhibitor; EAS, efficacy analysis set; GC; glucocorticoids. Data based on EAS population (N = 95).aCHARGE includes CHD7mutation or other unknown CHARGE mutations.bIncludes methylprednisolone with anti-thymocyte globulin [rabbit] administered just before implantation.cPatient had renal impairment (defined as serum creatinine levels >0.4 mg/dL at baseline).dPatient died 7.6 years after allogeneic processed thymus tissue-agdc implantation (due to respiratory failure).eNaïve CD4+ T-cell data at the year 1 visit was not available for these patients.Table 2Naive CD4+ T cells/mm3 Over Time After Allogeneic Processed Thymus Tissue-agdc ImplantationaPatientNaïve CD4+ T cells/mm30.5–0.9 years1.0–1.4 years1.5–1.9 years≥2 yearsPatients with <100 cells/mm3 at the year 1 visit165.5NA48721046, 80NA2813101475NA4NA90, 521NA454511.9,51.0NA119.9, 219.3356.662.7,22.954.0NA218.5711,0NA7481250,100276NA9NA27NA10NA67.6359.9NA11NA47.9294.4NAPatients with <100 cells/mm3 at the year 1 and year 2 visits1246456454131068NA94.7, 149144,2339.934.466.4,1091518.534.072.939.9Patients with <100 cells/mm3 at the year 2 visitb1616273355173.9NA6967EAS, efficacy analysis set; NA, not available.Data based on EAS population (N = 95).aBased on available naïve CD4+ T-cell data.bNaïve CD4+ T-cell data at the year 1 visit was not available for these patients.

Novel Multidimensional Liquid Chromatography Workflow with In-Loop Enzymatic Digests of Multiple Heart-Cuts for Fast and Flexible Characterization of Biotherapeutic Protein Variants

Multidimensional liquid chromatography (mD-LC) is becoming a powerful tool for complete characterization of individual peaks and protein variants through separation methods such as nondenaturing ion exchange (IEC) or size-exclusion chromatography coupled to reversed-phase (RP) chromatography. The flexibility of commercially available and customized mD-LC systems is still limited in terms of enzymatic peak processing between chromatographic dimensions. In this regard, only a few column-immobilized proteases are available for detailed peak characterization by mD-LC coupled to mass spectrometry (mD-LC-MS). Here, we present a purpose-built and automated multiple heart-cutting mD-LC design with a novel analytical workflow involving in-loop enzymatic heart-cut digestion between the first-dimensional column and transfer to the second dimension before MS or MS/MS analyses. The setup facilitates the spike-in of any enzyme to multiple heart-cuts for multilevel analysis, for example, for peptide mapping, fragment generation, or deglycosylation, to reduce heterogeneity and provide maximum flexibility in terms of incubation time for optimal peak characterization. We demonstrate the application of IEC coupled to RP-LC-MS and automated in-loop deglycosylation and on-column reduction of an IgG antibody combined with upper hinge region cleavage for Fab generation. We further employ mD-LC-MS and mD-LC-MS/MS to assess post-translational modifications of a bispecific antibody and to support molecule selection by evaluating the best downstream purification strategy. The novel design and automated workflow of the mD-LC system described here offers enhanced flexibility for in-solution processing and real-time monitoring of multiple heart-cuts enabling streamlined characterization of unknown biotherapeutic charge and size variants.

Dipole moment background measurement and suppression for levitated charge sensors.

Optically levitated macroscopic objects are a powerful tool in the field of force sensing, owing to high sensitivity, absolute force calibration, environmental isolation, and the advanced degree of control over their dynamics that have been achieved. However, limitations arise from the spurious forces caused by electrical polarization effects that, even for nominally neutral objects, affect the force sensing because of the interaction of dipole moments with gradients of external electric fields. Here, we introduce a technique to measure, model, and eliminate dipole moment interactions, limiting the performance of sensors using levitated objects. This process leads to a noise-limited measurement with a sensitivity of 3.3 × 10−5 e. As a demonstration, this is applied to the search for unknown charges of a magnitude much below that of an electron or for exceedingly small unbalances between electron and proton charges.

Unveiling charge dynamics of visible light absorbing oxysulfide for efficient overall water splitting

Oxysulfide semiconductor, Y2Ti2O5S2, has recently discovered its exciting potential for visible-light-induced overall water splitting, and therefore, imperatively requires the probing of unknown fundamental charge loss pathways to engineer the photoactivity enhancement. Herein, transient diffuse reflectance spectroscopy measurements are coupled with theoretical calculations to unveil the nanosecond to microsecond time range dynamics of the photogenerated charge carriers. In early nanosecond range, the pump-fluence-dependent decay dynamics of the absorption signal is originated from the bimolecular recombination of mobile charge carriers, in contrast, the power-law decay kinetics in late microsecond range is dominated by hole detrapping from exponential tail trap states of valence band. A well-calibrated theoretical model estimates various efficiency limiting material parameters like recombination rate constant, n-type doping density and tail-states parameters. Compared to metal oxides, longer effective carrier lifetime ~6 ns is demonstrated. Different design routes are proposed to realize efficiency beyond 10% for commercial solar-to-hydrogen production from oxysulfide photocatalysts.

Divergence and self-healing of a discrete vortex formed by phase-locked lasers

Optical beams carrying orbital angular momentum (optical vortices) are sought for various applications, such as optical communications, optical trapping and manipulation, and material processing. Many of these applications involve the propagation of such beams; therefore, the knowledge of various aspects such as beam size and beam divergence, as well as the effect of beam obstruction, is required. In this paper, we present a numerical study on the generation of high-power discrete vortices by phase locking a 1D ring array of lasers in a degenerate cavity that involves spatial Fourier filtering with a specifically designed amplitude mask. Further, we show that, for a given system size (number of lasers) and fixed distance between the nearest-neighbor lasers, the size of a discrete vortex and its divergence upon propagation do not depend on the orbital angular momentum (topological charge), as opposed to a continuous vortex (Laguerre–Gaussian/Bessel–Gauss beams). We also investigate the self-healing of a discrete vortex by obstructing it at the waist plane ( z = 0 ) as well as propagation plane ( z &gt; 0 ), and we show that a discrete vortex possesses good self-healing abilities. The propagation of a truncated discrete vortex has enabled us to identify an unknown topological charge and the rotation dynamics of intensity in a discrete vortex.

Estimation method for inverse problems with linear forward operator and its application to magnetization estimation from magnetic force microscopy images using deep learning

ABSTRACT This study considers an inverse problem, where the corresponding forward problem is given by a finite-dimensional linear operator T. The inverse problem has the following form: It is assumed that the number of patterns that the unknown quantity can take is finite. Then, even if the unknown quantity may be uniquely determined from the data. This case is the subject of this study. We propose a method for solving this inverse problem using numerical calculations. A famous inverse problem requires the estimation of the unknown magnetization distribution or magnetic charge distribution in an anisotropic permanent magnet sample from the magnetic force microscopy images. It is known that the solution of this problem is not unique in general. In this work, we consider the case where a magnetic sample comprises cubic cells, and the unknown magnetic moment is oriented either upward or downward in each cell. This discretized problem is an example of the above-mentioned inverse problem: Numerical calculations were carried out to solve this model problem employing our method and deep learning. The experimental results show that the magnetization can be estimated roughly up to a certain depth.

A simple dipole approach for the calculation of electrostatic field and onset corona voltage in wires-to-cylinders electrode configurations

This paper presents a semi-analytical approach for calculating the potential and electric field in a system of several equipotential groups of infinitely long parallel cylindrical conductors. The proposed method is a simplification of the successive dipole simulation method, presented earlier, taking into account the equality of potentials in each group of conductors with given potentials. This method was applied to calculate the electric field in the gap between W wires and W + 1 cylinders of a bipolar conductor system and used only W (W + 1) unknown dipole charges instead of W (2W + 1) in the original version of the successive dipole simulation method. The corona onset voltages were estimated in the conductor systems with W = 1 ÷ 33. The values of the electric field around the thin wires were accurate already in the first stage of the method. The estimations of the corona onset voltages for various discharge gaps were compared with the experimental values. The advantages of this formulation of the successive dipole simulation method are a simpler, clearer, and faster algorithm.

Local relations of nuclear charge radii

In this paper we study patterns of nuclear charge radii from three perspectives. The first is based on the so-called $\ensuremath{\delta}{R}_{i\mathrm{n}\ensuremath{-}j\mathrm{p}}$ relations, the root-mean-square deviation of which was reported to be 0.0072 fm for nuclei with both neutron number $N$ and proton number $Z$ $\ensuremath{\ge}8$, and are pointed out here to have actually a much smaller value, which is $\ensuremath{\approx}0.003$ fm for most nuclei with $N\ensuremath{\ge}28$ and $Z\ensuremath{\ge}28$. The second and third perspectives are new relations proposed in this paper. One is called the $\ensuremath{\delta}{R}_{\mathrm{nn}}$ relation enlightened from the so-called ``nonpairing'' interaction $\ensuremath{\delta}{V}_{\mathrm{nn}}$ in studies of nuclear binding energies, and the other is a linear dependence of nuclear charge radii in terms of valence nucleon numbers. All these relations are very accurate in most regions, and sizable deviations from these relations could be used to shed light on structural evolutions such as phase transitions and shape coexistence. About 830 unknown nuclear charge radii are enclosed in our Supplemental Material in this paper, with theoretical uncertainty below 0.03 fm.

A semi-analytical electrostatic dipole approach for systems of parallel metallic cylinders

A new semi-analytical approach is described for calculating the potential and electric field in a system of infinitely long parallel cylindrical conductors. The method is based on the dipole simulation technique and the method of successive dipole images. For a system of N conductors with predefined potential differences between them, this method leads to a linear system of n = N(N–1)/2 equations for n unknown fictitious line dipole charges. The positions of these n pairs of dipole charges with equal and opposite sign and the images of these and successive dipoles inside the conductors are strictly predetermined using a well-known analytical solution for the cylinder-to-cylinder case of the charge problem. The electrostatic potential and electric field in each point of interest can be calculated by superposition the effects of all the introduced dipoles. The advantages of this formulation of the charge simulation method are a clear and fast algorithm, providing increased accuracy with the successive introduction of image dipoles, and self-validation capability. The results of sample calculations for various configurations and parameters are presented and the possibility of obtaining accurate results with exponential convergence is shown.

Probing surface charge densities on optical fibers with a trapped ion

We describe a novel method to measure the surface charge densities on optical fibers placed in the vicinity of a trapped ion, where the ion itself acts as the probe. Surface charges distort the trapping potential, and when the fibers are displaced, the ion’s equilibrium position and secular motional frequencies are altered. We measure the latter quantities for different positions of the fibers and compare these measurements to simulations in which unknown charge densities on the fibers are adjustable parameters. Values ranging from −10 to +50 e µm−2 were determined. Our results will benefit the design and simulation of miniaturized experimental systems combining ion traps and integrated optics, for example, in the fields of quantum computation, communication and metrology. Furthermore, our method can be applied to any setup in which a dielectric element can be displaced relative to a trapped charge-sensitive particle.

Low-energy bound states, resonances, and scattering of light ions

We describe bound states, resonances and elastic scattering of light ions using a $\delta$-shell potential. Focusing on low-energy data such as energies of bound states and resonances, charge radii, asymptotic normalization coefficients, effective-range parameters, and phase shifts, we adjust the two parameters of the potential to some of these observables and make predictions for the nuclear systems $d+\alpha$, $\mbox{$^3$He}+\alpha$, $\mbox{$^3$He}+\alpha$, $\alpha+\alpha$, and $p+\mbox{$^{16}$O}$. We identify relevant momentum scales for Coulomb halo nuclei and propose how to apply systematic corrections to the potentials. This allows us to quantify statistical and systematic uncertainties. We present a constructive criticism of Coulomb halo effective field theory and compute the unknown charge radius of $^{17}$F.

Precision measurement of electrical charge in a hybrid optomechanical system with Michelson interferometer

In this work, we present a scheme to measure electrical charge by combining a cavity optomechanical system with Michelson interferometer. The optomechanical cavity with a charged movable mirror is placed in one arm of a Michelson interferometer, in which the cavity length is modified due to the Coulomb force between the charged moveable mirror with the unknown charge and the charged body with the known charge, leading to a change in the output of the cavity mode. In addition, a perfectly reflecting mirror is rigidly fixed in the other arm. The unknown electrical charge can be measured by the difference of output intensities in both arms of the Michelson interferometer. The theoretical derivation and the numerical simulation indicate our scheme is more sensitive to the external Coulomb force and the precision of the scheme can reach unity charge, due to resorting to the Michelson interferometer. Besides, the effect of temperature on the sensitivity of electrical charge detector is also discussed.

Electric field evaluation around slender conductors by collocation boundary element method

Evaluation of the electric field at the surface of a conductor, which is well described by the Poisson equation, is of great importance on many occasions in power systems. This paper proposes a collocation boundary element method where the unknown surface charge density function is assumed to be either azimuth independent or dependent. Detailed formulas, including the quadrature rules and how to accelerate the computation when the target point lies far away from the integral element, are proposed. Numerical examples are shown to confirm the convergence of the method, and manifest the great advantage for the evaluation of the electric field around slender conductors.

Suspended 2D Material Biosensor for Reliable Sensing

TMDs such as MoS2 is playing an important role in the field of FETs, photodetectors, thin film transistors and efficient biosensors because of their direct band-gap, high mobility, and biocompatibility. Despite these strengths, the performance and reliability of such atomic layer are easily influenced by supporting substrate. Interaction between the supporting substrate and MoS2 implies that interface control is vital for performance of devices consisting of monolayer MoS2. In particular, the Silicon dioxide (SiO2) supporting substrate has an uneven morphology and is chemically active because of trapped environmental gases, unknown functional groups, chemical adsorbates, and charges. Thus, adding another layer of MoS2 on the top of SiO2 cannot contribute charge transport clearly, which leads to the unreliable function of every single device. To solve the interface problem, suspended 2D layer devices have been reported by wet etching silicon di oxide underneath the monolayer. Freestanding MoS2 has shown 10 times greater back gate electronic mobility than the supporting on the SiO2 substrate, which is ~0.9 cm2/Vs [1]. However, the existing SiO2 requires hazardous chemical etchants such as hydrofluoric acid (HF), which is difficult to handle and affects the 2D film structure and purity [2]. Secondly, freestanding MoS2 sags between the two electrodes because of the high spacing (~ 2 µm), which makes it impossible to coat another layer such as hafnium oxide (HfO2) and antibodies on top of monolayer. Therefore, this structure impedes making top gate FET biosensors, which allows for only back gating. However, back gate mobility is far lesser than the top gate mobility which hinders making a highly sensitive FET-based biosensor because the sensitivity of a sensor depends on its mobility [3]. Moreover, when linkers/antibodies are directly attached to the bare channel, the transduction mechanism is the combination of the electrostatic gating, direct charge transfer and mobility modulation. Therefore, it is desirable to eliminate the density of defects by covering the bare channel material with insulating material and then functionalizing linkers and antibodies on the top of the insulator [3, 4]. In this work, CVD grown MoS2 channel material is transferred on self-assembled photolithographically patterned nano-gaps to achieve suspension and is covered with HfO2 to eliminate the direct functionalization of channel material. These nano-gap arrays provide mechanical strength to the monolayer and do not allow the supporting substrate to touch after coating another thin insulating layer as well as linkers/antibodies. HfO2 can be easily functionalized by linkers (Benzene 1, 4 dithiols) and antibodies (E-coli antibodies) to bring variation to the suspended 2D material by targeting a charged biomolecule (E-coli). In addition, termination of the supporting substrate leads to increments of electron mobility which are directly proportional to the sensitivity of the FET biosensor. The proposed FET biosensor has the capability to detect one molecule because of its single atomic layer as a channel material, its scalability due to the involvement of optical photolithography, and its fast response because of higher mobility. References Jin, T., et al., Suspended single-layer MoS2 devices. Journal of Applied Physics, 2013. 114(16): p. 164509.Zhang, F., et al., Etchant-free transfer of 2D nanostructures. Nanotechnology, 2017. 29(2): p. 025602.Sarkar, D., et al., MoS2 field-effect transistor for next-generation label-free biosensors. ACS nano, 2014. 8(4): p. 3992-4003.Kalantar-zadeh, K. and J.Z. Ou, Biosensors based on two-dimensional MoS2. ACS Sensors, 2015. 1(1): p. 5-16.

Narrow-Band Yellow-Orange Emitting La3–xCa1.5xSi6N11:Eu2+ (x ≈ 0.77): A Promising Phosphor for Next-Generation Amber pcLEDs

The nitridosilicate La3–xCa1.5xSi6N11:Eu2+ (x ≈ 0.77) was synthesized in a radiofrequency furnace starting from LaF3, La(NH2)3, CaH2, Si(NH)2, and EuF3. The crystal structure was solved and refined from single-crystal X-ray data in the tetragonal space group P4bm (no. 100) with a = 10.1142(6), c = 4.8988(3) A, and Z = 2. Thereby, the so far unknown charge balance mechanism in the system (La,Ca)3Si6N11, which is necessary as bivalent Ca2+ substitutes trivalent La3+, was clarified. Accordingly, charge balance is achieved by incorporation of Ca2+ on three cation sites, including an additional third site compared to the homeotypic La3Si6N11 structure type. The results are supported by Rietveld refinement on powder X-ray diffraction data as well as energy-dispersive X-ray spectroscopy. Fourier transform infrared spectroscopy indicates absence of N–H bonds. An optical band gap of ≈ 4.0 eV was determined using UV/vis reflectance spectroscopy. The Eu2+ doped compound exhibits a remarkably narrow emission in the y...

Computation of electric field inside substations with boundary element methods and adaptive cross approximation

Power system substations and HV power lines are sources of electric and magnetic fields of industrial frequency. Guidelines for permissible electric and magnetic field strengths regarding human exposure and electromagnetic compatibility (EMC) are provided by standards. In this paper a novel method for calculating 3D electric field near power system facilities is presented. Computation procedure is based on integral equations and boundary element methods. The influence of polynomial order of functions used to approximate the unknown linear charge densities over the elements is tested for constant, linear and cubic spline functions. Due to a complex geometry of substations, a large system of equations needs to be solved to find the unknown charge densities over the elements of the model. In order to reduce computational efforts adaptive cross approximation (ACA) is employed. The results of computation are in a good agreement with measurements.

Whispering gallery mode coulometry of the nanoparticle-microcavity interaction in aqueous solution

Charge influences the binding of virus and other nano-particles to microcavity bio-sensors, although surprisingly there have been no reports of the determination of either cavity charge density σw or nanoparticle charge qp using these sensors. In this letter, we experimentally demonstrate an approach for the determination of both. We use an opto-mechanical Whispering Gallery Mode (WGM) Carousel trap to extract the electrostatic interaction energy versus separation s between the cavity surface and a nanoparticle from WGM frequency fluctuations induced by the orbiting particle. Next, we fit this interaction energy to linearized wall-colloid theory (Debye-Hückel theory) for a particle whose charge is known and determine σw. With this microcavity charge density in hand, a larger particle having unknown charge and orbiting the same microcavity has its charge measured from its associated electrostatic interaction energy. This charge is found to be smaller by 10% when compared to results from independent zeta potential measurements and outside of one standard deviation. However, non-linear Gouy-Chapman theory when applied to our measured data arrives at a charge that overlaps zeta potential measurements. Our method is non-destructive, enabling the same particle to be passed on for further characterization.