Single Ion Research Articles

Effects of 4-Br-A23187 on Bacillus subtilis cells and unilamellar vesicles reveal it to be a potent copper ionophore.

Ionophores are small molecules or peptides that transport metal ions across biological membranes. Their transport capabilities are typically characterized in vitro using vesicles and single ion species. It is difficult to infer from these data which effects ionophores have on living cells in a complex environment (e.g., culture medium), since net ion movement is influenced by many factors including ion composition of the medium, concentration gradients, pH gradient, and protein-mediated transport processes across the membrane. To gain insights into the antibacterial mechanism of action of the semisynthetic polyether ionophore 4-Br-A23187, known to efficiently transport zinc and manganese in vitro, we investigated its effects on the gram-positive model organism Bacillus subtilis. In addition to monitoring cellular ion concentrations, the physiological impact of treatment was assessed on the proteome level. 4-Br-A23187 treatment resulted in an increase in intracellular copper levels, the extent of which depended on the copper concentration of the medium. Effects of copper accumulation mirrored by the proteomic response included oxidative stress, disturbance of proteostasis, metal and sulfur homeostasis. The antibiotic effect of 4-Br-A23187 is further aggravated by a decrease in intracellular manganese and magnesium. A liposome model confirmed that 4-Br-A23187 acts as copper ionophore in vitro.

Sample Preparation and Experimental Design for In Situ Multi-Beam Transmission Electron Microscopy Irradiation Experiments.

There is a need to understand materials exposed to overlapping extreme environments such as high temperature, radiation, or mechanical stress. When these stressors are combined there may be synergistic effects that enable unique microstructural evolution mechanisms to activate. Understanding of these mechanisms is necessary for the input and refinement of predictive models and critical for engineering of next generation materials. The basic physics and underlying mechanisms require advanced tools to be investigated. The in situ ion irradiation transmission electron microscope (I³TEM) is designed to explore these principles. To quantitatively probe the complex dynamic interactions in materials, careful preparation of samples and consideration of experimental design is required. Particular handling or preparation of samples can easily introduce damage or features that obfuscate the measurements. There is no one correct way to prepare a sample; however, many mistakes can be made. The most common errors and things to consider are highlighted within. The I³TEM has many adjustable variables and a large potential experimental space, therefore it is best to design experiments with a specific scientific question or questions in mind. Experiments have been performed on large number of sample geometries, material classes, and with many irradiation conditions. The following are a subset of examples that demonstrate unique in situ capabilities utilizing the I3TEM. Au nanoparticles prepared by drop casting have been used to investigate the effects of single ion strikes. Au thin films have been used in studies on the effects of multibeam irradiation on microstructure evolution. Zr films have been exposed to irradiation and mechanical tension to examine creep. Ag nanopillars were subjected to simultaneous high temperature, mechanical compression, and ion irradiation to study irradiation induced creep as well. These results impact fields including: structural materials, nuclear energy, energy storage, catalysis, and microelectronics in space environments.

Native Mass Spectrometry at the Convergence of Structural Biology and Compositional Proteomics.

Biology is driven by a vast set of molecular interactions that evolved over billions of years. Just as covalent modifications like acetylations and phosphorylations can change a protein's function, so too can noncovalent interactions with metals, small molecules, and other proteins. However, much of the language of protein-level biology is left either undiscovered or inferred, as traditional methods used in the field of proteomics use conditions that dissociate noncovalent interactions and denature proteins.Just in the past few years, mass spectrometry (MS) has evolved the capacity to preserve and subsequently characterize the complete composition of endogenous protein complexes. Using this "native" type of mass spectrometry, a complex can be activated to liberate some or all of its subunits, typically via collisions with neutral gas or solid surfaces and isolated before further characterization ("Native Top-Down MS," or nTDMS). The subunit mass, the parent ion mass, and the fragment ions of the activated subunits can be used to piece together the precise molecular composition of the parent complex. When performed en masse in discovery mode (i.e., "native proteomics"), the interactions of life─including protein modifications─will eventually be clarified and linked to dysfunction in human disease states.In this Account, we describe the current and future components of the native MS toolkit, covering the challenges the field faces to characterize ever larger bioassemblies. Each of the three pillars of native proteomics are addressed: (i) separations, (ii) top-down mass spectrometry, and (iii) integration with structural biology. Complexes such as endogenous nucleosomes can be targeted now using nTDMS, whereas virus particles, exosomes, and high-density lipoprotein particles will be tackled in the coming few years. The future work to adequately address the size and complexity of mega- to gigadalton complexes will include native separations, single ion mass spectrometry, and new data types. The use of nTDMS in discovery mode will incorporate native-compatible separation techniques to maximize the number of proteoforms in complexes identified. With a new wave of innovations, both targeted and discovery mode nTDMS will expand to include extremely scarce and exceedingly heterogeneous bioassemblies. Understanding the proteinaceous interactions of life and how they go wrong (e.g., misfolding, forming complexes in dysfunctional stoichiometries and configurations) will not only inform the development of life-restoring therapeutics but also deepen our understanding of life at the molecular level.

Low-energy excitations and magnetic anisotropy of the layered van der Waals antiferromagnet Ni2P2S6

The quasi-two-dimensional antiferromagnet Ni$_2$P$_2$S$_6$ belongs to the family of magnetic van der Waals compounds that provides a rich material base for the realization of fundamental models of quantum magnetism in low dimensions. Here, we report high-frequency/high-magnetic field electron spin resonance measurements on single crystals of Ni$_2$P$_2$S$_6$. The results enable to reliably determine the positive, 'easy'-plane type of the single ion anisotropy of the Ni$^{2+}$ ions with the upper limit of its magnitude $\lesssim 0.7$ meV. The resonance response reveals strongly anisotropic spin fluctuations setting in shortly above the N\'eel temperature $T_{\rm N} = 158$ K and extending in the antiferromagnetically ordered state down to low temperatures. There, a new low-energy magnon excitation gapped from the ground state by only $\sim 1$ meV was found. This magnon mode may explain unusual low temperature relaxation processes observed in a latest nuclear magnetic resonance experiments and together with the estimate of the single ion anisotropy they should enable setting up a realistic spin model for an accurate description of magnetic properties of Ni$_2$P$_2$S$_6$.

Experimental helium-beam radiography with a high-energy beam: Water-equivalent thickness calibration and first image-quality results.

A clinical implementation of ion-beam radiography (iRad) is envisaged to provide a method for on-couch verification of ion-beam treatment plans. The aim of this work is to introduce and evaluate a method for quantitative water-equivalent thickness (WET) measurements for a specific helium-ion imaging system for WETs that are relevant for imaging thicker body parts in the future. Helium-beam radiographs (αRads) are measured at the Heidelberg Ion-beam Therapy Center with an initial beam energy of 239.5 MeV/u. An imaging system based on three pairs of thin silicon pixel detectors is used for ion path reconstruction and measuring the energy deposition (dE) of each particle behind the object to be imaged. The dE behind homogeneous plastic blocks is related to their well-known WETs between 280.6 and 312.6 mm with a calibration curve that is created by a fit to measured data points. The quality of the quantitative WET measurements is determined by the uncertainty of the measured WET of a single ion (single-ion WET precision) and the deviation of a measured WET value to the well-known WET (WET accuracy). Subsequently, the fitted calibration curve is applied to an energy deposition radiograph of a phantom with a complex geometry. The spatial resolution (modulation transfer function at 10 % -MTF10% ) and WET accuracy (mean absolute percentage difference-MAPD) of the WET map are determined. In the optimal imaging WET-range from ∼280 to 300 mm, the fitted calibration curve reached a mean single-ion WET precision of 1.55 0.00%. Applying the calibration to an ion radiograph (iRad) of a more complex WET distribution, the spatial resolution was determined to be MTF10% = 0.49 0.03 lp/mm and the WET accuracy was assessed as MAPD to 0.21 %. Using a beam energy of 239.5 MeV/u and the proposed calibration procedure, quantitative αRads of WETs between ∼280 and 300 mm can be measured and show high potential for clinical use. The proposed approach with the resulting image qualities encourages further investigation toward the clinical application of helium-beamradiography.

Unveiling the Side-Chain Effect on Ionic Conductivity of Poly(ethylene oxide)-Based Polymer-Brush Electrolytes

Polymer-brush architectures have attracted great interests in solid-state electrolytes for battery applications due to the facilitated segmental dynamics and latent capacity to fabricate single ion conductors. The effect of side chain architectures on the ionic conductivity of the polymer-brush electrolytes (PBEs), however, still requires a systematic exploration. This work describes a detailed study on the structure–property relationship between the side chain architectures and the ion-conducting behaviors of PBEs. By means of thermodynamic, spectroscopic, and electrochemical characterizations, factors of both chain length and graft density are investigated to elucidate the mechanism. Our results show that as the chain length increases, the ionic conductivity exhibits first an increase in the short amorphous range and then a drop in the long crystalline range. Moreover, investigation on graft density demonstrates that the amorphous PBEs achieve the highest ionic conductivity at a fully grafted configuration, indicating the significance of branched side chain architecture. For crystalline PBEs, proper regulation of graft density can alleviate the crystallization of the side chains and therefore increase the ionic conductivity. These results would improve our understanding of ion-conducting behaviors in PBEs and provide insights for designing advanced solid polymer electrolytes.

Kinetics of reactions of NH4 + with some biogenic organic molecules and monoterpenes in helium and nitrogen carrier gases: A potential reagent ion for selected ion flow tube mass spectrometry.

To assess the suitability of NH4 + as a reagent ion for trace gas analysis by selected ion flow tube mass spectrometry, SIFT-MS, its ion chemistry must be understood. Thus, rate coefficients and product ions for its reactions with typical biogenic molecules and monoterpenes need to be experimentally determined in both helium, He, and nitrogen, N2 , carrier gases. NH4 + and H3 O+ were generated in a microwave gas discharge through an NH3 and H2 O vapour mixture and, after m/z selection, injected into He and N2 carrier gas. Using the conventional SIFT method, NH4 + reactions were then studied with M, the biogenic molecules acetone, 1-propanol, 2-butenal, trans-2-heptenal, heptanal, 2-heptanone, 2,3-heptanedione and 15 monoterpene isomers to obtain rate coefficients, k, and product ion branching ratios. Polarisabilities and dipole moments of the reactant molecules and the enthalpy changes in proton transfer reactions were calculated using density functional theory. The k values for the reactions of the biogenic molecules were invariably faster in N2 than in He but similar in both bath gases for the monoterpenes. Adducts NH4 + M were the dominant product ions in He and N2 for the biogenic molecules, whereas both MH+ and NH4 + M product ions were observed in the monoterpene reactions; the monoterpene ratio correlating (R2 =0.7) with the proton affinity, PA, of the monoterpene molecule as calculated. The data indicate that this adduct ion formation is the result of bimolecular rather than termolecular association. NH4 + can be a useful reagent ion for SIFT-MS analyses of molecules with PA(M) < PA(NH3 ) when the dominant single product ion is the adduct NH4 + M. For molecules with PA(M) > PA(NH3 ), such as monoterpenes, both MH+ and NH4 + M ions are likely products, which must be determined along with k by experiment.

Effects of trace elements on digester performance and microbial community response in anaerobic digestion systems

ABSTRACT Trace elements (TE), as micronutrients for microorganisms, have a significant impact on the stability of anaerobic digestion (AD). Studies have been conducted on process stability and performance of the AD of food waste (FW) by supplementing TEs. In this study, mesophilic batch biomethane potential (BMP) tests using FW were conducted to investigate the effect of TEs (Fe, Ni, Co, Se, and Mo) as single and mixed ions. In view of their scarcity, correlations between the microbial community and digester performance such as first-order hydrolysis coefficient (Kh), volatile fatty acids (VFA), methane yield, and methane production rate (MPR) have been developed. Ni2+ at 1 and 1.5 mg/L increased the methane yield by 27% and 23% respectively. Similarly, Co2+ at 0.1 and 0.5 mg/L increased the yield by 21% and 23% respectively, compared to control. Although Se4+ at all concentrations enhanced the methane yield, Fe2+ at only 50 mg/L increased methane yield by 22%. For mixed TEs, the combination of Ni2+ [1 mg/L] +Co2+ was the best and increased methane for all Co2+ concentrations (0.1, 0.4 and 0.5 mg/L) by 16%, 14% and 12% respectively. Firmicutes and Methanosaeta were the most abundant phyla among hydrolytic and methanogenic microbial groups, respectively, constituting 42%-61% and 60-80% of their respective microbial groups. The most significant positive correlations were observed between aceto/acidogenic microorganisms and final VFA concentrations with Pearson correlation factors of 0.91.

Interpretation of Ir L -edge isotropic x-ray absorption spectra across the pressure-induced dimerization transition in hyperhoneycomb β−Li2IrO3

The extended nature of atomic $5d$ orbitals, together with a relatively short $\ensuremath{\sim}3\phantom{\rule{0.16em}{0ex}}\AA{}$ Ir-Ir distance across edge-shared octahedra in honeycomb iridate lattices, leads to a tendency to disrupt the local, spin-orbit-entangled ${j}_{\mathrm{eff}}=\frac{1}{2}$ moments of ${\mathrm{Ir}}^{4+}$ ions in favor of dimerization and the formation of molecular orbitals, especially upon lattice compression. The sensitivity of Ir $L$-edge spectroscopy to both spin-orbit entanglement in ${j}_{\mathrm{eff}}$ states and the quenching of orbital degrees of freedom in dimerized states results in a peculiar evolution of x-ray absorption spectra across dimerization transitions, including energy shifts in the opposite direction for ${L}_{3}$ and ${L}_{2}$ leading absorption edges and substantial changes in their isotropic branching ratio. We present a theoretical description of the evolution of $5d$ electronic states, and related x-ray absorption spectra, in going from the single ion to the dimerized limit. The calculations reproduce the experimental results for hyper-honeycomb $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{Li}}_{2}{\mathrm{IrO}}_{3}$ [L. Veiga et al., Phys. Rev. B 100, 064104 (2019); L. Veiga et al., Phys. Rev. B 96, 140402(R) (2017)] and shed light into the weakening of the coupling between spin and orbital degrees of freedom as the strength of dimerization increases. The results provide a basis for the interpretation of $L$-edge x-ray absorption spectra in $5d$ systems where competition between the formation of local ${j}_{\mathrm{eff}}$ states and molecular orbitals is at play.

A two-step physical-chemical etching technique to improve laser damage resistance of fused silica

A two-step physical-chemical etching method, namely large incident angle ion beam etching followed by HF etching, is proposed to remove the damage precursors in fused silica surface to achieve good surface quality and significantly improve the laser damage resistance of fused silica. Ion beam etching with large incident angle is utilized to remove the metal impurities and most subsurface defects in fused silica surface, which can reduce the removal amount of subsequent HF etching of fused silica, thus suppressing the replication and expansion of the subsurface defects, deposition of reaction products and deterioration of surface shape during the HF etching process. After that, HF etching is used to remove the atomic-scale damaged layer and reduce the P–V value of the reflection surface shape induced by ion beam etching. Therefore, a better laser damage performance of fused silica can be obtained by the two-step etching method compared with single ion beam etching and single HF etching. The results show that the two-step physical-chemical etching can be developed to fabricate high-quality and high damage-resistant fused silica optical components with small etching amount and good surface quality for high-power laser application.

Stable-Isotope Dilution GC–MS Measurement of Metformin in Human Serum and Urine after Derivatization with Pentafluoropropionic Anhydride and Its Application in Becker Muscular Dystrophy Patients Administered with Metformin, l-Citrulline, or Their Combination

Metformin (N,N-dimethylguanylguanidine) is one of the most prescribed drugs with pleiotropic, exerted in part by not fully elucidated mechanisms of action. We developed and validated a gas chromatography–mass spectrometry (GC–MS) method for the quantitative analysis of metformin (metformin-d0) in 10-µL aliquots of human serum and urine using N,N-[dimethylo-2H6]guanylguanidine (metformin-d6) as the internal standard. The method involves evaporation of the samples to dryness, derivatization with pentafluoropropionic (PFP) anhydride in ethyl acetate (30 min, 65 °C), and extraction into toluene. The negative-ion chemical ionization GC–MS spectra of the PFP derivatives contain a single intense ion with mass-to-charge (m/z) ratios of m/z 383 for metformin-d0 and m/z 389 for metformin-d6. Our results suggest that all amine/imine groups of metformin-d0 and metformin-d6 are converted to their N,N,N-tripentafluoropropionyl derivatives, which cyclize to form a symmetric triazine derivative, of which the non-ring amine group is amidated. Quantification was performed by selected-ion monitoring (SIM) of m/z 383 and m/z 389. Upon validation, the method was applied to determine serum and urine metformin concentrations in 19 patients with Becker muscular dystrophy (BMD). Serum and urine samples were collected at baseline (Visit I), after six weeks of supplementation (Visit II) with metformin (3 × 500 mg/d; metformin group; n = 10) or l-citrulline (3 × 1500 mg/d; citrulline group; n = 9) followed by a six-week supplementation with 3 × 500 mg/d of metformin plus 3 × 1500 mg/d l-citrulline. At Visit I, the metformin concentration in the serum and urine was very low in both groups. The metformin concentrations in the serum and urine of the patients who first took metformin (MET group) were higher at Visit II and Visit III. The metformin concentration in the serum and urine samples of the patients who first took l-citrulline (CITR group) were higher at Visit III. The serum and urine concentrations of metformin were insignificantly lower in the CITR group at Visit III. The mean fractional excretion (FE) rate of metformin was 307% (Visit II) and 322% (Visit III) in the MET group, and 290% in the CITR group (Visit III). This observation suggests the accumulation of metformin in the kidney and its secretion in the urine. The GC–MS is suitable to measure reliably circulating and excretory metformin in clinical settings.

Application of Design of Experiments to the Analysis of Fruit Juice Deacidification Using Electrodialysis with Monopolar Membranes.

Despite the beneficial health effects of fruit juices, the high content of organic acids and low pH of some of them limit their consumption. The aim of this work was to study the deacidification of fruit juices using electrodialysis (ED) with monopolar membranes. Aqueous solutions of citric acid were used in ED deacidification experiments following a factorial design with citric acid concentration and electric current varying in the ranges of 5–25 g/L and 0.5–1 A, respectively. The design runs were characterized by a constant Faraday efficiency of 0.37 ± 0.03, suggesting that the triple-charged citrate ion (Cit3−) carried the electric charge through the anionic membranes. During deacidification, the pH increased in agreement with the decreasing concentration of the acid. Deacidification of pineapple juice or pineapple juice enriched with 20 g/L of citric acid using ED led to similar values of the Faraday efficiency, confirming that Cit3− is the main ion migrating through the anionic membrane. However, the decrease in titratable acidity during ED treatment was accompanied by a decrease in pH. Such behavior, already reported, was explained by considering proton generation during the transformation of the single (H2Cit−) and double-charged (HCit2−) citrate ions into the triple-charged ion (Cit3−) when entering the anionic membrane.

Single ion channel recording in 3D culture of stem cells using patch-clamp technique

Tri-dimensional (3D) cell aggregates or spheroids are considered to be closer to physiological conditions than traditional 2D cell culture. Mesenchymal stem cells (MSCs) assembling in spheroids have increased the survival of transplanted cells. The organization of stem cells in 3D culture affects cell microenvironment and their mechanical properties. The regulation of the biological processes that maintain crucial physiological reactions of MSCs is closely related to the functioning of ion channels. The pattern of expression, role and regulatory mechanisms of ion channels could be significantly different in 3D compared to 2D culture, and, thus, needed to be properly analyzed on the level of ionic currents. Electrophysiological data on the features of ion channels functioning in 3D cell culture models are currently very limited in the literature. This gap of knowledge may be associated with technical difficulties that exist when researchers try to apply the standard patch clamp method for the registration of ion channels in cells aggregated in spheroids. In this regard, our study focuses on solving emerging technical difficulties and presents an example of their successful solution. Here, we developed a specific approach and have recorded the activity of mechanosensitive stretch-activated ion channels (SACs) in endometrial MSCs (eMSCs) assembled in spheroids. Moreover, we observed functional interplay of SACs with potassium channels of big conductance (BK) in the plasma membrane of eMSC spheroids consistently to revealed earlier in routine 2D cultured cells. Additionally, we observed a significant decrease in the frequency of SACs activation in spheroids that may indicate the differences in the level of functional expression of channels in 3D culture comparing to 2D culture of eMSCs.

Effective-field theory with the probability distribution technique for a spin-3/2 core and spin-2 shell Ising nanowire: Thermodynamic properties and hysteresis behaviors

The probability distribution technique, exploited within the framework of effective field theory and the Ising model, was used to study the magnetic and thermal properties of a nanowire assimilated to a hexagonal shaped system of a core–shell structure and with mixed spins (3/2,2), respectively. The coupling between core and shell is ferrimagnetic. Under certain physical parameter values, the nanowire exhibits the compensation behavior. The hysteresis behavior was investigated in the presence of an external magnetic field by magnetizing and demagnetizing the nanowire, as well as the effects of single ion anisotropy, ferrimagnetic exchange interactions and temperature on hysteresis loops. The dependence of the shapes of loops on the physical parameters of the system has been elucidated. At low temperatures, the nanowire exhibits triple, quadruple, quintuple, sextuple, septuple and nonuple hysteresis loop behaviors, which have important technological applications. Furthermore, the thermodynamic properties of the nanowire was also studied by evaluating the susceptibility, the internal energy and specific heat for a variety of system physical parameters.

Single Artificial Ion Channels with Tunable Ion Transport Based on the Surface Modification of pH-Responsive Polymers.

Artificial ion channels with tunable ionic transport control and intelligent iontronic functions at the nanoscale have a wide application in logic computing and biosensing. Although some artificial ion channels with smart ion transport characteristics have been developed, most of them are constructed on porous membranes with undefined channel numbers. It is still challenging to achieve multiple ion transport features in single nanochannels and to control the ion flow more accurately with excellent repeatability. In this paper, a design strategy is presented to fabricate pH-responsive ion channels with various ion transport features based on a single polydimethylsiloxane (PDMS) nanochannel. The single-ion nanochannel developed by this approach can be further integrated into electronic systems on a chip. Three types of artificial ion channels are demonstrated and investigated systematically in this work. With symmetric or asymmetric pH stimuli, these ion channels can alternatively change their working states among an opened state, a closed state, and an ionic diode state. Four different ion transport features can be realized in a triple-gated ion channel system. With these advantages of the design, it is promising to build smart nanofluidic iontronic devices with widespread applicability in energy conversions, active ion transport control, and biological analysis.

Competition between single ion and single chain magnetism in stoichiometric spin chain oxides [Sr4Mn2CoO9]n [Sr5Mn3CoO12

Stoichiometric spin chain “Mn4+-Co2+” oxides [Sr4Mn2CoO9]n[Sr5Mn3CoO12] have been synthesized for n ​= ​1, 2, 3, 4, 5, ∞. The X-ray powder diffraction study of these oxides also formulated Sr1+x(Mn1-xCox)O3, shows that their hexagonal aperiodic structure (a≈9.6 ​Å, c1 ​~ ​2.6 ​Å, c2 ​~ ​3.9 ​Å; modulation vector q ​= ​γc1∗, with γ ​= ​c1/c2) consists of blocks of multiple (n) Mn2CoO9 trimeric units that alternate with single Mn3CoO12 tetrameric units. Competition between single ion (SIM) and single chain magnetism (SCM) is established from ac-susceptibility magnetic measurements: introduction of tetrameric units in trimeric chains hinders SIM signal which decreases with n and disappears for n ​= ​1. A model is proposed for the origin of SIM based on the presence of [Mn4+2Co2+Mn4+2O18]18−groups in the structure. This scheme is supported by the SIM signal observed for the n ​= ​∞ member Sr2Ca2Mn2Co0.5Zn0.5O9 that contains a majority of isolated [Mn4+2Co2+Mn4+2O18] groups.

Quantum simulation of a general anti-[formula omitted]-symmetric Hamiltonian with a trapped ion qubit

Non-Hermitian systems satisfying parity-time (PT) symmetry have aroused considerable interest owing to their exotic features. Anti-PT symmetry is an important counterpart of the PT symmetry, and has been studied in various classical systems. Although a Hamiltonian with anti-PT symmetry only differs from its PT-symmetric counterpart in a global ±i phase, the information and energy exchange between systems and environment are different under them. It is also suggested theoretically that anti-PT symmetry is a useful concept in the context of quantum information storage with qubits coupled to a bosonic bath. So far, the observation of anti-PT symmetry in individual quantum systems remains elusive. Here, we implement an anti-PT-symmetric Hamiltonian of a single qubit in a single trapped ion by a designed microwave and optical control-pulse sequence. We characterize the anti-PTphase transition by mapping out the eigenvalues at different ratios between coupling strengths and dissipation rates. The full information of the quantum state is also obtained by quantum state tomography. Our work allows quantum simulation of genuine open-system feature of an anti-PT-symmetric system, which paves the way for utilizing non-Hermitian properties for quantum information processing.

Adsorption kinetics and isotherms of binary metal ion aqueous solution using untreated venus shell

Among available technologies to remove heavy metals from wastewater, biosorption has gained more attention due to its high removal efficiency, friendly operation, and inexpensive cost. Despite many studies on metal adsorption from single ion solutions, kinetics and isotherms of binary metal ions simultaneously adsorbed onto biosorbents have not been thoroughly investigated to provide insight on involving mechanisms. This study explored the adsorption potential of untreated venus shells (UVS) that can be utilized in economical and environmentally-friendly ways. In this work, UVS of different sizes were prepared without chemical treatment as a biosorbent. Characterization of UVS was accomplished using nitrogen adsorption isotherm, FTIR, and SEM-EDX. Batch adsorption was carried out to study the effect of initial metal ion concentration, adsorbent dosage, and size on removing Cu(II) and Zn(II) from a binary solution of both metal ions using UVS. The experimental values of maximum adsorption capacities of Cu(II) and Zn(II) were 0.446 and 0.465 mg/g, respectively. The adsorption data were analyzed using the pseudo-first order, pseudo-second order, Elovich, and intraparticle diffusion rate equations. The pseudo-second order and the intraparticle diffusion model yielded the best fit to the experimental data for Cu(II) and Zn(II) ions, respectively. The equilibrium isotherm was examined using the Langmuir, Freundlich, Temkin, Dubinin–Radushkevich (D–R), and Elovich models. The Freundlich model best fits the Cu(II) and Zn(II) equilibrium adsorption data. The results indicated that the adsorption of Cu(II) and Zn(II) onto UVS-600 adsorbent could undergo a chemisorption mechanism. Both metal ions in an aqueous solution were competitively adsorbed onto the heterogeneous active sites available on the shell surfaces. Cu(II) and Zn(II) ions in the binary system could result in ionic interference between the adsorbed ions and the active sites.

Detecting and Compensating for Excess Ion Micromotion in the Single Ion Optical Frequency Standard

Detecting and Compensating for Excess Ion Micromotion in the Single Ion Optical Frequency Standard

Robustness of Semi-Superjunction 4H-SiC Power DMOSFETs to Single-Event Burnout from Heavy Ion Bombardment

We compare the failure mechanism and performance of a silicon carbide (SiC) semi-superjunction (semi-SJ) power DMOSFET against pure SJ and conventional DMOSFET when struck by a single heavy ion. The Single-Event Burnout (SEB) failure mechanism was identified as the thermal runaway from second breakdown resulting in mesoplasma formation. The semi-SJ design shifts the mesoplasma location from the drift/substrate interface seen in the control device structures to a location along the center of the P-pillar and closer towards the DMOSFET surface, thus significantly improving the SEB threshold voltage (VSEB). The VSEB varies with pillar width and ratio of pillar thickness to drift layer thickness. A maximum value of VSEB is reached when the pillar to drift layer ratio is 0.9 and the pillar width is 2.4 μm. The semi-SJ SEB/breakdown voltage ratio is 100% and 13% higher than the pure SJ and conventional DMOSFET, respectively. Using a new Figure of Merit (FoM), which accounts for the tradeoff between VSEB and on-state performance, we find that the SiC semi-SJ DMOSFET achieves a FoM that is 1.8 and 8 times higher than SJ and conventional DMOSFET, respectively, making the semi-SJ a competitive candidate for radiation hardened applications.