Conductance Data Research Articles

A Chemically Soldered Polyoxometalate Single-Molecule Transistor.

Polyoxometalates have been proposed in the literature as nanoelectronic components, where they could offer key advantages with their structural versatility and rich electrochemistry. Apart from a few studies on their ensemble behaviour (as monolayers or thin films), this potential remains largely unexplored. We synthesised a pyridyl‐capped Anderson–Evans polyoxometalate and used it to fabricate single‐molecule junctions, using the organic termini to chemically “solder” a single cluster to two nanoelectrodes. Operating the device in an electrochemical environment allowed us to probe charge transport through different oxidation states of the polyoxometalate, and we report here an efficient three‐state transistor behaviour. Conductance data fits a quantum tunnelling mechanism with different charge‐transport probabilities through different charge states. Our results show the promise of polyoxometalates in nanoelectronics and give an insight on their single‐entity electrochemical behaviour.

A Chemically Soldered Polyoxometalate Single‐Molecule Transistor

AbstractPolyoxometalates have been proposed in the literature as nanoelectronic components, where they could offer key advantages with their structural versatility and rich electrochemistry. Apart from a few studies on their ensemble behaviour (as monolayers or thin films), this potential remains largely unexplored. We synthesised a pyridyl‐capped Anderson–Evans polyoxometalate and used it to fabricate single‐molecule junctions, using the organic termini to chemically “solder” a single cluster to two nanoelectrodes. Operating the device in an electrochemical environment allowed us to probe charge transport through different oxidation states of the polyoxometalate, and we report here an efficient three‐state transistor behaviour. Conductance data fits a quantum tunnelling mechanism with different charge‐transport probabilities through different charge states. Our results show the promise of polyoxometalates in nanoelectronics and give an insight on their single‐entity electrochemical behaviour.

Analysis characteristic of cholesteryl acrylate conductivity with the addition of the PE-b-PEG doped ITO-nanoparticle in the development of liquid crystal technology

The study of liquid crystal material is very interesting and has the opportunity as a smart material such as cholesteryl acrylate. Liquid crystal cholesteryl acrylate can be made shynthesized by Acryloiloxy Butyloxy Benzoate (ABB) precursor and cholesterol. Cholesteryl acrylate was polymerized by the ultraviolet curing (UV-Curing) method to keep the crystal structure stable. During the polymerization process some ingredients are added which can increase and regulate the formation of liquid crystal structure phases. Cholesteryl acrylate can be doped by adding conductive oxide in the form of nano particle scale Indium Tin Oxide (18 nm). The optimum conductivity results were 5.70 × 10−7 S/m with the addition of ITO 10% w/w. The structure of the crystal phase formed can be directed by the addition of Polyethylene-block-Polyethylene Glycol during the UV-Curing process. The hydrophobic part of PE block will interact with hydrophobic liquid crystal molecules, while the hydrophilic part of the PEG block has a high affinity for the hydrophilic ITO electrode substrate. The added PE-b-PEG varies from 0.001 to 0.005 percent by weight of polymer cholesteryl acrylate composite. Conductance data is measured using LCR meters from a frequency of 50 Hertz to 5000 kHertz. The average conductance data for ITO is 0.09597838 S, cholesteryl acrylate is 5.20635 × 10−6 S, the polymer cholesteryl acrylate composite with doped ITO is 4.58284 × 10−6 S. When added PE-b-PEG 0,003 percent composite weight is obtained the highest average conductance data is 1.24234 × 10−5 S with an average conductivity value of 6.09 × 10−5 S/m. The varies composition of PE-b-PEG content is very influential to regulate the arrangement of crystals formed in electrical conductivity.

Subcellular proteomics combined with bioenergetic phenotyping reveals protein biomarkers of respiratory insufficiency in the setting of proofreading-deficient mitochondrial polymerase

The mitochondrial mutator mouse is a well-established model of premature aging. In addition to accelerated aging, these mice develop hypertrophic cardiomyopathy at ~13 months of age, presumably due to overt mitochondrial dysfunction. Despite evidence of bioenergetic disruption within heart mitochondria, there is little information about the underlying changes to the mitochondrial proteome that either directly underly or predict respiratory insufficiency in mutator mice. Herein, nLC-MS/MS was used to interrogate the mitochondria-enriched proteome of heart and skeletal muscle of aged mutator mice. The mitochondrial proteome from heart tissue was then correlated with respiratory conductance data to identify protein biomarkers of respiratory insufficiency. The majority of downregulated proteins in mutator mitochondria were subunits of respiratory complexes I and IV, including both nuclear and mitochondrial-encoded proteins. Interestingly, the mitochondrial-encoded complex V subunits, were unchanged or upregulated in mutator mitochondria, suggesting a robustness to mtDNA mutation. Finally, the proteins most strongly correlated with respiratory conductance were PPM1K, NDUFB11, and C15orf61. These results suggest that mitochondrial mutator mice undergo a specific loss of mitochondrial complexes I and IV that limit their respiratory function independent of an upregulation of complex V. Additionally, the role of PPM1K in responding to mitochondrial stress warrants further exploration.

A maximum extreme-value distribution model for switching conductance of oxide-RRAM in memory applications

In this work, we report an extensive experimental investigation of the important statistical properties of resistive random access memory (RRAM) switching conductance. We demonstrate the Gumbel statistics, a maximum extreme-value distribution for switching-filament conductance, as opposed to the minimum extreme-value distribution such as Weibull model. We apply a Poisson random statistical distribution for the spatial generation of percolation filaments to link the RRAM conductance measurements with device areas. As a result, we can derive two important relations: area scaling properties of percentiles and scale-factors. We show the validity of this maximum extreme-value distribution model by rigorously examining the vertical percentile-scaling characteristics of experimental data. The independently extracted shape-factor from the area-dependence of scale-factors captures the merged conductance distributions in good agreement with the experimental conductance data. It is revealed that larger variability associated with RRAM conductance measurements is directly linked to the maximum-valued statistical characteristics of this model. We also demonstrate that RRAM conductance, rather than resistance, is a fundamental statistical variable.

Conductance-Matrix Symmetries of a Three-Terminal Hybrid Device.

We present conductance-matrix measurements of a three-terminal superconductor-semiconductor hybrid device consisting of two normal leads and one superconducting lead. Using a symmetry decomposition of the conductance, we find that antisymmetric components of pairs of local and nonlocal conductances qualitatively match at energies below the superconducting gap, and we compare this finding with symmetry relations based on a noninteracting scattering matrix approach. Further, the local charge character of Andreev bound states is extracted from the symmetry-decomposed conductance data and is found to be similar at both ends of the device and tunable with gate voltage. Finally, we measure the conductance matrix as a function of magnetic field and identify correlated splittings in low-energy features, demonstrating how conductance-matrix measurements can complement traditional single-probe measurements in the search for Majorana zero modes.

Estimation of nonlinear water-quality trends in high-frequency monitoring data.

Recent advances in high-frequency water-quality sensors have enabled direct measurements of physical and chemical attributes in rivers and streams nearly continuously. Water-quality trends can be used to identify important watershed-scale changes driven by natural and anthropogenic influences. Statistical methods to estimate trends using high-frequency data are lacking. To address this gap, an evaluation of the generalized additive model (GAM) approach to test for trends in high-frequency data was conducted. Our proposed framework includes methods for handling serial correlation, trend estimation and slope-change detection, and trend interpretation at arithmetic scale for log-transformed variables. Water-temperature and turbidity data, representing two analytes with different temporal patterns, collected from the James River at Cartersville, Virginia, USA, were chosen for this analysis. Results indicated that the model, including flow, season, time covariates, and interaction between flow and season performed well for both analytes. The same model structure was applied to specific conductance data, collected from a small highly urbanized watershed, with satisfactory model performance. The water temperature GAM results indicated that the significant decreasing-then-increasing patterns after 2012 were mainly driven by air temperature changes. The turbidity trend was not significant over time. The specific conductance results showed a consistently upward trend over the last decade due to ever-increasing urbanization in the small watershed. This study suggests that the GAM method has great potential as a useful tool for trend analysis on high-frequency data, and for informing watershed managers of hydro-climatic and human influences on water quality by detecting crucial signal variation over time.

Nonlinearity exponent: A phase sensitive parameter in disordered systems

The real part of alternating current conductance Σ(T,f) of disordered systems shows nonOhmic behavior characterized by the existence of an onset frequency fc(T) below which Σ(T,f) retains its Ohmic value Σ0 but increases monotonically with frequency above fc(T). fc(T) scales with Σ0 as fc(T)∼Σ0(T,f)xf with xf as the nonlinearity exponent. By analyzing such experimental data of AC conductance varied by temperature and disorder on a wide variety of disordered systems, we show that xf has different values at different phases of a disordered system and can be used to identify the existence of different phases exhibited by such systems. Experimental results of nonOhmic conduction, existence of onset frequency fc(T), and the role of the onset exponent xf in identifying various phases of disordered systems are systematically analyzed within the framework of scaling formalism and explained with intra-chain conduction and tunneling between conducting grains separated by insulating regions.

Conductance and FTIR Spectroscopic Study of Triple-ion Formation of Tetrabutylphosphonium Methanesulfonate in Methylamine Solution

Triple-ion formation of tetrabutylphosphonium methanesulfonate [Bu4PCH3SO3] in methylamine solution has been reported quantitatively by conductometric study, and the observation has evident from the qualitative analysis of FT-IR spectroscopy. The ionic liquid exists as triple-ion state in low dielectric constant solution (methylamine solution having er<10). Thus, the conductance data have been analysized using the fuoss-kraus theory of triple-ion formation. After that, the results have been discussed in terms of driving forces i.e., H-bond formation, dipole-dipole interactions, and structural aspect (functional group) of the ionic liquid and methylamine molecules. Shifting of the stretching frequency of functional group of the solvent in presence and absence of the ionic liquid has been taken into account in FTIR spectroscopic study, and then the solvation consequence has been manifest by the change of the intensity.

Synthesis, characterization, DFT, In-vitro anti-microbial, cytotoxicity evaluation, and DNA binding interactions of transition metal complexes of quinoxaline Schiff base ligand

A series of Cr(III), Mn(II), Fe(III), Co(II), Cu(II) and Ni(II) transition metal complexes of the quinoxaline based Schiff base ligand were synthesized and characterized on the basis of analytical, conductance, magnetic moment, FT-IR, NMR, ESR, EDAX and electronic spectral data. The ligand behaves as bidentate OO donors through phenolic oxygen and carbonyl oxygen in the quinoxaline ring. The molecular structure of the quinoxaline Schiff base ligand and Cu(II) complex was investigated theoretically. The optimized molecular structure was obtained from Gaussian 09 program. The antimicrobial activity of the ligand and the complexes were screened for various bacterial and fungal strains and found to be good for Co(II) and Mn(II) complexes and moderate for the other synthesized complexes. The minimum inhibitory concentration of the Co(II) and Mn(II)complexes against S. aureus, S. paratyphi and A. niger were found to be 250 μg/ml, 125 μg/ml, 500 μg/ml and 250 μg/ml, 250 μg/ml , 500 μg/ml respectively. The anti-cancer activity of the ligand and the complexes were studied against the human breast cancer cell lines MCF-7 and found to be good for Cu(II), Co(II) and Mn(II) complexes. The in-vitro anti-oxidant activities of the complexes and found to be moderate for all complexes. The DNA binding ability of the complexes were checked and their binding constants were reported using absorption and emission spectral studies.

Thermodynamic Studies of Complexes of Amlodipine Besylate with Ni2+, Mg2+, Co2+ and Ca2+ cations in pure and in mixed binary solvent systems at 303.15, 313.15 and 323.15 K by Conductometric Method

The present work relates to the complexation reaction between Amlodipine Besylate[AML] with Ni2+, Mg2+, Co2+ and Ca2+ cation in dimethylsulfoxide (DMSO), pure methanol (MeOH) and their binary mixtures(DMSO-MeOH and DMSO-Water) by conductometric method. The conductance data show that the stoichiometry of the complexes formed between AML with Ni2+, Mg2+, Co2+ and Ca2+ cation in pure DMSO, pure MeOHas well as in the binary solvent mixtures was 1:1. The stability of AML complexes with Ni2+ , Mg2+, Co2+ and Ca2+ metal ion was observed to be sensitive to the nature of the solvent system. In case of DMSO-Water binary solvent systems there was a linear change in LogKf values but in case of DMSO-MeOH binary solvent systems non linear change in LogKf values observed.The negative values of ΔG0 show that the reaction is spontaneous and ability of the AML ligand to form stable complexes. However, the result shows positive value of ΔH0 which indicates that enthalpy is not driving force for the formation of the complexes. Furthermore, the positive value of ΔS0 indicates that entropy is a driving force for the complexation. The values of ΔH0 and ΔS0 for formation of the complexes were obtained from temperature dependence of the stability constants.

Template‐engineered metal macrocyclic complexes: Synthesis and biological activity

AbstractThree new azamacrocylic complexes of divalent transition‐metal ions were synthesized by taking Co(II), Ni(II), and Cu(II) metal ions as templates. The macrocyclic ligand (12Z,52Z,54E)‐11,12,13,14,15,16,51,52,53,54,55,56‐dodecahydro‐2,4,6,8‐tetraaza‐1 (2,4),5(4,2)‐pyrimidine‐3,7(1,2)‐dibenzenacyclooctaphane‐16,56‐dione was derived from o‐phenylenediamine (OPD) and 2‐thiobarbituric acid (TBA). All the complexes were fully characterized through spectroscopic techniques and elemental analyses. The structures of the macrocyclic complexes were determined by IR, UV–vis, ESI‐MS, TGA, molar conductance, magnetic moment, and electron spin resonance data. On the basis of the above studies, the complexes may be formulated as [MLX2], in which L is a macrocyclic ligand and X = CH3COO−. All the macrocyclic complexes were biologically screened to evaluate their antimicrobial efficacy. DNA binding study of two representative complexes was performed by UV–vis titrations.

Scanning tunneling Andreev microscopy of titanium nitride thin films

We report scanning tunneling microscopy results on 25- and 50-nm-thick films of superconducting TiN that show Andreev tunneling behavior at 0.5 K. At most locations on the topographically rough surfaces, we observe tip-sample current-voltage characteristics with a clear superconducting gap, as expected for superconductor-normal (S-N) tunneling through a low-transparency barrier, while in some places, we find a zero-voltage conductance peak, as expected for S-N Andreev tunneling through a highly transparent barrier. Fitting the Blonder-Tinkham-Klapwijk model to the conductance data allows an accurate extraction of the TiN superconducting gap $\mathrm{\ensuremath{\Delta}}$, by accounting for local variations in the tip-sample barrier height $Z$ and junction temperature $T$. From spatial maps of the model parameters, we find that both films show a strong inhomogeneity, with $\mathrm{\ensuremath{\Delta}}$ varying by as much as a factor of 2 from grain to grain. In the thicker film, however, correlations between $T,Z$, and $\mathrm{\ensuremath{\Delta}}$ suggest the grains are thermally isolated, perhaps due to internal stress. We discuss possible mechanisms that could produce these large correlated variations, including local heating and surface contamination, and consider some of the implications for devices made from such films.

Quantifying student engagement in learning about climate change using galvanic hand sensors in a controlled educational setting

Teaching climate change is complex because it requires a system-level understanding of many science disciplines and also because students may have preconceptions about climate change. Previous work shows students learn and retain science content better when they are engaged in the learning process. Active learning strategies engage students in learning science, but the engagement impact of active learning has not yet been assessed in a controlled environment using both biometric and self-reporting tools. Here, we analyze 52 university students’ engagement during several common active learning strategies in a controlled research setting. We collected biometric data from all participants with hand sensors that measured changes in skin conductance as a proxy for engagement. Participants self-reported their engagement as a control. The combined biometric and self-reported data show that skin conductance data matched self-reported engagement, confirming that skin conductance is a robust proxy for engagement. Overall, dialog was the most engaging activity, with engagement levels about 165% above baseline. Non-science majors had higher average engagement than science majors (137% vs. 53% above baseline, respectively). Notably, skin conductance data showed no statistically significant differences based on participants’ political or religious affiliations. In summary, our results demonstrate biometric sensors’ potential to measure and monitor engagement in a learning environment. Relevant for climate education, in-class dialog increases student engagement in learning climate science and is especially effective for non-science majors.

A physiological assessment of patient pain during surgery with wide-awake local anesthesia

PurposePatients receiving surgery with wide-awake local anesthesia typically report little or no intraoperative pain. However, self-report assessments of pain are susceptible to bias. In the present study, patient self-report ratings were supplemented with objective physiological measures of electrodermal activity. MethodsFifteen patients receiving forefoot surgery using wide-awake local anesthesia were recruited. Pain ratings and skin conductance responses were acquired during the initial anesthetic injection (into unanesthetized tissue), during a follow-up anesthetic injection (into anesthetized tissue), and during five intraoperative procedures. ResultsThe highest ratings of self-reported pain coincided with the initial anesthetic injection, and pain ratings were similarly low at all remaining measurement points. Fourteen patients reported no pain beyond the initial injection, whereas one patient reported minimal pain during two intraoperative procedures. Skin conductance data were consistent with pain ratings such that responses to the initial injection were significantly larger than responses at any subsequent measurement point. ConclusionThese results provide further evidence that patients experience little or no pain during surgery with wide-awake local anesthesia.

Determination of current transport and trap states density in AlInGaN/GaN heterostructures

The energy distribution and the relaxation time constant of the trap states with respect to conduction bands in the (Ni/Au) Schottky contact on AlInGaN/GaN heterostructures were investigated using the admittance technique. The potential dependent capacitance/conductance measurements were done in the frequency range of 5 kHz to 5 MHz at a temperature of 300 K. We found strong frequency dispersions at the accumulation regions and at the sharp transition regions (depletion region) in the capacitance curves. High frequency dispersion at the accumulation regions in C-V characteristics indicates that there is a high-density of surface traps between the metal–AlInGaN quaternary layer interfaces. Furthermore, the frequency dispersion at the sharp transition regions behavior can be attributed to the interface traps state between the AlInGaN quaternary layer and GaN layer. A detailed analysis of the frequency-dependent capacitance and conductance data was performed, assuming the models in which traps are located between the metal–AlInGaN interface (surface traps) and between AlInGaN/GaN interfaces (interface traps). The trap states density and time constants of the traps states were calculated as a function of energy separation from the conduction-band edge. The trap states' densities change between 1.3 × 1011 eV−1 cm−2 and 6.2 × 1011 eV−1 cm−2. Also, 4.8 to 5.3 μs time interval calculated for the relaxation times.

Psychological and physiological effects of applying self-control to the mobile phone.

This preregistered study examined the psychological and physiological consequences of exercising self-control with the mobile phone. A total of 125 participants were randomly assigned to sit in an unadorned room for six minutes and either (a) use their mobile phone, (b) sit alone with no phone, or (c) sit with their device but resist using it. Consistent with prior work, participants self-reported more concentration difficulty and more mind wandering with no device present compared to using the phone. Resisting the phone led to greater perceived concentration abilities than sitting without the device (not having external stimulation). Failing to replicate prior work, however, participants without external stimulation did not rate the experience as less enjoyable or more boring than having something to do. We also observed that skin conductance data were consistent across conditions for the first three-minutes of the experiment, after which participants who resisted the phone were less aroused than those who were without the phone. We discuss how the findings contribute to our understanding of exercising self-control with mobile media and how psychological consequences, such as increased mind wandering and focusing challenges, relate to periods of idleness or free thinking.

Depth‐ and Time‐Resolved Distributions of Snowmelt‐Driven Hillslope Subsurface Flow and Transport and Their Contributions to Surface Waters

AbstractMajor components of hydrologic and elemental cycles reside underground, where their complex dynamics and linkages to surface waters are obscure. We delineated seasonal subsurface flow and transport dynamics along a hillslope in the Rocky Mountains (USA), where precipitation occurs primarily as winter snow and drainage discharges into the East River, a tributary of the Gunnison River. Hydraulic and geochemical measurements down to 10 m below ground surface supported application of transmissivity feedback of snowmelt to describe subsurface flow and transport through three zones: soil, weathering shale, and saturated fractured shale. Groundwater flow is predicted to depths of at least 176 m, although a shallower limit exists if hillslope‐scale hydraulic conductivities are higher than our local measurements. Snowmelt during the high snowpack water year 2017 sustained flow along the weathering zone and downslope within the soil, while negligible downslope flow occurred along the soil during the low snowpack water year 2018. We introduce subsurface concentration‐discharge (C‐Q) relations for explaining hillslope contributions to C‐Q observed in rivers and demonstrate their calculations based on transmissivity fluxes and measured pore water specific conductance and dissolved organic carbon. The specific conductance data show that major ions in the hillslope pore waters, primarily from the weathering and fractured shale, are about six times more concentrated than in the river, indicating hillslope solute loads are disproportionately high, while flow from this site and similar regions are relatively smaller. This methodology is applicable in different representative environments within snow‐dominated watersheds for linking their subsurface exports to surface waters.

A Conductometric Study of Complexation Reaction between Kryptofix 22DD with Yttrium(III) Cation in Some Binary Mixed Non-aqueous Solvents

The complexation process between Y3+ cation and kryptofix 22DD was studied in ethyl acetate–dimethylformamide (EtOAc–DMF), ethyl acetate–methanol (EtOAc–MeOH), ethyl acetate–nitromethane (EtOAc–NM) and ethyl acetate–dimethylsulfoxide (EtOAc–DMSO) binary mixtures at different temperatures by using conductometric method. The conductance data show that in most cases, the stoichiometry of the complex formed between the macrocyclic ligand and the Y3+ cation is 1 : 1 [ML]. But in some systems such as, in the case of EtOAc–DMSO (90 mol % DMSO) binary solvent solution, in addition to formation of a 1 : 1 (ML) complex, a 1 : 2 (ML2) complex is formed in solution, which shows that the stoichoimetry of complexes may be changed by the nature of the medium. The stability order of (kryptofix 22DD · Y)3+complex in the studied binary solvent solutions at 25°C was found to be: EtOAc–MeOH > EtOAc–DMF > EtOAc–DMSO and in the case of pure non-aqueous solvents at 25°C it was: EtOAc > MeOH > DMF ∼ NM. A density functional theory (DFT) study of the interaction of yttrium(III) cation with kryptofix 22DD in the liquid phase for the pure organic solvents was performed. The results are in reasonably good agreement with the experimental data. A non-linear behavior was observed for changes of log Kf of (kryptofix 22DD · Y)3+ complex versus the composition of the binary mixed solvents, which was explained in terms of solvent–solvent interactions and also the preferential solvation of the species involved in the complexation reaction.

Sources, fate, and flux of geothermal solutes in the Yellowstone and Gardner Rivers, Yellowstone National Park, WY

The total discharge and thermal output from the numerous hydrothermal features in Yellowstone National Park (YNP) can be estimated from the chloride (Cl) flux in the Madison, Yellowstone, Falls, and Snake Rivers. Monitoring the Cl flux in these four major rivers provides a holistic view of the hydrothermal output from YNP and changes in the Cl flux may indicate changes in geothermal or magmatic activity. In this study, the source, fate, and flux of geothermal solutes in the Yellowstone River and Gardner Rivers were determined. Beginning in 2012, the fluxes of geothermal solutes, including Cl, were determined at monitoring sites in the Yellowstone and Gardner Rivers downstream of geothermal inputs within YNP. A method was developed using specific conductance as a surrogate measure for solute concentrations at these monitoring sites. Combining continuous (15-min) specific conductance and discharge data, Cl and other geothermal solute fluxes were determined and approximately 32% of the Cl flux exiting YNP is from the Yellowstone River watershed. Synoptic sampling of river water and discharge measurements were performed during low-flow conditions of September 2014 allowed for the determinations of geothermal solute sources and their downstream fate. Thus, the contribution of geothermal solutes from the various geothermal areas at the downstream monitoring sites was quantified. The thermal features draining into Yellowstone Lake account for 34% of the Cl flux at the Yellowstone River monitoring site which is located approximately 5 km north of YNP. The Gardner River, which captures geothermal water from Mammoth Hot Springs, is responsible for 22% of the Cl at the Yellowstone River monitoring site. Because the Yellowstone River watershed is large and contains numerous thermal areas, knowing the source and fate of geothermal solutes is import baseline information that can be used to identify future changes in thermal activity.