Sensing properties of separative paper-based extended-gate ion-sensitive field-effect transistor for cost effective pH sensor applications

NASA Astrophysics Data System (ADS)

Cho, Won-Ju; Lim, Cheol-Min

2018-02-01

In this study, we developed a cost-effective ion-sensing field-effect transistor (FET) with an extended gate (EG) fabricated on a separative paper substrate. The pH sensing characteristics of the paper EG was compared with those of other EGs fabricated on silicon, glass, or polyimide substrates. The fabricated paper-based EGFET exhibited excellent sensitivity close to the Nernst response limit as well as to that of the other substrate-based EGFETs. In addition, we found that all EGFETs, regardless of the substrate, have similar non-ideal behavior, i.e., drift phenomenon and hysteresis width. To investigate the degradation and durability of the paper EG after prolonged use, aging-effect tests were carried out in terms of the hysteresis width and sensitivity over a course of 30 days. As a result, the paper EG maintained stable pH sensing characteristics after 30 days. Therefore, we expect that paper EGFETs can provide a cost-effective sensor platform.

Mass spectrometric characterization of a high-field asymmetric waveform ion mobility spectrometer

NASA Astrophysics Data System (ADS)

Purves, Randy W.; Guevremont, Roger; Day, Stephen; Pipich, Charles W.; Matyjaszczyk, Matthew S.

1998-12-01

Ion mobility spectrometry (IMS) has become an important method for the detection of many compounds because of its high sensitivity and amenability to miniaturization for field-portable monitoring; applications include detection of narcotics, explosives, and chemical warfare agents. High-field asymmetric waveform ion mobility spectrometry (FAIMS) differs from IMS in that the electric fields are applied using a high-frequency periodic asymmetric waveform, rather than a dc voltage. Furthermore, in FAIMS the compounds are separated by the difference in the mobility of ions at high electric field relative to low field, rather than by compound to compound differences in mobility at low electric field (IMS). We report here the first cylindrical-geometry-FAIMS interface with mass spectrometry (FAIMS-MS) and the MS identification of the peaks observed in a FAIMS compensation voltage (CV) spectrum. Using both an electrometer-based-FAIMS (FAIMS-E) and FAIMS-MS, several variables that affect the sensitivity of ion detection were examined for two (polarity reversed) asymmetric waveforms (modes 1 and 2) each of which yields a unique spectrum. An increase in the dispersion voltage (DV) was found to improve the sensitivity and separation observed in the FAIMS CV spectrum. This increase in sensitivity and the unexpected dissimilarity in modes 1 and 2 suggest that atmospheric pressure ion focusing is occurring in the FAIMS analyzer. The sensitivity and peak locations in the CV spectra were affected by temperature, gas flow rates, operating pressure, and analyte concentration.

Portable, universal, and visual ion sensing platform based on the light emitting diode-based self-referencing-ion selective field-effect transistor.

PubMed

Zhang, Xiaowei; Han, Yanchao; Li, Jing; Zhang, Libing; Jia, Xiaofang; Wang, Erkang

2014-02-04

In this work, a novel and universal ion sensing platform was presented, which enables the visual detection of various ions with high sensitivity and selectivity. Coaxial potential signals (millivolt-scale) of the sample from the self-referencing (SR) ion selective chip can be transferred into the ad620-based amplifier with an output of volt-scale potentials. The amplified voltage is high enough to drive a light emitting diode (LED), which can be used as an amplifier and indicator to report the sample information. With this double amplification device (light emitting diode-based self-referencing-ion selective field-effect transistor, LED-SR-ISFET), a tiny change of the sample concentration can be observed with a distinguishable variation of LED brightness by visual inspection. This LED-based luminescent platform provided a facile, low-cost, and rapid sensing strategy without the need of additional expensive chemiluminescence reagent and instruments. Moreover, the SR mode also endows this device excellent stability and reliability. With this innovative design, sensitive determination of K(+), H(+), and Cl(-) by the naked eye was achieved. It should also be noticed that this sensing strategy can easily be extended to other ions (or molecules) by simply integrating the corresponding ion (or molecule) selective electrode.

Photocurable Polymers for Ion Selective Field Effect Transistors. 20 Years of Applications

PubMed Central

Abramova, Natalia; Bratov, Andrei

2009-01-01

Application of photocurable polymers for encapsulation of ion selective field effect transistors (ISFET) and for membrane formation in chemical sensitive field effect transistors (ChemFET) during the last 20 years is discussed. From a technological point of view these materials are quite interesting because they allow the use of standard photo-lithographic processes, which reduces significantly the time required for sensor encapsulation and membrane deposition and the amount of manual work required for this, all items of importance for sensor mass production. Problems associated with the application of this kind of polymers in sensors are analysed and estimation of future trends in this field of research are presented. PMID:22399988

Temperature sensitivity analysis of polarity controlled electrostatically doped tunnel field-effect transistor

NASA Astrophysics Data System (ADS)

Nigam, Kaushal; Pandey, Sunil; Kondekar, P. N.; Sharma, Dheeraj

2016-09-01

The conventional tunnel field-effect transistors (TFETs) have shown potential to scale down in sub-22 nm regime due to its lower sub-threshold slope and robustness against short-channel effects (SCEs), however, sensitivity towards temperature variation is a major concern. Therefore, for the first time, we investigate temperature sensitivity analysis of a polarity controlled electrostatically doped tunnel field-effect transistor (ED-TFET). Different performance metrics and analog/RF figure-of-merits were considered and compared for both devices, and simulations were performed using Silvaco ATLAS device tool. We found that the variation in ON-state current in ED-TFET is almost temperature independent due to electrostatically doped mechanism, while, it increases in conventional TFET at higher temperature. Above room temperature, the variation in ION, IOFF, and SS sensitivity in ED-TFET are only 0.11%/K, 2.21%/K, and 0.63%/K, while, in conventional TFET the variations are 0.43%/K, 2.99%/K, and 0.71%/K, respectively. However, below room temperature, the variation in ED-TFET ION is 0.195%/K compared to 0.27%/K of conventional TFET. Moreover, it is analysed that the incomplete ionization effect in conventional TFET severely affects the drive current and the threshold voltage, while, ED-TFET remains unaffected. Hence, the proposed ED-TFET is less sensitive towards temperature variation and can be used for cryogenics as well as for high temperature applications.

Constraining the sensitivity of iodide adduct chemical ionization mass spectrometry to multifunctional organic molecules using the collision limit and thermodynamic stability of iodide ion adducts

DOE PAGES

Lopez-Hilfiker, Felipe D.; Iyer, Siddarth; Mohr, Claudia; ...

2016-04-06

The sensitivity of a chemical ionization mass spectrometer (ions formed per number density of analytes) is fundamentally limited by the collision frequency between reagent ions and analytes, known as the collision limit, the ion–molecule reaction time, and the transmission efficiency of product ions to the detector. We use the response of a time-of-flight chemical ionization mass spectrometer (ToF-CIMS) to N 2O 5, known to react with iodide at the collision limit, to constrain the combined effects of ion–molecule reaction time, which is strongly influenced by mixing and ion losses in the ion–molecule reaction drift tube. A mass spectrometric voltage scanningmore » procedure elucidates the relative binding energies of the ion adducts, which influence the transmission efficiency of molecular ions through the electric fields within the vacuum chamber. Together, this information provides a critical constraint on the sensitivity of a ToF-CIMS towards a wide suite of routinely detected multifunctional organic molecules for which no calibration standards exist. Lastly, we describe the scanning procedure and collision limit determination, and we show results from the application of these constraints to the measurement of organic aerosol composition at two different field locations.« less

Ion optics for high power 50-cm-diam ion thrusters

NASA Technical Reports Server (NTRS)

Rawlin, Vincent K.; Millis, Marc G.

1989-01-01

The process used at the NASA-Lewis to fabricate 30 and 50-cm-diameter ion optics is described. The ion extraction capabilities of the 30 and 50-cm diameter ion optics were evaluated on divergent field and ring-cusp discharge chambers and compared. Perveance was found to be sensitive to the effects of the type and power of the discharge chamber and to the accelerator electrode hole diameter. Levels of up to 0.64 N and 20 kW for thrust and input power, respectively, were demonstrated with the divergent-field discharge chamber. Thruster efficiencies and specific impulse values up to 79 percent and 5000 sec., respectively, were achieved with the ring-cusp discharge chamber.

Entanglement-Based dc Magnetometry with Separated Ions*

NASA Astrophysics Data System (ADS)

Ruster, T.; Kaufmann, H.; Luda, M. A.; Kaushal, V.; Schmiegelow, C. T.; Schmidt-Kaler, F.; Poschinger, U. G.

2017-07-01

We demonstrate sensing of inhomogeneous dc magnetic fields by employing entangled trapped ions, which are shuttled in a segmented Paul trap. As sensor states, we use Bell states of the type |↑↓ ⟩ +ei φ|↓↑ ⟩ encoded in two 40Ca+ ions stored at different locations. The linear Zeeman effect leads to the accumulation of a relative phase φ , which serves for measuring the magnetic-field difference between the constituent locations. Common-mode magnetic-field fluctuations are rejected by the entangled sensor state, which gives rise to excellent sensitivity without employing dynamical decoupling and therefore enables accurate dc sensing. Consecutive measurements on sensor states encoded in the S1 /2 ground state and in the D5 /2 metastable state are used to separate an ac Zeeman shift from the linear dc Zeeman effect. We measure magnetic-field differences over distances of up to 6.2 mm, with accuracies down to 300 fT and sensitivities down to 12 pT /√{Hz }. Our sensing scheme features spatial resolutions in the 20-nm range. For optimizing the information gain while maintaining a high dynamic range, we implement an algorithm for Bayesian frequency estimation.

High Sensitivity pH Sensor Based on Porous Silicon (PSi) Extended Gate Field-Effect Transistor

PubMed Central

Al-Hardan, Naif H.; Abdul Hamid, Muhammad Azmi; Ahmed, Naser M.; Jalar, Azman; Shamsudin, Roslinda; Othman, Norinsan Kamil; Kar Keng, Lim; Chiu, Weesiong; Al-Rawi, Hamzah N.

2016-01-01

In this study, porous silicon (PSi) was prepared and tested as an extended gate field-effect transistor (EGFET) for pH sensing. The prepared PSi has pore sizes in the range of 500 to 750 nm with a depth of approximately 42 µm. The results of testing PSi for hydrogen ion sensing in different pH buffer solutions reveal that the PSi has a sensitivity value of 66 mV/pH that is considered a super Nernstian value. The sensor considers stability to be in the pH range of 2 to 12. The hysteresis values of the prepared PSi sensor were approximately 8.2 and 10.5 mV in the low and high pH loop, respectively. The result of this study reveals a promising application of PSi in the field for detecting hydrogen ions in different solutions. PMID:27338381

High Sensitivity pH Sensor Based on Porous Silicon (PSi) Extended Gate Field-Effect Transistor.

PubMed

Al-Hardan, Naif H; Abdul Hamid, Muhammad Azmi; Ahmed, Naser M; Jalar, Azman; Shamsudin, Roslinda; Othman, Norinsan Kamil; Kar Keng, Lim; Chiu, Weesiong; Al-Rawi, Hamzah N

2016-06-07

In this study, porous silicon (PSi) was prepared and tested as an extended gate field-effect transistor (EGFET) for pH sensing. The prepared PSi has pore sizes in the range of 500 to 750 nm with a depth of approximately 42 µm. The results of testing PSi for hydrogen ion sensing in different pH buffer solutions reveal that the PSi has a sensitivity value of 66 mV/pH that is considered a super Nernstian value. The sensor considers stability to be in the pH range of 2 to 12. The hysteresis values of the prepared PSi sensor were approximately 8.2 and 10.5 mV in the low and high pH loop, respectively. The result of this study reveals a promising application of PSi in the field for detecting hydrogen ions in different solutions.

High sensitivity field asymmetric ion mobility spectrometer

NASA Astrophysics Data System (ADS)

Chavarria, Mario A.; Matheoud, Alessandro V.; Marmillod, Philippe; Liu, Youjiang; Kong, Deyi; Brugger, Jürgen; Boero, Giovanni

2017-03-01

A high sensitivity field asymmetric ion mobility spectrometer (FAIMS) was designed, fabricated, and tested. The main components of the system are a 10.6 eV UV photoionization source, an ion filter driven by a high voltage/high frequency n-MOS inverter circuit, and a low noise ion detector. The ion filter electronics are capable to generate square waveforms with peak-to-peak voltages up to 1000 V at frequencies up to 1 MHz with adjustable duty cycles. The ion detector current amplifier has a gain up to 1012 V/A with an effective equivalent input noise level down to about 1 fA/Hz1/2 during operation with the ion filter at the maximum voltage and frequency. The FAIMS system was characterized by detecting different standard chemical compounds. Additionally, we investigated the use of a synchronous modulation/demodulation technique to improve the signal-to-noise ratio in FAIMS measurements. In particular, we implemented the modulation of the compensation voltage with the synchronous demodulation of the ion current. The analysis of the measurements at low concentration levels led to an extrapolated limit of detection for acetone of 10 ppt with an averaging time of 1 s.

Large area graphene ion sensitive field effect transistors with tantalum pentoxide sensing layers for pH measurement at the Nernstian limit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fakih, Ibrahim, E-mail: ibrahim.fakih@mail.mcgill.ca; Sabri, Shadi; Szkopek, Thomas, E-mail: thomas.szkopek@mcgill.ca

2014-08-25

We have fabricated and characterized large area graphene ion sensitive field effect transistors (ISFETs) with tantalum pentoxide sensing layers and demonstrated pH sensitivities approaching the Nernstian limit. Low temperature atomic layer deposition was used to deposit tantalum pentoxide atop large area graphene ISFETs. The charge neutrality point of graphene, inferred from quantum capacitance or channel conductance, was used to monitor surface potential in the presence of an electrolyte with varying pH. Bare graphene ISFETs exhibit negligible response, while graphene ISFETs with tantalum pentoxide sensing layers show increased sensitivity reaching up to 55 mV/pH over pH 3 through pH 8. Applying themore » Bergveld model, which accounts for site binding and a Guoy-Chapman-Stern picture of the surface-electrolyte interface, the increased pH sensitivity can be attributed to an increased buffer capacity reaching up to 10{sup 14} sites/cm{sup 2}. ISFET response was found to be stable to better than 0.05 pH units over the course of two weeks.« less

Large area graphene ion sensitive field effect transistors with tantalum pentoxide sensing layers for pH measurement at the Nernstian limit

NASA Astrophysics Data System (ADS)

Fakih, Ibrahim; Sabri, Shadi; Mahvash, Farzaneh; Nannini, Matthieu; Siaj, Mohamed; Szkopek, Thomas

2014-08-01

We have fabricated and characterized large area graphene ion sensitive field effect transistors (ISFETs) with tantalum pentoxide sensing layers and demonstrated pH sensitivities approaching the Nernstian limit. Low temperature atomic layer deposition was used to deposit tantalum pentoxide atop large area graphene ISFETs. The charge neutrality point of graphene, inferred from quantum capacitance or channel conductance, was used to monitor surface potential in the presence of an electrolyte with varying pH. Bare graphene ISFETs exhibit negligible response, while graphene ISFETs with tantalum pentoxide sensing layers show increased sensitivity reaching up to 55 mV/pH over pH 3 through pH 8. Applying the Bergveld model, which accounts for site binding and a Guoy-Chapman-Stern picture of the surface-electrolyte interface, the increased pH sensitivity can be attributed to an increased buffer capacity reaching up to 1014 sites/cm2. ISFET response was found to be stable to better than 0.05 pH units over the course of two weeks.

Novel H+-Ion Sensor Based on a Gated Lateral BJT Pair

PubMed Central

Yuan, Heng; Zhang, Jixing; Cao, Chuangui; Zhang, Gangyuan; Zhang, Shaoda

2015-01-01

An H+-ion sensor based on a gated lateral bipolar junction transistor (BJT) pair that can operate without the classical reference electrode is proposed. The device is a special type of ion-sensitive field-effect transistor (ISFET). Classical ISFETs have the advantage of miniaturization, but  they are difficult to fabricate by a single fabrication process because of the bulky and brittle reference electrode materials. Moreover, the reference electrodes need to be separated from the sensor device in some cases. The proposed device is composed of two gated lateral BJT components, one of which had a silicide layer while the other was without the layer. The two components were operated under the metal-oxide semiconductor field-effect transistor (MOSFET)-BJT hybrid mode, which can be controlled by emitter voltage and base current. Buffer solutions with different pH values were used as the sensing targets to verify the characteristics of the proposed device. Owing to their different sensitivities, both components could simultaneously detect the H+-ion concentration and function as a reference to each other. Per the experimental results, the sensitivity of the proposed device was found to be approximately 0.175 μA/pH. This experiment demonstrates enormous potential to lower the cost of the ISFET-based sensor technology. PMID:26703625

Magnetic field effect in fluorescence of excited fluorophore equilibrated with exciplex that reversibly dissociates into radical-ion pair undergoing the spin conversion.

PubMed

Dodin, Dmitry V; Ivanov, Anatoly I; Burshtein, Anatoly I

2012-07-14

The fluorescence of the photoexcited electron acceptor, (1)A∗, and the exciplex, (1)[D(+δ)A(-δ)] formed at contact of (1)A∗ with an electron donor (1)D, is known to be very sensitive to a magnetic field, assisting the spin conversion in the resulting geminate radical ion pair (RIP), (1, 3)[D(+)...A(-)]. The relative increase of the fluorescence in the highest magnetic field compared to the lowest one, known as the magnetic field effect, crucially depends on the dielectric constant of the solvent, ɛ. This phenomenon first studied experimentally is at first reproduced here theoretically by means of the so called integral encounter theory. It was shown to be very sensitive to the position of the exciplex energy level relative to the levels of exciplex precursors and the charged products of its dissociation. The results obtained strongly depend on the dielectric properties of the solvents as well as on the exciplex and RIP formation rates.

Ion peak narrowing by applying additional AC voltage (ripple voltage) to FAIMS extractor electrode.

PubMed

Pervukhin, Viktor V; Sheven, Dmitriy G

2010-01-01

The use of a non-uniform electric field in a high-field asymmetric waveform ion mobility spectrometry (FAIMS) analyzer increases sensitivity but decreases resolution. The application of an additional AC voltage to the extractor electrode ("ripple" voltage, U(ripple)) can overcome this effect, which decreases the FAIMS peak width. In this approach, the diffusion ion loss remains minimal in the non-uniform electric field in the cylindrical part of the device, and all ion losses under U(ripple) occur in a short portion of their path. Application of the ripple voltage to the extractor electrode is twice as efficient as the applying of U(ripple) along the total length of the device. 2010 American Society for Mass Spectrometry. Published by Elsevier Inc. All rights reserved.

A (201)Hg+ Comagnetometer for (199)Hg+ Trapped Ion Space Atomic Clocks

NASA Technical Reports Server (NTRS)

Burt, Eric A.; Taghavi, Shervin; Tjoelker, Robert L.

2011-01-01

A method has been developed for unambiguously measuring the exact magnetic field experienced by trapped mercury ions contained within an atomic clock intended for space applications. In general, atomic clocks are insensitive to external perturbations that would change the frequency at which the clocks operate. On a space platform, these perturbative effects can be much larger than they would be on the ground, especially in dealing with the magnetic field environment. The solution is to use a different isotope of mercury held within the same trap as the clock isotope. The magnetic field can be very accurately measured with a magnetic-field-sensitive atomic transition in the added isotope. Further, this measurement can be made simultaneously with normal clock operation, thereby not degrading clock performance. Instead of using a conventional magnetometer to measure ambient fields, which would necessarily be placed some distance away from the clock atoms, first order field-sensitive atomic transition frequency changes in the atoms themselves determine the variations in the magnetic field. As a result, all ambiguity over the exact field value experienced by the atoms is removed. Atoms used in atomic clocks always have an atomic transition (often referred to as the clock transition) that is sensitive to magnetic fields only in second order, and usually have one or more transitions that are first-order field sensitive. For operating parameters used in the (199)Hg(+) clock, the latter can be five orders of magnitude or more sensitive to field fluctuations than the clock transition, thereby providing an unambiguous probe of the magnetic field strength.

The Effects of Magnetic Exposure on the Nervous System: A study on the effects of low-strength low-frequency magnetic fields on neurotransmitter exocytosis and cell viability through ionic cyclotron resonance frequency

NASA Astrophysics Data System (ADS)

Saveriades, George

This PhD dissertation focuses on the study of the effects of magnetic exposure on biological systems using amperometry techniques and viability assays. In our prior work based on the cyclotron resonance model, chromaffin cells in physiological saline and Ca2+-free media were exposed for 5 minutes to a 2.7 muT magnetic field, with frequency sweeps going from 30-60 Hz (targeting several ions involved in exocytosis) and 44-48 Hz (targeting specifically Ca2+ ions), with noticeable effects on exocytosis. The present study extended the work on chromaffin cells by covering frequency sweeps for different ions, manipulating the time of exposure and the strength of the magnetic field. Furthermore, amperometry was conducted on acute coronal brain slices, to demonstrate that the recorded effects could be measured on neuronal tissue. The viability of chromaffin cells and primary neuronal cultures exposed to magnetic fields was also addressed. The results demonstrate that cellular exocytosis is sensitive to the frequency of the magnetic field it is exposed to, the strength of the magnetic field and the duration of exposure. No significant effects were established with regards to the viability of the cells exposed to magnetic fields.

Effects of retarded electrical fields on observables sensitive to the high-density behavior of the nuclear symmetry energy in heavy-ion collisions at intermediate energies

NASA Astrophysics Data System (ADS)

Wei, Gao-Feng; Li, Bao-An; Yong, Gao-Chan; Ou, Li; Cao, Xin-Wei; Liu, Xu-Yang

2018-03-01

Within the isospin- and momentum-dependent transport model IBUU11, we examine the relativistic retardation effects of electrical fields on the π-/π+ ratio and neutron-proton differential transverse flow in heavy-ion collisions at intermediate energies. Compared to the static Coulomb fields, the retarded electric fields of fast-moving charges are known to be anisotropic and the associated relativistic corrections can be significant. They are found to increase the number of energetic protons in the participant region at the maximum compression by as much as 25% but that of energetic neutrons by less than 10% in 197Au+197Au reactions at a beam energy of 400 MeV/nucleon. Consequently, more π+ and relatively fewer π- mesons are produced, leading to an appreciable reduction of the π-/π+ ratio compared to calculations with the static Coulomb fields. Also, the neutron-proton differential transverse flow, as another sensitive probe of high-density symmetry energy, is also decreased appreciably due to the stronger retarded electrical fields in directions perpendicular to the velocities of fast-moving charges compared to calculations using the isotropic static electrical fields. Moreover, the retardation effects on these observables are found to be approximately independent of the reaction impact parameter.

Selective layer-free blood serum ionogram based on ion-specific interactions with a nanotransistor

NASA Astrophysics Data System (ADS)

Sivakumarasamy, R.; Hartkamp, R.; Siboulet, B.; Dufrêche, J.-F.; Nishiguchi, K.; Fujiwara, A.; Clément, N.

2018-05-01

Despite being ubiquitous in the fields of chemistry and biology, the ion-specific effects of electrolytes pose major challenges for researchers. A lack of understanding about ion-specific surface interactions has hampered the development and application of materials for (bio-)chemical sensor applications. Here, we show that scaling a silicon nanotransistor sensor down to 25 nm provides a unique opportunity to understand and exploit ion-specific surface interactions, yielding a surface that is highly sensitive to cations and inert to pH. The unprecedented sensitivity of these devices to Na+ and divalent ions can be attributed to an overscreening effect via molecular dynamics. The surface potential of multi-ion solutions is well described by the sum of the electrochemical potentials of each cation, enabling selective measurements of a target ion concentration without requiring a selective organic layer. We use these features to construct a blood serum ionogram for Na+, K+, Ca2+ and Mg2+, in an important step towards the development of a versatile, durable and mobile chemical or blood diagnostic tool.

Biogenic volatile organic compound analyses by PTR-TOF-MS: Calibration, humidity effect and reduced electric field dependency.

PubMed

Pang, Xiaobing

2015-06-01

Green leaf volatiles (GLVs) emitted by plants after stress or damage induction are a major part of biogenic volatile organic compounds (BVOCs). Proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS) is a high-resolution and sensitive technique for in situ GLV analyses, while its performance is dramatically influenced by humidity, electric field, etc. In this study the influence of gas humidity and the effect of reduced field (E/N) were examined in addition to measuring calibration curves for the GLVs. Calibration curves measured for seven of the GLVs in dry air were linear, with sensitivities ranging from 5 to 10 ncps/ppbv (normalized counts per second/parts per billion by volume). The sensitivities for most GLV analyses were found to increase by between 20% and 35% when the humidity of the sample gas was raised from 0% to 70% relative humidity (RH) at 21°C, with the exception of (E)-2-hexenol. Product ion branching ratios were also affected by humidity, with the relative abundance of the protonated molecular ions and higher mass fragment ions increasing with humidity. The effect of reduced field (E/N) on the fragmentation of GLVs was examined in the drift tube of the PTR-TOF-MS. The structurally similar GLVs are acutely susceptible to fragmentation following ionization and the fragmentation patterns are highly dependent on E/N. Overall the measured fragmentation patterns contain sufficient information to permit at least partial separation and identification of the isomeric GLVs by looking at differences in their fragmentation patterns at high and low E/N. Copyright © 2015. Published by Elsevier B.V.

The effect of the earth's and stray magnetic fields on mobile mass spectrometer systems.

PubMed

Bell, Ryan J; Davey, Nicholas G; Martinsen, Morten; Short, R Timothy; Gill, Chris G; Krogh, Erik T

2015-02-01

Development of small, field-portable mass spectrometers has enabled a rapid growth of in-field measurements on mobile platforms. In such in-field measurements, unexpected signal variability has been observed by the authors in portable ion traps with internal electron ionization. The orientation of magnetic fields (such as the Earth's) relative to the ionization electron beam trajectory can significantly alter the electron flux into a quadrupole ion trap, resulting in significant changes in the instrumental sensitivity. Instrument simulations and experiments were performed relative to the earth's magnetic field to assess the importance of (1) nonpoint-source electron sources, (2) vertical versus horizontal electron beam orientation, and (3) secondary magnetic fields created by the instrument itself. Electron lens focus effects were explored by additional simulations, and were paralleled by experiments performed with a mass spectrometer mounted on a rotating platform. Additionally, magnetically permeable metals were used to shield (1) the entire instrument from the Earth's magnetic field, and (2) the electron beam from both the Earth's and instrument's magnetic fields. Both simulation and experimental results suggest the predominant influence on directionally dependent signal variability is the result of the summation of two magnetic vectors. As such, the most effective method for reducing this effect is the shielding of the electron beam from both magnetic vectors, thus improving electron beam alignment and removing any directional dependency. The improved ionizing electron beam alignment also allows for significant improvements in overall instrument sensitivity.

The effect of a radial electric field on ripple-trapped ions observed by neutral particle fluxes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heikkinen, J.A.; Herrmann, W.; Kurki-Suonio, T.

1997-10-01

The effect of a radial electric field on nonthermal ripple-trapped ions is investigated using toroidal Monte Carlo simulations for edge tokamak plasmas. The increase in the neutral particle flux from the ions trapped in local magnetic wells observed by the charge exchange (CX) detector at a low confinement to high confinement transition at ASDEX (Axially Symmetric Divertor Experiment). Upgrade tokamak [{ital Proceedings of the 20th European Conference on Controlled Fusion and Plasma Physics}, Lisbon (European Physical Society, Petit-Lancy, Switzerland, 1993), Vol. 17C, Part I, p. 267] is reproduced in the simulations by turning on a radial electric field near themore » plasma periphery. The poloidal and toroidal angles at which the CX detector signal is most sensitive to the radial electric field are determined. A fast response time of the signal in the range of 50{endash}100 {mu}s to the appearance of the electric field can be found in the simulations with a relatively large half-width of the negative electric field region. {copyright} {ital 1997 American Institute of Physics.}« less

Simulations of Dynamical Friction Including Spatially-Varying Magnetic Fields

NASA Astrophysics Data System (ADS)

Bell, G. I.; Bruhwiler, D. L.; Litvinenko, V. N.; Busby, R.; Abell, D. T.; Messmer, P.; Veitzer, S.; Cary, J. R.

2006-03-01

A proposed luminosity upgrade to the Relativistic Heavy Ion Collider (RHIC) includes a novel electron cooling section, which would use ˜55 MeV electrons to cool fully-ionized 100 GeV/nucleon gold ions. We consider the dynamical friction force exerted on individual ions due to a relevant electron distribution. The electrons may be focussed by a strong solenoid field, with sensitive dependence on errors, or by a wiggler field. In the rest frame of the relativistic co-propagating electron and ion beams, where the friction force can be simulated for nonrelativistic motion and electrostatic fields, the Lorentz transform of these spatially-varying magnetic fields includes strong, rapidly-varying electric fields. Previous friction force simulations for unmagnetized electrons or error-free solenoids used a 4th-order Hermite algorithm, which is not well-suited for the inclusion of strong, rapidly-varying external fields. We present here a new algorithm for friction force simulations, using an exact two-body collision model to accurately resolve close interactions between electron/ion pairs. This field-free binary-collision model is combined with a modified Boris push, using an operator-splitting approach, to include the effects of external fields. The algorithm has been implemented in the VORPAL code and successfully benchmarked.

Rectangular Ion Funnel: A New Ion Funnel Interface for Structures for Lossless Ion Manipulations

DOE PAGES

Chen, Tsung-Chi; Webb, Ian K.; Prost, Spencer A.; ...

2014-11-19

A recent achievement in Structures for Lossless Ion Manipulations (SLIM) is the ability for near lossless ion focusing, transfer, and trapping in sub-atmospheric pressure regions. While lossless ion manipulations are advantageously applied to the applications of ion mobility separations and gas phase reactions, ion introduction through ring electrode ion funnels or more conventional ion optics to SLIM can involve discontinuities in electric fields or other perturbations that result in ion losses. In this work, we investigated a new funnel design that aims to seamlessly couple to SLIM at the funnel exit. This rectangular ion funnel (RIF) was initially evaluated bymore » ion simulations, fabricated utilizing printed circuit board technology and tested experimentally. The RIF was integrated to a SLIM-TOFMS system, and the operating parameters, including RF, DC bias of the RIF electrodes, and electric fields for effectively interfacing with a SLIM were characterized. The RIF provided a 2-fold sensitivity increase without significant discrimination over a wide m/z range along with greatly improved SLIM operational stability.« less

Nanowire size dependence on sensitivity of silicon nanowire field-effect transistor-based pH sensor

NASA Astrophysics Data System (ADS)

Lee, Ryoongbin; Kwon, Dae Woong; Kim, Sihyun; Kim, Sangwan; Mo, Hyun-Sun; Kim, Dae Hwan; Park, Byung-Gook

2017-12-01

In this study, we investigated the effects of nanowire size on the current sensitivity of silicon nanowire (SiNW) ion-sensitive field-effect transistors (ISFETs). The changes in on-current (I on) and resistance according to pH were measured in fabricated SiNW ISFETs of various lengths and widths. As a result, it was revealed that the sensitivity expressed as relative I on change improves as the width decreases. Through technology computer-aided design (TCAD) simulation analysis, the width dependence on the relative I on change can be explained by the observation that the target molecules located at the edge region along the channel width have a stronger effect on the sensitivity as the SiNW width is reduced. Additionally, the length dependence on the sensitivity can be understood in terms of the resistance ratio of the fixed parasitic resistance, including source/drain resistance, to the varying channel resistance as a function of channel length.

Motional studies of one and two laser-cooled trapped ions for electric-field sensing applications

NASA Astrophysics Data System (ADS)

Domínguez, F.; Gutiérrez, M. J.; Arrazola, I.; Berrocal, J.; Cornejo, J. M.; Del Pozo, J. J.; Rica, R. A.; Schmidt, S.; Solano, E.; Rodríguez, D.

2018-03-01

We have studied the dynamics of one and two laser-cooled trapped ?Ca? ions by applying electric fields of different nature along the axial direction of the trap, namely, driving the motion with a harmonic dipolar field, or with white noise. These two types of driving induce distinct motional states of the axial modes: a coherent oscillation with the dipolar field, or an enhanced Brownian motion due to an additional contribution to the heating rate from the electric noise. In both scenarios, the sensitivity of an isolated ion and a laser-cooled two-ion crystal has been evaluated and compared. The analysis and understanding of this dynamics is important towards the implementation of a novel Penning trap mass-spectroscopy technique based on optical detection, aiming at improving precision and sensitivity.

Predictive simulations and optimization of nanowire field-effect PSA sensors including screening

NASA Astrophysics Data System (ADS)

Baumgartner, Stefan; Heitzinger, Clemens; Vacic, Aleksandar; Reed, Mark A.

2013-06-01

We apply our self-consistent PDE model for the electrical response of field-effect sensors to the 3D simulation of nanowire PSA (prostate-specific antigen) sensors. The charge concentration in the biofunctionalized boundary layer at the semiconductor-electrolyte interface is calculated using the propka algorithm, and the screening of the biomolecules by the free ions in the liquid is modeled by a sensitivity factor. This comprehensive approach yields excellent agreement with experimental current-voltage characteristics without any fitting parameters. Having verified the numerical model in this manner, we study the sensitivity of nanowire PSA sensors by changing device parameters, making it possible to optimize the devices and revealing the attributes of the optimal field-effect sensor.

Sensing small neurotransmitter-enzyme interaction with nanoporous gated ion-sensitive field effect transistors.

PubMed

Kisner, Alexandre; Stockmann, Regina; Jansen, Michael; Yegin, Ugur; Offenhäusser, Andreas; Kubota, Lauro Tatsuo; Mourzina, Yulia

2012-01-15

Ion-sensitive field effect transistors with gates having a high density of nanopores were fabricated and employed to sense the neurotransmitter dopamine with high selectivity and detectability at micromolar range. The nanoporous structure of the gates was produced by applying a relatively simple anodizing process, which yielded a porous alumina layer with pores exhibiting a mean diameter ranging from 20 to 35 nm. Gate-source voltages of the transistors demonstrated a pH-dependence that was linear over a wide range and could be understood as changes in surface charges during protonation and deprotonation. The large surface area provided by the pores allowed the physical immobilization of tyrosinase, which is an enzyme that oxidizes dopamine, on the gates of the transistors, and thus, changes the acid-base behavior on their surfaces. Concentration-dependent dopamine interacting with immobilized tyrosinase showed a linear dependence into a physiological range of interest for dopamine concentration in the changes of gate-source voltages. In comparison with previous approaches, a response time relatively fast for detecting dopamine was obtained. Additionally, selectivity assays for other neurotransmitters that are abundantly found in the brain were examined. These results demonstrate that the nanoporous structure of ion-sensitive field effect transistors can easily be used to immobilize specific enzyme that can readily and selectively detect small neurotransmitter molecule based on its acid-base interaction with the receptor. Therefore, it could serve as a technology platform for molecular studies of neurotransmitter-enzyme binding and drugs screening. Copyright © 2011 Elsevier B.V. All rights reserved.

Characterization of metal oxide field-effect transistors for first helical tomotherapy Hi-Art II unit in India.

PubMed

Kinhikar, Rajesh A; Pai, Rajeshree; Master, Zubin; Deshpande, Deepak D

2009-01-01

To characterize metal oxide semiconductor field-effect transistors (MOSFETs) for a 6-MV photon beam with a first helical tomotherapy Hi-Art II unit in India. Standard sensitivity MOSFETs were first calibrated and then characterized for reproducibility, field size dependence, angular dependence, fade effects, and temperature dependence. The detector sensitivity was estimated for static as well as rotational modes for three jaw settings (1.0 cm x 40 cm, 2.5 cm x 40 cm, and 5 cm x 40 cm) at 1.5-cm depth with a source-to-axis distance (SAD) of 85 cm in virtual water slabs. The A1SL ion chamber and thermoluminescence dosimeters (TLDs) were used to compare the results. No significant difference was found in the detector sensitivity for static and rotational procedures. The average detector sensitivity for static procedures was 1.10 mV/cGy (SD 0.02) while it was 1.12 mV/cGy (SD 0.02) for rotational procedures. The average detector sensitivity found was the same within the experimental uncertainty for static and rotational dose deliveries. The MOSFET reading was consistent and its reproducibility was excellent (+0.5%) while there was no significant dependence of field size. The angular dependence of less than 1.0% was observed. There was negligible fading effect of the MOSFET. The MOSFET response was found independent of temperature in the range 18 degrees-30 degrees. The ion chamber readings were assumed to be a reference for the estimation of the MOSFET calibration factor. The ion chamber and the TLD were in good agreement (+2%) with each other. This study deals only with the measurements and calibration performed on the surface of the phantom. MOSFET was calibrated and validated for phantom surface measurements for a 6-MV photon beam generated by a tomotherapy machine. The sensitivity of the detector was the same for both modes of treatment delivery with tomotherapy. The performance of the MOSFET was validated for and satisfactory for the helical tomotherapy Hi-Art II unit. However, MOSFET may be used for in vivo surface dosimetry only after it is calibrated under the conditions replicating as much as possible the manner in which the dosimeter will be used clinically.

Non-invasive screening for Alzheimer's disease by sensing salivary sugar using Drosophila cells expressing gustatory receptor (Gr5a) immobilized on an extended gate ion-sensitive field-effect transistor (EG-ISFET) biosensor.

PubMed

Lau, Hui-Chong; Lee, In-Kyu; Ko, Pan-Woo; Lee, Ho-Won; Huh, Jeung-Soo; Cho, Won-Ju; Lim, Jeong-Ok

2015-01-01

Body fluids are often used as specimens for medical diagnosis. With the advent of advanced analytical techniques in biotechnology, the diagnostic potential of saliva has been the focus of many studies. We recently reported the presence of excess salivary sugars, in patients with Alzheimer's disease (AD). In the present study, we developed a highly sensitive, cell-based biosensor to detect trehalose levels in patient saliva. The developed biosensor relies on the overexpression of sugar sensitive gustatory receptors (Gr5a) in Drosophila cells to detect the salivary trehalose. The cell-based biosensor was built on the foundation of an improved extended gate ion-sensitive field-effect transistor (EG-ISFET). Using an EG-ISFET, instead of a traditional ion-sensitive field-effect transistor (ISFET), resulted in an increase in the sensitivity and reliability of detection. The biosensor was designed with the gate terminals segregated from the conventional ISFET device. This design allows the construction of an independent reference and sensing region for simultaneous and accurate measurements of samples from controls and patients respectively. To investigate the efficacy of the cell-based biosensor for AD screening, we collected 20 saliva samples from each of the following groups: participants diagnosed with AD, participants diagnosed with Parkinson's disease (PD), and a control group composed of healthy individuals. We then studied the response generated from the interaction of the salivary trehalose of the saliva samples and the Gr5a in the immobilized cells on an EG-ISFET sensor. The cell-based biosensor significantly distinguished salivary sugar, trehalose of the AD group from the PD and control groups. Based on these findings, we propose that salivary trehalose, might be a potential biomarker for AD and could be detected using our cell-based EG-ISFET biosensor. The cell-based EG-ISFET biosensor provides a sensitive and direct approach for salivary sugar detection and may be used in the future as a screening method for AD.

A Hybrid Constant and Oscillatory Field Ion Mobility Analyzer in Structures for Lossless Ion Manipulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prabhakaran Nair Syamala Amma, Aneesh; Hamid, Ahme

2018-02-28

Ion mobility (IM) spectrometry is becoming an important approach for analyzing molecular ions in the gas phase with applications that span a multitude of scientific areas. There are a variety of IM-based approaches that utilize either constant or oscillatory electric fields. Here, we explore the combination of constant and oscillatory fields applied in a single device to affect the separation and filtering of ions based on their mobilities. The mobility analyzer allows confining and manipulating ions utilizing a combination of radio frequency (RF), direct current (DC) fields, and traveling waves (TW) in a structures for lossless ion manipulations (SLIM) module.more » In this work, we have investigated theoretically and experimentally the concept for continuous filtering of ions based on their mobilities where ions are mobility separated and selected by a combination of TW and constant fields providing opposing forces on the ions. The SLIM module was composed of two surfaces with mirror-image arrays of electrodes and had two regions where the different TW and opposing DC fields could be applied. By appropriately choosing the DC gradient and TW parameters for the two sections, it is possible to transmit ions of a selected mobility while filtering out others. The filtering capabilities are determined by the applied DC gradient and the TW parameters, such as frequency, amplitude and the TW sequence (i.e., the duty cycle of the traveling wave). The effect of different parameters on the sensitivity and the IM resolution of the device have been investigated.« less

A Hybrid Constant and Oscillatory Field Ion Mobility Analyzer Using Structures for Lossless Ion Manipulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prabhakaran, Aneesh; Hamid, Ahmed M.; Garimella, Sandilya V. B.

Ion mobility (IM) spectrometry is becoming an important approach for analyzing molecular ions in the gas phase with applications that span a multitude of scientific areas. There are a variety of IM-based approaches that utilize either constant or oscillatory electric fields. Here, we explore the combination of constant and oscillatory fields applied in a single device to affect the separation and filtering of ions based on their mobilities. The mobility analyzer allows confining and manipulating ions utilizing a combination of radio frequency (RF), direct current (DC) fields, and traveling waves (TW) in a structures for lossless ion manipulations (SLIM) module.more » In this work, we have investigated theoretically and experimentally the concept for continuous filtering of ions based on their mobilities where ions are mobility separated and selected by a combination of TW and constant fields providing opposing forces on the ions. The SLIM module was composed of two surfaces with mirror-image arrays of electrodes and had two regions where the different TW and opposing DC fields could be applied. By appropriately choosing the DC gradient and TW parameters for the two sections, it is possible to transmit ions of a selected mobility while filtering out others. The filtering capabilities are determined by the applied DC gradient and the TW parameters, such as frequency, amplitude and the TW sequence (i.e., the duty cycle of the traveling wave). The effect of different parameters on the sensitivity and the IM resolution of the device have been investigated.« less

Sensitive and comprehensive detection of chemical warfare agents in air by atmospheric pressure chemical ionization ion trap tandem mass spectrometry with counterflow introduction.

PubMed

Seto, Yasuo; Sekiguchi, Hiroshi; Maruko, Hisashi; Yamashiro, Shigeharu; Sano, Yasuhiro; Takayama, Yasuo; Sekioka, Ryoji; Yamaguchi, Shintaro; Kishi, Shintaro; Satoh, Takafumi; Sekiguchi, Hiroyuki; Iura, Kazumitsu; Nagashima, Hisayuki; Nagoya, Tomoki; Tsuge, Kouichiro; Ohsawa, Isaac; Okumura, Akihiko; Takada, Yasuaki; Ezawa, Naoya; Watanabe, Susumu; Hashimoto, Hiroaki

2014-05-06

A highly sensitive and specific real-time field-deployable detection technology, based on counterflow air introduction atmospheric pressure chemical ionization, has been developed for a wide range of chemical warfare agents (CWAs) comprising gaseous (two blood agents, three choking agents), volatile (six nerve gases and one precursor agent, five blister agents), and nonvolatile (three lachrymators, three vomiting agents) agents in air. The approach can afford effective chemical ionization, in both positive and negative ion modes, for ion trap multiple-stage mass spectrometry (MS(n)). The volatile and nonvolatile CWAs tested provided characteristic ions, which were fragmented into MS(3) product ions in positive and negative ion modes. Portions of the fragment ions were assigned by laboratory hybrid mass spectrometry (MS) composed of linear ion trap and high-resolution mass spectrometers. Gaseous agents were detected by MS or MS(2) in negative ion mode. The limits of detection for a 1 s measurement were typically at or below the microgram per cubic meter level except for chloropicrin (submilligram per cubic meter). Matrix effects by gasoline vapor resulted in minimal false-positive signals for all the CWAs and some signal suppression in the case of mustard gas. The moisture level did influence the measurement of the CWAs.

Nonfaradaic nanoporous electrochemistry for conductometry at high electrolyte concentration.

PubMed

Bae, Je Hyun; Kang, Chung Mu; Choi, Hyoungseon; Kim, Beom Jin; Jang, Woohyuk; Lim, Sung Yul; Kim, Hee Chan; Chung, Taek Dong

2015-02-17

Nanoporous electrified surfaces create a unique nonfaradaic electrochemical behavior that is sensitively influenced by pore size, morphology, ionic strength, and electric field modulation. Here, we report the contributions of ion concentration and applied ac frequency to the electrode impedance through an electrical double layer overlap and ion transport along the nanopores. Nanoporous Pt with uniform pore size and geometry (L2-ePt) responded more sensitively to conductivity changes in aqueous solutions than Pt black with poor uniformity despite similar real surface areas and enabled the previously difficult quantitative conductometry measurements at high electrolyte concentrations. The nanopores of L2-ePt were more effective in reducing the electrode impedance and exhibited superior linear responses to not only flat Pt but also Pt black, leading to successful conductometric detection in ion chromatography without ion suppressors and at high ionic strengths.

A self-amplified transistor immunosensor under dual gate operation: highly sensitive detection of hepatitis B surface antigen

NASA Astrophysics Data System (ADS)

Lee, I.-K.; Jeun, M.; Jang, H.-J.; Cho, W.-J.; Lee, K. H.

2015-10-01

Ion-sensitive field-effect transistors (ISFETs), although they have attracted considerable attention as effective immunosensors, have still not been adopted for practical applications owing to several problems: (1) the poor sensitivity caused by the short Debye screening length in media with high ion concentration, (2) time-consuming preconditioning processes for achieving the highly-diluted media, and (3) the low durability caused by undesirable ions such as sodium chloride in the media. Here, we propose a highly sensitive immunosensor based on a self-amplified transistor under dual gate operation (immuno-DG ISFET) for the detection of hepatitis B surface antigen. To address the challenges in current ISFET-based immunosensors, we have enhanced the sensitivity of an immunosensor by precisely tailoring the nanostructure of the transistor. In the pH sensing test, the immuno-DG ISFET showed superior sensitivity (2085.53 mV per pH) to both standard ISFET under single gate operation (58.88 mV per pH) and DG ISFET with a non-tailored transistor (381.14 mV per pH). Moreover, concerning the detection of hepatitis B surface antigens (HBsAg) using the immuno-DG ISFET, we have successfully detected trace amounts of HBsAg (22.5 fg mL-1) in a non-diluted 1× PBS medium with a high sensitivity of 690 mV. Our results demonstrate that the proposed immuno-DG ISFET can be a biosensor platform for practical use in the diagnosis of various diseases.Ion-sensitive field-effect transistors (ISFETs), although they have attracted considerable attention as effective immunosensors, have still not been adopted for practical applications owing to several problems: (1) the poor sensitivity caused by the short Debye screening length in media with high ion concentration, (2) time-consuming preconditioning processes for achieving the highly-diluted media, and (3) the low durability caused by undesirable ions such as sodium chloride in the media. Here, we propose a highly sensitive immunosensor based on a self-amplified transistor under dual gate operation (immuno-DG ISFET) for the detection of hepatitis B surface antigen. To address the challenges in current ISFET-based immunosensors, we have enhanced the sensitivity of an immunosensor by precisely tailoring the nanostructure of the transistor. In the pH sensing test, the immuno-DG ISFET showed superior sensitivity (2085.53 mV per pH) to both standard ISFET under single gate operation (58.88 mV per pH) and DG ISFET with a non-tailored transistor (381.14 mV per pH). Moreover, concerning the detection of hepatitis B surface antigens (HBsAg) using the immuno-DG ISFET, we have successfully detected trace amounts of HBsAg (22.5 fg mL-1) in a non-diluted 1× PBS medium with a high sensitivity of 690 mV. Our results demonstrate that the proposed immuno-DG ISFET can be a biosensor platform for practical use in the diagnosis of various diseases. Electronic supplementary information (ESI) available: Material preparation, surface functionalization and anti-HBsAg immobilization. See DOI: 10.1039/c5nr03146j

A scanning probe mounted on a field-effect transistor: Characterization of ion damage in Si.

PubMed

Shin, Kumjae; Lee, Hoontaek; Sung, Min; Lee, Sang Hoon; Shin, Hyunjung; Moon, Wonkyu

2017-10-01

We have examined the capabilities of a Tip-On-Gate of Field-Effect Transistor (ToGoFET) probe for characterization of FIB-induced damage in Si surface. A ToGoFET probe is the SPM probe which the Field Effect Transistor(FET) is embedded at the end of a cantilever and a Pt tip was mounted at the gate of FET. The ToGoFET probe can detect the surface electrical properties by measuring source-drain current directly modulated by the charge on the tip. In this study, a Si specimen whose surface was processed with Ga+ ion beam was prepared. Irradiation and implantation with Ga+ ions induce highly localized modifications to the contact potential. The FET embedded on ToGoFET probe detected the surface electric field profile generated by schottky contact between the Pt tip and the sample surface. Experimentally, it was shown that significant differences of electric field due to the contact potential barrier in differently processed specimens were observed using ToGOFET probe. This result shows the potential that the local contact potential difference can be measured by simple working principle with high sensitivity. Copyright © 2017 Elsevier Ltd. All rights reserved.

Phase-Sensitive Control Of Molecular Dissociation Through Attosecond Pump/Strong-Field Mid-IR Probe Spectroscopy

DTIC Science & Technology

2016-04-15

overarching goal of our program was to develop a novel laser and ion spectroscopy system and to use it for the study of strong-field light-matter...are accelerated into the ion TOF by means of a Fig. I.1 Schematic of ion spectroscopy with two color (EUV + mid-IR) laser fields, as constructed at...Abstract The overarching goal of our program was to develop a novel laser and ion spectroscopy system and to use it for the study of strong-field light

Multianalyte biosensor based on pH-sensitive ZnO electrolyte–insulator–semiconductor structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haur Kao, Chyuan; Chun Liu, Che; Ueng, Herng-Yih

2014-05-14

Multianalyte electrolyte–insulator–semiconductor (EIS) sensors with a ZnO sensing membrane annealed on silicon substrate for use in pH sensing were fabricated. Material analyses were conducted using X-ray diffraction and atomic force microscopy to identify optimal treatment conditions. Sensing performance for various ions of Na{sup +}, K{sup +}, urea, and glucose was also tested. Results indicate that an EIS sensor with a ZnO membrane annealed at 600 °C exhibited good performance with high sensitivity and a low drift rate compared with all other reported ZnO-based pH sensors. Furthermore, based on well-established pH sensing properties, pH-ion-sensitive field-effect transistor sensors have also been developed formore » use in detecting urea and glucose ions. ZnO-based EIS sensors show promise for future industrial biosensing applications.« less

Nonlinear Ion Harmonics in the Paul Trap with Added Octopole Field: Theoretical Characterization and New Insight into Nonlinear Resonance Effect.

PubMed

Xiong, Caiqiao; Zhou, Xiaoyu; Zhang, Ning; Zhan, Lingpeng; Chen, Yongtai; Nie, Zongxiu

2016-02-01

The nonlinear harmonics within the ion motion are the fingerprint of the nonlinear fields. They are exclusively introduced by these nonlinear fields and are responsible to some specific nonlinear effects such as nonlinear resonance effect. In this article, the ion motion in the quadrupole field with a weak superimposed octopole component, described by the nonlinear Mathieu equation (NME), was studied by using the analytical harmonic balance (HB) method. Good accuracy of the HB method, which was comparable with that of the numerical fourth-order Runge-Kutta (4th RK), was achieved in the entire first stability region, except for the points at the stability boundary (i.e., β = 1) and at the nonlinear resonance condition (i.e., β = 0.5). Using the HB method, the nonlinear 3β harmonic series introduced by the octopole component and the resultant nonlinear resonance effect were characterized. At nonlinear resonance, obvious resonant peaks were observed in the nonlinear 3β series of ion motion, but were not found in the natural harmonics. In addition, both resonant excitation and absorption peaks could be observed, simultaneously. These are two unique features of the nonlinear resonance, distinguishing it from the normal resonance. Finally, an approximation equation was given to describe the corresponding working parameter, q nr , at nonlinear resonance. This equation can help avoid the sensitivity degradation due to the operation of ion traps at the nonlinear resonance condition.

Defect Generation for a Hydrated Layer and Thermal Stability Based on Ba0.7Sr0.3TiO3/SiO2 as H+ Sensitive Layer in Ion-Sensitive Field-Effect Transistor Devices

NASA Astrophysics Data System (ADS)

Chen, Chun-Yuan; Chou, Jung-Chuan; Chou, Hsueh-Tao

2009-04-01

In this paper, we present a novel sensitive ion-sensitive field-effect transistor (ISFET) membrane based on Ba0.7Sr0.3TiO3 (BST)/SiO2 fabricated by sputtering deposition. The proposed device exhibits a linear shift in acidic solutions in the pH range from 1 to 10. The device sensitivity was about 50-55 mV/pH for different deposition times. We also examined the trapping behavior of the surface hydrated layer using the metal-insulator-semiconductor (MIS) structure. Results show that the hydration layer gives rise to stress polarity dependence of electron injection when immersed in pH buffer solutions. Injection from the gate electrode produces larger positive charges and interface state densities in contrast to the substrate injection, which causes simultaneous positive and negative charge trapping. A physical model that quantitatively describes the asymmetry associated with the hydrated diffusion layer is presented, and the temperature effects of BST/SiO2 ISFET devices in the range from 25 to 65 °C were examined. We observed that pH sensitivity increases with increasing temperature. The temperature coefficient of sensitivity (TCS) can be divided into two different ranges: 0.08 mV/pH °C between 25 and 45 °C, and 0.57 mV/pH °C between 45 and 65 °C. A better thermal stability is produced in the 25 and 45 °C range in comparison with other sensitive layers.

Producing smart sensing films by means of organic field effect transistors.

PubMed

Manunza, Ileana; Orgiu, Emanuele; Caboni, Alessandra; Barbaro, Massimo; Bonfiglio, Annalisa

2006-01-01

We have fabricated the first example of totally flexible field effect device for chemical detection based on an organic field effect transistor (OFET) made by pentacene films grown on flexible plastic structures. The ion sensitivity is achieved by employing a thin Mylar foil as gate dielectric. A sensitivity of the device to the pH of the electrolyte solution has been observed A similar structure can be used also for detecting mechanical deformations on flexible surfaces. Thanks to the flexibility of the substrate and the low cost of the employed technology, these devices open the way for the production of flexible chemical and strain gauge sensors that can be employed in a variety of innovative applications such as wearable electronics, e-textiles, new man-machine interfaces.

Classical impurity ion confinement in a toroidal magnetized fusion plasma.

PubMed

Kumar, S T A; Den Hartog, D J; Caspary, K J; Magee, R M; Mirnov, V V; Chapman, B E; Craig, D; Fiksel, G; Sarff, J S

2012-03-23

High-resolution measurements of impurity ion dynamics provide first-time evidence of classical ion confinement in a toroidal, magnetically confined plasma. The density profile evolution of fully stripped carbon is measured in MST reversed-field pinch plasmas with reduced magnetic turbulence to assess Coulomb-collisional transport without the neoclassical enhancement from particle drift effects. The impurity density profile evolves to a hollow shape, consistent with the temperature screening mechanism of classical transport. Corroborating methane pellet injection experiments expose the sensitivity of the impurity particle confinement time to the residual magnetic fluctuation amplitude.

New, high-efficiency ion trap mobility detection system for narcotics and explosives

NASA Astrophysics Data System (ADS)

McGann, William J.; Bradley, V.; Borsody, A.; Lepine, S.

1994-10-01

A new patented Ion Trap Mobility Spectrometer (ITMS) design is presented. Conventional IMS designs typically operate below 0.1% efficiency. This is due primarily to electric field driven, sample ion discharge on a shutter grid. Since 99.9% of the sample ions generated in the reaction region are lost in this discharge process, the sensitivity of conventional systems is limited. The new design provides greater detection efficiency than conventional designs through the use of an `ion trap' concept. The paper describes the plasma and sample ion dynamics in the reaction region of the new detector and discusses the advantages of utilizing a `field-free' space to generate sample ions with high efficiency. Fast electronic switching is described which is used to perturb the field-free space and pulse the sample ions into the drift region for separation and subsequent detection using pseudo real-time software for analysis and display of the data. Many applications for this new detector are now being considered including the detection of narcotics and explosives. Preliminary ion spectra, reduced mobility data and sensitivity data are presented for fifteen narcotics, including cocaine, THC and LSD are reported.

New high-efficiency ion-trap mobility detection system for narcotics

NASA Astrophysics Data System (ADS)

McGann, William J.

1997-02-01

A new patented Ion Trap Mobility Spectrometer design is presented. Conventional IMS designs typically operate below 0.1 percent efficiency. This is due primarily to electric field driven, sample ion discharge on a shutter grid. Since 99.9 percent of the sample ions generated in the reaction region are lost int his discharge process, the sensitivity of conventional systems is limited. The new design provides greater detection efficiency than conventional designs through the use of an 'ion trap' concept. The paper describes the plasma and sample ion dynamics in the reaction region of the new detector and discusses the advantages of utilizing a 'field-free' space to generate sample ions with high efficiency. Fast electronic switching is described which is used to perturb the field-free space and pulse the sample ions into the drift region for separation and subsequent detection using pseudo real-time software for analysis and display of the data. One application for this new detector is now being developed, a portable, hand-held system with switching capability for the detection of drugs and explosives. Preliminary ion spectra and sensitivity data are presented for cocaine and heroin using a hand sniffer configuration.

New high-efficiency ion trap mobility detection system for narcotics and explosives

NASA Astrophysics Data System (ADS)

McGann, William J.; Jenkins, Anthony; Ribiero, K.; Napoli, J.

1994-03-01

A new patented ion trap mobility spectrometer design is presented. Conventional IMS designs typically operate below 0.1% efficiency. This is due primarily to electrical-field-driven, sample ion discharge on a shutter grid. Since 99.9% of the sample ions generated in the reaction region are lost in this discharge process, the sensitivity of conventional systems is limited. The new design provides greater detection efficiency than conventional designs through the use of an `ion trap' concept. The paper describes the plasma and sample ion dynamics in the reaction region of the new detector and discusses the advantages of utilizing a `field-free' space to generate sample ions with high efficiency. Fast electronic switching is described which is used to perturb the field-free space and pulse the sample ions into the drift region for separation and subsequent detection using pseudo real-time software for analysis and display of the data. Many applications for this new detector are now being considered including the detection of narcotics and explosives. Preliminary ion spectra, reduced mobility data and sensitivity data are presented for fifteen narcotics, including cocaine, THC, and LSD are reported.

Improving the accuracy of ionization chamber dosimetry in small megavoltage x-ray fields

NASA Astrophysics Data System (ADS)

McNiven, Andrea L.

The dosimetry of small x-ray fields is difficult, but important, in many radiation therapy delivery methods. The accuracy of ion chambers for small field applications, however, is limited due to the relatively large size of the chamber with respect to the field size, leading to partial volume effects, lateral electronic disequilibrium and calibration difficulties. The goal of this dissertation was to investigate the use of ionization chambers for the purpose of dosimetry in small megavoltage photon beams with the aim of improving clinical dose measurements in stereotactic radiotherapy and helical tomotherapy. A new method for the direct determination of the sensitive volume of small-volume ion chambers using micro computed tomography (muCT) was investigated using four nominally identical small-volume (0.56 cm3) cylindrical ion chambers. Agreement between their measured relative volume and ionization measurements (within 2%) demonstrated the feasibility of volume determination through muCT. Cavity-gas calibration coefficients were also determined, demonstrating the promise for accurate ion chamber calibration based partially on muCT. The accuracy of relative dose factor measurements in 6MV stereotactic x-ray fields (5 to 40mm diameter) was investigated using a set of prototype plane-parallel ionization chambers (diameters of 2, 4, 10 and 20mm). Chamber and field size specific correction factors ( CSFQ ), that account for perturbation of the secondary electron fluence, were calculated using Monte Carlo simulation methods (BEAM/EGSnrc simulations). These correction factors (e.g. CSFQ = 1.76 (2mm chamber, 5mm field) allow for accurate relative dose factor (RDF) measurement when applied to ionization readings, under conditions of electronic disequilibrium. With respect to the dosimetry of helical tomotherapy, a novel application of the ion chambers was developed to characterize the fan beam size and effective dose rate. Characterization was based on an adaptation of the computed tomography dose index (CTDI), a concept normally used in diagnostic radiology. This involved experimental determination of the fan beam thickness using the ion chambers to acquire fan beam profiles and extrapolation to a 'zero-size' detector. In conclusion, improvements have been made in the accuracy of small field dosimetry measurements in stereotactic radiotherapy and helical tomotherapy. This was completed through introduction of an original technique involving micro-CT imaging for sensitive volume determination and potentially ion chamber calibration coefficients, the use of appropriate Monte Carlo derived correction factors for RDF measurement, and the exploitation of the partial volume effect for helical tomotherapy fan beam dosimetry. With improved dosimetry for a wide range of challenging small x-ray field situations, it is expected that the patient's radiation safety will be maintained, and that clinical trials will adopt calibration protocols specialized for modern radiotherapy with small fields or beamlets. Keywords. radiation therapy, ionization chambers, small field dosimetry, stereotactic radiotherapy, helical tomotherapy, micro-CT.

An ion-gated bipolar amplifier for ion sensing with enhanced signal and improved noise performance

NASA Astrophysics Data System (ADS)

Zhang, Da; Gao, Xindong; Chen, Si; Norström, Hans; Smith, Ulf; Solomon, Paul; Zhang, Shi-Li; Zhang, Zhen

2014-08-01

This work presents a proof-of-concept ion-sensitive device operating in electrolytes. The device, i.e., an ion-gated bipolar amplifier (IGBA), consists of a modified ion-sensitive field-effect transistor (ISFET) intimately integrated with a vertical bipolar junction transistor for immediate current amplification without introducing additional noise. With the current non-optimized design, the IGBA is already characterized by a 70-fold internal amplification of the ISFET output signal. This signal amplification is retained when the IGBA is used for monitoring pH variations. The tight integration significantly suppresses the interference of the IGBA signal by external noise, which leads to an improvement in signal-to-noise performance compared to its ISFET reference. The IGBA concept is especially suitable for biochips with millions of electric sensors that are connected to peripheral readout circuitry via extensive metallization which may in turn invite external interferences leading to contamination of the signal before it reaches the first external amplification stage.

The sensitivity of benzene cluster cation chemical ionization mass spectrometry to select biogenic terpenes

NASA Astrophysics Data System (ADS)

Lavi, Avi; Vermeuel, Michael P.; Novak, Gordon A.; Bertram, Timothy H.

2018-06-01

Benzene cluster cations are a sensitive and selective reagent ion for chemical ionization of select biogenic volatile organic compounds. We have previously reported the sensitivity of a field deployable chemical ionization time-of-flight mass spectrometer (CI-ToFMS), using benzene cluster cation ion chemistry, for detection of dimethyl sulfide, isoprene and α-pinene. Here, we present laboratory measurements of the sensitivity of the same instrument to a series of terpenes, including isoprene, α-pinene, β-pinene, D-limonene, ocimene, β-myrcene, farnesene, α-humulene, β-caryophyllene, and isolongifolene at atmospherically relevant mixing ratios (< 100 pptv). In addition, we determine the dependence of CI-ToFMS sensitivity on the reagent ion neutral delivery concentration and water vapor concentration. We show that isoprene is primarily detected as an adduct (C5H8 ṡ C6H6+) with a sensitivity ranging between 4 and 10 ncps ppt-1, which depends strongly on the reagent ion precursor concentration, de-clustering voltages, and specific humidity (SH). Monoterpenes are detected primarily as the molecular ion (C10H16+) with an average sensitivity, across the five measured compounds, of 14 ± 3 ncps ppt-1 for SH between 7 and 14 g kg-1, typical of the boreal forest during summer. Sesquiterpenes are detected primarily as the molecular ion (C15H24+) with an average sensitivity, across the four measured compounds, of 9.6 ± 2.3 ncps ppt-1, that is also independent of specific humidity. Comparable sensitivities across broad classes of terpenes (e.g., monoterpenes and sesquiterpenes), coupled to the limited dependence on specific humidity, suggest that benzene cluster cation CI-ToFMS is suitable for field studies of biosphere-atmosphere interactions.

Detection beyond the Debye screening length in a high-frequency nanoelectronic biosensor.

PubMed

Kulkarni, Girish S; Zhong, Zhaohui

2012-02-08

Nanosensors based on the unique electronic properties of nanotubes and nanowires offer high sensitivity and have the potential to revolutionize the field of Point-of-Care (POC) medical diagnosis. The direct current (dc) detection of a wide array of organic and inorganic molecules has been demonstrated on these devices. However, sensing mechanism based on measuring changes in dc conductance fails at high background salt concentrations, where the sensitivity of the devices suffers from the ionic screening due to mobile ions present in the solution. Here, we successfully demonstrate that the fundamental ionic screening effect can be mitigated by operating single-walled carbon nanotube field effect transistor as a high-frequency biosensor. The nonlinear mixing between the alternating current excitation field and the molecular dipole field can generate mixing current sensitive to the surface-bound biomolecules. Electrical detection of monolayer streptavidin binding to biotin in 100 mM buffer solution is achieved at a frequency beyond 1 MHz. Theoretical modeling confirms improved sensitivity at high frequency through mitigation of the ionic screening effect. The results should promise a new biosensing platform for POC detection, where biosensors functioning directly in physiologically relevant condition are desired. © 2012 American Chemical Society

Ion-induced electron emission microscopy

DOEpatents

Doyle, Barney L.; Vizkelethy, Gyorgy; Weller, Robert A.

2001-01-01

An ion beam analysis system that creates multidimensional maps of the effects of high energy ions from an unfocussed source upon a sample by correlating the exact entry point of an ion into a sample by projection imaging of the secondary electrons emitted at that point with a signal from a detector that measures the interaction of that ion within the sample. The emitted secondary electrons are collected in a strong electric field perpendicular to the sample surface and (optionally) projected and refocused by the electron lenses found in a photon emission electron microscope, amplified by microchannel plates and then their exact position is sensed by a very sensitive X Y position detector. Position signals from this secondary electron detector are then correlated in time with nuclear, atomic or electrical effects, including the malfunction of digital circuits, detected within the sample that were caused by the individual ion that created these secondary electrons in the fit place.

Hyperfine interaction mechanism of magnetic field effects in sequential fluorophore and exciplex fluorescence.

PubMed

Dodin, Dmitry V; Ivanov, Anatoly I; Burshtein, Anatoly I

2013-03-28

The magnetic field effect on the fluorescence of the photoexcited electron acceptor, (1)A∗, and the exciplex, (1)[D(+δ)A(-δ)] formed at contact of (1)A∗ with an electron donor (1)D, is theoretically explored in the framework of Integral Encounter Theory. It is assumed that the excited fluorophore is equilibrated with the exciplex that reversibly dissociates into the radical-ion pair. The magnetic field sensitive stage is the spin conversion in the resulting geminate radical-ion pair, (1, 3)[D(+)...A(-)] that proceeds due to hyperfine interaction. We confirm our earlier conclusion (obtained with a rate description of spin conversion) that in the model with a single nucleus spin 1/2 the magnitude of the Magnetic Field Effect (MFE) also vanishes in the opposite limits of low and high dielectric permittivity of the solvent. Moreover, it is shown that MFE being positive at small hyperfine interaction A, first increases with A but approaching the maximum starts to decrease and even changes the sign.

Single ion as a shot-noise-limited magnetic-field-gradient probe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walther, A.; Poschinger, U.; Ziesel, F.

2011-06-15

It is expected that ion-trap quantum computing can be made scalable through protocols that make use of transport of ion qubits between subregions within the ion trap. In this scenario, any magnetic field inhomogeneity the ion experiences during the transport may lead to dephasing and loss of fidelity. Here we demonstrate how to measure, and compensate for, magnetic field gradients inside a segmented ion trap, by transporting a single ion over variable distances. We attain a relative magnetic field sensitivity of {Delta}B/B{sub 0{approx}}5x10{sup -7} over a test distance of 140 {mu}m, which can be extended to the mm range, stillmore » with sub-{mu}m resolution. A fast experimental sequence is presented, facilitating its use as a magnetic-field-gradient calibration routine, and it is demonstrated that the main limitation is the quantum shot noise.« less

Experimental Characterization of Secular Frequency Scanning in Ion Trap Mass Spectrometers

NASA Astrophysics Data System (ADS)

Snyder, Dalton T.; Pulliam, Christopher J.; Wiley, Joshua S.; Duncan, Jason; Cooks, R. Graham

2016-07-01

Secular frequency scanning is implemented and characterized using both a benchtop linear ion trap and a miniature rectilinear ion trap mass spectrometer. Separation of tetraalkylammonium ions and those from a mass calibration mixture and from a pesticide mixture is demonstrated with peak widths approaching unit resolution for optimized conditions using the benchtop ion trap. The effects on the spectra of ion trap operating parameters, including waveform amplitude, scan direction, scan rate, and pressure are explored, and peaks at black holes corresponding to nonlinear (higher-order field) resonance points are investigated. Reverse frequency sweeps (increasing mass) on the Mini 12 are shown to result in significantly higher ion ejection efficiency and superior resolution than forward frequency sweeps that decrement mass. This result is accounted for by the asymmetry in ion energy absorption profiles as a function of AC frequency and the shift in ion secular frequency at higher amplitudes in the trap due to higher order fields. We also found that use of higher AC amplitudes in forward frequency sweeps biases ions toward ejection at points of higher order parametric resonance, despite using only dipolar excitation. Higher AC amplitudes also increase peak width and decrease sensitivity in both forward and reverse frequency sweeps. Higher sensitivity and resolution were obtained at higher trap pressures in the secular frequency scan, in contrast to conventional resonance ejection scans, which showed the opposite trend in resolution on the Mini 12. Mass range is shown to be naturally extended in secular frequency scanning when ejecting ions by sweeping the AC waveform through low frequencies, a method which is similar, but arguably superior, to the more usual method of mass range extension using low q resonance ejection.

Experimental Characterization of Secular Frequency Scanning in Ion Trap Mass Spectrometers.

PubMed

Snyder, Dalton T; Pulliam, Christopher J; Wiley, Joshua S; Duncan, Jason; Cooks, R Graham

2016-07-01

Secular frequency scanning is implemented and characterized using both a benchtop linear ion trap and a miniature rectilinear ion trap mass spectrometer. Separation of tetraalkylammonium ions and those from a mass calibration mixture and from a pesticide mixture is demonstrated with peak widths approaching unit resolution for optimized conditions using the benchtop ion trap. The effects on the spectra of ion trap operating parameters, including waveform amplitude, scan direction, scan rate, and pressure are explored, and peaks at black holes corresponding to nonlinear (higher-order field) resonance points are investigated. Reverse frequency sweeps (increasing mass) on the Mini 12 are shown to result in significantly higher ion ejection efficiency and superior resolution than forward frequency sweeps that decrement mass. This result is accounted for by the asymmetry in ion energy absorption profiles as a function of AC frequency and the shift in ion secular frequency at higher amplitudes in the trap due to higher order fields. We also found that use of higher AC amplitudes in forward frequency sweeps biases ions toward ejection at points of higher order parametric resonance, despite using only dipolar excitation. Higher AC amplitudes also increase peak width and decrease sensitivity in both forward and reverse frequency sweeps. Higher sensitivity and resolution were obtained at higher trap pressures in the secular frequency scan, in contrast to conventional resonance ejection scans, which showed the opposite trend in resolution on the Mini 12. Mass range is shown to be naturally extended in secular frequency scanning when ejecting ions by sweeping the AC waveform through low frequencies, a method which is similar, but arguably superior, to the more usual method of mass range extension using low q resonance ejection. Graphical Abstract ᅟ.

Exploring proximity effects and large depth of field in helium ion beam lithography: large-area dense patterns and tilted surface exposure.

PubMed

Flatabø, Ranveig; Agarwal, Akshay; Hobbs, Richard; Greve, Martin M; Holst, Bodil; Berggren, Karl K

2018-07-06

Helium ion beam lithography (HIL) is an emerging nanofabrication technique. It benefits from a reduced interaction volume compared to that of an electron beam of similar energy, and hence reduced long-range scattering (proximity effect), higher resist sensitivity and potentially higher resolution. Furthermore, the small angular spread of the helium ion beam gives rise to a large depth of field. This should enable patterning on tilted and curved surfaces without the need of any additional adjustments, such as laser-auto focus. So far, most work on HIL has been focused on exploiting the reduced proximity effect to reach single-digit nanometer resolution, and has thus been concentrated on single-pixel exposures over small areas. Here we explore two new areas of application. Firstly, we investigate the proximity effect in large-area exposures and demonstrate HIL's capabilities in fabricating precise high-density gratings on large planar surfaces (100 μm × 100 μm, with pitch down to 35 nm) using an area dose for exposure. Secondly, we exploit the large depth of field by making the first HIL patterns on tilted surfaces (sample stage tilted 45°). We demonstrate a depth of field greater than 100 μm for a resolution of about 20 nm.

Study of zeolite influence on analytical characteristics of urea biosensor based on ion-selective field-effect transistors

PubMed Central

2014-01-01

A possibility of the creation of potentiometric biosensor by adsorption of enzyme urease on zeolite was investigated. Several variants of zeolites (nano beta, calcinated nano beta, silicalite, and nano L) were chosen for experiments. The surface of pH-sensitive field-effect transistors was modified with particles of zeolites, and then the enzyme was adsorbed. As a control, we used the method of enzyme immobilization in glutaraldehyde vapour (without zeolites). It was shown that all used zeolites can serve as adsorbents (with different effectiveness). The biosensors obtained by urease adsorption on zeolites were characterized by good analytical parameters (signal reproducibility, linear range, detection limit and the minimal drift factor of a baseline). In this work, it was shown that modification of the surface of pH-sensitive field-effect transistors with zeolites can improve some characteristics of biosensors. PMID:24636423

Observations of barium ion jets in the magnetosphere using Doppler imaging systems and very sensitive imaging systems using imaging photon detectors

NASA Technical Reports Server (NTRS)

Rees, D.; Conboy, J.; Heinz, W.; Heppner, J. P.

1985-01-01

Observations of four shaped charge releases from rockets launched from Alaska are described. Results demonstrate that imaging and Doppler imaging instruments, based on exploiting the imaging photon detector, provide additional insight into the motion and development of low intensity targets such as the fast ion jets produced by shaped charge releases. It is possible to trace the motion of fast ion jets to very great distances, of the order of 50,000 km, outward along the Earth's magnetic field, when the conditions are suitable for the outward (upward) motion and/or acceleration of such ion jets. It is shown that ion jets, which fade below the lower sensitivity threshold of previous instruments, do not always disappear. There is no evidence of an abrupt field-aligned shear-type acceleration.

A Single-Ion Reservoir as a High-Sensitive Sensor of Electric Signals.

PubMed

Domínguez, Francisco; Arrazola, Iñigo; Doménech, Jaime; Pedernales, Julen S; Lamata, Lucas; Solano, Enrique; Rodríguez, Daniel

2017-08-21

A single-ion reservoir has been tested, and characterized in order to be used as a highly sensitive optical detector of electric signals arriving at the trapping electrodes. Our system consists of a single laser-cooled 40 Ca + ion stored in a Paul trap with rotational symmetry. The performance is observed through the axial motion of the ion, which is equivalent to an underdamped and forced oscillator. Thus, the results can be projected also to Penning traps. We have found that, for an ion oscillator temperature T axial  ≲ 10 mK in the forced-frequency range ω z  = 2π × (80,200 kHz), the reservoir is sensitive to a time-varying electric field equivalent to an electric force of 5.3(2) neV/μm, for a measured quality factor Q = 3875(45), and a decay time constant γ z  = 88(2) s -1 . This method can be applied to measure optically the strength of an oscillating field or induced (driven) charge in this frequency range within times of tens of milliseconds. Furthermore the ion reservoir has been proven to be sensitive to electrostatic forces by measuring the ion displacement. Since the heating rate is below 0.3 μeV/s, this reservoir might be used as optical detector for any ion or bunch of charged particles stored in an adjacent trap.

Development of poly-3-hexylthiophene based ISFET sensors for biomedical applications

NASA Astrophysics Data System (ADS)

Rai, Pratyush; Jung, Soyoun; Ji, Taeksoo; Varadan, Vijay K.

2007-04-01

Ion-sensitive Field-Effect Transistors (ISFETs) have been applied for in vitro and online detection for clinical purposes such as concentration of urea, penicillin-G and potassium ion (K+). They have proven to be highly sensitive, shown less response time, reproducible and smaller than the piecewise assembled conventional biosensors. Materials like p3HT, Tantalum Oxide and PVA-SbQ have show their merit as components of various FETs fabricated on silicon substrate. This paper discusses the feasibility of using them together along with design enhancements such as zigzag inter-digitated electrode. The results hitherto obtained have been analyzed and conclusions are drawn to set future course of experimentation to develop the ISFET for sensor applications.

Biomimetic Trehalose Biosensor Using Gustatory Receptor (Gr5a) Expressed in Drosophila Cells and Ion-Sensitive Field-Effect Transistor

NASA Astrophysics Data System (ADS)

Lau, Hui-Chong; Bae, Tae-Eon; Jang, Hyun-June; Kwon, Jae-Young; Cho, Won-Ju; Lim, Jeong-Ok

2013-04-01

The development of potential applications of biosensors using the sensory systems of vertebrates and invertebrates has progressed rapidly, especially in clinical diagnosis. The biosensor developed here involves the use of Drosophila cells expressing the gustatory receptor Gr5a and an ion-sensitive field-effect transistor (ISFET) sensor device. Gustatory receptor Gr5a is expressed abundantly in gustatory neurons and acts as a primary marker for tastants, especially sugar, in Drosophila. As a result, it could potentially serve as a good candidate for potential biomarkers of diseases in which the current knowledge of the cause and treatment is limited. The developed ISFET was based on the outstanding electrical characteristics of the metal-oxide-semiconductor field-effect transistor (MOSFET) with a subthreshold swing of 85 mV/dec, low leakage current of <10-12 and high on/off current ratio of 7.3×106. The SiO2 sensing membrane with a pH sensitivity of 34.9 mV/pH and drift rate 1.17 mV/h was sufficient for biosensing applications. In addition, the sensor device also showed significant compatibility with the Drosophila cells expressing Gr5a and their response to sugar, particularly trehalose. Moreover, the interactions between the transfected Drosophila cells and trehalose were consistent and reliable. This suggests that the developed ISFET sensor device could have potential use in the future as a screening device in diagnosis.

Biologically sensitive field-effect transistors: from ISFETs to NanoFETs.

PubMed

Pachauri, Vivek; Ingebrandt, Sven

2016-06-30

Biologically sensitive field-effect transistors (BioFETs) are one of the most abundant classes of electronic sensors for biomolecular detection. Most of the time these sensors are realized as classical ion-sensitive field-effect transistors (ISFETs) having non-metallized gate dielectrics facing an electrolyte solution. In ISFETs, a semiconductor material is used as the active transducer element covered by a gate dielectric layer which is electronically sensitive to the (bio-)chemical changes that occur on its surface. This review will provide a brief overview of the history of ISFET biosensors with general operation concepts and sensing mechanisms. We also discuss silicon nanowire-based ISFETs (SiNW FETs) as the modern nanoscale version of classical ISFETs, as well as strategies to functionalize them with biologically sensitive layers. We include in our discussion other ISFET types based on nanomaterials such as carbon nanotubes, metal oxides and so on. The latest examples of highly sensitive label-free detection of deoxyribonucleic acid (DNA) molecules using SiNW FETs and single-cell recordings for drug screening and other applications of ISFETs will be highlighted. Finally, we suggest new device platforms and newly developed, miniaturized read-out tools with multichannel potentiometric and impedimetric measurement capabilities for future biomedical applications. © 2016 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.

Biologically sensitive field-effect transistors: from ISFETs to NanoFETs

PubMed Central

Pachauri, Vivek

2016-01-01

Biologically sensitive field-effect transistors (BioFETs) are one of the most abundant classes of electronic sensors for biomolecular detection. Most of the time these sensors are realized as classical ion-sensitive field-effect transistors (ISFETs) having non-metallized gate dielectrics facing an electrolyte solution. In ISFETs, a semiconductor material is used as the active transducer element covered by a gate dielectric layer which is electronically sensitive to the (bio-)chemical changes that occur on its surface. This review will provide a brief overview of the history of ISFET biosensors with general operation concepts and sensing mechanisms. We also discuss silicon nanowire-based ISFETs (SiNW FETs) as the modern nanoscale version of classical ISFETs, as well as strategies to functionalize them with biologically sensitive layers. We include in our discussion other ISFET types based on nanomaterials such as carbon nanotubes, metal oxides and so on. The latest examples of highly sensitive label-free detection of deoxyribonucleic acid (DNA) molecules using SiNW FETs and single-cell recordings for drug screening and other applications of ISFETs will be highlighted. Finally, we suggest new device platforms and newly developed, miniaturized read-out tools with multichannel potentiometric and impedimetric measurement capabilities for future biomedical applications. PMID:27365038

Improving pH sensitivity by field-induced charge regulation in flexible biopolymer electrolyte gated oxide transistors

NASA Astrophysics Data System (ADS)

Liu, Ning; Gan, Lu; Liu, Yu; Gui, Weijun; Li, Wei; Zhang, Xiaohang

2017-10-01

Electrical manipulation of charged ions in electrolyte-gated transistors is crucial for enhancing the electric-double-layer (EDL) gating effect, thereby improving their sensing abilities. Here, indium-zinc-oxide (IZO) based thin-film-transistors (TFTs) are fabricated on flexible plastic substrate. Acid doped chitosan-based biopolymer electrolyte is used as the gate dielectric, exhibiting an extremely high EDL capacitance. By regulating the dynamic EDL charging process with special gate potential profiles, the EDL gating effect of the chitosan-gated TFT is enhanced, and then resulting in higher pH sensitivities. An extremely high sensitivity of ∼57.8 mV/pH close to Nernst limit is achieved when the gate bias of the TFT sensor sweeps at a rate of 10 mV/s. Additionally, an enhanced sensitivity of 2630% in terms of current variation with pH range from 11 to 3 is realized when the device is operated in the ion depletion mode with a negative gate bias of -0.7 V. Robust ionic modulation is demonstrated in such chitosan-gated sensors. Efficiently driving the charged ions in the chitosan-gated IZO-TFT provides a new route for ultrasensitive, low voltage, and low-cost biochemical sensing technologies.

Human perception of electric fields and ion currents associated with high-voltage DC transmission lines.

PubMed

Blondin, J P; Nguyen, D H; Sbeghen, J; Goulet, D; Cardinal, C; Maruvada, P S; Plante, M; Bailey, W H

1996-01-01

The objective of this study was to assess the ability of humans to detect the presence of DC electric field and ion currents. An exposure chamber simulating conditions present in the vicinity of high-voltage DC (HVDC) lines was designed and built for this purpose. In these experiments, the facility was used to expose observers to DC electric fields up to 50 kV/m and ion current densities up to 120 nA/m2. Forty-eight volunteers (25 women and 23 men) between the ages of 18 and 57 years served as observers. Perception of DC fields was examined by using two psychophysical methods: an adaptive staircase procedure and a rating method derived from signal-detection theory. Subjects completed three different series of observations by using each of these methods; one was conducted without ion currents, and the other two involved various combinations of electric fields and ion currents. Overall, subjects were significantly more likely to detect DC fields as the intensity increased. Observers were able to detect the presence of DC fields alone, but only at high intensities; the average threshold was 45 kV/m. Except in the most sensitive individuals, ion current densities up to 60 nA/m2 did not significantly facilitate the detection of DC fields. However, higher ion current densities were associated with a substantial lowering of sensory thresholds in a large majority of observers. Data analysis also revealed large variations in perceptual thresholds among observers. Normative data indicating DC field and ion current intensities that can be detected by 50% of all observers are provided. In addition, for the most sensitive observers, several other detection proportions were derived from the distribution of individual detection capabilities. These data can form the basis for environmental guidelines relating to the design of HVDC lines.

Ion transport and softening in a polymerized ionic liquid

DOE PAGES

Kumar, Rajeev; Bocharova, Vera; Strelcov, Evgheni; ...

2014-11-13

Polymerized ionic liquids (PolyILs) are promising materials for various solid state electronic applications such as dye-sensitized solar cells, lithium batteries, actuators, field-effect transistors, light emitting electrochemical cells, and electrochromic devices. However, fundamental understanding of interconnection between ionic transport and mechanical properties in PolyILs is far from complete. In this paper, local charge transport and structural changes in films of a PolyIL are studied using an integrated experiment-theory based approach. Experimental data for the kinetics of charging and steady state current–voltage relations can be explained by taking into account the dissociation of ions under an applied electric field (known as themore » Wien effect). Onsager's theory of the Wien effect coupled with the Poisson–Nernst–Planck formalism for the charge transport is found to be in excellent agreement with the experimental results. The agreement between the theory and experiments allows us to predict structural properties of the PolyIL films. We have observed significant softening of the PolyIL films beyond certain threshold voltages and formation of holes under a scanning probe microscopy (SPM) tip, through which an electric field was applied. Finally, the observed softening is explained by the theory of depression in glass transition temperature resulting from enhanced dissociation of ions with an increase in applied electric field.« less

Label-free detection of biomolecules with Ta2O5-based field effect devices

NASA Astrophysics Data System (ADS)

Branquinho, Rita Maria Mourao Salazar

Field-effect-based devices (FEDs) are becoming a basic structural element in a new generation of micro biosensors. Their numerous advantages such as small size, labelfree response and versatility, together with the possibility of on-chip integration of biosensor arrays with a future prospect of low-cost mass production, make their development highly desirable. The present thesis focuses on the study and optimization of tantalum pentoxide (Ta2O5) deposited by rf magnetron sputtering at room temperature, and their application as sensitive layer in biosensors based on field effect devices (BioFEDs). As such, the influence of several deposition parameters and post-processing annealing temperature and surface plasma treatment on the film¡¦s properties was investigated. Electrolyte-insulator-semiconductor (EIS) field-effect-based sensors comprising the optimized Ta2O5 sensitive layer were applied to the development of BioFEDs. Enzyme functionalized sensors (EnFEDs) were produced for penicillin detection. These sensors were also applied to the label free detection of DNA and the monitoring of its amplification via polymerase chain reaction (PCR), real time PCR (RT-PCR) and loop mediated isothermal amplification (LAMP). Ion sensitive field effect transistors (ISFETs) based on semiconductor oxides comprising the optimized Ta2O5 sensitive layer were also fabricated. EIS sensors comprising Ta2O5 films produced with optimized conditions demonstrated near Nernstian pH sensitivity, 58+/-0.3 mV/pH. These sensors were successfully applied to the label-free detection of penicillin and DNA. Penicillinase functionalized sensors showed a 29+/-7 mV/mM sensitivity towards penicillin detection up to 4 mM penicillin concentration. DNA detection was achieved with 30 mV/mugM sensitivity and DNA amplification monitoring with these sensors showed comparable results to those obtained with standard fluorescence based methods. Semiconductor oxides-based ISFETs with Ta2O5 sensitive layer were also produced. Finally, the high quality and sensitivity demonstrated by Ta2O5 thin films produced at low temperature by rf magnetron sputtering allows for their application as sensitive layer in field effect sensors.

Characterization of iron-doped lithium niobate for holographic storage applications

NASA Technical Reports Server (NTRS)

Shah, R. R.; Kim, D. M.; Rabson, T. A.; Tittel, F. K.

1976-01-01

A comprehensive characterization of chemical and holographic properties of eight systematically chosen Fe:LiNbO3 crystals is performed in order to determine optimum performance of the crystals in holographic storage and display applications. The discussion covers determination of Fe(2+) and Fe(3+) ion concentrations in Fe:LiNbO3 system from optical absorption and EPR measurements; establishment of the relation between the photorefractive sensitivity of Fe(2+) and Fe(3+) concentrations; study of the spectral dependence, the effect of oxygen annealing, and of other impurities on the photorefractive sensitivity; analysis of the diffraction efficiency curves for different crystals and corresponding sensitivities with the dynamic theory of hologram formation; and determination of the bulk photovoltaic fields as a function of Fe(2+) concentrations. In addition to the absolute Fe(2+) concentration, the relative concentrations of Fe(2+) and Fe(3+) ions are also important in determining the photorefractive sensitivity. There exists an optimal set of crystal characteristics for which the photorefractive sensitivity is most favorable.

Phonon-assisted field emission in silicon nanomembranes for time-of-flight mass spectrometry of proteins.

PubMed

Park, Jonghoo; Aksamija, Zlatan; Shin, Hyun-Cheol; Kim, Hyunseok; Blick, Robert H

2013-06-12

Time-of-flight (TOF) mass spectrometry has been considered as the method of choice for mass analysis of large intact biomolecules, which are ionized in low charge states by matrix-assisted-laser-desorption/ionization (MALDI). However, it remains predominantly restricted to the mass analysis of biomolecules with a mass below about 50,000 Da. This limitation mainly stems from the fact that the sensitivity of the standard detectors decreases with increasing ion mass. We describe here a new principle for ion detection in TOF mass spectrometry, which is based upon suspended silicon nanomembranes. Impinging ion packets on one side of the suspended silicon nanomembrane generate nonequilibrium phonons, which propagate quasi-diffusively and deliver thermal energy to electrons within the silicon nanomembrane. This enhances electron emission from the nanomembrane surface with an electric field applied to it. The nonequilibrium phonon-assisted field emission in the suspended nanomembrane connected to an effective cooling of the nanomembrane via field emission allows mass analysis of megadalton ions with high mass resolution at room temperature. The high resolution of the detector will give better insight into high mass proteins and their functions.

Development of an ion mobility spectrometer with UV ionization source to detect ketones and BTX

NASA Astrophysics Data System (ADS)

Ni, Kai; Guo, Jingran; Ou, Guangli; Lei, Yu; Wang, Xiaohao

2014-11-01

Ion mobility spectrometry (IMS) is an attractive material analysis technology for developing a miniaturized volatile organic compounds (VOCs) on-site monitoring sensor. Having simple instrumentation, IMS is especially suitable when portability and sensitivity are required. In this work, we designed an ion mobility spectrometer with UV ionization. The geometric parameters of the UV-IMS were optimized based on a numerical simulation. The simulation results demonstrated that the drift electric field in the drift region was approximately homogenous and in the reaction region had an ion focusing effect, which could improve the sensitivity and resolving power of the IMS. The UV-IMS has been constructed and used to detect VOCs, such as acetone, benzene, toluene and m-xylene (BTX). The resolution of these substance measured from the UV-IMS in the atmospheric conditions are about 30 and the limit of detection (LOD) is low to ppmv. The ion mobility module and electric circuit are integrated in a main PCB, which can facilitate mass production and miniaturization. The present UV-IMS is expected to become a tool of choice for the on-site monitoring for VOCs.

Biosensors based on enzyme field-effect transistors for determination of some substrates and inhibitors.

PubMed

Dzyadevych, Sergei V; Soldatkin, Alexey P; Korpan, Yaroslav I; Arkhypova, Valentyna N; El'skaya, Anna V; Chovelon, Jean-Marc; Martelet, Claude; Jaffrezic-Renault, Nicole

2003-10-01

This paper is a review of the authors' publications concerning the development of biosensors based on enzyme field-effect transistors (ENFETs) for direct substrates or inhibitors analysis. Such biosensors were designed by using immobilised enzymes and ion-selective field-effect transistors (ISFETs). Highly specific, sensitive, simple, fast and cheap determination of different substances renders them as promising tools in medicine, biotechnology, environmental control, agriculture and the food industry. The biosensors based on ENFETs and direct enzyme analysis for determination of concentrations of different substrates (glucose, urea, penicillin, formaldehyde, creatinine, etc.) have been developed and their laboratory prototypes were fabricated. Improvement of the analytical characteristics of such biosensors may be achieved by using a differential mode of measurement, working solutions with different buffer concentrations and specific agents, negatively or positively charged additional membranes, or genetically modified enzymes. These approaches allow one to decrease the effect of the buffer capacity influence on the sensor response in an aim to increase the sensitivity of the biosensors and to extend their dynamic ranges. Biosensors for the determination of concentrations of different toxic substances (organophosphorous pesticides, heavy metal ions, hypochlorite, glycoalkaloids, etc.) were designed on the basis of reversible and/or irreversible enzyme inhibition effect(s). The conception of an enzymatic multibiosensor for the determination of different toxic substances based on the enzyme inhibition effect is also described. We will discuss the respective advantages and disadvantages of biosensors based on the ENFETs developed and also demonstrate their practical application.

SU-E-T-562: Scanned Percent Depth Dose Curve Discrepancy for Photon Beams with Physical Wedge in Place (Varian IX) Using Different Sensitive Volume Ion Chambers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, H; Sarkar, V; Rassiah-Szegedi, P

2014-06-01

Purpose: To investigate and report the discrepancy of scanned percent depth dose (PDD) for photon beams with physical wedge in place when using ion chambers with different sensitive volumes. Methods/Materials: PDD curves of open fields and physical wedged fields (15, 30, 45, and 60 degree wedge) were scanned for photon beams (6MV and 10MV, Varian iX) with field size of 5x5 and 10x10 cm using three common scanning chambers with different sensitive volumes - PTW30013 (0.6cm3), PTW23323 (0.1cm3) and Exradin A16 (0.007cm3). The scanning system software used was OmniPro version 6.2, and the scanning water tank was the Scanditronix Wellhoffermore » RFA 300.The PDD curves from the three chambers were compared. Results: Scanned PDD curves of the same energy beams for open fields were almost identical between three chambers, but the wedged fields showed non-trivial differences. The largest differences were observed between chamber PTW30013 and Exradin A16. The differences increased as physical wedge angle increased. The differences also increased with depth, and were more pronounced for 6MV beam. Similar patterns were shown for both 5x5 and 10x10 cm field sizes. For open fields, all PDD values agreed with each other within 1% at 10cm depth and within 1.62% at 20 cm depth. For wedged fields, the difference of PDD values between PTW30013 and A16 reached 4.09% at 10cm depth, and 5.97% at 20 cm depth for 6MV with 60 degree physical wedge. Conclusion: We observed a significant difference in scanned PDD curves of photon beams with physical wedge in place obtained when using different sensitive volume ion chambers. The PDD curves scanned with the smallest sensitive volume ion chamber showed significant difference from larger chamber results, beyond 10cm depth. We believe this to be caused by varying response to beam hardening by the wedges.« less

Radiation sensors based on the generation of mobile protons in organic dielectrics.

PubMed

Kapetanakis, Eleftherios; Douvas, Antonios M; Argitis, Panagiotis; Normand, Pascal

2013-06-26

A sensing scheme based on mobile protons generated by radiation, including ionizing radiation (IonR), in organic gate dielectrics is investigated for the development of metal-insulator-semiconductor (MIS)-type dosimeters. Application of an electric field to the gate dielectric moves the protons and thereby alters the flat band voltage (VFB) of the MIS device. The shift in the VFB is proportional to the IonR-generated protons and, therefore, to the IonR total dose. Triphenylsulfonium nonaflate (TPSNF) photoacid generator (PAG)-containing poly(methyl methacrylate) (PMMA) polymeric films was selected as radiation-sensitive gate dielectrics. The effects of UV (249 nm) and gamma (Co-60) irradiations on the high-frequency capacitance versus the gate voltage (C-VG) curves of the MIS devices were investigated for different total dose values. Systematic improvements in sensitivity can be accomplished by increasing the concentration of the TPSNF molecules embedded in the polymeric matrix.

RF sheaths for arbitrary B field angles

NASA Astrophysics Data System (ADS)

D'Ippolito, Daniel; Myra, James

2014-10-01

RF sheaths occur in tokamaks when ICRF waves encounter conducting boundaries and accelerate electrons out of the plasma. Sheath effects reduce the efficiency of ICRF heating, cause RF-specific impurity influxes from the edge plasma, and increase the plasma-facing component damage. The rf sheath potential is sensitive to the angle between the B field and the wall, the ion mobility and the ion magnetization. Here, we obtain a numerical solution of the non-neutral rf sheath and magnetic pre-sheath equations (for arbitrary values of these parameters) and attempt to infer the parametric dependences of the Child-Langmuir law. This extends previous work on the magnetized, immobile ion regime. An important question is how the rf sheath voltage distributes itself between sheath and pre-sheath for various B field angles. This will show how generally previous estimates of the rf sheath voltage and capacitance were reasonable, and to improve the RF sheath BC. Work supported by US DOE grants DE-FC02-05ER54823 and DE-FG02-97ER54392.

Poster - Thurs Eve-09: Evaluation of a commercial 2D ion-chamber array for intensity modulated radiation therapy dose measurements.

PubMed

Mei, X; Bracken, G; Kerr, A

2008-07-01

Experimental verification of calculated dose from a treatment planning system is often essential for quality assurance (QA) of intensity modulated radiation therapy (IMRT). Film dosimetry and single ion chamber measurements are commonly used for IMRT QA. Film dosimetry has very good spatial resolution, but is labor intensive and absolute dose is not reliable. Ion chamber measurements are still required for absolute dose after measurements using films. Dosimeters based on 2D detector arrays that can measure 2D dose in real-time are gaining wider use. These devices provide a much easier and reliable tool for IMRT QA. We report the evaluation of a commercial 2D ion chamber array, including its basic performance characteristics, such as linearity, reproducibility and uniformity of relative ion chamber sensitivities, and comparisons between measured 2D dose and calculated dose with a commercial treatment planning system. Our analysis shows this matrix has excellent linearity and reproducibility, but relative sensitivities are tilted such that the +Y region is over sensitive, while the -Y region is under sensitive. Despite this behavior, our results show good agreement between measured 2D dose profiles and Eclipse planned data for IMRT test plans and a few verification plans for clinical breast field-in-field plans. The gamma values (3% or 3 mm distance-to-agreement) are all less than 1 except for one or two pixels at the field edge This device provides a fast and reliable stand-alone dosimeter for IMRT QA. © 2008 American Association of Physicists in Medicine.

High precision hyperfine measurements in Bismuth challenge bound-state strong-field QED

NASA Astrophysics Data System (ADS)

Ullmann, Johannes; Andelkovic, Zoran; Brandau, Carsten; Dax, Andreas; Geithner, Wolfgang; Geppert, Christopher; Gorges, Christian; Hammen, Michael; Hannen, Volker; Kaufmann, Simon; König, Kristian; Litvinov, Yuri A.; Lochmann, Matthias; Maaß, Bernhard; Meisner, Johann; Murböck, Tobias; Sánchez, Rodolfo; Schmidt, Matthias; Schmidt, Stefan; Steck, Markus; Stöhlker, Thomas; Thompson, Richard C.; Trageser, Christian; Vollbrecht, Jonas; Weinheimer, Christian; Nörtershäuser, Wilfried

2017-05-01

Electrons bound in highly charged heavy ions such as hydrogen-like bismuth 209Bi82+ experience electromagnetic fields that are a million times stronger than in light atoms. Measuring the wavelength of light emitted and absorbed by these ions is therefore a sensitive testing ground for quantum electrodynamical (QED) effects and especially the electron-nucleus interaction under such extreme conditions. However, insufficient knowledge of the nuclear structure has prevented a rigorous test of strong-field QED. Here we present a measurement of the so-called specific difference between the hyperfine splittings in hydrogen-like and lithium-like bismuth 209Bi82+,80+ with a precision that is improved by more than an order of magnitude. Even though this quantity is believed to be largely insensitive to nuclear structure and therefore the most decisive test of QED in the strong magnetic field regime, we find a 7-σ discrepancy compared with the theoretical prediction.

High precision hyperfine measurements in Bismuth challenge bound-state strong-field QED.

PubMed

Ullmann, Johannes; Andelkovic, Zoran; Brandau, Carsten; Dax, Andreas; Geithner, Wolfgang; Geppert, Christopher; Gorges, Christian; Hammen, Michael; Hannen, Volker; Kaufmann, Simon; König, Kristian; Litvinov, Yuri A; Lochmann, Matthias; Maaß, Bernhard; Meisner, Johann; Murböck, Tobias; Sánchez, Rodolfo; Schmidt, Matthias; Schmidt, Stefan; Steck, Markus; Stöhlker, Thomas; Thompson, Richard C; Trageser, Christian; Vollbrecht, Jonas; Weinheimer, Christian; Nörtershäuser, Wilfried

2017-05-16

Electrons bound in highly charged heavy ions such as hydrogen-like bismuth 209 Bi 82+ experience electromagnetic fields that are a million times stronger than in light atoms. Measuring the wavelength of light emitted and absorbed by these ions is therefore a sensitive testing ground for quantum electrodynamical (QED) effects and especially the electron-nucleus interaction under such extreme conditions. However, insufficient knowledge of the nuclear structure has prevented a rigorous test of strong-field QED. Here we present a measurement of the so-called specific difference between the hyperfine splittings in hydrogen-like and lithium-like bismuth 209 Bi 82+,80+ with a precision that is improved by more than an order of magnitude. Even though this quantity is believed to be largely insensitive to nuclear structure and therefore the most decisive test of QED in the strong magnetic field regime, we find a 7-σ discrepancy compared with the theoretical prediction.

High precision hyperfine measurements in Bismuth challenge bound-state strong-field QED

PubMed Central

Ullmann, Johannes; Andelkovic, Zoran; Brandau, Carsten; Dax, Andreas; Geithner, Wolfgang; Geppert, Christopher; Gorges, Christian; Hammen, Michael; Hannen, Volker; Kaufmann, Simon; König, Kristian; Litvinov, Yuri A.; Lochmann, Matthias; Maaß, Bernhard; Meisner, Johann; Murböck, Tobias; Sánchez, Rodolfo; Schmidt, Matthias; Schmidt, Stefan; Steck, Markus; Stöhlker, Thomas; Thompson, Richard C.; Trageser, Christian; Vollbrecht, Jonas; Weinheimer, Christian; Nörtershäuser, Wilfried

2017-01-01

Electrons bound in highly charged heavy ions such as hydrogen-like bismuth 209Bi82+ experience electromagnetic fields that are a million times stronger than in light atoms. Measuring the wavelength of light emitted and absorbed by these ions is therefore a sensitive testing ground for quantum electrodynamical (QED) effects and especially the electron–nucleus interaction under such extreme conditions. However, insufficient knowledge of the nuclear structure has prevented a rigorous test of strong-field QED. Here we present a measurement of the so-called specific difference between the hyperfine splittings in hydrogen-like and lithium-like bismuth 209Bi82+,80+ with a precision that is improved by more than an order of magnitude. Even though this quantity is believed to be largely insensitive to nuclear structure and therefore the most decisive test of QED in the strong magnetic field regime, we find a 7-σ discrepancy compared with the theoretical prediction. PMID:28508892

Ultra-sensitive and selective detection of mercury ion (Hg2+) using free-standing silicon nanowire sensors

NASA Astrophysics Data System (ADS)

Jin, Yan; Gao, Anran; Jin, Qinghui; Li, Tie; Wang, Yuelin; Zhao, Jianlong

2018-04-01

In this paper, ultra-sensitive and highly selective Hg2+ detection in aqueous solutions was studied by free-standing silicon nanowire (SiNW) sensors. The all-around surface of SiNW arrays was functionalized with (3-Mercaptopropyl)trimethoxysilane serving as Hg2+ sensitive layer. Due to effective electrostatic control provided by the free-standing structure, a detection limit as low as 1 ppt was obtained. A linear relationship (R 2 = 0.9838) between log(CHg2+ ) and a device current change from 1 ppt to 5 ppm was observed. Furthermore, the developed SiNW sensor exhibited great selectivity for Hg2+ over other heavy metal ions, including Cd2+. Given the extraordinary ability for real-time Hg2+ detection, the small size and low cost of the SiNW device, it is expected to be a potential candidate in field detection of environmentally toxic mercury.

Detection and Spatial Mapping of Mercury Contamination in Water Samples Using a Smart-Phone

PubMed Central

2014-01-01

Detection of environmental contamination such as trace-level toxic heavy metal ions mostly relies on bulky and costly analytical instruments. However, a considerable global need exists for portable, rapid, specific, sensitive, and cost-effective detection techniques that can be used in resource-limited and field settings. Here we introduce a smart-phone-based hand-held platform that allows the quantification of mercury(II) ions in water samples with parts per billion (ppb) level of sensitivity. For this task, we created an integrated opto-mechanical attachment to the built-in camera module of a smart-phone to digitally quantify mercury concentration using a plasmonic gold nanoparticle (Au NP) and aptamer based colorimetric transmission assay that is implemented in disposable test tubes. With this smart-phone attachment that weighs <40 g, we quantified mercury(II) ion concentration in water samples by using a two-color ratiometric method employing light-emitting diodes (LEDs) at 523 and 625 nm, where a custom-developed smart application was utilized to process each acquired transmission image on the same phone to achieve a limit of detection of ∼3.5 ppb. Using this smart-phone-based detection platform, we generated a mercury contamination map by measuring water samples at over 50 locations in California (USA), taken from city tap water sources, rivers, lakes, and beaches. With its cost-effective design, field-portability, and wireless data connectivity, this sensitive and specific heavy metal detection platform running on cellphones could be rather useful for distributed sensing, tracking, and sharing of water contamination information as a function of both space and time. PMID:24437470

Quantitative mass spectrometry methods for pharmaceutical analysis

PubMed Central

Loos, Glenn; Van Schepdael, Ann

2016-01-01

Quantitative pharmaceutical analysis is nowadays frequently executed using mass spectrometry. Electrospray ionization coupled to a (hybrid) triple quadrupole mass spectrometer is generally used in combination with solid-phase extraction and liquid chromatography. Furthermore, isotopically labelled standards are often used to correct for ion suppression. The challenges in producing sensitive but reliable quantitative data depend on the instrumentation, sample preparation and hyphenated techniques. In this contribution, different approaches to enhance the ionization efficiencies using modified source geometries and improved ion guidance are provided. Furthermore, possibilities to minimize, assess and correct for matrix interferences caused by co-eluting substances are described. With the focus on pharmaceuticals in the environment and bioanalysis, different separation techniques, trends in liquid chromatography and sample preparation methods to minimize matrix effects and increase sensitivity are discussed. Although highly sensitive methods are generally aimed for to provide automated multi-residue analysis, (less sensitive) miniaturized set-ups have a great potential due to their ability for in-field usage. This article is part of the themed issue ‘Quantitative mass spectrometry’. PMID:27644982

Detection of ionized gas molecules in air by graphene and carbon nanotube networks

NASA Astrophysics Data System (ADS)

Hao, Ji; Li, Bo; Yung, Hyun Young; Liu, Fangze; Hong, Sanghyung; Jung, Yung Joon; Kar, Swastik

The liquid phase ions sensing by graphene and carbon nanotube has been demonstrated in many publications due to the minimum gate voltage easily shift induced by ionic gating effect, but it is still unclear for vapor phase ions sensing. Here we want to report that the ionized gas molecules in air can be also very sensitively detected by graphene and carbon nanotube networks under very low applied voltage, which shows the very high charge to current amplification factor, the value can be up to 108 A/C, and the direction of current-change can be used to differentiate the positive and negative ions. In further, the field effect of graphene device induced by vapor phase ions was discussed. NSF ECCS 1202376, NSF ECCS CAREER 1351424 and NSF DMREF 1434824, a Northeastern University Provost's Tier-1 seed Grant for interdisciplinary research, Technology Innovation Program (10050481) from Ministry of Trade, Industry & Energy of Republic of Korea.

Field ion spectrometry: a new technology for cocaine and heroin detection

NASA Astrophysics Data System (ADS)

Carnahan, Byron L.; Day, Stephen; Kouznetsov, Viktor; Tarassov, Alexandre

1997-02-01

Field ion spectrometry, also known as transverse field compensation ion mobility spectrometry, is a new technique for trace gas analysis that can be applied to the detection of cocaine and heroin. Its principle is based on filtering ion species according to the functional dependence of their mobilities with electric field strength. Field ion spectrometry eliminates the gating electrodes needed in conventional IMS to pulse ions into the spectrometer; instead, ions are injected in to the spectrometer and reach the detector continuously, resulting in improved sensitivity. The technique enables analyses that are difficult with conventional constant field strength ion mobility spectrometers. We have shown that a filed ion spectrometer can selectively detect the vapors from cocaine and heroin emitted from both their base and hydrochloride forms. The estimated volumetric limits of detection are in the low pptv range, based on testing with standardized drug vapor generation systems. The spectrometer can detect cocaine base in the vapor phase, at concentrations well below its estimated 100 pptv vapor pressure equivalent at 20 degrees C. This paper describes the underlying principles of field ion spectrometry in relation to narcotic drug detection, and recent results obtained for cocaine and heroin. The work has been sponsored in part by the United States Advanced Research Projects Agency under contract DAAB10-95C-0004, for the DOD Counterdrug Technology Development Program.

Laser Induced Fluorescence Measurements in a Hall Thruster Plume as a Function of Background Pressure

NASA Technical Reports Server (NTRS)

Spektor, R.; Tighe, W. G.; Kamhawi, H.

2016-01-01

A set of Laser Induced Fluorescence (LIF) measurements in the near-field region of the NASA- 173M Hall thruster plume is presented at four background pressure conditions varying from 9.4 x 10(exp -6) torr to 3.3 x 10(exp -5) torr. The xenon ion velocity distribution function was measured simultaneously along the axial and radial directions. An ultimate exhaust velocity of 19.6+/-0.25 km/s achieved at a distance of 20 mm was measured, and that value was not sensitive to pressure. On the other hand, the ion axial velocity at the thruster exit was strongly influenced by pressure, indicating that the accelerating electric field moved inward with increased pressure. The shift in electric field corresponded to an increase in measured thrust. Pressure had a minor effect on the radial component of ion velocity, mainly affecting ions exiting close to the channel inner wall. At that radial location the radial component of ion velocity was approximately 1000 m/s greater at the lowest pressure than at the highest pressure. A reduction of the inner magnet coil current by 0.6 A resulted in a lower axial ion velocity at the channel exit while the radial component of ion velocity at the channel inner wall location increased by 1300 m/s, and at the channel outer wall location the radial ion velocity remained unaffected. The ultimate exhaust velocity was not significantly affected by the inner magnet current.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burrows, T.A.; Thoma, P.J.

Two types of ion-mobility detectors were evaluated in both laboratory and field tests. Laboratory test results show that these detectors are highly sensitive to dynamite and pistol powder and have good false-alarm agent rejection. Field tests of these two detectors revealed that they would detect dynamite and Ball-C-Propellent in free air. However, neither of the ion-mobility detectors would detect these explosives if the explosives were concealed.

Nanocrystalline SiC film thermistors for cryogenic applications

NASA Astrophysics Data System (ADS)

Mitin, V. F.; Kholevchuk, V. V.; Semenov, A. V.; Kozlovskii, A. A.; Boltovets, N. S.; Krivutsa, V. A.; Slepova, A. S.; Novitskii, S. V.

2018-02-01

We developed a heat-sensitive material based on nanocrystalline SiC films obtained by direct deposition of carbon and silicon ions onto sapphire substrates. These SiC films can be used for resistance thermometers operating in the 2 K-300 K temperature range. Having high heat sensitivity, they are relatively low sensitive to the magnetic field. The designs of the sensors are presented together with a discussion of their thermometric characteristics and sensitivity to magnetic fields.

Electric Field-Controlled Ion Transport In TiO2 Nanochannel.

PubMed

Li, Dan; Jing, Wenheng; Li, Shuaiqiang; Shen, Hao; Xing, Weihong

2015-06-03

On the basis of biological ion channels, we constructed TiO2 membranes with rigid channels of 2.3 nm to mimic biomembranes with flexible channels; an external electric field was employed to regulate ion transport in the confined channels at a high ionic strength in the absence of electrical double layer overlap. Results show that transport rates for both Na+ and Mg2+ were decreased irrespective of the direction of the electric field. Furthermore, a voltage-gated selective ion channel was formed, the Mg2+ channel closed at -2 V, and a reversed relative electric field gradient was at the same order of the concentration gradient, whereas the Na+ with smaller Stokes radius and lower valence was less sensitive to the electric field and thus preferentially occupied and passed the channel. Thus, when an external electric field is applied, membranes with larger nanochannels have promising applications in selective separation of mixture salts at a high concentration.

Highly efficient exciplex formation via radical ion pair recombination in X-irradiated alkane solutions for luminophores with short fluorescence lifetimes.

PubMed

Melnikov, Anatoly R; Kalneus, Evgeny V; Korolev, Valeri V; Dranov, Igor G; Kruppa, Alexander I; Stass, Dmitri V

2014-08-01

X-irradiation of alkane solutions of N,N-dimethylaniline with various organic luminophores produces characteristic emission bands ascribed to the corresponding exciplexes. In contrast to optical generation, which requires diffusion-controlled quenching of excited states, an additional channel of exciplex formation via irreversible recombination of radical ion pairs is operative here, which produces exciplexes in solution with high efficiency even for p-terphenyl and diphenylacetylene having fluorescence decay times of 0.95 ns and 8 ps, respectively. The exciplex emission band is sensitive to an external magnetic field and exerts a very large observed magnetic field effect of up to 20%, the maximum possible value under the conditions of the described experiment.

Local sensor based on nanowire field effect transistor from inhomogeneously doped silicon on insulator

NASA Astrophysics Data System (ADS)

Presnov, Denis E.; Bozhev, Ivan V.; Miakonkikh, Andrew V.; Simakin, Sergey G.; Trifonov, Artem S.; Krupenin, Vladimir A.

2018-02-01

We present the original method for fabricating a sensitive field/charge sensor based on field effect transistor (FET) with a nanowire channel that uses CMOS-compatible processes only. A FET with a kink-like silicon nanowire channel was fabricated from the inhomogeneously doped silicon on insulator wafer very close (˜100 nm) to the extremely sharp corner of a silicon chip forming local probe. The single e-beam lithographic process with a shadow deposition technique, followed by separate two reactive ion etching processes, was used to define the narrow semiconductor nanowire channel. The sensors charge sensitivity was evaluated to be in the range of 0.1-0.2 e /√{Hz } from the analysis of their transport and noise characteristics. The proposed method provides a good opportunity for the relatively simple manufacture of a local field sensor for measuring the electrical field distribution, potential profiles, and charge dynamics for a wide range of mesoscopic objects. Diagnostic systems and devices based on such sensors can be used in various fields of physics, chemistry, material science, biology, electronics, medicine, etc.

High-performance gas sensors with temperature measurement

PubMed Central

Zhang, Yong; Li, Shengtao; Zhang, Jingyuan; Pan, Zhigang; Min, Daomin; Li, Xin; Song, Xiaoping; Liu, Junhua

2013-01-01

There are a number of gas ionization sensors using carbon nanotubes as cathode or anode. Unfortunately, their applications are greatly limited by their multi-valued sensitivity, one output value corresponding to several measured concentration values. Here we describe a triple-electrode structure featuring two electric fields with opposite directions, which enable us to overcome the multi-valued sensitivity problem at 1 atm in a wide range of gas concentrations. We used a carbon nanotube array as the first electrode, and the two electric fields between the upper and the lower interelectrode gaps were designed to extract positive ions generated in the upper gap, hence significantly reduced positive ion bombardment on the nanotube electrode, which allowed us to maintain a high electric field near the nanotube tips, leading to a single-valued sensitivity and a long nanotube life. We have demonstrated detection of various gases and simultaneously monitoring temperature, and a potential for applications. PMID:23405281

Single-ion quantum lock-in amplifier.

PubMed

Kotler, Shlomi; Akerman, Nitzan; Glickman, Yinnon; Keselman, Anna; Ozeri, Roee

2011-05-05

Quantum metrology uses tools from quantum information science to improve measurement signal-to-noise ratios. The challenge is to increase sensitivity while reducing susceptibility to noise, tasks that are often in conflict. Lock-in measurement is a detection scheme designed to overcome this difficulty by spectrally separating signal from noise. Here we report on the implementation of a quantum analogue to the classical lock-in amplifier. All the lock-in operations--modulation, detection and mixing--are performed through the application of non-commuting quantum operators to the electronic spin state of a single, trapped Sr(+) ion. We significantly increase its sensitivity to external fields while extending phase coherence by three orders of magnitude, to more than one second. Using this technique, we measure frequency shifts with a sensitivity of 0.42 Hz Hz(-1/2) (corresponding to a magnetic field measurement sensitivity of 15 pT Hz(-1/2)), obtaining an uncertainty of less than 10 mHz (350 fT) after 3,720 seconds of averaging. These sensitivities are limited by quantum projection noise and improve on other single-spin probe technologies by two orders of magnitude. Our reported sensitivity is sufficient for the measurement of parity non-conservation, as well as the detection of the magnetic field of a single electronic spin one micrometre from an ion detector with nanometre resolution. As a first application, we perform light shift spectroscopy of a narrow optical quadrupole transition. Finally, we emphasize that the quantum lock-in technique is generic and can potentially enhance the sensitivity of any quantum sensor. ©2011 Macmillan Publishers Limited. All rights reserved

A Metal-Polydopamine Framework (MPDA) as an Effective Fluorescent Quencher for Highly Sensitive Detection of Hg (II) And Ag (I) ions Through Exonuclease III Activity.

PubMed

Ravikumar, Ayyanu; Panneerselvam, Perumal; Morad, Norhashimah

2018-05-24

In this paper, we propose a metal-polydopamine framework (MPDA) with specific molecular probe which appears to be the most promising approach to a strong fluorescence quencher. The MPDA framework quenching ability towards various organic fluorophore such as aminoethylcomarin acetate (AMCA), 6-carboxyfluorescein (FAM), carboxyteramethylrhodamine (TAMRA) and Cy5 are used to establish a fluorescent biosensor that can selectively recognize Hg2+ and Ag+ ion. The fluorescent quenching efficiency was sufficient to achieve more than 96%. The MPDA framework also exhibits different affinities with ssDNA and dsDNA. In addition, the FAM labelled ssDNA was adsorbed onto MPDA framework, based on their interaction with the complex formed between MPDA frameworks/ssDNA taken as a sensing platform. By taking advantage of this sensor highly sensitive and selective determination of Hg2+and Ag+ ions is achieved through Exonuclease III signal amplification activity. The detection limits of Hg2+and Ag+ achieved to be 1.2 pM and 34 pM respectively, were compared to co-existing metal ions and GO based sensors. Furthermore, the potential applications of this study establish the highly sensitive fluorescence detection targets in environmental and biological fields.

Heavy-Ion Microbeam Fault Injection into SRAM-Based FPGA Implementations of Cryptographic Circuits

NASA Astrophysics Data System (ADS)

Li, Huiyun; Du, Guanghua; Shao, Cuiping; Dai, Liang; Xu, Guoqing; Guo, Jinlong

2015-06-01

Transistors hit by heavy ions may conduct transiently, thereby introducing transient logic errors. Attackers can exploit these abnormal behaviors and extract sensitive information from the electronic devices. This paper demonstrates an ion irradiation fault injection attack experiment into a cryptographic field-programmable gate-array (FPGA) circuit. The experiment proved that the commercial FPGA chip is vulnerable to low-linear energy transfer carbon irradiation, and the attack can cause the leakage of secret key bits. A statistical model is established to estimate the possibility of an effective fault injection attack on cryptographic integrated circuits. The model incorporates the effects from temporal, spatial, and logical probability of an effective attack on the cryptographic circuits. The rate of successful attack calculated from the model conforms well to the experimental results. This quantitative success rate model can help evaluate security risk for designers as well as for the third-party assessment organizations.

Detection of Micrococcus luteus biofilm formation in microfluidic environments by pH measurement using an ion-sensitive field-effect transistor.

PubMed

Matsuura, Koji; Asano, Yuka; Yamada, Akira; Naruse, Keiji

2013-02-18

Biofilm formation in microfluidic channels is difficult to detect because sampling volumes are too small for conventional turbidity measurements. To detect biofilm formation, we used an ion-sensitive field-effect transistor (ISFET) measurement system to measure pH changes in small volumes of bacterial suspension. Cells of Micrococcus luteus (M. luteus) were cultured in polystyrene (PS) microtubes and polymethylmethacrylate (PMMA)-based microfluidic channels laminated with polyvinylidene chloride. In microtubes, concentrations of bacteria and pH in the suspension were analyzed by measuring turbidity and using an ISFET sensor, respectively. In microfluidic channels containing 20 μL of bacterial suspension, we measured pH changes using the ISFET sensor and monitored biofilm formation using a microscope. We detected acidification and alkalinization phases of M. luteus from the ISFET sensor signals in both microtubes and microfluidic channels. In the alkalinization phase, after 2 day culture, dense biofilm formation was observed at the bottom of the microfluidic channels. In this study, we used an ISFET sensor to detect biofilm formation in clinical and industrial microfluidic environments by detecting alkalinization of the culture medium. 

On the origin of enhanced sensitivity in nanoscale FET-based biosensors

PubMed Central

Shoorideh, Kaveh; Chui, Chi On

2014-01-01

Electrostatic counter ion screening is a phenomenon that is detrimental to the sensitivity of charge detection in electrolytic environments, such as in field-effect transistor-based biosensors. Using simple analytical arguments, we show that electrostatic screening is weaker in the vicinity of concave curved surfaces, and stronger in the vicinity of convex surfaces. We use this insight to show, using numerical simulations, that the enhanced sensitivity observed in nanoscale biosensors is due to binding of biomolecules in concave corners where screening is reduced. We show that the traditional argument, that increased surface area-to-volume ratio for nanoscale sensors is responsible for their increased sensitivity, is incorrect. PMID:24706861

Enhancing the pH sensitivity by laterally synergic modulation in dual-gate electric-double-layer transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Ning; Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201; Hui Liu, Yang

2015-02-16

The sensitivity of a standard ion-sensitive field-effect transistor is limited to be 59.2 mV/pH (Nernst limit) at room temperature. Here, a concept based on laterally synergic electric-double-layer (EDL) modulation is proposed in order to overcome the Nernst limit. Indium-zinc-oxide EDL transistors with two laterally coupled gates are fabricated, and the synergic modulation behaviors of the two asymmetric gates are investigated. A high sensitivity of ∼168 mV/pH is realized in the dual-gate operation mode. Laterally synergic modulation in oxide-based EDL transistors is interesting for high-performance bio-chemical sensors.

Enzymatic mechanisms of biological magnetic sensitivity.

PubMed

Letuta, Ulyana G; Berdinskiy, Vitaly L; Udagawa, Chikako; Tanimoto, Yoshifumi

2017-10-01

Primary biological magnetoreceptors in living organisms is one of the main research problems in magnetobiology. Intracellular enzymatic reactions accompanied by electron transfer have been shown to be receptors of magnetic fields, and spin-dependent ion-radical processes can be a universal mechanism of biological magnetosensitivity. Magnetic interactions in intermediate ion-radical pairs, such as Zeeman and hyperfine (HFI) interactions, in accordance with proposed strict quantum mechanical theory, can determine magnetic-field dependencies of reactions that produce biologically important molecules needed for cell growth. Hyperfine interactions of electrons with nuclear magnetic moments of magnetic isotopes can explain the most important part of biomagnetic sensitivities in a weak magnetic field comparable to the Earth's magnetic field. The theoretical results mean that magnetic-field dependencies of enzymatic reaction rates in a weak magnetic field that can be independent of HFI constant a, if H < a, and are determined by the rate constant of chemical transformations in the enzyme active site. Both Zeeman and HFI interactions predict strong magnetic-field dependence in weak magnetic fields and magnetic-field independence of enzymatic reaction rate constants in strong magnetic fields. The theoretical results can explain the magnetic sensitivity of E. coli cell and demonstrate that intracellular enzymatic reactions are primary magnetoreceptors in living organisms. Bioelectromagnetics. 38:511-521, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Modeling and simulation of a chemically stimulated hydrogel bilayer bending actuator

NASA Astrophysics Data System (ADS)

Sobczyk, Martin; Wallmersperger, Thomas

2017-04-01

Stimuli-sensitive hydrogels are polymeric materials, which are able to reversibly swell in water in response to evironmental changes. Relevant stimuli include variations of pH, temperature, concentration of specific ions etc. Stacked layers composed of multiple thin hydrogels - also referred to as hydrogel-layer composites - combine the distinct sensing properties of different hydrogels. This approach enables the development of sophisticated microfluidic devices such as bisensitive valves or fluid-sensitive deflectors. In order to numerically simulate the swelling of a polyelectrolyte hydrogel in response to an ion concentration change the multifield theory is adopted. The set of partial differential equations - including the description of the chemical, the electrical and the mechanical field - are solved using the Finite Element Method. Simulations are carried out on a two-dimensional domain in order to capture interactions between the different fields. In the present work, the ion transport is governed by diffusive and migrative fluxes. The distribution of ions in the gel and the solution bath result in an osmotic pressure difference, which is responsible for the mechanical deformation of the hydrogel-layer composite. The realized numerical investigation gives an insight into the evolution of the displacement field, the distribution of ions and the electric potential within the bulk material and the interface between gel and solution bath. The predicted behavior of the relevant field variables is in excellent agreement with results available in the literature.

Small field electron beam dosimetry using MOSFET detector.

PubMed

Amin, Md Nurul; Heaton, Robert; Norrlinger, Bern; Islam, Mohammad K

2010-10-04

The dosimetry of very small electron fields can be challenging due to relative shifts in percent depth-dose curves, including the location of dmax, and lack of lateral electronic equilibrium in an ion chamber when placed in the beam. Conventionally a small parallel plate chamber or film is utilized to perform small field electron beam dosimetry. Since modern radiotherapy departments are becoming filmless in favor of electronic imaging, an alternate and readily available clinical dosimeter needs to be explored. We have studied the performance of MOSFET as a relative dosimeter in small field electron beams. The reproducibility, linearity and sensitivity of a high-sensitivity microMOSFET were investigated for clinical electron beams. In addition, the percent depth doses, output factors and profiles have been measured in a water tank with MOSFET and compared with those measured by an ion chamber for a range of field sizes from 1 cm diameter to 10 cm × 10 cm for 6, 12, 16 and 20 MeV beams. Similar comparative measurements were also per-formed with MOSFET and films in solid water phantom. The MOSFET sensitivity was found to be practically constant over the range of field sizes investigated. The dose response was found to be linear and reproducible (within ± 1% for 100 cGy). An excellent agreement was observed among the central axis depth dose curves measured using MOSFET, film and ion chamber. The output factors measured with MOSFET for small fields agreed to within 3% with those measured by film dosimetry. Overall results indicate that MOSFET can be utilized to perform dosimetry for small field electron beam.

Ion Sensitive Transparent-Gate Transistor for Visible Cell Sensing.

PubMed

Sakata, Toshiya; Nishimura, Kotaro; Miyazawa, Yuuya; Saito, Akiko; Abe, Hiroyuki; Kajisa, Taira

2017-04-04

In this study, we developed an ion-sensitive transparent-gate transistor (IS-TGT) for visible cell sensing. The gate sensing surface of the IS-TGT is transparent in a solution because a transparent amorphous oxide semiconductor composed of amorphous In-Ga-Zn-oxide (a-IGZO) with a thin SiO 2 film gate that includes an indium tin oxide (ITO) film as the source and drain electrodes is utilized. The pH response of the IS-TGT was found to be about 56 mV/pH, indicating approximately Nernstian response. Moreover, the potential signals of the IS-TGT for sodium and potassium ions, which are usually included in biological environments, were evaluated. The optical and electrical properties of the IS-TGT enable cell functions to be monitored simultaneously with microscopic observation and electrical measurement. A platform based on the IS-TGT can be used as a simple and cost-effective plate-cell-sensing system based on thin-film fabrication technology in the research field of life science.

The 88-Inch Cyclotron: A One-Stop Facility for Electronics Radiation and Detector Testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kireeff Covo, M.; Albright, R. A.; Ninemire, B. F.

In outer space down to the altitudes routinely flown by larger aircrafts, radiation can pose serious issues for microelectronics circuits. The 88-Inch Cyclotron at Lawrence Berkeley National Laboratory is a sector-focused cyclotron and home of the Berkeley Accelerator Space Effects Facility, where the effects of energetic particles on sensitive microelectronics are studied with the goal of designing electronic systems for the space community. This paper describes the flexibility of the facility and its capabilities for testing the bombardment of electronics by heavy ions, light ions, and neutrons. Experimental capabilities for the generation of neutron beams from deuteron breakups and radiationmore » testing of carbon nanotube field effect transistor will be discussed.« less

Real-time in vivo dosimetry with MOSFET detectors in serial tomotherapy for head and neck cancer patients.

PubMed

Qi, Zhen-Yu; Deng, Xiao-Wu; Huang, Shao-Min; Shiu, Almon; Lerch, Michael; Metcalfe, Peter; Rosenfeld, Anatoly; Kron, Tomas

2011-08-01

A real-time dose verification method using a recently designed metal oxide semiconductor field effect transistor (MOSFET) dosimetry system was evaluated for quality assurance (QA) of intensity-modulated radiation therapy (IMRT). Following the investigation of key parameters that might affect the accuracy of MOSFET measurements (i.e., source surface distance [SSD], field size, beam incident angles and radiation energy spectrum), the feasibility of this detector in IMRT dose verification was demonstrated by comparison with ion chamber measurements taken in an IMRT QA phantom. Real-time in vivo measurements were also performed with the MOSFET system during serial tomotherapy treatments administered to 8 head and neck cancer patients. MOSFET sensitivity did not change with SSD. For field sizes smaller than 20 × 20 cm(2), MOFET sensitivity varied within 1.0%. The detector angular response was isotropic within 2% over 360°, and the observed sensitivity variation due to changes in the energy spectrum was negligible in 6-MV photons. MOSFET system measurements and ion chamber measurements agreed at all points in IMRT phantom plan verification, within 5%. The mean difference between 48 IMRT MOSFET-measured doses and calculated values in 8 patients was 3.33% and ranged from -2.20% to 7.89%. More than 90% of the total measurements had deviations of less than 5% from the planned doses. The MOSFET dosimetry system has been proven to be an effective tool in evaluating the actual dose within individual patients during IMRT treatment. Copyright © 2011 Elsevier Inc. All rights reserved.

The electric field induced by a gravitational wave in a superconductor - A principle for a new gravitational wave antenna

NASA Technical Reports Server (NTRS)

Peng, Huei; Torr, Douglas G.

1990-01-01

This paper investigates the effect of gravitational waves on a superconductor. It is found that the key properties of a superconductor, namely zero resistance and perfect diamagnetism, give rise to an important new effect, the presence of an induced electric field E in the interior of the superconductor. The E field reacts with the ions and superelectrons. It is argued that the induced E field might provide a significantly more sensitive means of detecting gravitational waves. It appears likely that existing resonant-mass superconducting antennas with L about 3m, Q about 10 to the 8th could be readily modified to detect E fields induced by GWs of dimensionless amplitude h about 10 to the -24th.

Cellular target of weak magnetic fields: ionic conduction along actin filaments of microvilli.

PubMed

Gartzke, Joachim; Lange, Klaus

2002-11-01

The interaction of weak electromagnetic fields (EMF) with living cells is a most important but still unresolved biophysical problem. For this interaction, thermal and other types of noise appear to cause severe restrictions in the action of weak signals on relevant components of the cell. A recently presented general concept of regulation of ion and substrate pathways through microvilli provides a possible theoretical basis for the comprehension of physiological effects of even extremely low magnetic fields. The actin-based core of microfilaments in microvilli is proposed to represent a cellular interaction site for magnetic fields. Both the central role of F-actin in Ca2+ signaling and its polyelectrolyte nature eliciting specific ion conduction properties render the microvillar actin filament bundle an ideal interaction site for magnetic and electric fields. Ion channels at the tip of microvilli are connected with the cytoplasm by a bundle of microfilaments forming a diffusion barrier system. Because of its polyelectrolyte nature, the microfilament core of microvilli allows Ca2+ entry into the cytoplasm via nonlinear cable-like cation conduction through arrays of condensed ion clouds. The interaction of ion clouds with periodically applied EMFs and field-induced cation pumping through the cascade of potential barriers on the F-actin polyelectrolyte follows well-known physical principles of ion-magnetic field (MF) interaction and signal discrimination as described by the stochastic resonance and Brownian motor hypotheses. The proposed interaction mechanism is in accord with our present knowledge about Ca2+ signaling as the biological main target of MFs and the postulated extreme sensitivity for coherent excitation by very low field energies within specific amplitude and frequency windows. Microvillar F-actin bundles shielded by a lipid membrane appear to function like electronic integration devices for signal-to-noise enhancement; the influence of coherent signals on cation transduction is amplified, whereas that of random noise is reduced.

An ion-neutral model to investigate chemical ionization mass spectrometry analysis of atmospheric molecules - application to a mixed reagent ion system for hydroperoxides and organic acids

NASA Astrophysics Data System (ADS)

Heikes, Brian G.; Treadaway, Victoria; McNeill, Ashley S.; Silwal, Indira K. C.; O'Sullivan, Daniel W.

2018-04-01

An ion-neutral chemical kinetic model is described and used to simulate the negative ion chemistry occurring within a mixed-reagent ion chemical ionization mass spectrometer (CIMS). The model objective was the establishment of a theoretical basis to understand ambient pressure (variable sample flow and reagent ion carrier gas flow rates), water vapor, ozone and oxides of nitrogen effects on ion cluster sensitivities for hydrogen peroxide (H2O2), methyl peroxide (CH3OOH), formic acid (HFo) and acetic acid (HAc). The model development started with established atmospheric ion chemistry mechanisms, thermodynamic data and reaction rate coefficients. The chemical mechanism was augmented with additional reactions and their reaction rate coefficients specific to the analytes. Some existing reaction rate coefficients were modified to enable the model to match laboratory and field campaign determinations of ion cluster sensitivities as functions of CIMS sample flow rate and ambient humidity. Relative trends in predicted and observed sensitivities are compared as instrument specific factors preclude a direct calculation of instrument sensitivity as a function of sample pressure and humidity. Predicted sensitivity trends and experimental sensitivity trends suggested the model captured the reagent ion and cluster chemistry and reproduced trends in ion cluster sensitivity with sample flow and humidity observed with a CIMS instrument developed for atmospheric peroxide measurements (PCIMSs). The model was further used to investigate the potential for isobaric compounds as interferences in the measurement of the above species. For ambient O3 mixing ratios more than 50 times those of H2O2, O3-(H2O) was predicted to be a significant isobaric interference to the measurement of H2O2 using O2-(H2O2) at m/z 66. O3 and NO give rise to species and cluster ions, CO3-(H2O) and NO3-(H2O), respectively, which interfere in the measurement of CH3OOH using O2-(CH3OOH) at m/z 80. The CO3-(H2O) interference assumed one of its O atoms was 18O and present in the cluster in proportion to its natural abundance. The model results indicated monitoring water vapor mixing ratio, m/z 78 for CO3-(H2O) and m/z 98 for isotopic CO3-(H2O)2 can be used to determine when CO3-(H2O) interference is significant. Similarly, monitoring water vapor mixing ratio, m/z 62 for NO3- and m/z 98 for NO3-(H2O)2 can be used to determine when NO3-(H2O) interference is significant.

High intensity ion beams from an atmospheric pressure inductively coupled plasma

NASA Astrophysics Data System (ADS)

Al Moussalami, S.; Chen, W.; Collings, B. A.; Douglas, D. J.

2002-02-01

This work is directed towards substantially improving the sensitivity of an inductively coupled plasma mass spectrometer (ICP-MS). Ions produced in the ICP at atmospheric pressure have been extracted with comparatively high current densities. The conventional approach to ion extraction, based on a skimmed molecular beam, has been abandoned, and a high extraction field arrangement has been adopted. Although the new approach is not optimized, current densities more than 180 times greater than that of a conventional interface have been extracted and analyte sensitivities ˜10-100× greater than those reported previously for quadrupole ICP-MS have been measured.

Fusion-neutron-yield, activation measurements at the Z accelerator: design, analysis, and sensitivity.

PubMed

Hahn, K D; Cooper, G W; Ruiz, C L; Fehl, D L; Chandler, G A; Knapp, P F; Leeper, R J; Nelson, A J; Smelser, R M; Torres, J A

2014-04-01

We present a general methodology to determine the diagnostic sensitivity that is directly applicable to neutron-activation diagnostics fielded on a wide variety of neutron-producing experiments, which include inertial-confinement fusion (ICF), dense plasma focus, and ion beam-driven concepts. This approach includes a combination of several effects: (1) non-isotropic neutron emission; (2) the 1/r(2) decrease in neutron fluence in the activation material; (3) the spatially distributed neutron scattering, attenuation, and energy losses due to the fielding environment and activation material itself; and (4) temporally varying neutron emission. As an example, we describe the copper-activation diagnostic used to measure secondary deuterium-tritium fusion-neutron yields on ICF experiments conducted on the pulsed-power Z Accelerator at Sandia National Laboratories. Using this methodology along with results from absolute calibrations and Monte Carlo simulations, we find that for the diagnostic configuration on Z, the diagnostic sensitivity is 0.037% ± 17% counts/neutron per cm(2) and is ∼ 40% less sensitive than it would be in an ideal geometry due to neutron attenuation, scattering, and energy-loss effects.

Monte Carlo study of out-of-field exposure in carbon-ion radiotherapy with a passive beam: Organ doses in prostate cancer treatment.

PubMed

Yonai, Shunsuke; Matsufuji, Naruhiro; Akahane, Keiichi

2018-04-23

The aim of this work was to estimate typical dose equivalents to out-of-field organs during carbon-ion radiotherapy (CIRT) with a passive beam for prostate cancer treatment. Additionally, sensitivity analyses of organ doses for various beam parameters and phantom sizes were performed. Because the CIRT out-of-field dose depends on the beam parameters, the typical values of those parameters were determined from statistical data on the target properties of patients who received CIRT at the Heavy-Ion Medical Accelerator in Chiba (HIMAC). Using these typical beam-parameter values, out-of-field organ dose equivalents during CIRT for typical prostate treatment were estimated by Monte Carlo simulations using the Particle and Heavy-Ion Transport Code System (PHITS) and the ICRP reference phantom. The results showed that the dose decreased with distance from the target, ranging from 116 mSv in the testes to 7 mSv in the brain. The organ dose equivalents per treatment dose were lower than those either in 6-MV intensity-modulated radiotherapy or in brachytherapy with an Ir-192 source for organs within 40 cm of the target. Sensitivity analyses established that the differences from typical values were within ∼30% for all organs, except the sigmoid colon. The typical out-of-field organ dose equivalents during passive-beam CIRT were shown. The low sensitivity of the dose equivalent in organs farther than 20 cm from the target indicated that individual dose assessments required for retrospective epidemiological studies may be limited to organs around the target in cases of passive-beam CIRT for prostate cancer. Copyright © 2018 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Investigation of effect of solenoid magnet on emittances of ion beam from laser ablation plasma

NASA Astrophysics Data System (ADS)

Ikeda, Shunsuke; Romanelli, Mark; Cinquegrani, David; Sekine, Megumi; Kumaki, Masafumi; Fuwa, Yasuhiro; Kanesue, Takeshi; Okamura, Masahiro; Horioka, Kazuhiko

2014-02-01

A magnetic field can increase an ion current of a laser ablation plasma and is expected to control the change of the plasma ion current. However, the magnetic field can also make some fluctuations of the plasma and the effect on the beam emittance and the emission surface is not clear. To investigate the effect of a magnetic field, we extracted the ion beams under three conditions where without magnetic field, with magnetic field, and without magnetic field with higher laser energy to measure the beam distribution in phase space. Then we compared the relations between the plasma ion current density into the extraction gap and the Twiss parameters with each condition. We observed the effect of the magnetic field on the emission surface.

Investigation of effect of solenoid magnet on emittances of ion beam from laser ablation plasma.

PubMed

Ikeda, Shunsuke; Romanelli, Mark; Cinquegrani, David; Sekine, Megumi; Kumaki, Masafumi; Fuwa, Yasuhiro; Kanesue, Takeshi; Okamura, Masahiro; Horioka, Kazuhiko

2014-02-01

A magnetic field can increase an ion current of a laser ablation plasma and is expected to control the change of the plasma ion current. However, the magnetic field can also make some fluctuations of the plasma and the effect on the beam emittance and the emission surface is not clear. To investigate the effect of a magnetic field, we extracted the ion beams under three conditions where without magnetic field, with magnetic field, and without magnetic field with higher laser energy to measure the beam distribution in phase space. Then we compared the relations between the plasma ion current density into the extraction gap and the Twiss parameters with each condition. We observed the effect of the magnetic field on the emission surface.

Instrument response measurements of ion mobility spectrometers in situ: maintaining optimal system performance of fielded systems

NASA Astrophysics Data System (ADS)

Wallis, Eric; Griffin, Todd M.; Popkie, Norm, Jr.; Eagan, Michael A.; McAtee, Robert F.; Vrazel, Danet; McKinly, Jim

2005-05-01

Ion Mobility Spectroscopy (IMS) is the most widespread detection technique in use by the military for the detection of chemical warfare agents, explosives, and other threat agents. Moreover, its role in homeland security and force protection has expanded due, in part, to its good sensitivity, low power, lightweight, and reasonable cost. With the increased use of IMS systems as continuous monitors, it becomes necessary to develop tools and methodologies to ensure optimal performance over a wide range of conditions and extended periods of time. Namely, instrument calibration is needed to ensure proper sensitivity and to correct for matrix or environmental effects. We have developed methodologies to deal with the semi-quantitative nature of IMS and allow us to generate response curves that allow a gauge of instrument performance and maintenance requirements. This instrumentation communicates to the IMS systems via a software interface that was developed in-house. The software measures system response, logs information to a database, and generates the response curves. This paper will discuss the instrumentation, software, data collected, and initial results from fielded systems.

Integrated multi-ISE arrays with improved sensitivity, accuracy and precision

NASA Astrophysics Data System (ADS)

Wang, Chunling; Yuan, Hongyan; Duan, Zhijuan; Xiao, Dan

2017-03-01

Increasing use of ion-selective electrodes (ISEs) in the biological and environmental fields has generated demand for high-sensitivity ISEs. However, improving the sensitivities of ISEs remains a challenge because of the limit of the Nernstian slope (59.2/n mV). Here, we present a universal ion detection method using an electronic integrated multi-electrode system (EIMES) that bypasses the Nernstian slope limit of 59.2/n mV, thereby enabling substantial enhancement of the sensitivity of ISEs. The results reveal that the response slope is greatly increased from 57.2 to 1711.3 mV, 57.3 to 564.7 mV and 57.7 to 576.2 mV by electronic integrated 30 Cl- electrodes, 10 F- electrodes and 10 glass pH electrodes, respectively. Thus, a tiny change in the ion concentration can be monitored, and correspondingly, the accuracy and precision are substantially improved. The EIMES is suited for all types of potentiometric sensors and may pave the way for monitoring of various ions with high accuracy and precision because of its high sensitivity.

Electric currents in the subsolar region of the Venus lower ionosphere

NASA Technical Reports Server (NTRS)

Cole, K. D.; Hoegy, W. R.

1994-01-01

The ion and electron momentum equations, along with Ampere's law, are solved for the ion and electron drift velocities and the electric field in the subsolar Venus ionosphere, assuming a partially ionized gas and a single ion species having the ion mean mass. All collision terms among the ions, electrons and neutral particles are retained in the equations. A general expression for the evolution of the magnetic field is derived and compared with earlier expressions. Subsolar region data in the altitude range 150-300 km from the Pioneer Venus Orbiter are used to calculate altitude profiles of the components of the current due to the electric field, gradients of pressure, and gravity. Altitude profiles of the ion and electron velocities as well as the electric field, electrodynamic heating, and the energy density are determined. Only orbits having a complete set of measured plasma temperatures and densities, neutral densities, and magnetic field were considered for analysis; the results are shown only for orbit 202. The vertical velocity at altitudes above 220 km is upgoing for orbit 202. This result is consistent with observations of molecular ions at high altitudes and of plasma flow to the nightside, both of which require upward velocity of ions from the dayside ionosphere. Above about 230 km the momentum equations are extremely sensitive to the altitude profiles of density, temperature, and magnetic field.

DNA as Sensors and Imaging Agents for Metal Ions

PubMed Central

Xiang, Yu

2014-01-01

Increasing interests in detecting metal ions in many chemical and biomedical fields have created demands for developing sensors and imaging agents for metal ions with high sensitivity and selectivity. This review covers recent progress in DNA-based sensors and imaging agents for metal ions. Through both combinatorial selection and rational design, a number of metal ion-dependent DNAzymes and metal ion-binding DNA structures that can selectively recognize specific metal ions have been obtained. By attaching these DNA molecules with signal reporters such as fluorophores, chromophores, electrochemical tags, and Raman tags, a number of DNA-based sensors for both diamagnetic and paramagnetic metal ions have been developed for fluorescent, colorimetric, electrochemical, and surface Raman detections. These sensors are highly sensitive (with detection limit down to 11 ppt) and selective (with selectivity up to millions-fold) toward specific metal ions. In addition, through further development to simplify the operation, such as the use of “dipstick tests”, portable fluorometers, computer-readable discs, and widely available glucose meters, these sensors have been applied for on-site and real-time environmental monitoring and point-of-care medical diagnostics. The use of these sensors for in situ cellular imaging has also been reported. The generality of the combinatorial selection to obtain DNAzymes for almost any metal ion in any oxidation state, and the ease of modification of the DNA with different signal reporters make DNA an emerging and promising class of molecules for metal ion sensing and imaging in many fields of applications. PMID:24359450

Optimization of Urea-EnFET Based on Ta2O5 Layer with Post Annealing

PubMed Central

Lue, Cheng-En; Yu, Ting-Chun; Yang, Chia-Ming; Pijanowska, Dorota G.; Lai, Chao-Sung

2011-01-01

In this study, the urea-enzymatic field effect transistors (EnFETs) were investigated based on pH-ion sensitive field effect transistors (ISFETs) with tantalum pentoxide (Ta2O5) sensing membranes. In addition, a post N2 annealing was used to improve the sensing properties. At first, the pH sensitivity, hysteresis, drift, and light induced drift of the ISFETs were evaluated. After the covalent bonding process and urease immobilization, the urea sensitivity of the EnFETs were also investigated and compared with the conventional Si3N4 sensing layer. The ISFETs and EnFETs with annealed Ta2O5 sensing membranes showed the best responses, including the highest pH sensitivity (56.9 mV/pH, from pH 2 to pH 12) and also corresponded to the highest urea sensitivity (61 mV/pCurea, from 1 mM to 7.5 mM). Besides, the non-ideal factors of pH hysteresis, time drift, and light induced drift of the annealed samples were also lower than the controlled Ta2O5 and Si3N4 sensing membranes. PMID:22163862

Optimization of urea-EnFET based on Ta2O5 layer with post annealing.

PubMed

Lue, Cheng-En; Yu, Ting-Chun; Yang, Chia-Ming; Pijanowska, Dorota G; Lai, Chao-Sung

2011-01-01

In this study, the urea-enzymatic field effect transistors (EnFETs) were investigated based on pH-ion sensitive field effect transistors (ISFETs) with tantalum pentoxide (Ta(2)O(5)) sensing membranes. In addition, a post N(2) annealing was used to improve the sensing properties. At first, the pH sensitivity, hysteresis, drift, and light induced drift of the ISFETs were evaluated. After the covalent bonding process and urease immobilization, the urea sensitivity of the EnFETs were also investigated and compared with the conventional Si(3)N(4) sensing layer. The ISFETs and EnFETs with annealed Ta(2)O(5) sensing membranes showed the best responses, including the highest pH sensitivity (56.9 mV/pH, from pH 2 to pH 12) and also corresponded to the highest urea sensitivity (61 mV/pC(urea), from 1 mM to 7.5 mM). Besides, the non-ideal factors of pH hysteresis, time drift, and light induced drift of the annealed samples were also lower than the controlled Ta(2)O(5) and Si(3)N(4) sensing membranes.

Longitudinal and transverse dynamics of ions from residual gas in an electron accelerator

NASA Astrophysics Data System (ADS)

Gamelin, A.; Bruni, C.; Radevych, D.

2018-05-01

The ion cloud produced from residual gas in an electron accelerator can degrade machine performances and produce instabilities. The ion dynamics in an accelerator is governed by the beam-ion interaction, magnetic fields and eventual mitigation strategies. Due to the fact that the beam has a nonuniform transverse size along its orbit, the ions move longitudinally and accumulate naturally at some points in the accelerator. In order to design effective mitigation strategies it is necessary to understand the ion dynamics not only in the transverse plane but also in the longitudinal direction. After introducing the physics behind the beam-ion interaction, we show how to get accumulation points for a realistic electron storage ring lattice. Simulations of the ion cloud dynamics, including the effect of magnetic fields on the ions, clearing electrodes and clearing gaps are shown. Longitudinal ion trapping due to the magnetic mirror effect in the dipole fringe fields is also detailed. Finally, the effectiveness of clearing electrode using longitudinal clearing fields is discussed and compared to clearing electrodes producing transverse field only.

Pulse-Driven Capacitive Lead Ion Detection with Reduced Graphene Oxide Field-Effect Transistor Integrated with an Analyzing Device for Rapid Water Quality Monitoring.

PubMed

Maity, Arnab; Sui, Xiaoyu; Tarman, Chad R; Pu, Haihui; Chang, Jingbo; Zhou, Guihua; Ren, Ren; Mao, Shun; Chen, Junhong

2017-11-22

Rapid and real-time detection of heavy metals in water with a portable microsystem is a growing demand in the field of environmental monitoring, food safety, and future cyber-physical infrastructure. Here, we report a novel ultrasensitive pulse-driven capacitance-based lead ion sensor using self-assembled graphene oxide (GO) monolayer deposition strategy to recognize the heavy metal ions in water. The overall field-effect transistor (FET) structure consists of a thermally reduced graphene oxide (rGO) channel with a thin layer of Al 2 O 3 passivation as a top gate combined with sputtered gold nanoparticles that link with the glutathione (GSH) probe to attract Pb 2+ ions in water. Using a preprogrammed microcontroller, chemo-capacitance based detection of lead ions has been demonstrated with this FET sensor. With a rapid response (∼1-2 s) and negligible signal drift, a limit of detection (LOD) < 1 ppb and excellent selectivity (with a sensitivity to lead ions 1 order of magnitude higher than that of interfering ions) can be achieved for Pb 2+ measurements. The overall assay time (∼10 s) for background water stabilization followed by lead ion testing and calculation is much shorter than common FET resistance/current measurements (∼minutes) and other conventional methods, such as optical and inductively coupled plasma methods (∼hours). An approximate linear operational range (5-20 ppb) around 15 ppb (the maximum contaminant limit by US Environmental Protection Agency (EPA) for lead in drinking water) makes it especially suitable for drinking water quality monitoring. The validity of the pulse method is confirmed by quantifying Pb 2+ in various real water samples such as tap, lake, and river water with an accuracy ∼75%. This capacitance measurement strategy is promising and can be readily extended to various FET-based sensor devices for other targets.

Molecular wake shield gas analyzer

NASA Technical Reports Server (NTRS)

Hoffman, J. H.

1980-01-01

Techniques for measuring and characterizing the ultrahigh vacuum in the wake of an orbiting spacecraft are studied. A high sensitivity mass spectrometer that contains a double mass analyzer consisting of an open source miniature magnetic sector field neutral gas analyzer and an identical ion analyzer is proposed. These are configured to detect and identify gas and ion species of hydrogen, helium, nitrogen, oxygen, nitric oxide, and carbon dioxide and any other gas or ion species in the 1 to 46 amu mass range. This range covers the normal atmospheric constituents. The sensitivity of the instrument is sufficient to measure ambient gases and ion with a particle density of the order of one per cc. A chemical pump, or getter, is mounted near the entrance aperture of the neutral gas analyzer which integrates the absorption of ambient gases for a selectable period of time for subsequent release and analysis. The sensitivity is realizable for all but rare gases using this technique.

Small field electron beam dosimetry using MOSFET detector

PubMed Central

Heaton, Robert; Norrlinger, Bern; Islam, Mohammad K.

2010-01-01

The dosimetry of very small electron fields can be challenging due to relative shifts in percent depth‐dose curves, including the location of dmax, and lack of lateral electronic equilibrium in an ion chamber when placed in the beam. Conventionally a small parallel plate chamber or film is utilized to perform small field electron beam dosimetry. Since modern radiotherapy departments are becoming filmless in favor of electronic imaging, an alternate and readily available clinical dosimeter needs to be explored. We have studied the performance of MOSFET as a relative dosimeter in small field electron beams. The reproducibility, linearity and sensitivity of a high‐sensitivity microMOSFET were investigated for clinical electron beams. In addition, the percent depth doses, output factors and profiles have been measured in a water tank with MOSFET and compared with those measured by an ion chamber for a range of field sizes from 1 cm diameter to 10 cm× 10 cm for 6, 12, 16 and 20 MeV beams. Similar comparative measurements were also performed with MOSFET and films in solid water phantom. The MOSFET sensitivity was found to be practically constant over the range of field sizes investigated. The dose response was found to be linear and reproducible (within ±1% for 100 cGy). An excellent agreement was observed among the central axis depth dose curves measured using MOSFET, film and ion chamber. The output factors measured with MOSFET for small fields agreed to within 3% with those measured by film dosimetry. Overall results indicate that MOSFET can be utilized to perform dosimetry for small field electron beam. PACS number: 87.55.Qr

Binding and release of brain calcium by low-level electromagnetic fields: A review

NASA Astrophysics Data System (ADS)

Adey, W. R.; Bawin, S. M.

Evidence has accumulated that sensitivity of brain tissue to specific weak oscillating electromagnetic fields occurs in the absence of significant tissue heating (less than 0.1°C). This review focuses on the ‘windowed’ character of sensitivities of calcium binding and electrical activity in brain tissue to low-frequency modulation and intensity characteristics of impressed RF fields. ELF fields decrease calcium efflux from isolated chick and cat cerebral tissue by about 15% only in narrow amplitude and frequency ‘windows,’ between 6 and 20 Hz and between 10 and 100 V/m (approximate tissue gradient, 10-7 V/cm). VHF (147 MHz) and UHF (450 MHz) fields increase calcium efflux from isolated chick brain by about 15% when amplitude modulated between 6 and 20 Hz, but only for incident fields in the vicinity of 1.0 mW/cm2. We have now shown that this increased efflux in response to 16-Hz amplitude-modulated 450-MHz, 0.75-mW/cm2 field exposure is insensitive to variations in calcium concentration from 0 to 4.16 mM in the testing solution but is enhanced by addition of hydrogen ions (0.108 mM 0.1 N HCl) and inhibited in the absence of normal bicarbonate ion levels (2.4 mM). In the presence of lanthanum ions (2.0 mM), which block transmembrane movement of calcium, exposure to these EM fields decreases the 45Ca2 + efflux. Low-frequency gradients may be transduced in a specific class of extracellular binding sites, normally occupied by calcium ions and susceptible to competitive hydrogen ion binding. Transductive coupling may involve coherent charge states between anionic sites on membrane surface glycoproteins, with longrange cooperative interactions triggered by weak extracellular electric fields. Proton ‘tunneling’ may occur at boundaries between coherent and noncoherent charge zones.

Assessing the sensitivity of benzene cluster cation chemical ionization mass spectrometry toward a wide array of biogenic volatile organic compounds

NASA Astrophysics Data System (ADS)

Lavi, Avi; Vermeuel, Michael; Novak, Gordon; Bertram, Timothy

2017-04-01

Chemical ionization mass spectrometry is a real-time, sensitive and selective measurement technique for the detection of volatile organic compounds (VOCs). The benefits of CIMS technology make it highly suitable for field measurements that requires fast (10Hz and higher) response rates, such as the study of surface-atmosphere exchange processes by the eddy covariance method. The use of benzene cluster cations as a regent ion was previously demonstrated as a sensitive and selective method for the detection of select biogenic VOCs (e.g. isoprene, monoterpenes and sesquiterpenes) [Kim et al., 2016; Leibrock and Huey, 2000]. Quantitative analysis of atmospheric trace gases necessitates calibration for each analyte as a function of atmospheric conditions. We describe a custom designed calibration system, based on liquid evaporation, for determination of the sensitivity of the benzene-CIMS to a wide range of organic compounds at atmospherically relevant mixing ratios (<200 ppt). We report on the effect of atmospheric water vapor and oxygen concentrations on instrument response for isoprene and a wide range of monoterpenes and sesquiterpenes. To gain mechanistic insight into the ion-molecule reactions and the role of water vapor and oxygen, we compare our measured sensitivities with a computational analysis of the charge distribution between the analyte, reagent ion and water molecules in the gas phase. These parameters provide insight on the ionization mechanism and provide parameters for quantification of organic molecules measured during field campaigns. References Kim, M. J., M. C. Zoerb, N. R. Campbell, K. J. Zimmermann, B. W. Blomquist, B. J. Huebert, and T. H. Bertram (2016), Revisiting benzene cluster cations for the chemical ionization of dimethyl sulfide and select volatile organic compounds, Atmos Meas Tech, 9(4), 1473-1484, doi:10.5194/amt-9-1473-2016. Leibrock, E., and L. G. Huey (2000), Ion chemistry for the detection of isoprene and other volatile organic compounds in ambient air, Geophys Res Lett, 27(12), 1719-1722, doi:Doi 10.1029/1999gl010804.

Interface and process for enhanced transmission of non-circular ion beams between stages at unequal pressure

DOEpatents

Tang, Keqi [Richland, WA; Shvartsburg, Alexandre A [Richland, WA; Smith, Richard D [Richland, WA

2008-03-04

The invention discloses a new interface with non-circular conductance limit aperture(s) useful for effective transmission of non-circular ion beams between stages with different gas pressure. In particular, the invention provides an improved coupling of field asymmetric waveform ion mobility spectrometry (FAIMS) analyzers of planar or side-to-side geometry to downstream stages such as mass spectrometry or ion mobility spectrometry. In this case, the non-circular aperture is rectangular; other geometries may be optimum in other applications. In the preferred embodiment, the non-circular aperture interface is followed by an electrodynamic ion funnel that may focus wide ion beams of any shape into tight circular beams with virtually no losses. The jet disrupter element of the funnel may also have a non-circular geometry, matching the shape of arriving ion beam. The improved sensitivity of planar FAIMS/MS has been demonstrated in experiments using a non-contiguous elongated aperture but other embodiments (e.g., with a contiguous slit aperture) may be preferable, especially in conjunction with an ion funnel operated at high pressures.

Effect of magnetic field inhomogeneity on ion cyclotron motion coherence at high magnetic field.

PubMed

Vladimirov, Gleb; Kostyukevich, Yury; Hendrickson, Christopher L; Blakney, Greg T; Nikolaev, Eugene

2015-01-01

A three-dimensional code based on the particle-in-cell algorithm modified to account for the inhomogeneity of the magnetic field was applied to determine the effect of Z(1), Z(2), Z(3), Z(4), X, Y, ZX, ZY, XZ(2) YZ(2), XY and X(2)-Y(2) components of an orthogonal magnetic field expansion on ion motion during detection in an FT-ICR cell. Simulations were performed for magnetic field strengths of 4.7, 7, 14.5 and 21 Tesla, including experimentally determined magnetic field spatial distributions for existing 4.7 T and 14.5 T magnets. The effect of magnetic field inhomogeneity on ion cloud stabilization ("ion condensation") at high numbers of ions was investigated by direct simulations of individual ion trajectories. Z(1), Z(2), Z(3) and Z(4) components have the largest effect (especially Z(1)) on ion cloud stability. Higher magnetic field strength and lower m/z demand higher relative magnetic field homogeneity to maintain cloud coherence for a fixed time period. The dependence of mass resolving power upper limit on Z(1) inhomogeneity is evaluated for different magnetic fields and m/z. The results serve to set the homogeneity requirements for various orthogonal magnetic field components (shims) for future FT-ICR magnet design.

High-resolution high-sensitivity elemental imaging by secondary ion mass spectrometry: from traditional 2D and 3D imaging to correlative microscopy

NASA Astrophysics Data System (ADS)

Wirtz, T.; Philipp, P.; Audinot, J.-N.; Dowsett, D.; Eswara, S.

2015-10-01

Secondary ion mass spectrometry (SIMS) constitutes an extremely sensitive technique for imaging surfaces in 2D and 3D. Apart from its excellent sensitivity and high lateral resolution (50 nm on state-of-the-art SIMS instruments), advantages of SIMS include high dynamic range and the ability to differentiate between isotopes. This paper first reviews the underlying principles of SIMS as well as the performance and applications of 2D and 3D SIMS elemental imaging. The prospects for further improving the capabilities of SIMS imaging are discussed. The lateral resolution in SIMS imaging when using the microprobe mode is limited by (i) the ion probe size, which is dependent on the brightness of the primary ion source, the quality of the optics of the primary ion column and the electric fields in the near sample region used to extract secondary ions; (ii) the sensitivity of the analysis as a reasonable secondary ion signal, which must be detected from very tiny voxel sizes and thus from a very limited number of sputtered atoms; and (iii) the physical dimensions of the collision cascade determining the origin of the sputtered ions with respect to the impact site of the incident primary ion probe. One interesting prospect is the use of SIMS-based correlative microscopy. In this approach SIMS is combined with various high-resolution microscopy techniques, so that elemental/chemical information at the highest sensitivity can be obtained with SIMS, while excellent spatial resolution is provided by overlaying the SIMS images with high-resolution images obtained by these microscopy techniques. Examples of this approach are given by presenting in situ combinations of SIMS with transmission electron microscopy (TEM), helium ion microscopy (HIM) and scanning probe microscopy (SPM).

Influence of dilution water ionic composition on acute major ion toxicity to the mayfly Neocloeon triangulifer

EPA Science Inventory

Both field and laboratory studies have shown that mayflies (Ephemeroptera) tend to be relatively sensitive to elevated major ion concentrations, but very little is known about how ionic composition influences these responses. The present study evaluated the toxicity of various m...

Quantification of diesel exhaust gas phase organics by a thermal desorption proton transfer reaction mass spectrometer

NASA Astrophysics Data System (ADS)

Erickson, M. H.; Wallace, H. W.; Jobson, B. T.

2012-02-01

A new approach was developed to measure the total abundance of long chain alkanes (C12 and above) in urban air using thermal desorption with a proton transfer reaction mass spectrometer (PTR-MS). These species are emitted in diesel exhaust and may be important precursors to secondary organic aerosol production in urban areas. Long chain alkanes undergo dissociative proton transfer reactions forming a series of fragment ions with formula CnH2n+1. The yield of the fragment ions is a function of drift conditions. At a drift field strength of 80 Townsends, the most abundant ion fragments from C10 to C16 n-alkanes were m/z 57, 71 and 85. The PTR-MS is insensitive to n-alkanes less than C8 but displays an increasing sensitivity for larger alkanes. Higher drift field strengths yield greater normalized sensitivity implying that the proton affinity of the long chain n-alkanes is less than H2O. Analysis of diesel fuel shows the mass spectrum was dominated by alkanes (CnH2n+1), monocyclic aromatics, and an ion group with formula CnH2n-1 (m/z 97, 111, 125, 139). The PTR-MS was deployed in Sacramento, CA during the Carbonaceous Aerosols and Radiative Effects Study field experiment in June 2010. The ratio of the m/z 97 to 85 ion intensities in ambient air matched that found in diesel fuel. Total diesel exhaust alkane concentrations calculated from the measured abundance of m/z 85 ranged from the method detection limit of ~1 μg m-3 to 100 μg m-3 in several air pollution episodes. The total diesel exhaust alkane concentration determined by this method was on average a factor of 10 greater than the sum of alkylbenzenes associated with spark ignition vehicle exhaust.

Magnetomigration of rare-earth ions in inhomogeneous magnetic fields.

PubMed

Franczak, Agnieszka; Binnemans, Koen; Jan Fransaer

2016-10-05

The effects of external inhomogenous (gradient) magnetic fields on the movement of the rare-earth ions: Dy 3+ , Gd 3+ and Y 3+ , in initially homogeneous aqueous solutions have been investigated. Differences in the migration of rare-earth ions in gradient magnetic fields were observed, depending on the magnetic character of the ions: paramagnetic ions of Dy 3+ and Gd 3+ move towards regions of the sample where the magnetic field gradient is the strongest, while diamagnetic ions of Y 3+ move in the opposite direction. It has been showed that the low magnetic field gradients, such the ones generated by permanent magnets, are sufficient to observe the magnetomigration effects of the ions in solution. The present work clearly establishes the behavior of magnetically different ions in initially homogeneous aqueous solutions exposed to magnetic field gradients. To this avail, a methodology for measuring the local concentration differences of metal ions in liquid samples was developed.

Pickup Ion Velocity Distributions at Titan: Effects of Spatial Gradients

NASA Technical Reports Server (NTRS)

Hartle, R. E.; Sittler, E. C.

2004-01-01

The principle source of pickup ions at Titan is its neutral exosphere, extending well above the ionopause into the magnetosphere of Saturn or the solar wind, depending on the moon's orbital position. Thermal and nonthermal processes in the thermosphere generate the distribution of neutral atoms and molecules in the exosphere. The combination of these processes and the range of mass numbers, 1 to over 28, contribute to an exospheric source structure that produces pickup ions with gyroradii that are much larger or smaller than the corresponding scale heights of their neutral sources. The resulting phase space distributions are dependent on the spatial structure of the exosphere as well as that of the magnetic field and background plasma. When the pickup ion gyroradius is less than the source gas scale height, the pickup ion velocity distribution is characterized by a sharp cutoff near the maximum speed, which is twice that of the ambient plasma times the sine of the angle between the magnetic field and the flow velocity. This was the case for pickup H(sup +) ions identified during the Voyager 1 flyby. In contrast, as the gyroradius becomes much larger than the scale height, the peak of the velocity distribution in the source region recedes from the maximum speed. Iri addition, the amplitude of the distribution near the maximum speed decreases. These more beam like distributions of heavy ions were not observed from Voyager 1 , but should be observable by more sensitive instruments on future spacecraft, including Cassini. The finite gyroradius effects in the pickup ion velocity distributions are studied by including in the analysis the possible range of spatial structures in the neutral exosphere and background plasma.

Charge multiplication effect in thin diamond films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Skukan, N., E-mail: nskukan@irb.hr; Grilj, V.; Sudić, I.

2016-07-25

Herein, we report on the enhanced sensitivity for the detection of charged particles in single crystal chemical vapour deposition (scCVD) diamond radiation detectors. The experimental results demonstrate charge multiplication in thin planar diamond membrane detectors, upon impact of 18 MeV O ions, under high electric field conditions. Avalanche multiplication is widely exploited in devices such as avalanche photo diodes, but has never before been reproducibly observed in intrinsic CVD diamond. Because enhanced sensitivity for charged particle detection is obtained for short charge drift lengths without dark counts, this effect could be further exploited in the development of sensors based on avalanchemore » multiplication and radiation detectors with extreme radiation hardness.« less

Measurement of the line-of-sight velocity of high-altitude barium clouds A technique

NASA Technical Reports Server (NTRS)

Mende, S. B.; Harris, S. E.

1982-01-01

It is demonstrated that for maximizing the scientific output of future ionospheric and magnetospheric ion cloud release experiments a new type of instrument is required which will measure the line-of-sight velocity of the ion cloud by the Doppler technique. A simple instrument was constructed using a 5-cm diam solid Fabry-Perot etalon coupled to a low-light-level integrating TV camera. It was demonstrated that the system has both the sensitivity and spectral resolution for detection of ion clouds and measurement of their line-of-sight Doppler velocity. The tests consisted of (1) a field experiment using a rocket barium cloud release to check sensitivity, and (2) laboratory experiments to show the spectral resolving capabilities of the system. The instrument was found to be operational if the source was brighter than approximately 1 kR, and it had a wavelength resolution much better than 0.2 A, which corresponds to approximately 12 km/sec or in the case of barium ion an acceleration potential of 100 V. The instrument is rugged and, therefore, simple to use in field experiments or on flight instruments. The sensitivity limit of the instrument can be increased by increasing the size of the etalon.

Comparative analysis of full-gate and short-gate dielectric modulated electrically doped Tunnel-FET based biosensors

NASA Astrophysics Data System (ADS)

Sharma, Dheeraj; Singh, Deepika; Pandey, Sunil; Yadav, Shivendra; Kondekar, P. N.

2017-11-01

In this work, we have done a comprehensive study between full-gate and short-gate dielectrically modulated (DM) electrically doped tunnel field-effect transistor (SGDM-EDTFET) based biosensors of equivalent dimensions. However, in both the structures, dielectric constant and charge density are considered as a sensing parameter for sensing the charged and non-charged biomolecules in the given solution. In SGDM-EDTFET architecture, the reduction in gate length results a significant improvement in the tunneling current due to occurrence of strong coupling between gate and channel region which ensures higher drain current sensitivity for detection of the biomolecules. Moreover, the sensitivity of dual metal SGDM-EDTFET is compared with the single metal SGDM-EDTFET to analyze the better sensing capability of both the devices for the biosensor application. Further, the effect of sensing parameter i.e., ON-current (ION), and ION/IOFF ratio is analysed for dual metal SGDM-EDTFET in comparison with dual metal SGDM-EDFET. From the comparison, it is found that dual metal SGDM-EDTFET based biosensor attains relatively better sensitivity and can be utilized as a suitable candidate for biosensing applications.

Second generation measurement of the electric dipole moment of the electron using trapped ThF+ ions

NASA Astrophysics Data System (ADS)

Ng, Kia Boon; Zhou, Yan; Gresh, Daniel; Cairncross, William; Grau, Matthew; Ni, Yiqi; Ye, Jun; Cornell, Eric

2016-05-01

ThF+ has been chosen as the candidate for a second generation measurement of the electric dipole moment of the electron (eEDM). Compared to the current HfF+ eEDM experiment, ThF+ has several advantages: (i) the eEDM-sensitive state (3Δ1) is the ground state, which facilitates a long coherence time; (ii) its effective electric field (38 GV/cm) is 50% larger than that of HfF+, which promises a direct increase of the eEDM sensitivity; and (iii) the ionization energy of neutral ThF is lower than its dissociation energy, which introduces greater flexibility in rotational state-selective photoionization via core-nonpenetrating Rydberg states. Here, we present progress of our experimental setup, preliminary spectroscopic data of multi-photon ionization, and discussions of new features in ion trapping, state preparation and population readout.

Effects of Preferential Solvation Revealed by Time-Resolved Magnetic Field Effects

PubMed Central

2017-01-01

External magnetic fields can impact recombination yields of photoinduced electron transfer reactions by affecting the spin dynamics in transient, spin-correlated radical pair intermediates. For exciplex-forming donor–acceptor systems, this magnetic field effect (MFE) can be investigated sensitively by studying the delayed recombination fluorescence. Here, we investigate the effect of preferential solvation in microheterogeneous solvent mixtures on the radical pair dynamics of the system 9,10-dimethylanthracene (fluorophore)/N,N-dimethylaniline (quencher) by means of time-resolved magnetic field effect (TR-MFE) measurements, wherein the exciplex emission is recorded in the absence and the presence of an external magnetic field using time-correlated single photon counting (TCSPC). In microheterogeneous environments, the MFE of the exciplex emission occurs on a faster time scale than in iso-dielectric homogeneous solvents. In addition, the local polarity reported by the exciplex is enhanced compared to homogeneous solvent mixtures of the same macroscopic permittivity. Detailed analyses of the TR-MFE reveal that the quenching reaction directly yielding the radical ion pair is favored in microheterogeneous environments. This is in stark contrast to homogeneous media, for which the MFE predominantly involves direct formation of the exciplex, its subsequent dissociation to the magneto-sensitive radical pair, and re-encounters. These observations provide evidence for polar microdomains and enhanced caging, which are shown to have a significant impact on the reaction dynamics in microheterogeneous binary solvents. PMID:28263599

Effects of Preferential Solvation Revealed by Time-Resolved Magnetic Field Effects.

PubMed

Pham, Van Thi Bich; Hoang, Hao Minh; Grampp, Günter; Kattnig, Daniel R

2017-03-30

External magnetic fields can impact recombination yields of photoinduced electron transfer reactions by affecting the spin dynamics in transient, spin-correlated radical pair intermediates. For exciplex-forming donor-acceptor systems, this magnetic field effect (MFE) can be investigated sensitively by studying the delayed recombination fluorescence. Here, we investigate the effect of preferential solvation in microheterogeneous solvent mixtures on the radical pair dynamics of the system 9,10-dimethylanthracene (fluorophore)/N,N-dimethylaniline (quencher) by means of time-resolved magnetic field effect (TR-MFE) measurements, wherein the exciplex emission is recorded in the absence and the presence of an external magnetic field using time-correlated single photon counting (TCSPC). In microheterogeneous environments, the MFE of the exciplex emission occurs on a faster time scale than in iso-dielectric homogeneous solvents. In addition, the local polarity reported by the exciplex is enhanced compared to homogeneous solvent mixtures of the same macroscopic permittivity. Detailed analyses of the TR-MFE reveal that the quenching reaction directly yielding the radical ion pair is favored in microheterogeneous environments. This is in stark contrast to homogeneous media, for which the MFE predominantly involves direct formation of the exciplex, its subsequent dissociation to the magneto-sensitive radical pair, and re-encounters. These observations provide evidence for polar microdomains and enhanced caging, which are shown to have a significant impact on the reaction dynamics in microheterogeneous binary solvents.

Ion-selective electrolyte-gated field-effect transistors: prerequisites for proper functioning

NASA Astrophysics Data System (ADS)

Kofler, Johannes; Schmoltner, Kerstin; List-Kratochvil, Emil J. W.

2014-10-01

Electrolyte-gated organic field-effect transistors (EGOFETs) used as transducers and amplifiers in potentiometric sensors have recently attracted a significant amount of scientific interest. For that reason, the fundamental prerequisites to achieve a proper potentiometric signal amplification and transduction are examined. First, polarizable as well as non-polarizable semiconductor- and gate-electrolyte- interface combinations are investigated by normal pulse voltammetry. The results of these measurements are correlated with the corresponding transistor characteristics, clarifying the functional principle of EGOFETs and the requirements for high signal amplification. In addition to a good electrical performance, the EGOFET-transducers should also be compatible with the targeted sensing application. Accordingly, the influence of different gate materials and electrolytes on the sensing abilities, are discussed. Even though all physical requirements are met, EGOFETs typically exhibit irreversible degradation, if the gate potential exceeds a certain level. For that reason, EGOFETs have to be operated using a constant source-drain operation mode which is presented by means of an H+ (pH) sensitive ion-sensor.

Ion Velocity Measurements for the Ionospheric Connections Explorer

NASA Astrophysics Data System (ADS)

Heelis, R. A.; Stoneback, R. A.; Perdue, M. D.; Depew, M. D.; Morgan, W. A.; Mankey, M. W.; Lippincott, C. R.; Harmon, L. L.; Holt, B. J.

2017-10-01

The Ionospheric Connections Explorer (ICON) payload includes an Ion Velocity Meter (IVM) to provide measurements of the ion drift motions, density, temperature and major ion composition at the satellite altitude near 575 km. The primary measurement goal for the IVM is to provide the meridional ion drift perpendicular to the magnetic field with an accuracy of 7.5 m s-1 for all daytime conditions encountered by the spacecraft within 15° of the magnetic equator. The IVM will derive this parameter utilizing two sensors, a retarding potential analyzer (RPA) and an ion drift meter (IDM) that have a robust and successful flight heritage. The IVM described here incorporates improvements in the design and operation to produce the most sensitive device that has been fielded to date. It will specify the ion drift vector, from which the component perpendicular to the magnetic field will be derived. In addition it will specify the total ion density, the ion temperature and the fractional ion composition. These data will be used in conjunction with measurements from the other ICON instruments to uncover the important connections between the dynamics of the neutral atmosphere and the ionosphere through the generation of dynamo currents perpendicular to the magnetic field and collisional forces parallel to the magnetic field. Here the configuration and operation of the IVM instrument are described, as well as the procedures by which the ion drift velocity is determined. A description of the subsystem characteristics, which allow a determination of the expected uncertainties in the derived parameters, is also given.

Effects of convection electric field on upwelling and escape of ionospheric O(+)

NASA Technical Reports Server (NTRS)

Cladis, J. B.; Chiu, Yam T.; Peterson, William K.

1992-01-01

A Monte Carlo code is used to explore the full effects of the convection electric field on distributions of upflowing O(+) ions from the cusp/cleft ionosphere. Trajectories of individual ions/neutrals are computed as they undergo multiple charge-exchange collisions. In the ion state, the trajectories are computed in realistic models of the magnetic field and the convection, corotation, and ambipolar electric fields. The effects of ion-ion collisions are included, and the trajectories are computed with and without simultaneous stochastic heating perpendicular to the magnetic field by a realistic model of broadband, low frequency waves. In the neutral state, ballistic trajectories in the gravitational field are computed. The initial conditions of the ions, in addition to ambipolar electric field and the number densities and temperatures of O(+), H(+), and electrons as a function of height in the cusp/cleft region were obtained from the results of Gombosi and Killeen (1987), who used a hydrodynamic code to simulate the time-dependent frictional-heating effects in a magnetic tube during its motion though the convection throat. The distribution of the ion fluxes as a function of height are constructed from the case histories.

Effect of mobile ions on the electric field needed to orient charged diblock copolymer thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dehghan, Ashkan; Shi, An-Chang; Schick, M.

We examine the behavior of lamellar phases of charged/neutral diblock copolymer thin films containing mobile ions in the presence of an external electric field. We employ self-consistent field theory and focus on the aligning effect of the electric field on the lamellae. Of particular interest are the effects of the mobile ions on the critical field, the value required to reorient the lamellae from the parallel configuration favored by the surface interaction to the perpendicular orientation favored by the field. We find that the critical field depends strongly on whether the neutral or charged species is favored by the substrates.more » In the case in which the neutral species is favored, the addition of charges decreases the critical electric field significantly. The effect is greater when the mobile ions are confined to the charged lamellae. In contrast, when the charged species is favored by the substrate, the addition of mobile ions stabilizes the parallel configuration and thus results in an increase in the critical electric field. The presence of ions in the system introduces a new mixed phase in addition to those reported previously.« less

Ion temperatures in HIP-1 and SUMMA from charge-exchange neutral optical emission spectra

NASA Technical Reports Server (NTRS)

Patch, R. W.; Lauver, M. R.

1976-01-01

Ion temperatures were obtained from observations of the H sub alpha, D sub alpha, and He 587.6 nm lines emitted from hydrogen, deuterium, and helium plasmas in the SUMMA and HIP-1 mirror devices at Lewis Research Center. Steady state discharges were formed by applying a radially inward dc electric field between cylindrical or annular anodes and hollow cathodes located at the peaks of the mirrors. The ion temperatures were found from the Doppler broadening of the charge-exchange components of spectral lines. A statistical method was developed for obtaining scaling relations of ion temperature as a function of current, voltage, and magnetic flux density. Derivations are given that take into account triangular monochromator slit functions, loss cones, and superimposed charge-exchange processes. In addition, the Doppler broadening was found to be sensitive to the influence of drift on charge-exchange cross section. The effects of finite ion-cyclotron radius, cascading, and delayed emission are reviewed.

Differential Ion Mobility Separations in up to 100 % Helium Using Microchips

PubMed Central

Shvartsburg, Alexandre A.; Ibrahim, Yehia M.; Smith, Richard D.

2014-01-01

The performance of differential IMS (FAIMS) analyzers is much enhanced by gases comprising He, especially He/N2 mixtures. However, electrical breakdown has limited the He fraction to ~50 %–75 %, depending on the field strength. By the Paschen law, the threshold field for breakdown increases at shorter distances. This allows FAIMS using chips with microscopic channels to utilize much stronger field intensities (E) than “full-size” analyzers with wider gaps. Here we show that those chips can employ higher He fractions up to 100 %. Use of He-rich gases improves the resolution and resolution/sensitivity balance substantially, although less than for full-size analyzers. The optimum He fraction is ~80 %, in line with first-principles theory. Hence, one can now measure the dependences of ion mobility on E in pure He, where ion-molecule cross section calculations are much more tractable than in other gases that form deeper and more complex interaction potentials. This capability may facilitate quantitative modeling of high-field ion mobility behavior and, thus, FAIMS separation properties, which would enable a priori extraction of structural information about the ions. PMID:24402673

Probing Surface Electric Field Noise with a Single Ion

DTIC Science & Technology

2013-07-30

potentials is housed inside a Faraday cage providing more than 40 dB of attenuation for electromagnetic fields in the range of frequencies between 200...and measuring the ion quantum state [16]. Thus, by measuring the effect of electric field noise on the motional quantum state of the ion, one can probe...understand these effects . In summary, we have probed the electric field noise near an aluminum-copper surface at room temperature using a single trapped ion

Cellular defibrillation: interaction of micro-scale electric fields with voltage-gated ion channels.

PubMed

Kargol, Armin; Malkinski, Leszek; Eskandari, Rahmatollah; Carter, Maya; Livingston, Daniel

2015-09-01

We study the effect of micro-scale electric fields on voltage-gated ion channels in mammalian cell membranes. Such micro- and nano-scale electric fields mimic the effects of multiferroic nanoparticles that were recently proposed [1] as a novel way of controlling the function of voltage-sensing biomolecules such as ion channels. This article describes experimental procedures and initial results that reveal the effect of the electric field, in close proximity of cells, on the ion transport through voltage-gated ion channels. We present two configurations of the whole-cell patch-clamping apparatus that were used to detect the effect of external stimulation on ionic currents and discuss preliminary results that indicate modulation of the ionic currents consistent with the applied stimulus.

Status and outlook of CHIP-TRAP: The Central Michigan University high precision Penning trap

NASA Astrophysics Data System (ADS)

Redshaw, M.; Bryce, R. A.; Hawks, P.; Gamage, N. D.; Hunt, C.; Kandegedara, R. M. E. B.; Ratnayake, I. S.; Sharp, L.

2016-06-01

At Central Michigan University we are developing a high-precision Penning trap mass spectrometer (CHIP-TRAP) that will focus on measurements with long-lived radioactive isotopes. CHIP-TRAP will consist of a pair of hyperbolic precision-measurement Penning traps, and a cylindrical capture/filter trap in a 12 T magnetic field. Ions will be produced by external ion sources, including a laser ablation source, and transported to the capture trap at low energies enabling ions of a given m / q ratio to be selected via their time-of-flight. In the capture trap, contaminant ions will be removed with a mass-selective rf dipole excitation and the ion of interest will be transported to the measurement traps. A phase-sensitive image charge detection technique will be used for simultaneous cyclotron frequency measurements on single ions in the two precision traps, resulting in a reduction in statistical uncertainty due to magnetic field fluctuations.

High-sensitivity pH sensor using separative extended-gate field-effect transistors with single-walled carbon-nanotube networks

NASA Astrophysics Data System (ADS)

Pyo, Ju-Young; Cho, Won-Ju

2018-04-01

We fabricate high-sensitivity pH sensors using single-walled carbon-nanotube (SWCNT) network thin-film transistors (TFTs). The sensing and transducer parts of the pH sensor are composed of separative extended-sensing gates (ESGs) with SnO2 ion-sensitive membranes and double-gate structure TFTs with thin SWCNT network channels of ∼1 nm and AlO x top-gate insulators formed by the solution-deposition method. To prevent thermal process-induced damages on the SWCNT channel layer due to the post-deposition annealing process and improve the electrical characteristics of the SWCNT-TFTs, microwave irradiation is applied at low temperatures. As a result, a pH sensitivity of 7.6 V/pH, far beyond the Nernst limit, is obtained owing to the capacitive coupling effect between the top- and bottom-gate insulators of the SWCNT-TFTs. Therefore, double-gate structure SWCNT-TFTs with separated ESGs are expected to be highly beneficial for high-sensitivity disposable biosensor applications.

Controlling nonsequential double ionization of Ne with parallel-polarized two-color laser pulses.

PubMed

Luo, Siqiang; Ma, Xiaomeng; Xie, Hui; Li, Min; Zhou, Yueming; Cao, Wei; Lu, Peixiang

2018-05-14

We measure the recoil-ion momentum distributions from nonsequential double ionization of Ne by two-color laser pulses consisting of a strong 800-nm field and a weak 400-nm field with parallel polarizations. The ion momentum spectra show pronounced asymmetries in the emission direction, which depend sensitively on the relative phase of the two-color components. Moreover, the peak of the doubly charged ion momentum distribution shifts gradually with the relative phase. The shifted range is much larger than the maximal vector potential of the 400-nm laser field. Those features are well recaptured by a semiclassical model. Through analyzing the correlated electron dynamics, we found that the energy sharing between the two electrons is extremely unequal at the instant of recollison. We further show that the shift of the ion momentum corresponds to the change of the recollision time in the two-color laser field. By tuning the relative phase of the two-color components, the recollision time is controlled with attosecond precision.

Dynamics of photogenerated nonequilibrium electronic states in Ar+-ion-irradiated SrTiO3

NASA Astrophysics Data System (ADS)

Kumar, Dushyant; Hossain, Z.; Budhani, R. C.

2015-05-01

A metallic surface is realized on stoichiometric and insulating (100) SrTiO3 by Ar+-ion irradiation. The sheet carrier density and Hall mobility of the layer are ˜4.0 ×1014cm-2 and ˜2 ×103cm2/Vs , respectively, at 15 K for the irradiation dose of ˜4.2 ×1018ions/cm2 . These samples display ultraviolet light sensitive photoconductivity (PC) which is enhanced abruptly below the temperature (≈100 K) where SrTiO3 crystal undergoes an antiferrodistortive cubic-to-tetragonal (Oh1→D4h 18 ) structural phase transition. This behavior of PC maps well with the temperature dependence of dielectric function and electric field induced conductivity. The longevity of the PC state also shows a distinct change below ≈100 K. At T >100 K its decay is thermally activated with an energy barrier of ≈36 meV, whereas at T <100 K it becomes independent of temperature. We have examined the effect of electrostatic gating on the lifetime of the PC state. One nontrivial result is the ambient temperature quenching of the photoconducting state by the negative gate field. This observation opens avenues for designing a solid state photoelectric switch. The origin and lifetime of the PC state are understood in the light of field effect induced band bending, defect dynamics, and thermal relaxation processes.

Nitrogen Gas Field Ion Source (GFIS) Focused Ion Beam (FIB) Secondary Electron Imaging: A First Look.

PubMed

Schmidt, Marek E; Yasaka, Anto; Akabori, Masashi; Mizuta, Hiroshi

2017-08-01

The recent technological advance of the gas field ion source (GFIS) and its successful integration into systems has renewed the interest in the focused ion beam (FIB) technology. Due to the atomically small source size and the use of light ions, the limitations of the liquid metal ion source are solved as device dimensions are pushed further towards the single-digit nanometer size. Helium and neon ions are the most widely used, but a large portfolio of available ion species is desirable, to allow a wide range of applications. Among argon and hydrogen, $${\\rm N}_{2}^{{\\plus}} $$ ions offer unique characteristics due to their covalent bond and their use as dopant for various carbon-based materials including diamond. Here, we provide a first look at the $${\\rm N}_{2}^{{\\plus}} $$ GFIS-FIB enabled imaging of a large selection of microscopic structures, including gold on carbon test specimen, thin metal films on insulator and nanostructured carbon-based devices, which are among the most actively researched materials in the field of nanoelectronics. The results are compared with images acquired by He+ ions, and we show that $${\\rm N}_{2}^{{\\plus}} $$ GFIS-FIB can offer improved material contrast even at very low imaging dose and is more sensitive to the surface roughness.

Oxidation-state sensitive imaging of cerium dioxide by atomic-resolution low-angle annular dark field scanning transmission electron microscopy.

PubMed

Johnston-Peck, Aaron C; Winterstein, Jonathan P; Roberts, Alan D; DuChene, Joseph S; Qian, Kun; Sweeny, Brendan C; Wei, Wei David; Sharma, Renu; Stach, Eric A; Herzing, Andrew A

2016-03-01

Low-angle annular dark field (LAADF) scanning transmission electron microscopy (STEM) imaging is presented as a method that is sensitive to the oxidation state of cerium ions in CeO2 nanoparticles. This relationship was validated through electron energy loss spectroscopy (EELS), in situ measurements, as well as multislice image simulations. Static displacements caused by the increased ionic radius of Ce(3+) influence the electron channeling process and increase electron scattering to low angles while reducing scatter to high angles. This process manifests itself by reducing the high-angle annular dark field (HAADF) signal intensity while increasing the LAADF signal intensity in close proximity to Ce(3+) ions. This technique can supplement STEM-EELS and in so doing, relax the experimental challenges associated with acquiring oxidation state information at high spatial resolutions. Published by Elsevier B.V.

Electro- and Magneto-Modulated Ion Transport through Graphene Oxide Membranes

PubMed Central

Sun, Pengzhan; Zheng, Feng; Wang, Kunlin; Zhong, Minlin; Wu, Dehai; Zhu, Hongwei

2014-01-01

The control of ion trans-membrane transport through graphene oxide (GO) membranes is achieved by electric and magnetic fields. Electric field can either increase or decrease the ion transport through GO membranes depending on its direction, and magnetic field can enhance the ion penetration monotonically. When electric field is applied across GO membrane, excellent control of ion fluidic flows can be done. With the magnetic field, the effective anchoring of ions is demonstrated but the modulation of the ion flowing directions does not occur. The mechanism of the electro- and magneto-modulated ion trans-membrane transport is investigated, indicating that the electric fields dominate the ion migration process while the magnetic fields tune the structure of nanocapillaries within GO membranes. Results also show that the ion selectivity of GO membranes can be tuned with the electric fields while the transport of ions can be enhanced synchronously with the magnetic fields. These excellent properties make GO membranes promising in areas such as field-induced mass transport control and membrane separation. PMID:25347969

Out-of-equilibrium chiral magnetic effect from chiral kinetic theory

NASA Astrophysics Data System (ADS)

Huang, Anping; Jiang, Yin; Shi, Shuzhe; Liao, Jinfeng; Zhuang, Pengfei

2018-02-01

Recently there has been significant interest in the macroscopic manifestation of chiral anomaly in many-body systems of chiral fermions. A notable example is the Chiral Magnetic Effect (CME). Enthusiastic efforts have been made to search for the CME in the quark-gluon plasma created in heavy ion collisions. A crucial challenge is that the extremely strong magnetic field in such collisions may last only for a brief moment and the CME current may have to occur at so early a stage that the quark-gluon matter is still far from thermal equilibrium. This thus requires modeling of the CME in an out-of-equilibrium setting. With the recently developed theoretical tool of chiral kinetic theory, we make a first phenomenological study of the CME-induced charge separation during the pre-thermal stage in heavy ion collisions. The effect is found to be very sensitive to the time dependence of the magnetic field and also influenced by the initial quark momentum spectrum as well as the relaxation time of the system evolution toward thermal equilibrium. Within the present approach, such pre-thermal charge separation is found to be modest.

Adsorption Site of Gas Molecules on Defective Armchair Graphene Nanoribbon Formed Through Ion Bombardment

NASA Astrophysics Data System (ADS)

Auzar, Zuriana; Johari, Zaharah; Sakina, S. H.; Alias, N. Ezaila

2018-02-01

High sensitivity and selectivity is desired in sensing devices. The aim of this study is to investigate the use of the ion bombardment process in creating a defect on graphene nanoribbons (GNR), which significantly affects sensing properties, in particular adsorption energy, charge transfer and sensitivity. A process has been developed to form the defect on the GNR surface using molecular dynamic (MD) with a reactive force field with nitrogen ion. The sensing properties were calculated using the extended Huckel theory when oxygen (O2) and ammonia (NH3) molecules are exposed to different areas on the defective site. Through simulation, it was found that the ion bombardment process formed various types of defects on the GNR surface. Most notably, molecules adsorbed on the ripple area considerably improve the sensitivity by more than 50%. This indicates that the defect on the armchair graphene nanoribbon (AGNR) surface can be a method to enhance graphene-based sensing performance.

Bunker probe: A plasma potential probe almost insensitive to its orientation with the magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Costea, S., E-mail: stefan.costea@uibk.ac.at; Schneider, B. S.; Schrittwieser, R.

Due to their ability to suppress a large part of the electron current and thus measuring directly the plasma potential, ion sensitive probes have begun to be widely tested and used in fusion devices. For these probes to work, almost perfect alignment with the total magnetic field is necessary. This condition cannot always be fulfilled due to the curvature of magnetic fields, complex magnetic structure, or magnetic field reconnection. In this perspective, we have developed a plasma potential probe (named Bunker probe) based on the principle of the ion sensitive probe but almost insensitive to its orientation with the totalmore » magnetic field. Therefore it can be used to measure the plasma potential inside fusion devices, especially in regions with complex magnetic field topology. Experimental results are presented and compared with Ball-Pen probe measurements taken under identical conditions. We have observed that the floating potential of the Bunker probe is indeed little affected by its orientation with the magnetic field for angles ranging from 90° to 30°, in contrast to the Ball-Pen probe whose floating potential decreases towards that of a Langmuir probe if not properly aligned with the magnetic field.« less

Aspect sensitive E- and F-region SPEAR-enhanced incoherent backscatter observed by the EISCAT Svalbard radar

NASA Astrophysics Data System (ADS)

Dhillon, R. S.; Robinson, T. R.; Yeoman, T. K.

2009-01-01

Previous studies of the aspect sensitivity of heater-enhanced incoherent radar backscatter in the high-latitude ionosphere have demonstrated the directional dependence of incoherent scatter signatures corresponding to artificially excited electrostatic waves, together with consistent field-aligned signatures that may be related to the presence of artificial field-aligned irregularities. These earlier high-latitude results have provided motivation for repeating the investigation in the different geophysical conditions that obtain in the polar cap ionosphere. The Space Plasma Exploration by Active Radar (SPEAR) facility is located within the polar cap and has provided observations of RF-enhanced ion and plasma line spectra recorded by the EISCAT Svalbard UHF incoherent scatter radar system (ESR), which is collocated with SPEAR. In this paper, we present observations of aspect sensitive E- and F-region SPEAR-induced ion and plasma line enhancements that indicate excitation of both the purely growing mode and the parametric decay instability, together with sporadic E-layer results that may indicate the presence of cavitons. We note consistent enhancements from field-aligned, vertical and also from 5° south of field-aligned. We attribute the prevalence of vertical scatter to the importance of the Spitze region, and of that from field-aligned to possible wave/irregularity coupling.

Exploring drivers of sodium salt toxicity to the mayfly Neocloeon triangulifer, and comparing trends in mayfly and daphnid responses to major ions

EPA Science Inventory

Field studies have shown that mayflies (Ephemeroptera) tend to be more sensitive than other benthic macroinvertebrates to elevated levels of total dissolved solids in streams. While work with other species has shown that major ion toxicity is dependent on the ionic composition o...

Induced-Charge Enhancement of the Diffusion Potential in Membranes with Polarizable Nanopores

NASA Astrophysics Data System (ADS)

Ryzhkov, I. I.; Lebedev, D. V.; Solodovnichenko, V. S.; Shiverskiy, A. V.; Simunin, M. M.

2017-12-01

When a charged membrane separates two salt solutions of different concentrations, a potential difference appears due to interfacial Donnan equilibrium and the diffusion junction. Here, we report a new mechanism for the generation of a membrane potential in polarizable conductive membranes via an induced surface charge. It results from an electric field generated by the diffusion of ions with different mobilities. For uncharged membranes, this effect strongly enhances the diffusion potential and makes it highly sensitive to the ion mobilities ratio, electrolyte concentration, and pore size. Theoretical predictions on the basis of the space-charge model extended to polarizable nanopores fully agree with experimental measurements in KCl and NaCl aqueous solutions.

Systematic measurements of ion-proton differential streaming in the solar wind.

PubMed

Berger, L; Wimmer-Schweingruber, R F; Gloeckler, G

2011-04-15

The small amount of heavy ions in the highly rarefied solar wind are sensitive tracers for plasma-physics processes, which are usually not accessible in the laboratory. We have analyzed differential streaming between heavy ions and protons in the solar wind at 1 AU. 3D velocity vector and magnetic field measurements from the Solar Wind Electron Proton Alpha Monitor and the Magnetometer aboard the Advanced Composition Explorer were used to reconstruct the ion-proton difference vector v(ip) = v(i) - v(p) from the 12 min 1D Solar Wind Ion Composition Spectrometer observations. We find that all 44 analyzed heavy ions flow along the interplanetary magnetic field at velocities which are smaller than, but comparable to, the local Alfvén speed C(A). The flow speeds of 35 of the 44 ion species lie within the range of ±0.15C(A) around 0.55C(A), the flow speed of He(2+).

Influence of Chloride Ion and Temperature on the Corrosion Behavior of Ni-Fe-Cr Alloy 028

NASA Astrophysics Data System (ADS)

Zhang, L. N.; Dong, J. X.; Szpunar, J. A.; Zhang, M. C.; Basu, R.

Recently, the working condition of tubing systems used in oil and natural gas industries are severer than before with the increasing exploitation of acidic gas fields. The corrosion problems induced from the corrosive environment with chloride ion medium and high temperature have been much more concerned. The presence of chloride ion can accelerate the dissolution of metals. The corrosion performance is also sensitive to the operating temperature. Classic localized corrosions such as the pitting or the crevice type due to environmental temperature and chloride ion.

Roles of ion transport in control of cell motility.

PubMed

Stock, Christian; Ludwig, Florian T; Hanley, Peter J; Schwab, Albrecht

2013-01-01

Cell motility is an essential feature of life. It is essential for reproduction, propagation, embryonic development, and healing processes such as wound closure and a successful immune defense. If out of control, cell motility can become life-threatening as, for example, in metastasis or autoimmune diseases. Regardless of whether ciliary/flagellar or amoeboid movement, controlled motility always requires a concerted action of ion channels and transporters, cytoskeletal elements, and signaling cascades. Ion transport across the plasma membrane contributes to cell motility by affecting the membrane potential and voltage-sensitive ion channels, by inducing local volume changes with the help of aquaporins and by modulating cytosolic Ca(2+) and H(+) concentrations. Voltage-sensitive ion channels serve as voltage detectors in electric fields thus enabling galvanotaxis; local swelling facilitates the outgrowth of protrusions at the leading edge while local shrinkage accompanies the retraction of the cell rear; the cytosolic Ca(2+) concentration exerts its main effect on cytoskeletal dynamics via motor proteins such as myosin or dynein; and both, the intracellular and the extracellular H(+) concentration modulate cell migration and adhesion by tuning the activity of enzymes and signaling molecules in the cytosol as well as the activation state of adhesion molecules at the cell surface. In addition to the actual process of ion transport, both, channels and transporters contribute to cell migration by being part of focal adhesion complexes and/or physically interacting with components of the cytoskeleton. The present article provides an overview of how the numerous ion-transport mechanisms contribute to the various modes of cell motility.

Ion implantation reduces radiation sensitivity of metal oxide silicon /MOS/ devices

NASA Technical Reports Server (NTRS)

1971-01-01

Implanting nitrogen ions improves hardening of silicon oxides 30 percent to 60 percent against ionizing radiation effects. Process reduces sensitivity, but retains stability normally shown by interfaces between silicon and thermally grown oxides.

High sensitive detection of copper II ions using D-penicillamine-coated gold nanorods based on localized surface plasmon resonance.

PubMed

Hong, Yoochan; Jo, Seongjae; Park, Joohyung; Park, Jinsung; Yang, Jaemoon

2018-05-25

In this paper, we describe the development of a nanoplasmonic biosensor based on the localized surface plasmon resonance (LSPR) effect that enables a sensitive and selective recognition of copper II ions. First, we fabricated the nanoplasmonics as LSPR substrates using gold nanorods (GNR) and the nano-adsorption method. The LSPR sensitivity of the nanoplasmonics was evaluated using various solvents with different refractive indexes. Subsequently, D-penicillamine (DPA)-a chelating agent of copper II ions-was conjugated to the surface of the GNR. The limit of detection (LOD) for the DPA-conjugated nanoplasmonics was 100 pM. Furthermore, selectivity tests were conducted using various divalent cations, and sensitivity tests were conducted on the nanoplasmonics under blood-like environments. Finally, the developed nanoplasmonic biosensor based on GNR shows great potential for the effective recognition of copper II ions, even in human blood conditions.

Human dopamine receptor nanovesicles for gate-potential modulators in high-performance field-effect transistor biosensors

NASA Astrophysics Data System (ADS)

Park, Seon Joo; Song, Hyun Seok; Kwon, Oh Seok; Chung, Ji Hyun; Lee, Seung Hwan; An, Ji Hyun; Ahn, Sae Ryun; Lee, Ji Eun; Yoon, Hyeonseok; Park, Tai Hyun; Jang, Jyongsik

2014-03-01

The development of molecular detection that allows rapid responses with high sensitivity and selectivity remains challenging. Herein, we demonstrate the strategy of novel bio-nanotechnology to successfully fabricate high-performance dopamine (DA) biosensor using DA Receptor-containing uniform-particle-shaped Nanovesicles-immobilized Carboxylated poly(3,4-ethylenedioxythiophene) (CPEDOT) NTs (DRNCNs). DA molecules are commonly associated with serious diseases, such as Parkinson's and Alzheimer's diseases. For the first time, nanovesicles containing a human DA receptor D1 (hDRD1) were successfully constructed from HEK-293 cells, stably expressing hDRD1. The nanovesicles containing hDRD1 as gate-potential modulator on the conducting polymer (CP) nanomaterial transistors provided high-performance responses to DA molecule owing to their uniform, monodispersive morphologies and outstanding discrimination ability. Specifically, the DRNCNs were integrated into a liquid-ion gated field-effect transistor (FET) system via immobilization and attachment processes, leading to high sensitivity and excellent selectivity toward DA in liquid state. Unprecedentedly, the minimum detectable level (MDL) from the field-induced DA responses was as low as 10 pM in real- time, which is 10 times more sensitive than that of previously reported CP based-DA biosensors. Moreover, the FET-type DRNCN biosensor had a rapid response time (<1 s) and showed excellent selectivity in human serum.

Effect of tapered magnetic field on expanding laser-produced plasma for heavy-ion inertial fusion

DOE PAGES

Kanesue, Takeshi; Ikeda, Shunsuke

2016-12-20

A laser ion source is a promising candidate as an ion source for heavy ion inertial fusion (HIF), where a pulsed ultra-intense and low-charged heavy ion beam is required. It is a key development for a laser ion source to transport laser-produced plasma with a magnetic field to achieve a high current beam. The effect of a tapered magnetic field on laser produced plasma is demonstrated by comparing the results with a straight solenoid magnet. The magnetic field of interest is a wider aperture on a target side and narrower aperture on an extraction side. Furthermore, based on the experimentallymore » obtained results, the performance of a scaled laser ion source for HIF was estimated.« less

A CMOS-Compatible, Low-Noise ISFET Based on High Efficiency Ion-Modulated Lateral-Bipolar Conduction

PubMed Central

Chang, Sheng-Ren; Chen, Hsin

2009-01-01

Ion-sensitive, field-effect transistors (ISFET) have been useful biosensors in many applications. However, the signal-to-noise ratio of the ISFET is limited by its intrinsic, low-frequency noise. This paper presents an ISFET capable of utilizing lateral-bipolar conduction to reduce low-frequency noise. With a particular layout design, the conduction efficiency is further enhanced. Moreover, the ISFET is compatible with the standard CMOS technology. All materials above the gate-oxide are removed by simple, die-level post-CMOS process, allowing ions to modulate the lateral-bipolar current directly. By varying the gate-to-bulk voltage, the operation mode of the ISFET is controlled effectively, so is the noise performance measured and compared. Finally, the biasing conditions preferable for different low-noise applications are identified. Under the identified biasing condition, the signal-to-noise ratio of the ISFET as a pH sensor is proved to be improved by more than five times. PMID:22408508

Development of a transcutaneous blood-constituent monitoring method using a suction effusion fluid collection technique and an ion-sensitive field-effect transistor glucose sensor.

PubMed

Ito, N; Kayashima, S; Kimura, J; Kuriyama, T; Arai, T; Kikuchi, M; Nagata, N

1994-05-01

The paper describes a method for the transcutaneous monitoring of blood constituents. It combines the use of a suction effusion fluid (SEF) collecting technique with a silicon on sapphire/ion-sensitive field-effect transistor (SOS/ISFET) biosensor. SEF is directly collected by a weak evacuation through skin from which the stratum corneum has been removed. An SEF collecting cell with a stainless-steel mesh at the bottom is kept in a weak vacuum condition, and SEF is sucked up through the mesh and deposited in a reservoir above. An ISFET glucose sensor is able to detect glucose concentrations in very small SEF samples through the use of two small ISFETs and an immobilised enzyme membrane. The reliability of transcutaneously obtained SEF was first confirmed in an experiment using rabbits. A clinical analyser was used to determine levels of glucose, urea nitrogen and creatinine in SEF obtained transcutaneously; these results are compared with results obtained by the same analyser directly from sera. The ISFET glucose sensor was successfully tested on human subjects for the monitoring of blood glucose levels. During these tests, glucose level changes in the SEF followed actual blood glucose level changes with a slight time delay. Results suggest the feasibility of non-invasive, transcutaneous monitoring of low molecular weight substances in the blood without the use of ordinary blood sampling.

Influence of asymmetries in the magnetic draping pattern at Titan on the emission of energetic neutral atoms

NASA Astrophysics Data System (ADS)

Kabanovic, Slawa; Feyerabend, Moritz; Simon, Sven; Meeks, Zachary; Wulms, Veit

2018-03-01

We model the emission of energetic neutral atoms (ENAs) that are generated by the interaction between energetic ions from Saturn's magnetosphere and neutrals from the upper atmosphere of the giant planet's largest moon Titan. The trajectories of the parent ions and the resulting ENA emission morphology are highly sensitive to the electromagnetic field configuration near the moon. We therefore compare the ENA emission pattern for spatially homogeneous fields to the emission obtained from a magnetohydrodynamic (MHD) and a hybrid (kinetic ions, fluid electrons) model of Titan's magnetospheric interaction, by computing the trajectories of several billion energetic test particles. While the MHD model takes into account the draping of the magnetic field lines around Titan, the hybrid approach also considers the significant asymmetries in the electromagnetic fields due to the large gyroradii of pick-up ions from Titan's ionosphere. In all three models, the upstream parameters correspond to the conditions during Cassini's TA flyby of Titan. The shape, magnitude, and location of the ENA emission maxima vary considerably between these three field configurations. The magnetic pile-up region at Titan's ramside deflects a large number of the energetic parent ions, thereby reducing the ENA flux. However, the draped magnetic field lines in Titan's lobes rotate the gyration planes of the incident energetic ions, thereby facilitating the observable ENA production. Overall, the ENA flux calculated for the MHD model is weaker than the emission obtained for the electromagnetic fields from the hybrid code. In addition, we systematically investigate the dependency of the ENA emission morphology on the energy of the parent ions and on the upstream magnetic field strength.

Cooling and heating of the quantum motion of trapped cadmium(+) ions

NASA Astrophysics Data System (ADS)

Deslauriers, Louis

The quest for a quantum system best satisfying the stringent requirements of a quantum information processor has made tremendous progress in many fields of physics. In the last decade, trapped ions have been established as one of the most promising architectures to accomplish the task. Internal states of an ion which can have extremely long coherence time can be used to store a quantum bit, and therefore allow many gate operations before the coherence is lost. Entanglement between multiple ions can be established via Coulomb interactions mediated by appropriate laser fields. Entangling schemes usually require the ions to be initialized to near their motional ground state. The interaction of fluctuating electric fields with the motional state of the ion leads to heating and thus to decoherence for entanglement generation limiting the fidelity of quantum logic gates. Effective ground state cooling of trapped ion motion and suppression of motional heating are thus crucial to many applications of trapped ions in quantum information science. In this thesis, I describe the implementation and study of several components of a Cadmium-ion-based quantum information processor, with special emphasis on the control and decoherence of trapped ion motion. I first discuss the building and design of various ion traps that were used in this work. I also report on the use of ultrafast laser pulses to photoionize and load cadmium ions in a variety of rf Paul trap geometries. A detailed analysis of the photoionization scheme is presented, along with its dependence on controlled experimental parameters. I then describe the implementation of Raman sideband cooling on a single trapped 111Cd+ ion to the ground state of motion, where a ground state population of 97% was achieved. The efficacy of this cooling technique is discussed with respect to different initial motional state distributions and its sensitivity to the presence of motional heating. I also present an experiment where the motion of a single trapped 112Cd+ ion is sympathetically cooled by directly Doppler cooling a 114Cd+ ion in the same trap. The implications of this result are relevant to the scaling of a trapped ion quantum computer, where the unwanted motion of an ion crystal can be quenched while not affecting the internal states of the qubit ions. (Abstract shortened by UMI.)

Evaluation of Kodak EDR2 film for dose verification of intensity modulated radiation therapy delivered by a static multileaf collimator.

PubMed

Zhu, X R; Jursinic, P A; Grimm, D F; Lopez, F; Rownd, J J; Gillin, M T

2002-08-01

A new type of radiographic film, Kodak EDR2 film, was evaluated for dose verification of intensity modulated radiation therapy (IMRT) delivered by a static multileaf collimator (SMLC). A sensitometric curve of EDR2 film irradiated by a 6 MV x-ray beam was compared with that of Kodak X-OMAT V (XV) film. The effects of field size, depth and dose rate on the sensitometric curve were also studied. It is found that EDR2 film is much less sensitive than XV film. In high-energy x-ray beams, the double hit process is the dominant mechanism that renders the grains on EDR2 films developable. As a result, in the dose range that is commonly used for film dosimetry for IMRT and conventional external beam therapy, the sensitometric curves of EDR2 films cannot be approximated as a linear function, OD = c * D. Within experimental uncertainty, the film sensitivity does not depend on the dose rate (50 vs 300 MU/min) or dose per pulse (from 1.0 x 10(-4) to 4.21 x 10(-4) Gy/pulse). Field sizes and depths (up to field size of 10 x 10 cm2 and depth = 10 cm) have little effect on the sensitometric curves. Percent depth doses (PDDs) for both 6 and 23 MV x rays were measured with both EDR2 and XV films and compared with ion chamber data. Film data are within 2.5% of the ion chamber results. Dose profiles measured with EDR2 film are consistent with those measured with an ion chamber. Examples of measured IMRT isodose distributions versus calculated isodoses are presented. We have used EDR2 films for verification of all IMRT patients treated by SMLC in our clinic. In most cases, with EDR2 film, actual clinical daily fraction doses can be used for verification of composite isodose distributions of SMLC-based IMRT.

Polarization: A Key Difference between Man-made and Natural Electromagnetic Fields, in regard to Biological Activity.

PubMed

Panagopoulos, Dimitris J; Johansson, Olle; Carlo, George L

2015-10-12

In the present study we analyze the role of polarization in the biological activity of Electromagnetic Fields (EMFs)/Electromagnetic Radiation (EMR). All types of man-made EMFs/EMR - in contrast to natural EMFs/EMR - are polarized. Polarized EMFs/EMR can have increased biological activity, due to: 1) Ability to produce constructive interference effects and amplify their intensities at many locations. 2) Ability to force all charged/polar molecules and especially free ions within and around all living cells to oscillate on parallel planes and in phase with the applied polarized field. Such ionic forced-oscillations exert additive electrostatic forces on the sensors of cell membrane electro-sensitive ion channels, resulting in their irregular gating and consequent disruption of the cell's electrochemical balance. These features render man-made EMFs/EMR more bioactive than natural non-ionizing EMFs/EMR. This explains the increasing number of biological effects discovered during the past few decades to be induced by man-made EMFs, in contrast to natural EMFs in the terrestrial environment which have always been present throughout evolution, although human exposure to the latter ones is normally of significantly higher intensities/energy and longer durations. Thus, polarization seems to be a trigger that significantly increases the probability for the initiation of biological/health effects.

Polarization: A Key Difference between Man-made and Natural Electromagnetic Fields, in regard to Biological Activity

PubMed Central

Panagopoulos, Dimitris J.; Johansson, Olle; Carlo, George L.

2015-01-01

In the present study we analyze the role of polarization in the biological activity of Electromagnetic Fields (EMFs)/Electromagnetic Radiation (EMR). All types of man-made EMFs/EMR - in contrast to natural EMFs/EMR - are polarized. Polarized EMFs/EMR can have increased biological activity, due to: 1) Ability to produce constructive interference effects and amplify their intensities at many locations. 2) Ability to force all charged/polar molecules and especially free ions within and around all living cells to oscillate on parallel planes and in phase with the applied polarized field. Such ionic forced-oscillations exert additive electrostatic forces on the sensors of cell membrane electro-sensitive ion channels, resulting in their irregular gating and consequent disruption of the cell’s electrochemical balance. These features render man-made EMFs/EMR more bioactive than natural non-ionizing EMFs/EMR. This explains the increasing number of biological effects discovered during the past few decades to be induced by man-made EMFs, in contrast to natural EMFs in the terrestrial environment which have always been present throughout evolution, although human exposure to the latter ones is normally of significantly higher intensities/energy and longer durations. Thus, polarization seems to be a trigger that significantly increases the probability for the initiation of biological/health effects. PMID:26456585

Polarization: A Key Difference between Man-made and Natural Electromagnetic Fields, in regard to Biological Activity

NASA Astrophysics Data System (ADS)

Panagopoulos, Dimitris J.; Johansson, Olle; Carlo, George L.

2015-10-01

In the present study we analyze the role of polarization in the biological activity of Electromagnetic Fields (EMFs)/Electromagnetic Radiation (EMR). All types of man-made EMFs/EMR - in contrast to natural EMFs/EMR - are polarized. Polarized EMFs/EMR can have increased biological activity, due to: 1) Ability to produce constructive interference effects and amplify their intensities at many locations. 2) Ability to force all charged/polar molecules and especially free ions within and around all living cells to oscillate on parallel planes and in phase with the applied polarized field. Such ionic forced-oscillations exert additive electrostatic forces on the sensors of cell membrane electro-sensitive ion channels, resulting in their irregular gating and consequent disruption of the cell’s electrochemical balance. These features render man-made EMFs/EMR more bioactive than natural non-ionizing EMFs/EMR. This explains the increasing number of biological effects discovered during the past few decades to be induced by man-made EMFs, in contrast to natural EMFs in the terrestrial environment which have always been present throughout evolution, although human exposure to the latter ones is normally of significantly higher intensities/energy and longer durations. Thus, polarization seems to be a trigger that significantly increases the probability for the initiation of biological/health effects.

Evaluation of ion-implanted-silicon detectors for use in intraoperative positron-sensitive probes.

PubMed

Raylman, R R; Wahl, R L

1996-11-01

The continuing development of probes for use with beta (positron and electron) emitting radionuclides may result in more complete excision of tracer-avid tumors. Perhaps one of the most promising radiopharmaceuticals for this task is 18F-labeled-Fluoro-2-Deoxy-D-Glucose (FDG). This positron-emitting agent has been demonstrated to be avidly and rapidly absorbed by many human cancers. We have investigated the use of ion-implanted-silicon detectors in intraoperative positron-sensitive surgical probes for use with FDG. These detectors possess very high positron detection efficiency, while the efficiency for 511 keV photon detection is low. The spatial resolution, as well as positron and annihilation photon detection sensitivity, of an ion-implanted-silicon detector used with 18F was measured at several energy thresholds. In addition, the ability of the device to detect the presence of relatively small amounts of FDG during surgery was evaluated by simulating a surgical field in which some tumor was left intact following lesion excision. The performance of the ion-implanted-silicon detector was compared to the operating characteristics of a positron-sensitive surgical probe which utilizes plastic scintillator. In all areas of performance the ion-implanted-silicon detector proved superior to the plastic scintillator-based probe. At an energy threshold of 14 keV positron sensitivity measured for the ion-implanted-silicon detector was 101.3 cps/kBq, photon sensitivity was 7.4 cps/kBq. In addition, spatial resolution was found to be relatively unaffected by the presence of distant sources of annihilation photon flux. Finally, the detector was demonstrated to be able to localize small amounts of FDG in a simulated tumor bed; indicating that this device has promise as a probe to aid in FDG-guided surgery.

Charged Particle Detection: Potential of Love Wave Acoustic Devices

NASA Astrophysics Data System (ADS)

Pedrick, Michael; Tittmann, Bernhard

2006-03-01

An investigation of the dependence of film density on group and phase velocities in a Love Wave Device shows potential for acoustic-based charged particle detection (CPD). Exposure of an ion sensitive photoresist to charged particles causes localized changes in density through either scission or cross-linking. A theoretical model was developed to study ion fluence effects on Love Wave sensitivity based on: ion energy, effective density changes, layer thickness and mode selection. The model is based on a Poly(Methyl Methacralate) (PMMA) film deposited on a Quartz substrate. The effect of Helium ion fluence on the properties of PMMA has previously been studied. These guidelines were used as an initial basis for the prediction of helium ion detection in a PMMA layer. Procedures for experimental characterization of ion effects on the material properties of PMMA are reviewed. Techniques for experimental validation of the predicted velocity shifts are discussed. A Love Wave Device for CPD could potentially provide a cost-effective alternative to semiconductor or photo-based counterparts. The potential for monitoring ion implantation effects on material properties is also discussed.

Device for two-dimensional gas-phase separation and characterization of ion mixtures

DOEpatents

Tang, Keqi [Richland, WA; Shvartsburg, Alexandre A [Richland, WA; Smith, Richard D [Richland, WA

2006-12-12

The present invention relates to a device for separation and characterization of gas-phase ions. The device incorporates an ion source, a field asymmetric waveform ion mobility spectrometry (FAIMS) analyzer, an ion mobility spectrometry (IMS) drift tube, and an ion detector. In one aspect of the invention, FAIMS operating voltages are electrically floated on top of the IMS drift voltage. In the other aspect, the FAIMS/IMS interface is implemented employing an electrodynamic ion funnel, including in particular an hourglass ion funnel. The present invention improves the efficiency (peak capacity) and sensitivity of gas-phase separations; the online FAIMS/IMS coupling creates a fundamentally novel two-dimensional gas-phase separation technology with high peak capacity, specificity, and exceptional throughput.

Super-Nernstian pH sensors based on WO3 nanosheets

NASA Astrophysics Data System (ADS)

Kuo, Chao-Yin; Wang, Shui-Jinn; Ko, Rong-Ming; Tseng, Hung-Hao

2018-04-01

The effects of the surface morphology of hydrothermally grown WO3 nanosheets (NSs) and sputtering WO3 film on the performance of pH sensing electrodes are presented and compared in the pH range of 2–12. Using a separated electrode of an extended-gate field-effect transistor (EGFET) configuration, the WO3 nanosheet (NS) pH sensor shows a sensitivity of 63.37 mV/pH, a good linearity of 0.9973, a low voltage hysteresis of 4.79 mV, and a low drift rate of 3.18 mV/h. In contrast, the film-type one shows a typical sensitivity of only 50.08 mV/pH and a linearity of 0.9932. The super-Nernstian response could be attributed to the significant increase in the number of surface ion adsorption sites of the NS structure and the occurrence of local electric field enhancement over the sharp edges and corners of WO3 NSs.

Analyte concentration at the tip of a nanopipette.

PubMed

Calander, Nils

2009-10-15

Concentration of molecules within the tips of nanopipettes when applying a DC voltage is herein investigated using finite-element simulations. The ion concentrations and fluxes due to diffusion, electro-migration, and electro-osmotic flow, and the electric potential are determined by the simultaneous solution of the Nernst-Planck, Poisson, and Navier-Stokes equations within the water solution containing sodium and chloride ions and negatively charged molecules. The electric potential within the pipette glass wall is at the same time determined by the Poisson equation together with appropriate boundary conditions and accounts for a field effect through the wall. Fixed negative surface charge on both the internal and external glass surfaces of the nanopipette is included together with the field effect through the glass wall to account for the electric double layer and the electro-osmosis. The inclusion of the field effect through the pipette wall is new compared to previous modeling of similar structures and is shown to be crucial for the behavior at the tip. It is demonstrated that the concentration of molecules is a consequence of ionic charge accumulation at the tip screening the electric field, thereby slowing down the electrophoretic motion of the molecules, which is further slowed down or stopped by the oppositely directed electro-osmosis. It is also shown that the trapping is very sensitive to the properties of the molecule, that is, its electrophoretic mobility and diffusion coefficient, the properties of the pipette, the ionic strength of the solution, and the applied electric field.

Electromagnetic fields (UHF) increase voltage sensitivity of membrane ion channels; possible indication of cell phone effect on living cells.

PubMed

Ketabi, N; Mobasheri, H; Faraji-Dana, R

2015-03-01

The effects of ultra high frequency (UHF) nonionizing electromagnetic fields (EMF) on the channel activities of nanopore forming protein, OmpF porin, were investigated. The voltage clamp technique was used to study the single channel activity of the pore in an artificial bilayer in the presence and absence of the electromagnetic fields at 910 to 990 MHz in real time. Channel activity patterns were used to address the effect of EMF on the dynamic, arrangement and dielectric properties of water molecules, as well as on the hydration state and arrangements of side chains lining the channel barrel. Based on the varied voltage sensitivity of the channel at different temperatures in the presence and absence of EMF, the amount of energy transferred to nano-environments of accessible groups was estimated to address the possible thermal effects of EMF. Our results show that the effects of EMF on channel activities are frequency dependent, with a maximum effect at 930 MHz. The frequency of channel gating and the voltage sensitivity is increased when the channel is exposed to EMF, while its conductance remains unchanged at all frequencies applied. We have not identified any changes in the capacitance and permeability of membrane in the presence of EMF. The effect of the EMF irradiated by cell phones is measured by Specific Absorption Rate (SAR) in artificial model of human head, Phantom. Thus, current approach applied to biological molecules and electrolytes might be considered as complement to evaluate safety of irradiating sources on biological matter at molecular level.

Self-Assembled Films of Dendrimers and Metallophthalocyanines as FET-Based Glucose Biosensors

PubMed Central

Vieira, Nirton C.S.; Figueiredo, Alessandra; de Queiroz, Alvaro A.A.; Zucolotto, Valtencir; Guimarães, Francisco E.G.

2011-01-01

Separative extended gate field effect transistor (SEGFET) type devices have been used as an ion sensor or biosensor as an alternative to traditional ion sensitive field effect transistors (ISFETs) due to their robustness, ease of fabrication, low cost and possibility of FET isolation from the chemical environment. The layer-by-layer technique allows the combination of different materials with suitable properties for enzyme immobilization on simple platforms such as the extended gate of SEGFET devices enabling the fabrication of biosensors. Here, glucose biosensors based on dendrimers and metallophthalocyanines (MPcs) in the form of layer-by-layer (LbL) films, assembled on indium tin oxide (ITO) as separative extended gate material, has been produced. NH3+ groups in the dendrimer allow electrostatic interactions or covalent bonds with the enzyme (glucose oxidase). Relevant parameters such as optimum pH, buffer concentration and presence of serum bovine albumin (BSA) in the immobilization process were analyzed. The relationship between the output voltage and glucose concentration shows that upon detection of a specific analyte, the sub-products of the enzymatic reaction change the pH locally, affecting the output signal of the FET transducer. In addition, dendritic layers offer a nanoporous environment, which may be permeable to H+ ions, improving the sensibility as modified electrodes for glucose biosensing. PMID:22163704

Control of Chemical Effects in the Separation Process of a Differential Mobility / Mass Spectrometer System

PubMed Central

Schneider, Bradley B.; Coy, Stephen L.; Krylov, Evgeny V.; Nazarov, Erkinjon G.

2013-01-01

Differential mobility spectrometry (DMS) separates ions on the basis of the difference in their migration rates under high versus low electric fields. Several models describing the physical nature of this field mobility dependence have been proposed but emerging as a dominant effect is the clusterization model sometimes referred to as the dynamic cluster-decluster model. DMS resolution and peak capacity is strongly influenced by the addition of modifiers which results in the formation and dissociation of clusters. This process increases selectivity due to the unique chemical interactions that occur between an ion and neutral gas phase molecules. It is thus imperative to bring the parameters influencing the chemical interactions under control and find ways to exploit them in order to improve the analytical utility of the device. In this paper we describe three important areas that need consideration in order to stabilize and capitalize on the chemical processes that dominate a DMS separation. The first involves means of controlling the dynamic equilibrium of the clustering reactions with high concentrations of specific reagents. The second area involves a means to deal with the unwanted heterogeneous cluster ion populations emitted from the electrospray ionization process that degrade resolution and sensitivity. The third involves fine control of parameters that affect the fundamental collision processes, temperature and pressure. PMID:20065515

Electrokinetic supercharging with a system-induced terminator and an optimized capillary versus electrode configuration for parts-per-trillion detection of rare-earth elements in CZE.

PubMed

Xu, Zhongqi; Kawahito, Kouji; Ye, Xiaoxue; Timerbaev, Andrei R; Hirokawa, Takeshi

2011-05-01

A further improvement of electrokinetic supercharging (EKS) methodology has been proposed, with the objective to enhance the sensitivity of the conventional CZE-UV method down to a single-digit part per trillion (ppt) level. The advanced EKS procedure is based on a novel phenomenon displaying the formation of a zone with an increased concentration of the hydrogen ion, capable to perform the function of a terminator, behind the sample zone upon electrokinetic injection. In combination with a visualizing co-ion of BGE, protonated 4-methylbenzylamine, acting as the leading ion, such system-induced terminator a effected the transient ITP state to efficiently concentrate cationic analytes prior to CZE. Furthermore, to amass more analyte ions within the effective electric field at the injection stage, a standard sample vial was replaced with an elongated vial that allowed the sample volume to be increased from 500 to 900 μL. Alongside, this replacement made the upright distance between the electrode and the capillary tips prolonged to 40.0 mm to achieve high-efficiency electrokinetic injection. The computer simulation was used for profiling analyte concentration, pH, and field strength in order to delineate formation of the terminator during sample injection. The proposed preconcentration strategy afforded an enrichment factor of 80,000 and thereby the LODs of rare-earth metal ions at the ppt level, e.g. 0.04 nM (6.7 ng/L) for erbium(III). Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Making Shock Waves in Microfluidics: The Physics and Applications of Isotachophoresis

NASA Astrophysics Data System (ADS)

Santiago, Juan

2007-11-01

Microfluidics lies at the interfaces between engineering, chemistry, and biology, and aims to develop chemical laboratories on a chip. An important technique is on-chip capillary electrophoresis which has been applied to a wide range of chemical and biochemical assay applications over the last decade. Perhaps the best way of improving the sensitivity of on-chip electrophoresis is to integrate an online sample preconcentration method. At Stanford, we are developing methods to concentrate ions into small volumes using a method called isotachophoresis (ITP). In ITP, sample ions are injected between the high mobility co-ions of a leading electrolyte (LE) and the low mobility co-ions of a trailing electrolyte (TE). Upon application of an electric field, the disparate ion mobilities of the LE and TE cause sample species to segregate and focus into a series of narrow self-sharpening zones which migrate at equal velocity (hence ``isotacho''). ITP-type processes have been studied and used for more than 60 years, and yet there remain significant challenges in the robust modeling of these transport processes and the creation of widely applicable assays. We use ITP to create sample ion concentration ``shock waves'' in microchannels. These concentration waves can be integrated with on-chip electrophoresis for high sensitivity assays, and novel modes of operation. The talk will summarize the basic physics of ITP, experimental studies of ITP, models of ITP, and the development of novel ITP-assays with unprecedented sensitivity and new functionality. For example, using leading-to-sample ion concentration ratios of 10^15 and local electric fields of ˜4 kV/cm, we can achieve order one micron wide ITP zones. We can achieve million fold preconcentration in 120 s and can detect 100 attomolar sample concentrations (to our knowledge the highest demonstrated sensitivity for an electrophoresis-related assay). We have also developed a method that uses ITP to separate, indirectly detect, and identify the electrophoretic mobilities of unlabeled (non-fluorescent) analytes using surrogate fluorescent molecules. Our goal is the development of novel on-chip ITP assays which expand the design space of microfluidic devices.

Scanning retarding field analyzer for plasma profile measurements in the boundary of the Alcator C-Mod tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brunner, D.; LaBombard, B.; Ochoukov, R.

2013-03-15

A new Retarding Field Analyzer (RFA) head has been created for the outer-midplane scanning probe system on the Alcator C-Mod tokamak. The new probe head contains back-to-back retarding field analyzers aligned with the local magnetic field. One faces 'upstream' into the field-aligned plasma flow and the other faces 'downstream' away from the flow. The RFA was created primarily to benchmark ion temperature measurements of an ion sensitive probe; it may also be used to interrogate electrons. However, its construction is robust enough to be used to measure ion and electron temperatures up to the last-closed flux surface in C-Mod. Amore » RFA probe of identical design has been attached to the side of a limiter to explore direct changes to the boundary plasma due to lower hybrid heating and current drive. Design of the high heat flux (>100 MW/m{sup 2}) handling probe and initial results are presented.« less

Advance in multi-hit detection and quantization in atom probe tomography.

PubMed

Da Costa, G; Wang, H; Duguay, S; Bostel, A; Blavette, D; Deconihout, B

2012-12-01

The preferential retention of high evaporation field chemical species at the sample surface in atom-probe tomography (e.g., boron in silicon or in metallic alloys) leads to correlated field evaporation and pronounced pile-up effects on the detector. The latter severely affects the reliability of concentration measurements of current 3D atom probes leading to an under-estimation of the concentrations of the high-field species. The multi-hit capabilities of the position-sensitive time-resolved detector is shown to play a key role. An innovative method based on Fourier space signal processing of signals supplied by an advance delay-line position-sensitive detector is shown to drastically improve the time resolving power of the detector and consequently its capability to detect multiple events. Results show that up to 30 ions on the same evaporation pulse can be detected and properly positioned. The major impact of this new method on the quantization of chemical composition in materials, particularly in highly-doped Si(B) samples is highlighted.

Dynamic behaviour of the silica-water-bio electrical double layer in the presence of a divalent electrolyte.

PubMed

Lowe, B M; Maekawa, Y; Shibuta, Y; Sakata, T; Skylaris, C-K; Green, N G

2017-01-25

Electronic devices are becoming increasingly used in chemical- and bio-sensing applications and therefore understanding the silica-electrolyte interface at the atomic scale is becoming increasingly important. For example, field-effect biosensors (BioFETs) operate by measuring perturbations in the electric field produced by the electrical double layer due to biomolecules binding on the surface. In this paper, explicit-solvent atomistic calculations of this electric field are presented and the structure and dynamics of the interface are investigated in different ionic strengths using molecular dynamics simulations. Novel results from simulation of the addition of DNA molecules and divalent ions are also presented, the latter of particular importance in both physiological solutions and biosensing experiments. The simulations demonstrated evidence of charge inversion, which is known to occur experimentally for divalent electrolyte systems. A strong interaction between ions and DNA phosphate groups was demonstrated in mixed electrolyte solutions, which are relevant to experimental observations of device sensitivity in the literature. The bound DNA resulted in local changes to the electric field at the surface; however, the spatial- and temporal-mean electric field showed no significant change. This result is explained by strong screening resulting from a combination of strongly polarised water and a compact layer of counterions around the DNA and silica surface. This work suggests that the saturation of the Stern layer is an important factor in determining BioFET response to increased salt concentration and provides novel insight into the interplay between ions and the EDL.

Comment on "Effects of Magnetic Field Gradient on Ion Beam Current in Cylindrical Hall Ion Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raitses, Y.; Smirnov A.; Fisch, N.J.

It is argued that the key difference of the cylindrical Hall thruster (CHT) as compared to the end-Hall ion source cannot be exclusively attributed to the magnetic field topology [Tang et al. J. Appl. Phys., 102, 123305 (2007)]. With a similar mirror-type topology, the CHT configuration provides the electric field with nearly equipotential magnetic field surfaces and a better suppression of the electron cross-field transport, as compared to both the end-Hall ion source and the cylindrical Hall ion source of Tang et al.

Low temperature annealed amorphous indium gallium zinc oxide (a-IGZO) as a pH sensitive layer for applications in field effect based sensors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Narendra; Samtel Centre for Display Technologies, Indian Institute of Technology Kanpur, Kanpur-208016; Kumar, Jitendra

The use of a-IGZO instead of the conventional high-k dielectrics as a pH sensitive layer could lead to the simplification of fabrication steps of field effect based devices. In this work, the pH sensitivities of a-IGZO films directly deposited over a SiO{sub 2}/Si surface were studied utilizing electrolyte-insulator-semiconductor (EIS) structures. Annealing of the films was found to affect the sensitivity of the devices and the device with the film annealed at 400 {sup o}C in N{sub 2} ambience showed the better sensitivity, which reduced with further increase in the annealing temperature to 500 {sup o}C. The increased pH sensitivity withmore » the film annealed at 400 {sup o}C in N{sub 2} gas was attributed to the enhanced lattice oxygen ions (based on the XPS data) and improved C-V characteristics, while the decrease in sensitivity at an increased annealing temperature of 500 {sup o}C was attributed to defects in the films as well as the induced traps at the IGZO/SiO{sub 2} interface based on the stretched accumulation and the peak in the inversion region of C-V curves. This study could help to develop a sensor where the material (a-IGZO here) used as the active layer in a thin film transistors (TFTs) possibly could also be used as the pH sensitive layer without affecting the TFT characteristics, and thus obviating the need of high-K dielectrics for sensitivity enhancement.« less

Resonant coherent excitation of relativistic Ar 17+ ions channeled in a Si crystal

NASA Astrophysics Data System (ADS)

Azuma, T.; Ito, T.; Yamazaki, Y.; Komaki, K.; Sano, M.; Torikoshi, M.; Kitagawa, A.; Takada, E.; Murakami, T.

1998-02-01

We observed resonant coherent excitation (RCE) of 1s electron to n=2 states in Ar 17+ through measurements of the survived fraction of 390 MeV/u hydrogen-like Ar 17+ channeled in a Si crystal. We adopted a totally depleted Si surface barrier detector as a target crystal as well as a probe of the energy deposition. The charge state of emerged ions was measured by a combination of a charge separation magnet and a 2D-position sensitive detector. We observed the RCE for planar channeled ions by tilting the target Si crystal from the direction of [1 1 0] axis in the (2 2¯ 0) , (0 0 4) , and (1 1¯ 1) planes. Prominent resonances at tilt angles under the resonance condition were observed. Moreover, each resonance profile is split into several lines due to the l· s interaction and the Stark effect originating in the static crystal field. The energy deposition in the crystal gives the information of the amplitude of the ion trajectory. The resonance peak position, intensity and width in the survived fraction of Ar 17+ reflect the position dependent strength of the crystal field, the RCE and the electron loss probabilities. They are in good accord with our calculation of the transition energy and probability.

An integrated semiconductor device enabling non-optical genome sequencing.

PubMed

Rothberg, Jonathan M; Hinz, Wolfgang; Rearick, Todd M; Schultz, Jonathan; Mileski, William; Davey, Mel; Leamon, John H; Johnson, Kim; Milgrew, Mark J; Edwards, Matthew; Hoon, Jeremy; Simons, Jan F; Marran, David; Myers, Jason W; Davidson, John F; Branting, Annika; Nobile, John R; Puc, Bernard P; Light, David; Clark, Travis A; Huber, Martin; Branciforte, Jeffrey T; Stoner, Isaac B; Cawley, Simon E; Lyons, Michael; Fu, Yutao; Homer, Nils; Sedova, Marina; Miao, Xin; Reed, Brian; Sabina, Jeffrey; Feierstein, Erika; Schorn, Michelle; Alanjary, Mohammad; Dimalanta, Eileen; Dressman, Devin; Kasinskas, Rachel; Sokolsky, Tanya; Fidanza, Jacqueline A; Namsaraev, Eugeni; McKernan, Kevin J; Williams, Alan; Roth, G Thomas; Bustillo, James

2011-07-20

The seminal importance of DNA sequencing to the life sciences, biotechnology and medicine has driven the search for more scalable and lower-cost solutions. Here we describe a DNA sequencing technology in which scalable, low-cost semiconductor manufacturing techniques are used to make an integrated circuit able to directly perform non-optical DNA sequencing of genomes. Sequence data are obtained by directly sensing the ions produced by template-directed DNA polymerase synthesis using all-natural nucleotides on this massively parallel semiconductor-sensing device or ion chip. The ion chip contains ion-sensitive, field-effect transistor-based sensors in perfect register with 1.2 million wells, which provide confinement and allow parallel, simultaneous detection of independent sequencing reactions. Use of the most widely used technology for constructing integrated circuits, the complementary metal-oxide semiconductor (CMOS) process, allows for low-cost, large-scale production and scaling of the device to higher densities and larger array sizes. We show the performance of the system by sequencing three bacterial genomes, its robustness and scalability by producing ion chips with up to 10 times as many sensors and sequencing a human genome.

Recent developments of ion beam induced luminescence at the external scanning microbeam facility of the LABEC laboratory in Florence

NASA Astrophysics Data System (ADS)

Colombo, E.; Calusi, S.; Cossio, R.; Giuntini, L.; Giudice, A. Lo; Mandò, P. A.; Manfredotti, C.; Massi, M.; Mirto, F. A.; Vittone, E.

2008-04-01

A new ionoluminescence (IL) apparatus has been successfully installed at the external scanning microbeam facility of the 3 MV Tandetron accelerator of the INFN LABEC in Firenze; the apparatus for photon detection has been fully integrated in the existing ion beam analysis (IBA) set-up, for the simultaneous acquisition of IL and PIXE/PIGE/BS spectra and maps. The potential of the new set-up is illustrated in this paper by some results extracted by the analysis of art objects and advanced semiconductor materials. In particular, the adequacy of the new IBA set-up in the field of cultural heritage is pointed out by the coupled PIXE/IL micro-analysis of a lapis lazuli stone; concerning applications in material science, IL spectra from a N doped diamond sample were acquired and compared with CL analyses to evaluate the relevant sensitivities and the effect of ion damage.

Alignment, orientation, and Coulomb explosion of difluoroiodobenzene studied with the pixel imaging mass spectrometry (PImMS) camera.

PubMed

Amini, Kasra; Boll, Rebecca; Lauer, Alexandra; Burt, Michael; Lee, Jason W L; Christensen, Lauge; Brauβe, Felix; Mullins, Terence; Savelyev, Evgeny; Ablikim, Utuq; Berrah, Nora; Bomme, Cédric; Düsterer, Stefan; Erk, Benjamin; Höppner, Hauke; Johnsson, Per; Kierspel, Thomas; Krecinic, Faruk; Küpper, Jochen; Müller, Maria; Müller, Erland; Redlin, Harald; Rouzée, Arnaud; Schirmel, Nora; Thøgersen, Jan; Techert, Simone; Toleikis, Sven; Treusch, Rolf; Trippel, Sebastian; Ulmer, Anatoli; Wiese, Joss; Vallance, Claire; Rudenko, Artem; Stapelfeldt, Henrik; Brouard, Mark; Rolles, Daniel

2017-07-07

Laser-induced adiabatic alignment and mixed-field orientation of 2,6-difluoroiodobenzene (C 6 H 3 F 2 I) molecules are probed by Coulomb explosion imaging following either near-infrared strong-field ionization or extreme-ultraviolet multi-photon inner-shell ionization using free-electron laser pulses. The resulting photoelectrons and fragment ions are captured by a double-sided velocity map imaging spectrometer and projected onto two position-sensitive detectors. The ion side of the spectrometer is equipped with a pixel imaging mass spectrometry camera, a time-stamping pixelated detector that can record the hit positions and arrival times of up to four ions per pixel per acquisition cycle. Thus, the time-of-flight trace and ion momentum distributions for all fragments can be recorded simultaneously. We show that we can obtain a high degree of one-and three-dimensional alignment and mixed-field orientation and compare the Coulomb explosion process induced at both wavelengths.

Structure and Composition of the Distant Lunar Exosphere: Constraints from ARTEMIS Observations of Ion Acceleration in Time-Varying Fields

NASA Technical Reports Server (NTRS)

Halekas, J. S.; Poppe, A. R.; Farrell, W. M.; McFadden, J. P.

2016-01-01

By analyzing the trajectories of ionized constituents of the lunar exosphere in time-varying electromagnetic fields, we can place constraints on the composition, structure, and dynamics of the lunar exosphere. Heavy ions travel slower than light ions in the same fields, so by observing the lag between field rotations and the response of ions from the lunar exosphere, we can place constraints on the composition of the ions. Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) provides an ideal platform to utilize such an analysis, since its two-probe vantage allows precise timing of the propagation of field discontinuities in the solar wind, and its sensitive plasma instruments can detect the ion response. We demonstrate the utility of this technique by using fully time-dependent charged particle tracing to analyze several minutes of ion observations taken by the two ARTEMIS probes 3000-5000 km above the dusk terminator on 25 January 2014. The observations from this time period allow us to reach several interesting conclusions. The ion production at altitudes of a few hundred kilometers above the sunlit surface of the Moon has an unexpectedly significant contribution from species with masses of 40 amu or greater. The inferred distribution of the neutral source population has a large scale height, suggesting that micrometeorite impact vaporization and/or sputtering play an important role in the production of neutrals from the surface. Our observations also suggest an asymmetry in ion production, consistent with either a compositional variation in neutral vapor production or a local reduction in solar wind sputtering in magnetic regions of the surface.

Magnetic field affects enzymatic ATP synthesis.

PubMed

Buchachenko, Anatoly L; Kuznetsov, Dmitry A

2008-10-01

The rate of ATP synthesis by creatine kinase extracted from V. xanthia venom was shown to depend on the magnetic field. The yield of ATP produced by enzymes with 24Mg2+ and 26Mg2+ ions in catalytic sites increases by 7-8% at 55 mT and then decreases at 80 mT. For enzyme with 25Mg2+ ion in a catalytic site, the ATP yield increases by 50% and 70% in the fields 55 and 80 mT, respectively. In the Earth field the rate of ATP synthesis by enzyme, in which Mg2+ ion has magnetic nucleus 25Mg, is 2.5 times higher than that by enzymes, in which Mg2+ ion has nonmagnetic, spinless nuclei 24Mg or 26Mg. Both magnetic field effect and magnetic isotope effect demonstrate that the ATP synthesis is an ion-radical process, affected by Zeeman interaction and hyperfine coupling in the intermediate ion-radical pair.

Preparation of Ion Exchange Films for Solid-Phase Spectrophotometry and Solid-Phase Fluorometry

NASA Technical Reports Server (NTRS)

Hill, Carol M.; Street, Kenneth W.; Tanner, Stephen P.; Philipp, Warren H.

2000-01-01

Atomic spectroscopy has dominated the field of trace inorganic analysis because of its high sensitivity and selectivity. The advantages gained by the atomic spectroscopies come with the disadvantage of expensive and often complicated instrumentation. Solid-phase spectroscopy, in which the analyte is preconcentrated on a solid medium followed by conventional spectrophotometry or fluorometry, requires less expensive instrumentation and has considerable sensitivity and selectivity. The sensitivity gains come from preconcentration and the use of chromophore (or fluorophore) developers and the selectivity is achieved by use of ion exchange conditions that favor the analyte in combination with speciative chromophores. Little work has been done to optimize the ion exchange medium (IEM) associated with these techniques. In this report we present a method for making ion exchange polymer films, which considerably simplify the solid-phase spectroscopic techniques. The polymer consists of formaldehyde-crosslinked polyvinyl alcohol with polyacrylic acid entrapped therein. The films are a carboxylate weak cation exchanger in the calcium form. They are mechanically sturdy and optically transparent in the ultraviolet and visible portion of the spectrum, which makes them suitable for spectrophotometry and fluorometry.

[Retrieval of Copper Pollution Information from Hyperspectral Satellite Data in a Vegetation Cover Mining Area].

PubMed

Qu, Yong-hua; Jiao, Si-hong; Liu, Su-hong; Zhu, Ye-qing

2015-11-01

Heavy metal mining activities have caused the complex influence on the ecological environment of the mining regions. For example, a large amount of acidic waste water containing heavy metal ions have be produced in the process of copper mining which can bring serious pollution to the ecological environment of the region. In the previous research work, bare soil is mainly taken as the research target when monitoring environmental pollution, and thus the effects of land surface vegetation have been ignored. It is well known that vegetation condition is one of the most important indictors to reflect the ecological change in a certain region and there is a significant linkage between the vegetation spectral characteristics and the heavy metal when the vegetation is effected by the heavy metal pollution. It means the vegetation is sensitive to heavy metal pollution by their physiological behaviors in response to the physiological ecology change of their growing environment. The conventional methods, which often rely on large amounts of field survey data and laboratorial chemical analysis, are time consuming and costing a lot of material resources. The spectrum analysis method using remote sensing technology can acquire the information of the heavy mental content in the vegetation without touching it. However, the retrieval of that information from the hyperspectral data is not an easy job due to the difficulty in figuring out the specific band, which is sensitive to the specific heavy metal, from a huge number of hyperspectral bands. Thus the selection of the sensitive band is the key of the spectrum analysis method. This paper proposed a statistical analysis method to find the feature band sensitive to heavy metal ion from the hyperspectral data and to then retrieve the metal content using the field survey data and the hyperspectral images from China Environment Satellite HJ-1. This method selected copper ion content in the leaves as the indicator of copper pollution level, using stepwise multiple linear regression and cross validation on the dataset which is consisting of 44 groups of copper ion content information in the polluted vegetation leaves from Dexing Copper Mine in Jiangxi Province to build up a statistical model by also incorporating the HJ-1 satellite images. This model was then used to estimate the copper content distribution over the whole research area at Dexing Copper Mine. The result has shown that there is strong statistical significance of the model which revealed the most sensitive waveband to copper ion is located at 516 nm. The distribution map illustrated that the copper ion content is generally in the range of 0-130 mg · kg⁻¹ in the vegetation covering area at Dexing Copper Mine and the most seriously polluted area is located at the South-east corner of Dexing City as well as the mining spots with a higher value between 80 and 100 mg · kg⁻¹. This result is consistent with the ground observation experiment data. The distribution map can certainly provide some important basic data on the copper pollution monitoring and treatment.

Method and apparatus for ion cyclotron spectrometry

DOEpatents

Dahl, David A [Idaho Falls, ID; Scott, Jill R [Idaho Falls, ID; McJunkin, Timothy R [Idaho Falls, ID

2010-08-17

An ion cyclotron spectrometer may include a vacuum chamber that extends at least along a z-axis and means for producing a magnetic field within the vacuum chamber so that a magnetic field vector is generally parallel to the z-axis. The ion cyclotron spectrometer may also include means for producing a trapping electric field within the vacuum chamber that includes at least a first section that induces a first magnetron effect that increases a cyclotron frequency of an ion and at least a second section that induces a second magnetron effect that decreases the cyclotron frequency of an ion. The cyclotron frequency changes induced by the first and second magnetron effects substantially cancel one another so that an ion traversing the at least first and second sections will experience no net change in cyclotron frequency.

New ways to develop biosensors towards addressing practical problems

NASA Astrophysics Data System (ADS)

Starodub, N. F.

2013-11-01

The main modern approaches which were realized at the development of new generation of biosensors intended for application in field of diagnostics, food quality control and environmental monitoring are presented. The main attention was paid to creation of the multi-parametrical and multi-functional enzymatic and immune biosensors which were realized for the complex diagnostics of diabetes, autoimmune state and for the control of process of sugar production. The label-free bioaffine devices based on the nano-porouse silicon (NPS) with the registration of specific formed signal by chemiluminescence (ChL) and photoresistivity and intended for the determination mycotoxins and diagnostics of retroviral bovine leukemia (RBL) are analyzed too. Improving of ion sensitive field effect transistors (ISFETs) through changing silicon nitride on the cerium oxide is discussed as perspective approach in case of micotoxins and Salmonella control. In the conclusion the possibility to replace biological sensitive elements by artificial ones is considered.

Detection of radio frequency perturbations using an ion beam diagnostic (abstract)

NASA Astrophysics Data System (ADS)

Howard, S.; Si, J.; Crowley, T. P.; Connor, K. A.; Schoch, P. M.; Schatz, J. G.

2001-01-01

Presently, experiments are underway at the Plasma Dynamics Laboratory at Rensselaer Polytechnic Institute to demonstrate that the techniques developed for heavy ion beam probe diagnostics (HIBP) can be used to measure radio frequency (rf) fluctuations in plasmas. We hope to measure fluctuations in plasma density and magnetic and electric fields. This will provide a direct measurement of the electric and magnetic fields in the plasma during ICRF heating and thereby improve understanding of heating deposition and wave physics. In addition, the field and the density measurements will be used to determine the plasma reaction to the heating experiments. It is expected that the density measurements will be easiest to interpret, while the electric field measurement will be the most difficult to interpret. The diagnostic issues that will be important in taking data at rf frequencies include faster electronics, signal levels, and path effects. We have used a current to voltage amplifier design to measure 0-500 kHz fluctuations in several previous experiments. By reducing the gain and changing some components, a very similar design is capable of operation at rf frequencies. The modified circuit has been tested up to 15 MHz and worked well. The number of beam ions striking the detector plate in one rf period will be too small to obtain good enough statistics for fluctuation measurements, and therefore, averages over many cycles will be required. We expect to be able to achieve millisecond time resolution in the experiments. The global nature of the modes will tend to make path effects important in the HIBP signals. On the other hand, since the beam will take more than one period to cross the plasma, phase shifts may cancel some of these effects. In addition, a path effect term due to dA/dt will be much more important relative to the electric potential than in lower frequency experiments. The initial experimental plan is to do a series of measurements in which a lithium ion beam passes through an argon helicon plasma. The helicon plasma was chosen because its high density (of order 1019 m-3) will produce a larger HIBP signal than can be obtained from other small plasmas. The helicon plasma is formed within a solenoidal magnetic field of 1 kG on axis. The plasma is excited by an rf antenna that is a modification of the type used in Boswell's experiments.1 The rf power source is presently a 500 W, 13.56 MHz generator. From calculation of final trajectories we have determined that 16-29 keV Li ions can be used to probe a plasma with 1 kG magnetic field on axis. If the signal levels with a lithium beam are too small, a molecular hydrogen source will be used. For testing the basic operation of the ion beam probe we will use a simple plate detector mounted on the output flange. These preliminary experiments will be used to determine the feasibility of measuring density and magnetic field fluctuations. A second set of experiments using a more traditional HIBP energy analyzer as a detector is also planned. This detector will also be able to measure electric field effects on the probing ions. It will also be less sensitive to UV noise from the plasma.

Effects of molecular weight and cationization agent on the sensitivity of Bi cluster secondary ion mass spectrometry.

PubMed

Fujii, Makiko; Shishido, Rie; Satoh, Takaya; Suzuki, Shigeru; Matsuo, Jiro

2016-07-30

Bi cluster secondary ion mass spectrometry (SIMS) is one of the most promising tools for precise analysis of synthetic polymers. However, the sensitivity in the high-mass region is still insufficient compared with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). Accordingly, the effects of metal assistance (cationization agents) were investigated in this study. To investigate the effects caused by varying the ionization agent, three different polyethylene glycol (PEG) samples were prepared, one with an Ag-deposited film, and two others mixed with Ag and Na, respectively. The measurements were performed by using a commercial Bi cluster SIMS and MALDI-TOFMS systems. The mass spectrum obtained with MALDI-TOFMS was used as a reference molecular weight distribution to evaluate the effects of molecular weight and primary ion species (Bi + , Bi 3 + , Bi 3 2 + ) on the sensitivity of Bi cluster SIMS. The intensity of each secondary ion was the highest in Bi 3 2 + irradiation, and the lowest in Bi + irradiation. Regarding the cationization agents, the secondary ion yield was the highest for the sample mixed with Ag, while the degree of decay of sensitivity along with the increase in molecular weight was the smallest for the sample mixed with Na. It was suggested that the cationization mechanism consists of pre-formed ionization and gas-phase ionization processes. The sensitivity of Bi cluster SIMS decreases to approximately one-fiftieth in every 1000 u. These results might help in understanding the mechanism of cationization and further enhancement of secondary ion yields of polymers. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Coupling between electrolyte and organic semiconductor in electrolyte-gated organic field effect transistors (Conference Presentation)

NASA Astrophysics Data System (ADS)

Biscarini, Fabio; Di Lauro, Michele; Berto, Marcello; Bortolotti, Carlo A.; Geerts, Yves H.; Vuillaume, Dominique

2016-11-01

Organic field effect transistors (OFET) operated in aqueous environments are emerging as ultra-sensitive biosensors and transducers of electrical and electrochemical signals from a biological environment. Their applications range from detection of biomarkers in bodily fluids to implants for bidirectional communication with the central nervous system. They can be used in diagnostics, advanced treatments and theranostics. Several OFET layouts have been demonstrated to be effective in aqueous operations, which are distinguished either by their architecture or by the respective mechanism of doping by the ions in the electrolyte solution. In this work we discuss the unification of the seemingly different architectures, such as electrolyte-gated OFET (EGOFET), organic electrochemical transistor (OECT) and dual-gate ion-sensing FET. We first demonstrate that these architectures give rise to the frequency-dependent response of a synapstor (synapse-like transistor), with enhanced or depressed modulation of the output current depending on the frequency of the time-dependent gate voltage. This behavior that was reported for OFETs with embedded metal nanoparticles shows the existence of a capacitive coupling through an equivalent network of RC elements. Upon the systematic change of ions in the electrolyte and the morphology of the charge transport layer, we show how the time scale of the synapstor is changed. We finally show how the substrate plays effectively the role of a second bottom gate, whose potential is actually fixed by the pH/composition of the electrolyte and the gate voltage applied.

Mass spectrometric measurements of atmospheric composition

NASA Technical Reports Server (NTRS)

Hoffman, J. H.

1974-01-01

The development of a magnetic sector field analyzer for continuous sampling and measurement of outer planetary atmospheres is discussed. Special features of the analyzer include a dynamic range of 10 to the minus 7th power, a mass range from 1 to 48 AMU, two ion sensitivities, a special scan time of 35 sec at 14 BPS, and the use of ion counting techniques for analysis.

Functional Testing and Characterisation of ISFETs on Wafer Level by Means of a Micro-droplet Cell#

PubMed Central

Poghossian, Arshak; Schumacher, Kerstin; Kloock, Joachim P.; Rosenkranz, Christian; Schultze, Joachim W.; Müller-Veggian, Mattea; Schöning, Michael J.

2006-01-01

A wafer-level functionality testing and characterisation system for ISFETs (ion-sensitive field-effect transistor) is realised by means of integration of a specifically designed capillary electrochemical micro-droplet cell into a commercial wafer prober-station. The developed system allows the identification and selection of “good” ISFETs at the earliest stage and to avoid expensive bonding, encapsulation and packaging processes for non-functioning ISFETs and thus, to decrease costs, which are wasted for bad dies. The developed system is also feasible for wafer-level characterisation of ISFETs in terms of sensitivity, hysteresis and response time. Additionally, the system might be also utilised for wafer-level testing of further electrochemical sensors.

Microfabricated ion trap array

DOEpatents

Blain, Matthew G [Albuquerque, NM; Fleming, James G [Albuquerque, NM

2006-12-26

A microfabricated ion trap array, comprising a plurality of ion traps having an inner radius of order one micron, can be fabricated using surface micromachining techniques and materials known to the integrated circuits manufacturing and microelectromechanical systems industries. Micromachining methods enable batch fabrication, reduced manufacturing costs, dimensional and positional precision, and monolithic integration of massive arrays of ion traps with microscale ion generation and detection devices. Massive arraying enables the microscale ion traps to retain the resolution, sensitivity, and mass range advantages necessary for high chemical selectivity. The reduced electrode voltage enables integration of the microfabricated ion trap array with on-chip circuit-based rf operation and detection electronics (i.e., cell phone electronics). Therefore, the full performance advantages of the microfabricated ion trap array can be realized in truly field portable, handheld microanalysis systems.

Hydration free energies of cyanide and hydroxide ions from molecular dynamics simulations with accurate force fields

USGS Publications Warehouse

Lee, M.W.; Meuwly, M.

2013-01-01

The evaluation of hydration free energies is a sensitive test to assess force fields used in atomistic simulations. We showed recently that the vibrational relaxation times, 1D- and 2D-infrared spectroscopies for CN(-) in water can be quantitatively described from molecular dynamics (MD) simulations with multipolar force fields and slightly enlarged van der Waals radii for the C- and N-atoms. To validate such an approach, the present work investigates the solvation free energy of cyanide in water using MD simulations with accurate multipolar electrostatics. It is found that larger van der Waals radii are indeed necessary to obtain results close to the experimental values when a multipolar force field is used. For CN(-), the van der Waals ranges refined in our previous work yield hydration free energy between -72.0 and -77.2 kcal mol(-1), which is in excellent agreement with the experimental data. In addition to the cyanide ion, we also study the hydroxide ion to show that the method used here is readily applicable to similar systems. Hydration free energies are found to sensitively depend on the intermolecular interactions, while bonded interactions are less important, as expected. We also investigate in the present work the possibility of applying the multipolar force field in scoring trajectories generated using computationally inexpensive methods, which should be useful in broader parametrization studies with reduced computational resources, as scoring is much faster than the generation of the trajectories.

Real-time detection of mercury ions in water using a reduced graphene oxide/DNA field-effect transistor with assistance of a passivation layer

DOE PAGES

Chang, Jingbo; Zhou, Guihua; Gao, Xianfeng; ...

2015-08-01

Field-effect transistor (FET) sensors based on reduced graphene oxide (rGO) for detecting chemical species provide a number of distinct advantages, such as ultrasensitivity, label-free, and real-time response. However, without a passivation layer, channel materials directly exposed to an ionic solution could generate multiple signals from ionic conduction through the solution droplet, doping effect, and gating effect. Therefore, a method that provides a passivation layer on the surface of rGO without degrading device performance will significantly improve device sensitivity, in which the conductivity changes solely with the gating effect. In this work, we report rGO FET sensor devices with Hg 2+-dependentmore » DNA as a probe and the use of an Al 2O 3 layer to separate analytes from conducting channel materials. The device shows good electronic stability, excellent lower detection limit (1 nM), and high sensitivity for real-time detection of Hg 2+ in an underwater environment. Our work shows that optimization of an rGO FET structure can provide significant performance enhancement and profound fundamental understanding for the sensor mechanism.« less

Silicon-ion-implanted PMMA with nanostructured ultrathin layers for plastic electronics

NASA Astrophysics Data System (ADS)

Hadjichristov, G. B.; Ivanov, Tz E.; Marinov, Y. G.

2014-12-01

Being of interest for plastic electronics, ion-beam produced nanostructure, namely silicon ion (Si+) implanted polymethyl-methacrylate (PMMA) with ultrathin nanostructured dielectric (NSD) top layer and nanocomposite (NC) buried layer, is examined by electric measurements. In the proposed field-effect organic nanomaterial structure produced within the PMMA network by ion implantation with low energy (50 keV) Si+ at the fluence of 3.2 × 1016 cm-2 the gate NSD is ion-nanotracks-modified low-conductive surface layer, and the channel NC consists of carbon nanoclusters. In the studied ion-modified PMMA field-effect configuration, the gate NSD and the buried NC are formed as planar layers both with a thickness of about 80 nm. The NC channel of nano-clustered amorphous carbon (that is an organic semiconductor) provides a huge increase in the electrical conduction of the material in the subsurface region, but also modulates the electric field distribution in the drift region. The field effect via the gate NSD is analyzed. The most important performance parameters, such as the charge carrier field-effect mobility and amplification of this particular type of PMMA- based transconductance device with NC n-type channel and gate NSD top layer, are determined.

Quaternary ammonium promoted ultra selective and sensitive fluorescence detection of fluoride ion in water and living cells.

PubMed

Li, Long; Ji, Yuzhuo; Tang, Xinjing

2014-10-21

Highly selective and sensitive fluorescent probes with a quaternary ammonium moiety have been rationally designed and developed for fast and sensitive fluorescence detection of fluoride ion (F(-) from NaF, not TBAF) in aqueous solution and living cells. With the sequestration effect of quaternary ammonium, the detection time was less than 2 min and the detection limit of fluoride ion was as low as 0.57 ppm that is among the lowest detection limits in aqueous solutions of many fluoride fluorescence probes in the literature.

Investigation of mixed ion fields in the forward direction for 220.5 MeV/u helium ion beams: comparison between water and PMMA targets.

PubMed

Aricò, G; Gehrke, T; Jakubek, J; Gallas, R; Berke, S; Jäkel, O; Mairani, A; Ferrari, A; Martišíková, M

2017-10-03

Currently there is a rising interest in helium ion beams for radiotherapy. For benchmarking of the physical beam models used in treatment planning, there is a need for experimental data on the composition and spatial distribution of mixed ion fields. Of particular interest are the attenuation of the primary helium ion fluence and the build-up of secondary hydrogen ions due to nuclear interactions. The aim of this work was to provide such data with an enhanced precision. Moreover, the validity and limits of the mixed ion field equivalence between water and PMMA targets were investigated. Experiments with a 220.5 MeV/u helium ion pencil beam were performed at the Heidelberg Ion-Beam Therapy Center in Germany. The compact detection system used for ion tracking and identification was solely based on Timepix position-sensitive semiconductor detectors. In comparison to standard techniques, this system is two orders of magnitude smaller, and provides higher precision and flexibility. The numbers of outgoing helium and hydrogen ions per primary helium ion as well as the lateral particle distributions were quantitatively investigated in the forward direction behind water and PMMA targets with 5.2-18 cm water equivalent thickness (WET). Comparing water and PMMA targets with the same WET, we found that significant differences in the amount of outgoing helium and hydrogen ions and in the lateral particle distributions arise for target thicknesses above 10 cm WET. The experimental results concerning hydrogen ions emerging from the targets were reproduced reasonably well by Monte Carlo simulations using the FLUKA code. Concerning the amount of outgoing helium ions, significant differences of 3-15% were found between experiments and simulations. We conclude that if PMMA is used in place of water in dosimetry, differences in the dose distributions could arise close to the edges of the field, in particular for deep seated targets.

Studies on low energy beam transport for high intensity high charged ions at IMP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Y., E-mail: yangyao@impcas.ac.cn; Lu, W.; Fang, X.

2014-02-15

Superconducting Electron Cyclotron Resonance ion source with Advanced design in Lanzhou (SECRAL) is an advanced fully superconducting ECR ion source at IMP designed to be operational at the microwave frequency of 18–24 GHz. The existing SECRAL beam transmission line is composed of a solenoid lens and a 110° analyzing magnet. Simulations of particle tracking with 3D space charge effect and realistic 3D magnetic fields through the line were performed using particle-in-cell code. The results of the beam dynamics show that such a low energy beam is very sensitive to the space charge effect and significantly suffers from the second-order aberrationmore » of the analyzing magnet resulting in large emittance. However, the second-order aberration could be reduced by adding compensating sextupole components in the beam line. On this basis, a new 110° analyzing magnet with relatively larger acceptance and smaller aberration is designed and will be used in the design of low energy beam transport line for a new superconducting ECR ion source SECRAL-II. The features of the analyzer and the corresponding beam trajectory calculation will be detailed and discussed in this paper.« less

Role of deposition and annealing of the top gate dielectric in a-IGZO TFT-based dual-gate ion-sensitive field-effect transistors

NASA Astrophysics Data System (ADS)

Kumar, Narendra; Sutradhar, Moitri; Kumar, Jitendra; Panda, Siddhartha

2017-03-01

The deposition of the top gate dielectric in thin film transistor (TFT)-based dual-gate ion-sensitive field-effect transistors (DG ISFETs) is critical, and expected not to affect the bottom gate TFT characteristics, while providing a higher pH sensitive surface and efficient capacitive coupling between the gates. Amorphous Ta2O5, in addition to having good sensing properties, possesses a high dielectric constant of ˜25 making it well suited as the top gate dielectric in a DG ISFET by providing higher capacitive coupling (ratio of C top/C bottom) leading to higher amplification. To avoid damage of the a-IGZO channel reported to be caused by plasma exposure, deposition of Ta2O5 by e-beam evaporation followed by annealing was investigated in this work to obtain sensitivity over the Nernst limit. The deteriorated bottom gate TFT characteristics, indicated by an increase in the channel conductance, confirmed that plasma exposure is not the sole contributor to the changes. Oxygen vacancies at the Ta2O5/a-IGZO interface, which emerged during processing, increased the channel conductivity, became filled by optimum annealing in oxygen at 400 °C for 1 h, which was confirmed by an x-ray photoelectron spectroscopy depth profiling analysis. The obtained pH sensitivity of the TFT-based DG ISFET was 402 mV pH-1, which is about 6.8 times the Nernst limit (59 mV pH-1). The concept of capacitive coupling was also demonstrated by simulating an a-IGZO-based DG TFT structure. Here, the exposure of the top gate dielectric to the electrolyte without applying any top gate bias led to changes in the measured threshold voltage of the bottom gate TFT, and this obviated the requirement of a reference electrode needed in conventional ISFETs and other reported DG ISFETs. These devices, with high sensitivities and requiring low volumes (˜2 μl) of analyte solution, could be potential candidates for utilization as chemical sensors and biosensors.

Large voltage modulation in superconducting quantum interference devices with submicron-scale step-edge junctions

NASA Astrophysics Data System (ADS)

Lam, Simon K. H.

2017-09-01

A promising direction to improve the sensitivity of a SQUID is to increase its junction's normal resistance value, Rn, as the SQUID modulation voltage scales linearly with Rn. As a first step to develop highly sensitive single layer SQUID, submicron scale YBCO grain boundary step edge junctions and SQUIDs with large Rn were fabricated and studied. The step-edge junctions were reduced to submicron scale to increase their Rn values using focus ion beam, FIB and the measurement of transport properties were performed from 4.3 to 77 K. The FIB induced deposition layer proves to be effective to minimize the Ga ion contamination during the FIB milling process. The critical current-normal resistance value of submicron junction at 4.3 K was found to be 1-3 mV, comparable to the value of the same type of junction in micron scale. The submicron junction Rn value is in the range of 35-100 Ω, resulting a large SQUID modulation voltage in a wide temperature range. This performance promotes further investigation of cryogen-free, high field sensitivity SQUID applications at medium low temperature, e.g. at 40-60 K.

Ion heating and characteristics of ST plasma used by double-pulsing CHI on HIST

NASA Astrophysics Data System (ADS)

Hanao, Takafumi; Hirono, Hidetoshi; Hyobu, Takahiro; Ito, Kengo; Matsumoto, Keisuke; Nakayama, Takashi; Oki, Nobuharu; Kikuchi, Yusuke; Fukumoto, Naoyuki; Nagata, Masayoshi

2013-10-01

Multi-pulsing Coaxial Helicity Injection (M-CHI) is an efficient current drive and sustainment method used in spheromak and spherical torus (ST). We have observed plasma current/flux amplification by double pulsing CHI. Poloidal ion temperature measured by Ion Doppler Spectrometer (IDS) has a peak at plasma core region. In this region, radial electric field has a negative peak. At more inboard side that is called separatrix between closed flux region and inner open flux region, poloidal flow has a large shear and radial electric field changes the polarity. After the second CHI pulse, we observed sharp and rapid ion heating at plasma core region and separatrix. In this region, the poloidal ion temperature is selective heating because electron temperature is almost uniform. At this time, flow shear become larger and radial electric field is amplified at separatorix. These effects produce direct heating of ion through the viscous flow damping. Furthermore, we observed decrease of electron density at separatrix. Decreased density makes Hall dynamo electric field as two-fluid effect. When the ion temperature is increasing, dynamo electric field is observed at separatrix. It may have influence with the ion heating. We will discuss characteristic of double pulsing CHI driven ST plasmas and correlation of direct heating of ion with dynamo electric field and any other parameters.

Monte Carlo study of microdosimetric diamond detectors

NASA Astrophysics Data System (ADS)

Solevi, Paola; Magrin, Giulio; Moro, Davide; Mayer, Ramona

2015-09-01

Ion-beam therapy provides a high dose conformity and increased radiobiological effectiveness with respect to conventional radiation-therapy. Strict constraints on the maximum uncertainty on the biological weighted dose and consequently on the biological weighting factor require the determination of the radiation quality, defined as the types and energy spectra of the radiation at a specific point. However the experimental determination of radiation quality, in particular for an internal target, is not simple and the features of ion interactions and treatment delivery require dedicated and optimized detectors. Recently chemical vapor deposition (CVD) diamond detectors have been suggested as ion-beam therapy microdosimeters. Diamond detectors can be manufactured with small cross sections and thin shapes, ideal to cope with the high fluence rate. However the sensitive volume of solid state detectors significantly deviates from conventional microdosimeters, with a diameter that can be up to 1000 times the height. This difference requires a redefinition of the concept of sensitive thickness and a deep study of the secondary to primary radiation, of the wall effects and of the impact of the orientation of the detector with respect to the radiation field. The present work intends to study through Monte Carlo simulations the impact of the detector geometry on the determination of radiation quality quantities, in particular on the relative contribution of primary and secondary radiation. The dependence of microdosimetric quantities such as the unrestricted linear energy L and the lineal energy y are investigated for different detector cross sections, by varying the particle type (carbon ions and protons) and its energy.

Nb3Sn superconducting magnets for electron cyclotron resonance ion sources.

PubMed

Ferracin, P; Caspi, S; Felice, H; Leitner, D; Lyneis, C M; Prestemon, S; Sabbi, G L; Todd, D S

2010-02-01

Electron cyclotron resonance (ECR) ion sources are an essential component of heavy-ion accelerators. Over the past few decades advances in magnet technology and an improved understanding of the ECR ion source plasma physics have led to remarkable performance improvements of ECR ion sources. Currently third generation high field superconducting ECR ion sources operating at frequencies around 28 GHz are the state of the art ion injectors and several devices are either under commissioning or under design around the world. At the same time, the demand for increased intensities of highly charged heavy ions continues to grow, which makes the development of even higher performance ECR ion sources a necessity. To extend ECR ion sources to frequencies well above 28 GHz, new magnet technology will be needed in order to operate at higher field and force levels. The superconducting magnet program at LBNL has been developing high field superconducting magnets for particle accelerators based on Nb(3)Sn superconducting technology for several years. At the moment, Nb(3)Sn is the only practical conductor capable of operating at the 15 T field level in the relevant configurations. Recent design studies have been focused on the possibility of using Nb(3)Sn in the next generation of ECR ion sources. In the past, LBNL has worked on the VENUS ECR, a 28 GHz source with solenoids and a sextupole made with NbTi operating at fields of 6-7 T. VENUS has now been operating since 2004. We present in this paper the design of a Nb(3)Sn ECR ion source optimized to operate at an rf frequency of 56 GHz with conductor peak fields of 13-15 T. Because of the brittleness and strain sensitivity of Nb(3)Sn, particular care is required in the design of the magnet support structure, which must be capable of providing support to the coils without overstressing the conductor. In this paper, we present the main features of the support structure, featuring an external aluminum shell pretensioned with water-pressurized bladders, and we analyze the expected coil stresses with a two-dimensional finite element mechanical model.

Rotating field mass and velocity analyzer

NASA Technical Reports Server (NTRS)

Smith, Steven Joel (Inventor); Chutjian, Ara (Inventor)

1998-01-01

A rotating field mass and velocity analyzer having a cell with four walls, time dependent RF potentials that are applied to each wall, and a detector. The time dependent RF potentials create an RF field in the cell which effectively rotates within the cell. An ion beam is accelerated into the cell and the rotating RF field disperses the incident ion beam according to the mass-to-charge (m/e) ratio and velocity distribution present in the ion beam. The ions of the beam either collide with the ion detector or deflect away from the ion detector, depending on the m/e, RF amplitude, and RF frequency. The detector counts the incident ions to determine the m/e and velocity distribution in the ion beam.

Normal axonal ion channel function in large peripheral nerve fibers following chronic ciguatera sensitization.

PubMed

Vucic, Steve; Kiernan, Matthew C

2008-03-01

Although the acute clinical effects of ciguatera poisoning, due to ingestion of ciguatoxin, are mediated by activation of transient Na+ channels, the mechanisms underlying ciguatera sensitization remain undefined. Axonal excitability studies were performed by stimulating the median motor and sensory nerves in two patients with ciguatera sensitization. Excitability parameters were all within normal limits, thereby arguing against dysfunction of axonal membrane ion channels in large-diameter fibers in ciguatera sensitization.

Coordination ability determined transition metal ions substitution of Tb in Tb-Asp fluorescent nanocrystals and a facile ions-detection approach.

PubMed

Duan, Jiazhi; Ma, Baojin; Liu, Feng; Zhang, Shan; Wang, Shicai; Kong, Ying; Du, Min; Han, Lin; Wang, Jianjun; Sang, Yuanhua; Liu, Hong

2018-04-26

Although the synthesis and fluorescent properties of lanthanide-amino acid complex nanostructures have been investigated extensively, limited studies have been reported on metal ions' substitution ability for the lanthanide ions in the complex and their effect on the fluorescent property. In this study, taking biocompatible Tb-aspartic acid (Tb-Asp) complex nanocrystals as a model, the substitution mechanism of metal ions, particularly transition metals, for Tb ions in Tb-Asp nanocrystals and the change in the fluorescent property of the Tb-Asp nanocrystals after substitution were systematically investigated. The experimental results illustrated that metal ions with higher electronegativity, higher valence, and smaller radius possess stronger ability for Tb ions' substitution in Tb-Asp nanocrystals. Based on the effect of substituting ions' concentration on the fluorescent property of Tb-Asp, a facile method for copper ions detection with high sensitivity was proposed by measuring the fluorescent intensity of Tb-Asp nanocrystals' suspensions containing different concentrations of copper ions. The good biocompatibility, great convenience of synthesis and sensitive detection ability make Tb-Asp nanocrystals a very low cost and effective material for metal ions detection, which also opens a new door for practical applications of metal-Asp coordinated nanocrystals.

Sensitive glow discharge ion source for aerosol and gas analysis

DOEpatents

Reilly, Peter T. A. [Knoxville, TN

2007-08-14

A high sensitivity glow discharge ion source system for analyzing particles includes an aerodynamic lens having a plurality of constrictions for receiving an aerosol including at least one analyte particle in a carrier gas and focusing the analyte particles into a collimated particle beam. A separator separates the carrier gas from the analyte particle beam, wherein the analyte particle beam or vapors derived from the analyte particle beam are selectively transmitted out of from the separator. A glow discharge ionization source includes a discharge chamber having an entrance orifice for receiving the analyte particle beam or analyte vapors, and a target electrode and discharge electrode therein. An electric field applied between the target electrode and discharge electrode generates an analyte ion stream from the analyte vapors, which is directed out of the discharge chamber through an exit orifice, such as to a mass spectrometer. High analyte sensitivity is obtained by pumping the discharge chamber exclusively through the exit orifice and the entrance orifice.

Advances in ultrasensitive mass spectrometry of organic molecules.

PubMed

Kandiah, Mathivathani; Urban, Pawel L

2013-06-21

Ultrasensitive mass spectrometric analysis of organic molecules is important for various branches of chemistry, and other fields including physics, earth and environmental sciences, archaeology, biomedicine, and materials science. It finds applications--as an enabling tool--in systems biology, biological imaging, clinical analysis, and forensics. Although there are a number of technical obstacles associated with the analysis of samples by mass spectrometry at ultratrace level (for example analyte losses during sample preparation, insufficient sensitivity, ion suppression), several noteworthy developments have been made over the years. They include: sensitive ion sources, loss-free interfaces, ion optics components, efficient mass analyzers and detectors, as well as "smart" sample preparation strategies. Some of the mass spectrometric methods published to date can achieve sensitivity which is by several orders of magnitude higher than that of alternative approaches. Femto- and attomole level limits of detection are nowadays common, while zepto- and yoctomole level limits of detection have also been reported. We envision that the ultrasensitive mass spectrometric assays will soon contribute to new discoveries in bioscience and other areas.

Magnetopause reconnection under various space weather conditions

NASA Astrophysics Data System (ADS)

Chen, L.; Argall, M. R.; Shuster, J. R.; Li, G.; Karimabadi, H.; Daughton, W. S.; Germaschewski, K.; Torbert, R. B.; Bhattacharjee, A.

2013-12-01

In order to develop predictive capabilities for the Sun-Earth connection, the question of how various reconnection upstream conditions influence particle energization and the stability of the reconnection current layer needs to be answered. Using magnetopause reconnection events observed by the Cluster spacecraft, we address this question by comparing the observed plasma and field features in the vicinity of the magnetopause current layer for a wide range of geomagnetic conditions including nominal times and the most severe magnetic storms. Outstanding features include: 1. Plasmoid-like structures, when observed, tend to appear in series and more frequently on the magnetosheath side of the magnetopause current layer. These plasmoids contain accelerated electrons and ions up to ~100 keV, and can prevail in guide fields ranging from nearly zero to a strength approximately equal to the reconnecting field. Associated with each of these plasmoids are a bipolar DC component and intense fluctuations in the electric fields. 2. The fastest ion outflow jets occur in the magnetospheric side of the magnetopause. 3. The plasma density transition is in general removed from the magnetopause current layer to the magnetospheric side, in contrast to the predictions of a PIC simulation and THEMIS observations [1]. Feature 1 suggests that the current layer is unstable to plasmoid formation, and that the plasmoids are effective energization sites for plasmas. The above features are not sensitive functions of the degrees of upstream asymmetries. The observation results will be compared with PIC, global hybrid as well as global Hall MHD simulations to achieve fundamental understanding of asymmetric reconnection, separating two-fluid, ion kinetic and electron kinetic effects. [1] Mozer and Pritchett, JGR, 2008

Electrostatic ion instabilities in the presence of parallel currents and transverse electric fields

NASA Technical Reports Server (NTRS)

Ganguli, G.; Palmadesso, P. J.

1988-01-01

The electrostatic ion instabilities are studied for oblique propagation in the presence of magnetic field-aligned currents and transverse localized electric fields in a weakly collisional plasma. The presence of transverse electric fields result in mode excitation for magnetic field aligned current values that are otherwise stable. The electron collisions enhance the growth while ion collisions have a damping effect. These results are discussed in the context of observations of low frequency ion modes in the auroral ionosphere by radar and rocket experiments.

Comment on 'Effects of magnetic field gradient on ion beam current in cylindrical Hall ion source' [J. Appl. Phys. 102, 123305 (2007)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raitses, Y.; Smirnov, A.; Fisch, N. J.

It is argued that the key difference in the cylindrical Hall thruster (CHT) as compared to the end-Hall ion source cannot be exclusively attributed to the magnetic field topology [Tang et al., J. Appl. Phys. 102, 123305 (2007)]. With a similar mirror-type topology, the CHT configuration provides the electric field with nearly equipotential magnetic field surfaces and a better suppression of the electron cross-field transport, as compared to both the end-Hall ion source and the cylindrical Hall ion source of [Tang et al., J. Appl. Phys. 102, 123305 (2007)].

Ion Viscosity Mediated by Tangled Magnetic Fields: An Application to Black Hole Accretion Disks

NASA Technical Reports Server (NTRS)

Subramanian, Prasad; Becker, Peter A.; Kafatos, Menas

1996-01-01

We examine the viscosity associated with the shear stress exerted by ions in the presence of a tangled magnetic field. As an application, we consider the effect of this mechanism on the structure of black hole accretion disks. We do not attempt to include a self-consistent description of the magnetic field. Instead, we assume the existence of a tangled field with coherence length lambda(sub coh), which is the average distance between the magnetic 'kinks' that scatter the particles. For simplicity, we assume that the field is self-similar, and take lambda(sub coh) to be a fixed fraction zeta of the local disk height H. Ion viscosity in the presence of magnetic fields is generally taken to be the cross-field viscosity, wherein the effective mean free path is the ion Larmor radius lambda(sub L), which is much less than the ion-ion Coulomb mean free path A(sub ii) in hot accretion disks. However, we arrive at a formulation for a 'hybrid' viscosity in which the tangled magnetic field acts as an intermediary in the transfer of momentum between different layers in the shear flow. The hybrid viscosity greatly exceeds the standard cross-field viscosity when (lambda/lambda(sub L)) much greater than (lambda(sub L)/lambda(sub ii)), where lambda = ((lambda(sub ii)(sup -1) + lambda(sub (coh)(sup -1))(sup -1) is the effective mean free path for the ions. This inequality is well satisfied in hot accretion disks, which suggests that the ions may play a much larger role in the momentum transfer process in the presence of magnetic fields than was previously thought. The effect of the hybrid viscosity on the structure of a steady-state, two-temperature, quasi-Keplerian accretion disk is analyzed. The hybrid viscosity is influenced by the degree to which the magnetic field is tangled (represented by zeta = lambda(sub coh)), and also by the relative accretion rate M/M(sub E), where M(sub E) = L(sub E)/c(sup 2) and L(sub E) is the Eddington luminosity. We find that ion viscosity in the presence of magnetic fields (hybrid viscosity) can dominate over conventional magnetic viscosity for fields that are tangled on sufficiently small scales.

Effects Of Electric Field On Hydrocarbon-Fueled Flames

NASA Technical Reports Server (NTRS)

Yuan, Z.-G.; Hegde, U.

2003-01-01

It has been observed that flames are susceptible to electric fields that are much weaker than the breakdown field strength of the flame gases. When an external electric field is imposed on a flame, the ions generated in the flame reaction zone drift in the direction of the electric forces exerted on them. The moving ions collide with the neutral species and change the velocity distribution in the affected region. This is often referred to as ionic wind effect. In addition, the removal of ions from the flame reaction zone can alter the chemical reaction pathway of the flame. On the other hand, the presence of space charges carried by moving ions affects the electric field distribution. As a result, the flame often changes its shape, location and color once an external electric field is applied. The interplay between the flame movement and the change of electric field makes it difficult to determine the flame location for a given configuration of electrodes and fuel source. In normal gravity, the buoyancy-induced flow often complicates the problem and hinders detailed study of the interaction between the flame and the electric field. In this work, the microgravity environment established at the 2.2 Second Drop Tower at the NASA Glenn Research Center is utilized to effectively remove the buoyant acceleration. The interaction between the flame and the electric field is studied in a one-dimensional domain. A specially designed electrode makes flame current measurements possible; thus, the mobility of ions, ion density, and ionic wind effect can be evaluated.

Method and apparatuses for ion cyclotron spectrometry

DOEpatents

Dahl, David A [Idaho Falls, ID; Scott, Jill R [Idaho Falls, ID; McJunkin, Timothy R [Idaho Falls, ID

2012-03-06

An ion cyclotron spectrometer may include a vacuum chamber that extends at least along a z-axis and means for producing a magnetic field within the vacuum chamber so that a magnetic field vector is generally parallel to the z-axis. The ion cyclotron spectrometer may also include means for producing a trapping electric field within the vacuum chamber. The trapping electric field may comprise a field potential that, when taken in cross-section along the z-axis, includes at least one section that is concave down and at least one section that is concave up so that ions traversing the field potential experience a net magnetron effect on a cyclotron frequency of the ions that is substantially equal to zero. Other apparatuses and a method for performing ion cyclotron spectrometry are also disclosed herein.

Effect of axial magnetic field on a 2.45 GHz permanent magnet ECR ion source.

PubMed

Nakamura, T; Wada, H; Asaji, T; Furuse, M

2016-02-01

Herein, we conduct a fundamental study to improve the generation efficiency of a multi-charged ion source using argon. A magnetic field of our electron cyclotron resonance ion source is composed of a permanent magnet and a solenoid coil. Thereby, the axial magnetic field in the chamber can be tuned. Using the solenoid coil, we varied the magnetic field strength in the plasma chamber and measured the ion beam current extracted at the electrode. We observed an approximately three times increase in the Ar(4+) ion beam current when the magnetic field on the extractor-electrode side of the chamber was weakened. From our results, we can confirm that the multi-charged ion beam current changes depending on magnetic field intensity in the plasma chamber.

First results from the new RIKEN superconducting electron cyclotron resonance ion source (invited).

PubMed

Nakagawa, T; Higurashi, Y; Ohnishi, J; Aihara, T; Tamura, M; Uchiyama, A; Okuno, H; Kusaka, K; Kidera, M; Ikezawa, E; Fujimaki, M; Sato, Y; Watanabe, Y; Komiyama, M; Kase, M; Goto, A; Kamigaito, O; Yano, Y

2010-02-01

The next generation heavy ion accelerator facility, such as the RIKEN radio isotope (RI) beam factory, requires an intense beam of high charged heavy ions. In the past decade, performance of the electron cyclotron resonance (ECR) ion sources has been dramatically improved with increasing the magnetic field and rf frequency to enhance the density and confinement time of plasma. Furthermore, the effects of the key parameters (magnetic field configuration, gas pressure, etc.) on the ECR plasma have been revealed. Such basic studies give us how to optimize the ion source structure. Based on these studies and modern superconducting (SC) technology, we successfully constructed the new 28 GHz SC-ECRIS, which has a flexible magnetic field configuration to enlarge the ECR zone and to optimize the field gradient at ECR point. Using it, we investigated the effect of ECR zone size, magnetic field configuration, and biased disk on the beam intensity of the highly charged heavy ions with 18 GHz microwaves. In this article, we present the structure of the ion source and first experimental results with 18 GHz microwave in detail.

Influence of Electric Fields and Conductivity on Pollen Tube Growth assessed via Electrical Lab-on-Chip

PubMed Central

Agudelo, Carlos; Packirisamy, Muthukumaran; Geitmann, Anja

2016-01-01

Pollen tubes are polarly growing plant cells that are able to rapidly respond to a combination of chemical, mechanical, and electrical cues. This behavioural feature allows them to invade the flower pistil and deliver the sperm cells in highly targeted manner to receptive ovules in order to accomplish fertilization. How signals are perceived and processed in the pollen tube is still poorly understood. Evidence for electrical guidance in particular is vague and highly contradictory. To generate reproducible experimental conditions for the investigation of the effect of electric fields on pollen tube growth we developed an Electrical Lab-on-Chip (ELoC). Pollen from the species Camellia displayed differential sensitivity to electric fields depending on whether the entire cell or only its growing tip was exposed. The response to DC fields was dramatically higher than that to AC fields of the same strength. However, AC fields were found to restore and even promote pollen growth. Surprisingly, the pollen tube response correlated with the conductivity of the growth medium under different AC frequencies—consistent with the notion that the effect of the field on pollen tube growth may be mediated via its effect on the motion of ions. PMID:26804186

Ponderomotive ion acceleration in dense magnetized laser-irradiated thick target plasmas

NASA Astrophysics Data System (ADS)

Sinha, Ujjwal; Kaw, Predhiman

2012-03-01

When a circularly polarized laser pulse falls on an overdense plasma, it displaces the electrons via ponderomotive force creating a double layer. The double layer constitutes of an ion and electron sheath with in which the electrostatic field present is responsible for ion acceleration. In this paper, we have analyzed the effect a static longitudinal magnetic field has over the ion acceleration mechanism. The longitudinal magnetic field changes the plasma dielectric constant due to cyclotron effects which in turn enhances or reduces the ponderomotive force exerted by the laser depending on whether the laser is left or right circularly polarized. Also, the analysis of the ion space charge region present behind the ion sheath of the laser piston that undergoes coulomb explosion has been explored for the first time. We have studied the interaction of an incoming ion beam with the laser piston and the ion space charge. It has been found that the exploding ion space charge has the ability to act as an energy amplifier for incoming ion beams.

The Effects of Ion heating in Martian Magnetic Crustal Fields: Particle Tracing and Ion Distributions

NASA Astrophysics Data System (ADS)

Fowler, C. M.; Andersson, L.

2014-12-01

Ion heating is a process that may allow low energy ions within the Martian ionosphere to be accelerated and escape. Ion heating can be especially efficient if the ions stay in the heating region for long time durations. With this in mind, the magnetic crustal field regions on Mars are particularly interesting. We focus on ions present within these regions, where changes in magnetic field strength and direction can heat these ions. Since crustal magnetic fields can maintain a trapped particle population it is unclear how efficiently plasma can be built up that can later escape to space. We investigate here two drivers: rotation of the planet and the solar wind pressure. As crustal fields rotate from the wake of the planet to the sub solar point and back, they experience compression and expansion over time scales of ~24 hours. The solar wind pressure on the other hand can cause variations over much shorter time scales (minutes). The effect of these two drivers using a particle tracing simulation that solves the Lorentz force is presented. O+ ions are seeded within the simulation box. The magnetic environment is a linear sum of a dipole field and a solar wind magnetic field. The dipole field represents the magnetic crustal field and the dipole strength is chosen to be consistent with MGS magnetometer observations of Martian crustal field regions. By increasing the solar wind strength the magnetic dipole is compressed. Decreasing solar wind strength allows the dipole to expand. Small magnitude, short time scale variations can be imposed over the top of this larger variation to represent short time scale solar wind variations. Since the purpose of this analysis is to understand the changes of the ion distribution inside the crustal field, simplistic assumptions of the field outside the crustal field can be made. Initial results are presented, with the focus on two main questions: (a) can low energy ions be heated and escape the closed dipole field lines as a result of varying magnetic fields; (b) is the compression and relaxation of the crustal field due to rotation important for the oxygen escape rates when compared to the particle evolution due to high frequency changes in magnetic field and the lifetimes of these ions.

Spacer engineered Trigate SOI TFET: An investigation towards harsh temperature environment applications

NASA Astrophysics Data System (ADS)

Mallikarjunarao; Ranjan, Rajeev; Pradhan, K. P.; Artola, L.; Sahu, P. K.

2016-09-01

In this paper, a novel N-channel Tunnel Field Effect Transistor (TFET) i.e., Trigate Silicon-ON-Insulator (SOI) N-TFET with high-k spacer is proposed for better Sub-threshold swing (SS) and OFF-state current (IOFF) by keeping in mind the sensitivity towards temperature. The proposed model can achieve a Sub-threshold swing less than 35 mV/decade at various temperatures, which is desirable for designing low power CTFET for digital circuit applications. In N-TFET source doping has a significant effect on the ON-state current (ION) level; therefore more electrons will tunnel from source to channel region. High-k Spacer i.e., HfO2 is used to enhance the device performance and also it avoids overlapping of transistors in an integrated circuits (IC's). We have designed a reliable device by performing the temperature analysis on Transfer characteristics, Drain characteristics and also on various performance metrics like ON-state current (ION), OFF-state current (IOFF), ION/IOFF, Trans-conductance (gm), Trans-conductance Generation Factor (TGF), Sub-threshold Swing (SS) to observe the applications towards harsh temperature environment.

Photodetachment dynamics in a time-dependent oscillating electric field

NASA Astrophysics Data System (ADS)

Wang, De-hua; Xu, Qin-feng; Du, Jie

2017-03-01

Using the time-dependent form of closed orbit theory, as developed by Haggerty and Delos [M.R. Haggerty, J.B. Delos, Phys. Rev. A 61, 053406 (2000)], and by Yang and Robicheaux [B.C. Yang, F. Robicheaux, Phys. Rev. A 93, 053413 (2016)], we study the photodetachment dynamics of a hydrogen negative ion in a time-dependent oscillating electric field. Compared to the photodetachment in a static electric field, the photodetachment dynamics of a negative ion in the time-dependent oscillating electric field become much more complicated but more interesting. Since the applied electric field is oscillating with time, the photodetachment cross section of the negative ion in the oscillating electric field is time-dependent. In a time-dependent framework, we put forward an analytical formula for calculating the instantaneous photodetachment cross section of this system. Our study suggests that the instantaneous photodetachment cross section exhibits oscillatory structure, which depends sensitively on the frequency of the oscillating electric field. With increasing frequency of the oscillating electric field, the number of closed orbits increases and the oscillatory structure in the photodetachment cross section becomes much more complicated. The connection between the detached electron's closed orbit with the oscillating cross section is analyzed quantitatively. This study provides a clear and intuitive picture for the photodetachment processes of a negative ion in the presence of an oscillating electric field. We hope that our work will be useful in guiding future experimental research.

High sensitive detection of copper II ions using D-penicillamine-coated gold nanorods based on localized surface plasmon resonance

NASA Astrophysics Data System (ADS)

Hong, Yoochan; Jo, Seongjae; Park, Joohyung; Park, Jinsung; Yang, Jaemoon

2018-05-01

In this paper, we describe the development of a nanoplasmonic biosensor based on the localized surface plasmon resonance (LSPR) effect that enables a sensitive and selective recognition of copper II ions. First, we fabricated the nanoplasmonics as LSPR substrates using gold nanorods (GNR) and the nano-adsorption method. The LSPR sensitivity of the nanoplasmonics was evaluated using various solvents with different refractive indexes. Subsequently, D-penicillamine (DPA)—a chelating agent of copper II ions—was conjugated to the surface of the GNR. The limit of detection (LOD) for the DPA-conjugated nanoplasmonics was 100 pM. Furthermore, selectivity tests were conducted using various divalent cations, and sensitivity tests were conducted on the nanoplasmonics under blood-like environments. Finally, the developed nanoplasmonic biosensor based on GNR shows great potential for the effective recognition of copper II ions, even in human blood conditions.

Correlation between y-type ions observed in ion trap and triple quadrupole mass spectrometers.

PubMed

Sherwood, Carly A; Eastham, Ashley; Lee, Lik Wee; Risler, Jenni; Vitek, Olga; Martin, Daniel B

2009-09-01

Multiple reaction monitoring mass spectrometry (MRM-MS) is a technique for high-sensitivity targeted analysis. In proteomics, MRM-MS can be used to monitor and quantify a peptide based on the production of expected fragment peaks from the selected peptide precursor ion. The choice of which fragment ions to monitor in order to achieve maximum sensitivity in MRM-MS can potentially be guided by existing MS/MS spectra. However, because the majority of discovery experiments are performed on ion trap platforms, there is concern in the field regarding the generalizability of these spectra to MRM-MS on a triple quadrupole instrument. In light of this concern, many operators perform an optimization step to determine the most intense fragments for a target peptide on a triple quadrupole mass spectrometer. We have addressed this issue by targeting, on a triple quadrupole, the top six y-ion peaks from ion trap-derived consensus library spectra for 258 doubly charged peptides from three different sample sets and quantifying the observed elution curves. This analysis revealed a strong correlation between the y-ion peak rank order and relative intensity across platforms. This suggests that y-type ions obtained from ion trap-based library spectra are well-suited for generating MRM-MS assays for triple quadrupoles and that optimization is not required for each target peptide.

Effect of ion-neutral collisions on the evolution of kinetic Alfvén waves in plasmas

NASA Astrophysics Data System (ADS)

Goyal, R.; Sharma, R. P.

2018-03-01

This paper studies the effect of ion-neutral collisions on the propagation of kinetic Alfvén waves (KAWs) in inhomogeneous magnetized plasma. The inhomogeneity in the plasma imposed by background density in a direction transverse as well as parallel to the ambient magnetic field plays a vital role in the localization process. The mass loading of ions takes place due to their collisions with neutral fluid leading to the damping of the KAWs. Numerical analysis of linear KAWs in inhomogeneous magnetized plasma is done for a fixed finite frequency taking into consideration the ion-neutral collisions. There is a prominent effect of collisional damping on the wave localization, wave magnetic field, and frequency spectrum. A semi-analytical technique has been employed to study the magnetic field amplitude decay process and the effect of wave frequency in the range of ion cyclotron frequency on the propagation of waves leading to damping.

Highly Sensitive Aluminium(III) Ion Sensor Based on a Self-assembled Monolayer on a Gold Nanoparticles Modified Screen-printed Carbon Electrode.

PubMed

See, Wong Pooi; Heng, Lee Yook; Nathan, Sheila

2015-01-01

A new approach for the development of a highly sensitive aluminium(III) ion sensor via the preconcentration of aluminium(III) ion with a self-assembled monolayer on a gold nanoparticles modified screen-printed carbon electrode and current mediation by potassium ferricyanide redox behavior during aluminium(III) ion binding has been attempted. A monolayer of mercaptosuccinic acid served as an effective complexation ligand for the preconcentration of trace aluminium; this led to an enhancement of aluminium(III) ion capture and thus improved the sensitivity of the sensor with a detection limit of down to the ppb level. Under the optimum experimental conditions, the sensor exhibited a wide linear dynamic range from 0.041 to 12.4 μM. The lower detection limit of the developed sensor was 0.037 μM (8.90 ppb) using a 10 min preconcentration time. The sensor showed excellent selectivity towards aluminium(III) ion over other interference ions.

On-site Rapid Detection of Trace Non-volatile Inorganic Explosives by Stand-alone Ion Mobility Spectrometry via Acid-enhanced Evaporization

PubMed Central

Peng, Liying; Hua, Lei; Wang, Weiguo; Zhou, Qinghua; Li, Haiyang

2014-01-01

New techniques for the field detection of inorganic improvised explosive devices (IEDs) are urgently developed. Although ion mobility spectrometry (IMS) has been proved to be the most effective method for screening organic explosives, it still faces a major challenge to detect inorganic explosives owing to their low volatilities. Herein, we proposed a strategy for detecting trace inorganic explosives by thermal desorption ion mobility spectrometry (TD-IMS) with sample-to-sample analysis time less than 5 s based on in-situ acidification on the sampling swabs. The responses for typical oxidizers in inorganic explosives, such as KNO3, KClO3 and KClO4 were at least enhanced by a factor of 3000 and their limits of detection were found to be subnanogram. The common organic explosives and their mixtures with inorganic oxidizers were detected, indicating that the acidification process did not affect the detection of organic explosives. Moreover, the typical inorganic explosives such as black powders, firecrackers and match head could be sensitively detected as well. These results demonstrated that this method could be easily employed in the current deployed IMS for on-site sensitive detection of either inorganic explosives or organic ones. PMID:25318960

Investigation of mixed ion fields in the forward direction for 220.5 MeV/u helium ion beams: comparison between water and PMMA targets

NASA Astrophysics Data System (ADS)

Aricò, G.; Gehrke, T.; Jakubek, J.; Gallas, R.; Berke, S.; Jäkel, O.; Mairani, A.; Ferrari, A.; Martišíková, M.

2017-10-01

Currently there is a rising interest in helium ion beams for radiotherapy. For benchmarking of the physical beam models used in treatment planning, there is a need for experimental data on the composition and spatial distribution of mixed ion fields. Of particular interest are the attenuation of the primary helium ion fluence and the build-up of secondary hydrogen ions due to nuclear interactions. The aim of this work was to provide such data with an enhanced precision. Moreover, the validity and limits of the mixed ion field equivalence between water and PMMA targets were investigated. Experiments with a 220.5 MeV/u helium ion pencil beam were performed at the Heidelberg Ion-Beam Therapy Center in Germany. The compact detection system used for ion tracking and identification was solely based on Timepix position-sensitive semiconductor detectors. In comparison to standard techniques, this system is two orders of magnitude smaller, and provides higher precision and flexibility. The numbers of outgoing helium and hydrogen ions per primary helium ion as well as the lateral particle distributions were quantitatively investigated in the forward direction behind water and PMMA targets with 5.2-18 cm water equivalent thickness (WET). Comparing water and PMMA targets with the same WET, we found that significant differences in the amount of outgoing helium and hydrogen ions and in the lateral particle distributions arise for target thicknesses above 10 cm WET. The experimental results concerning hydrogen ions emerging from the targets were reproduced reasonably well by Monte Carlo simulations using the FLUKA code. Concerning the amount of outgoing helium ions, significant differences of 3-15% were found between experiments and simulations. We conclude that if PMMA is used in place of water in dosimetry, differences in the dose distributions could arise close to the edges of the field, in particular for deep seated targets. The results presented in this publication are part of: Arico’, Giulia: Ion Spectroscopy for improvement of the Physical Beam Model for Therapy Planning in Ion Beam Therapy, PhD Thesis, University of Heidelberg, 2016.

Magnetic and optical effects in TiO2 based dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Kannan U., M.; Jammalamadaka, S. Narayana

2018-04-01

We report on the magnetic effects on the solar cell efficiency of TiO2 based dye sensitized solar cells (DSSC). The strong spin orbit coupling of rare earth Ho3+ ions introduced by the addition of Ho2O3 into the photoanode resulted in a 28% enhancement in the power conversion efficiency of DSSC. Such an enhancement in the efficiency may be attributed to the improved lifetime of photo generated excitons as a result of the accelerated intersystem crossing phenomenon. This observation is supported by our photoluminescence (PL) measurements where we could observe a decrease in the photo emission intensity with the addition of Ho2O3. In addition, we have used a low magnetic field of 100 Oe to further enhance the overall efficiency to 5.6%, which in turn proves that the Lorentz force plays a significant role in magnetic field controlled charge transport in DSSC. Finally, we have carried out a transfer matrix model based theoretical simulation for studying the optical properties of the multilayer device stack.

Assimilation of thermospheric measurements for ionosphere-thermosphere state estimation

NASA Astrophysics Data System (ADS)

Miladinovich, Daniel S.; Datta-Barua, Seebany; Bust, Gary S.; Makela, Jonathan J.

2016-12-01

We develop a method that uses data assimilation to estimate ionospheric-thermospheric (IT) states during midlatitude nighttime storm conditions. The algorithm Estimating Model Parameters from Ionospheric Reverse Engineering (EMPIRE) uses time-varying electron densities in the F region, derived primarily from total electron content data, to estimate two drivers of the IT: neutral winds and electric potential. A Kalman filter is used to update background models based on ingested plasma densities and neutral wind measurements. This is the first time a Kalman filtering technique is used with the EMPIRE algorithm and the first time neutral wind measurements from 630.0 nm Fabry-Perot interferometers (FPIs) are ingested to improve estimates of storm time ion drifts and neutral winds. The effects of assimilating remotely sensed neutral winds from FPI observations are studied by comparing results of ingesting: electron densities (N) only, N plus half the measurements from a single FPI, and then N plus all of the FPI data. While estimates of ion drifts and neutral winds based on N give estimates similar to the background models, this study's results show that ingestion of the FPI data can significantly change neutral wind and ion drift estimation away from background models. In particular, once neutral winds are ingested, estimated neutral winds agree more with validation wind data, and estimated ion drifts in the magnetic field-parallel direction are more sensitive to ingestion than the field-perpendicular zonal and meridional directions. Also, data assimilation with FPI measurements helps provide insight into the effects of contamination on 630.0 nm emissions experienced during geomagnetic storms.

Toroidal ripple transport of beam ions in the mega-ampere spherical tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

McClements, K. G.; Hole, M. J.

The transport of injected beam ions due to toroidal magnetic field ripple in the mega-ampere spherical tokamak (MAST) is quantified using a full orbit particle tracking code, with collisional slowing-down and pitch-angle scattering by electrons and bulk ions taken into account. It is shown that the level of ripple losses is generally rather low, although it depends sensitively on the major radius of the outer midplane plasma edge; for typical values of this parameter in MAST plasmas, the reduction in beam heating power due specifically to ripple transport is less than 1%, and the ripple contribution to beam ion diffusivitymore » is of the order of 0.1 m{sup 2} s{sup -1} or less. It is concluded that ripple effects make only a small contribution to anomalous transport rates that have been invoked to account for measured neutron rates and plasma stored energies in some MAST discharges. Delayed (non-prompt) losses are shown to occur close to the outer midplane, suggesting that banana-drift diffusion is the most likely cause of the ripple-induced losses.« less

MOSFET detectors in quality assurance of tomotherapy treatments.

PubMed

Cherpak, Amanda; Studinski, Ryan C N; Cygler, Joanna E

2008-02-01

The purpose of this work was to characterize metal oxide semiconductor field-effect transistors (MOSFETs) in a 6 MV conventional linac and investigate their use for quality assurance of radiotherapy treatments with a tomotherapy Hi-Art unit. High sensitivity and standard sensitivity MOSFETs were first calibrated and then tested for reproducibility, field size dependence, and accuracy of measuring surface dose in a 6 MV beam as well as in a tomotherapy Hi-Art unit. In vivo measurements were performed on both a RANDO phantom and several head and neck cancer patients treated with tomotherapy and compared to TLD measurements and treatment plan doses to evaluate the performance of MOSFETs in a high gradient radiation field. The average calibration factor found was 0.345+/-2.5%cGy/mV for the high sensitivity MOSFETs tested and 0.901+/-2.4%cGy/mV for the standard sensitivity MOSFETs. MOSFET measured surface doses had an average agreement with ion chamber measurements of 1.55% for the high sensitivity MOSFET and 5.23% for the standard sensitivity MOSFET when averaged over all trials and field sizes tested. No significant dependence on field size was found for the standard sensitivity MOSFETs, however a maximum difference of 5.34% was found for the high sensitivity MOSFET calibration factors in the field sizes tested. Measurements made with MOSFETS on head and neck patients treated on a tomotherapy Hi-Art unit had an average agreement of (3.26+/-0.03)% with TLD measurements, however the average of the absolute difference between the MOSFET measurements and the treatment plan skin doses was (12.2+/-7.5)%. The MOSFET measured patient skin doses also had good reproducibility, with inter-fraction deviations ranging from 1.4% to 6.6%. Similar results were found from trials using a RANDO phantom. The MOSFETs performed well when used in the tomotherapy Hi-Art unit and did not increase the overall treatment set-up time when used for patient measurements. It was found that MOSFETs are suitable detectors for surface dose measurements in both conventional beam and tomotherapy treatments and they can provide valuable skin dose information in areas where the treatment planning system may not be accurate.

Investigation of Ion Transmission Effects on Intact Protein Quantification in a Triple Quadrupole Mass Spectrometer

NASA Astrophysics Data System (ADS)

Wang, Evelyn H.; Appulage, Dananjaya Kalu; McAllister, Erin A.; Schug, Kevin A.

2017-09-01

Recently, direct intact protein quantitation using triple quadrupole mass spectrometry (QqQ-MS) and multiple reaction monitoring (MRM) was demonstrated (J. Am. Soc. Mass Spectrom. 27, 886-896 (2016)). Even though QqQ-MS is known to provide extraordinary detection sensitivity for quantitative analysis, we found that intact proteins exhibited a less than 5% ion transmission from the first quadrupole to the third quadrupole mass analyzer in the presence of zero collision energy (ZCE). With the goal to enhance intact protein quantitation sensitivity, ion scattering effects, proton transfer effects, and mass filter resolution widths were examined for their contributions to the lost signal. Protein standards myoglobin and ubiquitin along with small molecules reserpine and vancomycin were analyzed together with various collision induced dissociation (CID) gases (N2, He, and Ar) at different gas pressures. Mass resolution settings played a significant role in reducing ion transmission signal. By narrowing the mass resolution window by 0.35 m/z on each side, roughly 75%-90% of the ion signal was lost. The multiply charged proteins experienced additional proton transfer effects, corresponding to 10-fold signal reduction. A study of increased sensitivity of the method was also conducted with various MRM summation techniques. Although the degree of enhancement was analyte-dependent, an up to 17-fold increase in sensitivity was observed for ubiquitin using a summation of multiple MRM transitions. Biological matrix, human urine, and equine plasma were spiked with proteins to demonstrate the specificity of the method. This study provides additional insight into optimizing the use and sensitivity of QqQ-MS for intact protein quantification. [Figure not available: see fulltext.

Effects of Stopping Ions and LET Fluctuations on Soft Error Rate Prediction.

DOE PAGES

Weeden-Wright, S. L.; King, Michael Patrick; Hooten, N. C.; ...

2015-02-01

Variability in energy deposition from stopping ions and LET fluctuations is quantified for specific radiation environments. When compared to predictions using average LET via CREME96, LET fluctuations lead to an order-of-magnitude difference in effective flux and a nearly 4x decrease in predicted soft error rate (SER) in an example calculation performed on a commercial 65 nm SRAM. The large LET fluctuations reported here will be even greater for the smaller sensitive volumes that are characteristic of highly scaled technologies. End-of-range effects of stopping ions do not lead to significant inaccuracies in radiation environments with low solar activity unless the sensitivevolumemore » thickness is 100 μm or greater. In contrast, end-of-range effects for stopping ions lead to significant inaccuracies for sensitive- volume thicknesses less than 10 μm in radiation environments with high solar activity.« less

Low-Pressure, Field-Ionizing Mass Spectrometer

NASA Technical Reports Server (NTRS)

Hartley, Frank; Smith, Steven

2009-01-01

A small mass spectrometer utilizing a miniature field ionization source is now undergoing development. It is designed for use in a variety of applications in which there are requirements for a lightweight, low-power-consumption instrument that can analyze the masses of a wide variety of molecules and ions. The device can operate without need for a high-vacuum, carrier-gas feed radioactive ionizing source, or thermal ionizer. This mass spectrometer can operate either in the natural vacuum of outer space or on Earth at any ambient pressure below 50 torr (below about 6.7 kPa) - a partial vacuum that can easily be reached by use of a small sampling pump. This mass spectrometer also has a large dynamic range - from singly charged small gas ions to deoxyribonucleic acid (DNA) fragments larger than 104 atomic mass units - with sensitivity adequate for detecting some molecules and ions at relative abundances of less than one part per billion. This instrument (see figure) includes a field ionizer integrated with a rotating-field mass spectrometer (RFMS). The field ionizer effects ionization of a type characterized as "soft" in the art because it does not fragment molecules or initiate avalanche arcing. What makes the "soft" ionization mode possible is that the distance between the ionizing electrodes is less than mean free path for ions at the maximum anticipated operating pressure, so that the ionizer always operates on the non-breakdown side of the applicable Paschen curve (a standard plot of breakdown potential on the ordinate and pressure electrode separation on the abscissa). The field ionizer in this instrument is fabricated by micromachining a submicron-thick membrane out of an electrically nonconductive substrate, coating the membrane on both sides to form electrodes, then micromachining small holes through the electrodes and membrane. Because of the submicron electrode separation, even a potential of only 1 V applied between the electrodes gives rise to an electric field with a strength of in excess of a megavolt per meter strong enough to ionize any gas molecules passing through the holes. An accelerator grid and an electrostatic deflector focus the ions from the field ionizer into the rotating-field cell of the RFMS. The potentials applied to the electrodes of the cell to generate the rotating electric field typically range from 1 to 13 V. The ions travel in well-defined helices within this cell, after which they are collected in a Faraday cup. The mass of most of the molecules reaching the Faraday cup decreases with increasing frequency of rotation of the electric field in the cell. Therefore, the frequency of rotation of the electric field is made to vary in order to scan through a desired range of ion masses: For example, lightweight gas molecules are scanned at frequencies in the megahertz range, while DNA and other large organic molecules are scanned at kilohertz frequencies.

Recent Developments in Microwave Ion Clocks

NASA Astrophysics Data System (ADS)

Prestage, John D.; Tjoelker, Robert L.; Maleki, Lute

We review the development of microwave-frequency standards based on trapped ions. Following two distinct paths, microwave ion clocks have evolved greatly in the last twenty years since the earliest Paul-trap-based units. Laser-cooled ion frequency standards reduce the second-order Doppler shift from ion micromotion and thermal secular motion achieving good signal-to-noise ratios via cycling transitions where as many as ~10^8 photons per second per ion may be scattered. Today, laser-cooled ion standards are based on linear Paul traps which hold ions near the node line of the trapping electric field, minimizing micromotion at the trapping-field frequency and the consequent second-order Doppler frequency shift. These quadrupole (radial) field traps tightly confine tens of ions to a crystalline single-line structure. As more ions are trapped, space charge forces some ions away from the node-line axis and the second-order Doppler effect grows larger, even at negligibly small secular temperatures. Buffer-gas-cooled clocks rely on large numbers of ions, typically ~10^7, optically pumped by a discharge lamp at a scattering rate of a few photons per second per ion. To reduce the second-order Doppler shift from space charge repulsion of ions from the trap node line, novel multipole ion traps are now being developed where ions are weakly bound with confining fields that are effectively zero through the trap interior and grow rapidly near the trap electrode ``walls''.

Ion temperature effects on magnetotail Alfvén wave propagation and electron energization: ION TEMPERATURE EFFECTS ON ALFVÉN WAVES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Damiano, P. A.; Johnson, J. R.; Chaston, C. C.

2015-07-01

A new 2-D self-consistent hybrid gyrofluid-kinetic electron model in dipolar coordinates is presented and used to simulate dispersive-scale Alfvén wave pulse propagation from the equator to the ionosphere along an L = 10 magnetic field line. The model is an extension of the hybrid MHD-kinetic electron model that incorporates ion Larmor radius corrections via the kinetic fluid model of Cheng and Johnson (1999). It is found that consideration of a realistic ion to electron temperature ratio decreases the propagation time of the wave from the plasma sheet to the ionosphere by several seconds relative to a ρi=0 case (which alsomore » implies shorter timing for a substorm onset signal) and leads to significant dispersion of wave energy perpendicular to the ambient magnetic field. Additionally, ion temperature effects reduce the parallel current and electron energization all along the field line for the same magnitude perpendicular electric field perturbation.« less

New Hypotesis of Combined Magnetic Field Action on Gravitropic Reaction

NASA Astrophysics Data System (ADS)

Bogatina, Nina; Sheykina, Nadezhda

2012-07-01

It is shown in the work that all biological effects of combined magnetic field (CMF) may be explained if we take into account the electrical field of cell membrane. We noticed before, that the pressure of starch gain and of calcium ion on membrane were of the one and the same order ~ 10-5 N/ m2. Such a small pressure was supposed not enough to lead to any biological effects. But if we take into account the pressure of calcium ion in electric field of membrane, that is more by many orders, we can see that even very small pressure adding may change the picture. New channels for Ca2+ ions may be opened and the size of channels may be increased. It is shown in the work that such a hypothesis may explain all biological effects of CMF on gravitropic reaction of roots obtained by us before. That were negative gravitropism of roots in CMF tuned on cyclotron resonance of Ca2+ ions, starch gains distribution in cell, noise effects, the threshold effect of static magnetic field and so on.

Magnetic Compensation for Second-Order Doppler Shift in LITS

NASA Technical Reports Server (NTRS)

Burt, Eric; Tjoelker, Robert

2008-01-01

The uncertainty in the frequency of a linear-ion-trap frequency standard (LITS) can be reduced substantially by use of a very small magnetic inhomogeneity tailored to compensate for the residual second-order Doppler shift. An effect associated with the relativistic time dilatation, one cause of the second-order Doppler shift, is ion motion that is attributable to the trapping radio-frequency (RF)electromagnetic field used to trap ions. The second-order Doppler shift is reduced by using a multi-pole trap; however it is still the largest source of systematic frequency shift in the latest generation of LITSs, which are among the most stable clocks in the world. The present compensation scheme reduces the frequency instability of the affected LITS to about a tenth of its previous value. The basic principles of prior generation LITSs were discussed in several prior NASA Tech Briefs articles. Below are recapitulated only those items of basic information necessary to place the present development in context. A LITS includes a microwave local oscillator, the frequency of which is stabilized by comparison with the frequency of the ground state hyperfine transition of 199Hg+ ions. The comparison involves a combination of optical and microwave excitation and interrogation of the ions in a linear ion trap in the presence of a nominally uniform magnetic field. In the current version of the LITS, there are two connected traps (see figure): (1) a quadrupole trap wherein the optical excitation and measurement take place and (2) a 12-pole trap (denoted the resonance trap), wherein the microwave interrogation takes place. The ions are initially loaded into the quadrupole trap and are thereafter shuttled between the two traps. Shuttling ions into the resonance trap allows sensitive microwave interrogation to take place well away from loading interference. The axial magnetic field for the resonance trap is generated by an electric current in a finely wound wire coil surrounded by magnetic shields. In the quadrupole and 12-pole traps, the potentials are produced by RF voltages applied to even numbers (4 and 12, respectively) of parallel rods equally spaced around a circle. The polarity of the voltage on each rod is opposite that of the voltage on the adjacent rod. As a result, the amplitude of the RF trapping field is zero along the centerline and increases, with radius, to a maximum value near the rods.

Ion Selectivity in the KcsA Potassium Channel from the Perspective of the Ion Binding Site

PubMed Central

Dixit, Purushottam D.; Merchant, Safir; Asthagiri, D.

2009-01-01

To understand the thermodynamic exclusion of Na+ relative to K+ from the S2 site of the selectivity filter, the distribution PX(ɛ) (X = K+ or Na+) of the binding energy (ɛ) of the ion with the channel is analyzed using the potential distribution theorem. By expressing the excess chemical potential of the ion as a sum of mean-field 〈ɛ〉 and fluctuation μexflux,X contributions, we find that selectivity arises from a higher value of μflux,Na+ex relative to μflux,K+ex. To understand the role of site-site interactions on μexflux,X, we decompose PX(ɛ) into n-dependent distributions, where n is the number of ion-coordinating ligands within a distance λ from the ion. For λ comparable to typical ion-oxygen bond distances, investigations building on this multistate model reveal an inverse correlation between favorable ion-site and site-site interactions: the ion-coordination states that most influence the thermodynamics of the ion are also those for which the binding site is energetically less strained and vice versa. This correlation motivates understanding entropic effects in ion binding to the site and leads to the finding that μexflux,X is directly proportional to the average site-site interaction energy, a quantity that is sensitive to the chemical type of the ligand coordinating the ion. Increasing the coordination number around Na+ only partially accounts for the observed magnitude of selectivity; acknowledging the chemical type of the ion-coordinating ligand is essential. PMID:19289040

Gallium nitride junction field-effect transistor

DOEpatents

Zolper, John C.; Shul, Randy J.

1999-01-01

An all-ion implanted gallium-nitride (GaN) junction field-effect transistor (JFET) and method of making the same. Also disclosed are various ion implants, both n- and p-type, together with or without phosphorous co-implantation, in selected III-V semiconductor materials.

Theoretical studies of the dependence of EPR parameters on local structure for the tetragonal Er(3+) centres in YVO4 and ScVO4.

PubMed

Chai, Rui-Peng; Hao, Dan-Hui; Kuang, Xiao-Yu; Liang, Liang

2015-11-05

The dependences of the EPR parameters on the local distortion parameters Δθ and ΔR as well as the crystal-field parameters have been studied by diagonalizing the 364×364 complete energy matrices for a tetragonal Er(3+) centre in the YVO4 and ScVO4 crystals. The results show that the local distortion angle Δθ and the fourth-order crystal-field parameter Ā4 are most sensitive to the EPR g-factors g// and g⊥, whereas the local distortion length ΔR and the second-order parameter Ā2 are less sensitive to the g-factors. Furthermore, we found that the abnormal EPR g-factors for the Er(3+) ion in the ScVO4 may be ascribed to the stronger nephelauxetic effect and covalent bonding effect, as a result of an expanded local distortion for the Er(3+) centre in the ScVO4 crystal. Simultaneously, the contributions of the J-J mixing effects from the terms of excited states to the EPR parameters have been evaluated quantitatively. Copyright © 2015 Elsevier B.V. All rights reserved.

Advanced space propulsion thruster research

NASA Technical Reports Server (NTRS)

Wilbur, P. J.

1981-01-01

Experiments showed that stray magnetic fields can adversely affect the capacity of a hollow cathode neutralizer to couple to an ion beam. Magnetic field strength at the neutralizer cathode orifice is a crucial factor influencing the coupling voltage. The effects of electrostatic accelerator grid aperture diameters on the ion current extraction capabilities were examined experimentally to describe the divergence, deflection, and current extraction capabilities of grids with the screen and accelerator apertures displaced relative to one another. Experiments performed in orificed, mercury hollow cathodes support the model of field enhanced thermionic electron mission from cathode inserts. Tests supported the validity of a thermal model of the cathode insert. A theoretical justification of a Saha equation model relating cathode plasma properties is presented. Experiments suggest that ion loss rates to discharge chamber walls can be controlled. A series of new discharge chamber magnetic field configurations were generated in the flexible magnetic field thruster and their effect on performance was examined. A technique used in the thruster to measure ion currents to discharge chamber walls is described. Using these ion currents the fraction of ions produced that are extracted from the discharge chamber and the energy cost of plasma ions are computed.

Selective ion accumulation in an ICP/ITMS using a filtered noise field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eiden, G.C.; Barinaga, C.J.; Koppenaal, D.W.

1995-12-31

Selective accumulation of ions in an ion trap mass spectrometer (ITMS) has been characterized using both single frequency and broadband resonant excitation. The goal of this work is to enhance selective accumulation of ions from plasmas and other external ion sources. The charge capacity of the ITMS is 10{sup 6} to 10{sup 7} ions, although the mass spectrum is distorted at much lower space charge. Detection of trace ions necessitates selective detection schemes such as selective trapping or optical detection. The authors report results of selective trapping studies for Sr, Y, and Zr solutions (100 ppb Y and 1 ppbmore » each Sr, Zr). {open_quotes}Background{close_quotes} ions in mass channels adjacent to the channel of interest is a worst case situation with respect to selective ejection and abundance sensitivity. Real samples will often have matrix ion m/z values much further removed from the m/z of the ions of interest. Thus, the authors also give results for a multielement solution. Ions from an inductively coupled plasma ion source are endcap injected into the ITMS. Broadband waveforms were generated by an HST-1000 (Teledyne MEC) instrument, using the filtered noise field (FNF) method. The experiment is controlled by the ITMS electronics and ICMS software. The sequence of experimental events is: ion injection at q{sub z} = 0.4 (typical), collisionally cool ions, set trapping potential for resonant excitation (q{sub z} = 0.2 to 0.6), analysis rf ramp.« less

Effect of radial plasma transport at the magnetic throat on axial ion beam formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yunchao, E-mail: yunchao.zhang@anu.edu.au; Charles, Christine; Boswell, Rod

2016-08-15

Correlation between radial plasma transport and formation of an axial ion beam has been investigated in a helicon plasma reactor implemented with a convergent-divergent magnetic nozzle. The plasma discharge is sustained under a high magnetic field mode and a low magnetic field mode for which the electron energy probability function, the plasma density, the plasma potential, and the electron temperature are measured at the magnetic throat, and the two field modes show different radial parametric behaviors. Although an axial potential drop occurs in the plasma source for both field modes, an ion beam is only observed in the high fieldmore » mode while not in the low field mode. The transport of energetic ions is characterized downstream of the plasma source using the delimited ion current and nonlocal ion current. A decay of ion beam strength is also observed in the diffusion chamber.« less

A novel EIS field effect structures coated with TESUD-PPy-PVC-dibromoaza[7]helicene matrix for potassium ions detection.

PubMed

Tounsi, Moncef; Ben Braiek, Mourad; Barhoumi, Houcine; Baraket, Abdoullatif; Lee, Michael; Zine, Nadia; Maaref, Abderrazak; Errachid, Abdelhamid

2016-04-01

In this work, we describe the development of new Aza[7]helicene-containing PVC-based membranes for the K(+) ions quantification. Here, silicon nitride-based structures (Si-p/SiO2/Si3N4) were developed and the surface was activated, functionalized with an aldehyde-silane (11-(Triethoxysilyl)undecanal (TESUD)), functionalized with polypyrrole (PPy), and coated with the polyvinylchloride (PVC)-membrane containing the Aza[7]helicene as ionophore. All stages of functionalization process have been thoroughly studied by contact angle measurements (CAMs) and atomic force microscopy (AFM). The developed ion-selective electrode (ISE) was then applied using electrochemical impedance spectroscopy (EIS) for the detection of potassium ions. A linear range was observed between 1.0 × 10(-8) M to 1.0 × 10(-3) M and a detection limit of 1.0 × 10(-8) M was observed. The EIS results have showed a good sensitivity to potassium ion using this novel technique. The target helicene exhibited good solubility and excellent thermal stability with a high decomposition temperature (Td > 300 °C) and it indicates that helicene may be a promising material as ionophore for ion-selective electrodes (ISEs) elaboration. Copyright © 2016 Elsevier B.V. All rights reserved.

Calcium Signaling during Salt Stress and in the Regulation of Ion Homeostasis.

PubMed

Manishankar, P; Wang, N; Köster, P; Alatar, A A; Kudla, J

2018-05-24

Soil composition largely defines the living conditions of plants and represents one of their most relevant, dynamic and complex environmental cues. The effective concentrations of many either tolerated or essential ions and compounds in the soil usually differ from the optimum that would be most suitable for plants. In this regard, salinity - caused by excess of NaCl - represents a widespread adverse growth condition but also shortage of ions like K+, NO3- and Fe2+ restrains plant growth. During the past years many components and mechanisms that function in the sensing and establishment of ion homeostasis have been identified and characterized. Here, we reflect on recent insights that extended our understanding of components and mechanisms, which govern and fine-tune plant salt stress tolerance and ion homeostasis. We put special emphasis on mechanisms that allow for interconnection of the salt overly sensitivity pathway with plant development and discuss newly emerging functions of Ca2+ signaling in salinity tolerance. Moreover, we review and discuss accumulating evidence for a central and unifying role of Ca2+ signaling and Ca2+ dependent protein phosphorylation in regulating sensing, uptake, transport and storage processes of various ions. Finally, based on this cross-field inventory, we deduce emerging concepts and arising questions for future research.

Differential Impact of the Monovalent Ions Li+, Na+, K+, and Rb+ on DNA Conformational Properties

PubMed Central

2015-01-01

The present report demonstrates that the conformational properties of DNA in solution are sensitive to the type of monovalent ion. Results are based on the ability of a polarizable force field using the classical Drude oscillator to reproduce experimental solution X-ray scattering data more accurately than two nonpolarizable DNA models, AMBER Parmbsc0 and CHARMM36. The polarizable model is then used to calculate scattering profiles of DNA in the presence of four different monovalent salts, LiCl, NaCl, KCl, and RbCl, showing the conformational properties of DNA to vary as a function of ion type, with that effect being sequence-dependent. The primary conformational mode associated with the variations is contraction of the DNA minor groove width with decreasing cation size. These results indicate that the Drude polarizable model provides a more realistic representation of ion–DNA interactions than additive models that may lead to a new level of understanding of the physical mechanisms driving salt-mediated biological processes involving nucleic acids. PMID:25580188

Optical Measurements of Strong Radio-Frequency Fields Using Rydberg Atoms

NASA Astrophysics Data System (ADS)

Miller, Stephanie Anne

There has recently been an initiative toward establishing atomic measurement standards for field quantities, including radio-frequency, millimeter-wave, and micro-wave electric fields. Current measurement standards are obtained using dipole antennas, which are fundamentally limited in frequency bandwidth (set by the physical size of the antenna) and accuracy (due to the metal perturbing the field during the measurement). Establishing an atomic standard rectifies these problems. My thesis work contributes to an ongoing effort towards establishing the viability of using Rydberg electromagnetically induced transparency (EIT) to perform atom-based measurements of radio-frequency (RF) fields over a wide range of frequencies and field strengths, focusing on strong-field measurements. Rydberg atoms are atoms with an electron excited to a high principal quantum number, resulting in a high sensitivity to an applied field. A model based on Floquet theory is implemented to accurately describe the observed atomic energy level shifts from which information about the field is extracted. Additionally, the effects due to the different electric field domains within the measurement volume are accurately modeled. Absolute atomic measurements of fields up to 296 V/m within a +/-0.35% relative uncertainty are demonstrated. This is the strongest field measured at the time of data publication. Moreover, the uncertainty is over an order of magnitude better than that of current standards. A vacuum chamber setup that I implemented during my graduate studies is presented and its unique components are detailed. In this chamber, cold-atom samples are generated and Rydberg atoms are optically excited within the ground-state sample. The Rydberg ion detection and imaging procedure are discussed, particularly the high magnification that the system provides. By analyzing the position of the ions, the spatial correlation g(2) (r) of Rydberg-atom distributions can be extracted. Aside from ion detection, EIT is implemented in the cold-atom samples. By measuring the timing of the probe photons exiting the EIT medium, the temporal correlation function g(2)(tau) can be extracted, yielding information about the timing between two different arbitrary photons. An experimental goal using this setup is to look at g(2)(tau) in conjunction with g(2)(r) for Rydberg atoms. Progress and preliminary measurements of ion detection and EIT spectra are presented including observed qualitative behaviors.

Neutral winds and electric fields from model studies using reduced ionograms

NASA Technical Reports Server (NTRS)

Baran, D. E.

1974-01-01

A relationship between the vertical component of the ion velocity and electron density profiles derived from reduced ionograms is developed. Methods for determining the horizontal components of the neutral winds and electric fields by using this relationship and making use of the variations of the inclinations and declinations of the earth's magnetic field are presented. The effects that electric fields have on the neutral wind calculations are estimated to be small but not second order. Seasonal and latitudinal variations of the calculated neutral winds are presented. From the calculated neutral winds a new set of neutral pressure gradients is determined. The new pressure gradients are compared with those generated from several static neutral atmospheric models. Sensitivity factors relating the pressure gradients and neutral winds are calculated and these indicate that mode coupling and harmonic generation are important to studies which assume linearized theories.

Microelectrode array measurement of potassium ion channel remodeling on the field action potential duration in rapid atrial pacing rabbits model.

PubMed

Sun, Juan; Yan, Huang; Wugeti, Najina; Guo, Yujun; Zhang, Ling; Ma, Mei; Guo, Xingui; Jiao, Changan; Xu, Wenli; Li, Tianqi

2015-01-01

Atrial fibrillation (AF) arises from abnormalities in atrial structure and electrical activity. Microelectrode arrays (MEA) is a real-time, nondestructive measurement of the resting and action potential signal, from myocardial cells, to the peripheral circuit of electrophysiological activity. This study examined the field action potential duration (fAPD) of the right atrial appendage (RAA) by MEA in rapid atrial pacing (RAP) in the right atrium of rabbits. In addition, this study also investigated the effect of potassium ion channel blockers on fAPD. 40 New Zealand white rabbits of either sex were randomly divided into 3 groups: 1) the control, 2) potassium ion channel blocker (TEA, 4-Ap and BaCl2), and 3) amiodarone groups. The hearts were quickly removed and right atrial appendage sectioned (slice thickness 500 μm). Each slice was perfused with Tyrode's solution and continuously stimulated for 30 minutes. Sections from the control group were superfused with Tyrode's solution for 10 minutes, while the blocker groups and amiodarone were both treated with their respective compounds for 10 minutes each. The fAPD of RAA and action field action potential morphology were measured using MEA. In non-pace (control) groups, fAPD was 188.33 ± 18.29 ms after Tyrode's solution superfusion, and 173.91 ± 6.83 ms after RAP. In pace/potassium ion channel groups, TEA and BaCl2 superfusion prolonged atrial field action potential (fAPD) (control vs blocker: 176.67 ± 8.66 ms vs 196.11 ± 10.76 ms, 182.22 ± 12.87 ms vs 191.11 ± 13.09 ms with TEA and BaCl2 superfusion, respectively, P < 0.05). 4-AP superfusion significantly prolonged FAPD. In pace/amiodarone groups, 4-Ap superfusion extended fAPD. MEA was a sensitive and stable reporter for the measurement of the tissue action potential in animal heart slices. After superfusing potassium ion channel blockers, fAPD was prolonged. These results suggest that Ito, IKur and IK1 remodel and mediate RAP-induced atrial electrical remodeling. Amiodarone alter potassium ion channel activity (Ito, IKur, IK1 and IKs), shortening fAPD.

Plasma research in electric propulsion at Colorado State University

NASA Technical Reports Server (NTRS)

Wilbur, P. J.; Kaufman, H. R.

1976-01-01

The effect of electron bombardment ion thruster magnetic field configurations on the uniformity of the plasma density and the ion beam current density are discussed. The optimum configuration is a right circular cylinder which has significant fields at its outer radii and one end but is nearly field free within the cylinder and at the extraction grid end. The production and loss of the doubly charged ions which effect sputtering damage within thrusters are modeled and the model is verified for the mercury propellant case. Electron bombardment of singly charged ions is found to be the dominant double ion production mechanism. The low density plasma (approx. one million elec/cubic centimeter which exists in the region outside of the beam of thrust producing ions which are drawn from the discharge chamber is discussed. This plasma is modeled by assuming the ions contained in it are generated by a charge exchange process in the ion beam itself. The theoretical predictions of this model are shown to agree with experimental measurements.

Effect of magnetic field configuration on the multiply charged ion and plume characteristics in Hall thruster plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Holak; Lim, Youbong; Choe, Wonho, E-mail: wchoe@kaist.ac.kr

2015-04-13

Multiply charged ions and plume characteristics in Hall thruster plasmas are investigated with regard to magnetic field configuration. Differences in the plume shape and the fraction of ions with different charge states are demonstrated by the counter-current and co-current magnetic field configurations, respectively. The significantly larger number of multiply charged and higher charge state ions including Xe{sup 4+} are observed in the co-current configuration than in the counter-current configuration. The large fraction of multiply charged ions and high ion currents in this experiment may be related to the strong electron confinement, which is due to the strong magnetic mirror effectmore » in the co-current magnetic field configuration.« less

Curing behavior and reaction kinetics of binder resins for 3D-printing investigated by dielectric analysis (DEA)

NASA Astrophysics Data System (ADS)

Möginger, B.; Kehret, L.; Hausnerova, B.; Steinhaus, J.

2016-05-01

3D-Printing is an efficient method in the field of additive manufacturing. In order to optimize the properties of manufactured parts it is essential to adapt the curing behavior of the resin systems with respect to the requirements. Thus, effects of resin composition, e.g. due to different additives such as thickener and curing agents, on the curing behavior have to be known. As the resin transfers from a liquid to a solid glass the time dependent ion viscosity was measured using DEA with flat IDEX sensors. This allows for a sensitive measurement of resin changes as the ion viscosity changes two to four decades. The investigated resin systems are based on the monomers styrene and HEMA. To account for the effects of copolymerization in the calculation of the reaction kinetics it was assumed that the reaction can be considered as a homo-polymerization having a reaction order n≠1. Then the measured ion viscosity curves are fitted with the solution of the reactions kinetics - the time dependent degree of conversion (DC-function) - for times exceeding the initiation phase representing the primary curing. The measured ion viscosity curves can nicely be fitted with the DC-function and the determined fit parameters distinguish distinctly between the investigated resin compositions.

Breaking through the false coincidence barrier in electron–ion coincidence experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Osborn, David L.; Hayden, Carl C.; Hemberger, Patrick

Photoelectron Photoion Coincidence (PEPICO) spectroscopy holds the promise of a universal, isomer-selective, and sensitive analytical technique for time-resolved quantitative analysis of bimolecular chemical reactions. Unfortunately, its low dynamic range of ~10 3 has largely precluded its use for this purpose, where a dynamic range of at least 10 5 is generally required. This limitation is due to the false coincidence background common to all coincidence experiments, especially at high count rates. Electron/ion pairs emanating from separate ionization events but arriving within the ion time of flight (TOF) range of interest constitute the false coincidence background. Although this background has uniformmore » intensity at every m/z value, the Poisson scatter in the false coincidence background obscures small signals. In this paper, temporal ion deflection coupled with a position-sensitive ion detector enables suppression of the false coincidence background, increasing the dynamic range in the PEPICO TOF mass spectrum by 2–3 orders of magnitude. The ions experience a time-dependent electric deflection field at a well-defined fraction of their time of flight. This deflection defines an m/z- and ionization-time dependent ion impact position for true coincidences, whereas false coincidences appear randomly outside this region and can be efficiently suppressed. When cold argon clusters are ionized, false coincidence suppression allows us to observe species up to Ar 9 +, whereas Ar 4 + is the largest observable cluster under traditional operation. As a result, this advance provides mass-selected photoelectron spectra for fast, high sensitivity quantitative analysis of reacting systems.« less

Breaking through the false coincidence barrier in electron–ion coincidence experiments

DOE PAGES

Osborn, David L.; Hayden, Carl C.; Hemberger, Patrick; ...

2016-10-31

Photoelectron Photoion Coincidence (PEPICO) spectroscopy holds the promise of a universal, isomer-selective, and sensitive analytical technique for time-resolved quantitative analysis of bimolecular chemical reactions. Unfortunately, its low dynamic range of ~10 3 has largely precluded its use for this purpose, where a dynamic range of at least 10 5 is generally required. This limitation is due to the false coincidence background common to all coincidence experiments, especially at high count rates. Electron/ion pairs emanating from separate ionization events but arriving within the ion time of flight (TOF) range of interest constitute the false coincidence background. Although this background has uniformmore » intensity at every m/z value, the Poisson scatter in the false coincidence background obscures small signals. In this paper, temporal ion deflection coupled with a position-sensitive ion detector enables suppression of the false coincidence background, increasing the dynamic range in the PEPICO TOF mass spectrum by 2–3 orders of magnitude. The ions experience a time-dependent electric deflection field at a well-defined fraction of their time of flight. This deflection defines an m/z- and ionization-time dependent ion impact position for true coincidences, whereas false coincidences appear randomly outside this region and can be efficiently suppressed. When cold argon clusters are ionized, false coincidence suppression allows us to observe species up to Ar 9 +, whereas Ar 4 + is the largest observable cluster under traditional operation. As a result, this advance provides mass-selected photoelectron spectra for fast, high sensitivity quantitative analysis of reacting systems.« less

Rescattering effects on intensity interferometry and initial conditions in relativistic heavy ion collisions

NASA Astrophysics Data System (ADS)

Li, Yang

The properties of the quark-gluon plasma are being thoroughly studied by utilizing relativistic heavy ion collisions. After its invention in astronomy in the 1950s, intensity interferometry was found to be a robust method to probe the spatial and temporal information of the nuclear collisions also. Although rescattering effects are negligible in elementary particle collisions, it may be very important for heavy ion collisions at RHIC and in the future LHC. Rescattering after production will modify the measured correlation function and make it harder to extract the dynamical information from data. To better understand the data which are dimmed by this final state process, we derive a general formula for intensity interferometry which can calculate rescattering effects easily. The formula can be used both non-relativistically and relativistically. Numerically, we found that rescattering effects on kaon interferometry for RHIC experiments can modify the measured ratio of the outward radius to the sideward radius, which is a sensitive probe to the equation of state, by as large as 15%. It is a nontrivial contribution which should be included to understand the data more accurately. The second part of this thesis is on the initial conditions in relativistic heavy ion collisions. Although relativistic hydrodynamics is successful in explaining many aspects of the data, it is only valid after some finite time after nuclear contact. The results depend on the choice of initial conditions which, so far, have been very uncertain. I describe a formula based on the McLerran-Venugopalan model to compute the initial energy density. The soft gluon fields produced immediately after the overlap of the nuclei can be expanded as a power series of the proper time t. Solving Yang-Mills equations with color current conservation can give us the analytical formulas for the fields. The local color charges on the transverse plane are stochastic variables and have to be taken care of by random walks. It is found that the fields are mainly longitudinal at early time. The initial energy densities are computed both for RHIC and LHC.

The slow collisional E×B ion drift characterized as the major instability mechanism of a poorly magnetized plasma column with an inward-directed radial electric field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pierre, Thiéry

2016-04-15

The low-frequency instability of a cylindrical poorly magnetized plasma with an inward-directed radial electric field is studied changing the gas pressure and the ion cyclotron frequency. The unstable frequency always decreases when the gas pressure is increased indicating collisional effects. At a fixed pressure, the unstable frequency increases with the magnetic field when the B-field is low and decreases at larger magnetic field strength. We find that the transition between these two regimes is obtained when the ion cyclotron frequency equals the ion-neutrals collision frequency. This is in agreement with the theory of the slow-ion drift instability induced by themore » collisional slowing of the electric ion drift [A. Simon, Phys. Fluids 6, 382 (1963)].« less

Nanoscale detection of bacteriophage triggered ion cascade (Invited Paper)

NASA Astrophysics Data System (ADS)

Dobozi-King, Maria; Seo, Sungkyu; Kim, Jong U.; Cheng, Mosong; Kish, Laszlo B.; Young, Ryland

2005-05-01

In an era of potential bioterrorism and pandemics of antibiotic-resistant microbes, bacterial contaminations of food and water supplies is a major concern. There is an urgent need for the rapid, inexpensive and specific identification of bacteria under field conditions. Here we describe a method that combines the specificity and avidity of bacteriophages with fluctuation analysis of electrical noise. The method is based on the massive, transitory ion leakage that occurs at the moment of phage DNA injection into the host cell. The ion fluxes require only that the cells be physiologically viable (i.e., have energized membranes) and can occur within seconds after mixing the cells with sufficient concentrations of phage particles. To detect these fluxes, we have constructed a nano-well, a lateral, micron-size capacitor of titanium electrodes with gap size of 150 nm, and used it to measure the electrical field fluctuations in microliter (mm3) samples containing phage and bacteria. In mixtures where the analyte bacteria were sensitive to the phage, large stochastic waves with various time and amplitude scales were observed, with power spectra of approximately 1/f2 shape over at 1 - 10 Hz. Development of this SEPTIC (SEnsing of Phage-Triggered Ion Cascades) technology could provide rapid detection and identification of live, pathogenic bacteria on the scale of minutes, with unparalleled specificity. The method has a potential ultimate sensitivity of 1 bacterium/microliter (1 bacterium/mm3).

Quasi-One-Dimensional Particle-in-Cell Simulation of Magnetic Nozzles

NASA Technical Reports Server (NTRS)

Ebersohn, Frans H.; Sheehan, J. P.; Gallimore, Alec D.; Shebalin, John V.

2015-01-01

A method for the quasi-one-dimensional simulation of magnetic nozzles is presented and simulations of a magnetic nozzle are performed. The effects of the density variation due to plasma expansion and the magnetic field forces on ion acceleration are investigated. Magnetic field forces acting on the electrons are found to be responsible for the formation of potential structures which accelerate ions. The effects of the plasma density variation alone are found to only weakly affect ion acceleration. Strongly diverging magnetic fields drive more rapid potential drops.

Optimization of a charge-state analyzer for electron cyclotron resonance ion source beams.

PubMed

Saminathan, S; Beijers, J P M; Kremers, H R; Mironov, V; Mulder, J; Brandenburg, S

2012-07-01

A detailed experimental and simulation study of the extraction of a 24 keV He(+) beam from an ECR ion source and the subsequent beam transport through an analyzing magnet is presented. We find that such a slow ion beam is very sensitive to space-charge forces, but also that the neutralization of the beam's space charge by secondary electrons is virtually complete for beam currents up to at least 0.5 mA. The beam emittance directly behind the extraction system is 65 π mm mrad and is determined by the fact that the ion beam is extracted in the strong magnetic fringe field of the ion source. The relatively large emittance of the beam and its non-paraxiality lead, in combination with a relatively small magnet gap, to significant beam losses and a five-fold increase of the effective beam emittance during its transport through the analyzing magnet. The calculated beam profile and phase-space distributions in the image plane of the analyzing magnet agree well with measurements. The kinematic and magnet aberrations have been studied using the calculated second-order transfer map of the analyzing magnet, with which we can reproduce the phase-space distributions of the ion beam behind the analyzing magnet. Using the transfer map and trajectory calculations we have worked out an aberration compensation scheme based on the addition of compensating hexapole components to the main dipole field by modifying the shape of the poles. The simulations predict that by compensating the kinematic and geometric aberrations in this way and enlarging the pole gap the overall beam transport efficiency can be increased from 16% to 45%.

Gallium nitride junction field-effect transistor

DOEpatents

Zolper, J.C.; Shul, R.J.

1999-02-02

An ion implanted gallium-nitride (GaN) junction field-effect transistor (JFET) and method of making the same are disclosed. Also disclosed are various ion implants, both n- and p-type, together with or without phosphorus co-implantation, in selected III-V semiconductor materials. 19 figs.

Differential polarization of cortical pyramidal neuron dendrites through weak extracellular fields

PubMed Central

Obermayer, Klaus

2018-01-01

The rise of transcranial current stimulation (tCS) techniques have sparked an increasing interest in the effects of weak extracellular electric fields on neural activity. These fields modulate ongoing neural activity through polarization of the neuronal membrane. While the somatic polarization has been investigated experimentally, the frequency-dependent polarization of the dendritic trees in the presence of alternating (AC) fields has received little attention yet. Using a biophysically detailed model with experimentally constrained active conductances, we analyze the subthreshold response of cortical pyramidal cells to weak AC fields, as induced during tCS. We observe a strong frequency resonance around 10-20 Hz in the apical dendrites sensitivity to polarize in response to electric fields but not in the basal dendrites nor the soma. To disentangle the relative roles of the cell morphology and active and passive membrane properties in this resonance, we perform a thorough analysis using simplified models, e.g. a passive pyramidal neuron model, simple passive cables and reconstructed cell model with simplified ion channels. We attribute the origin of the resonance in the apical dendrites to (i) a locally increased sensitivity due to the morphology and to (ii) the high density of h-type channels. Our systematic study provides an improved understanding of the subthreshold response of cortical cells to weak electric fields and, importantly, allows for an improved design of tCS stimuli. PMID:29727454

Iron Oxide Nanoparticle-Micelles (ION-Micelles) for Sensitive (Molecular) Magnetic Particle Imaging and Magnetic Resonance Imaging

PubMed Central

Starmans, Lucas W. E.; Burdinski, Dirk; Haex, Nicole P. M.; Moonen, Rik P. M.; Strijkers, Gustav J.; Nicolay, Klaas; Grüll, Holger

2013-01-01

Background Iron oxide nanoparticles (IONs) are a promising nanoplatform for contrast-enhanced MRI. Recently, magnetic particle imaging (MPI) was introduced as a new imaging modality, which is able to directly visualize magnetic particles and could serve as a more sensitive and quantitative alternative to MRI. However, MPI requires magnetic particles with specific magnetic properties for optimal use. Current commercially available iron oxide formulations perform suboptimal in MPI, which is triggering research into optimized synthesis strategies. Most synthesis procedures aim at size control of iron oxide nanoparticles rather than control over the magnetic properties. In this study, we report on the synthesis, characterization and application of a novel ION platform for sensitive MPI and MRI. Methods and Results IONs were synthesized using a thermal-decomposition method and subsequently phase-transferred by encapsulation into lipidic micelles (ION-Micelles). Next, the material and magnetic properties of the ION-Micelles were analyzed. Most notably, vibrating sample magnetometry measurements showed that the effective magnetic core size of the IONs is 16 nm. In addition, magnetic particle spectrometry (MPS) measurements were performed. MPS is essentially zero-dimensional MPI and therefore allows to probe the potential of iron oxide formulations for MPI. ION-Micelles induced up to 200 times higher signal in MPS measurements than commercially available iron oxide formulations (Endorem, Resovist and Sinerem) and thus likely allow for significantly more sensitive MPI. In addition, the potential of the ION-Micelle platform for molecular MPI and MRI was showcased by MPS and MRI measurements of fibrin-binding peptide functionalized ION-Micelles (FibPep-ION-Micelles) bound to blood clots. Conclusions The presented data underlines the potential of the ION-Micelle nanoplatform for sensitive (molecular) MPI and warrants further investigation of the FibPep-ION-Micelle platform for in vivo, non-invasive imaging of fibrin in preclinical disease models of thrombus-related pathologies and atherosclerosis. PMID:23437371

Iron oxide nanoparticle-micelles (ION-micelles) for sensitive (molecular) magnetic particle imaging and magnetic resonance imaging.

PubMed

Starmans, Lucas W E; Burdinski, Dirk; Haex, Nicole P M; Moonen, Rik P M; Strijkers, Gustav J; Nicolay, Klaas; Grüll, Holger

2013-01-01

Iron oxide nanoparticles (IONs) are a promising nanoplatform for contrast-enhanced MRI. Recently, magnetic particle imaging (MPI) was introduced as a new imaging modality, which is able to directly visualize magnetic particles and could serve as a more sensitive and quantitative alternative to MRI. However, MPI requires magnetic particles with specific magnetic properties for optimal use. Current commercially available iron oxide formulations perform suboptimal in MPI, which is triggering research into optimized synthesis strategies. Most synthesis procedures aim at size control of iron oxide nanoparticles rather than control over the magnetic properties. In this study, we report on the synthesis, characterization and application of a novel ION platform for sensitive MPI and MRI. IONs were synthesized using a thermal-decomposition method and subsequently phase-transferred by encapsulation into lipidic micelles (ION-Micelles). Next, the material and magnetic properties of the ION-Micelles were analyzed. Most notably, vibrating sample magnetometry measurements showed that the effective magnetic core size of the IONs is 16 nm. In addition, magnetic particle spectrometry (MPS) measurements were performed. MPS is essentially zero-dimensional MPI and therefore allows to probe the potential of iron oxide formulations for MPI. ION-Micelles induced up to 200 times higher signal in MPS measurements than commercially available iron oxide formulations (Endorem, Resovist and Sinerem) and thus likely allow for significantly more sensitive MPI. In addition, the potential of the ION-Micelle platform for molecular MPI and MRI was showcased by MPS and MRI measurements of fibrin-binding peptide functionalized ION-Micelles (FibPep-ION-Micelles) bound to blood clots. The presented data underlines the potential of the ION-Micelle nanoplatform for sensitive (molecular) MPI and warrants further investigation of the FibPep-ION-Micelle platform for in vivo, non-invasive imaging of fibrin in preclinical disease models of thrombus-related pathologies and atherosclerosis.

Mobility-Selected Ion Trapping and Enrichment Using Structures for Lossless Ion Manipulations

DOE PAGES

Chen, Tsung-Chi; Ibrahim, Yehia M.; Webb, Ian K.; ...

2016-01-11

The integration of ion mobility spectrometry (IMS) with mass spectrometry (MS) and the ability to trap ions in IMS-MS measurements is of great importance for performing reactions, accumulating ions, and increasing analytical measurement sensitivity. The development of Structures for Lossless Ion Manipulations (SLIM) offers the potential for ion manipulations in a more reliable and cost-effective manner, while opening opportunities for much more complex sequences of manipulations. Here, we demonstrate an ion separation and trapping module and a method based upon SLIM that consists of a linear mobility ion drift region, a switch/tee and a trapping region that allows the isolationmore » and accumulation of mobility-separated species. The operation and optimization of the SLIM switch/tee and trap are described and demonstrated for the enrichment of the low abundance ions. Lastly, we observed a linear increase in ion intensity with the number of trapping/accumulation events using the SLIM trap, illustrating its potential for enhancing the sensitivity of low abundance or targeted species.« less

Anomalous transport of charged dust grains in a magnetized collisional plasma: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Bezbaruah, Pratikshya; Das, Nilakshi

2018-05-01

Anomalous diffusion of charged dust grains immersed in a plasma in the presence of strong ion-neutral collision, flowing ions, and a magnetic field has been observed. Molecular Dynamics simulation confirms the deviation from normal diffusion in an ensemble of dust grains probed in laboratory plasma chambers. Collisional effects are significant in governing the nature of diffusion. In order to have a clear idea on the transport of particles in a real experimental situation, the contribution of streaming ions and the magnetic field along with collision is considered through the relevant interaction potential. The nonlinear evolution of Mean Square Displacement is an indication of the modification in particle trajectories due to several effects as mentioned above. It is found that strong collision and ion flow significantly affect the interparticle interaction potential in the presence of the magnetic field and lead to the appearance of the asymmetric type of Debye Hückel (D H) potential. Due to the combined effect of the magnetic field, ion flow, and collision, dusty plasma exhibits a completely novel behavior. The coupling parameter Γ enhances the asymmetric D H type potential arising due to ion flow, and this may drive the system to a disordered state.

Analysis of retarding field energy analyzer transmission by simulation of ion trajectories

NASA Astrophysics Data System (ADS)

van de Ven, T. H. M.; de Meijere, C. A.; van der Horst, R. M.; van Kampen, M.; Banine, V. Y.; Beckers, J.

2018-04-01

Retarding field energy analyzers (RFEAs) are used routinely for the measurement of ion energy distribution functions. By contrast, their ability to measure ion flux densities has been considered unreliable because of lack of knowledge about the effective transmission of the RFEA grids. In this work, we simulate the ion trajectories through a three-gridded RFEA using the simulation software SIMION. Using idealized test cases, it is shown that at high ion energy (i.e., >100 eV) the transmission is equal to the optical transmission rather than the product of the individual grid transparencies. Below 20 eV, ion trajectories are strongly influenced by the electric fields in between the grids. In this region, grid alignment and ion focusing effects contribute to fluctuations in transmission with ion energy. Subsequently the model has been used to simulate the transmission and energy resolution of an experimental RFEA probe. Grid misalignments reduce the transmission fluctuations at low energy. The model predicts the minimum energy resolution, which has been confirmed experimentally by irradiating the probe with a beam of ions with a small energy bandwidth.

Photocontrol of Voltage-Gated Ion Channel Activity by Azobenzene Trimethylammonium Bromide in Neonatal Rat Cardiomyocytes

PubMed Central

Frolova, Sheyda R.; Gaiko, Olga; Tsvelaya, Valeriya A.; Pimenov, Oleg Y.; Agladze, Konstantin I.

2016-01-01

The ability of azobenzene trimethylammonium bromide (azoTAB) to sensitize cardiac tissue excitability to light was recently reported. The dark, thermally relaxed trans- isomer of azoTAB suppressed spontaneous activity and excitation propagation speed, whereas the cis- isomer had no detectable effect on the electrical properties of cardiomyocyte monolayers. As the membrane potential of cardiac cells is mainly controlled by activity of voltage-gated ion channels, this study examined whether the sensitization effect of azoTAB was exerted primarily via the modulation of voltage-gated ion channel activity. The effects of trans- and cis- isomers of azoTAB on voltage-dependent sodium (INav), calcium (ICav), and potassium (IKv) currents in isolated neonatal rat cardiomyocytes were investigated using the whole-cell patch-clamp technique. The experiments showed that azoTAB modulated ion currents, causing suppression of sodium (Na+) and calcium (Ca2+) currents and potentiation of net potassium (K+) currents. This finding confirms that azoTAB-effect on cardiac tissue excitability do indeed result from modulation of voltage-gated ion channels responsible for action potential. PMID:27015602

Trapped atomic ions for quantum-limited metrology

NASA Astrophysics Data System (ADS)

Wineland, David

2017-04-01

Laser-beam-manipulated trapped ions are a candidate for large-scale quantum information processing and quantum simulation but the basic techniques used can also be applied to quantum-limited metrology and sensing. Some examples being explored at NIST are: 1) As charged harmonic oscillators, trapped ions can be used to sense electric fields; this can be used to characterize the electrode-surface-based noisy electric fields that compromise logic-gate fidelities and may eventually be used as a tool in surface science. 2) Since typical qubit logic gates depend on state-dependent forces, we can adapt the gate dynamics to sensitively detect additional forces. 3) We can use extensions of Bell inequality measurements to further restrict the degree of local realism possessed by Bell states. 4) We also briefly describe experiments for creation of Bell states using Hilbert space engineering. This work is a joint effort including the Ion-Storage group, the Quantum processing group, and the Computing and Communications Theory group at NIST, Boulder. Supported by IARPA, ONR, and the NIST Quantum Information Program.

Sensitive Precise p H Measurement with Large-Area Graphene Field-Effect Transistors at the Quantum-Capacitance Limit

NASA Astrophysics Data System (ADS)

Fakih, Ibrahim; Mahvash, Farzaneh; Siaj, Mohamed; Szkopek, Thomas

2017-10-01

A challenge for p H sensing is decreasing the minimum measurable p H per unit bandwidth in an economical fashion. Minimizing noise to reach the inherent limit imposed by charge fluctuation remains an obstacle. We demonstrate here graphene-based ion-sensing field-effect transistors that saturate the physical limit of sensitivity, defined here as the change in electrical response with respect to p H , and achieve a precision limited by charge-fluctuation noise at the sensing layer. We present a model outlining the necessity for maximizing the device carrier mobility, active sensing area, and capacitive coupling in order to minimize noise. We encapsulate large-area graphene with an ultrathin layer of parylene, a hydrophobic polymer, and deposit an ultrathin, stoichiometric p H -sensing layer of either aluminum oxide or tantalum pentoxide. With these structures, we achieve gate capacitances ˜0.6 μ F /cm2 , approaching the quantum-capacitance limit inherent to graphene, along with a near-Nernstian p H response of ˜55 ±2 mV /p H . We observe field-effect mobilities as high as 7000 cm2 V-1 s-1 with minimal hysteresis as a result of the parylene encapsulation. A detection limit of 0.1 m p H in a 60-Hz electrical bandwidth is observed in optimized graphene transistors.

Solubility of NaCl in water by molecular simulation revisited.

PubMed

Aragones, J L; Sanz, E; Vega, C

2012-06-28

In this paper, the solubility of NaCl in water is evaluated by using computer simulations for three different force fields. The condition of chemical equilibrium (i.e., equal chemical potential of the salt in the solid and in the solution) is obtained at room temperature and pressure to determine the solubility of the salt. We used the same methodology that was described in our previous work [E. Sanz and C. Vega, J. Chem. Phys. 126, 014507 (2007)] although several modifications were introduced to improve the accuracy of the calculations. It is found that the predictions of the solubility are quite sensitive to the details of the force field used. Certain force fields underestimate the experimental solubility of NaCl in water by a factor of four, whereas the predictions of other force fields are within 20% of the experimental value. Direct coexistence molecular dynamic simulations were also performed to determine the solubility of the salt. Reasonable agreement was found between the solubility obtained from free energy calculations and that obtained from direct coexistence simulations. This work shows that the evaluation of the solubility of salts in water can now be performed in computer simulations. The solubility depends on the ion-ion, ion-water, and water-water interactions. For this reason, the prediction of the solubility can be quite useful in future work to develop force fields for ions in water.

Characterization of applied fields for ion mobility in traveling wave based structures for lossless ion manipulations (SLIM)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamid, Ahmed M.; Prabhakaran Nair Syamala Amma, Aneesh; Garimella, Venkata BS

2018-03-21

Ion mobility (IM) is rapidly gaining attention for the analysis of biomolecules due to the ability to distinguish the shapes of ions. However, conventional constant electric field drift tube IM has limited resolving power, constrained by practical limitations on the path length and maximum applied voltage. The implementation of traveling waves (TW) in IM removes the latter limitation, allowing higher resolution to be achieved using extended path lengths. These can be readily obtainable in structures for lossless ion manipulations (SLIM), which are fabricated from electric fields that are generated by appropriate potentials applied to arrays of electrodes patterned on twomore » parallel surfaces. In this work we have investigated the relationship between the various SLIM variables, such as electrode dimensions, inter-surface gap, and the TW applied voltages, that directly impact the fields experienced by ions. Ion simulation and theoretical calculations have been utilized to understand the dependence of SLIM geometry and effective electric field. The variables explored impact both ion confinement and the observed IM resolution in Structures for Lossless Ion Manipulations (SLIM) modules.« less

Characterization of applied fields for ion mobility separations in traveling wave based structures for lossless ion manipulations (SLIM)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamid, Ahmed M.; Prabhakaran, Aneesh; Garimella, Sandilya V. B.

Ion mobility (IM) is rapidly gaining attention for the analysis of biomolecules due to the ability to distinguish the shapes of ions. However, conventional constant electric field drift tube IM has limited resolving power, constrained by practical limitations on the path length and maximum applied voltage. The implementation of traveling waves (TW) in IM removes the latter limitation, allowing higher resolution to be achieved using extended path lengths. These can be readily obtainable in structures for lossless ion manipulations (SLIM), which are fabricated from electric fields that are generated by appropriate potentials applied to arrays of electrodes patterned on twomore » parallel surfaces. In this work we have investigated the relationship between the various SLIM variables, such as electrode dimensions, inter-surface gap, and the TW applied voltages, that directly impact the fields experienced by ions. Ion simulation and theoretical calculations have been utilized to understand the dependence of SLIM geometry and effective electric field. The variables explored impact both ion confinement and the observed IM resolution in Structures for Lossless Ion Manipulations (SLIM) modules.« less

Field Effect Sensors for Nucleic Acid Detection: Recent Advances and Future Perspectives

PubMed Central

Veigas, Bruno; Fortunato, Elvira; Baptista, Pedro V.

2015-01-01

In the last decade the use of field-effect-based devices has become a basic structural element in a new generation of biosensors that allow label-free DNA analysis. In particular, ion sensitive field effect transistors (FET) are the basis for the development of radical new approaches for the specific detection and characterization of DNA due to FETs’ greater signal-to-noise ratio, fast measurement capabilities, and possibility to be included in portable instrumentation. Reliable molecular characterization of DNA and/or RNA is vital for disease diagnostics and to follow up alterations in gene expression profiles. FET biosensors may become a relevant tool for molecular diagnostics and at point-of-care. The development of these devices and strategies should be carefully designed, as biomolecular recognition and detection events must occur within the Debye length. This limitation is sometimes considered to be fundamental for FET devices and considerable efforts have been made to develop better architectures. Herein we review the use of field effect sensors for nucleic acid detection strategies—from production and functionalization to integration in molecular diagnostics platforms, with special focus on those that have made their way into the diagnostics lab. PMID:25946631

Magnetical asymmetry effect in capacitively coupled plasmas: effects of the magnetic field gradient, pressure, and gap length

NASA Astrophysics Data System (ADS)

Yang, Shali; Chang, Lijie; Zhang, Ya; Jiang, Wei

2018-03-01

By applying the asymmetric magnetic field to a discharge, the dc self-bias and asymmetric plasma response can be generated even in a geometrically and electrically symmetric system. This is called magnetical asymmetric effect (MAE), which can be a new method to control the ion energy and flux independently (Yang et al 2017 Plasma Process. Polym. 14 1700087). In the present work, the effects of magnetic field gradient, gas pressure and gap length on MAE are investigated by using a one-dimensional implicit particle-in-cell/Monte Carlo collision simulation. It found that by appropriately increasing the magnetic field gradient and the gap length, the range of the self-bias voltage will be enlarged, which can be used as the effective approach to control the ion bombarding energy at the electrodes since the ion energy is determined by the voltage drop across the sheath. It also found that the ion flux asymmetry will disappear at high pressure when the magnetic field gradient is relative low, due to the frequent electron-neutral collisions can disrupt electron gyromotion and thus the MAE is greatly reduced.

The effect of the geomagnetic field on negative voltage spheres in the ionospheric plasma: Fluid simulation

NASA Astrophysics Data System (ADS)

Ma, T.-Z.; Schunk, R. W.

1994-07-01

Experiments involving the interaction of spherical conducting objects biases with hight voltages in the Low-Earth-Orbit (LEO) environment have been conducted and designed. In these experiments, both positive and negative voltages have been applied to the spheres. Previously, there have been theoretical and numerical studies of positive voltage spheres in plasmas with and without magnetic fields. There also have been studies of negative voltage objects in unmagnetized plasmas. Here, we used a fluid model to study the plasma response to a negative voltage sphere immersed in a magnetized plasma. Our main purpose was to investigate the role of the magnetic field during the early-time interaction between the negative voltage sphere and the ambient plasma in the LEO environment. In this study, different applied voltages, magnetic field strengths, and rise-times of the applied voltages were considered. It was found that with the strength of the geomagnetic field the ions are basically not affected by the magnetic field on the time scale of hundreds of plasma periods considered in this study. The ion density distribution around the sphere and the collected ion flux by the sphere are basically the same as in the case without the magnetic field. The electron motion is strongly affected by the magnetic field. One effect is to change the nature of the electron over-shoot oscillation from regular to somewhat turbulent. Although the electrons move along the magnetic field much more easily than across the magnetic field, some redirection effect causes the electron density to distribute as if the magnetic field effect is minimal. The sheath struture and the electric field around the sphere tend to be spherical. A finite rise-time of the applied voltage reduces the oscillatory activities and delays the ion acceleration. However, the effect of the rise-time depends on both the duration of the rise-time and the ion plasma period.

Role of the electric field in selective ion filtration in nanostructures.

PubMed

Park, Yong; Kim, Sueon; Jang, In Hyuk; Nam, Young Suk; Hong, Hiki; Choi, Dukhyun; Lee, Won Gu

2016-02-21

Nafion has received great attention as a proton conductor that can block negative ions. Here, we report the effect of a Nafion coating on an anodic aluminium oxide (AAO) nanoporous membrane on its function of ion rejection and filtering depending on the electric field. In our experiments, Nafion, once coated, was used to repel the negative ions (anions) from the coated surface, and then selectively allowed positive ions (cations) to pass through the nanopores in the presence of an electric field. To demonstrate the proof-of-concept validation, we coated Nafion solution onto the surface of AAO membranes with 20 nm nanopores average diameter at different solution concentration levels. Vacuum filtration methods for Nafion coating were vertically applied to the plane of an AAO membrane. An electric field was then applied to the upper surface of the Nafion-coated AAO membrane to investigate if ion rejection and filtering was affected by the presence of the electric field. Both anions and cations could pass through the AAO nanopores without an electric field applied. However, only cations could well pass through the AAO nanopores under an electric field, thus effectively blocking anions from passing through the nanopores. This result shows that ion filtration of electrons has been selectively performed while the system also works as a vital catalyst in reactivating Nafion via electrolysis. A saturated viscosity ratio of Nafion solution for the coating was also determined. We believe that this approach is potentially beneficial for better understanding the fundamentals of selective ion filtration in nanostructures and for promoting the use of nanostructures in potential applications such as ion-based water purification and desalination system at the nanoscale in a massively electrically integrated format.

Inductively coupled plasma mass spectrometry (ICP-MS) and laser ablation ICP-MS for isotope analysis of long-lived radionuclides

NASA Astrophysics Data System (ADS)

Becker, J. Sabine

2005-04-01

For a few years now inductively coupled plasma mass spectrometry has been increasingly used for precise and accurate determination of isotope ratios of long-lived radionuclides at the trace and ultratrace level due to its excellent sensitivity, good precision and accuracy. At present, ICP-MS and also laser ablation ICP-MS are applied as powerful analytical techniques in different fields such as the characterization of nuclear materials, recycled and by-products (e.g., spent nuclear fuel or depleted uranium ammunitions), radioactive waste control, in environmental monitoring and in bioassay measurements, in health control, in geochemistry and geochronology. Especially double-focusing sector field ICP mass spectrometers with single ion detector or with multiple ion collector device have been used for the precise determination of long-lived radionuclides isotope ratios at very low concentration levels. Progress has been achieved by the combination of ultrasensitive mass spectrometric techniques with effective separation and enrichment procedures in order to improve detection limits or by the introduction of the collision cell in ICP-MS for reducing disturbing interfering ions (e.g., of 129Xe+ for the determination of 129I). This review describes the state of the art and the progress of ICP-MS and laser ablation ICP-MS for isotope ratio measurements of long-lived radionuclides in different sample types, especially in the main application fields of characterization of nuclear and radioactive waste material, environmental research and health controls.

Metal cation detection in positive ion mode electrospray ionization mass spectrometry using a tetracationic salt as a gas-phase ion-pairing agent: evaluation of the effect of chelating agents on detection sensitivity.

PubMed

Xu, Chengdong; Dodbiba, Edra; Padivitage, Nilusha L T; Breitbach, Zachary S; Armstrong, Daniel W

2012-12-30

The detection of metal cations continues to be essential in many scientific and industrial areas of interest. The most common electrospray ionization mass spectrometry (ESI-MS) approach involves chelating the metal ions and detecting the organometallic complex in the negative ion mode. However, it is well known that negative ion mode ESI-MS is generally less sensitive than the positive ion mode. To achieve greater sensitivity, it is necessary to examine the feasibility of detecting the chelated metal cations in positive ion mode ESI-MS. Since highly solvated native metal cations have relatively low ionization efficiency in ESI-MS, and can be difficult to detect in the positive ion mode, a tetracationic ion-pairing agent was added to form a complex with the negatively charged metal chelate. The use of the ion-pairing agent leads to the generation of an overall positively charged complex, which can be detected at higher m/z values in the positive ion mode by electrospray ionization linear quadrupole ion trap mass spectrometry. Thirteen chelating agents with diverse structures were evaluated in this study. The nature of the chelating agent played as important a role as was previously determined for cationic pairing agents. The detection limits of six metal cations reached sub-picogram levels and significant improvements were observed when compared to negative ion mode detection where the metal-chelates were monitored without adding the ion-pairing reagent (IPR). Also, selective reaction monitoring (SRM) analyses were performed on the ternary complexes, which improved detection limits by one to three orders of magnitude. With this method it was possible to analyze the metal cations in the positive ion mode ESI-MS with the advantage of speed, sensitivity and selectivity. The optimum solution pH for this type of analysis is 5-7. Tandem mass spectrometry (MS/MS) further increases the sensitivity. Speciation is straightforward making this a broadly useful approach for the analysis of metal ions. Copyright © 2012 John Wiley & Sons, Ltd.

Heat flux modeling using ion drift effects in DIII-D H-mode plasmas with resonant magnetic perturbations

DOE PAGES

Wingen, Andreas; Schmitz, Oliver; Evans, Todd E.; ...

2014-01-01

The heat flux patterns measured in low-collisionality DIII-D H-mode plasmas strongly deviate from simultaneously measured CII emission patterns, used as indicator of particle flux, during applied resonant magnetic perturbations. While the CII emission clearly shows typical striations, which are similar to magnetic footprint patterns obtained from vacuum field line tracing, the heat flux is usually dominated by one large peak at the strike point position. The vacuum approximation, which only considers applied magnetic fields and neglects plasma response and plasma effects, cannot explain the shape of the observed heat flux pattern. One possible explanation is the effect of particle drifts.more » This is included in the field line equations and the results are discussed with reference to the measurement. Electrons and ions show di fferent drift motions at thermal energy levels in a guiding center approximation. While electrons hardly deviate from the field lines, ions can drift several centimetres away from field line flux surfaces. A model is presented in which an ion heat flux, based on the ion drift motion from various kinetic energies as they contribute to a thermal Maxwellian distribution, is calculated. The simulated heat flux is directly compared to measurements with a varying edge safety factor q95. This analysis provides evidence for the dominate e ect of high-energy ions in carrying heat from the plasma inside the separatrix to the target. High-energy ions are deposited close to the unperturbed strike line while low-energy ions can travel into the striated magnetic topology.« less

Dynamics of a reconnection-driven runaway ion tail in a reversed field pinch plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, J. K., E-mail: jkanders@wisc.edu; Kim, J.; Bonofiglo, P. J.

2016-05-15

While reconnection-driven ion heating is common in laboratory and astrophysical plasmas, the underlying mechanisms for converting magnetic to kinetic energy remain not fully understood. Reversed field pinch discharges are often characterized by rapid ion heating during impulsive reconnection, generating an ion distribution with an enhanced bulk temperature, mainly perpendicular to magnetic field. In the Madison Symmetric Torus, a subset of discharges with the strongest reconnection events develop a very anisotropic, high energy tail parallel to magnetic field in addition to bulk perpendicular heating, which produces a fusion neutron flux orders of magnitude higher than that expected from a Maxwellian distribution.more » Here, we demonstrate that two factors in addition to a perpendicular bulk heating mechanism must be considered to explain this distribution. First, ion runaway can occur in the strong parallel-to-B electric field induced by a rapid equilibrium change triggered by reconnection-based relaxation; this effect is particularly strong on perpendicularly heated ions which experience a reduced frictional drag relative to bulk ions. Second, the confinement of ions varies dramatically as a function of velocity. Whereas thermal ions are governed by stochastic diffusion along tearing-altered field lines (and radial diffusion increases with parallel speed), sufficiently energetic ions are well confined, only weakly affected by a stochastic magnetic field. High energy ions traveling mainly in the direction of toroidal plasma current are nearly classically confined, while counter-propagating ions experience an intermediate confinement, greater than that of thermal ions but significantly less than classical expectations. The details of ion confinement tend to reinforce the asymmetric drive of the parallel electric field, resulting in a very asymmetric, anisotropic distribution.« less

Re-Verification of the IRHN57133SE and IRHN57250SE for Single Event Gate Rupture and Single Event Burnout

NASA Technical Reports Server (NTRS)

Scheick, Leif

2010-01-01

The vertical metal oxide semiconductor field-effect transistor (MOSFET) is a widely used power transistor onboard a spacecraft. The MOSFET is typically employed in power supplies and high current switching applications. Due to the inherent high electric fields in the device, power MOSFETs are sensitive to heavy ion irradiation and can fail catastrophically as a result of single event gate rupture (SEGR) or single event burnout (SEB). Manufacturers have designed radiation-hardened power MOSFETs for space applications. These radiation hardened devices are not immune to SEGR or SEB but, rather, can exhibit them at a much more damaging ion than their non-radiation hardened counterparts. See [1] through [5] for more information.This effort was to investigate the SEGR and SEB responses of two power MOSFETs from IR(the IRHN57133SE and the IRHN57250SE) that have recently been produced on a new fabrication line. These tests will serve as a limited verification of these parts, but it is acknowledged that further testing on the respective parts may be needed for some mission profiles.

Ion wake field effects on the dust-ion-acoustic surface mode in a semi-bounded Lorentzian dusty plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Myoung-Jae; Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr; Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180-3590

The dispersion relation for the dust ion-acoustic surface waves propagating at the interface of semi-bounded Lorentzian dusty plasma with supersonic ion flow has been kinetically derived to investigate the nonthermal property and the ion wake field effect. We found that the supersonic ion flow creates the upper and the lower modes. The increase in the nonthermal particles decreases the wave frequency for the upper mode whereas it increases the frequency for the lower mode. The increase in the supersonic ion flow velocity is found to enhance the wave frequency for both modes. We also found that the increase in nonthermalmore » plasmas is found to enhance the group velocity of the upper mode. However, the nonthermal particles suppress the lower mode group velocity. The nonthermal effects on the group velocity will be reduced in the limit of small or large wavelength limit.« less

The Power Spectrum of Ionic Nanopore Currents: The Role of Ion Correlations.

PubMed

Zorkot, Mira; Golestanian, Ramin; Bonthuis, Douwe Jan

2016-04-13

We calculate the power spectrum of electric-field-driven ion transport through nanometer-scale membrane pores using both linearized mean-field theory and Langevin dynamics simulations. Remarkably, the linearized mean-field theory predicts a plateau in the power spectral density at low frequency ω, which is confirmed by the simulations at low ion concentration. At high ion concentration, however, the power spectral density follows a power law that is reminiscent of the 1/ω(α) dependence found experimentally at low frequency. On the basis of simulations with and without ion-ion interactions, we attribute the low-frequency power-law dependence to ion-ion correlations. We show that neither a static surface charge density, nor an increased pore length, nor an increased ion valency have a significant effect on the shape of the power spectral density at low frequency.

Physical Processes in the Heliospheric Interface Region and their Implications for ENA Images

NASA Astrophysics Data System (ADS)

Gruntman, M.; Roelof, E. C.; McComas, D. J.; Funsten, H. O.; Krimigis, S. M.; Mitchell, D. G.

2009-12-01

The recent in situ measurements of particles and fields by Voyager 1 and 2 spacecraft and global heliospheric maps in fluxes of energetic neutral atoms (ENAs) obtained by IBEX and Cassini/INCA have challenged our established concepts of the heliosphere interaction with the surrounding local interstellar medium. We review the physics of the interaction in an attempt to identify most important processes determining the dynamics and properties of the heliospheric sheath region. The non-thermal ion component and interstellar magnetic field clearly play significant roles in the interaction, as well as the flow of the warm interstellar plasma. We stress here that the basic conservation laws for energetic ions and neutrals constrain the processes that must be included in any valid formulation of particle transport. The termination shock can be viewed as a continuous source of energetic ions that are transported throughout the inner heliosheath, through the heliopause, and outward through the outer heliosheath and into the local interstellar medium. ENA images integrate the ENA production by energetic ions along lines of sight (LOS) that extend in principle to infinity, and hence are quite sensitive to the way that energetic ions and ENAs eventually escape this huge (~1000AU) system. Non-thermal ion and ENA space densities can be changed by three mechanisms: spatial transport (which by itself only rearranges the numbers of energetic ions and ENAs), energy gain and loss of ions in electric field, and elastic and inelastic collisions. Thus, only if these mechanisms are properly included in computational models can the salient features observed ENA images be replicated by the model simulations.

Aharonov-Bohm Effect in the Photodetachment Microscopy of Hydrogen Negative Ions in an Electric Field

NASA Astrophysics Data System (ADS)

Wang, Dehua

2014-09-01

The Aharonov-Bohm (AB) effect in the photodetachment microscopy of the H- ions in an electric field has been studied on the basis of the semiclassical theory. After the H- ion is irradiated by a laser light, they provide a coherent electron source. When the detached electron is accelerated by a uniform electric field, two trajectories of a detached electron which run from the source to the same point on the detector, will interfere with each other and lead to an interference pattern in the photodetachment microscopy. After the solenoid is electrified beside the H- ion, even though no Lorentz force acts on the electron outside the solenoid, the photodetachment microscopy interference pattern on the detector is changed with the variation in the magnetic flux enclosed by the solenoid. This is caused by the AB effect. Under certain conditions, the interference pattern reaches the macroscopic dimensions and could be observed in a direct AB effect experiment. Our study can provide some predictions for the future experimental study of the AB effect in the photodetachment microscopy of negative ions.

Potential Measurements of Coronal Magnetic Field Strengths Using Line Ratios in EUV and X-ray Spectra

NASA Astrophysics Data System (ADS)

Beiersdorfer, Peter; Scofield, J. H.; Lepson, J. K.; Osten, R.; Smith, R. K.

2006-09-01

We will discuss a class of lines from highly charged ions that are sensitive to the strength of the ambient magnetic field. Calculations show that the magnitude of field strengths that can be measured ranges from a few hundred gauss to several tens of kilogauss depending on the particular ion emitting the line. These calculations have been verified in the laboratory by studying the spectra of S VII, Ar IX, and Fe XVII. As an example of the diagnostic utility, the possibility of using these lines to determine the coronal magnetic field strength of Prox Cen will be presented. This work was supported by NASA Astronomy and Physics Research and Analysis program work order NNH04AA751, and was performed under the auspices of the Department of Energy by the University of California Lawrence Livermore National Laboratory under Contract No. W-7405-ENG-48.

Microfabricated cylindrical ion trap

DOEpatents

Blain, Matthew G.

2005-03-22

A microscale cylindrical ion trap, having an inner radius of order one micron, can be fabricated using surface micromachining techniques and materials known to the integrated circuits manufacturing and microelectromechanical systems industries. Micromachining methods enable batch fabrication, reduced manufacturing costs, dimensional and positional precision, and monolithic integration of massive arrays of ion traps with microscale ion generation and detection devices. Massive arraying enables the microscale cylindrical ion trap to retain the resolution, sensitivity, and mass range advantages necessary for high chemical selectivity. The microscale CIT has a reduced ion mean free path, allowing operation at higher pressures with less expensive and less bulky vacuum pumping system, and with lower battery power than conventional- and miniature-sized ion traps. The reduced electrode voltage enables integration of the microscale cylindrical ion trap with on-chip integrated circuit-based rf operation and detection electronics (i.e., cell phone electronics). Therefore, the full performance advantages of microscale cylindrical ion traps can be realized in truly field portable, handheld microanalysis systems.

Time-Resolved Magnetic Field Effects Distinguish Loose Ion Pairs from Exciplexes

PubMed Central

2013-01-01

We describe the experimental investigation of time-resolved magnetic field effects in exciplex-forming organic donor–acceptor systems. In these systems, the photoexcited acceptor state is predominantly deactivated by bimolecular electron transfer reactions (yielding radical ion pairs) or by direct exciplex formation. The delayed fluorescence emitted by the exciplex is magnetosensitive if the reaction pathway involves loose radical ion pair states. This magnetic field effect results from the coherent interconversion between the electronic singlet and triplet radical ion pair states as described by the radical pair mechanism. By monitoring the changes in the exciplex luminescence intensity when applying external magnetic fields, details of the reaction mechanism can be elucidated. In this work we present results obtained with the fluorophore-quencher pair 9,10-dimethylanthracene/N,N-dimethylaniline (DMA) in solvents of systematically varied permittivity. A simple theoretical model is introduced that allows discriminating the initial state of quenching, viz., the loose ion pair and the exciplex, based on the time-resolved magnetic field effect. The approach is validated by applying it to the isotopologous fluorophore-quencher pairs pyrene/DMA and pyrene-d10/DMA. We detect that both the exciplex and the radical ion pair are formed during the initial quenching stage. Upon increasing the solvent polarity, the relative importance of the distant electron transfer quenching increases. However, even in comparably polar media, the exciplex pathway remains remarkably significant. We discuss our results in relation to recent findings on the involvement of exciplexes in photoinduced electron transfer reactions. PMID:24041160

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kanesue, Takeshi; Ikeda, Shunsuke

A laser ion source is a promising candidate as an ion source for heavy ion inertial fusion (HIF), where a pulsed ultra-intense and low-charged heavy ion beam is required. It is a key development for a laser ion source to transport laser-produced plasma with a magnetic field to achieve a high current beam. The effect of a tapered magnetic field on laser produced plasma is demonstrated by comparing the results with a straight solenoid magnet. The magnetic field of interest is a wider aperture on a target side and narrower aperture on an extraction side. Furthermore, based on the experimentallymore » obtained results, the performance of a scaled laser ion source for HIF was estimated.« less

THE IBEX RIBBON AND THE PICKUP ION RING STABILITY IN THE OUTER HELIOSHEATH. II. MONTE-CARLO AND PARTICLE-IN-CELL MODEL RESULTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niemiec, J.; Florinski, V.; Heerikhuisen, J.

2016-08-01

The nearly circular ribbon of energetic neutral atom (ENA) emission discovered by NASA’s Interplanetary Boundary EXplorer satellite ( IBEX ), is most commonly attributed to the effect of charge exchange of secondary pickup ions (PUIs) gyrating about the magnetic field in the outer heliosheath (OHS) and the interstellar space beyond. The first paper in the series (Paper I) presented a theoretical analysis of the pickup process in the OHS and hybrid-kinetic simulations, revealing that the kinetic properties of freshly injected proton rings depend sensitively on the details of their velocity distribution. It was demonstrated that only rings that are notmore » too narrow (parallel thermal spread above a few km s{sup −1}) and not too wide (parallel temperature smaller than the core plasma temperature) could remain stable for a period of time long enough to generate ribbon ENAs. This paper investigates the role of electron dynamics and the extra spatial degree of freedom in the ring ion scattering process with the help of two-dimensional full particle-in-cell (PIC) kinetic simulations. A good agreement is observed between ring evolution under unstable conditions in hybrid and PIC models, and the dominant modes are found to propagate parallel to the magnetic field. We also present more realistic ribbon PUI distributions generated using Monte Carlo simulations of atomic hydrogen in the global heliosphere and examine the effect of both the cold ring-like and the hot “halo” PUIs produced from heliosheath ENAs on the ring stability. It is shown that the second PUI population enhances the fluctuation growth rate, leading to faster isotropization of the solar-wind-derived ring ions.« less

The IBEX Ribbon and the Pickup Ion Ring Stability in the Outer Heliosheath II. Monte-Carlo and Particle-in-cell Model Results

NASA Astrophysics Data System (ADS)

Niemiec, J.; Florinski, V.; Heerikhuisen, J.; Nishikawa, K.-I.

2016-08-01

The nearly circular ribbon of energetic neutral atom (ENA) emission discovered by NASA’s Interplanetary Boundary EXplorer satellite (IBEX), is most commonly attributed to the effect of charge exchange of secondary pickup ions (PUIs) gyrating about the magnetic field in the outer heliosheath (OHS) and the interstellar space beyond. The first paper in the series (Paper I) presented a theoretical analysis of the pickup process in the OHS and hybrid-kinetic simulations, revealing that the kinetic properties of freshly injected proton rings depend sensitively on the details of their velocity distribution. It was demonstrated that only rings that are not too narrow (parallel thermal spread above a few km s-1) and not too wide (parallel temperature smaller than the core plasma temperature) could remain stable for a period of time long enough to generate ribbon ENAs. This paper investigates the role of electron dynamics and the extra spatial degree of freedom in the ring ion scattering process with the help of two-dimensional full particle-in-cell (PIC) kinetic simulations. A good agreement is observed between ring evolution under unstable conditions in hybrid and PIC models, and the dominant modes are found to propagate parallel to the magnetic field. We also present more realistic ribbon PUI distributions generated using Monte Carlo simulations of atomic hydrogen in the global heliosphere and examine the effect of both the cold ring-like and the hot “halo” PUIs produced from heliosheath ENAs on the ring stability. It is shown that the second PUI population enhances the fluctuation growth rate, leading to faster isotropization of the solar-wind-derived ring ions.

Proton-sensing transistor systems for detecting ion leakage from plasma membranes under chemical stimuli.

PubMed

Imaizumi, Yuki; Goda, Tatsuro; Schaffhauser, Daniel F; Okada, Jun-Ichi; Matsumoto, Akira; Miyahara, Yuji

2017-03-01

The membrane integrity of live cells is routinely evaluated for cytotoxicity induced by chemical or physical stimuli. Recent progress in bioengineering means that high-quality toxicity validation is required. Here, we report a pH-sensitive transistor system developed for the continuous monitoring of ion leakage from cell membranes upon challenge by toxic compounds. Temporal changes in pH were generated with high reproducibility via periodic flushing of HepG2 cells on a gate insulator of a proton-sensitive field-effect transistor with isotonic buffer solutions with/without NH 4 Cl. The pH transients at the point of NH 4 Cl addition/withdrawal originated from the free permeation of NH 3 across the semi-permeable plasma membranes, and the proton sponge effect produced by the ammonia equilibrium. Irreversible attenuation of the pH transient was observed when the cells were subjected to a membrane-toxic reagent. Experiments and simulations proved that the decrease in the pH transient was proportional to the area of the ion-permeable pores on the damaged plasma membranes. The pH signal was correlated with the degree of hemolysis produced by the model reagents. The pH assay was sensitive to the formation of molecularly sized pores that were otherwise not measurable via detection of the leakage of hemoglobin, because the hydrodynamic radius of hemoglobin was greater than 3.1nm in the hemolysis assay. The pH transient was not disturbed by inherent ion-transporter activity. The ISFET assay was applied to a wide variety of cell types. The system presented here is fast, sensitive, practical and scalable, and will be useful for validating cytotoxins and nanomaterials. The plasma membrane toxicity and hemolysis are widely and routinely evaluated in biomaterials science and biomedical engineering. Despite the recent development of a variety of methods/materials for efficient gene/drug delivery systems to the cytosol, the methodologies for safety validation remain unchanged in many years while leaving some major issues such as sensitivity, accuracy, and fast response. The paper describes a new way of measuring the plasma membrane leakage in real time upon challenge by toxic reagents using a solid-state transistor that is sensitive to proton as the smallest indicator. Our system was reliable and was correlated to the results from hemolysis assay with advanced features in sensitivity, fast response, and wide applicability to chemical species. The downsizing and integration features of semiconductor fabrication technologies may realize cytotoxicity assays at the single-cell level in multi-parallel. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Electric field measurement in microwave discharge ion thruster with electro-optic probe.

PubMed

Ise, Toshiyuki; Tsukizaki, Ryudo; Togo, Hiroyoshi; Koizumi, Hiroyuki; Kuninaka, Hitoshi

2012-12-01

In order to understand the internal phenomena in a microwave discharge ion thruster, it is important to measure the distribution of the microwave electric field inside the discharge chamber, which is directly related to the plasma production. In this study, we proposed a novel method of measuring a microwave electric field with an electro-optic (EO) probe based on the Pockels effect. The probe, including a cooling system, contains no metal and can be accessed in the discharge chamber with less disruption to the microwave distribution. This method enables measurement of the electric field profile under ion beam acceleration. We first verified the measurement with the EO probe by a comparison with a finite-difference time domain numerical simulation of the microwave electric field in atmosphere. Second, we showed that the deviations of the reflected microwave power and the beam current were less than 8% due to inserting the EO probe into the ion thruster under ion beam acceleration. Finally, we successfully demonstrated the measurement of the electric-field profile in the ion thruster under ion beam acceleration. These measurements show that the electric field distribution in the thruster dramatically changes in the ion thruster under ion beam acceleration as the propellant mass flow rate increases. These results indicate that this new method using an EO probe can provide a useful guide for improving the propulsion of microwave discharge ion thrusters.

Nonlinear waves in electron-positron-ion plasmas including charge separation

NASA Astrophysics Data System (ADS)

Mugemana, A.; Moolla, S.; Lazarus, I. J.

2017-02-01

Nonlinear low-frequency electrostatic waves in a magnetized, three-component plasma consisting of hot electrons, hot positrons and warm ions have been investigated. The electrons and positrons are assumed to have Boltzmann density distributions while the motion of the ions are governed by fluid equations. The system is closed with the Poisson equation. This set of equations is numerically solved for the electric field. The effects of the driving electric field, ion temperature, positron density, ion drift, Mach number and propagation angle are investigated. It is shown that depending on the driving electric field, ion temperature, positron density, ion drift, Mach number and propagation angle, the numerical solutions exhibit waveforms that are sinusoidal, sawtooth and spiky. The introduction of the Poisson equation increased the Mach number required to generate the waveforms but the driving electric field E 0 was reduced. The results are compared with satellite observations.

Critical factors determining the quantification capability of matrix-assisted laser desorption/ionization– time-of-flight mass spectrometry

PubMed Central

Wang, Chia-Chen; Lai, Yin-Hung; Ou, Yu-Meng; Chang, Huan-Tsung; Wang, Yi-Sheng

2016-01-01

Quantitative analysis with mass spectrometry (MS) is important but challenging. Matrix-assisted laser desorption/ionization (MALDI) coupled with time-of-flight (TOF) MS offers superior sensitivity, resolution and speed, but such techniques have numerous disadvantages that hinder quantitative analyses. This review summarizes essential obstacles to analyte quantification with MALDI-TOF MS, including the complex ionization mechanism of MALDI, sensitive characteristics of the applied electric fields and the mass-dependent detection efficiency of ion detectors. General quantitative ionization and desorption interpretations of ion production are described. Important instrument parameters and available methods of MALDI-TOF MS used for quantitative analysis are also reviewed. This article is part of the themed issue ‘Quantitative mass spectrometry’. PMID:27644968

Fusion proton diagnostic for the C-2 field reversed configurationa)

NASA Astrophysics Data System (ADS)

Magee, R. M.; Clary, R.; Korepanov, S.; Smirnov, A.; Garate, E.; Knapp, K.; Tkachev, A.

2014-11-01

Measurements of the flux of fusion products from high temperature plasmas provide valuable insights into the ion energy distribution, as the fusion reaction rate is a very sensitive function of ion energy. In C-2, where field reversed configuration plasmas are formed by the collision of two compact toroids and partially sustained by high power neutral beam injection [M. Binderbauer et al., Phys. Rev. Lett. 105, 045003 (2010); M. Tuszewski et al., Phys. Rev. Lett. 108, 255008 (2012)], measurements of DD fusion neutron flux are used to diagnose ion temperature and study fast ion confinement and dynamics. In this paper, we will describe the development of a new 3 MeV proton detector that will complement existing neutron detectors. The detector is a large area (50 cm2), partially depleted, ion implanted silicon diode operated in a pulse counting regime. While the scintillator-based neutron detectors allow for high time resolution measurements (˜100 kHz), they have no spatial or energy resolution. The proton detector will provide 10 cm spatial resolution, allowing us to determine if the axial distribution of fast ions is consistent with classical fast ion theory or whether anomalous scattering mechanisms are active. We will describe in detail the diagnostic design and present initial data from a neutral beam test chamber.

Charge collection and SEU mechanisms

NASA Astrophysics Data System (ADS)

Musseau, O.

1994-01-01

In the interaction of cosmic ions with microelectronic devices a dense electron-hole plasma is created along the ion track. Carriers are separated and transported by the electric field and under the action of the concentration gradient. The subsequent collection of these carriers induces a transient current at some electrical node of the device. This "ionocurrent" (single ion induced current) acts as any electrical perturbation in the device, propagating in the circuit and inducing failures. In bistable systems (registers, memories) the stored data can be upset. In clocked devices (microprocessors) the parasitic perturbation may propagate through the device to the outputs. This type of failure only effects the information, and do not degrade the functionally of the device. The purpose of this paper is to review the mechanisms of single event upset in microelectronic devices. Experimental and theoretical results are presented, and actual questions and problems are discussed. A brief introduction recalls the creation of the dense plasma of electron-hole pairs. The basic processes for charge collection in a simple np junction (drift and diffusion) are presented. The funneling-field effect is discussed and experimental results are compared to numerical simulations and semi-empirical models. Charge collection in actual microelectronic structures is then presented. Due to the parasitic elements, coupling effects are observed. Geometrical effects, in densely packed structures, results in multiple errors. Electronic couplings are due to the carriers in excess, acting as minority carriers, that trigger parasitic bipolar transistors. Single event upset of memory cells is discussed, based on numerical and experimental data. The main parameters for device characterization are presented. From the physical interpretation of charge collection mechanisms, the intrinsic sensitivity of various microelectronic technologies is determined and compared to experimental data. Scaling laws and future trends are finally discussed.

Investigation of polarization effects in the gramicidin A channel from ab initio molecular dynamics simulations.

PubMed

Timko, Jeff; Kuyucak, Serdar

2012-11-28

Polarization is an important component of molecular interactions and is expected to play a particularly significant role in inhomogeneous environments such as pores and interfaces. Here we investigate the effects of polarization in the gramicidin A ion channel by performing quantum mechanics/molecular mechanics molecular dynamics (MD) simulations and comparing the results with those obtained from classical MD simulations with non-polarizable force fields. We consider the dipole moments of backbone carbonyl groups and channel water molecules as well as a number of structural quantities of interest. The ab initio results show that the dipole moments of the carbonyl groups and water molecules are highly sensitive to the hydrogen bonds (H-bonds) they participate in. In the absence of a K(+) ion, water molecules in the channel are quite mobile, making the H-bond network highly dynamic. A central K(+) ion acts as an anchor for the channel waters, stabilizing the H-bond network and thereby increasing their average dipole moments. In contrast, the K(+) ion has little effect on the dipole moments of the neighboring carbonyl groups. The weakness of the ion-peptide interactions helps to explain the near diffusion-rate conductance of K(+) ions through the channel. We also address the sampling issue in relatively short ab initio MD simulations. Results obtained from a continuous 20 ps ab initio MD simulation are compared with those generated by sampling ten windows from a much longer classical MD simulation and running each window for 2 ps with ab initio MD. Both methods yield similar results for a number of quantities of interest, indicating that fluctuations are fast enough to justify the short ab initio MD simulations.

Top-gated field-effect LaAlO{sub 3}/SrTiO{sub 3} devices made by ion-irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hurand, S.; Jouan, A.; Feuillet-Palma, C.

2016-02-01

We present a method to fabricate top-gated field-effect devices in a LaAlO{sub 3}/SrTiO{sub 3} two-dimensional electron gas (2-DEG). Prior to the gate deposition, the realisation of micron size conducting channels in the 2-DEG is achieved by an ion-irradiation with high-energy oxygen ions. After identifying the ion fluence as the key parameter that determines the electrical transport properties of the channels, we demonstrate the field-effect operation. At low temperature, the normal state resistance and the superconducting T{sub c} can be tuned over a wide range by a top-gate voltage without any leakage. A superconductor-to-insulator quantum phase transition is observed for amore » strong depletion of the 2-DEG.« less

Laser ablation inductively coupled plasma mass spectrometry for direct isotope ratio measurements on solid samples

NASA Astrophysics Data System (ADS)

Pickhardt, Carola; Dietze, Hans-Joachim; Becker, J. Sabine

2005-04-01

Isotope ratio measurements have been increasingly used in quite different application fields, e.g., for the investigation of isotope variation in nature, in geoscience (geochemistry and geochronology), in cosmochemistry and planetary science, in environmental science, e.g., in environmental monitoring, or by the application of the isotope dilution technique for quantification purposes using stable or radioactive high-enriched isotope tracers. Due to its high sensitivity, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is today a challenging mass spectrometric technique for the direct determination of precise and accurate isotope ratios in solid samples. In comparison to laser ablation quadrupole ICP-MS (LA-ICP-QMS), laser ablation coupled to a double-focusing sector field ICP-MS (LA-ICP-SFMS) with single ion detection offers a significant improvement of sensitivity at low mass resolution, whereby isotope ratios can be measured with a precision to 0.1% relative standard deviation (R.S.D.). In LA-ICP-SFMS, many disturbing isobaric interferences of analyte and molecular ions can be separated at the required mass resolution (e.g., 40Ar16O+ and 56Fe+ for iron isotope ratio measurements). The precision on isotope ratio measurements was improved by one order of magnitude via the simultaneous detection of mass-separated ion currents of isotopes using multiple ion collectors in LA-ICP-MS (LA-MC-ICP-MS). The paper discusses the state of the art, the challenges and limits in isotope ratio measurements by LA-ICP-MS using different instrumentations at the trace and ultratrace level in different fields of application as in environmental and biological research, geochemistry and geochronology with respect to their precision and accuracy.

(In)validity of the constant field and constant currents assumptions in theories of ion transport.

PubMed Central

Syganow, A; von Kitzing, E

1999-01-01

Constant electric fields and constant ion currents are often considered in theories of ion transport. Therefore, it is important to understand the validity of these helpful concepts. The constant field assumption requires that the charge density of permeant ions and flexible polar groups is virtually voltage independent. We present analytic relations that indicate the conditions under which the constant field approximation applies. Barrier models are frequently fitted to experimental current-voltage curves to describe ion transport. These models are based on three fundamental characteristics: a constant electric field, negligible concerted motions of ions inside the channel (an ion can enter only an empty site), and concentration-independent energy profiles. An analysis of those fundamental assumptions of barrier models shows that those approximations require large barriers because the electrostatic interaction is strong and has a long range. In the constant currents assumption, the current of each permeating ion species is considered to be constant throughout the channel; thus ion pairing is explicitly ignored. In inhomogeneous steady-state systems, the association rate constant determines the strength of ion pairing. Among permeable ions, however, the ion association rate constants are not small, according to modern diffusion-limited reaction rate theories. A mathematical formulation of a constant currents condition indicates that ion pairing very likely has an effect but does not dominate ion transport. PMID:9929480

Resonant ion acceleration by plasma jets: Effects of jet breaking and the magnetic-field curvature.

PubMed

Artemyev, A V; Vasiliev, A A

2015-05-01

In this paper we consider resonant ion acceleration by a plasma jet originating from the magnetic reconnection region. Such jets propagate in the background magnetic field with significantly curved magnetic-field lines. Decoupling of ion and electron motions at the leading edge of the jet results in generation of strong electrostatic fields. Ions can be trapped by this field and get accelerated along the jet front. This mechanism of resonant acceleration resembles surfing acceleration of charged particles at a shock wave. To describe resonant acceleration of ions, we use adiabatic theory of resonant phenomena. We show that particle motion along the curved field lines significantly influences the acceleration rate. The maximum gain of energy is determined by the particle's escape from the system due to this motion. Applications of the proposed mechanism to charged-particle acceleration in the planetary magnetospheres and the solar corona are discussed.

Enhancement in sensitivity of copper sulfide thin film ammonia gas sensor: Effect of swift heavy ion irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sagade, Abhay Abhimanyu; Sharma, Ramphal; Department of Chemistry, Hanyang University, Sungdong-Ku, Haengdang-dong 17, Seoul 133-791

2009-02-15

The studies are carried out on the effect of swift heavy ion (SHI) irradiation on surface morphology and electrical properties of copper sulfide (Cu{sub x}S) thin films with three different chemical compositions (x values). The irradiation experiments have been carried out on Cu{sub x}S films with x=1.4, 1.8, and 2 by 100 MeV gold heavy ions at room temperature. These as-deposited and irradiated thin films have been used to detect ammonia gas at room temperature (300 K). The SHI irradiation treatment on x=1.4 and 1.8 copper sulfide films enhances the sensitivity of the gas sensor. The results are discussed consideringmore » high electronic energy deposition by 100 MeV gold heavy ions in a matrix of copper sulfide.« less

Ion-temperature-gradient sensitivity of the hydrodynamic instability caused by shear in the magnetic-field-aligned plasma flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mikhailenko, V. V., E-mail: vladimir@pusan.ac.kr; Mikhailenko, V. S.; Faculty of Transportation Systems, Kharkiv National Automobile and Highway University, 61002 Kharkiv

2014-07-15

The cross-magnetic-field (i.e., perpendicular) profile of ion temperature and the perpendicular profile of the magnetic-field-aligned (parallel) plasma flow are sometimes inhomogeneous for space and laboratory plasma. Instability caused either by a gradient in the ion-temperature profile or by shear in the parallel flow has been discussed extensively in the literature. In this paper, (1) hydrodynamic plasma stability is investigated, (2) real and imaginary frequency are quantified over a range of the shear parameter, the normalized wavenumber, and the ratio of density-gradient and ion-temperature-gradient scale lengths, and (3) the role of inverse Landau damping is illustrated for the case of combinedmore » ion-temperature gradient and parallel-flow shear. We find that increasing the ion-temperature gradient reduces the instability threshold for the hydrodynamic parallel-flow shear instability, also known as the parallel Kelvin-Helmholtz instability or the D'Angelo instability. We also find that a kinetic instability arises from the coupled, reinforcing action of both free-energy sources. For the case of comparable electron and ion temperature, we illustrate analytically the transition of the D'Angelo instability to the kinetic instability as (a) the shear parameter, (b) the normalized wavenumber, and (c) the ratio of density-gradient and ion-temperature-gradient scale lengths are varied and we attribute the changes in stability to changes in the amount of inverse ion Landau damping. We show that near a normalized wavenumber k{sub ⊥}ρ{sub i} of order unity (i) the real and imaginary values of frequency become comparable and (ii) the imaginary frequency, i.e., the growth rate, peaks.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Xing; Ibrahim, Yehia M.; Chen, Tsung-Chi

We report the first evaluation of a platform coupling a high speed field asymmetric ion mobility spectrometry microchip (µFAIMS) with drift tube ion mobility and mass spectrometry (IMS-MS). The µFAIMS/IMS-MS platform was used to analyze biological samples and simultaneously acquire multidimensional information of detected features from the measured FAIMS compensation fields and IMS drift times, while also obtaining accurate ion masses. These separations thereby increase the overall separation power, resulting increased information content, and provide more complete characterization of more complex samples. The separation conditions were optimized for sensitivity and resolving power by the selection of gas compositions and pressuresmore » in the FAIMS and IMS separation stages. The resulting performance provided three dimensional separations, benefitting both broad complex mixture studies and targeted analyses by e.g. improving isomeric separations and allowing detection of species obscured by “chemical noise” and other interfering peaks.« less

Beyond Poisson-Boltzmann: Fluctuation effects and correlation functions

NASA Astrophysics Data System (ADS)

Netz, R. R.; Orland, H.

2000-02-01

We formulate the exact non-linear field theory for a fluctuating counter-ion distribution in the presence of a fixed, arbitrary charge distribution. The Poisson-Boltzmann equation is obtained as the saddle-point of the field-theoretic action, and the effects of counter-ion fluctuations are included by a loop-wise expansion around this saddle point. The Poisson equation is obeyed at each order in this loop expansion. We explicitly give the expansion of the Gibbs potential up to two loops. We then apply our field-theoretic formalism to the case of a single impenetrable wall with counter ions only (in the absence of salt ions). We obtain the fluctuation corrections to the electrostatic potential and the counter-ion density to one-loop order without further approximations. The relative importance of fluctuation corrections is controlled by a single parameter, which is proportional to the cube of the counter-ion valency and to the surface charge density. The effective interactions and correlation functions between charged particles close to the charged wall are obtained on the one-loop level.

Calcium ions in aqueous solutions: Accurate force field description aided by ab initio molecular dynamics and neutron scattering

NASA Astrophysics Data System (ADS)

Martinek, Tomas; Duboué-Dijon, Elise; Timr, Štěpán; Mason, Philip E.; Baxová, Katarina; Fischer, Henry E.; Schmidt, Burkhard; Pluhařová, Eva; Jungwirth, Pavel

2018-06-01

We present a combination of force field and ab initio molecular dynamics simulations together with neutron scattering experiments with isotopic substitution that aim at characterizing ion hydration and pairing in aqueous calcium chloride and formate/acetate solutions. Benchmarking against neutron scattering data on concentrated solutions together with ion pairing free energy profiles from ab initio molecular dynamics allows us to develop an accurate calcium force field which accounts in a mean-field way for electronic polarization effects via charge rescaling. This refined calcium parameterization is directly usable for standard molecular dynamics simulations of processes involving this key biological signaling ion.

Effects of the crustal magnetic fields on the Martian atmospheric ion escape rate

NASA Astrophysics Data System (ADS)

Ramstad, R.; Barbash, S.; Futaana, Y.; Nilsson, H.; Holmstrom, M.

2015-12-01

Eight years (2007-2015) of ion flux measurements from Mars Express are used to empirically investigate the influence of the Martian crustal magnetic fields on the atmospheric ion escape rate. We combine ASPERA-3/IMA (Analyzer of Space Plasmas and Energetic Atoms/Ion Mass Analyzer) measurements taken during nominal upstream solar wind and solar Extreme Ultraviolet (EUV) conditions to compute global average ion distribution functions for varying solar zenith angles (SZA) of the strongest crustal field. Escape rates are subsequently calculated from each of the average distribution functions. A statistically significant increase in escape rate is found for high dayside SZA, compared to low SZA.

Identification and quantification of cardiac glycosides in blood and urine samples by HPLC/MS/MS.

PubMed

Guan, F; Ishii, A; Seno, H; Watanabe-Suzuki, K; Kumazawa, T; Suzuki, O

1999-09-15

Cardiac glycosides (CG) are of forensic importance because of their toxicity and the fact that very limited methods are available for identification of CG in biological samples. In this study, we have developed an identification and quantification method for digoxin, digitoxin, deslanoside, digoxigenin, and digitoxigenin by high-performance liquid chromatography tandem mass spectrometry (HPLC/MS/MS). CG formed abundant [M + NH4]+ ions and much less abundant [M + H]+ ions as observed with electrospray ionization (ESI) source and ammonium formate buffer. Under mild conditions for collision-induced dissociation (CID), each [M + NH4]+ ion fragmented to produce a dominant daughter ion, which was essential to the sensitive method of selected reaction monitoring (SRM) quantification of CG achieved in this study. SRM was compared with selected ion monitoring (SIM) regarding the effects of sample matrixes on the methodology. SRM produced lower detection limits with biological samples than SIM, while both methods produced equal detection limits with CG standards. On the basis of the HPLC/MS/MS results for CG, we have proposed some generalized points for conducting sensitive SRM measurements, in view of the property of analytes as well as instrumental conditions such as the type of HPLC/MS interface and CID parameters. Analytes of which the molecular ion can produce one abundant daughter ion with high yield under CID conditions may be sensitively measured by SRM. ESI is the most soft ionization source developed so far and can afford formation of the fragile molecular ions that are necessary for sensitive SRM detection. Mild CID conditions such as low collision energy and low pressure of collision gas favor production of an abundant daughter ion that is essential to sensitive SRM detection. This knowledge may provide some guidelines for conducting sensitive SRM measurements of very low concentrations of drugs or toxicants in biological samples.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Tsung-Chi; Ibrahim, Yehia M.; Webb, Ian K.

The integration of ion mobility spectrometry (IMS) with mass spectrometry (MS) and the ability to trap ions in IMS-MS measurements is of great importance for performing reactions, accumulating ions, and increasing analytical measurement sensitivity. The development of Structures for Lossless Ion Manipulations (SLIM) offers the potential for ion manipulations in a more reliable and cost-effective manner, while opening opportunities for much more complex sequences of manipulations. Here, we demonstrate an ion separation and trapping module and a method based upon SLIM that consists of a linear mobility ion drift region, a switch/tee and a trapping region that allows the isolationmore » and accumulation of mobility-separated species. The operation and optimization of the SLIM switch/tee and trap are described and demonstrated for the enrichment of the low abundance ions. Lastly, we observed a linear increase in ion intensity with the number of trapping/accumulation events using the SLIM trap, illustrating its potential for enhancing the sensitivity of low abundance or targeted species.« less

Parg deficiency confers radio-sensitization through enhanced cell death in mouse ES cells exposed to various forms of ionizing radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shirai, Hidenori; Fujimori, Hiroaki; Gunji, Akemi

Highlights: •Parg{sup −/−} ES cells were more sensitive to γ-irradiation than Parp-1{sup −/−} ES cells. •Parg{sup −/−} cells were more sensitive to carbon-ion irradiation than Parp-1{sup −/−} cells. •Parg{sup −/−} cells showed defects in DSB repair after carbon-ion irradiation. •PAR accumulation was enhanced after carbon-ion irradiation compared to γ-irradiation. -- Abstract: Poly(ADP-ribose) glycohydrolase (Parg) is the main enzyme involved in poly(ADP-ribose) degradation. Here, the effects of Parg deficiency on sensitivity to low and high linear-energy-transfer (LET) radiation were investigated in mouse embryonic stem (ES) cells. Mouse Parg{sup −/−} and poly(ADP-ribose) polymerase-1 deficient (Parp-1{sup −/−}) ES cells were used and responsesmore » to low and high LET radiation were assessed by clonogenic survival and biochemical and biological analysis methods. Parg{sup −/−} cells were more sensitive to γ-irradiation than Parp-1{sup −/−} cells. Transient accumulation of poly(ADP-ribose) was enhanced in Parg{sup −/−} cells. Augmented levels of phosphorylated H2AX (γ-H2AX) from early phase were observed in Parg{sup −/−} ES cells. The induction level of p53 phophorylation at ser18 was similar in wild-type and Parp-1{sup −/−} cells and apoptotic cell death process was mainly observed in the both genotypes. These results suggested that the enhanced sensitivity of Parg{sup −/−} ES cells to γ-irradiation involved defective repair of DNA double strand breaks. The effects of Parg and Parp-1 deficiency on the ES cell response to carbon-ion irradiation (LET13 and 70 keV/μm) and Fe-ion irradiation (200 keV/μm) were also examined. Parg{sup −/−} cells were more sensitive to LET 70 keV/μm carbon-ion irradiation than Parp-1{sup −/−} cells. Enhanced apoptotic cell death also accompanied augmented levels of γ-H2AX in a biphasic manner peaked at 1 and 24 h. The induction level of p53 phophorylation at ser18 was not different between wild-type and Parg{sup −/−} cells. The augmented level of poly(ADP-ribose) accumulation was noted after carbon-ion irradiation compared to γ-irradiation even in the wild-type cells. An enhanced poly(ADP-ribose) accumulation was further observed in Parg{sup −/−} cells. Both Parg{sup −/−} cells and Parp-1{sup −/−} cells did not show sensitization to Fe-ion irradiation. Parg deficiency sensitizes mouse ES cells to a wide therapeutic range of LET radiation through the effects on DNA double strand break repair responses and enhanced cell death.« less

A flowing atmospheric pressure afterglow as an ion source coupled to a differential mobility analyzer for volatile organic compound detection.

PubMed

Bouza, Marcos; Orejas, Jaime; López-Vidal, Silvia; Pisonero, Jorge; Bordel, Nerea; Pereiro, Rosario; Sanz-Medel, Alfredo

2016-05-23

Atmospheric pressure glow discharges have been widely used in the last decade as ion sources in ambient mass spectrometry analyses. Here, an in-house flowing atmospheric pressure afterglow (FAPA) has been developed as an alternative ion source for differential mobility analysis (DMA). The discharge source parameters (inter-electrode distance, current and helium flow rate) determining the atmospheric plasma characteristics have been optimized in terms of DMA spectral simplicity with the highest achievable sensitivity while keeping an adequate plasma stability and so the FAPA working conditions finally selected were: 35 mA, 1 L min(-1) of He and an inter-electrode distance of 8 mm. Room temperature in the DMA proved to be adequate for the coupling and chemical analysis with the FAPA source. Positive and negative ions for different volatile organic compounds were tested and analysed by FAPA-DMA using a Faraday cup as a detector and proper operation in both modes was possible (without changes in FAPA operational parameters). The FAPA ionization source showed simpler ion mobility spectra with narrower peaks and a better, or similar, sensitivity than conventional UV-photoionization for DMA analysis in positive mode. Particularly, the negative mode proved to be a promising field of further research for the FAPA ion source coupled to ion mobility, clearly competitive with other more conventional plasmas such as corona discharge.

Structure and luminescent property of complexes of aryl carboxylic acid-functionalized polystyrene with Eu(III) and Tb(III) ions.

PubMed

Gao, Baojiao; Shi, Nan; Qiao, Zongwen

2015-11-05

Via polymer reactions, naphthoic acid (NA) and benzoic acid (BA) were bonded onto the side chains of polystyrene (PS), respectively, and two aryl carboxylic acid-functionalized polystyrenes, PSNA and PSBA, were obtained. Using PSNA and PSBA as macromolecule ligands and Eu(3+) and Tb(3+) ions as central ions, various luminescent binary polymer-rare earth complexes were prepared. At the same time, with 1,10-phenanthroline (Phen) and 4,4'-bipyridine (Bipy) as small-molecule co-ligands, various ternary polymer-rare earth complexes were also prepared. On the basis of characterizing PSNA, PSBA and complexes, the relationship between structure and luminescent property for these prepared complexes were mainly investigated. The study results show that the macromolecule ligands PSNA and PSBA, or the bonded NA and BA ligands, can strongly sensitize the fluorescence emissions of Eu(3+) ion or Tb(3+) ion, but the sensitization effect is strongly dependent on the structure of the ligands and the property of the central ions, namely it is strongly dependent on the matching degree of energy levels. The fluorescence emission of the binary complex PS-(NA)3-Eu(III) is stronger than that PS-(BA)3-Eu(III), indicating ligand NA has stronger sensitization action for Eu(3+) ion than ligand BA; the binary complex PS-(BA)3-Tb(III) emit strong characteristic fluorescence of Tb(3+) ion, displaying that ligand BA can strongly sensitize Tb(3+) ion, whereas the binary complex PS-(NA)3-Tb(III) nearly does not emit the characteristic fluorescence of Tb(3+) ion, showing that ligand NA does not sensitize Tb(3+) ion. The fluorescence intensity of the ternary complexes is much stronger than that of the binary complexes in the same series. Copyright © 2015 Elsevier B.V. All rights reserved.

Ultrasensitive detection of target analyte-induced aggregation of gold nanoparticles using laser-induced nanoparticle Rayleigh scattering.

PubMed

Lin, Jia-Hui; Tseng, Wei-Lung

2015-01-01

Detection of salt- and analyte-induced aggregation of gold nanoparticles (AuNPs) mostly relies on costly and bulky analytical instruments. To response this drawback, a portable, miniaturized, sensitive, and cost-effective detection technique is urgently required for rapid field detection and monitoring of target analyte via the use of AuNP-based sensor. This study combined a miniaturized spectrometer with a 532-nm laser to develop a laser-induced Rayleigh scattering technique, allowing the sensitive and selective detection of Rayleigh scattering from the aggregated AuNPs. Three AuNP-based sensing systems, including salt-, thiol- and metal ion-induced aggregation of the AuNPs, were performed to examine the sensitivity of laser-induced Rayleigh scattering technique. Salt-, thiol-, and metal ion-promoted NP aggregation were exemplified by the use of aptamer-adsorbed, fluorosurfactant-stabilized, and gallic acid-capped AuNPs for probing K(+), S-adenosylhomocysteine hydrolase-induced hydrolysis of S-adenosylhomocysteine, and Pb(2+), in sequence. Compared to the reported methods for monitoring the aggregated AuNPs, the proposed system provided distinct advantages of sensitivity. Laser-induced Rayleigh scattering technique was improved to be convenient, cheap, and portable by replacing a diode laser and a miniaturized spectrometer with a laser pointer and a smart-phone. Using this smart-phone-based detection platform, we can determine whether or not the Pb(2+) concentration exceed the maximum allowable level of Pb(2+) in drinking water. Copyright © 2014 Elsevier B.V. All rights reserved.

Numerical simulation of plasma processes driven by transverse ion heating

NASA Technical Reports Server (NTRS)

Singh, Nagendra; Chan, C. B.

1993-01-01

The plasma processes driven by transverse ion heating in a diverging flux tube are investigated with numerical simulation. The heating is found to drive a host of plasma processes, in addition to the well-known phenomenon of ion conics. The downward electric field near the reverse shock generates a doublestreaming situation consisting of two upflowing ion populations with different average flow velocities. The electric field in the reverse shock region is modulated by the ion-ion instability driven by the multistreaming ions. The oscillating fields in this region have the possibility of heating electrons. These results from the simulations are compared with results from a previous study based on a hydrodynamical model. Effects of spatial resolutions provided by simulations on the evolution of the plasma are discussed.

Selective and sensitized spectrophotometric determination of trace amounts of Ni(II) ion using α-benzyl dioxime in surfactant media

NASA Astrophysics Data System (ADS)

Ghaedi, Mehrorang

2007-02-01

Highly sensitive and interference-free sensitized spectrophotometric method for the determination of Ni(II) ions is described. The method is based on the reaction between Ni(II) ion and benzyl dioxime in micellar media in the presence of sodium dodecyl sulfate (SDS). The absorbance is linear from 0.1 up to 25.0 μg mL -1 in aqueous solution with repeatability (RSD) of 1.0% at a concentration of 1 μg mL -1 and a detection limit of 0.12 ng mL -1 and molar absorption coefficient of 68,600 L mol -1 cm -1. The influence of reaction variables including type and amount of surfactant, pH, and amount of ligand and complexation time and the effect of interfering ions are investigated. The proposed procedure was applied to the determination of trace amounts of Ni(II) ion in tap water, river water, chocolate and vegetable without separation or organic solvent extraction.

Effects of heavy ion to the primary culture of mouse brain cells

NASA Technical Reports Server (NTRS)

Nojima, Kumie; Nakadai, Taeko; Kohno, Yukio; Vazquez, Marcelo E.; Yasuda, Nakahiro; Nagaoka, Shunji

2004-01-01

To investigate effects of low dose heavy particle radiation to CNS system, we adopted mouse neonatal brain cells in culture being exposed to heavy ions by HIMAC at NIRS and NSRL at BNL. The applied dose varied from 0.05 Gy up to 2.0 Gy. The subsequent biological effects were evaluated by an induction of apoptosis and neuron survival focusing on the dependencies of the animal strains, SCID, B6, B6C3F1, C3H, used for brain cell culture, SCID was the most sensitive and C3H the least sensitive to particle radiation as evaluated by 10% apoptotic criterion. The LET dependency was compared with using SCID and B6 cells exposing to different ions (H, C, Ne, Si, Ar, and Fe). Although no detectable LET dependency was observed in the high LET (55-200 keV/micrometers) and low dose (<0.5 Gy) regions. The survivability profiles of the neurons were different in the mouse strains and ions. In this report, a result of memory and learning function to adult mice after whole-body and brain local irradiation at carbon ion and iron ion.

Extended linear ion trap frequency standard apparatus

NASA Technical Reports Server (NTRS)

Prestage, John D. (Inventor)

1995-01-01

A linear ion trap for frequency standard applications is provided with a plurality of trapping rods equally spaced and applied quadruple rf voltages for radial confinement of atomic ions and biased level pins at each end for axial confinement of the ions. The trapping rods are divided into two linear ion trap regions by a gap in each rod in a common radial plane to provide dc discontinuity, thus dc isolating one region from the other. A first region for ion-loading and preparation fluorescence is biased with a dc voltage to transport ions into a second region for resonance frequency comparison with a local oscillator derived frequency while the second region is held at zero voltage. The dc bias voltage of the regions is reversed for transporting the ions back into the first region for fluorescence measurement. The dual mode cycle is repeated continuously for comparison and feedback control of the local oscillator derived frequency. Only the second region requires magnetic shielding for the resonance function which is sensitive to any ambient magnetic fields.

pH- and ion-sensitive polymers for drug delivery

PubMed Central

Yoshida, Takayuki; Lai, Tsz Chung; Kwon, Glen S; Sako, Kazuhiro

2013-01-01

Introduction Drug delivery systems (DDSs) are important for effective, safe, and convenient administration of drugs. pH- and ion-responsive polymers have been widely employed in DDS for site-specific drug release due to their abilities to exploit specific pH- or ion-gradients in the human body. Areas covered Having pH-sensitivity, cationic polymers can mask the taste of drugs and release drugs in the stomach by responding to gastric low pH. Anionic polymers responsive to intestinal high pH are used for preventing gastric degradation of drug, colon drug delivery and achieving high bioavailability of weak basic drugs. Tumor-targeted DDSs have been developed based on polymers with imidazole groups or poly(β-amino ester) responsive to tumoral low pH. Polymers with pH-sensitive chemical linkages, such as hydrazone, acetal, ortho ester and vinyl ester, pH-sensitive cell-penetrating peptides and cationic polymers undergoing pH-dependent protonation have been studied to utilize the pH gradient along the endocytic pathway for intracellular drug delivery. As ion-sensitive polymers, ion-exchange resins are frequently used for taste-masking, counterion-responsive drug release and sustained drug release. Polymers responding to ions in the saliva and gastrointestinal fluids are also used for controlled drug release in oral drug formulations. Expert opinion Stimuli-responsive DDSs are important for achieving site-specific and controlled drug release; however, intraindividual, interindividual and intercellular variations of pH should be considered when designing DDSs or drug products. Combination of polymers and other components, and deeper understanding of human physiology are important for development of pH- and ion-sensitive polymeric DDS products for patients. PMID:23930949

High pressure effects in high-field asymmetric waveform ion mobility spectrometry.

PubMed

Wang, Yonghuan; Wang, Xiaozhi; Li, Lingfen; Chen, Chilai; Xu, Tianbai; Wang, Tao; Luo, Jikui

2016-08-30

High-Field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS) is an analytical technique based on the principle of non-linear electric field dependence of coefficient of mobility of ions for separation that was originally conceived in the Soviet Union in the early 1980s. Being well developed over the past decades, FAIMS has become an efficient method for the separation and characterization of gas-phase ions at ambient pressure, often in air, to detect trace amounts of chemical species including explosives, toxic chemicals, chemical warfare agents and other compounds. However the resolution of FAIMS and ion separation capability need to be improved for more applications of the technique. The effects of above-ambient pressure varying from 1 to 3 atm on peak position, resolving power, peak width, and peak intensity are investigated theoretically and experimentally using micro-fabricated planar FAIMS in purified air. Peak positions, varying with pressure in a way as a function of dispersion voltage, could be simplified by expressing both compensation and dispersion fields in Townsend units for E/N, the ratio of electric field intensity (E) to the gas number density (N). It is demonstrated that ion Townsend-scale peak positions remain unchanged for a range of pressures investigated, implying that the higher the pressure is, stronger compensation and separation fields are needed within limits of air breakdown field. Increase in pressure is found to separate ions that could not be distinguished in ambient pressure, which could be interpreted as the differentials of ions' peak compensation voltage expanded wider than the dilation of peak widths leading to resolving power enhancement with pressure. Increase in pressure can also result in an increase in peak intensity. Copyright © 2016 John Wiley & Sons, Ltd.

Shielded capacitive electrode

DOEpatents

Kireeff Covo, Michel

2013-07-09

A device is described, which is sensitive to electric fields, but is insensitive to stray electrons/ions and unlike a bare, exposed conductor, it measures capacitively coupled current while rejecting currents due to charged particle collected or emitted. A charged particle beam establishes an electric field inside the beam pipe. A grounded metallic box with an aperture is placed in a drift region near the beam tube radius. The produced electric field that crosses the aperture generates a fringe field that terminates in the back surface of the front of the box and induces an image charge. An electrode is placed inside the grounded box and near the aperture, where the fringe fields terminate, in order to couple with the beam. The electrode is negatively biased to suppress collection of electrons and is protected behind the front of the box, so the beam halo cannot directly hit the electrode and produce electrons. The measured signal shows the net potential (positive ion beam plus negative electrons) variation with time, as it shall be observed from the beam pipe wall.

AlN metal-semiconductor field-effect transistors using Si-ion implantation

NASA Astrophysics Data System (ADS)

Okumura, Hironori; Suihkonen, Sami; Lemettinen, Jori; Uedono, Akira; Zhang, Yuhao; Piedra, Daniel; Palacios, Tomás

2018-04-01

We report on the electrical characterization of Si-ion implanted AlN layers and the first demonstration of metal-semiconductor field-effect transistors (MESFETs) with an ion-implanted AlN channel. The ion-implanted AlN layers with Si dose of 5 × 1014 cm-2 exhibit n-type characteristics after thermal annealing at 1230 °C. The ion-implanted AlN MESFETs provide good drain current saturation and stable pinch-off operation even at 250 °C. The off-state breakdown voltage is 2370 V for drain-to-gate spacing of 25 µm. These results show the great potential of AlN-channel transistors for high-temperature and high-power applications.

An electrostatic autoresonant ion trap mass spectrometer.

PubMed

Ermakov, A V; Hinch, B J

2010-01-01

A new method for ion extraction from an anharmonic electrostatic trap is introduced. Anharmonicity is a common feature of electrostatic traps which can be used for small scale spatial confinement of ions, and this feature is also necessary for autoresonant ion extraction. With the aid of ion trajectory simulations, novel autoresonant trap mass spectrometers (ART-MSs) have been designed based on these very simple principles. A mass resolution approximately 60 is demonstrated for the prototypes discussed here. We report also on the pressure dependencies, and the (mV) rf field strength dependencies of the ART-MS sensitivity. Importantly the new MS designs do not require heavy magnets, tight manufacturing tolerances, introduction of buffer gases, high power rf sources, nor complicated electronics. The designs described here are very inexpensive to implement relative to other instruments, and can be easily miniaturized. Possible applications are discussed.

Influence of dilution water composition on acute major ion toxicity to the mayfly Neocloeon triangulifer.

EPA Science Inventory

A number of field studies have shown that mayflies (Ephemeroptera) tend to be more sensitive than other benthic macroinvertebrates to elevated levels of total dissolved solids in streams. Until relatively recently, difficulties with culturing have limited the use of mayflies as ...

A highly sensitive electron spectrometer for crossed-beam collisional ionization: A retarding-type magnetic bottle analyzer and its application to collision-energy resolved Penning ionization electron spectroscopy

NASA Astrophysics Data System (ADS)

Yamakita, Yoshihiro; Tanaka, Hideyasu; Maruyama, Ryo; Yamakado, Hideo; Misaizu, Fuminori; Ohno, Koichi

2000-08-01

A highly sensitive electron energy analyzer which utilizes a "magnetic bottle" combined with a retarding electrostatic field has been developed for Penning ionization electron spectroscopy. A beam of metastable rare-gas atoms is crossed with a continuous supersonic sample beam in the source region of the analyzer. The emitted electrons are collected by an inhomogeneous magnetic field (the magnetic bottle effect) with a high efficiency of nearly 4π solid angle, which is more than 103 times higher than that of a conventional hemispherical analyzer. The kinetic energy of electrons is analyzed by scanning the retarding field in a flight tube of the analyzer in the presence of a weak magnetic field. The velocity of the metastable atoms can also be resolved by a time-of-flight method in the present instrument. Examples of Penning ionization electron energy spectra as a function of collision energy are presented for Ar and N2 with metastable He*(2 3S) atoms. This instrument has opened the possibility for extensive studies of Penning ionization electron spectroscopy for low-density species, such as clusters, ions, electronically excited species, unstable or transient species, and large molecules with low volatility.

Direct numerical simulation of the effect of an electric field on flame stability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belhi, Memdouh; Domingo, Pascale; Vervisch, Pierre

2010-12-15

The role of electric fields in stabilising combustion is a well-known phenomenon. Among the possible mechanisms favouring the anchorage of the flame base, the ion-driven wind acting directly on flow momentum ahead of the flame base could be the leading one. Direct numerical simulation has been used to verify this hypothesis and lead to a better understanding of diffusion flame base anchoring in the presence of an externally applied voltage. In this context, a simplified modelling approach is proposed to describe combustion in the presence of electric body forces. The model reproduces the tendencies of experimental observations found in themore » literature. The sensitivity of the flame lift-off height to the applied voltage is studied and the modification of the velocity field ahead of the flame base induced by the electric volume forces is highlighted. (author)« less

[Modulating effect of weak combined magnetic fields on duration of mealworm beetle Tenebrio molitor metamorphosis stage].

PubMed

Novikov, V V; Sheĭman, I M; Iablokova, E V; Fesenko, E E

2014-01-01

It is shown that an exposure of pupae of the mealworm beetle Tenebrio molitor to the combined static (42 μT) and very weak alternating (250 nT) magnetic fields exerts different influence, depending on the frequency of the alternating magnetic field, on duration of metamorphosis processes in these insects. For instance, an exposure of pupae to weak combined magnetic fields, adjusted to the frequency of ion cyclotron resonance for glutaminic acid (4,4 Hz), stimulates metamorphosis process--a transitional stage from pupae to imago lasts shorter. An inhibiting effect was observed when adjusted to the frequency of ion cyclotron resonance for Ca2 (32,2 Hz). At some frequencies this effect is not seen. For instance, an exposure at a frequency of ion cyclotron resonance for K+ (16,5 Hz) exerts no noticeable effect on the duration of the pupal metamorphosis stage.

Development of a pepper pot emittance probe and its application for ECR ion beam studies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kondrashev, S.; Barcikowski, A.; Mustapha, B.

2009-07-21

A pepper pot-scintillator screen system has been developed and used to measure the emittance of DC ion beams extracted from a high-intensity permanent magnet ECR ion source. The system includes a fast beam shutter with a minimum dwell time of 18 ms to reduce the degradation of the CsI(Tl) scintillator by DC ion beam irradiation and a CCD camera with a variable shutter speed in the range of 1 {micro}s-65 s. On-line emittance measurements are performed by an application code developed on a LabVIEW platform. The sensitivity of the device is sufficient to measure the emittance of DC ion beamsmore » with current densities down to about 100 nA/cm{sup 2}. The emittance of all ion species extracted from the ECR ion source and post-accelerated to an energy of 75-90 keV/charge have been measured downstream of the LEBT. As the mass-to-charge ratio of ion species increases, the normalized RMS emittances in both transverse phase planes decrease from 0.5-1.0 {pi} mm mrad for light ions to 0.05-0.09 {pi} mm mrad for highly charged {sup 209}Bi ions. The dependence of the emittance on ion's mass-to-charge ratio follows very well the dependence expected from beam rotation induced by decreasing ECR axial magnetic field. The measured emittance values cannot be explained by only ion beam rotation for all ion species and the contribution to emittance of ion temperature in plasma, non-linear electric fields and non-linear space charge is comparable or even higher than the contribution of ion beam rotation.« less

Exploiting enzyme catalysis in ultra-low ion strength media for impedance biosensing of avian influenza virus using a bare interdigitated electrode.

PubMed

Fu, Yingchun; Callaway, Zachary; Lum, Jacob; Wang, Ronghui; Lin, Jianhan; Li, Yanbin

2014-02-18

Enzyme catalysis is broadly used in various fields but generally applied in media with high ion strength. Here, we propose the exploitation of enzymatic catalysis in ultra-low ion strength media to induce ion strength increase for developing a novel impedance biosensing method. Avian influenza virus H5N1, a serious worldwide threat to poultry and human health, was adopted as the analyte. Magnetic beads were modified with H5N1-specific aptamer to capture the H5N1 virus. This was followed by binding concanavalin A (ConA), glucose oxidase (GOx), and Au nanoparticles (AuNPs) to create bionanocomposites through a ConA-glycan interaction. The yielded sandwich complex was transferred to a glucose solution to trigger an enzymatic reaction to produce gluconic acid, which ionized to increase the ion strength of the solution, thus decreasing the impedance on a screen-printed interdigitated array electrode. This method took advantages of the high efficiency of enzymatic catalysis and the high susceptibility of electrochemical impedance on the ion strength and endowed the biosensor with high sensitivity and a detection limit of 8 × 10(-4) HAU in 200 μL sample, which was magnitudes lower than that of some analogues based on biosensing methods. Furthermore, the proposed method required only a bare electrode for measurements of ion strength change and had negligible change on the surficial properties of the electrode, though some modification of magnetic beads/Au nanoparticles and the construction of a sandwich complex were still needed. This helped to avoid the drawbacks of commonly used electrode immobilization methods. The merit for this method makes it highly useful and promising for applications. The proposed method may create new possibilities in the broad and well-developed enzymatic catalysis fields and find applications in developing sensitive, rapid, low-cost, and easy-to-operate biosensing and biocatalysis devices.

Improving the performance of methylene blue sensitized photopolymer by doping with nickel ion

NASA Astrophysics Data System (ADS)

Aswathy, G.; Rajesh, C. S.; Sreekumar, K.; Joseph, R.; Kartha, C. Sudha

2016-05-01

Holographic performance of an economically cheap metal ion doped photopolymer material is presented. We investigated the effect of incorporation of nickel ion into the methylene blue sensitized poly (vinyl alcohol)/acrylamide (MBPVA/AA) photopolymer system. The composition and preliminary characterization of the developed photopolymer material is reported. The presence of nickel ion improves the diffraction efficiency, stability of the material and it operates in a wide range of spatial frequencies (550-2000 lines/mm) at exposure energy of 100 mJ/cm2. When nickel ion concentration was 0.01 mM, maximum diffraction efficiency of 84% at exposure energy of 100 mJ/cm2 with spatial frequency 1335 lines/mm could be achieved for gratings recorded using wavelength of 632.8 nm. The material showed panchromaticity with more than 70% diffraction efficiency in both blue and green regions. Effects of humidity and temperature on the stored gratings were studied by keeping films in different environmental conditions. Suitability of recording large area holograms was also explored.

Development of Ion Chemosensors Based on Porphyrin Analogues.

PubMed

Ding, Yubin; Zhu, Wei-Hong; Xie, Yongshu

2017-02-22

Sensing of metal ions and anions is of great importance because of their widespread distribution in environmental systems and biological processes. Colorimetric and fluorescent chemosensors based on organic molecular species have been demonstrated to be effective for the detection of various ions and possess the significant advantages of low cost, high sensitivity, and convenient implementation. Of the available classes of organic molecules, porphyrin analogues possess inherently many advantageous features, making them suitable for the design of ion chemosensors, with the targeted sensing behavior achieved and easily modulated based on their following characteristics: (1) NH moieties properly disposed for binding of anions through cooperative hydrogen-bonding interactions; (2) multiple pyrrolic N atoms or other heteroatoms for selectively chelating metal ions; (3) variability of macrocycle size and peripheral substitution for modulation of ion selectivity and sensitivity; and (4) tunable near-infrared emission and good biocompatibility. In this Review, design strategies, sensing mechanisms, and sensing performance of ion chemosensors based on porphyrin analogues are described by use of extensive examples. Ion chemosensors based on normal porphyrins and linear oligopyrroles are also briefly described. This Review provides valuable information for researchers of related areas and thus may inspire the development of more practical and effective approaches for designing high-performance ion chemosensors based on porphyrin analogues and other relevant compounds.

Optical transitions in highly charged californium ions with high sensitivity to variation of the fine-structure constant.

PubMed

Berengut, J C; Dzuba, V A; Flambaum, V V; Ong, A

2012-08-17

We study electronic transitions in highly charged Cf ions that are within the frequency range of optical lasers and have very high sensitivity to potential variations in the fine-structure constant, α. The transitions are in the optical range despite the large ionization energies because they lie on the level crossing of the 5f and 6p valence orbitals in the thallium isoelectronic sequence. Cf(16+) is a particularly rich ion, having several narrow lines with properties that minimize certain systematic effects. Cf(16+) has very large nuclear charge and large ionization energy, resulting in the largest α sensitivity seen in atomic systems. The lines include positive and negative shifters.

Using GPU parallelization to perform realistic simulations of the LPCTrap experiments

NASA Astrophysics Data System (ADS)

Fabian, X.; Mauger, F.; Quéméner, G.; Velten, Ph.; Ban, G.; Couratin, C.; Delahaye, P.; Durand, D.; Fabre, B.; Finlay, P.; Fléchard, X.; Liénard, E.; Méry, A.; Naviliat-Cuncic, O.; Pons, B.; Porobic, T.; Severijns, N.; Thomas, J. C.

2015-11-01

The LPCTrap setup is a sensitive tool to measure the β - ν angular correlation coefficient, a β ν , which can yield the mixing ratio ρ of a β decay transition. The latter enables the extraction of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element V u d . In such a measurement, the most relevant observable is the energy distribution of the recoiling daughter nuclei following the nuclear β decay, which is obtained using a time-of-flight technique. In order to maximize the precision, one can reduce the systematic errors through a thorough simulation of the whole set-up, especially with a correct model of the trapped ion cloud. This paper presents such a simulation package and focuses on the ion cloud features; particular attention is therefore paid to realistic descriptions of trapping field dynamics, buffer gas cooling and the N-body space charge effects.

Ion mobility spectrometry for food quality and safety.

PubMed

Vautz, W; Zimmermann, D; Hartmann, M; Baumbach, J I; Nolte, J; Jung, J

2006-11-01

Ion mobility spectrometry is known to be a fast and sensitive technique for the detection of trace substances, and it is increasingly in demand not only for protection against explosives and chemical warfare agents, but also for new applications in medical diagnosis or process control. Generally, a gas phase sample is ionized by help of ultraviolet light, ss-radiation or partial discharges. The ions move in a weak electrical field towards a detector. During their drift they collide with a drift gas flowing in the opposite direction and, therefore, are slowed down depending on their size, shape and charge. As a result, different ions reach the detector at different drift times, which are characteristic for the ions considered. The number of ions reaching the detector are a measure of the concentration of the analyte. The method enables the identification and quantification of analytes with high sensitivity (ng l(-1) range). The selectivity can even be increased - as necessary for the analyses of complex mixtures - using pre-separation techniques such as gas chromatography or multi-capillary columns. No pre-concentration of the sample is necessary. Those characteristics of the method are preserved even in air with up to a 100% relative humidity rate. The suitability of the method for application in the field of food quality and safety - including storage, process and quality control as well as the characterization of food stuffs - was investigated in recent years for a number of representative examples, which are summarized in the following, including new studies as well: (1) the detection of metabolites from bacteria for the identification and control of their growth; (2) process control in food production - beer fermentation being an example; (3) the detection of the metabolites of mould for process control during cheese production, for quality control of raw materials or for the control of storage conditions; (4) the quality control of packaging materials during the production of polymeric materials; and (5) the characterization of products - wine being an example. The challenges of such applications were operation in humid air, fast on-line analyses of complex mixtures, high sensitivity - detection limits have to be, for example, in the range of the odour limits - and, in some cases, the necessity of mobile instrumentation. It can be shown that ion mobility spectrometry is optimally capable of fulfilling those challenges for many applications.

Near-membrane electric field calcium ion dehydration.

PubMed

Barger, James P; Dillon, Patrick F

2016-12-01

The dehydration of ion-water complexes prior to ion channel transit has focused on channel protein-mediated dissociation of water. Ion dehydration by the membrane electric field has not previously been considered. Near membrane electric fields have previously been shown to cause the disassociation of non-covalently bound small molecule-small molecule, small molecule-protein, and protein-protein complexes. It is well known that cosmotropic, structure making ions such as calcium and sodium significantly bind multiple water ions in solution. It is also known that these ions are often not hydrated as they pass through membrane ion channels. Using capillary electrophoresis, the range of electric fields needed to strip water molecules from calcium ions has been measured. Ion migration velocity is a linear function of the electric field. At low electric fields, the migration rate of calcium ion was shown to be linearly related to the applied electric field. Using a form of the Stoke's equation applicable to ion migration, the hydrated calcium radius was found to be 0.334nm, corresponding to a water hydration shell of 5.09 water molecules. At higher electric fields, the slope of the calcium migration velocity as a function of the electric field increased, which was modeled as a decrease in the radius of the migrating ion as the water was removed. Using a tanh function to model the transition of the ion from a hydrated to a stripped state, the transition had a midpoint at 446V/cm, and was 88% complete at 587V/cm with a correlation coefficient of 0.9996. The migration velocity of the stripped calcium ion was found to be a function of both the decrease in radius and an increase in the effective, electronic viscosity of the dipole medium through which the dehydrated ion moved. The size of the electric field needed to dehydrate calcium occurs 6-7nm from the cell membrane. Calcium ions within this distance from the membrane will be devoid of water molecules when they reach the calcium selective channel pore entrances, all known to be approximately 1-2nm from the membrane. No matter what the calcium pore structure, calcium ions reaching the channel entrance will be devoid of a water shell. Copyright © 2016 Elsevier Ltd. All rights reserved.

Developing a polymeric sensor to monitor intracellular conditions

NASA Astrophysics Data System (ADS)

Mudarri, Timothy C.; Leo, Donald J.; Wood, Brett C.; Shires, Peter K.

2004-07-01

Ionic electroactive polymers have been developed as mechanical sensors or actuators, taking advantage of the electromechanical coupling of the materials. This research attempts to take advantage of the chemomechanical and chemoelectrical coupling by characterizing the transient response as the polymer undergoes an ion exchange, thus using the polymer for ionic sensing. Nafion is a biocompatible material, and an implantable polymeric ion sensor which has applications in the biomedical field for bone healing research. An ion sensor and a strain gauge could determine the effects of motion allowed at the fracture site, thus improving rehabilitation procedures for bone fractures. The charge sensitivity of the material and the capacitance of the material were analyzed to determine the transient response. Both measures indicate a change when immersed in ionic salt solutions. It is demonstrated that measuring the capacitance is the best indicator of an ion exchange. Relative to a flat response in deionized water (+/-2%), the capacitance of the polymer exhibits an exponential decay of ~25% of its peak when placed in a salt solution. A linear correlation between the time constant of the decay and the ionic size of the exchanging ion was developed that could reasonably predict a diffusing ion. Tests using an energy dispersive spectrometer (EDS) indicate that 90% of the exchange occurs in the first 20 minutes, shown by both capacitance decay and an atomic level scan. The diffusion rate time constant was found to within 0.3% of the capacitance time constant, confirming the ability of capacitance to measure ion exchange.

Energy deposition measurements of single 1H, 4He and 12C ions of therapeutic energies in a silicon pixel detector

NASA Astrophysics Data System (ADS)

Gehrke, T.; Burigo, L.; Arico, G.; Berke, S.; Jakubek, J.; Turecek, D.; Tessonnier, T.; Mairani, A.; Martišíková, M.

2017-04-01

In the field of ion-beam radiotherapy and space applications, measurements of the energy deposition of single ions in thin layers are of interest for dosimetry and imaging. The present work investigates the capability of a pixelated detector Timepix to measure the energy deposition of single ions in therapeutic proton, helium- and carbon-ion beams in a 300 μm-thick sensitive silicon layer. For twelve different incident beams, the measured energy deposition distributions of single ions are compared to the expected energy deposition spectra, which were predicted by detailed Monte Carlo simulations using the FLUKA code. A methodology for the analysis of the measured data is introduced in order to identify and reject signals that are either degraded or caused by multiple overlapping ions. Applying a newly proposed linear recalibration, the energy deposition measurements are in good agreement with the simulations. The twelve measured mean energy depositions between 0.72 MeV/mm and 56.63 MeV/mm in a partially depleted silicon sensor do not deviate more than 7% from the corresponding simulated values. Measurements of energy depositions above 10 MeV/mm with a fully depleted sensor are found to suffer from saturation effects due to the too high per-pixel signal. The utilization of thinner sensors, in which a lower signal is induced, could further improve the performance of the Timepix detector for energy deposition measurements.

TU-H-CAMPUS-TeP2-03: High Sensitivity and High Resolution Fiber Based Micro-Detector for Sub-Millimeter Preclinical Dosimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Izaguirre, E; Pokhrel, S; Knewtson, T

2016-06-15

Purpose: Current precision of small animal and cell micro-irradiators has continuously increased during the past years. Currently, preclinical irradiators can deliver sub-millimeter fields with micrometric precision but there are no water equivalent dosimeters to determine small field profiles and dose in the orthovoltage range of energies with micrometric resolution and precision. We have developed a fiber based micro-dosimeter with the resolution and dosimetric accuracy required for radiobiological research. Methods: We constructed two prototypes of micro-dosimeters based on different compositions of fiber scintillators to study the spatial resolution and dosimetric precision of small animal and cell micro-irradiators. The first has greenmore » output and the second has blue output. The blue output dosimeter has the highest sensitivity because it matches the spectral sensitivity of silicon photomultipliers. A blue detector with 500um cross section was built and tested respect to a CC01 ion chamber, film, and the 1500um green output detector. Orthovoltage fields from 1×1mm2 to 5×5mm2 were used for detector characteristics comparison. Results: The blue fiber dosimeter shows great agreement with films and matches dose measurements with the gold-standard ion chamber for 5×5mm2 fields. The detector has the appropriate sensitivity to measure fields from 1×1mm2 to larger sizes with a 1% dosimetric accuracy. The spatial resolution is in the sub-millimeter range and the spectral matching with the photomultiplier allows reducing the sensor cross section even further than the presented prototype. These results suggest that scintillating fibers combined with silicon photomultipliers is the appropriate technology to pursue micro-dosimetry for small animals and disperse cell samples. Conclusion: The constructed detectors establish a new landmark for the resolution and sensitivity of fiber based microdetectors. The validation of the detector in our small animal and cell irradiator shows that they are appropriate for preclinical and micro single cell irradiation quality assurance and dosimetry.« less

Programmable ion-sensitive transistor interfaces. III. Design considerations, signal generation, and sensitivity enhancement

NASA Astrophysics Data System (ADS)

Jayant, Krishna; Auluck, Kshitij; Rodriguez, Sergio; Cao, Yingqiu; Kan, Edwin C.

2014-05-01

We report on factors that affect DNA hybridization detection using ion-sensitive field-effect transistors (ISFETs). Signal generation at the interface between the transistor and immobilized biomolecules is widely ascribed to unscreened molecular charges causing a shift in surface potential and hence the transistor output current. Traditionally, the interaction between DNA and the dielectric or metal sensing interface is modeled by treating the molecular layer as a sheet charge and the ionic profile with a Poisson-Boltzmann distribution. The surface potential under this scenario is described by the Graham equation. This approximation, however, often fails to explain large hybridization signals on the order of tens of mV. More realistic descriptions of the DNA-transistor interface which include factors such as ion permeation, exclusion, and packing constraints have been proposed with little or no corroboration against experimental findings. In this study, we examine such physical models by their assumptions, range of validity, and limitations. We compare simulations against experiments performed on electrolyte-oxide-semiconductor capacitors and foundry-ready floating-gate ISFETs. We find that with weakly charged interfaces (i.e., low intrinsic interface charge), pertinent to the surfaces used in this study, the best agreement between theory and experiment exists when ions are completely excluded from the DNA layer. The influence of various factors such as bulk pH, background salinity, chemical reactivity of surface groups, target molecule concentration, and surface coatings on signal generation is studied. Furthermore, in order to overcome Debye screening limited detection, we suggest two signal enhancement strategies. We first describe frequency domain biosensing, highlighting the ability to sort short DNA strands based on molecular length, and then describe DNA biosensing in multielectrolytes comprising trace amounts of higher-valency salt in a background of monovalent saline. Our study provides guidelines for optimized interface design, signal enhancement, and the interpretation of FET-based biosensor signals.

Hall Effect–Mediated Magnetic Flux Transport in Protoplanetary Disks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bai, Xue-Ning; Stone, James M.

2017-02-10

The global evolution of protoplanetary disks (PPDs) has recently been shown to be largely controlled by the amount of poloidal magnetic flux threading the disk. The amount of magnetic flux must also coevolve with the disk, as a result of magnetic flux transport, a process that is poorly understood. In weakly ionized gas as in PPDs, magnetic flux is largely frozen in the electron fluid, except when resistivity is large. When the disk is largely laminar, we show that the relative drift between the electrons and ions (the Hall drift), and the ions and neutral fluids (ambipolar drift) can playmore » a dominant role on the transport of magnetic flux. Using two-dimensional simulations that incorporate the Hall effect and ambipolar diffusion (AD) with prescribed diffusivities, we show that when large-scale poloidal field is aligned with disk rotation, the Hall effect rapidly drags magnetic flux inward at the midplane region, while it slowly pushes flux outward above/below the midplane. This leads to a highly radially elongated field configuration as a global manifestation of the Hall-shear instability. This field configuration further promotes rapid outward flux transport by AD at the midplane, leading to instability saturation. In quasi-steady state, magnetic flux is transported outward at approximately the same rate at all heights, and the rate is comparable to the Hall-free case. For anti-aligned field polarity, the Hall effect consistently transports magnetic flux outward, leading to a largely vertical field configuration in the midplane region. The field lines in the upper layer first bend radially inward and then outward to launch a disk wind. Overall, the net rate of outward flux transport is about twice as fast as that of the aligned case. In addition, the rate of flux transport increases with increasing disk magnetization. The absolute rate of transport is sensitive to disk microphysics, which remains to be explored in future studies.« less

Heavy Ion Irradiated Ferromagnetic Films: The Cases of Cobalt and Iron

NASA Astrophysics Data System (ADS)

Lieb, K. P.; Zhang, K.; Müller, G. A.; Gupta, R.; Schaaf, P.

2005-01-01

Polycrystalline, e-gun deposited Co, Fe and Co/Fe films, tens of nanometers thick, have been irradiated with Ne, Kr, Xe and/or Fe ions to fluences of up to 5 × 1016 ions/cm2. Changes in the magnetic texture induced by the implanted ions have been measured by means of hyperfine methods, such as Magnetic Orientation Mössbauer Spectroscopy (Fe), and by Magneto-Optical Kerr Effect and Vibrating Sample Magnetometry. In Co and CoFe an hcp → fcc phase transition has been observed under the influence of Xe-ion implantation. For 1016 Xe-ions/cm2, ion beam mixing in the Co/Fe system produces a soft magnetic material with uniaxial anisotropy. The effects have been correlated with changes in the microstructure as determined via X-ray diffraction. The influences of internal and external strain fields, an external magnetic field and pre-magnetization have been studied. A comprehensive understanding of the various effects and underlying physical reasons for the modifications appears to emerge from these investigations.

Highly Sensitive and Selective In-Situ SERS Detection of Pb(2+), Hg(2+), and Cd(2+) Using Nanoporous Membrane Functionalized with CNTs.

PubMed

Shaban, Mohamed; Galaly, A R

2016-05-04

Porous Anodic Alumina (PAA) membrane was functionalized with CoFe2O4 nanoparticles and used as a substrate for the growing of very long helical-structured Carbon Nanotubes (CNTs) with a diameter less than 20 nm. The structures and morphologies of the fabricated nanostructures were characterized by field emission- scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), and Raman spectroscopy. By uploading the CNTs on PAA, the characteristic Raman peaks of CNTs and PAA showed 4 and 3 times enhancement, respectively, which leads to more sensitive Surface-Enhanced Raman Spectroscopy (SERS) substrates. For comparison, PAA and CNTs/PAA arrays were used as SERS substrates for the detection of Hg(2+), Cd(2+), and Pb(2+). The proposed sensor demonstrated high sensitivity and selectivity between these heavy metal ions. CNTs/PAA sensor showed excellent selectivity toward Pb(2+) over other metal ions, where the enhancement factor is decreased from ~17 for Pb(2+) to ~12 for Hg(2+) and to ~4 for Cd(2+). Therefore, the proposed CNTs/PAA sensor can be used as a powerful tool for the determination of heavy metal ions in aqueous solutions.

Highly Sensitive and Selective In-Situ SERS Detection of Pb2+, Hg2+, and Cd2+ Using Nanoporous Membrane Functionalized with CNTs

PubMed Central

Shaban, Mohamed; Galaly, A. R.

2016-01-01

Porous Anodic Alumina (PAA) membrane was functionalized with CoFe2O4 nanoparticles and used as a substrate for the growing of very long helical-structured Carbon Nanotubes (CNTs) with a diameter less than 20 nm. The structures and morphologies of the fabricated nanostructures were characterized by field emission- scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), and Raman spectroscopy. By uploading the CNTs on PAA, the characteristic Raman peaks of CNTs and PAA showed 4 and 3 times enhancement, respectively, which leads to more sensitive Surface-Enhanced Raman Spectroscopy (SERS) substrates. For comparison, PAA and CNTs/PAA arrays were used as SERS substrates for the detection of Hg2+, Cd2+, and Pb2+. The proposed sensor demonstrated high sensitivity and selectivity between these heavy metal ions. CNTs/PAA sensor showed excellent selectivity toward Pb2+ over other metal ions, where the enhancement factor is decreased from ~17 for Pb2+ to ~12 for Hg2+ and to ~4 for Cd2+. Therefore, the proposed CNTs/PAA sensor can be used as a powerful tool for the determination of heavy metal ions in aqueous solutions. PMID:27143512

ToF-SIMS and Laser-SNMS Imaging of Heterogeneous Topographically Complex Polymer Systems.

PubMed

Pelster, Andreas; Körsgen, Martin; Kurosawa, Takako; Morita, Hiromi; Arlinghaus, Heinrich F

2016-10-04

Heterogeneous polymer coatings, such as those used in organic electronics and medical devices, are of increasing industrial importance. In order to advance the development of these types of systems, analytical techniques are required which are able to determine the elemental and molecular spatial distributions, on a nanometer scale, with very high detection efficiency and sensitivity. The goal of this study was to investigate the suitability of laser postionization secondary neutral mass spectrometry (Laser-SNMS) with a 157 nm postionization laser beam to image structured polymer mixtures and compare the results with time-of-flight secondary ion mass spectrometry (ToF-SIMS) measurements using Bi 3 + primary ions. The results showed that Laser-SNMS is better suited than ToF-SIMS for unambiguous detection and submicrometer imaging of the wide range of polymers investigated. The data also showed that Laser-SNMS has the advantage of being much more sensitive (in general higher by more than an order of magnitude and peaking at up to 3 orders of magnitude) than ToF-SIMS while also showing superior performance on topographically complex structured insulating surfaces, due to significantly reduced field effects and a higher dynamic range as compared to ToF-SIMS. It is concluded that Laser-SNMS is a powerful complementary technique to ToF-SIMS for the analysis of heterogeneous polymers and other complex structured organic mixtures, providing submicrometer resolution and high sensitivity.

High Content Screening in Zebrafish Speeds up Hazard Ranking of Transition Metal Oxide Nanoparticles

PubMed Central

Lin, Sijie; Zhao, Yan; Xia, Tian; Meng, Huan; Zhaoxia, Ji; Liu, Rong; George, Saji; Xiong, Sijing; Wang, Xiang; Zhang, Haiyuan; Pokhrel, Suman; Mädler, Lutz; Damoiseaux, Robert; Lin, Shuo; Nel, Andre E.

2014-01-01

Zebrafish is an aquatic organism that can be used for high content safety screening of engineered nanomaterials (ENMs). We demonstrate, for the first time, the use of high content bright-field and fluorescence-based imaging to compare the toxicological effect of transition metal oxide (CuO, ZnO, NiO and Co3O4) nanoparticles in zebrafish embryos and larvae. High content bright-field imaging demonstrated potent and dose-dependant hatching interference in the embryos, with the exception of Co3O4 which was relatively inert. We propose that the hatching interference was due to the shedding of Cu and Ni ions, compromising the activity of the hatching enzyme, ZHE1, similar to what we previously proposed for Zn2+. This hypothesis is based on the presence of metal–sensitive histidines in the catalytic center of this enzyme. Co-introduction of a metal ion chelator, diethylene triamine pentaacetic acid (DTPA), reversed the hatching interference of Cu, Zn and Ni. While neither the embryos nor larvae demonstrated morphological abnormalities, high content fluorescence-based imaging demonstrated that CuO, ZnO and NiO could induce increased expression of the heat shock protein 70:enhanced green fluorescence protein (hsp70:eGFP) in transgenic zebrafish larvae. Induction of this response by CuO required a higher nanoparticle dose than the amount leading to hatching interference. This response was also DTPA sensitive. In conclusion, we demonstrate that high content imaging of embryo development, morphological abnormalities and HSP70 expression can be used for hazard ranking and determining the dose-response relationships leading to ENM effects on the development of the zebrafish embryo. PMID:21851096

Colliding or co-rotating ion beams in storage rings for EDM search

NASA Astrophysics Data System (ADS)

Koop, I. A.

2015-11-01

A new approach to search for and measure the electric dipole moment (EDM) of the proton, deuteron and some other light nuclei is presented. The idea of the method is to store two ion beams, circulating with different velocities, in a storage ring with crossed electric and magnetic guiding fields. One beam is polarized and its EDM is measured using the so-called ‘frozen spin’ method. The second beam, which is unpolarized, is used as a co-magnetometer, sensitive to the radial component of the ring’s magnetic field. The particle’s magnetic dipole moment (MDM) couples to the radial magnetic field and mimics the EDM signal. Measuring the relative vertical orbit separation of the two beams, caused by the presence of the radial magnetic field, one can control the unwanted MDM spin precession. Examples of the parameters for EDM storage rings for protons and other species of ions are presented. The use of crossed electric and magnetic fields helps to reduce the size of the ring by a factor of 10-20. We show that the bending radius of such an EDM storage ring could be about 2-3 m. Finally, a new method of increasing the spin coherence time, the so-called ‘spin wheel’, is proposed and its applicability to the EDM search is discussed.

Techniques for the measurements of the line of sight velocity of high altitude Barium clouds

NASA Technical Reports Server (NTRS)

Mende, S. B.

1981-01-01

It is demonstrated that for maximizing the scientific output of future ion cloud release experiments a new type of instrument is required which will measure the line of sight velocity of the ion cloud by the Doppler Technique. A simple instrument was constructed using a 5 cm diameter solid Fabry-Perot etalon coupled to a low light level integrating television camera. It was demonstrated that the system has both the sensitivity and spectral resolution for the detection of ion clouds and the measurement of their line of sight Doppler velocity. The tests consisted of (1) a field experiment using a rocket barium cloud release to check the sensitivity, (2) laboratory experiments to show the spectral resolving capabilities of the system. The instrument was found to be operational if the source was brighter than about 1 kilorayleigh and it had a wavelength resolution much better than .2A which corresponds to about 12 km/sec or an acceleration potential of 100 volts.

A comparative study between different alternatives to prepare gaseous standards for calibrating UV-Ion Mobility Spectrometers.

PubMed

Criado-García, Laura; Garrido-Delgado, Rocío; Arce, Lourdes; Valcárcel, Miguel

2013-07-15

An UV-Ion Mobility Spectrometer is a simple, rapid, inexpensive instrument widely used in environmental analysis among other fields. The advantageous features of its underlying technology can be of great help towards developing reliable, economical methods for determining gaseous compounds from gaseous, liquid and solid samples. Developing an effective method using UV-Ion Mobility Spectrometry (UV-IMS) to determine volatile analytes entails using appropriate gaseous standards for calibrating the spectrometer. In this work, two home-made sample introduction systems (SISs) and a commercial gas generator were used to obtain such gaseous standards. The first home-made SIS used was a static head-space to measure compounds present in liquid samples and the other home-made system was an exponential dilution set-up to measure compounds present in gaseous samples. Gaseous compounds generated by each method were determined on-line by UV-IMS. Target analytes chosen for this comparative study were ethanol, acetone, benzene, toluene, ethylbenzene and xylene isomers. The different alternatives were acceptable in terms of sensitivity, precision and selectivity. Copyright © 2013 Elsevier B.V. All rights reserved.

Chloride ion transport and overexpression of TMEM16A in a guinea-pig asthma model.

PubMed

Kondo, M; Tsuji, M; Hara, K; Arimura, K; Yagi, O; Tagaya, E; Takeyama, K; Tamaoki, J

2017-06-01

TMEM16A, a Ca-activated Cl channel, regulates various physiological functions such as mucin secretion. However, the role of TMEM16A in hyper-secretion in asthma is not fully understood. The aim of this study is to evaluate Cl ion transport via TMEM16A and determine the localization of TMEM16A in a guinea-pig asthma model. Guinea-pigs were sensitized with ovalbumin (OVA) i.p. on Days 1 and 8. On Day 22, we assessed OVA challenge-induced Cl ion transport in the sensitized tracheas ex vivo in an Ussing chamber, compared with the non-sensitized tracheas. We then examined the effect of T16Ainh-A01, a TMEM16A inhibitor, on the increase in Cl ion transport. The tracheal epithelium was immunostained with an anti-TMEM16A antibody. Epithelial cells from guinea-pig tracheas were cultured at the air-liquid interface in the presence of IL-13 for in vitro study. We studied the effect of TMEM16A inhibitors on Ca-dependent agonist, uridine triphosphate (UTP)-induced increases in Cl ion transport in the cultured cells. The cells were immunostained with an anti-TMEM16A antibody, an anti-MUC5AC antibody and an anti-α-tubulin antibody. OVA challenge induced an increase in short circuit current within 1 min in the OVA-sensitized tracheas but not in the non-sensitized tracheas, which was inhibited by pretreatment of T16Ainh-A01. Sensitized tracheas showed goblet cell metaplasia with more positive TMEM16A immunostaining, particularly in the apical portion compared with the non-sensitized tracheas. The in vitro UTP-induced increase in Cl ion transport was strongly inhibited by pretreatment with T16Ainh-A01, benzbromarone, and niflumic acid. TMEM16A was positively immunostained at the apical portion and in the MUC5AC-positive area in IL-13-induced goblet cell metaplasia. Antigen challenge and Ca-dependent agonist treatment increased Cl ion transport via the overexpression of TMEM16A in goblet cell metaplasia in a guinea-pig asthma model. TMEM16A inhibitors may be useful for the treatment of hyper-secretion in asthma. © 2017 John Wiley & Sons Ltd.

Time-of-flight mass spectrometry: Introduction to the basics.

PubMed

Boesl, Ulrich

2017-01-01

The intention of this tutorial is to introduce into the basic concepts of time-of-flight mass spectrometry, beginning with the most simple single-stage ion source with linear field-free drift region and continuing with two-stage ion sources combined with field-free drift regions and ion reflectors-the so-called reflectrons. Basic formulas are presented and discussed with the focus on understanding the physical relations of geometric and electric parameters, initial distribution of ionic parameters, ion flight times, and ion flight time incertitude. This tutorial is aimed to help the applicant to identify sources of flight time broadening which limit good mass resolution and sources of ion losses which limit sensitivity; it is aimed to stimulate creativity for new experimental approaches by discussing a choice of instrumental options and to encourage those who toy with the idea to build an own time-of-flight mass spectrometer. Large parts of mathematics are shifted into a separate chapter in order not to overburden the text with too many mathematical deviations. Rather, thumb-rule formulas are supplied for first estimations of geometry and potentials when designing a home-built instrument, planning experiments, or searching for sources of flight time broadening. © 2016 Wiley Periodicals, Inc. Mass Spec Rev 36:86-109, 2017. © 2016 Wiley Periodicals, Inc.

Characterization of applied fields for ion mobility separations in traveling wave based structures for lossless ion manipulations (SLIM)

DOE PAGES

Hamid, Ahmed M.; Prabhakaran, Aneesh; Garimella, Sandilya V. B.; ...

2018-03-26

Ion mobility (IM) is rapidly gaining attention for the separation and analysis of biomolecules due to the ability to distinguish the shapes of ions. However, conventional constant electric field drift tube IM separations have limited resolving power, constrained by practical limitations on the path length and maximum applied voltage. The implementation of traveling waves (TW) in IM removes the latter limitation, allowing higher resolution to be achieved using extended path lengths. Both of these can be readily obtained in Structures for Lossless Ion Manipulations (SLIM), which are fabricated from arrays of electrodes patterned on two parallel surfaces where potentials aremore » applied to generate appropriate electric fields between the surfaces. Here we have investigated the relationship between the primary SLIM variables, such as electrode dimensions, inter-surface gap, and the applied TW voltages, that directly impact the fields experienced by ions. Ion trajectory simulations and theoretical calculations have been utilized to understand the dependence of SLIM geometry and effective electric fields on IM resolution. The variables explored impact both ion confinement and the observed IM resolution using SLIM modules.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garimella, Sandilya V. B.; Ibrahim, Yehia M.; Tang, Keqi

A novel concept for ion spatial peak compression is described, and discussed primarily in the context of ion mobility spectrometry (IMS). Using theoretical and numerical methods, the effects of using non-constant (e.g., linearly varying) electric fields on ion distributions (e.g., an ion mobility peak) is evaluated both in the physical and temporal domains. The application of linearly decreasing electric field in conjunction with conventional drift field arrangements is shown to lead to a reduction in IMS physical peak width. When multiple ion packets in a selected mobility window are simultaneously subjected to such fields, there is ion packet compression, i.e.,more » a reduction in peak widths of all species. This peak compression occurs with a modest reduction of resolution, but which can be quickly recovered as ions drift in a constant field after the compression event. Compression also yields a significant increase in peak intensities. In addition, approaches for peak compression in traveling wave IMS are also discussed. Ion mobility peak compression can be particularly useful for mitigating diffusion driven peak spreading over very long path length separations (e.g., in cyclic multi-pass arrangements), and for achieving higher S/N and IMS resolution over a selected mobility range.« less

Characterization of applied fields for ion mobility separations in traveling wave based structures for lossless ion manipulations (SLIM)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamid, Ahmed M.; Prabhakaran, Aneesh; Garimella, Sandilya V. B.

Ion mobility (IM) is rapidly gaining attention for the separation and analysis of biomolecules due to the ability to distinguish the shapes of ions. However, conventional constant electric field drift tube IM separations have limited resolving power, constrained by practical limitations on the path length and maximum applied voltage. The implementation of traveling waves (TW) in IM removes the latter limitation, allowing higher resolution to be achieved using extended path lengths. Both of these can be readily obtained in Structures for Lossless Ion Manipulations (SLIM), which are fabricated from arrays of electrodes patterned on two parallel surfaces where potentials aremore » applied to generate appropriate electric fields between the surfaces. Here we have investigated the relationship between the primary SLIM variables, such as electrode dimensions, inter-surface gap, and the applied TW voltages, that directly impact the fields experienced by ions. Ion trajectory simulations and theoretical calculations have been utilized to understand the dependence of SLIM geometry and effective electric fields on IM resolution. The variables explored impact both ion confinement and the observed IM resolution using SLIM modules.« less

Negative ion beam injection apparatus with magnetic shield and electron removal means

DOEpatents

Anderson, Oscar A.; Chan, Chun F.; Leung, Ka-Ngo

1994-01-01

A negative ion source is constructed to produce H.sup.- ions without using Cesium. A high percentage of secondary electrons that typically accompany the extracted H.sup.- are trapped and eliminated from the beam by permanent magnets in the initial stage of acceleration. Penetration of the magnetic field from the permanent magnets into the ion source is minimized. This reduces the destructive effect the magnetic field could have on negative ion production and extraction from the source. A beam expansion section in the extractor results in a strongly converged final beam.

Polyamidoamine dendrimers as sweeping agent and stationary phase for rapid and sensitive open-tubular capillary electrophoretic determination of heavy metal ions.

PubMed

Ge, Ying; Guo, Yujun; Qin, Weidong

2014-04-01

Polyamidoamine (PAMAM) dendrimer generation 2.5 was synthesized and evaluated as sweeping agent for in-column enrichment and as stationary phase for capillary electrochromatographic separation of heavy metal ions, viz., Pb(II), Cu(II), Hg(II), Zn(II) and Co(II), in a running buffer containing 4-(2-pyridylazo)resorcinol (PAR) as a chromogenic reagent. During experiment, a plug of aqueous PAMAM generation 2.5 solution was first introduced to the capillary, followed by electrokinetic injection of the heavy metal ions under a positive voltage. In this step, PAMAM acted as a sweeping agent, stacking the metal ions on the analyte/PAMAM boundary by forming metal ion-PAMAM complexes. The second preconcentration process occurred when PAR, a stronger ligand, moving toward the injection end under the electric field, reached and re-swept the metal ion-PAMAM zone, forming metal ion-PAR complexes. During separation, the neutral PAMAM moved toward the detector with the electroosmotic flow, dynamically coating the capillary wall, forming stationary phases that affected the separation of the metal ions. Due to the function of PAMAM, the detection sensitivity and resolution of the heavy metal ions improved significantly. Under the optimum conditions, the detection limits were 0.299, 0.184, 0.774, 0.182 and 0.047 μg/L for Pb(II), Cu(II), Hg(II), Zn(II) and Co(II), respectively. The method was successfully applied to the determination of heavy metals in snow, tap and rain water samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Miniature chemical ionization mass spectrometer for light aircraft measurements of tropospheric ammonia

NASA Astrophysics Data System (ADS)

Silver, J. A.; Bomse, D. S.; Massick, S. M.; Zondlo, M. A.

2003-12-01

Tropospheric ammonia plays important roles in the nucleation, growth, composition, and chemistry of aerosol particles. Unfortunately, high frequency and sensitive measurements of gas phase ammonia are lacking in most airborne-based field campaigns. Chemical ionization mass spectrometers (CIMS) have shown great promise for ammonia measurements, but CIMS instruments typically consume large amounts of power, are highly labor intensive, and are very heavy for most airborne platforms. These characteristics of CIMS instruments severely limit their potential deployment on smaller and lighter aircraft, despite the strong desire for ammonia measurements in atmospheric chemistry field campaigns. To this end, a CIMS ammonia instrument for light aircraft is being developed using a double-focusing, miniature mass spectrometer. The size of the mass spectrometer, comparable to a small apple, allows for higher operating pressures (0.1 mTorr) and lower pumping requirements. Power usage, including pumps and electronics, is estimated to be around 300 W, and the overall instrument including pumps, electronics, and permeation cells is expected to be about the size of a small monitor. The ion source uses americium-241 to generate protonated water ions which proton transfer to form ammonium ions. The ion source is made with commercially available ion optics to minimize machining costs. Mass spectra over its working range (~ 5-120 amu) are well represented by Gaussian shaped peaks. By examining the peak widths as a function of mass location, the resolution of the instrument was determined experimentally to be around 110 (m/delta m). The sensitivity, selectivity, power requirements, size, and performance characteristics of the miniature mass spectrometer will be described along with the possibilities for CIMS measurements on light aircraft.

Sharpening of field emitter tips using high-energy ions

DOEpatents

Musket, Ronald G.

1999-11-30

A process for sharpening arrays of field emitter tips of field emission cathodes, such as found in field-emission, flat-panel video displays. The process uses sputtering by high-energy (more than 30 keV) ions incident along or near the longitudinal axis of the field emitter to sharpen the emitter with a taper from the tip or top of the emitter down to the shank of the emitter. The process is particularly applicable to sharpening tips of emitters having cylindrical or similar (e.g., pyramidal) symmetry. The process will sharpen tips down to radii of less than 12 nm with an included angle of about 20 degrees. Because the ions are incident along or near the longitudinal axis of each emitter, the tips of gated arrays can be sharpened by high-energy ion beams rastered over the arrays using standard ion implantation equipment. While the process is particularly applicable for sharpening of arrays of field emitters in field-emission flat-panel displays, it can be effectively utilized in the fabrication of other vacuum microelectronic devices that rely on field emission of electrons.

New evidence for electrotropism in some plant species

NASA Astrophysics Data System (ADS)

Gorgolewski, S.; Rozej, B.

The ever-present global Atmospheric Electrical F ield (AEF) is used by many plant species. There are many natural habitats with electrotropic plants and habitats with no AEF. The plants growing there are not electrotropic, like the plants growing under the canopies of the trees or the Arecibo radio telescope. Examples are given of different plants which belong to one or the other class, and the criteria how to distinguish them. In addition to natural habitat observations, laboratory experiments were run in search of the sensitivity to electrotropic effect in different electric field intensities and directions. It was established that in very strong fields (of the order of 1 MV/m) all plants respond immediately to the field. This type of reaction is due to the Coulomb forces, but electrotropism depends on electric field interaction with ions in plant tissues. We use a "reference field" (130 V/m) and stronger fields in the several kV/m range which enhance plant growth rate and size similar to plant growth hormones. Surprising effects were also observed with reversed field polarity. In conclusion electrotropic pl nts deprived of the electrical field do not develop asa expected, as can be seen in BIOSPHERE 2. It was a sad example of what happens when one forgets to provide the plants with this vital natural environmental factor. Electrical fields of different intensity and direction are cheap and easy to generate. More plants were investigated in order to verify their response to electrical fields. Effect of several kV/m horizontal fields, was compared with the vertical 130 V/m field (ued as a reference) and it was shown that electrotropic sensitivity can be found easily. Surprisingly even the nonelectrotropic plants, whose initial growth rate does not depend on the field strength, when they develop leaves begin to lean towards the positive electrode, and become elect rotropic. Ground based fitotron experiments enable us to select cheaply plants which shall be suitable for food production in space using electical fields to restore to plants the sense of direction of growth.

Incoherent radar spectra in the auroral ionosphere in the presence of a large electric field: The effect of O+-O+ Coulomb collisions

NASA Astrophysics Data System (ADS)

Barghouthi, I. A.

2005-06-01

We have used Monte Carlo simulations of O+ velocity distributions in the high latitude F- region to improve the calculation of incoherent radar spectra in auroral ionosphere. The Monte Carlo simulation includes ionneutral, O+-O collisions (resonant charge exchange and polarization interaction) as well as O+-O+ Coulomb self-collisions. At high altitudes, atomic oxygen O and atomic oxygen ion O+ dominate the composition of the auroral ionosphere and consequently, the influence of O+-O+ Coulomb collisions becomes significant. In this study we consider the effect of O+-O+ Coulomb collisions on the incoherent radar spectra in the presence of large electric field (100 mVm-1). As altitude increases (i.e. the ion-to-neutral density ratio increases) the role of O+-O+ Coulomb self-collisions becomes significant, therefore, the one-dimensional, 1-D, O+ ion velocity distribution function becomes more Maxwellian and the features of the radar spectrum corresponding to non-Maxwellian ion velocity distribution (e.g. baby bottle and triple hump shapes) evolve to Maxwellian ion velocity distribution (single and double hump shapes). Therefore, O+-O+ Coulomb self-collisions act to isotropize the 1-D O+ velocity distribution by transferring thermal energy from the perpendicular direction to the parallel direction, however the convection electric field acts to drive the O+ ions away from equilibrium and consequently, non-Maxwellian O+ ion velocity distributions appeared. Therefore, neglecting O+-O+ Coulomb self-collisions overestimates the effect of convection electric field.

Generation of Raman lasers from nitrogen molecular ions driven by ultraintense laser fields

NASA Astrophysics Data System (ADS)

Yao, Jinping; Chu, Wei; Liu, Zhaoxiang; Xu, Bo; Chen, Jinming; Cheng, Ya

2018-03-01

Atmospheric lasing has aroused much interest in the past few years. The ‘air–laser’ opens promising potential for remote chemical sensing of trace gases with high sensitivity and specificity. At present, several approaches have been successfully implemented for generating highly coherent laser beams in atmospheric condition, including both amplified-spontaneous emission, and narrow-bandwidth stimulated emission in the forward direction in the presence of self-generated or externally injected seed pulses. Here, we report on generation of multiple-wavelength Raman lasers from nitrogen molecular ions ({{{N}}}2+), driven by intense mid-infrared laser fields. Intuitively, the approach appears problematic for the small nonlinear susceptibility of {{{N}}}2+ ions, whereas the efficiency of Raman laser can be significantly promoted in near-resonant condition. More surprisingly, a Raman laser consisting of a supercontinuum spanning from ∼310 to ∼392 nm has been observed resulting from a series near-resonant nonlinear processes including four-wave mixing, stimulated Raman scattering and cross phase modulation. To date, extreme nonlinear optics in molecular ions remains largely unexplored, which provides an alternative means for air–laser-based remote sensing applications.

Ultrananocrystalline Diamond Membranes for Detection of High-Mass Proteins

NASA Astrophysics Data System (ADS)

Kim, H.; Park, J.; Aksamija, Z.; Arbulu, M.; Blick, R. H.

2016-12-01

Mechanical resonators realized on the nanoscale by now offer applications in mass sensing of biomolecules with extraordinary sensitivity. The general idea is that perfect mechanical mass sensors should be of extremely small size to achieve zepto- or yoctogram sensitivity in weighing single molecules similar to a classical scale. However, the small effective size and long response time for weighing biomolecules with a cantilever restricts their usefulness as a high-throughput method. Commercial mass spectrometry (MS), on the other hand, such as electrospray ionization and matrix-assisted laser desorption and ionization (MALDI) time of flight (TOF) and their charge-amplifying detectors are the gold standards to which nanomechanical resonators have to live up to. These two methods rely on the ionization and acceleration of biomolecules and the following ion detection after a mass selection step, such as TOF. The principle we describe here for ion detection is based on the conversion of kinetic energy of the biomolecules into thermal excitation of chemical vapor deposition diamond nanomembranes via phonons followed by phonon-mediated detection via field emission of thermally emitted electrons. We fabricate ultrathin diamond membranes with large lateral dimensions for MALDI TOF MS of high-mass proteins. These diamond membranes are realized by straightforward etching methods based on semiconductor processing. With a minimal thickness of 100 nm and cross sections of up to 400 ×400 μ m2 , the membranes offer extreme aspect ratios. Ion detection is demonstrated in MALDI TOF analysis over a broad range from insulin to albumin. The resulting data in detection show much enhanced resolution as compared to existing detectors, which can offer better sensitivity and overall performance in resolving protein masses.

Atomic physics effects on tokamak edge drift-tearing modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hahm, T.S.

1993-03-01

The effects of ionization and charge exchange on the linear stability of drift-tearing modes are analytically investigated. In particular, the linear instability threshold {Delta}{sup Th}, produced by ion sound wave coupling is modified. In the strongly collisional regime, the ionization breaks up the near cancellation of the perturbed electric field and the pressure gradient along the magnetic field, and increases the threshold. In the semi-collisional regime, both ionization and charge exchange act as drag on the ion parallel velocity, and consequently decrease the threshold by reducing the effectiveness of ion sound wave propagation.

Atomic physics effects on tokamak edge drift-tearing modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hahm, T.S.

1993-03-01

The effects of ionization and charge exchange on the linear stability of drift-tearing modes are analytically investigated. In particular, the linear instability threshold [Delta][sup Th], produced by ion sound wave coupling is modified. In the strongly collisional regime, the ionization breaks up the near cancellation of the perturbed electric field and the pressure gradient along the magnetic field, and increases the threshold. In the semi-collisional regime, both ionization and charge exchange act as drag on the ion parallel velocity, and consequently decrease the threshold by reducing the effectiveness of ion sound wave propagation.

Gamma-Ray Pulsar Light Curves in Offset Polar Cap Geometry

NASA Technical Reports Server (NTRS)

Harding, Alice K.; DeCesar, Megan; Miller, M. Coleman

2011-01-01

Recent studies have shown that gamma-ray pulsar light curves are very sensitive to the geometry of the pulsar magnetic field. Pulsar magnetic field geometries, such as the retarded vacuum dipole and force-free magnetospheres, used to model high-energy light curves have distorted polar caps that are offset from the magnetic axis in the direction opposite to rotation. Since this effect is due to the sweepback of field lines near the light cylinder, offset polar caps are a generic property of pulsar magnetospheres and their effects should be included in gamma-ray pulsar light curve modeling. In slot gap models (having two-pole caustic geometry), the offset polar caps cause a strong azimuthal asymmetry of the particle acceleration around the magnetic axis. We have studied the effect of the offset polar caps in both retarded vacuum dipole and force-free geometry on the model high-energy pulse profile. We find that. corn pared to the profile:-; derived from :-;ymmetric caps, the flux in the pulse peaks, which are caustics formed along the trailing magnetic field lines. increases significantly relative to the off-peak emission. formed along leading field lines. The enhanced contrast produces greatly improved slot gap model fits to Fermi pulsar light curves like Vela, which show very little off-peak emIssIon.

Magnetized retarding field energy analyzer measuring the particle flux and ion energy distribution of both positive and negative ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rafalskyi, Dmytro; Aanesland, Ane; Dudin, Stanislav

2015-05-15

This paper presents the development of a magnetized retarding field energy analyzer (MRFEA) used for positive and negative ion analysis. The two-stage analyzer combines a magnetic electron barrier and an electrostatic ion energy barrier allowing both positive and negative ions to be analyzed without the influence of electrons (co-extracted or created downstream). An optimal design of the MRFEA for ion-ion beams has been achieved by a comparative study of three different MRFEA configurations, and from this, scaling laws of an optimal magnetic field strength and topology have been deduced. The optimal design consists of a uniform magnetic field barrier createdmore » in a rectangular channel and an electrostatic barrier consisting of a single grid and a collector placed behind the magnetic field. The magnetic barrier alone provides an electron suppression ratio inside the analyzer of up to 6000, while keeping the ion energy resolution below 5 eV. The effective ion transparency combining the magnetic and electrostatic sections of the MRFEA is measured as a function of the ion energy. It is found that the ion transparency of the magnetic barrier increases almost linearly with increasing ion energy in the low-energy range (below 200 eV) and saturates at high ion energies. The ion transparency of the electrostatic section is almost constant and close to the optical transparency of the entrance grid. We show here that the MRFEA can provide both accurate ion flux and ion energy distribution measurements in various experimental setups with ion beams or plasmas run at low pressure and with ion energies above 10 eV.« less

Ion Velocity Measurements in a Linear Hall Thruster (Postprint)

DTIC Science & Technology

2005-06-14

Hall Thruster in a high vacuum environment. The ionized propellant velocities were measured using laser induced fluorescence of the excited state xenon ionic transition at 834.7 nm. Ion velocities were interrogated from the channel exit plane to a distance 30 mm from it. Both axial and cross-field (along the electron Hall current direction) velocities were measured. The results presented here, combined with those of previous work, highlight the high sensitivity of electron mobility inside and outside the channel, depending on the background gas density, type of wall

Determining single-ion and spatial exchange anisotropies by pulsed-field magnetometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manson, J. L.; Villa, J. A.; Singleton, John

2017-02-13

The magnetic ground-state of the Q1D S = 1 antiferromagnetic (AFM) chain is sensitive to the single-ion anisotropy (D) and the relative strength of intra- (J) and interchain (J’) exchange interactions. The ratios D/J and J’/J dictate the material’s placement on the phase diagram for which three competing phases are known to theoretically exist: Haldane, XY and quantum paramagnetic. We identified [Ni(HF 2)(pyz) 2]SbF 6 (pyz = pyrazine) as a candidate in which to explore proximity to these phases.

Ion diagnostics of a discharge in crossed electric and magnetic fields for electric propulsion

NASA Astrophysics Data System (ADS)

Mazouffre, S.; Kulaev, V.; Luna, J. Pérez

2009-08-01

The velocity distribution function (VDF) of metastable Xe+ ions was measured along the channel centerline of the high-power PPS®X000 Hall effect thruster by means of laser induced fluorescence (LIF) spectroscopy at 834.72 nm for various discharge voltages (300-700 V) and propellant mass flow rates (6-15 mg s-1). The development of the on-axis profile of the velocity dispersion reveals the interrelation between ionization and acceleration layers. The ion velocity profiles are in accordance with outcomes of a hybrid numerical model in which the electron mobility is assessed from particle-in-cell simulations. The axial distribution of the effective electric field is inferred from the mean ion velocity profile, despite the parasitic effect due to ions created in the acceleration region. Most of the acceleration process takes place outside the thruster channel. The electric field augments and it moves upstream when the applied voltage is ramped up. The impact of the xenon mass flow rates is found to depend upon the voltage. A novel approach based on the moments of the experimental VDFs in combination with the Boltzmann's equation is introduced in order to determine the real electric field distribution. The method also provides the ionization frequency profile. The LIF diagnostics reveals the existence at the end of the acceleration region of fast ions of which the kinetic energy is above the supplied energy. The fraction of these supra-sped up ions grows when the voltage increases. The ion VDFs were also recorded in the plasma plume far field by way of a retarding potential analyzer (RPA). The shape of the RPA traces as well as their evolution with operating conditions are in agreement with trends observed by means of LIF spectroscopy. Finally, physical mechanisms at the origin of supra-sped up ions are discussed in light of numerical simulation outcomes and a set of new experimental results.

Examination of ionic wind and cathode sheath effects in a E-field premixed flame with ion density measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jacobs, Stewart V., E-mail: svj0001@uah.edu; Xu, Kunning G., E-mail: gabe.xu@uah.edu

2016-04-15

The effect of the ionic wind on a premixed methane-air flame under a DC electric field is studied via mapping of the ion density with Langmuir probes. Ion densities were observed to increase near the burner with increasing electrode voltage up to 6 kV. Past this electrode supply voltage, ion densities ceased increasing and began to decline in some locations within the premixed flame. The increased ion density is caused by an increase in ionic wind force and cathode sheath thickness. The plateau in density is due to the cathode sheath fully encompassing the flame front which is the ion source,more » thereby collecting all ions in the flame. The spatial density data support the ionic wind hypothesis and provide further explanation of its limits based on the plasma sheath.« less

A neoclassical drift-magnetohydrodynamical fluid model of the interaction of a magnetic island chain with a resonant error-field in a high temperature tokamak plasma

NASA Astrophysics Data System (ADS)

Fitzpatrick, Richard

2018-04-01

A two-fluid, neoclassical theory of the interaction of a single magnetic island chain with a resonant error-field in a quasi-cylindrical, low-β, tokamak plasma is presented. The plasmas typically found in large hot tokamaks lie in the so-called weak neoclassical flow-damping regime in which the neoclassical ion stress tensor is not the dominant term in the ion parallel equation of motion. Nevertheless, flow-damping in such plasmas dominates ion perpendicular viscosity, and is largely responsible for determining the phase velocity of a freely rotating island chain (which is in the ion diamagnetic direction relative to the local E × B frame at the rational surface). The critical vacuum island width required to lock the island chain is mostly determined by the ion neoclassical poloidal flow damping rate at the rational surface. The stabilizing effect of the average field-line curvature, as well as the destabilizing effect of the perturbed bootstrap current, is the same for a freely rotating, a non-uniformly rotating, and a locked island chain. The destabilizing effect of the error-field averages to zero when the chain is rotating and only manifests itself when the chain locks. The perturbed ion polarization current has a small destabilizing effect on a freely rotating island chain, but a large destabilizing effect on both a non-uniformly rotating and a locked island chain. This behavior may account for the experimentally observed fact that locked island chains are much more unstable than corresponding freely rotating chains.

Multi-mode acquisition (MMA): An MS/MS acquisition strategy for maximizing selectivity, specificity and sensitivity of DIA product ion spectra.

PubMed

Williams, Brad J; Ciavarini, Steve J; Devlin, Curt; Cohn, Steven M; Xie, Rong; Vissers, Johannes P C; Martin, LeRoy B; Caswell, Allen; Langridge, James I; Geromanos, Scott J

2016-08-01

In proteomics studies, it is generally accepted that depth of coverage and dynamic range is limited in data-directed acquisitions. The serial nature of the method limits both sensitivity and the number of precursor ions that can be sampled. To that end, a number of data-independent acquisition (DIA) strategies have been introduced with these methods, for the most part, immune to the sampling issue; nevertheless, some do have other limitations with respect to sensitivity. The major limitation with DIA approaches is interference, i.e., MS/MS spectra are highly chimeric and often incapable of being identified using conventional database search engines. Utilizing each available dimension of separation prior to ion detection, we present a new multi-mode acquisition (MMA) strategy multiplexing both narrowband and wideband DIA acquisitions in a single analytical workflow. The iterative nature of the MMA workflow limits the adverse effects of interference with minimal loss in sensitivity. Qualitative identification can be performed by selected ion chromatograms or conventional database search strategies. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

TiO₂ Nanowire Networks Prepared by Titanium Corrosion and Their Application to Bendable Dye-Sensitized Solar Cells.

PubMed

Jin, Saera; Shin, Eunhye; Hong, Jongin

2017-10-12

TiO₂ nanowire networks were prepared, using the corrosion of Ti foils in alkaline (potassium hydroxide, KOH) solution at different temperatures, and then a further ion-exchange process. The prepared nanostructures were characterized by field emission scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The wet corroded foils were utilized as the photoanodes of bendable dye-sensitized solar cells (DSSCs), which exhibited a power conversion efficiency of 1.11% under back illumination.

Effect of Monovalent Ion Parameters on Molecular Dynamics Simulations of G-Quadruplexes.

PubMed

Havrila, Marek; Stadlbauer, Petr; Islam, Barira; Otyepka, Michal; Šponer, Jiří

2017-08-08

G-quadruplexes (GQs) are key noncanonical DNA and RNA architectures stabilized by desolvated monovalent cations present in their central channels. We analyze extended atomistic molecular dynamics simulations (∼580 μs in total) of GQs with 11 monovalent cation parametrizations, assessing GQ overall structural stability, dynamics of internal cations, and distortions of the G-tetrad geometries. Majority of simulations were executed with the SPC/E water model; however, test simulations with TIP3P and OPC water models are also reported. The identity and parametrization of ions strongly affect behavior of a tetramolecular d[GGG] 4 GQ, which is unstable with several ion parametrizations. The remaining studied RNA and DNA GQs are structurally stable, though the G-tetrad geometries are always deformed by bifurcated H-bonding in a parametrization-specific manner. Thus, basic 10-μs-scale simulations of fully folded GQs can be safely done with a number of cation parametrizations. However, there are parametrization-specific differences and basic force-field errors affecting the quantitative description of ion-tetrad interactions, which may significantly affect studies of the ion-binding processes and description of the GQ folding landscape. Our d[GGG] 4 simulations indirectly suggest that such studies will also be sensitive to the water models. During exchanges with bulk water, the Na + ions move inside the GQs in a concerted manner, while larger relocations of the K + ions are typically separated. We suggest that the Joung-Cheatham SPC/E K + parameters represent a safe choice in simulation studies of GQs, though variation of ion parameters can be used for specific simulation goals.

Effect of Mg or Ag addition on the evaporation field of Al.

PubMed

Aruga, Yasuhiro; Nako, Hidenori; Tsuneishi, Hidemasa; Hasegawa, Yuki; Tao, Hiroaki; Ichihara, Chikara; Serizawa, Ai

2013-09-01

It is known that the distribution of the charge-states as well as the evaporation field shift to higher values as the specimen temperature is decreased at a constant rate of evaporation. This study has explored the effect of Mg or Ag addition on the evaporation field of Al in terms of the charge state distribution of the field evaporated Al ions. The fractional abundance of Al(2+) ions with respect to the total Al ions in Al-Mg alloy is lower than that in pure Al, whereas it shows higher level in the Al-Ag alloy at lower temperatures. The temperature dependence of the fractional abundance of Al(2+) ions has been also confirmed, suggesting that Al atoms in the Al-Mg alloy need lower evaporation field, while higher field is necessary to evaporate Al atoms in the Al-Ag alloy, compared with pure Al. This tendency is in agreement with that of the evaporation fields estimated theoretically by means of measurements of the work function and calculations of the binding energy of the pure Al, Al-Mg and Al-Ag alloys. Copyright © 2012 Elsevier B.V. All rights reserved.

Reduced voltage sensitivity in a K+-channel voltage sensor by electric field remodeling

PubMed Central

González-Pérez, Vivian; Stack, Katherine; Boric, Katica; Naranjo, David

2010-01-01

Propagation of the nerve impulse relies on the extreme voltage sensitivity of Na+ and K+ channels. The transmembrane movement of four arginine residues, located at the fourth transmembrane segment (S4), in each of their four voltage-sensing domains is mostly responsible for the translocation of 12 to 13 eo across the transmembrane electric field. Inserting additional positively charged residues between the voltage-sensing arginines in S4 would, in principle, increase voltage sensitivity. Here we show that either positively or negatively charged residues added between the two most external sensing arginines of S4 decreased voltage sensitivity of a Shaker voltage-gated K+-channel by up to ≈50%. The replacement of Val363 with a charged residue displaced inwardly the external boundaries of the electric field by at least 6 Å, leaving the most external arginine of S4 constitutively exposed to the extracellular space and permanently excluded from the electric field. Both the physical trajectory of S4 and its electromechanical coupling to open the pore gate seemed unchanged. We propose that the separation between the first two sensing charges at resting is comparable to the thickness of the low dielectric transmembrane barrier they must cross. Thus, at most a single sensing arginine side chain could be found within the field. The conserved hydrophobic nature of the residues located between the voltage-sensing arginines in S4 may shape the electric field geometry for optimal voltage sensitivity in voltage-gated ion channels. PMID:20194763

CIP (cleaning-in-place) stability of AlGaN/GaN pH sensors.

PubMed

Linkohr, St; Pletschen, W; Schwarz, S U; Anzt, J; Cimalla, V; Ambacher, O

2013-02-20

The CIP stability of pH sensitive ion-sensitive field-effect transistors based on AlGaN/GaN heterostructures was investigated. For epitaxial AlGaN/GaN films with high structural quality, CIP tests did not degrade the sensor surface and pH sensitivities of 55-58 mV/pH were achieved. Several different passivation schemes based on SiO(x), SiN(x), AlN, and nanocrystalline diamond were compared with special attention given to compatibility to standard microelectronic device technologies as well as biocompatibility of the passivation films. The CIP stability was evaluated with a main focus on the morphological stability. All stacks containing a SiO₂ or an AlN layer were etched by the NaOH solution in the CIP process. Reliable passivations withstanding the NaOH solution were provided by stacks of ICP-CVD grown and sputtered SiN(x) as well as diamond reinforced passivations. Drift levels about 0.001 pH/h and stable sensitivity over several CIP cycles were achieved for optimized sensor structures. Copyright © 2012 Elsevier B.V. All rights reserved.

Ambipolar Electric Field, Photoelectrons, and Their Role in Atmospheric Escape From Hot Jupiters

NASA Technical Reports Server (NTRS)

Cohen, O.; Glocer, A.

2012-01-01

Atmospheric mass loss from Hot Jupiters can be large due to the close proximity of these planets to their host star and the strong radiation the planetary atmosphere receives. On Earth, a major contribution to the acceleration of atmospheric ions comes from the vertical separation of ions and electrons, and the generation of the ambipolar electric field. This process, known as the "polar wind," is responsible for the transport of ionospheric constituents to Earth's magnetosphere, where they are well observed. The polar wind can also be enhanced by a relatively small fraction of super-thermal electrons (photoelectrons) generated by photoionization.We formulate a simplified calculation of the effect of the ambipolar electric field and the photoelectrons on the ion scale height in a generalized manner. We find that the ion scale height can be increased by a factor of 2-15 due to the polar wind effects. We also estimate a lower limit of an order of magnitude increase of the ion density and the atmospheric mass-loss rate when polar wind effects are included.

Modeling of fast neutral-beam-generated ion effects on MHD-spectroscopic observations of resistive wall mode stability in DIII-D plasmas [Modeling of fast neutral-beam-generated ion effects on MHD spectroscopic observations of RWM stability in DIII-D plasmas

DOE PAGES

Turco, Francesca; Turnbull, Alan D.; Hanson, Jeremy M.; ...

2015-02-03

Experiments conducted at DIII-D investigate the role of drift kinetic damping and fast neutral beam injection (NBI)-ions in the approach to the no-wall β N limit. Modelling results show that the drift kinetic effects are significant and necessary to reproduce the measured plasma response at the ideal no-wall limit. Fast neutral-beam ions and rotation play important roles and are crucial to quantitatively match the experiment. In this paper, we report on the model validation of a series of plasmas with increasing β N, where the plasma stability is probed by active magnetohydrodynamic (MHD) spectroscopy. The response of the plasma tomore » an externally applied field is used to probe the stable side of the resistive wall mode and obtain an indication of the proximity of the equilibrium to an instability limit. We describe the comparison between the measured plasma response and that calculated by means of the drift kinetic MARS-K code, which includes the toroidal rotation, the electron and ion drift-kinetic resonances, and the presence of fast particles for the modelled plasmas. The inclusion of kinetic effects allows the code to reproduce the experimental results within ~13% for both the amplitude and phase of the plasma response, which is a significant improvement with respect to the undamped MHD-only model. The presence of fast NBI-generated ions is necessary to obtain the low response at the highest β N levels (~90% of the ideal no-wall limit). Finally, the toroidal rotation has an impact on the results, and a sensitivity study shows that a large variation in the predicted response is caused by the details of the rotation profiles at high β N.« less

Ion photon emission microscope

DOEpatents

Doyle, Barney L.

2003-04-22

An ion beam analysis system that creates microscopic multidimensional image maps of the effects of high energy ions from an unfocussed source upon a sample by correlating the exact entry point of an ion into a sample by projection imaging of the ion-induced photons emitted at that point with a signal from a detector that measures the interaction of that ion within the sample. The emitted photons are collected in the lens system of a conventional optical microscope, and projected on the image plane of a high resolution single photon position sensitive detector. Position signals from this photon detector are then correlated in time with electrical effects, including the malfunction of digital circuits, detected within the sample that were caused by the individual ion that created these photons initially.

Evidence for electrotropism in some plant species

NASA Astrophysics Data System (ADS)

Gorgolewski, S.; Rożej, B.

2001-01-01

The ever-present global Atmospheric Electrical Field (AEF) is used by many plant species. There are many natural habitats with electrotropic plants and habitats with no AEF. The plants growing there are not electrotropic, like the plants growing under the canopies of the trees or the Arecibo radio telescope. Examples are given of different plants which belong to one or the other class, and the criteria how to distinguish them. In addition to natural habitat observations, laboratory experiments were run in search of the sensitivity of electrotropic effect to different electric field intensities. During a few years, it was established that in very strong fields (of the order of 1 MV/m) all plants respond immediately to the field. This type of reaction is due to the Coulomb forces, but electrotropism depends on electric field interaction with ions. The "reference field" (130 V/m) was always used with stronger fields in the several kV/m range which enhance plant growth rate and size similar to plant growth hormones. Surprising effects were also observed with reversed and horizontal field polarity. In conclusion electrotropic plants deprived of the electrical field do not develop as expected, as can be seen in Biosphere 2. This is an instructive example of what happens when we forget to provide the plants with this vital natural environmental factor. Electrical fields of different intensity, directions and configurations are cheap and easy to generate.

Three-dimensional, two-species magnetohydrodynamic studies of the early time behaviors of the Combined Release and Radiation Effects Satellite G2 barium release

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Lianghai, E-mail: xielh@nssc.ac.cn; Li, Lei; Wang, Jingdong

2014-04-15

We present a three-dimensional, two-species (Ba{sup +} and H{sup +}) MHD model to study the early time behaviors of a barium release at about 1 R{sub E} like Combined Release and Radiation Effects Satellite G2, with emphasis placed on the three-dimensional evolution of the barium cloud and its effects on the ambient plasma environment. We find that the perturbations caused by the cloud are the combined results of the initial injection, the radial expansion, and the diamagnetic effect and propagate as fast MHD waves in the magnetosphere. In return, the transverse expansion and the cross-B motion of barium ions aremore » constrained by the magnetic force, which lead to a field-aligned striation of ions and the decoupling of these ions from the neutrals. Our simulation shows the formation and collapse of the diamagnetic cavity in the barium cloud. The estimated time scale for the cavity evolution might be much shorter if photoionization time scale and field aligned expansion of barium ions are considered. In addition, our two species MHD simulation also finds the snowplow effect resulting from the momentum coupling between barium ions and background H{sup +}, which creates density hole and bumps in the background H{sup +} when barium ions expanding along the magnetic field lines.« less

Ion-kill dosimetry

NASA Technical Reports Server (NTRS)

Katz, R.; Cucinotta, F. A.; Fromm, M.; Chambaudet, A.

2001-01-01

Unanticipated late effects in neutron and heavy ion therapy, not attributable to overdose, imply a qualitative difference between low and high LET therapy. We identify that difference as 'ion kill', associated with the spectrum of z/beta in the radiation field, whose measurement we label 'ion-kill dosimetry'.

Maxwell-Chern-Simons hydrodynamics for the chiral magnetic effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oezoender, Sener

2010-06-15

The rate of vacuum-changing topological solutions of the gluon field, sphalerons, is estimated to be large at the typical temperatures of heavy-ion collisions, particularly at the Relativistic Heavy Ion Collider. Such windings in the gluon field are expected to produce parity-odd bubbles, which cause separation of positively and negatively charged quarks along the axis of the external magnetic field. This chiral magnetic effect can be mimicked by Chern-Simons modified electromagnetism. Here we present a model of relativistic hydrodynamics including the effects of axial anomalies via the Chern-Simons term.

Simulation of RF power and multi-cusp magnetic field requirement for H- ion sources

NASA Astrophysics Data System (ADS)

Pathak, Manish; Senecha, V. K.; Kumar, Rajnish; Ghodke, Dharmraj. V.

2016-12-01

A computer simulation study for multi-cusp RF based H- ion source has been carried out using energy and particle balance equation for inductively coupled uniformly dense plasma considering sheath formation near the boundary wall of the plasma chamber for RF ion source used as high current injector for 1 Gev H- Linac project for SNS applications. The average reaction rates for different reactions responsible for H- ion production and destruction have been considered in the simulation model. The RF power requirement for the caesium free H- ion source for a maximum possible H- ion beam current has been derived by evaluating the required current and RF voltage fed to the coil antenna using transformer model for Inductively Coupled Plasma (ICP). Different parameters of RF based H- ion source like excited hydrogen molecular density, H- ion density, RF voltage and current of RF antenna have been calculated through simulations in the presence and absence of multicusp magnetic field to distinctly observe the effect of multicusp field. The RF power evaluated for different H- ion current values have been compared with the experimental reported results showing reasonably good agreement considering the fact that some RF power will be reflected from the plasma medium. The results obtained have helped in understanding the optimum field strength and field free regions suitable for volume emission based H- ion sources. The compact RF ion source exhibits nearly 6 times better efficiency compare to large diameter ion source.

Parametric dependence of ion temperature and electron density in the SUMMA hot-ion plasma using laser light scattering and emission spectroscopy

NASA Technical Reports Server (NTRS)

Snyder, A.; Patch, R. W.; Lauver, M. R.

1980-01-01

Hot-ion plasma experiments were conducted in the NASA Lewis SUMMA facility. A steady-state modified Penning discharge was formed by applying a radially inward dc electric field of several kilovolts near the magnetic mirror maxima. Results are reported for a hydrogen plasma covering a wide range in midplane magnetic flux densities from 0.5 to 3.37 T. Input power greater than 45 kW was obtained with water-cooled cathodes. Steady-state plasmas with ion kinetic temperatures from 18 to 830 eV were produced and measured spectroscopically. These ion temperatures were correlated with current, voltage, and magnetic flux density as the independent variables. Electron density measurements were made using an unusually sensitive Thomson scattering apparatus. The measured electron densities range from 2.1 x 10 to the 11th to 6.8 x 10 to the 12th per cu cm.

Study of the effects of E × B fields as mechanism to carbon-nitrogen plasma immersion ion implantation on stainless steel samples

NASA Astrophysics Data System (ADS)

Pillaca, E. J. D. M.; Ueda, M.; Oliveira, R. M.; Pichon, L.

2014-08-01

Effects of E × B fields as mechanism to carbon-nitrogen plasma immersion ion implantation (PIII) have been investigated. This magnetic configuration when used in PIII allows obtaining high nitrogen plasma density close to the ion implantation region. Consequently, high ions dose on the target is possible to be achieved compared with standard PIII. In this scenario, nitrogen and carbon ions were implanted simultaneously on stainless steel, as measured by GDOES and detected by X-ray diffraction. Carbon-tape disposed on the sample-holder was sputtered by intense bombardment of nitrogen ions, being the source of carbon atoms in this experiment. The implantation of both N and C caused changes on sample morphology and improvement of the tribological properties of the stainless steel.

CALUTRON

DOEpatents

Clark, A.F.

1959-06-16

A means of eliminating oscillating electrons from the arc slit region of calutron ion sources is offered. Free electrons and ions generated by the beam bombarding atoms of ambient atmosphere are discharged by a fin arrangement which sets up an electric field. The discharged ions travel toward a recess in which a fin and blister'' effect limits oscillations to one region from which they are removed by reversed electric fields. (T.R.H.)

Effects of density gradient caused by multi-pulsing CHI on two-fluid flowing equilibria of spherical torus plasmas

NASA Astrophysics Data System (ADS)

Kanki, T.; Nagata, M.

2014-10-01

Two-fluid dynamo relaxation is examined to understand sustainment mechanism of spherical torus (ST) plasmas by multi-pulsing CHI (M-CHI) in the HIST device. The steeper density gradient between the central open flux column (OFC) and closed flux regions by applying the second CHI pulse is observed to cause not only the E × B drift but also the ion diamagnetic drift, leading the two-fluid dynamo. The purpose of this study is to investigate the effects of the steep change in the density gradient on the ST equilibria by using the two-fluid equilibrium calculations. The toroidal magnetic field becomes from a diamagnetic to a paramagnetic profile in the closed flux region while it remains a diamagnetic profile in the OFC region. The toroidal ion flow velocity is increased from negative to positive values in the closed flux region. Here, the negative ion flow velocity is the opposite direction to the toroidal current. The poloidal ion flow velocity between the OFC and closed flux regions is increased, because the ion diamagnetic drift velocity is changed in the same direction as the E × B drift velocity through the steeper ion pressure gradient. As a result, the strong shear flow and the paramagnetic toroidal field are generated in the closed flux region. Here, the ion flow velocity is the same direction as the poloidal current. The radial electric field shear between the OFC and closed flux regions is enhanced due to the strong dependence on the magnetic force through the interaction of toroidal ion flow velocity and axial magnetic field. The two-fluid effect is significant there due to the ion diamagnetic effect.

Kinetic Alfven wave explanation of the Hall signals in magnetic reconnection

NASA Astrophysics Data System (ADS)

Dai, L.; Wang, C.; Zhang, Y.; Duan, S.; Lavraud, B.; Burch, J. L.; Pollock, C.; Torbert, R. B.

2017-12-01

Magnetic reconnection is initiated in a small diffusion region but can drive global-scale dynamics in Earth's magnetosphere, solar flares, and astrophysical systems. Understanding the processes at work in the diffusion region remains a main challenge in space plasma physics. Recent in-situ observations from MMS and THEMIS reveal that the electric field normal to the reconnection current layer, often called the Hall electric field (En), is mainly balanced by the ion pressure gradient. Here we present theoretical explanations indicating that this observation fact is a manifestation of Kinetic Alfven Waves (KAW) physics. The ion pressure gradient represents the finite gyroradius effect of KAW, leading to ion intrusion across the magnetic field lines. Electrons stream along the magnetic field lines to track ions, resulting in field-aligned currents and the associated pattern of the out-of-plane Hall magnetic field (Bm). The ratio En/Bm is on the order of the Alfven speed, as predicted by the KAW theory. The KAW physics further provides new perspectives on how ion intrusion may trigger electric fields suitable for reconnection to occur.

The influence of Mars' magnetic topology on atmospheric escape

NASA Astrophysics Data System (ADS)

Curry, S.; Luhmann, J. G.; DiBraccio, G. A.; Dong, C.; Xu, S.; Mitchell, D.; Gruesbeck, J.; Espley, J. R.; Connerney, J. E. P.; McFadden, J. P.; Ma, Y. J.; Brain, D.

2017-12-01

At weakly magnetized planets such as Mars and Venus, the solar wind directly interacts with the upper atmosphere where ions can be picked up and swept away by the background convection electric field. These pick-up ions have a gyroradius on the planetary scale that is largely dominated by the interplanetary magnetic field (IMF). But at Mars, their trajectory is also influenced by the existence of remanent crustal magnetic fields, which are thought to create a shielding effect for escaping planetary ions when they are on the dayside. Consequently, the magnetic topology changes at Mars as magnetic reconnection occurs between the draped (IMF) and the crustal magnetic fields (closed). The resulting topology includes open field lines in the solar wind with one footprint attached to the planet. Using magnetohydrodynamic (MHD) and test particle simulations, we will explore the influence of the magnetic topology on ion escape. We will present escape rates for planetary ions for different crustal field positions during different IMF configurations, with +/-BY and +/-BZ components in the Mars Sun Orbit (MSO) coordinate system. We will also compare global maps of ion outflow and escape with open / closed magnetic field line maps and compare our results with ion fluxes and magnetic field data from the Mars Atmospheric and Volatile EvolutioN (MAVEN) mission. Our results relating the dynamic magnetic field topology at Mars and planetary ion escape are an important aspect of magnetospheric physics and planetary evolution, both of which have applications to our own solar system and the increasing number of exoplanets discovered every year.

Phenomenology of anomalous chiral transports in heavy-ion collisions

NASA Astrophysics Data System (ADS)

Huang, Xu-Guang

2018-01-01

High-energy Heavy-ion collisions can generate extremely hot quark-gluon matter and also extremely strong magnetic fields and fluid vorticity. Once coupled to chiral anomaly, the magnetic fields and fluid vorticity can induce a variety of novel transport phenomena, including the chiral magnetic effect, chiral vortical effect, etc. Some of them require the environmental violation of parity and thus provide a means to test the possible parity violation in hot strongly interacting matter. We will discuss the underlying mechanism and implications of these anomalous chiral transports in heavy-ion collisions.

Fast ion transport during applied 3D magnetic perturbations on DIII-D

DOE PAGES

Van Zeeland, Michael A.; Ferraro, Nathaniel M.; Grierson, Brian A.; ...

2015-06-26

In this paper, measurements show fast ion losses correlated with applied three-dimensional (3D) fields in a variety of plasmas ranging from L-mode to resonant magnetic perturbation (RMP) edge localized mode (ELM) suppressed H-mode discharges. In DIII-D L-mode discharges with a slowly rotatingmore » $n=2$ magnetic perturbation, scintillator detector loss signals synchronized with the applied fields are observed to decay within one poloidal transit time after beam turn-off indicating they arise predominantly from prompt loss orbits. Full orbit following using M3D-C1 calculations of the perturbed fields and kinetic profiles reproduce many features of the measured losses and points to the importance of the applied 3D field phase with respect to the beam injection location in determining the overall impact on prompt beam ion loss. Modeling of these results includes a self-consistent calculation of the 3D perturbed beam ion birth profiles and scrape-off-layer ionization, a factor found to be essential to reproducing the experimental measurements. Extension of the simulations to full slowing down timescales, including fueling and the effects of drag and pitch angle scattering, show the applied $n=3$ RMPs in ELM suppressed H-mode plasmas can induce a significant loss of energetic particles from the core. With the applied $n=3$ fields, up to 8.4% of the injected beam power is predicted to be lost, compared to 2.7% with axisymmetric fields only. These fast ions, originating from minor radii $$\\rho >0.7$$ , are predicted to be primarily passing particles lost to the divertor region, consistent with wide field-of-view infrared periscope measurements of wall heating in $n=3$ RMP ELM suppressed plasmas. Edge fast ion $${{\\text{D}}_{\\alpha}}$$ (FIDA) measurements also confirm a large change in edge fast ion profile due to the $n=3$ fields, where the effect was isolated by using short 50 ms RMP-off periods during which ELM suppression was maintained yet the fast ion profile was allowed to recover. Finally, the role of resonances between fast ion drift motion and the applied 3D fields in the context of selectively targeting regions of fast ion phase space is also discussed.« less

Preliminary result of rapid solenoid for controlling heavy-ion beam parameters of laser ion source

DOE PAGES

Okamura, M.; Sekine, M.; Ikeda, S.; ...

2015-03-13

To realize a heavy ion inertial fusion driver, we have studied a possibility of laser ion source (LIS). A LIS can provide high current high brightness heavy ion beams, however it was difficult to manipulate the beam parameters. To overcome the issue, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The rapid ramping magnetic field could enhance limited time slice of the current and simultaneously the beam emittance changed accordingly. This approach may also useful to realize an ion source for HIF power plant.

DEVELOPMENT OF A METHOD FOR THE OBSERVATION OF LIGHTNING IN PROTOPLANETARY DISKS USING ION LINES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muranushi, Takayuki; Akiyama, Eiji; Inutsuka, Shu-ichiro

2015-12-20

In this paper, we propose observational methods for detecting lightning in protoplanetary disks. We do so by calculating the critical electric field strength in the lightning matrix gas (LMG), the parts of the disk where the electric field is strong enough to cause lightning. That electric field accelerates multiple positive ion species to characteristic terminal velocities. In this paper, we present three distinct discharge models with corresponding critical electric fields. We simulate the position–velocity diagrams and the integrated emission maps for the models. We calculate the measure-of-sensitivity values for detection of the models and for distinguishing between the models. Atmore » the distance of TW Hya (54 pc), LMG that occupies 2π in azimuth and has 25 AU < r < 50 AU is detectable at 1200σ to 4000σ. The lower limits of the radii of 5σ-detectable LMG clumps are between 1.6 AU and 5.3 AU, depending on the models.« less

pH-Sensitive stimulus-responsive nanocarriers for targeted delivery of therapeutic agents

PubMed Central

Karimi, Mahdi; Eslami, Masoud; Sahandi-Zangabad, Parham; Mirab, Fereshteh; Farajisafiloo, Negar; Shafaei, Zahra; Ghosh, Deepanjan; Bozorgomid, Mahnaz; Dashkhaneh, Fariba; Hamblin, Michael R.

2016-01-01

In recent years miscellaneous smart micro/nanosystems that respond to various exogenous/endogenous stimuli including temperature, magnetic/electric field, mechanical force, ultrasound/light irradiation, redox potentials, and biomolecule concentration have been developed for targeted delivery and release of encapsulated therapeutic agents such as drugs, genes, proteins, and metal ions specifically at their required site of action. Owing to physiological differences between malignant and normal cells, or between tumors and normal tissues, pH-sensitive nanosystems represent promising smart delivery vehicles for transport and delivery of anticancer agents. Furthermore, pH-sensitive systems possess applications in delivery of metal ions and biomolecules such as proteins, insulin, etc., as well as co-delivery of cargos, dual pH-sensitive nanocarriers, dual/multi stimuli-responsive nanosystems, and even in the search for new solutions for therapy of diseases such as Alzheimer’s. In order to design an optimized system, it is necessary to understand the various pH-responsive micro/nanoparticles and the different mechanisms of pH-sensitive drug release. This should be accompanied by an assessment of the theoretical and practical challenges in the design and use of these carriers. PMID:26762467

Ion-mobility study of two functionalized pentacene structural isomers using a modified electrospray/triple quadrupole mass spectrometer

NASA Astrophysics Data System (ADS)

Prada, Svitlana V.; Bohme, Diethard K.; Baranov, Vladimir I.

2007-03-01

We report ion-mobility measurements with a modified triple quadrupole mass spectrometer fitted with an ion molecule reactor (IMR) designed to investigate ion molecule reactivity in organic mass spectrometry. Functionalized pentacene ions, which are generally unreactive were chosen for study to decouple drift/diffusion effects from reactivity (including clustering). The IMR is equipped with a variable axial electrostatic drift field (ADF) and is able to trap ions. These capabilities were successfully employed in the measurement of ion mobilities in different modes of IMR operation. Theoretical modeling of the drift dynamics and the special localization of the large ion packet was successfully implemented. The contribution of the quadrupole RF field to the drift dynamics also was taken into consideration.

On the fluctuations that drive small ions toward, and away from, interfaces between polar liquids and their vapors

PubMed Central

Noah-Vanhoucke, Joyce; Geissler, Phillip L.

2009-01-01

Contrary to the expectations from classic theories of ion solvation, spectroscopy and computer simulations of the liquid–vapor interface of aqueous electrolyte solutions suggest that ions little larger than a water molecule can prefer to reside near the liquid's surface. Here we advance the view that such affinity originates in a competition between strong opposing forces, primarily due to volume exclusion and dielectric polarization, that are common to all dense polar liquids. We present evidence for this generic mechanism from computer simulations of (i) water and (ii) a Stockmayer fluid near its triple point. In both cases, we show that strong surface enhancement of small ions, obtained by tuning solutes' size and charge, can be accentuated or suppressed by modest changes in either of those parameters. Statistics of solvent polarization, when the ion is held at and above the Gibbs dividing surface, highlight a basic deficiency in conventional models of dielectric response, namely, the neglect of interfacial flexibility. By distorting the solution's boundary, an ion experiences fluctuations in electrostatic potential and in electric field whose magnitudes attenuate much more gradually (as the ion is removed from the liquid phase) than for a quiescent planar interface. As one consequence, the collective responses that determine free energies of solvation can resolve very differently in nonuniform environments than in bulk. We show that this persistence of electric-field fluctuations additionally shapes the sensitivity of solute distributions to ion polarizability. PMID:19720991

Photofunctional hybrids of lanthanide functionalized bio-MOF-1 for fluorescence tuning and sensing.

PubMed

Shen, Xiang; Yan, Bing

2015-08-01

A series of luminescent Ln(3+)@bio-MOF-1 (Ln=Eu, Tb, bio-MOF-1=Zn8(ad)4(BPDC)6O⋅2Me2NH2 (ad=adeninate, BPDC=biphenyldicarboxylate)) are synthesized via postsynthetic cation exchange by encapsulating lanthanide ions into an anionic metal-organic framework (MOF), and their photophysical properties are studied. After loading 2-thenoyltrifluroacetone (TTA) as sensitized ligand by a gas diffusion ("ship-in-bottle") method, it is found that the luminescent intensity of Eu(3+) is enhanced. Especially, when loading two different lanthanide cations into bio-MOF-1, the luminescent color can be tuned to close white (light pink) light output. Additionally, bio-MOF-1 and Eu(3+)@bio-MOF-1 are selected as representative samples for sensing metal ions. When bio-MOF-1 is immersed in the aqueous solutions of different metal ions, it shows highly sensitive sensing for Fe(3+) as well as Eu(3+)@bio-MOF-1 immersed in the DMF solutions of different metal ion. The results are benefit for the further application of functionalized bio-MOFs in practical fields. Copyright © 2015 Elsevier Inc. All rights reserved.

Single-Molecule Bioelectronics

PubMed Central

Rosenstein, Jacob K.; Lemay, Serge G.; Shepard, Kenneth L.

2014-01-01

Experimental techniques which interface single biomolecules directly with microelectronic systems are increasingly being used in a wide range of powerful applications, from fundamental studies of biomolecules to ultra-sensitive assays. Here we review several technologies which can perform electronic measurements of single molecules in solution: ion channels, nanopore sensors, carbon nanotube field-effect transistors, electron tunneling gaps, and redox cycling. We discuss the shared features among these techniques that enable them to resolve individual molecules, and discuss their limitations. Recordings from each of these methods all rely on similar electronic instrumentation, and we discuss the relevant circuit implementations and potential for scaling these single-molecule bioelectronic interfaces to high-throughput arrayed sensing platforms. PMID:25529538

Metal Oxides and Ion-Exchanging Surfaces as pH Sensors in Liquids: State-of-the-Art and Outlook

PubMed Central

Kurzweil, Peter

2009-01-01

Novel applications of online pH determinations at temperatures from -35 °C to 130 °C in technical and biological media, which are all but ideal aqueous solutions, require new approaches to pH monitoring. The glass electrode, introduced nearly hundred years ago, and chemical sensors based on field effect transistors (ISFET) show specific drawbacks with respect to handling and long-time stability. Proton sensitive metal oxides seem to be a promising and alternative to the state-of-the-art measuring methods, and might overcome some problems of classical hydrogen electrodes and reference electrodes. PMID:22408563

Old tree with new shoots: silver nanoparticles for label-free and colorimetric mercury ions detection

NASA Astrophysics Data System (ADS)

Gao, Shuyan; Jia, Xiaoxia; Chen, Yanli

2013-01-01

Mercury in the environment from global mercury emissions as well as various forms of contamination poses severe threats to both human health and the environment. Long-term exposure to high levels of Hg-based toxins results in serious and irreversible damage of the central nervous system and other organs. Therefore, the development of effective sensing systems for mercury detection becomes an increasing demand. In this article, a yogurt-mediated silver nanostructure is reported to be unprecedentedly used in the naked-eye and label-free detection of mercury. The method relies on the redox reaction resulting from the electrode potential difference between Ag+/Ag (0.7996 V) and Hg2+/Hg2 2+ (0.920 V) that makes colorless Hg2+ ions which oxidize colored silver nanoparticle (AgNP) to colorless Ag+. The labor-intensive modification of AgNPs and expensive labeling are avoided, and the traditional AuNPs are substituted by AgNPs in this Hg2+ ions sensing platform, which makes it facile, low-cost, and particularly useful for home, clinic, or field applications as well as resource-limited conditions. This sensing system achieves a detection limit as low as 10 nM, lower than the toxicity level of Hg2+ ions in drinking water (30 nM) defined by World Health Organization, and exhibits excellent selectivity, largely free from the matrix effect of the real water samples. This visual label-free Hg2+ ions sensing motif shows great promise for sensing Hg2+ ions in terms of sensitivity, selectivity, cost, and maneuverability. It is also a good example for the organic combination of green chemistry and functional materials, which may trigger interest in furthering biosystems for environmental science applications.

Construction of Uranyl Selective Electrode Based on Complex of Uranyl Ion with New Ligand Carboxybenzotriazole in PVC Matrix Membrane

NASA Astrophysics Data System (ADS)

Abu-Dalo, M. A.; Al-Rawashdeh, N. A. F.; Al-Mheidat, I. R.; Nassory, N. S.

2015-10-01

In the present study uranyl selective electrodes in polyvinyl chloride (PVC) matrix membrane were prepared based on a complex of uranyl ion (UO2) with carboxybenzotriazole (CBT) as ligand. The effect of the nature of plasticizer in PVC matrix were evaluated using three different plasticizers, these are dibutyl phthalate (DBP), dioctyl phthalate (DOP) and bis(2-ethylhexyl) sebacate (BHS). The results of this study indicated that the best plasticizer could be used is the DBP, which may be attributed to its lowest viscosity value compared to DOP and BHS. The electrodes with DBP as plasticizer exhibits a Nernstian response with a slope of 28.0 mV/ decade, over a wide range of concentration from 3.0×10-5-6.0×10-2 M and a detection limit of 4.0×10-6 M. It can be used in the pH range of 4.0-10.0 with a response time of less than 10 s for DBP and 25 s for both DOP and BHS. The effects of ions interferences on the electrode response were evaluated. The di- and tri-valent cations were found to interfere less than univalent cations, which was attributed to the high diffusion and the exchange rate between the univalent ions and the uranyl ion solution. The electrodes were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron microscopy (SEM). The results of the standard addition method were satisfactory with errors less than 7%. The developed electrode was found to be fast, sensitive and reliable indicated its potential use in measuring the uranly ion concentration in the field.

Effects of internal structure on equilibrium of field-reversed configuration plasma sustained by rotating magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yambe, Kiyoyuki; Inomoto, Michiaki; Okada, Shigefumi

The effects of an internal structure on the equilibrium of a field-reversed configuration (FRC) plasma sustained by rotating magnetic field is investigated by using detailed electrostatic probe measurements in the FRC Injection Experiment apparatus [S. Okada, et al., Nucl. Fusion. 45, 1094 (2005)]. An internal structure installed axially on the geometrical axis, which simulates Ohmic transformer or external toroidal field coils on the FRC device, brings about substantial changes in plasma density profile. The internal structure generates steep density-gradients not only on the inner side but on the outer side of the torus. The radial electric field is observed tomore » sustain the ion thermal pressure-gradient in the FRC without the internal structure; however, the radial electric field is not sufficient to sustain the increased ion thermal pressure-gradient in the FRC with the internal structure. Spontaneously driven azimuthal ion flow will be accountable for the imbalance of the radial pressure which is modified by the internal structure.« less

Ultralow dose effects in ion-beam induced grafting of polymethylmethacrylate (PMMA)

NASA Astrophysics Data System (ADS)

Corelli, J. C.; Steckl, A. J.; Pulver, D.; Randall, J. N.

We have investigated the process of image enhancement in high resolution lithography through polymer grafting techniques. Sensitivity gains of 10 3-10 4 were obtained for H +, X-ray, e-beam and deep-UV irradiations. Ultralow dose effects in 60 keV H + irradiated PMMA have been observed through the use of the acrylic acid (AA) monomer grafting with irradiated PMMA. At conventional doses of 10 10 cm -2 an inner structure of each feature is revealed. At doses of (1-2) X 10 9 cm -2, discrete events within the exposed regions are observable. This is the first time that individual events have been observable in a lithography process and sets the upper limit in the useful sensitivity of the resist and ion lithography process. This effect is directly observable only with ions, because of their higher efficiency per particle than either photons or electrons.

Computed versus measured ion velocity distribution functions in a Hall effect thruster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garrigues, L.; CNRS, LAPLACE, F-31062 Toulouse; Mazouffre, S.

2012-06-01

We compare time-averaged and time-varying measured and computed ion velocity distribution functions in a Hall effect thruster for typical operating conditions. The ion properties are measured by means of laser induced fluorescence spectroscopy. Simulations of the plasma properties are performed with a two-dimensional hybrid model. In the electron fluid description of the hybrid model, the anomalous transport responsible for the electron diffusion across the magnetic field barrier is deduced from the experimental profile of the time-averaged electric field. The use of a steady state anomalous mobility profile allows the hybrid model to capture some properties like the time-averaged ion meanmore » velocity. Yet, the model fails at reproducing the time evolution of the ion velocity. This fact reveals a complex underlying physics that necessitates to account for the electron dynamics over a short time-scale. This study also shows the necessity for electron temperature measurements. Moreover, the strength of the self-magnetic field due to the rotating Hall current is found negligible.« less

Influence of in-situ ion-beam sputter cleaning on the conditioning effect of vacuum gaps

NASA Astrophysics Data System (ADS)

Kobayashi, Shinichi; Kojima, Hiroyuki; Saito, Yoshio

1994-05-01

An ion beam sputtering technique was used to clean the electrode surfaces of vacuum gaps. Ions of the sputtering gas were irradiated by means of an ion gun in a vacuum chamber attached to a breakdown measurement chamber. By providing in situ ion-beam sputter cleaning, this system makes it possible to make measurements free from contamination due to exposure to the air. The sputtering gas was He or Ar, and the electrodes were made of oxygen-free copper (purity more than 99.96%). An impulse voltage with the wave form of 64/700 microsecond(s) was applied to the test gap, and the pressure in the breakdown measurement chamber at the beginning of breakdown tests was 1.3 X 10-8 Pa. These experiments showed that ion-beam sputter cleaning results in higher breakdown fields after a repetitive breakdown conditioning procedure, and that He is more effective in improving hold- off voltages after the conditioning (under the same ion current density, the breakdown field was 300 MV/m for He sputtering and 200 MV/m for Ar sputtering). The breakdown fields at the first voltage application after the sputtering cleaning, on the other hand, were not improved.

Spatial proximity effects on the excitation of sheath RF voltages by evanescent slow waves in the ion cyclotron range of frequencies

NASA Astrophysics Data System (ADS)

Colas, Laurent; Lu, Ling-Feng; Křivská, Alena; Jacquot, Jonathan; Hillairet, Julien; Helou, Walid; Goniche, Marc; Heuraux, Stéphane; Faudot, Eric

2017-02-01

We investigate theoretically how sheath radio-frequency (RF) oscillations relate to the spatial structure of the near RF parallel electric field E ∥ emitted by ion cyclotron (IC) wave launchers. We use a simple model of slow wave (SW) evanescence coupled with direct current (DC) plasma biasing via sheath boundary conditions in a 3D parallelepiped filled with homogeneous cold magnetized plasma. Within a ‘wide-sheath’ asymptotic regime, valid for large-amplitude near RF fields, the RF part of this simple RF  +  DC model becomes linear: the sheath oscillating voltage V RF at open field line boundaries can be re-expressed as a linear combination of individual contributions by every emitting point in the input field map. SW evanescence makes individual contributions all the larger as the wave emission point is located closer to the sheath walls. The decay of |V RF| with the emission point/sheath poloidal distance involves the transverse SW evanescence length and the radial protrusion depth of lateral boundaries. The decay of |V RF| with the emitter/sheath parallel distance is quantified as a function of the parallel SW evanescence length and the parallel connection length of open magnetic field lines. For realistic geometries and target SOL plasmas, poloidal decay occurs over a few centimeters. Typical parallel decay lengths for |V RF| are found to be smaller than IC antenna parallel extension. Oscillating sheath voltages at IC antenna side limiters are therefore mainly sensitive to E ∥ emission by active or passive conducting elements near these limiters, as suggested by recent experimental observations. Parallel proximity effects could also explain why sheath oscillations persist with antisymmetric strap toroidal phasing, despite the parallel antisymmetry of the radiated field map. They could finally justify current attempts at reducing the RF fields induced near antenna boxes to attenuate sheath oscillations in their vicinity.

Hooked differential mobility spectrometry apparatus and method therefore

DOEpatents

Shvartsburg, Alexandre A [Richland, WA; Tang, Keqi [Richland, WA; Ibrahim, Yehia M [Richland, WA; Smith, Richard D [Richland, WA

2009-02-17

Disclosed are a device and method for improved interfacing of differential mobility spectrometry (DMS) or field asymmetric waveform ion mobility spectrometry (FAIMS) analyzers of substantially planar geometry to subsequent or preceding instrument stages. Interfacing is achieved using curved DMS elements, where a thick ion beam emitted by planar DMS analyzers or injected into them for ion filtering is compressed to the gap median by DMS ion focusing effect in a spatially inhomogeneous electric field. Resulting thinner beams are more effectively transmitted through necessarily constrained conductance limit apertures to subsequent instrument stages operated at a pressure lower than DMS, and/or more effectively injected into planar DMS analyzers. The technology is synergetic with slit apertures, slit aperture/ion funnels, and high-pressure ion funnel interfaces known in the art which allow for increasing cross-sectional area of MS inlets. The invention may be used in integrated analytical platforms, including, e.g., DMS/MS, LC/DMS/MS, and DMS/IMS/MS that could replace and/or enhance current LC/MS methods, e.g., for proteomics research.

Effect of electron-to-ion mass ratio on radial electric field generation in tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Zhenqian; Dong, Jiaqi; Sheng, Zhengmao

Generation of coherent radial electric fields in plasma by drift-wave turbulence driven by plasma inhomogeneities is ab initio studied using gyro-kinetic particle simulation for conditions of operational tokamaks. In particular, the effect of the electron-to-ion mass ratio epsilon on the entire evolution of the plasma is considered. In conclusion, it is found that the electric field can be increased, and the turbulence-induced particle transport reduced, by making epsilon smaller, in agreement with many existing experimental observations.

Effect of electron-to-ion mass ratio on radial electric field generation in tokamak

DOE PAGES

Li, Zhenqian; Dong, Jiaqi; Sheng, Zhengmao; ...

2017-11-21

Generation of coherent radial electric fields in plasma by drift-wave turbulence driven by plasma inhomogeneities is ab initio studied using gyro-kinetic particle simulation for conditions of operational tokamaks. In particular, the effect of the electron-to-ion mass ratio epsilon on the entire evolution of the plasma is considered. In conclusion, it is found that the electric field can be increased, and the turbulence-induced particle transport reduced, by making epsilon smaller, in agreement with many existing experimental observations.

Inertial Currents in Isotropic Plasma

NASA Technical Reports Server (NTRS)

Heinemann, M.; Erickson, G. M.; Pontius, D. H., Jr.

1993-01-01

The magnetospheric convection electric field contributes to Birkeland currents. The effects of the field are to polarize the plasma by displacing the bounce paths of the ions from those of electrons, to redistribute the pressure so that it is not constant along magnetic field lines, and to enhance the pressure gradient by the gradient of the bulk speed. Changes in the polarization charge during the convection of the plasma are neutralized by electrons in the form of field-aligned currents that close through the ionosphere. The pressure drives field-aligned currents through its gradient in the same manner as in quasi-static plasma, but with modifications that are important if the bulk speed is of the order of the ion thermal speed; the variations in the pressure along field lines are maintained by a weak parallel potential drop. These effects are described in terms of the field-aligned currents in steady state, isotropic, MED plasma. Solutions are developed by taking the MHD limit of two-fluid solutions and illustrated in the special case of Maxwellian plasma for which the temperature is constant along magnetic field lines. The expression for the Birkeland current density is a generalization of Vasyliunas' expression for the field-aligned current density in quasi-static plasma and provides a unifying expression when both pressure gradients and ion inertia operate simultaneously as sources of field-aligned currents. It contains a full account of different aspects of the ion flow (parallel and perpendicular velocity and vorticity) that contribute to the currents. Contributions of ion inertia to field-aligned currents will occur in regions of strong velocity shear, electric field reversal, or large gradients in the parallel velocity or number density, and may be important in the low-latitude boundary layer, plasma sheet boundary layer, and the inner edge region of the plasma sheet.

Inertial currents in isotropic plasma

NASA Technical Reports Server (NTRS)

Heinemann, M.; Erickson, G. M.; Pontius, D. H. JR.

1994-01-01

The magnetospheric convection electric field contributes to Birkeland currents. The effects of the field are to polarize the plasma by displacing the bounce paths of the ions from those of electrons, to redistribute the pressure so that it is not constant along magnetic field lines, and to enhance the pressure gradient by the gradient of the bulk speed. Changes in the polarization charge during the convection of the plasma are neutralized by electrons in the form of field-aligned currents that close through the ionosphere. The pressure drives field-aligned currents through its gradient in the same manner as in quasi-static plasma, but with modifications that are important if the bulk speed is of the order of the ion thermal speed; the variations in the pressure along field lines are maintained by a weak parallel potential drop. These effects are described in terms of the field-aligned currents in steady state, isotropic, magnetohyrodynamic (MHD) plasma. Solutions are developed by taking the MHD limit of two-fluid solutions and illustrated in the special case of Maxwellian plasma for which the temperature is constant along magnetic field lines. The expression for the Birkeland current density is a generalization of Vasyliunas' expression for the field-aligned current density in quasi-static plasma and provides a unifying expression when both pressure gradients and ion inertia operate simultaneously as sources of field-aligned currents. It contains a full account of different aspects of the ion flow (parallel and perpendicular velocity and vorticity) that contribute to the currents. Contributions of ion inertia to field-aligned currents will occur in regions of strong velocity shear, electric field reversal, or large gradients in the parallel velocity or number density, and may be important in the low-latitude boundary layer, plasma sheet boundary layer, and the inner edge region of the plasma sheet.

Inertial currents in isotropic plasma

NASA Technical Reports Server (NTRS)

Heinemann, M.; Erickson, G. M.; Pontius, D. H., Jr.

1994-01-01

The magnetospheric convection electric field contributes to Birkeland currents. The effects of the field are to polarize the plasma by displacing the bounce paths of the ions from those of electrons, to redistribute the pressure so that it is not constant along magnetic field lines, and to enhance the pressure gradient by the gradient of the bulk speed. Changes in the polarization charge during the convection of the plasma are neutralized by electrons in the form of field-aligned currents that close through the ionosphere. The pressure drives field-aligned currents through its gradient in the same manner as in quasi-static plasmas, but with modifications that are important if the bulk speed is of the order of the ion thermal speed; the variations in the pressure along field lines are maintained by a weak parallel potential drop. These effects are described in terms of the field-aligned currents in steady state, isotropic, MHD plasma. Solutions are developed by taking the MHD limit ot two-fluid solutions and illustrated in the special case of Maxwellian plasma for which the temperature is constant along magnetic field lines. The expression for the Birkeland current density is a generalization of Vasyliunas' expression for the field-aligned current density in quasi-static plasma and provides a unifying expression when both pressure gradients and ion inertia operate simultaneously as sources of field-aligned currents. It contains a full account of different aspects of the ion flow (parallel and perpendicular velocity and vorticity) that contribute to the currents. Contributions of ion inertia to field-aligned currents will occur in regions of strong velocity shear, electric field reversal, or large gradients in the parallel velocity or number density, and may be important in the low-latitude boundary layer, plasma sheet boundary layer, and the inner edge region of the plasma sheet.

Measurement of volatile plant compounds in field ambient air by thermal desorption-gas chromatography-mass spectrometry.

PubMed

Cai, Xiao-Ming; Xu, Xiu-Xiu; Bian, Lei; Luo, Zong-Xiu; Chen, Zong-Mao

2015-12-01

Determination of volatile plant compounds in field ambient air is important to understand chemical communication between plants and insects and will aid the development of semiochemicals from plants for pest control. In this study, a thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) method was developed to measure ultra-trace levels of volatile plant compounds in field ambient air. The desorption parameters of TD, including sorbent tube material, tube desorption temperature, desorption time, and cold trap temperature, were selected and optimized. In GC-MS analysis, the selected ion monitoring mode was used for enhanced sensitivity and selectivity. This method was sufficiently sensitive to detect part-per-trillion levels of volatile plant compounds in field ambient air. Laboratory and field evaluation revealed that the method presented high precision and accuracy. Field studies indicated that the background odor of tea plantations contained some common volatile plant compounds, such as (Z)-3-hexenol, methyl salicylate, and (E)-ocimene, at concentrations ranging from 1 to 3400 ng m(-3). In addition, the background odor in summer was more abundant in quality and quantity than in autumn. Relative to previous methods, the TD-GC-MS method is more sensitive, permitting accurate qualitative and quantitative measurements of volatile plant compounds in field ambient air.

Space charge effect in spectrometers of ion mobility increment with planar drift chamber.

PubMed

Elistratov, A A; Sherbakov, L A

2007-01-01

The effect of space charge on the ion beam in a spectrometer of ion mobility increment with the planar drift chamber has been investigated. A model for the drift of ions under a non-uniform high-frequency electric field(1-3) has been developed recently. We have amplified this model by taking space charge effect into account. The ion peak shape taking into consideration the space charge effect is obtained. The output current saturation effect limiting the rise of the ion peak with increasing ion density at the input of the drift chamber of a spectrometer is observed. We show that the saturation effect is caused by the following phenomenon. The maximum possible output ion density exists, depending on the ion type (constant ion mobility, k(0)) and the time of the motion of ions through the drift chamber. At the same time, the ion density does not depend on the parameters of the drift chamber.

Sensitivity of early-life stage golden trout to low pH and elevated aluminum

USGS Publications Warehouse

Delonay, Aaron J.; Little, Edward E.; Woodward, Daniel F.; Brumbaugh, William G.; Farag, Aïda M.; Rabeni, Charles F.

1993-01-01

Early-life-stage golden trout (Oncorhynchus aguabonita aguabonita) were exposed to acid and Al to examine the response and determine the sensitivity of a western, alpine salmonid to conditions simulating an episodic pH depression. Freshly fertilized eggs, alevins, and swim-up larvae were exposed for 7 d to one of 12 combinations of pH and Al, and surviving fish were held to 40 d post-hatch to determine the effect of exposure on subsequent survival and recovery. Golden trout are sensitive to conditions simulating episodic acidification events typically observed in the field. Significant mortality occurred when the pH of test waters was below 5.0 in the absence of Al or when pH was 5.5 in the presence of 100 μg/L total Al. Behavioral impairments were sensitive indicators of low pH and Al stress. Impaired locomotory and feeding behavior occurred at pH 5.5 without Al and at Al concentrations > 50 μg/L. In contrast, growth, RNA-to-DNA ratio, and whole-body ion concentration were relatively less sensitive indicators of sublethal acid and Al stress.

The Effect of Precipitating Electrons and Ions on Ionospheric Conductance and Inner Magnetospheric Electric Fields 142106

NASA Astrophysics Data System (ADS)

Chen, M.; Lemon, C.; Hecht, J. H.; Evans, J. S.; Boyd, A. J.

2016-12-01

We investigate how scattering of electrons by waves and of ions by field-line curvature in the inner magnetosphere affect precipitating energy flux distributions and how the precipitating particles modify the ionospheric conductivity and electric potentials during magnetic storms. We examine how particle precipitation in the evening sector affects the development of the Sub-Auroral Polarization Stream (SAPS) electric field that is observed at sub-auroral latitudes in that sector as well as the electric field in the morning sector. Our approach is to use the magnetically and electrically self-consistent Rice Convection Model - Equilibrium (RCM-E) of the inner magnetosphere to simulate the stormtime precipitating particle distributions and the electric field. We use parameterized rates of whistler-generated electron pitch-angle scattering from Orlova and Shprits [JGR, 2014] that depend on equatorial radial distance, magnetic activity (Kp), and magnetic local time (MLT) outside the simulated plasmasphere. Inside the plasmasphere, parameterized scattering rates due to hiss [Orlova et al., GRL, 2014] are employed. Our description for the rate of ion scattering is more simplistic. We assume that the ions are scattered at a fraction of strong pitch-angle scattering where the fraction is scaled by epsilon, the ratio of the gyroradius to the field-line radius of curvature, when epsilon is greater than 0.1. We compare simulated trapped and precipitating electron/ion flux distributions with measurements from Van Allen Probes/MagEIS, POES and DMSP, respectively, to validate the particle loss models. DMSP observations of electric fields are compared with the simulation results. We discuss the effect of precipitating electrons and ions on the SAPS and the inner magnetospheric electric field through the data-model comparisons.

Characteristics of cometary picked-up ions in a global model of Giacobini-Zinner

NASA Astrophysics Data System (ADS)

Kimmel, C. D.; Luhmann, J. G.; Phillips, J. L.; Fedder, J. A.

1987-08-01

Energetic ions observed during the International Cometary Explorer (ICE) spacecraft flyby of comet Giacobini-Zinner provide information about both the constitution of comets and the plasma physical processes associated with their interaction with the solar wind. In this investigation the details of ion 'pickup,' in the limit where small-scale fluctuations in the plasma and magnetic field are neglected, are modeled by following the motion of a large number of initially cold, heavy (mass 18) ions in a global magnetohydrodynamic model of the local plasma and magnetic field. The results indicate how the background or macroscopic velocity and magnetic field structure of the comet can affect the average spatial and spectral characteristics of the observed cometary ions. These effects, which occur by virtue of forces associated with the compression and the curvature of the magnetic field in the presence of the stagnating plasma flow, can explain the double maxima in the time series of the energetic ion flux observed along the ICE trajectory.

Characteristics of cometary picked-up ions in a global model of Giacobini-Zinner

NASA Technical Reports Server (NTRS)

Kimmel, C. D.; Luhmann, J. G.; Phillips, J. L.; Fedder, J. A.

1987-01-01

Energetic ions observed during the International Cometary Explorer (ICE) spacecraft flyby of comet Giacobini-Zinner provide information about both the constitution of comets and the plasma physical processes associated with their interaction with the solar wind. In this investigation the details of ion 'pickup,' in the limit where small-scale fluctuations in the plasma and magnetic field are neglected, are modeled by following the motion of a large number of initially cold, heavy (mass 18) ions in a global magnetohydrodynamic model of the local plasma and magnetic field. The results indicate how the background or macroscopic velocity and magnetic field structure of the comet can affect the average spatial and spectral characteristics of the observed cometary ions. These effects, which occur by virtue of forces associated with the compression and the curvature of the magnetic field in the presence of the stagnating plasma flow, can explain the double maxima in the time series of the energetic ion flux observed along the ICE trajectory.

Oblique propagating electromagnetic ion - Cyclotron instability with A.C. field in outer magnetosphere

NASA Astrophysics Data System (ADS)

Pandey, R. S.; Singh, Vikrant; Rani, Anju; Varughese, George; Singh, K. M.

2018-05-01

In the present paper Oblique propagating electromagnetic ion-cyclotron wave has been analyzed for anisotropic multi ion plasma (H+, He+, O+ ions) in earth magnetosphere for the Dione shell of L=7 i.e., the outer radiation belt of the magnetosphere for Loss-cone distribution function with a spectral index j in the presence of A.C. electric field. Detail for particle trajectories and dispersion relation has been derived by using the method of characteristic solution on the basis of wave particle interaction and transformation of energy. Results for the growth rate have been calculated numerically for various parameters and have been compared for different ions present in magnetosphere. It has been found that for studying the wave over wider spectrum, anisotropy for different values of j should be taken. The effect of frequency of A.C. electric field and angle which propagation vector make with magnetic field, on growth rate has been explained.

Graphene/blue-phosphorus heterostructure as potential anode materials for sodium-ion batteries

NASA Astrophysics Data System (ADS)

Fan, Kaimin; Tang, Ting; Wu, Shiyun; Zhang, Zhiyuan

2018-01-01

The first-principles calculations based on density functional theory (DFT) have been implemented to investigate the graphene/blue-phosphorus (G/BP) heterostructure as potential anode material for SIBs. The adsorption and diffusion behaviors of sodium (Na) in G/BP heterostructure and the effect of external electric field on Na adsorption have been investigated. The results indicate that G/BP heterostructure with Na adsorption is metallic due to Na incorporation, which is of benefit for electronic conductivity as anode material. The results show that the design of G/BP heterostructure is an efficient scheme to enhance the Na adsorption in G/BP without affecting the high mobility of Na in the G/BP heterostructure surface. The present work demonstrates that the external electric field can effectively modulate the adsorption of Na, and the adsorption behavior of Na is more sensitive to the external electric field when E > 0.10 V Å-1 in G/BP heterostructure. The Mulliken population analysis and DOS calculations have been performed to explore the charge transfer and the interaction between Na and G/BP.

Crystal-field analysis of U3+ ions in K2LaX5 (X=Cl, Br or I) single crystals

NASA Astrophysics Data System (ADS)

Karbowiak, M.; Edelstein, N.; Gajek, Z.; Drożdżyński, J.

1998-11-01

An analysis of low temperature absorption spectra of U3+ ions doped in K2LaX5 (X=Cl, Br or I) single crystals is reported. The energy levels of the U3+ ion in the single crystals were assigned and fitted to a semiempirical Hamiltonian representing the combined atomic and crystal-field interactions at the Cs symmetry site. An analysis of the nephelauxetic effect and crystal-field splittings in the series of compounds is also reported.

Sensitive and selective detection of Cu(II) ion: A new effective 1,8-naphthalimide-based fluorescence 'turn off' sensor.

PubMed

Huang, Guozhen; Li, Chuang; Han, Xintong; Aderinto, Stephen Opeyemi; Shen, Kesheng; Mao, Shanshan; Wu, Huilu

2018-06-01

The present study reports the development of a new 1,8-naphthalimide-based fluorescent sensor V for monitoring Cu(II) ions. The sensor exhibited pH independence over a wide pH range 2.52-9.58, and indicated its possible use for monitoring Cu(II) ions in a competitive pH medium. The sensor also showed high selectivity and sensitivity towards the Cu(II) ions over other competitive metal ions in DMSO-HEPES buffer (v/v, 1:1; pH 7.4) with a fluorescence 'turn off' mode of 79.79% observed. A Job plot indicated the formation of a 1:1 binding mode of the sensor with Cu(II) ions. The association constant and detection limit were 1.14 × 10 6  M -1 and 4.67 × 10 -8 M, respectively. The fluorescence spectrum of the sensor was quenched due to the powerful paramagnetic nature of the Cu(II) ions. Potential application of this sensor was also demonstrated when determining Cu(II) ion levels in two different water samples. Copyright © 2018 John Wiley & Sons, Ltd.

Development and Evaluation of an Externally Air-Cooled Low-Flow torch and the Attenuation of Space Charge and Matrix Effects in Inductively Coupled Plasma Mass Spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Praphairaksit, Narong

2000-09-12

An externally air-cooled low-flow torch has been constructed and successfully demonstrated for applications in inductively coupled plasma mass spectrometry (ICP-MS). The torch is cooled by pressurized air flowing at ~70 L/min through a quartz air jacket onto the exterior of the outer tube. The outer gas flow rate and operating RF forward power are reduced considerably. Although plasmas can be sustained at the operating power as low as 400 W with a 2 L/min of outer gas flow, somewhat higher power and outer gas flows are advisable. A stable and analytical useful plasma can be obtained at 850 W withmore » an outer gas flow rate of ~4 L/min. Under these conditions, the air-cooled plasma produces comparable sensitivities, doubly charged ion ratios, matrix effects and other analytical merits as those produced by a conventional torch while using significantly less argon and power requirements. Metal oxide ion ratios are slightly higher with the air-cooled plasma but can be mitigated by reducing the aerosol gas flow rate slightly with only minor sacrifice in analyte sensitivity. A methodology to alleviate the space charge and matrix effects in ICP-MS has been developed. A supplemental electron source adapted from a conventional electron impact ionizer is added to the base of the skimmer. Electrons supplied from this source downstream of the skimmer with suitable amount and energy can neutralize the positive ions in the beam extracted from the plasma and diminish the space charge repulsion between them. As a result, the overall ion transmission efficiency and consequent analyte ion sensitivities are significantly improved while other important analytical aspects, such as metal oxide ion ratio, doubly charged ion ratio and background ions remain relatively unchanged with the operation of this electron source. This technique not only improves the ion transmission efficiency but also minimizes the matrix effects drastically. The matrix-induced suppression of signal for even the most troublesome combination of light analyte and heavy matrix elements can be attenuated from 90-99% to only 2-10% for 2 mM matrix solutions with an ultrasonic nebulizer. The supplemental electron current can be adjusted to ''titrate'' out the matrix effects as desired.« less

Sci-Sat AM: Radiation Dosimetry and Practical Therapy Solutions - 05: Not all geometries are equivalent for magnetic field Fano cavity tests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malkov, Victor N.; Rogers, David W.O.

The coupling of MRI and radiation treatment systems for the application of magnetic resonance guided radiation therapy necessitates a reliable magnetic field capable Monte Carlo (MC) code. In addition to the influence of the magnetic field on dose distributions, the question of proper calibration has arisen due to the several percent variation of ion chamber and solid state detector responses in magnetic fields when compared to the 0 T case (Reynolds et al., Med Phys, 2013). In the absence of a magnetic field, EGSnrc has been shown to pass the Fano cavity test (a rigorous benchmarking tool of MC codes)more » at the 0.1 % level (Kawrakow, Med.Phys, 2000), and similar results should be required of magnetic field capable MC algorithms. To properly test such developing MC codes, the Fano cavity theorem has been adapted to function in a magnetic field (Bouchard et al., PMB, 2015). In this work, the Fano cavity test is applied in a slab and ion-chamber-like geometries to test the transport options of an implemented magnetic field algorithm in EGSnrc. Results show that the deviation of the MC dose from the expected Fano cavity theory value is highly sensitive to the choice of geometry, and the ion chamber geometry appears to pass the test more easily than larger slab geometries. As magnetic field MC codes begin to be used for dose simulations and correction factor calculations, care must be taken to apply the most rigorous Fano test geometries to ensure reliability of such algorithms.« less

Space charge effect in spectrometers of ion mobility increment with cylindrical drift chamber.

PubMed

Elistratov, A A; Sherbakov, L A

2007-01-01

We have amplified the model for the drift of ions under a non-uniform high-frequency electric field by taking space charge effect into account. By this means, we have investigated the effect of space charge on the dynamics of a single type of ions in a spectrometer of ion mobility increment with a cylindrical drift chamber. The counteraction of the space charge effect and the focusing effect is investigated. The output ion current saturation caused by the effect of the space charge is observed. The shape of the ion peak taking into consideration the space charge effect has been obtained. We show that the effect of the space charge is sufficient for the relative ion density greater than 10 ppt by order of magnitude (for a cylindrical geometry spectrometer with typical parameters).

Measurement and Simulation of First-Orbit Fast-Ion D-Alpha Emission and the Application to Fast-Ion Loss Detection in the DIII-D Tokamak

NASA Astrophysics Data System (ADS)

Bolte, Nathan; Heidbrink, W. W.; Pace, D. C.; van Zeeland, M. A.; Chen, X.

2015-11-01

A new fast-ion diagnostic method uses passive emission of D-alpha radiation to determine fast-ion losses quantitatively. The passive fast-ion D-alpha simulation (P-FIDAsim) forward models the Doppler-shifted spectra of first-orbit fast ions that charge exchange with edge neutrals. Simulated spectra are up to 80 % correlated with experimental spectra. Calibrated spectra are used to estimate the 2D neutral density profile by inverting simulated spectra. The inferred neutral density shows the expected increase toward each x-point and an average value of 8 × 10 9 cm-3 at the plasma boundary and 1 × 10 11 cm-3 near the wall. Measuring and simulating first-orbit spectra effectively ``calibrates'' the system, allowing for the quantification of more general fast-ion losses. Sawtooth crashes are estimated to eject 1.2 % of the fast-ion inventory, in good agreement with a 1.7 % loss estimate made by TRANSP. Sightlines sensitive to passing ions observe larger sawtooth losses than sightlines sensitive to trapped ions. Supported by US DOE under SC-G903402, DE-FC02-04ER54698.

Room Temperature Ammonia Gas Sensing Using Mixed Conductor based TEMPOS Structures.

PubMed

Saroch, Mamta; Srivastava, Sunita; Fink, Dietmar; Chandra, Amita

2008-10-14

The current/voltage characteristics of mixed (ion+electron) conductor-based 'TEMPOS' (Tunable Electronic Material with Pores in Oxide on Silicon) structures are reported. TEMPOS are novel electronic MOS-like structures having etched swift heavy ion tracks (i.e., nanopores) in the dielectric layer filled with some conducting material. The three contacts (two on top and one on the bottom), which resemble the classical bipolar or field effect transistor arrangements are, in principle, interchangeable when the overall electrical resistance along the tracks and on the surface are similar. Consequently, three configurations are obtained by interchanging the top contacts with the base contact in electronic circuits. The current/voltage characteristics show a diode like behaviour. Impedance measurements have been made for TEMPOS structures with tracks filled with ion conductors and also mixed conductors to study the ammonia sensing behaviour. The impedance has been found to be a function of frequency and magnitude of the applied signal and concentration of the ammonia solution. This is attributed to the large number of charge carriers (here protons) available for conduction on exposure to ammonia and also to the large surface to volume ratio of the polymer composites embedded in the ion tracks. The measurement of both, the real and imaginary parts of impedance allows one to enhance the detection sensitivity greatly.

Room Temperature Ammonia Gas Sensing Using Mixed Conductor based TEMPOS Structures

PubMed Central

Saroch, Mamta; Srivastava, Sunita; Fink, Dietmar; Chandra, Amita

2008-01-01

The current/voltage characteristics of mixed (ion+electron) conductor-based ‘TEMPOS’ (Tunable Electronic Material with Pores in Oxide on Silicon) structures̵ are reported. TEMPOS are novel electronic MOS-like structures having etched swift heavy ion tracks (i.e., nanopores) in the dielectric layer filled with some conducting material. The three contacts (two on top and one on the bottom), which resemble the classical bipolar or field effect transistor arrangements are, in principle, interchangeable when the overall electrical resistance along the tracks and on the surface are similar. Consequently, three configurations are obtained by interchanging the top contacts with the base contact in electronic circuits. The current/voltage characteristics show a diode like behaviour. Impedance measurements have been made for TEMPOS structures with tracks filled with ion conductors and also mixed conductors to study the ammonia sensing behaviour. The impedance has been found to be a function of frequency and magnitude of the applied signal and concentration of the ammonia solution. This is attributed to the large number of charge carriers (here protons) available for conduction on exposure to ammonia and also to the large surface to volume ratio of the polymer composites embedded in the ion tracks. The measurement of both, the real and imaginary parts of impedance allows one to enhance the detection sensitivity greatly. PMID:27873874

Differential multi-electron emission induced by swift highly charged gold ions penetrating carbon foils

NASA Astrophysics Data System (ADS)

Rothard, H.; Moshammer, R.; Ullrich, J.; Kollmus, H.; Mann, R.; Hagmann, S.; Zouros, T. J. M.

2007-05-01

First results on swift heavy ion induced electron emission from solids obtained with a reaction microscope are presented. This advanced technique, which is successfully used since quite some time to study electron ejection in ion-atom collisions, combines the measurement of the time-of-flight of electrons with imaging techniques. A combination of electric and magnetic fields guides the ejected electrons onto a position sensitive detector, which is capable to accept multiple hits. From position and time-of-flight measurement the full differential emission characteristics of up to 10 electrons per single incoming ion can be extracted. As a first example, we show energy spectra, angular distributions and the multiplicity distribution of electrons from impact of Au24+ (11 MeV/u) on a thin carbon foil (28 μg/cm2).

Phase-field based Multiscale Modeling of Heterogeneous Solid Electrolytes: Applications to Nanoporous Li 3 PS 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Jia-Mian; Wang, Bo; Ji, Yanzhou

Modeling the effective ion conductivities of heterogeneous solid electrolytes typically involves the use of a computer-generated microstructure consisting of randomly or uniformly oriented fillers in a matrix. But, the structural features of the filler/matrix interface, which critically determine the interface ion conductivity and the microstructure morphology, have not been considered during the microstructure generation. In using nanoporous β-Li 3PS 4 electrolyte as an example, we develop a phase-field model that enables generating nanoporous microstructures of different porosities and connectivity patterns based on the depth and the energy of the surface (pore/electrolyte interface), both of which are predicted through density functionalmore » theory (DFT) calculations. Room-temperature effective ion conductivities of the generated microstructures are then calculated numerically, using DFT-estimated surface Li-ion conductivity (3.14×10 -3 S/cm) and experimentally measured bulk Li-ion conductivity (8.93×10 -7 S/cm) of β-Li 3PS 4 as the inputs. We also use the generated microstructures to inform effective medium theories to rapidly predict the effective ion conductivity via analytical calculations. Furthemore, when porosity approaches the percolation threshold, both the numerical and analytical methods predict a significantly enhanced Li-ion conductivity (1.74×10 -4 S/cm) that is in good agreement with experimental data (1.64×10 -4 S/cm). The present phase-field based multiscale model is generally applicable to predict both the microstructure patterns and the effective properties of heterogeneous solid electrolytes.« less

Phase-field based Multiscale Modeling of Heterogeneous Solid Electrolytes: Applications to Nanoporous Li 3 PS 4

DOE PAGES

Hu, Jia-Mian; Wang, Bo; Ji, Yanzhou; ...

2017-09-07

Modeling the effective ion conductivities of heterogeneous solid electrolytes typically involves the use of a computer-generated microstructure consisting of randomly or uniformly oriented fillers in a matrix. But, the structural features of the filler/matrix interface, which critically determine the interface ion conductivity and the microstructure morphology, have not been considered during the microstructure generation. In using nanoporous β-Li 3PS 4 electrolyte as an example, we develop a phase-field model that enables generating nanoporous microstructures of different porosities and connectivity patterns based on the depth and the energy of the surface (pore/electrolyte interface), both of which are predicted through density functionalmore » theory (DFT) calculations. Room-temperature effective ion conductivities of the generated microstructures are then calculated numerically, using DFT-estimated surface Li-ion conductivity (3.14×10 -3 S/cm) and experimentally measured bulk Li-ion conductivity (8.93×10 -7 S/cm) of β-Li 3PS 4 as the inputs. We also use the generated microstructures to inform effective medium theories to rapidly predict the effective ion conductivity via analytical calculations. Furthemore, when porosity approaches the percolation threshold, both the numerical and analytical methods predict a significantly enhanced Li-ion conductivity (1.74×10 -4 S/cm) that is in good agreement with experimental data (1.64×10 -4 S/cm). The present phase-field based multiscale model is generally applicable to predict both the microstructure patterns and the effective properties of heterogeneous solid electrolytes.« less

CdS quantum dots as fluorescence probes for the sensitive and selective detection of highly reactive HSe- ions in aqueous solution.

PubMed

Wu, Chuan-Liu; Zhao, Yi-Bing

2007-06-01

Water-soluble cadmium sulfide (CdS) quantum dots (QDs) capped by mercaptoacetic acid were synthesized by aqueous-phase arrested precipitation, and characterized by transmission electron microscopy, spectrofluorometry, and UV-Vis spectrophotometry. The prepared luminescent water-soluble CdS QDs were evaluated as fluorescence probes for the detection of highly reactive hydrogen selenide ions (HSe(-) ions). The quenching of the fluorescence emission of CdS QDs with the addition of HSe(-) ions is due to the elimination of the S(2-) vacancies which are luminescence centers. Quantitative analysis based on chemical interaction between HSe(-) ions and the surface of CdS QDs is very simple, easy to develop, and has demonstrated very high sensitivity and selectivity features. The effect of foreign ions (common anions and biologically relevant cations) on the fluorescence of the CdS QDs was examined to evaluate the selectivity. Only Cu(2+) and S(2-) ions exhibit significant effects on the fluorescence of CdS QDs. With the developed method, we are able to determine the concentration of HSe(-) ions in the range from 0.10 to 4.80 micromol L(-1), and the limit of detection is 0.087 micromol L(-1). The proposed method was successfully applied to monitor the obtained HSe(-) ions from the reaction of glutathione with selenite. To the best of our knowledge, this is the first report on fluorescence analysis of HSe(-) ions in aqueous solution.

Exploring the Surface Sensitivity of ToF-SIMS by Measuring the Implantation and Sampling Depths of Bin and C60 Ions in Organic Films

PubMed Central

Muramoto, Shin; Brison, Jeremy; Castner, David G.

2011-01-01

The surface sensitivity of Binq+ (n = 1, 3, 5, q = 1, 2) and C60q+ (q = 1, 2) primary ions in static time-of-flight secondary ion mass spectrometry (ToF-SIMS) experiments were investigated for molecular trehalose and polymeric tetraglyme organic films. Parameters related to surface sensitivity (impact crater depth, implantation depth, and molecular escape depths) were measured. Under static ToF-SIMS conditions (primary ion doses of 1 × 1012 ions/cm2), the 25 keV Bi1+ primary ions were the most surface sensitive with a molecular escape depth of 1.8 nm for protein films with tetraglyme overlayers, but they had the deepest implantation depth (~18 and 26 nm in trehalose and tetraglyme films, respectively). The 20 keV C60++ primary ions were the second most surface sensitive with a slightly larger molecular escape depth of 2.3 nm. The most important factor that determined the surface sensitivity of the primary ion was its impact crater depth, or the amount of surface erosion. The most surface sensitive primary ions, Bi1+ and C60++, created impact craters with depths of 0.3 and 1.0 nm, respectively, in tetraglyme films. In contrast, Bi5++ primary ions created impact craters with a depth of 1.8 nm in tetraglyme films and were the least surface sensitive with a molecular escape depth of 4.7 nm. PMID:22084828

Measurement of ultra-low ion energy of decelerated ion beam using a deflecting electric field

NASA Astrophysics Data System (ADS)

Thopan, P.; Suwannakachorn, D.; Tippawan, U.; Yu, L. D.

2015-12-01

In investigation on ultra-low-energy ion bombardment effect on DNA, an ion beam deceleration lens was developed for high-quality ultra-low-energy ion beam. Measurement of the ion energy after deceleration was necessary to confirm the ion beam really decelerated as theoretically predicted. In contrast to conventional methods, this work used a simple deflecting electrostatic field after the deceleration lens to bend the ion beam. The beam bending distance depended on the ion energy and was described and simulated. A system for the measurement of the ion beam energy was constructed. It consisted of a pair of parallel electrode plates to generate the deflecting electrical field, a copper rod measurement piece to detect ion beam current, a vernier caliper to mark the beam position, a stepping motor to translate the measurement rod, and a webcam-camera to read the beam bending distance. The entire system was installed after the ion-beam deceleration lens inside the large chamber of the bioengineering vertical ion beam line. Moving the measurement rod across the decelerated ion beam enabled to obtain beam profiles, from which the beam bending distance could be known and the ion beam energy could be calculated. The measurement results were in good agreement with theoretical and simulated results.

Production of intense negative hydrogen beams with polarized nuclei by selective neutralization of negative ions

DOEpatents

Hershcovitch, Ady

1987-01-01

A process for selectively neutralizing H.sup.- ions in a magnetic field to produce an intense negative hydrogen ion beam with spin polarized protons. Characteristic features of the process include providing a multi-ampere beam of H.sup.- ions that are intersected by a beam of laser light. Photodetachment is effected in a uniform magnetic field that is provided around the beam of H.sup.- ions to spin polarize the H.sup.- ions and produce first and second populations or groups of ions, having their respective proton spin aligned either with the magnetic field or opposite to it. The intersecting beam of laser light is directed to selectively neutralize a majority of the ions in only one population, or given spin polarized group of H.sup.- ions, without neutralizing the ions in the other group thereby forming a population of H.sup.- ions each of which has its proton spin down, and a second group or population of H.sup.o atoms having proton spin up. Finally, the two groups of ions are separated from each other by magnetically bending the group of H.sup.- ions away from the group of neutralized ions, thereby to form an intense H.sup.- ion beam that is directed toward a predetermined objective.

A generalized semikinetic (GSK) model for mesoscale auroral plasma transport

NASA Astrophysics Data System (ADS)

Brown, David Gillespie

1993-12-01

The auroral region of the Earth's ionosphere-magnetosphere system is a complex and active part of the Earth's environment. In order to study the transport of ionospheric plasma in this region, we have developed a generalized semikinetic (GSK) model which combines the tracking of ionospheric ion gyrocenters (between stochastic impulses from waves), with a generalized fluid treatment of ionospheric electrons and Liouville mapping of magnetospheric plasma components. This model has been used to simulate the effects of 'self-consistent' heating ('self consistent' in the sense that heating occurs only where the modelled plasma is unstable) due to the current-driven ion cyclotron instability in the return current regions. Our results include generation of 'conics' whose wings are drawn in towards the upsilon(parallel)-axis at higher energies (such distributions were subsequently found in recent studies of DE-1 data for this region) and an alternative formation mechanism for toroidal (or 'ring'-shaped) ion velocity-space distributions. We also present results illustrating the effects of combining large scale electric fields (generated by anisotropic magnetospheric plasma distributions) with wave heating by a presumed distribution of wave spectra. In the presence of an upwards electric field the addition of wave heating increases the density of the O(sup +) 'beam' ('ion feeder' effect), while a downwards hot plasma-induced electric field increases the time which ions spend within the heating region ('pressure cooker' effect), resulting in greater ion energization.

Nasal delivery of analgesic ketorolac tromethamine thermo- and ion-sensitive in situ hydrogels.

PubMed

Li, Xin; Du, Lina; Chen, Xu; Ge, Pingju; Wang, Yu; Fu, Yangmu; Sun, Haiyan; Jiang, Qingwei; Jin, Yiguang

2015-07-15

Ketorolac tromethamine (KT) was potent to treat moderate to moderately severe pains. However, KT solutions for nasal delivery lost quickly from the nasal route. Thermo- and ion-sensitive in-situ hydrogels (ISGs) are appropriate for nasal drug delivery because the intranasal temperature maintains ∼37 °C and nasal fluids consist of plentiful cations. In this study, a novel nasal thermo- and ion-sensitive ISG of KT was prepared with thermo-sensitive poloxamer 407 (P407) and ion-sensitive deacetylated gellan gum (DGG). The optimal formulation of the KT ISG consisted of 3% (w/v) DGG and 18% (w/v) P407 and its viscosity was up to 7.63 Pas at 37 °C. Furthermore, penetration enhancers and bacterial inhibitors were added and their fractions in the ISG were optimized based on transmucosal efficiencies and toxicity on toad pili. Sulfobutyl ether-β-cyclodextrin of 2.5% (w/v) and chlorobutanol of 0.5% (w/v) were chosen as the penetration enhancer and the bacterial inhibitor, respectively. The Fick's diffusion and dissolution of KT could drive it continuous release from the dually sensitive ISG according to the in vitro investigation. Two methods, writhing frequencies induced by acetic acid and latency time of tails retracting from hot water, were used to evaluate the pharmacodynamics of the KT ISG on the mouse models. The writhing frequencies significantly decreased and the latency time of tail retracting was obviously prolonged (p<0.05) for the KT ISG compared to the control. The thermo- and ion-sensitive KT ISG had appropriate gelation temperature, sustained drug release, improved intranasal absorption, obvious pharmacodynamic effect, and negligible nasal ciliotoxicity. It is a promising intranasal analgesic formulation. Copyright © 2015. Published by Elsevier B.V.

High Electrochemical Sensitivity of TiO2- x Nanosheets and an Electron-Induced Mutual Interference Effect toward Heavy Metal Ions Demonstrated Using X-ray Absorption Fine Structure Spectra.

PubMed

Zhou, Wen-Yi; Li, Shan-Shan; Song, Jie-Yao; Jiang, Min; Jiang, Tian-Jia; Liu, Jin-Yun; Liu, Jin-Huai; Huang, Xing-Jiu

2018-04-03

Mutual interference is a severe issue that occurs during the electrochemical detection of heavy metal ions. This limitation presents a notable drawback for its high sensitivity to specific targets. Here, we present a high electrochemical sensitivity of ∼237.1 μA cm -2 μM -1 toward copper(II) [Cu(II)] based on oxygen-deficient titanium dioxide (TiO 2- x ) nanosheets. We fully demonstrated an atomic-level relationship between electrochemical behaviors and the key factors, including the high-energy (001) facet percentage, oxygen vacancy concentration, surface -OH content, and charge carrier density, is fully demonstrated. These four factors were quantified using Raman, electron spin resonance, X-ray photoelectron spectroscopy spectra, and Mott-Schottky plots. In the mutual interference investigation, we selected cadmium(II) [Cd(II)] as the target ion because of the significant difference in its stripping potential (∼700 mV). The results show that the Cd(II) can enhance the sensitivity of TiO 2- x nanosheets toward Cu(II), exhibiting an electron-induced mutual interference effect, as demonstrated by X-ray absorption fine structure spectra.

Probing electric and magnetic fields with a Moiré deflectometer

NASA Astrophysics Data System (ADS)

Lansonneur, P.; Bräunig, P.; Demetrio, A.; Müller, S. R.; Nedelec, P.; Oberthaler, M. K.

2017-08-01

A new contact-free approach for measuring simultaneously electric and magnetic field is reported, which considers the use of a low energy ion source, a set of three transmission gratings and a position sensitive detector. Recently tested with antiprotons (Aghion et al., 2014) [1] at the CERN Antiproton Decelerator facility, this paper extends the proof of principle of a moiré deflectometer (Oberthaler et al., 1996) [2] for distinguishing electric from magnetic fields and opens the route to precision measurements when one is not limited by the ion source intensity. The apparatus presented, whose resolution is mainly limited by the shot noise is able to measure fields as low as 9 mVm-1 Hz-1/2 for electric component and 100 μG Hz-1/2 for the magnetic component. Scaled to 100 nm pitch for the gratings, accessible with current state-of-the-art technology [3], the moiré fieldmeter would be able to measure fields as low as 22 μVm-1 Hz-1/2 and 0.2 μG Hz-1/2.

On the role of the quasi-parallel bow shock in ion pickup - A lesson from Venus?

NASA Technical Reports Server (NTRS)

Luhmann, J. G.; Russell, C. T.; Phillips, J. L.; Barnes, A.

1987-01-01

Previous observations at Venus show convincing evidence of planetary O(+) ion pickup by the largescale motional -V x B electric field in the magnetosheath when the interplanetary magnetic field is perpendicular to the solar wind flow. However, the presence of magnetic field fluctuations in the magnetosheath downstream from the quasi-parallel bow shock should allow pickup to occur even when the upstream magnetic field B and plasma velocity V are practically coaligned. Single-particle calculations are used to demonstrate the convecting magnetic field fluctuations similar to those observed in the Venus magnetosheath when the subsolar bow shock is quasi-parallel can efficiently accelerate cold planetary ions by means of the electric field associated with their transverse components. This ion pickup process, which is characterized by a spatial dependence determined by the bow shock shape and the orientation of the upstream magnetic field, is likely also to occur at Mars and may be effective at comets.

On the microscopic fluctuations driving the NMR relaxation of quadrupolar ions in water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carof, Antoine; Salanne, Mathieu; Rotenberg, Benjamin, E-mail: benjamin.rotenberg@upmc.fr

Nuclear Magnetic Resonance (NMR) relaxation is sensitive to the local structure and dynamics around the probed nuclei. The Electric Field Gradient (EFG) is the key microscopic quantity to understand the NMR relaxation of quadrupolar ions, such as {sup 7}Li{sup +}, {sup 23}Na{sup +}, {sup 25}Mg{sup 2+}, {sup 35}Cl{sup −}, {sup 39}K{sup +}, or {sup 133}Cs{sup +}. Using molecular dynamics simulations, we investigate the statistical and dynamical properties of the EFG experienced by alkaline, alkaline Earth, and chloride ions at infinite dilution in water. Specifically, we analyze the effect of the ionic charge and size on the distribution of the EFGmore » tensor and on the multi-step decay of its auto-correlation function. The main contribution to the NMR relaxation time arises from the slowest mode, with a characteristic time on the picosecond time scale. The first solvation shell of the ion plays a dominant role in the fluctuations of the EFG, all the more that the ion radius is small and its charge is large. We propose an analysis based on a simplified charge distribution around the ion, which demonstrates that the auto-correlation of the EFG, hence the NMR relaxation time, reflects primarily the collective translational motion of water molecules in the first solvation shell of the cations. Our findings provide a microscopic route to the quantitative interpretation of NMR relaxation measurements and open the way to the design of improved analytical theories for NMR relaxation for small ionic solutes, which should focus on water density fluctuations around the ion.« less

The 15 cm mercury ion thruster research 1975

NASA Technical Reports Server (NTRS)

Wilbur, P. J.

1975-01-01

Doubly charged ion current measurements in the beam of a SERT II thruster are shown to introduce corrections which bring its calculated thrust into close agreement with that measured during flight testing. A theoretical model of doubly charged ion production and loss in mercury electron bombardment thrusters is discussed and is shown to yield doubly-to-singly charged ion density ratios that agree with experimental measurements obtained on a 15 cm diameter thruster over a range of operating conditions. Single cusp magnetic field thruster operation is discussed and measured ion beam profiles, performance data, doubly charged ion densities, and discharge plasma characteristics are presented for a range of operating conditions and thruster geometries. Variations in the characteristics of this thruster are compared to those observed in the divergent field thruster and the cusped field thruster is shown to yield flatter ion beam profiles at about the same discharge power and propellant utilization operating point. An ion optics test program is described and the measured effects of grid system dimensions on ion beamlet half angle and diameter are examined. The effectiveness of hollow cathode startup using a thermionically emitting filament within the cathode is examined over a range of mercury flow rates and compared to results obtained with a high voltage tickler startup technique. Results of cathode plasma property measurement tests conducted within the cathode are presented.

Controlling Emergent Ferromagnetism at Complex Oxide Interfaces

NASA Astrophysics Data System (ADS)

Grutter, Alexander

The emergence of complex magnetic ground states at ABO3 perovskite heterostructure interfaces is among the most promising routes towards highly tunable nanoscale materials for spintronic device applications. Despite recent progress, isolating and controlling the underlying mechanisms behind these emergent properties remains a highly challenging materials physics problems. In particular, generating and tuning ferromagnetism localized at the interface of two non-ferromagnetic materials is of fundamental and technological interest. An ideal model system in which to study such effects is the CaRuO3/CaMnO3 interface, where the constituent materials are paramagnetic and antiferromagnetic in the bulk, respectively. Due to small fractional charge transfer to the CaMnO3 (0.07 e-/Mn) from the CaRuO3, the interfacial Mn ions are in a canted antiferromagnetic state. The delicate balance between antiferromagnetic superexchange and ferromagnetic double exchange results in a magnetic ground state which is extremely sensitive to perturbations. We exploit this sensitivity to achieve control of the magnetic interface, tipping the balance between ferromagnetic and antiferromagnetic interactions through octahedral connectivity modification. Such connectivity effects are typically tightly confined to interfaces, but by targeting a purely interfacial emergent magnetic system, we achieve drastic alterations to the magnetic ground state. These results demonstrate the extreme sensitivity of the magnetic state to the magnitude of the charge transfer, suggesting the potential for direct electric field control. We achieve such electric field control through direct back gating of a CaRuO3/CaMnO3 bilayer. Thus, the CaRuO3/CaMnO3 system provides new insight into how charge transfer, interfacial symmetry, and electric fields may be used to control ferromagnetism at the atomic scale.

Formation of Dawn-Dusk Asymmetry in Earth's Magnetotail Thin Current Sheet: A Three-Dimensional Particle-In-Cell Simulation

NASA Astrophysics Data System (ADS)

Lu, San; Pritchett, P. L.; Angelopoulos, V.; Artemyev, A. V.

2018-04-01

Using a three-dimensional particle-in-cell simulation, we investigate the formation of dawn-dusk asymmetry in Earth's magnetotail. The magnetotail current sheet is compressed by an external driving electric field down to a thickness on the order of ion kinetic scales. In the resultant thin current sheet (TCS) where the magnetic field line curvature radius is much smaller than ion gyroradius, a significant portion of the ions becomes unmagnetized and decoupled from the magnetized electrons, giving rise to a Hall electric field Ez and an additional cross-tail current jy caused by the unmagnetized ions being unable to comove with the electrons in the Hall electric field. The Hall electric field transports via E × B drift magnetic flux and magnetized plasma dawnward, causing a reduction of the current sheet thickness and the normal magnetic field Bz on the duskside. This leads to an even stronger Hall effect (stronger jy and Ez) in the duskside TCS. Thus, due to the internal kinetic effects in the TCS, namely, the Hall effect and the associated dawnward E × B drift, the magnetotail dawn-dusk asymmetry forms in a short time without any global, long-term effects. The duskside preference of reconnection and associated dynamic phenomena (such as substorm onsets, dipolarizing flux bundles, fast flows, energetic particle injections, and flux ropes), which has been pervasively observed by spacecraft in the past 20 years, can thus be explained as a consequence of this TCS asymmetry.

Integrated Photonic Nanofences: Combining Subwavelength Waveguides with an Enhanced Evanescent Field for Sensing Applications.

PubMed

Cadarso, Victor J; Llobera, Andreu; Puyol, Mar; Schift, Helmut

2016-01-26

Photonic nanofences consisting of high aspect ratio polymeric optical subwavelength waveguides have been developed for their application into photonic sensing devices. They are up to millimeter long arrays of 250 nm wide and 6 μm high ridges produced by an advanced lithography process on a silicon substrate enabling their straightforward integration into complex photonic circuits. Both simulations and experimental results show that the overlap of the evanescent fields propagating from each photonic nanofence allows for the formation of an effective waveguide that confines the overall evanescent field within its limits. This permits a high interaction with the surrounding medium which can be larger than 90% of the total guided light intensity (approximately 20000 times larger than the evanescent field of a standard waveguide with equivalent dimensions). In this work, we not only investigate the photonic properties of these structures but also demonstrate their successful integration into a photonic sensor. An absorbance-based sensor for the determination of lead in water samples is therefore achieved by the combination of the photonic nanofences with an ion-sensitive optical membrane. The experimental results for lead detection in water show a sensitivity of 0.102 AU/decade, and a linear range between 10(-6) M and 10(-2) M Pb(II). A detection limit as low as 7.3 nM has been calculated according to IUPAC for a signal-to-noise ratio of 3.

Plasticizer Effects in the PVC Membrane of the Dibasic Phosphate Selective Electrode

PubMed Central

Carey, Clifton

2016-01-01

The PVC membrane of an ion-selective electrode (ISE) sensitive to dibasic phosphate ions (HPO4-ISE) has not been optimized for maximum selectivity, sensitivity, and useable ISE lifetime and further work was necessary to improve its performance. Two areas of investigation are reported here: include the parameters for the lipophilicity of the plasticizer compound used and the amount of cyclic polyamine ionophore incorporated in the PVC membrane. Six candidate plasticizers with a range of lipophilicity were evaluated for their effect on the useable lifetime, sensitivity, and selectivity of the ISE against 13 different anions. Selectivity was determined by a modified fixed interferent method, sensitivity was determined without interferents, and the usable lifetime evaluated at the elapsed time where 50% of the HPO4-ISE failed (L50). The results show that choosing a plasticizer that has a lipophilicity similar to the ionophore's results in the best selectivity and sensitivity and the longest L50. PMID:27347487

Measurement of Rapid Amiloride-Dependent pH Changes at the Cell Surface Using a Proton-Sensitive Field-Effect Transistor.

PubMed

Schaffhauser, Daniel; Fine, Michael; Tabata, Miyuki; Goda, Tatsuro; Miyahara, Yuji

2016-03-30

We present a novel method for the rapid measurement of pH fluxes at close proximity to the surface of the plasma membrane in mammalian cells using an ion-sensitive field-effect transistor (ISFET). In conjuction with an efficient continuous superfusion system, the ISFET sensor was capable of recording rapid changes in pH at the cells' surface induced by intervals of ammonia loading and unloading, even when using highly buffered solutions. Furthermore, the system was able to isolate physiologically relevant signals by not only detecting the transients caused by ammonia loading and unloading, but display steady-state signals as would be expected by a proton transport-mediated influence on the extracellular proton-gradient. Proof of concept was demonstrated through the use of 5-(N-ethyl-N-isopropyl)amiloride (EIPA), a small molecule inhibitor of sodium/hydrogen exchangers (NHE). As the primary transporter responsible for proton balance during cellular regulation of pH, non-electrogenic NHE transport is notoriously difficult to detect with traditional methods. Using the NHE positive cell lines, Chinese hamster ovary (CHO) cells and NHE3-reconstituted mouse skin fibroblasts (MSF), the sensor exhibited a significant response to EIPA inhibition, whereas NHE-deficient MSF cells were unaffected by application of the inhibitor.

On the Effect of IMF Turning on Ion Dynamics at Mercury

NASA Technical Reports Server (NTRS)

Delcourt, D. C.; Moore, T. E.; Fok, M.-C. H.

2011-01-01

We investigate the effect of a rotation of the Interplanetary Magnetic Field (IMF) on the transport of magnetospheric ion populations at Mercury. We focus on ions of planetary origin and investigate their large-scale circulation using three-dimensional single-particle simulations. We show that a nonzero Bx component of the IMF leads to a pronounced asymmetry in the overall circulation pattern . In particular, we demonstrate that the centrifugal acceleration due to curvature of the E x B drift paths is more pronounced in one hemisphere than the other, leading to filling of the magnetospheric lobes and plasma sheet with more or less energetic material depending upon the hemisphere of origin. Using a time-varying electric and magnetic field model, we investigate the response of ions to rapid (a few tens of seconds) re-orientation of the IMF. We show that, for ions with gyroperiods comparable to the field variation time scale, the inductive electric field should lead to significant nonadiabatic energization, up to several hundreds of eVs or a few keVs. It thus appears that IMP turning at Mercury should lead to localized loading of the magnetosphere with energetic material of planetary origin (e.g., Na+).

Effect of moisture on the field dependence of mobility for gas-phase ions of organophosphorus compounds at atmospheric pressure with field asymmetric ion mobility spectrometry.

PubMed

Krylova, N; Krylov, E; Eiceman, G A; Stone, J A

2003-05-15

The electric field dependence of the mobilities of gas-phase protonated monomers [(MH+(H2O)n] and proton-bound dimers [M2H+(H2O)n] of organophosphorus compounds was determined at E/N values between 0 and 140 Td at ambient pressure in air with moisture between 0.1 and 15 000 ppm. Field dependence was described as alpha (E/N) and was obtained from the measurements of compensation voltage versus field amplitude in a planar high-field asymmetric waveform ion mobility spectrometer. The alpha function for protonated monomers to 140 Td was constant from 0.1 to 10 ppm moisture in air with onset of effect at approximately 50 ppm. The value of alpha increased 2-fold from 100 to 1000 ppm at all E/N values. At moisture values between 1000 and 10 000 ppm, a 2-fold or more increase in alpha (E/N) was observed. In a model proposed here, field dependence for mobility through changes in collision cross sections is governed by the degree of solvation of the protonated molecule by neutral molecules. The process of ion declustering at high E/N values was consistent with the kinetics of ion-neutral collisional periods, and the duty cycle of the waveform applied to the drift tube. Water was the principal neutral above 50 ppm moisture in air, and nitrogen was proposed as the principal neutral below 50 ppm.

Kinetic response of ionospheric ions to onset of auroral electric fields

NASA Technical Reports Server (NTRS)

Chiu, Y. T.; Kan, J. R.

1981-01-01

By examining the exact analytic solution of a kinetic model of collisional interaction of ionospheric ions with atmospheric neutrals in the Bhatnagar-Gross-Krook approximation, we show that the onset of intense auroral electric fields in the topside ionosphere can produce the following kinetic effects: (1) heat the bulk ionospheric ions to approximately 2 eV, thus driving them up to higher altitudes where they can be subjected to collisionless plasma processes; (2) produce a non-Maxwellian superthermal tail in the distribution function; and (3) cause the ion distribution function to be anisotropic with respect to the magnetic field with the perpendicular average thermal energy exceeding the parallel thermal energy.

Vortex focusing of ions produced in corona discharge.

PubMed

Kolomiets, Yuri N; Pervukhin, Viktor V

2013-06-15

Completeness of the ion transportation into an analytical path defines the efficiency of ionization analysis techniques. This is of particular importance for atmospheric pressure ionization sources like corona discharge, electrospray, ionization with radioactive ((3)H, (63)Ni) isotopes that produce nonuniform spatial distribution of sample ions. The available methods of sample ion focusing are either efficient at reduced pressure (~1Torr) or feature high sample losses. This paper deals with experimental research into atmospheric pressure focusing of unipolar (positive) ions using a highly swirled air stream with a well-defined vortex core. Effects of electrical fields from corona needle and inlet capillary of mass spectrometer on collection efficiency is considered. We used a corona discharge to produce an ionized unipolar sample. It is shown experimentally that with an electrical field barrier efficient transportation and focusing of an ionized sample are possible only when a metal plate restricting the stream and provided with an opening covered with a grid is used. This gives a five-fold increase of the transportation efficiency. It is shown that the electric field barrier in the vortex sampling region reduces the efficiency of remote ionized sample transportation two times. The difference in the efficiency of light ion focusing observed may be explained by a high mobility and a significant effect of the electric field barrier upon them. It is possible to conclude based on the experimental data that the presence of the field barrier narrows considerably (more than by one and half) the region of the vortex sample ion focusing. Copyright © 2013 Elsevier B.V. All rights reserved.

Study of interactions between metal ions and protein model compounds by energy decomposition analyses and the AMOEBA force field

NASA Astrophysics Data System (ADS)

Jing, Zhifeng; Qi, Rui; Liu, Chengwen; Ren, Pengyu

2017-10-01

The interactions between metal ions and proteins are ubiquitous in biology. The selective binding of metal ions has a variety of regulatory functions. Therefore, there is a need to understand the mechanism of protein-ion binding. The interactions involving metal ions are complicated in nature, where short-range charge-penetration, charge transfer, polarization, and many-body effects all contribute significantly, and a quantitative description of all these interactions is lacking. In addition, it is unclear how well current polarizable force fields can capture these energy terms and whether these polarization models are good enough to describe the many-body effects. In this work, two energy decomposition methods, absolutely localized molecular orbitals and symmetry-adapted perturbation theory, were utilized to study the interactions between Mg2+/Ca2+ and model compounds for amino acids. Comparison of individual interaction components revealed that while there are significant charge-penetration and charge-transfer effects in Ca complexes, these effects can be captured by the van der Waals (vdW) term in the AMOEBA force field. The electrostatic interaction in Mg complexes is well described by AMOEBA since the charge penetration is small, but the distance-dependent polarization energy is problematic. Many-body effects were shown to be important for protein-ion binding. In the absence of many-body effects, highly charged binding pockets will be over-stabilized, and the pockets will always favor Mg and thus lose selectivity. Therefore, many-body effects must be incorporated in the force field in order to predict the structure and energetics of metalloproteins. Also, the many-body effects of charge transfer in Ca complexes were found to be non-negligible. The absorption of charge-transfer energy into the additive vdW term was a main source of error for the AMOEBA many-body interaction energies.

Silicon nanowire field-effect transistors for the detection of proteins

NASA Astrophysics Data System (ADS)

Madler, Carsten

In this dissertation I present results on our efforts to increase the sensitivity and selectivity of silicon nanowire ion-sensitive field-effect transistors for the detection of biomarkers, as well as a novel method for wireless power transfer based on metamaterial rectennas for their potential use as implantable sensors. The sensing scheme is based on changes in the conductance of the semiconducting nanowires upon binding of charged entities to the surface, which induces a field-effect. Monitoring the differential conductance thus provides information of the selective binding of biological molecules of interest to previously covalently linked counterparts on the nanowire surface. In order to improve on the performance of the nanowire sensing, we devised and fabricated a nanowire Wheatstone bridge, which allows canceling out of signal drift due to thermal fluctuations and dynamics of fluid flow. We showed that balancing the bridge significantly improves the signal-to-noise ratio. Further, we demonstrated the sensing of novel melanoma biomarker TROY at clinically relevant concentrations and distinguished it from nonspecific binding by comparing the reaction kinetics. For increased sensitivity, an amplification method was employed using an enzyme which catalyzes a signal-generating reaction by changing the redox potential of a redox pair. In addition, we investigated the electric double layer, which forms around charges in an electrolytic solution. It causes electrostatic screening of the proteins of interest, which puts a fundamental limitation on the biomarker detection in solutions with high salt concentrations, such as blood. We solved the coupled Nernst-Planck and Poisson equations for the electrolyte under influence of an oscillating electric field and discovered oscillations of the counterion concentration at a characteristic frequency. In addition to exploring different methods for improved sensing capabilities, we studied an innovative method to supply power to implantable biosensors wirelessly, eliminating the need for batteries. A metamaterial split ring resonator is integrated with a rectifying circuit for efficient conversion of microwave radiation to direct electrical power. We studied the near-field behavior of this rectenna with respect to distance, polarization, power, and frequency. Using a 100 mW microwave power source, we demonstrated operating a simple silicon nanowire pH sensor with light indicator.

Effects of a parallel electric field and the geomagnetic field in the topside ionosphere on auroral and photoelectron energy distributions

NASA Technical Reports Server (NTRS)

Min, Q.-L.; Lummerzheim, D.; Rees, M. H.; Stamnes, K.

1993-01-01

The consequences of electric field acceleration and an inhomogeneous magnetic field on auroral electron energy distributions in the topside ionosphere are investigated. The one-dimensional, steady state electron transport equation includes elastic and inelastic collisions, an inhomogeneous magnetic field, and a field-aligned electric field. The case of a self-consistent polarization electric field is considered first. The self-consistent field is derived by solving the continuity equation for all ions of importance, including diffusion of O(+) and H(+), and the electron and ion energy equations to derive the electron and ion temperatures. The system of coupled electron transport, continuity, and energy equations is solved numerically. Recognizing observations of parallel electric fields of larger magnitude than the baseline case of the polarization field, the effect of two model fields on the electron distribution function is investigated. In one case the field is increased from the polarization field magnitude at 300 km to a maximum at the upper boundary of 800 km, and in another case a uniform field is added to the polarization field. Substantial perturbations of the low energy portion of the electron flux are produced: an upward directed electric field accelerates the downward directed flux of low-energy secondary electrons and decelerates the upward directed component. Above about 400 km the inhomogeneous magnetic field produces anisotropies in the angular distribution of the electron flux. The effects of the perturbed energy distributions on auroral spectral emission features are noted.

Effects of a Parallel Electric Field and the Geomagnetic Field in the Topside Ionosphere on Auroral and Photoelectron Energy Distributions

NASA Technical Reports Server (NTRS)

Min, Q.-L.; Lummerzheim, D.; Rees, M. H.; Stamnes, K.

1993-01-01

The consequences of electric field acceleration and an inhomogencous magnetic field on auroral electron energy distributions in the topside ionosphere are investigated. The one- dimensional, steady state electron transport equation includes elastic and inelastic collisions, an inhomogencous magnetic field, and a field-aligned electric field. The case of a self-consistent polarization electric field is considered first. The self-consistent field is derived by solving the continuity equation for all ions of importance, including diffusion of 0(+) and H(+), and the electron and ion energy equations to derive the electron and ion temperatures. The system of coupled electron transport, continuity, and energy equations is solved numerically. Recognizing observations of parallel electric fields of larger magnitude than the baseline case of the polarization field, the effect of two model fields on the electron distribution function in investigated. In one case the field is increased from the polarization field magnitude at 300 km to a maximum at the upper boundary of 800 km, and in another case a uniform field is added to the polarization field. Substantial perturbations of the low energy portion of the electron flux are produced: an upward directed electric field accelerates the downward directed flux of low-energy secondary electrons and decelerates the upward directed component. Above about 400 km the inhomogencous magnetic field produces anisotropies in the angular distribution of the electron flux. The effects of the perturbed energy distributions on auroral spectral emission features are noted.

Co-Registered In Situ Secondary Electron and Mass Spectral Imaging on the Helium Ion Microscope Demonstrated Using Lithium Titanate and Magnesium Oxide Nanoparticles.

PubMed

Dowsett, D; Wirtz, T

2017-09-05

The development of a high resolution elemental imaging platform combining coregistered secondary ion mass spectrometry and high resolution secondary electron imaging is reported. The basic instrument setup and operation are discussed and in situ image correlation is demonstrated on a lithium titanate and magnesium oxide nanoparticle mixture. The instrument uses both helium and neon ion beams generated by a gas field ion source to irradiate the sample. Both secondary electrons and secondary ions may be detected. Secondary ion mass spectrometry (SIMS) is performed using an in-house developed double focusing magnetic sector spectrometer with parallel detection. Spatial resolutions of 10 nm have been obtained in SIMS mode. Both the secondary electron and SIMS image data are very surface sensitive and have approximately the same information depth. While the spatial resolutions are approximately a factor of 10 different, switching between the different images modes may be done in situ and extremely rapidly, allowing for simple imaging of the same region of interest and excellent coregistration of data sets. The ability to correlate mass spectral images on the 10 nm scale with secondary electron images on the nanometer scale in situ has the potential to provide a step change in our understanding of nanoscale phenomena in fields from materials science to life science.

Measurement of drug facilitated sexual assault agents in simulated sweat by ion mobility spectrometry.

PubMed

Demoranville, Leonard T; Verkouteren, Jennifer R

2013-03-15

Ion mobility spectrometry has found widespread use for the detection of explosives and illicit drugs. The technique offers rapid results with high sensitivity and little sample preparation. As such, it is well suited for field deployed screening settings. Here the response of ion mobility spectrometers for three drug-facilitated sexual assault (DFSA) agents - flunitrazepam, ketamine, and MDMA - and related metabolites has been studied in the presence of a simulated sweat. While all three DFSA agents present certain challenges for qualitative identification, IMS can provide useful information to guide the early treatment and investigation of sexual assault cases. Used as a presumptive test, the identification of DFSA agents would later require confirmatory analysis by other techniques. Published by Elsevier B.V.

Fast Ion Effects During Test Blanket Module Simulation Experiments in DIII-D

NASA Astrophysics Data System (ADS)

Kramer, G. J.; Budny, R.; Nazikian, R.; Heidbrink, W. W.; Kurki-Suonio, T.; Salmi, A.; Schaffer, M. J.; van Zeeland, M. A.; Shinohara, K.; Snipes, J. A.; Spong, D.

2010-11-01

The fast beam-ion confinement in the presence of a scaled mock-up of two Test Blanket Modules (TBM) for ITER was studied in DIII-D. The TBM on DIII-D has four vertically arranged protective carbon tiles with thermocouples placed at the back of each tile. Temperature increases of up to 200^oC were measured for the two tiles closest to the midplane when the TBM fields were present. These measurements agree qualitatively with results from the full orbit-following beam-ion code, SPIRAL, that predict beam-ion losses to be localized on the central two carbon tiles when the TBM fields present. Within the experimental uncertainties no significant change in the fast-ion population was found in the core of these plasmas which is consistent with SPIRAL analysis. These experiments indicate that the TBM fields do not affect the fast-ion confinement in a harmful way which is good news for ITER.

The dynamo of the diurnal tide and its effect on the thermospheric circulation

NASA Technical Reports Server (NTRS)

Mayr, H. G.; Harris, I.; Herrero, F. A.

1990-01-01

A theoretical multiconstituent model (including O, N2, and O2) which describes the interactions between neutral winds, dynamo electric fields, and ion drifts is used to interpret observations that revealed a dominance of the fundamental diurnal tide in the upper thermosphere and at equatorial latitudes, and its effect on the thermospheric circulation. The model is shown to reproduce reasonably well the magnitudes of the neutral winds, ion drift velocities, and the ratio between the two. A solution for the neutral winds in which the dynamo electric field is forced to zero shows that the dynamo-induced ion drift is very important in accelerating the neutral atmosphere at higher altitudes. The dynamo interaction primarily affects the curl component of the field; its effect on the temperature and density perturbations is small.

Ion-Selective Electrodes.

ERIC Educational Resources Information Center

Arnold, Mark A.; Meyerhoff, Mark E.

1984-01-01

Literature on ion-selective electrodes (ISEs) is reviewed in seven sections: books, conferences, reviews; potentiometric membrane electrodes; glass and solid-state membrane electrodes; liquid and polymer membrane ISEs; coated wire electrodes, ion-selective field effect transistors, and microelectrodes; gas sensors and selective bioelectrode…

4D ML reconstruction as a tool for volumetric PET-based treatment verification in ion beam radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Bernardi, E., E-mail: elisabetta.debernardi@unimib.it; Ricotti, R.; Riboldi, M.

2016-02-15

Purpose: An innovative strategy to improve the sensitivity of positron emission tomography (PET)-based treatment verification in ion beam radiotherapy is proposed. Methods: Low counting statistics PET images acquired during or shortly after the treatment (Measured PET) and a Monte Carlo estimate of the same PET images derived from the treatment plan (Expected PET) are considered as two frames of a 4D dataset. A 4D maximum likelihood reconstruction strategy was adapted to iteratively estimate the annihilation events distribution in a reference frame and the deformation motion fields that map it in the Expected PET and Measured PET frames. The outputs generatedmore » by the proposed strategy are as follows: (1) an estimate of the Measured PET with an image quality comparable to the Expected PET and (2) an estimate of the motion field mapping Expected PET to Measured PET. The details of the algorithm are presented and the strategy is preliminarily tested on analytically simulated datasets. Results: The algorithm demonstrates (1) robustness against noise, even in the worst conditions where 1.5 × 10{sup 4} true coincidences and a random fraction of 73% are simulated; (2) a proper sensitivity to different kind and grade of mismatches ranging between 1 and 10 mm; (3) robustness against bias due to incorrect washout modeling in the Monte Carlo simulation up to 1/3 of the original signal amplitude; and (4) an ability to describe the mismatch even in presence of complex annihilation distributions such as those induced by two perpendicular superimposed ion fields. Conclusions: The promising results obtained in this work suggest the applicability of the method as a quantification tool for PET-based treatment verification in ion beam radiotherapy. An extensive assessment of the proposed strategy on real treatment verification data is planned.« less

Ion mobility spectrometer using frequency-domain separation

DOEpatents

Martin, Stephen J.; Butler, Michael A.; Frye, Gregory C.; Schubert, W. Kent

1998-01-01

An apparatus and method is provided for separating and analyzing chemical species in an ion mobility spectrometer using a frequency-domain technique wherein the ions generated from the chemical species are selectively transported through an ion flow channel having a moving electrical potential therein. The moving electrical potential allows the ions to be selected according to ion mobility, with certain of the ions being transported to an ion detector and other of the ions being effectively discriminated against. The apparatus and method have applications for sensitive chemical detection and analysis for monitoring of exhaust gases, hazardous waste sites, industrial processes, aerospace systems, non-proliferation, and treaty verification. The apparatus can be formed as a microelectromechanical device (i.e. a micromachine).

Probing microscopic material properties inside simulated membranes through spatially resolved three-dimensional local pressure fields and surface tensions

PubMed Central

Kasson, Peter M.; Hess, Berk; Lindahl, Erik

2013-01-01

Cellular lipid membranes are spatially inhomogeneous soft materials. Materials properties such as pressure and surface tension thus show important microscopic-scale variation that is critical to many biological functions. We present a means to calculate pressure and surface tension in a 3D-resolved manner within molecular-dynamics simulations and show how such measurements can yield important insight. We also present the first corrections to local virial and pressure fields to account for the constraints typically used in lipid simulations that otherwise cause problems in highly oriented systems such as bilayers. Based on simulations of an asymmetric bacterial ion channel in a POPC bilayer, we demonstrate how 3D-resolved pressure can probe for both short-range and long-range effects from the protein on the membrane environment. We also show how surface tension is a sensitive metric for inter-leaflet equilibrium and can be used to detect even subtle imbalances between bilayer leaflets in a membrane-protein simulation. Since surface tension is known to modulate the function of many proteins, this effect is an important consideration for predictions of ion channel function. We outline a strategy by which our local pressure measurements, which we make available within a version of the GROMACS simulation package, may be used to design optimally equilibrated membrane-protein simulations. PMID:23318532

The effects of dielectric decrement and finite ion size on differential capacitance of electrolytically gated graphene

NASA Astrophysics Data System (ADS)

Daniels, Lindsey; Scott, Matthew; Mišković, Z. L.

2018-06-01

We analyze the effects of dielectric decrement and finite ion size in an aqueous electrolyte on the capacitance of a graphene electrode, and make comparisons with the effects of dielectric saturation combined with finite ion size. We first derive conditions for the cross-over from a camel-shaped to a bell-shaped capacitance of the diffuse layer. We show next that the total capacitance is dominated by a V-shaped quantum capacitance of graphene at low potentials. A broad peak develops in the total capacitance at high potentials, which is sensitive to the ion size with dielectric saturation, but is stable with dielectric decrement.

Miniature Ion-Mobility Spectrometer

NASA Technical Reports Server (NTRS)

Hartley, Frank T.

2006-01-01

The figure depicts a proposed miniature ion-mobility spectrometer that would be fabricated by micromachining. Unlike prior ion-mobility spectrometers, the proposed instrument would not be based on a time-of-flight principle and, consequently, would not have some of the disadvantageous characteristics of prior time-of-flight ion-mobility spectrometers. For example, one of these characteristics is the need for a bulky carrier-gas-feeding subsystem that includes a shutter gate to provide short pulses of gas in order to generate short pulses of ions. For another example, there is need for a complex device to generate pulses of ions from the pulses of gas and the device is capable of ionizing only a fraction of the incoming gas molecules; these characteristics preclude miniaturization. In contrast, the proposed instrument would not require a carrier-gas-feeding subsystem and would include a simple, highly compact device that would ionize all the molecules passing through it. The ionization device in the proposed instrument would be a 0.1-micron-thick dielectric membrane with metal electrodes on both sides. Small conical holes would be micromachined through the membrane and electrodes. An electric potential of the order of a volt applied between the membrane electrodes would give rise to an electric field of the order of several megavolts per meter in the submicron gap between the electrodes. An electric field of this magnitude would be sufficient to ionize all the molecules that enter the holes. Ionization (but not avalanche arcing) would occur because the distance between the ionizing electrodes would be less than the mean free path of gas molecules at the operating pressure of instrument. An accelerating grid would be located inside the instrument, downstream from the ionizing membrane. The electric potential applied to this grid would be negative relative to the potential on the inside electrode of the ionizing membrane and would be of a magnitude sufficient to generate a moderate electric field. Positive ions leaving the membrane holes would be accelerated in this electric field. The resulting flux of ions away from the ionization membrane would create a partial vacuum that would draw more of the gas medium through the membrane. The figure depicts a filter electrode and detector electrodes located along the sides of a drift tube downstream from the accelerator electrode. These electrodes would apply a transverse AC electric field superimposed on a ramped DC electric field. The AC field would effect differential transverse dispersal of ions. At a given instant of time, the trajectories of most of the ions would be bent toward the electrodes, causing most of the ions to collide with the electrodes and thereby become neutralized. The DC field would partly counteract the dispersive effect of the AC field, straightening the trajectories of a selected species of ions; the selection would vary with the magnitude of the applied DC field. The straightening of the trajectories of the selected ions would enable them to pass into the region between the detector electrodes. Depending on the polarity of the voltage applied to the detector electrodes, the electric field between the detector electrodes would draw the selected ions to one of these electrodes. Hence, the current collected by one of the detector electrodes would be a measure of the abundance of ions of the selected species. The ramping of the filter- electrode DC voltage would sweep the selection of ions through the spectrum of ionic species.

Alpha Channeling in Open-System Magnetic Devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fisch, Nathaniel

The Grant DE-SC0000736, Alpha Channeling in Open-System Magnetic Devices, is a continuation of the Grant DE-FG02-06ER54851, Alpha Channeling in Mirror Machines. In publications funded by DE-SC0000736, the grant DE-FG02-06ER54851 was actually credited. The key results obtained under Grant DE-SC0000736, Alpha Channeling in Open-System Magnetic Devices, appear in a series of publications. The earlier effort under DE-FG02- 06ER54851 was the subject of a previous Final Report. The theme of this later effort has been unusual confinement effects, or de-confinement effects, in open-field magnetic confinement devices. First, the possibilities in losing axisymmetry were explored. Then a number of issues in rotating plasmamore » were addressed. Most importantly, a spinoff application to plasma separations was recognized, which also resulted in a provisional patent application. (That provisional patent application, however, was not pursued further.) Alpha channeling entails injecting waves into magnetically confined plasma to release energy from one particular ion while ejecting that ion. The ejection of the ion is actually a concomitant effect in releasing energy from the ion to the wave. In rotating plasma, there is the opportunity to store the energy in a radial electric field rather than in waves. In other words, the ejected alpha particle loses its energy to the radial potential, which in turn produces plasma rotation. This is a very useful effect, since producing radial electric fields by other means are technologically more difficult. In fact, one can heat ions, and then eject them, to produce the desired radial field. In each case, there is a separation effect of different ions, which generalizes the original alpha-channeling concept of separating alpha ash from hydrogen. In a further generalization of the separation concept, a double-well filter represents a new way to produce high-throughput separations of ions, potentially useful for nuclear waste remediation.« less

Negative electrospray ionization on porous supporting tips for mass spectrometric analysis: electrostatic charging effect on detection sensitivity and its application to explosive detection.

PubMed

Wong, Melody Yee-Man; Man, Sin-Heng; Che, Chi-Ming; Lau, Kai-Chung; Ng, Kwan-Ming

2014-03-21

The simplicity and easy manipulation of a porous substrate-based ESI-MS technique have been widely applied to the direct analysis of different types of samples in positive ion mode. However, the study and application of this technique in negative ion mode are sparse. A key challenge could be due to the ease of electrical discharge on supporting tips upon the application of negative voltage. The aim of this study is to investigate the effect of supporting materials, including polyester, polyethylene and wood, on the detection sensitivity of a porous substrate-based negative ESI-MS technique. By using nitrobenzene derivatives and nitrophenol derivatives as the target analytes, it was found that the hydrophobic materials (i.e., polyethylene and polyester) with a higher tendency to accumulate negative charge could enhance the detection sensitivity towards nitrobenzene derivatives via electron-capture ionization; whereas, compounds with electron affinities lower than the cut-off value (1.13 eV) were not detected. Nitrophenol derivatives with pKa smaller than 9.0 could be detected in the form of deprotonated ions; whereas polar materials (i.e., wood), which might undergo competitive deprotonation with the analytes, could suppress the detection sensitivity. With the investigation of the material effects on the detection sensitivity, the porous substrate-based negative ESI-MS method was developed and applied to the direct detection of two commonly encountered explosives in complex samples.

Impact parameter smearing effects on isospin sensitive observables in heavy ion collisions

NASA Astrophysics Data System (ADS)

Li, Li; Zhang, Yingxun; Li, Zhuxia; Wang, Nan; Cui, Ying; Winkelbauer, Jack

2018-04-01

The validity of impact parameter estimation from the multiplicity of charged particles at low-intermediate energies is checked within the framework of the improved quantum molecular dynamics model. The simulations show that the multiplicity of charged particles cannot estimate the impact parameter of heavy ion collisions very well, especially for central collisions at the beam energies lower than ˜70 MeV/u due to the large fluctuations of the multiplicity of charged particles. The simulation results for the central collisions defined by the charged particle multiplicity are compared to those by using impact parameter b =2 fm and it shows that the charge distribution for 112Sn+112Sn at the beam energy of 50 MeV/u is different evidently for two cases; and the chosen isospin sensitive observable, the coalescence invariant single neutron to proton yield ratio, reduces less than 15% for neutron-rich systems Sn,132124+124Sn at Ebeam=50 MeV/u, while the coalescence invariant double neutron to proton yield ratio does not have obvious difference. The sensitivity of the chosen isospin sensitive observables to effective mass splitting is studied for central collisions defined by the multiplicity of charged particles. Our results show that the sensitivity is enhanced for 132Sn+124Sn relative to that for 124Sn+124Sn , and this reaction system should be measured in future experiments to study the effective mass splitting by heavy ion collisions.